Thermodynamic evaluation of phase equilibria in the CaCl2-MgCl2-CaF2-MgF2 system

The phase diagram of the CaCl₂-CaF₂-MgCl₂-MgF₂ reciprocal ternary system was calculated thermodynamically from available data on the common-ion binary subsystems and from available data on the CaCl₂-MgF₂ join. This join is very nearly quasibinary and divides the system into two quasiternary systems: the CaCl₂-MgF₂-CaF₂ system with a ternary eutectic calculated at 724 +-5 °C and the CaC₂-MgF₂-MgCl₂ system with a ternary eutectic calculated at 561 +-5 °C.     

Al2O3含量对CaO-SiO2-Al2O3-CaF2-Na2O保护渣结晶性能的影响

为控制结晶器保护渣结晶性能,采用热丝法构建保护渣的CCT与TTT曲线,以探讨Al2O3含量对其结晶性能的影响规律.结果表明,随Al2O3增加,保护渣临界冷却速度减小,结晶能力减弱.     

A model for the oxidation of ZrB2, HfB2 and TiB2

A mechanistic model that interprets the oxidation behavior of the diborides of Zr, Hf and Ti in the temperature range of ∼1000–1800 °C was formulated. Available thermodynamic data and literature data for vapor pressures and diffusivities were used to evaluate the model. Good correspondence was obtained between theory and experiments for weight gain, recession and scale thickness as functions of temperature and oxygen partial pressure. At temperatures below about 1400 °C, the rate-limiting step is the diffusion of dissolved oxygen through a film of liquid boria in capillaries at the base of the oxidation product. At higher temperatures, the boria is lost by evaporation, and the oxidation rate is limited by Knudsen diffusion of molecular oxygen through the capillaries between nearly columnar blocks of the oxide, MO₂.     

Ag_2CO_3修饰TiO_2增强其光催化降解甲基橙研究

在TiO_2表面沉积Ag_2CO_3制备了Ag_2CO_3/TiO_2异质结光催化剂。用X射线衍射、比表面(BET)、能量散射X射线谱(EDS)表征催化剂的结构和组成,用表面光电压谱(SPV)研究了光催化剂的光生电荷分离特性,并考察了异质结光催化剂对甲基橙的光催化降解活性。结果表明,Ag2CO3沉积在TiO_2表面有效增加了异质结光生电子-空穴分离速率,从而增强了光催化剂对甲基橙的光催化降解性能。     

Influence of the structure of TiO2, CeO2, and CeO2-TiO2 supports on the activity of Ru catalysts in the catalytic wet air oxidation of acetic acid

Ru catalysts, supported on TiO 2 , CeO 2 , and CeO 2 -TiO 2 , were prepared by the impregnation method. The effect of the structure of the supports on the activity of Ru catalysts was investigated in the catalytic wet air oxidation (CWAO) of acetic acid under 230℃ and 5 MPa in a batch reactor. Physical properties including the surface area, crystalline phase, and surface components of the Ru catalysts were characterized by N 2 adsorption, X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy ...     

钠-葡萄糖共转运体2抑制剂在治疗2型糖尿病中的应用

糖尿病患者需要长期应用降糖药物控制血糖及防止并发症,因此研发疗效好、不良反应少的降糖药物尤为重要。钠-葡萄糖共转运体2(SGLT2)抑制剂为近些年来研究较多的一种用于2型糖尿病的新药物,有望在糖尿病患者的治疗中取得良好的效果。本文对该类药物的发展过程、代表药物、药理作用及不良反应等方面进行综述。     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3-SiO2 and CrO-Cr2O3-SiO2-Al2O3 systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃-SiO₂ and CrO-Cr₂O₃-SiO₂-Al₂O₃ systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Fe2O3-TiO2掺杂对MgO-Al2O3-SiO2系玻璃晶化行为的影响

采用差热分析、X-ray衍射分析、扫描电镜等测试手段，研究了Fe2O3-TiO2掺杂对MgO—Al2O3-SiO2系玻璃晶化行为的影响。结果表明：Fe2O3-TiO2的加入降低了原始玻璃的晶形转变温度，促进了玻璃的晶化；通过适当的热处理，可以得到以Fe^2＋固溶堇青石相与α-堇青石相为主晶相的显微结构。     

