Characterization of diamond films deposited on titanium and its alloys

Titanium and its alloys have important applications for example in aerospace or as bioimplants. Some of these applications would be improved by diamond coatings. However the large thermal expansion mismatch between diamond and titanium or its alloys creates high residual stresses, up to about 7 GPa at 800 °C, which represent an important drawback. In this study, polycrystalline diamond films were deposited on pure titanium and Ti-6Al-4V in a classical tubular microwave plasma reactor from C-H(-O)-containing gas mixtures, at a temperature in the range 600–900 °C. Raman spectroscopy provided information about the diamond grain stress, which is obviously related to the deposition temperature. X-ray diffraction indicates the presence of titanium carbide or oxycarbide. Some other characterizations by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) are reported. It is shown that XPS coupled to argon ionic etching allows us to study the first steps of the deposition process. The structure and the chemical composition at the interface of a thicker deposit are obtained by TEM and EELS.     

Synthesis of titanium oxide and titanium nitride nano-particles with narrow size distribution by supersonic thermal plasma expansion

The paper reports the synthesis of nano-crystalline ceramics like titanium dioxide and titanium nitride using a plasma chemical experimental reactor powered by a multi-segment (cascaded) arc plasma torch. The precursor-laden plasma beam emerging from the torch anode section expands supersonically through a converging nozzle to a low-pressure collection chamber. This results in a uniform and controlled gas dynamic quenching ensuring rapid synthesis of pure, un-coagulated free-flowing particles with a narrow size distribution. Simple Langmuir probes and calorimetric energy balance methods are used for plasma and reactor characterization, while X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), Raman and X-ray photoelectron spectroscopy (XPS) techniques have been used for product analysis. It is shown that size distribution of both the product particles is comparatively narrower than that found in most thermal plasma assisted laboratory synthesis studies. The expansion process was observed to produce a non-equilibrium electron population, which could charge up the particles after nucleation and hence could curb unwanted coagulation.     

CNT/TiO2复合材料的合成、表征及其光催化性能分析

采用多壁碳纳米管(MWCNTs)为原料,分别以异丙醇钛(TIP)、丙氧基钛(TPP)和四丁氧基钛(TNB)为钛源,苯作为溶刺,制备了CNT/TiO2复合材料.利刖N2吸附等温线,扫描电子显微镜(SEM),X-射线衍射(XRD),能量分散性X-射线分析(EDX)以及紫外吸收光谱对所制CNT/TiO2复合材料进行了表征.并在紫外光照射下,通过亚甲蓝(MB,C16H18N3S·Cl·3H2O)水溶液的转,变测试了CNT/TiO2复合材料的光催化性能.研究结果表明:CNT/TiO2复合材料对MB的降解作用不仅有MWCNT的吸附性和TiO2的光催化性,而且还有MWCNT和TiO2之间的电子转移性.     

Laser-assisted production of spherical TiO2 nanoparticles in water

TiO(2) nanoparticles with controllable average diameter have been obtained by laser ablation in water. A monomode ytterbium doped fiber laser (YDFL) was used to ablate a metallic titanium target placed in deionized water. The resulting colloidal solutions were subjected to laser radiation to study the resizing effect. The crystalline phases, morphology and optical properties of the obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), x-ray energy dispersive spectroscopy (EDS) and UV-vis absorption spectroscopy. The colloidal suspensions produced consisting of titanium dioxide crystalline nanoparticles show almost perfect spherical shape with diameters ranging from 3 to 40 nm. The nanoparticles are polycrystalline and exhibit anatase as well as rutile phases.     

Analytical electron microscopy of thin films and interfaces

In this paper a brief overview is presented of some of the techniques available with transmission electron microscopy (TEM) to characterize thin films and interfaces. The critical role that sample preparation plays is discussed. Examples of the application of many of the analytical techniques used in TEM are given. These include nano area electron diffraction, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. High resolution imaging is available at atomic resolution and new methods are being developed to analyze the images including computer simulation. Imaging of magnetic domains is important to the study of materials used in digital data storage.     

