Changes In Surface Characteristics Research Articles

무전해 니켈도금된 다중벽 탄소나노튜브의 첨가가 알루미나강화 에폭시 복합재료의 열전도도 및 파괴인성에 미치는 영향

본 연구에서는 무전해 니켈도금에 따른 탄소나노튜브의 표면특성변화가 알루미나강화 에폭시 복합재료의 열전도도 및 파괴인성에 미치는 영향에 대하여 살펴보았다. 무전해 니켈도금된 탄소나노튜브의 표면특성은 주사전자현미경(SEM), X-선 광전자분광기(XPS), X-선 회절분석(XRD)을 통하여 알아보았다. 열전도도는 열전도율 측정 시스템으로 측정하였고, 파괴인성은 만능시험기(UTM)를 이용한 임계응력세기인자(<TEX>$K_{IC}$</TEX>)를 측정하여 분석하였다. 실험결과, 무전해 니켈도금은 탄소나노튜브의 표면특성의 변화를 가져오며, 니켈도금된 MWCNTs(Ni-MWCNTs)가 들어있는 경우 미처리 MWCNTs와 비교하여 우수한 열전도도 및 파괴인성을 보였다. 이는 Ni-MWCNTs와 에폭시수지와의 분자간 상호작용의 향상 때문이라 판단된다. In this work, the effect of electroless Ni-plating of multi-walled carbon nanotubes (MWCNTs) on thermal conductivity and fracture toughness properties of MWCNTs/<TEX>$Al_2O_3$</TEX>/epoxy composites was investigated. The surface properties of the Ni-plated MWCNTs were determined by scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD) analyses. Thermal conductivity was tested using a thermal conductivity measuring system. The fracture toughness of the composites was carried out through the critical stress intensity factor (<TEX>$K_{IC}$</TEX>) measurement. As a result, the electroless Ni-plated MWCNTs led to a significant change of surface characteristics of the MWCNTs. Thermal conductivity and fracture toughness of the MWCNTs/<TEX>$Al_2O_3$</TEX>/epoxy composites were greater than those of non-treated ones. These results were probably due to the improvement of intermolecular interaction between the Ni-MWCNTs and the matrix resins.

Surface modification of a commercial thin-film composite polyamide reverse osmosis membrane through graft polymerization of N-isopropylacrylamide followed by acrylic acid

Surface modifications including physical and chemical treatments are effective approaches to improve the fouling and chlorine resistances of the commercial thin-film composite (TFC) aromatic polyamide reverse osmosis (RO) membranes. However, the major problem facing the modification is the influence on membrane performance. In this study, surface modification of a commercial TFC RO membrane was performed through redox initiated graft polymerization of N-isopropylacrylamide (NIPAm) followed by acrylic acid (AA) and the modified membrane showed improved membrane properties. Membrane characterization was conducted through ATR-FTIR analysis, zeta-potential analysis, contact angle measurement and cross-flow permeation test. Changes in surface characteristics confirmed the graft polymerizations of NIPAm and AA. The surface of the membrane became more hydrophilic and negatively charged after modification. The membrane modified under certain conditions showed both increased water flux and salt rejection. Fouling experiments with bovine serum albumin (BSA) aqueous solution demonstrated that the modification could mitigate the deposition of foulants on the membrane surface through enhancing electrostatic repulsion and lowering hydrophobic interaction between BSA molecules and membrane surface and thereby improving fouling resistance. Furthermore, chlorination tests also showed that surface modification through graft polymerization of NIPAm followed by AA could effectively enhance the chlorine stability of the polyamide membrane.

Change of Surface and Electrical Characteristics of Silicon Wafer by Wet Etching(1) - Surface Morphology Changes as a Function of HF Concentration -

The electrical properties and surface morphology changes of a silicon wafer as a function of the HF concentration as the wafer is etched were studied. The HF concentrations were 28, 30, 32, 34, and 36 wt%. The surface morphology changes of the silicon wafer were measured by an SEM (<TEX>$80^{\circ}$</TEX> tilted at <TEX>${\times}200$</TEX>) and the resistivity was measured by assessing the surface resistance using a four-point probe method. The etching rate increased as the HF concentration increased. The maximum etching rate 27.31 <TEX>${\mu}m/min$</TEX> was achieved at an HF concentration of 36 wt%. A concave wave formed on the wafer after the wet etching process. The size of the wave was largest and the resistivity reached 7.54 <TEX>$ohm{\cdot}cm$</TEX> at an 30 wt% of HF concentration. At an HF concentration of 30 wt%, therefore, a silicon wafer should have good joining strength with a metal backing as well as good electrical properties.

