Thermo Gravimetric Analysis Research Papers

Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide

2007, Carbon

Reduction of a colloidal suspension of exfoliated graphene oxide sheets in water with hydrazine hydrate results in their aggregation and subsequent formation of a high-surface-area carbon material which consists of thin graphene-based... more

Fig. 7. The Raman spectra of SP-1 graphite (top), GO (middle), and the reduced GO (bottom).

Fig. 8. Conductivity as a function of the volume fraction of three different graphitic powders: pristine graphite (SP-1), GO, and reduced GO. To determine the extent to which the chemical reduction of exfoliated GO restores the electrical properties of the graphitic network, we measured the room-temperature electrical conductivities of compressed-powder samples of the pristine graphite, GO, and the reduced GO at 30% rel- ative humidity (Fig. 8). The results of the fits to the exper- imental data are summarised in Table 1. The extrapolated intrinsic conductivity, o,, of the reduced GO is probably

Fitting parameters describing percolation transport for the three graphitic powders shown in Fig. 8 over-estimated due to the limited data range available as a result of the low compressibility and possible spatial vari- ations in the density of the material. More reliable are the conductivity data for the reduced GO, which can be mea- sured at higher powder compression. This conductivity (~2 x 10° S/m) is about 5 orders of magnitude better than the conductivity of GO, and closely approaches that of pristine graphite (approximately 10 times lower than the conductivity of pristine graphite powder at only about 10% of the bulk graphite density). Such high intrinsic con- ductivity of the reduced GO in spite of the presence of oxy- gen (potential acceptor sites) might be an indication of: (1) quite conductive particle-to-particle interfaces, which often determines the overall percolation conductivity; (ii) a very dense conductive network with many cross-linked connec- tions; and (iii) possible ionic channels of charge transfer across the sample. This last mechanism is definitely a dom- inant one in the electrical conduction of GO powder and a reason for its high sensitivity to temperature and environ- mental humidity. In contrast, the conductivity of the reduced GO is based primarily on inter-particle contacts and is much less sensitive to environmental conditions. Peer 7 1 Y ow ae ce 4 é a4 Table 1

Fig. 2. (a) An SEM image of aggregated reduced GO sheets. (b) A platelet having an upper bound thickness at a fold of ~2 nm. At the resolution limit of the FEG SEM used here, the following are relevant parameters of the microscope and of the specimen. Of the microscope: spot size and flux of e-beam (e-current, density, solid angle/aperture size), energy of the electrons in the primary beam, electromagnetic lens alignment, type of detectors used and their operating parameters. Of the sample: geometry (such as edges, roughness, thickness, and orientation with respect to e-beam), material (such as density, atomic number, electrical conductivity, and composition), substrate or matrix (what the specimen is affixed to or a part of). There is also the role of the operator expertise. Thus for (b) and discussion of a measured value for the fold thickness of about 2 nm, we suggest a confidence limit of roughly +1 nm. Surface area measurement of the reduced GO sheets via nitrogen gas absorption yielded a BET value of 466 m7/g (Fig. 3). This high specific surface area is partially an indi- cation of the degree of GO exfoliation prior to the reduc- tion. However, it is still lower than the theoretical specific surface area for completely exfoliated and isolated graph- ene sheets (~2,620 m7/g [20]), potentially due to the agglomeration of the graphene oxide sheets upon reduc- tion. While this agglomeration can result in the partial overlapping and coalescing of the reduced sheets and low- ers the surface area of the bulk materials, the crumpled Although GO is thermally unstable and starts to lose mass upon heating even below 100 °C, the major mass los: occurs at ~200°C, presumably due to pyrolysis of the labile oxygen-containing functional groups, yielding CO CO3;, and steam [27,44]. Hence, the thermal decompositior

Fig. 6. The Cls XPS spectra of: (a) GO, (b) reduced GO. Adapted from reference [18]. The significant structural changes occurring during the chemical processing from pristine graphite to GO, and then to the reduced GO, are also reflected in their Raman spec- tra (Fig. 7). The Raman spectrum of the pristine graphite, as expected, displays a prominent G peak as the only fea- ture at 1581 cm, corresponding to the first-order scatter- ing of the E2g mode [47]. In the Raman spectrum of GO, the G band is broadened and shifted to 1594 cm7!. In addi- tion, the D band at 1363 cm~' becomes prominent, indicat- ing the reduction in size of the in-plane sp* domains, possibly due to the extensive oxidation. The Raman spec- trum of the reduced GO also contains both G and D bands (at 1584 and 1352cm™', respectively); however, with an increased D/G intensity ratio compared to that in GO. This change suggests a decrease in the average size of the sp” domains upon reduction of the exfoliated GO [47], and can be explained if new graphitic domains were created that are smaller in size to the ones present in GO before reduction, but more numerous in number.

Fig. 1. A non-contact mode AFM image of exfoliated GO sheets with three height profiles acquired in different locations During the hydrazine reduction of graphene oxide sheets dispersed in water, the brown-colored dispersion turns In our work, sufficiently dilute colloidal suspensions of GO prepared with the aid of ultrasound are clear, homog- enous, and stable indefinitely [18]. AFM images of GO

Fig. 3. Nitrogen adsorption and desorption isotherms for reduced exfoliated GO. The shape of the isotherm indicates that the material contains both micro and mesopores [53].

The °C MAS NMR spectra of GO and the reduced GO indicate significant structural change induced by the reduc- tion. In the spectrum of GO (Fig. 5), the peaks at 57 and 68 ppm represent the '°C nuclei in the epoxide and hydro- xyl groups, respectively [24-27]. The resonance at 130 ppm belongs to the un-oxidized sp” carbons of the graphene net- work and that at 188 ppm presumably arises from the car- bonyl groups. In the ‘°C spectrum of the reduced GO, the peaks from the oxygenated and the carbonyl carbons are absent. The remaining prominent feature is the resonance at 117 ppm that is broadened by chemical shift distribu- tion and corresponds to variations of carbon atom environments. Fig. 4. Normalized TGA plots for GO and the reduced GO. The downward slopes are due to normal instrument drift.

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Characterization of pressmud: A sugar industry waste

by Chandrajit Balomajumder and

2011, Fuel

The increasing demand of energy has been a prime source of motivation for the development of alternate fuels. The concept of biological degradation of organic wastes by anaerobic digestion for the generation of methane has been used by... more

Composition of elements for the sample shown in Fig. 2b obtained from FE SEM analysis.

General composition of pressmud [5]. Table 1

Composition of elements for the sample shown in Fig. 2a obtained from FE SEM analysis.

Fig. 3. Number cumulative graph (Full scale) of pressmud sample.

Fig. 2. Micrographs of pressmud sample: (a) FE SEM analysis, magnification 1000 x: (b) FE SEM analysis, magnification 4000.

A typical nutrient contents of pressmud [6]. Table 2

Fig. 1. A schematic diagram of formation of pressmud waste in sugar mill.

Fig. 4. Result of X-ray diffraction analysis of pressmud sample.

Various organic materials having potential for biogas generation.

