Oxidation behavior of TiAlZrCr/(Ti,Al,Zr,Cr)N gradient films deposited by multi-arc ion plating

The two Ti-Al-Zr targets and one pure Cr target were used to prepare the TiAlZrCr/（Ti, Al, Zr, Cr）N gradient films on high speed steel （WlSCr4V） substrates by multi-arc ion plating technique. Short-term isothermal （at 600 ℃, 700 ℃, 800℃ and 900 ℃ for 4 h） and long-terra cyclic （at 700℃ and 800℃ for 100 h） high temperature oxidation behavior of the gradient films were studied. Then the oxide scales formed on the film specimens were characterized by scanning electron microscopy （SEM）, energy dispersion X-ray spectroscopy （EDS） and X-ray diffraction （XRD）. It was showed that, under short-term isothermal condition, the high temperature oxidation resistance of the gradient film was excellent up to 800 ℃ and an oxide scale comprising TiO2 was observed. On the other hand, under long-term cyclic high temDerature condition, the oxidation resistance of the gradient film was excellent at about 700 ℃.

Determination of Ni^(2+) in Waters with Sodium Polyacrylate as a Binding Phase in Diffusive Gradients in Thin-films

An aqueous solution containing sodium polyacrylate（PAAS） was used in diffusive gradient in thin-films technique（DGT） to measure DGT-labile Ni2＋ concentrations.The DGT devices（PAAS DGT） were validated in four types of solutions,including synthetic river water containing metal ions with complexing EDTA or that without complexing EDTA,natural river water（Ling River,Jinzhou,China） spiked with Ni2＋,and an industrial wastewater （Jinzhou,China）.Results show that only free metal ions were measured by PAAS DGT,recovery=97.36% in the solutions containing only free metal ions,recovery=49.62% in a solution with metal/EDTA molar ratio of 2：1 and recovery=0 in the solutions with metal/EDTA molar ratios of 1：1 and 1：2.These indicated that the complexes of Ni-EDTA were DGT-inert.The DGT performance in spiked river water（recovery=18.24%） and in industrial wastewater（recovery=12.25%） were investigated,which indicated that the measurement of metals by this DGT device did not include the humic substances complexed fractions of metals.The binding properties of PAAS DGT for Ni2＋ were investigated under different conditions of pH value and ionic strength.Conditional stability constants（lgK） of PAAS-Ni complexes were also evaluated.

Facing targets sputtered iron nitride gradient films

Iron nitride film is a qualifed material for high-density magnetic recording head for its excellent magnetic properties and good corrosion resistance. It is well known that there are four iron nitride phases, α″-Fe16N2, γ′-Fe4N, ε-FexN,（2【x≤3） and ζ-Fe2N. Their saturation magnetization （Ms） and Curie temperature decrease with the increase of

Evaluation of the Bioavailability of Metals in Sediment from the Southern Coastal Wetland of the Qiantang Estuary by Using Diffusive Gradients in Thin Films Technique

Metal pollution has become an major issue governing the wetland ecosystem health.The southern coastal wetland of the Qiangtang Estuary are facing unusual perturbation due to rapid development along the embayment in recent decades.This study evaluated the bioavailability of metals(Cu,Pb,Cd,Cr and Zn)in the sediment of the southern coastal wetland of the Qiangtang Es-tuary using diffusive gradients in thin films(DGT)techniques and compared with several methods based on total metal content.The results showed that the contents of Cr,Pb,Cd and Cu in sediment,as detected using DGT,were considerably correlated with the exchangeable fraction and the content in Phragmites australis roots,while a weak correlation was observed for Zn.Therefore,DGT analysis could be used to evaluate the bioavailability and potential risk of Cr,Cd,Pb and Cu for P.australis.Quantitative indices,such as DGT concentration,bioaccumulation in P.australis,geoaccumulation index(Igeo)and potential ecological risk index(RI),revealed that Cd was a major potential ecological risk factor along the southern coast wetland of the Qiantang Estuary,especially in the upstream region,which is potentially more vulnerable to the anthropogenic pollution.

