Preparation of K<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>13</Subscript>/TiO<Subscript>2</Subscript> bio-ceramic on titanium substrate by micro-arc oxidation

K₂Ti₆O₁₃/TiO₂ bio-ceramic coatings are prepared successfully by micro-arc oxidation on titanium substrate in pure KOH electrolyte solution. The coating is prepared at various applied current density (150–500 mA/cm²) and in KOH electrolyte with different concentrations (0.5–1.2 mol/L). The composition and surface morphologies of coatings are strongly dependent on the applied current density and the electrolyte concentration. On the condition of lower current density and electrolyte concentration, K₂Ti₆O₁₃ phase almost cannot be formed. The phase is mainly composed of rutile and K₂Ti₆O₁₃ with increasing current density and electrolyte concentration. The surface morphologies are composed of whiskers and porous structures. The ability of K₂Ti₆O₁₃/TiO₂ bio-ceramic films inducing apatite deposition is evaluated by soaking it in biological model fluids. The results show the K₂Ti₆O₁₃/TiO₂ bio-ceramic coatings possess excellent capability of inducing bone-like apatite to deposit.     

氧化时间对钛合金钻杆微弧氧化膜层结构和性能的影响

采用脉冲直流微弧氧化方法在钛合金钻杆表面制备了不同氧化时间下的TiO_2陶瓷膜层,用扫描电镜、X射线衍射仪、显微硬度计、球盘摩擦试验机及电化学工作站等分析了膜层的形貌、结构、组成以及膜层的硬度、摩擦磨损性能和耐蚀性。结果表明,随着氧化时间的延长,膜层的厚度增加,但膜层的硬度、耐磨性和耐腐蚀性先增加后降低。经不同氧化时间处理后,膜层的相结构主要由金红石型TiO_2和锐钛矿型TiO_2组成,此外还含有少量的Al2TiO5晶体和SiO_2非晶态。微观形貌分析表明,随着氧化时间延长,膜层表面粗糙度延长。在本实验条件下,当氧化时间为40min时,微弧氧化膜层的综合性能较好。     

Effect of metal-ion-to-fuel ratio on the phase formation of bioceramic phosphates synthesized by self-propagating combustion

Abstract

Synthetic calcium hydroxyapatite (HAP, Ca₁₀ (PO₄)₆ (OH)₂) is a well-known bioceramic material used in orthopedic and dental applications because of its excellent biocompatibility and bone-bonding ability due to its structural and compositional similarity to human bone. Here we report, for the first time, the synthesis of HAP by combustion employing tartaric acid as a fuel. Calcium nitrate is used as the source of calcium and diammonium hydrogen phosphate serves as the source of phosphate ions. Reaction processing parameters such as the pH, fuel-oxidant ratio and autoignition temperature are controlled and monitored. The products were characterized by powder x-ray diffraction, which revealed the formation of a hexagonal hydroxyapatite phase. Fourier transform infrared spectroscopy (FT-IR) spectra showed that the substitution of a carbonate ion occurs at the phosphate site. The morphology of the particles was imaged by scanning electron microscopy, which also revealed that the particles are of submicron size. Thermal analysis showed that the phase formation takes place at the time of combustion. Surface area and porosity analysis showed that the surface area is high and that the pores are of nanometer size. The mean grain size of the HAP powder, determined by the Debye–Scherrer formula, is in the range 20–30 nm. Chemical analyses to determine the Ca : P atomic ratio in synthesized ceramics were performed, and it was found to be 1 : 1.66.     

微弧氧化时间对AZ61镁合金陶瓷膜形貌及性能的影响

用现有的微弧氧化方法制备的镁合金陶瓷膜厚度有限,且属于多孔结构。采用电流密度0.4 A/dm2,在AZ61镁合金表面制备了陶瓷膜;研究了不同微弧氧化时间(30,50,70,90,120,160 m in)对陶瓷膜微观性能的影响。结果表明:在电流密度一定的条件下,处理时间对陶瓷膜微观组织和性能有着较大的影响,随氧化时间延长,阳极电压、陶瓷膜厚度和粗糙度增大;孔隙率先增大后减小,最大值出现在70 m in时,陶瓷膜表面熔融物颗粒和孔隙尺寸增大且分布不均;50 m in时陶瓷膜耐蚀性最好。     

