镁合金微弧氧化的负载模型及仿真分析

为了确定镁舍金微弧氧化负载对电源形式及参数的要求,基于电化学和电弧物理理论,对单极性和双极性脉冲输出方式下的负载波形进行分析,建立了负载等效电路模型。微弧氧化负载呈现极强的电容性,其负载模型可简化为1个电容和2个电阻等效的一阶RC系统。通过构造电阻可调的强制放电回路,用matlab软件对负载波形曲线进行参数拟合,对等效电路简化模型参数进行了定量分析。所得模型中电容和电阻的数值与计算机仿真结果相符。     

不同表面处理工艺压铸镁合金涂层耐蚀性研究

为了研究不同表面处理工艺下压铸镁合金涂层的抗腐蚀性能,通过浸泡腐蚀和电化学腐蚀的方法,比较了微弧氧化和无铬化学氧化等表面处理试样的耐蚀性.结果表明,无铬化学氧化和微弧氧化处理能显著提高镁合金表面耐蚀性,而以微弧氧化处理更优;且两种处理方法覆盖层对孔洞、裂纹不敏感.根据交流阻抗图谱,拟合得到了微弧氧化、无铬化学氧化和未处理三种试样电化学腐蚀时体系的等效电路,拟合结果与实测结果吻合.XRD分析表明这两种处理方法得到的覆盖层中主体相均为Mg3Al2Si3O12等含硅的尖晶石型氧化物和Mg0.36Al2.44O4、MgAl2O4等不含硅的镁、铝复合氧化物,有利于提高镁合金耐蚀性.     

铝合金微弧氧化陶瓷膜性能及其影响因素探讨

微弧氧化是一个复杂的电化学过程,研究多种因素对氧化陶瓷膜层的影响,对良好陶瓷膜层的制备及相关产品的质量改善具有指导作用.为了说明微弧氧化过程中能量的实质作用,引入氧化功率概念,以LY12铝合金为样品,采用脉冲电源,在一定的脉宽、频率条件下,改变微弧氧化时间、微弧氧化功率等参数,获得相应的铝陶瓷膜,通过对相关样品进行膜层厚度、膜层硬度测量,得到一系列数据,研究并找出其变化规律.试验表明:在相同氧化时间及氧化面积下,随着加载功率的增大,微弧氧化陶瓷膜层的厚度、硬度呈增加趋势;在相同的条件下,在一定的时间范围内,随着氧化时间的延长,膜层厚度呈增长趋势;在相同工艺参数情况下,随着工件面积的增大,微弧氧化膜层的厚度呈降低趋势.     

镁合金微弧氧化专利进展

综述了近年来国内外在镁合金微弧氧化领域的专利技术的进展情况.查新结果表明,采用微孤氧化技术的镁合金专利产品有发动机汽缸盖、眼镜框架、笔记本计算机外壳等.开展镁合金微弧氧化技术的基础条件之一是电源,为此,按照专利中所采用的直流电源、脉冲电源、交流电源等电源的不同对该技术进行了总结.简要分析了今后镁合金微弧氧化专利技术的开发重点.     

微弧氧化电源特性和参数对膜层性能及电能消耗的影响

随着微弧氧化技术及其工业应用的发展,作为关键设备的电源对微弧氧化的影响得到了广泛的关注。综述了电源特性和参数对膜层性能以及工艺能耗影响方面的研究,总结了电源工作模式和电流密度、电压、频率等电参数对膜层相组成、表面形态、耐蚀性等性能以及工艺能耗的影响规律,指出电源特性和参数的影响本质上是电源脉冲能量的影响,能精确控制脉冲能量的电源是今后的发展方向。     

LY12铝合金微弧氧化陶瓷层的电化学腐蚀行为

为了系统了解微弧氧化电参数对铝合金微弧氧化膜耐蚀性的影响,采用自制的设备以恒流法在硅酸盐系电解液中对LY12铝合金进行微弧氧化处理.研究了频率、占空比、时间等参数对铝合金微弧氧化陶瓷层电化学腐蚀行为的影响.用扫描电镜(SEM)和电化学工作站等手段,分析了不同能量参数制备的陶瓷层的微观结构及耐蚀性.结果表明:随着频率增加...     

直流和直流脉冲电源对镁合金微弧氧化膜层性能的影响

采用直流和直流脉冲电源对AZ91D镁合金进行微弧氧化处理,得到具有相同厚度的氧化膜,通过显微硬度测定、扫描电镜观察和极化曲线测试等手段研究了不同电源对微弧氧化膜层性能的影响.结果表明:直流电源下膜层的生长速率大于脉冲直流电源下的;用不同电源处理得到的氧化膜,硬度基本相同;脉冲直流电源下氧化膜的表面形貌、耐蚀性好于直流电源下的,高频下氧化膜的表面形貌、耐蚀性优于低频下的氧化膜.     

