TiN/Al2O3纳米多层膜的共格外延生长及超硬效应

采用多靶磁控溅射法制备了一系列具有不同Al₂O₃调制层厚度的TiN/Al₂O₃纳米多层膜. 利用X射线能量色散谱、X射线衍射、扫描电子显微镜、高分辨透射电子显微镜和微力学探针表征了多层膜的成分、微结构和力学性能. 研究结果表明，在TiN/Al₂O₃纳米多层膜中，单层膜时以非晶态存在的Al₂O₃层在厚度小于1.5 nm时因TiN晶体层的模板效应而晶化，并与TiN层形成共格外延生长，相应地，多层膜产生硬度明显升高的超硬效应，最高硬度可达37.9 GPa. 进一步增加多层膜中Al₂O₃调制层的层厚度，Al₂O₃层逐渐形成非晶结构并破坏了多层膜的共格外延生长，使得多层膜的硬度逐步降低. 关键词： 2O₃纳米多层膜')" href="#">TiN/Al₂O₃纳米多层膜 外延生长 非晶晶化 超硬效应     

Al(OH)3溶胶浓度对TC4钛合金微弧氧化膜特性的影响

利用自制多功能微弧氧化(MAO)电源,在保持电学参数和处理时间不变的条件下对TC4钛合金表面进行了MAO处理,研究了Al(OH)₃溶胶浓度对钛合金MAO膜的生长特性、微观结构、相结构和电致变色特性的影响.结果表明:随着Al(OH)₃溶胶浓度(体积分数)C的增加,膜层的生长速率由慢到快逐渐增加,膜表面微孔尺寸和粗糙度逐渐增大,而微孔密度逐渐减小;当C≤10%时,膜层由锐钛矿相TiO₂组成,而当C>10%时,膜层中开始出现金红石相TiO₂并随着C的增加其相对含量逐渐增大,并在C=40%时,膜层全部由金红石相TiO₂组成;在pH＝2.0的HCl溶液中的循环伏安测试结果表明,C≤20%制备试样的膜层颜色变化不明显,随着C的进一步增加,制备试样的膜层颜色变化逐渐明显,并在C=40%时,其着色呈蓝色且色泽均匀;该试样在循环伏安测试过程中还表现出了良好的稳定性和可逆性. 关键词： 微弧氧化 氧化膜 微观结构 电致变色     

阴极电压脉冲占空比对钛合金微弧氧化膜特性的影响

利用自制多功能微弧氧化电源,在保持双极性电压脉冲幅度不变的条件下,研究了阴极电压脉冲占空比（d_c）对钛合金微弧氧化膜特性的影响.结果表明：阴、阳极的峰值电流随处理时间的变化分为几个不同阶段,各阶段的开始和结束时间与d_c密切相关.氧化膜主要由金红石和锐钛矿相TiO₂组成,金红石相TiO₂的相对含量在d_c=50%附近随d_c的 关键词： 微弧氧化 钛合金 占空比     

电解等离子体法制备Al2O3陶瓷层及其特性研究

利用电弧喷铝并重熔后进行电解等离子体处理(EPP)的方法在Q235钢基体上制备出呈冶金结 合的Al₂O₃陶瓷层.利用XRD，SEM和EDS等手段对陶瓷层的成分和显 微组织进行了分析， 测定了陶瓷层的耐蚀性能和耐磨性能.实验结果表明，陶瓷层主要由α-Al₂O3，γ-Al₂O₃，θ-Al₂O₃以及一 些非晶相组成，组织致密，耐蚀性能和耐磨性能良好. 关键词： 电解等离子体处理 陶瓷层 复合技术 生长机理     

分散第二相γ-Al2O3对β-Li2SO4离子导电性的影响

本文研究了分散第二相γ-Al₂O₃对β-Li₂SO₄离子导电性的影响。β-Li₂SO₄(γ-Al₂O₃)的电导率随γ-Al₂O₃含量的增加而提高,到γ-Al₂O₃为50mol％时达到极大。当温度为253℃时,β-Li₂SO< 关键词：     

