Effect of La_2O_3 Addition on Sintering Properties of Magnesia

Light burned magnesia powders with different particle sizes were obtained by calcining crystalline magnesite. Sintered magnesia was prepared from the light burned magnesia powders by adding different amounts of La_2O_3. The effect of the La_2O_3 addition on the densification of magnesia was studied. The results show that the densification of sintered magnesia can be promoted both by reducing the particle size of the light burned powder and by adding small amounts of La_2O_3. The effect of the La_2O_3 addition is more significant: the maximum bulk density of the sintered magnesia can reach 3.49 g · cm~(-3) and the apparent porosity can be reduced to 0.33%. During sintering, Ca~(2+) from the impurities enters La_2O_3 lattices, causing lattice distortion of La_2O_3 thus promoting the formation of La4.67(SiO_4)_3 O phase and CaLa_4(SiO_4)_3 O phase, which fill the pores between the MgO grains and promote the densification of sintered magnesia.     

CaO熟料的早期水化放热过程及水化程度

研究了用于膨胀剂的CaO熟料早期水化放热过程及其在水泥浆体中的水化程度.结果表明,在CaO熟料-水体系中,CaO熟料水化放热过程与水泥熟料类似,分为表面水化加速期、诱导期、内部水化加速期和衰退期四个阶段.量化了该过程的时间节点.在水固比为0.35的CaO熟料-硅酸盐水泥浆体体系中,CaO熟料掺量4％ ～8％时,CaO熟料在水泥浆体中水化24 h时的反应度约85.5％.这是氧化钙膨胀剂在混凝土中水化2 d后膨胀效能增加缓慢的主要原因.     

丙烷在La_2O_3－V_2O_5及La_2O_3－MoO_3催化剂上的氧化脱氢

研究了Ｌａ_２Ｏ_３－Ｖ_２Ｏ_５及Ｌａ_２Ｏ_３－ＭＯＯ_３两个催化体系对丙烷氧化脱氢反应的活性以及反应体系中加入ＣＯ_２对Ｃ_３Ｈ_６选择性及其产率的影响；并对这二个催化体系进行了比较。     

La_2O_3表面修饰NiFe_2O_4的制备及气敏性能

采用低温固相反应法合成NiFe2O4纳米粉体,通过浸渍法在粉体表面修饰La2O3,用X射线衍射仪、扫描电镜和X射线光电子能谱仪表征修饰后粉体的结构及形貌,并测试不同质量（下同）含量La2O3的旁热式气敏元件的气敏性能。结果表明：La2O3为无定形结构;La2O3含量等于4%时,NiFe2O4气敏元件对1000μL/L的...     

磷酸铝对改善CaO系合成砂抗水化性的影响

调查了磷酸铝对CaO系合成砂的抗水化性的影响，结果可知添加磷酸铝可以提高抗水化性，尤其是添加量为5％(质量)时，提高抗水化性的效果最大；组织的致密化和结晶的长大有助于改善抗水化性；α—Na2Ca4(PO4)2SiO4等a—Si—P—Na系生成物在晶界和空隙周围生成后可以提高抗水化性。     

Effect of Pelletized Graphite Addition on Properties of Al_2O_3-SiC-C Castables

Al_2O_3-SiC-C castables with pelletized graphite addition of 0,2%,4% or 6%( by mass,the same hereinafter) were prepared using brown fused corundum( 8- 5,5- 3 and 3- 1 mm),dense fused corundum( ≤1 and 0. 045 mm) and Si C( ≤1 and ≤0. 064mm) as main starting materials with mass ratio of aggregate∶ matrix = 71∶ 29,2% silicon powder and 0. 4%B4C as antioxidants,and pelletized graphite as carbon source. Effect of pelletized graphite addition on physical properties,oxidation resistance,slag resistance and thermal shock resistance of Al_2O_3-SiC-C castables was researched. The results show that: with the increase of pelletized graphite addition,the required water amount of castables increases,the bulk density and strength reduce;with 4% pelletized graphite,the castable performs the best oxidation resistance; the increase of graphite is beneficial to the improvement of slag penetration resistance and corrosion resistance; with 6% pelletized graphite,the thermal shock resistance is the best.     

