Silver-doped calcium phosphate nanopowders prepared by electrostatic spraying

Silver-doped calcium phosphate nanopowders were successfully prepared by the cost-effective electrostatic spray-pyrolysis process. The properties of the silver-doped nanopowder annealed at 500°C for 30 min were investigated through X-ray diffraction analysis, field emission scanning electron microscope, and Fourier transform infrared spectroscopy. The silver-doped nanopowders with 70–90 nm particle size showed an antibacterial performance against Escherichia coli.     

Study of physicochemical and biological properties of calcium phosphate coatings prepared by RF magnetron sputtering of silicon-substituted hydroxyapatite

Coatings based on pure silicon and silicon-substituted hydroxyapatite were grown by RF magnetron sputtering. The coating surface morphology, phase and elemental composition were studied by scanning electron microscopy, energy-dispersive X-ray analysis, and infrared spectroscopy. It was found that coatings are X-ray-amorphous, their elemental composition being controlled by the sputtered target composition. The distribution of elements over the coating surface is homogeneous. Medical and biological properties of coatings were studied in vivo and in vitro. Osteogenic properties of coatings were studied. Coatings grown by sputtering of a stoichiometric hydroxyapatite target are biocompatible without osteoinductive activity. The introduction of silicate ions into the hydroxyapatite structure that forms an electrode target significantly enhances the in vivo effect of CaP magnetron coatings on the osteogenic activity and stromal bone-marrow stem cells.     

Highly efficient Yb-doped silica fibers prepared by powder sinter technology

We report on the characteristics of an active fiber with core material made by sintering of Yb-doped silica powders as an alternative to a conventional modified chemical vapor deposition (MCVD) technique. This material provides the possibility to design very large and homogenously rare-earth doped active fiber cores. We have determined a fiber background attenuation of 20 dB/km and measured a slope efficiency of 80%. These values are comparable to established fibers made by MCVD technology.     

Highly adhesive metal plating on Zylon fiber via iodine pretreatment

Highly adhesive metal plating was performed on poly(p-phenylene-2,6-benzobisoxazole) fiber named Zylon^® via iodine pretreatment followed by electroless plating. First, iodine components were selectively doped into the inner part of the fiber near the surface through iodine vapor exposure. The doped iodine was converted to palladium iodide particles by treating with palladium chloride solution. After the reduction of the iodide to metal palladium particles, electroless copper plating was conducted on the fiber. A uniform copper layer was deposited on the fiber surface and exhibited high durability in durability tests such as ultrasonic exposure, tape peeling-off, and corrosion in NaCl solution. This durability was attributed to the palladium particles formed at the fiber surface that served as an anchor for the plated layer as well as an electroless plating catalyst. The plated fibers also possessed electrical conductivity. Although the tensile strength of the Zylon^® fiber decreased from 5.8 to 4.9 GPa after undergoing the pretreatment and plating processes, the light shielding effect improved the light resistance of the plated fibers in terms of tensile properties. After 18 days of xenon lamp exposure, the plated fibers retained 74% of its initial strength, whereas that of untreated fibers decreased to 43%.     

Roughness simulation for thin films prepared by atomic layer deposition

The kinetic lattice Monte Carlo method for film growth simulation without taking crystallization into account was applied to study the roughness of the HfO₂ film grown by atomic layer deposition at 100–500°C from HfCl₄ and H₂O. The calculations were performed using a simplified kinetic mechanism of the growth of HfO₂ films obtained by reducing the detailed kinetic mechanism developed earlier. Ab initio quantum-chemical calculations were performed to determine the kinetic parameters of diffusion processes on the surface of hafnium oxide that could influence film roughness. Because of the special features of atomic layer deposition, the rate of film growth and film roughness were finite even if surface relaxation was ignored. It was found that, irrespective of the temperature, the diffusion of hydrogen and adsorbed HfCl₄ complexes did not change the profile of the growing film and only insignificantly increased the mean rate of growth. The results obtained were also qualitatively applicable to zirconium dioxide at fairly low (≤100°C) temperatures in the absence of crystallization.     

Nanotribological behavior of ZnO films prepared by atomic layer deposition

We used atomic layer deposition to form ZnO thin-film coatings on Si substrates and then evaluate the effect of pile-up using the nanoscratch technique under a ramped mode. The wear volume decreased with increasing annealing temperature from room temperature to 400 °C for a given load. Elastic-to-plastic deformation occurred during sliding scratch processing between the groove and film for loading penetration of 30 nm. The onset of non-elastic behavior and greater contact pressure were evident for loading penetration of 150 nm; thus, full plastic deformation occurred as a result of a substrate effect. We suspect that elastic–plastic failure events were related to edge bulging between the groove and film, with elastic–plastic deformation attributable to adhesion discontinuities and/or cohesion failure of the ZnO films.     

