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31.
Wenhui MA Gang XIE Hua WANGFaculty of Materials Metallurgical Engineering Kunming University of Science Technology Kunming China Manuscript received January in revised form May 《材料科学技术学报》2002,18(3):286-287
The thermal expansion behavior of La1-xSrxMn1-yCoyO3-δ (x=0.2-0.4, y=0.1-0.3) perovskites in air has been investigated. The average linear thermal expansion coefficients increased with increasing Sr content up to 40 mole fraction or Co content up to 30 mole fraction. The expansion is generally attributed to an increase in the average cation radius as some of the cations in the perovskite are reduced in valence when oxygen ions are removed from the structure. 相似文献
32.
以溴和苯基取代的对苯二甲酰氯及2,2′-二甲基联苯-4,4′-二甲酰氯作为单体,分别与甲基、叔丁基、苯基取代的对苯二酚经熔融缩聚反应,合成一类具有刚性棒状结构的全芳香液晶聚酯。聚酯的热性质以TGA、DSC,热台偏光显微镜研究。所有的聚酯均为热致性液晶,它们具有相对较低的转变温度,在普通的有机溶剂中具有较好的溶解性质。 相似文献
33.
Fresh niobium hydroxide was first precipitated from NbF5 solution using an aqueous ammonium hydroxide under basic conditions. Then a simple procedure of mixing lithium and niobium hydroxides together and heating at a low temperature (400 °C) produced pure ultrafine single phase LiNbO3 (LN). In the literature, this is the lowest temperature so far reported on the formation of LN. The phase content and lattice parameters are determined by X-ray diffraction (XRD). The average particle size and morphology were studied by transmission electron microscopy (TEM). 相似文献
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35.
Y.X. Li 《Materials Letters》2007,61(22):4366-4369
TiC/Al composite was successfully synthesized utilizing laser ignited self-propagating high-temperature synthesis (SHS) of Al-C-Ti system with the different C/Ti molar ratio. When the molar ratio of C to Ti is below 1:1 in the starting materials, in addition to fine TiC particulates, a large amount of Al3Ti phase was found in the composites; however, when the molar ratio of C to Ti is 1:1 in the starting materials, the Al3Ti phase was almost completely eliminated and the distribution of TiC particulates generally appeared to be more homogeneous throughout the products synthesized. 相似文献
36.
Mushroom-like ZnO microcrystals have been prepared via a solution calcination route, using Zn(NO3)2 as Zn source in the absence of any surfactants, templates or catalysts. This is the first example to prepare mushroom-like crystals as semiconductors, which are expected to show particular physical properties. The ZnO products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) spectrum measurements. A suitable concentration of Zn(NO3)2 solution was important for the growth of the mushroom-like products. The reported synthetic procedure is straightforward and inexpensive, and thus can be readily adopted to produce large quantities of mushroom-like ZnO microcrystals. 相似文献
37.
Two-phase (B2+L12) nickel aluminide intermetallic compounds were synthesized by the pressure-assisted volume combustion synthesis (CS). The production and characterization of the samples containing NiAl+Ni3Al were investigated. Aluminum (99% pure, 15 μm) and carbonyl nickel (99.8 pure, 4-7 μm) powders were used. The production of intermetallic compound was carried out at 1050 °C under 150 MPa uniaxial pressure in open air atmosphere in an electrical resistance furnace for 60 min. The formation temperature of intermetallic compound was determined by differential scanning calorimeter (DSC) analysis, and exothermic temperature of powder mixture was determined as 653 °C. The characterization of samples was confirmed by optical microscope, SEM and XRD analysis. It was observed that the structure of compound has very low porosity and the formation of NiAl was completed successfully. The relative density of test materials measured according to Archimedes’ principle was 98.04%. The microhardness of test materials was about 351 HVN1. 相似文献
38.
Preexposing rats to the context facilitates subsequent contextual fear conditioning. This effect depends on the hippocampus (J. W. Rudy, R. M. Barrientos, & R. C. O'Reilly, 2002). The authors report that inactivating the basolateral region of the amygdala (BLA) by injecting muscimol, a GABAA agonist, before or after preexposure reduced this effect. In contrast, bilateral injections of anisomycin, a protein synthesis inhibitor, into BLA did not impair the consolidation of the context memory. However, when injected after fear conditioning, anisomycin impaired consolidation of both contextual and auditory-cue fear conditioning. Results are consistent with 2 ideas about the amygdala's contribution to memory: (a) It modulates memory formation in other regions of the brain, and (b) it is a storage site for cue-shock associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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As an alternative to previously developed catalytic FeCrAlloy fibre mat burners based on perovskite catalysts, new catalytic burners have been developed based on Pd catalyst on lantana-stabilised Al2O3 and different fibre structures (NIT100A, NIT100S and NIT200S by ACOTECH NV). All development steps are considered, shifting from catalyst preparation (based on combustion synthesis of γ-Al2O3) to the optimisation of lantana and Pd loadings, from the definitions of the best catalyst-deposition conditions (washcoating) to the catalytic burners performances, determined in an ad hoc developed combustion chamber. The results show almost half pollutants emissions and better performance compared to various non-catalytic counterparts, especially as far as CO and NOx emissions are concerned. Some flame instability problems were though registered, especially for one of the catalytic burner mattresses employed, at low specific power inputs and excesses of air (<375 kW/m2 and <12%, respectively). Further, PdO/Pd transition is shown to influence the dynamic behaviour of the catalytic burners. 相似文献