Effect of Y_2O_3 Addition on Sintering Properties and Microstructure of Spinel Materials

The effect of Y_2O_3 addition on the sintering properties and microstructure of spinel was investigated using alumina-rich spinel as the raw material. The phase constitution and microstructure of the specimens were characterized by XRD and SEM,and the pore structure of the specimens was measured by a mercury porosimeter. The results indicate that a viscous melt forms wrapping around spinel crystals by adding a little Y_2O_3 powders(1 mass%),yttrium alumina garnet will crystallize around spinel crystals by adding more Y_2O_3 powders( ≥3 mass%); the sintering properties of the spinel are significantly improved by adding Y_2O_3 powders less than 3 mass%,while they will be relatively weakened by adding Y_2O_3 powders more than 3 mass%.     

PP/La_2O_3纳米复合材料的制备与性能研究

通过熔融共混和注塑成型制备出不同纳米稀土(NRE)含量的聚丙烯/氧化镧(PP/La2O3)纳米复合材料,并对该复合材料的力学性能进行了详细研究。结果表明:PP/La2O3纳米复合体系的力学性能受La2O3添加量的影响较大,随La2O3用量的增加,材料的屈服强度与屈服点伸长率均呈先增大后减小的趋势,且均在La2O3用量为1份时出现极大值;另外XRD分析结果显示该复合体系具有两种PP晶型。通过加入La2O3以及对体系进行退火可调节复合材料的内在结构,由此达到控制材料性能的目的。     

La_2O_3对锂铝硅系统微晶玻璃的影响

研究了稀土氧化物Ｌａ２Ｏ３对Ｌｉ２Ｏ－Ａｌ２Ｏ３－ＳｉＯ２系微晶玻璃的加工性能及物理特性的影响。结果表明,少量Ｌａ２Ｏ３能增加玻璃液的粘度,玻璃的熔融温度和析晶温度比未加Ｌａ２Ｏ３的分别增加２０℃和５℃左右。该微晶玻璃的热膨胀系数随Ｌａ２Ｏ３含量的增加而降低。当Ｌａ２Ｏ３加入到０．１摩尔百分比时,其热膨胀系数比未加Ｌａ２Ｏ３的相同组成的微晶玻璃降低约３３％。     

Effect of Microsilica Addition on Properties of CMA72 Bonded Al_2O_3-MgO Castables

CMA72 bonded Al_2O_3-MgO castable is promising for application of steel ladle wall,because of unique combination of thermo-mechanical properties,slag corrosion resistance and cost benefit. In these castables,microsilica can be introduced to counterbalance the expansion generated by spinel formation. In this paper,the effect of microsilica dosage on properties of castables was evaluated. Expansion,expressed by the permanent linear change( PLC),is highly dependent on the dosage of microsilica. Unexpected expansion occurs when the dosage of microsilica is too low due to dominant effect of spinel and CA_6 formation. Too high dosage results in sintering shrinkage,which is related to amount of liquid phase generated by microsilica addition. In addition,HMOR declines dramatically with increasing microsilica dosage. Considering the balance between expansion control and hot property retention,1. 0 mass% of microsilica is recommended for the castable containing 4 mass%of magnesia.     

添加Al2O3对玻璃与可伐合金封接性能的影响

通过测定玻璃在可伐合金表面的接触角,研究了添加Al2O3颗粒对玻璃润湿性的影响,并从气密性、绝缘电阻、爬坡高度和玻璃的抗开裂性能四个指标分析了添加Al2O3颗粒对改善玻璃与可伐合金封接性能的影响.结果表明,添加Al2O3的数量和粒度都将影响玻璃的润湿性能,Al2O3数量的增加和粒度的减小将降低玻璃在可伐合金表面的润湿性能,同时添加Al2O3还可强化基体玻璃的抗破坏能力.在DM308基体玻璃中添加10wt％ Al2O3颗粒后,极大改善了基体玻璃的封接性能,封接件的气密性、绝缘电阻、玻璃沿引线爬坡高度以及玻璃绝缘子抗开裂性能大大提高.     

