Preparation and Characterization of Lanthanum-Incorporated Hydroxyapatite Coatings on Titanium Substrates

Titanium (Ti) has been widely used in clinical applications for its excellent biocompatibility and mechanical properties. However, the bioinertness of the surface of Ti has motivated researchers to improve the physicochemical and biological properties of the implants through various surface modifications, such as coatings. For this purpose, we prepared a novel bioactive material, a lanthanum-incorporated hydroxyapatite (La-HA) coating, using a dip-coating technique with a La-HA sol along with post-heat treatment. The XRD, FTIR and EDX results presented in this paper confirmed that lanthanum was successfully incorporated into the structure of HA. The La-HA coating was composed of rod-like particles which densely compacted together without microcracks. The results of the interfacial shear strength test indicated that the incorporation of lanthanum increased the bonding strength of the HA coating. The mass loss ratios under acidic conditions (pH = 5.5) suggested that the La-HA coatings have better acid resistance. The cytocompatibility of the La-HA coating was also revealed by the relative activity of alkaline phosphatase, cellular morphology and cell proliferation assay in vitro. The present study suggested that La-HA coated on Ti has promising potential for applications in the development of a new type of bioactive coating for metal implants.     

粉末涂料在非金属底材上的应用

详述了可用于诸如木材、塑料、陶瓷、纸张、卡纸板等非金属底材上涂装的UV固化的各类粉末涂料及其施工应用技术的最新研究进展。     

我国水热法生长高档宝石晶体的现状及发展趋势

阐述了国内外水热法生长高档宝石晶体的历史与现状,介绍了桂林矿产地质研究院在水热法生长高档宝石方面的科研成果和技术水平,指出水热法合成晶体材料的发展方向是完善生长工艺、降低成本、占领市场和合成新型功能晶体、拓宽应用领域.     

Effect of Albumin on the Growth Characteristics of Hydroxyapatite Coatings on Alumina Substrates

A potent biomolecule, egg albumin (EA), has been used in the biomimetic coating of hydroxyapatite (HAp) on α-Al₂O₃ substrate. The same experiment was repeated without using EA and the results have been compared. In both cases, the substrates were incubated up to 6 days in SBF (simulated body fluid) at 37°C with a periodic replacement by freshly prepared SBF at 48-h intervals. The presence of EA influenced the growth and morphology of HAp crystals. Without EA, the HAp coating comprises irregular-shaped, serrated-edged plates whereas with EA, thick and regular-edged HAp crystal plates were observed on the α-Al₂O₃ substrate.     

Calculation of Stresses in Amorphous Nickel–Phosphorus Coatings on Metallic Substrates

The stresses in amorphous nickel–phosphorus (14 at. % P) coatings prepared by chemical deposition on metallic substrates are calculated. The calculations are performed under the assumption that amorphous nickel–phosphorus coatings on a metallic substrate can be considered glass seals with a metal, for which available methods of calculating stresses are well developed. The influence of several factors on the stresses arising in amorphous nickel–phosphorus coatings is elucidated.     

Calcium and Zinc Containing Bactericidal Glass Coatings for Biomedical Metallic Substrates

The present work presents new bactericidal coatings, based on two families of non-toxic, antimicrobial glasses belonging to B₂O₃–SiO₂–Na₂O–ZnO and SiO₂–Na₂O–Al₂O₃–CaO–B₂O₃ systems. Free of cracking, single layer direct coatings on different biomedical metallic substrates (titanium alloy, Nb, Ta, and stainless steel) have been developed. Thermal expansion mismatch was adjusted by changing glass composition of the glass type, as well as the firing atmosphere (air or Ar) according to the biomedical metallic substrates. Formation of bubbles in some of the glassy coatings has been rationalized considering the reactions that take place at the different metal/coating interfaces. All the obtained coatings were proven to be strongly antibacterial versusEscherichia coli (>4 log).     

Effect of Flaw State on the Strength of Brittle Coatings on Soft Substrates

A study is made of the role of flaw state on the strength properties of brittle ceramic coating layers bonded to soft polycarbonate substrates. We introduce Vickers radial cracks at prescribed loads into the coating undersurfaces prior to bonding to control the sizes and locations of the starting flaws. A spherical indenter is then loaded on the top bilayer surfaces, directly above the Vickers indentation sites, subjecting the radial cracks to flexural tensile stress. Radial crack responses are monitored in situ , using a camera located below the transparent substrate. Critical loads to cause radial crack instability, and ensuing growth of the arrested cracks, are recorded. Conventional biaxial flexure tests on corresponding monolith coating materials provide a baseline for data comparison. Relative to the monolith flexure specimens, the bilayers show higher strengths, the more so the larger the flaw, indicating enhanced flaw tolerance. A simple fracture mechanics analysis of the radial crack evolution in the concentrated-load field, with due account for distribution of flexural tensile stresses at the coating undersurface, is unable to account completely for the enhanced bilayer strengths for the larger Vickers flaws. It is hypothesized that the epoxy used to bond the bilayer components enters the cracks, causing crack-wall adherence and providing an increased resistance to radial crack instability. The fracture mechanics are nevertheless able to account for the arrest and subsequent stable extension of the radial cracks beyond the critical loads once this extraneous adherence has been overcome.     

