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A hydrothermal deposition method was utilized to fabricate Ca-P composite coating induced by the layer-by-layer (LbL) assembled polyvinylpyrrolidone/deoxyribonucleic acid (PVP/DNA)20 multilayer on AZ31 alloy. The surface morphology and compositions were characterized by SEM, EDS, FTIR and XRD. Besides, the corrosion resistance and degradation behavior of the coating were tested via electrochemical polarization, impedance spectroscopy and immersion measurements. Results show that the main components of Ca-P coatings are hydroxyapatite, Ca3(PO4)2 and Mg3(PO4)2·nH2O. The LbL-assembled DNA and PVP promote the adsorption of Ca-P deposits on the sample surface, and structures and functional groups of the polyelectrolyte in the outermost layer are the primary influencing factor for the induction of the Ca-P coating. Carboxyl groups have the best biomineralization effect among all related functional groups. The enhanced corrosion resistance and adhesion highlight a promising use of (PVP/DNA)20-induced Ca-P coatings in the field of biomedical magnesium alloys.

Biodegradable magnesium (Mg)-based alloys have aroused great concern owing to their promising characteristics as temporary implants for orthopedic application. But their undesirably rapid corrosion rate under physiological conditions has limited the actual clinical application. This study reports the use of a novel biomimetic polyelectrolyte multilayer template, based on polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) via layer-by-layer (LbL) assembly, to improve the corrosion resistance of the alloy. Surface characterization techniques (field-emission scanning electron microscopy, Fourier transform infrared (FTIR) spectrophotometer and X-ray diffractometer) confirmed the formation of biomineralized Ca–P coating on AZ31 alloy. Both hydrogen evolution and electrochemical corrosion tests demonstrated that the corrosion protection of the polyelectrolyte-induced Ca–P coating on AZ31 alloy. The formation mechanism of biomineralized Ca–P coating was proposed., Graphical abstract Image 1, Highlights • A novel LbL assembled template induces a compact and thick Ca–P coating. • (PVP/PAA)5.5 template improves the binding force of the Ca–P coating. • The templates-induced Ca–P coating exhibits a good corrosion protection for Mg alloy. • Free PAA and PVP may go against the nucleation and growth of the Ca–P crystals. • (PVP/PAA)5.5 template is beneficial to the formation of the crystalline Ca–P coating.

A crosslinked ciprofloxacin (CIP) and polymethyltrimethoxysilane (PMTMS) with an inner micro-arc oxidation (MAO) coating was designed to improve the corrosion resistance and antibacterial property of magnesium alloy AZ31. Surface morphology and roughness of the obtained coating were characterized through scanning electron microscopy (SEM) and three-dimensional surface profilometry. Structural components and chemical compositions of the composite coatings were detected via Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectrometry (EDS). Corrosion resistance of the coatings was investigated by means of electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves and hydrogen evolution measurements. Cytocompatibility and antibacterial performance of the coatings were probed using in vitro cytotoxicity tests (MTT), live/dead cell staining and plate counting method. Results indicate that the MAO/CIP-PMTMS coating possesses enhanced corrosion resistance, antibacterial ability and cytocompatibility. It provides a way to effectively curb the sudden release and short release period of drugs, due to the reversible esterification reaction between -COOH in CIP and Si-OH in PMTMS during the coating formation and degradation process. And it holds a great potential in the applications of medical devices and bone implant materials.

The specific features of electric current variation against time were studied by keeping the anode and cathode pulse voltage to be constant. The maximum thickness of the films fabricated by microarc oxidation was found to be closely related to the voltage. The surface morphology of the coatings can be divided into different stages according to the variation of electric current. A method for obtaining high micro hardness coating has been discussed.

Arrays of silicon micro-tips were made by etching the p-type (1 0 0) silicon wafers which had SiO2 masks with alkaline solution. The density of the micro-tips is 2×104 cm−2. The Scanning Electron Microscope (SEM) photos showed that the tips in these arrays are uniform and orderly. The CNx thin film, with the thickness of 1.27 μm was deposited on the silicon micro-tip arrays by using the middle frequency magnetron sputtering technology. The SEM photos showed that the films on the tips are smoothly without particles. Keeping the sharpness of the tips will benefit the properties of field emission. The X-ray photoelectron spectrum (XPS) showed that carbon, nitrogen and oxygen are the three major elements in the surfaces of the films. The percents of them are C: 69.5%, N: 12.6% and O: 17.9%. The silicon arrays coated with CNx thin films had shown a good field emission characterization. The emission current intensity reached 3.2 mA/cm2 at 32.8 V/μm, so it can be put into use. The result showed that the silicon arrays coated with CNx thin films are likely to be good field emission cathode. The preparation and the characterization of the samples were discussed in detail.

