摘要:Most reports on the fabrication of high-quality Gallium nitride (GaN) are typically based on physical techniques that require very expensive equipment. Therefore, the electrodeposition was adopted and examined to develop a simple and economical method for GaN synthesis. GaN films are synthesized on aluminum substrates that are heat-treated at various temperatures using a low-cost and low-temperature electrochemical deposition technique. The electrochemical behavior of source ions in aqueous solutions is examined by cyclic voltammetry (CV).?In the solution at pH 1.5 containing 0.1M Ga(NO3)3, 2.5 M NH4NO3 and 0.6 M H3BO3, reduction of gallium and nitrate ions are observed in CV. The presence of hexagonal GaN and gallium oxide (Ga2O3) phases is detected for the films deposited on Al substrates at -3.5 mAcm-2 for 3 h. The energy dispersive X-ray and mapping results reveal that Ga, O, and N coexist in these films. Raman analysis shows hexagonal GaN formation on Al substrates. The changes in the morphology and preferred orientation of GaN were found, which was caused by the reactivity of aluminum surface and the aluminum oxide layer formed by the heat treatment.
摘要:Laser Chemical Machining (LCM) is a non-conventional processing method, which enables very accurate and precise ablation of metallic surfaces. Material ablation results from laser-induced thermal activation of heterogeneous chemical reactions between electrolytes and a metallic surface. However, when processing metallic surfaces with LCM, large fluctuations in ablation quality can occur due to rising bubbles. The for-mation of bubbles during laser chemical machining and their influence on the ablation quality has not been investigated. For a more detailed investigation of the bubbles, ablation experiments on Titanium and Ce-ramic under different thermal process conditions were performed. The experiments were recorded by a high-speed camera. The evaluation of the video sequences was performed using Matlab. The resulting bubbles were analyzed regarding their size and frequency. The results show that boil-ing bubbles formed on both materials during processing. Titanium also produces smaller bubbles, which can be identified as process bubbles ac-cording to their size. Furthermore, it was found that undisturbed laser chemical ablation can be achieved in the presence of a boiling process, since both boiling bubbles and process bubbles were detected during machining within the process window.
摘要:In the construction of biosensors, enzymes function as mediators converting biological signals generated by specific biological processes, into electrochemical signals. The ideology of bio-sensor design is retention of electron transfer activity of the enzyme utilizing superior interfacial architecture. In this work a Schiff-base macromolecule has been synthesized by reflux of 2, 3-diaminonaphthalene and pyrrole-2-carboxaldehyde starting materials. The Schiff-base ligand was subsequently complexed with FeCl2?4H2O under reflux, to produce the Fe-Schiff-base complex. The Schiff-base ligand and Fe-Schiff-base complex were characterized using nuclear magnetic resonance (NMR) spectroscopy, Ultra Violet/Visible (UV/Vis) spectroscopy, Fourier transfer infrared resonance (FTIR) and electron energy loss spectroscopy (EELS) to confirm the structure of the synthesis products. NMR spectroscopy confirmed the imide linkage of Schiff-base formation as two symmetrical peaks at 8.1 and 7.7 ppm respectively. Comparison of starting materials and product spectra by UV/Vis spectroscopy confirmed the disappearance of the diaminonaphthalene peak at 250 nm as evidence of complete conversion to product. FTIR spectroscopy of the Schiff-base ligand confirmed the formation of the imine bond at 1595 cm-1. EELS spectra comparing FeCl2?4H2O and the Fe-Schiff-base complex, showed good agreement in the energy loss profiles associated with changes to the electronic arrangement of Fe d-orbitals. EDS clearly identified a spectral band for Fe (7 - 8 eV) in the Fe-Schiff-base complex. Electrochemical evaluation of the Fe-Schiff-base complex was compared to the electrochemical signature of denatured cytochrome-C using cyclic voltammetry and square wave voltammetry. The Fe2+/Fe3+ quasi-reversible behavior for iron in the metallated complex was observed at -0.430 V vs. Ag/AgCl, which is consistent with reference values for iron in macromolecular structures.