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Synthesis and characterization of hydrozincite and its conversion into zinc oxide nanoparticles

by Hyung-shik Shin

2008, Journal of Alloys and Compounds

Faceted nanoparticles of zinc oxide were successfully achieved via thermal annealing of hydrozincite (Zn 5 (CO 3 ) 2 (OH) 6 ) powder at different annealing temperatures, i.e. 300, 500 700 and 900 • C in air for 2 h using sol-gel method by... more

Fig. 8. Typical FTIR spectra of annealed zinc oxide nanoparticles (a) at 300 °C, (b) at 500°C, (c) at 700°C and (d) at 900°C. Fig. 8(a) represents the FTIR spectrum of annealed hydroz- incite powder. The band at 450 cm7! is correlated to zinc oxide. The bands at 3200-3600cm™! correspond to O-H mode of vibration. The stretching mode of vibration of C—O is observed at 1531cm7!. The bands at 1642 and 2355cm7! are due to the C=O and CO? groups. When the annealing temperature was

Fig. 2. (a and b) Low and high magnification FESEM images of annealed hydrozincite powder at 300 °C. Whereas (c and d) Low and high magnification images of annealed hydrozincite powder at 500°C. Zinc acetate dihydrate (Zn(CH3COOH)2-2H20O) and urea (NH2CONH?2) were used for the synthesis of zinc oxide nanoparticles by using sol-gel method. The chemicals were purchased from Aldrich Chemical Corporation and used Chemical routes were equally investigated to explore the synthesis of nanostructures of ZnO. For example, Music et al. presented the synthesis of zinc oxide nanoparticles of about 100nm in size using ZnCly Zn(CH3COO)2-2H20,

Fig. 5. The X-ray diffraction pattern of as-grown hydrozincite powder prepared by the sol-gel method at 70°C in 6h refluxing time. Marked (*) points indicate the unidentified peaks. R. Wahab et al. / Journal of Alloys and Compounds 461 (2008) 66-71

Fig. 6. (a-d) Typical X-ray diffraction pattern at different annealing tempera- tures, i.e. 300, 500, 700 and 900 °C, respectively. The composition of the synthesized powder was analyzed by the FTIR spectroscopy. Figs. 7 and 8 shows the FTIR spectrum acquired in the range of 400-4000cm7! at room tempera- ture. Fig. 7 shows the FTIR spectra of as grown hydrozincite (Zns5(CO3)2(OH)¢) powder. This spectrum shows the basic fea- tures of zinc carbonate group. The broadband between 3455 and 3358cm7! belongs to the adsorbed H2O molecule. The peak centered at 2369 and 2221 cm™! denotes the presence of COp.

Fig. 3. (a and b) Low and high magnification FESEM images of the annealed hydrozincite powder at 700°C and (c and d) low and high magnification images | annealed hydrozincite powder at 900°C.

Fig. 4. (a) Low magnification TEM image of annealed hydrozincite powder at 300°C and (b) presents the typical high resolution transmission electron microscopy (HRTEM) of annealed hydrozincite powder; the image clearly show the distance between two lattice fringes is ~0.52 nm. The corresponding SAED pattern (inset) indicates the crystallinity of the synthesized products. After refluxing, the white aqueous solution was washed with methanol three or four times to remove ionic impurities and dried at room tempera- ture for further analysis. The dried samples were annealed in air ambient at without further purification. In a typical experiment: 0.3 M zinc acetate dihydrate (Zn(CH3COOH) -2H20) and 2 M urea (NH2CONH)2) were dissolved in 100 ml deionized water and stirred for 30 min. The solution was then transferred in a three-necked refluxing pot and refluxed for 6h at 70°C. The solutions pH was measured as 12.6 by the expandable ion analyzer (EA 940, Orian, United

Fig. 7. Typical FTIR spectrum of as-grown hydrozincite powder prepared by the sol-gel method at 70°C in 6h refluxing time.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Provided for non-commercial research and education use Not for reproduction, distribution or commercial use.

Fig. 1. The typical FESEM image of as-grown hydrozincite powder, prepared by the sol-gel method by refluxing for 6h at at 70°C.

Fig. 9. Typical TGA analysis of as-grown hydrozincite powder from room temperature to 700°C. R. Wahab et al. / Journal of Alloys and Compounds 461 (2008) 66-71

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Fabrication and characterization of novel macroporous cellulose–alginate hydrogels

by bo duan

2009, Polymer

Novel macroporous hydrogels were prepared by blending of cellulose and sodium alginate (SA) solution, and then cross-linking with epichlorohydrin. The resulting cellulose/SA hydrogels were characterized by solid-state 13 C NMR, wide-angle... more

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Jute as raw material for the preparation of microcrystalline cellulose

by Md Sarwar Jahan

2011, Cellulose

Cellulose was extracted at a yield of 59.8% from jute fibres based on the formic acid/ peroxyformic acid process at an atmospheric pressure. The amounts of dissolved lignin and hemicelluloses were determined in the spent liquor. The... more

Fig. 2 TEM micrograph of MCC1 and MCC2 relatively small (6.5 wt%). It can be seen in Fig. 3 that there were no other degradation peaks except that of cellulose, which supported the conclusion that the MCC samples we prepared are very pure. The weight osses of these products have three stages: (1) dehydration of absorbed water (<200 °C), (2) cellu- ose chain scissions (200 ~ 380 °C) (Gassan and Bledzki 2001), due to the breaks of C-C and C—O bonds; (3) aromatization (>380 °C), leading to the formation of the residual char. The decomposition peaks of the maximum mass loss were at 337, 313 and 315 °C for cellulose and MCC1 and MCC2, respectively. The negatively charged sulfate groups introduced into the outer surface of the cellulose crystals decreased thermal stability (Fahma et al. 2010). It was reported (Alemdar and Sain 2008) that

Table 2. Chemical compositions of spent liquor (% on original material) Table 3. Dimension characteristics of MCC1 and MCC2 and sugar composition in cellulose acid hydrolysis liquor

can be converted into xylitol, yeast, furfural anc others in the chemical or enzymatic processes.

Fig. 4 FT-IR spectra of cellulose, MCC1 and MCC2

Fig. 3. Thermal degradation behaviors of cellulose, MCC1 and MCC2

Fig. 5 X-ray diffraction patterns of cellulose, MCC1 and MCC2 The X-ray diffraction pattern of the MCC samples is shown in Fig. 5. The peak at 2-theta = 22° is sharper for MCC2, indicative of a higher crystallinity degree in the structure of MCC2. The crystallinity index of cellulose of 68.7% was found, which increased to 74.9% for MCC2. It was reported that the crystallin- ity degree increased with the transformation of micro to nano- fibrils (Lee et al. 2009). Leonard and Martin (2002) observed that the crystallinity degree of jute fibre was 71%, which is similar to that of ramie or fibre was 71%, which is similar to that of ramie or

treatment at an atmospheric pressure. Xylose/xylan The sugar compositions (monomeric and oligo- meric) in the formic acid spent liquor are shown in Table 2. Under the employed conditions, 10.6% of the sugars of the jute can be extracted. Xylose/xylan accounted for nearly 80% of the total sugars dissolved during the treatment, while the glucose/ glucan content was only 8.9% of the total sugars in the spent liquor. Pan and Sano (2005) reported that 63.5% of xylose/xylan was dissolved in the spent liquor during the acetic acid treatment of wheat straw, while cellulose was highly protected. Lam et al. (2001) observed that above 80% of pentose sugars were dissolved from rice straw in the formic acid treatment at an atmospheric pressure. Xylose/xylan

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Antibacterial and bioactive silver-containing Na 2 O·CaO·2SiO 2 glass prepared by sol–gel method

by Michelina Catauro

2004, Journal of Materials Science-materials in Medicine

The antibacterial effect of addition of silver oxide to Na2O·CaO·2SiO2 glass have been studied. Silver containing and silver free Na2O·CaO·2SiO2 glasses have been prepared by sol–gel synthesis using tetramethil orthosilicate, sodium... more

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Structural, thermal, mechanical and dynamic mechanical properties of cenosphere filled polypropylene composites

by Arijit Das

2011, Materials & Design

Polypropylene (PP)/cenosphere based composites were fabricated and characterized for their structural/ morphological and mechanical properties such as tensile, flexural, impact and dynamic mechanical properties such as storage and loss... more

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An investigation of dynamic mechanical, thermal, and electrical properties of housing materials for outdoor polymeric insulators

by Ernst Gockenbach

2004, European Polymer Journal

The present paper reports the results about a study of mechanical, thermal, dynamic mechanical and electrical properties of housing (weather shed) materials for outdoor polymeric insulators. Silicone rubber, ethylene-propylenediene... more

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Spray pyrolytic synthesis of large area NiOx thin films from aqueous nickel acetate solutions

by Kwang-Deog Jung

2006, Applied Surface Science

Non-stoichiometric nickel oxide thin films were prepared by pyrolytic decomposition of aerosol droplets of aqueous nickel acetate solution. Conventional un-nebulized spray pyrolysis system was used for the synthesis of thin films. The... more

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Synthesis and characterization of polyaniline rubber composites

by Basavaraj Mulimani

2008, Composites Science and Technology

Polyaniline-carboxylic acid functionalized multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites were prepared in sodium dodecyl sulfate (SDS) emulsion. First, the c-MWNTs were dispersed in SDS emulsion then the aniline was... more

Scheme 1. Schematic representation of the formation mechanism of the PAni/c-MWNT nanocomposites in the presence of SDS emulsion.