Change of Surface and Electrical Characteristics of Silicon Wafer by Wet Etching(2) - Relationship between Surface Roughness and Electrical Properties -

The relationship the between electrical properties and surface roughness (Ra) of a wet-etched silicon wafer were studied. Ra was measured by an alpha-step process and atomic force microscopy (AFM) while varying the measuring range <TEX>$10{\times}10$</TEX>, <TEX>$40{\times}40$</TEX>, and <TEX>$1000{\times}1000{\mu}m$</TEX>. The resistivity was measured by assessing the surface resistance using a four-point probe method. The relationship between the resistivity and Ra was explained in terms of the surface roughness. The minimum error value between the experimental and theoretical resistivities was 4.23% when the Ra was in a range of <TEX>$10{\times}10{\mu}m$</TEX> according to AFM measurement. The maximum error value was 14.09% when the Ra was in a range of <TEX>$40{\times}40{\mu}m$</TEX> according to AFM measurement. Thus, the resistivity could be estimated when the Ra was in a narrow range.

Surface pattern recording in Sb2Se3 thin films

Results on the modification of Sb2Se3 thin film surface topology by irradiation followed by wet-etching are given. Comparison of study results revealed the possible role of purely electronic and thermal processes in the relief formation. The latter is supposed to be connected with radiation-induced defect creation, free volume increase under the increased fluidity conditions as well as with the possible additional influence of electrostatic forces and stress. Changes in surface characteristics are presented and potential applications of this treatment are discussed.

Chemical modulation of crystalline state of calcium oxalate with nickel ions

BackgroundWe explored that the presence of nickel ions in the precipitation medium affected size, shape and crystalline phase of the precipitated particles of calcium oxalate, whereas the applied synthesis conditions strongly influenced their uniformity. MethodsAqueous solutions of oxalic acid and calcium chloride, containing varying amounts of nickel sulfate, were mixed at room temperature and allowed to sonicate for various periods of time. The obtained particles were characterized by SEM, XRD, TG/DTA, and FTIR. ResultsResults revealed that particle morphology of calcium oxalate and their hydration states were dependent upon the chemical composition of the reactant solutions. For instance, the particles precipitated out in the form of dihydrate and having prismatic, and discs shaped particle morphology, when nickel ions were introduced in the starting reactant solution in different amounts. In contrast, the calcium oxalate particles precipitated under identical conditions in the absence of nickel ions were in the form of flakes with corrugated edges. Obvious variations were also found in the XRD patterns and crystallite size of these three solids. Heat treatment produced changes in the surface morphology of these particles due to loss of material and converted them calcium oxide. ConclusionsGentle mixing of aqueous solutions of calcium chloride and oxalic acid in the absence and presence of nickel ions produced precipitated particles of calcium oxalate. Chemical composition of the reactant solutions and their order of mixing were found to be the key parameters in controlling the particle morphology and their hydration/crystalline state. Heat treatment at the elevated temperature transformed the as-prepared calcium oxalate to calcium oxide with visible changes in surface features of the particles.

Behavior of HPC with Fly Ash after Elevated Temperature

For use in fire resistance calculations, the relevant thermal properties of high-performance concrete (HPC) with fly ash were determined through an experimental study. These properties included compressive strength, cubic compressive strength, cleavage strength, flexural strength, and the ultrasonic velocity at various temperatures (20, 100, 200, 300, 400 and 500∘C) for high-performance concrete. The effect of temperature on compressive strength, cubic compressive strength, cleavage strength, flexural strength, and the ultrasonic velocity of the high-performance concrete with fly ash was discussed according to the experimental results. The change of surface characteristics with the temperature was observed. It can serve as a reference for the maintenance, design, and the life prediction of high-performance concrete engineering, such as high-rise building, subjected to elevated temperatures.

