Surface modification of Ti-49.8at%Ni alloy by Ti ion implantation：phase transformation,corrosion, and cell behavior

The Ti?49.8at%Ni alloy was modified by Ti ion implantation to improve its corrosion resistance and biocompatibility. The chemical composition and morphologies of the TiNi alloy surface were determined using atomic force microscopy (AFM), auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The results revealed that Ti ion implantation caused the reduction of Ni concentration and the formation of a TiO2 nano-film on the TiNi alloy. The phase transformation temperatures of the Ti–TiNi alloy remained almost invariable after Ti ion implantation. Electrochemical tests indicated that the corrosion resistance of TiNi increased after Ti ion im-plantation. Moreover, the Ni ion release rate in 0.9% NaCl solution for the TiNi alloy remarkably decreased due to the barrier effect of the TiO2 nano-film. The cell proliferation behavior on Ti-implanted TiNi was better than that on the untreated TiNi after cell culture for 1 d and 3 d.     

Surface modification of Ti-49.8at%Ni alloy by Ti ion implantation: phase transformation,corrosion, and cell behavior

The Ti-49.8at%Ni alloy was modified by Ti ion implantation to improve its corrosion resistance and biocompatibility. The chemical composition and morphologies of the Ti Ni alloy surface were determined using atomic force microscopy(AFM), auger electron spectroscopy(AES), and X-ray photoelectron spectroscopy(XPS). The results revealed that Ti ion implantation caused the reduction of Ni concentration and the formation of a Ti O2 nano-film on the Ti Ni alloy. The phase transformation temperatures of the Ti–Ti Ni alloy remained almost invariable after Ti ion implantation. Electrochemical tests indicated that the corrosion resistance of Ti Ni increased after Ti ion implantation. Moreover, the Ni ion release rate in 0.9% Na Cl solution for the Ti Ni alloy remarkably decreased due to the barrier effect of the Ti O2 nano-film. The cell proliferation behavior on Ti-implanted Ti Ni was better than that on the untreated Ti Ni after cell culture for 1 d and 3 d.     

Preparation of silicon carbide nitride films on Si substrate by pulsed high-energy density plasma

Thin films of silicon carbide nitride (SiCN) were prepared on (111) oriented silicon substrates by pulsed high-energy density plasma (PHEDP). The evolution of the chemical bonding states between silicon, nitrogen and carbon was investigated as a function of discharge voltage using X-ray photoelectron spectroscopy. With an increase in discharge voltage both the C 1s and N 1s spectra shift to lower binding energy due to the formation of C-Si and N-Si bonds. The Si-C-N bonds were observed in the deconvolved C 1s and N 1s spectra. The X-ray diffractometer (XRD) results show that there were no crystals in the films. The thickness of the films was approximately 1-2 μm with scanning electron microscopy (SEM).     

Reactive ion etching of poly(vinylidene fluoride-trifluoroethylene) copolymer for flexible piezoelectric devices

A microfabrication process for poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE)) based flexible piezoelectric devices is proposed using heat controlled spin coating and reactive ion etching(RIE) techniques.Dry etching of P(VDF-TrFE) in CF 4 +O2 plasma is found to be more effective than that using SF 6 +O2 or Ar+O2 feed gas with the same radiofrequency power and pressure conditions.A maximum etching rate of 400 nm/min is obtained using the CF 4 +O2 plasma with an oxygen concentration of 60% at an antenna power of 200 W and a platen power of 20 W.The oxygen atoms and fluorine atoms are found to be responsible for the chemical etching process.Microstructuring of P(VDF-TrFE) with a feature size of 10 m is achieved and the patterned films show a high remanent polarization of 63.6mC/m 2.     

