Investigation of the microhardness and the electrical resistivity of undercooled Ni-10 at.% Si alloys

Ni-10 at.% Si alloys (Ni and Si of purity of 99.99%) were prepared by arc melting method under argon atmosphere in a water-cooled copper hearth with a non-consumable tungsten electrode and titanium getter. Spherical-shaped Ni-10 at.% Si alloy melts are undercooled in a containerless electromagnetic levitation apparatus. The effects of undercooling (ΔT) on the microstructure, electrical resistivity (ρ) and microhardness (HV) were investigated. The experimental results reveal that with the increase of the undercooling of the melts from 16 to 110 K, the microstructures undergo transition from coarse dendritic morphology to ultra fine dendritic morphology. The measurements of microhardness of the samples were performed by using a microhardness test device. The dependence of microhardness on undercooling was analyzed and it has been found that with increasing the undercooling the HV increases. Variations of electrical resistivity of the Ni-10 at.% Si alloy with the temperature in the range of 300-800 K were also determined by using a standard d.c. four-point probe technique. The resistivity of samples increases with increasing temperature and undercooling.     

金刚石膜热沉金属化Ti/Ni/Au体系的研究

利用电子束蒸镀实现了Ti/Ni/Au多层膜在CVD金刚石膜上的金属化,并研究了预处理和后处理工艺对多层膜在基底上结合的影响,发现高温预处理对多层膜和基底的结合有明显的改善.参照国标GJB 126-86进行了热循环试验,未发现多层膜从金刚石膜脱落.利用背散射谱研究了Ti/Ni/Au金属化体系在真空中分别加热400℃和500℃,60 min 金属层的热稳定性.结果发现:优化工艺金刚石膜和金属层间的良好结合和稳定性满足金刚石膜热沉应用的要求.     

A positron study on the effect of As,Sb, W,and Ti on the annealing of defects in cold-rolled Ni

The peak height of the 2γ-angular correlation curve is measured as a function of the sample temperature during time linear heating of cold-rolled Ni dilute alloyed with Sb, As, W or Ti (0.03 to 1.4 at.%). The effect of these foreign elements on the annealing of defects is very different. In Ni alloyed with As or Sb the formation of a large number of three-dimensional vacancy clusters is observed indicated by a strong increase of the peak height. Obviously As and Sb atoms act as nucleation centres for the vacancy clustering. The addition of W to Ni leads to a shift of the vacancy annealing to higher temperatures. In Ni alloyed with Ti relative smooth peak height recovery curves are observed. Positron lifetime measurements show that no vacancy clusters are formed. The effect of the impurities on the vacancy annealing correlates with their binding enthalpy for vacancies in Ni.     

Investigation of metal–GaN and metal–AlGaN contacts by XPS depth profiles and by electrical measurements

Metal/GaN Schottky contacts have been studied by X-ray photoelectron spectroscopy (XPS). Au/GaN, Pt/GaN, Pd/GaN are sharp while Ti/GaN is diffuse with the following composition, starting from the surface: Ti+TiN, Ti+Ti_xGa_yN, Ti+Ti_xGa_yN+Ga, GaN+Ga. Au/AlGaN and Ni/AlGaN contacts are much broader than Au/GaN: Al and Ga are found more than 100 Å away from the interface. Schottky barrier height was measured for the Au/GaN, Pd/GaN, Pt/GaN, Au/AlGaN and Ni/AlGaN contacts.     

Positron lifetime study in BaTiO3 ceramics with different Ba/Ti ratios

The positron lifetime spectra in 0.25 at.% La-doped BaTiO₃ with different Ba/Ti ratios have been measured at room temperature. It was found from the experiments that with deviating from exact stoichiometry the positron lifetime τ₂ decreases and the intensity I₂ increases for Ba/Ti ratio smaller than stoichiometric and they have more significantly similar changes for Ba/Ti ratio larger than stoichiometric. The non-monotonic dependence of positron lifetime parameters on Ba/Ti ratio is regarded as that the τ₂ component is contributed together by positrons annihilating at the grain boundaries and Ba vacancies and/or Ti vacancies, and small deviations from exact stoichiometry would be expected to increase the concentration of defects such as Ba vacancies for Ba/Ti < and Ti vacancies for Ba/Ti > 1.     