Bioactive calcium phosphate coating formed on micro-arc oxidized magnesium by chemical deposition

In order to improve the bioactivity of the micro-arc oxidized magnesium, a calcium phosphate coating was formed on the surface of micro-arc oxidized magnesium using a chemical method. The microstructures of the substrate and the calcium phosphate coating before and after the simulated body fluids (SBF) incubation were characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy and scanning electron microscopy. The results showed that the calcified coating was composed of calcium deficient hydroxyapatite (HA) and dicalcium phosphate dihydrate (DCPD). After SBF incubation, some new apatite formation on the calcified coating surface from SBF could be found. The corrosion behaviours of the samples in SBF were also investigated by potentiodynamic polarization curves and immersion tests. The results showed that calcium phosphate coating increased the corrosion potential, and decreased the hydrogen gas release.     

The impact of calcium phosphate on FITC-BSA loading of sonochemically prepared PLGA nanoparticles for inner ear drug delivery elucidated by two different fluorimetric quantification methods

Although therapeutically active proteins are highly efficacious, their content in protective nanoparticles is often too low to elicit adequate plasma levels. A strategy to increase protein loading is the in-situ generation of calcium phosphate as a protein adsorbent. To verify this approach, a highly sensitive and reliable fluorimetric method for quantification of incorporated fluorescein-labelled bovine serum albumin (FITC-BSA) as a model protein drug was developed. Dequenching the fluorescein label by pronase E, which digests the protein backbone, and dissolving the nanoparticle matrix in acetonitrile enabled FITC-BSA quantification in the nanogram per milliliter range. This test was confirmed by a second assay involving alkaline hydrolysis of FITC-BSA and the matrix. Nanoparticles prepared with calcium phosphate contained 40 µg FITC-BSA/mg and nanoparticles without calcium phosphate only 15 µg FITC-BSA/mg, representing a 2.7-fold increase in model protein loading. In this work the nanoparticle preparation procedure was optimized in terms of size for administration in the inner ear, but the range of applications is not limited.     

The effect of iridium precursor on oxide-supported iridium catalysts prepared by atomic layer deposition

Alumina, silica and beta zeolite supported iridium catalysts were prepared by atomic layer deposition (ALD) from two different metal precursors, Ir(acac)₃ and Ir(thd)(COD). The use of Ir(thd)(COD) in ALD is reported for the first time. The aim was to investigate the effect of the precursor on catalyst surface species, chemical state and characteristics.Controllable ALD reaction was successful with both iridium precursors on alumina and with Ir(acac)₃ on β zeolite. On these catalysts, iridium particle sizes were very small (1-3 nm). Instead, some thermal decomposition of both precursors was observed during deposition on silica. At conditions, where no or very little decomposition of the precursors took place, the differences in the chemical state and characteristics of the as-prepared Ir/support samples were negligible, In ALD, Ir(acac)₃ is slightly more stable at high deposition temperatures (>200 °C) while Ir(thd)(COD) enables the utilization of larger temperature range since it vaporizes at lower temperature compared to Ir(acac)₃. The results thus indicate that Ir(thd)(COD) is a suitable new precursor for ALD.     

Microstructure of yttric calcium phosphate bioceramic coatings synthesized by laser cladding

The yttric calcium phosphate (CaP) coatings were in situ prepared on pure titanium substrate by laser cladding. The morphologies and phases constitution of CaP coatings were studied by electron probe microanalysis, X-ray diffraction and so on. The bonding state between the coating and the substrate is fine metallurgical combination, and the addition of yttria can fine the structure and increase the tensile strength of the coatings. The X-ray result shows that the coating is composed of the phases of HA, α-Ca₂P₂O₇, β-Ca₂P₂O₇ and CaTiO₃.     

Hydrogenated diamond-like carbon film deposited on UHMWPE by RF-PECVD

In this work, investigations were conducted to analyze the properties of diamond-like carbon (DLC) film deposited on ultra-high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) at a low temperature of 50 °C. Composition and structure of the films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Hardness and wettability of the film were tested. Tribological characterizations were carried out on a universal micro-tribometer, and reciprocating friction against ZrO₂ ball was adopted with 25% bovine serum as lubrication. Results show that DLC film was successfully deposited on UHMWPE surface by RF-PECVD and the sp³ content was about 20% in the film. The film increased the macrohardness of the substrate by about 42% and the wettability was improved too. Tribology test showed a higher friction coefficient but a much smaller wear volume after the deposition due to the surface roughening and strengthening.     

