Characterization of surface oxide films and cell toxicity evaluations with a quenched titanium surface

This study characterizes the surface of the oxide film that forms on titanium metal through the use of thermal and quenching treatments in cold water and investigates the effects of the surface characteristics and cellular interactions of a modified titanium surface. A range of sample groups were prepared in heat treatments of pure titanium at 600°C, 700°C, 800°C, 900°C, and 1000°C and subsequent quenching in cold water. The surface topography, roughness, crystallite size and crystal intensity were found to depend on the heating temperature. An increased surface roughness was observed with increases in the heating temperature and the quenching. The surface roughness was in the range of 0.15 μm–1.07 μm. In vitro cell responses were evaluated with mouse osteoblast MC3T3 cells in terms of cell proliferation and differentiation. MTT assays showed an increase in the living cell density and proliferation upon heating and quenching the titanium surface. The results of this study indicate that the cell toxicity was sensitive to the surface roughness and that it decreased as the roughness of the Ti increased.     

TC4钛合金表面氧化镧催渗渗硼工艺优化

以渗层厚度和表面硬度为评定依据,采用正交试验对TC4钛合金表面氧化镧催渗渗硼工艺进行优化。结果表明,渗硼温度对渗硼层影响最大,其次为渗硼时间、B₄C含量和La₂O₃含量。最优的催渗渗硼工艺为：渗硼温度1050 ℃,渗硼时间20 h,渗硼剂配比20wt%B₄C+4wt%La₂O₃+76wt%SiC。渗层表面由TiB、Ti₂B₅、TiC和Ti组成;与未添加氧化镧渗硼层相比,添加氧化镧渗硼层厚度与表面硬度明显提高,耐磨性也得到显著改善。     

Preparation and in vitro biocompatibility of hybrid oxide layer on titanium surface

A new technique combining microarc oxidation (MAO) and electrophoresis was introduced to develop a biocompatible oxide layer on pure titanium implant surface. Originally developed alkaline electrolyte containing nano-scale hydroxyapatite powder suspension was used in the new technique. In the electric field, nano-scale hydroxyapatite powder was electrophoretically moved and sintered into the gradually-formed oxide layer on titanium anode. Physio-chemical properties and in vitro biological performance of the newly-formed surface were examined and evaluated. A 8.5-μm thick oxide layer with high surface energy and roughness, which was composed of titanium dioxide and calcium phosphates as well as hydroxyapatite, was formed on titanium surface by the modified MAO technique. Osteoblasts cultured on the modified MAO titanium surface showed significantly increased alkaline phosphatase (ALP) activity comparing to machined and MAO titanium surface. Natural oxide surface of titanium could be transformed into a hybrid oxide layer by modified MAO treatment. The modified titanium surface, which is rough and porous, contains calcium phosphates and proved to be more biocompatible in vitro.     

Thermochemical surface treatment of titanium

Abstract

Titanium has very poor tribological properties. Various coatings can be used, for example, TiN, to improve them, but the loading is limited by the low strength of the substrate. Thermochemical treatments produce a layer that is sufficiently thick to support a load, but have to be carried out at high temperatures, 950 and 1050°C, for oxidation and nitriding processes respectively, degrading the core properties. An alternative treatment is desirable that could produce a substantive load bearing layer with good wear properties at 850°C or lower. The obvious candidate species were oxygen, nitrogen and carbon to form hardened diffusion layers, under a thin TiO₂, TiN or TiC surface layer. Nitrogen was not found to be sufficiently active at lower treatment temperature to have any beneficial effects and tended to block the diffusion of other species. Layers formed using various sources of nascent nitrogen, carbon and oxygen were studied. It was found that all the species forming hardened surface layers with the highest values of surface hardness and case depth (72 μm and 922 HV after 24 h at 850°C) were produced using carbon monoxide.     

Improvement of erosion resistance of titanium with different surface treatments

To improve the erosion resistance of titanium, several surface treatment methods were applied: (1) duplex treatment with carbon nitride film deposited on a plasma-nitrided layer, (2) diamond coating, and (3) laser alloying. Duplex treatment could improve the erosion resistance of titanium under a low impact velocity of erosion particles. However, under a high velocity of erosion particles, because of the shallow depth of the plasma-nitrided layer and low load-bearing capacity of carbon nitride layer on the plasma-nitrided specimen, the improvement of erosion resistance was not significant. Diamond coatings with a thickness of 15 μm made no significant improvement on the erosion resistance of the titanium substrate. The large-area spallation of diamond coating during erosion was observed, probably due to the high residual stresses, poor load-bearing capacity, and brittle nature of diamond coatings. Compared with untreated Ti substrate, the erosion resistance of the laser-alloyed (nitrided) specimen was improved significantly. The erosion mechanisms for laser-nitrided titanium were characterized by chipping, brittle fracture, and formation of large flakes in the laser-nitrided layers.     

