水热条件下坡缕石在NaOH溶液中的行为及结构变化

分别用1,2和3 mol·L^-1的NaOH溶液,在不同的温度条件下对坡缕石进行了侵蚀实验。对反应后的固相产物进行了XRD和SEM分析,对浸出液中的金属阳离子进行了原子吸收光谱分析。讨论了反应温度和碱溶液浓度对碱溶后产物的影响。XRD和SEM结果表明,c_NaOH≤2 mol·L^-1时,坡缕石经碱溶液侵蚀后,可以生成蒙脱石和方沸石,其中反应温度的升高有利于方沸石的形成,碱溶液浓度的升高有利于蒙脱石的形成。当碱溶液浓度达到3 mol·L^-1,反应温度为200 ℃时,最终产物为SiO₂。浸出液的定量分析结果显示,坡缕石与碱溶液的反应过程中,Na⁺对八面体阳离子的置换具有选择性,置换顺序为：Al³⁺＞Fe³⁺(Fe²⁺)＞Mg²⁺。     

层状Co3O4的制备及其电化学电容行为

以P123为模板水热合成制备了Co₂(OH)₂CO₃前驱体，200 ℃热处理后得到了具有层状结构的Co₃O₄。循环伏安、恒流放电等电化学测试表明，200 ℃所得Co₃O₄电极在6 mol·L^-1 KOH溶液中和-0.1～0.5 V(vs Ag/AgCl)电位范围内，具有较好的循环稳定性能，单电极比电容达到505 F·g^-1。     

纳米级TiO2粉体的制备研究——Ⅱ.絮凝剂及其浓度的影响

采用溶胶-凝胶-超临界流体干燥(SCFD)法制备纳米级TiO₂超细粉，详细考察了不同絮凝剂及其浓度对TiO₂织构和结构性质的影响。结果表明，利用强碱溶液作为絮凝剂，浓度为5 mol·L^-1是制备大孔高比表面TiO₂超细粉较为适宜的条件。     

聚合氯化铝中Al13形态的分离纯化方法及特性

采用柱层析法、沉淀置换法和乙醇-丙酮混合溶剂法对聚合氯化铝(PAC)中的Al₁₃形态进行了分离提纯, 采用Al-Ferron逐时络合比色法, ²⁷Al NMR, TEM, SEM, 电位测定法, 粒度测定法等多种现代分析仪器和方法对不同分离提纯方法得到的Al₁₃形态进行了分析表征和比较, 并初步比较研究了Al₁₃形态的水处理效果. 实验结果表明, 不同分离纯化方法得到的 Al₁₃形态具有不同的结构形貌、粒度分布、电性和水处理效果. 乙醇-丙酮混合溶剂法得到的Al₁₃形态具有良好的纯度和水处理效果. 该研究初步证实了Al₁₃是PAC中的最佳絮凝形态.     

聚合氯化铝中Al13形态的分离纯化方法及特性

采用柱层析法、沉淀置换法和乙醇-丙酮混合溶剂法对聚合氯化铝(PAC)中的Al₁₃形态进行了分离提纯, 采用Al-Ferron逐时络合比色法, ²⁷Al NMR, TEM, SEM, 电位测定法, 粒度测定法等多种现代分析仪器和方法对不同分离提纯方法得到的Al₁₃形态进行了分析表征和比较, 并初步比较研究了Al₁₃形态的水处理效果. 实验结果表明, 不同分离纯化方法得到的 Al₁₃形态具有不同的结构形貌、粒度分布、电性和水处理效果. 乙醇-丙酮混合溶剂法得到的Al₁₃形态具有良好的纯度和水处理效果. 该研究初步证实了Al₁₃是PAC中的最佳絮凝形态.     

尖晶石型LiMn2O4的制备及超级电容性能研究

采用高温固相法制备LiMn₂O₄。X射线衍射结果表明800 ℃下得到尖晶石型LiMn₂O₄。利用恒流充放电、循环伏安和交流阻抗等研究了LiMn₂O₄电极材料在2 mol·L^-1 (NH₄)₂SO₄溶液中的超级电容性能。循环伏安测试结果表明LiMn₂O₄电极材料在0～1 V电位窗口范围内具有较好的方形特征；恒流充放电结果表明充放电曲线呈现出较规整的三角形对称分布，放电曲线呈直线关系，5 mA·cm^-2下的放电比容量为141 F·g^-1，具有较高的充放电效率，循环性能稳定；交流阻抗结果也显示LiMn₂O₄电极材料在2 mol·L^-1 (NH₄)₂SO₄中具有典型的电容阻抗特性。     

室温下电化学活化CO2与环氧化合物反应合成环碳酸酯

室温下用铝为牺牲阳极, 以四丁基溴化铵/N,N-二甲基甲酰胺作电解质溶液, 在无隔膜电解池中电化学活化CO₂, 与环氧化合物反应, 合成了环状碳酸酯. 考察了不同电极材料、导电盐、CO₂的压力以及溶剂等因素对电合成结果的影响, 结果表明以Pt为阴极, 在0.05 mol•L^－1 Bu₄NBr/DMF电解质溶液中和4 MPa CO₂下, 环状碳酸酯产率可高达65%～98%.     