Properties including step coverage of TiN thin films prepared by atomic layer deposition

The physical properties including the step coverage of the TiN films deposited by atomic layer deposition (ALD) technique, using TiCl₄ and NH₃ as the precursors have been investigated. The deposition rate of the TiN film is constant and moderately high (0.6 Å per cycle) under an optimum deposition condition. The film resistivity is appreciably low (200 μΩ cm). The XRD analysis results indicate polycrystalline nature of the TiN films with a (1 1 1) preferred orientation. The XPS and AES analysis results establish that the Cl impurity concentration in the TiN films is lower than 1 at.% and the ratio of Ti and N by atomic concentration in the TiN films is nearly equal to 1:1 AFM analysis reveals that the RMS surface roughness is low. Also it is found by SEM observation that the step coverage of the TiN films with trenches (the aspect ratio being 10:1) is excellent. One hundred percent conformality is observed for both the side/bottom and the side/top sections.     

Properties of calcium phosphate coatings deposited by high-power ion beam ablation plasma

Biocompatible hydroxyapatite coatings (Ca₁₀(PO₄)₆(OH)₂) are used in stomatology and orthopedic surgery as an original structure for production of medical materials. These coatings have been deposited on Si, Ti and VT15-alloy substrates from ablation plasma formed under the impact of pulsed high-power ion beams on a calcium phosphate ceramic target. The nanohardness, Young’s modulus, elastic recovery, adhesion of coatings to substrates, friction constant, and surface roughness were measured.     

Influence of adhesive layer properties on laser-generated ultrasonic waves in thin bonded plates

This paper studies quantitatively the generation of Lamb waves in thin bonded plates subjected to laser illumination, after considering the viscoelasticity of the adhesive layer. The displacements of such plates have been calculated in the frequency domain by using the finite element method, and the time domain response has been reconstructed by applying an inverse fast Fourier transform. Numerical results are presented showing the normal surface displacement for several configurations: a single aluminum plate, a three-layer bonded plate, and a two-layer plate. The characteristics of the laser-generated Lamb waves for each particular case have been investigated. In addition, the sensitivity of the transient responses to variations of material properties (elastic modulus, viscoelastic modulus, and thickness) of the adhesive layer has been studied in detail.     

Inhomogeneity of calcium phosphate coatings deposited by laser ablation at high deposition rate

Calcium phosphate coatings were deposited with a KrF excimer laser onto titanium alloy to study their homogeneity. Deposition was performed at a high deposition rate under a water vapour atmosphere of 45 Pa and at a substrate temperature of 575 °C. Samples were also submitted to annealing under the same conditions of deposition for different times just after deposition. The effects of the annealing were also investigated. The morphology of the coatings was studied by scanning electron microscopy. Their structure and phase distribution was analysed by X-ray diffractometry and infrared and micro-Raman spectroscopies. Besides the non-uniform thickness, the results reveal an inhomogeneity in the spatial distribution of calcium phosphate phases in the coatings. The phase distribution can be almost completely correlated with the deposition rate. High deposition rates (0.5 nm/pulse) occurring in the centre of deposition results in the formation of amorphous calcium phosphate, while lower deposition rates favour the presence of hydroxyapatite and alpha tricalcium phosphate. At intermediate deposition rates, beta tricalcium phosphate is found, probably because the superimposed effect of energetic particles bombardment. The annealing process promotes the crystallisation of the amorphous material. The importance of the deposition rate in the phases obtained is stated after comparing these results with a previous work where homogeneous hydroxyapatite coatings were obtained under the same conditions of laser fluence, temperature and pressure, but at lower deposition rates. Received: 22 November 2001 / Accepted: 12 March 2002 / Published online: 5 July 2002 RID="*" ID="*"Corresponding author. Fax: +34-93/402-1138, E-mail: jmfernandez@fao.ub.es     

离子束溅射和离子辅助淀积DWDM滤光片的膜厚均匀性

用离子束溅射和离子辅助淀积技术制备DWDM滤光片的关键问题是必须获得优良的膜层厚度均匀性。采用实验修正膜层厚度修正板的办法获得了较好的均匀性分布 ,给出了实验配置、实验方法和实验结果 ,并对实验结果作了分析讨论     

Thermal conductivity of the Nb3Ge layer prepared by the continuous deposition method

The paper describes the measurement of thermal conductivity of the stainless steel tape on which the superconductive Nb₃Ge layer was vapour-deposited on both sides by the continuous method. The stainless steel 50 m substrate covered by the 2 m Nb layer was deposited with the layer of Nb₃Ge of the thickness of 10 m. Thermal conductivity in the temperature range within 5 up to 80 K was measured in lengthwise direction using the thermopotentiometric method in the bath cryostat. In the same experimental arrangement the measurement of thermal conductivity of the substrate and of the tape with the deposited layer of Nb₃Ge was performed. Specific thermal conductivity of the Nb₃Ge layer was calculated on the basis of measured values.