Increase In Surface Free Energy Research Articles

Surface free energy predominates in cell adhesion to hydroxyapatite through wettability

The initial adhesion of cells to biomaterials is critical in the regulation of subsequent cell behaviors. The purpose of this study was to investigate a mechanism through which the surface wettability of biomaterials can be improved and determine the effects of biomaterial surface characteristics on cellular behaviors. We investigated the surface characteristics of various types of hydroxyapatite after sintering in different atmospheres and examined the effects of various surface characteristics on cell adhesion to study cell-biomaterial interactions. Sintering atmosphere affects the polarization capacity of hydroxyapatite by changing hydroxide ion content and grain size. Compared with hydroxyapatite sintered in air, hydroxyapatite sintered in saturated water vapor had a higher polarization capacity that increased surface free energy and improved wettability, which in turn accelerated cell adhesion. We determined the optimal conditions of hydroxyapatite polarization for the improvement of surface wettability and acceleration of cell adhesion.

Improvement and Evaluation of the Interlaminar Bonding Strength of FDM Parts by Atmospheric-Pressure Plasma

Additive Manufacturing has the feature that the on-demand manufacture of the arbitrary shape can be performed. However, as one of weak points, interlaminar bonding strength is low. It is because the building principle is based on lamination. This research aims at improvement in the adhesive strength between laminations by performing hydrophilization treatment to the lamination plane of a FDM parts using atmospheric pressure plasma. Atmospheric-pressure plasma is characterized by generating glow-discharge condition under an atmospheric pressure. It can use for surface treatment etc. using active species (radical ion, an electron, etc.). For example, they are cleaning effects, such as soil removal of an organic substance, an effect to the roughened surface for forming unevenness in the surface, etc. Although a tensile test is usually performed on evaluation of adhesive strength, a lot of hours are needed for experimental preparation. The surface free energy of an object surface is effective as one of the evaluation indices for evaluating the adhesive strength of a lamination plane. However, in order to find an experimental condition in research initial stages, such as material search and manufacturing conditions, it can become effective in respect of an hour and cost to use surface free energy as an evaluation index. In this paper, the effect to the surface free energy by atmospheric pressure plasma is investigated first. And the influence on the rupture strength improvement by atmospheric pressure plasma is investigated. Next, it is searched for the effective irradiation conditions of atmospheric pressure plasma. The influence of the atmospheric pressure plasma to the building parts of FDM was experimented based on surface free energy. The rupture test was done and improvement in rupture stress was confirmed by plasma irradiation. The result that the irradiation range and irradiation distance of an atmospheric-pressure-plasma head had large influence on the increase in surface free energy was obtained. It was observed that surface free energy increases about 75% to an initial sample by irradiation of atmospheric pressure plasma.

Atmospheric-pressure DBD plasma-assisted surface modification of polymethyl methacrylate: A study on cell growth/proliferation and antibacterial properties

This paper reports polymethyl methacrylate (PMMA) surface modification by atmospheric-pressure oxygen dielectric barrier discharge (DBD) plasma to improve its biocompatibility and antibacterial effects. The role of plasma system parameters, such as electrode gap, treatment time and applied voltage, on the surface characteristics and biological responses was studied. The surface characteristics of PMMA films before and after the plasma treatments were analyzed by water contact angle (WCA) goniometry, atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Also, acid–base approach was used for evaluation of surface free energy (SFE) and its components. Stability of plasma treatment or aging effect was examined by repeating water contact angle measurements in a period of 9 days after treatment. Moreover, the antibacterial properties of samples were investigated by bacterial adhesion assay against Escherichia coli. Additionally, all samples were tested for the biocompatibility by cell viability assay of mouse embryonic fibroblast. WCA measurements indicated that the surface wettability of PMMA films was improved by increasing surface free energy via oxygen DBD plasma treatments. AFM measurement revealed that surface roughness was slightly increased after treatments, and ATR-FTIR analysis showed that more polar groups were introduced on the plasma-treated PMMA film surface. The results also demonstrated an enhancement of antibacterial performance of the modified surfaces. Furthermore, it was observed that plasma-treated samples exhibited significantly better biocompatibility, comparing to the pristine one.

