Influence Of Surface Modification Research Articles

Influence of Surface Modifications on Dispersion Stability of Zinc Powder

Zinc powders were firstly modified by mechanic-chemistry method using titanate coupling agent,silane coupling agents and sodium dodecylbenzenesulfonate.Their dispersion stabilities were investigated via measuring the height with the sedimentation method.The results showed that different species and concentrations of surface modifier have dramatic effects on the dispersion stability.The dispersion stability of the zinc powder modified by 1.0% titanate coupling agent was significantly improved and close to that of imported zinc powder.

A study of tribological and mechanical properties of PTFE composites filled with surface treated K2Ti6O13 whisker

AbstractK2Ti6O13 whisker was modified with n‐octadecyltrichlorosilane (OTS), fluorosurfactant (FSK), and silane coupling agent (KH‐550), respectively. The surface energy of K2Ti6O13 whisker was calculated based on Van Oss‐Chaudhury‐Good function. Then the influence of surface modification on the tribological and mechanical properties of K2Ti6O13 whisker filled polytetrafluoroethylene (PTFE) composites was studied. Surface energy calculation shows that the surface energy of OTS‐treated K2Ti6O13 whisker is only 29.0 mJ/m2, which is the closest to the value of pure PTFE. Among all samples, the PTFE composite filled with OTS‐treated K2Ti6O13 whisker shows the best antiwear property, tensile strength, and impact strength, which is about 19 to 33%, 15 and 55% higher than that of untreated K2Ti6O13 whisker filled PTFE, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of internal oxidation on wear behavior of ultrafine-grained Nb–Zr

The influence of surface modification by internal oxidation on dry sliding wear behavior of ultrafine-grained (UFG) Nb–Zr was investigated using a pin-on-disc type tribometer. The results show that improvement in strength by grain refinement via equal-channel angular pressing/extrusion has no substantial effect on the wear resistance of the non-oxidized UFG samples as compared to the coarse-grained material. This was attributed to the complex wear mechanisms operating in this alloy, such as adhesion leading to smearing, tribo-chemical reactions resulting in strong oxidative wear and also abrasion bringing about scratches and deep grooves. However, internal oxidation by heat-treatment significantly improved the wear resistance of Nb–Zr, especially under low to medium applied pressures due to the hardened diffusion zone with ZrO2 nanoparticles formed in the subsurface layer. Moreover, the improvement was more pronounced in the UFG material, which is attributed to increased diffusion in the UFG microstructure. When the applied pressure was increased above 0.5MPa, however, the wear rate increased considerably due to the elimination of the hardened subsurface layer. Still, even under high pressures, the oxidized samples demonstrated lower weight loss as compared to non-oxidized samples. Based on the investigations of the worn surfaces, it was determined that internal oxidation mostly eliminates the complex wear mechanisms operational in the non-oxidized samples, especially under low/medium loads. Improvement in wear properties by internal oxidation along with enhanced mechanical properties and previously demonstrated good biocompatibility and superior fatigue performance make internally oxidized UFG NbZr a promising candidate for biomedical applications in the human body.

Influence of various surface treated silica nanoparticles on the electrochemical properties of SiO 2/polyurethane nanocoatings

Various organosilane-treated SiO 2 nanoparticles were dispersed in a 2-pack polyurethane coating. The influence of surface modification and silica content on the electrochemical behaviour of the resultant nanocoatings was investigated. Electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) variations were examined. The surface chemistry of nanoparticles and its effect on the resultant nanocoating morphology were also studied utilising FTIR, and TEM analyses. The results reveal that the presence of more hydrophobic groups and longer-lengthed hydrophobic chains on the surface of nanoparticles, greatly improves the interfacial interactions at the polymer/filler interfaces resulting in a better corrosion performance.

The influence of surface modification on the structure and properties of a calcium carbonate filled poly(ethylene terephthalate)

Calcium carbonate (CaCO 3) nanoparticles were successfully prepared via a carbonization route with polyethylene glycol phosphate 1000 (PGP) as the modifying agent to improve the dispersion and increase the compatibility between nanoparticles and poly(ethylene terephthalate) (PET) matrix. PET/CaCO 3 nanocomposites were prepared by further in situ polymerization with 5 wt.% CaCO 3 nanoparticles. The microstructure and dispersion of CaCO 3 nanoparticles in the nanocomposites were investigated. It was found that well dispersion was obtained up to 5 wt.% of the surface treated CaCO 3 loading for PET/CaCO 3 nanocomposites. Compared to the nanocomposites filled with the blank CaCO 3, a significant improvement in thermal stability and crystallinity properties was observed with the addition of 5 wt.% of the surface treated CaCO 3.