Effect of Al Addition on Properties of Al_2O_3-SiC-C Dry Ramming Mixes for BF Trough

Aluminium powders were introduced to Al2O3-SiC-C dry ramming mixes in order to improve sintering properties and oxidation resistance according to their service conditions and installation methods. Properties such as bulk density, porosity, modulus of rupture, crushing strength and hot modulus of rupture as a function of aluminium addition were investigated in the present work. The microstructure and thermodynamics for the heat treated specimens were also analyzed. The results show that as aluminium addition...     

Effects of Spherical Aggregates Addition on Properties of Al_2O_3-SiO_2 System Castables

Compared with traditional aggregates,spherical aggregates with high flowability,easy control of particle size distribution and favor of dense packing and so on,are expected to replace traditional aggregates as important raw materials for future high performance refractories. Therefore,investigation of effects of spherical aggregates addition on properties of refractories becomes very meaningful. Using A70 mullite traditional aggregates and A70 mullite spherical aggregates, bauxite homogenization powder,microsilica,and calcium aluminate cement as raw materials,different Al_2O_3-SiO_2system low cement castables were prepared by replacing conventional aggregates with spherical aggregates. The effect of spherical aggregates addition on workability and mechanical properties of castables after heated at different temperatures was researched,and microstructure of the specimen was analyzed by SEM. Compared with traditional irregularly shaped aggregates,spherical aggregates endow castables with better flowability and easy pump ability. By introduction of spherical aggregates into the castables,flowability and pumpability are significantly improved,and water addition and ball completely sunk time are reduced. The introduction of spherical aggregates is favorable to density and cold crushing strength of castables,but unfavorable to CMOR. The effect of spherical aggregates addition on HMOR at1 400 ℃ can be negligible. Microstructure analysis showsthat the boundary bonding between spherical aggregates and matrix is strong,similar to the traditional aggregates.     

La_2O_3-TiO_2系陶瓷物相与介电性能研究

固相法合成La2 O3 TiO3 系陶瓷介质材料 ,XRD、SEM、EDS分析其结构、形貌和成分。高精度电容测量仪测试其介电性能。La2 O3/TiO2 比 1∶2、2∶9组分可获得极低介质损耗 ,XRD分析主晶相为La2 Ti2 O7和La4 Ti9O2 4 。La2 O3/TiO2 比 1∶3组分可获得La2 / 3TiO3、La4 Ti9O2 4 复相。缺陷型钙钛矿相La2 / 3TiO3不利于介质损耗降低。EDS分析表明晶界富集Si杂质 ,有效促进了液相烧结     

CaO掺杂对钡硼硅系微晶玻璃性能的影响

本文采用固相法制备了具有高热膨胀系数的BaO-B2O3-SiO2 (BaBSi)系微晶玻璃.CaO部分替代BaO的掺杂方法制备BaBSi系微晶玻璃,研究CaO掺杂对微晶玻璃性能的影响.通过SEM、XRD和DSC对微晶玻璃材料的热、力和电学性能的分析表明:随着CaO掺杂含量的增加,微晶玻璃中方石英晶相含量显著减少,而石英晶相含量明显增加;随着CaO掺杂含量的增加,微晶玻璃的抗弯强度呈现减小的变化趋势,微晶玻璃的热膨胀系数也在一定范围内变小,同时微晶玻璃的热膨胀系数随温度的变化更趋于线性化,更加优化了微晶玻璃的热学性能.在950℃的烧结温度条件下,CaO掺杂量为8％(质量分数)时制备的微晶玻璃具有良好的综合性能,高热膨胀系数(12.51×10-6/℃),高抗弯强度(170 MPa),低介电常数(6.2)及低介电损耗(0.06％).     

