Catalytic Synthesis of Tert-Butyl Acetate by Nd2O3/Al2O3-Nd2O3/ZnO

Nd2O3 was used to support Al2O3 and ZnO to prepare a supported solid base catalyst and investigate the effect of catalyst and reaction conditions on the synthesis of tert-butyl acetate. The composited oxide of Nd2O3/Al2O3-Nd2O3/ZnO exhibited excellent catalytic activity for the synthsis of tert-butyl acetate. The molar ratio of tert-butanol to acetic anhydride is 31, the catalyst in total amount of reactant nearly 0.5%, and reaction time 6 h. With the above conditions, yield of the reaction could reach to 65%. The structure of product were verified by the FT-IR, Element analysis, and MS, which proved that the product was tert-butyl acetate.     

Wettability of Molten Steel／Na2O-Li2O-SiO2-B2O3 Slag System

Thewettability phenomenonbetweenmoltensteelandmetallurgicalslagisoneofthemostimpor tantsubjectsinsteelmakingprocess.Theformationofsteel slagemulsions ,andtheformationandelimina tionofnon metallicinclusionsinsteelaretypicalex amples.Theinterfacialtensionan…     

热压固结与传统液相烧结对WC-20Co-1Y2O3硬质合金组织结构与性能的影响

研究了低于共晶温度下热压固结与传统液相烧结对用超细原料制备的WC-20Co-1Y2O3硬质合金组织结构与性能的影响.研究结果表明热压固结的合金具有组织结构致密、细小、均匀、各向同性的特点,但是合金中存在较多的钴池,采用超细原料、较高的液相烧结温度制备高钴硬质合金,合金中的稀土不能对合金中晶粒非均匀长大产生有效的抑制作用,合金晶粒组织呈现双模结构,其中粗大WC大多为极状晶,因而合金韧性较高.     

Effect of Y2O3 and Dy2O3 on Microstructure and Mechanical Behaviors of Aluminum Nitride Ceramics

The effects of two types of additives, Y2O3 and Dy2O3, on the sintering and mechanical behaviors of AlN ceramics were investigated. The experimental results show that the sintering temperature can be decreased and the mechanical behavior can be improved by adding rare earth in AlN ceramics. The strength of AlN ceramics with Y2O3 and Dy2O3 are 326 and 320 MPa, respectively, which are 97.6% and 93.9% higher than the un-doped AlN ceramics. The fracture behavior on the fracture surfaces of rare earth oxide AlN ceramics was found to be a mixed mode of transgranular fracture and intergranular fracture. As a result, it is concluded that the improvement of bending strength of AlN ceramics with Y2O3 and Dy2O3 addition are mainly achieved by strengthening the grain boundary.     

碳化硅陶瓷的放电等离子烧结

采用添加了Al₂O₃和Y₂O₃助烧剂的碳化硅微粉为原料,通过放电等离子烧结(SPS)技术快速制备了碳化硅陶瓷.分析了材料致密化过程,并重点研究了烧结工艺参数对材料致密度和力学性能的影响规律.结果表明,当SPS工艺参数的烧结温度和压力分别为1600℃和50MPa时,经过5min的烧结,碳化硅陶瓷的致密度可达到99.1%,硬度为HV2550,断裂韧性达8.34MPa·m^1/2,弯曲强度达684MPa.     

La2O3对激光熔覆TiC/Ni基复合涂层的影响

利用CO2横流激光器在低碳钢基体表面熔覆含稀土氧化物La2O3的镍基TiC金属陶瓷复合层,研究了不同含量的La2O3对激光熔覆镍基金属陶瓷复合层组织及性能的影响。结果表明,加入适量的稀土氧化物La2O3可有效改善激光熔覆复合层的显微组织,减少复合层中的裂纹、孔洞、夹杂;加速复合层中TiC颗粒的溶解和改善TiC颗粒的形状变化,同时,熔覆复合层的耐磨性和耐蚀性明显提高。     

烧结温度对碳化硅陶瓷力学性能的影响

采用硼、碳助剂无压烧结制备碳化硅陶瓷。针对烧结温度与碳化硅烧结体密度、抗弯强度以及硬度之间的关系进行了试验研究,并对不同温度下制备的烧结体进行了显微结构形貌观察和XRD图谱分析。结果表明,烧结温度在2190～2220℃范围内可以制备密度高、力学性能好的碳化硅陶瓷。其相对密度超过96%;抗弯强度接近400MPa;维氏硬度23GPa以上。在试验温度范围内,密度与抗弯强度之间的关系近似为线性关系,密度越高抗弯强度和硬度性能越好。     