Figure 1. FT-IR spectra of MWNTs and c-MWNTs.

Figure 6. Raman spectra of (a) MWNTs & c-MWNTs and (b) PAni & PAni/c-MWNT nanocomposites.

Figure 9. Room temperature conductivity of PAni/c-MWNT nanocomposites as a function of c-MWNT content.

Figure 2. FE-SEM images of MWNTs (a) before and (b) after oxidation. is the z—-z electron interaction between the MWNTs and the aniline monomer”? and the other is the hydrogen bond interaction between the carboxyl groups of the c-MWNTs and amine groups of the aniline monomers. Such a strong

Figure 8. X-ray diffractrograms of c-MWNT, PAni, and PAni/c-MWNT nanocomposites. Some of the peaks in the spectra of the PAni/c-MWNT nanocomposites are shifted as compared to that of the pure PAni. For example, the band at 1130 cm! is shifted to 1119 cm’. The shift of this band to a lower frequency range may be due to the protonated state of PAni, and the extent of the shift depends on the c-MWNT content. Figure 7 also reveals that the intensity of some of the peaks of the PAni nanocomposites is decreased compared to that of PAni. This difference can be explained as follows: when the aniline monomers are introduced into the micellar-aided emulsion, they are adsorbed onto the surface of the MWNTs. Therefore, the polymer chains are constrained to grow around the tubes. Such adsorption and constrained motion of the chains will restrict the modes of vibrations in PAni, leading to the difference in the IR spectra. Since the in-plane deformation of the C-C bond of the quinoid ring of the PAni in the composites is greatly decreased, this suggests that there is an interaction between the quinoid ring of the PAni and the The XRD of tubular composites shows peaks at 26= 15°, 20°, and 25°, which are similar to pure PAni matrix, revealing that no additional crystalline order have been introduced into the composites. The increase in the intensity of the peat at 25° (Figure 8, inset) with increasing c- MWNTs content can be attributed to the concentration of MWNTs, which have higher scattering factors. From the XRD study, it can be concluded that, the PAni/c-MWNT composites are partially crystalline.

Figure 7. FT-IR spectra of PAni and PAni/c-MWNT nano- composites. The spectrum obtained after coating the PAni on the c-MWNTs reveals the presence of the polymer overlayer. The PAni/c-MWNT composites show nearly identical numbers and positions of the main IR bands. However, there are several differences between the FT-IR spectra of the PAni/

Figure 3. FE-SEM images of (a) 95/05, (b) 90/10, and (c) 80/20 PAni/c-MWNT nanocom- posites (each given at two magnifications).

Figure 5. UV-Visible spectra of c-MWNTs, PAni and PAni/ c-MWNT nanocomposites. oxidation state of PAni (emeraldine salt). As commonly observed for emeraldine salts, the benzenoid band at 1480cm~! is more intense than that of the quinoid band at 1562cm~!. The strong characteristic band appearing at 1124cm | was described by MacDiarmid and co-workers” as the “electron-like band” and is considered to be a measure of the delocalization of the electrons and, thus, is indicative of

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Montmorillonite intercalated with vitamin B 1 as drug carrier

by Hari Bajaj

2009, Applied Clay Science

Vitamin B 1 (thiamine hydrochloride, VB 1 ) intercalated into montmorillonite (MMT), which was characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), and thermo gravimetric analysis (TGA). The... more

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Preparation and characterization of N-heterocyclic chitosan derivative based gels for biomedical applications

by Santosh Kumar

2009, International Journal of Biological Macromolecules

The novel N-heterocyclic chitosan aerogel derivatives were prepared by reacting 79% deacetylated chitosan separately with 4-pyridinecarboxaldehyde and 2,6-pyridinedicarboxaldehyde followed by subsequent solvent exchange into acetone,... more

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Synthesis and characterization of zinc-organic frameworks with 1, 4-benzenedicarboxylic acid and azobenzene-4, 4'-dicarboxylic acid

by thai nguyen

2011, Advances in Natural …

The solvothermal reactions of 1,4-bezenedicarboxylic acid (H 2 BDC) or azobenzene-4,4 -dicarboxylic acid (H 2 ABD) with zinc ions/clusters lead to the formation of four crystalline materials. All of these compounds were characterized by... more

Table 1. Pore parameters calculated from the nitrogen adsorption data.

Figure 3. XRD patterns of BZ2 (a), AZ2 (b) and AZ1 (c). 3.2.2. Thermo-gravimetric analysis (TGA). TGA curve of BZ2, showing its thermal stability up to 500°C. The material experienced two main weight changes. The first step slope of mass loss (15%) around 200°C was attributed to the vaporization of dichloromethane and DMF residing in the pore. The other weight loss accounted for the framework decomposition of the organic linker (50%) between 460°C and 600°C. Clearly, after being activated with a trap filled in liquid nitrogen under vacuum, the TGA curve exhibited only one main weight loss around 460 °C, meaning that guest molecules were evacuated completely. However, due to the humidity, the small mass loss was still observed on the BZ2 activated curve (figure 4(a)). The TGA curve of AZ2 showed

Figure 1. Microscope images of crystalline materials synthesized in DMF at 80°C, 12h, pH 4.18, [H»BDC] : Zn?* = 1: 1, [H;BDC] = 0.1 M (a, BZ1), in DMF at 100°C, 24h, pH 4.82, [H,BDC] : Zn?* = 1 : 4, [H] BDC] = 0.01 M (b, BZ2/DMP), in DEF at 100°C, 24h, pH 4.64, [H)BDC] : Zn?* = 1 : 4, [HyBDC] = 0.01 M (c, BZ2/DEP). 2.2.2. Synthesis of MOFs from azobenzene-1,4-dicarboxylic acid and zinc nitrate. The mixtures with mole ratios of H,ABD to zinc nitrate (H,ABD: Zn) varying from 1:1 to 1:5 were dissolved in 10 ml DMF. In each experiment with a certain H»ABD : Zn mole ratio, the concentration of HxABD was varied from 0.01 M to 0.001 M. The reaction mixture was put in a 20 ml reaction vial, which was capped and heated in an isothermal oven from 80°C to 100°C for 12—72 h, and then cooled to room temperature. The red sheet-shaped crystals were collected by decanting from mother liquor. The washing and solvent exchange procedures were the same as described above in section 2.2.1. Finally, the crystals were dried under vacuum at 150°C for 10h. XA-Tay diffraction data were recorded on a Do Advance Bruker powder diffractometer with Cu-Ka radiation (A = 1.542 A). The thermal behavior of synthesized materials was recorded on a TGA Q500 analyzer with a heating rate of 10°C min! in nitrogen. Nitrogen physisorption measurements were carried out on a Quantachrome Autosorb-1C system. Prior to the measurement, the sample was outgassed at 150—200°C for 10h.

Figure 2. Microscope images of crystalline materials synthesized in DMF at 90°C, [H>ABD]: Zn** = 1 : 1, [H,ABD] =0.01M (a, AZ1), at 85°C, [H,ABD]: Zn** = 2: 5, [H; ABD] = 0.004M (b, AZ2). 3.1.2. MOFs from azobenzene-1,4-dicarboxylic acid and zinc nitrate. The products of the reaction of zinc nitrate and H,ABD in DMF were coded as AZ1 and AZ2. Compound AZI was formed at equivalent HyABD: Zn mole ratio and 0.010M concentration of H2ABD (figure 2(a)). When this concentration was reduced to a very low value of 0.004M and H,ABD : Zn mole ratio was decreased to 2 : 5, the product AZ2 was obtained.

