化学气相沉积法制备SiC/SiO2梯度复合涂层的热力学分析

SiC/SiO2复合涂层是显著改善先进高温气冷用石墨抗氧化性能的一个理想涂层体系,但目前其优化的化学气相沉积工艺还未见诸报道.本研究利用HSC-CHEMISTRY 4.1分析了化学气相沉积工艺对制备的SiC/SiO2复合涂层的影响.分析结果表明:载气中加入足够的氢气对制备不含杂质的SiC/SiO2复合涂层很有必要;合适的沉积温度为1100～1200℃;最佳反应物浓度为:SiCl4摩尔分数为1%～2%,沉积SiC涂层时CH4与SiCl4的摩尔比为1,沉积SiO2涂层时水蒸气与SiCl4摩尔比为2,通过逐渐改变CVD气氛中的水蒸气与CH4的比例来沉积SiC/SiO2梯度过渡层.     

脉冲电沉积CeO2-SiO2／Ni—W-P纳米复合镀层性能研究

为了探讨脉冲参数对CeO2-SiO2/Ni-W-P四元纳米复合镀层性能的影响,采用脉冲沉积的方法,在普通碳钢表面制备了CeO2-SiO2/Ni-W-P纳米复合镀层.在脉冲关断时间1 000μs和脉冲峰值电流密度30 A/dm2下,研究了脉冲导通时间对纳米复合镀层组织及性能的影响,采用能谱分析、硬度测试、扫描电镜(SEM)等技术对镀层化学组成、沉积速率、显微硬度和表面形貌进行了表征.结果表明,纳米复合镀层中CeO2和SiO2颗粒的质量分数随着脉冲导通时间的延长而增加,当脉冲导通时间为400～600μs时,沉积速率为32.33～38.22μm/h,显微硬度为609～674 HV;脉冲导通时间由100μs增加到400μs时,纳米复合镀层晶粒尺寸降低,但当脉冲导通时间再由400μs增加到1000μs时,纳米复合镀层晶粒尺寸又有所增加.     

沉积电压对SiC-C/C复合材料表面水热电泳沉积SiC_n-MoSi_2复合抗氧化涂层的影响

采用水热电泳沉积法在SiC-C/C复合材料表面制备纳米碳化硅和二硅化钼的复相(SiC_n-MoSi_2)抗氧化涂层.分别采用XRD和SEM等测试手段对涂层的晶相组成和显微结构进行了表征.主要研究了沉积电压对涂层显微结构及高温抗氧化性能的影响,分析了涂层试样在1500℃下的静态氧化行为及热循环失效机理.结果表明:外涂层主要由MoSi_2和β-SiC晶相组成.当沉积电压为100～180V时,外涂层的致密程度、厚度及抗氧化性能随着沉积电压的升高而提高.沉积电压过高(220V)时,复合涂层中出现裂纹等缺陷,涂层的氧化保护能力相应减弱.抗氧化性能测试表明复合涂层可在1500℃的静态空气中有效保护C/C复合材料346h,失重率仅1.41wt%.涂层的高温失效是由于涂层试样在热循环过程中产生了贯穿性裂纹导致的.     

不同载气温度条件下低压冷喷涂Al-Al2O3复合涂层的沉积特性

目前,对低压冷喷涂Al-Al₂O₃复合涂层的研究主要集中在工艺和性能方面,对颗粒的沉积特性和机理的研究较少。为此,利用低压冷喷涂技术沉积Al-Al₂O₃复合涂层,研究了不同载气温度对复合涂层沉积特性的影响规律,采用扫描电镜(SEM)、三维轮廓仪对复合涂层的厚度、表面形貌、显微组织进行了分析。结果表明:不同载气温度(300,400,500,600℃)制备的Al-Al₂O₃复合涂层厚度依次为213.34,321.62,920.64,986.97μm,复合涂层厚度随载气温度升高而增加,尤其当冷喷涂载气温度由400℃变为500℃时,沉积层厚度增幅达186.25%;复合涂层表面最大高度差H_max和粗糙度R_a随载气温度升高呈增加趋势,载气温度为400℃时复合涂层表面质量最优,当载气温度由400℃变为500℃时H_max和R_a增幅最大,分别为72.68%和52.22%,随载气温度的升高复合涂层表面质量下降;复合涂层中形变Al颗粒的扁平率随载气温度升高呈下降趋势,复合涂层中Al颗粒由塑性变形量较大的扁平状(300℃)逐渐变为塑性变形量较小的椭球形(600℃),随载气温度升高Al-Al₂O₃涂层的沉积率突增和颗粒扁平率下降归因于Al颗粒的热软化效应。     