Evaluation of Cadmium Bioavailability in Soils Using Diffusive Gradients in Thin Film Technique and Traditional Methods

The developed technique of diffusive gradients in thin film( DGT) has been suggested as a promising tool for evaluation of cadmium( Cd) availability in soils,but there exists considerable debate on its suitability. In this study,Cd bioavailability in soils was systemically investigated by comparing this technique with seven traditional methods, including soil solution concentration and six commonly used extraction methods( HAc,EDTA,Na c,NH4Ac,CaCl2 and MgCl2). Two typical plants( wheat and maize) were examined for Cd uptake. Maize was more sensitive to increasing exposure to Cd in soils than wheat when the added amounts of Cd ranged from 3. 5 to 5. 0 mg · kg-1,accompanied by the significant decreases of shoot and root biomasses. Cd concentrations in shoots and roots of two plants increased continuously with increasing levels of Cd in soils. Cd uptake was higher in wheat than that in maize. The bioavailable concentrations of Cd measured by all methods increased nearly linearly with increasing addition of Cd in soils. Positive correlations were observed between various bioavailable indicators of Cd in soils and Cd concentrations in two plants. The extractable Cd by six chemical extractants was considerably higher for maize than for wheat,while the DGT-measured and soil solution concentrations of Cd were lower for maize than for wheat,following the same trend as plant Cd uptake. The results imply that DGT measurement can effectively predict the bioavailable levels of Cd in soil solutions and that it is an ideal tool for prediction of Cd bioavailability in soils.

Controlled wrinkling analysis of thin films on gradient substrates

The paper investigates continuously changing wrinkle patterns of thin films bonded to a gradient substrate. Three types of gradient substrates including exponential, power-law, and symmetry models are considered. The Galerkin method is used to dis- cretize the governing equation of film bonded to gradient substrates. The wavelength and the normalized amplitude of the wrinkles for substrates of various material gradients are obtained. The numerical simulation based on the finite element method （FEM） is used to evolve the wrinkle patterns. The result agrees well with that of the analytical model. It is concluded that localization of wrinkle patterns strongly depends on the material gradient. The critical membrane force depends on both the minimum value of wrinkle stiffness and the gradient of wrinkle stiffness when the wrinkle stiffness is at its minimum. This work provides a better understanding for local wrinkle formation caused by gradient substrates.

Effects of gradient interlayer on residual stress and cracking in TiN thin films

The influence of a gradient interlayer on the residual stress and cracking in TiN thin films was studied as a function of the thickness of gradient interlayer. Both X ray in situ tensile testing and grazing method were used to measure the residual stress in thin films. In TiN films, there exists a residual stress of 10 GPa, which can be remarkably decreased by a gradient interlayer between film and substrate. The cracking behavior of films after tension shows that the crack of film/substrate system begins at interface between film and substrate.

Fabrication of ZnO-based thick film varistors with high potential gradient

ZnO-based thick film varistors have been fabricated by Y203 doping and low-temperature sintering, of which the sample with the best electrical properties has a high potential gradient value of 3159.4 V/mm. The effects of Y2O3 doping concentration and sintering temperature on the potential gradient of the samples were systematically investigated. The results show that the sample with the best electrical properties can be obtained by doping 0.08 mol% Y2O3 and sintering at 725℃. Under these optimum preparation conditions, the leakage current and the nonlinear coefficient are found to be 36.4 gA and 13.1. The sample with the best electrical properties has a grain size of 1.290um, a single grain boundary voltage of 4.08 V, a barrier height of 0.81 eV, and a depletion layer width of 10.2 nm, which are determined by thermionic emission. Small grain size with good grain boundary characteristics is beneficial to improve the electrical properties of varistors and promote the potential gradient.

Composition and structure of Ti-C/DLC graded composite films

The Ti C→DLC gradient composite films were characterized systematically. The elemental depth profile and elemental chemical state evolution were determined by X ray photoelectron spectroscopy (XPS). The transmission electron microscope (TEM) and high resolution transmission electron microscopy (HRTEM) were used to study the structure of interfacial zone between DLC film and Ti C layers. Results show that there are composition transition zone between DLC film and either Ti C layer or steel substrate on condition that pre deposited Ti layers on the steel substrate then plasma based bias deposited DLC films. In Ti C graded layer, the chemical state of titanium and carbon are changed gradually. The structures of zone in Ti C layer near the DLC film is consisted of random oriented nanocrystallines TiC dispersed in amorphous DLC matrix. The structure of the zone between DLC film and Ti C graded layer is gradually changed too.

