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Abstract  

The production of bulk high T c superconducting phase (2223) by EDTA-gel (ethylenediaminetetraacetic acid) techniques has been investigated. It is shown that close control of pH is necessary for the production of a well-complexed precursor which allows subsequent decomposition in two stages at 300 and 800�C. The problem of carbonate formation was investigated experimentally and solved. Precursors are characterised by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) and the sintering behaviour was monitored by dilatometry. At least three different phases Bi2Sr2Cax−1CuxO8+y (BSCCO); where x=1, 2, 3 were identified within superconducting pellets using XRD, named as Bi2Sr2CuO7 (2201), Bi2Sr2CaCu2O9 (2212) and Bi2Sr2Ca3O10 (2223). The superconducting properties of the sintered samples were studied by vibrating sample magnetometer (VSM). Transition to a superconducting state around 80 K appeared in samples (sintered at 845�C) containing the Bi2Sr2Ca1Cu2Oy (2212) phase. Liquid phase sintering of the samples aided the formation of Bi2Sr2Ca2Cu3Ox (2223) phase at high temperature (860�C), which showed a superconducting transition temperature of 108 K.

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Abstract  

Sintered hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) are the two most common bio-ceramics for bone substitute. Although their composition are analogous to the constituent of human hard tissue, but some disadvantages are always exist till now, such as they need a high temperature sintering process, and this would lose the functional groups for bioactivity and closed the micro- pores without any interconnections, that hamper the body fluid transportation and angiogenesis during regeneration. Furthermore, the sintered ceramics with block and fixed size is difficult to fit non-regular defect area. In this study, the mixtures of Ca(H2PO4)2H2O and CaCO3 were adjusted firstly, then distilled water were introduced in wet chemical method, and a biphasic ceramic of HAp/β-TCP will be obtained after drying and sintering, then the result product that prepared by wet chemical method will be the sample in this investigation. The physical properties of result powders were characterized by DTA/TG, XRD and SEM, respectively, the particle size of two bio-ceramics that after heat treatment were found under 5 μm in SEM examination. Powder type calcium phosphate ceramics with the Ca/P molar ratio of 1.67 can be as bone cement by mixing with polymeric binder, the fine particle product of the setting cement will possess micro-pores and macro-pores that after suitable heat treatment process, and this is good for fluid transportation and tissue regeneration.

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Abstract  

An apparatus was designed and constructed for investigation of the tritium release rate from neutron-irradiated materials for fusion reactors. The design principles, as well as safe handling of tritium and complete trapping of tritium components released, are described and the tritium release rates obtained with this apparatus are discussed for sintered lithium fluoride pellets.

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Abstract  

X-ray fluorescence energy dispersive analysis is applied for the determination of Ta and W in sintering compounds. The combination of selective excitation and very simple mathematical procedures permits the determination of the concentrations of the two adjacent elements /Ta and W/ even when the sample contains only few per cent of Ta. Other possible applications are shown.

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Abstract  

The process of incorporation of radioactive wastes into a suitable matrix to form a stable product for long term disposal has been studied. The changes, occuring during the thermal treatment with glassy materials, i.e. drying, transformation processes, sintering, melting, etc. have been followed using emanation (radon) thermal analysis. This method was found useful in solving the problems of process development.

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Abstract  

Thermochemical properties of two kinds of composite material of synthetic zeolite ZSM5 in potassium form (K-ZSM5) with AgI have been studied. The composites have been prepared by treating the silver form of synthetic zeolite ZSM5 (Ag-ZSM5) with potassium iodide solution under different experimental conditions. One of the composites was additionally sintered at temperature 500C for 20 h. Both composites have been characterized by TG, DTG, DTA, EDS analysis, X-ray powder diffractometry and X-ray photoelectron spectroscopy. The methods of thermal analysis as well as X-ray powder diffractometry and XPS confirmed the differences between the two composites caused by sintering during the synthesis. The content of AgI in the surface layer was different. No changes of the zeolitic mineral dimensions are observed.

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Summary Superconducting phases in the BSCCO and Pb-BSCCO systems have been produced by ethylenediaminetetraacetic acid (EDTA) gel derived route using nitrates of metal salts. Thermal decomposition and formation of various phases of gel and calcined powder of both BSCCO and Pb-BSCCO have been investigated by thermoanalytical and XRD techniques. It has been observed that Pb-containing system shows high volume of high T c phase as compared to Pb-free system at the same sintering temperature. Thermal behavior (TG) indicates that sample doped with Pb decomposed in a series of steps when compared with Pb-free sample, which decomposed in a single step. The effect of Pb is shown to lower the sintering temperature (845°C) of formation of high T c phase (2223). However, in the Pb-free sample the high T c phase produced at higher temperature (860°C).

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Abstract  

The electrical properties of ZnO varistors are induced by a sintering step. The phenomena occurring during this thermal treatment have been studied through model systems whose nature and composition are well defined. The pure BiSbO4 and Bi3 Zn2 Sb3 O14 phases have been synthetised by Direct Oxidation of a Precursory Alloy (DOPA) and characterized using XRD method. Each one of these phases can react with zinc monoxide through an invariant isobaric reaction in the ZnO–Bi2 O3 –Sb2 O3 system: – at 998C 17/3<ZnO>+2/3<Bi3 Zn2 Sb3 O14 > arrow <Zn7 Sb2 O12 > + ((Bi2 O3 )) – at 1058C 7<ZnO>+2<BiSbO4 > arrow <Zn7 Sb2 O12 >+((Bi2 O3 )) These thermodynamic considerations can explain the thermal domain of the sintering reaction described in the literature.

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Aluminate sodalite ceramics, (Sr8Al12O24)(CrO4)2) — SACR, have been prepared from solution spray-dried precursors. The spray drying of a mixed aqueous nitrate solution gave an anhydrous powder which was thermally decomposed in air at 1350 °C to give a crystalline SACR powder with a median volume diameter of 4–6 μm. The SACR powder was dry pressed and sintered to >90% density. The yellow SACR powder showed two phase transitions between 10 and 45 °C with a 25 ° intermediate phase region indicative of a low defect concentration in the crystalline structure. A colour change observed in the sintered ceramic (changing to a mixed green/yellow) and a narrowing of the phase transition region (15–40 °C) are discussed. Dielectric measurements were consistent with the presence of two extrinsic ferroelectric transitions at 17 and 35 °C.

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Abstract  

The radiation heating caused by the10B(n, )7Li-reaction in boron carbide (B4 C) neutron filters used for epithermal neutron activation analysis has been examined by measuring rates of temperature rise and steady-state temperatures of sintered and powdered B4C filters placed in dry air and reactor pool-water during irradiation, respectively. Maximum equilibrium temperatures of 195°C for air-cooled sintered, and 50°C for water-cooled powdered B4C were observed, confirming the necessity for efficient cooling of the filter during irradiation. It is noted that the accumulation of the10B(n, )7Li-reaction products in B4C and other boron compounds may severely limit the reuse of the filters in subsequent irradiations.

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