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1.
The phase diagrams for the ternary systems H 2O?+?2-butanol?+?K 2HPO 4/KH 2PO 4 (pH?=?7) and H 2O?+?2-butanol?+?Na 2CO 3 at 298.15?K were determined. Experimental binodals and tie lines for these systems are presented. The experimental results were correlated using an improved regular solution theory. The agreement between the correlation and experimental data is good. 相似文献
2.
Plasma Chemistry and Plasma Processing - Peculiarities of the etching kinetics and mechanisms for Si and SiO2 in the HBr?+?Cl2?+?O2 inductively coupled plasma were... 相似文献
3.
Millions of people around the world have been suffering from Alzheimer’s disease (AD) everyday. Rivastigmine tartrate is a potential AD drug. A crystallization process can enhance purities of rivastigmine tartrate properly. Predictive models for solubilities of rivastigmine tartrate will improve subsequent industrial crystallization process design. In this work, the solubility of rivastigmine tartrate in (H2O?+?isopropanol), (H2O?+?ethanol), and (H2O?+?acetonitrile) binary solvent systems in the temperature range of 278.15–333.15 K under atmospheric pressure was measured and investigated by employing the analytical stirred-flask method. Binary solvent systems of rivastigmine tartrate overcame drawbacks of mono-solvent crystallization systems, such as high viscosity. Three thermodynamic models, including modified Apelblat equation, the general cosolvency model, and the Jouyban–Acree model, were employed to correlate with the obtained experimental solubility data. Moreover, the calculations of apparent thermodynamic properties of rivastigmine tartrate dissolution process involving the Gibbs free energy, enthalpy, and entropy were accomplished by using the van’t Hoff analysis. Among the three models, the modified Apelblat equation is the most suitable one for predicting the solubility behavior of rivastigmine tartrate in binary solvent systems. Based on the data from modified Apelblat equation, a crystallization process of (H2O?+?ethanol) binary solvent mixture was developed. 相似文献
4.
A detailed theoretical study on the reaction mechanisms for the formations of H 2O 2 + 3O 2 from the self-reaction of HO 2 radicals under the effect of NH 3, H 3N···H 2O, and H 2SO 4 catalysts was performed using the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ method. The rate constant was computed using canonical variational transition state theory (CVT) with small curvature tunneling (SCT). Our results indicate that NH 3-, H 3N···H 2O-, and H 2SO 4-catalyzed reactions could proceed through both one-step and stepwise routes. Calculated rate constants show that the catalyzed routes in the presence of the three catalysts all prefer stepwise pathways. Compared to the catalytic efficiency of H 2O, the efficiencies of NH 3, H 3N···H 2O, and H 2SO 4 are much lower due to their smaller relative concentrations. The present results have provided a definitive example of how basic and acidic catalysts influence the atmospheric reaction of HO 2 + HO 2 → H 2O 2 + 3O 2. These results further encourage one to consider the effects of basic and acidic catalysts on the related atmospheric reactions. Thus, the present investigation should have broad implications in the gas-phase reactions of the atmosphere. 相似文献
5.
Plasma Chemistry and Plasma Processing - In this work, we investigated the etching characteristics of SiOxNy thin films in CF4?+?CHF3?+?O2 inductively coupled radiofrequency... 相似文献
6.
Journal of Thermal Analysis and Calorimetry - Complex perovskites BaCa(1?+?y)/3Nb(2???y)/3O3???δ (y?=?0, 0.18 and 0.5) with... 相似文献
7.
Ion exchange of Li for Na in the layered compounds NaEuTiO 4 and Na 2Eu 2Ti 3O 10 transforms the (NaO) 2 rock-salt layers into Li 2O 2 antifluorite layers. Li can be inserted reversibly into the Li 2O 2 layers to reduce the Eu 3+ to Eu 2+, not the Ti(IV) to Ti(III). An internal electric field perpendicular to the layers is reduced by Li insertion; this field induces a ferroic displacement of the Ti(IV) toward the alkali-ion layers that is eliminated as the internal electric field vanishes in Li 2?+?2x Eu 2Ti 3O 10 with x?≈?1. The spins of the (EuO) 2 and the (EuTiO 3) 2 bilayers of Li 1?+?x EuTiO 4 and Li 2?+?2x Eu 2Ti 3O 10 with x?≈?1 order at low temperature into ferromagnetic Eu–Eu chains that form a 2D ferromagnetic spiral spin configuration in zero magnetic field. The M- H curve shows zero coercivity and zero remanence, but the M of a polycrystalline sample rises to 4 μ B/Eu in an H?=?1 T and approaches saturation above 5 μ B/Eu in 5 T. 相似文献
9.
The decomposition kinetics of peroxide products contained in the liquid phase of the LiOH-H 2O 2-H 2O ternary system were studied, and the applicability of the solubility method to studying this system was demonstrated for hydrogen peroxide concentrations in the liquid phase from 2 to 6 wt % and temperatures of 21–33°C. The stabilizing influence of solid Li 2O 2 · H 2O on hydrogen peroxide decomposition was demonstrated. The temperature and concentration boundaries of existence were determined for the Li 2O 2 · H 2O phase, whose identity was verified by chemical analysis and qualitative X-ray powder diffraction analysis. 相似文献
12.
Ohne Zusammenfassung 相似文献
13.
根据稀土离子能级的特点,对Ga2O3-La2O3-Yb2O3-Er2O3(HO2O3)体系的光谱性质进行了探讨,发现它们有二类发光性质:Stokes发光和反Stokes发光,研究了发光强度和发射波长与掺杂离子的依赖关系,观察到由能量的共振转移引起的荧光浓度猝灭现象,并取得了最大发光强度时的掺杂离子浓度和一些规律性结果. 相似文献
15.