MoO3在多孔γ-Al2 O3中固熔分散的研究

用MoO₃与多孔γ-Al₂O₃载体以机械混合法制备了一系列MoO₃/γ-Al₂O₃样品.用扫描电子显微镜、X射线衍射、X射线光电子能谱分析、综合热分析(TG/DTA)和正电子湮没谱学研究了MoO₃加载于γ-Al₂O₃后固熔分散过程.分别测量了不同含量的MoO₃/γ-Al_{2关键词： 正电子湮没谱学 三氧化钼 分散 逐次加载}     

低温燃烧合成法制备的氧化铝陶瓷粉体的发光特性

α-Al₂O₃∶C单晶具有优良的热释光特性,被用做热释光剂量计,但α-Al₂O₃∶C晶体剂量计的形状不易加工,生产成本高且碳在晶体中难以掺杂均匀。采用低温燃烧合成法以无水乙醇为溶剂,尿素为染料,硝酸铝为反应物制备少团簇、分散均匀的片状α-Al₂O₃∶C陶瓷粉体。探讨不同点火温度和不同退火温度对其光致发光特性的影响,不同退火温度对热释光特性的影响以及热释光与辐射剂量(90Sr β)的关系。通过分析α-Al₂O₃∶C陶瓷粉体的光致发光光谱得出：α-Al₂O₃∶C陶瓷粉体的发射波长在395 nm附近,点火温度T≤800℃时,点火温度为500 ℃制备的α-Al₂O₃∶C陶瓷粉体的光致发光强度最强;在相同点火温度T=500 ℃下,经不同温度退火制备α-Al₂O₃∶C陶瓷粉体,点火温度为500 ℃制备的α-Al₂O₃∶C陶瓷粉体经1 000 ℃退火后光致发光强度最强。通过分析α-Al₂O₃∶C陶瓷粉体的热释光曲线得出：退火后的α-Al₂O₃∶C陶瓷粉体在200 ℃左右的热释光峰值占主导,900 ℃退火的α-Al₂O₃∶C陶瓷粉体在200 ℃附近的热释光峰值最强;通过峰高法对900 ℃高温退火处理后的α-Al₂O₃∶C陶瓷粉体位于200 ℃左右的热释光峰做剂量响应曲线,可以看出,在1～50 Gy剂量范围内具有良好的热释光剂量线性响应关系,在50～200 Gy剂量范围内出现超线性响应关系。与α-Al₂O₃∶C晶体(1～10 Gy)和多孔Al₂O₃∶C薄膜(1～10 Gy)相比,α-Al₂O₃∶C陶瓷粉体的线性剂量响应范围明显扩大。此研究可为提高氧化铝陶瓷粉体的热释光性能提供思路。     

通孔阳极氧化铝膜的制备及其性能的研究

在15% H₂SO₄阳极氧化液中添加硝酸镨制备阳极氧化铝(AAO)膜以提高AAO膜的性能,采用化学腐蚀和微波处理相结合的方法,去除AAO膜的阻挡层,制备通孔的AAO膜。分别研究镨的添加量、氧化电压对AAO膜的厚度和硬度的影响及腐蚀时间、微波处理时间分别对AAO膜的阻挡层的影响,分别用能谱和扫描电镜等对AAO膜进行了表征。在15% H₂SO₄阳极氧化液中添加硝酸镨,制备出的AAO膜具有更大的厚度和硬度,当氧化电压为23 V时,在15% H₂SO₄+0.14 Pr g·L-1混合液中制备的AAO膜的厚度和硬度分别为162 μm和275.1 HV,与在阳极氧化液为15% H₂SO₄溶液中制备的AAO膜的厚度和硬度(150 μm和224.8 HV)相比,分别提高8.0%和22.4%。当氧化电压在19～23 V范围时,AAO膜的厚度随着氧化电压的增大而增加;AAO膜的硬度随着氧化电压的增大而减小。将AAO膜在35 ℃和5% H₃PO₄溶液中腐蚀13 min,再用超声波处理10 min,可得到通孔的AAO膜。腐蚀后AAO膜表面絮状物为Al₂O₃。     

