镁合金表面处理技术现状和发展趋势

多种表面处理技术应用于镁合金的防护上,以便改善镁合金的性能,扩大镁合金的应用领域,提高镁合金材料的使用寿命.论述了镁合金表面处理技术,包括化学氧化、阳极氧化、金属涂层、有机物涂层等研究和应用的现状;着重阐述了微弧氧化技术具有膜层与基体结合强度高、硬度高、耐磨性好、抗腐蚀能力强、热稳定性好等优点;概述了微弧氧化技术国内外研究与应用现状,并提出微弧氧化技术是镁合金表面处理的重点.     

电解液对镁合金微弧氧化层耐蚀性的影响

为了提高镁合金基体的耐蚀性,采用微弧氧化法在镁合金表面制备了MgO-ZrO2复合陶瓷层,利用XRD和SEM研究了膜层的相组成、结构及生长过程,并用LK98C电化学综合系统测试了其耐蚀性.实验结果表明：三种电解液中,K2ZrF6-KOH耐蚀性能较好;在交流阻抗测试结果中,镁基体出现了点蚀;K2ZrF6为8g/L,KOH为3.2g/L时,电荷转移电阻较高,达到4.058×105Ω.     

Synthesis of Fluorescent Carbon Quantum Dots and Their Application in the Plant Cell Imaging

Carbon quantum dots(CQDs) exhibit tremendous advantages for plant growth study due to its strong fluorescence and good biocompatibility. The fluorescent CQDs were synthesized by the onestep microwave method with the raw materials of citric acid(CA) and urea(UR), and expressed a unique green fluorescence with the optimal excitation wavelength of over 400 nm through adjusting the doping of N elements. It is demonstrated that CQDs can act as deliver media in plant and fluorescent probes for plant cell imaging through directly cultivated in the seedlings of melon and wheat, respectively. Based on the effects of the fluorescent CQDs on plants growth, we can further study the mechanisms of the ions transport in plants.     

Poly(dopamine)-assisted Bioactive Coating on the Surface of Porous Poly (Ether Ether Ketone) to Promote Osteogenic Differentiation of rBMSC

A facile modification strategy is developed to promote the proliferation and osteogenic differentiation of rat bone marrow stromal cells (rBMSCs) through deposition of a bioactive calcium silicate (CS) coating on the porous surface of poly (ether-ether-ketone) (PEEK) with the assistance of poly(dopamine) (PDA).The porous structures are etched on the surface of PEEK after sulfonation treatment.A poly(dopamine) layer is coated on the porous surface of the sulfonated PEEK (SPEEK),which provides anchoring groups for the subsequent deposition of the CS layer.Results show that the CS coating on the porous surface of SPEEK significantly improve the hydrophilicity and biomineralization formation of hydroxyapatite.Compared with PEEK,SPEEK-PDA-CS displays higher bioactivity to promote the proliferation and osteogenic differentiation of rBMSCs,including the increase of ALP activity and formation of calcium nodules,the expression of osteogenic differentiation-related genes.These results are beneficial to extending clinical applications of PEEK-based implants for bone tissue repair and orthopedic surgery.     

Corrosion behavior of amorphous/nanocrystalline Al-Cr-Fe film deposited by double glow plasmas technique

In order to improve the corrosion resistance of AZ31 magnesium alloy, the amorphous/nanocrystal Al-Cr-Fe film has been successfully prepared on AZ31 magnesium alloy by double glow plasma technology. The amorphous/nanocrystalline consists of two different regions, i.e., an amorphous layer on outmost surface and an underlying lamellar nanocrystalline layer with a grain size of less than 10 nm. The corrosion behavior of amorphous/nanocrystalline Al-Cr-Fe film in 3.5% NaCl solution is investigated using an electrochemical polarization measurement. Compared with the AZ31 magnesium alloy, the amorphous/nanocrystalline Al-Cr-Fe film exhibits more positive corrosion potentials and lower corrosion current densities than that of AZ31 magnesium alloy. XPS measurement reveals that the passive film formed on the Al-Cr-Fe film after the anodic polarization tests is strongly enriched in Cr₂O₃, Fe₂O₃ and Al₂O₃ at outer surface of the film and in the inner layer consists of Cr₂O₃, FeO and Al₂O₃. Supported by the National Natural Science Foundation of China (Grant Nos. 50571045 and 50704022) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2007591)     