Ohmic contact properties of p-type surface conductive layer on H-terminated diamond films prepared by DC arc jet CVD

With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current (DC) arc jet chemical vapor deposition (CVD) are considered to be one of the most promising materials for high-frequency and high-power electronic devices. In this paper, high-quality self-standing polycrystalline diamond films with the diameter of 100 mm were prepared by DC arc jet CVD, and then, the p-type surface conductive layer with the sheet carrier density of 1011-1013 cm?2 on the H-terminated diamond film was obtained by micro-wave hydrogen plasma treatment for 40 min. Ti/Au and Au films were deposited on the H-terminated diamond surface as the ohmic contact electrode, respectively, afterwards, they were treated by rapid vacuum annealing at different temperatures. The properties of these two types of ohmic contacts were investigated by measuring the specific contact resistance using the transmission line method (TLM). Due to the formation of Ti-related carbide at high temperature, the specific contact resistance of Ti/Au contact gradually decreases to 9.95 × 10?5 Ω·cm2 as the temperature increases to 820℃. However, when the annealing temperature reaches 850℃, the ohmic contact for Ti/Au is degraded significantly due to the strong diffusion and reaction between Ti and Au. As for the as-deposited Au contact, it shows an ohmic contact. After annealing treatment at 550℃, low specific contact resistance was detected for Au contact, which is derived from the enhancement of interdiffusion between Au and diamond films.     

Simple nanofabrication of a superhydrophobic and transparent biomimetic surface

This paper describes a simple fabrication method for creating superhydrophobic and transparent glass surfaces that mimic natural surfaces such as lotus leaves, moth eyes or cicada wings. Nanostructured glass surfaces were created by a combination of colloidal lithography and plasma etching. A colloidal mask was formed simply by the spin coating of the polystyrene beads and with modification of the interparticle distance between the beads. The etching of the glasses was conducted by CF4 plasma. Tower-shaped nanostructures at an aspect ratio of 1：4 were treated using fluoroalkylsilane selfassembled monolayers （SAMs） to obtain the hydrophobic surfaces. The treated glass surfaces showed superhydrophobicity with a water contact angle of around 150° and a hexadecane contact angle of around 110° Furthermore, the nanostructured glass was transparent to visible light.     

Mechanistic Details of Surface Reactions in Atomic Layer Deposition (ALD) Processes

1 Results The reaction mechanisms of the atomic layer deposition (ALD) processes used for thin-film growth have been characterized by a combination of surface sensitive techniques. Our early studies focused on the deposition of TiN films from TiCl4 and ammonia,starting with the independent characterization of each of the two half steps comprising the ALD process. It was found that exposure of the substrate to TiCl4 leads to the initial deposition of titanium in the 3 oxidation state; only at a later stage most of the Ti atoms retain the 4 state expected for molecular TiCl4. The Cl:Ti final ratio at the end of the TiCl4 deposition was found to reach a value of≈3.5,indicating some chlorine removal. Subsequent treatment with ammonia removes most of the remaining Cl and deposits the required nitrogen,as expected,but some chlorine is still seen on the surface,most likely because of HCl readsorption. The buildup of thicker films was then tested by performing multiple cycles with alternating exposures to TiCl4 and NH3. Similar films could be deposited on glass and on W,Ni and Cu foils. Interestingly,depth-profiling studies show that the resulting films consist of a Ti3N4 layer on top of TiN. This suggests that the reduction of titanium takes place during the exposure of the surface to TiCl4,not NH3,and that it is the first reaction of the cycle the rate limiting in the whole ALD process. Additional work was performed aimed at identifying the origin of the oxygen contamination often seen in these films. Incorporation of water or oxygen from the background was ruled out,and diffusion of oxygen from the substrate was proposed.Similar conclusions were reached from studies with TaCl5. In particular,partial reduction of the tantalum atoms is seen in the initial stages of the TaCl5 uptake,suggesting again precursor disproportionation rather than reaction with ammonia as the mechanism for Ta3 formation. A signal likely due to tantalum oxide is seen in the XPS spectra,but ammonia treatments do lead to the replacement of most of the chlorine by nitrogen. The oxide signal is the last to be removed upon sputtering,suggesting that the oxide layer may form at the interface between the substrate and the growing TaN film.     

