水热预处理对铝合金表面ZnAl-LDHs涂层防腐蚀性能的影响

目的提高表面ZnAl-LDHs涂层对铝合金的防腐蚀保护性能。方法首先将6061铝合金放入水热反应釜中,加入去离子水,在120℃温度下水热反应30 min。将经过水热预处理的铝合金分别放入50、80℃的0.005 mol/L的Zn(NO3)2溶液中浸泡4 h,在铝合金表面制备出ZnAl-LDHs涂层。利用XRD、SEM、EDS、EIS和极化曲线等技术,分析不同制备条件下,铝合金表面ZnAl-LDHs层的形貌、结构及其对铝合金的防腐蚀保护性能。结果水热预处理后,铝合金表面形成Al(OH)3和AlO(OH)混合层,在其上生长形成的ZnAl-LDHs涂层具有较优的层状结构、较高的结晶度和更加细小致密的纳米片。电化学阻抗和极化曲线的测试结果表明,表面ZnAl-LDHs层可以降低6061铝合金的腐蚀电流密度,提高腐蚀电位和电化学阻抗。水热预处理后的铝合金在80℃溶液中形成的ZnAl-LDHs层,其自腐蚀电流密度(J(corr))仅有0.018μA/cm^2,比未水热处理的铝合金上获得的ZnAl-LDHs层(0.101μA/cm^2)更低,在50℃溶液中形成的ZnAl-LDHs层也观察到相同的现象。结论通过水热预处理可在6061铝合金表面形成Al(OH)3和AlO(OH)混合层,将其作为ZnAl-LDHs层原位生长的前驱体,可以促进ZnAl-LDHs的结晶形核,提高其形核率,使ZnAl-LDHs层的纳米片更细小致密,从而使ZnAl-LDHs层对铝合金具有更好的防腐蚀保护性能。     

ZnO-TiO_2核壳纳米线结构及其热稳定性研究

采用热还原法和原子层沉积技术制备了ZnO-TiO_2核壳纳米线,研究沉积厚度、沉积温度及退火对于ZnO-TiO_2核壳纳米线晶化和结构的影响。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨率透射电镜(HRTEM)等手段对退火前后核壳纳米线进行表征。结果表明:沉积厚度和温度的增加有利于TiO_2壳层发生非晶向晶化的转变;500℃退火提高了TiO_2的结晶性,但可能会使细核壳纳米线(ZnO纳米线直径80 nm)产生波浪形变形,使150℃沉积的非晶TiO_2壳层形成凸出晶粒,并导致其界面处ZnO缺失。     

电子束诱导非晶GaAs晶化的形核与长大

利用高分辨电子显微镜对电子束辐射诱发非晶GaAs晶化过程现象进行了原位观察。结果表明，具有几个原子大小的原子簇在辐射初期产生，并作为晶化的核心在随后的辐射过程中不断长大；大部分结晶晶粒保持相同的晶体取向，其余少量不同取向的晶粒也与前者保持孪晶关系。电子束辐照诱发非晶GaAs晶化的速率与电子束流密度有关；电子束辐照非晶GaAs结晶不是电子束诱发材料温度升高的结果，而与电子能量有关。本文对辐照晶化的机制和结晶过程进行了讨论。     

Amorphous sol-gel SiO2 film for protection of Ti6Al4V alloy against high temperature oxidation

Amorphous SiO₂ thin films were deposited on Ti6Al4V alloy by sol-gel processing. Isothermal and cyclic oxidation tests of the coated and uncoated specimens were performed at 700 and 800 °C. The SiO₂ film exhibited beneficial effects on the oxidation resistance of the alloy. Titania scales formed on the uncoated specimens, and severe spallation and stratification of the scales were observed. The oxidation rates of the silica coated specimens were decreased significantly. The silica film shrunk to about a quarter in thickness, probably by mechanism of crystallization of silica and evaporation of the organic additments. The oxide scales formed on the coated specimens were multilayered. Beneath the silica film, formation of a thick rutile titania layer followed by a thin alumina layer occurred. Above the silica film, alumina plus minor titania layer formed. It is deduced therefore that the growth of the multilayered and mixed oxide scales was dominated by both outward diffusion of metal and inward diffusion of oxygen.     

