电流密度对无氰镉-钛合金镀层的影响

采用金相显微镜、电化学工作站、划线法、霍尔槽实验以及比色法,通过测试镀层样品的外观,耐蚀性、结合力、镀液的分散性能以及镀层的钛含量分析了电流密度对无氰镉-钛合金镀层的影响。研究结果表明,电流密度为2 A/dm~2时镀层外观、耐蚀性、结合力等性能最佳,镀液分散能力最好,镀层钛含量最高,得到的镀层结晶细致,均匀。     

计时电位法测定电镀电流效率

本文根据“计时电位法”测定电镀电流效率的原理和方法,详细研究了电沉积锌、铜、镍、铬、银、锡和镍-铁合金的电流效率的测试条件。讨论基体金属和阳极溶解液组成对测定结果的影响,并提出最佳测试条件。研究结果进一步表明,“计时电位法”测定电流效率是一种快速方便的新方法,若使用DDC-2型或DD-1型电镀参数测试仪,其测量误差小于±1％。     

Surface characterisation of DC plasma electrolytic oxidation treated 6082 aluminium alloy: Effect of current density and electrolyte concentration

Plasma electrolytic oxidation (PEO) is a specialised but well-developed process which has found applications in aerospace, oil/gas, textile, chemical, electrical and biomedical sectors. A novel range of coatings having technologically attractive physical and chemical properties (e.g. wear- and corrosion-resistance) can be produced by suitable control of the electrolyte as well as electrical parameters of the PEO process. Oxide ceramic films, 3 to 40 μm thick, were produced on 6082 aluminium alloy by DC PEO using 5 to 20 A/dm² current density in KOH electrolyte with varied concentration (0.5 to 2.0 g/l). Phase analysis (composition and crystallite size) was carried out using X-ray diffraction and TEM techniques. Residual stresses associated with the crystalline coating phase (α-Al₂O₃) were evaluated using the X-ray diffraction Sin²ψ method. Nanoindentation studies were conducted to evaluate the hardness and elastic modulus. SEM, SPM and TEM techniques were utilised to study surface as well as cross-sectional morphology and nano features of the PEO coatings. Correlations between internal stress and coating thickness, surface morphology and phase composition are discussed. It was found that, depending on the current density and electrolyte concentration used, internal direct and shear stresses in DC PEO alumina coatings ranged from − 302 ± 19 MPa to − 714 ± 22 MPa and − 25 ± 12 MPa to − 345 ± 27 MPa, respectively. Regimes of PEO treatment favourable for the production of thicker coatings with minimal stress level, dense morphology and relatively high content of α-Al₂O₃ phase are identified.     

新型磁流变液压伺服阀测试系统控制器设计

新型磁流变伺服阀由磁流变阻尼阀构成,阻尼阀由专用的电流控制器控制,依据电流调节改变磁场强度达到控制阻尼阀中液体阻尼力大小的目的。分析了电流控制器的设计原理,据此基于虚拟仪器技术设计出操作软件,针对电流控制器的特点和技术指标,改变输入电压大小以调节电流控制器的输出电流,在阻尼阀动态工作过程中实时监测输入和输出信号以提供分析数据。实验结果显示,该控制器可使得阻尼阀工作稳定,伺服系统性能达到设计要求。     

精密轧管技术现状

随着近20年精密轧管(Accu Roll)技术的飞速发展,精密轧管机组已经成为国内热轧无缝钢管生产的第二大主力机型。介绍了精密轧管技术的现状;指出了精密轧管技术存在的问题;探讨了精密轧管工艺改进的方向和可能性,如采用轧制荒管头尾削尖技术进一步提高芯棒限动速度的可能性,提高机组产能的途径及采用精密轧管机组生产大直径(Φ508mm以上)钢管等。分析认为,精密轧管机组投资少、技术先进,值得研究和选择。     

开关型CMOS霍尔磁敏传感器的设计

介绍一种开关型CMOS霍尔磁敏传感器的设计，采用正交电流的方法和斩波稳零放大器来实现对失调电压的抑制和有效信号的放大，并通过一个定时控制电路实现对整个芯片的管理，在保证测量灵敏度的条件下，使电路中功耗较大的信号检测和放大部分周期性地进入睡眠状态，大大降低了芯片的功耗。同时芯片还实现了对双磁极信号的检测。     

电子式互感器数字输出接口

依据电子式电流互感器标准IEC60044-8,对电子式互感器的数字输出接口进行了研究,对规约中规定的电子式互感器的结构、数字输出的物理层、链路层及应用层进行了详细分析,并提出了具体的解决方案,其中采用DSP作为其主处理器连同一些外围电路来实现规约中所描述的MU的功能电路可以满足系统的实时性和可靠性,系统还可以根据现场需要方便地进行扩展.讨论了电子式互感器的应用对变电站的影响及其应用前景.     

Correlation between current frequency and electrochemical properties of Mg alloy coated by micro arc oxidation

The present work investigated the electrochemical behavior of Mg alloy subjected to micro arc oxidation coating for 120 s with respect to current frequencies from 60 Hz to 2000 Hz. The microstructure and chemical compound of thin coating layers with a thickness of ~ 3 μm were analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. The microstructural observations on the surface and cross sections revealed that both the size of pores and the number of discharge channels decreased significantly as the current frequency increased, resulting in a compact coating layer. This was primarily attributed to the transition time of the alternating electrical wave, which was determined by the current frequencies tested. Based on potentiodynamic polarization tests, the sample coated at a frequency of 2000 Hz demonstrated the highest polarization resistance of 6.37 × 10⁵ Ω cm², implying that the corrosion resistance was superior to that obtained under other conditions due to its condensed structure. This electrochemical response was also interpreted in relation to the equivalent circuit model.     

一种新型燕尾槽导轨设计及其调整的方法实现

为了满足飞机垂尾加载试验设备在倾斜悬挂状态下沿导轨平稳运动,采用变形燕尾槽结构设计了一种新型导轨。导轨内设可调斜铸块,易于加工安装和调整间隙,抗震耐磨,具有更好的承受倾斜力及倾覆力矩的能力。该设计利用设备自身的伺服驱动器驱动加载设备移动,根据驱动电流曲线指导导轨的安装调整,使驱动电流峰值减少22%,提高了导轨的装配精度。     

Swelling effect of a polymer electrolyte membrane on the development of a semi-empirical cell voltage model

We developed a new cell voltage model which depends on the current density response of the proton exchange membrane fuel cell (PEMFC). The proposed model focuses on the conductivity of a PEMFC fuel cell. The model for conductivity of a polymer electrolyte membrane, Nafion, uses the thermodynamic function to represent water activity. We observed membrane conductivity by monitoring the chemical potential of the swelling of the hydrogel. The swelling equilibrium of the ionized hydrogel is governed by the free energy of mixing, the free energy of elasticity, and the concentration of counterions with fixed charges on the gel network. A cell voltage equation with reasonable boundary conditions, including the swelling effect, which plays a major role in determining the cell voltage of a PEMFC, was newly developed.