Effects of helium on titanium films and the helium diffusion

Using direct current-magnetron sputtering, Helium-trapped Ti films with a He/Ar mixture was studied. The relative helium content, helium depth profiles for the Ti films and crystallization capacity were analyzed by Enhanced Proton Backscattering Spectrometry （EPBS） and X-ray diffraction （XRD）. It was found that helium diffusion enhanced as more helium trapping into Ti films, and the He holding ratios were 95.9%, 94.9%, 93.9%, 82.8% when the Ti films with the He/Ti of concentrations of 9.7 at.%, 19.5 at.%, 19.7 at.%, 48.3 at.% were measured again 4 months later, respectively. The diffraction peaks became weak and wider, the peak of （002） plane was shifted to smaller diffraction angles and the relevant interplanar spacing d（hk,） increased gradually as more helium trapping into Ti films. The main peak was made trending to the （101） plane by both higher deposition temperature and more helium trapping.     

Structure and composition-dependent optical properties of (PbxSr1-x)TiO3 (x=0.4, 0.6) nanotube arrays

Lead strontium titanate(Pb_xSr_(1-x))TiO_3(x=0.4,0.6) nanotubes were synthesized by sol-gel template method via spin coating.The structures and morphology of the as-prepared samples were characterized by X-ray diffractometry.scanning electron microscopy and transmission electron microscopy.X-ray photoelectron spectroscopy was used to determine the chemical composition of the sample and the valence state of elements.Raman spectroscopy of the as-prepared(Pb_xSr_(1-x))TiO_3(x=0.4,0.6) nanotubes at room temp...     

Effect of Pd ions in the chemical etching solution

The acrylonitrile-butadiene-styrene (ABS) surface was etched by dipping it into chromic acid-sulfuric acid containing a trace amount of palladium. The surface roughness, activity, and valence bond were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results showed that with the increase of Pd concentration in the etching solution the ABS surface roughness reduced. The ratio of O to C increases and forms a large amount of O=C-O functional groups by dipping into Pd contained etching solution, thus the amount of colloids palladium adsorption increases. The carboxyl group acts as the adsorption site for the Pd/Sn catalyst.     

Preparation of BST nanocrystals embedded in SiO<Subscript>2</Subscript> film by magnetron sputtering for nonvolatile memory applications

We develop a method that uses magnetron sputtering to fabricate barium strontium titanate (BST) nanocrystals embedded in dielectric SiO2 films.Transmission electron microscope images show that the BST nanocrystals have an average diameter of 5 nm and are well distributed in the SiO2 film.In addition,we also analyze the BST nanocrystals composition deviation during the sputtering process by electron dispersive spectroscopy.     

钛酸锶钡拉曼光谱的理论计算与实验研究

钛酸钡是一种重要的铁电体，在居里温度130 ℃附近介电常数最大，为了降低钛酸钡的居里温度，通常在钛酸钡中掺杂锶.采用水热合成法制备了钛酸锶钡粉末，并且建立2×2×1的超晶胞进行第一性原理计算.随着锶掺杂量的增加，其XRD衍射峰向右偏移，说明钛酸锶钡的晶胞结构逐渐从四方相转变到立方相.计算结果表明:随着锶掺杂量增加，钛酸锶钡的晶胞参数逐渐减小；晶胞参数c与a的比值逐渐减小，与实验相符；Raman光谱特征峰的强度逐渐减弱，说明掺杂后钛酸锶钡的自发极化程度逐渐减弱，Ti和O分别偏离晶胞体心和面心的位移逐渐减小.由于掺杂后钡原子被比其原子半径小的锶原子取代，使得晶胞参数变小，阻碍了Ti的自发偏移，Ti只需要较低的热振动能即可克服与O的库仑作用，稳定位于晶胞体心，居里温度(居里点)随之下降.     

