脉冲偏压对离子束辅助电弧离子镀TiN/Cu纳米复合膜结构及硬度的影响

采用离子束辅助电弧离子镀技术在高速钢基体上制备TiN/Cu纳米复合薄膜,考察了基体脉冲负偏压对薄膜成分、结构及硬度的影响。用X射线光电子谱、X射线衍射、扫描电镜、透射电镜和纳米压痕等方法分别测试了薄膜的化学成分、结构、表面形貌、硬度以及弹性模量。结果表明,在氮离子束的轰击作用下,随着脉冲偏压幅值从-100 V增加到-900 V时,薄膜中Cu含量先增加而后略有降低,在1.05%~2.50%(原子比)范围内变化。同时,脉冲偏压对薄膜的结构也有明显影响,在-100 V出现TiN(111)择优取向,当基体偏压增加到-300 V以上时,择优取向改变为TiN(220)择优。薄膜的Cu2p峰均对应纯金属Cu,薄膜的晶粒尺寸约在11~17 nm范围内变化。硬度和弹性模量随着偏压幅值增加而增大,当偏压为-900 V时,薄膜硬度和弹性模量达到最大值,分别为29.92 GPa,476 GPa,对应的铜含量为1.91%。     

轴对称磁场对电弧离子镀TiN-Cu纳米复合膜性能的影响

在电弧离子镀靶后端加入轴对称线圈磁场,制备了TiN-Cu纳米复合膜。观察线圈磁场强度对靶表面电弧斑点游动速率和弧柱形状的影响,及其对沉积薄膜的表面形貌、沉积速率、纳米压痕硬度和弹性模量的影响。结果表明,提高线圈磁场强度可提高电弧斑点的游动速率,进而降低靶表面金属液滴喷射几率,减小沉积薄膜中大颗粒的尺寸和数量。X射线衍射(XRD)谱显示,沉积薄膜只含有TiN相,未出现金属Cu或其化合物的衍射峰;薄膜呈现明显的(111)晶面择优取向。随着线圈磁场强度的提高薄膜沉积速率、压痕硬度和弹性模量先增加,达到最大值后又略有减少,其最大硬度和弹性模量分别达到35.46GPa和487.61GPa。     

二氧化铈对准晶真空蒸镀薄膜的影响

采用DMD-450真空镀膜仪将Al65Cu20Fe15准晶粉末沉积在Q235钢表面制备薄膜。研究了二氧化铈对薄膜的组织和结构的影响。采用透射电镜（TEM）、扫描电镜（SEM）、X射线衍射仪（XRD）等分析了薄膜的组织结构和表面形貌。利用纳米压痕仪（MTS）测试了薄膜的显微硬度和弹性模量。结果表明：通过准晶粉末真空蒸镀可以形成准晶薄膜。其组成相有CuAl2，A1Cu3 and I（Al65Cu20Fe15）相等。薄膜的成分取决于制备工艺。二氧化铈对薄膜的结构没有产生明显的影响。但是薄膜的显微硬度和弹性模量随二氧化铈添加量的增加而提高。当二氧化铈添加量为5％（质量分数）时，薄膜的显微硬度达到9．0GPa，弹性模量最高达到190GPa。此外，二氧化铈的添加明显增加了薄膜的耐蚀性能。     

纳米Ti-Si-N薄膜的高温热稳定性

用直流等离子体增强化学气相沉积(PCVD)方法在不锈钢基体上制备了Ti-Si-N硬质纳米复合薄膜,研究了Si含量对薄膜硬度的影响及高温退火对薄膜晶粒尺寸及其硬度的影响.结果表明:薄膜的硬度随着Si含量的增加有先增大后减小的趋势,最大硬度可达70 GPa以上.薄膜表现出了较高的热稳定性能,对于晶粒尺寸在4 nm以下的薄膜,Ti-Si-N薄膜的纳米结构和硬度可以维持在1000℃以上.沉积态薄膜的晶粒尺寸是影响薄膜再结晶温度的主要因素.薄膜的高热稳定性是由于沉积过程中发生的自发调幅分解形成了纳米复合结构,偏析使得纳米晶晶界具有强的热力学稳定性.     

氧杂质致Ti-Si-N薄膜高硬度损失的机理

基于纳米复合Ti-Si-N薄膜硬度对界面相微结构及微尺度变化极为敏感的实验事实,定量表征了薄膜的硬度与氧杂质含量的关系.结果表明,与高纯度薄膜40-55 GPa高硬度比较,1%-1.5%的氧杂质含量导致薄膜的硬度下降到30 GPa左右.根据纳米晶界面原子模型和实验结果,氧杂质与纳米尺度界面交互作用所引发的微尺度缺陷是硬度下降的诱因,晶界面的氧杂质密度是薄膜高硬度损失程度的决定因素,单个纳米晶周围的氧杂质覆盖度达到10个原子以上时,薄膜的硬度只能达到30 GPa.     