摘要:Titanium alloys are widely used in the aerospace industries because of their excellent strength-to-weight ratio, high resistance to corrosion, high chemical reactivity and low thermal conductivity and ability to withstand high temperatures. However, these properties make titanium alloys difficult to machine. Drilling of titanium alloy may generate high temperature and high cutting forces. This paper is aimed at determining the suitable cutting parameters in the drilling of titanium alloys to minimize the cutting temperature and cutting forces. A finite element 3D model of the drilling process is simulated in this research. A combination of drilling speeds and feed rates are simulated to obtain the resulting responses of cutting force and temperature. The central composite design (CCD) is used to generate different combinations of cutting parameters to reduce the number of experiments and optimize the temperature and cutting force responses. Results show at the drilling speed of 5000 rpm with a feed rate of 0.1 mm/rev, temperature and cutting force significantly reduced.
摘要:The synthesis of the thenoyltrifluoroacetone compound doped with terbium, dysprosium and europium encapsulated in a silica matrix (TTA:Tb:Dy:Eu@SiO2) were performed by the sol-gel method. The precursors to obtain the vitreous phase (SiO2) were: Tetraethylorthosilicate (TEOS, C8H2O4Si, 98%, Aldrich), and ethyl alcohol (CH3CH2OH, 99.5%, Meyer), distilled water and 0.05 ml of hydrochloric acid (HCl, Meyer). The sample with molar ratio 20:80 TTA:Tb:Dy:Eu@SiO2 has the best emission intensity. Thermogravimetric analysis (TGA) shown that silica encapsulated samples decompose at lower temperatures than pure TTA:Tb:Dy:Eu luminescent material. Fourier Transform Infrared (IR-TF) shown the characteristic Si-O-Si bands that are presented at a wavelength of 1049, 853 and 440 cmǃ confirming that the luminescent material is encapsulated in a silica matrix, finally X-ray diffraction (XRD) shown that TTA:Tb:Dy:Eu@SiO2 composite is amorphous.
摘要:The fundamental scientific problem for micro- and nano-electronics has been solved—methods for creating and investigating properties of physically doped materials with spatially inhomogeneous structure at the micro- and nano-meter scale have been developed. For the application of functional nanocomposite film coatings based on carbides of various transition metals structured by nanocarbon, for the first time in the world, we developed a new technique for their plasma deposition on a substrate without the use of reaction gases (hydrocarbons such as propane, acetylene, etc.). We have created nanostructured film materials, including those with increased strength and wear resistance, heterogeneous at the nanoscale, physically doped with nanostructures—quantum traps for free electrons. We learned how to simultaneously spray (in a plasma of a stationary magnetron discharge) carbides and graphite from a special mosaic target (carbide + carbon) made mechanically. As a result of such stationary sputtering of carbides and carbon, plasma nanostructured coatings were obtained from nanocarbides, metal nanocrystals and nanocarbon. Our design of such a target made it possible to intensively cool it in the magnetron body and spray its parts (carbide + carbon) simultaneously with a high power density of a constant plasma discharge—in the range of values from 40 W/cm2 to 125 W/cm2. Such sputtering with a change in the power or the initial relative surface areas of various parts of the mosaic target (carbon and carbide) made it possible to change the average density of carbide, metal and carbon in a nanostructured (nanocarbon and metal nanostructures) coating. The changed relative density of various components of the nanocomposite (nanostructures of carbide, metal, and carbon in the form of graphite) significantly affected the physical properties of the nanocomposite coating. The creating method of multiphase nanostructured composite coatings (based on carbides of transition metals) with high hardness of 30 GPa, a low coefficient of friction to dry 0.13 - 0.16, with high heat resistance up to 3000°C and thermal stability in the nanocrystalline state over 1200°C is developed. It is established that the presence of nanographite in the composite significantly improves the impact strength and extends the range of possible applications, compared with pure carbides. The solution to this problem will allow creating new nanostructured materials, investigating their various physical parameters with high accuracy, designing, manufacturing and operating devices with new technical and functional capabilities, including for the nuclear industry and rocket science.
摘要:The results of atmospheric pressure plasma treatments using diffuse coplanar surface barrier discharge (type of surface dielectric barrier discharge) on chromium surfaces are reported. A significant increase of surface wettability was observed after short plasma exposition. A quantitative value of surface wettability, i.e. the surface free energy, changed from 29 mJ/m2 to over 80 mJ/m2. In time, a hydrophobic recovery of the plasma treated surfaces was observed. Careful study by surface free energy measurements and x-ray photoelectron spectroscopy was performed to be able explaining the effects of plasma treatment. Studied samples were treated in air, oxygen and nitrogen plasma and aged in air and vacuum. Main reasons for increased wettability and aging effect are surface cleaning and transformations in chromium oxide. Additionally, generation of surface nitrate groups was found on the chromium surface as a result of plasma treatment in humid air.