基体合金化改善氧化铝短纤维与铝液基体间的浸润性研究

提出通过基体合金化改善Al2O3(sf)/Al界面浸润性的想法,添加的合金元素M须满足以下两个条件:(1)元素M的表面能必须小于Al的,即ΓM<ΓAl;(2)元素M的氧化物生成Gibbs自由能要小于氧化铝的。试验证明,元素镁是一种良好的润湿增强剂,稀土元素镧可在镁的基础上进一步增强润湿,但未发现其在界面上生成任何反应产物。     

高含量La_2O_3/Y_2O_3对钼合金微观组织与性能的影响

采用粉末冶金方法制备了不同质量分数La_2O_3/Y_2O_3复合稀土氧化物掺杂的钼合金,观察了钼合金物相构成、显微组织和断口形貌,测试了其力学性能。结果表明:掺杂La-2O_3/Y_2O_3钼合金的物相组成为La_2O_3、Y_2O_3和Mo;锻造态钼合金横截面的晶粒尺寸随La_2O_3/Y_2O_3含量增加而减小,锻造态钼合金纵截面的显微组织为明显的纤维状织构组织形态;锻造态Mo(La_2O_3)3.0(Y_2O_3)0.5钼合金的横截面断口为韧窝断裂和少量解理断裂,纵截面断口为沿晶脆性断裂;合金抗弯强度和弯曲角随La_2O_3/Y_2O_3含量的增加先增加后降低,Mo(La_2O_3)3.0(Y_2O_3)0.5钼合金抗弯强度达到1133 MPa,弯曲角达到38°。     

Phase Constitution in Mixed Gd_2O_3 and B_4C by Sintering at High Temperature

The phase constitution in mixed Gd2O3 and B4C by sintering in graphite tube furnace at the temperature of 100～1489 ℃ in argon atmosphere was studied by means of XRD and TG-DTA. The results show that the impurity C reacts with O in the B4C at the temperature of 367～458 ℃. When the temperature is 800 ℃, Gd2O3 reacts with B4C, and the reaction products include GdB6, GdB4, GdBO3, GdBC and B. GdBC changes into GdB4 at 1200 ℃. When the temperature is 1470 ℃, GdB6 is obtained by the reaction of GdB4 with elemental B. The content of GdB6 is increasing with the prolonging time.     

Effect of Y2O3 and Sm2O3 on Sintering and Mechanical Behaviors of Alumina Ceramics

The effects of Y2O3 and Sm2O3 doping on the sintering temperature, microstructure and mechanical behaviors of Al2O3 ceramics were investigated. The experimental results show that the sintering temperature can be decreased and the mechanical behavior can be improved by adding rare earth in alumina ceramics. The relative density of rare-earthdoped alumina ceramics reaches 98.8% after sintering at 1600 ℃ for 2 h, and its bending strength and fracture toughness reach 439 MPa and 5.28 MPa·m1/2,respectively.Introduction of Y2O3 and Sm2O3 in Al2O3 can restrain the growth of grains, refine the size of grains, and thus form a fine-grained structure. The fracture characteristic is the mixed modes of intergranular and transgranular fracture.     

CeO_2对SiC_p/Al-Si复合材料中析出Si影响机理的研究

采用粉末冶金法制备含CeO_2的SiC_p/Al-Si复合材料,研究CeO_2的添加量对复合材料显微组织的影响,探讨CeO_2在烧结过程中对Si析出的作用机理。结果表明,添加CeO_2可以有效细化析出Si颗粒的平均尺寸,并提高析出Si颗粒的数量。CeO_2的最佳添加质量分数为0.6%,过高或过低的CeO_2含量会降低细化效果。CeO_2作为析出Si相的非均匀形核基底,提高了析出Si相的形核率,从而细化析出Si颗粒尺寸,提高了析出Si颗粒的数量。     