Specific Features of the Atomic Structure of Ti50Ni25Cu25 Alloy Rapidly Quenched from Melt

Crystallography Reports - A complex study of the structure of Ti50Ni25Cu25 alloy obtained in the initial amorphous state by rapid quenching (melt spinning) have been performed for the first time....     

Flux growth and characterization of Ti‐ and Ni‐doped forsterite single crystals

Forsterite monocrystals doped with Ti and Ni were grown by the flux growth technique. A suitable mixture of flux (MoO₃, V₂O₅, Li₂CO₃) and nutrient was slowly cooled down to 750 °C from 1250 °C or 1350 °C. The crystals were then characterized by powder and single‐crystal X‐ray diffraction, scanning electron microscopy and differential scanning calorimetry (DSC). Variations observed in crystal size were attributed by both the varying experimental conditions in which they had been obtained, and to the amount of Ni substituted for Mg in the structure. High abundances of doped forsterite required a cooling rate of 1.8 K h^‐1. These synthetic, well‐characterized Ti and Ni doped forsterite crystals may have potential for exploitation in industrial fields. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Zur Diffusion von Hf und Ti in Ni

The diffusion coefficients and solubilities of Hf in Ni were measured with the electronprobe at sandwich samples. The temperature dependence of the diffusion coefficients of Hf in Ti was compared with the corresponding values of the system Ti in Ni. In both systems was found a good accordance with the Arrhenius relation within four orders of magnitude. The solubility of Hf in Ni is found to be nearly by the factor 2 larger than the values known from earlier papers.     

Hydrogen in Cu?Ti and Ni?Ti Metallic Glasses

The hydrogen solubility and its effect on the crystallization of Cu Ti and Ni Ti glasses were studied by differential scanning calorimetry, thermogravimetry, and X-ray diffraction. Dependence of the crystallization products of the hydrogenated Ti-based alloys on the hydrogen content was found. Whereas in Cu-Ti alloys hydrogenation leads to drastic decreasing in the thermal stability due to phase separation in the amorphous state and to formation of microcrystalline structure during crystallization, in Ni Ti system hydrogen produces hydrides with Ni as well with Ti, which after heat treatment decompose, and finally the same crystalline phases as in unhydrogenated alloy are formed. The isothermal crystallization kinetics of the maximum hydrogenated Cu₅₀Ti₅₀ amorphous alloy was also investigated to obtain additional information about this transformation leading to nano-crystalline material.     

化学溶液法制备涂层导体过渡层La2Zr2O7厚膜的研究

为制备高质量的双轴织构La2Zr2O7(LZO)涂层导体过渡层,本文采用化学溶液法(Chemical solution deposition,简称CSD法),以乙酰丙酮镧和乙酰丙酮锆为溶质,丙酸为溶剂配制成前驱盐溶液,在立方织构的Ni-5 at;W基底上用快速一步法退火工艺制备了LZO种子层及双层LZO厚膜.SEM观察种子层呈岛状均匀排列,符合种子层形貌特点.XRD结果显示0.06 mol/L浓度种子层上制备的LZO厚膜具有很强的双轴立方织构,其中(222)面Phi扫描和(400)面摇摆曲线半高宽值分别为6.37°和5.82°.SEM观察发现120 nm厚的LZO薄膜表面平整,无裂纹,为后续沉积YBCO提供了很好的模板.     

On normal kinetics in the case of some refractory and transition metals' crystallization

In given work the crystal growth kinetics connected with some refractory and transition metals is considered. For melts of Fe, Co, Ni, Cr, Zr, Ti, Ag, Cu, and Pb in the vicinity of melting temperatures the solid phase growth is described by means of a fluctuation theory applied for the macro-systems. By virtue of the “unlimited” and limited spectrum solid state particle concentration fluctuations' theory some effective kinetic coefficients have been estimated in the work. The effective kinetic coefficients are specific in the case of normal crystal growth kinetics. In the case of the crystallization of Fe, Co, Ni, Cr, Zr, Ti, Ag, Cu, and Pb-melts a comparison between two effective kinetic coefficients (based on the fluctuation theory and so-called equilibrium growth points density) has been realized. In most cases a satisfactory agreement between the effective kinetic coefficients has been observed.     