反应磁控溅射ZrN/AlON纳米多层膜的晶体生长和超硬效应

采用Zr靶和Al₂O₃靶通过在Ar，N₂混合气氛中进行反应磁控溅射的方法制备了不同AlON调制层厚和不同ZrN调制层厚的两个系列的ZrN/AlON纳米多层膜.利用X射线能量色散谱仪、X射线衍射仪、高分辨透射电子显微镜和微力学探针研究了多层膜的成分、微结构和力学性能.结果表明，在Ar，N₂混合气氛中对Al₂O₃进行溅射的过程中，N原子会部分取代Al₂O₃中的氧原子，形成AlON化合物.在ZrN/AlON纳米多层膜中，由于受到ZrN晶体调制层的模板作用，溅射条件下以非晶态存在的AlON层在其厚度小于0.9nm时被强制晶化并与ZrN层形成共格外延生长；相应地，多层膜的硬度明显提高，最高硬度达到33.0GPa.进一步增加多层膜中AlON调制层的厚度，AlON层形成非晶结构，破坏了多层膜的共格外延生长，导致其硬度逐步降低. 关键词： ZrN/AlON纳米多层膜 外延生长 非晶晶化 力学性能     

α-Al2O3:C晶体的热释光和光释光特性

以高纯α-Al₂O₃和石墨为原料,采用温梯法生长了α-Al₂O₃：C晶体,使用Ris TL/OSL-DA-15型热释光和光释光仪研究了其热释光和光释光特性.α-Al₂O₃：C晶体在462K附近有单一热释光峰,发射波长位于410nm.随着辐照剂量的增加,热释光强度逐渐增强,462K的热释光特征峰位置保持不变.α-Al₂O₃：C晶体的 关键词： 2O₃：C')" href="#">α-Al₂O₃：C 热释光 光释光     

Ultra-hard ceramic coatings fabricated through microarc oxidation on aluminium alloy

Ultra-hard ceramic coatings with microhardness of 2535 Hv have been synthesized on the Al alloy substrate by microarc oxidation (MAO) technique. The effects of anodic current density (j_a) and the ratio of cathodic to anodic current density (j_c/j_a) on the mechanical and corrosion resistance properties of MAO coatings have been studied by microhardness and pitting corrosion tests, respectively. In addition, the phase composition and microstructure of the coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the coatings prepared at high anodic current density consist mainly of α-Al₂O₃, while those fabricated at low anodic current density are almost composed of γ-Al₂O₃. Microhardness test shows that the coatings have high microhardness, and the highest one is found in the coating formed at j_a = 15 A/dm² and j_c/j_a = 0.7. Pitting corrosion test shows that the structure of coatings is strongly influenced by the varying j_c/j_a.     

The effects of anodic and cathodic processes on the characteristics of ceramic coatings formed on titanium alloy through the MAO coating technology

This paper reports on the investigation into the effects of the different anodic j_a and cathodic j_c current densities on the variations of the anodic and cathodic processes and the associated changes in the characteristics of the coatings synthesized on Ti-6Al-4V alloy substrate by microarc oxidation technique. The coated samples were subjected to coating thickness and cross-section fracture observation. Phase and elemental composition at different depth of the coatings were evaluated through X-ray diffraction and energy dispersive spectrum analyses. The experimental results indicate that the increase of j_a leads to the increasing slope of anodic voltage U₊ versus oxidation time plots, the larger coating thickness and the more coarse surface morphology of MAO coatings; while the aggrandizement of the cathodic process results in the lower growth rate and more uniform structure of coatings. The changes of the elements distribution from the interface towards the coating surface with variation of j_a and j_c are affected by the Ti anodic dissolution and the electromigration of electriferous particles, such as Al(OH)₄⁻, in electrolytes.     