Study on the Mechanism of Adhesion Improvement Using Dry-Ice Blasting for Plasma-Sprayed Al2O3 Coatings

The mechanisms of adhesion improvement of plasma-sprayed Al2O3 coatings using dry-ice blasting were investigated. In this study, the change of substrate surface characteristics in both the topography and the wettability due to the treatment of dry-ice blasting was mainly studied. The effect of dry-ice blasting on Al2O3 splat morphology with different treatment durations was also examined. The residual stress of plasma-sprayed Al2O3 coatings using dry-ice blasting was measured by curvature method and compared to that of coatings deposited with conventional air cooling. Based on these numerous assessment tests, it could be concluded that the adhesion improvement of Al2O3 coatings could be attributed to the cleaning effect of dry-ice blasting on different organic substances adsorbed on the substrates and the peening effect.

Evidence for flash floods over deserts from loss of coherence in InSAR imagery

Flash floods in complex terrain play an important role for sediment transport in arid regions and thus potentially for dust production, but observations of these phenomena are scarce over most of the world's deserts. Here, methods from radar interferometry, applied to 8 years (2003–2010) of ENVISAT Advanced Synthetic Aperture Radar data over the northwestern Sahara, are used to demonstrate the potential of these data to identify significant flash floods. Loss of coherence between two consecutive images is indicative of changes in surface characteristics. Tropical Rainfall Measuring Mission daily precipitation estimates, together with the digital elevation model from the Shuttle Radar Topography Mission, are analyzed to assess the likelihood of these changes to be related to flash floods. Four interferometric pairs representing periods with different rainfall amounts are examined with regard to changes in surface characteristics caused by precipitation. To do this, ratios of coherences are calculated, highlighting the changes in soil texture through loss of coherence in particular for desert valleys. Many pixels within wadis show large coherence during dry periods and a significant loss during wet periods, while others show low coherence irrespective of rainfall, possibly due to Aeolian processes. In the long term, findings from this study will be used to investigate the relation between flash floods and interannual variability of local dust emission fluxes.

산-염기 표면처리된 MWNTs의 첨가가 탄소섬유 강화 복합재료의 기계적 계면특성에 미치는 영향

In this work, the effect of chemical treatments of multi-walled carbon nanotubes (MWNTs) on the mechanical interfacial properties of carbon fiber fabric-reinforced composites was investigated. The surface properties of the MWNTs were determined by acid and base values, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The mechanical interfacial properties of the composites were assessed by interlaminar shear stress (ILSS) and critical stress intensity factor (). The chemical treatments based on acid and base reactions led to a significant change of surface characteristics of the MWNTs, especially A-MWNTs/carbon fibers/epoxy composites had higher mechanical properties than those of B-MWNTs and non-treated MWNTs/carbon fibers/epoxy composites. These results were probably due to the improvement of interfacial bonding strength, resulting from the acid-base interaction and hydrogen bonding between the epoxy resins and the MWNT fillers.

Effectiveness of antibacterial copper additives in silicone implants

Staphylococcus epidermidis plays a major role in capsular contractures of silicone breast implants. This invitro study evaluates the antibacterial effect of copper on S. epidermidis in silicone implants. Specimens of a silicone material used for breast augmentation (Cu0) and specimens coated with different copper concentrations (Cu1, Cu2) were artificially aged. Surface roughness and surface free energy were assessed. The specimens were incubated in an S. epidermidis suspension. We assessed the quantification and the viability of adhering bacteria by live/dead cell labeling with fluorescence microscopy. Additionally, inhibition of bacterial growth was evaluated by agar diffusion, broth culture, and quantitative culture of surface bacteria. No significant differences in surface roughness and surface free energy were found between Cu0, Cu1 and Cu2. Aging did not change surface characteristics and the extent of bacterial adhesion. Fluorescence microscopy showed that the quantity of bacteria on Cu0 was significantly higher than that on Cu1 and Cu2. The ratio of dead to total adhering bacteria was significantly lower on Cu0 than on Cu1 and Cu2, and tended to be higher for Cu2 than for Cu1. Quantitative culture showed equal trends. Copper additives seem to have anti-adherence and bactericidal effects on S. epidermidis invitro.

