Computer Simulation of Kinetics of Spinodal Decomposition in the Tetragonal TiO2–SnO2 System

Computer simulation was carried out for the kinetics of spinodal decomposition in the tetragonal TiO₂–SnO₂ system on the basis of a nonlinear diffusion equation. A time evolution of the microstructure and the effect of coherent strain on the separated two phases were investigated by Langer's approximate method and the finite difference method. It was shown that the composition fluctuations develop in the first stage of the spinodal decomposition, and the formation of interface and the grain growth appear in the second stage. The local stress field and the local strain field with the coherence of the lattice were calculated. Subsequently the appearance of the interface dislocations in the (100) and (010) planes was demonstrated to occur in the third stage. Physical interpretation was given to the experimental observations for the tetragonal TiO₂–SnO₂ system on the basis of those calculations.     

Phase Separation by Spinodal Decomposition in the Tetragonal System

Coherent spinodal curves for the [001] and [100] directions were calculated for the system TiO₂-SnO₂. Inside the [001] spinodal curve, the crystalline solutions decomposed by a modulated phase composed of TiO₂-rich and SnO₂-rich plates perpendicular to the [001] direction. No modulation of structure was observed at compositions and temperatures between the [001] coherent spinodal and the equilibrium curve. The kinetics of the decomposition showed that the wavelength of the modulation decreased in the early stages of the separation, reaching minimum observable values of approximately 110 Å at 925°C, 170 Å at 1000°C, and 240 Å at 1150°C. In the second stage when the coherency was lost, the wavelength increased. Theoretical calculations to find the elastic free energy/unit volume to cause fluctuation of composition in the spinodal process were worked out for the tetragonal system. The calculations were done for an arbitrary direction and involved elastic constants. The theoretical prediction and the experimental results for the system TiO₂-SnO₂ agreed well.     

等压似三元相图在尿素加热分解工序上的应用

本文是新编《尿素工学》一书的一些补充。叙述了用等压似三元相图计算尿素工艺中减压加热分解工序中的甲铵分解率，总氨蒸出率以及分解后的气液组成的方法。提供的算图可作为传统的水溶液全循环法各种分解压力和加热温度条件下上述各参数计算之用。     

Phase relations in the Barium Titanate—Titanium Oxide System

Phase relations in the BaTiO₃—TiO₂ system were studied at temperatures above 1300°C in air. Quenching experiments were performed with high-purity reagents, and a new equilibrium phase diagram was constructed. Results include redetermination of the liquidus boundaries, the eutectic temperature, the melting or decomposition temperatures of the stable compounds in the system, the cubic—hexagonal transition in BaTiO₃, and the solid solubility of TiO₂ in BaTiO₃.     

用复分解相图分析纯净盐生成条件

通过对复分解相图的分析,阐述了纯净盐生成的必备条件,介绍了复分解生产原则流程,用不同体系的相图,对应用实例进行了分析。     

甲基磺酸亚锡的热分析研究

用热重和示差扫描热分析法研究了甲基磺酸亚锡的热分解过程,其热分解过程分为三个阶段;在60～100℃脱水,在390～407℃甲基磺酸亚锡分解生成无机盐SnSO4;在407～425℃生成SnO.采用DTA-TGA技术研究了甲基磺酸亚锡在氮气中的非等温热分解机理及动力学. 根据TGA曲线确定了热分解过程中的中间产物及最终产物.运用Achar法和Coats-Redfern法对非等温动力学数据进行分析,得到热分解反应的机理函数和动力学参数.     

二丁基氧化锡合成方法的工艺改进

用复合溶剂代替乙醚作溶剂,通过格氏反应由四氯化锡制得粗四丁基锡(简称TBT),四丁基锡含量≥85%,三丁基氯化锡含量≤15%,将粗TBT与四氯化锡在催化剂的作用下反应,反应完毕后,将反应物用酸洗,分相制得粗二丁基氯化锡,再减压脱水制得精二丁基氯化锡,二丁基氯化锡和氢氧化钠反应制得二丁基氧化锡,以SnCl4为原料合成二丁基氧化锡的小试收率以含锡量计为95.26%.     

