Structural and morphological characteristics of nanocrystalline copper electrodeposits from acid sulphate electrolytes

Copper is the presently favoured and future interconnect material in high-end microprocessors and memory devices because of its low electrical resistivity and higher electromigration than aluminium. The present investigation deals with the electrodeposition of nanocrystalline copper onto brass metallic foil from electrolytes containing copper sulphate (CuSO₄·5H₂O) as the source of metal ion and sulphuric acid (H₂SO₄). Benzotriazole (0.5?g?L^??1) and sodium lauryl sulphate (0.1?g?L^??1) were used as additives. The electrolyte was mechanically agitated and the temperature was maintained at 3°C?±?2°C. These additives have been found to be effective in reducing the grain size, grain boundaries and improving surface morphology of the copper films. They also improve the throwing power of the deposition electrolytes and hardness of deposits. X-ray diffraction (XRD) patterns obtained for the electrodeposited copper films showed polycrystalline cubic structure. The crystal size of the copper films was calculated by both XRD and atomic force microscopy (AFM) analysis. A uniform and pore free surface morphology was observed under SEM, and AFM investigation revealed the grain refining brought about by the additives.     

Hardness and elastic modulus of amorphous and nanocrystalline SiC and Si films

Hydrogen-free amorphous and nanocrystalline films were prepared by magnetron sputtering of the SiC or Si targets. Mechanical properties (hardness, elastic modulus, intrinsic stress) and film structures were investigated in dependence on the substrate bias and temperature. It was found that both hardness and elastic modulus of all amorphous a-SiC films prepared at different substrate temperatures and biases are always lower than those for bulk α-SiC single crystal while the hardness of partially crystalline SiC films is higher and the elastic modulus lower than those for α-SiC one. In contrast, both hardness and elastic modulus of all amorphous Si films are always lower than those for nanocrystalline Si films which show approximately the same value as the Si single crystal.     

Thermal stability of nanocrystalline Ni- and Co-based pulsed current electrodeposits: correlation of calorimetric measurements and microstructure development upon annealing

The exceptional properties associated with nanocrystalline materials are, to a large extent, a result of their high inter-crystalline volume fraction. However, the intrinsic instability of the nanostructured state may compromise the gain in properties by the occurrence of grain growth during exposure at elevated temperatures. Thermal stability is, therefore, a fundamental materials issue for nanocrystalline materials. This article describes what can be deduced from calorimetric measurements in the context of what is known about the microstructural evolution upon annealing of nanocrystalline Ni- and Co-based pulsed current electrodeposits. Special emphasis is put on interpreting the shape of the curves obtained by a differential scanning calorimetry (DSC). The temperature ranges for relaxation, segregation, precipitation, as well as abnormal and normal grain growth can be predicted. Also, by evaluating the shift in peak temperature with heating rate (Kissinger plot), the activation energies for grain growth can be obtained for the different materials.     

Microstructural study of NiCrAlY electrodeposits

Pulse electrodeposition technique was used to co-deposit Ni with NiCrAlY powder on Ni-based high temperature alloy substrate. Pure nickel anode was immersed in a standard Watt’s bath containing fine particles of NiCrAlY powder that were entrapped during electrodeposition to form a NiCrAlY electrodeposit on cathode specimen surface. Diffusion heat treatment was conducted in argon at ≈1150°C and the samples were oxidized at 1000°C in air. Scanning and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray diffraction were used to characterize the microstructure and identify the phases. Pulse electrodeposition resulted in dense and fine-grained deposit with the formation of Al₂O₃ oxide at the coating surface after exposure to high temperature.     

Influence of nanocrystalline Ni–Ti reaction agent on self-propagating high-temperature synthesized porous NiTi

Nanocrystalline Ni–Ti was used in self-propagating high-temperature synthesis (SHS) to fabricate porous NiTi. The SHS of porous NiTi using elemental powders was also prepared for comparison. Results showed that the main phase was NiTi with unreacted Ni when using elemental powders, which is detrimental to medical use. A large amount of Ti₂Ni secondary phase was also detected. By employing mechanically alloyed nanocrystalline Ni–Ti as a reaction agent, the secondary intermetallic phase (i.e. Ti₂Ni) was significantly reduced and the unreacted Ni was eliminated. The addition of 25 wt% nanocrystalline Ni–Ti reaction agent produced porous NiTi with an average porosity of 52–55 vol% and a general pore size of 100–600 μm under preheating temperatures of 200 and 300 °C. This general pore size in the range of 100–600 μm is beneficial to biomedical application for osseointegration. By further increase of the reaction agent to 50 wt% in the reactant, a porous NiTi part was produced at ambient temperature (i.e. no preheating was necessary) and a dense part was formed at preheated temperature of 200 °C due to the large amount of energies in the nanocrystalline reaction agent. This revealed that the use of nanocrystalline reaction agent effectively lowered the activation barriers for combustion synthesis reaction.     

Co-Ni纳米合金的制备与表征

以NaBH4为还原剂、油酸为分散剂、采用液相还原法制备了Co-Ni纳米合金,利用XRD、SEM和VSM对试样进行了表征.研究结果表明,在N2气保护下,经500 ℃焙烧,试样由无定形态转化为晶态;颗粒呈球形,平均粒径为35 nm;Co-Ni合金的抗氧化能力较强,在常温下不易被氧化;饱和磁化强度为83.7 A·m2/kg,矫顽力趋近于零,呈现超顺磁性.     

