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911.
Study of various binding materials like potassium bromide, poly(vinyl alcohol), starch, silver and aluminum has been carried out using laser-induced breakdown spectroscopy (LIBS). The role of matrix effects using these five binders on LIBS signal intensity was investigated for better performance of LIBS technique as a quantitative analytical tool. For comparative study of different binders, the signal intensity of different Mg lines at 518.3, 517.2, 383.8 and 279.5 nm wavelengths were recorded for pellets prepared with known concentrations of Mg in these binders. The influence of laser energy on ablated mass under different binding materials and its correlation with LIBS signal intensity has been explored. Optical scanning microscopy images of the ablated crater were studied to understand the laser ablation process. The study revealed that the binding material plays an important role in the generation of LIBS signal. The relative signal intensity measured for a standard Mg line (at 518.3 nm) were 735, 538, 387, 227 and 130 for potassium bromide, starch, poly(vinyl alcohol), silver and aluminum as binders, respectively. This indicates clearly that potassium bromide is better as a binder for LIBS studies of powder samples. 相似文献
912.
913.
以糠酸、甲醇、氢气为原料,采用连续流动固定床微反应器,Pd-Ni/γ-Al2O3为催化剂,使糠酸一步加氢甲酯化生成α-四氢糠酸甲酯.研究了反应的温度,压力,气、液体流速,进料流量等因素对催化反应的影响.结果表明:在1.5MPa,250℃,氢气空速3300 h-1,液体空速3.0 h-1(氢油比为50)时,糠酸转化率为96.6%,四氢糠酸甲酯的选择性97.2.0%,产率94.0%.催化剂稳定性较好,连续运转280小时后未见活性下降.该反应体系活性高,选择性好,反应压力低,催化剂性能稳定,操作简单,产物易分离. 相似文献
914.
Organic phase conversion of bulk (wurtzite) ZnO to nanophase (wurtzite and zinc blende) ZnO 总被引:1,自引:0,他引:1
Lauren P. Snedeker Aditi S. Risbud Ombretta Masala Jin Ping Zhang Ram Seshadri 《Solid State Sciences》2005,7(12):1500
We describe the all-organic phase conversion of bulk commercial ZnO in the wurtzite modification to sub-30 nm ZnO that we find to be partially in the zinc blende [, a=4.568(3) Å] modification. The conversion involves refluxing ZnO in 2,4-pentanedione (acetylacetone) at 413 K to form the zinc 2,4-pentanedionate, which is decomposed by heating at 573 K in an appropriate high-temperature solvent such as dibenzylether to form nanophase ZnO. This nanophase, partially zinc blende ZnO can also be obtained in a single step by heating commercial zinc 2,4-pentanedionate in refluxing dibenzylether. Thermodiffractometry suggests that the conversion of zinc blende ZnO to wurtzite ZnO commences near 650 K. 相似文献
915.
从通识教育的时代要求和化学的学科地位出发,首先讨论了在化学类通识课程建设中引入跨学科视角的意义和可操作性。随后以通识课"化学与社会"的建设为例,系统地分享了引入跨学科视角后的课程设计理念和内容框架建设,通过课堂实施方案的论述和特色实例的分享总结了课程实施经验,并以学生访谈资料分析讨论了课程取得的效果和需要进一步完善的方向。以期为跨学科理念在化学教育教学实践中的转化和落地开拓思路、提供经验。 相似文献
916.
摘要运用多参考微扰理论(Multireference MΦller-Plesset theory)计算了SSCH3垂直激发能及其S-C与S-S两种断键方式的绝热(Adiabatic)与非绝热(Diabatic)的基态和激发态势能曲线, 研究了在193nm激光作用下SSCH3的光解离过程, 理论计算值与实验值相符. 相似文献
917.
Monoanionic tridentate ligands LHa and LHb containing ONSe and ONTe donor sequences and their Pd2+ and Pt2+ derivatives were synthesized and characterized. The formation of a five- and a six-membered ring around the central metal atom and associative phenomena in solutions provide extra stability to the metal complexes. 相似文献
918.
Barkia H. Belkbir L. Jayaweera S. A. A. 《Journal of Thermal Analysis and Calorimetry》2003,71(1):97-106
Organic matter evolution and kinetics of combustion of Tarfaya and Timahdit oil shales have been examined by thermogravimetry (TG) and by differential thermal analysis (DTA). An agreement is observed between both techniques where it was found that combustion of organic matter occurs in two steps. Kissinger's method applied on experimental results gives an activation energy of the same magnitude for the first step of both oil shales (103 kJ mol–1) whereas the second is 148 kJ mol–1 for Timahdit and 118 kJ mol–1 for Tarfaya.The changes in specific surface area during thermal combustion of Timahdit and Tarfaya oil shales have been studied by thermogravimetric gas sorption balance and correlated with experimental results obtained on TG/DTA in air. For Timahdit oil shale oxidation products, specific surface areas calculated from nitrogen adsorption data shows a slight increase during the temperature domain of 280 to 430°C and after this temperature, they increase sharply. However, data obtained with Tarfaya oil shales shows a significant increase at the temperature of maximum oxidation of the first stage of combustion of organic matter.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
919.
920.
HaiYangLIU ChangXiangCHEN 《中国化学快报》2002,13(7):633-636
Two new C27 steroidal glycosides, named taccaoside A(1) and B(2), were isolated from the traditional Chinese herb Tacca plantaginea. The spectroscopic and chemical evidences revealed their structures to be 26-O-β-D-glucopyranosyl-(25R)-3β,26-dihydroxy furost-5,20-diene-3-O-[α-L-rhamnopyranosyl(1→2)]-[α-L-rhamnopyranosyl(1→3)]-β-D-glucopyranoside(1) and 26-O-β-D-glucopyranosyl-(25R)-3β,26-dihydroxy furost-5,20-diene-3-O-[α-L-rhamnopyranosyl-(1→2)]-[β-D-glucopyranosyl(1→3)-α-L-rhamnopyranosyl(1→3)]-β-D-glucopyranoside(2),respectively. 相似文献