Influence of Surface Modifications on Graphite Surface Properties and their Impact on Anode Performance in Lithium-Ion Batteries

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Wear Resistance Property of AM60 Magnesium Alloy Modified by Plasma Surface Treatment

In this work, an attempt has been made to improve the wear and abrasion properties of AM60 magnesium alloy by surface modification using a self-designed plasma generator as thermal source. The influence of surface modification on the microstructure and wear resistance of melting layer was studied by optical microscope (OP), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and friction experiment, respectively. The results show that microhardness of the surface-melted samples is obviously higher than untreatment sample. The wear resistance has been enhanced by solid solution strengthening and grain refining strengthening.

Influence of Surface Modifications on Interfacial Interaction of Zeolite Filled Polymer Composites

Interfacial interaction in zeolite filled polymer composites was investigated in this study. Two types of polymer which are polypropylene (PP) and ethylene vinyl acetate (EVA) were used as matrix in the preparation of the composites. Moreover, different modifications of zeolite filled polymer composites such as zeolite surface treatment with vinyl silane and alkylammonium and also chemical crosslinking were done to improve the interfacial adhesion between zeolite and polymer matrix. The zeolite filled polymer composites were homogenized using Thermo Haake Polydrive internal mixer and then compression molded into sheets according to standard test specimen. Uniaxial tensile test was performed in order to evaluate the mechanical behavior of the composites. The obtained experimental data for ultimate stress was correlated with Pukanszky theoretical model. The experimental results for all systems of zeolite filled polymer composites showed a good fit to the Pukanszky model. Interfacial interaction for each system of zeolite filled polymer composites was theoretically evaluated by determining the parameter B through this model. The value of parameter B for all zeolite filled polymer composite systems differs significantly from one another thus suggesting the applicability of this Pukanszky model in characterizing the filler-matrix interfacial adhesion.

Cell Growth in a Porous Microcellular Structure: Influence of Surface Modification and Nanostructures

Abstract : This study investigates the growth, morphology and cell viability of bone cells (osteoblasts) inside microcellular graphitic foam having an interconnected porosity. This type of substrate can be useful as a scaffolding material for tissue growth, but has not been adequately investigated. The influence of various surface treatments was studied: an inorganic hydrophilic coating (silica), an organic coating (collagen), and grafting of carbon nanotubes (CNT) have been reported. It is seen that all foams have acceptable biocompatibility. Silica and collagen coatings tend to have more cell growth along pore walls but do not have any significant influence on overall nuclear density or cell viability. On the other hand, nanotube attachment results in simultaneous increase of cell proliferation, density and viability. These results indicate that attaching carbon nanotubes on surfaces of future implants may provide a hierarchical nanostructure with increased biocompatible surface area for improved cell attachment.

Influence of Surface Modification on the Fabrication of Polymer / Hydroxyapatite Bone Composite by means of Biomimetic Process

Influence of Surface Modification on the Fabrication of Polymer / Hydroxyapatite Bone Composite by means of Biomimetic Process

Analysis of Mechanical, Thermal, and Dynamic Mechanical Behaviors of Different Polymer-Coated Sisal Fibers

In this study, the surface of sisal fiber has been modified by coating with different polymers. The influence of surface modification on tensile strength, thermal behavior, storage modulus, and dissipation factors has been determined by using fiber tensile tester, differential scanning calorimetry, and dynamic mechanical analysis. Tensile strengths of uncoated sisal fiber and sisal coated with low-density polyethylene, polystyrene (PS), polyvinyl alcohol, polypropylene, polyester, and araldite epoxy are 593.0, 280, 381, 184.8, 198.3, 273.6, and 104.1 MPa, respectively. In the coated fibers, the maximum tensile strength was found for PS-coated sisal fiber and minimum for epoxy-coated sisal fiber, which is explained based on their fractured microstructures. The storage modulus value of PS-coated sisal fiber determined at 100°C for all frequency was maximum.

Influence of surface modification on the adhesion between Nitinol wire and fluoropolymer films.