粉末靶脉冲磁控溅射制备CrBMoS固体润滑硬质涂层

粉末靶封闭非平衡磁场脉冲磁控溅射是一种方便靶材配比、节约靶材成本的高效磁控溅射工艺,其特点是将固体粉末按成分需求配比,直接作为磁控靶体。CrB_2则因其高硬度而常被作为硬质耐磨材料使用,MoS_2因其低摩擦系数常作为固体润滑剂使用。本研究则将CrB_2和MoS_2两种粉末按Cr∶Mo原子比1∶1混合,利用粉末靶封闭非平衡磁场脉冲磁控溅射系统在304不锈钢表面制备硬质固体润滑涂层,探讨脉冲频率对CrBMoS涂层结构及性能的影响。用示波器测量靶电位曲线,分别用扫描电子显微镜、X射线衍射分析涂层形貌及相结构,表面形貌轮廓仪测量涂层厚,纳米压痕仪检测涂层纳米硬度,划痕仪测量涂层结合力及摩擦磨损实验机测量涂层摩擦系数。结果表明,在脉冲"开-关"状态转换时,靶电位由"负"转"正"过程中,"正"电位突升。随脉冲频率增高,涂层的沉积速率降低,沉积速率与有效沉积时间因子成正比。涂层致密、无缺陷,涂层晶体择优取向分别为CrB_2(111)及MoS_2(200)。涂层纳米硬度最高可达19 GPa,摩擦系数最小低至0.02。结果表明粉末靶封闭非平衡脉冲磁控溅射法制备的CrBMoS涂层具有较高硬度的同时,还具有良好的固体润滑效果。     

K3合金复合涂层高温防护性能研究

采用电弧离子镀技术在K3镍基高温合金基材上分别沉积NiCrAlYSi涂层和NiCrAlYSi AlYSi沉积-扩散型复合涂层,研究两种涂层在1100℃下的高温氧化行为和900℃下的燃气热腐蚀行为.结果表明,NiCrAlYSi AlYSi复合涂层具有比单一的NiCrAlYSi涂层更加优良的抗高温氧化性能,而NiCrAlYSi涂层的抗燃气热腐蚀性能则优于NiCrAlYSi AlYSi复合涂层.     

CNx/TiN多层复合涂层抗水蚀性能的研究

采用多弧-磁控溅射镀膜机在不锈钢2Cr13衬底上沉积CNx/TiN多层复合涂层.利用光电子能谱仪(XPS)和透射电子衍射(TED)对涂层的组成和结构进行分析.利用自行研制的高压水蚀试验装置对不锈钢、高铬铸铁、司太立合金以及CNx/TiN多层复合涂层的抗水蚀性能进行对比试验,最后对涂层的水蚀失效机理进行了探讨.试验结果表明:CNx/TiN多层复合涂层具有较高的硬度、附着力、抗热冲击性能以及优异的抗水蚀性能,是一种优良的汽轮机末级叶片抗水蚀用涂层.     

陶瓷颗粒添加对热喷涂不锈钢涂层耐蚀性的影响

采用超音速火焰喷涂(HVAF)方法成功制备出不同种类及粒度陶瓷颗粒复合的不锈钢涂层,系统研究陶瓷颗粒的种类及粒度对复合涂层的硬度、孔隙率与耐蚀性能的影响;通过扫描电子显微镜、全自动硬度计、Image Pro Plus软件以及电化学工作站等分析测试技术对不锈钢/陶瓷颗粒复合涂层的微观结构、硬度及腐蚀行为进行系统表征与分析.结果表明:粗粒径棕刚玉(Al2O3)复合的不锈钢涂层的孔隙率低(0.7863％)、硬度高(637HV0.1)且耐蚀性能优异,其自腐蚀电位为-454.14 mV、自腐蚀电流密度为22.208 mA·cm-2;细粒径碳化硅(SiC)复合的不锈钢涂层具有较高的硬度(600HV0.1)及较好的耐蚀性能,其自腐蚀电位为-463.68 mV、自腐蚀电流密度为23.738 mA·cm-2.     