不同Fe(Ⅲ)化合物与ClO-热溶液中化学反应的跟踪观察

采用分光光度法跟踪5种不同的Fe(Ⅲ)化合物分别与高碱度NaClO溶液共热到80 ℃时所发生的变化，发现Fe(Ⅲ)首先被氧化为Fe(Ⅵ)；在聚合硫酸铁、六氟合铁酸钾和氢氧化铁参与的反应体系中，Fe(Ⅵ)在分解生成Fe(OH)₃沉淀的同时，还有Fe(Ⅵ)紫色溶液变成Fe(Ⅳ)绿色溶液的反应存在；在硝酸铁和三氯化铁参与的反应体系中，只有Fe(Ⅵ)分解生成Fe(OH)₃沉淀的反应存在。在反应过程中，聚合硫酸铁、硝酸铁所参与的反应体系中，前者生成Fe(Ⅳ)溶液浓度最高：1.25 × 10^-3 mol·L^-1，后者生成Fe(Ⅵ)溶液浓度最高：0.23 mol·L^-1。     

YAlO3的体色与缺陷平衡的关系

利用固相扩散法在1 450 ℃下制备了YAlO₃粉末样品和陶瓷片样品,并在不同温度和不同气氛(air, O₂ or N₂)下对样品进行退火处理调制了其缺陷浓度。基于漫反射光谱和交流阻抗谱分析了YAlO₃样品的体色与其缺陷浓度之间的关系。研究结果表明YAlO₃具有p型导电机理,其浅棕色体色是由阳离子空位引起的。在高温和氮气氛下处理该材料其缺陷浓度减少,体色变浅。第一性原理计算结果认为YAlO₃中的主要缺陷应该是铝空位V_Al^×。     

较为宽松条件下水热合成铁酸铋粉体

Bismuth ferrite(BiFeO₃) powders were hydrothermally synthesized by using FeCl₃·6H₂O and BiCl₃ as staring materials, NaOH as a mineralizer and NH₄Cl as an additive. The results show that pure BiFeO₃ powders can be synthesized under loose hydrothermal conditions of reaction temperature ranging from 140 to 230 ℃ and NaOH concentration ranging from 2 mol·L^-1 to 5 mol·L^-1. Moreover, the morphologies of the products can be controlled by changing the hydrothermal conditions.     

高效率变色WO3多聚体/1，10-DAD自组装薄膜的制备

A novel high-efficient photochromic self-assembly multilayered film has been fabricated from WO3 and 1,10-DAD solution using molecular deposition technique.The dependence of photochromic behavior on with WO3 in the WO3-polymer/1,10-DAD self-assembly film was discussed in comparison with WO3/4,4-BAMBp system.The results clearly show that organic molecules determine the charge density of the photo-induced charge-tracsfer complexes,andthus manipu-late the structure and the photochromic properties of the films.     

High Temperature Reactions in the MoO3-Ag2O System

High-temperature reactions were investigated in the MoO₃-Ag₂O system by means of X-ray, DTA and scanning microscopy methods, and a model was proposed according to which first an Ag₂Mo₄O₁₃ phase was formed at the MoO₃ and Ag₂O (or metallic Ag) interface. Subsequently, at the Ag₂Mo₄O₁₃-Ag₂O contact area a layer of Ag₂Mo₂O₇ appeared. If the amount of silver oxide is sufficiently high, a layer of Ag₂MoO₄ is formed between the Ag₂O and Ag₂Mo₂O₇ phases. This revised version was published online in July 2006 with corrections to the Cover Date.     

高温高压Li3N-hBN体系cBN转变的热力学分析

以经典热力学第二定律ΔG<0为依据,分析了静态高温高压触媒法合成立方氮化硼(cBN)过程中发生的可能反应.考虑温度和压强对反应物相体积的影响,计算了六方氮化硼(Li3N-hBN)体系中hBN+Li3N→Li3BN2,h BN→cBN及Li3BN2→Li3N+cBN反应在高温高压条件下的ΔG.结果证实,Li3BN2由Li3N与hBN在高温高压(T>1300 K,P>3.0 GPa)条件下反应得到,在cBN的合成(T=1600～1800 K,P=4.6～6.0 GPa)条件下,hBN和Li3BN2都有向cBN转化的倾向,但由hBN向cBN直接转变的反应自由能比Li3BN2分解生成cBN的反应自由能更负,反应的可能性更大.探讨了高温高压条件下立方氮化硼的转变机理。     

High resolution and the accurate measurement of intensities

Absolute intensities in several vibration rotation bands of CO₂ and in the pure rotation spectrum of CO have been measured. The results have been used to assess the precision and accuracy which such measurements can attain when made with a high resolution Fourier transform spectrometer.     

