Effect of Purging Gas on Wetting Behavior of Sn-3.5Ag Lead-Free Solder on Nickel-Coated Aluminum Substrate

The wetting characteristics of Sn-3.5Ag lead-free solder alloy on nickel-coated aluminum substrates in air (ambient), nitrogen, and argon atmospheres were investigated. The contact angles for the solder alloy obtained under air and argon atmospheres were in the range of 36°-38°. With nitrogen atmosphere the contact angle was found to be significantly lower at about 26°. Solder solidifying in air exhibited needle-shaped tin-rich dendrites surrounded by a eutectic matrix. The amount of tin dendrites decreased in argon atmosphere. However, the morphology of tin dendrites transformed from needle-shaped to nearly non-dendritic shape as the soldering atmosphere was changed from air to nitrogen. The interfacial microstructures revealed the presence of Ni₃Sn and Ni₃Sn₄ IMCs at the interface. The enhanced wettability observed under nitrogen atmosphere is attributed to the higher thermal conductivity of nitrogen gas and the formation of higher amount of Ni₃Sn IMCs at the interface compared to air and argon atmospheres.     

Study on microstructure and its formation mechanism,and mechanical properties of TiB2–TiC laminated Ti(C5N5) composite ceramic cutting tool material

TiB₂–TiC laminated Ti(C₅N₅) composite ceramic cutting tool materials are prepared at the argon and vacuum sintering atmospheres respectively. The microstructure and mechanical properties of the composite are investigated. It is found that the composite includes the bulk and surface layer before sintering, while the new diffusion and transitional layers are formed after sintering. The Ni binder phase is rich in the diffusion layer, and the diffusion layer of the composite sintered at the vacuum atmosphere is narrower. The formation of layers is driven by the outward diffusion of the N element which results in the depletion of carbo-nitrides and the flowing of the melting Ni phase during the sintering. The composite exhibits the higher flexural strength and surface hardness than the monolithic Ti(C₅N₅) material. The Ni-rich diffusion layer acts as a tough subsurface in the composite, which can strengthen the effect of grain pulling-out as well as absorb the crack propagating energy. The flexural strength of the composite sintered at the vacuum atmosphere is slightly higher than at the argon atmosphere, while there are no obvious differences in the hardness and fracture toughness between these two composites.     

Nanostructured graphite-hydrogen system prepared by mechanical milling under hydrogen and argon atmospheres

Nanostructured graphite was prepared by mechanical milling under hydrogen and argon atmospheres. The hydrogen concentration in the sample prepared by miling under hydrogen atmosphere reaches up to 7.4 mass % (CH_0.95). Judging from the radial distribution function determined by the neutron diffraction measurement, there are two types of deuterium (hydrogen) coordinations. On the other hand, the hydrogen concentration does not exceed 0.5 mass % by the gas-phase hydrogenation for the sample prepared by milling under argon atmosphere. Part of this work was published in theApplied Physics Letters (American Institute of Physics), Volume 75, Page 3093–3095,15 November 1999; by S. Orimo, G. Majer, T. Fukunaga, A. Züttel, L. Schlapbach and H. Fujii     

Über die Oxidschichtbildung einer Titanlegierung während einer Li2O-haltigen Schutzgasbehandlung bei hohen Temperaturen

Oxide layer formation on a titanium alloy during a high temperature treatment in protective gas containing Li₂O The adhesion of an oxide scale can be improved considerably by the incorporation of Li₂O in the lattice of the growing scale. The oxide layer on Ti alloys generally consists of three zones, an external TiO₂, an intermediate Ti₂O₃ and an internal TiO zone. When, however, the oxidizing gas contains Li₂O, only two layers can be identified, viz. an internal TiO₂ layer (1/8 of the total oxide thickness) and an external Li₂TiO₃ layer. The latter is responsible for the good adhesion; it is obtained primarily in combustion gases obtained by near stoichiometric combustion of natural gas. In gases obtained by sub-stoichiometric combustion TiO₂ is formed perferentially and the adhesion of the oxide layer is low     