柠檬酸对WP催化剂噻吩加氢脱硫性能影响

以柠檬酸(CA)为助剂,采用共浸渍和程序升温还原的方法制备了不同n(CA)/n(WP)的WP催化剂。并用X射线衍射(XRD)、比表面积测定(BET)、扫描电镜(SEM)、热重(TG)分析等方法对催化剂进行了表征,通过高压微反评价了催化剂的噻吩加氢脱硫(HDS)性能。结果表明,柠檬酸并没有改变WP的本体结构,但具有阻止WP晶相颗粒生长的作用,并提高了WP催化剂的BET比表面积。加入柠檬酸改变了硝酸根的分解过程,降低了催化剂的起始磷化还原温度和磷化还原过程终结温度,有利于活性组分在催化剂表面的分散。柠檬酸对WP催化剂噻吩HDS反应有利。Cat-5催化剂具有相对最好的HDS活性,与不加柠檬酸的催化剂相比,其噻吩转化率提高近20.4%。     

高应变速率下Mg-Gd-Y镁合金动态

为了研究Mg-Gd-Y镁合金在高应变速率下的动态拉伸性能及失效机制,采用分离式Hopkinson拉杆(SHTB)装置在室温下且应变速率为1 400~3 000 s^-1范围内对其进行了动态拉伸实验,并利用光学显微镜和扫描电子显微镜对动态拉伸后的镁合金试样进行了分析.结果表明,在动态拉伸载荷作用下,Mg-Gd-Y镁合金沿ED方向呈现连续屈服现象.应变速率增大后,Mg-Gd-Y镁合金具有正应变速率效应.在动态拉伸载荷作用下,Mg-Gd-Y镁合金的断口形貌呈解理断裂特征,镁合金的变形方式为孪生和滑移,且滑移为主要变形方式。     

Corrosion Resistance of AZ91 Magnesium Alloy after Laser Remelting Treatment

The main objective of the study was the modification of the surface layer of magnesium alloy by the CO_2 laser. The studied material was the commercial AZ91 magnesium alloy. The effectiveness of the alternations caused by the remelting process was verified on the basis of microscopic observation and corrosion investigations, i e, recording of potentiodynamic polarization curves, electrochemical noise measurements and hydrogen evolution rate measurements. For the adopted range of the treatment parameters, favourable changes were observed in the surface layer such as the refinement of structure and more uniform arrangement of individual phases. As a consequence of those favourable structural changes the improvement of the corrosion resistance of the alloy was achieved in comparison to its non-remelted equivalent. For the treated material corrosion rates expressed as corrosion current densities were at least three times lower than the appropriate values for the untreated alloy comparing them for the same period of samples immersion in the test solution. The obtained results have confirmed the effectiveness of the applied surface treatment resulting in favourable changes in the structure and corrosion properties of the AZ91 magnesium alloy.     

多羧酸交联整理中聚合羧酸的应用

对马来酸三元共聚物(TPMA)与柠檬酸(CA)混拼工艺技术作了探讨.     

柠檬酸对NiMoP/Al2O3⁃USY催化剂活性影响

以Ni、Mo为活性组分,Al₂O₃?USY为载体,通过向NiMoP浸渍液中添加柠檬酸,考察柠檬酸对催化剂催化活性的影响。对催化剂进行表征,结果表明随着浸渍液中柠檬酸浓度增大,催化剂表面总酸量呈先增加后减小的趋势,当n_L/n_Ni=1.0时,催化剂表面酸量最大;催化剂活性相MoS₂堆积层数逐渐增加,平均片层长度逐渐增大。340 ℃实验条件下,当n_L/n_Ni=1.0时,催化剂的催化活性最好,脱硫率和脱氮率分别为99.6%、99.7%,优于未添加柠檬酸的催化剂。     

镁合金电镀镍涂层的耐蚀性能

以化学镀镍作为保护层,对AZ91D镁合金进行直流电镀镍涂层以提高其耐腐蚀性能,并对镁合金表面两个不同厚度的镀镍涂层进行了比较.采用SEM对涂层的表面形态进行了研究.在X射线下纹理明显.镍涂层硬度约560VHN,远远高于AZ91D镁合金基底的硬度(约100VHN).电化学测量结果表明,在已经研究的镁合金涂层中,镍镀层有最低的腐蚀电流密度和最高的腐蚀电位.加速腐蚀实验中AZ91D镁合金镀镍具有很高的耐腐蚀性能.     