SiCp/Al复合材料微弧氧化膜的组织结构及性能

采用微弧氧化技术对SiC体积分数分别为17vol%和55vol%的两种SiCp/Al复合材料进行处理。分析了两种材料微弧氧化膜的组织、形貌、相组成,测定了膜层的粗糙度、显微硬度、结合力,考察了膜层的耐磨和耐蚀性。结果表明:SiC的含量对SiCp/Al复合材料微弧氧化膜的表面形貌、粗糙度、相组成、结合力及摩擦磨损性能均有影响。17vol%SiCp/2009Al复合材料的微弧氧化膜较55vol%SiCp/6061Al复合材料更平整,微孔大小更均匀。55vol%SiCp/6061Al复合材料的微弧氧化膜的粗糙度(3.308 μm)比17vol%SiCp/2009Al复合材料(2.140 μm)大,表面熔融物堆积更多。两种材料的微弧氧化膜中均含有Al、Si、O、C、W等元素。55vol%SiCp/6061Al复合材料的微弧氧化膜中Mullite(SiO₂-Al₂O₃)相、α-Al₂O₃相、β-Al₂O₃相较多。17vol%SiCp/2009Al复合材料的微弧氧化膜的结合(38.55 N)较55vol%SiCp/6061Al(11.5 N)复合材料好。55vol%SiCp/6061Al复合材料的微弧氧化膜摩擦系数较大,磨损较严重。微弧氧化处理能有效改善两种SiCp/Al复合材料的耐蚀性。      

电解液组成及工艺条件对镁合金微弧氧化过程的影响

在含有NaAlO2的电解液中以恒电流方式对镁合金进行微弧氧化。研究了电解液中NaAlO2、甘油、NaF的浓度以及电流密度和氧化时间对镁合金微弧氧化过程中电压-时间曲线和氧化膜厚度的影响。结果表明:电解液中只含有NaAlO2时即可产生火花放电现象,但得到的氧化膜较薄;甘油的加入可明显抑制尖端放电现象,NaF的加入可以显著增加氧化膜厚度,随着电流密度的增大,微弧氧化所需起火时间迅速缩短,而击穿电压并无明显变化,氧化膜厚度明显增加。采用扫描电子显微镜观察了镁合金微弧氧化陶瓷膜的微观形貌,在微弧氧化膜的表面存在明显的孔洞和放电通道,这些通道呈熔融状态结合在一起。     

铝合金表面微弧氧化纳米SiO2复合涂层的元素及物相分析

为提高微弧氧化层性能,通过向微弧氧化电解液中添加纳米SiO2颗粒,在7A52铝合金表面制备了纳米SiO2复合微弧氧化层.利用扫描电镜、能谱仪和X射线衍射仪表征了纳米SiO2复合微弧氧化层的微观组织、元素分布特征及物相组成.研究表明:纳米SiO2颗粒与微弧氧化层复合生长到一起,在微弧氧化层中大致均匀分布;纳米SiO2在微弧氧化层中主要以无定形态存在,同时SiO2与微弧氧化层主体成分Al2O3发生相变反应,生成新物相-莫来石.     

Effect of metal-ion-to-fuel ratio on the phase formation of bioceramic phosphates synthesized by self-propagating combustion

Synthetic calcium hydroxyapatite (HAP, Ca₁₀ (PO₄)₆ (OH)₂) is a well-known bioceramic material used in orthopedic and dental applications because of its excellent biocompatibility and bone-bonding ability due to its structural and compositional similarity to human bone. Here we report, for the first time, the synthesis of HAP by combustion employing tartaric acid as a fuel. Calcium nitrate is used as the source of calcium and diammonium hydrogen phosphate serves as the source of phosphate ions. Reaction processing parameters such as the pH, fuel-oxidant ratio and autoignition temperature are controlled and monitored. The products were characterized by powder x-ray diffraction, which revealed the formation of a hexagonal hydroxyapatite phase. Fourier transform infrared spectroscopy (FT-IR) spectra showed that the substitution of a carbonate ion occurs at the phosphate site. The morphology of the particles was imaged by scanning electron microscopy, which also revealed that the particles are of submicron size. Thermal analysis showed that the phase formation takes place at the time of combustion. Surface area and porosity analysis showed that the surface area is high and that the pores are of nanometer size. The mean grain size of the HAP powder, determined by the Debye–Scherrer formula, is in the range 20–30 nm. Chemical analyses to determine the Ca : P atomic ratio in synthesized ceramics were performed, and it was found to be 1 : 1.66.     

Influence of the polysaccharide galactomannan on the dielectrical characterization of hydroxyapatite ceramic

Hydroxyapatite (HAP), Ca₁₀(PO₄)₆(OH)₂, has a wide range of biomedical applications because it is excellent biocompatibility and similar to natural bone tissue. The synthesis of the nanocrystalline powders of hydroxyapatite (HAP) was developed by the high energy method of dry mechanical alloying. The Ca(OH)₂ and CaHPO₄ were used in the preparation. Galactomannans are polysaccharides that occur in the endosperm of the seeds of leguminous plants as cell wall storage components was obtained from seeds of Adenanthera pavonina L. family Leguminosae (Fabaceae) and subfamily Mimosoideae. The nanocrystalline powders of hydroxyapatite were mixed with 10% (Gal 90), 20% (Gal 80) and 30% (Gal 70) of galactomannan. The aim of the study was to investigate influence of the galactomannan on the electrical characterization of bioceramic materials based on hydroxyapatite. The samples were studied by X-ray diffraction (XRD) was recorded to confirm the formation of a single phase solid solution and comportment this phase through the Rietveld analysis, scanning electron microscopy (SEM) and Dielectric measurements in the 10 Hz–100 MHz frequency range, at room temperature, have been performed. The presence of nanocrystals was confirmed by X-ray diffraction of HAP with size crystallite of 110 nm.     