Shape-memory effect in Co-Ni single crystal

The thermal shape-memory effect at room temperature for Co-32% Ni(mass fraction) magnetic shape memory alloy of single crystal was presented. When compressing the sample along the [001] direction at room temperature, strain can be recovered to some extent during later heating and the recovery rate varies with the pre-strain.But no obvious recoverable strain can be obtained along other crystal directions. For the thermal-mechanical training of the sample along [001], the recovery strain decreases obviously during the second round of compress and nearly no recovery happens after the third round of compress. A possible mechanism based on reversible motions of Shockley partial dislocations was proposed.     

Preparation of amorphous-nanocrystalline composite structured Ni-P electrodeposits

Amorphous-nanocrystalline composite structured Ni-P deposits (with phosphorus content of 5-9 wt.%) show better corrosion resistance than that of microcrystalline structured Ni-P deposits, and better abrasion resistance than that of amorphous Ni-P deposits. In order to get amorphous-nanocrystalline composite structured Ni-P deposits on AISI 431 stainless steel, electroplating parameters that affect phosphorus content in Ni-P deposits (temperature, current density, pH, H₃PO₃ concentration and agitation rate) are analysed by orthogonal experimental design (OED) in this paper. The analysis indicates that pH value and phosphorous acid concentration are key variables, their interactive effect on Ni-P composition should be taken into account. The effects of pH and H₃PO₃ concentration of the electroplating bath on phosphorus content in Ni-P deposits are further examined by the method of steepest ascent and central composition design (CCD). On the basis of results and discussion in experimental design sections, various Ni-P deposits with approx. 5-9 wt.% phosphorus can be galvanostatically electroplated by controlling the key variables and these deposits are confirmed to be amorphous-nanocrystalline composite structure in XRD, TEM tests.     

Co-Ni型超高强度钢的微观组织结构与力学性能

利用透射电镜、扫描电镜等试验手段研究了回火温度对2000 MPa和2200 MPa两种强度级别Co-Ni超高强度钢的微观结构、断口形貌与力学性能的影响。结果表明,两种强度级别Co-Ni超高强度钢的强化均与M2C碳化物有关。Co-Ni超高强度钢在400~450℃回火韧性出现谷值,产生的原因与板条边界存在Fe3C、M3C及M2C处于共格状态,使马氏体基体产生强烈静畸变有关,冲击试样断口微观形貌表现为准解理断裂。Co-Ni超高强度钢在480~510℃回火,马氏体板条内析出细小、弥散的M2C,粗大片状Fe3C被细小、弥散的MC取代,使其具有比较好的强韧性配合。     

Microstructure evolution and hardening mechanisms of Ni-P electrodeposits

Ni-P alloy coatings with different phosphorus contents were prepared by electroplating in a nickel sulfate bath containing phosphorous acid (H₃PO₃). Hardening mechanism, such as dispersion hardening of Ni nano crystals in amorphous matrix of the as-deposited Ni-P coating and coarsening weakening of Ni₃P for the high P coating after 1 h of heat treatment at 400 °C were concluded from the experimental data. Hardening mechanism of Ni-P alloys were further discussed based on the microstructure evolution with increasing deposit P content and during the heat treatment by using high resolution TEM (HR-TEM). A maximum hardness was observed for the as-deposited and heat-treated Ni-P alloys with 4 wt.% and 6 wt.% P, respectively. These composition ranges corresponding to the microstructure with high hardness proposed are believed to be useful for the industrial applications and further study.     

Identification of an anomalous phase in Ni-W electrodeposits

In the present work Ni-W layers electrodeposited from electrolytes based on NiSO₄, Na₂WO₄, citrate, glycine and triethanolamine are characterized with glow discharge optical emission spectroscopy (GD-OES) and X-ray diffraction analysis (XRD). XRD showed the occurrence of an anomalous phase in the deposits, associated with the presence of an appreciable amount of carbon as identified with GD-OES. The anomalous phase is metastable at room temperature and vanishes upon annealing at 550 °C in air.     

Property enhancement of nickel electrodeposits by anodic current pulses

The yield and tensile strengths of nickel electrodeposits were increased by a factor of three by the periodic imposition of an anodic current pulse. The time periods between pulses were much longer than those used in periodic reversal plating. The increased strength was attributed to grain refinement resulting from nucleation on surfaces which became passivated during the anodic pulses. The reduced adhesion between layers plated between pulses resulted in a reduction in the coefficients of friction.     

Co-Ni合金镀层组织结构及性能研究

采用金相显微镜和X射线衍射(XRD)分析测定了Co-Ni镀层和纯Ni镀层的微观形貌和晶体结构;研究了Co-Ni镀层和纯Ni镀层的力学性能、高温抗软化性能以及摩擦磨损性能.结果表明,Co-Ni镀层是具有六方密排结构(hcp)的,以Co为溶剂,Ni溶解在Co中的单相固溶体,而纯Ni镀层为单一的面心立方结构(fcc).与纯Ni镀层相比,Co-Ni镀层具有优异的力学性能和良好的高温抗软化性能.Co-Ni镀层所具有的六方密排结构(hcp)的组织结构降低了它的摩擦系数,使得Co-Ni镀层具有良好的耐磨损性能.     

洛氏硬度试验中测量不确定度的评定

介绍了测量硬度不确定度的原理，并以金属材料洛氏硬度试验结果的不确定度的评定作为不确定度在理化检验中应用的一个实例。     

ON THE STRENGTHENING MECHANISM OF HIGH Co-Ni ULTRAHIGH STRENGTH STEEL

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