COALESCENCE BETWEEN SMALL BUBBLES:EFFECTS OF SURFACE TENSION GRADIENT

When two small bubbles approach each other, a dimpled thin liquid film is formed between them. A model is developed for the dynamics of the thinning film with mobile interfaces, in which the effects of interfacial mobility and physical properties on the drainage and rupture of a dimpled liquid film are investigated. The model predicts the coalescence time, which is the time required for the thinning and the rupture of the liquid film, given only the radii of the bubbles and the required physical properties of the liquid and the surface, such as surface tension, London-van der waals constant, and surface diffusion coefficient. The predicted result is in agreement with the experimental results in the literature.

High-throughput fabrication and semi-automated characterization of oxide thin film transistors

High throughput experimental methods are known to accelerate the rate of research,development,and deployment of electronic materials.For example,thin films with lateral gradients in composition,thickness,or other parameters have been used alongside spatially-resolved characterization to assess how various physical factors affect the material properties under varying measurement conditions.Similarly,multi-layer electronic devices that contain such graded thin films as one or more of their layers can also be characterized spatially in order to optimize the performance.In this work,we apply these high throughput experimental methods to thin film transistors(TFTs),demonstrating combinatorial channel layer growth,device fabrication,and semi-automated characterization using sputtered oxide TFTs as a case study.We show that both extrinsic and intrinsic types of device gradients can be generated in a TFT library,such as channel thickness and length,channel cation compositions,and oxygen atmosphere during deposition.We also present a semi-automated method to measure the 44 devices fabricated on a 50 mm×50 mm substrate that can help to identify properly functioning TFTs in the library and finish the measurement in a short time.Finally,we propose a fully automated characterization system for similar TFT libraries,which can be coupled with high throughput data analysis.These results demonstrate that high throughput methods can accelerate the investigation of TFTs and other electronic devices.

水平内螺纹管中超临界RP-3航空煤油换热数值研究

针对航空换热器的应用,对水平内螺纹管中RP-3航空煤油的超临界换热进行了数值研究,着重考察煤油压力和螺纹升角对换热的影响。基于管截面温度、密度、局部质量流速、流线分布状况,揭示周向非均匀传热恶化的机理。通过类气膜温度梯度和旋流动能的演变以定量表征类气膜程度和旋流强度。提出了适用于周向四个位置努塞尔数预测的换热关联式。结果表明:流动性差的类气膜在冷流体和热壁面之间形成阻隔,导致传热恶化问题。浮升力作用致使流场和温度场出现畸变,类气膜厚度周向不均,产生局部超厚类气膜,对应的传热恶化加剧。厚类气膜区和二次流涡在浮升力和螺纹旋流耦合机制下沿流动方向不断逆时针改变位置。提高煤油压力有利于削弱和延后类气膜效应,且使旋流强度下降。随着螺纹升角增大,类气膜效应略有削弱和后延,旋流强度显著提高。换热关联式预测偏差普遍位于±10%的误差范围。

紫外光对沥青梯度老化行为的影响研究

沥青混合料在外界环境的影响下很容易发生氧化老化,且沥青内部化学组分众多,对宏观性能均有一定的影响。本研究基于分子动力学模拟等手段,从微观的角度研究紫外光对沥青膜老化梯度行为的影响。通过建立集料—沥青—集料三层模型,模拟了不同温度下氧气在沥青膜中的扩散行为;通过傅里叶红外光谱测试及原子力学显微镜测试,分析了老化后试件化学组分的变化情况并通过力曲线图计算研究了试样微观力学的变化。结果表明,氧分子在沥青膜内的活性会随着温度升高而提高,氧分子浓度的增加使沥青发生氧化反应的概率增加。温度较低时,沥青路面的老化主要受紫外老化的影响。随着老化时间的增加,沥青膜内部会随老化程度差异的增大而发生流动混合,表层的老化程度最大甚至可以下降约30%,老化程度会随老化天数进行一定的重分布。

草状氧化铝微结构渐变折射率的计算及实验研究

针对草状氧化铝的微纳结构对折射率的影响,采用台体计算法与柱体计算法计算氧化铝的体积,使用Clausius-Mossotti方程式与MATLAB软件拟合计算微纳结构的折射率变化,使用TFC软件进行拟合,最终计算出草状氧化铝的渐变折射率,研究其微结构的形貌特征及渐变折射率的分布,计算其可见光减反射性能。采用电子束沉积氧化铝薄膜,通过对沉积温度、水煮工艺等参数的优化,获得了不同结构的草状氧化铝纳米薄膜,制备了可见光波段420~680 nm的减反射薄膜。

