柠檬酸根对电沉积羟基磷灰石/氧化锆过渡涂层的影响

先后分别在含有ZrO2+的电解液和含有Ca2+、PO43-和柠檬酸根的电解液中,用电化学恒电流方法,于钛表面上制得柠檬酸根-羟基磷灰石/氧化锆过渡涂层。采用扫描电镜(SEM)、能谱仪(EDS)、X-射线衍射(XRD)、红外光谱(FTIR)和万能力学测试仪对过渡涂层进行分析,并对电沉积各个阶段的微观生长机理进行了探讨。结果表明柠檬酸根延长了HA晶体的形核孕育期,涂层由疏松的微米级菊花瓣状变化为致密的近纳米级针状(或片状),ZrO2作为过渡涂层,很好的缓解了HA与钛基热膨胀系数不匹配等缺点。拉伸试验表明,过渡涂层的结合强度较HA涂层从7.40 MPa增加到27.11 MPa。     

钛基多孔HA/SiO2复合涂层的制备及性能研究

为了制得表面多孔且与基材结合强度高的羟基磷灰石(HA)涂层,实验中以正丁醇为分散介质,以SiO2粉末为添加剂,纯钛片为基材,电泳沉积制备羟基磷灰石/二氧化硅/壳聚糖/(HA/SiO2/CS)复合涂层,经后续热处理得到多孔HA/SiO2复合涂层,采用扫描电镜(SEM)、傅立叶红外光谱仪(FT-IR)、X射线衍射仪(XRD)、万能材料试验机对涂层的表面形貌、组成、结构和结合强度进行测试和表征,并通过模拟体液(SBF)浸泡法对复合涂层的生物活性进行评价.结果表明:当悬浮液中的HA/SiO2/CS质量比为1∶1∶1时,制得的HA/SiO2/CS涂层经700℃热处理后获得的HA/SiO2复合涂层孔洞分布均匀,大孔孔径在10～15μm,小孔孔径在1～5μm;涂层与基材的结合强度达到25.5 MPa;多孔HA/SiO2复合涂层在SBF中浸泡7 d后,涂层表面碳磷灰石化;说明实验中添加SiO2所制得的多孔HA/SiO2复合涂层与钛基材结合强度高,且具有良好的生物活性.     

脉冲电化学沉积法制备羟基磷灰石/壳聚糖复合涂层的研究

采用脉冲电化学沉积法在钛金属表面制备出羟基磷灰石/壳聚糖(HA/CS)复合涂层,实现CS与HA在微观尺寸上的复合与杂化.比较了脉冲电位与恒电位模式下复合涂层的形成,研究了电位高低及壳聚糖浓度对复合涂层性能的影响.结果表明,与恒电位模式比较,脉冲电位下制备的涂层较均匀、结晶性好、CS含量高,并且HA与CS杂化程度高.脉冲...     

电化学共沉积HA/胶原复合涂层及其生物性能初探

应用电化学恒电流共沉积法在医用纯钛基底上制备羟基磷灰石(HA)/胶原(collagen)复合涂层.SEM和XPS等测试表明:复合涂层呈特定有序的纳-微米二级多孔结构,化学组分为HA和胶原的有机-无机复合.借助体外细胞的培养实验观察种植于不同材料表面的细胞贴壁及生长形态,显示电化学共沉积的复合涂层具有比纯HA或纯钛表面更好的生物相容性.     

电位阶跃法沉积羟基磷灰石的研究

采用电化学方法在钛金属基底上沉积羟基磷灰石(HA)。系统考察了阶跃电位、沉积时间等实验条件对涂层质量的影响。在一定温度下经碱液处理后获得的羟基磷灰石(HA)涂层的形貌和结构分别用扫描电子显微镜(SEM)和X-射线衍射(XRD)进行了表征；用粘结拉伸法测得涂层的界面结合强度达7．44MPa，并在模拟生物体液中考察了生物活性以及电化学腐蚀性能。     

水热电沉积羟基磷灰石涂层的研究

在0.0105mol/LCa(NO₃)₂,0.0063mol/LNH₄H₂PO₄,0.1mol/LNaNO₃,pH=4.6的电解液中,控制温度60～200℃,恒电流0.4mA/cm²,通过水热电沉积法制备羟基磷灰石涂层.实验结果表明,涂层晶体端面呈六边形棒状结构,涂层组分为缺钙磷灰石Ca_10-x(HPO₄)_x(PO₄)_6-x(OH)_2-x.经800℃烧结后涂层分解为HA和β-TCP的混合物.随温度升高,涂层n(Ca)/n(P)不断增大,涂层组分逐渐接近计量比的HA.涂层质量和结合强度随温度升高先增后减,在160℃时达到最大值16.7MPa     

