溶液电导率对LYl2铝合金微弧氧化陶瓷层的生长速度和致密度的影响

探讨了微弧氧化溶液体系电导率对陶瓷层生长速度的影响，并以击穿场强作为反映陶瓷层致密度的物理参量，测定了实验条件下电导率与击穿场强的关系。结果表明，陶瓷层的生长速度与溶液电导率之间有近似线性的正比增长关系；而陶瓷层的击穿场强即致密度随电导率的升高呈现先升后降的变化趋势。     

不同电导率溶液中镁合金微弧氧化陶瓷层的生长规律及耐蚀性

利用扫描电镜(SEM)和盐雾腐蚀试验等手段,研究了镁合金在不同电导率溶液中微弧氧化处理生成陶瓷层的生长规律及耐蚀性。结果表明:随溶液电导率的增大,发生微弧氧化现象的起弧电压减小,微弧氧化陶瓷层厚度表现出近似线性增长,陶瓷层表面微孔数目逐渐减少,微孔孔径逐渐增大,陶瓷层内显微缺陷数量逐渐增多;陶瓷层的耐蚀性随电导率的增大表现出先增后减的变化趋势,在溶液电导率为4 (?·m)-1～6 (?·m)-1 时,陶瓷层的耐蚀性较好。     

铝合金微弧氧化磷酸盐体系电解液研究及陶瓷层分析

通过正交试验,以陶瓷层生长速度为主要研究指标,并结合陶瓷膜层的表观质量,对磷酸盐体系电解液配方进行了研究,确定适宜的电解液配方为:14.0 g/L Na5P3O10、0.5g/L NaOH、2.0g/L Na2WO3、2.0g/L EDTA二钠.微弧氧化陶瓷层基本相为α-Al2O3和γ-Al2O3,两相比例随电解液电导率的增大而提高.陶瓷层生长速度随电解液电导率的提高而增加,但过大的电导率将使表面质量下降.     

铝合金微弧氧化陶瓷层光泽度性能的研究

为了探索工艺参数对铝合金微弧氧化陶瓷层表面光泽度的影响规律,加速微弧氧化产品在光学领域的应用,采用MA0240／750电源设备对6061铝合金试样进行微弧氧化处理和用电导率仪测量溶液的电导率,分别利用WGG60-E4光泽度计量仪和JM6460扫描电子显微镜进行光泽度测量和表面形貌组织观察,研究了电流密度大小、溶液温度和试样尺寸等因素对铝合金微弧氧化陶瓷层光泽度的影响,研究结果表明：在微弧氧化前期阶段,陶瓷层的光泽度随着氧化时间的延长呈指数规律下降,并且电流密度和溶液温度都对陶瓷层的光泽度变化具有重要的影响,电流密度越大和溶液温度越高,光泽度随氧化时间延长而下降的速度越快,到了中后期,它们对光泽度大小无影响,光泽度大小都变为2．5且不随氧化时间而变化;试样尺寸大小对陶瓷层光泽度大小无影响,不同尺寸试样的光泽度随时间的延长按照η=519．8e^-1的指数规律下降。     

AZ91D压铸镁合金微弧氧化膜层的显微硬度分析

为了研究压铸镁合金AZ91D微弧氧化膜层显微硬度,在三种溶液及不同电参数条件下制备了微弧氧化膜层,分析了脉冲频率、占空比、电压、溶液成分及其电导率等参数对膜层显微硬度的影响.试验结果表明,镁合金微弧氧化处理可使其表面硬度大幅提高.锆盐溶液处理膜层的显微硬度高,与膜层相组成中含有ZrO2陶瓷有关.电源脉冲频率、占空比、电压、处理时间参数的增加,都使镁合金微弧氧化膜层的显微硬度增加.在一定范围内增加溶液的电导率,可使膜层的显微硬度提高.     

合金微弧氧化技术研究及应用进展

综述了微弧氧化技术的基本原理,介绍了铝、镁、钛合金微弧氧化陶瓷层的组织结构和性能,总结和分析了不同工艺参数如电压、电流密度、氧化时间等对陶瓷层性能的影响规律,介绍了槽液体系如酸碱度、添加剂种类及溶液电导率等对微弧氧化陶瓷层性能的影响,及微弧氧化技术在Al、Mg、Ti及其合金中的应用.     