钛及钛合金的激光表面改性研究现状

硬度低、耐磨性能差是制约钛合金发展的关键问题,而激光表面改性处理是解决这一问题的有效途径。结合近年来激光表面改性处理的研究进展,综述了激光表面处理的影响因素,激光表面处理表层的组织、性能及缺陷控制,并指出了目前存在的问题和今后研究的重点方向。     

Vacuum-plasma sprayed nanostructured titanium oxide films

Nanostructured titanium oxide films were fabricated by vacuum-plasma spraying. The microstructure of the films was characterized with SEM, TEM, and XRD. The chemical state of the titanium oxide of the films was analyzed using XPS. The results indicated that the vacuum-plasma sprayed nanostructured titanium oxide films possessed a corallike structure with small pores and agglomerated grains, which was composed of nanosized particles. The main phases of the films were anatase and rutile, and their relative content was determined by the plasma parameters. Low-valence titanium cations were also found in the films.     

Morphology of oxide scales formed on titanium

High-temperature oxidation of several pure metals and their alloys gives rise to multilayered corrosion scales. This curious morphology has not been the subject of a specific investigation, and its interpretation remains widely open. This paper presents results on titanium foil oxidized in pure oxygen leading to this phenomenon. It analyzes the significant features of the stratification as a function of the main parameters of the reaction kinetics such as temperature, oxygen pressure, oxidation time, and initial thickness of the metallic foil. All the results, including those previously reported, show the importance and the consistency of the studied phenomenon as well as the incapability of providing an unequivocal intepretation at the present time. The analysis of the main results, such as the appearance of a macroscopic order, the existence of boundary limits, and the nonequilibrium state of the structure, shows that a consistent set of data exists to give a meaningful interpretation of multilayered corrosion scales in terms of a nonlinear, far-from-equilibrium organization.     

Detection of breakaway oxidation with Acoustic Emission during titanium oxide scale growth

Extensive in-situ analysis of high temperature breakaway oxidation of titanium metal has been performed using the Acoustic Emission (AE) technique. Depending on temperature and oxidising atmosphere, different model cases were examined: with breakaway (900 °C/O₂), without breakaway (750 °C/O₂ and 900 °C/H₂O). Two specific population of AE hits were observed before and after breakaway. Contrary to the pre-breakaway population, the post-breakaway population exhibited low AE activity characterised by high values of energy. A critical energy value of E = 3 fJ was determined as a frontier between signals resulting from oxide parabolic growth and signals resulting from rapid linear growth.     

Surface structure of multicomponent oxide coatings on titanium

Data on the surface structure of Cu-Ni containing oxide films formed on titanium under the effect of electric spark and arc discharges are considered at the scale of tens to hundreds nanometers. The surface sites of films around electric discharge channels are perforated with pores of diameters around 10 nm. Spheroids with diameters of tens to hundreds of nanometers, which chiefly elements contain involved in the electrolyte components including heightened amounts of copper and carbon, are distributed over the surface. Furthermore, agglomerates formed by planar particles with sizes of tens to hundreds of nanometers of irregular geometric shapes are also present on the surface. Elemental compositions of the film surface and planar agglomerates coincide. The particles are supposedly the products of the electric-discharge erosion of the film material.     

Recent advances in surface hardening of titanium

Titanium and its alloys are used significantly in defense, aerospace and biomedical device components. However, their poor wear resistance and surface integrity leads to galling and seizure of surfaces when contact or relative motions of surfaces are involved. Surface hardening of Ti is therefore actively pursued to minimize the wear and fretting of components in these applications. The purpose of this review is to highlight some of the recent advances in surface hardening of Ti and its alloys, especially by diffusion of interstitial elements such as nitrogen, oxygen, and boron. These interstitial elements react with Ti to form hard and wear resistant compound layers at the surface and thereby, enhance the wear/abrasion properties. The recent developments pertaining to these surface hardening techniques in terms of the process parameters, microstructural details and enhancement in mechanical/wear properties are summarized in this review.     