P_2O_5-V_2O_5-TiO_2(简写为P-V-Ti)对芳烃氧化有良好的催化效果.丁烷氧化催化剂P-V体系的体相和表面结构已有一些报道.但P_2O_5对V-Ti的影响文献较少报道.本文用XRD,IR,TPD和ESR考察了P-V-Ti体系. 1.试剂和催化剂:草酸、偏钒酸铵、二氧化钛均为化学纯.将V_2O_5:TiO_2=11:89(重量)样品分别按 P/V原子比为0.1,0.3,0.6,1.0,1.5和2.5制成编号为P-0.1,P-0.3,P-O.6,P-1.0,P-1.5和P-2.5的催化剂. 相似文献
16.
利用abinitio方法,在UHF,UMP2及不同基组3-21G,6-31G^*,6-311+G^*和UMP2(full)/6-311+G^*水平上,研究了O~2/O~2^.^-自交换电子转移反应。优化了电子转移前后反应物和产物的结构,研究了体系能量的变化,计算了自交换电子转移反应的内重组能。对UHF方法和UMP2方法的计算结果进行了比较,并与实验结果进行了对照。结果表明UHF方法由于没有考虑组态相互作用,计算结果存在较大偏差,UMP2(full)/6-311+G^*水平上的计算结果与实验值吻合较好。在UMP2(full)/6-311+G^*水平上计算了气相自交换电子转移反应速率常数。在优化了电子转移复合物结构的基础上考虑了溶剂效应的影响,计算了水溶液中的溶剂重组能。研究结果表明O~2/O~2^.^-体系电子转移反应的活化能主要来源于溶剂重组能的贡献。最后计算了该反应在水溶液中的反应速率常数。理论计算结果与实验值吻合得很好。 相似文献
17.
The hydrogen transfer reaction in the reaction of HOSO + NO 2 with and without H 2O have been investigated using multicomponent quantum-mechanics method, which can directly take nuclear quantum effect (NQE) of light nuclei into account. For the case of the reaction without H 2O, our calculation reveals that the reaction leading to trans-HONO is preferred. For the reaction with H 2O, water-non-mediated and water-mediated (hydrogen-relay) hydrogen transfer mechanism are investigated. The NQE of hydrogen nucleus lowers the relative energy of the stationary point structures and reduces the activation barrier of the reactions. The largest stabilization is found in the transition state structure of the hydrogen-relay type reaction. H/D isotope effects for the reactions are also analyzed. In particular, H/D isotope effect on the activation barrier is analyzed in detail with the aid of the active strain model. 相似文献
18.
盐水溶液中存在过饱和现象,硼酸盐溶液的过饱和即是一例.其中,镁础酸盐体系过饱和溶液在不同浓度和温度条件下的液固相关系曾有多次报道[‘-’];给出过许多有益的结果,也探讨了镁硼酸盐的结晶反应机理并拟合出相应的结晶动力学方程.这些工作对认识盐水溶液过饱和现象有重要意义.为了更广泛地认识和了解不同棚酸盐水溶液中的过饱和现象,本文采用动力学方法,首先对Li20·2B203-HZO过饱和溶液结晶过程进行了研究.1实验初始反应溶液中Li。O/BZO。(摩尔比)为1/2,按此配比计算并称取需要量的Li0H·H。O(A.R.)、H。… 相似文献
19.
Abstract Reactions of Mo(CO) 6 with Na 2WO 4 · 2H 2O in refluxing carboxylic anhydride produce the triangular bioxo-capped mixed-metal carboxylate clusters Na[MoW 2O 2(O 2CR) 9] (R = Me, 1; Et, 2), the propionate being hydrolyzed in 2M HCl containing ZnCl 2 to form [MoW 2O 2(O 2CEt) 6(H 2O) 3]ZnCl 4·2H 2O ( 3). Cluster 2 is converted to the incomplete cuboidal tetraanion [MoW 2O 4(O 2CEt) 8] 4- upon reacting with Cr(CO) 6 in propionic anhydride at 120°, the latter species being trapped by Cr 3± and Na ± ions in the reaction mixture to afford the octanuclear heterometallic chain-like cluster Na 2Cr 2 [MoW 2O 4(O 2CEt) 8] 2 ( 4). Clusters 1, 3 and 4 have been characterized by X-ray crystallography with the following crystal data, for 1: monoclinic, space group P2 1/ c, a = 16.666(8), b = 11.096(3), c = 16.541(7) Å, β = 94.60(4)°, V = 3048.9 Å 3, Z = 4, R, Rw = 0.070, 0.079; for 3, monoclinic, space group Cm, a = 10.259(3), b = 15.756(3), c = 10.870(3) Å, β = 96.18(3)°, V = 1746.8 Å 3, Z = 2, R, Rw = 0.028, 0.034; for 4, triclinic, space group P-1, a = 13.013(5), b = 14.005(4), c = 12.357(4) Å, α = 109.71(2), β = 117.77(3), γ = 90.41(3)°, V = 1838.9 Å 3, Z = 1, R, Rw = 0.037, 0.042. 相似文献
20.
采用结晶动力学方法对MgO-B2O3-28%MgCl2-H2O体系0℃时过饱和溶液的结晶过程进行了研究,结晶析出固相通过化学分析确定了组成,并用X-射线粉末衍射和红外光谱等对其进行了表征.给出了该体系0℃时的热力学非平衡态相图.该相图有4个相区,分别与H3BO3、MgO@3B2O3@7.5H2O、2MgO@2B2O3@MgCl2@14H2O和3Mg(OH)2@MgCl2@8H2O相对应. 相似文献
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