稀土氧化物掺杂BaTiO3陶瓷的击穿问题研究

研究了BaTiO3基陶瓷的耐压性能.对陶瓷材料的烧结工艺尤其是在还原性气氛的烧成条件下,掺杂BaTiO3基陶瓷中发生的各种缺陷反应机制进行了初步的研究,总结和阐述了掺杂剂浓度、烧成条件对BaTiO3基陶瓷耐压强度的影响.结果表明Y2O3掺杂对钛酸钡瓷体击穿场强的影响由Y2O3在瓷体中的缺陷化学反应所决定,在掺杂质量分数≤1.0%范围内,在≤0.5%之前,瓷体击穿场强呈下降趋势,之后则保持不变或稍有上升;MnO2掺杂对钛酸钡瓷体击穿场强的影响由MnO2在瓷体中的缺陷化学反应与MnO2在瓷体晶界层的分布共同决定,总体表现为随掺杂浓度的增加瓷体击穿电压逐渐下降;Y2O3和MnO2共同掺杂时,它们之间对钛酸钡瓷体击穿场强的调制规律是相对独立的,只是在击穿场强的绝对值方面有所影响;氧分压越低的烧结机制,越容易引起瓷体击穿场强的下降.     

YAG/8YSZ双陶瓷热障涂层等温氧化性能研究

本文对比研究了YAG/8YSZ双陶瓷和8YSZ单陶瓷热障涂层体系的抗高温氧化性能。采用爆炸喷涂(D-GUN)在310S耐热不锈钢基体上制备粘结层(NiCoCrAlY),用大气等离子喷涂(APS)分别在粘结层试样上制备YAG/8YSZ双陶瓷和8YSZ单陶瓷热障涂层,利用SEM和XRD分析涂层氧化前后截面与表面特征,对比研究2种热障涂层体系在1100 ℃等温氧化不同时间后的氧化增重动力学、YAG陶瓷层微观结构与物相及TGO生长过程和生长动力学。结果表明,YAG陶瓷层在1100 ℃等温氧化200 h后无明显相结构转变,孔隙率稍有降低;YAG/8YSZ双陶瓷层体系较8YSZ单陶瓷层体系氧化增重速率降低1.7倍,TGO生长速率降低1.4倍,粘结层β-NiAl相消耗速度及岛状氧化物生长速度更低,表现出更好的抗高温氧化性能。     

铝酸钠溶液电导率数学模型的研究

以铝酸钠溶液苛性碱浓度、分子比和溶液温度为因子,采用三因子二次回归正交试验建立了铝酸钠溶液电导率数学模型,分析了溶液电导率与溶液苛性碱浓度、分子比和溶液温度的关系。结果表明在一定的分子比、溶液温度和苛性钠浓度条件下铝酸钠溶液的电导率随着溶液苛性钠的增大而减小;当苛性钠浓度和温度一定时,溶液的电导率与溶液分子比呈抛物线关系,并在试验范围内随着分子比的增大而增大。铝酸钠溶液的电导率随着溶液温度升高而增大,近似直线关系。     

CO_2对X70钢在近中性pH值溶液中硫酸盐还原菌腐蚀行为的影响

对不同CO_2浓度下硫酸盐还原菌(SRB)在近中性pH值(NS4)溶液的生长曲线,以及SRB生长周期对溶液pH值和电导率的影响进行了研究。采用极化曲线、电化学阻抗技术和扫描电镜(SEM)研究了CO_2浓度对X70钢在有菌的NS4溶液中的腐蚀行为。结果表明:CO_2在SRB代谢过程中起到了迟效碳源的作用,使SRB繁殖出现二次生长。SRB新陈代谢消耗了有机碳并释放出无机离子使溶液电导率在SRB对数生长期增加。SRB二次生长期消耗无机碳源(CO_2)和化合物时并不产生新的离子导致溶液电导率下降。SRB生长周期对溶液pH值没有影响,pH值随时间和CO_2浓度增加而略有增加。X70钢在有菌溶液中表面膜层表现出圈状裂纹,随CO_2浓度增加,X70钢在NS4菌液中表面膜层致密性变差。CO_2促进了金属表面点蚀的发展。     

Metallization of Thin Al2O3 Layers in Power Electronics Using Cold Gas Spraying

A successful combination of insulating substrates with conducting metal coatings produced by cold spraying could open new industrial application areas like the fabrication of power electronic components. For minimizing the number of industrial process steps, insulating ceramic layers should ideally be processed by thermal spray techniques. Thus, this study investigates the impact behavior and coating formation of ductile metallic feedstock powders onto brittle ceramic coatings. With respect to high electrical conductivity of the metallic lines and good electrical insulation of the ceramic interlayer, copper was cold gas sprayed on previously thermally sprayed Al₂O₃ coatings. Successful cold coating formation requires different strategies for the activation of the ceramic layer to increase adhesion and to avoid brittle failure. These both can be achieved either by applying a bondcoat on the ceramic layer or using heated substrates during the cold spray process.     