废弃SCR脱硝催化剂与废NaCl盐焙烧回收催化剂中的钛、钒、钨（英文）

通过废弃选择性催化还原(SCR)脱硝催化剂与废NaCl盐焙烧,可以将催化剂中的钨和钒与钛分离。在最佳浸出条件下(焙烧温度900℃,焙烧时间3 h,废盐与废催化剂的质量比为0.5,浸出温度80℃,反应时间60 min),钨和钒的浸出率分别达到84.63%和66.42%,同时钛的损失率仅为1.3%。废NaCl盐和焙烧温度可以促进锐钛矿型TiO₂转化为金红石型TiO₂,反应后得到了金红石型TiO₂。金红石型TiO₂中的钛的价态为四价,晶格氧和化学吸附氧分别占57.26%和42.74%。该方法可以同时解决2种废弃物的处置问题。     

CuCr25阴极材料在不同环境气氛下的电弧烧蚀行为及机理

研究了9 kV电压下CuCr25阴极材料在氧气、氩气和二氧化碳气氛下的电弧烧蚀行为。燃弧时间和电弧能量按照氧气、氩气、二氧化碳的环境气氛变化顺序依次减小,而击穿强度的变化趋势则相反。利用扫描电子显微镜和三维激光共聚焦显微镜分析了在电弧的高温、高能量作用下CuCr25材料表面形成的熔池、凸起、孔洞、飞溅和裂纹等烧蚀形貌。结果表明：CuCr25材料在氧气中烧蚀得最严重,在二氧化碳中电弧烧蚀最轻微,这可能与电弧能量的差异有关。X射线光电子能谱分析结果显示,在氧气和二氧化碳中电弧烧蚀表面发生氧化反应,生成了CuO、CrO₃和Cr₂O₃,而在氩气环境中没有新的化合物形成。     

Influence of calcination atmosphere on photocatalytic reactivity of K2La2Ti3O10 for water splitting

The layered perovskite type oxide K2La2Ti3O10 powders were prepared under air, Ar and H2 calcination atmospheres by sol-gel method and characterized by X-ray diffractometry, UV-Vis diffuse reflectance and X-ray photoelectron spectroscopy. The influence of the calcination atmosphere on the photocatalytic reactivity of K2La2Ti3O10 for hydrogen production was investigated. The photocatalytic reactivity of K2La2Ti3O10 prepared under air, Ar and H2 atmospheres was compared with that prepared under ultraviolet and visible light radiation using Г as electronic donor. The results show that K2La2Ti3O10 prepared under Ar and H2 atmospheres has higher photocatalytic activity for hydrogen production than that prepared under air atmosphere. The hydrogen production rates under ultraviolet irradiation are 127.5, 81.3 and 57.0 μmol/（L·h） and those under visible light irradiation are 40.2, 30.2 and 16.5 μmol/（L2h） respectively when K2La2Ti3O10 is prepared under Ar, H2 and air atmospheres.     

Microstructure, dielectric and ferroelectric properties of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (NBTB) and 0.05BiFeO3-0.95NBTB ceramics: Effect of sintering atmosphere

0.94Bi_0.5Na_0.5TiO₃-0.06BaTiO₃ (NBTB) and 0.05BiFeO₃-0.95NBTB (BF-doped NBTB) lead-free ceramics were prepared by solid state reaction method. The ceramics were sintered at 1180 °C for 2 h in O₂ and N₂. All ceramics exhibited a single phase of perovskite structure. Relative amount of tetragonal phase was related to the sintering atmospheres. Both grain size and shape were influenced by the sintering atmospheres. Sintering the ceramics in N₂ weakened their dielectric anomalies corresponding to the transition from ferroelectric phase to the so-called “intermediate phase”. When the NBTB and BF-doped NBTB ceramics were sintered in N₂, their maximum dielectric constant and the degree of diffuseness of the transition from the “intermediate phase” to paraelectric phase increased, but their Curie temperatures decreased. The difference in dielectric properties of the ceramics sintered in different atmospheres was closely related to the difference in oxygen vacancy concentration. The correlation between ferroelectric properties and sintering atmospheres is associated with a competing effect among oxygen vacancy concentration, A-site vacancy concentration and percentage of tetragonal phase.     

