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101.
阳离子替换磷灰石固溶体的比晶体化学 总被引:3,自引:0,他引:3
利用XTD,IR对不同阳离子替换的磷灰石(Ap)固溶体进行了比较晶体化学研究,结果表明:端元二价阳离子对Ap晶格常数(a0,c0)影响是线性的,符合Vegard规律,有较好的x-V习性,可作为阳离子半径测定的"结构尺";对于Cl-PO4体系的Ap,端元离子半径须在0.095~0.134nm之间才能形成空间群为P63/m的Ap结构;异价固溶体可以研究Ca(1)、Ca(2)位置的结晶化学差异,Ca(2)位在晶核形成期生成且决定了晶胞的框架,而Ca(1)位主要影响Co;随阳离子半径增加,[PO4]四面体的ν4,ν3,ν1红外振动峰向低频方向红移;Ap结构中发现"铅异常",形成原因是铅在Ca(2)位的较大电负性。 相似文献
102.
The reversible reaction NH3 + H ⇌ H2 + NH2, which plays an important role in NH3 fuel combustion, is studied with a theoretical approach that combines the high-accuracy extrapolated ab initio thermochemistry (HEAT) protocol with semiclassical transition state theory (SCTST). The calculated forward reaction is endothermic by 11.8 ± 1 kJ/mol, in nearly perfect agreement with the active thermochemical tables (ATcT) value of 11.5 ± 0.2 kJ/mol. Using this improved thermochemistry yields better rate constants, especially at low temperatures. Experimental rate constants available from 400 to 2000 K for the forward and reverse reaction pathways can be reproduced (within 20%) by the calculations from first principles. 相似文献
103.
Divergence-free wavelet solution to the Stokes problem 总被引:2,自引:0,他引:2
Yingchun Jiang 《分析论及其应用》2007,23(1):83-91
In this paper, we use divergence-free wavelets to give an adaptive solution to the velocity field of the Stokes problem. We first use divergence-free wavelets to discretize the divergence-free weak formulation of the Stokes problem and obtain a discrete positive definite linear system of equations whose coefficient matrix is quasi-sparse; Secondly, an adaptive scheme is used to solve the discrete linear system of equations and the error estimation and complexity analysis are given. 相似文献
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根据文献报道的实验数据分析了同构同阴离子稀土化合物的阳离子质量(m)和摩尔体积(V)分别对其晶格热容(C)的贡献,根据得到的数据提出了体积-质量近似公式:Cx=(1-f).C1+f.C2+Cm.(mx-m'x).以估算稀土化合物的晶格热容.式中C1和C2分别为两个参考物质的晶格热容;f=(Vx-V1)(V2-V1);Cm为稀土化合物的阳离子质量变化lg时其摩尔(晶格)热容的变化,它与温度的关系被导出为:Cm=0.084e[-0.0074t]-0.27e[-0.065T];mx和m'x分别为待估算热容物质的阳离子质量和"假想"阳离子质量,m'x=(1-f).m1+f.m2。 相似文献
106.
本文试用前文建立的基团电负性, 通过研究ΔΔFH°(RX/CH3X)与基团电负性xG的定量关系, 从而建立一个简单方法用以计算几乎所有烷基衍生物RX(X=F, OH, Cl, NH2,Br, SH, I, OH3)的标准生成热。 相似文献
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108.
双烃链正,负离子表面活性剂复合物水溶液的表面化学性质研究 总被引:4,自引:0,他引:4
本文研究了具有双烃链的正、负离子表面活性剂混合水溶液的表面和液相性质、。负离子表面活性剂是琥珀酸二己酯磺酸钠[简写为(C6)2SNa],正离子表面活性剂是氯化二正辛基羟乙基甲基铵[(C8)2NCl]和氯化辛基羟乙基二甲基铵[C8NCl]。为了增加复合物的溶解度,在铵基上引入了羟乙基。测定了表面张力-浓度关系,用GIBBS公式计算表面吸附量和吸附分子面积。结果表明,由于正、负表面活性离子之间的强烈相互作用,所研究的两种混合物体系的表面活性远高于单独的表面活性剂。在等摩尔混合和离子强度0.1mol/kg情况下,(C6)2SNa-(C8)2NCl体系的吸附层组成是对称的(摩尔比为1:1),且在临界胶团浓度(cmc)以上析出新相,表明此cmc实质上是复合物的溶解度;而(C6)2SNa-C8NCl体系的吸附层为不对称组成(摩尔比非1:1),在cmc以上可能形成相当大的胶团,两种体系混合溶液的起泡性有极大差异。 相似文献
109.
Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titration were used to characterize the chemical properties of the resins. The adsorption experiments were carried out using the bottle-point technique, and the effects of the surface chemistry on the adsorption were discussed. The adsorption data fit well with the Freundlich model, indicating the heterogeneity of the resins surface. It could be seen from the experimental results that the adsorption capacity increased with the increase in the total surface concentration of oxygen-containing groups. The pH dependence and the effects of ionic strength were also discussed. The kinetic adsorption data fit well with the pseudo-second order model, and the results showed that the surface oxygen-containing groups have little effect on the adsorption rate. 相似文献
110.