多元醇PG-TAM二元体系相图

多元醇在固-固相变时能够可逆地吸收大量的热而被用做贮热材料,特别是三羟甲基乙烷(PG)和三羟氨基甲烷(TAM)构成的二元体系,有很宽的适宜于太阳能贮存的温度范围。为了材料的选择,现利用差热分析(DTA)、X-射线衍射及变温红外光谱技术测定了PG-TAM二元体系相图。确定后的相图表明,从室温升温至熔化的过程中,相图在一定的组成范围内出现了三个低共熔点,分别为71℃、111℃和165℃。由于多元醇分子中存在-OH,因而多元醇分子间能形成氢键。随着温度的升高,多元醇发生固-固相变,分子间存在的氢键逐渐受到破坏,-OH伸缩振动的特征吸收波数向高波数发生突跃。变温红外光谱测得的-OH特征吸收峰位移发生突跃的温度区间恰好与体系各自DTA测得的相转变温度相吻合,多元醇的晶体结构、分子的大小是影响二元体系不同相态间互溶度的重要因素。     

Pitzer热力学模型介绍及其在盐水体系相图计算中的应用

文章详细介绍了Pitzer热力学模型的计算原理和推导过程。并用该热力学模型计算了存在二级电离平衡的H2SO4-H2O体系的水活度数据。计算过程体现了HSO4-物种的引入对准确计算体系的水活度至关重要。该二元体系的模型参数范围也由0~55℃扩展到0~100℃。结果表明:模型计算值与实验值十分吻合,Pitzer热力学模型以及重新确定的模型参数能够很好的描述和预测H2SO4-H2O体系在多温下的热力学性质。     

Elastic Effect on Domain Morphology and Kinetics of Spinodal Decomposition in the Tetragonal System

A method was proposed for calculation of the effect of elastic strain on spinodal decomposition in the tetragonal system. An effective free energy for the composition field was derived by eliminating elastic fields which are coherently induced by composition inhomogeneities It was shown that anisotropic long-range interactions between composition fields play a major role in determining both the domainmorphology and domain growth law of spinodal decomposition with the coherence of the lattice. Computers simulations were performed on the basis of a two-dimensional model by taking into account those long-range interactions. The results demonstrated the appearance of lamella structure and its coarsening in the late stage of the phase separation The calculation for the TiO₂-SnO₂ system showed slow coarsening due to the anisotropic elastic long -range interactions The asymptotic growth of the lamella size was described by λα tⁿ, where n is 0.18.     

维生素C结晶物系相图的测定

采用差式扫描量热仪测得维生素Ｃ结晶物系的ＤＳＣ谱图,根据谱图数据提出了维生素Ｃ－水－乙醇物系的固液相图,并结合定量分析,计算其结晶热,对结晶工艺条件的确定以及结晶器的设计具有指导意义。     

纳米氧化铟锡制备方法研究

介绍了近年来纳米氧化铟锡(ITO)粉末几种常用的制备方法,着重讨论了共沉淀法,溶胶-凝胶法,水热法等工艺,并比较了几种制备方法的优缺点。共沉淀法具有流程简单,操作容易控制,环境污染少,产品性能稳定等特点,是较有前途的方法。     

Growth and Phase Transformation of Nanometer-Sized Titanium Oxide Powders Produced by the Precipitation Method

We report an in situ TEM investigation of the growth and transformation in nanometer-sized titania powders. The powders were produced through precipitation of titanium tetrachloride under different pH conditions. The initial phase of the produced powders was amorphous or was a mixture of anatase and brookite according to the pH conditions. During calcination, the anatase particles grew and transformed into rutile. The transformation temperature increased with increasing pH value. In situ TEM observations showed that the anatase particles were absorbed into rutile, and then rutile particles grew by coalescence. Furthermore, small pores were observed to form in samples prepared with high pH from the effects of hydroxyl ions and zeta potential. Pore formation increased the surface area, which delayed the transformation and nucleation of rutile. This explains the difference of growth and transformation of titania powders produced under different pH conditions during calcination.     

Sulfate Decomposition and Sodium Oxide Activity in Soda–Lime–Silica Glass Melts

Reaction equilibrium constants for the sulfate decomposition process, which releases oxygen and sulfur oxide gas in soda–lime–silica glass melts, have been determined. The chemical solubility of SO₂, probably in the form of sulfite ions in soda–lime–silica melts, has also been determined. The chemical solubility value of SO₂, dissolving as sulfite, ranges between 0.02 and 0.06 wt% SO ₃ ²⁻ at 1 bar SO₂ pressure in the temperature range of 1600–1800 K. Results of square-wave-voltammetry studies and measurements of the temperature-dependent sulfur retention after the fining process of commercial float glass melts and a model soda–lime–silica melt, with 74 wt% SiO₂, 16 wt% Na₂O, and 10 wt% CaO, are presented. The measured sulfur retention data and the results of the square-wave-voltammetry studies are used to determine the equilibrium constant of the sulfate decomposition reaction in the temperature range of 1600–1800 K. The thermodynamic relations and properties found for sulfate decomposition are used to derive activities of sodium oxide in soda–lime–silica melts. Literature values for sodium oxide activities in these glass melts are rare. In this study, these activities have been determined by a method, based on the measurement of sulfate decomposition equilibrium constants and the residual sulfate concentrations in glass melts, equilibrated with almost pure sodium sulfate galls.     