添加SnO2的RuO2＋TiO2／Ti钛阳极的组织形貌

采用溶胶凝胶(Sol-gel)法，经涂刷、烧结、退火等工艺制备了添加不同含量SnO2的RuO2 SnO2 TiO2／Ti涂层钛阳极。并通过X射线衍射(XRD)、差热分析(DTA)、透射电镜(TEM)分析了SnO2组元对RuO2 TiO2 SnO2／Ti钛阳极涂层组织、晶粒尺寸和外观形貌的影响。结果表明：本实验所获涂层颗粒为纳米结构，且添加SnO2组元有显著细化涂层晶粒的效果：阳极涂层主要组成物相为(Ru，Sn,Ti)O2固溶体，SnO2组元含量增加、退火温度升高，该固溶体能稳定存在；添加SnO2组元的RuO2 SnO2 TiO2涂层晶粒外观呈较理想等轴状特征。     

Phase Equilibria in the TeO2-CdI2 System

Using differential thermal analysis, x-ray diffraction analysis and density measurements the phase diagram of the TeO₂-CdI₂ system is built. It is characterized with four non-variant equilibria: the temperatures of the eutectic, monotectic, peritectic and peritectoidal points are at 345, 565, 470 and 240 °C, respectively. As a result of the passing of peritectic and peritectoidal reactions, two intermediate compounds with composition CdI₂·3TeO₂ (A) and 2CdI₂·3TeO₂ (B) are formed, both crystallizing in monoclinic lattice system with near unit cell parameters. The intermediate compounds A and B possess narrow solid-solution regions. The B passes through polymorphous transition, which, depending on the composition, varies between 245 and 265 °C. The two intermediate compounds, together with the initial TeO₂ and CdI₂, determine the presence of 16 phase fields: 5 monophase (melt L, α-TeO₂, β-B, α-A and α-B) and 11 two-phase. These characteristics of the phase diagram of the TeO₂-CdI₂ system (two intermediate compounds with complicated compositions CdI₂·3TeO₂ and 2CdI₂·3TeO₂, two low-temperature eutectic and monotectic transitions at T_E = 345 and T_M = 570 °C, respectively, are sufficient precondition for obtaining of new oxychalcohalide glasses with wide region of glass formation in three-component systems from the Me_nCh_m-TeO₂-CdI₂ kind (Me_nCh_m—glassformer).     

Kinetics and mechanisms of the oxidation of chromium in H2-H2O-H2S gas mixtures

The oxidation of pure chromium in H₂-H₂O-H₂S gas mixtures was studied as a function of gas composition at 900°C. Oxidation kinetics were measured using a thermogravimetric apparatus, and the oxidation products were characterized using scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Chromia scales formed when the H₂O/H₂S ratio was about 10 or greater. Scales that comprised a mixture of Cr₂O₃ and chromium sulfides formed when the H₂O/H₂S ratio was about 3, even though Cr₂O₃ was the thermodynamically stable phase under these conditions; i.e., a kinetic boundary exists for pure chromium in H₂-H₂O-H₂S gas mixtures. The transition from chromia scale formation to the formation of scales containing both oxide and sulfide with a change in gas composition (decrease in the H₂O/H₂S ratio) is associated with an inhibition of the overgrowth of growing, metastable sulfide nuclei by the thermodynamically stable Cr₂O₂ phase. Presulfidation experiments confirmed that metastable chromium sulfide can continue to grow after H₂O is added to the gas phase when the H₂O/H₂S ratio in the gas phase is less than a critical value at the temperature of interest.     

Na2O·8TeO2晶相的转变分解机理探索

以Na2O-TeO2玻璃系统中发现的一个新晶相Na2O·8TeO2(NT8)为研究对象,通过热分析和X-射线衍射等分析手段,着重探讨了该晶相的形成条件和分解条件,分析了该晶相发生转变的过程和机理.结果发现该晶相在330℃下能够稳定存在,而在330～340 ℃之间则会分解成Na2O·4TeO2(NT4)和TeO2两种晶体.在由NT8向NT4和TeO2的转变过程中出现了两个热效应,先是一个吸热反应,然后是一个放热反应,这说明在NT8向NT4和TeO2的转变过程中,出现了一个中间相,该中间相为一种非晶相.作者认为,NT8向NT4和TeO2的转变分为两个步骤,第一步是由NT8向中间非晶相的转变,第二步是中间非晶相向NT4和TeO2的转变,而且由NT8向中间相转变的过程与由中间相向NT4和TeO2转变的过程是同时进行的.     

