Electrodeposition of graphene oxide-hydroxyapatite composite coating on titanium substrate

In this work, graphene oxide (GO)/hydroxyapatite (HA) composite coatings were successfully prepared on titanium substrate by electrophoretic deposition technology. Subsequently, microstructure, phase composition, adhesion strength, hydrophilicity, corrosion resistance, bioactivity, antibacterial activity and biocompatibility of the coating were evaluated. The adhesion strength of coating increased by 76% from 6.46 MPa to 17.81 MPa with 0 wt% GO to 12 wt% GO and the corrosion rate of coating with 8 wt% GO was achieved at the minima of (1.493 × 10^-3mm/a). Biomineralization experiment indicated the excellent bioactivity of GO/HA composite coatings. The water contact angle of the composite coatings increased from 20.6°(0 wt% GO) to 38.1°(12 wt%GO). The antibacterial rates of coating with 5 wt% GO was 96.7%, while declined to 25% after thermal treatment. In-vitro L929 cell culture experiments indicated the composite coatings with 5 wt% GO exhibited good biocompatibility.     

AC vs. DC electrophoretic deposition of hydroxyapatite on titanium

In this study, electrophoretic deposition (EPD) of hydroxyapatite (HA) powder on titanium plate was performed using butanol as solvent under direct current (DC) and alternating current (AC) fields. The zeta potential of the suspensions was measured to define their stability and the charge on the particles. Coating thickness was varied by adjusting the voltage and time of deposition. Surface morphology and cross section thickness were studied using scanning electron microscopy and image analysis software. Surface crack density was calculated from the micrographs. The results showed that the samples of similar thickness have higher grain density when coated using AC as compared to DC EPD. This facile but novel test proves the capability of AC-EPD to attain denser and uniform HA coatings from non-aqueous medium.     

Studies on electrodeposited nickel–yttria doped ceria composite coatings

Incorporation of ceria particles into the Ni matrix was found to improve the corrosion resistance of pure Ni coatings. With the aim of further improving the corrosion resistance of Ni-ceria, yttria was doped with ceria and used as distributed phase. About 8-mol% yttria doped ceria (8YDC) particles synthesized by a solution combustion process were dispersed in a nickel sulfamate bath and electrodeposition was carried out to prepare Ni–8YDC composite coatings at various current densities. The microhardness of the composite coatings was determined. Optical microscopy confirmed the incorporation of 8YDC particles into the Ni matrix. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to characterize the corrosion behavior of the Ni–8YDC coatings. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) were used to characterize the corroded samples. The results were compared with those for Ni and Ni–CeO₂ coatings. The wear behavior of Ni–8YDC was studied. Wear tracks were characterized by MicroRaman Spectroscopy.     

电沉积复合镀层的研究现状

近年来,电沉积复合镀层由于其独特的物理、化学、生物和机械性能而得到了迅速发展。在此,介绍了电沉积复合镀层的分类、特性及应用。     

Structural characterization of YSZ/Al2O3 nanostructured composite coating fabricated by electrophoretic deposition and reaction bonding

Suspension of YSZ and Al particles in acetone in presence of 1.2 g/l iodine as dispersant was used for electrophoretic deposition of green form YSZ/Al coating. Results revealed that applied voltage of 6 V and deposition time of 3 min were appropriate for deposition of green composite form coating. After deposition, a nanostructured dense YSZ/Al₂O₃ composite coating was fabricated by oxidation of Al particles at 600 °C for 2 h and subsequently sintering heat treatment at 1000 °C for 2 h. Melting and oxidation of Al particles in the green form composite coating not only caused reaction bonding between the particles but also lowered the sintering temperature of the ceramic coating about 200 °C. The EDS maps confirmed that the composition of fabricated coating was uniform and Al₂O₃ particles were dispersed homogenously in YSZ matrix.     

