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51.
52.
含稀土硅化铁热电材料的电学性能初探 总被引:1,自引:0,他引:1
采用悬浮真空熔炼和800℃,168h真空退火方法制备了含稀土Sm的FeSi2基金属硅化物,并对其晶体结构、See-beck系数、电阻率进行了初步研究。实验发现,名义组成为Fe0.6Sm0.4Si2的试样的热电功率因子从室温时的0.26×10-4W·m-1K-2随温度上升到500℃时的1.6×10-4W·m-1K-2,比不含Sm或含Sm量很少的对比试样高一个数量级左右。其原因被认为是由于Sm的外层4f电子的贡献。 相似文献
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54.
Phaseformation processes are considered at the level of a mesocell of a mixture with the use of the state diagram for a binary system. Consecutive schemes of metallochemical reactions of formation and decomposition of intermetallide compounds in a mixture of nickel and aluminum powders are suggested. The problem of diffusion annealing of this mixture is numerically solved for two different conditions: at a constant temperature and at a temperature slowly increasing by a linear law. 相似文献
55.
Amy?Richards Chakra?WijesunderaEmail author Phil?Salisbury 《Journal of the American Oil Chemists' Society》2005,82(12):869-874
Lipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore
an important criterion by which oils are judged for usefulness in various food applications. In this study a method based
on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the
use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison
with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected
to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC-MS.
Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile
lipid oxidation products hexanal and trans,trans-2,4-heptadienal. The PV calculated using this formula correlated (R
2=0.73) with those measured by conventional methods.
Presented in part at the 96th Annual Meeting of the AOCS, 1–4 May 2005, Salt Lake City, UT. 相似文献
56.
D,L-丙交酯在有机锡化合物四苯基锡(Ph4Sn)、三正丁基醋酸锡(Bu3SnOAc)、辛酸亚锡(SnOct2)等催化剂引发下开环聚合,得到高分子量的聚D,L-乳酸,讨论了聚合单体D,L-丙交酯纯度、聚合温度、聚合时间、聚合体系真空度以及引发剂有机锡催化剂与聚合单体D,L-丙交酯的比例对聚D,L-乳酸合成的影响,通过红外光谱和核磁共振光谱对聚D,L-乳酸的结构进行了表征。实验结果表明,D,L-丙交酯开环聚合反应的较佳工艺路线是:D,L-丙交酯重结晶5次,聚合温度140℃,聚合时间24 h,聚合体系真空度13.3~133.3 Pa,引发剂有机锡催化剂与单体D,L-丙交酯比例0.2‰~0.5‰,此时聚D,L-乳酸的粘均分子量最高,分别达到32.46×104,33.43×104和41.36×104。 相似文献
57.
将K2CO3和TiO2通过高温固相反应制得K2Ti4O9,经酸化处理后得到H2Ti4O9,用正十二胺乙醇溶液与之反应,获得正十二胺柱撑的层状化合物,采用X射线衍射(XRD)、红外光谱(IR)等方法对所得材料进行结构表征,并初步研究了有机胺支撑前后钛酸材料的吸附性能,实验结果表明:在钛酸钾材料的层间引入正十二胺有机基团后,层间距加大,吸附能力大大提高。 相似文献
58.
Dickschat JS Bode HB Wenzel SC Müller R Schulz S 《Chembiochem : a European journal of chemical biology》2005,6(11):2023-2033
The volatiles released by agar plate cultures of two strains of the myxobacterium Stigmatella aurantiaca (strains Sg a15 and DW4/3-1) were collected in a closed-loop stripping apparatus (CLSA) and analyzed by GC-MS. Large numbers of substances from different compound classes (ketones, esters, lactones, terpenes, and sulfur and nitrogen compounds) were identified; several of them are reported from natural sources for the first time. The volatiles 2-methyltridecan-4-one (17), its isomer 3-methyltridecan-4-one (20), and the higher homologue 2-methyltetradecan-4-one (18) were identified in the extracts of both strains and were synthesized. In addition, strain Sg a15 produced 2,12-dimethyltridecan-4-one (19), 2-methyltridec-2-en-4-one (23), and a series of phenyl ketones, among them 1-phenyldecan-1-one (14) and 9-methyl-1-phenyldecan-1-one (16), whereas strain DW4/3-1 emitted traces of 10-methylundecan-2-one (21). The biosynthesis of 14 and 16 was examined in feeding experiments with deuterated precursors carried out on agar plate cultures. The leucine-derived starter unit isovalerate was shown to be incorporated into 16, as was phenylalanine-derived benzoic acid into both 14 and 16. The results point to formation both of the phenyl ketones and of the structurally related aliphatic ketones through an unusual head-to-head coupling between a starter unit such as benzoyl-CoA and a fatty acyl-CoA, followed by decarboxylation. 相似文献
59.
As part of a study of the chemistry of the steam-stimulated recovery of heavy oils, the hydrolysis and subsequent desulphurization of tetrahydrothiophene and thiophene by aqueous solutions of vanadyl and nickel salts was investigated. Vanadyl sulphate and vanadyl chloride were shown to behave very differently, emphasizing that these salts have different molecular species in aqueous solutions. 相似文献
60.