Way For Surface Modification Research Articles

Surface modification of NiTi alloy via a TiN coating functionalized with biomimic multilayer films

In this study, dextran sulfate (DS)/chitosan (CHI) multilayer films were fabricated on TiN-coated NiTi alloy to reduce Ni ion release and improve biocompatibility. The successful formation of TiN coating and DS/CHI multilayer films was demonstrated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Inductively coupled plasma mass spectrometry (ICP-MS) test showed that the Ni ion release from NiTi alloy significantly decreased after surface modification. Cytocompatibility including osteoblasts adhesion and differentiation function was evaluated in vitro. The results suggest that this surface modification process is beneficial for osteoblasts growth on NiTi alloy substrate. The approach presented here provides an attractive way for surface modification of NiTi alloy to meet the requirements of biomedical applications.

Synthesis and characterization of platinum supported on surface-modified ordered mesoporous carbons by self-assembly and their electrocatalytic performance towards oxygen reduction reaction

Abstract Ordered mesoporous carbons (OMCs) were fabricated by an organic–organic self-assembly process. Surface-modified OMCs were also prepared via the conventional acid-oxidation, H2O2 oxidation and 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (AEPTMS) grafted routes. Pt nanoparticles (NPs) supported on OMC (Pt/OMC) and modified OMC (Pt/OMC-H2SO4, Pt/OMC-H2O2 and Pt/OMC-AEPTMS) were synthesized and characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), transmission electron microscopy (TEM) analysis. It was found that acid-oxidation (H2SO4/HNO3) method led to formation of a much wider Pt distribution with mean particle size of 6.8 nm. Unlike Pt/OMC-H2SO4 samples, Pt NPs (ca. 2.0 nm) were supported uniformly on AEPTMS-modified OMC with low electrical conductivity. Among three surface-modified methods, the H2O2 treatment method was an easily controllable way for surface modification of OMC which possesses desirable electrical conductivity, well-dispersed and nanosized Pt (ca. 3 nm). Accordingly, the Pt/OMC-H2O2 samples were observed to have superior electrocatalytic activity for oxygen reduction reaction as compared to synthesized Pt/OMC, Pt/OMC-H2SO4, Pt/OMC-AEPTMS and the commercial electrocatalysts (Pt supported on XC-72).

Al2O3–ZrO2 ceramic coatings fabricated on WE43 magnesium alloy by cathodic plasma electrolytic deposition

Al2O3–ZrO2 ceramic coatings were successfully prepared on WE43 magnesium alloy by cathodic plasma electrolytic deposition (CPED) technique. Surface morphology, elemental and phase composition of the coatings were investigated by scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). Furthermore, the electrochemical corrosion behavior of the coated magnesium alloy in simulated body fluids was evaluated. The results showed that the ceramic coatings were composed of t-ZrO2, α-Al2O3 and γ-Al2O3 phases with rough and coarse surfaces. The potentiodynamic polarization test indicated that corrosion resistance of WE43 magnesium alloy was significantly improved by CPED treatment. The approach presented here should be an attractive way for surface modification of Mg and its alloys.

Surface modification of a commercial thin film composite polyamide reverse osmosis membrane by carbodiimide-induced grafting with poly(ethylene glycol) derivatives

Based on the existing carboxylic acid groups on surface of used commercial thin film composite polyamide reverse osmosis membrane, two kinds of poly(ethylene glycol) derivatives with different chains were grafted by carbodiimide-induced method to improve the antifouling property. The membranes before and after modification were characterized by attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and static contact angle measurement. Moreover, the water flux, NaCl rejection and fouling experiments were also conducted. The changes of chemical composition and morphology on membrane surfaces indicated the successful grafting of poly(ethylene glycol) derivatives. Compared to unmodified membrane, the modified membranes were more resistant to fouling in protein and cationic surfactant feeding solutions. The method in this study provided a new way for surface modification of commercial polyamide reverse osmosis membranes.

Computerized design of advanced straight and skew bevel gears produced by precision forging

The computerized design of advanced straight and skew bevel gears produced by precision forging is proposed. Modifications of the tooth surfaces of one of the members of the gear set are proposed in order to localize the bearing contact and predesign a favorable function of transmission errors. The proposed modifications of the tooth surfaces will be computed by using a modified imaginary crown-gear and applied in manufacturing through the use of the proper die geometry. The geometry of the die is obtained for each member of the gear set from their theoretical geometry obtained considering its generation by the corresponding imaginary crown-gear. Two types of surface modification, whole and partial crowning, are investigated in order to get the more effective way of surface modification of skew and straight bevel gears. A favorable function of transmission errors is predesigned to allow low levels of noise and vibration of the gear drive. Numerical examples of design of both skew and straight bevel gear drives are included to illustrate the advantages of the proposed geometry.

Cathodic immobilization of tertiary C―H moieties onto glassy carbon via secondary alkyl halides. A versatile way for surface modification

The complex structure of glassy carbon is exploited by means of its powerful reacting abilities under cathodic charge in aprotic solvents at quite negative potentials. Under polarization, the preliminary stage corresponds to the formation of nucleophilic centers (by reduction of graphitized and/or fullerenized) dispersed at (or in the vicinity of) the surface of such polarized materials. In the presence of electrophilic organic species such as organic halides, surface modification(s) may be obtained. These processes are expected to correspond to nucleophilic substitution (SN). While primary alkyl halides were reported to be easily fixed onto carbon in common polar aprotic solvents, secondary (and tertiary) alkyl halides were noticed to be not reactive under such conditions. Contrariwise, aprotic solvents with high dielectric constant (like propylene carbonate) permit to boost the interfacial reactivity of those halides. Thus, secondary bromides and iodides lead to compact deposits possessing tertiary protons identified by a two-electron oxidation step at about +1.2V vs. Ag/AgCl. Specifically, 2-bromoadamantane yields an organic layer assigned to grafted 2-adamantyl moiety. The chemical versatility of such deposits is presented.