n?SiO2的表面改性及其增强环氧树脂复合材料的性能

纳米粒子在聚合物中均匀、稳定分散,是纳米复合材料具有优良性能的前提。文中通过选择表面活性剂改性纳米SiO2,提高纳米粒子在环氧树脂中的分散性,制备出不同含量的n–SiO2/环氧树脂聚合物复合材料,探讨了纳米SiO2对复合材料强度的影响规律。研究结果表明:改性后的纳米SiO2粒子在聚合物体系中呈单分散状态,均匀分布的纳米粒子与基体结合紧密,其在基体中起到了物理交联点的作用,对剪切力的抵抗能力增强,提高了复合材料的综合性能。加入6%质量分数的纳米粒子,复合材料的拉伸剪切强度可提高35.1%。     

SnO2掺杂对TiO2压敏电阻器性能的影响

采用固相合成法制备了SnO2掺杂的TiO2基压敏电阻系列样品，并通过XRD和SEM分析，以及Ⅰ-Ⅴ矿曲线测量对材料的结构和电学性能进行了研究。结果表明：SnO2的掺杂抑制了晶粒的生长，晶界相含量增加。电性能测试结果显示，SnO2的掺杂量在0～1．5mo1％内，击穿场强随SnO2掺杂量的增加单调递增；非线性系数先增加后又减小，掺杂量为0．8mol％的样品具有最大的非线性系数（α=8.3）。并对以上的实验结果从理论上给予了分析。     

锻造最新前沿技术研究综述(下)

《锻造最新前沿技术研究综述》(上)见《锻造与冲压》2021年第1期 近似超塑性技术 对具有微晶质的材料组织超塑性的研究(晶粒的平均尺寸通常不超过10～20μm),是在提高温度和相对低的变形速度(通常在10-4～10-3s-1)下进行的.事实上已经确定,任何多晶体材料,包括铝基、钛基、镍基等工业合金都能转变为超塑性组织状...     

Pt-Pd/CeO2-SiO2催化剂的稳定性研究

以浸渍法制备Pt-Pd/CeO2-SiO2催化剂(Pt-Pd/CS),与Pt-Pd/Al2O3催化剂进行耐硫和耐热稳定性对比。用比表面(BET)、X射线衍射(XRD)和高分辨率透射电镜(HRTEM)等表征催化剂,用模拟气小样方法(SGB)评价催化活性。结果表明,Pt-Pd/CS具有比Pt-Pd/Al2O3催化剂更好的热稳定性和耐硫性。780℃,10 h老化后,Pt-Pd/Al2O3性能轻微下降,而Pt-Pd/CS催化剂中CeO2与贵金属的相互作用增强,NO氧化活性提高。在SO2气氛中,两种催化剂的低温活性均显劣化,但在350℃以上时,Pt-Pd/CS的活性反而提高;Pt-Pd/Al2O3对SO2的饱和吸附时间和吸附量分别为Pt-Pd/CS的3倍以上,因此活性衰减迅速。     

Na2O-B2O3-SiO2系统溶胶-凝胶-玻璃转变过程反应机理

采用高温热饱和方法制备干胶时,水解和聚合反应继续进行,聚合反应使链状分子向枝状分子转变,Na2O-B2O3-SiO2系统干胶在100℃干燥后,Q2,Q3,Q4 3种类型的基团同时存在.当在600℃烧成的Na2O-B2O3-SiO2系统干胶时Q4基团占主要了,这时硅胶网络由较低聚合度变成较高聚合度的硅氧网络了.但在600℃烧成的Na2O-B2O3-SiO2系统玻璃对称性差,该峰对称性差的原因可以这样理解,即基团中Si原子有1个或2个被硼原子取代而导致的结果,即形成了Si-O-B键,在600℃得到加强,这一现象已经被红外吸收光谱的结果得到证实.     

Pd^2＋离子对TiO2光催化薄膜化学稳定性的影响

采用Sol—Gel工艺在普通玻璃表面制备出均匀、透明的添加0．3％～0．5％贵金属Pd^2 的TiO2-SiO2复合薄膜。通过对薄膜的XRD，SEM表征及薄膜耐酸、碱化学稳定性的检测，结果表明，在TiO2—SiO2薄膜中添加Pd^2 ，增强了TiO2薄膜的光催化活性，由于Pd^2 所起到阻滞剂的作用，使晶粒尺寸减小，表面呈多孔合理结构，改善了TiO2薄膜的显微结构，使薄膜的化学稳定性得到明显的提高。