Creation of a hard microrelief on a titanium surface processed by microplasma discharges with a current amplitude of 200 A and pulse duration of 20 ms

The interaction of microplasma discharges with samples made of VT1 commercial titanium was studied experimentally. The amplitude of the current pulses of microplasma discharges was 200 A, the pulse duration was 20 ms, and the number of current pulses was from 1 to 10. After microplasma processing, a 10-μm-thick solid remelted surface layer with an increased hardness formed on the titanium samples. As compared to the initial state of titanium samples, the surface layer hardened by microplasma discharges possesses improved parameters: the microhardness increases fivefold, the maximum admissible pressure applied to the samples during friction increases more than 20-fold, the friction wear rate is reduced by three orders of magnitude, and the friction coefficient decreases sixfold.     

Effect of microplasma discharges on aluminum surfaces

Excitation of microplasma discharges on the surfaces of V95 aluminum alloy samples placed in a uniform pulsed plasma flow was studied experimentally. Strong localized interaction of microplasma discharges with aluminum leads to the melting and subsequent fast cooling of micrometer-size regions on the sample surface. Due to the multiple action of microplasma discharges, a continuous remelted layer with a thickness of up to 20 μm forms on the aluminum surface. The physical, structural, and tribotechnical properties of this layer differ substantially from those before microplasma processing.     

Determination of the electron temperature in microplasma discharges excited on a titanium surface

Results are presented from experimental studies of the emission spectra of microplasma discharges excited on a titanium surface by a pulsed plasma flow. The excited discharges are maintained by current pulses with an amplitude of 200 A and a duration of 20 ms. Analysis of more than 100 spectral lines of titanium atoms and ions in the wavelength range of 350–800 nm shows that the electron temperature of a microplasma discharge is in the range of 0.2–1.3 eV.     

Initiation of microplasma discharges at the edge of a dielectric film deposited on a metal surface

Excitation of microplasma discharges in the interaction of a plasma flow with a metal surface partially covered with a dielectric film is investigated experimentally and theoretically. A new phenomenon—the excitation of microplasma discharges at the boundary between the free metal surface and the area covered with the film—is discovered. Microplasma discharges at the edge of the dielectric film are initiated by a strong electric field that arises between the free metal surface and the outer surface of the film in the interaction with the plasma flow. This field gives rise to surface breakdowns at the film edge, followed by the development of primary microplasma discharges. In turn, the dense plasma of primary microplasma discharges causes secondary microplasma discharges, which also arise at the edge of the dielectric film after the external plasma flow has already terminated. Microplasma discharges gradually evaporate the dielectric film, and the surface cleaned of the film acquires a microrelief due to the local melting and subsequent fast cooling of the metal at the sites of microplasma discharges.     

Propagation of Microplasma Discharge over Titanium Surface Covered with Thin Dielectric Film

Plasma Physics Reports - Propagation and structure of the pulsed microplasma discharge initiated on the titanium sample surface covered with a thin dielectric film with a thickness of approximately...     

Application of microwave discharge for the synthesis of TiB2 and BN nano- and microcrystals in a mixture of Ti-B powders in a nitrogen atmosphere

Synthesis of titanium diboride and boron nitride nano- and microcrystals by means of a pulsed microwave discharge in a mixture of Ti-B powders in a nitrogen atmosphere is considered. For this purpose, a new type of reactor with a free surface of the powder mixture was used. The reactor design permits free expansion of the reaction products into the reactor volume and their deposition on the reactor walls. Conditions for the synthesis of TiB₂ and BN compounds were studied as functions of the energy input in the discharge, the powder component ratio, the rate of the nitrogen flow through the reactor, and the structure and phase composition of the compounds deposited on the reactor walls. The synthesis of boron nitride and titanium diboride in crystal structures is proven. An important role in the process of synthesis is played by the heating of the mixture due to the titanium diboride synthesis reaction, its behavior in the bulk of the reactor, and the titanium concentration in the powder mixture. It is also found that, as the number of discharges in the bulk of the reactor increases, a dust cloud forms. The luminescence of this cloud indicates that the initiated discharge proceeds not only on the powder surface and in the powder bulk, but also in the reactor volume.     

Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis

The high operational and capital costs of polymer electrolyte water electrolysis technology originate from limited catalyst utilization and the use of thick membrane electrolytes. This is due to the coarse surface structure of the state‐of‐the‐art titanium porous transport layer materials used. Therefore, a series of materials with three different microporous layers (MPLs) with advanced interface properties are fabricated and characterized. It is shown that these sintered multilayer structures, made from economically viable titanium powders, have improved interface properties with low surface roughness, as characterized by X‐ray laboratory and synchrotron‐based tomographic microscopy. The transport layer materials provide superior electrochemical performance in comparison to conventional single‐layer structures, with up to three times higher catalyst layer utilization and a ≈60 mV decrease in (anodic) mass transport overpotential at 2 A cm^?2. The MPLs combine preferential surface properties with high open porosity and low tortuosity of sinter materials, enabling for the first time the use of thin membranes, in combination with anodic titanium transport layers. The fundamental mechanism of the MPL effect is elucidated and shown to be based on a homogeneous contact pressure distribution, resulting in high catalyst utilization and low mass transport losses.     

Interactions between cells and titanium surfaces

The interaction between cells and implant materials is determined by the surface structure and/or surface composition of the material. In the past years, titanium and titanium alloys have proved their superiority over other implant materials in many clinical applications. This predominant behaviour is caused by a dense passive oxide layer which forms within milliseconds in oxidizing media. Titanium dioxide layers of 100 nm thickness were produced on the surface of cp-titanium grade 2, and on an experimental alloy of high vanadium content (Ti1.5Al25V) as a harmful control. The layers were produced by thermal and anodic oxidation and by coating by means of the sol-gel process. The resulting oxide layers were characterized with respect of their structure and chemical composition. In cell tests (proliferation, MTT, morphology, actin staining), the reaction of the cells was examined. It was shown that the sol-gel-produced titanium oxide layer is able to shield the cells from toxic alloying elements, with the result that the cell reaction is influenced only by the thin titanium oxide surface layer and not by the composition of the bulk material.     

Improving Osteoblast Response In Vitro by a Nanostructured Thin Film with Titanium Carbide and Titanium Oxides Clustered around Graphitic Carbon

Introduction

Recently, we introduced a new deposition method, based on Ion Plating Plasma Assisted technology, to coat titanium implants with a thin but hard nanostructured layer composed of titanium carbide and titanium oxides, clustered around graphitic carbon. The nanostructured layer has a double effect: protects the bulk titanium against the harsh conditions of biological tissues and in the same time has a stimulating action on osteoblasts.

Results

The aim of this work is to describe the biological effects of this layer on osteoblasts cultured in vitro. We demonstrate that the nanostructured layer causes an overexpression of many early genes correlated to proteins involved in bone turnover and an increase in the number of surface receptors for α3β1 integrin, talin, paxillin. Analyses at single-cell level, by scanning electron microscopy, atomic force microscopy, and single cell force spectroscopy, show how the proliferation, adhesion and spreading of cells cultured on coated titanium samples are higher than on uncoated titanium ones. Finally, the chemistry of the layer induces a better formation of blood clots and a higher number of adhered platelets, compared to the uncoated cases, and these are useful features to improve the speed of implant osseointegration.

Conclusion

In summary, the nanostructured TiC film, due to its physical and chemical properties, can be used to protect the implants and to improve their acceptance by the bone.     

Locally Addressable Electrochemical Patterning Technique (LAEPT) applied to poly(L-lysine)-graft-poly(ethylene glycol) adlayers on titanium and silicon oxide surfaces