钛沉积工艺制备TiN/cBN和TiC/金钢石涂层颗粒(英文)

用钛熔盐沉积及热处理工艺分别制备碳化钛涂覆的立方碳化硼颗粒(TiN/cBN)及碳化钛涂覆的金刚石颗粒(TiC/金刚石)。将cBN或金刚石颗粒分别与钛粉和KCl、NaCl和K2TiF6熔盐混合。将所得混合物在Ar气氛中加热至900°C,然后在H2气氛中于1000°C进行热处理。采用扫描电镜、X射线衍射和聚焦离子束技术对所制得颗粒进行表征。结果表明:cBN和金刚石颗粒表面已覆盖了纳米钛层。对Ti/cBN和TiC/金刚石涂层颗粒进行热处理后,颗粒表面沉积的Ti层与cBN和金刚石颗粒发生了原位化学反应,分别转化为钛化合物TiN和TiC。     

Ti-42Al-8Nb合金氧化膜的XPS研究

以Ti-42Al-8Nb(at%)合金为研究对象,将其置于900℃空气气氛中氧化20 h,重点采用XPS手段对合金表面氧化膜结构、相组成及成分分布进行了分析。结果表明:合金经20 h氧化后,XRD结果显示氧化膜主要由Al_2O_3和Ti O_2混合物组成,而经XPS结果分析可知氧化膜最外层只有Ti O_2一种物质,次外层由Al2O3、3种不同价态的Ti氧化物及少量Ti N组成,且沿基体到外表层的方向,Ti的高价氧化物含量逐渐增多,最外表面只有Ti O_2,另外2种低价Ti氧化物含量为零,说明整个系统通过O原子的溶解、扩散完成氧化过程,导致氧化反应随时间和样品深度发生阶段性变化,从而使氧化膜沿深度方向表现出物质种类及其含量的不同。     

Sample thickness dependence of giant magnetoimpedance under low fields for La0.67Sr0.33Mn0.98Co0.02O3 manganites

The La_0.67Sr_0.33Mn_0.98Co_0.02O₃ plate sintered at 1250 °C shows a low field magnetoresistance (LFMR) effect under fields H < 4.6 kOe. However, the DC magnetoresistance ΔR/R₀ is very small, only −1.84% under H = 4.6 kOe. The character of helical growth was observed on grain surface of La_0.67Sr_0.33Mn_0.98Co_0.02O₃ phase. The LFMR is connected with the interface of grain or grain boundary, while the giant magnetoimpedance under low fields for La_0.67Sr_0.33Mn_0.98Co_0.02O₃ sintered plates strongly depends upon the plate thickness. With an increase of sample thickness, the magnetoimpedance increases and the frequency, where the maximum magnetoimpedance occurs, shifts to low frequencies. A giant magnetoimpedance of −15.6% and a large AC magnetoresistance of −30.5% could be obtained under a very small field H = 600 Oe for the plate with a thickness of 3 mm.     

Effects of La content on the properties of Ba1−xLaxTiO3 powders prepared by spray pyrolysis

Nano-sized Ba_1?xLa _x TiO₃ (0 ≤ x ≤ 0.03) powders were prepared by ultrasonic spray pyrolysis from the spray solution with citric acid. The mean sizes of the primary particles decreased from 110 nm to 59 nm when the x of the Ba_1?xLa_xTiO₃ powders was changed from 0 to 0.03. The BET surface areas of the powders changed from 9.1 m²/g to 16.9 m²/g. The pure BaTiO₃ and La-doped BaTiO₃ powders had both tetragonal and cubic crystal structures. The average grain size of the sintered BaTiO₃ specimen was 2.8 µm, while those of the La-doped BaTiO₃ pellets ranged from 1.04 µm to 0.68 µm according to the doping concentrations of La. The dielectric constant of Ba_1?xLa_xTiO₃ (0.01 ≤ x ≤ 0.03) pellets ranged from 2500 to 3855 when sintered at 1280 °C.     