限量供油条件下微柱阵列束油表面润滑增效特性研究

在润滑轨道两侧制备以防指纹油涂层(Anti-fingerprint coating,AFC)修饰的微柱阵列(Micropillar array,MA),形成润湿性梯度束油的润滑增效表面.使用点接触光弹流润滑油膜测量仪测量了该表面在限量供油往复运动条件下的油膜厚度以及油池形态,探究了往复频率、束油轨道宽度和载荷对润滑性能的影响,同时与未经AFC修饰的微柱阵列束油表面和仅以AFC形成的束油表面进行了对比.结果表明:制备的经AFC修饰的微柱阵列束油表面比其他2个束油表面有更好的润滑特性,往复运动条件(4 Hz)下明显改善了行程中点及两端点处的润滑状态,相对原始未处理表面行程中点处中心油膜厚度最高提升了51.4%.表面在束油轨道宽度接近Hertz接触区宽度时集油效果最强,随着轨道宽度增加集油效果减弱.载荷对微柱束油阵列表面的集油效果影响显著,随着载荷增大轨道机械分离作用变强、毛细回流作用减弱,造成集油能力和油膜厚度下降.

原位覆盖控制沉积物磷释放效果的验证评估

文章通过覆盖材料(方解石、湖沙或方解石+湖沙)对底泥磷释放的阻控实验以及利用梯度扩散薄膜(DGT)的底泥原位测试,验证评估覆盖剂对呼伦湖沉积物磷的生态修复效果。结果发现:(1)方解石、方解石+湖沙或湖沙能有效降低表层沉积物的DGT-P浓度(CDGT(PO_(4)^(3-)-P)),沉积物/水界面扩散通量和上覆水溶解反应性磷;方解石、方解石+湖沙覆盖的表层沉积物的CDGT(PO_(4)^(3-)-P)峰值或平均值明显低于对照样;方解石、方解石+湖沙的上覆水DRP的去除率分别超过78%和81%;方解石+湖沙可以将沉积物/水界面无机磷扩散通量降低至负值;(2)方解石和方解石+湖沙能明显地降低表层沉积物总磷(TP)、活性磷(NH_(4)Cl-P和BD-P)含量及其占TP的百分比,沉积物反应性磷再补给系数r减少而惰性成份(NaOH_(85)-P和Ca-P)及其占TP的百分比增加;(3)方解石+湖沙覆盖的表层沉积物TP变化范围:-45~-30 mg/kg;磷提取相(NH_(4)Cl-P、BD-P、Ca-P和NaOH_(85)-P)含量变化值,磷提取相变化量占对照沉积物对应提取成份的百分比分别为-17~-10 mg/kg (-38.46%~-29.31%);-23~-16 mg/kg (-46.15%~-32.86%);10~15 mg/kg (2.41%~3.63%)和8~14 mg/kg(3.20%~3.99%);r降低范围:0.02~0.19。综上,方解石的吸附或阻隔作用能降低沉积物总磷和活性磷,降低沉积物磷再补给能力;NH_(4)Cl-P和BD-P被转化为情性成份(NaOH_(85)-P和Ca-P),磷迁移性降低。覆盖剂对沉积物磷内源负荷控制效果为方解石+湖沙>方解石>湖沙。方解石+湖沙的磷阻控机制是方解石对磷的吸附,磷和方解石的共沉淀以及湖沙的物理阻隔;方解石+湖沙的多层覆盖是一种应用价值较高的沉积物原位修复技术。

春夏季巢湖湖滨沉积物-水界面磷动态与内源释放潜力

采用传统采样和薄膜扩散梯度技术(DGT),分析了春夏季巢湖西北部湖滨上覆水、间隙水及沉积物中磷形态和DGT有效态磷铁(DGT-P、DGT-Fe)的动态变化及扩散通量.结果表明,初夏季(6月)湖滨上覆水磷含量显著降低,可能源于藻类生长吸收营养盐;而间隙水磷形态含量季节差异显著.巢湖西北部湖滨沉积物无机磷主要为自生磷(Auth-P),占无机磷(IP)比例为19.7%~61.3%.湖滨带消落区(S1、S2)沉积物磷含量明显低于堤坝隔离区(S3),但受有机质水平、水动力扰动等因素影响,具有更高的磷释放潜力;夏季沉积物内源磷释放潜力高于春季.DGT-P和DGT-Fe的相关分析结果表明,湖滨带消落区沉积物内源磷释放主要受控于铁结合态磷还原过程,而堤坝隔离区沉积物受铁磷循环调控作用较弱.