Characterization of plasma nitrided pure titanium by X-ray absorption spectroscopy

To date, the exact nature of the plasma nitriding mechanism and the role of energetic particle bombardment are not well understood. The purpose of this work has been to obtain a more detailed knowledge about the evolution of the plasma nitrided surface layer as a function of the energy of the bombarding particles. Nitrided layers were produced at the surface of pure titanium specimens at various flux energies by Intensified Plasma-Assisted Processing (IPAP), a triode plasma technique developed in our laboratory. X-ray Absorption Near Edge Structure (XANES) spectroscopy and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy were used to characterize the local structure of the titanium nitride layers. Cross sections of the processed specimens were studied by Auger electron spectroscopy and electron microscopy. The results showed that increasing flux energy promotes the formation of a well-ordered TiN layer at the surface. Low flux energies produce significantly lower fractions of the TiN phase at the surface, as well as thinner nitrided layers. A structural model was suggested and quantitatively tested based on the XANES and EXAFS measurements.     

Use of titanium and zirconium in centrifugally cast heat resistant steel

Abstract

Low carbon 25Cr–35Ni steel (HP type steel) modified with titanium and zirconium has been produced by centrifugal casting. The different phases present in the as cast and aged conditions were described by light optical and scanning electron microscopy with secondary electron imaging and energy dispersive spectroscopy. Results suggest that the use of titanium as a microalloying element reduces secondary precipitation during aging. Moreover, secondary precipitates in the microalloyed steel are much finer and more evenly distributed. On the other hand, zirconium oxides was found to be potential nucleation sites for primary titanium rich carbides contributing to an optimum distribution of these carbides in the tubes. These differences together with the higher stability of the titanium containing primary carbides are responsible for the improvement on ductility and creep resistance found in the present work.     

Characterization of structures and surface states of the nanodiamond synthesized by detonation

Nanodiamond is a relatively new nanomaterial with broad prospects for application. In this paper, a variety of methods were used to analyze comprehensively the structures and the surface states of the nanodiamond synthesized by detonation, for example, X-ray diffraction (XRD) spectroscopy, energy diffraction spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman) and differential scanning calorimeter (DSC). The results show that, the nanodiamond particles are spherical or elliptical in shape. The average grain size is approximately 5 nm. The surfaces of the nanodiamond contain hydroxy, carbonyl, carboxyl, ether-based resin, and other functional groups. The initial oxidation temperature of the nanodiamond in the air is about 550 °C, which is lower than that of the bulk diamond.     

The effect of sodium-ion implantation on the properties of titanium

This paper deals with the surface modification of titanium by sodium-ion implantation and with the effect of this modification on structure, corrosion resistance, bioactivity and cytocompatibility. The Na ions were implanted with doses of 1 x 10(17) and 4 x 10(17) ions/cm(2) at an energy of 25 keV. The chemical composition of the surface layers formed during the implantation was examined by secondary-ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS), and their microstructure--by transmission electron microscopy (TEM). The corrosion resistance was determined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C, after exposure in SBF for various times. The surfaces of the samples were examined by optical microscopy, by scanning electron microscopy (SEM-EDS), and by atomic force microscopy (AFM). Biocompatibility of the modified surface was evaluated in vitro in a culture of the MG-63 cell line and human osteoblast cells. The TEM results indicate that the surface layers formed during the implantation of Na-ions are amorphous. The results of the electrochemical examinations obtained for the Na-implanted titanium samples indicate that the implantation increases corrosion resistance. Sodium-ion implantation improves bioactivity and does not reduce biocompatibility.     

Development of miniaturized electron probe X-ray microanalyzer

A miniaturized electron probe X-ray microanalyzer (EPMA) with a small chamber including the electron source and the sample stage was realized using a pyroelectric crystal as an electron source. The EPMA we propose is the smallest reported so far. Performance of the EPMA was evaluated by investigating energy of obtained continuous X-rays and lower detection limits of transition metals (titanium, iron, and nickel). End point energy (Duane-Hunt limit) of continuous X-rays of 45 keV was obtained. However, it is expected that the EPMA can analyze characteristic X-rays with energy less than 20 keV. The EPMA was able to measure titanium, iron, and nickel wires whose projected areas were more than 0.03 mm(2).     