Electrodeposition and characterization of thermoelectric Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films

Bi₂Se₃ thin films were electrochemically deposited on Ti and indium tin oxide-coated glass substrates, respectively, at room temperature, using Bi(NO₃)₃·5H₂O and SeO₂ as starting materials in diluted HNO₃ solution. A conventional three-electrode cell was used with a platinum sheet as a counter electrode, and a saturated calomel electrode was used as a reference electrode. The films were annealed in argon atmosphere. The influence of cold isostatic pressing before annealing on the microstructure and thermoelectric properties of the films was investigated. X-ray diffraction analysis indicates that the film grown on the indium tin oxide-coated glass substrate is pure rhombohedral Bi₂Se₃, and the film grown on the Ti substrate consists of both rhombohedral and orthorhombic Bi₂Se₃.     

Synthesis and characterization of monoclinic TiO<Subscript>2</Subscript> nanosheets

A novel two-step method for the synthesis of monoclinic titanium oxide （i.e. TiO2（B）） nanosheets is presented in this report. The method is featured by two steps： 1） synthesis of hydrogen titanate nanosheets, followed by 2） calcination of the titanate nanosheets at elevated temperatures. The hydrogen titanate nanosheets were prepared first by autoclaving anatase TiO2 powders, obtained by air cal- cining an ethanol-gel of Ti（OH）4 at 500℃, in aqueous NaOH （10 mol/L） at 150-200℃, and then by washing with hydro- chloric acid under supersonic irradiation. While sizes of the nanosheets were found to increase with increasing the temperature of the hydrothermal treatment, the calcination at 400-500℃ of the hydrogen titanate nanosheets that were synthesized at higher autoclaving temperatures （180-200℃） produced monoclinic TiO2 nanosheets with a uniform morphology. By contrast, the same calcination of the titanate nanosheets synthesized at the autoclaving temperature 180℃ led to anatase TiO2 nanoparticles.     

Silicon field emission arrays coated with CN<Subscript>x</Subscript> thin films

Arrays of silicon micro-tips were made by etching the p-type (1 0 0) silicon wafers which had SiO₂ masks with alkaline solution. The density of the micro-tips is 2×10⁴ cm⁻². The Scanning Electron Microscope (SEM) photos showed that the tips in these arrays are uniform and orderly. The CN_x thin film, with the thickness of 1.27 μm was deposited on the silicon micro-tip arrays by using the middle frequency magnetron sputtering technology. The SEM photos showed that the films on the tips are smoothly without particles. Keeping the sharpness of the tips will benefit the properties of field emission. The X-ray photoelectron spectrum (XPS) showed that carbon, nitrogen and oxygen are the three major elements in the surfaces of the films. The percents of them are C: 69.5%, N: 12.6% and O: 17.9%. The silicon arrays coated with CN_x thin films had shown a good field emission characterization. The emission current intensity reached 3.2 mA/cm² at 32.8 V/μm, so it can be put into use. The result showed that the silicon arrays coated with CN_x thin films are likely to be good field emission cathode. The preparation and the characterization of the samples were discussed in detail. Foundation item: Supported by the National Natural Science Foundation of China (19975035) Biography: Chen Ming an (1978-), male, Ph. D candidate, research direction: novel functional materials film and ion beam modification of materials.     