Incorporation of Al and Na in Hydrothermally Synthesized Tobermorite

Calcium silicate hydrate and its Al‐substituted form synthesized by a hydrothermal process were investigated by X‐ray diffraction, compositional analysis, and magic‐angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, in order to determine the mechanism of Al and Na incorporation in the tobermorite structure with varying molar ratios of Ca/Si and Al/Si. At a high molar ratio of Ca/Si, the silicate chains of tobermorite are ruptured, the degree of polymerization of the silicate chains is lowered, and the high calcium concentration lowers the content of Na₂O in the structure. Solid‐state ²⁹Si and ²⁷Al MAS NMR spectroscopy confirm that all Al atoms were incorporated in the silicate chains of tobermorite. The tetrahedrally coordinated Al (Al(IV)) could either act as the bridging tetrahedron () for the dreierketten chain of tobermorite, or be present in Q³ sites that link two dreierketten chains together. Therefore, the degree of polymerization of the silicate chains of tobermorite is increased at high molar ratio of Al/Si. Furthermore, the greater charge deficit due to the replacement of Si⁴⁺ by Al³⁺ ions is compensated by increased adsorption or binding of Na⁺.     

Thermal Analysis of Amorphous Phases in Hydroxyapatite Coatings

The amorphous phase in hydroxyapatite coatings has been examined by using X-ray diffractometry, Fourier transform infrared spectroscopy, optical microscopy, and thermal analysis methods. The amorphous phase mostly consists of a dehydroxylated calcium phosphate. When heated, crystallization of hydroxyl-rich areas produces hydroxyapatite, followed by diffusion of hydroxyl ions, thus increasing the amount of crystalline phase. Hydroxyl-deficient amorphous areas crystallize to oxyapatite at 700°C. Thus, crystallization occurs over a range of temperatures and is dependent on the hydroxyl content of the amorphous phase and the partial water-vapor pressure. The activation energies of crystallization to hydroxyapatite, diffusion of hydroxyl ions, and crystallization to oxyapatite are 274, 230, and 440 kJ/mol, respectively. Shrinkage from these processes leads to a crack network and decreases the mechanical strength of the coating.     

Particle Size Comparison of Hydrothermally Synthesized Cobalt and Zinc Aluminate Spinels

Nanosized CoAl₂O₄ and ZnAl₂O₄ powders with particle sizes of 67 and 6.5 nm are synthesized under hydrothermal conditions at 245°C for 20 h. The precursors are reacted at different temperatures to provide intermediate phase transformations using X-ray diffraction (XRD), infrared (IR) spectra, and thermal gravity and differential thermal analysis (TG-DTA). XRD patterns and IR spectra demonstrate that the CoAl layered double hydroxide structure (CoAl-LDHs) is more stable than ZnAl layered double hydroxide structure (ZnAl-LDHs) when they are hydrothermally treated. The different thermal stability of the CoAl- and ZnAl-LDHs results in the different aluminum source, e.g., β-Al(OH)₃ for ZnAl₂O₄ vs γ-AlO(OH) for CoAl₂O₄, when the aluminate spinels are formed. The different aluminum sources lead to the particle size difference. The phenomenon is reasonably expounded based on the nucleation theory from the microscopic scale.     

羟基磷灰石和含氟羟基磷灰石涂层的制备技术

羟基磷灰石(HA)生物陶瓷涂层被认为是目前最好的用于替代人体硬组织的一种生物医用材料,具有很高的外科应用价值.含氟羟基磷灰石(FHA)涂层由于比羟基磷灰石涂层的溶解度低、热膨胀系数小且生物活性好,有着更为广泛的应用前景.对羟基磷灰石及其涂层的各种制备方法进行了概述,同时介绍了溶胶-凝胶法制备含氟羟基磷灰石涂层的技术特点,并对未来的发展前景进行了分析.     