Microstructure and corrosion resistance behavior of ceramic coatings on biomedical NiTi alloy prepared by micro-arc oxidation

In this paper, ceramic coatings were prepared on biomedical NiTi alloys by micro-arc oxidation (MAO) in constant voltage mode. The current density-time response was recorded during the MAO process. The microstructure, element distribution and phase composition of the coatings prepared at different MAO treatment times were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), thin-film X-ray diffraction (TF-XRD) and X-ray photoelectron spectroscopy (XPS). The corrosion behavior of the coatings in 0.9% NaCl solution was evaluated by the potentiodynamic polarization test. It is found that the coatings become more compact with increasing the MAO treatment time, and the growth rate of coating decreases. The results of TF-XRD, EDS and XPS indicate that the coatings are composed of a large amount of γ-Al₂O₃ and a little α-Al₂O₃, TiO₂ and Ni₂O₃. The Ni content of the coatings is about 3 at.%, which is greatly lower than that of NiTi substrate. The bonding strength of coating-substrate is higher than 40 MPa for all the samples in this study. The corrosion resistance of the coatings is about two orders of magnitude higher than that of the uncoated NiTi alloy.     

Evolution of micro-arc oxidation behaviors of the hot-dipping aluminum coatings on Q235 steel substrate

Micro-arc oxidation (MAO) is not applicable to prepare ceramic coatings on the surface of steel directly. In this work, hybrid method of MAO and hot-dipping aluminum (HDA) were employed to fabricate composite ceramic coatings on the surface of Q235 steel. The evolution of MAO coatings, such as growth rate, thickness of the total coatings, ingrown and outgrown coatings, cross section and surface morphologies and phase composition of the ceramic coatings were studied. The results indicate that both the current density and the processing time can affect the total thickness, the growth rate and the ratio of ingrown and outgrown thickness of the ceramic coatings. The total thickness, outgrown thickness and growth rate have maximum values with the processing time prolonged. The time when the maximum value appears decreases and the ingrown dominant turns to outgrown dominant little by little with the current density increasing. The composite coatings obtained by this hybrid method consists of three layers from inside to outside, i.e. Fe-Al alloy layer next to the substrate, aluminum layer between the Fe-Al layer and the ceramic coatings which is as the top exterior layer. Metallurgical bonding was observed between every of the two layers. There are many micro-pores and micro-cracks, which act as discharge channels and result of quick and non-uniform cooling of melted sections in the MAO coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al₂O₃ oxides. The crystal Al₂O₃ phase includes κ-Al₂O₃, θ-Al₂O₃ and β-Al₂O₃. Compared with the others, the β-Al₂O₃ content is the least. The MAO process can be divided into three periods, namely the common anodic oxidation stage, the stable MAO stage and the ceramic coatings destroyed stage. The exterior loose part of the ceramic coatings was destroyed badly in the last period which should be avoided during the MAO process.     

Effect of NaAlO2 concentrations on microstructure and corrosion resistance of Al2O3/ZrO2 coatings formed on zirconium by micro-arc oxidation

In this study, Al₂O₃/ZrO₂ composite coatings were prepared on Zr substrates by micro-arc oxidation (MAO) in the NaAlO₂-containing electrolytes, and the effect of NaAlO₂ concentration on the microstructure, bond strength, microhardness and corrosion resistance of coatings was systematically investigated. The study reveals that the adequate NaAlO₂ in the electrolyte (>0.2 M) is essential to the formation of needle-like α-Al₂O₃ in the coatings, and the amount of α-Al₂O₃ rises with the increase of the NaAlO₂ concentration. m-ZrO₂ and t-ZrO₂ are present in all of the coatings, but their relative amount largely depends on the amount of Al₂O₃. It is also found that as the NaAlO₂ concentration increases from 0.2 to 0.3 M, the coating becomes denser and thicker, and its bond strength, maximum microhardness and corrosion resistance increases as well. The coating formed at 0.3 M NaAlO₂ demonstrates the highest bond strength of 52 MPa, the maximum microhardness of 1600 Hv_0.2N and the superior corrosion resistance. However, the overhigh concentration of NaAlO₂ (0.35 M) is found harmful to the coating's microstructure and properties.     