Influence of carbon nanotubes coatings onto carbon fiber by oxidative treatments combined with electrophoretic deposition on interfacial properties of carbon fiber composite

To improve the interfacial performance of carbon fiber (CF) and epoxy resin, carbon nanotubes (CNTs) coatings were utilized to achieve this purpose through coating onto CF by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition (EPD) process. The influence of electrophoretically deposited CNTs coatings on the surface properties of CFs were investigated by Fourier transform infrared spectrometer, atomic force microscopy, scanning electron microscopy and dynamic contact angle analysis. The results indicated that the deposition of carbon nanotubes introduced some polar groups to carbon fiber surfaces, enhanced surface roughness and changed surface morphologies of carbon fibers. Surface wettability of carbon fibers may be significantly improved by increasing surface free energy of the fibers due to the deposition of CNTs. The thickness and density of the coatings increases with the introduction of pretreatment of the CF during the EPD process. Short beam shear test was performed to examine the effect of carbon fiber functionalization on mechanical properties of the carbon fiber/epoxy resin composites. The interfacial adhesion of CNTs/CF reinforced epoxy composites showed obvious enhancement of interlaminar shear strength by 60.2% and scanning electron microscope photographs showed that the failure mode of composites was changed after the carbon fibers were coated with CNTs.

The study of air-plasma treatment on corn starch/poly(ε-caprolactone) films

In spite of usefulness of synthetic polymers in every aspects of life, the environmental hazards limit their use. Starch based biodegradable polymers is one of the solutions to it. Packaging has a major share in use of synthetic polymers. For packaging application, it is necessary to have good surface and barrier properties of the material. Plasma surface modification of materials is a promising solution to enhance surface properties. In the present paper, cornstarch/poly(ε-caprolactone) (CSPCL) films were treated in air-plasma for different durations of time. The effect of air-plasma treatment on surface properties and biodegradation was studied. The extent of etching was evaluated from weight change (%) study. Changes in surface chemical composition were analyzed using ATR-FTIR and XPS. The contact angle and surface free energy (SFE) study indicate that air-plasma treatment leads to hydrophilization of CSPCL films. The changes in surface topography of plasma processed films were analyzed using AFM and SEM. The roughness caused by etching and increase in surface free energy facilitates the improvement in adhesive properties like printability and peel strength. Changes in barrier properties were studied using water vapor and oxygen transmission rate. Effect of air-plasma treatment on biodegradation of treated and untreated samples was studied by simulating natural biodegradation conditions in a controlled environment using indoor soil burial method and with a single bacterial system comprising of a commonly occurring soil bacterium, Bacillus subtilis MTCC 121. While the soil system is indicative of biodegradation due to macro as well as micro elements, a single microbial system will identify the interaction between the microorganisms and modified surface thus showing the effect of air-plasma treatment on the degradation process. Biodegradation by indoor soil burial method was assessed by measuring loss in tensile properties and growth of soil micro flora on surface by optical light microscopy (OLM). Biodegradation by B. subtilis was assessed by measuring increase in its number along with the changes it brought about in the sample surface by optical light microscopy and SEM. It was observed that such surface modifications enhanced the biodegradation rate along with finding application in packaging field, thus providing a green solution for the increasing packaging utilization and addressing environmental concerns.

Enhanced lead-free solder wettability of oxidized-nickel by Ar–H2 plasmas for flip chip bumping

Solder wettability (SW) of oxidized-nickel (ON) with liquid lead-free solder (LFS) (96.5Sn–3.5Ag) is notably improved by Ar–H2 plasmas from 0 % wetting of nickel substrate oxidized in air gases at 200 °C for 2 h to 100 % wetting of ON substrate treated by Ar–H2 plasmas at certain plasma settings. The SW of ON substrates with LFS is dependent on the surface characteristics of ON substrates. The enhanced SW of ON substrates with LFS by Ar–H2 plasmas is mostly due to a decrease in polar surface free energy and an increase in dispersive surface free energy on the surfaces of ON substrates. The ratios of the compositions of O to Ni are critical to the SW of ON substrate with LFS. The atomic compositions of Ni and O on ON substrates are analyzed by an energy-dispersive X-ray spectroscope. The nickel oxides NiO and Ni2O3 on the surfaces of ON substrate are identified by an X-ray photoelectron spectroscope.