Figure 5. Adsorption-desorption isotherms of nitrogen over synthesized materials after evacuation at 150 °C—200 °C for 10h.

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Crystal structure and characterization of a novel organic crystal: 4-Dimethylaminobenzophenone

by Anandha krishnan

2009, Materials Research Bulletin

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Synthesis and Characterization of Ricinoleamide-Based Polyurethane

by Fahmina Zafar

Journal of The American Oil Chemists Society

Ricinus communis (RC) oil-based materials are currently receiving increasing attention because of economic and environmental concerns. In the present work, RC oil—a natural triol has been utilized for the development of an advanced... more

(aromatic peaks)[r, s, q] while C-NMR (Fig. 4) spectra of pure PUR-1 shows the spectral peaks at 149-152 ppm (>C=O urethane and free —NCO)[q, n], 127-132 ppm (aromatic ring carbons)[r, s, t, u, v, w], 65-69 ppm (-CH,—O and —CH-O-)[a’, p] and 18.5 ppm (CH; attached to aro- matic ring)[x]. These spectral bands are the characteristic bands of TDI based polyurethanes [13, 17]. Closer exami- nation of 'H-NMR spectra of HERA and PUR-1 reveals that pure PUR-1 shows suppressed characteristic peaks of -OH, —CH-OH and CH,—OH compared to HERA (sect. 2.1) at 5.26 ppm [-CH(OH)], 4.85 ppm and (—CH,—OH), 3.59 ppm [CH(OH)], 3.56 and 3.49 ppm (-CH2—OH), while

1,241, 1,164 and 1,097 cm!) of RC oil disappeared with the appearance of new bands at 1,622, 1,078.9, 1,052.9 cm~' for amide carbonyl, primary and secondary alcoholic groups (C—O stretching), respectively, as well as the presence of a broad band at 3,369 cm! instead of 3,422.1 cm! confirming the amidation of RC oil. In PUR spectra, the hydroxyl band of HERA (3,369.3 cm‘) diminished and was centered at 3,290.9 cm~'. The presence of new bands at 3,339 cm! (N-H stretching of urethane linkages), 1,716 cm~' (urethane carbonyl stretching), 1,228 cm”! (NCOO- stretching), 2,273 (free NCO stretch- ing), and 697 (N-H of urethane) [13, 16, 17] as well as bands at 3,069, 1,605.5, and 744.5 for aromatic ring of TDI confirm the urethanation of HERA. 'H-NMR (Fig. 3) spectra of pure PUR-1 shows the characteristic peaks at 4.01-4.43 ppm {m, —CH O C (=O)NH- and —CH, O C (=O)NH-, urethane} [n, p], 2.2 ppm (s, —CH3; of TDDJ[t], and 6.9-7.38 ppm requirement of polyurethanes, i.e., to prepare high or low molecular weight polyurethane. In this case, at each ratio, we have an excess of hydroxyl groups (Table 1), which based on general principles of polyaddition reactions lead to low molecular weight PUR, which may find applications as coating and adhesive materials [14]. It is worth mentioning that the urethanation reaction was carried out by using a “one-shot” technique. In this method, all the ingredients (HERA and TDI) are mixed simulta- neously and the resulting mixture is allowed to polymerize directly. The advantage of using this method is that no intermediate prepolymer preparation is necessary [15]. FTIR spectra (Fig. 2): It is observed in the spectra of HERA that the characteristic bands of ester carbonyl (at 1,745,

The thermal stability of PUR-1 is shown in Fig. 5. It reveals that the degradation of PUR-1 was observed in the range of 150-390 °C. This may be correlated to the decomposition of urethane bonds followed by the volatilization of the decomposition products. It is reported that polyurethanes generally exhibit relatively low thermal stability due to the presence of labile urethane groups. The onset of this bond dissociation occurs around <300 °C through the dissocia- tion of isocyanate and alcohol, the formation of primary amine and olefins, or the formation of secondary amines that result in the loss of CO, from the urethane bond, depending upon the type of isocyanate and polyol employed [18]. The decomposition of the urethane bond in PUR-1 takes place at quite high temperatures due to any allo- phanate and biuret linkages formed during the curing reaction, they reopen quite readily on heating at a relatively high temperature as they are most thermolabile [18]. The degradation in the range of 390-410 °C may be correlated to the decomposition of the amide bond, aromatic ring and aliphatic alkyl chain of the fatty acid followed by the vol- atilization of the decomposition products, respectively. The polyol used in this study is based on HERA. So, the main chain cleavage may result in the formation of 16-undeca- noic acid and heptanal as evident by the thermal degrada- tion of ricinoleic acid [19]. Derivative TGA curves (DTG) of PUR-1 shows almost single step thermal degradation, which matches with TGA of the same. This step incurs about 85 wt% loss correlated to a cross-linked, homogenous

Table 2, Physico-chemical tests of HERA and different compositions of PUR TDI attributed to the inclusion of increased urethane con- tent in the polymer backbone. The solubility test reveals that all PUR compositions (before curing) are completely soluble (100%) in EMK, chloroform, carbon tetrachloride, DMF (Dimethylformam- ide), DMSO (Dimethy] sulfoxide), THF (Tetrahydrofuran) and diethyl ether while they have 20% solubility in methyl alcohol, ethyl alcohol, and insoluble in water. The higher solubility of these resins in polar and non-polar solvents except H,O and alcohol is due to the presence of long fatty acid hydrocarbon chains and polar groups of the resin.

Fig. 6 DSC thermogram of PUR-1 network of cured PUR-1 (Sect. 3.2) that results in their single-step thermal degradation behavior as (not separate but one) single entity favored by chain entanglements. DSC thermograms (Fig.6) show small endotherms at 115-140 °C (centered at 129.5 °C) followed by an exo- therm attributed to the reaction of the remaining unreacted groups in the PUR-1 backbone. TGA/DTG thermograms do not show significant decomposition in the former temper- ature range. After 230 °C, a strong exothermal reaction is observed due to the degradation of the PUR-1 backbone. The temperature range between 300-420 °C shows a maximum weight loss in the TGA/DTG thermogram.

The data for physico-chemical properties of HERA and different compositions of PUR are given in Table 2. It reveals that the percent hydroxy] content of PUR decreases gradually from PUR-0.8 to PUR-1.2, that is, with increases in the amount of TDI. The trend can be attributed to the consumption of hydroxyl groups of HERA during uretha- nation reaction with TDI. The specific gravity and refrac- tive index of PUR increase with the increased content of

Table 1 Chemical composition for the synthesis of PUR The synthesized PUR were dissolved in the solvent (EMK) and filtered, repeatedly for purification. The solvent was removed from the filtrate with the help of rotary vacuum evaporator to obtain pure PUR-0.8, PUR-1 and PUR-1.2, which were taken for characterization. This operation was performed to remove any impurity (gel fraction, if any), which was not obtained here.