基于元胞自动机AZ31镁合金固溶处理研究

镁合金具有导热导电性好、电磁屏蔽性能优越、与环境相容性良好等诸多优点。但是镁合金在室温下塑性较差,导致其在轧制过程中易出现裂纹从而影响其质量。为了有效提高其可塑性,在加工前往往需要对其进行固溶处理。基于此,通过金相实验,得到AZ31镁合金管材原始晶粒组织,基于晶粒长大的热力学机制、曲率驱动机制和能量耗散机制,建立元胞自动机模型,针对镁合金建立了三大晶粒演变规则,研究AZ31镁合金在不同温度和不同时间下晶粒演变规律与边数变化情况,最终获得晶粒均匀分布且以六边形为主的微观组织。通过晶粒长大拓扑学分析与晶粒尺寸分布统计,得出晶粒尺寸在不同温度和时间内呈正态分布,其中六边形晶粒最多;在此基础上,建立固溶情况下的晶粒长大数学模型,合理预测并控制AZ31镁合金固溶后的晶粒尺寸和最终性能,分析了晶粒长大动力学,得出镁合金生长指数为0.87,并通过实验验证了元胞自动机模型的正确性和合理性,为研究镁合金在变形过程中的晶粒演变奠定基础。     

Quick surface treatment of AZ31B by AC micro-arc oxidation

In order to explore an effective way to shorten treatment time and enhance the quality of treatment coating, AC micro-arc oxidation was conducted to treat the surface of AZ31 B deformation magnesium alloy in KF+KOH treatment solution. The infl uences of micro-arc oxidation parameters such as concentration of KF, concentration of KOH, output voltage of booster, temperature of treatment solution, and treatment time on treatment coating thickness were raveled out under different conditions. The structure and composition of treatment coating were determined, the growth mechanism of treatment coating was discussed, and the quick surface treatment technology for compact treatment coating with maximum thickness was developed. The experimental results show that: A maximum 33 μm-thick compact treatment coating, consisting of MgF2 and MgO mainly, can be formed on AZ31 B in 112 s under the conditions of 1 132 g/L KF, 382 g/L KOH, 66 V for output voltage of booster and 34 ℃ of treatment solution which were optimized by a genetic algorithm from the model established by artifi cial neural networks. There are no "crater-shaped" pores in this treatment coating as the heat shock resulting from the smooth variation of AC sinusoidal voltage is far smaller than that of the rigidly varied DC or pulse current. The treatment time is only one sixth of that adopted in the other surface treatment technology at best, principally for the reason that the coating can always grow irrespective of the electric potential of AZ31 B. This investigation lays a fi rm foundation for the extensive application of magnesium alloy.     

CA缓凝剂对再生石膏性能的影响及其机理

系统研究了柠檬酸缓凝剂对再生石膏性能的影响,以及其性能变化规律,并结合化学反应相关理论、红外光谱和扫描电镜对其作用机理进行了分析。结果表明：加入柠檬酸缓凝剂后,原生石膏的凝结时间延长,强度大幅度的降低;而相比未掺加缓凝剂的再生石膏(R-P)而言,掺加缓凝剂的再生石膏(R-CP)标稠需水量降低,凝结时间延长,1 d强度有所降低,但干强度却有小幅度的升高。对于未掺加缓凝剂的原生石膏(POP)而言,其对应的再生石膏需水量增加,凝结时间延长,强度降幅达40-50%;而对于掺加缓凝剂的原生石膏(POCP)而言,R-CP有较小幅度地需水量增加,凝结时间和干强度降低,1 d强度却有所升高。分析表明,原生石膏中加入柠檬酸缓凝剂后,柠檬酸与Ca2+结合形成CaCit-,阻止石膏晶体在C轴上的生长,延迟水化,形成粗棒状的晶体,从而降低石膏的强度;而其对应的再生半水石膏依旧保持原有的短棒状,降低其用水量,且R-CP中的CaCit-可以再次与石膏中Ca2+结合,起到效果较差的缓凝作用,延迟再生石膏的水化。     

硅烷膜固化方式对AZ91镁合金耐蚀性的影响

为了改善AZ91镁合金的耐蚀性,采用包括加热固化、碱液固化和微电水固化在内的3种不同固化方式制备了硅烷膜,并对其耐蚀性进行了研究.采用光学显微镜和扫描电子显微镜观察了试样的腐蚀形貌,并采用极化曲线分析了硅烷膜的耐蚀性.结果表明,经硅烷化处理后,AZ91镁合金表面可以形成一层硅烷膜,且很好地抑制了镁合金的腐蚀;对比3种不同固化方式后发现,碱液固化效果最佳,其次是加热固化,微电水固化效果虽不及前两者,但也有较好的效果.     

