Room and high temperature wear behaviour of Ni matrix micro- and nano-SiC composite electrodeposits

In the frame of the research domain of the production of metal matrix composite deposits the aim of this work is the production of Ni matrix composite coatings containing either micro- or nano-SiC particles and their characterization. The electrodeposition has been carried out under DC conditions using a nickel sulfammate plating bath into which the particles were suspended. The composite coatings were tested and compared to pure nickel deposits regarding the microstructure, microhardness and wear resistance under high load at both room temperature and 300 °C. The codeposition of the SiC particles changed the microstructure of the nickel matrix and the preferential orientation of the Ni grains leading to a noticeable improvement on both microhardness and wear resistance. The pure nickel deposit presents a pseudocolumnar structure and a preferential [100] orientation. The codeposition of the μSiC particles slightly modified the dimensions and the orientation of the pseudocolumns and led to a [110] preferential orientation of the Ni grains. The microstructural modifications and the presence of the SiC particles in the metal matrix lead to a 51% increase of the microhardness, a 63% decrease of the wear coefficient at 300 °C while it did not offer any improvement at the wear resistance at room temperature. The codeposition of nSiC particles leads to a noticeable grain refinement and the loss of a preferential orientation. The microstructural modifications in this case lead to a 67% increase of the microhardness, a 70% decrease of the wear coefficient at room temperature and an 88% decrease of the wear coefficient at 300 °C in comparison to the pure nickel deposits. The improved wear resistance of the Ni/nSiC deposits is attributed to their compact microstructure and to the absence of a preferential orientation which was maintained also after wearing, contrary to the other two types of deposits.     

Residual stresses of Ni alloy electrodeposits containing low levels of Fe,P, and B

The effects of process parameters including the alloying elements, additive, pH, temperature and current types on the residual stresses of Ni alloys electrodeposited from a Ni sulfamate bath were investigated using a method involving a flexible bent strip. From the results, it was believed that the residual stresses of the Ni alloy deposits initially depended on a hydride then the alloying elements with increasing levels of those concentrations in the solutions. As the pH of the electrolytes changed from 1 to 3.5, the residual stresses in the deposits varied directly and intensively with the concentration of the NH₄ in the solution. By increasing the temperature of the electrolytes from 50 °C to 70 °C, the tensile stresses in the deposits were decreased by the lower hydride that resulted from the decline in the hydrogen evolution reaction. The measured stress values with the current types showed a decrease in the order of the direct current, the pulse current (PC) and the periodic reverse current (PRC). The compactness of the deposit produced by the PC and the increased oxide and decreased hydride during the reverse pulse current of the PRC appeared to degenerate the tensile stresses.     

Thermal non-linear behaviour in optical linear encoders

Thermal errors in machine tools are some of the major inaccuracy sources. For their correction, two approaches can be followed: consider the machine as a whole or its constituent members. Errors caused by linear encoders are examined. The mutual effects between aluminium extrusion and glass scale result in thermal coefficient changes. Besides, non-linearities with respect to length modification are found as a consequence of the different stress conditions in different sections of the encoder. This behaviour makes the simple linear thermal correction of optical linear encoder measurements inaccurate. The research presented here tries to identify and to estimate non-linearities caused by the linear encoder as a method to improve thermal error correction procedures.     

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.     

Movement of carrier recombination zone in organic light emitting devices by applied voltage

We fabricated organic light emitting devices that consist of three different emitting layers in series between hole transport layer (HTL) and electron transport layer (ETL), in order to investigate the carrier recombination zone in the devices. Since the three different emitting layers are constructed to emit different colors, the carrier recombination zone can be observed from the luminescence. The predominant recombination zone was found to be relatively far from the HTL–EML hetero-interface at low applied voltage (around 7 V). When the applied voltage increases to 11 V, the recombination zone tends to shift towards the hetero-interface. As the applied voltage increases further, interestingly the recombination zone tends to go back away from the HTL–EML interface due to the electron crossover to the HTL or electron diffusion back to the far side from the interface.     

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.     