脉冲宽度对镁合金微弧氧化的影响

为了研究双极性脉冲微弧氧化电源脉冲宽度对镁合金微弧氧化的影响,在恒流、一定频率,占空比10%～30%对应的脉冲宽度140～430us条件下对镁合金微弧氧化进行了研究.结果发现:随着脉冲宽度的增加,起弧电压逐渐降低,膜层的成膜速率随着脉冲宽度的增加先增大,到一定值后开始减小;随着脉冲宽度的增加,膜层表面的孔洞数量减少,但孔洞尺寸增加.因此,镁合金微弧氧化过程中脉冲宽度要控制在200～300us范围内.     

负脉冲对铝合金微弧氧化膜耐蚀性影响的研究

利用自行研制的100kW微弧氧化设备对LY12铝合金进行微弧氧化表面处理.采用IM6e电化学工作站测试了负脉冲个数分别为0,2,4,8时,微弧氧化LY12铝合金在5%NaCl溶液中的极化曲线,并对极化曲线的塔费尔斜率分析.研究表明,微弧氧化30 min后,陶瓷层厚度由不加负脉冲时的56μm减小到施加8个负脉冲时的31μm.随负脉冲个数增多,陶瓷层的生长时间变短,溶解时间变长,陶瓷层厚度减薄.加载负脉冲可使LY12铝合金微弧氧化陶瓷层的腐蚀电流降为原来的1/10,耐蚀性大幅度增加.负脉冲为4个时制备陶瓷层的腐蚀电流最小,仅为10.3μA,腐蚀速度最低,耐蚀性最好.     

大面积镁合金件的微弧氧化工艺研究

通过对不同大面积镁合金轮毂在微弧氧化过程中的现象分析及工艺测试,探讨了镁合金在微弧氧化过程中的一般规律,并对大面积镁合金件微弧氧化过程中的电流、电压等重要参数进行了研究,优化出用于大面积镁合金件微弧氧化的电参数,可为微弧氧化工艺及电源设计提供参考.     

Analysis of pulse transformer by distributed parameter theory

The pulse responses of magnetically coupled pulse transformers of arbitrary turn ratio n:1 are considered in the framework of a distributed parameter theory. Equivalent circuits for the calculation of pulse risetime and flat-top responses are introduced for inverting- and noninverting-type transformers, respectively. With these equivalent circuits, the pulse risetime responses are calculated more precisely than with the lumped-parameter circuit theory. Measured responses of pulse transformers agree well with the theoretical predictions     

脉冲偏压下电弧离子镀等离子体负载的等效电路模型及其定量表征

为了解决电弧离子镀（AIP）工艺中脉冲偏压电源与AIP等离子体负载间的匹配问题，结合脉冲偏压下AIP工艺实验，运用等离子体鞘层理论、电路理论和仿真模拟技术，得到AIP等离子体负载本质上是由鞘层引起的容性负载，在电路中可以等效为电容和电阻相并联的单元；根据AIP等离子体鞘层演化的特性，将AIP等离子体负载的等效电容表征为与时间无关而只与脉冲偏压幅度和等离子体相关参数有关的量，AIP等离子体负载的等效电阻，可以在直流偏压下通过测量与脉冲偏压幅值对应的AIP等离子体负载电流来确定。经验证，本文建立的AIP等离子体负载的等效电路模型及其定量表征是有效的。     

夹心式复合变幅杆换能器频率方程的推导

应用复合变幅杆及夹心式换能器结构,研制了一种新型夹心式发射换能器。根据等效电路理论推导了这种夹心式复合变幅杆换能器的等效电路模型,得出了换能器频率方程。考虑黄铜电极片对压电振子的密度及等效纵波声速的影响,应用等效参数理论修正了频率方程。通过实验验证,误差由修正前的2.09%降低到修正后的0.64%。     

Non-quasi-static small-signal modeling and analytical parameter extraction of SOI FinFETs

Accurate modeling and analytical parameter extraction of the non-quasi-static small-signal model of FinFETs are presented using a three-dimensional device simulator. Using simple Y- and Z-matrices calculations, the extrinsic gate-to-drain/source capacitance and source/drain resistance are de-embedded from the small-signal equivalent circuit. The analytical parameter extractions are performed by Y-parameter analysis after removing the extrinsic gate-to-drain/source capacitance and source/drain resistance. Accuracy of the model and extraction method is verified with the device-simulation data up to 700 GHz. Without any complex fitting and optimization steps, the total modeling rms error of the Y-parameter up to 700 GHz was calculated to be only 1.9 % in the saturation region and 2.1 % in the linear region. Also, the bias dependencies of the small-signal parameters are presented.     