Direct Bonding between Silicone and Glass by Atmospheric-Pressure Surface Modification

We experimentally demonstrated the differences of surface modification effects on silicon-based polymer of soft-type silicone-rubber and hard-type silicone-resin in contact angle and bonding strength by exposure of oxygen plasma, atmospheric pressure plasma, and vacuum-ultraviolet light, in order to investigate the availability of non-vacuum process of atmospheric plasma and vacuum-ultraviolet light for high-throughput surface modifications and bonding. We also propose the use of a hard silicone-resin for Micro Electro Mechanical Systems (MEMS) and Micro-Total Analysis Systems (μ-TAS) material to overcome drawbacks of silicone-rubber, such as easy deformation and destruction of micro / nano structures caused by its softness. As a result, any modification method successfully modified the surface of both silicone-rubber and silicone-resin up to about 10° in contact angle, and bonded to glass. However, the bonding strength between silicone-resin and glass by vacuum ultraviolet light was one order of magnitude smaller than that by oxygen plasma and atmospheric plasma bonding. The results suggest that atmospheric plasma satisfies both high-speed non-vacuum process and high-efficient way for surface modification and the following bonding.

The surface parameters modifications at nano scale for biomedical applications

Functional coatings deposition is an effective way of surface modification with direct control of stoichiometry, impurity elements, functional groups and surface charges. Modified surface properties such as composition, roughness, wettability have effect on the most important processes at biomaterial interface. The aim of present study was the analysis of surface roughness and surface free energy parameters of oxide Al2O3 and Ta2O5 coatings and the possibility to separate the influence of such factors on the regularities and mechanisms of nano materials interactions with the biological objects.

The Compound Tribological Properties of Nano-Ceramic Lubricating Additives and Ni-W-P Alloy Coating

The major solving ways for the material wear are surface modification and lubrication. However, the application of only one solution can not achieve desirable effect. Ni–W–P alloy coating has high hardness and high wear resistance, and is an effect way of surface modification on the 45 steel. In the friction process, the nano ceramic lubricating additives deposited on the friction surface of Ni-W-P alloy coating so as to form a protective lubricating film, therefore realizing in-situ repair on the friction surface during operation. The nano ceramic particles achieve the antiwear and friction reducing effects by the micro polishing effect, the filling and repairing effects, ball bearing effect, multiphase microcrystal effect. Experiment results confirm that Ni-W-P alloy coating and nano ceramic lubricating additive have excellent synergistic effect, and form double protection for the metal substrate, e.g., the wear resistance of Ni-W-P alloy coating (with heat treatment and the oil with nano ceramic additives) has increased hundreds times than 45 steel as the metal substrate with basic oil, zero wear is achieved，which break through the bottleneck of previous separate research of the above-mentioned the two.

Influence of a new surface modification of intraocular lenses with fluoroalkylsilan on the adherence of endophthalmitis-causing bacteria in vitro

Dynasilan is a fluoroalkylsilan that is able to interact with surface active centres on intraocular lenses (IOL), offering a new way for surface modification of different IOL materials. The purpose of this in vitro study was to investigate the influence of this new surface modification on the adherence of two typical endophthalmitis causing bacteria (Staphylococcus epidermidis, Propionibacterium acnes). In a pilot experiment, the effect of Dynasilan coating on the adherence of S. epidermidis was tested on glass slides. Forty-two Dynasilan-modified and 42 unmodified IOL (14 PMMA, 14 silicone and 14 hydrogel) were incubated at 37 degrees C in brain heart infusion broth (10(8) CFU/ml) with either S. epidermidis for 24 h or with P. acnes for 1 h. Subsequently, the adherent bacteria were resuspended using ultrasonification at 35 kHz for 3x45 s. After dilution series and incubation at 37 degrees C on Petri dishes for 24 h and 3 days, respectively, the colonies were counted. In the pilot experiment, a markedly lower number of adherent S. epidermidis was observed on Dynasilan-modified glass slides. Of all IOL materials incubated with S. epidermidis, those modified with Dynasilan showed a lower mean number of adherent bacteria (mean 1.37x10(7); SD 2.37x10(7)) than those untreated (2.43x10(7); SD 3.04x10(7)). IOLs incubated with P. acnes showed a significantly lower mean number of adherent bacteria of 2.51x10(4) (SD 2.71x10(4)) on Dynasilan-modified IOLs versus 6.27x10(4) (SD 7.70x10(4)) on untreated IOLs. The presented in vitro results indicate that Dynasilan surface modification is able to reduce the adherence of S. epidermidis and P. acnes on all IOL materials tested. Further studies regarding the stability of this modification and its biocompatibility must be performed.

Graft Polymerization of Vinyl Monomers onto Nanosized Silicon Carbide Particles

For the purpose of preparing polymer composites filled with SiC nanoparticles to be used in tribological applications, grafting polymerization onto the particles was carried out as a way of surface modification. It is believed that the interfacial interaction in the composites can be tailored in this way. The SiC surface was pre-treated with a silane coupling agent, followed by radical grafting polymerization of acrylamide and styrene, respectively. Infrared spectroscopy and measurement of dispersiveness in solvent demonstrate that the desired polymer chains have been covalently bonded to the surface of the nanoparticles. In addition, the polymerization conditions were investigated and the controlling factors were established accordingly.