The protein-resistant polycationic graft polymer, poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG), was uniformly adsorbed onto a homogenous titanium surface and subsequently subjected to a direct current (dc) voltage. Under the influence of an ascending cathodic and anodic potential, there was a steady and gradual loss of PLL-g-PEG from the conductive titanium surface while no desorption was observed on the insulating silicon oxide substrates. We have implemented this difference in the electrochemical response of PLL-g-PEG on conductive titanium and insulating silicon oxide regions as a biosensing platform for the controlled surface functionalization of the titanium areas while maintaining a protein-resistant background on the silicon oxide regions. A silicon-based substrate was micropatterned into alternating stripes of conductive titanium and insulating silicon oxide with subsequent PLL-g-PEG adsorption onto its surfaces. The surface modified substrate was then subjected to +1800 mV (referenced to the silver electrode). It was observed that the potentiostatic action removed the PLL-g-PEG from the titanium stripes without inducing any polyelectrolyte loss from the silicon oxide regions. Time-of-flight secondary ions mass spectroscopy and fluorescence microscopy qualitatively confirmed the PLL-g-PEG retention on the silicon oxide stripes and its absence on the titanium region. This method, known as "Locally Addressable Electrochemical Patterning Technique" (LAEPT), offers great prospects for biomedical and biosensing applications. In an attempt to elucidate the desorption mechanism of PLL-g-PEG in the presence of an electric field on titanium surface, we have conducted electrochemical impedance spectroscopy experiments on bare titanium substrates. The results showed that electrochemical transformations occurred within the titanium oxide layer; its impedance and polarization resistance were found to decrease steadily upon both cathodic and anodic polarization resulting in the polyelectrolyte desorption from the titanium surface.     

Microwave capillary torch as a means for modifying the electrophysical characteristics of metal surfaces

An experiment layout based on a pulsed capillary microwave torch and making it possible to excite an explosive emission microplasma on a metal surface in open air is implemented for the first time. It is shown that a microrelief in the form of micron-size microcraters forms on the initially smooth surface under the action of microsparks. As a result, the maximum secondary electron emission yield σ_max decreases from ～2 for the untreated surface to ～0.4 for the rough treated surface and remains low for a long time when exposed to atmospheric air.     

Microstructure analysis and wear behavior of titanium cermet femoral head with hard TiC layer

Titanium cermet was successfully synthesized and formed a thin gradient titanium carbide coating on the surface of Ti6Al4V alloy by using a novel sequential carburization under high temperature, while the titanium cermet femoral head was produced. The titanium cermet phase and surface topography were characterized with X-ray diffraction (XRD) and backscattered electron imaging (BSE). And then the wear behavior of titanium cermet femoral head was investigated by using CUMT II artificial joint hip simulator. The surface characterization indicates that carbon effectively diffused into the titanium alloys and formed a hard TiC layer on the Ti6Al4V alloys surface with a micro-porous structure. The artificial hip joint experimental results show that titanium cermet femoral head could not only improve the wear resistance of artificial femoral head, but also decrease the wear of UHMWPE joint cup. In addition, the carburized titanium alloy femoral head could effectively control the UHMWPE debris distribution, and increase the size of UHMWPE debris. All of the results suggest that titanium cermet is a prospective femoral head material in artificial joint.     

Morphology and chemical characterization of Ti surfaces modified for biomedical applications

The aim of the present work is to characterize in detail the chemical composition and morphology of titanium surfaces subjected to various environments. Modifications consisted of exposure of Ti to acidic, alkaline or polymer solutions. Such modifications result in chemical and/or morphological changes in the Ti surface. Special attention has been given to identifying the factors influencing cell adhesion and growth. SEM examinations provided morphological characterization of the Ti samples. Surface analytical techniques such as AES or XPS combined with Ar(+) ion sputtering allowed examination of the chemical properties of the Ti surface after chemical pretreatments and investigating the chemical composition of the Ti oxide layer. Raman spectroscopy investigations allowed determination of the crystalline phases of the Ti-oxide layers and characterization of the dextran-modified surface. The results show large differences in the morphology of Ti pretreated with different procedures whereas only minor differences in the chemistry of the surfaces were found. High-resolution Auger investigations have revealed that all the chemical modifications of Ti surfaces resulted in the formation of a titanium oxide layer. XPS confirmed that TiO(2) is the main component of the chemically modified Ti surface. The Raman spectroscopy investigations showed that the titanium surface with a dextran coating is rich in hydroxyl groups. All the surfaces investigated exhibit a hydrophilic character. The possible influence of various surface features on surface biocompatibility is discussed.     

