高价稀土氧化矿物中氯离子的测定

文中对分析测定高价稀土氧化矿物中痕量氯离子时介质条件的影响进行了探索，从中得出了分析测定的最佳条件，并利用紫外分光光度计间接测定了高价氧化镨矿物中氯离子的含量，为生产单位提供了一种简便、经济的分析检验方法。     

炼钢用渣线砖材料性能提高的研究

利用氧化镧和氧化铝材料制作新的渣线砖,并与镁碳砖进行了抗渣侵蚀性对比研究,证明铝酸镧材料比镁碳材料制作成的渣线砖抗渣性能有较大提高.     

镧热还原氧化钐过程镧的表面富集现象探索

对镧热还原氧化钐的反应产物镧渣,通过扫描电镜及X射线能谱仪进行了显微观察和成分分析,结果发现：镧热还原氧化钐过程中,还原剂金属镧由反应物料的内部扩散至表面并产生富集,造成金属镧利用率及金属钐收率下降。通过配料优化试验,找出了提高金属镧利用率及金属钐收率的方法。     

镧热还原氧化钐过程温度梯度及压力梯度与钐收率关系的探讨

对镧热还原氧化钐反应产物镧渣进行了化学分析和热重分析,得到坩埚不同部位物料的钐收率,结合试验结果,探讨了镧热还原氧化钐过程温度,压力梯度与金属钐收率的关系.     

熔盐电解法处置镧钐渣废料制备镧钐中间合金

近些年来,由于金属钐的需求量递增,镧热还原生产金属钐后残余的镧钐渣处置成为难题。本文研究了镧钐渣在不同温度和时间下的焙烧产物转化过程,发现在550℃下焙烧2 h可以将镧钐渣全部转换为氧化物,满足电解原料要求。以钨电解为阴极、石墨为阳极,在3000 A电解槽中采用LiF-LaF3氟盐体系电解制备LaSm中间合金。研究了电解时间、电解温度、电解质配比以及阴极电流效率等电解技术指标对电解产物杂质、电流效率以及稀土收得率之间的影响,并对电解制备得的LaSm中间合金做了表征分析。研究表明,当LaF3:LiF（质量比）为75:25时,电解温度为970℃,阴极电流密度为4.5～7 A·cm-2工艺条件进行电解,获得的电流效率、稀土收得率最高,电解杂质含量最低。本文为镧热还原生产金属钐后残余的镧钐渣规模持续化处置提供了切实可行的解决方案,实现了镧钐渣中镧和钐的二次回收利用。     

镧热还原氧化钐烧结堆料对金属钐收率的影响研究

进行了镧热还原氧化钐时，烧结堆料对金属钐收率影响的研究。采用化学分析法和热重法得到的坩埚不同部位物料的金属钐收率，静水称量法测定镧渣的孔隙率，证实了镧热还原氧化钐过程在坩埚底部存在烧结堆料现象。根据试验结果分析了烧结堆料的原因，并进行了优化试验，提高了金属钐的收率。     

镧热还原氧化钐过程动力学控速环节的探索

讨论了镧热还原氧化钐过程的一般动力学过程，探讨了在制备金属钐温度下的动力学控速环节，分析了影响控速环节的因素，通过镧渣分析和配料优化实验，找出了提高反应速度的方法。     

由还原渣提取高纯氧化铥和氧化镥新工艺研究

研究了以铥、镱、镥富集物经金属镧热还原法提取金属镱后所得的还原渣为原料，经酸溶配料，用稀土硫酸钠复盐沉淀除去镧，滤液用Ｐ５Ｓ７萃淋树脂萃取色层法提取高纯氧化铥、氧化镱，氧化镥（纯度均大于９９．９５％），并获得较高的收率。确定了稀土硫酸钠复盐沉淀除镧和萃取色层法分离铥、镱、镥的最佳分离条件。     

