Microstructural evolution and mechanical properties of aging high nitrogen austenitic stainless steels

The microstructural evolution of 18Cr18Mn2Mo0.77N high nitrogen austenitic stainless steel in aging treatment was investigated by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that hexagonal intergranular and cellular Cr2N with a=0.478 nm and c=0.444 nm and body-centered cubic intermetallic χ phase with a=0.892 nm precipitate gradually in the isothermal aging treatment. The matrix nitrogen depletion due to the intergranular Cr2N pre...     

Effect of Nitrogen Ion Implantation on the Structure and Corrosion Resistance of Equiatomic NiTi Shape Memory Alloy

To protect the surface of NiTi from corrosion, an ion implantation method was proposed. In the present work, a surface oxidized sample was implanted with nitrogen at energy of 100 keV. The corrosion resistarwe property was examined by the anodic polarization method in a simulated body fluid （SBF） at a temperature of 37 ℃ and contrasted to non-implanted NiTi samples. The composition and structure of the implanted layers were investigated by XPS. The experimental results from the electrochemical measurements provide an evidence that the nitrogen ion-implantation increases the corrosion resistance of NiTi shape memory alloy.     

Load Dependence of Nanohardness in Nitrogen Ion Implanted Ti6AI4V Alloy and Fractal Characterization

Three different nitrogen ion doses were implanted into a Ti6A14V alloy to improve its mechanical surface properties for the application of artificial joints. The titanium nitride phase and nitrogen element distribution profile were characterized with X-ray photoelectron spectroscopy （XPS）. Nano-indentation tests were carried out on the surface of the Ti6A14V alloy and implanted samples on a large scale of applied loads. The XPS analysis results indicate that nitrogen diffuses into the titanium alloy and forms a hard TiN layer on the Ti6A14V alloy. The nanohardness results reveal that nitrogen ion implantation effectively enhances the surface hardness of Ti6A14V. In addition, the nanohardness clearly reveals load dependence over a large segment of the applied loads. Thus a concept of nanohardness fractal dimension is first proposed and the dual fractal model can effectively describe nonlinear deformation in indentation areas on the Ti6A14V surface. The fractal dimension shows a decreased trend in two regions of applied loads, indicating a decrease of the self-similarity complexity in surface indentation owing to an increase in nanohardness after nitrogen ion implantation.     

Load Dependence of Nanohardness in Nitrogen Ion Implanted Ti6Al4V Alloy and Fractal Characterization

Three different nitrogen ion doses were implanted into a Ti6Al4V alloy to improve its mechanical surface properties for the application of artificial joints. The titanium nitride phase and nitrogen element distribution profile were characterized with X-ray photoelectron spectroscopy (XPS). Nano-indentation tests were carried out on the surface of the Ti6Al4V alloy and implanted samples on a large scale of applied loads. The XPS analysis results indicate that nitrogen diffuses into the titanium alloy and forms a hard TiN layer on the Ti6Al4V alloy. The nanohardness results reveal that nitrogen ion implantation effectively enhances the surface hardness of Ti6Al4V. In addition, the nanohardness clearly reveals load dependence over a large segment of the applied loads. Thus a concept of nanohardness fractal dimension is first proposed and the dual fractal model can effectively describe nonlinear deformation in indentation areas on the Ti6Al4V surface. The fractal dimension shows a decreased trend in two regions of applied loads, indicating a decrease of the self-similarity complexity in surface indentation owing to an increase in nanohardness after nitrogen ion implantation.     

Reduction of deep level defects in unintentionally doped 4H-SiC homo-epilayers by ion implantation

In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 ℃ annealing, meanwhile, deep level defects are decreased.     

Effects of COOH~+ ion implantation on hemocompatibility of polypropylene

Carboxyl ion (COOH+) implantation was performed at 50 keV with different fluences for polypropylene. Hemocompatibility tests show that blood coagulation time and recalcification time of polypropylene were enhanced significantly with the increasing fluence. At the same time, the human endothelial cells grown on the surface of the implanted samples exhibited normal cellular growth and morphology. X-ray photoelectron spectroscopy and water contact angle analysis showed that COOH+ ion implantation rearranges chemical bonds and produces some new polar O-containing groups on the surface. The formation of polar functional groups, together with increase of roughness, induced an increase in hydrophilicity, which in turn improved the surface hemocompatibility of polypropylene.     

Effects of COOH+ ion implantation on hemocompatibility of polypropylene

Carboxyl ion (COOH⁺) implantation was performed at 50 keV with different fluences for polypropylene. Hemocompatibility tests show that blood coagulation time and recalcification time of polypropylene were enhanced significantly with the increasing fluence. At the same time, the human endothelial cells grown on the surface of the implanted samples exhibited normal cellular growth and morphology. X-ray photoelectron spectroscopy and water contact angle analysis showed that COOH⁺ ion implantation rearranges chemical bonds and produces some new polar O-containing groups on the surface. The formation of polar functional groups, together with increase of roughness, induced an increase in hydrophilicity, which in turn improved the surface hemocompatibility of polypropylene.     