Inactivation of Escherichia coli Cells in Aqueous Solution by Atmospheric-Pressure N2, He,Air, and O2 Microplasmas

Atmospheric-pressure N₂, He, air, and O₂ microplasma arrays have been used to inactivate Escherichia coli cells suspended in aqueous solution. Measurements show that the efficiency of inactivation of E. coli cells is strongly dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N₂ and He microplasma arrays, air and O₂ microplasma arrays may be utilized to more efficiently kill E. coli cells in aqueous solution. The efficiencies of inactivation of E. coli cells in water can be well described by using the chemical reaction rate model, where reactive oxygen species play a crucial role in the inactivation process. Analysis indicates that plasma-generated reactive species can react with E. coli cells in water by direct or indirect interactions.     

Formation of a strong electric field resulting in the excitation of microplasma discharges at the edge of a dielectric film on a metal in a plasma flow

Results are presented from experimental and analytical studies of the processes resulting in the excitation of microplasma discharges (MPDs) on a metal surface partially covered with a thin dielectric film under the action of an external plasma flow in vacuum. It is shown experimentally that MPDs are excited at the interface between the open metal surface and the region covered by the dielectric film. The probability of MPD excitation is investigated as a function of the thickness of the dielectric film deposited on the metal. It is found that, for a film thickness of 1 μm, the probability of MPD excitation is close to unity. As the film thickness decreases below ~10 nm or increases above ~10 μm, the probability of MPD excitation is reduced by more than two orders of magnitude. A two-dimensional kinetic numerical code is developed that allows one to model the processes of Debye sheath formation and generation of a strong electric field near the edge of a finite-thickness dielectric film on a metal surface in a plasma flow for different configurations of the film edge. It is shown that the maximum value of the tangential component of the electric field is reached at the film edge and amounts to E _max ≈ |φ₀|/2d (where φ₀ < 0 is the electric potential applied to the metal and d is the film thickness), which for typical conditions of experiments on the excitation of MPDs on metal surfaces (φ₀ ≈–400 V, d ≈ 1 μm) yields E _max ≈ 2 MV/cm. The results of kinetic simulations confirm the qualitative idea about the mechanism of the formation of a strong electric field resulting in the excitation of MPDs at the edge of a dielectric film on a metal surface in a plasma flow and agree with experimental data.     

Proteome analysis of the plasma protein layer adsorbed to a rough titanium surface

In this study a label-free proteomic approach was used to investigate the composition of the layer of protein adsorbed to rough titanium (Ti) after exposure to human blood plasma. The influence of the protein layer on the surface free energy (SFE) of the Ti was evaluated by contact angle measurements. Ti discs were incubated with blood plasma for 180?min at 37?°C, and the proteins recovered were subjected to liquid chromatography coupled to tandem mass spectrometry analysis. A total of 129 different peptides were identified and assigned to 25 distinct plasma proteins. The most abundant proteins were fibronectin, serum albumin, apolipoprotein A-I, and fibrinogen, comprising 74.54% of the total spectral counts. Moreover, the protein layer increased the SFE of the Ti (p?<?0.05). The layer adsorbed to the rough Ti surface was composed mainly of proteins related to cell adhesion, molecule transportation, and coagulation processes, creating a polar and hydrophilic interface for subsequent interactions with host cells.     

Resource-Limited Heterotrophic Prokaryote Production and Its Potential Environmental Impact Associated with Mn Nodule Exploitation in the Northeast Equatorial Pacific

Shipboard enrichment incubation experiments were performed to elucidate the limiting resources for heterotrophic prokaryotic production and to discuss the potential impact of bottom water and sediment discharges in relation to manganese (Mn) nodule exploitation on the heterotrophic prokaryotes in the oligotrophic northeast equatorial Pacific. Compared to an unamended control, the production of heterotrophic prokaryotes increased 25-fold in water samples supplemented with amino acids (i.e., organic carbon plus nitrogen), whereas the production increased five and two times, respectively, in samples supplemented with either glucose or ammonium alone. These results indicate that heterotrophic prokaryote production in the northeast equatorial Pacific was co-limited by the availability of dissolved organic carbon and inorganic nitrogen. In samples from the nutrient-depleted surface mixed layer (10-m depth), the addition of a slurry of bottom water and sediment doubled heterotrophic prokaryote production compared to an unamended control, whereas sonicating the slurry prior to addition quadrupled the production rate. However, little difference was observed between an unamended control and slurry-amended samples in the subsurface chlorophyll a (Chl a) maximum (SCM) layer. Thus, the impact of slurry discharge is more significant at the nutrient-depleted surface mixed layer than at the high-nutrient SCM layer. The greatly enhanced prokaryote production resulting from the addition of sonicated slurry further suggests that dissociated organic carbon may directly stimulate heterotrophic prokaryote production in the surface mixed layer. Overall, the results suggest that the surface discharge of bottom water and sediments during manganese nodule exploitation could have a significant environmental impact on the production of heterotrophic prokaryotes that are currently resource limited.     

