Papers by Keyword: Thermal Stability

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Authors: Yu Wang, Hong Li, Ying Guo Yang, Geng Wu Ji, Kong Chao Shen, Hao Liang Sun, Jiong Li, Zheng Jiang, Fei Song
Abstract: The beta-phase of Zn4Sb3 has been regarded as a very promising thermoelectric material since middle nineties, owing to its unique merit: intermediate temperature region (200-400 °C), made of cheap, non-toxic and abundant elements and high thermoelectric property. However, the thermal stability of Zn4Sb3 seems to be an inherent obstacle for the practical application during the working temperatures. Herein, magnesium doped Zn-Sb semiconductor (Mg0.04Zn3.96Sb3) was investigated thoroughly in-situ during thermal annealing up to 600 K, whilst both microstructure and electronic structures were recorded via the combination of synchrotron-based two dimensional X-ray diffraction techniques and the X-ray photoemission spectroscopy. While the time-resolved grazing incidence XRD reveals the preserved crystal structures during thermal annealing to 600 K, XPS measurement demonstrate the robustness of electronic structures. On basis of these findings, it was concluded in the end that the doping of magnesium significantly improves the thermal stability of zinc-antimonite compounds and introduces minor influence on the electronic structure of Zn-Sb alloy. Our study may propose an effective approach towards the wild application of Zn4Sb3 related thermoelectric materials.
Authors: Radomír Kužel, Zdeněk Matěj, Miloš Janeček
Abstract: X-ray diffraction (XRD) studies of ECAP (equal-channel angular pressing) materials were performed after annealing and by in-situ measurements in XRD high-temperature chamber for samples prepared by different number of passes and number of revolutions, respectively. Main attention was given to Cu and Cu-Zr samples. Significant dependence on number of passes was found for ECAP samples. In-situ measurements were focused not only on temperature dependence but also on time evolution of the diffraction line profiles. Evaluation in terms of dislocation densities, correlation and crystallite size and its distribution was performed by our own software MSTRUCT developed for total powder diffraction pattern fitting. Abnormal growth of some grains with annealing is well-known for copper and leads to the creation of bimodal microstructure. Therefore a special care must be given to the evaluation and a model of two Cu components (larger and smaller crystallites) was fitted to the data if an indication of some crystallite growth appears either in the XRD line profile shape or in two-dimensional diffraction patterns.
Authors: Hai Feng Guo, Feng Ye, Xiu Lan He, Hai Jiao Zhang
Abstract: Alkyl phosphates, the products from the reaction between phosphorous pentoxide and various alcohols, were used as the in-situ templates of nanostructure as well as phosphorus source of HAP. The obtained precursor samples had ordered nanostructures:lamellar structure for dodecyl and n-octyl phospahes templated samples, cubic for n-pentyl and hexagonal for ethyl phosphates templated samples. The calcined ethyl phosphate templated sample was pure HAP with a specific surface area of 42m2/g, and sustained with an orderly hexagonal nanostructure at 400°C. But the calcination at 400°C caused the collapse of other alkyl phosphates templated nanostructures.
Authors: Mohammad Mizanur Rahman Khan, Wan Ahmad Kamil Mahmood, Yee Keat Wee, Hanis binti Azizan
Abstract: The comparison of the influence of CaO and CuO alone and combined CaO/CuO on the diameter, surface morphology and thermal stability of polyaniline (PANI) nanofibers is reported. The possible incorporation of CaO and CuO in PANI was revealed by both fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV–vis). It was found that the diameter of PANI nanofibers varied for the addition of CaO and CuO alone compared to their combined use. Field emission scanning electron microscopy (FESEM) showed that the addition of CaO, CuO and CaO/CuO consistently produce composite material in nanofibers structures. This nanofibers shows regular and uniform surface morphology and without secondary growth and agglomeration of the primary nanofibers. Thermogravimetric analysis (TGA) data showed better thermal stability for all composite materials as compared to PANI nanofibers.