热喷涂制Ni阻挡层在碲化铋热电器件中的应用*

在碲化铋热电制冷器件的服役过程中,焊料与热电材料间的元素扩散将严重制约器件的正常使用,目前最常用在两者间加Ni阻挡层的方法来改善这种问题,以往采用电镀、等离子烧结等制备Ni镀层的方法会产生界面镀层厚度不易控制、镀层易氧化的问题,而热喷涂由于其镀速快、镀层厚度易控制和镀后表面较平整、耐氧化、结合强度高等优点,可作为制备Ni阻挡层的更好选择。采用热喷涂技术制备不同厚度的Ni阻挡层,并对其分别进行200℃下24、72和144 h的退火试验。首先探究不同Ni层厚度的p型(Bi_0.4Sb_1.6Te₃)和n型(Bi₂Te_2.7Se_0.3)碲化铋材料退火前后对镀层硬度和防扩散效果的影响,并将不同Ni层厚度的p、n型碲化铋材料制备成热电器件进行服役性能测试。结果表明：退火对p型材料镀Ni层硬度影响较小,其值变化在10%以内,但对n型材料镀Ni层的硬度影响较大,其最大硬度值下降56.36%;Ni是p型碲化铋材料较好的扩散阻挡层,能显著减少Bi_0.4Sb...     

ZrO2／NiFGM中微观残余热应力分析

陶瓷—金属FGM成分沿厚度方向变化，微观残余热应力分析对确定FGM材料体系极为重要。按球对称模型采用弹性理论进行分析，确定了微观残余热应力与陶瓷和金属相的弹性性能、在FGM中的位置的关系。结果表明，微观应力具有短程分布特点，并且在同一梯度层内最大微观应力处于相界面处。同时，通过对ZrO2／Ni FGM制备过程中的陶瓷—金属界面应力的分析表明，FGM制备过程中可能在基体中产生大量微裂纹。     

Hydrothermal synthesis and optical properties of Ni doped ZnO hexagonal nanodiscs

Single crystalline Ni-doped ZnO hexagonal nanodiscs are successfully synthesized. Zinc acetate, nickel nitrate, sodium hydroxide and poly (vinyl pyrrolidone) (PVP) were mixed together and transferred to a 100 ml Teflon-lined stainless steel autoclave which kept at 150 °C for 24 h. The morphology and microstructure were determined by field emission scanning electron microscopy (FE-SEM), X-ray diffraction transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence (PL) spectroscopy. The investigation confirmed that the products were of the wurtzite structure of ZnO. The doped hexagonal nanodiscs have edge length 30 nm and thickness of 45 nm. EDX result showed that the amount of Ni in the product is about 12%. Photoluminescence of these doped hexagonal nanodiscs exhibits a blue shift and weak ultraviolet (UV) emission peak, compared with pure ZnO, which may be induced by the Ni-doping. The growth mechanism of the doped hexagonal nanodiscs was also discussed.     

Effect of substrate pretreatment on the porosity in thin nickel electrodeposits

Substrate pretreatment affects the porosity of thin nickel electrolytic coatings which is a combined function of the composition and the roughness of the substrate surface. Electropolishing the substrate surface is an effective method of reducing coating porosity, whereas coatings plated on either electroetched or mechanically ground substrates are relatively porous owing to the remaining oxide layer on the substrate and the increased roughness of the substrate. For nickel coatings plated on mechanically ground rough substrates, the relationship between nickel porosity, apparent coating thickness and substrate roughness has been examined.     

Thermal Decomposition Kinetics of Ni(Ⅱ) Complex with Norfloxacin

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Microstructural analysis of low Ni content Zn alloy electrodeposited under applied magnetic field

The codeposition behaviour of Zn and Ni has been studied in sulphate electrolytes in presence of a superimposed magnetic field up to 1 T parallel to the surface. Structural analysis by X-Ray diffraction (XRD) method revealed that the alloys consisted of a mixture of zinc, η-phase and γ-phase. The results showed that the magnetic field B was responsible for variations of the alloy structural parameters (lattice imperfection and texture) for low pH. When the pH of electrolyte was increased, the effect of the magnetic field was erased. It was suggested that the preferential growth direction of Zn-Ni alloy was induced by the mass-transport enhancement of H⁺ ions promoted by B which induced an increase of the pH near the cathode. Then, for high value of pH up to 3.5, the crystallographic orientation (101) of Zn was always favoured to the prejudice of the Ni₅Zn₂₁ phase.     