AZ91D镁合金电火花堆焊组织及腐蚀性能

采用与母材同质的电极材料,在AZ91D镁合金母材上进行电火花堆焊,研究了焊缝的组织、界面特征及腐蚀性能.结果表明,通过优化的工艺参数可以获得组织均匀、致密的电火花堆焊焊缝.焊缝组织晶粒尺寸在1~5μm之间,由过饱和的α-Mg相、Mg₁₇Al₁₂相以及亚稳态Al Mg相所组成;焊缝与母材之间为冶金结合,形成超薄层熔化互扩散结晶型结合界面,母材一侧没有形成明显热影响区,焊缝保持电极原有的成分;焊缝耐蚀性能优于母材,细化的晶粒组织提高腐蚀的均匀性,过饱和的α-Mg相和晶界上网状连续分布的β相降低腐蚀速率,是其耐蚀性能提高的主要因素.     

Coating of hydroxyapatite films on metal substrates by seeded hydrothermal deposition

Hydroxyapatite (HAP) was successfully coated on various metal substrates by a novel seeded hydrothermal deposition method. A nanoscale HAP seed layer was first formed by a short electrochemical synthesis. The seed layer promotes HAP crystal growth onto the surface during a subsequent hydrothermal crystallization step. The surface morphology and microstructure of the HAP coatings can be regulated by varying the reaction temperature, solution pH, calcium-to-phosphorus molar ratio in the starting solution, and hydrothermal deposition time. The new method has advantages over many other reported HAP deposition techniques in that it produces highly crystalline, crack-free, adherent films of uniform thickness. In all the films, the HAP crystals are preferentially oriented with the c-axis normal to the substrate. The as-developed HAP coatings are attractive for applications in the area of bioactive surface modification of metallic implants where the microstructure of the film is advantageous for promoting bone growth.     

氢对黄铜脱锌层引起拉应力的影响

黄铜表面在氨水中腐蚀或应力腐蚀时形成脱锌层 ,由此产生一个附加拉应力。实验结果表明 ,脱锌层拉应力σp 随黄铜试样中氢含量w(H)的升高而线性升高 ,即σp/MPa =13.2 5 .2× 10 -6w(H)。黄铜中的氢含量达到 3× 10 -6时 ,可使黄铜在氨水中的应力腐蚀敏感性升高 10 %。氢促进黄铜应力腐蚀的原因是氢含量的增大会引起脱锌层拉应力的增大。     

热膨胀方法研究Zr基块体非晶合金的晶化过程

利用电弧熔炼及铜模快速铸造法制备Zr41.2Ti13.8Cu12.5Ni10Be22.5块体非晶合金,通过热膨胀法测试晶化过程,与差示扫描量热法进行对比。通过高分辨电子显微镜观察晶化初期晶核的形成和长大规律。结果表明,热膨胀系数测试块体非晶合金的结构弛豫、玻璃转变、过冷液相区、晶化开始温度和晶化过程中不同晶化峰温度与差示扫描量热法测试结果完全吻合。在高分辨像中观察到近似球形的纳米晶粒和晶格条纹。然而,在高分辨像中很难辨认出晶化初期微小的晶化区域,只有对其进行快速傅里叶变换才能发现微小区域的晶化基本特征。     