Phase Diagram for Liquid Crystalline Polymer/ Polycarbonate Blends

A novel mechanism to form binary polymer blends is through phase separation by spinodal decomposition in the unstable region of the phase diagram. The present work investigates the effects of thermally‐induced phase separation by spinodal decomposition on the morphology development of liquid crystalline polymer/polycarbonate blends. Moreover, a thermodynamic binary phase diagram is obtained using a twin‐screw extruder at various processing melt temperatures. Differential scanning calorimetry and scanning electron microscopy were used to study the miscibility of the blends and the resulting morphology. A thermodynamic binary phase diagram exhibiting a lower critical solution temperature was obtained. The droplet size distribution of the blend was also obtained and discussed in light of the Cahn‐Hilliard theory.     

双液系气-液平衡相图的 Origin 绘制方法简

Origin是一款功能强大的专业数据分析与科技绘图软件。运用Origin软件对“双液系气一液平衡相图”的数据进行处理并绘图,可克服传统手工绘图费时费力的缺点,结果科学精确且方便快捷;与Excel软件所绘得的相图进行对比发现,Origin绘得的相图更为科学合理。物理化学实验教学中引入Origin软件的介绍,可提高学生使用计算机综合处理数据的能力,也为其日后的本科论文及科学研究工作奠定了基础。     

Temperature Dependence of Electrical Condutivity in Polycrystalline Tin Oxide

The electrical conductivity of polycrystalline SnO₂ in air was measured between 400° and 1400°C using samples prepared by hot isostatic pressing and normal sintering. The apparent activation energy for conduction above 800°C was 1.3 to 1.4 eV in the hot isostatically pressed sample and 1.9 to 2.0 eV in the normally sintered sample. This difference can be interpreted as a result of the pore contributing an additional blocking effect to conduction. Also we found that the electrical conductivity above 1150°C bent down slightly from the linear regime when using a cumulative slope model.     

纳米氧化锡在丙烯酸乳液中的吸水性与电性能研究

叙述了丙烯酸乳液涂层中不同含量的纳米氧化锡与普通氧化锡和聚乙烯塑料薄膜之间的吸水性和表面电性能关系,说明在丙烯酸乳液中加入同样含量的氧化锡时,纳米氧化锡和普通氧化锡在PE薄膜表面呈现出的表面电性能和吸水性能有不同的情况和变化规律,由此说明,同种材质的纳米材料与普通材料会有不同的基本物理性能。     

Thermal Decomposition of Titanium Alkoxide and Silicate Ester in Organic Solvent: A New Method for Synthesizing Large-Surface-Area, Silica-Modified Titanium(IV) Oxide of High Thermal Stability

Silica-modified titanium oxide (S-TiO₂) powders that have an anatase structure were synthesized via the thermal decomposition of mixtures of titanium(IV) isopropoxide (TIP) and tetramethyl orthosilicate (TMOS) in toluene at 300°C. These S-TiO₂ materials had high rutile-transformation temperatures and maintained large surface areas at elevated temperatures (550°–1000°C). For example, the product that was prepared from a 9:1 TIP:TMOS mixture transformed to rutile at ∼1100°C and possessed a surface area of 160 m²/g, even after calcination at 800°C for 1 h.     

化学共沉淀法制备纳米铋掺杂氧化锡的影响因素研究

以SnCl4.5H2O和Bi(NO3)3.5H2O为原料,氨水为沉淀剂,采用化学共沉淀法制备了铋掺杂氧化锡（BTO）纳米粉体,研究了反应温度、滴定终点pH值、铋掺杂量,煅烧温度和分散剂PEG-600对所得的纳米BTO粉体物相、晶粒度和形貌的影响,对粉末的前驱体进行综合热分析（TG-DTA）,用X-射线衍射（XRD）,扫描电镜(SEM)对产物的结构和形貌进行表征,得到共沉淀法制备纳米BTO粉体的最佳条件：反应温度60℃,滴定终点pH值为3,煅烧温度600℃;该条件下制得BTO粉体的电阻率最小为3.48Ω•cm。