Hydrophilicity characterization of Al2O3-coated MoS2 particles by using thin layer wicking and sessile drop method

When hydrophobic particles are employed to prepare self-lubricating electroless composite coatings, they usually require surface modification to improve their wettability. The study focuses on the resultant change in wettability of the MoS2 particles with an inorganic coating. Al2O3-coated MoS2 particles were prepared by using a heterogeneous nucleation process. Then, particle surface morphology and structure were examined by using SEM, EDS and XRD. Contact angle measurements were conducted by using a thin layer wicking technique and a sessile drop method in order to determine the surface free energy components of the bare and the coated MoS2 particles. Our results showed the MoS2 particles were successfully coated with an Al2O3 layer, which is an amorphous structure. The decreased water contact angle indicates an enhanced hydrophilicity for the coated particles. This decrease depends more strongly on a significant decrease of a new parameter ratio, γ+/γ−, than on a slight increase in total surface free energy. The surface energy component of the bare MoS2 is very consistent with that of Talc, and that of the Al2O3-coated one is very similar to that of alumina, apart from the base component.

Influence of graphene oxide coatings on carbon fiber by ultrasonically assisted electrophoretic deposition on its composite interfacial property

Graphene oxide coatings were utilized to enhance the interfacial properties of carbon fibers. In this work, a facile route is proposed to prepare graphene oxide/carbon fiber hybrid fiber via ultrasonically assisted electrophoretic deposition (EPD) without complex chemical reactions and long processing time. Surface functional group, surface roughness and surface morphologies of carbon fibers were examined by Fourier transform infrared spectrometer (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Surface free energy of the fiber was characterized by dynamic contact angle analysis (DCAA). The results indicated that the deposition of graphene oxide introduced some polar groups to carbon fiber surfaces and changed the surface morphologies of carbon fibers. Surface wettability of carbon fibers may be significantly improved by increasing surface free energy of the fibers due to the deposition of graphene oxide. Comparing the results with EPD-only, ultrasonically assisted EPD increased the thickness and uniformity of graphene oxide coatings whereas only sparse deposition formed without ultrasonic. Short beam shear test was performed to examine the impact of carbon fiber functionalization on the mechanical properties of the carbon fiber/epoxy resin composites. An improvement of 55% from 36.7 to 56.9MPa in interlaminar shear strength confirms the remarkable improvement in the interfacial adhesion strength of the composites.

Effects of surface treatment of aluminium alloy 1050 on the adhesion and anticorrosion properties of the epoxy coating

The objective of this work is to investigate the effects of zirconium-based (Zr) conversion coating on the adhesion properties and corrosion resistance of an epoxy/polyamide coating applied on the aluminium alloy 1050 (AA1050). Field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectrum (EDS), atomic force microscope (AFM) and contact angle measuring device were employed in order to characterize the surface characteristics of the Zr treated AA1050 samples. The epoxy/polyamide coating was applied on the untreated and Zr treated samples. The epoxy coating adhesion to the aluminium substrate was evaluated by pull-off test before and after 30 days immersion in 3.5% w/w NaCl solution. In addition, the electrochemical impedance spectroscopy (EIS) and salt spray tests were employed to characterize the corrosion protection properties of the epoxy coating applied on the AA1050 samples. Results revealed that the surface treatment of AA1050 by zirconium conversion coating resulted in the increase of surface free energy and surface roughness. The dry and recovery (adhesion strength after 30 days immersion in the 3.5wt% NaCl solution) adhesion strengths of the coatings applied on the Zr treated aluminium samples were greater than untreated sample. In addition, the adhesion loss of the coating applied on the Zr treated aluminium substrate was lower than other samples. Also, the results obtained from EIS and salt spray test clearly revealed that the Zr conversion coating could enhance the corrosion protective performance of the epoxy coating significantly.

Influence of surface treatment of contaminated zirconia on surface free energy and resin cement bonding

Influences of contamination and cleaning methods on the bonding of resin cement to zirconia ceramics were examined. Airborne particle-abraded zirconia (IPS e.max ZirCAD) specimens were contaminated with saliva and cleaned with tap water (SC) or by application of 37% phosphoric acid (PA), Ivoclean (IC), or additional airborne particle abrasion (AB). Specimens without contamination served as controls. After application of Monobond Plus to the surface of the specimens, resin cement was mixed and inserted into a mold. Surface free energies of the specimens were determined by measuring contact angles. Surface treatment and storage conditions significantly influenced bond strength, while there was no significant interaction between the two factors. Surface free energies of the SC and IC groups were significantly lower than those of the other groups. Additional AB of saliva-contaminated zirconia increased the strength of bonding with the resin cement as well as increased surface free energy.