Authors: Asghari Jila, Khoje Golshad
Abstract: Composite of Cadmium sulphide (CdS) nanoparticle on the surface of polystyrene- co- maleic anidride (St-co-MMA) were prepared via surfactant free emulsion polymerization. Methylmetacrylate (MMA) was used as auxiliary monomer which co-polymerized with styren (St) and provided the side for coordinating with Cd2+. By the coordination of Cd2+ ions to methyl metacrylate, decoration of the Cd2+ ions on the surface of copolymer were prepared successfully. With the release of S2- ions from the thioacetamide (TAA), CdS was formed on the surface of nanorods copolymer in facile method. Fourier transform infrared spectroscopy (FT-IR) of nanocomposite was confirmed the polymerization of monomers. Structure and morphology of CdS nanoparticles have been characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD measurements suggest the cubic structure for CdS and the particles size was estimated to about 3.35 nm by applying Scherrer’s equation. The SEM analysis confirmed the nanorode structure of CdS/ (St-co-MMA) composite. The photoluminescence (PL) and UV–Vis spectroscopy revealed the quantum confinement effect in the CdS/ (St-co-MMA) nanocomposite. Using effective mass approximation (EMA) method particle sizes were calculated from the shift in optical band gap. The thermal properties of the CdS/ (MMA-co-St) were explored by thermal gravimetric analysis (TGA). The improved thermal stability of nanocomposite was attributed to the interaction of CdS nanoparticles with polymer. The CdS/ (MMA-co-St) nanocomposite exhibited a glass transition temperature around 250C.
Authors: Dao Rong Lu, Zhi Xian Li, Ying Chun Xie
Abstract: A new method was used to synthesize the cathode material Li1+xV3O8, and it simplified the process of preparing and shortened the time of reaction in comparison with previous Sol-gel method with the citric acid. The characteristics of Li1+xV3O8 were investigated by X-ray diffraction, thermogravimetry and differential thermal analysis, and transmission electron microscopy, which showed the material Li1+xV3O8 with a good thermal stability had been obtained via the new method. The electrochemical performance of Li1+xV3O8 was measured, which indicated that the material obtained had a remarkable discharge capacity of 380mAh/g and a good cycle performance.
Authors: Qiang Xiao, Wen Fa Xiao, Xin Xin Liu, Li Tao Dong
Abstract: A novel cement fluid loss additive P1301, which can resist high temperature and high salt content, was synthesized using the monomers of 2-acrylamido-2-methyl-propane sulphonic acid (AMPS), acrylic acid (AA), acrylamide (AM) and n-vinyl-2-pyrrolidone (NVP) by the method of aqueous solution polymerization. Through the orthogonal experiment find the optimum process: the ratio of monomers AMPS: AA: AM: NVP at 4:3:2:1, reaction PH at 11, reaction temperature at 60°C and reaction time about 4 hours. The IR spectrum show that the polymer with the structure of all the monomers. The aging test, thermal performance test and the fluid loss performance testing show that the forpolymers P1301 has an excellent thermal stability that can be used in 240°Cand strong salt tolerance. The fluid loss additive P1301 has an excellent tolerance to salt and high temperature.
Authors: Qiang Xiao, Wen Fa Xiao, Xin Xin Liu
Abstract: A novel cement fluid loss additive P1402, which synthesized using the monomers of 2-acrylamido-2-methyl-propane sulphonic acid (AMPS), acrylic acid (AA), N,N dimethyl acrylamide (DMAM) and N-Vinyl-2-pyrrolidone (NVP) by the method of aqueous solution polymerization. The ratio of monomers AMPS:AA:DMAM:NVP at 2:1.5:1:1, reaction PH at 10.8, reaction temperature at 65°Cand reaction time about 5 hours. The IR spectrum of P1402 show that the polymer with the structure of all the monomers .The fluid loss performance testing show that the forpolymers P1402 has an excellent thermal stability. The fluid loss additive P1402 has an excellent tolerance to salt and high temperature.
Authors: Chong Mu Lee, Seung Mo Kang, Keun Bin Yim, Sook Joo Kim, Hyoun Woo Kim
Abstract: Epoxy molding compounds (EMC) with higher thermal stabilities are urgently needed as the light emitting diode (LED) becomes brighter and the wavelength of the its light becomes shorter. This paper proposes a simple reliable method of evaluating the thermal stabilities of commercial EMCs. The transmittances of most commercial EMC samples for high power short wavelength LED packages were decreased by heat treatment at 150oC for 200hr. Also the thermal stabilities of the samples were confirmed by measuring the weight losses through TGA. The experimental results suggest that employing a good heatsink is indispensable in highly bright short wavelength LED packages.
Authors: Bo Wang, Bin Lin, Kun Zhao
Abstract: A numerical analysis method of the thermal stability of the resin concrete is proposed in this paper. A 3D aggregate accumulation model based on the predecessors theory is established and a 2D cross section is directly captured from it. In order to simplify the analysis, a kind of conversion program is developed. The thermal expansion coefficient of established model is close to previous research results. It confirms the analysis method is correct. By the results, a reliable formula is found to calculate the thermal expansion coefficient and a method to reduce the thermal expansion coefficient of resin concrete is proposed.
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