Fortification of Ni–Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocomposite coatings prepared by pulse and direct current methods

Ni–Y₂O₃ nanocomposite coatings were prepared under direct current (DC) and pulse current (PC) using acetate bath. The microstructure and corrosion resistance of the coatings were characterized by means of XRD, SEM, AFM, and EIS. The results showed that the microstructure and performances of the coatings were greatly affected by Y₂O₃ content on the deposits prepared by DC and PC methods. The microhardness and corrosion resistance were enhanced in the optimum percentage of Y₂O₃ composite coatings. The PC composite coatings were exhibited compact surface, higher microhardness, and good corrosion resistance compared with that of the DC composite coatings.     

Effect of α-Al2O3 on the properties of cold sprayed Al/α-Al2O3 composite coatings on AZ91D magnesium alloy

Composite coatings using pure Al powder blended with α-Al₂O₃ as feedstock were deposited on AZ91D magnesium alloy substrates by cold spray (CS). The content of α-Al₂O₃ in the feedstock was 25 wt.% and 50 wt.%, respectively. The effects of α-Al₂O₃ on the porosity, microhardness, adhesion and tensile strength of the coatings were studied. Electrochemical tests were carried out in neutral 3.5 wt.% NaCl solution to evaluate the effect of α-Al₂O₃ on the corrosion behavior of the coatings. The results showed that the composite coatings possessed lower porosity, higher adhesion strength and tensile strength than cold sprayed pure Al coating. The corrosion current densities of the composite coatings were similar to that of the pure Al coating and much higher than that of bare AZ91D magnesium alloy.     

Formation of Al2O3 coatings on NiTi alloy by micro-arc oxidation method

Rough and porous Al₂O₃ coatings containing Ca and P were prepared on Ti–50.8 at.% Ni alloy by micro-arc oxidation (MAO) technique. The microstructure, elemental and phase composition of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) and thin-film X-ray diffraction (TF-XRD). The thickness of the coatings was measured by eddy current coating thickness gauge. The corrosion resistance and the nickel release of the coated and uncoated samples were examined by potentiodynamic polarization tests and immersion tests in Hank’s solution, respectively. The results show that the coatings are mainly composed of γ-Al₂O₃ crystal phase. The Ni content of the coatings is about 3.5 at.%, which is greatly lower than that of NiTi substrate. With increasing treatment time, both thickness and roughness of the coatings increase. The corrosion resistance of the coated samples is about two orders of magnitude higher than that of the uncoated NiTi alloy. The concentration of Ni released from coated NiTi samples is much lower than that of uncoated NiTi sample. It can be reduced in the factor of one-seventh compared with the uncoated NiTi sample after 3 weeks immersion in Hank’s solution.     

Effects of duty ratio at low frequency on growth mechanism of micro-plasma oxidation ceramic coatings on Ti alloy

The aim of this work is to study the effects of duty ratio on the growth mechanism of the ceramic coatings on Ti-6Al-4V alloy prepared by pulsed single-polar MPO at 50 Hz in NaAlO₂ solution. The phase composition of the coatings was studied by X-ray diffraction, and the morphology and the element distribution in the coating were examined through scanning electron microscopy and energy dispersive spectroscopy. The thickness of the coatings was measured by eddy current coating thickness gauge. The corrosion resistance of the coated samples was examined by linear sweep voltammetry technique in 3.5% NaCl solution. The changes of the duty ratio (D) of the anode process led to the changes of the mode of the spark discharge during the pulsed single-polar MPO process, which further influenced the structure and the morphology of the ceramic coatings. The coatings prepared at D = 10% were composed of a large amount of Al₂TiO₅ and a little γ-Al₂O₃ while the coatings prepared at D = 45% were mainly composed of α-Al₂O₃ and γ-Al₂O₃. The coating thickness and the roughness were both increased with the increasing D due to the formation of Al₂O₃. The formation of Al₂TiO₅ resulted from the spark discharge due to the breakdown of the oxide film, while the formation of Al₂O₃ resulted from the spark discharge due to the breakdown of the vapor envelope. The ceramic coatings improved the corrosion resistance of Ti-6Al-4V alloy. And the surface morphology and the coating thickness determined the corrosion resistance of the coated samples prepared at D = 45% was better than that of the coated samples prepared at D = 10%.