Quantitative secondary neutral mass spectroscopy of thin films

A secondary ion mass spectrometer, having a liquid metal primary ion beam capable of focusing down to below 100 nm, has been adapted so that it can operate in conventional secondary ion or secondary neutral analysis mode. An electron beam is used to ionize the neutral species in the secondary neutral mass spectroscopy (SNMS) mode. Optimum operating conditions are reported including the use of an energy filter, which is shown to reduce background signals significantly. Typical results for various types of thin film coatings are reported including semiconductor materials, multilayer structures, metal oxides and metal alloys. A comparison of the SNMS data with that obtained in the secondary ion mass spectroscopy mode shows that the new technique provides more reliable quantitative data.     

A brief review of quantitative aspects of electron energy loss spectroscopy and imaging

Abstract

This review addresses a number of aspects of electron energy loss spectroscopy (EELS) for quantitative analysis, including: procedures for the quantification of EELS elemental analysis and mapping with an indication of the accuracies and detection sensitivities; procedures for the extraction of valence band electronic structures using low loss spectroscopy; and an outline of methods available for the quantitative determination of local valencies, coordinations, and bond lengths of atomic species using electron loss near edge and extended fine structures (ELNES and EXELFS). Additionally, a number of applications of quantitative EELS in spatially resolved studies of interfaces and defects are highlighted.     

Preparation and characterization of selenium incorporated anodic conversion coatings on titanium surfaces for biomedical applications

An anodic spark deposition process was used for preparation of inorganic, glass-ceramic like conversion coatings. The microstructure of the layers was characterized by surface and solid state techniques such as scanning electron microscopy, electron probe microanalysis and Raman spectroscopy. The porous coatings, typically up to 8 μm thick, consist mainly of titanium oxides and amounts of incorporated electrolyte constituents like Se, Ca or P. Beside nano crystalline anatase phases, a mostly amorphous structure is proposed in which network-forming [PO₄] tetrahedras and [TiO₆] octahedras in various degrees of condensation are connected. A drastic modification of the film structure was observed when selenium was incorporated into the glassy oxide structure of the coating. In these cases no nano crystalline phases of titanium oxides or other chemical compounds were detected. First cell culture investigations show a significant improvement of the biological properties. Cell proliferation and TGF-beta-expression of these coatings in comparison with commercial pure titanium (CPT) with native titanium oxide films were examined.     

Amorphous transition metal carbides

Titanium carbide films were deposited by chemical vapor deposition from tris(2,2'-bipyridine)titanium. Other films of titanium carbide and niobium carbide were obtained by electron beam vaporization of the corresponding crystalline compound. X-ray and electron diffraction studies showed that the structure of the deposits ranged from microcrystalline to amorphous. The coatings were analyzed by secondary ion mass spectroscopy, Auger electron spectroscopy and electron spectroscopy for chemical analysis. The results of these studies lead to an understanding of the formation and nature of the films. The objective is to modify the mechanical properties of brittle transition metal carbides.     

工艺参数对Ar~+改性无氧铜表面形貌及二次电子发射的影响

为了降低材料的二次电子发射系数,本文对高导电无氧铜(OFHC,简称无氧铜)进行离子束表面改性处理,并研究其最优工艺条件,重点考查了温度、时间等工艺参数对表面形貌以及二次电子发射系数(δ)的影响。利用扫描电镜、能谱仪等对表面形貌及成分进行分析并在此基础上对改性后样品的表面形貌形成机理进行了初步探讨。实验得出最佳工艺为:在600℃下离子束改性处理1 h。该参数下处理的无氧铜样品的二次电子发射系数降低63.5%。     

Synthesis of cobalt-orthotitanate inverse spinel nano particles via a novel low temperature solvothermal method: structural,opto-electronical,morphological, surface characterization and photo-catalytical application in mineralization of Remazol Red RB 133