Microporous Silica Xerogel Membrane with High Selectivity and High Permeance for Carbon Dioxide Separation

The asymmetric microporous silica xerogel membrane was prepared by sol-gel method. A multi-layer (asymmetric) structure was obtained by silica xerogel layer on top of mesoporous silica layer (mean pore diameter of 4 nm), supported by porous alumina tube (mean pore diameter of 0.1 m). The ratio of the permeances, CO₂/N₂ for this membrane attained more than 60 at 298 K. This value is considerably higher than the theoretical Knudsen value (CO₂/N₂ = 0.8). The gas permeances of this membrane were about 5–10 times higher than the previous membrane. Application of the membrane to an enrichment of CO₂ from air was also investigated. CO₂ in the air (about 300 ppm) was concentrated to more than 1000 ppm by using the membrane at 298 K.     

High Photocatalytic Activity of F-Doped TiO2 Film on Glass

The photoreactivity of sol-gel (SG)-TiO₂ films was enhanced significantly with addition of a small amount of trifluoroacetic acid (TFA) into the starting solution. The promoting effect was confirmed in two separate experiments of the methylsiloxane monolayer oxidation and the photocurrent measurements. The results of film characterization indicated that the absorption coefficient for ultraviolet light ( < 360 nm) increases due to film densification and the crystallinity is improved upon F doping. The improvement in the photoreactivity was ultimately attributed to the increase in the rate at which the photogenerated charge carriers reach the surface in the photostationary state.     

High Efficiency Annular Denuder for Formaldehyde Monitoring

Abstract

A practical and correct methodology for evaluating CH₂O in air without sampling artifact formation is presented. Formaldehyde is collected on an annular denuder coated with bisulfite-triethanolamine. The sorbent layer is extracted with water and the solution analyzed by the chromotropic acid (CTA) procedure. Sorption efficiency and loading capacity have been investigated along with storage stability.

Results of laboratory validation studies have indicated that a small annular denuder was able to sample about 300 μg CH₂O without an appreciable decrease in the initial collection efficiency (99% at 2.5 1 min^?1).

Tests on storage stability before and after exposure have also demonstrated that both oxidation of bisulfite and release of CH₂O did not occur for time periods as long as 1 month.     

Low-Temperature CH4 Total Oxidation on Catalysts Based on High Surface Area SnO2

Pure SnO₂, sulfated SnO₂-SO₄ ^2- and Pd supported on SnO₂ and SnO₂-SO₄ ^2- were prepared from SnO₂ precursor with high surface area, and used for CH₄ deep oxidation. The catalysts were characterized by means of N₂-BET, XRD, TG-DTA, XPS and TPD. SnO₂-SO₄ ^2- shows higher activity than SnO₂, due to the presence of more active oxygen species, superacid sites and its higher BET surface area. Pd/SnO₂ and Pd/SnO₂-SO₄ ^2- display essentially the same activity to each other, while it is much higher than the activity on SnO₂ and SnO₂-SO₄ ^2-. The main reason is ascribed to the concerted action between Pd and the supports.     

Photocatalytic Activity of High Aspect Ratio TiO2 Nanorods

In this article, TiO₂ nanorods (aspect ratio >20) were prepared through a polyol process and doped with metal ions (Cu²⁺, Ni²⁺, Fe³⁺, and Cr³⁺). Compared with TiO₂ nanoparticles, the TiO₂ nanorods displayed relatively higher photocatalytic activity for the degradation of copper sulfophthalocyanine. Moreover, the photocatalytic activity was greatly enhanced when the metal ions were doped in the TiO₂ nanorods.     

High pressure induced coordination evolution in chain compound Li2CuO2

Using diamond anvil cell technique with angle dispersive X-ray diffraction (ADXD) of synchrotron radiation and electrical conductivity measurements, we have observed that CuO₂ chain compound Li₂CuO₂ transforms from ambient orthorhombic symmetry into a new phase at above 5.4 GPa and room temperature. The new phase was found to be of monoclinic structure with an increased oxygen coordination number of Cu²⁺ from four at ambient to six at high pressure that provides a structural basis of the evolution of principle physical properties. The high pressure phase of Li₂CuO₂ is discussed in line with the first principle calculations.