Processing Parameter Effects and Thermal Properties of Y<Subscript>2</Subscript>Si<Subscript>2</Subscript>O<Subscript>7</Subscript> Nanostructured Environmental Barrier Coatings Synthesized by Solution Precursor Induction Plasma Spraying

The solution precursor plasma spray process, in which a solution of metal salts is axially injected into an induction thermal plasma, is suitable for deposition of nanostructured environmental barrier coatings. The effects of main processing parameters, namely the solution precursor concentration, spraying distance, reactor pressure, and atomization gas flow rate, have been analyzed using D-optimal design of experiments regarding the deposition rate and coating porosity responses. Among these four parameters, the solution precursor concentration had the greatest influent on the coating structure, followed by the spraying distance and reactor pressure, and finally the atomization gas flow rate with a small contribution. It is pointed out that the species that impact on the substrate are agglomerates of nanoparticles. The equivalent thermal conductivity of selected coatings was computed from experimental temperature evolution curves obtained by laser flash thermal diffusivity analysis, using two methods: a multilayer finite-element model with optimization, and a multilayer thermal diffusion model. The results of the two models agree, with coatings exhibiting low thermal conductivity between 0.7 and 1 W/(m K) at 800 °C.     

高导热涂层制备及其性能研究进展

随着高集成技术、微电子封装技术、大功率LED技术以及超级计算机的迅猛发展,小型化、微型化与轻薄化成为现代及未来电子设备、电子电路的发展潮流,因此对散热要求越来越高.目前电子器件及设备主要应用导热硅脂、导热硅胶及复合材料来实现散热.若在器件及设备上制备一层具有高热导率、耐腐蚀、结合强度良好的导热涂层,可以更好地实现散热....     

氢气流量对大气等离子喷涂TiO2涂层导电性的影响

采用大气等离子喷涂方法制备TiO2涂层,研究氢气流量的变化对TiO2涂层的显微结构、相结构以及导电性的影响.随着氢气流量的增加,TiO2涂层的孔隙率减少,缺氧相增加,涂层的电阻率随之减小.同时在通电升温条件下涂层的电导率随温度的升高而增加.结果表明,大气等离子喷涂TiO2涂层主要由金红石相、锐钛矿相和缺氧相Magneli(TinO2n-1,n=4～10)组成,各相的含量与等离子气中氢气的流量有关.     

氮含量对直流磁控溅射(TiAlTaCrZr)N涂层力学及钛合金切削性能影响研究

解决传统刀具耐磨涂层导热性差的问题。本文采用直流磁控溅射方法,在不同氮气流量下制备了(TiAlTaCrZr)N涂层,研究了不同氮含量对涂层微结构和硬度、结合力、导热等性能的影响。随着氮气流量的增加,涂层中N含量增加,涂层微观结构会由纳米晶向柱状晶转变。涂层的硬度从TiAlTaCrZr 涂层的11.0 GPa增加到5 SCCM氮流量时(TiAlTaCrZr)N 涂层的20.6 GPa。涂层在氮气流量为5 SCCM时膜基结合力可达到130 N以上,之后随着氮含量增加逐渐降低。(TiAlTaCrZr)N涂层的导热性均优于TiAlN涂层的导热性,但随着氮含量增加导热性降低。(TiAlTaCrZr)N涂层的高导热性、高结合力、高硬度等特性使其在钛合金高速切削时切削距离比TiAlN涂层提高175%,这为钛合金加工提供了一种新型耐磨涂层。     

Zink in Korrosionsschutzüberzügen

Zink in anti-corrosion coatings Zinc in anti-corrosion coatings is being increasingly used for hot-dip galvanising, electrolytic galvanisation, metal spraying and zinc dust coatings. The author discusses the reasons for this development and the experience gathered with zinc in anti-corrosion coatings. Mention is made of certain specific problems such as the duplex system consisting of hot-dip galvanisation plus coating of freshly hot-dip galvanised surfaces; the question of coatings for insulating materials made of hot-dip galvanised sheeting; the relationship between service life and the thickness of the coating; the penetration of zinc flower with varnishings, etc.     