Nanometer structure and conductor mechanism of polymer modified by metal ion implantation

Polyethylene terephthalate (PET) has been modified by Ag, Ti, Cu and Si ion implantation with a dose ranging from 1 × 1016 to 2 × 1017 ions/cm2 using a metal vapor vacuum arc (MEVVA) source. The electrical properties of PET have been improved by metal ion implantation. The resistivity of implanted PET decreased obviously with an increase in ion dose. The results show that the conductive behavior of a metal ion implanted sample is different from Si-implantation samples. In order to un-derstant the mechanism of electrical conduction, the structures of implanted layer were observed in detail by XRD and TEM. The nano carbon particles were dispersed in implanted PET. The nano metallic particles were built up in metallic ion implanted layers with dose range from 1 × 1016 to 1 × 1017 ions/ cm2. The nanometer metal net structure was formed in implanted layer when a dose of 2 × 1017ions/ cm2 is reached. Anomalous fractal growths were observed. These surface structure changes revealed conducting mechanism evo     

The modification behaviour for Si implanted PET

Polymeric solids have low density, high ability to form intricate shapes, versatile electronic properties and low manufacturing cost. However their uses are still limited by their inherent softness and unexpected dielectric properties. In order to enhance their electrical and mechanical properties, ion implantation techniques have been explored[1—3]. Recent studies have shown that ion implantation is very effective for improving surface properties of polymers such as surface hardness and wear…     

类金刚石薄膜的离子注氮研究

以25～35kV的高能离子束将离子化的双原子分子N+2注入非晶态碳膜,硬度可提高10GPa量级.分析研究表明:离子注氮并没有改变碳膜的非晶态结构,但所有拉曼结构参数发生变化,且碳、氮结合能峰位发生化学位移;显然注入的氮和碳形成化学键,并可能形成新相. 结论:类金刚石薄膜离子注氮可合成氮化的类金刚石,改变化学结构,提高机械性能.     

Experimental studies of N~+ implantation into CVD diamond thin films

The effects of N+ implantation under various conditions on CVD diamond films were analyzed with Raman spectroscopy, four-point probe method, X-ray diffraction (XRD), Rutherford backseattering spectroscopy (RBS), ultraviolet photoluminescence spectroscopy (UV-PL), Fourier transformation infrared absorption spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the N+ implantation doping without any graphitization has been successfully realized when 100 keV N+ ions at a dosage of 2 × 1016 cm-2 were implanted into diamond films at 550℃ . UV-PL spectra indicate that the implanted N+ ions formed an electrically inactive deep-level impurity in diamond films. So the sheet resistance of the sample after N+ implantation changed little. Carbon nitride containing C≡N covalent bond has been successfully synthesized by 100 keV, 1.2×1018 N/cm2 N+ implantation into diamond films. Most of the implanted N+ ions formed C≡N covalent bonds with C atoms. The others were free state nitroge     

动态时效对Al-Cu-Mg-Ag合金组织与力学性能的影响

对Al-Cu-Mg-Ag新型耐热铝合金进行预时效+中温轧制变形+终时效的动态时效工艺处理,采用硬度测试、拉伸性能测试,结合金相显微组织分析和透射电子显微分析,探究动态时效对其力学性能与微观组织的影响。结果表明：动态时效能够提高合金的时效硬化速率,随着变形量的增大,合金的峰时效时间逐渐减小,峰值硬度逐渐增大。动态时效能够改变晶粒形貌,随着变形量的增大,晶粒的纵横比增大,位错数量增多,强化相数量增多尺寸减小,使得合金强度随着变形量的增大而逐渐增大,但伸长率逐渐减小。变形量为50%合金的强度最高,抗拉强度和屈服强度最大,分别为527.4 MPa和467.0 MPa,伸长率保持在较高值9.1%。     

旋转滑动弧等离子体固氮的物理特性

采用旋转滑动弧等离子体（RGA）进行固氮实验研究. 为了考察在N₂/O₂气氛下放电的物理特性,利用光谱仪、高速摄影仪、示波器等进行研究,考察放电参数、气体体积流量对于氮气的振动温度、氮气的转动温度和电弧特性的影响,以及以上因素对于RGA固氮效果的综合影响. 实验结果表明,放电过程可以生产大量NO_x气体,通过光谱检测可以清晰观测到NO的γ带系、氮气第二正带系和氮气离子第一负带系. 增加放电的氧气体积分数,氮气的振动温度将升高,并伴随着固氮产出的提高;在一定范围内（10%~40%）,氧气体积分数提升在提升固氮效果的同时,对放电稳定性有不利影响. 综合分析表明,接近空气的放电气氛（氧气体积分数为20%）或直接采用空气放电,能够实现旋转滑动弧等离子体放电固氮的最佳效果.     