氯离子对难处理金精矿生物预氧化-炭浸氰化的影响

高盐矿区往往缺乏淡水资源供生产使用。针对矿区盐水现状,进行高砷难处理金精矿生物氧化-氰化提金试验,考查不同氯离子浓度对硫化物氧化率、金浸出率等技术指标的影响。结果表明,氯离子浓度对金精矿生物氧化的不利影响随着浓度的升高而增强,氯离子浓度1.5 g/L以上时,硫化物的氧化率显著降低,10 g/L氯离子盐水生物氧化延长至18 d,砷浸出率88.4%,硫氧化率仅为35.3%。相同生物氧化渣在相同氰化条件下采用清水和10 g/L氯离子盐水进行氰化浸出时,盐水将降低金的浸出率。1.5 g/L、5 g/L氯离子盐水生物氧化10 d后的氧化渣采用10 g/L氯离子盐水氰化,金的浸出率分别比清水氰化时的分别低2.8、3.4个百分点。难处理金精矿生物氧化砷浸出率均高于硫氧化率,表明毒砂氧化率高于黄铁矿,金浸出率与毒砂氧化率的相关性较黄铁矿氧化率更加密切。     

同还原渣提取高纯氧化铥和氧化镥新工艺研究

研究了以铥、镱、镥富集物经金属镧热还原法提取金属镱石所得的还原渣为原料，经酸溶配料，用稀土硫酸钠复盐沉淀除去镧，滤液用Ｐ５０７萃淋树脂萃取色层法提取高纯氧化铥、氧化镱，氧化镥（纯度均大于９９．９５％），并获得较高的收率。确定了稀土硫酸钠复盐沉淀除镧和萃取色层法分离铥、镱、镥的最佳分离条件。     

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In order to accurately control the rare earth content in liquid steel in electroslag remelting (ESR) process, according to the ion and molecule coexistence theory (IMCT) of slag structure and corresponding phase diagrams, a thermodynamic calculating model for the evaluation of mass action concentrations (designated by Ni for structure unit i) for La2O3-Al2O3-CaF2 slag system was formulated. The results show that the calculated values of NLa2O3 are in good agreement with the reported measured values, indicating that this calculating model can wholly embody the characteristics of the slag system. The activity of La2O3 decreases with the increasing of the Al2O3 and CaF2 content, and Al2O3 is stronger than CaF2 in decreasing the activity of La2O3. But the activity of La2O3 increase with the increasing in temperature at the composition range of 30% La2O3, 20% Al2O3, 50% CaF2. Above all, the activity of La2O3 in La2O3-Al2O3-CaF2 slag system can be quantitatively analyzed by this thermodynamic model, and this model can provide a theoretical basis for precisely controlling the lanthanum content in molten steel in ESR process.     

Al_2O_3La_2O_3Y_2O_3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al2O3La2O3Y2O3/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al2O3/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y2O3、La2O3稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al2O3La2O3Y2O3/Cu材料的抗熔焊性和抗烧损性优于Al2O3/Cu材料的性能.在直流阻性负载条件下Al2O3La2O3Y2O3/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.     

La2O3含量及退火温度对钼合金晶粒尺寸及显微硬度的影响

本文研究了La2O3含量及退火温度对钼合金晶粒尺寸及显微硬度的影响规律,利用位错理论分析了La2O3对晶粒长大和显微硬度的影响机理。结果表明：随着第二相颗粒La2O3含量的增加,钼合金晶粒长大和再结晶的退火温度有升高的趋势;La2O3的强化效果并非随含量增加而线性增大,添加的La2O3含量处在0.27%～0.49%范围时,钼合金显微硬度的增幅最大,当La2O3含量大于0.49%时显微硬度增幅减小;随着退火温度的升高,钼合金显微硬度逐渐降低。     

Effects of Rare-Earth La2O3 Addition on Microstructures and Electrical Properties of SrTiO3 Varistor-Capacitor Dual Functional Ceramics

Generally, metal oxide varistors used for the pro tection of electrical circuits are based on ZnO andTiO2[1,2]. ZnO varistor, which is widely used due toits high non linearity coefficient, is composed of ZnOceramics with minor oxide additive…     

High thermal stable gold catalyst supported on La2O3 doped Fe2O3 for low-temperature CO oxidation

La2O3 doped Fe2O3 support was prepared by co-precipitation method,and gold was loaded by deposition-precipitation.Thermal stability of gold catalyst was enhanced considerably by La2O3 doping.Even when calcined at 500 oC for 12 h,the catalyst doped with La2O3 could convert 90% of CO at 28.9 oC,while the catalyst without La2O3 doping achieved 90% CO conversion at 43.5 oC.Characterization techniques,such as N2 adsorption-desorption,X-ray diffraction(XRD),transmission electron microscopic(TEM) and thermogravime...     