汽车金属闪光漆涂装缺陷的现场分析

针对汽车涂装过程中金属闪光漆涂膜比较常见的几种缺陷问题,经过试验,从现场施工角度分析了缺陷产生的原因及调整措施。     

桂林水热法合成祖母绿宝石的生长原理、鉴定特征和发展前景

作者阐述了桂林早期水热法生长祖母绿技术的设备、工艺及生长原理的一般细节,并着重阐述了桂林水热法合成祖母绿的外观特征、镜下特征及宝石学特征,天然祖母绿与桂林水热法合成祖母绿在红外光谱、包裹体方面的区分特征,国内外水热法生长祖母绿在生长工艺技术、鉴定特征方面的区别,桂林水热法生长祖母绿工艺技术的改进与发展前景.旨在进一步推动我国水热法生长祖母绿的研究成果能早日实现工业化开发利用.     

非饱和重塑Q3黄土抗剪强度分析

以宝兰客专隧道典型黄土为研究背景,探讨了含水率对重塑Q3黄土抗剪特性的影响,并通过数据拟合得到重塑Q3黄土破坏强度与含水率之间的关系表达式。结果表明:随着含水率的增加,土样的破坏强度随之减小;在同一含水率下,随着围压的增加,其抗剪强度逐渐增大。在低围压下试样有明显的峰值,为脆性破坏;在较高围压下试样为塑性破坏。含水率较低时,剪应变呈现出应变软化及弱硬化状态;含水率较高时,剪应变呈现出硬化及强硬化状态。在轴向应变较小时,重塑Q3黄土的应力-应变呈现出近似线性的关系;当轴向应变较大时,应力-应变呈现出高度的非线性关系。通过线性回归方法以围压和含水率数据回归出重塑黄土的破坏强度计算式,对比计算数据和实测数据,发现它们之间的相对误差较小,实测值与计算值的变化趋势基本一致,本研究成果可以为类似工程提供依据。     

Stress Analysis of Elastic-Plastic Contact Damage in Ceramic Coatings on Metal Substrates

An elastic-plastic analysis of damage in ceramic coatings on metal substrates from contacts with spherical indenters is made using finite element modeling. Computations are carried out specifically for plasma-sprayed alumina:titania on a soft steel. The algorithm assumes an elastic sphere with frictionless contact on a flat elastic-plastic layered specimen, and incrementally evaluates the expanding contact field as a function of applied load. Two key aspects of the contact field are examined: (i) the indentation stress-strain curve; (ii) the damage zone geometry. Composite coating/substrate indentation stress-strain curves are computed for two coating thicknesses, using input material parameters from iterative fits to data from control tests on free-standing coating and substrate materials. Contours of principal shear stresses, most notably those contours corresponding to yield zone boundaries in both the softer substrate and the harder coating, are mapped out in the fully plastic region. Corresponding distributions of tensile stresses are also mapped out, and are shown to correlate with the locations of transverse fractures in the coating. General implications concerning material and geometrical design of ceramic-based layer structures are discussed.     

Product Development with Thermally Sprayed Functional Coatings on Glass and Glass–Ceramics Substrates

Oxides and metal–oxide layer composites were plasma-sprayed under atmospheric conditions onto glass and glass–ceramic substrates and the coatings were characterized. The adhesion mechanism on a glass–ceramic was investigated using splat morphology analysis and electron microscopy. Adhesion mechanism of thermally sprayed coatings on glass and glass–ceramic surfaces differs qualitatively from metal substrates. The glass surface cannot be grit blasted prior to spray coating, however sufficient adhesion is mediated through chemical interaction; therefore, wetting behavior of the impinging particles plays an important role. Splat formation close to the interface and formation of residual stress in the coatings are discussed. Examples for several industrial applications with ceramic and metal ceramic multilayer coatings are presented.     

家电板用金属闪光卷材面漆的研制

选择适宜单体制备的高分子线形聚酯树脂作为主成膜物，六甲氧基甲基三聚氰胺作为固化剂，再配以铝粉定向助剂，防沉剂配制成聚酯氨基金属闪光卷材面漆，介绍了该面漆的原材料，生产工艺和性能指标，讨论了影响涂层性能的因素。     

纳米羟基磷灰石的溶胶-凝胶制备及其特性研究

采用溶胶-凝胶法制备羟基磷灰石的前体物--无定形磷酸钙(ACP),并进行晶化处理得到纳米羟基磷灰石(HAP).在Ca/P＝1.67的条件下,Ca(OEt)2和H3PO4在乙醇溶液中发生反应,合成ACP凝胶体.采用化学滴定法、透射电镜(TEM),X射线衍射法(XRD),BET,傅立叶红外吸收光谱分析法(FTIR)对晶化处理前后的ACP粉料进行的性能测试表明:溶胶-凝胶法制备的HAP粉料具有粒度小、晶化处理活性高、相纯度和结晶度优良的特点.