微波ECR等离子体中铝合金的全方位氮离子注入

使用微波ECR等离子体对LD10铝合金材料进行全方位氮离子注入。AES深度分布结果表明,在30KV注入电压下,注入深度约有150mm。对相互垂直的两不同表面进行的硬度分析表明,全方位氮离子注入对试样的不同表面改性效果相同,硬度均获得明显提高。     

银川地区地下水氮污染原因及防治

通过对银川地区1991～2000年的地下水水质动态监测数据分析发现其地下水氮污染严重,其中 尤以氨氮污染最为严重,对其氮污染的成因作进一步分析得出:引起潜水氮污染的主要因子是农田大量施 用化肥和地面污水下渗,引起承压水氮污染的主要因子是大量开采承压水造成的潜水对其越流补给,最后 提出了相应的防治措施。     

Retrogression characteristics of a novel Al-Cu-Li-X alloy

Retrogression characteristics of a novel Al-Cu-Li-X alloy of 2A97 were studied by hardness testing, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The retrogression treatments of aging at 155°C for 12 h followed by aging at 220 and 240°C were chosen by determining the peak temperature of δ' precipitation at 230°C by DSC. The retrogression treatment at a lower temperature of 220°C causes the precipitation and coarsening of δ' and θ' phases in the matrix, resulting in an ...     

基于室内环境模拟的再生沥青混合料老化影响因素

为了解决不同环境因素对路面工程中未经压实的再生沥青混合料(recycled asphalt mixture,RAP)老化程度影响的问题,以松散的再生沥青混合料为研究对象,利用特制的室内模拟老化试验装置,通过控制温度、湿度、老化时间、氧气浓度等因素,对新制备密级配沥青混合料AC-13进行特定环境条件下模拟老化试验.结果表明:松散RAP混合料的老化程度随试验温度升高而增加,随空气湿度增加和氧气浓度下降而降低;不同试验温度下,沥青老化的成长速度和试验终值均不相同,表明老化过程中的化学反应因温度不同而有所差异;在通入纯氮气的试验中,沥青没有发生任何老化作用,表明沥青的老化只受氧化作用影响;环球法测软化点的试验结果对温度变化较为敏感,动态剪切流变仪(dynamic shear rheometer,DSR)测定的动态复数剪切模量在表征沥青老化程度时存在一定迟滞效应;老化后沥青混合料低温性能出现衰减,主要原因是沥青长期老化作用导致.     

Surface wear resistance properties of Ta＋N implanted W18Cr4V high speed steel

High-speed steel W18Cr4V is commonly used in industries such as blade and mould manufacturers because of its high level of hardness and toughness, red-hardness and resistance. Ion implantation is an effective method to improve the wear resis-tance of W18Cr4V. In our investigation, Ta and Ta+N ion implantation was performed on W18Cr4V high-speed steel. The surface properties after implantation were evaluated by measuring friction coefficients while the carbonyl phase of the surface was ana-lyzed by X-ray diffraction analysis. It was found that the friction coefficients of the treated samples were much lower. Samples implanted with Ta+N had a lower friction coefficients than samples implanted only with Ta. This can be attributed to the formation of a new chemical compound, Fe7Ta3, on both surfaces. An even harder chemical compound, Fe2N, was formed on both sttrfaces of Ta+N implanted samples.     

Research on Surface Modification of 96 Al2O3 by Ni Ion Implantation

A matrix of 96 Al2O3 ceramics was implanted with Ni ion of different dosages and energies using a MEVVA implanter. Then metallic structures of copper were made on the implanted ceramics, by using selective electroless copper plating. In addition, the characteristics and microstructure of the implanted layer were studied by using the SEM, RBS and XPS. The results show that： 1） the implanted Ni exits as Ni^2, Ni^2＋, and Ni^3＋ in the surface of Al2O3 and metal Ni particles precipitate on ceramics during implantation; 2） the concentration of Ni submits to the Gauss distribution along the direction of implantation on the surface of Al2O3 and high Ni concentration on the surface can be obtained if the Ni is implanted with low energy and a high dosage and 3） Ni ion implantation can activate the surface of Al2O3 and induce electroless copper plating on the ceramics.     

Effect of copper ions implantation on the corrosion behavior of ZIRLO alloy in 1 mol/L H2SO4

1. IntroductionZIRLO alloy is widely used in the nuclear industrybecause of its low thermal neutron capture cross sec-tion, favorable mechanical properties, and good corro-sion resistance. For example, ZIRLO alloy can serve asfuel cladding, spreaders for …