Preparation, Characterisation and Catalytic Behaviour of a New TeVMoO Crystalline Phase

TeM_xMo_1.7O mixed oxides (M = V and/or Nb; x = 0-1.7) have been prepared by calcination of the corresponding salts at 600 °C in an atmosphere of N₂. A new crystalline phase, with a Te/V/Mo atomic ratio of 1/0.2-1.5/1.7, has been isolated and characterised by XRD and IR spectroscopy. This phase is observed in the TeVMo or TeVNbMo mixed oxide but not in the TeNbMo mixed oxide. The new crystalline phase shows an XRD pattern similar to Sb₄Mo₁₀O₃₁ and probably corresponds to the M1 phase recently proposed by Aouine et al. (Chem. Commun. 1180, 2001) to be present in the active and selective MoVTeNbO catalysts. Although these catalysts present a very low activity in the propane oxidation, they are active and selective in the oxidation of propene to acrolein and/or acrylic acid. However, the product distribution depends on the catalyst composition. Acrolein or acrylic acid can be selectively obtained from propene on Nb-free or Nb-containing TeVMo catalysts, respectively. The presence of both V and Nb, in addition to Mo and Te, appears to be important in the formation of acrylic acid from propene.     

碲粉涂料防止铸件渗漏作用的探讨

介绍用碲涂料解决铸件渗漏的方法,对碲粉涂料防渗漏的作用形式、机理进行了探讨,并指出一些使用中的注意事项.     

基于改进粒子群算法的后向泵浦RFA设计北大核心CSCD

为了满足第六代移动通信(6G)系统对光通信网络的高速率及大容量的要求,进一步提高光传输网络中光纤放大器的带宽、响应速率及放大倍数等成为目前的研究重点。在使用碲酸盐光纤作为光纤增益介质的同时,提出一种改进粒子群优化算法,通过在迭代过程中动态的调整速度、位置及惯性权重值,获得更高收敛速度,增强全局搜索的能力。应用该算法对拉曼光纤放大器的各个泵浦光参数配置进行优化、分析及仿真验证,最终设计出平均开关增益为23.738 8 dB,增益平坦度为0.209 8 dB的后向泵浦拉曼光纤放大器。结果表明,改进的粒子群优化算法对拉曼放大器泵浦光的参数配置有很强的适应性,能够获得较低的增益平坦度,对未来拉曼光纤放大器的设计具有一定的参考意义。     

Optical properties of samarium doped zinc-tellurite glasses

Glasses with the composition, (Sm₂ O ₃) _x (ZnO)_(40-x)(TeO ₂)₍₆₀₎, were prepared by conventional melt quenching method. The density, molar volume, and optical energy band gap of these glasses have been measured. The refractive index, molar refraction and polarizability of oxide ion have been calculated by using Lorentz-Lorentz relations. Optical absorption spectra of these glasses were recorded in the range 300–700 nm at room temperature. The oxide ion polarizabilities deduced from two different quantities, viz. refractive index and optical energy band gap, agree well compared with other glasses. The nonlinear variation of the above optical parameters with respect to samarium dopant has been explained.     

A Generalized Crystallographic Description of All Tellurium Nanostructures

Despite tellurium being less abundant in the Earth's crust than gold, platinum, or rare‐earth elements, the number of industrial applications of tellurium has rapidly increased in recent years. However, to date, many properties of tellurium and its associated compounds remain unknown. For example, formation mechanisms of many tellurium nanostructures synthesized so far have not yet been verified, and it is unclear why tellurium can readily transform to other compounds like silver telluride by simply mixing with solutions containing silver ions. This uncertainty appears to be due to previous misunderstandings about the tellurium structure. Here, a new approach to the tellurium structure via synthesized structures is proposed. It is found that the proposed approach applies not only to these structures but to all other tellurium nanostructures. Moreover, some unique tellurium nanostructures whose formation mechanism are, until now, unconfirmed can be explained.     

氯化亚锡还原-分光光度法测定铅铋合金中痕量碲

在铅铋合金中,使用SnCl₂还原Te时,Cl^—与溶液中大量存在的Pb²⁺生成PbCl₂沉淀,对其中痕量Te的分析产生严重的干扰。实验选用HCl去除大量Pb²⁺,利用SnCl₂在酸性介质中具有较强的还原性,使溶液中Te⁴⁺还原为Te单质,吸收一定波长的光,以此建立了分光光度法测定铅铋合金中痕量Te的方法。试验讨论了酸性体系的选择、HCl浓度、SnCl₂溶液加入量、显色温度、测量时间等对吸光度的影响。实验表明,在3.0 mol/L HCl体系中加入0.4 mL 0.1 g/mL SnCl₂溶液,30 ℃保温15 min后测量,显色体系在410 nm波长下的吸光度保持稳定,稳定时间超过60 min。Te在0.1~50 μg/g范围内服从比尔定律,校准曲线线性相关系数(r)为0.999 8,表观摩尔吸光系数为7.16×10³ L·mol^-1·cm^-1,Te的检出限为0.06 μg/g,定量限为0.20 μg/g。按照实验方法测定铅铋合金中Te,结果的相对标准偏差(RSD,n=6)为0.040%~1.3%,加标回收率为97%~106%,测定值与电感耦合等离子体质谱法(ICP-MS)结果基本一致。     

ICP-AES测定酸泥中硒碲含量

研究建立了王水溶样—电感耦合等离子体原子发射光谱测定酸泥中硒、碲含量的分析方法,通过实验对仪器工作参数、分析线的选择等进行了研究,确定了合适的分析线和仪器分析条件,并对本方法进行了精密度和准确度实验。实验结果显示,硒的相对标准偏差(RSD,n=7)为1.40%~1.67%,加标回收率为99.4%~107.7%,碲的相对标准偏差(RSD,n=7)为1.82%~2.44%,加标回收率为95.0%~104.0%,满足样品中硒、碲分析测定要求。     

碲阳极泥的控制及处理方法

碲电积精炼过程产生碲阳极泥,其碲含量占到总碲量的3%~20%,导致碲的直收率降低。碲阳极泥的主要成分是高碲酸钠,由阳极产生的氧气将部分亚碲酸钠氧化形成的难溶疏松颗粒状或片状结晶,大部分沉降到槽底,少量粘附在阴极板面。高价碲盐在结晶长大、沉降、粘附过程中会夹带低价态碲盐,加大碲的损耗。采取改变阳极结构、在阳极套涤纶布袋、在电解液中加入适量还原剂、增加排氧设施和用热碱液搅拌洗涤出槽阳极泥的措施,阳极泥中的碲含量可控制到3%以下,最优指标达到1.5%。碲阳极泥的主要处理方法有酸浸自还原法、混酸酸溶置换法和硫化还原法,处理方法各有优劣,可以根据实际的现场工艺进行选择。