摘要:The present paper reports the unusual enhancement of endurance life of ball bearings subjected to carbonitriding treatment. The microstructure was characterized by scanning electron microscopy and correlated with hardness and X-ray diffraction analysis. Endurance tests at 90% reliability revealed that the carbonitrided bearings exhibit nearly ten times more life than the non-carbonitrided bearings. This is attributed to synergic combination of retained austenitic, fine martensitic microstructure and ultrafine carbide precipitates obtained by carbonitriding treatment.
摘要:Amorphous carbon (a-C) thin films have been synthesized by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) on n-type silicon and quartz substrates, aiming at the application of the films for photovoltaic solar cells. Argon, acetylene and trimethylboron were used as a carrier, source and dopant gases. Analytical methods such as X-ray photoelectron spectroscopy (XPS), Hall Effect measurement, JASCO V-570 UV/VIS/NIR spectroscopy, Raman spectroscopy, Transmission electron microscopy (TEM) and Solar simulator were employed to investigate chemical, optical, structural and electrical properties of the a-C films. Two types of solar cells of configuration p-C/n-Si and p-C/i-C/n-Si have been fabricated and their current-voltage characteristics under dark and illumination (AM 1.5, 100 mW/cm2) have been studied. The two solar cells showed rectifying curves under the dark condition confirming the heterojunction carbon based solar cell between p-C and n-Si. When illuminated by the solar simulator light the devices showed photovoltaic behavior. The heterojunction device (p-C/i-C/n-Si) having inserted intrinsic carbon film between p-C and n-Si exhibited significant enhancement of the conversation efficiency (0.167% to 2.349%) over the device (p-C/n-Si).
摘要:For the seventies, scientists focused their researches to find techniques to produce high quality films. One of the ideas, for example, was to generate an ionized cluster beam (ICB) formed by inert gas condensation (IGC) from evaporation of material. This method generates non-agglomerated nanoparticles to be deposited onto any substrate. However, the synthesis of spherical and well-dispersed nanoparticles remains, today, a major technological issue. Several trials have been performed with magnetron sputtering that has the advantage of producing very pure atomic vapour from a wide variety of solid materials or composites, and therefore in this configuration offers the possibility to synthesize nanoparticles in a gaz phase with potential numerous applications. In this paper, we describe several results of our laboratory and we show how it is possible to synthesize non-agglomerated nanoparticles with a narrow size distribution in the nm range. Detailed examples of Ag, TiO2, Au, Y, C, Co and Fe are given. We illustrate their current use in applications including catalyst to produce aligned Multi-Wall Carbon Nanotubes, seeding layer to promote anatase TiO2 crystallisation for photocatalytic material, superhydrophobic material and nanoparticle for nanomedecine.
摘要:We investigated the surface potential dynamics of a ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIMNT) single crystal using Kelvin probe force microscopy (KPFM). The initial surface potential is a function of the applied bias since it reflects the interplay between the polarisation and screen charges. It is suggested that the different rates of tip injected charges are responsible for the asymmetric behaviour of the initial surface potential dependent on the sign of the applied bias. The polarisation, screen and tip injected charges are considered to explain the difference in surface potential dynamics.
摘要:The epitaxial growth of Ge on Si(111) covered with the 0.3 nm thick SiO2 film is studied by scanning tunneling microscopy. Nanoareas of bare Si in the SiO2 film are prepared by Ge deposition at a temperature in the range of 570℃-650℃ due to the formation of volatile SiO and GeO molecules. The surface morphology of Ge layers grown further at 360℃-500℃ is composed of facets and large flat areas with the Ge(111)-c(2 × 8) reconstruction which is typical of unstrained Ge. Orientations of the facets, which depend on the growth temperature, are identified. The growth at 250℃-300℃ produces continuous epitaxial Ge layers on Si(111). A comparison of the surface morphology of Ge layers grown on bare and SiO2-film covered Si(111) surfaces shows a significantly lower Ge-Si intermixing in the latter case due to a reduction in the lattice strain. The found approach to reduce the strain suggests the opportunity of the thin continuous epitaxial Ge layer formation on Si(111).