CN x /SiCN composite films were prepared on titanium (Ti) alloy substrates by Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD). As a buffer layer, SiCN ensured the adhesion of the CNx thin films on Ti substrates. X-ray diffraction (XRD) measurement revealed that the composite films possessed α-C3N4 structure. The microhardness of the films was 48 to 50 GPa. In order to test the characteristics of wear and corrosion resistances, we prepared Ti alloy samples with and without CN x /SiCN composite films. Also for strengthening the effect of wear and corrosion, the wear tests were carried out under high load (12 MPa) and in 0.9% NaCl solution. Results of the wear tests and the corrosive electrochemical measurements showed that the samples coated with CN x films had excellent characteristics of wear and corrosion resistances compared with Ti alloy substrate samples.

SiCN thin films were synthesized by a radio frequency chemical vapor deposition (RFCVD) system on P-type Si (1 0 0) wafers using C2H4, SiH4 and N2 as raw materials, In order to get rid of the oxygen absorbed on the surface and improve the characteristics of electron field emission, Ar+ ions of low energy were used to bombard the samples. The field emission characteristics of SiCN thin films before and after Ar+ bombardment were studied in the super vacuum environment of 10−6 Pa. It was showed that the turn-on field (defined as the point where the current-voltage curve shows a sharp increase in the current density) decreased from 38 V/μm before bombardment to 25 V/μm after bombardment. And the maximum emission current density increased from 159.2 to 267.4 μA/cm2. The composition before and after Ar+ bombardment was compared using X-ray photoelectron spectroscopy (XPS). Our results illustrated that the field emission characteristics were improved after the bombardment of Ar+.

CNx thin films were prepared using low pressure plasma enhanced chemical vapour deposition, and then bombarded by low-energy N2+. The compositions before and after N2+ bombardment were compared using x-ray photoelectron spectroscopy. The electron field emission characteristics of CNx thin films before and after N2+ bombardment were studied under the pressure of 10-6 Pa. For the samples, the turn-on emission field decreased from 2.5 V/µm to 1.2 V/µm while the stable current density increased from 0.5 mA/cm2 to a value larger than 1 mA/cm2 before and after the bombardment. Our results illustrate that the field emission characteristics were improved after the bombardment of N+2.

The specific features of current variation during different stages of the microarc oxidation process were studied on the timescale. The cathodic current was found to be closely related to the microarc discharge. The discharge was responsible for the formation of a dense coating with unique physical characteristics. A method for obtaining high-quality coating has been discussed.

Diamond films have been grown on high pressure synthesized cubic boron nitride (c-BN) particles by hot-filament chemical vapor deposition method, and heteroepitaxial diamond films on the c-BN (100) facets with no-evident defects were obtained, but polycrystalline diamond films were formed only on the c-BN (111) facets.

Nitrogen was implanted into the chemical vapor deposition(CVD) diamond films, and the electron fieldemission properties of the nitrogenated diamond films were investigated. Raman and xray photoelectron spectroscopy(XPS) measurement revealed that nitrogenimplantation damaged the structure of diamond film and promoted the formations of sp2 C—C and sp2 C—N bonding. By increasing the implantation dose， the threshold field of the emission of the diamond film could be lowered from 18V/μm to 4V/μm. The enhancement of field emission for nitrogenimplanted CVD diamond films was attributed to the increase of the fraction of sp2 C bonds and the formation of defect bands within the bulk diamond band gap induced by nitrogenimplantation, which could alter the work function and elevate the Feimi level. Consequently, the energy barrier on diamond surface for electron tunneling was reduced.

The variation of electrical parameters during microarc oxidation(MAO) of aluminium alloys at constant voltage has been studied by means of a laboratory-made data acquisition system. Experimental results show that the variations of the cath odic and anodic current amplitude and effective working current in an electrical loop with the duration of treatment show obviously five stages, and the variati ons of dynamic positive resistance and the rate of change of resistance in coati ngs also show different stages, while the variations of dynamic negative resista nce and the rate of change of resistance with oxidation time are not evident. Du ring the MAO process, the dynamic positive resistance is always not equal to the negative resistance, and the former is generally greater than the latter in gen eral. Scanning electron microscopy analysis shows that the surface morphology of MAO coatings is macro-porous and its variations with treatment time are in ste ps.

Ultra-hard ceramic coatings with microhardness of 42.14GPa have been synthesized on the Al alloy substrate by microarc oxidation (MAO) technique. The effects of anodic current density ja and the ratio of cathodic to anodic current density jc/ja on the mechanical property and phase composition of MAO coatings have been studied by microhardness test and x-ray diffraction, respectively. In addition, the microstructure and corrosion resistance of the coatings were analyzed by scanning electron microscopy and pitting corrosion test, respectively. The results show that the samples prepared at high anodic current density consist mainly of α-Al2O3, while the samples fabricated at low anodic current density are composed almost entirely of γ-Al2O3. Microhardness test shows that these kinds of samples have high hardness, and the microhardness of the coating prepared at ja=15A/dm2 and jc/ja=0.7 is t highest of all coatings prepared. Pitting corrosion test shows that the structure of coatings is strongly influenced by the variation in jc/ja.