造孔剂对电泳沉积制备多孔HA涂层及其生物活性的影响

采用水热法制得的羟基磷灰石(HA)纳米粉体,分别与造孔剂葡萄糖(Glu)、壳聚糖(CS)、炭粉(C)3种微粒(＜38.5 μm)配置成质量比1∶1的悬浮液,电泳沉积 烧结制备钛基多孔HA涂层,并对制得的3种多孔HA涂层在模拟体液浸泡前后的表面形貌、化学组成及物相变化进行表征。 结果表明,经700 ℃烧结处理后制得的3种多孔HA涂层在1.5倍人体模拟体液中浸泡5 d后,多孔HA涂层表面均被层状生长的碳磷灰石颗粒完全覆盖,颗粒直径在5~25 μm,说明这些多孔HA涂层均具有良好的生物活性。 其中以CS为造孔剂制得的多孔HA涂层结合强度最高,达19.5 MPa,有望开发成为新型的人骨植入生物陶瓷材料。     

电诱导牙釉质表面羟基磷灰石涂层形成的研究

以含Ca(NO₃)₂、NH₄H₂PO₄和NaNO₃组成的溶液作为电解液,在人牙釉质表面电诱导制备了羟基磷灰石(HA)涂层。应用X射线衍射(XRD)﹑扫描电镜(SEM)和能谱分析(EDS)对形成涂层后的牙釉质样品进行分析和表征,研究了电解液初始pH值﹑电流密度和温度的变化对涂层的组成﹑结构和形貌的影响。研究结果表明这些因素对涂层的组分(HA)没有显著影响,而对涂层中HA晶体c轴的择优取向度的影响则较显著。当控制电解液的初始pH值为6﹑电流密度为0.5 mA·cm^-2﹑温度为55 ℃的时候,涂层中HA晶体沿c轴方向择优取向生长,且择优取向度和牙釉柱的HA较为接近。     

HA/CuO/SrCO3梯度复合涂层的制备及体外生物活性

在羟基磷灰石(HA)悬浮液中, 以正丁醇为分散介质, 三乙醇胺为乳化剂, 成骨微量元素化合物CuO 和SrCO₃作为添加剂, Ti片为基材, 壳聚糖(CS)为造孔剂, 依次通过区带电泳分布并在反向电场作用下电 泳沉积, 得到HA/CS/CuO/SrCO₃复合涂层, 经700 ℃高温煅烧2 h后, 制得HA/CuO/SrCO₃复合涂层. 通过X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 场发射扫描电子显微镜(FESEM)、 能量色散光谱仪(EDS)、 劳埃德万能材料试验机、 电化学工作站、 模拟体液培养和抑菌实验等手段对复合涂层进行测试与表征. 结果表明, Ca, Cu和Sr 元素含量在HA/CuO/SrCO₃复合涂层的径向上均呈现梯度分布; 复合涂层与钛基材的结合强度达33.0 MPa; 循环伏安(CV)曲线和Tafel极化曲线测试表明, 复合涂层在N-2-羟乙基哌嗪-N′-2-乙磺酸(HEPES)模拟体液(H-SBF)中电化学性能稳定, 耐腐蚀性较强; 在H-SBF中培养24 d后, 复合涂层表面完全碳磷灰石化; 抑菌实验发现, 复合涂层粉末对大肠杆菌和金黄色葡萄球菌的抑菌率分别为81.82%和71.86%.     

荆棘状羟基磷灰石棒的电化学法制备及性能表征

先后在低浓度和高浓度的钙、磷电解液中,采用两步电化学沉积法在纯钛金属表面制备了荆棘状羟基磷灰石棒(THA)。微观结构分析表明,THA的主干是由HA单晶构成,直径为100~200 nm,叉刺为HA多晶结构,直径为10~50 nm,它们在钛金属表面构成了具有两重微纳形貌的多孔涂层。溶解性实验与接触角测试结果表明,与单纯的HA棒涂层相比,这种THA涂层具有较高的钙离子释放速度和优异的表面润湿性。     

A study of the effect of waste from production of fluoropolymers on properties of zinc-fluoropolymer composite electrochemical coatings

Possibility of depositing zinc-fluoroplastic composite electrochemical coatings from ammonium chloride electrolytes, with the role of a dispersed phase played by liquid wastes from production of fluoropolymers and secondary suspensions of F-4D and F-4MD fluoroplastics, was studied. The optimal deposition parameters of composite coatings were determined. The effect of liquid wastes on the buildup of internal stresses in coatings and on the corrosion resistance of zinc-fluoroplastic composite electrochemical coatings was examined.     