Surface functionalization of graphenelike materials by carbon monoxide atmospheric plasma treatment for improved wetting without structural degradation

Oxygen plasma treatment has been extensively used to functionalize the surface of graphenelike materials. However, functionalization is usually accompanied by degradation of the structure, which may affect mechanical and electrical performance. Atmospheric plasma treatment (APT) of HOPG was performed to compare the effect of surface modification using carbon monoxide (CO) as the active gas, in comparison to O2. Both Raman and STM demonstrated nanoscale degradation of the structure when using the O2 treatment. CO treated specimens exhibited no observable damage to the material with high levels of oxygen incorporation. Instead, a well ordered monolayer of oxygen-containing film was observed on the surface of the specimens which could accommodate high levels of surface oxygen. Changes in surface characteristics were analyzed using x-ray photoelectron spectroscopy (XPS) as a function of duration. The results indicated that the use of O2 plasma resulted in only a limited oxygen uptake (O/C = 0.11), while CO APT resulted in tailorable surface O/C ratios as high as 0.65, a result not observed even when using low-pressure radio frequency plasmas. XPS analysis and Auger spectroscopy confirmed that a tailorable level of carbonyl functional groups could be evenly distributed throughout the surface. Contact angle measurements verified the formation of a highly stable hydrophilic surface. The CO treatment was also successfully applied to other nanocarbon materials such as graphene nanoplatelets with similar results.

Surface functionalization without lattice degradation of highly crystalline nanoscaled carbon materials using a carbon monoxide atmospheric plasma treatment

Atmospheric plasma treatments on various forms of carbon were performed to compare the effect of surface modification using carbon monoxide (CO) as the active gas, in comparison to the conventionally used O2. Changes in surface characteristics were analyzed using X-ray photoelectron spectroscopy (XPS) as a function of duration. The results indicated that use of O2 plasma resulted in only a limited oxygen uptake (O/C=0.11), while CO treatments resulted in tailorable surface O/C ratios as high as 0.69, a result not attainable when using low-pressure RF plasmas (O/C<0.1). High-resolution XPS analysis and Auger spectroscopy confirmed that a tailorable level of carbonyl functional groups could be evenly distributed throughout the surface. Both Raman and scanning tunneling microscopy (STM) indicated nano-scale degradation of the structure when using the O2 treatment. On the other hand, CO treated specimens exhibited no observable damage to the material with high levels of oxygen incorporation. Contact angle measurements verified the formation of a highly stable hydrophilic surface and excellent dispersion was observed in an aqueous solution on treated specimens after CO treatment. The CO treatment was also successfully applied to SWCNT with similar results and no degradation of structure.

Changes in Surface Characteristics of Anodized Titanium Arising from Water Immersion

Changes in Surface Characteristics of Anodized Titanium Arising from Water Immersion

612 放電表面処理における面性状の経時変化 : 表面粗さに影響する要因(OS4-3 オーガナイズドセッション《材料・組織と加工》)

612 放電表面処理における面性状の経時変化 : 表面粗さに影響する要因(OS4-3 オーガナイズドセッション《材料・組織と加工》)

NaOH 활성화된 탄소나노섬유의 직접 메탄올 연료전지용 연료극 촉매의 담지체로서의 특성 고찰

Porous carbon nanofibers(CNF) were synthesized via NaOH activation at 700~, and the porous CNF-supported PtRu catalysts were evaluated for the anode in direct methanol fuel cells. The change of surface characteristics by NaOH activation was examined by analyses of the specific surface area and pore size distribution. The morphological and structural modification was investigated under scanning electron microscopy. The activity of catalysts supported on porous CNFs was examined by cyclic voltammograms and single cell tests. The pore formation on CNF by the NaOH activation was discussed, concerning the catalyst activity, when they were applied as catalyst supports.

Nucleate boiling heat transfer in nanofluids with carbon nanotubes up to critical heat fluxes

In this study, pool boiling heat transfer coefficients (HTCs) and critical heat fluxes (CHF) are measured on a smooth square flat copper heater in a pool of pure water with and without carbon nanotubes (CNTs) dispersed at 60°C. Tested aqueous nanofluids are prepared using multi-walled CNTs whose volume concentrations are 0.0001, 0.001, 0.01, and 0.05%. For the dispersion of CNTs, DISPERBYK 184 is used in distilled water. Pool boiling HTCs are taken from 10 kW/m2 to critical heat flux for all tested fluids. Test results show that the pool boiling HTCs of the nanofluids are lower than those of pure water in entire nucleate boiling regime. On the other hand, critical heat flux is enhanced greatly showing up to 150% increase at the CNT concentration of 0.001% as compared to that of pure water. This is related to the change in surface characteristics by the deposition of CNTs. This deposition makes a thin CNT layer on the surface and the active nucleation sites of the surface are decreased due to this layer. The thin CNT layer acts as the thermal resistance and also decreases the bubble generation rate resulting in a decrease in pool boiling HTCs. The same layer, however, decreases the contact angle on the test surface and extends the nucleate boiling regime to very high heat flux range and reduces the formation of large vapor canopy at near CHF. Thus, a significant increase in CHF results.