The Application of Radio Frequency Magnetron Sputtering for Fluoropolymer Surface Modification

The paper investigated the properties of the multilayer system: metal with polymer layer modified by radio frequency magnetron sputtering of a solid target made from hydroxyapatite. The material of the polymer layer is thermoplastic copolymer of tetrafluoroethylene with vinylidene fluoride. The roughness parameters of metal, polymer, and hybrid substrates are determined using atomic-force microscope. Calcium phosphate coatings increase the surfaces roughness of polymer and metal materials, thus presenting a stimulating factor for the attachment and proliferation of osteogenic cells. Wettability of the coatings was investigated by the “sit” drop method of the “Krüss Easy Drop” installation by measuring the effective contact angle. The hydrophobic polymer surface becomes hydrophilic after modification and the surface free energy increases.

Multiscale test research on interfacial adhesion property of cold mix asphalt

In order to establish proper evaluation methods and indicators for cold mix asphalt (CMA), various scales test methods were used to study the interfacial behavior between asphalt binder and aggregate. The surface free energy of asphalt binder was tested using sessile drop method, and the surface free energy of aggregate was measured using column wicking method. The adhesion work between asphalt and aggregate, moisture damage resistance indices were calculated using the basic surface free energy components. Macro mechanical adhesion property between asphalt binder and aggregate in two conditions (dry and damp) were obtained through the pull-off test. A freeze–thaw splitting test was conducted to verify the effectiveness of energy indices. The results show that diluents and additives used in cold mix asphalt can increase surface free energy of pure asphalt. Limestone has the largest surface free energy, and the largest adhesion work to asphalt in dry condition. Cohesion failure usually occurs in dry condition, while adhesion failure corresponds to damp condition. There are strong correlations between macro mechanical evaluation indicators and surface free energy calculated indices, which indicates that energy indices are a good method to quantize the moisture damage resistance of CMA. Limestone is generally better at resisting moisture damage than granite and basalt.

Wplyw wyladowan koronowych na wybrane wlasciwosci warstwy wierzchniej polilaktydu przeznaczonego do autokatalitycznego metalizowania

The effect of the modification of poly(lactic acid) (PLA) surface layer using corona treatment in air or nitrogen was evaluated by determination of oxidation degree, contact angle measurements and surface free energy calculations. It was found that as a result of corona discharge the degree of PLA sur- face layer oxidation increases independently of the applied unit activation energy E j as well as the type of atmosphere used. However, the degree of nitriding of the samples modified under nitrogen increases with an increase of E j value and is higher than for the samples modified in air. It was also found that coro- na discharges in both air and nitrogen atmospheres result in the changes in contact angle values of water and diiodomethane on PLA surface layer as well as an increase of surface free energy.

Spherulite growth rate and fold surface free energy of the form II mesophase in isotactic polybutene-1 and random butene-1/ethylene copolymers

The spherulite growth rate of isotactic polybutene-1 and random butene-1/ethylene copolymers has been measured in a wide range of temperatures between the glass transition and the melting temperature. The presence of ethylene co-units in the butene-1 chain leads to a distinct decrease of both the maximum spherulite growth rate and the temperature of fastest growth. The data were analyzed within the frame of the Hoffman–Lauritzen theory of crystallization to obtain form II mesophase surface free energies. The robust performed analysis revealed that the form II mesophase fold surface free energy in random copolymers of butene-1 with less than 5 mol% ethylene is 50–100 % higher than in the homopolymer. It is suggested that the increase of the fold surface free energy is related to the exclusion of ethylene chain defects from crystallization and their accumulation at the basal planes of the form II mesophase.