Modeling Thermal Conductivity of Thermally Sprayed Coatings with Intrasplat Cracks

Thermal spraying is one of the most important approaches for depositing thermally insulating ceramic top coatings for advanced gas turbines due to the low thermal conductivity of the coating resulting from its lamellar structure. The thermal conductivity of the coating has been explained based on the concept of thermal contact resistance and correlated to microstructural aspects such as splat bonding ratio, splat thickness, and the size of the bonded areas. However, the effect of intrasplat cracks on the thermal conductivity was usually neglected, despite the fact that intrasplat cracking is an intrinsic characteristic of thermally sprayed ceramic coatings. In this study, a model for the thermal conductivity of a thermally sprayed coating taking account of the effect of intrasplat cracks besides intersplat thermal contact resistance is proposed for further understanding of the thermal conduction behavior of thermally sprayed coatings. The effect of the intersplat bonding ratio on the thermal conductivity of the coating is examined by using the model. Results show that intrasplat cracks significantly decrease the thermal conductivity by cutting off some heat flux paths within individual splats. This leads to a deviation from the typical ideal thermal contact resistance model which presents cylindrical symmetry. Based on the modified model proposed in this study, the contribution of intrasplat cracks to the thermal resistivity can be estimated to be 42–57 % for a typical thermally sprayed ceramic coating. The results provide an additional approach to tailor the thermal conductivity of thermally sprayed coatings by controlling the coating microstructure.     

Self-Enhancing Thermal Insulation Performance of Bimodal-Structured Thermal Barrier Coating

Nanostructured thermal barrier coatings (nano-TBCs) are being extensively studied because of their excellent thermal barrier properties. The occurrence of sintering in TBCs is inevitable in service; however, accelerated sintering of the nano-TBCs may cause premature failure. This study focuses on the changes of microstructure and thermal conductivity of bimodal nano-TBCs during thermal exposure. Results show that there are two stages in the sintering process. It was found that the thermal conductivity increased rapidly in the first stage (from 0 to 20 h), with the rate of increase in normalized thermal conductivity equal to 140% of bimodal coating. The continuous healing of the pores was the main structural change. During the following stage (20 to 100 h), the thermal conductivity decreased with the rate of increase in normalized thermal conductivity equal to ??8% of bimodal coating. The change of structure was the opening of pores. Furthermore, self-enhancing behavior of bimodal composite coatings was discovered. The phenomenon of inevitable sintering in thermodynamics can be used to introduce large-aspect-ratio pores in the in-depth direction, which can greatly slow down the increase in thermal conductivity in service and ultimately increase the lifetime of the thermal insulation. Based on a full study of the sintering mechanism of composite coatings, the present study sheds light on the structural adjustments that lead to a lower thermal conductivity and longer service life in the advanced TBC during high-temperature service.     

Study of the effect of DMSO concentration on the thickness of the PSS insulating barrier in PEDOT:PSS thin films

One of the most used secondary dopants in thin film processing of PEDOT:PSS is dimethyl sulfoxide (DMSO). In this work, we present results that explain, from the point of view of impedance spectroscopy, the mechanism of the increase in the conductivity observed on films based on PEDOT:PSS. The results obtained with this technique, combined with others such as AFM, and Raman and UV–vis–NIR spectroscopies, clearly show that there is a thinning of the insulating barrier of PSS surrounding conductive grains of PEDOT. It is shown that the thickness of the insulating barrier is related strongly and inversely with the onset frequency of AC conductivity. However, this is not the only existing effect, because for values beyond the optimal concentration of DMSO, we observe a decrease in the conductivity related with an increase of the separation of the PEDOT grains. The AC measurements and the AFM images also show the clear interplay between the increase of the PEDOT average grain size and the separation between them.     

NaCl、NaBr、Nal在DMATk溶液中的电导率

钠盐在酰胺衍生物水混合溶剂中的电导率、摩尔电导率是研究溶液热力学性质的重要参数。它集中反映了指定溶剂中离子之间及离子与溶剂分子之间的相互作用。对离子溶剂化、离子缔合及溶液结构理论的研究与应用具有重要的意义。随着生物化工的发展,有机物水溶液热力学性质的测定及研究日益受到重视。为了更系统研究不同的取代基对迁移性质的影响,本文研究NaCl、NaBr、NaI与DMA（N,N-二甲基乙酰胺）水溶液的电导率,测定了NaCl、NaBr、Nal分别在浓度为0．1mol／L、0．2mol／L、0．3mol／L的DMA水溶液中,在298K、299K、300K、301K、302K五个温度下的电导率,根据公式Am=（λ液-λ剂）X10^-3／c计算NaCl、NaBr、NaI的摩尔电导率人。使用Origin软件进行线形分析,NaCl、NaBr、NaI在混合溶剂DMA和H20中随温度的增加,其摩尔电导率随之增加,且基本符合线性关系。