Synthesis of nonlinear optical fluorinated polyimide/inorganic composites for photonic devices

A nonlinear optical （NLO） active alkoxysilane chromophore （SGDRI） was synthesized. A fluorinated polyimide/SGDR1 composite was prepared to improve the poor temporal stability of second-order NLO effects of the reported poled sol-gel film. The poled composite film was characterized by FTIR, DSC, TGA and UV-Vis. The composite displays good hydrophobic properties, nigh glass wansifion temperature（266 ℃）, and high decomposition temperature （433 ℃）. The second harmonic coefficient d33 of the composite was measured to be 16.77 pm/V by using maker fringe technique. The new NLO composite exhibits 85 % of the original d33 over 720 h at 100 ℃ and possesses much better stability than the reported sot-get film.     

Thermal stability of microstructure and mechanical properties of Ni/Ru multilayers

The microstructure, hardness and thermal stability of Ni/Ru multilayers prepared by evaporation deposition were investigated by X-ray diffraction, transmission electron microscopy, vacuum annealing and nanoindenation. The hardness values of as deposited multilayers increase, while their elastic modulus values decrease, with decreasing periodicity. After annealing at low temperature (below 450 °C), the decrease in hardness of multilayers with larger periodicity is more remarkable than that of multilayers with smaller periodicity due to coarsening of the in-plane grain size. The higher temperature (600 °C) annealing results in the breakdown of the periodical structure and a significant drop in hardness for multilayers with smaller periodicity. The results were discussed according to Orowan-type single dislocation bowing mechanism.     

低Ni型LNG钢的热变形行为及力学性能

通过单道次、双道次压缩试验,研究了低Ni型LNG钢的高温奥氏体动态再结晶及静态再结晶行为,并采用两阶段控制轧制及超快速冷却技术进行不同轧制工艺下的热轧试验,通过热模拟及热轧试验研究了低Ni型LNG钢的热变形行为及力学性能。结果表明,在高温(1000~1050 ℃)、低应变速率(0.1~0.5 s^-1)下奥氏体容易发生动态再结晶,确定了发生再结晶的临界条件,并建立了动态再结晶动力学模型。试验钢在较高温度(800~1050 ℃)、较长道次间隔时间(60 s)下静态软化现象明显,容易发生静态再结晶。依据热模拟试验结果制定热轧试验工艺,通过控制精轧开轧温度和终轧温度调控高温奥氏体再结晶行为,从而细化晶粒,改善低Ni钢的冲击性能。精轧开轧温度920 ℃、终轧温度770 ℃时,低Ni钢的低温冲击吸收能量为180.1 J,屈服强度为595.1 MPa,抗拉强度为717.8 MPa。     

The Kinetics and Mechanism of Thermal Oxidation of Electrolessly Deposited Ni–B and Ni–W–B Alloys

The kinetics and mechanism of thermal oxidation of electrolessly reduced Ni–B and Ni–W–B alloys are studied by precision thermogravimetry and x-ray photoelectron spectroscopy. It is shown that the oxidation is mainly determined by properties of boron oxides. At temperatures over 300°C, the oxidation is accompanied by a sublimation of boron oxides formed. Traces of water and hydrogen in freshly deposited alloys affect significantly both the kinetics of the alloys oxidation and sublimation of the oxides. The vitreous oxide film well adsorbs water vapor and can be readily removed from the sample surface.     

焊接热循环对10Ni5CrMoV钢组织的影响

采用模拟焊接热循环的方法，研究了不同峰温和ｔ８／５条件下１０Ｎｉ５ＣｒＭｏＶ钢热影响区组织的变化，金相观察发现，峰温在Ａｃ１～Ａｃ３之间时，其组织为细小的马氏体和高温回火马氏体的混合组织；峰温超过Ａｃ３时，冷却后均转变为马氏体，且发生自回火现象，峰温越高，奥氏体晶粒粗大，冷却后形成的马氏体板条束尺寸也越大，随着ｔ８／５的增加，其组织由自回火马氏体（含少量孪晶马氏体）自回火马氏体＋下贝氏体，自回火马     

Automatic programming of robot-mounted 3D optical scanning devices to easily measure parts in high-variant assembly

In times of increasing product variance and demand for highest quality, 100% inspection of parts is often mandatory along the supply chain and the incoming goods control of assembly processes, respectively. A promising approach to reach this goal is the use of robot-assisted measurement systems. However, such systems require high efforts to program the robot for every new part and thus are seldom implemented in high-variant assembly systems. Consequently, this work proposes a system for automated programming of robot-mounted optical scanning devices. Additionally, algorithms to automatically extract measurement features and generate collision-free robot scanning paths from CAD models are described.