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Green synthesis and stabilization of gold nanoparticles in chemically modified chitosan matrices

by Omotayo Arotiba

2011

Chitosan-N-2-methylhydroxypyridine-6-methylcorboxylate (Ch-PDC) and chitosan-N-2methylhydroxypyridine-6-methylhydroxy thiocarbohydrazide (Ch-PDC-Th) were synthesized for the first time using chitosan as precursor. Chitosan, Ch-PDC,... more

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Study on the structure and properties of nanocomposites based on high-density polyethylene/starch blends

by homeira shariatpanahi

Journal of Polymer Research

The effects of nanoclay on the structure and final properties of high density polyethylene (HDPE)/thermoplastic starch (TPS) blends were investigated. Neat blends as well as nanoclay containing samples were prepared by melt blending in an... more

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HfB2/SiC as a protective coating for 2D Cf/SiC composites: Effect of high temperature oxidation on mechanical properties

by G. Marino and

2008, Surface and Coatings Technology

In the field of thermal shielding for aerospace applications C f /SiC composites are raising great interest, provided that they are protected from oxidation by suitable coatings. Conversely, ultra high temperature ceramics, and in... more

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Investigation and analysis of electrical aging of XLPE insulation for medium voltage covered conductors manufactured in Brazil

by Alvaro De Queiroz

2013, IEEE Transactions on Dielectrics and Electrical Insulation

Today the knowledge of the ageing status of an electrical installation and its components is of fundamental interest for correctly inferring on the network economics. In Brazil, covered conductors must withstand an ageing test combining... more

Today the knowledge of the ageing status of an electrical installation and its components is of fundamental interest for correctly inferring on the network economics. In Brazil, covered conductors must withstand an ageing test combining the stresses of heat, voltage to ground and corona. The observed failures indicate the necessity of complementary tests. In this paper Fourier transform infrared spectroscopy (FTIR), electron spin resonance (ESR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), contact angle and scanning electron microscopy (SEM) measurements on artificially aged and unaged cross-linked polyethylene (XLPE) insulation of medium voltage covered conductors is reported. The ESR spectroscopy results show clear evidence of the presence of free radicals in all unaged and aged XLPE insulation cables suggesting inadequate manufacture and processing conditions. The FTIR showed the presence of carbonyl groups in both, unaged and aged XLPE insulation indicating that oxidation process occurred during the manufacturing process. The TGA analysis demonstrates that the decomposition temperature of XLPE insulation did not change significantly except for one of the manufactures. It was observed in DSC analysis that the ageing of the XLPE insulation causes a decrease in intensity and broadening of the peak corresponding to fusion heat, indicating the bond scission in the backbone of the XLPE. The contact angle measurements showed hydrophilic character for all unaged and aged XLPE insulation possibly due to some oxidation during cables manufacturing. After ageing the contact angle is about 23.1° and 52.4°, indicating a significant increasing in the hydrophilicity of the XLPE insulation. The increase in hydrophilicity of aged XLPE insulation appears to be due to the increase in oxygen functional groups and the results are consistent with the FTIR spectroscopy measurements. The defects observed in SEM analysis of unaged XLPE insulation indicate a nonuniform mechanical and thermal stresses during cables manufacturing.

Figure 7. ATR-FTIR absorption spectrum in the range of 4000 to 700 cm' of the XLPE insulation II. Sample of different sites of new (a, b) and aged XLPE (c) cables.

The TGA analysis demonstrates that the decomposition temperature of XLPE insulation (I) did not change significantly for unaged and aged samples. The XLPE cable II unaged and aged samples degrades in a single step beginning at 250 °C and ending around 280 °C with a total mass loss of 90-95%. The TGA analysis indicates that the thermal stability of aged XLPE sample Ill was slightly lower compared to the unaged XLPE sample.

Figure 5. ATR-FTIR absorption spectrum in the range of 4000 to 700 cm’ of the XLPE insulation I. Sample of different sites of new (a, b) and aged XLPE (c) cables. The FTIR spectra of samples (a,b) are superimposed. Figure 6. ATR-FTIR absorption spectrum in the range of 2000 to 700 cm" for XLPE insulation II. Different sites position in a new (a, b) and aged (c) cables.

Figure 2. The test set up for the dielectric compatibility test.

Figure 3. Common damages developed along a covered conductor tested according to Brazilian recommendations [20].

Figure 14. DSC heating thermogrammes of XLPE insulation of I(a), I(b), Il(c), 1V(d) and V(e) manufacturers: unaged (A) and aged (B) cables.

Figure 15. Degree of crystallinity of unaged (black) and aged (gray) commercial XLPE insulation:

Figure 9. ATR-FTIR absorption spectrum in the range of 4000 to 700 cm’! of the XLPE insulation V. Sample of different sites new (a, b) and aged (c) XPLE insulation.

Figure 16. Water drops (10 wL) on the surface of unaged (A) and aged (B) XLPE sample IV. Figure 16 ilustrates the shapes of water drops placed on an unaged and aged XLPE manufacturer IV. The results illustrate a profound increase in the hydrophilicity of the XLPE sample IV surface after ageing process. This effect is due to the oxidation processes during aging that renders a more hydrophilic surface.

Figure 4. Typical corona identification during the ageing test, as observed not on the interfaces but along the cable — Two occurrences one close to the spacer insulator — that developed to a full short circuit and other on the right quite close to edge of the picture.

Figure 11 . Trans-vinylene (-C=C-) index (TVI) for unaged (Black) and aged (Gray) XLPE cables: I(a), II(b), HI(c), IV(d) and V(e). principle be altered in order to minimize them. However, the associated costs may make such alterations no desirable for the Brazilian industry of XLPE cables.

Figure 10. Oxidation index of XLPE insulation calculated in according to Equation (1): I(a), Ib), T(c), TV(d) and V(e). Unaged samples (black) and aged samples (gray).

Due to our investigations and experience in the field of advanced analytical tools such as spectroscopy, thermal analysis and microscopic techniques for the quality control of polymers we carry out these tests on XLPE covered conductors of some Brazilian major manufacturers. At this sense, this paper has focused on the application of Fourier transform infrared (FTIR), electron spin resonance (ESR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) as analytical tools on the monitoring of XLPE insulation cables process. Such characterizations techniques certainly may contribute to a better quality control of XLPE cables of manufacturers in Brazil. Figure 1. XLPE covered conductors analyzed on this paper: I (a), II (b), III (c), IV (d) and V (e). All cables were 25 kV and cross section of 95 mm’.

Figure 18. Scanning electron microscopy of commercial XLPE insulation: Cable I (a) unaged (b) aged.

Figure 21. Scanning electron microscopy of commercial XLPE insulation: Cable IV (a) unaged (b) aged.

Figure 22. Scanning electron microscopy of commercial XLPE insulation: Cable V (a) unaged (b) aged.

Figure 8. ATR-FTIR absorption spectrum in the range of 4000 to 700 cm’ of the XLPE insulation IV. Sample of different sites of new (a, b) and aged XLPE (c) cables. The FTIR spectra of samples (a,b) are superimposed.

Figure 12. ESR spectra of samples of XLPE insulation after aging (a) and free radical concentration (b). Black: unaged XLPE and Gray: aged XLPE insulation, respectively.

Figure 19. Scanning electron microscopy of commercial XLPE insulation: Cable II (a) unaged (b) aged.

Figure 20. Scanning electron microscopy of commercial XLPE insulation: Cable III (a) unaged (b) aged.

SEM photomicrographs of the XLPE insulation of commercial unaged and aged cables are shown in Figures 18-22. Figure 17. Contact angle characteristics for XLPE insulation for unaged (black) and aged (gray) cables samples: I(a), I(b), Il(c), IV(d) and V¢e). Although the OI measurement of aged and unaged samples IV can be considered low, their surface exhibits a high roughness relatively to other XLPE samples. The dramatic

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Preparation, thermal properties and thermal reliability of microencapsulated n-eicosane as novel phase change material for thermal energy storage

by ali karaipekli

2011, Energy Conversion and Management

This paper deals with the preparation, characterization, thermal properties and thermal reliability of novel form-stable composite phase change materials (PCMs) composed of eutectic mixtures of fatty acids and expanded vermiculite for... more

Comparison of thermal properties of the prepared composite PCMs with that of some composite PCMs in literature. Table 4

Fig. 2. The photograph views and SEM images of expanded VMT before and after CA-LA impregnation.

Fig. 5. FTIR spectra of the form-stable composite PCMs after thermal cycling.

Thermal properties of the composite PCMs after 5000 thermal cycling. Table 5

Fig. 3. (a) FTIR spectrum of the form-stable composite PCMs and (b) DSC curves of the form-stable composite PCMs. temperatures of eutectic mixtures in the composites, the phase change temperatures of composites are very close to pure eutectic mixtures. The decrease in phase change temperatures is due to weak attractive interaction between fatty acid molecules and inner surface wall of the porous material. These results are in agreement with that reported by Radhakrishnan and Gubbins [26]; Radhak- rishnan et al. [27]; Zhang et al. [15]; Karaipekli and Sari [11]. In On the other hand, the latent heats of melting (AH,,) were found to be 61.03 kJ/kg, 72.05 kJ/kg and 71.53 kJ/kg for CA-LA/ VMT, CA-PA/VMT, and CA-SA/VMT, respectively as the latent

Fig. 6. The SEM micrographs of the form-stable composite PCMs (a) before thermal cycling and (b) after thermal cycling.

