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121.
Enthalpies of solution have been measured from 5 to 85°C for aqueous tetraethyl- and tetrapropylammonium bromides, and the integral heat method is employed to evaluate
for these electrolytes over a wide temperature range. Data taken from the literature have been used to evaluate
for aqueous Bu4NBr over a similar temperature range. These data, along with similar data for Me4NBr, previously reported, have been used to evaluate absolute ionic heat capacities. While the absolute values agree only qualitatively with two other methods of division, the temperature dependences of the three methods essentially agree up to 65°C. Heat capacities due to structural effects on the solvent, obtained by subtracting the inherent heat capacities of the ions, are extraordinarily positive for all four tetraalkylammonium ions and have negative temperature coefficients, indicating that all four ions, including the tetramethylammonium ion, are structure-making ions. 相似文献
122.
Skuban S. J. Skuban F. Lukić S. R. Cvejić ž 《Journal of Thermal Analysis and Calorimetry》2003,71(2):439-444
The object of the paper is an investigation of the glasses of the (As2S3)x(AsSe0.5Te0.5I)100-x. type for 65≤;x≤;95, using methods of thermomechanical analysis. Values of the thermal coefficients of linear expansion in solid and visco-plastic
phase were determined. it was shown that introducing arsenic-sulfide in glass-matrix AsChI, i.e. (AsSe0.5Te0.5I), leads to an increasing stability of these glasses. The characteristic temperatures of softening Tg and the temperature of the beginning of deformation tw increase by increasing content of As2S3. The analytical forms of dependence of four significant physical values αg, αl, Tg, Tw, as a function of As2S3 content in the structure of glasses were fitted.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
123.
N. Garti A. Aserin I. Tiunova S. Ezrahi 《Journal of Thermal Analysis and Calorimetry》1998,51(1):63-78
Sub-zero temperature DSC measurements were conducted to evaluate the behavior of water in non-ionic microemulsions. Two surfactant
systems were studied. The first, based on ethoxylated fatty alcohol, octaethylene glycol monon-dodecylether [hereafter referred to as C12(EO)8] and also containing water, pentanol and dodecane at a fixed weight ratio of 1:1. The second system, based on oligomeric
ethoxylated siloxanes, water and dodecanol as oil phase. In both systems it was found that in up to 30 wt.% of the total water
content, all water molecules solubilize in the amphiphilic phase and are bound to the ethylene oxide (hereafter referred to
as EO) head-groups. No free water exists in the surfactant aggregates’ core. Up to three molecules of water are bound to each
EO group.
In the first system, the behavior changes significantly upon adding more water. The added pentanol allows further swelling
and the water penetrates into the amphiphile structures and forms a reservoir of free water. Structures are deformed and grow
from elongated channels (up to 15–20 wt.% water), via illdefined (one-dimensional growth) local lamellar structures (up to
ca. 60 wt.% water) to spherical normal, O/W micelles (at ≥85 wt.% water).
In contrast, the oligomeric systems, due to geometrical restrictions of the amphiphiles and the nature of their curvature
that prevents inversion, cannot further solubilize water in the surfactant aggregates’ core, causing phase separation to occur.
Part of the results presented in this paper were included in S. E.’s doctoral thesis in Applied Chemistry at The Hebrew University
of Jerusalem, Israel. 相似文献
124.
还原温度对超细K-Co-Mo催化剂合成低碳醇性能的影响 总被引:2,自引:0,他引:2
用溶胶-凝胶法合成了K-Co-Mo催化剂.样品经不同温度还原后,用于低碳醇的合成.XRD和HRTEM结果表明,样品是超细粒子,粒子尺寸为2~5nm.考察了催化剂的还原温度和反应条件对催化剂性能的影响.实验结果表明,还原温度对催化剂的活性有较大的影响,最佳还原温度为500℃.最佳反应温度范围为310~330℃.升高压力和空速可以提高醇的收率和选择性.在空速14400h-1,压力6.0MPa和温度310℃的条件下,醇的选择性为55.8%,收率为520.0g/(kg·h),MeOH/C2+OH为0.27.催化剂稳定性良好,在200h的寿命实验中,活性基本不变.与文献中催化剂相比,超细K-Co-Mo催化剂对合成醇具有较高的活性和选择性,尤其是对C2+OH的合成明显高于其他合成醇催化剂体系. 相似文献
125.