印制电路板在板级跌落冲击的易损度探究

目的研究标准冲击载荷下印制电路板的挠度响应以及各参数对电路板脆值的影响。方法考虑印制电路板在三角脉冲下的跌落冲击,将四边点支的电路板简化成梁的模型。将脉冲激励考虑为内在的位移,建立模型求解电路板的挠度和加速度响应,进而与电路板的本身特性比较,来考虑电路板的可靠性。结果当受到三角脉冲跌落冲击时,板的最大挠度变形和最大加速度都发生在板的中间位置附近,并且发生在中间时刻。结论为电路板在三角形脉冲下跌落冲击提供其可靠性的理论依据。     

Graphene/Silicon Heterojunction Schottky Diode for Vapors Sensing Using Impedance Spectroscopy

A graphene(G)/Silicon(Si) heterojunction Schottky diode and a simple method that evaluates its electrical response to different chemical vapors using electrochemical impedance spectroscopy (EIS) are implemented. To study the impedance response of the device of a given vapor, relative impedance change (RIC) as a function of the frequency is evaluated. The minimum value of RIC for different vapors corresponds to different frequency values (18.7, 12.9 and 10.7 KHz for chloroform, phenol, and methanol vapors respectively). The impedance responses to phenol, beside other gases used as model analytes for different vapor concentrations are studied. The equivalent circuit of the device is obtained and simplified, using data fitting from the extracted values of resistances and capacitances. The resistance corresponding to interphase G/Si is used as a parameter to compare the performance of this device upon different phenol concentrations and a high reproducibility with a 4.4% relative standard deviation is obtained. The efficiency of the device fabrication, its selectivity, reproducibility and easy measurement mode using EIS makes the developed system an interesting alternative for gases detection for environmental monitoring and other industrial applications.     

永冲电化学腐蚀制备n型多孔硅及其发光性能

采用脉冲电化学腐蚀法,以n型单晶硅为衬底制备多孔硅（n—PS）,通过扫描电镜（SEM）、室温500—700nm范围内荧光光谱,系统研究腐蚀时间、占空比和脉冲频率对n-PS的结构形貌和可见光区室温光致发光特性（PL）的影响,结果表明,相比直流电化学腐蚀方法,脉冲腐蚀能获得孔径分布均匀且发光强度更高的多孔硅;随腐蚀时间、占空比和脉冲频率等腐蚀条件的变化,其发光峰位及发光强度均有明显改变;当等效腐蚀时间为30min、占空比为0．5、脉冲频率为10Hz时,制备的n—PS的PL强度较高,发光性能较好。     

脉冲偏压下电弧离子镀等离子体负载的等效电路模型及其定量表征

为了解决电弧离子镀(AIP)工艺中脉冲偏压电源与AIP等离子体负载间的匹配问题,结合脉冲偏压下AIP工艺实验,运用等离子体鞘层理论、电路理论和仿真模拟技术,得到AIP等离子体负载本质上是由鞘层引起的容性负载,在电路中可以等效为电容和电阻相并联的单元;根据AIP等离子体鞘层演化的特性,将AIP等离子体负载的等效电容表征为与时间无关而只与脉冲偏压幅度和等离子体相关参数有关的量,AIP等离子体负载的等效电阻,可以在直流偏压下通过测量与脉冲偏压幅值对应的AIP等离子体负载电流来确定.经验证,本文建立的AIP等离子体负载的等效电路模型及其定量表征是有效性的.     

Electrical equivalence of electrospray ionization with conducting and nonconducting needles.

An electrical equivalent circuit is derived for the electrospray process. It is a series circuit which consists of the power supply, the electrochemical contact to the solution, the solution resistance (R(s)), a constant-current regulator which represents the processes of charge separation and charge transport in the gap between the spray needle aperture and the counter electrode, and charge neutralization at the counter electrode. A current i, established by the constant-current regulator flows throughout the entire circuit. Current-voltage curves are developed for each element in the circuit. From these it is shown that in the case where R(s) is negligible (the power supply is connected directly to a conducting needle) the shape of the current-voltage curve is dictated by the constant-current regulator established by the charge separation process, the gap, and the counter electrode. The solution resistance may be significant if a nonconducting needle is used so that the electrochemical contact to the solution is remote from the tip. Experiments with a nonconducting spray needle quantify the effect of the solution resistance on the current-voltage curve. Subtracting the iRs voltage from Vapp (power supply voltage) yields the current-voltage curve for the constant-current regulator. When iRs drop is a significant fraction of Vapp, the current-voltage curve of the constant-current regulator is changed substantially from the case when the solution resistance is negligible.     

Equivalent circuit for broadband underwater transducers

A method is presented to determine the equivalent circuits of broadband transducers with 2 resonances in the frequency band of interest. The circuit parameters are refined by least-squares fitting the measured electrical conductance data with this model. The method is illustrated by computing the conductance and susceptance of the equivalent circuits of 3 types of broadband transducers and comparing them with the measured values. The equivalent circuit of a transducer is necessary for designing filters that match the impedances of the transducer and the power amplifier that drives the transducer.