Ni掺杂对Ba_(0.7)Sr_(0.3)TiO_3热演变及相组成的影响

掺杂是改善Ba0.7Sr0.3TiO3（BST）性能的重要方法之一,而认识其热演变过程和相组成有助于制备性能优异的BST.本文选取分析纯醋酸镍Ni（Ac）2、醋酸钡Ba（Ac）2、醋酸锶Sr（Ac）2、和化学纯钛酸丁酯Ti（OC4H9）4为主要原料,冰醋酸HAc为溶剂和酸度调节剂、乙二醇-甲醚C3H8O2为摩尔浓度调节剂,采用溶胶-凝胶法按组分为Ba0.7Sr0.3（Ti1-xNix）O3（x=0,0.05,0.10,0.20和0.30）的化学计量比在醋酸溶液体系中制备了未掺杂和掺Ni的钛酸锶钡的凝胶和粉末.运用DSC研究了Ni的掺入对BST热演变过程影响.采用慢扫描和快扫描XRD技术分析了Ni掺杂对相组成、晶面间距和晶粒尺寸的影响.Ni掺杂强烈影响BST体系的热演变过程特别是晶化过程,由未掺杂BST体系的双相变过程逐渐变成单相变过程,加快了反应速率.经750℃晶化退火0.5h的Ni掺杂BST体系,得到单一的纯BST相不是单相变过程而是双相变过程.XRD分析结果表明,在相同热经历状况下,Ni掺杂BST体系晶化反应充分完全,BST相结晶性良好,当Ni掺入量到0.05时得单一的BST相 随Ni掺入量进一步增多,BST体系中（Ba,Sr）CO3相的含量增多.BST晶体（110）晶面间距d随Ni的掺入增大而增大,且晶粒尺寸逐渐减小.     

基于钛酸锶钡陶瓷的宽带频率选择表面设计

设计了一种基于钛酸锶钡陶瓷的新型宽带频率选择表面,其基本单元尺度为亚波长,按照三角晶格进行排列。通过调节单元的共振频率,实现了三个共振模式耦合而形成宽带工作的阻带。模拟结果表明,电磁波在0°入射的时候,频率选择表面的带宽为7.8 GHz。当钛酸锶钡陶瓷的相对介电常数由115降低到85时,阻带带宽可以增大到8.7 GHz。该设计具有良好的宽带特性,在电子对抗和隐身领域具有重要的军事价值。     

Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO<Subscript>2</Subscript>) electrodes

The electrochemical oxidation capabilities of two high-performance electrodes, the boron-doped diamond film on Ti (Ti/BDD) and the lead oxide film on Ti (Ti/PbO₂), were discussed. Hydroxyl radicals (·HO) generated on the electrode surface were detected by using p-nitrosodimethylaniline (RNO) as the trapping reagent. Electrochemical oxidation measurements, including the chemical oxygen demand (COD) removal and the current efficiency (CE), were carried out via the degradation of p-nitrophenol (PNP) under the galvanostatic condition. The results indicate that an indirect reaction, which is attributed to free hydroxyl radicals with high activation, conducts on the Ti/BDD electrode, while the absorbed hydroxyl radicals generated at the Ti/PbO₂ surface results in low degradation efficiency. Due to quick mineralization which combusts PNP to CO₂ and H₂O absolutely by the active hydroxyl radical directly, the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO₂ electrode, notwithstanding the number of hydroxyl radicals produced on PbO₂ is higher than that on the BDD surface.     

磁控溅射表面镀膜对Nd2Fe14B稀土永磁体抗腐蚀性能的影响

在Nd₂Fe₁₄B稀土永磁体基体表面,采用磁控溅射（直流+射频）技术制备了Ti/Ni,Ti/Al和Al/Ni等二元合金薄膜和Ti/Al/Ni三元合金薄膜。并通过中性盐雾试验、腐蚀失重计算、电化学腐蚀试验、金相观察等方式,对比研究了不同表面处理对Nd₂Fe₁₄B稀土永磁体基体抗腐蚀性能的影响,并构建了腐蚀模型。研究发现：Ti/Ni,Ti/Al和Al/Ni等二元合金薄膜和Ti/Al/Ni三元合金薄膜均有效地提高了Nd₂Fe₁₄B稀土永磁体基体耐中性盐雾腐蚀和电化学腐蚀的能力;Ti/Al/Ni三元合金薄膜较Ti/Ni,Ti/Al和Al/Ni等二元合金薄膜有更优良的综合耐腐蚀性能,其磁控溅射工艺参数为：Ar流量60 sccm,基片温度常温,Ni,Al,Ti的溅射功率都为250 W,基片转速20 r·min^-1,镀膜均速0.3 nm·s^-1,总计溅射时间1 h。