Chemical and physical properties of vermiculite used in the preparation of the composites.

Thermal properties of eutectic mixtures of fatty acids and the form-stable composite PCMs. Table 2

Fig. 1. Melting temperatures of binary mixtures of fatty acids versus weight combination of the components.

Fig. 4. DSC curves of the form-stable composite PCMs after thermal cycling.

Calculated latent heat capacities of the prepared composite PCMs. Table 3

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Characterization and thermal degradation of polypropylene–montmorillonite nanocomposites

by Luciano Falqui

2006, Polymer Degradation and Stability

Polypropylene (PP)emontmorillonite nanocomposites have been prepared using isotactic PP homopolymers with different rheological properties, and a maleic anhydride grafted PP. Morphology and structure of the composites were investigated by... more

Fig. 2. Lorentz corrected plots of RN (+); QN (@); and GN (X).

Fig. 1. WAXD profiles of RN (a); QN (b); GN (c); and Nanofil 848 (d).

SAXS results for PP samples and nanocomposites Table |

Fig. 6. TGA (solid line) and DTG (dashed line) thermograms under air atmo sphere of G (Ml and (J) and GN (@ and ©).

Fig. 3. TEM microphotographs of the GN sample at different magnifications.

Fig. 4. TGA (solid line) and DTG (dashed line) thermograms under air atmo- sphere of R (MM and (J) and RN (@ and ©).

Crystallization and melting behaviour data for PP samples an nanocomposites Table 2

Fig. 5. TGA (solid line) and DTG (dashed line) thermograms under air atmo- sphere of Q (Ml and (J) and QN (@ and ©).

TGA data under nitrogen and air atmosphere for PP samples anc nanocomposites

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Synthesis and characterization of polyaniline–carboxylated PVC composites: Application in development of ammonia sensor

by Rajiv Prakash

2008, Sensors and Actuators B-chemical

Poly(o-methylaniline) (POTO), poly(o-methoxyaniline) (POAS), poly(2,5-dimethylaniline) (PDMA), poly-(2,5-dimethoxyaniline) (PDOA), and nanocomposite based on multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs)... more

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Influence of processing technique on morphology and mechanical properties of PVC nanocomposites

by Nazdaneh Yarahmadi

2010, European Polymer Journal

This study aims to compare the influence of processing techniques and procedures on the morphology and mechanical properties of polyvinyl chloride (PVC) nanocomposites. PVC nanocomposites with 5 phr montmorillonite (MMT) clay were... more

Fig. 4. Representative images from the SEM analysis, (a) GM-MC2 and (b) GM-RM2. The left upper part of (a) shows an agglomerate of OMMT.

Fig. 3. Selected images from the TEM analysis, (a) PGM-MC2, (b) GM-RM2 and (c) GM-RM1. Note the difference in magnification.

* Standard deviation. Results from the tensile and impact strength tests. Table 4

Fig. 5. WAXD analysis of the microcompounded nanocomposites.

Fig. 1. Molecular structure for the organic intercalants, Ry: Ci7H35, Ro: CigH33 47-53%, CigH37 41-51%. The roll mill used was a Schwabenthan Polymix 150 L. The composites were prepared at 185°C for 3 min. The gap between the rolls was kept as narrow as possible.

Results from the WAXD analysis of the clays. Table 3

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Improving easy care properties of cotton fabric via dual effect of ester and ionic crosslinking

by Moustafa Abd El-Aziz

2011, Carbohydrate Polymers

To enhance the easy care finishing properties of cotton fabric along with maintaining its mechanical properties, a new route based on ionic crosslinking was employed. In this research work, pre-cationized cotton fabric was crosslinked... more

The nitrogen content of cationized cotton fabric equal 0.0891%; [ammonium citrate], 6%; [SHP], 6%; AC/SHP molar ratio, 1; wet pick-up, 100%; drying, 100°C/3 min; curin 180°C/90s. Control sample is the cationized sample which have nitrogen content of 0.0891% then crosslinked with 6% ammonium citrate. Effect of concentration of SME on the performance properties of treated cotton fabrics. Table 2

Fig. 2. Effect of ammonium citrate concentration and nitrogen content on wet wrin- kle recovery angle of cotton fabric.

(b): SEM of cotton fabric crosslinked with ammonium citrate.

Fig. 3. Effect of ammonium citrate concentration and nitrogen content on the fabric tensile strength.

citrate using thermo gravimetric analysis and Scan Electron Micro- scope (SEM). Untreated cotton samples were also investigated for comparison.

‘he nitrogen content of cationized cotton fabric equal 0.0891%; [ammonium citrate], 6%; [SHP], 6%; AC/SHP molar ratio, 1; wet pick-up, 100%; drying, 100°C/3 min; curing 80°C/90s. Comparative study on the effect of ammonium citrate vis a vis citric acid. Table 1

Fig.4. Effect of ammonium citrate concentration and nitrogen content on the white- ness indices (WI) of treated cotton fabrics. It was believed that polycarboxylic acids, such as citric acid, can crosslink cellulosic fabrics through an anhydride intermedi- ate mechanism (Fouda & Fahmy, 2011; Schindler & Hauser, 2004). To enhance the ester crosslinking of cotton fabrics along with minimizing the loss in the mechanical properties, cotton fabrics were pre-cationized then crosslinked with ammonium citrate. The effect of cationization level and citric acid concentration as well as

Fig. 1. Effect of ammonium citrate concentration and nitrogen content on dry wrin- kle recovery angle of cotton fabric.

Fig. 5. TGA of untreated (blank), crosslinked and crosslinked pre-cationized cotton fabrics.

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Design, Fabrication and Performance Study of a Biomass Solid Waste Pyrolysis System for Alternative Liquid Fuel Production

by Md. Rafiqul Islam

2004

A laboratory scale fluidized bed pyrolysis system has been designed and fabricated for obtaining liquid fuel from biomass solid wastes. The components of the system are: fluidized bed reactor, gas preheating chamber, reactor feeder,... more

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Protein-based bioplastics: effect of thermo-mechanical processing

by Antonio Guerrero

2007, Rheologica Acta

Bioplastics based on glycerol and different proteins (wheat gluten, albumen, rice and albumen/gluten blends) have been manufactured to determine the effect that processing and further thermal treatments exert on different... more

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Interpenetrating biopolymer network based hydrogels for an effective drug delivery system

by Sharif Ahmad

2012, Carbohydrate Polymers

Discovery of hydrogels has resulted in developing competent controlled-release drug delivery systems. Present study describes the synthesis and characterization of novel pH responsive hydrogels of chitosan, hydroxyl ethyl cellulose (HEC)... more

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Effect of compaction on the kinetics of thermal decomposition of dolomite under non-isothermal condition

by saikat pramanik

2005, Journal of Materials Science

Many workers [1–9] studied the kinetics of dolomite decomposition to study the effects of different parameters like, gas (CO2, N2 etc.) pressures, water vapor, presence of other impurities, particle size and grain size of the dolomite... more

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Preparations and thermal properties of micro- and nano-BN dispersed HDPE composites

by Jaewoo Kim

2010, Thermochimica Acta

The thermal properties of micro-sized boron nitride (BN) and nano-sized BN dispersed high density polyethylene (HDPE) composites were investigated by means of differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA).... more

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Fabrication of carbon nanofiber-driven electrodes from electrospun polyacrylonitrile/polypyrrole bicomponents for high-performance rechargeable lithium-ion batteries

by ozan toprakci

2010, Journal of Power Sources

Carbon nanofibers were prepared through electrospinning a blend solution of polyacrylonitrile and polypyrrole, followed by carbonization at 700 • C. Structural features of electrospun polyacrylonitrile/polypyrrole bicomponent nanofibers... more

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Synthesis and characterization of surfactant stabilized nanocolloidal dispersion of silver chloride in aqueous medium

by Reinaldo Atencio

2014

• Surfactant stabilized AgCl nanoparticles in aqueous medium were synthesized.