Building Interfacial Nanostructures by Size-Controlled Chemical Etching

Development of soft chemical processes for the synthesis of interfacial architectures with well-defined structural nano-motifs organized over large areas in two dimensions is an important branch of nanotechnology. The present study deals with the fabrication of gold nanostructures using size-selective chemical etching of continuous gold films on glass support with titanium and chromium adhesive layers. In this process, which is called self-passivated surface etching, a gold film is etched in the presence of citric acid, resulting in gold nanostructures adhering to the metal support. The size-controlled chemical dissolution of gold is driven by a competing reaction between self-organized passivation of surface nano-motifs by citric acid shells and soft etching by a nonoxidative composition containing hydrochloric acid and hydrogen peroxide in water. According to these results, the presence of a chemically stable adhesive layer (titanium), citric acid in solution, and agitation are critical factors to be considered. However, the nature of the adhesive layer is the most influential factor. The following technique presents a simple method for the rapid fabrication of a nanostructured gold substrate that has the ability to support both propagating and localized surface plasmon resonances simultaneously.     

Micromechanical evaluation of mineralized multilayers

The biomechanical stability of osseointegrated implants is of particular importance, especially the stability which is achieved from structural manipulation at the interface between the implant surface and the bone tissues. Nanoscale β-tricalcium phosphate-immobilized titanium was prepared by discharge into a physiological buffered saline solution. Compared with hydroxyapatite, it has been shown to be effective in generating a bone-like chemical structure on the surface by cooperative interaction between osteoblastic cells and the β-tricalcium phosphate. The present study, after cell cultivation, investigates the nanostructures and biomechanical property differences of a mineralized layer formed on two samples of nano-calcium phosphate-immobilized titanium. A scanning probe microscope study revealed that the mineralized tissue formed on the β-tricalcium phosphate samples after 1 week of cell culture showed significantly higher roughness, compared with hydroxyapatite samples. Nanoindentation micromechanical evaluation of the in vitro generated multilayered structures exhibited thicker bone-like mineralized layers on the β-tricalcium phosphate samples. A successful modification of titanium implants through the cooperative interaction between osteoblastic cells and nano β-tricalcium phosphate is anticipated.     

不同处理方法对钛瓷结合强度影响的研究

目的:观察微弧氧化表面处理方法在钛瓷结合方面的作用。方法:将试样分为三组,微弧氧化组,预氧化组,光滑组:对各组钛试件表面进行瓷粉烧结。根据ISO 9693标准,对钛瓷间的三点弯曲结合强度进行测试,并对钛瓷结合界面和瓷剥脱面进行SEM和EDX观察与分析。结果:处理方法不同,钛表面形貌及相结构也不同。钛试样微弧氧化组,预氧化组,光滑组与瓷的结合强度分别是:42.40±4.35Mpa,34.28±2.84Mpa和28.58±2.74Mpa,微弧氧化组的钛瓷结合强度与不进行微弧氧化处理组的钛瓷结合强度相比在统计学上有显著差异(P<0.05);预氧化组的钛瓷结合强度大于光滑组(P<0.05),但明显小于微弧氧化组(P<0.01);未进行微弧氧化处理组的钛瓷界面间可见有明显裂隙;而微弧氧化组的钛瓷界面瓷与钛基体结合紧密,无任何气泡、孔隙存在。结论:钛表面微弧氧化处理后可有效提高钛瓷的结合强度。