中间层类型对类金刚石涂层键合结构和性能的影响行为

采用阴极电弧离子镀和等离子体增强化学气相沉积(PECVD)相结合的技术方法,在304不锈钢基体上分别沉积制备了Ti/DLC和Ti/Ti N/Ti Al N/DLC复合涂层。选用原子力显微镜、拉曼光谱对涂层的形貌和结构进行表征测试。同时,利用显微硬度计、划痕测试仪系统地分析了涂层的显微硬度和界面结合性能,并研究了其摩擦磨损行为。研究结果表明:Ti/Ti N/Ti Al N/DLC复合涂层体系具有较高硬度(~2130HV)的同时结合性能最优(结合力~53.7 N),抗磨损能力最强。在相同试验条件下,无涂层的基体摩擦系数为0.45,单层DLC、Ti/DLC和Ti/Ti N/Ti Al N/DLC涂层的摩擦系数则分别为0.15、0.12和0.07。Ti/Ti N/Ti Al N/DLC复合涂层可有效提高304不锈钢的耐磨损性能,降低摩擦系数。     

低温熔盐电沉积羟基磷灰石复合涂层的研究

为了提高羟基磷灰石涂层的结合强度,在AlCl3-NaCl-TiCl3低温熔盐体系中加入HA微粒,复合电沉积制备Al-Ti/HA复合涂层,并对涂层的表面形貌、结构和结合强度进行了研究.结果表明: HA微粒均匀分散在Al-Ti合金镀层中,其共沉积量随电流密度的减小和熔盐中HA浓度的增大而增强;涂层的结合强度随HA共沉积量的增大而增强,当HA的共沉积量为40.1%(质量分数)时,Al-Ti/HA复合涂层的结合强度达到28.1 MPa.     

钛表面仿生矿化及其对成骨细胞行为的影响

采用仿生矿化法对商用纯钛进行表面处理,经过处理的样品表面形成一层薄的钙磷涂层,SEM和EDX分析表明,涂层晶体构型均一;XRD和FTIR分析晶体组成主要为碳酸羟基磷灰石.采用成骨细胞体外培养方法,探讨仿生矿化涂层对于细胞初期附着、增殖的影响.认为钙磷涂层可以提高成骨细胞的初期附着率,而对于细胞的增殖行为影响不大.     

Microstructural study of a titanium-based biocomposite produced by the powder metallurgy process with TiH2 and nanometric β-TCP powders

A titanium-based composite with Ca-P phases was prepared in situ by powder metallurgy processing with TiH₂ and nanometric β-TCP powders. Crystal phases of the as-fabricated composite are found to be α-Ti, CaTiO₃ and Ti_xP_y phase(s). The Ti_xP_y and CaTiO₃ phases resulted from the reaction between titanium and β-TCP at about 1135 °C. The composite presented a mean compressive strength of 635 MPa and a lower contact angle than pure titanium.     

Biomimetic calcium phosphate coatings on nitric-acid-treated titanium surfaces

This study describes biomimetic calcium phosphate (Ca-P) coatings formation under simulated physiological conditions on Ti surfaces that go through nitric acid treatment (NT). In the present study, nitric acid treatment was used to treat Ti specimens so that Ti specimens could have the ability to induce Ca-P formation. After careful selection of the NT parameters, Ca-P coatings success fully formed on the nitric-acid-treated Ti surfaces in a supersaturated calcium phosphate solution (SCPS) and in the simulated body fluid (SBF). Before NT, the Ti specimen should go through mixed acid etching to increase its surface roughness because rough surfaces lead to good adherence between coatings and substrates. Amorphous Ca-P coatings were formed on the Ti surfaces by immersing the NT Ti specimens in SBF, while octacalcium phosphate (OCP) coatings were formed in the SCPS after 3 days of immersion. The study firstly proved that nitric acid treatment is not only just for surface passivation but also is another bioactive treatment as an alternative to the alkaline treatment and two-step method. The experimental results also confirmed that the conventional nitric acid treatment of a titanium surface does not increase the titanium oxide on the Ti surfaces. However, extending the nitric acid treatment time and enhancing the nitric acid treatment temperature help to increase Ti surface ability of Ca-P induction in simulated physiological environments. Ti specimens that had 600 min of NT at 60 °C had the best Ca-P induction ability under biomimetic conditions.     