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Influence of paraffin wax characteristics on the formulation of wax-based binders and their debinding from green molded parts using two comparative techniques

by fathi S soliman

2009, Journal of Materials Processing Technology

The influence of paraffin wax characteristics on the formulation of wax-based binders has been examined. Four paraffin waxes (PW 1 , PW 2 , PW 3 and PW 4) were physically and molecularly evaluated and four binder systems 1-4 were... more

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Synthesis, characterization and microwave dielectric properties of nanocrystalline CaZrO 3 ceramics

by Sam Solomon

2008, Journal of Alloys and Compounds

Spinel MgGa 2 O 4 ceramic materials were synthesized by solid-state method. MgGa 2 O 4 powders were investigated with X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, Raman spectrum, X-ray photoelectron... more

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Application of calcined waste fish (Labeo rohita) scale as low-cost heterogeneous catalyst for biodiesel synthesis

by Sandeep Bepari

2011, Bioresource Technology

This paper explores the feasibility of converting waste Rohu fish (Labeo rohita) scale into a high-performance, reusable, low-cost heterogeneous catalyst for synthesis of biodiesel from soybean oil. The thermo-gravimetric analysis (TGA)... more

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Synthesis of oleic acid capped copper nano-particles via reduction of copper salt by SFS

by Pawan Khanna

2008, Materials Chemistry and Physics

Synthesis of oleic acid capped copper nano-particles has been carried out by use of sodium formaldehyde sulfoxylate (SFS) in aqueous medium. Nano-copper can be effectively coated with polyvinyl alcohol (PVA). Phase-pure nano-Cu can be... more

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Synthesis of ZnFe2O4 from metallic zinc and iron by wet-milling process

by TEZER FIRAT

2005, Materials Science and Engineering: B

Nanosized zinc ferrite (ZnFe 2 O 4 ) has been prepared directly from metallic iron (Fe) and zinc (Zn) powders by using wet-milling technique. Structural and magnetic properties of the samples were investigated by X-ray diffraction (XRD),... more

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Physico-chemical properties and solubility behaviour of multi-substituted hydroxyapatite powders containing silicon

by Giandomenico Logroscino and

2008, Materials Science and Engineering: C

Hydroxyapatite powders characterized by ionic substitutions both in anionic and cationic sites were successfully prepared by synthesis in aqueous medium. The process parameters were set up to allow the simultaneous substitution of the... more

*Values related to the ACP phase present in this sample. Chemical analysis of the as-obtained powders, showing the comparison between the expected and actual molar ratios of substituting ions

(a) and (b) indicate the first and second branch of the release curves of silicon respectively. Release kinetic data of multi-substituted HA powders in SBF at 37.4 °C

Fig. 4. TG spectra of multi-substituted HA powders: a) HA;; b) Si-HA-1; c) MHA; d) Si-MHA; e) CHA; f) Si-CHA-2.

Weight fraction of the various elements in the substituted HA powders, derived by chemical and thermo-gravimetric analyses

Fig. 3. Comparison between IR spectra of a) HA;; b) Si-HA-1; c) Si-HA-2; d) Si-HA-3. A value of Xc=0.15 (Si-CHA-2) yields a carbonate substitution of 75% of the initial amount, and simultaneously, ~ 50% of the silicon introduced; starting from X.=0.33 instead (Si-CHA-3), the silicon present in the powder decreases up to ~ 10% of the initial amount and, correspondingly, the carbonate substitution is limited to ~35%. Finally, when X¥¢=0.67 (Si- CHA-1), as already described above, the crystalline apatite phase structure collapses: the silicon was completely eliminated during powder washing and no more detectable by ICP analysis. The behaviour exhibited by the Si-CHA samples reveals the competition arising between the silicon and carbonate ion to occupy the phosphate site. The substitution efficiency of silicate Fig. 4 shows some representative thermo-gravimetric (TG) spectra of the investigated HA powders. A similar behaviour: the carbonated HA powd 1 samples show a ers (CHA and Si- CHA2, see Fig. 4e,f) exhibit a higher weight loss in the region 500-1100 °C, where the decomposition of carbonate takes place. All the powders without carbonate ad ded, however, ex- perience a weight loss of ~2.5 wt.% (see Table 2), confirming the spontaneous carbonation revealed by FTIR analysis. TG analysis also confirms the presence of ca powder, detected by XRD analysis: Fig. cite in Si-CHA-1 5 shows the TG spectrum of Si-CHA-1 superposed to a TG spectrum of calctum carbonate: the weight loss due to CaCO3 decomposition abruptly occurs in the range ~650—800°C and is evidenced by the elimination of carbon dioxide. Si-CHA-1 exhibits a similar behaviour in the same temperature range, while the remaining HA powders show a smooth weight decrease in the region 500—1100 °C, which addresses to the loss of the CO3

Fig. 2. IR spectra of multi-substituted HA powders: a) HA;; b) Si-HA-1; c) MHA; d) Si-MHA; e) CHA; f) Si-CHA-2.

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Thermal and mechanical properties of environment-friendly ‘green’ plastics from stearic acid modified-soy protein isolate

by Preeti Lodha

2005, Industrial Crops and Products

Most plastics, at present, are petroleum-based and do not degrade over many decades under normal environmental conditions. As a result, efforts towards developing environment-friendly and biodegradable 'green' plastics for various... more

Most plastics, at present, are petroleum-based and do not degrade over many decades under normal environmental conditions. As a result, efforts towards developing environment-friendly and biodegradable 'green' plastics for various commercial applications have gained significant momentum in recent years. Soy protein isolate (SPI)-based 'green' plastics have been shown to suffer from high moisture sensitivity and low strength. These properties have limited their use in most commercial applications. They are also difficult to process into sheets without any plasticizer. The commonly used plasticizer, glycerol, tends to leach out over time producing time-dependent properties, which is highly undesirable for commercial applications. The objectives of the current research are to reduce the moisture sensitivity and simultaneously improve the tensile properties of SPI by incorporation of stearic acid without affecting its biodegradability. The effect of stearic acid and glycerol on the tensile and thermal properties of SPI has been characterized using various techniques to determine the interaction mechanisms between stearic acid and soy protein. Mechanical properties were characterized using Instron tensile tester. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) techniques have been used to determine the effects of stearic acid and glycerol on the surface chemistry, thermal transitions and thermal degradation of the stearic acid modified SPI plastic (resin). The tensile test results show that Young's modulus increased on increasing the stearic acid content, reaching the maximum value at about 25% (by weight of SPI powder) stearic acid. Further increase in stearic acid content from 25 to 30% led to a reduction in Young's modulus. The moisture content, fracture stress, strain, and energy at break decreased steadily on increasing the stearic acid from 0 to 30% for SPI containing 30% glycerol. At 25% stearic acid content, the modulus and the fracture stress increased significantly, whereas the fracture strain, energy at break and the moisture content decreased on reducing glycerol content. Scanning electron microscopy photomicrographs of fractured surfaces showed a layered structure for stearic acid modified-SPI resin. TGA measurements showed that the thermal degradation of stearic acid modified-SPI resin initiated at higher temperature than the SPI resin. DSC scans indicated that stearic acid modified-SPI resin had a small degree of crystallinity, which was confirmed by X-ray diffraction patterns. Modifying SPI resin with stearic acid has been successful in obtaining better tensile and thermal properties as well as reduced moisture sensitivity without any processing problems.