Photocatalytic antibacterial activity of TiO2–SiO2 thin films: The effect of composition on cell adhesion and antibacterial activity

• The effect of composition of TiO 2 –SiO 2 thin films on cell adhesion was studied. • The effect of surface composition on surface free energy was studied. • SiO 2 addition favors for cell adhesion. • Strong relation was found between the bacterial adhesion and antibacterial activity. Colloidal solutions of SiO 2 –TiO 2 mixed oxides having different SiO 2 contents were synthesized by sol–gel technique and thin films were deposited over glass slides by using dip coating technique. The samples were characterized by XRD, SEM, AFM and methylene blue adsorption methods. The surface free energy of thin films was measured by sessile drop method by using diiodomethane, glycerol and water as probe liquids. The photocatalytic antibacterial activity of the samples was determined for Escherichia coli XL1-blue by using artificial solar irradiation. The surface characterization studies revealed the presence of small crystallites of anatase phase, enhanced dispersion of TiO 2 particles and increasing surface free energy at elevated SiO 2 content. Highest photocatalytic antibacterial activity was obtained over 92 wt% SiO 2 containing sample and strong correlation was found between the bacterial adhesion and antibacterial activity. Surface-adhered E. coli cells having direct contact with TiO 2 particles were inactivated at a higher rate than suspended cells.

Anin vitroinvestigation of bacteria-osteoblast competition on oxygen plasma-modified PEEK

Polyetheretherketone (PEEK) films were oxygen plasma treated to increase surface free energy and characterized by X-ray photoelectron microscopy, atomic force microscopy, and water contact angles. A parallel plate flow chamber was used to measure Staphylococcus epidermidis, Staphylococcus aureus, and U-2 OS osteosarcomal cell-line adhesion to the PEEK films in separate monocultures. In addition, bacteria and U-2 OS cells were cocultured to model competition between osteoblasts and contaminating bacteria for the test surfaces. Plasma treatment of the surfaces increased surface oxygen content and decreased the hydrophobicity of the materials, but did not lead to a significant difference in bacterial or U-2 OS cell adhesion in the monocultures. In the S. epidermidis coculture experiments, the U-2 OS cells adhered in greater numbers on the treated surfaces compared to the untreated PEEK and spread to a similar extent. However, in the presence of S. aureus, cell death of the U-2 OS occurred within 10 h on all surfaces. The results of this study suggest that oxygen plasma treatment of PEEK may maintain the ability of osteoblast-like cells to adhere and spread, even in the presence of S. epidermidis contamination, without increasing the risk of preoperative bacterial adhesion. Therefore, oxygen plasma-treated PEEK remains a promising method to improve implant surface free energy for osseointegration.

Wetting of carbon nanotube functionalised nylon and its usage as flexible electrode in electrowetting on dielectric

The nylons functionalised with single walled carbon nanotubes (SWCNTs) at pH 2.5 and 3.5 display the time dependence of the water droplet contact angle, which is attributed to the adsorption of water molecules onto the nylon–water contact surface and the consequent increase in surface free energy. The contact angle of nylons functionalised at pH 4.5, 6.5 and 8.0 varies marginally with contact time, presumably owing to the presence of a large amount of SWCNTs on the nylon surface. Using the obtained nylon as a flexible electrode, an electrowetting on a dielectric system is designed. The contact angle decreases with the increase of the applied voltage and the electrowetting response is sensitive to the surface free energy of the water droplet. A low surface free energy is preferable for actuating the movement of the water droplet at a low-driving voltage.