Initial adhesion of Listeria monocytogenes to solid surfaces under liquid flow

Some strains of the food borne pathogen Listeria monocytogenes persist in food processing environments. The exact reason behind this phenomenon is not known, but strain differences in the ability to adhere to solid surfaces could offer an explanation. In the present work, initial adhesion of nine strains of L. monocytogenes was investigated under liquid flow at two levels of shear stress on six different surfaces using a flow chamber set-up with microscopy measurements. The surfaces tested were glass and PVC, and glass coated with beef extract, casein, and homogenised and unhomogenised milk. In addition, the effect of prior environmental stress (5% NaCl, low nutrient availability) on initial adhesion was investigated. The hydrophobicity of the investigated surfaces was determined by contact angle measurements and the surface properties of the investigated L. monocytogenes strains were determined using Microbial Adhesion To Solvents (MATS). All surfaces with the exception of PVC were found to be hydrophilic. Strain differences were found to significantly influence the initial adhesion rate (IAR) of all nine strains to all the surfaces (p<0.05) at both low and high shear stress. Furthermore, there was a significant effect of the surfaces tested (p<0.05) in the adhesion ability of almost all strains. The IAR was affected by flow rate (shear stress) as seen by a decrease in adhesion at high shear stress for most strains. A significant effect of interactions between strain-surface and strain-shear stress (p<0.001) was observed but not of interactions between surface-shear stress. No correlation between surface hydrophobicity and IAR was observed. Addition of 5% NaCl during propagation resulted in a decrease in IAR whilst propagation in low nutrient media caused an increase indicating a general change in surface characteristics under these conditions. Known persisting strains did not display general better adherence.

TiO&lt;sub&gt;2&lt;/sub&gt; and ZnO Water Sol Preparation by Sol–Gel Method and Application on Polyester Fabric of Antistatic Finishing

Abstract：Pure TiO2 water sol, pure ZnO water sol and three compound TiO2/ZnO water sols are prepared under low temperature. Then the padding and baking process is used to put the functional sol liquid on the fabric. SEM is use to analyzed the change of surface feature and the result show that all of the water sol except pure ZnO water sol liquid formed a thin film on the fiber The stability of pure ZnO water sol is the best one and the pure TiO2 water sol is the worst one at temperature of 15°C. The compound water sols stabilities are between these two water sols and with the more amount of ZnO, the stability last longer. Both mole of TiO2 and ZnO with the rate of 5 to 5 and 7 to 3 display the best antistatic behavior, but the washing fastnesses are not good. After treatment, the moisture regain displays most dramatically changes; the next one is whiteness of fabric, but the other physical and mechanical properties have a little change.

Pool boiling heat transfer of functionalized nanofluid under sub-atmospheric pressures

A water-based functionalized nanofluid was made by surface functionalizing the ordinary silica nanoparticles. The functionalized nanoparticles were water-soluble and could still keep dispersing well even at the mass concentration of 10% and no sedimentation was observed. An experimental study was carried out to investigate the pool boiling heat transfer characteristics of functionalized nanofluid at atmospheric and sub-atmospheric pressures. The same work was also performed for DI water and traditional nanofluid consisted of water and ordinary silica nanoparticles for the comparison. Experimental results show that there exist great differences between pool boiling heat transfer characteristics of functionalized and traditional nanofluid. The differences mainly result from the changes of surface characteristics of the heated surface during the boiling. A porous deposition layer exists on the heated surface during the boiling of traditional nanofluid; however, no layer exists for functionalized nanofluid. Functionalized nanofluid can slightly increase the heat transfer coefficient comparing with the water case, but has nearly no effects on the critical heat flux. It is mainly due to the changes of the thermoproperties of nanofluids. Traditional nanofluid can significantly enhance the critical heat flux, but conversely deteriorates the heat transfer coefficient. It is mainly due to effect of surface characteristics of the heated surface during the boiling. Therefore, the pool boiling heat transfer of nanofluids is governed by both the thermoproperties of nanofluids and the surface characteristics of the heated surface.