低红外发射率陶瓷层/金属层/陶瓷层复合薄膜高温性能研究

目的研究热处理工艺对陶瓷层/金属层/陶瓷层复合薄膜低红外发射性能的影响,并分析复合薄膜的有效工作温度。方法采用多弧离子镀方法在Ni基K424合金基底上制备了AlCrN/Cr/AlCrN和AlCrSiN/Cr/AlCrSiN两种复合薄膜,分别在700~800℃和800~900℃大气环境下对样品进行了热处理。利用X射线衍射仪、场发射高分辨率透射电子显微镜、X射线光电子能谱仪、电子探针显微分析仪、辉光放电质谱仪和傅里叶变换红外光谱仪,对样品的微观结构、化学组成和表面辐射特性进行了分析。通过建模计算了两种样品在不同温度下的氧化活化能和扩散系数,对比了其抗氧化性能和抗扩散性能。结果样品中的陶瓷层呈纳米晶-非晶结构特征,AlCrN和AlCrSiN陶瓷层中的纳米晶分别为hcp-Cr2N和hcp-AlN。非晶AlCrN介质会在750℃结晶形成面心立方相的Cr(Al)N,加入Si元素可以将其结晶温度提高至850℃。在氧化初期,由于纳米晶的不同,AlCrN和AlCrSiN陶瓷层的表面分别形成富Cr和富Al的氧化层,而由于fcc-Cr(Al)N的形成,以及氧化铬和氧化铝之间极高的溶解度,最终样品表面会形成铝、铬混合的氧化层。当非晶AlCrN介质结晶后,O元素通过晶界深入样品内部导致样品的红外发射率急剧增大,使其低发射特性失效。同时,结晶后的复合薄膜中陶瓷层的氧化活化能降低,Ni元素的扩散系数增大。结论纳米晶-非晶结构的陶瓷层具有更优异的抗氧化性能和抗扩散性能,加入Si元素可以提高样品的抗氧化性能,AlCrSiN/Cr/AlCrSiN复合薄膜可应用于850℃以下的低红外发射率应用。     

Microstructure of chromium nitride layer on stainless steel for polymer electrolyte membrane fuel cell separator

The microstructure of the chromium nitride layer formed on 316L Stainless Steel (SS) by electroplating Cr and subsequent thermal nitriding was investigated by electron microscopy. Thermal nitriding was carried out at a nitrogen partial pressure of 100 torr at 1100 °C for 2 h. The X-ray Diffraction (XRD) patterns showed that the structure of electroplated chromium was not crystalline and that the nitrided layer was composed of only hexagonal Cr₂N phase nitride. The nitride layer showed uniform and columnar-shaped grains of chromium nitride and contained many micro-pores that may have formed due to the volume difference between the amorphous chromium and the crystalline chromium nitride. Chromium oxide was also observed in the nitride layer. It was discovered that the number of micro-pores and oxide particles needs to be decreased in order to improve the interfacial contact resistance.     

HRTEM study of crystallization of Zr–Cu–Ni metallic glass

Employing differential scanning calorimetry (DSC) and high-resolution transmission electron microscopy (HRTEM), the micromechanism for crystallization of Zr₇₀Cu₂₀Ni₁₀ metallic glass under isothermal annealing conditions has been investigated. It is found that the relationship between the annealing temperature and the peak position, incubation time and ending time in the isothermal annealing DSC traces of Zr₇₀Cu₂₀Ni₁₀ metallic glass obeys a first-order exponential function. However, the time–temperature transformation curves of Zr₇₀Cu₂₀Ni₁₀ metallic glass at different crystallized volume fractions can be well fitted by a second-order exponential function. It is observed that at the initial crystallization stage some ordered atomic clusters precipitate first, acting as nucleation sites and facilitating the subsequent crystallization process, and the crystal growth process mainly proceeds through the atomic depositing on the previously formed crystals. This behavior confirms that the new micromechanism for crystallization of amorphous alloys proposed by Lu and Wang can also be applied to the new series of zirconium based amorphous alloys.     

YT30刀具表面磁控溅射AlTiCrN涂层的微观组织及摩擦性能

为改善刀具性能以及优化磁控溅射参数,研究了AlTiCrN涂层的制备工艺优化过程,并对其组织结构与膜基结合力进行了分析,比较了不同载荷条件下的涂层耐磨性。研究结果表明,沉积时间120 min,沉积功率200 W为较优的磁控溅射参数。AlTiCrN涂层的物相组成为AlTiCrN、Al和CrN。AlTiCrN(111)峰表现为尖锐的衍射峰结构,涂层达到了很高的结晶程度。涂层主要由三角锥结构组成,间隙内还生成了许多细小晶粒。涂层上层区域主要由柱状晶构成,下层主要由纤维晶粒构成。AlTiCrN涂层进行划痕测试发现载荷为19 N和32 N的部位出现了摩擦力突变。通过磁控溅射涂层的YT30刀具比未镀膜刀具有更低的摩擦因数,表明对刀具进行AlTiCrN涂层涂覆后能够显著改善刀具耐磨性。当加载载荷增大后,涂覆涂层的刀具磨痕深度表现出更为平缓过渡。提高载荷到5 N后,在磨痕的两侧形成了大量的磨屑,其宽度也明显增大,并未发生涂层剥落现象。     