One of the current challenges for the medical device industry is how to manufacture and assemble biomedical implants consisting of a metallic wire component and a fluorocarbon film without the use of an adhesive. In an attempt to answer this question, samples of Nitinol wire and fluorinated ethylene-propylene (FEP) film were surface modified by various treatments before being thermally bonded into a composite pull-out strength test specimen and mechanically tested to determine their adhesion strength. The two surface treatments for Nitinol wire included mechanical roughening with sandpaper, and adding a fluorocarbon coating followed by polymerization and curing by a helium plasma treatment. The two surface treatments for FEP film included helium plasma and helium-oxygen plasma under atmospheric conditions. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements were also taken to characterize the appearance and chemistry of the surfaces before and after modification. A unique pull-out strength test method was developed to assess the level of adhesion between these various candidates. The pull-out force for untreated Nitinol bonded to untreated FEP film was 30.5 +/- 2.4 N. Significant improvements of up to 14% in this level of adhesion were obtained with the mechanically roughened Nitinol wire bonded to the helium plasma treated films. However, coating the wire with a liquid fluorocarbon monomer mixture (TG-10) was not successful and after thermal bonding to FEP film the level of adhesion decreased by over 80%. Thus, the bonding strength between the wire and the film can be significantly improved by mechanically roughening the Nitinol wire and treating the FEP film with helium plasma prior to thermal bonding.

In vitro blood compatibility of poly (hydroxybutyrate-co-hydroxyhexanoate) and the influence of surface modification by alkali treatment

In vitro blood compatibility of poly (hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) was evaluated in comparison with poly (L-lactic acid) (PLLA) by a haemolysis assay, in vitro platelet adhesion test and coagulation measurements including plasma recalcification time (PRT), plasma prothrombin time (PT) and kinetic clotting time. The results showed that PHBHHx exhibited better blood compatibility than PLLA. Furthermore, PHBHHx film was modified by NaOH treatment to improve the surface hydrophilic property and the influence of the surface modification on the blood compatibility was investigated. Surface properties including hydrophilic property, surface appearance and functional groups were characterized by water contact angle measurement, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the hydrophilic property of PHBHHx film was obviously improved by the NaOH treatment. It was also shown that the NaOH treatment could significantly enhance the blood compatibility of PHBHHx by prolonging PRT, PT, and kinetic clotting time and decreasing platelet activation. It is thought that the improvement in the hydrophilic property mainly contributes to the enhancement of blood compatibility.

Influence of surface modification and long-term exposure on mechanical creep properties of γ-TiAl G4

An investigation of the corrosion processes were performed for coated and uncoated γ-TiAl G4, an alloy designed to work in the temperature range 750 – 800°C, where oxidation and corrosion phenomena occur. An aluminising pack cementation treatment was used to improve the oxidation resistance of this γ-TiAl G4 alloy. Cyclic corrosion tests were performed at 800°C in air for up to 800 1-hour cycles with a Na2SO4/NaCl mixture. The influence of both aluminisation and the corrosion phenomena on the creep behaviour was investigated. The cyclic corrosion resistance of the coated γ- TiAl G4 was shown to be improved by aluminising. The pack cementation treatment had no detrimental effect on the creep behaviour. Moreover, neither is creep affected by the corrosion of coated specimens. As corroded uncoated specimen exhibited good creep behaviour, it can be concluded that this alloy is suitable, even without coating, for turbine applications in hot corrosion atmospheres at least up to 800°C.

Influence of surface modification on thermal stability and flammability of cross-linked rubbers

The paper discusses the test results of thermal stability and flammability of cross-linked diene rubbers containing silica prepared “in situ” from alkoxysilane precursors. The effect of the surface modification of unfilled vulcanizates by means of aqueous solutions of halogens, boron and organo-phosphoric compounds on their flammability was also assessed. The thermal analysis has been performed in air with the use of derivatography. The flammability of vulcanizates has been determined by the method of oxygen index and in air. It has been found that the modification of the vulcanizates with tetraethoxysilane that makes it possible to form silica “in situ” considerably reduces the flammability of cross-linked rubbers. The surface modification of the vulcanizates with halide and organo-phosphoric compounds allows one to radically decrease their flammability. The boric flame-retardant agents are the most effective modifiers. The most beneficial results were obtained with the use of boric acid.