氮分压对反应溅射(Ti,Al)N薄膜微结构与力学性能的影响

采用Ti-Al复合靶在不同氮分压下制备了一系列(Ti,Al)N薄膜,用EDS、XRD、TEM和微力学探针表征了薄膜的沉积速率、化学成分、微结构和力学性能.结果表明,氮分压对(Ti,Al)N薄膜影响显著:合适的氮分压可以得到化学计量比的(Ti,Al)N薄膜,薄膜为单相组织,并呈现(111)择优取向,最高硬度和弹性模量分别达到34.4GPa和392GPa;过低的氮分压不但会造成薄膜贫氮,而且薄膜中的Al含量偏低,硬度不高;过高的氮分压下,由于存在"靶中毒"现象,尽管薄膜的成分无明显变化,但会大大降低其沉积速率,并使薄膜形成纳米晶或非晶态结构,薄膜的硬度也较低.     

反应磁控溅射碳化钒薄膜的微结构与力学性能

在Ar、C2H2混合气氛中通过反应磁控溅射法制备了一系列不同碳含量的碳化钒薄膜,利用EDX、XRD、SEM、AFM和微力学探针表征了薄膜的微结构和力学性能.研究了C2H2分压对薄膜成分、相组成、微结构以及硬度和弹性模量的影响.结果表明,采用在At-C2H2混合气体中的射频反应磁控溅射技术可以方便地合成碳化钒薄膜.但是,只有在C2H2分压为混合气体总压约4%附近很窄的范围内才可获得力学性能优异的碳化钒薄膜.其硬度和弹性模量分别达到35.5GPa和358GPa,此时,薄膜为NaCI结构的VC,且具有柱状生长的特征.随着C2H2分压的提高,薄膜形成六方结构的7-VC,并逐渐产生非晶碳相,硬度和弹性模量随之降低.     

脉冲激光诱导钛表面氮化的研究

介绍了在氮气气氛下,用脉冲激光照射钛表面实现钛的诱导氮化的实验结果.利用扫描电镜(SEM)、X射线衍射(XRD)和拉曼光谱对氮化表面进行了结构表征和性能分析.X射线衍射(XRD)结果显示氮化层的主要成分是a-Ti相和δ-TiN相,同时含有少量的a-Ti(N)固溶体.随着激光平均功率的增加,氮化层中δ-TiN相和α-Ti(N)固溶体含量逐渐增加,相应的氮含量也逐渐增加.纳米硬度测试结果显示氮化层的纳米硬度和弹性模量较基材钛明显增加,2mN载荷下测得氮化层的纳米硬度和弹性模量分别在11.5～15GPa和200～250GPa之间.     

电沉积参数对镍-纳米金刚石复合镀层性能的影响

目前有关纳米复合镀层电沉积的研究还不够深入、系统。以瓦特镀镍液为基础,在Q235A钢基体上制备镍-纳米金刚石复合镀层,研究了纳米金刚石浓度、搅拌速度对镍-纳米金刚石复合镀层性能的影响规律。在测试纳米金刚石复合镀液中镍的还原行为时发现,随着纳米金刚石浓度的升高,镍离子的极化程度呈现先升高后下降的趋势,镀液中纳米金刚石浓度为8.0 g/L时极化程度最大,同等条件下直流电沉积制备的复合镀层硬度、弹性模量分别为4.66 GPa和195.2 GPa,而双脉冲电沉积制备的镀层硬度和弹性模量分别达到5.23 GPa和197.4 GPa。     

离子束流和基底温度对ZrN/TiAlN纳米多层膜性能的影响

本文利用高真空离子束辅助沉积系统(IBAD),在室温下制备了ZrN、TiAlN和一系列ZxN/TiAlN纳米多层膜,利用XRD、纳米力学测试系统和多功能材料表面性能实验仪,分析了束流和基底温度对薄膜的微结构和机械性能的影响.结果表明大部分多层膜的纳米硬度与弹性模量值都高于两种个体材料硬度的平均值,当辅助束流为5 mA时,多层膜硬度达到30.6 GPa.基底温度的升高,会显著降低薄膜的残余应力,但对薄膜的硬度,摩擦系数没有明显影响.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.