基于梯度扩散薄膜(DGT)技术评估玉米农田土壤中铅的生物有效性及动力学过程

为验证梯度扩散薄膜(DGT)技术在准确评估自然环境下玉米农田土壤中铅(Pb)的生物有效性的可行性,并基于该技术探究土壤中Pb的动力学过程,本研究使用DGT技术、土壤溶液法和单独提取法测定了湖南省凤凰县内种植玉米的农田土壤中Pb的可提取态含量,并与玉米不同部位中Pb的含量进行了线性拟合分析;利用DGT技术结合DGT诱导土壤/沉积物通量(DIFS)模型模拟了土壤内部Pb的动力学过程。结果表明:35%的土壤点位中Pb的含量超过湖南省Pb背景值,但不存在玉米粒中Pb超标的情况(GB 2762—2022)。Pb在玉米不同部位迁移富集能力较低,且主要富集在根部,难以向地上部位迁移。不同方法测定的土壤中Pb的生物有效态含量分别为DGT技术(1.32±2.49)µg·L^(-1)、土壤溶液(2.23±3.75)µg·L^(-1)、二乙基三胺五乙酸(DTPA)单独提取法(5.79±2.51)mg·kg^(-1)、醋酸(HAc)单独提取法(0.81±0.49)mg·kg^(-1)和氯化钙(CaCl_(2))单独提取法(0.05±0.13)mg·kg^(-1)。DGT技术对玉米不同部位Pb含量的预测效果优于其他方法,且对叶中Pb含量的预测效果最佳。研究区大部分土壤固相Pb补给液相的能力较低,但固相上Pb的释放量较为稳定,仍可能会对当地造成潜在的生态风险。整体而言,DGT技术是评估玉米农田土壤中Pb生物有效性的最佳方法,其测定的Pb含量对玉米叶部Pb含量预测效果最佳,但对粒中Pb含量预测效果较差。此外,DGT技术可以结合DIFS模型深入分析土壤内部Pb的动力学的过程,为土壤污染的精准防控提供科学依据。

DLC膜对金刚石纳米柱NV色心发光收集强度的影响

金刚石氮空位(NV)色心发光收集强度的提高是实现单光子源技术的关键。本工作将锥状的类金刚石(DLC)梯度减反膜引入纳米柱色心单光子源中,旨在从色心的自发辐射速率与光子收集效率两方面提高NV色心的发光收集强度。采用时域有限差分(FDTD)法对带有DLC膜的金刚石纳米柱复合结构进行了光学仿真,探究了不同结构参数的DLC薄膜对金刚石纳米柱NV色心光子收集强度、出射效率及自发辐射速率的影响,并且通过优化得到了最大收集强度下的结构参数。仿真结果表明,引入DLC膜能够使金刚石纳米柱中NV色心获得更高的光子出射效率(≥1%),并且能够改变纳米柱内部电场分布,使色心自发辐射速率增加16.8%,最终使光子的总收集强度增加15.5%。

土壤重金属植物有效性的化学评价法综述

随着城市化、工业化发展的脚步加快,土壤重金属污染成为国内外普遍关注的环境问题。土壤中的重金属可能被植物或者农作物吸收,并经由食物链对人体造成健康风险。目前,土壤中重金属含量的测定及污染程度的评估以土壤重金属总量为主,但土壤重金属总量既无法反映重金属的地球化学过程,也无法准确评估土壤中重金属的污染程度,导致土壤中重金属对生物以及环境造成的危害程度难以被精准地评价。而土壤重金属的植物有效性可表征土壤中重金属的赋存状态以及植物吸收过程,能更精准地评估其对人体及环境造成的危害程度。本文介绍了生物有效性及植物有效性概念的发展历程,系统总结和对比了常用于土壤重金属植物有效性评价的化学方法[包括化学提取法(单独提取法和连续提取法)、自由离子活度法、同位素稀释法和梯度扩散薄膜(DGT)技术]的原理及其在土壤重金属植物有效性的测定工作中的应用,以期进一步推动国内外有关土壤中重金属植物有效性的研究以及土壤中重金属污染防治工作。