Effect of Surfactants on Electrodeposition of the Sn–Ni Alloy from Oxalate Solutions

The effects of surfactants on the electrolytic deposition of tin–nickel alloys from oxalate–ammonium electrolytes were determined. The adsorption of the nonionic surfactant at the interface decreases the rate of charge transfer across the interface. As a result, the electrochemical stage of the electroreduction of metals slows down, and the alloy is deposited in the form of shiny finely crystalline coatings. The range of optimum surfactant concentrations in the oxalate–ammonium electrolyte was determined based on the simulation of the interface impedance obtained during the alloy deposition and the electron microscopy studies of the obtained coatings.     

Layer-by-layer fabrication of broad-band superhydrophobic antireflection coatings in near-infrared region

Broad-band superhydrophobic antireflective (AR) coatings in near infrared (NIR) region were readily fabricated on silicon or quartz substrates by a layer-by-layer (LbL) assembly technique. First, a porous poly(diallyldimethylammonium chloride) (PDDA)/SiO2 nanoparticle multilayer coating with AR property was prepared by LbL deposition of PDDA and 200 nm SiO2 nanoparticles. PDDA was then alternately assembled with sodium silicate on the PDDA/SiO2 nanoparticle coating to prepare a two-level hierarchical surface. Superhydrophobic AR coating with a water contact angle of 154 degrees was finally obtained after chemical vapor deposition of a layer of fluoroalkylsilane on the hierarchical surface. Quartz substrate with the as-fabricated superhydrophobic AR coating has a maximal transmittance above 98% of incidence light in the NIR region, which is increased by five percent compared with bare quartz substrate. Simultaneously, the superhydrophobic property endows the AR coating with water-repellent ability. Such superhydrophobic AR coatings can effectively avoid the disturbance of water vapor on their AR property and are expected to be applicable under humid environments.     

Electrochemical Processing of Reaction-bonded Ceramic Composite Coatings

Ceramic matrix composite coatings are currently of much interest for application in high-temperature and highly corrosive environments. Formation of ceramic coatings by electrochemical processing is a relatively new mean^[1-2]. It presents several advantages over alternative coating techniques, the thickness and morphology of the deposit can be controlled by the electrochemical parameters, relatively uniform deposits are obtainable on complex shapes, the deposition rate is higher than that using most other methods and the equipment required is of low cost Recently we developed a novel fabrication technique for the production of ceramic/ceramic and ceramic/metal composite coatings by electrochemical processing^[3]. The technique combined two electrochemical deposition methods, electrophoretic deposition (EPD) and electrolytic deposition (ELD), which can produce uniform composite layers of closely controlled thickness on both metallic and ceramic substrates at ambient temperature with inexpensive equipment. However, the main problem associated with electrochemical processing is the difficulty in sintering of the coatings. First, high temperature is required for sintering of the coatings. Secondly, the volume shrinkage of the coatings during sintering leads to the formation of cracks in coatings bonded to metal substrates. So a reaction forming technique, reaction bonding process, also has been developed to produce near net-shape ceramic coatings, which overcome problems caused by the shrinkage of ceramics during sintering.     

Evaluating the electrochemical capacitance of surface-charged nanoparticle oxide coatings

While transition metal oxides have been thoroughly investigated as coatings for electrochemical capacitors due to their pseudocapacitance, little work has been done investigating other oxide coatings. There exists a whole class of nanoporous oxides typically synthesized by sol-gel chemistry techniques that have very high differential capacitance. This high differential capacitance has been attributed to the surface potential of these materials and the close approach of counterions near the surface of these oxides. This study focuses on investigating the electrochemical capacitance of non-transition metal oxide nanoparticle coatings when deposited on supporting electrodes. Here, we show that, by adding coatings of SiO(2), AlOOH, TiO(2), and ZrO(2) nanoparticles to graphite support electrodes, we can increase the electrochemical capacitance. We also show that the measured electrochemical capacitance of these oxide-coated electrodes directly relates to the electrophoretic mobility of these materials with the lowest values in capacitance occurring at or near the respective isoelectric pH (pH(IEP)) of each oxide.     