Preparation of hydroxyapatite-containing titania coating on titanium substrate by micro-arc oxidation

Hydroxyapatite-containing titania coatings on titanium substrates were formed by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH₃COO)₂Ca·H₂O) and sodium phosphate monobasic dihydrate (NaH₂PO₄·2H₂O) using a pulse power supply. Scanning electron microscopy (SEM) with Energy dispersive X-ray spectrometer (EDX) and X-ray diffraction (XRD) were employed to characterize the microstructure, elemental composition and phase components of the coatings. The coatings were rough and porous, without apparent interface to the titanium substrates. All the oxidized coatings contained Ca and P as well as Ti and O, and the porous coatings were made up of anatase, rutile and hydroxyapatite. Such MAO films are expected to have significant applications as artificial bone joints and dental implants.     

Bi2MoO6 dielectric thin films fabricated by thermal oxidation of Bi/Mo thin films at ultra-low temperature

Bi/Mo multilayer thin films are deposited on Si/SiO₂/Pt substrates by direct current magnetron sputtering. The effect of annealing temperature on the microstructure, dielectric and electrical properties of the as-sputtered films is characterized systematically. X-ray diffraction data indicate that the films annealed at 450–600 °C are a mixture of diphase with the main phase Bi₂MoO₆ and secondary phase Bi₂Mo₂O₉. Results of scanning electron microscope observation show that the films annealed at 500–550 °C are dense and uniform, in particular the films annealed at 500 °C exhibit optimal dielectric and electrical properties with dielectric constant as high as 37.5, dielectric loss 1.06 %, temperature coefficient of dielectric constant ?10.86 ppm °C^?1 at 1 kHz, and leakage current density of 1.46 × 10^?7 A mm^?2 at an electric field of 18.2 kV mm^?1. With the advantages of ultralow densification temperature (500 °C) and very high sputtering deposition rate (76 nm min^?1), it is anticipated that thermal oxidation method of the sputtered Bi/Mo thin films could be a promising technique for fabrication of Bi₂MoO₆ ceramic thin film embedded-capacitors.     

微弧氧化技术国内外研究进展

综述了微弧氧化工艺自20世纪60年代产生至今在电源、电解液和基体合金方面的发展过程,总结了微弧氧化膜的化学成分及相结构从基体到膜表面的分布规律及电流密度、氧化时间、电压、电解液组分等因素对陶瓷膜生长和性能的影响规律.同时指出微弧氧化技术虽具有广泛的应用前景,但在理论研究和生产成本控制等方面仍存在不足之处.     

Exoemission Analysis of Energy Levels in the Surface Layer of Biocompatible Ca10(PO4)6(OH)2

Thermostimulated exoelectron emission from sintered hydroxyapatite (HAP), Ca₁₀(PO₄)₆(OH)₂, prepared by the alkoxy method was studied in the temperature range 300–800 K. The results were used to determine trap depths, the frequency factor in the Boltzmann probability of thermal release, lifetime of conduction-band electrons, and charge density at active centers in the surface layer of the material. The exoelectron emission data are correlated with earlier thermostimulated current measurements and structural studies of phase transitions in HAP. Possible lines of further research are discussed.     

Porous TiO2 films on Ti implants for controlled release of tetracycline-hydrochloride (TCH)

Micro- and nano-porous TiO₂ films were created on the surface of Ti implants using micro-arc oxidation and anodic titanium oxide treatments, respectively, to load a sol-gel derived silica xerogel for the controlled release of the antibiotic drug, tetracycline-hydrochloride (TCH). When the silica xerogel containing TCH was loaded into porous TiO₂ films, a very high drug loading efficiency was observed compared to when it was loaded in Ti implants without a TiO₂ film. Moreover, TCH was released in a controlled manner for up to 7 days.     

Ceramic Films Containing Ca,P and Al Formed on Surface of TC4 Alloy by Micro-Arc Oxidation

Ceramic films containing Ca, P and Al were prepared on surface of TC4 alloy by micro-arc oxidation using direct current supply to enhance its seawater and plankton corrosion resistance. XRD, EDS, SEM and EPMA were employed to characterize the microstructure and the phase composition. The results showed that 15 μm-ceramic films which was uniform and compact were formed on TC4 . The mass proportion of Ca, P and Al is about 2 : 3 : 4. There was AlPO4 crystal but Ca was not crystal. Cyclic Volt-Ampere test showed that the corrosion resistance of theceramic films was much better than that of the TC4 substrate.     