폴리카보네이트 필름 표면 처리가 증착 SiOx베리어층 접착에 미치는 영향

폴리카보네이트(PC) 필름을 유연기판으로 사용하기 위해서는 <TEX>$SiO_x$</TEX> 증착에 의한 베리어 특성 개선이 필요하며 이때 베리어 층과 PC 계면 접착력이 매우 중요하다. 본 연구에서는 언더 코팅, UV/<TEX>$O_3$</TEX> 및 저온 플라즈마와 같은 다양한 표면 처리 방법에 의하여 PC 필름 표면을 개질하여 표면의 물리적 화학적 변화가 증착된 베리어 층 계면 접착력에 미치는 영향을 살펴보았다. 표면 처리 전의 PC 필름은 표면 거칠기 및 표면 에너지가 매우 낮아 <TEX>$SiO_x$</TEX> 베리어 층과의 접착력이 현저히 떨어짐을 알 수 있었다. PC 필름을 저온 플라즈마로 표면 처리한 결과, 표면의 거칠기 증가와 극성 관능기 생성에 의하여 극성 표면 에너지가 향상되는 반면 UV/<TEX>$O_3$</TEX> 처리의 경우, 표면 거칠기 변화 없이 표면에 생성된 극성 관능기에 의해 극성 표면 에너지가 증가됨을 알 수 있었다. 이러한 표면의 변화는 베리어층과 PC 기판의 계면 접착력 증가에 기여함을 알 수 있었다. 표면 처리 방법으로 언더 코팅을 사용하는 경우 표면에 에너지를 가하지 않아도 코팅제의 아크릴산과 <TEX>$SiO_x$</TEX>의 접착력 향상에 의하여 PC 필름과의 계면 접착력이 증가되며 유무기 하이브리드 다층 구조에 의한 베리어 특성 개선이 함께 일어남을 알 수 있었다. The interfacial adhesion strength is very important in <TEX>$SiO_x$</TEX> deposited PC film for the barrier enhanced polycarbonate (PC) flexible substrate. In this study, PC films were treated by undercoating, UV/<TEX>$O_3$</TEX> and low temperature plasma and then the effect of physical and chemical surface modifications on the interfacial adhesion strength between PC film and <TEX>$SiO_x$</TEX> barrier layer were studied. It was found that untreated PC film shows significantly low interfacial adhesion strength due to the smooth surface and low surface free energy of PC. Low temperature plasma treatments resulted in the increase of both surface roughness and surface free energy due to etching and the appearance of polar molecules on the PC surface. However, UV/<TEX>$O_3$</TEX> treatment only shows the increase of surface free energy by developed polar molecules on the surface. These surface modifications caused the enhancement of surface interfacial strength between PC film and <TEX>$SiO_x$</TEX> barrier. In the case of undercoating, it was found that the increase of surface interfacial strength was achieved by adhesion between various acrylic acid on acrylate coated surface and <TEX>$SiO_x$</TEX> without increase of polar surface energy. In addition, the barrier property is also improved by organic-inorganic hybrid multilayer structure.

Investigation of plasma-induced thermal, structural and wettability changes on low density polyethylene powder

We demonstrate here the structural, thermal, and wettability characteristics of low density polyethylene powder before and after plasma treatments. The plasma treatment was carried out using different working gas i.e. air, oxygen and a mixture of hydrogen and oxygen at an atmospheric pressure of 100 Pa. The plasma treatment time was kept constant at 2 min for all the specimens. Fourier transform infrared (FTIR), dynamic capillary rising using Washburn method, differential scanning calorimetry (DSC), and thermogravimetric analysis has been carried out for both pristine and plasma treated polyethylene specimens. Our study shows that there is 88% increase in the wettability after plasma treatments. Plasma treatment in air atmosphere gives the maximum wettability. Thermogravimetric analysis (TGA) investigation shows plasma treatment in the H2 + O2 mixture atmosphere gives maximum thermal stability whereas the DSC results reveal the lowest crystallinity for plasma treatment in air atmosphere. The lowest latent heat of fusion (154 J/g) calculated from the melting curve of DSC is observed for LDPE treated in air atmosphere. The FTIR spectroscopy of the plasma-treated LDPE powder reveals that plasma treatment introduces polar group on the LDPE surface leading to the increased surface free energy and surface active sites. The CH2 concentration increases after plasma treatments.

Tensile strength, oxidation resistance and wettability of carbon fibers coated with a TiC layer using a molten salt method

Titanium carbide (TiC) coating were synthesized on Polyacrylonitrile (PAN)-based carbon fibers by a molten salt method using the molten salt mixture composed of LiCl, KCl and KF as a reaction medium. The surface morphology, tensile strength and oxidation resistance of the uncoated and TiC-coated carbon fibers were investigated. The wettability of these fibers by molten magnesium (Mg) and aluminum (Al) was also examined. TiC coatings obtained have a thickness of approximately 0.05–0.6μm and are found to be uniform and adherent to the carbon fibers. After being coated with a uniform and continuous TiC layer, the tensile strength of the carbon fibers decreases and their oxidation resistance is improved significantly. An increase in the TiC coating thickness leads to the reduction in the tensile strength of the carbon fibers and the improvement of their oxidation resistance. The oxidation activation energy of the carbon fibers increases from 127 to 170kJ/mol after being coated with a 124nm thick layer of TiC. Coating of carbon fibers with TiC also induces an increase in the total surface free energy of the carbon fibers, and as a result the wettability of carbon fibers with molten Mg and Al is improved remarkably. TiC coating is found to be stable at 1000°C in molten Mg. However it is readily decomposed by the molten Al at high temperature, which brings about carbon fibers being attacked by the molten Al and the consequent severe damage of carbon fibers.