兴安落叶松木素化学结构特性的研究

从兴安落叶松的边材、心材和经0．1mol／NaOH抽提过的心材中分离出二氧六环木素，用化学分析和光谱分析研究了分离木素的化学结构特性．结果表明兴安落叶松的边材和心材术素都是典型的针叶材木素，三种分离木素的元素组成、官能团含量和光谱性质没有显著差异，心材多酚类化合你又少与木素存在化学连接，只是心材木素的缩合程度略高，分子量低于边材术素．兴安落叶松边材、心材和经0．lmol／NaOH抽提的心材的二氧六环木素C9单元式分别为C9H8.80O3.06（OCH3）0.96C9H8.80O3.14（OCH3）0.93和C9H8.55O3.03（OCH3）0.96，与马尾松二氧六环木素十分相似。     

Corrosion and wear resistant electrodeposited composite coatings

Composite electroplating is a method allowing to co-deposit fine particles of metallic or non metallic compounds into the plated layers in order to improve the surface properties. The aim of the present work was to compare the performance of pure nickel and Ni-SiC nano-structured composite coatings as far as corrosion, wear and abrasion resistance were concerned. The characteristics of the coatings were assessed by scanning electron microscopy, micro hardness test, Taber Abrader test, electrochemical impedance spectroscopy and wear corrosion measurements. Additionally accelerated salt spray tests were performed. The results obtained in this study indicate that the co-deposition of nickel and SiC nano-particles leads to uniform deposits possessing better abrasion, wear and corrosion properties.     

Electrophoretic deposition of biomimetic zinc substituted hydroxyapatite coatings with chitosan and carbon nanotubes on titanium

In this study, a biomimetic method was used to prepare hydroxyapatite (HAP) and zinc substituted HAP (ZnHAP) nanoparticles, in which silk fibroin was used as template. The morphology of HAP is rod-like, while ZnHAP changes to wrinkled sheets. HAP and ZnHAP nanoparticles were used to coat titanium by EPD with additional chitosan and multiwalled carbon nanotubes. Phase composition, morphology and structure were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared and Raman spectroscopy. The results showed that the composite coatings containing HAP and ZnHAP had homogeneous morphology and good apatite formation ability. The ZnHAP composite coating possessed class 5B adhesive strength using tape test. Furthermore, the ZnHAP composite coating had better corrosion resistance compared to the HAP composite coatings.     

Papillae mimetic hairy composite spheres towards lotus leaf effect coatings

An effective approach is proposed to fabricate a robust superhydrophobic coating constructed from hairy composite spheres. The hairy spheres mimic structure of the papillae on the surface of lotus leaf. The synthesis is based on template method and the corresponding PANi hairy spheres are prepared by polymerization induced diffusion growth via nanosized channels of a polymer cage. The composite spheres become more robust by coating a layer of inorganic materials onto the PANi hairy spheres. By using a middle adhesive layer of epoxy resin, the hairy spheres can be tightly attached to the substrate. The superhydrophobic coating is achieved with a contact angle of 159.9 ± 1.9° and tilt angle below 2° by a post hydrophobic modification with octadecyltrichlorosilane. Such coating is robust enough to resist water flushing and organic solvents. This method can be scaled up for almost all kinds of substrates.     

引氟量对钛表面电沉积含氟羟基磷灰石涂层的影响

根据电沉积磷灰石陶瓷技术,通过在含有Ca(NO3)2·4H2O、NH4H2PO4、NaNO3及H2O2的电解液中加入不同浓度的氟化钠作为引氟剂,在钛片表面进行电化学沉积,分别采用扫描电镜(SEM)、X射线衍射(XRD)、傅立叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)对所得涂层的表面形貌和理化性质进行分析.结果表明,通过上述方法可以在钛表面制备纳米晶含氟羟基磷灰石(FHA)涂层,涂层的含氟量与电解液中加入NaF的浓度有关.当NaF浓度低于0.012 mol/L时,随着引氟量的增加,所得FHA涂层的含氟量也相应增加;当NaF浓度高于0.012 mol/L后,涂层的含氟量不发生明显变化.     

The effect of heat treatment on the structure and hardness of pulse electrodeposited NiP-WC composite coatings

In the present work pure nickel-phosphorous and nickel-phosphorous composite coatings with WC particles (mean diameter 200 nm) have been produced under both direct and pulse current conditions, from a modified, organic-free, Watts bath. The produced coatings were thermally treated at various temperatures and the structure, morphology and the microhardness of the deposits were examined after each cycle of heat treatment. Imposition of pulse current conditions led to composite deposits with high-incorporation percentage of WC particles in the matrix. Also, the presence of WC particles resulted in coatings with enhanced microhardness values and retarded diffusion phenomena in the deposits during thermal treatment. Annealing of all coatings at 400 °C revealed complete crystallization of the matrix to the phases of Ni, Ni₂P and Ni₃P accompanied by a significant increase of microhardness for all deposits. Further heating at higher temperatures demonstrated a decrease in microhardness of both kinds of deposits. The experimental data proved that it is possible to produce NiP-WC composite coatings under specific pulse current conditions followed by proper thermal treatment that exhibited considerable enhanced microhardness.     