Direct current electric field adjustable phase transformation behavior in (Pb,La)(Zr,Ti)O3 antiferroelectric thick films

(Pb,La)(Zr,Ti)O₃ antiferroelectric 1.4 μm-thick films have been prepared on Pt (111)/Ti/SiO₂/Si(100) substrates by sol–gel process. The structures and dielectric properties of the antiferroelectric thick films were investigated. The films displayed pure perovskite structure with (100)-preferred orientation. The surface of the films was smooth, compact and uniform. The antiferroelectric (AFE) characterization have been demonstrated by P (polarization)-E (electric field) and C(capacitance)-V (DC bias) curves. The AFE–ferroelectric (FE) and FE-to-paraelectric (PE) phase transition were also investigated as coupling functions of temperature and direct current electric field. With the applied field increased, the temperature of AFE-to-FE phase transition decreased and the FE-to-PE phase shifted to high temperature. The AFE-to-FE phase transition was adjustable by direct current electric field. (Pb,La) (Zr,Ti) O₃ antiferroelectric films have broad application prospects in microelectromechanical systems because of the phase transition.     

Dielectric permittivity and loss of hydroxyapatite screen-printed thick films

In this paper we did a study on the structural and electrical properties of bioceramic hydroxiapatite (HA) thick films. The films were prepared in two layers using the screen printing technique on Al₂O₃substrates. Mechanical alloying has been used successfully to produce nanocrystalline powders of hydroxyapatite (HA) to be used in the films. We also look for the effect of the grain size of the HA in the final properties of the film. The samples were studied using X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and electric measurements. We did a study of the dielectric permittivity and the loss of the films in the radio-frequency of the spectra. The X-ray diffraction (XRD) patterns of the films indicates that all the peaks associated to HA phase is present in the films. One can notice that, for all the films there is a decrease of the DC with the increase of the frequency. The values of the dielectric constant of the films are in between 4 and 9 (at 1 KHz), as a function of the flux material concentration. The loss is decreasing as we increase the frequency for all the films. These results strongly suggests that the screen-printing HA thick films are good candidates for applications in biocompatible coatings of implant materials but also for the insulating materials of electronic circuits and dielectric layer in bio-sensors.     

6063铝材微弧氧化最佳电流密度和槽液温度的探讨

目前的铝合金微弧氧化工艺存在电流密度高、槽液温度范围窄等不足,使其应用受到了限制.为此,从铝材低电流密度和宽槽液温度方面研究了6063铝材的微弧氧化工艺,探讨了微弧氧化工艺中电流密度及槽液温度对起弧电压、起弧时间及膜层厚度等的影响.结果表明,同等条件下,电流密度越大,则起弧电压越低,起弧时间越短,膜层越厚;槽液温度越高,则起弧电压越低,起弧时间越短,膜层越厚;在10 min内,得到12μm厚度的膜层,同等时间内比普通阳极氧化膜厚提高4倍;微弧氧化膜的表面显微硬度相对6063铝材高7倍以上.     

微弧氧化生成含钙磷氧化钛生物薄膜的结构

采用秃弧氧化在钛合金表层生成了含钙和磷的氧化钛薄膜,探讨了电解液组分及电压对薄膜形态、相组成及钙／磷原子比的影响。结果表明：薄膜由锐钛矿TiO2和金红石TiO2构成,呈内层致密、外层多孔的形态,且膜中钙／磷原子比由内至外逐渐增大;随电压增大,膜中非晶量增多、孔洞尺寸及钙／磷原子比增大,但有微裂纹呈现;增大电解液钙／磷酯比可提高膜中钙／磷原子比。     

Composition and mechanical properties of hard ceramic coating containing α-Al2O3 produced by microarc oxidation on Ti–6Al–4V alloy

Ceramic coatings with 1100–1600 HK_{50 g} hardness were deposited on Ti–6Al–4V alloy substrates using a microarc oxidation (MAO) technique, based on a dielectric barrier discharge created during anodic oxidation in an aqueous electrolyte. The influences of electrolyte concentration, deposition time and the cathodic to anodic current ratio Ic/Ia on phase composition and mechanical properties of the coatings have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis methods (EPMA), as well as microhardness measurement, direct pull-off and impact tests. The results show α-Al₂O₃ phase, which greatly improved the hardness of the coatings, can be obtained at high concentration of NaAlO₂ and its relative content increases with decreasing Ic/Ia ratio. The direct pull-off test and impact test results indicate that the films have the excellent adhesion with the substrate.