亚硫酸钠-柠檬酸钾体系络合剂对镀金层性能的影响

目的 研究亚硫酸钠-柠檬酸钾体系络合剂对可伐基板镀金层共晶焊接性能的影响机理,从而优化络合剂含量工艺范围,提升镀金层金锗共晶可焊性。方法 采用扫描电子显微镜及能谱仪（SEM-EDS）、X射线衍射仪（XRD）、极化曲线等分析方法,结合镀金层孔隙、金锗共晶焊接润湿性和剪切强度测试,研究了亚硫酸钠-柠檬酸钾体系络合剂,对镀金层表面金锗焊料润湿性,金锗共晶层结合力、表面和截面形貌、结晶状态、孔隙,以及金锗共晶焊接界面微观形貌等的影响。结果 亚硫酸钠和柠檬酸钾均能起到络合剂作用,当络合剂亚硫酸钠质量浓度为120～160 g/L和柠檬酸钾质量浓度为40～60 g/L时,络合剂含量的增加可使镀金液阴极过电位明显增大,从而使所制备的镀金层结晶更加致密。当络合剂亚硫酸钠质量浓度为160～200 g/L、柠檬酸钾质量浓度为60～100g/L时,电沉积的镀金层表面明显平整,截面形貌致密,孔隙少,且以（311）晶面择优生长,晶粒尺寸为43.7nm,晶面间距为0.123nm,金锗焊料润湿良好,金锗共晶层结合力较大,剪切强度可达3 MPa以上,可满足金锗共晶焊接使用要求。结论 亚硫酸钠-柠檬酸钾体系络合剂含量对镀...     

脉冲激光沉积及硒化法制备Cu(In,Ga)Se2薄膜研究

采用脉冲激光沉积和硒化后热处理的方法在石英衬底上制备Cu(In,Ga)Se2（简写为CIGS）薄膜，研究脉冲激光沉积（PLD）技术在制备CIGS薄膜太阳能电池材料上的应用，分析了不同预制层沉积顺序及厚度对CIGS薄膜组织结构、表面形貌、成分以及光学性能的影响。实验结果表明：(1)利用PLD技术及后硒化处理的工艺，制得的CIGS太阳能电池吸收层具有纯相和高结晶度等特性；(2)CuGa/In金属预制层的叠层顺序和叠层数、硒化退火温度对薄膜的结晶质量、晶粒尺寸、成分都具有重要的影响，其中叠层顺序影响最为明显；(3)样品均表现出对可见光区具有透射率低和吸收系数高的光学特性。本工作为制备性能优良的CIGS太阳能电池吸收层，提供了一个新颖的工艺手段。     

Preparation of colloidal Sb2O5 from arsenic-alkali residue

The stable colloidal antimony pentoxide was prepared by oxidation of the mixture of Sb2O3 and Sb2O5 obtained from arsenic-alkali residue by hydrometallurgical process, with hydrogen peroxide as oxidant and phosphoric acid as stabilizer. Effects of main factors were investigated. The theories on thermodynamics, kinetics and electrical double layer（EDL） were used to analyze the experimental phenomena and results. The results show that no＇aging time is the most beneficial to forming colloid, when molar ratio of phosphoric acid to antimony is in the range from 0.8 to 1.0 and 1.0 to 1.3, the particle sizes of sol with the concentration of 10% and 15% antimony pentoxide by mass are both smaller. With increasing concentration of the mixture of antimony oxide from 10% to 20%, the reaction time decreases from 90 to about 30 min, but the optimized range of molar ratio of H3PO4 to antimony increases. The reaction temperature is not the main factor on particle size with the existence of H3PO4 in the temperaturd range from 60 to 90℃.     