Biomimetic coatings on titanium: a crystal growth study of octacalcium phosphate

The biomimetic approach allows the coating of metal implants with different calcium-phosphate (Ca-P) phases. Films elaborated at physiological conditions exhibited structures closely resembling those of bone mineral. For instance, octacalcium phosphate (OCP, Ca₈(HPO₄)₂(PO₄)₄ · 5H₂O) crystals have been deposited on titanium through a two-step procedure. After cleaning and etching, Ti6Al4V plates were immersed for 24 h into a simulated body fluid (SBF1). A thin amorphous carbonated Ca-P layer precipitated on the metal substrate. Secondly, these thinly Ca-P coated titanium substrates were immersed for 48 h into another simulated body fluid (SBF2). The thin amorphous carbonated Ca-P layer induced the fast precipitation of a second Ca-P layer of 55 m in thickness composed of OCP crystals. The measurements of Ca and P concentrations versus soaking time in SBF2 showed that the carbonated Ca-P layer partially dissolved before the deposition of the OCP coating. X-ray diffraction (XRD) revealed that OCP crystals grew epitaxially on the substrate. OCP is known to be one of the precursors during the bone mineralization process, thereby, this new generation of biomimetic coatings are promising for orthopedic surgery. © 2001 Kluwer Academic Publishers     

纳米HA/PA6复合材料的体外生物活性

研究了PA6和纳米HA/PA6复合材料在模拟体液(SBF)中的行为变化,用IR,XRD,SEM和EDS等手段对材料的表面变化进行了分析,讨论了PA6和纳米HA/PA6复合材料的稳定性、亲水性和生物活性。结果表明:在SBF中PA6的吸水率大概在6%左右,纳米HA/PA6复合材料的吸水率有少量下降,PA6和纳米HA/PA6复合材料出现一定的溶解和降解。在SBF中,PA6表面形成Ca,P化合物中的Ca/P比例为1.12,与HA的理论值1.67有一定的差别;HA/PA6复合材料在其表面形成了HA沉积物和碳酸取代的磷灰石沉积物,Ca/P逐步变化为1.67,表现出较好的生物活性。复合材料表面沉积的HA和原来合成的HA具有相近的结晶形貌,该复合材料可作为优良的骨修复填充材料和组织工程支架材料。      

Hydroxyapatite coating by biomimetic method on titanium alloy using concentrated SBF

This article reports a biomimetic approach for coating hydroxyapatite on titanium alloy at ambient temperature. In the present study, coating was obtained by soaking the substrate in a 5 times concentrated simulated body fluid (5XSBF) solution for different periods of time with and without the use of CaO-SiO₂ based glass as a possible source of nucleating agent of apatite formation. Optical microscopic and SEM observations revealed the deposition of Ca-P layer on the titanium alloy by both the methods. Thickness of coating was found to increase with the increase in immersion time. The use of glass did not help the formation of apatite nuclei on the substrate and the coating obtained by this method was also not uniform. EDX analysis indicated that the coating consisted of Ca-P based apatite globules, mostly in agglomerated form, and its crystallinity was poor as revealed by XRD.     

Surface modification of three-dimensional Ca-P/PHBV nanocomposite scaffolds by physical entrapment of gelatin and its in vitro biological evaluation

The properties of bone tissue engineering scaffolds such as architecture, porosity, mechanical properties and surface properties have significant effects on cellular response and play an important role in bone regeneration. In this study, three-dimensional nanocomposite scaffolds consisting of calcium phosphate (Ca-P) nanoparticles and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) copolymer with controlled external and internal architectures were successfully produced via selective laser sintering (SLS), one of the versatile rapid prototyping techniques. The Ca-P/PHBV nanocomposite scaffolds had a porosity of (61.75±1.24)%, compressive strength of (2.16±0.21) MPa and Young’s modulus of (26.98±2.29) MPa. The surface modification of scaffolds by gelatin was achieved through physical entrapment. The amount of entrapped gelatin could be controlled by varying the solvent composition and reaction time. The surface modification improved the hydrophilicity of scaffolds but did not significantly affect the surface morphology and mechanical properties. Osteoblast-like cells (SaOS-2) were cultured on scaffolds with and without gelatin surface modification. The majority of SaOS-2 cells were viable and proliferated in both types of scaffolds for up to 14 d in culture, as indicated by MTT assay and live and dead assay. Surface modification significantly increased cell proliferation for surface modified scaffolds, which could be due to the improvement in hydrophilicity of the scaffolds.     