摘要:The experimental arrangement in this investigation was one in which a poly(o-aminophenol) (POAP) film was supported on a thin gold film electrode whose thickness is of the order of the mean free path of conduction electrons of gold. This arrangement allows one to apply the surface resistance technique to study the electrochemical processes occurring at the metal film surface coated with the polymer film. The dependence of the resistance change of the thin gold film electrode on the external electrolyte composition for polymer thickness lower than 0.25 mC.cm-2, was attributed to a competition, at the gold film surface, between the redox process of the polymer and adsorption of different ion species contained in the electrolyte. This competition reflects a discontinuous character of polymer thickness lower than 0.25 mC.cm-2 at the metal polymer interface. The resistance response of the metal film becomes independent of both the external electrolyte composition and polymer thickness for polymer thickness higher than 0.8 mC.cm-2. Then, POAP thicknesses higher than 0.8 mC.cm-2 seem to be compact enough at the metal polymer interface to prevent the interaction of the species contained in the supporting electrolyte with the gold film surface. The increase of the gold film resistance in going from the reduced to the oxidized state for POAP thicknesses higher than 0.8 mC.cm-2 was attributed to the redox conversion of poly(o-aminophenol) from amine to imine groups. This resistance increase was explained as a transition from specular to diffuse scattering of conduction electrons of gold at the gold poly(o-aminophenol) interface due to a less compact distribution of oxidised sites of POAP as compared with that of the reduced ones. An attenuation of the resistance response of the gold film was observed when the POAP films were deactivated either by contact with a ferric cation solution or prolonged potential cycling. The deactivation of the polymer film was attributed to the creation of inactive gaps within the redox sites configuration of POAP. The surface resistance technique allows one to detect different redox sites configurations of POAP on the gold film, according to the method used to deactivate the polymer films. In this work, it is demonstrated that the surface resistance technique can be employed to study not only the ability of a POAP film to inhibit the interaction of different species in solution with a metal surface but also the deactivation of the polymer film.
摘要:Snails’ protection is essential because this species is to maintain a balanced ecology of water sources. They occur in rivers as well as ponds and balance the pH level of water. But these sources of water are contaminated by effluents, pollutants, acid rain, particulates, biological wastes etc. They can change the pH of water. Water is absorber of carbon dioxide and it converts carbon dioxide into carbonic. Other above mentioned wastes also increase the concentration of H+ ions in water. They produce hostile environment for snails. The outer part of snails is made of CaCO3. It produces chemical reaction in acidic medium and corrosion reaction is accelerated, and thus deterioration starts on the surface of snails. This medium makes their survival become miserable. For this work, corrosion of the snails’ study in the pH values of water is 6.5 in H2CO3 environment. The corrosion rates of snails were calculated by gravimetric methods and potentiostat technique. Aloe Vera was used for corrosion protection in acidic medium. The surface adsorption phenomenon was studied by Langmuir isotherm. Aloe Vera formed thin surface film on the interface of snails which adhered with chemical bonding. It was confirmed by activation energy, heat of adsorption, free energy, enthalpy and entropy. The results of surface coverage area and inhibitors efficiency indicated that Aloe Vera developed a strong protective barrier in the acidic medium.
摘要:New magnetic air-stable nanogranular Fe thin films of 10 ± 1.2 nm thickness were prepared onto silicon wafers at 150℃ under inert atmosphere by controlled Chemical Vapor Deposition (CVD) of triiron dodecacarbonyl (Fe3(CO)12). These thin films, composed of sintered elemental Fe nanoparticles of 4.1 ± 0.7 nm diameter, are protected from air oxidation by a very thin carbon layer. The saturation magnetization of these thin Fe coatings was found to be close to that of bulk iron. The electrical resistivity behavior of the ferromagnetic thin films is similar to that of a semiconductor. In the present manuscript, these Fe thin coatings on Si wafers have been used as a catalyst for synthesizing crystalline carbon nanotubes (CNTs), by CVD using ethylene as a carbon precursor.
摘要:To determine the nucleation region location of Si nano-crystal grains, pulsed laser ablation of Si target is performed in Ar gas of 10 Pa at room temperature with laser fluence of 4 J/cm2, the substrates are located horizontal under ablation spot with different vertical distance. Characteristics of deposited grains are described by scanning electron microscopy, Raman scattering and X-ray diffraction spectra, the results indicate that deposition position on substrates in a certain range is relative to target surface, which changes according to different vertical distance of substrates to ablation spot. Grain size increased?at first and then decreased with addition of lateral distances to target in the range, but the integral distribution rule was independent of position of substrates. Combining with hydrodynamics model, nucleation division model, thermokinetic equation and flat parabolic motion, spatial nucleation region location of grains is obtained through numerical calculations, which is 2.7 mm-43.2 mm to target surface along the plume axis.