PEO及其与LiClO4复合体系的非等温结晶动力学

用示差扫描量热法(DSC)研究了聚氧化乙烯(PEO)及其与高氯酸锂(LiClO4)复合体系的非等温结晶过程。依次用Jeziorny方法、一种结合Avrami和Ozawa方程的方法分析了以上体系中PEO的非等温结晶过程,得到了PEO在不同体系中非等温结晶时的动力学参数。动力学参数表明LiClO4晶粒缩短了PEO的结晶时间,使复合体系中PEO的结晶速率大于PEO体系的,但PEO体系形成更完善晶体;为使二者达到相同的相对结晶度,PEO体系需要更大的冷却速率。结果表明,LiClO4晶粒能够有效地将PEO的结晶相转变成非晶相,即LiClO4可有效地抑制PEO的结晶过程。     

Structure and microhardness of rapidly solidified foils of binary indium alloys

Structure of indium and binary indium-based alloys obtained by rapid solidification has been investigated. In the rapidly solidified foils of indium and its binary alloys with tin, lead, bismuth, zinc, and antimony (to 0.6 at %), there is formed a (101) texture, and in the alloys that contain a higher concentration of antimony, an (001) texture. The foils of the alloys that contain to 4 at % bismuth, lead, and cadmium and to 8 at % tin are single-phase. In the foils of the alloys containing zinc and antimony, dispersed particles of zinc and indium antimonide are precipitated.     

Crystallization of a chemical conversion layer that forms on AZ91D magnesium alloy in carbonic acid

This investigation studied the crystallization of a chemical conversion layer that formed on AZ91D Mg alloy in carbonic acid. The layer was an amorphous precursor to a crystalline Mg–Al layered double hydrotalcite, which improved the corrosion resistance of the alloy. The precursor must be treated with a strongly alkaline solution, causing the leaching out of amphoteric Al³⁺. The leaching step evidently caused crystallization from an amorphous precursor layer to a crystalline coating. Nuclear magnetic resonance analysis indicated that Al³⁺, which was originally randomly coordinated with surrounding OH⁻ in the precursor, coordinated octahedrally with OH⁻ groups in the crystalline conversion coating.     

Microstructure and 3D microtomographic characterization of porosity of MAO surface layers formed on aluminium and 2214-T6 alloy

A fine characterization of the microstructure of the MAO coatings formed on aluminium (purity 99,999%) and its alloy 2214-T6 was observed using field emission gun scanning electron microscopy (FEG-SEM) with energy dispersive spectrometry (EDS) and X-ray microtomography (XMT). In addition, the influence of current frequency (pure aluminium) and the precipitates of substrate were investigated (case of 2214-T6 alloy).The MAO surface layers formed on aluminium and its alloy 2214-T6 can be divided into two parts: the outer layer with high porosity (so-call porous layer) and the inner layer with low porosity (so-call dense layer). However, the porosity of the inner layer increases toward the MAO layer/substrate interface. It is found that, both the thickness and the porosity increase when the current frequency decreases. The porosity of the MAO coating can be attributed to discharges formation in the vicinity of the MAO coating/substrate interface.In the particular case of 2214-T6 aluminium alloy (3.9% Cu), with coarse non-valve metal rich precipitates aligned perpendicular to the surface of the work electrode; the transformation of precipitates under discharge effect can provoke the formation of big channels, which go through the MAO surface layer. This last one induces local formation of a layer rich electrolyte species toward the substrate.     

Microstructure of Nitrided Aluminum Alloys Using an Electron-Beam-Excited-Plasma （EBEP）

Nitriding of surface of aluminum alloys was carried out with using an electron-beam-excited-plasma (EBEP) technique. The EBEP is sustained by electron impact ionization with energetic electron beam. Two kinds of substrates,aluminum alloys AA5052 and AA5083, were exposed to the down flow of EBEP source at 843 K for 45min. The specimens were characterized with respect to following properties: crystallographic structure (XRD), morphology (SEM) and the cross sectional microstructures of the nitrided layer was observed using a scanning electron microscopy (SEM). There are some Al2O3 particles on the surface of the nitrided AA5052 and AA5083. The AlN layers were formed on the substrates with the thickness of 4.5μm for AA5052 and 0.5μm for AA5083. A relatively uniform nitrided surface layer composed of AlN can be observed on the AA5052 substrate. The grains size near the interfaces between the substrate and AlN layer were smaller than that near the surface. On the surface of AlN layer, the concentration of nitrogen was high and in the middle of AlN layer it had a constant concentration like the aluminum and the concentration was decreased with approaching to the interface. On the surface of nitrided AA5083, a uniform AlN layer was not formed as the reason for the high nitriding temperature.