Catalytic Reduction of SO2 on CeO2-La2O3 Rare Earth Mixed Compounds

Adding rare earth oxide CeO2 with variable valences to La2O3 formed a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers were all γ-Al2O3, were used as the catalyst for the reduction of SO2 by CO. The activation process of this catalyst and the impact of temperature and reactant concentration on the activation process were investigated. Using X-ray diffraction, the structure characteristics of catalyst before and after reaction were analyzed to reveal the change of phase structure. The result shows that the rare earth oxide mixtures composing of CeO2 and La2O3, as the catalyst for the reduction of SO2 by CO, diminish activation temperature 50～100℃ less and have higher activity than a single oxide CeO2 or La2O3. The reason possibl is that La2O3 goes into in the lattice of CeO2 to form solid phase complex CeO2-La2O3 and increases the capability of CeO2-La2O3/γ-Al2O3 catalyst to store oxygen, which supplies the redox of CeO2 reaction with a better condition. At the same time, elemental sulfur formed in the redox reaction impels La203 to be transformed to activation phase La2O2S in a lower temperature, which can be explained with the synergism between redox reaction and COS intermediate mechanism reaction.     

Influence of La2O3 on crystallization behavior of free-fluoride mould flux and heat transfer of slag films

In order to research the influence of La2O3 on crystallization behavior of free-fluoride mould flux and the heat transfer of slag film,free-fluoride mould flux with various La2O3 content were investigated by using self-made mould simulator,comprehensive thermal analyzer and SEM-EDS.With the increase of La2O3 content from 0% to 20%,the crystallization ratios of mould flux films were improved from 2% to 90% and the thicknesses of films were also enhanced over two times.Moreover,crystallization temperature was greatly raised and its increasing extent reached 100 oC.It could also decrease the melting temperature of casting powder about 50 oC.However,the undissolved La2O3 particles appeared in slag film if the ratio of La2O3 in free-fluoride mould flux was much too high.     

La_2O_3掺杂对V_2O_5-WO_3/TiO_2催化剂SCR性能的影响

通过共沉淀法将La组分掺入到TiO_2载体中,采用浸渍法将V和W组分负载到La_2O_3-TiO_2复合氧化物上,制备出V2O5-WO3/La_2O_3-TiO_2催化剂。考察不同La_2O_3掺杂量对其NH3催化还原NO性能的影响,同时通过多种物理化学手段进行表征分析。XRD,NH_3-in situ DRIFTS,H_2-TPR,XPS和UV-vis DRS测试结果表明,元素La与Ti以La-O-Ti键相互作用,生成高度分散的镧物种,也使得TiO_2具有更好的热稳定性,但由于LaO_x物种与VO_x物种和WO_x物种之间的相互作用,降低了催化剂的氧化还原性和表面Brnsted酸数量,从而降低了其催化活性。     

Effect of Gd2O3 and La2O3 on BaTiO3 -Based Ceramics

The addition of rare-earth oxides Gd2O3 and La2O3 to BaTiO3-based ceramics can restrain the growth of grain size, which obtained small grain size below 1 μm and high density. The dielectric constant at room temperature increased and the curve of ε-T was flattened which illustrated that the ferroelectricity of BaTiO3-based ceramics was weakened. In addition, it is illustrated that Gd2O3 leads to chemical nonhomogeneous property, i.e. core-shell structure and La2 O3 leads to chemical homogenous property, which take different effects on capacitance- temperature characteristic.     

La2O3在空气中稳定性的研究

通过对 L a2 O3 粉末在空气中吸水的增重测定及增重前后的 X射线衍射结构分析 ,发现 L a2 O3 吸水之后转变成 L a(OH) 3 。因此 ,L a2 O3 是一种化学性质不稳定的化合物 ,从前文献中关于“L a2 O3 是一种化学性质稳定的氧化物”的观点值得商榷。