Dispersing and Doping of BaTiO3 Powder by Adsorption

Dispersing and doping of BaTiO3 powder by adsorption method were investigated.Ultrafine BaTiO3 powders were dispersed in the aqueous with ammoniumized citrate (NH4-CA) or ammoniumized citric Ianthanum chelate (NH4-La-CA) as dispersant by ultrasonic bath. Better dispersion of BaTiO3 slurry was obtained in the aqueous with NH4-La-CA than that of NH4-CA when the mass ratio of citric acid (CA) to BaTiO3.Was less than 0.007. The pH value hardly affects the dispersion property of BaTiO3 suspension dispersed by NH4-La-CA. BaTiO3 powder could be well dispersed (median size D50=0.45 μm) and also doped with high uniformity of added components by adsorbing citric acid chelate on surface. Compared with solid mixing, better microstructure and properties of La/Mn codoped ceramics were obtained by adsorption method.     

Nanosized Nickel Oxides Derived from the Citrate Gel Process and Performances for Electrochemical Capacitors

Nanosized nickel oxide powders were prepared by thermal decomposition of the nickel citrate gel precursors. The thermal decomposition and powder materials derived from calcination of these gel precursors with various ratios of citric acid （CA） to nickel at different temperatures and times were characterized by thermal analysis （TG/DTA）, scanning electron microscopy （SEM）, x-ray diffraction （XRD）, and measurement of specific surface area （BET） with porosity analyses. The optimized processing conditions of calcination temperature 400℃ for 1 hour with the CA/Ni ratio of 1.2, were determined to produce the nanosized nickel oxide pow- ders with a high specific surface area of 181 m^2/g, nanometer particle sizes of 15-25 nm, micro-pore diameter distribution between 4-10 nm. The capacitance characteristics of the nanosized nickel oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） exhibiting both a double-layer capacitance and a faradaic pseudocapacitance. The nanosized nickel oxide electrode shows a high cyclic stability and is promising for high performance electrochemical capacitors.     

Growth characterization of anodic film on AZ91D magnesium alloy in an electrolyte of Na2SiO3 and KF

Anodization of AZ91D magnesium alloy in the electrolyte solution of 0.5 mol/L of sodium silicate and 1.0 mol/L of potassium fluoride was investigated. The anodic films were characterized using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The corrosion resistance of the various anodized alloys was evaluated by a fast corrosion test using the solution of hydrochloric acid and potassium dichromate. The results showed that the addition of KF resulted in the presence of NaF in the anodic film. The thickness of the anodic film formed under a constant current density of 20 mA/cm2 for 16 min at 60℃ exceeded 100 μm. The growth of the anodic film could be divided into three stages based on the anodizing time; the growth rate was much faster during stage Ⅱ than in stages Ⅰ and Ⅲ. The anodic film exhibited the highest corrosion resistance for the AZ91 alloy,which is attributed to the fact that the anodization was maintained until the end of stage Ⅱ.     

Microstructure and flow stress of Mg-12Gd-3Y-0.5Zr magnesium alloy

The microstructure and flow stress of the Mg-12Gd-3Y-0.5Zr magnesium alloy was investigated by compression test at temperatures ranging from 350 to 500 ℃ and the strain rates ranging from 0.01 to 20 s-1. The flow stress of the magnesium alloy increased with strain rate and decreased with deformation temperature. Flow stress can be expressed in terms of the Zener-Hollomon parameter Z, which describes the combined influence of the strain rate and temperature using an Arrhenius function.The values of the deformation activation energy were estimated to be 245.9 and 171.5 kJ/mol at deformation temperatures below 400 ℃ and above 400 ℃, respectively. Two constitutive equations were developed to quantify the effect of the deformation conditions on the flow stress of the magnesium alloy. The effects of deformation temperature and strain rate on the microstructure of the magnesium alloy were also examined and quantified by measuring the volume fraction of dynamically recrystallized grain Xd. Xd increased with increasing of deformation temperature. When the deformation temperature was below 475 ℃, Xd decreased with strain rate until it reached 0.15 s-1, then it increased again. When the deformation temperature was above 475 ℃, Xd increased with strain rate.     

液体中镁合金表面电火花Al-Nd合金化研究

以Al-Nd铸造合金为电极、蒸馏水和煤油为电介液,对ZM5镁合金进行电火花合金化。采用金相分析、能谱分析和扫描电镜对合金化层的形貌和成分进行研究。结果表明,应用液体中电火花合金化技术,可以在镁合金表面制备合金化层;以蒸馏水为电介液、放电电压为80～100 V,或以煤油为电介液、放电电压为40～60 V时,合金化层较连续、致密,其最大厚度可以达到50μm。