Investigation of oil palm based Kraft and auto-catalyzed organosolv lignin susceptibility as a green wood adhesives

The aim of this study is to highlight the application and potentiality of oil palm based lignins in the synthesis of green phenolic resins. The delignification processes were conducted using Kraft and auto-catalyzed ethanol–water pulping processes. The extracted lignins were characterized using elemental analysis, Fourier transform-infrared, ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, molecular weight distribution (M_n, M_w and polydispersity), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The obtained FTIR results revealed that the Kraft lignin contained substantial amounts of guaiacyl units with smaller amounts of syringyl units. The molecular weight of Kraft lignin was 1564 g mol⁻¹ which is higher than organosolv lignin at 1231 g mol⁻¹. The activated free ring position (2.99%) of Kraft lignin was comparatively higher than that of organosolv lignin (2.06%) which was measured using Mannich reactivity analysis. Thermal analysis of Kraft lignin showed higher thermal stability compared to organosolv lignin. The structural and thermal characteristics implied that Kraft lignin had higher potential for the production of green phenolic resins when compared with organosolv lignin.     

电沉积纳米复合镀层的研究现状

纳米复合电沉积是一种新兴的复合表面技术。阐述了纳米颗粒与金属共沉积的机理、工艺条件对纳米复合电沉积的影响。以及纳米复合共沉积的应用。纳米与金属共沉积可明显提高镀层的硬度、耐磨、耐蚀、光催化和电接触性能。指出了纳米复合电沉积现存的问题，并为今后的研究提出了建议。     

In vitro assessment of zinc apatite coatings on titanium surfaces

In this paper, coatings of hydroxyapatite partially substituted with zinc (ZnHA) were produced on titanium substrates by a two-step hydrothermal process using a precursor solution rich in calcium, phosphate and zinc. Activation of titanium surfaces was performed by oxidation with an acidic HF/HNO₃ solution. The coated substrates were then converted into HA by immersion in an alkali 0.1 M NaOH solution. The ZnHA samples were characterized by several techniques and their in vitro behavior was studied in comparison to hydroxyapatite (HA) and titanium (Ti-control) samples. A uniform and homogeneous calcium-deficient carbonate apatite coating was obtained for all samples, both doped and undoped with zinc. The percentage of zinc incorporated in the coatings is 7 at%, and the Ca/P ratio is 1.61(±0.01) for both types of samples, suggesting that Zn is incorporated substitutionally, replacing Ca atoms into the HA structure. The incorporation of Zn in the HA structure changed the crystals morphology, reduced crystals sizes and decreased the deposition rate showing that zinc is an inhibitor of the growth of HA crystal. X-ray diffraction showed that HA is the single crystalline phase present after alkali treatment. The coating adhesion strength was evaluated in terms of the critical load (Lc) obtained from scratch tests and no significant difference was found between the two tested groups, indicating the good adhesion of ZnHA to Ti substrates. The in vitro response of human osteoblasts (HOB) exposed to the surfaces of HA and ZnHA coatings was evaluated. The results of Live/Dead tests showed cell viability for all samples surfaces, but the adhesion and proliferation tests showed that ZnHA samples presented better adhered and spread cells compared with HA. ZnHA coatings presented cells with elongated or polygonal shapes and clearly more spread than HA. Quantitative analysis showed that there was a significantly higher number of cells adhered to ZnHA coatings compared to HA, indicating the zinc incorporation stimulates osteoblast proliferation.     

