2005年中国钽铌工业的统计与分析

2005年，世界钽铌工业总需求保持稳步增长。在世界消费类电子产品持续增长的带动下，中国钽铌工业也出现了明显的增长势头，总产值达到14．42亿元，与2004年比增长了11．09％。宁夏东方有色金属集团有限公司开发的150000μFV/g电容器级钽粉已供用户试用，并且研制出了适合目前铌电容器使用的80000～100000μFV/g高比容铌粉及NbO粉。2005年，世界铌粉、丝、制品市场需求呈现大幅增长，中国电容器级钽粉、丝的出口量都达到了总产量的85％以上，加工制品出口量也达到了75％以上。     

介孔磷酸铌一锅法催化葡萄糖制备5-羟甲基糠醛

水热法制得介孔磷酸铌(m-NbP)固体酸催化剂,并用X-射线衍射(XRD)、氮气吸脱附、扫描电镜(SEM)、透射电镜(TEM)、氨气程序升温脱附(NH_3-TPD)、吡啶吸附红外光谱(Py-FTIR)等手段对m-NbP进行了结构和酸性质表征。将m-NbP用于催化水-DMSO两相体系葡萄糖一锅法合成5-羟甲基糠醛(5-HMF),考察了催化剂用量、水与DMSO体积比、反应温度、反应时间及催化剂循环利用次数对5-HMF收率的影响,并与其他三种催化剂(Amberlyst-15、Nb_2O_5及m-NbP-F127)比较催化性能。结果表明,m-NbP具有介孔结构和大量表面强酸性位,因而催化性能突出;当m(葡萄糖)∶m(m-NbP)=2∶1、V(水)∶V(DMSO)=1∶1、170℃反应1.5 h时,5-HMF的收率高达47.0%,且m-NbP经烧焦再生可重复利用5次而无明显失活。因此,m-NbP固体酸催化性能突出,能够高效催化葡萄糖一锅法制备5-HMF。     

Conductive Nanocrystalline Niobium Carbide as High‐Efficiency Polysulfides Tamer for Lithium‐Sulfur Batteries

Rational design of functional interlayer is highly significant in pursuit of high‐performance Li‐S batteries. Herein, a nanocrystalline niobium carbide (NbC) is developed via a facile and scalable autoclave technology, which is, for the first time, employed as the advanced interlayer material for Li‐S batteries. Combining the merits of strong polysulfides (PS) anchoring with high electric conductivity, the NbC‐coated membrane enables efficiently tamed PS shuttling and fast sulfur electrochemistry, achieving outstanding cyclability with negligible capacity fading rate of 0.037% cycle^?1 over 1500 cycles, superb rate capability up to 5 C, high areal capacity of 3.6 mA h cm^?2 under raised sulfur loading, and reliable operation even in soft‐package cells. This work offers a facile and effective method of promoting Li‐S batteries for practical application.     

Synthesis and microwave dielectric properties of new high quality Mg2NdNbO6 ceramics

New high‐quality microwave dielectric ceramics Mg₂NdNbO₆ were prepared by conventional solid‐state sintering method. The phases, micro‐structures and microwave dielectric properties of Mg₂NdNbO₆ ceramics were investigated at sintering temperature in the range of 1275°C‐1400°C. The X‐ray diffraction patterns showed that the peaks of the compounds were attributed to two phases, including the main crystalline phase of NdNbO₄ that was indexed as the monoclinic phase and MgO as the second phase. Well‐developed microstructures of Mg₂NdNbO₆ ceramics can be achieved, and the grain size reached the maximum value (1.63 μm) at 1375°C. As the sintering temperature increased, the dielectric constant, temperature coefficient of resonant frequency and apparent density remained almost unchanged, however, the significant change in the quality factor was observed. At 1375°C, Mg₂NdNbO₆ ceramics possessed excellent microwave dielectric properties: ε_r = 16.22, Q × f = 116 000 GHz and τ_f = ?30.96 ppm/°C.     

High niobium oxide content in germanate glasses: Thermal,structural, and optical properties

Niobium alkali germanate glasses were synthesized by the melt‐quenching technique. The ternary system (90‐x)GeO₂–xNb₂O₅–10K₂O forms homogeneous glasses with x ranging from 0 to 20 mol%. Samples were investigated by DSC and XRD analysis, FTIR and Raman spectroscopy, and optical absorption. Structural and physical features are discussed in terms of Nb₂O₅ content. The niobium content increase in the glass network strongly modifies the thermal, structural and optical properties of alkali germanate glasses. DSC, Raman and FTIR analysis suggest niobium addition promotes NbO₆ groups insertion close to GeO₄ units of the glass network. XRD analysis also pointed out that samples containing high niobium oxide contents exhibit preferential niobium oxide‐rich phase after crystallization after heat treatment, which is similar to orthorhombic Nb₂O₅. Absorption spectra revealed high transmission range between 400 nm to 6.2 μm, added to a considerably decreased hydroxyl group content as the addition of niobium in the alkali germanate network. The niobium oxide‐rich phase crystallization process was studied and activation energy was determined, as well as nucleation and crystal growth temperatures and time for obtaining transparent glass‐ceramics.     