Preparation of Calcium Phosphate/Chitosan Membranes by Electrochemical Deposition Technique

In this paper, the electrochemical deposition was used to form calcium phosphate/chitosan (Ca-P/chitosan) membranes on the surface of AZ91D magnesium alloy coated with a microarc oxidization (MAO) membrane. The surface appearance, chemical compositions, and crystalline structures of the Ca-P/chitosan membranes were detected by using scanning electron microscope (SEM), X-ray diffractometer (XRD), and energy-dispersive spectroscopy (EDS). They showed that the surface morphology of the membranes had a remarkable modification after introducing chitosan to Ca-P membrane, and the binding force was distinctly increased between the metal substrate and the membrane. The composite membranes were composed of Tricalcium Phosphate (TCP), Dibasic Calcium Phosphate (DCP), and Hydroxyapatite (HAP). Immersion was tested in simulated body fluid (SBF) and the corrosion resistance of the membranes was evaluated by electrochemical measurements. Results exhibit the composite membranes have low corrosion rate and superior stability.     

Characterisation of calcium phosphate/titanium dioxide hybrid coatings

The role of titanium dioxide (TiO₂) as a means to engender enhanced stability into calcium phosphate (Ca-P) coatings has been well recognised. Several different methods have been used to create such Ca-P/TiO₂ hybrid layers on a range of substrates. This paper reports the properties of a Ca-P/TiO₂ system created by the sputter deposition of hydroxyapatite onto a titanium surface and the subsequent thermal diffusion of TiO₂ through the porous Ca-P layer. The role of temperature in determining the surface contribution from TiO₂ has been determined. Coatings annealed up to 600 °C did not exhibit any hybrid nature in the uppermost surface, however the coatings annealed to 700 °C did show the presence of both HA and rutile TiO₂. The surfaces annealed to 800 °C were predominantly rutile TiO₂. It was also observed that the Ca/P ratio decreased with increasing annealing temperature and that the coating annealed to 700 °C had a value of 1.82 ± 0.07, which was closest to stoichiometric HA. Furthermore, the coatings that were annealed to 700 °C displayed a Ca-P/TiO₂ hybrid nature, specifically in their uppermost surface and supported the growth and proliferation of osteoblast-like cells more readily when compared to the HA coatings or the rutile TiO₂ surfaces.     

Bioactive glass induced in vitro apatite formation on composite GBR membranes

The aim of this study was to investigate in vitro bioactivity of different thermoplastic biodegradable barrier membranes. Three experimental GBR membranes were fabricated using Poly(epsilon-caprolactone-co-D: ,L-lactide) P(CL/DL-LA) and particulate bioactive glass S53P4 (BAG; granule size 90-315 microm): (A) composite membrane with 60-wt.% of BAG, (B) membrane coated with BAG; and (C) copolymer membrane without BAG. Membranes were immersed in simulated body fluid (SBF), and their surfaces were characterized with SEM, XRD and EDS after 6 and 12 h and after 1, 3, 5, 7, and 14 days. Calcium phosphate (Ca-P) surface formation was observed on both composite membranes (A and B) but not on the copolymer membrane without bioactive glass (C). The Ca-P precipitation appeared to be initiated on the bioactive glass followed by growth of the layer along the polymer surface. In 6-12 h ion dissolution of the bioactive glass led to formation of the silica rich layer on the surface of the exposed glass granules on composite membrane B whereas only small amounts of silica was observed on the polymer surface of the composite membrane A. At 24 h nucleation of Ca-P precipitation was observed, and by 3-5 days membrane surface was covered with a uniform Ca-P layer transforming from amorphous to low crystalline structure. At 7 days composition and structure of the apatite surface resembled the apatite in bone. Once nucleated, the surface topography seemed to have significant effect on the growth of the apatite layer.