Synthesis and characterization of lithium-carbon compounds for hydrogen storage

Three carbon materials were prepared for the synthesis of Li-C compounds, such as Li intercalated graphite. The materials were as-received high purity polycrystalline graphite (G), graphite milled under a hydrogen atmosphere (HG), and graphite milled an argon atmosphere (AG). With respect to the difference for them, HG preserved a better crystalline structure than AG. Each material was milled with Li, where the products are denoted as Li-G, Li-HG, and Li-AG. In XRD patterns of Li-G and Li-HG, the peaks corresponding to LiC₆ and LiC₁₂ were revealed, while no peaks were observed in the case of Li-AG. However, the formation of lithium carbide Li₂C₂ was suggested for Li-AG by a thermal analysis under an inert gas. After the hydrogenation, LiH was formed for all the compounds, and graphite was recovered for Li-G and Li-HG. Each hydrogenated compound desorbed H₂ with different profile by heating up to 500 °C. As a reaction product, Li₂C₂ was formed for the hydrogenated Li-HG and Li-AG. In the case of the hydrogenated Li-G with better crystalline structure, Li intercalated graphite were formed after the dehydrogenation. Therefore, it is concluded that the hydrogen absorption and desorption process of Li intercalated graphite was different from those of Li₂C₂.     

On the use of TiO2 in Ti(C,N)-WC/Mo2C-(Ta,Nb)C-Co/Ni cermets

In this study, Ti(C,N)-WC/Mo₂C-(Ta,Nb)C-Co/Ni cermets with varying [Mo]/([W] + [Mo]) mole ratios and constant [W] + [Mo] content were prepared by using TiO₂ and carbon as substitutes for a part of Ti(C,N). In situ carbothermal reaction took place with subsequent liquid phase sintering. The thermal behavior and outgassing behavior were conducted using differential thermal analysis/thermal gravity analysis (DTA-TG) and mass-spectrometric evolving gas analysis (MS-EGA). The microstructure was investigated by scanning electron microscopy (SEM). After being sintered in N₂ atmosphere, cermets without TiO₂ additions generally showed rimless microstructures with black grains independently distributed from other phases, whereas the cermets with TiO₂ addition showed complete core-rim microstructures. The average grain size generally decreased with increasing Mo content, and increased with increasing TiO₂ substitution. Moreover, the average grain size increased with decreased N₂ pressure from 50 mbar to 10 mbar at any [Mo]/([Mo] + [W]) ratio. The most interesting result was for the Mo-free cermets with 5 mol% TiO₂ and 10 mol% TiO₂ addition sintered in 50 mbar N₂: both the hardness and fracture toughness increased compared with the cermets without TiO₂ addition. The HV-K_IC behavior of the majority of the cermets was superior to the industrial grades.     

Kinetics of interaction of Mg-based mechanically activated alloys with hydrogen

Parameters of interaction of hydrogen with magnesium powders and structure of powder magnesium alloys alloyed with different metals and oxides (such as Fe, Ni, Al, Cu, Ti, Pd, NiPd, V₂O₅, and VH₂) prepared by mechanical activation under either argon or hydrogen atmosphere in a vibration mill have been studied. The mechanically activated alloys absorb to 7 wt% hydrogen at 300°C for 20 min. For most of the additions used, the effect of the grain size and type of addition on the rate of hydrogen absorption was found to manifest itself only at the stage of the formation of the MgH₂ phase upon mechanical activation in the hydrogen atmosphere; virtually no effect is observed upon subsequent hydrogenation. The temperature of the hydrogen desorption also depends only slightly on the addition kind. The increase in the hydrogenation rate of the Mg-based alloys resulting from the mechanical activation was shown to be due to the formation of a specific structural state of the particle surface, which exhibits a high catalytic activity for the hydrogen sorption. A study of the mechanically activated alloys by proton nuclear magnetic resonance showed a substantial increase in the rate of proton spin-lattice relaxation as compared to that observed for MgH₂ produced by direct hydrogenation. This can be due to the interaction of protons with paramagnetic centers formed at the imperfect surface of mechanically activated Mg particles.     

Effects of the lanthanum content on the microstructure and properties of the molybdenum alloy

The effects of the lanthanum content on the microstructure and properties of molybdenum alloy were investigated. The molybdenum powders with various lanthanum contents were prepared by a solid-liquid doping method and reduction under hydrogen atmosphere, which could be processed into sintered molybdenum and rotary swaged molybdenum. The results indicated that the grain sizes of the alloys became finer and the tensile strength increased with increasing La content. The La₂O₃ particles could adsorb impurity elements that existed on the grain boundary and generate the amorphous structure around the particle. The rotary swaged Mo with 0.1 wt.% La was the highest tensile strength, and the rotary swaged Mo with 0.03 wt.% La possessed the highest elongation to failure of 42%. In addition, the electrical resistivity of the rotary swaged Mo increased at first and later decreased with increasing La content.     