Nd~(3 )、Dy~(3 )、Yb~(3 )与L-酪氨酸甘氨酸三元固态配合物的合成与表征

在乙醇溶液中合成了三种稀土与Ｌ－酪氨酸、甘氨酸的三元固态配合物ＲＥ（Ｔｙｒ）１．５（Ｇｌｙ）４（ＣｌＯ４）３（ＲＥ＝Ｎｄ３＋、Ｄｙ３＋、Ｙｂ３＋）。并通过摩尔电导、红外光谱、热谱等进行了表征。     

The compaction of silicon carbide and compositions based on it: An analysis of domestic and foreign experience

Domestic and foreign experience in compaction of silicon carbide and compositions based on it in order to produce construction and shock resistant materials is generalized. The size, phase, and other characteristics of carbide powders of different producers are compared, and different production variants of compaction (solid-phase sintering, hot isostatic pressing, and sintering in high-pressure chambers), the relation of thermal-force parameters and properties of obtained materials, and the nanolevel of powders and forming structure are considered.     

Nd对Ru/Al2O3氨合成催化剂性能的影响

采用等体积浸渍法制备了一系列Ru-Nd/Al2O3氨合成催化剂。通过TPD、CO化学脉冲吸附法等手段研究了Nd对催化剂的性能影响。结果表明,Nd的加入抑制了H2的吸附,促进了N2的解离吸附,同时修饰了载体,使Ru金属分散度提高。研究还表明,当Nd的含量在8%左右,反应温度在475℃时,催化剂的活性最高。     

Wetting of Al2O3-Based Oxide Ceramics by Molten Aluminum

The temperature dependence has been determined for the wetting by molten aluminum of materials based on aluminum oxide (polycor and corundum). A temperature range has been identified in which the wetting increases significantly. There is no effect on the wetting characteristics of these oxide materials from the addition to the aluminum of up to 25% silicon, 33% copper, or 6% nickel.     

蓝色长余辉发光材料CaAl2O4∶Eu2+, Dy3+的制备

用溶胶—凝胶法(Sol—gel)制备蓝色长余辉发光材料CaAl2O4∶Eu2+,Dy3+(CED),用差热分析(DTA)、红外光谱分析(IR)、X射线粉晶衍射(XRD)、荧光光度计对合成制备产物进行了系列分析测定,确定了制备的最佳条件,产物的激发波长为328nm,发射波长为440nm。     

Preparing of Nano-Sized Power RE2O3(RE = La,Y,Gd) by Pyrolying Precursors

The precursors RE (HSal) 3 ( RE = La, Y, Gd; HSal = C6 H4 (OH) COO) were synthesized by the rheological phase reaction method. The mechanism and products of thermal decomposition of precursors was studied by using TG,DTA, gas chromatography-mass spectrometry (GC-MS). Nano-sized RE2O3 ( RE = La, Y and Gd) power were obtained by thermal decomposition of the precursors in air at 800 ℃. TEM measurement indicates that RE2O3 are spherical particles. The middle level diameter ( d50 ) of the particles are 19.3 ( La2O3 ) , 53.8 ( Y2O3 ) and 28.6 nm( Gd2O3 ) respectively by means of laser particles size analyzer.     

Research on Glass Forming Ability of Er2O3 -Al2O3 -B2O3 -SiO2 System

The glass forming range of Er2O3-Al2O3-B2O3-SiO2 system was explored, and the effect of the content of Al2 O3 and Er2 O3 on glass-forming region was experimentally examined. It is shown that the region of glass formation range expends when the content of Al2O3 is changed from 15% to 20%, while it shrinks when the content of Er2O3 is changed from 20% to 30%. At the same time, the glass forming ability of Er2O3-Al2O3-B2O3-SiO2 system was also discussed using a value of β, which is an indication of crystallization tendency of glasses, calculated from thermo-analysis data. It is found that the glass forming ability of Er2O3-Al2O3-B2O3- SiO2 glasses is poor, while the glasses network may be enhanced when Al2O3 is added to the system, the glass forming ability being heightened. In addition, the crystallization temperatures of the rare earth glasses were determined using differential thermal analysis technique. The Er2O3-Al2O;-B2O3-SiO2 glass samples were heat treated at 1000,1100 and 1260℃ respectively. The results show that it is the Er2O3 phase that separates out from the glasses after crystaline heat treatment, and it is tiered up in glasses, as detected through XRD and SEM. This indicates that the phase separation occurs when the glasses are heated, Er3 being mainly distributed in the boron rich phase, then separated out from glasses, while the silicate rich phase remaining glassy state.