Sliding wear behaviors of electrodeposited nickel composite coatings containing micrometer and nanometer La2O3 particles

Micrometer and nanometer La₂O₃ particles were codeposited with nickel by electroplating from a nickel sulfamate bath. The wear behaviors of the composite coatings were evaluated sliding against AISI 1045 steel under non-lubricated conditions. It was found that the incorporation of the La₂O₃ particles enhances the microhardness and wear resistance of Ni coatings. The wear resistance of the Ni composite coating containing nano-sized La₂O₃ particles is higher than that of the Ni composite coating containing micro-sized La₂O₃ particles. The codeposition of the smaller nanometer La₂O₃ particles with Ni effectively reduces the size of Ni crystals and significantly increases the hardness of the composite coatings, resulting in significantly improved wear resistance of the nano-sized La₂O₃/Ni composite coating.     

Reproducibility and stability of N–Al codoped p-type ZnO thin films

Reproducible and stable p-type ZnO thin films have been prepared by the N–Al codoping method. Secondary ion mass spectroscopy measurements demonstrate that N and Al are incorporated into ZnO. The resistivity, carrier concentration, and Hall mobility are typically of 50–100 Ωcm, 1×10¹⁷–8×10¹⁷ cm⁻³, and 0.1–0.6 cm²/Vs, respectively, for the N–Al codoped p-type ZnO films. Hall measurement, X-ray diffraction, and optical transmission were carried out to investigate the changes of the properties with the storage period. Results show that the p-type characteristics of the N–Al codoped ZnO films are of acceptable reproducibility and stability. In addition, the N–Al codoped p-type ZnO films have good crystallinity and optical quality. The properties are time independent.     

Dynamic Response Analysis of Fuzzy Stochastic Truss Structures under Fuzzy Stochastic Excitation

A novel method (Fuzzy factor method) is presented, which is used in the dynamic response analysis of fuzzy stochastic truss structures under fuzzy stochastic step loads. Considering the fuzzy randomness of structural physical parameters, geometric dimensions and the amplitudes of step loads simultaneously, fuzzy stochastic dynamic response of the truss structures is developed using the mode superposition method and fuzzy factor method. The fuzzy numerical characteristics of dynamic response are then obtained by using the random variable’s moment method and the algebra synthesis method. The influences of the fuzzy randomness of structural physical parameters, geometric dimensions and step load on the fuzzy randomness of the dynamic response are demonstrated via an engineering example, and Monte-Carlo method is used to simulate this example, verifying the feasibility and validity of the modeling and method given in this paper.     

Development of piezoelectric monomorph actuator using electrophoretic deposition

In the present work, investigation of the functional property of piezoelectric graded monomorph actuator systems is presented. The functional graded actuators were fabricated by electrophoretic deposition (EPD) using pure PZT and doped PZT materials. Actuators developed have shown gradual gradient variation in microstructure. It is noted that the trend in microstructural gradient does not represent similar trend in piezoelectric property gradient. The displacement of microstructural graded and both piezoelectric and microstructural graded actuators were measured in the static condition. The latter was also measured under dynamic condition. The results show that the proper gradient distribution of the piezoelectric properties is important to improve the electromechanical performance of the actuator.     

Investigation of the size effect on optical properties of polycrystalline Ge deposition by pulse laser deposition

The size effect of optical properties of the polycrystalline Ge/Si films prepared by pulse laser deposition (PLD) is investigated by photoluminescence (PL) and photocurrent (PC) spectra. The size of Ge nanocrystals is precisely controlled by the pulsed deposition time and then observed by the atomic force microscopy (AFM). The average size of Ge nanocrystals is about 2, 5 and 25 nm for 1, 2 and 3 min deposited sample, respectively. The size effect on optical properties of Ge nanocrystals has been analyzed by photoluminescence (PL) and photocurrent (PC) spectra. The PL peaks shift from 0.799 eV for 1 min to 0.762 eV for 3 mins; at the same time, the photocurrent peaks of the films sharply changes from 0.781 eV to 0.749 eV, the shifts of PL and PC are contributed to the quantum size effect of Ge nanocrystals.     

A three-dimensional inverse finite-element method applied to experimental eddy-current imaging data

Eddy-current techniques can be used to create electrical conductivity mapping of an object. The eddy-current imaging system in this paper is a magnetic induction tomography (MIT) system. MIT images the electrical conductivity of the target based on impedance measurements from pairs of excitation and detection coils. The inverse problem here is ill-posed and nonlinear. Current state-of-the-art image reconstruction methods in MIT are generally based on linear algorithms. In this paper, a regularized Gauss-Newton scheme has been implemented based on an edge finite-element forward solver and an efficient formula for the Jacobian matrix. Applications of Tikhonov and total variation regularization have been studied. Results are presented from experimental data collected from a newly developed MIT system. The paper also presents further progress in using an MIT system for molten metal flow visualization in continuous casting by applying the proposed algorithm in a real experiment in a continuous casting pilot plant of Corus RD&T, Teesside Technology Centre.     

Sr and Ba substitution in charge ordered Pr0.5Ca0.5MnO3: Sharp steps in the magnetic and transport properties for a narrow composition range

The magnetic and transport properties of Pr_0.5Ca_0.5−xA_xMnO₃ (A = Sr, Ba) have been investigated in this paper. The substitution of Ca with bigger cations such as Sr and Ba can favour the field-induced ferromagnetism and induce sharp steps in the magnetization versus field and resistivity versus field curves. These properties strongly depend on the thermal history of the samples. All the results have been interpreted by a martensitic-like mechanism based on phase separation induced by A-site size mismatch. The above model can also explain the result that the less efficient ability of Sr substitution than Ba substitution to induce ferromagnetism and sharp steps. Another interesting feature in the system is the existence of an optimum substitution range to induce magnetization steps and reach high field-induced magnetization values for both Sr (x = 0.07–0.10) and Ba (x = 0.01–0.08) substitution. We suggest that the disappearance of the steps beyond the optimum substitution range possibly results from the different nature of phase separation in the optimum substitution range and beyond this range.     

Synthesis of CdS nanoplates by PAA-assisted hydrothermal approach

Triangular and hexagonal CdS nanoplates, with average size about 100 nm and average thickness range from 10 to 30 nm, have been synthesized in the presence of poly (acrylic acid) (PAA) assisted hydrothermal process at 180 °C. The structural characteristics, morphology, and optical properties of the as-prepared CdS products were investigated. UV–vis spectroscopy measurement reveals that the products show a strong quantum size effect. Based on the experiment results, the possible formation mechanism of CdS nanoplates has been proposed.     

α钛合金在室温和低温的冲击韧性

为了考察Al,Sn,Zr,Mo合金元素对α钛合金在室温和77 K低温(液氮)下的缺口冲击韧性(冲击值Ak)的影响,采用示波冲击试验机测试了Ti-2Al,Ti-2Sn,Ti-2Zr和Ti-1Mo 4种α钛合金在室温和77K下的Ak值,并计算了表征其冲击韧性的弹性变形功、塑性变形功和裂纹扩展撕裂功.用扫描电镜观察了4种合金冲击试样断口的形貌.计算数据和显微组织表明,4种合金均显示韧性特征,4种合金元素对冲击韧性贡献的顺序为:Mo＞Zr＞Sn＞Al.