Influence of Surface Modification with Carboxylic Acids on Performance of Polymer/Titania Photovoltaic Devices

Polymer/titania nanoparticle hybrid bulk heterojunction photovoltaic devices were fabricated, and the influences of nanoparticle content and surface modifiers on the photophysical and photovoltaic properties were investigated by photoluminescence measurements, current–voltage characterization, and intensity-modulated photovoltage spectroscopy. The results revealed that dodecanoic-acid-modified titania yields the best dispersibility in organic solvent and the highest device performance, and that the open-circuit voltage and electron lifetime are strongly dependent on the molecular structure of the modifiers and nanoparticle content. In addition, a longer electron lifetime is accompanied by a higher open-circuit voltage of the device.

Dye sensitized solar cells (DSSCs) based on modified iron phthalocyanine nanostructured TiO 2 electrode and PEDOT:PSS counter electrode

An iron phthalocyanine with tetra-sulphonated substituents (FeTsPc) was used as photosentizer for the development of dye sensitized nanostructured TiO 2 solar cells. The influence of surface modification (TiO 2 film treated with HCl and HNO 3) and thermal annealing of TiO 2 photo-electrode on the performance of dye sensitized solar cell (DSSC) having structure FTO/TiO 2–FeTsPc/electrolyte/PEDOT:PSS (carbon added)/FTO was investigated through the analysis of current–voltage characteristics under illumination and electrochemical impedance spectra (EIS). The improvement in crystallinity of TiO 2, decrease in the internal surface area and adsorbed amount of dye and increase in the lifetime of injected electrons upon thermal annealing of TiO 2 photo-electrode affects the photovoltaic properties of DSSC. The increase in power conversion efficiency of DSSC based on nitric acid treatment for the photo-electrode is mainly attributed to the increase in photocurrent. A comparative photovoltaic investigation of DSSCs using HCl-treated TiO 2 photo-electrode, indicates that the HNO 3-treated photo-electrode retards back electron transfer at the interface with electrolyte and increases the amount of dye.

Ozone sensors based on SnO 2 films modified by SnO 2–Au nanocomposites synthesized by the SILD method

We consider the influence of surface modification by SnO 2–Au nanocomposites on the conductivity response of SnO 2 films to ozone. SnO 2–Au nanocomposites with an Au/Sn ratio ∼1 were synthesized by the Successive Ionic Layer Deposition (SILD) method. The thickness of the Au–SnO 2 nanocomposites deposited on the surface of the SnO 2 films was controlled through a change of the number of deposition cycles. It was established that the indicated modification promotes optimization of sensor parameters. It was shown that sensors with a modified surface had a higher sensitivity to ozone and a shorter recovery time. An explanation of the observed effects is given.

Surface Modification of Nano-Rare Earth on the Tribological and Mechanical Properties of Polytetrafluoroethylene Nanocomposites

In this paper, the surface of nano-lanthanum oxide was modified, and the different surface characteristics of modified nano-lanthanum oxide were analyzed. Meanwhile, the influence of surface modification on the tribological and mechanical properties of polytetrafluoroethylene nanocomposites was investigated. Results indicate that the tribological properties, degradation temperature, notched impact and tensile strength of polytetrafluoroethylene nanocomposites filled with modified nano-lanthanum oxide can be increased simultaneously. A uniform transfer film can be observed on the counterpart surface. Results also show that the smaller the difference of surface energy between filler and matrix is, the higher wear resistance and mechanical properties the polymer nanocomposites will have.

Influence of surface modification and long-term exposure on mechanical creep properties of γ-TiAl G4

An investigation of the corrosion processes were performed for coated and uncoated γ-TiAl G4, an alloy designed to work in the temperature range 750 – 800°C, where oxidation and corrosion phenomena occur. An aluminising pack cementation treatment was used to improve the oxidation resistance of this γ-TiAl G4 alloy. Cyclic corrosion tests were performed at 800°C in air for up to 800 1-hour cycles with a Na2SO4/NaCl mixture. The influence of both aluminisation and the corrosion phenomena on the creep behaviour was investigated. The cyclic corrosion resistance of the coated γ- TiAl G4 was shown to be improved by aluminising. The pack cementation treatment had no detrimental effect on the creep behaviour. Moreover, neither is creep affected by the corrosion of coated specimens. As corroded uncoated specimen exhibited good creep behaviour, it can be concluded that this alloy is suitable, even without coating, for turbine applications in hot corrosion atmospheres at least up to 800°C.