Crystallization of the amorphous phase and martensitic transformations in multicomponent (Ti,Hf,Zr)(Ni,Cu)-based alloys

Shape memory materials with specific microstructure can be obtained from amorphous precursors. Rapidly solidified amorphous and crystalline–amorphous ribbons have been produced by planar flow casting for a number of multicomponent TiNi-based alloys of pseudobinary 50:50 and 55:45 compositions with substitutions of Zr, Hf, Nb for Ti and Cu, Co, Pd, Ag, Al for Ni. The glass transition and crystallization behavior of the amorphous phase as well as the martensitic transformations in the crystallized materials have been studied by differential scanning calorimetry. To control the crystal structure at different stages of crystallization, X-ray diffractometry and transmission electron microscopy were used. The effects of crystallization conditions and the resulting microstructural state on the martensitic transformation characteristics have been investigated. The transformation temperature intervals are shown to depend on the mean size of the parent phase crystals.     

Interaction in the molten system Rb2O‐P2O5‐TiO2‐NiO. Crystal structure of the langbeinite‐related Rb2Ni0.5Ti1.5(PO4)3

The interaction in the molten system Rb₂O‐P₂O₅‐TiO₂‐NiO was investigated at different molar ratios Rb/P = 0.5‐1.3, fixed Ti/P = 0.15, Ti/Ni = 1.0 at temperature range 1073–953 K. The conditions of formation of complex phosphates RbTi₂(PO₄)₃, Rb₂Ni_0.5Ti_1.5(PO₄)₃ and RbNiPO₄ have been determined. The new phosphate Rb₂Ni_0.5Ti_1.5(PO₄)₃ (space group P2₁3, a = 9.9386(2) Å) has been obtained and investigated by the single crystal X‐ray diffraction and FTIR‐spectroscopy. It has langbeinite‐like structure, that is built up from mixed (Ni/Ti)O₆‐octahedra and РО₄‐tetrahedra. Rubidium atoms are located in closed cavities of 3D‐framework.     

MeV electron irradiation induced crystallization in metallic glasses: Atomic structure,crystallization mechanism and stability of an amorphous phase under the irradiation

MeV electron irradiation via high voltage electron microscopy can lead to amorphous-to-crystal transition (i.e., crystallization) as well as crystal-to-amorphous transition (i.e., solid-state amorphization). Irradiation-induced crystallization can be observed in various alloy systems such as Co-, Fe-, Ni-, Pd-, and Zr-based metallic glasses, indicating that this phenomenon has wide generality in metallic materials. Irradiation-induced crystallization mechanism was discussed based on the following factors; (1) an increase in free energy for an amorphous phase, (2) the formation of crystalline clusters through modification of the atomic configuration near radiation induced defects, and (3) enhanced diffusion. The stability of an amorphous phase against irradiation-induced crystallization can be estimated from the thermal crystallization temperature (T_x), and Ni–Nb based metallic glasses have a tendency for high stability against irradiation because of high T_x.     

Effect of structural transformations on the texture of Ni?Fe base alloys

1. Processes of texture formation were studied in three Ni Fe system alloys containing Mo and Ti (alloy No. 1), Cr, Ti and Al (alloy No. 2) and Co, Ti and Al (alloy No. 3). The deformation texture is identical in all alloys which agrees with the proximity of stacking fault energies as estimated from X-ray data. 2. Annealing leads to a pronounced diffusion and alteration of the texture in alloy No. 1, but does not alter the texture type and intensity in alloy No. 2, whereas in alloy No. 3 the typical strain texture components are intensified. 3. Structure processes governing texture formation were identified as recrystallization in alloy No. 1, and oriented γ–γ′ transformation in alloys No. 2 and 3 where the intergranular boundaries were blocked by heterogenous precipitation of phases not possessing fcc structure.     