Synthesis and characterization of La2Ti2O7 employed for photocatalytic degradation of reactive red 22 dyestuff in aqueous solution

Perovskite structured La₂Ti₂O₇ catalyst prepared by polymerized complex method was characterized and examined the photocatalytic activity by decomposing an azo dyestuff, Reactive Red 22, in aqueous solutions under UV irradiation. La₂Ti₂O₇ powders prepared by polymerized complex method exhibit higher surface areas, better homogeneity and are more sensitive to solution than those prepared by solid-state method. The first derivatives of UV–vis DRS patterns confirmed the complete crystallization of La₂Ti₂O₇ sintered at temperatures higher than 900 °C. The effects of sintering temperature of catalyst and solution pH of photocatalytic reaction were studied. The photocatalytic decomposition of Reactive Red 22 per unit surface area was found to be higher for experiments using La₂Ti₂O₇ than using TiO₂. However, the electron–hole recombination was found to be more obvious for La₂Ti₂O₇ than for TiO₂ because the network of metal cations constructed within La₂Ti₂O₇ enhances the mobility of photogenerated electrons and holes.     

Sinterability and dielectric properties of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 composite ceramics

The composite ceramics of Ba_0.55Sr_0.4Ca_0.05TiO₃-CaTiSiO₅-Mg₂TiO₄ (BSCT-CTS-MT) were prepared by the conventional solid-state route. The sintering performance, phase structures, morphologies, and dielectric properties of the composite ceramics were investigated. The BSCT-CTS-MT ceramics were sintered at 1100 °C and possessed dense microstructure. The dielectric constant was tailored from 1196 to 141 as the amount of Mg₂TiO₄ increased from 0 to 50 wt%. The dielectric constant and dielectric loss of 40 wt% Ba_0.55Sr_0.4Ca_0.05TiO₃-10 wt% CaTiSiO₅-50 wt% Mg₂TiO₄ was 141 and 0.0020, respectively, and the tunability was 8.64% under a DC electric field of 8.0 kV/cm. The Curie peaks were broadened and depressed after the addition of CaTiSiO₅. The optimistic dielectric properties made it a promising candidate for the application of tunable capacitors and phase shifters.     

锂离子吸附剂(H2TiO3)的合成及吸附性能

选取TiO2为钛源、Li2CO3为锂源,采用高温固相法合成锂吸附剂前躯体Li2TiO3,并探讨锂钛比、焙烧温度、焙烧时间等因素对合成Li2TiO3性质的影响.将Li2TiO3用一定浓度的盐酸酸洗脱锂后制得偏钛酸型锂吸附剂H2TiO3,酸洗过程中锂的抽出率达到98.86％,而离子筛中的钛溶损却很小.采用XRD和SEM等分析手段对TiO2、Li2TiO3和H2TiO3及其吸附锂后的样品进行表征.最后应用伪一级和伪二级动力学方程对H2TiO3的吸附性能进行研究,并对吸附过程进行拟合从而计算相应的速率常数.结果表明:H2TiO3对锂离子具有较大的吸附能力,吸附过程符合伪二级动力学方程,表明吸附过程主要为化学吸附:在LiCl溶液中的吸附平衡数据符合Langmuir 等温吸附方程,表明吸附过程为单层吸附.     

Effect of rapid quenching on the microstructure and electrochemical characteristics of La_（0.6）Ce_（0.4）Ni_（3.6）Co_（0.65）Mn_（0.4）Al_（0.2）Ti_（0.05_（FeB）_（0.1） hydrogen storage alloy

In order to improve the cycling stability of AB₅ type alloy electrodes, rapid quenching technology and new alloy composition design were employed. A hydrogen storage alloy with nominal composition La_0.6Ce_0.4Ni_3.6Co_0.65Mn_0.4Al_0.2Ti_0.05(FeB)_0.1 was prepared by vacuum magnetic levitation melting under high purity argon atmosphere, followed by rapid quenching at different cooling rates. XRD results show that all alloys exhibit the single-phase CaCu₅-type structure. Electrochemical tests indicate that rapid quenching can slightly improve the cycling life of the alloy. Nevertheless, the high-rate dischargeability of the quenched alloys is lower than that of the as-cast alloy.