Fracture toughness and adhesion of thermally grown titanium oxide on medical grade pure titanium

The mechanical properties and adhesion characteristics of a thin thermally grown titanium oxide film on commercially pure titanium were examined. Tensile tests were used to introduce controlled strains in the thermally grown oxide (TGO), through the titanium substrate, to study the damage evolution and to quantitatively evaluate the intrinsic strength and fracture toughness of the TGO layer. Details of the TGO adhesion behaviour were explored. Nanoindentation was used to determine the Young's modulus and hardness of the TGO. Tensile loading resulted in multiple cracking to occur in the TGO layer along with distinctive inclined cracking driven by shear band deformation in the titanium substrate. The fracture toughness of the TGO was determined to be 1.8 ± 0.6 MPa m^1/2. Localised delamination of the TGO was observed but only when the titanium substrate was strained well within the plastic deformation region by more than about 2.5%.     

综合利用钛铁矿制备二氧化钛、钛酸锂和磷酸铁锂

以钛铁矿为原料,经机械活化-盐酸浸出得到水解钛渣和富铁浸出液;用H2O2将水解钛渣中的Ti配位溶出,得到配位浸出液,并以其为反应物制备纳米级片状的过氧钛化合物;该过氧钛化合物经洗涤、煅烧制备得到纳米级片状的TiO2,其纯度高达99.31%(质量分数)。将过氧钛化合物与Li2CO3混合,球磨后煅烧合成性能优良的锂离子电池负极材料Li4Ti5O12。以富铁浸出液为原料,经选择性沉淀制备含少量Al和Ti的FePO4.xH2O,并以其为前驱体制备了Al-Ti掺杂的LiFePO4。该LiFePO4在1C和2C倍率下的首次放电比容量分别达151.3和140.1(mA.h)/g,循环100次之后容量无衰减。该方法也可用于钛白粉副产品硫酸亚铁的回收利用,制备性能优异的LiFePO4。     

微弧氧化工艺参数对Ti-6Al-4V钛合金表面氧化膜厚度及表面形态的影响

为了提高Ti-6Al-4V钛合金表面的生物活性,在乙酸钙和磷酸二氢钠溶液中对Ti-6Al-4V钛合金进行微弧氧化,研究氧化时间,电压,占空比等对氧化膜厚度及其表面形态的影响。结果表明,在一定条件下,随氧化时间的增加,氧化膜厚度以指数关系增加,而膜层表面孔洞逐渐变小,最终封闭;随着电压的提高,膜层厚度增加平缓,但电压过大时,膜层反而变薄,氧化膜表面微孔的数量减少,但微孔的孔径逐渐增大;占空比的提高使得膜层厚度增加,同时伴随有膜层孔洞分布的均匀性变差,表面粗糙度增加。     

钛及钛合金表面转化膜的应用及发展

对钛及钛合金的表面转化膜处理技术进行了综述,主要包括化学氧化、阳极氧化、硅烷化、磷酸盐转化等。阐述了各种处理方法的工艺过程及其作用效果,分别指出了各种方法的优缺点。同时展望了其今后的应用及发展前景。     

Luminescence from band-gap photo-excitation of titanium anodic oxide films

Luminescence light from the anodic thin oxide films formed on titanium in neutral phosphate solution was measured by photo-excitation of ultra-violet light irradiation with 3.82 eV energy. The luminescence light is observed with a peak of about 3 eV energy that corresponds to the band-gap energy of the n-type semiconductive TiO₂ oxide. It can therefore be presumed that the luminescence is induced by de-excitation or recombination between electrons in the conduction band and holes in the valence band. The peak wavelength of the luminescence light changes with the formation potential of the oxide film from 409 nm at 1 V to 425 nm at 6 V. The shift of the peak may reflect an amorphous-crystalline transition with increase of potential.     

电化学参数对制取氧化钛薄膜的影响

采用阳极氧化法制取氧化钛薄膜.研完了电压大小与薄膜颜色之间的关系、电压加戴方式对薄膜表面的彩响以及不同磷酸浓度对成膜过程的影响.结果表明:不同氧经电压下制备出不同颜色的氧化膜,电压大小是决定氧化膜颜色的主要因素;采用缓加渐进方式加压有利于形成无斑点、表面均匀的薄膜;阻挡层电阻和厚度随磷酸浓度的增加而减小.