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Sorption studies of CO2, CH4, N2, CO, O2 and Ar on nanoporous aluminum terephthalate [MIL-53(Al)]

by Rajesh Shantilal Somani

2011, Journal of Porous Materials

Aluminum terephthalate, MIL-53(Al), metalorganic framework synthesized hydrothermally and purified by solvent extraction method was used as an adsorbent for gas adsorption studies. The synthesized MIL-53(Al) was characterized by powder... more

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Evaluation of radish ( Raphanus sativus L.) peroxidase activity after high-pressure treatment with carbon dioxide

by debora oliveira

2006, Journal of Supercritical Fluids

The objective of this work was to assess the influence of compressed CO 2 on the specific activity of peroxidase (POD) from radish (Raphanus sativus L.). The protein concentrate, in phosphate buffer, was obtained through the precipitation... more

Fig. 1. Schematic diagram of apparatus for treatment of protein concentrate from radish in compressed CO3. (1) CO2-reservoir; (2) check valve; (3) pump syringe; (4) sphere valve; (5) pressure indicator; (6) pressure transducer; (7) thermostatic bath with reactor; (8) micrometring valve; (9) temperature indicator.

Effects of process variables on the treatment of POD at high pressure “Significant at 5% of confidence (t-test). Table 3

Fig. 2. Effect of lyophilization procedure and high pressure processing on the activity of POD concentrated extracts from radish. SA refers to the specific activity of the extracts in each point and RA refers to the residual activity in relation to the initial specific activity.

Protein concentration (precipitation with (NH4)2SO4 80% saturation) of the enzymatic extracts from radish

T: experimental temperature; P: experimental pressure; time: time of exposure of the extract at compressed carbon dioxide; rate: rate of decompression of the high-pressure system; pr COd: ratio of carbon dioxide density by the critical carbon dioxide density. The standard error of mean was used to estimate the uncertainty of the mean value of residual activity (bold values) in each experimental run. Experimental conditions and results of submission of the radish enzymatic concentrated extracts in compressed carbon dioxide

Fig. 3. TGA analysis of protein concentrate from radish. Curve 1: treated at high pressure; curve 2: sample lyophilized by 12h; curve 3: sample lyophilized by 24h. new sample of concentrated enzymatic extract was obtained, with an initial POD activity of 128.1 U/mg. This sample was submitted at high pressure (experimental condition 1) resulting in a POD activity of 271.5 U/mg (residual activity of 212%). After processing at high pressure, the sample was lyophilized by 12h, resulting in an activity of 206.0 U/mg (residual activ- ity in relation to the original sample of 161%). Although the lyophylization procedure promotes a decrease in the POD activ- ity, the lyophilized sample by 12h presented a residual activ- ity around 160%, while the protein concentrate lyophilized Another set of experimental runs was performed in order to verify the activity of the protein concentrate after submit- ting at high pressure (experimental condition | of Table 2). A

Scheme 1. Reaction of amine and carbon dioxide.

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Release studies of corrosion inhibitors from cerium titanium oxide nanocontainers

by Ioannis Kartsonakis

2011, Journal of Nanoparticle Research

Cerium titanium oxide nanocontainers were synthesized through a two-step process and then loaded with corrosion inhibitors 2-mercaptobenzothiazole (2-MB) and 8-hydroxyquinoline (8-HQ). First, polystyrene nanospheres (PS) were produced... more

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Effect of Cu–Cr co-substitution on magnetic properties of nanocrystalline magnesium ferrite

by Muhammad Iqbal

2012, Journal of Magnetism and Magnetic Materials

This study deals with the temperature and composition dependence of magnetization and magnetic anisotropy of Cu 2 þ -Cr 3 þ co-substituted magnesium ferrite, Mg 1 À x Cu x Cr x Fe 2 À x O 4 (x ¼0.0-0.5). The synthesized materials are... more

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Study of cyclic hot corrosion of nanostructured Cr/Co��Al coatings on superalloy

by ramesh chandra

2011

a b s t r a c t Nanostructured Cr/Co-Al coatings were deposited on Superni-718 substrate by DC/RF magnetron sputtering in the present work. Hot corrosion studies were conducted on bare substrate and the Cr/Co-Al coated Superni-718 after... more

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Microwave-assisted synthesis and investigation of SnO2 nanoparticles

by Erman baki

2009, Materials Letters

Microwave technique was adopted for preparation of tin dioxide nanoparticles with particles size ranging from 10 to 11 nm within 10 min. The formation of monocrystalline SnO 2 nanoparticles was confirmed by the XRD (X-Ray Diffraction) and... more

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Effect of initial particle size on phase transformation temperature of surfactant capped Fe3O4 nanoparticles

by John Philip

2011, Journal of Applied Physics

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A Novel Biodegradable Green Poly( l Aspartic Acid-Citric Acid) Copolymer for Antimicrobial Applications

by Kokkarachedu Varaprasad

Journal of Polymers and The Environment

Poly (l-aspartic acid-citric acid) green copolymers were developed using thermal polymerization of aspartic acid (ASP) and citric acid (CA) followed by direct bulk melt condensation technique. Antibacterial properties of copolymer of... more

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Carbon nanoparticles/whiskers reinforced composites and their tensile response

by Ashfaq Adnan

2004, Composites Part A: Applied Science and Manufacturing

A promising technique to develop polymer matrix composites by reinforcing carbon nanoparticles/whiskers through an extrusion process is described. Linear low density polyethylene (LLDPE) powder and carbon nanoparticles/whiskers are first... more

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Synthesis and hydrogen storage properties of carbon nanotubes

by Rakhi Raghavan baby

2008, International Journal of Hydrogen Energy

Multi-walled carbon nanotubes (MWNT) have been synthesized by chemical vapor decomposition of acetylene over rare-earth (RE) based AB2AB2 alloy hydride catalysts. The AB2AB2 alloy hydride catalysts have been prepared by hydrogen... more

Fig. 1. Powder X-ray diffractogram of C-15 Laves phase rare-earth basec AB» alloy (DyFe).

Fig. 5. Raman spectrum of purified MWNT obtained from rare-earth based AB» alloy hydride catalyst.

Fig. 6. Hydrogen adsorption isotherms of MWNT obtained from (a) DyNiy alloy hydride catalyst, (b) DyCo alloy hydride catalyst and (c) DyFe> alloy hydride catalyst (closed symbols indicate purified MWNT and open symbols indicate as-grown MWNT).

Fig. 4. TGA curve for purified and as-grown MWNT obtained from rare-earth based AB» alloy hydride catalyst. Fig. 3. (a) SEM image of purified MWNT, (b) TEM image of as-grown MWNT and (c) TEM image of purified MWNT obtained from rare-earth based AB» alloy hydride catalyst.

Fig. 2. Powder X-ray diffractogram of (a) as-grown MWNT and (b) purified MWNT obtained from rare-earth based AB» alloy hydride catalyst.

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Iron oxide in a silica matrix prepared by the sol–gel method

by Maria Zaharescu

2007, Thin Solid Films

Fe x O y -SiO 2 nanocomposites were prepared by sol-gel method by using two SiO 2 sources and Fe(SO 4 ) 2 ·7H 2 O as raw materials. The amorphous gels were thermally treated up to 1000°C. The initial gel and the thermally treated samples... more

Fig. 2. Méssbauer spectra of Fe,O,—SiO, nanocomposites obtained for sample: MTEOS annealed at 1000 °C.

Fig. 1. TG, DTG and DTA curves of Fe,O,—SiO, initial gels prepared with: a— MTEOS (sample MT), b—TEOS (sample TH) (heating rate=10 °C/min).

Fig. 3. Méssbauer spectra of Fe,O,—SiO, nanocomposites obtained for samples TEOS annealed at 1000 °C.

FT-IR vibration bands (cm ') of as prepared and annealed samples at 550° and 1000 °C Table 1

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Theoretical and experimental studies of vibrational spectra and thermodynamical analysis of 3′-bromopropiophenone and 4′-bromo-3-chloropropiophenone

by Sethu Gunasekaran

Journal of Molecular Modeling

Quantum chemical calculations of molecular geometries, vibrational wavenumbers and thermodynamical properties of 3′-bromopropiophenone and 4′-bromo-3-chloropropiophenone were carried out using Hartree-Fock (HF) and density functional... more

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