工艺条件对电沉积Ni-金刚石复合镀层性能的影响

研究了温度、电流密度、pH等工艺条件对镍-金刚石复合镀层性能的影响。实验表明,在金刚石含量为40 g/L的瓦特镀镍液中,当电流密度为1.5 A/dm2、温度为40℃、pH为3.8时,在45#钢上可获得性能较好的镍-金刚石复合镀层,且沉积速率适中。镀层中金刚石微粒含量为11%~13%(质量分数),镀层硬度为2100 MPa左右,耐磨性能较好。     

Phase and structure formation mechanisms of SHS synthesized composite coatings

High performance composite coatings were synthesized by self-propagation high-temperature synthesis followed by gravitational-separation process based on thermite reaction. The phase, structure and composition of generated composite coatings were investigated, and formation mechanism was studied by thermodynamic analysis. Results showed that phase composition of Al-Fe₂O₃ reaction system consisted of Al₂O₃, Fe and FeAl₂O₄. In Al-Fe₂O₃/Al-Cr₂O₃ composite reaction system, Fe-Cr alloy was formed and FeAl₂O₄ phase disappeared, which could improve the corrosion resistance of composite coatings. Furthermore, the addition of SiO₂ in SHS reaction favored the formation of low-melting point phase Al₂O₃·SiO₂, which filled into voids of Al₂O₃ dendrites and reduced the porosity of composite coatings, thus improving their strength and densification level. Moreover, the generated transition structure in different reaction systems could buffer the residual stress to promote the binding between the composite coating and steel pipe.     

A review on the preparation and application of BN composite coatings

Hexagonal boron nitride (h-BN) is a kind of functional ceramic material with excellent physical and chemical properties. This paper analyzes it from the aspects of mechanical, thermal, electrical and wetting properties. However, the high melting point of hexagonal boron nitride makes it difficult to prepare coating materials by traditional sintering process. This paper summarizes several processes for preparing h-BN composite coatings. Then, several application forms of h-BN composite coatings are reviewed according to the characteristics of h-BN composite coatings, and the future application prospects of h-BN coatings are forecasted in view of the existing problems.     

Structure and mechanical properties of hydroxyapatite coatings produced on titanium using plasma spraying with induction preheating

Coatings of hydroxyapatite (HAp) were prepared by plasma spraying with induction preheating of titanium substrate from 200 to 1000 °C. The combination of conventional plasma spraying and induction preheating ensured high mechanical properties of HAp coatings. The coatings produced in the temperature range 400–600 °C were characterized by homogeneous nanostructure of splats with an average grain size of 12–31 nm. According to the results of nanoindentation HAp coatings with high hardness 0.9–1.2 GPa and elastic modulus 7–16 GPa were formed on the titanium.     

在钛基上电泳沉积羟基磷灰石生物陶瓷涂层的研究

将羟基磷灰石(HAP)电泳沉积在钛基材上，得到了结构稳定的HAP生物陶瓷涂层。研究了电场强度、悬浮液温度、电泳时间、分散介质及HAP浓度对涂层形貌的影响。通过红外光谱仪(FTIR)和X射线衍射仪(XRD)对涂层的组成及结构进行了分析，并采用扫描电镜(SEM)对涂层煅烧前后的微观形貌进行了观察。结果表明：在正丁醇作为分散剂、悬浮液温度30℃、电场强度250V／cm、电泳时间300s以及HAP浓度5．0g／L的条件下可制得形貌较好的HAP生物陶瓷涂层；经二次电泳沉积及煅烧后得到的HAP生物陶瓷涂层均匀致密．     

Hydroxyapatite-carboxymethyl cellulose-graphene composite coating development on AZ31 magnesium alloy: Corrosion behavior and mechanical properties

In this study, hydroxyapatite (HA) coatings containing carboxymethyl cellulose (CMC) and graphene (Gr) were developed on AZ31 magnesium alloy through two-step electrophoretic deposition method. The morphology and chemical bonding of coatings were characterized and also the phase identification was done using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, respectively. Moreover, the corrosion behavior of the applied coatings was compared with the bare AZ31 Mg alloy substrate in the simulated body fluid by the means of potentiodynamic polarization test and electrochemical impedance spectroscopy. Obtained results revealed that the novel HA-CMC-Gr coating possesses the highest corrosion resistance compared to the HA, HA-CMC, and HA-Gr coatings due to its uniform and compact structure. To investigate the mechanical properties and to elucidate the effect of CMC on the adhesion of coating-alloy interface, pull-off test was employed, where results demonstrated that the addition of CMC increases the adhesion force from 1.06 MPa to 1.62 MPa. Besides, the modulus of elasticity and the hardness of HA and HA-Gr composite coatings were compared by applying nanoindentation test. Interestingly, it is detected that the presence of Gr has considerably increased the elastic modulus of the coating by approximately 30% in comparison to the pure HA coating.