Synthesis of single phase cobalt-orthotitanate inverse spinel nano particles is reported for the first time via a novel solvothermal method at low calcination temperature at 400?°C. The pure phase cobalt-orthotitanate spinel nano particles were prepared using cobalt nitrate and titanium tetraisopropoxide (1:1 molar ratio) as cobalt and titanium sources. The synthesised Co₂TiO₄ nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, surface area analyses (Brauner–Emmett–Teller) (BET) and UV–Vis diffuse reflectance spectroscopy. The XRD results proved the formation of a single phase cobalt-orthotitanate (Co₂TiO₄) nanoparticles by calcination temperature of 400?°C. The FE-SEM results showed that nano particles possess a uniform spherical morphology with an average size of 51 nm. Porosity and specific surface area of cobalt-orthotitanate nano particles was measured by nitrogen adsorption using BET and the results showed surface area of 44.47 m²/g. DRS results showed an optical band gap value of 1.802 eV for cobalt-orthotitanate nano powder. An excellent performance as a nano photo-catalyst toward the degradation of Remazol Red RB 133 (RR133) as a single azo textile dye with excellent efficiency. Mineralization of RR133 by highly active cobalt-orthotitanate nano-catalyst coated on glass surface was applied and 97% TOC removal was observed. This is due to high electron–hole charge separation and high surface area of nano-catalyst.     

Electronic states spectroscopy of Hydroxyapatite ceramics

Photoluminescence, surface photovoltage spectroscopy and high-resolution characterization methods (Atomic Force Microscopy, Scanning Electron Microscopy, X-ray spectroscopy and DC conductivity) are applied to nanostructured Hydroxyapatite (HAp) bioceramics and allowed to study electron (hole) energy states spectra of the HAp and distinguish bulk and surface localized levels. The measured trap spectra show strong sensitivity to preliminary heat treatment of the ceramics. It is assumed that found deep electron (hole) charged states are responsible for high bioactivity of the HAp nanoceramics.     

医用多孔金属的制备及其生物活化研究进展

医用多孔金属材料,特别是多孔钛及钛合金能够提供与人体骨组织相匹配的力学性能,并促进骨组织长入以提高其与骨的固定度,在人体硬组织修复与替换方面具有广泛的应用前景。重点围绕多孔钛及钛合金的制备方法及适用于其复杂孔隙结构的表面生物活化方法,综述了各种方法在多孔钛及钛合金上的应用现状。目前适用于多孔钛及钛合金制备的技术主要有粉末冶金法、钛纤维烧结法、自蔓延高温合成法、选区电子束熔化技术和选区激光熔化技术,适用于多孔钛及钛合金表面生物活化的技术主要有溶胶凝胶法、仿生矿化法、电化学沉积法和微弧氧化法。多孔钛及钛合金的力学相容性和表面生物活性需要同时满足临床要求,才能进一步扩大其在医学领域的应用范围。     

Surface characterization of titanium oxide films synthesized by ion beam enhanced deposition

In this article, titanium oxide films were prepared by ion beam enhanced deposition where titanium was evaporated by electron beam and simultaneously bombarded with xenon ion beams at an energy of 40 keV in an O₂ environment. X-ray photoelectron spectroscopy and Auger electron spectroscopy were used to research the chemical state and composition of the titanium oxide films. The results show that surface of the film was fully oxidized. After the surface was removed by argon ion sputtering, the results show that Ti²⁺, Ti³⁺ and Ti⁴⁺ states exist on the sputtered surface. The atomic concentration of all the three titanium states were calculated. The chemical shift of O 1s peak was also observed on the near surface.     

Super-Wideband Electromagnetic Absorbing TiC/SiOC Ceramic/Glass Composites Derived from Polysiloxane and Titanium Isopropoxide with Low Thickness (<1 mm)

Herein, TiC/SiOC ceramic/glass composites with excellent electromagnetic wave (EMW) absorbing performance are fabricated by pyrolysis of polycarbosiloxane and titanium (IV) isopropoxide (TTIP). By taking advantage of the polymer-derived route, the phase compositions and microstructures are easily tuned. The composites are investigated by X-ray diffraction (XRD) analysis, scanning electron microscope, and transmission electron microscopy/energy dispersive spectroscopy. Nanoscaled TiC is formed and uniformly distributed without clustering within the SiOC matrix. Thermogravimetric Analysis (TGA) and in situ XRD results revealed good thermal stability and oxidation resistance mechanism. The presented material system (TiC/SiOC) shows a super-wide microwave absorption bandwidth (EAB) of 13.5 GHz, including the entire Ka-band (26.5–40 GHz) with a low thickness requirement (<1 mm). The superior EMW absorption properties of the ceramics are attributed to the optimal interface polarization, as well as the ordering, concentration, and interconnectivity of the conductive network, which all determine the electrical conductivity in the composites.