Effect of CeO_2 and Calcination Temperature on Hydration Resistance of CaO Aggregates

Active lime was used to produce Ca(OH)_2fine powder.And then Ca(OH)_2fine powder with analytically pure CeO_2fine powder(0,0.2%,0.4%,0.6%,0.8%and1.0%by mass,respectively)were mixed via wet mixing.After drying and ball milling,the specimens were pressed and fired at 1 450℃,1 500℃,1 550℃,1 600℃and1 650℃,respectively.The hydration resistance of the specimens was evaluated by measuring the mass gain after soaking the specimens in a chamber kept at 20℃and90%relative humidity.The influences of CeO_2and calcination temperature on the hydration resistance of CaO aggregates were investigated by determination of bulk density,apparent porosity,and XRD,SEM and EDS analysis.The results show that:(1)the sintering of CaO aggregates is promoted by CeO_2addition and the hydration resistance of CaO aggregates is improved;(2)CeO_2mainly locates in CaO grain boundary,some CeO_2is solved in the CaO grains which improves CaO sintering;(3)the appropriate calcination temperature is 1 550℃.When the calcination temperature is below 1 550℃,the specimens are sintered inadequately.The density and hydration resistance of CaO aggregates are nearly stable when the calcination temperature is above 1 550℃.     

Dy_2O_3和La_2O_3掺杂对BaTiO_3铁电陶瓷介电特性的影响

对BaTiO3 和BaTiO3-Nb2 O5-Co2 O3 系组成进行了Dy2 O3 和La2 O3 稀土改性的研究 ,考察了该系统的介电温度特性和耐电性能 ,观察了样品的显微结构 ,讨论了Dy2 O3 和La2 O3 在改变BaTiO3 铁电温谱特性的作用 .结果表明 :Dy2 O3 和La2 O3 的掺杂效果存在差异 ,Dy2 O3掺杂明显促使BaTiO3 细晶化 ,而La2 O3 掺杂呈现出对BaTiO3 基介质材料的Curie峰更强的压峰和移峰效应 .在BaTiO3-Nb2 O5-Co2 O3-Dy2 O3 系统中可获取高介高压特性瓷料 ,其介电常数≈ 3 0 0 0 ,tgδ <1.5 % ,介电温谱符合“X7R”标准 ,击穿强度可达 7～ 8kV/mm     

CaO含量对Al2O3-MgO-CaO系浇注料性能的影响

高纯度的Al2O3-MgO-CaO系浇注料正广泛应用于精炼钢包的透气砖、座砖、工作衬及包壁修补料等,纯铝酸钙水泥既是Al2O3-MgO-CaO系统浇注料的结合剂,同时又是浇注料中CaO的主要来源.本试验通过改变纯铝酸钙水泥的加入量来改变CaO的含量,探究高温下形成的CA6等矿相对体系性能的影响.结果发现:氧化钙以本研究中的纯铝酸水泥形式引入时,随其引入量的增加,材料经110 ℃处理后的物理性能呈现优化的趋势;CA6形成产生的体积膨胀在促进结构的致密化的同时,当达到一定程度时,会导致材料结构劣化,因此材料经1550 ℃处理及5次热循环后,其物理性能呈现先提高后降低的趋势.综合各项性能认为,纯铝酸钙水泥加入量在5wt%~8wt%时其高温强度及抗热震性能较为优异.     

TiO2加入量对MgO - TiO2-Al2O3系熟料特性的影响

制作MgO含量相同、TiO2含量不同的各种熟料，测定熟料特性，研究TiO2加入量对MgO-TiO2-AlO3，系熟料特性的影响。TiO2含量不同，各种熟料的矿物组成中尖晶石固溶体的成分不同。TiO2和Al2O3共存可提高抗热化性和抗热震性。TiO2能促进烧结的进行。     

K2O—CaO—Al2O3—SiO2系统玻璃的分相

本文研究了Ｋ２Ｏ－Ａｌ２Ｏ３－ＳｉＯ２玻璃的分相行为，从中发现该系统在液相线下的亚稳不混溶区能一直扩展到含ＳｉＯ２量为５３－６０ｍｏｌ％的截面，Ｋ２Ｏ的引入能使该系统的不混溶温度升高，其分相的结构形貌的液滴状，滴状相是富硅相，含有ＳｉＯ２，Ａｌ２Ｏ３和Ｋ２Ｏ，其尺寸大小服从对数正态分布。