纳米氧化铜的制备及常温脱硫效能研究 总被引:3,自引:0,他引:3
采用硝酸铜为原料、氢氧化钠溶液为沉淀剂、使用体积比为1∶1的乙醇-水溶液为分散剂的直接沉淀法制备,通过改变工艺条件得到了三种纳米氧化铜产品,平均粒径分别为25.63,10.74和7.57 nm。采用TG-DTA、FIR、XRD和TEM等对纳米氧化铜进行表征。对产品的常温脱硫活性进行了穿透试验,并与已开发的其他常温精脱硫产品进行了比较,结果表明纳米氧化铜应用于H2S脱硫,可在常温条件下具有优异的脱硫活性,对H2S的脱除精度可以达到0.05 mg·m-3以下。经过优选,产品在3 000 h-1空速下穿透硫容达到25.3%,高于同类型的其他脱硫剂产品。 相似文献
126.
Luciani G. Costantini A. Branda F. Scardi P. Lanotte L. 《Journal of Thermal Analysis and Calorimetry》2003,72(1):105-111
A traditional TG apparatus was modified by placing two permanent magnets producing a controlled magnetic field (TG(M): Magneto
Thermogravimetry). This technique proved to be useful to study both structural relaxation and crystallisation of ferromagnetic
metallic glasses. Results obtained for the amorphous alloys Fe40Ni40P14B6 and Fe62.5Co6Ni7.5Zr6Nb2Cu1B15, are reported in this paper. Structural relaxation can be evaluated by measuring changes in Curie temperature induced by
thermal treatments. Crystallisation in TG(M) is detected through a change in the measured apparent mass (difference between
the sample mass and magnetic force driving it upward). These results were confirmed by DSC analysis. Whether the obtained
crystalline phase is ferromagnetic, it can be identified through its Curie temperature, measured by TG(M). In fact the value
of 770°C measured as Curie temperature of crystallised Fe62.5Co6Ni7.5Zr6Nb2Cu1B15led to conclude that the only ferromagnetic crystalline phase is a-Fe. These hypothesis was confirmed by XRD analysis, showing
that the first crystallisation yields to a-Fe nanocrystals.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
127.
采用对掺入La_2O_3的石墨棒原位活化并结合交换电极回放方法制备了产率较高的金属富勒烯,并用甲苯高温热提取的方法有效地提取出La@C_(2n),其中La@C_(74)为可溶性金属富勒烯增加了新成员.同时,首次采用解吸电子轰击质谱对提取物进行了表征,讨论了提取物的ESR谱. 相似文献
128.
129.
130.
La-Fe-M(M=Al, Si)化合物磁热性能研究进展 总被引:5,自引:1,他引:5
介绍了La-Fe-M(M=AI,Si)化合物在磁热性能研究方面的最新进展。具有NaZn13型晶体结构,含高浓度Fe的La-Fe—M(M=AI,Si)化合物为良好的软磁材料;用少量的Co替代化合物中Si,Al元素可以将化合物的居里温度提高至室温;对La(Fe1-yCoy)xSi13-x化合物,适量的Si,Co组合可使化合物在室温产生可与Gd5Si2Ge2比拟的磁热效应;加入适量的间隙原子H,也可使La(FexSi1-x)13在室温的磁热性能远远大于金属Gd;对含Si量低及含Si量高的La(FexSi1-x)13化合物在相转变点附近由温度和磁场诱导相变的本质做了详细阐述。 相似文献