The formation of submonolayer thorium coatings on a silicon oxide surface by electrochemical deposition

Data are reported on the mechanisms of the formation of submonolayer coatings based on thorium oxide on the surface of Si(111) single crystal with natural oxide as a result of electrochemical deposition. It is experimentally shown that the deposition of thorium atoms from an acetone solution of Th(NO₃)₄ onto the surface of natural silicon oxide leads to the formation of defects in the thin silicon oxide layer, which is accompanied by the deposition of thorium nanoclusters onto a pure silicon surface. The observed effects have been qualitatively explained assuming the breakdown of natural silicon oxide due to the presence of an electrical double layer in the near-surface region of the cathode.     

Alloying during codeposition of copper and tin out of silicofluoride electrolytes

A technique for obtaining binary Cu-Sn alloys containing 20–35 mol % Sn is proposed. The technique—the electrochemical deposition out of silicofluoride electrolytes—ensures a high deposition rate of coatings (25–50 μm h^?1). The formation of intermetallic compound Cu₁₀Sn₃ is found to occur at a high current density, in conditions of the tin reduction depolarization and the copper reduction superpolarization. The alloys consist of submicron grains. Apart from crystalline Cu₁₀Sn₃, they include x-ray-amorphous tin (2–12 mol %) and tin oxides (≤1–3 mol %). The alloys feature high hardness (4200 MPa), corrosion resistance, and solderability.     

Electrochemical studies on Zn deposition and dissolution in sulphate electrolyte

The electrochemical deposition and dissolution of Zn on Pt electrode in sulphate electrolyte was investigated by electrochemical methods in an attempt to contribute to the better understanding of the more complex Zn–Cr alloy electrodeposition process. A decrease of the Zn electrolyte pH (from 5.4 to 1.0) so as to minimise/avoid the formation of hydroxo-products of Cr in the electrolyte for deposition of alloy coatings decreases the current efficiency for the Zn reaction, but the rate of the cathode reaction increases significantly due to intense hydrogen evolution. The results of the investigations in Zn electrolytes with pH 1.0–1.6 indicate that Zn bulk deposition is preceded by hydrogen evolution, stepwise Zn underpotential deposition (UPD) and formation of a Zn–Pt alloy. Hydrogen evolution from H₂O starts in the potential range of Zn bulk deposition. Data obtained from the electrochemical quartz crystal microbalance (EQCM) measurements support the assumption that electrochemical deposition of Zn proceeds at potentials more positive than the reversible potential of Zn. Anodic potentiodynamic curves for galvanostatically and potentiostatically deposited Zn layers provide indirect evidence about the dissolution of Zn from an alloy with the Pt substrate. The presumed potential of co-deposition of Cr (−1.9 V vs. Hg/Hg₂SO₄) is reached at a current density of about 300 mA cm⁻².     

Formation of microstructured silicon surfaces by electrochemical etching using colloidal crystal as mask

Silicon disk arrays and silicon pillar arrays with a close-packed configuration having an ordered periodicity were fabricated by the electrochemical etching of a silicon substrate through colloidal crystals used as a mask. The colloidal crystals were directly prepared by the self-assembly of polystyrene particles on a silicon substrate. The transfer of a two-dimensional hexagonal array of colloidal crystals to the silicon substrate could be achieved by the selective electrochemical etching of the exposed silicon surfaces, which were located in interspaces among adjacent particles. The diameter of the tip of the silicon pillars could be controlled easily by changing the anodization conditions, such as current density and period of electrochemical etching.     

Fabrication and Characterisation of Leak-Tight Glassy Carbon Electrodes,Sealed in Glass Employing Silicon Coating,for Use in Electrochemical Detection

Abstract

Glassy carbon discs have been coated with silicon in a chemical vapour deposition process to obtain leak-tight electrodes, sealed in glass. Electrodes with coatings thicker than 5μm prove to be leak-tight in contrast with uncoated ones. Silicon-coated electrodes show faster decay of charging current, less noise and decreased background current. Leak-tightness and electron microscope information correlate well with the electrochemical data. All results can be ascribed to the absence of a void between glassy carbon and glass at Si-coated electrodes. By silicon coating, signal-to-noise ratios are improved with a factor of about 5, as is demonstrated for catecholamines and metabolites in liquid chromatography with electrochemical detection.