Ammonium complex of niobium as a precursor for the preparation of Nb2O5/Al2O3 catalysts

Ammonium oxalate complex of niobium was investigated as an aqueous precursor for the preparation of x% Nb₂O₅/Al₂O₃ (x=5, 10, 20 and 30 wt.%) samples. Catalysts with the same Nb₂O₅ contents were also prepared from the traditional niobium oxalate/oxalic acid aqueous solution. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), infrared spectroscopy of chemisorbed pyridine and X-ray photoelectron spectroscopy (XPS). A comparison with the preparation method using the niobium oxalate salt was performed. The results showed that the niobium precursor influence the species growing leading to phases with different reducibility. The XPS revealed the presence of multilayers of niobium oxide on the Nb₂O₅/Al₂O₃ samples prepared by using niobium ammonium oxalate complex, while the ones obtained from niobium oxalate led to Nb₂O₅ particles islands. The addition of niobium oxide decreased the fraction of Lewis acid sites and increased the fraction of Brønsted acid sites, independent of the precursor salt. However, the creation of BAS was more pronounced on the Nb₂O₅/Al₂O₃ samples prepared from niobium oxalate.     

Crystallization of Li2O · Al2O3· 6SiO2 Glasses Containing Niobium Pentoxide as Nucleating Dopant

Niobium pentoxide (T form, orthorhombic system) was utilized to promote devitrification in Li₂O · Al₂O₃· 6SiO₂ glasses. Two or more mole percentage of this nucleating dopant enhanced crystallization in these glasses. Glasses containing 4.0 and 8.0 mol% T-Nb₂O₅ exhibited a high tendency to form dispersed TT-Nb₂O₅ (monoclinic system) precipitates during the glass quenching process. The crystallization process in glasses containing 2.0 or 4.0 mol% T-Nb₂O₅ occurred as microphase separation, followed by the formation of dispersed TT-Nb₂O₅ crystalline precipitates (760°C), followed by β-quartz solid-solution ( ss ) formation (850° to 900°C) heterogeneously nucleated from the precipitates. β-quartz( ss ) transformed to β-spodumene( ss ), along with a polymorphic transition from the TT-Nb₂O₅ to M-Nb₂O₅ (tetragonal system) crystalline phase.     

碳、铌对ASME S30432奥氏体耐热钢晶间腐蚀性能的影响

研究了碳、铌含量对ASME S30432钢晶间腐蚀性能的影响.结果表明:当碳含量在0.058%～0.110%变化时,随碳含量增加该钢的晶间腐蚀敏感性增加,易发生晶界腐蚀;铌含量由0.30%增加到0.70%对抗晶间腐蚀性能有改善,含碳量对晶间腐蚀的影响比铌明显;铌含量与碳含量的比值至少在5.8以上才可能对晶间腐蚀有抑制作用.     

Very low voltage sputter coating

Very low voltage sputter coating, in the range 175–300 V, has been used to produce finely structured thin films of noble and refractory metals for use in high resolution scanning electron microscopy. There is a marked diminution in the particle size with a decrease in cathode voltage. Although the sputtering times are longer than with conventional diode sputter coating, such times are shorter than those required to produce similar films by Penning or ion-beam sputtering. The refractory metals produce films which are fine grained and suitable for high resolution studies. The method has been used to sputter coat thin layers of aluminium. All attempts at sputtering carbon have failed; the reasons for this are discussed in some detail.     

钛合金与铌合金电子束焊温度场数值模拟

钛合金与铌合金是具有优良使用性能的两种合金材料,这两种材料被广泛用于航空、航天、核工业等重要领域.文中采用有限元分析软件ANSYS,对钛合金与铌合金电子束焊的温度场进行了模拟研究,利用双热源模型模拟电子束焊温度场,研究了异种金属焊接的建模方法、函数载荷的加载技巧,着重分析了钛合金(7715D)和铌合金(C-103)的焊接性,采用热源向铌一侧偏置的方法来保证焊接熔深的一致.最后得到了不同焊接热输入条件下钛合金与铌合金焊接过程中的最佳偏置距离.