A new approach of creating Au‐Sn solder bumps from electroplating

A homogeneous melting eutectic Au/Sn solder bump for laser chip application has been developed. The under‐bump metallization consists of a Ni wetting layer, a plating seed layer of Pt/Au/Ti multi‐layer scheme. The solder is electroplated as a sequence of Ni, Au and Sn layers. The bump can be exposed to multi‐step reflow cycles. The reflow of the solder as plated starts with a phase forming process in the solid state which results in an eutectic‐like phase and the near eutectic dand z phases. The dand z phases dissolve during the liquid state stage of the reflow at temperatures between 300 and 350 °C. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

EXAFS and XANES Studies on 3d Transition Metal Intercalation Compounds M x TiS2

Abstract

EXAFS and XANES spectra of Ti K-edge have been measured for 3d transition metal intercalation compounds M _x TiS₂ (M = Mn, Fe, Co and Ni; x ≤ 0.33). We have found that the interatomic distance between Ti and the first nearest neighbor S atoms, R(Ti-S), increases with the guest concentration x. The variation in XANES spectra with x reveals the reduction of the valence state of Ti atoms upon intercalation of M. From these results as well as the M K-edge EXAFS data studied previously, we have proposed a simple model on the local structure of M _x TiS₂ to reproduce the observed values of R(Ti-S) by averaging local shift of S atoms caused by intercalation.     

Growth,composition, ferroelectric and magnetic properties of new multiferroic Pb3.3Mn4.8Ni1.1Ti0.56O15.3 single crystals

Multiferroic single crystals in the novel system Pb‐Mn‐Ni‐Ti‐O have been grown by the high temperature solution growth method. At room temperature the crystals are indexed in the hexagonal space group P6₃cm. The dielectric and magnetic properties along with the temperature dependence of the c‐lattice parameter have been studied in the temperature range 2 K ‐ 500 К. The magnetic measurements reveal a paramagnetic to antiferromagnetic phase transition around 48 K. The dielectric permittivity exhibits a maximum at 430 K, indicating ferroelectric to paraelectric phase transition. The temperature dependent Raman and XRD measurements around 430 K reveal an anomaly and abrupt change of the lattice parameter along the z‐axis respectively, thus confirming the ferroelectric‐to‐paraelectric phase transition.     

SiO2对低温烧结压电陶瓷PMNNS的性能影响

在烧结温度为1020℃下,采用固相二步合成法制备了Pb(Ni1/3Nb2/3)0.05(Mn1/3Nb2/3)0.04(Mn1/3Sb2/3)0.01(Zr1/2Ti1/2)0.9O3(PMNNS)压电陶瓷,研究了加入不同掺杂量的SiO2对陶瓷的结构与机电性能的影响。结果表明:加入SiO2可以明显地降低烧结温度;而且当SiO2的掺杂量为0.1%时,陶瓷的性能最佳,其性能如下:d33=331 pC/N,tanδ=0.0041,kp=0.62,Qm=1326,εr=917。     

Ti、V、Ni、Mo对CVD金刚石涂层形核影响

基于密度泛函理论,计算分析了CH₃基团在含有过渡金属元素Ti、V、Ni、Mo的孕镶金刚石颗粒硬质合金基底表面的吸附能、Mulliken电荷分布、电荷密度差和态密度(density of states, DOS)等一系列性质,研究Ti、V、Ni、Mo对孕镶金刚石颗粒硬质合金基底化学气相沉积(chemical vapor deposition, CVD)金刚石涂层形核阶段的影响及其作用机理。计算结果表明:与CH₃基团在WC表面及金刚石表面的吸附相比,Ti、V、Ni、Mo与C原子间有较强的弱相互作用,这使得其对CH₃基团有更强的吸附能力(其中Ti>V>Mo>Ni);吸附能力大小与各原子的价电子结构相关,含有Ti元素的表面对CH₃的吸附最稳定;CH₃基团与Ni原子间更易发生电荷的转移形成共价键,Mo有利于促进CH₃基团的脱氢反应;形核阶段适当添加Ti、V、Ni、Mo这几种过渡金属元素将有利于增加形核密度,改善CVD金刚石膜基界面结合强度。