摘要:This research work is focused on both experimental and numerical analysis of laser surface hardening of AISI M2 high speed tool steel. Experimental analysis aims at clarifying effect of different laser processing parameters on properties and performance of laser surface treated specimens. Numerical analysis is concerned with analytical approaches that provide efficient tools for estimation of surface temperature, surface hardness and hardened depth as a function of laser surface hardening parameters. Results indicated that optimization of laser processing parameters including laser power, laser spot size and processing speed combination is of considerable importance for achieving maximum surface hardness and deepest hardened zone. In this concern, higher laser power, larger spot size and lower processing speed are more efficient. Hardened zone with 1.25 mm depth and 996 HV surface hardness was obtained using 1800 W laser power, 4 mm laser spot size and 0.5 m/min laser processing speed. The obtained maximum hardness of laser surface treated specimen is 23% higher than that of conventionally heat treated specimen. This in turn has resulted in 30% increase in wear resistance of laser surface treated specimen. Numerical analysis has been carried out for calculation of temperature gradient and cooling rate based on Ashby and Easterling equations. Then, surface hardness and hardened depth have been numerically estimated based on available Design-Expert software. Numerical results indicated that cooling rate of laser surface treated specimen is high enough to be beyond the nose of the CCT diagram of the used steel that in turn resulted in a hard/martensitic structure. Numerically estimated values of surface temperature, surface hardness and hardened depth as a function of laser processing parameters are in a good agreement with experimental results. Laser processing charts indicating expected values of surface temperature, surface hardness and hardened depth as a function of different wider range of laser processing parameters are proposed.
摘要:This article should not be considered as a full review of current methods for non-destructive testing of surface layers. Rather, it is a subjective in this area. However, the article provides some review of the challenges posed by the current state of surface layers treatment techniques on the area of Non-Destructive materials evaluation: enhancement of the sensitivity to the type of defects, increasing resolution to submicron values, the requirement to diagnose the surface layers with depth resolution of properties, diagnosis of multilayer multicomponent surface layers and coatings, treated with concentrated energy.
摘要:The microstructure, phase consistence and microhardness of thermal sprayed coatings were investigated. The tungsten and chromium carbide coatings and also composite NiCrSiB coating were analyzed. The microstructure of coatings were observed by using optical microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Almost equiaxial carbide particles settled inside the surrounded material of coating were found. The cracks propagating thorough the particles and along boundaries between the particles and surrounded material were observed. This phenomenon was connected with the porosity of coatings. The decarburization process was detected in coatings by phase composition investigation using X-ray method. The decarburization process was the reason due to which beside initial Cr3C2 the Cr7C3 and Cr23C6 particles were found. In the tungsten coatings beside the initial WC carbides the W2Cones were found.
摘要:The sonication-driven dispersion of single-walled carbon nanotubes (SWCNTs) in aqueous surfactant solution has been monitored by UV-vis-NIR spectroscopy and scanning electron microscopy. Dispersion of SWCNTs experiments reveal that the maximum concentration of dispersed SWCNTs corresponds to the maximum UV-vis-NIR absorbance of the solution. With higher surfactant concentration the dispersion rate of SWCNTs increases and low temperature sonication is required to achieve maximum dispersion. Dispersion of higher SWCNT concentrations requires longer sonication time. For effective dispersion the optimal concentration of surfactant is 1.5 wt%, the concentration of SWCNTs that can be homogeneously dispersed in aqueous solution is about 0.4 mg/ml.
摘要:It has been attempted to immobilize organic mono layer on semiconductor surface as functional materials. Silicon surface was especially noticed to develop highly efficient and functional devices, and the silicon devices were expected for the immobilized surface with organic layer. Then we have attempted the immobilization by the mono layer on the hydrogen terminated silicon surface with the alkyl base indicated hydrophobic by using a surfactant. We have observed interactions of immobilized molecules and organic molecules adsorbed on hydrogen terminated Si(111), which is aerosol OT as known surfactant and 4-cyanophenol as shown amphipathic molecule. The aerosol OT inhibited oxidation of Si(111) surface by adsorption to the hydrogen terminated surface to indicate hydrophobic. The 4-cyanophenol made the surface oxide by adsorption, and was desorbed by forming hydrophilic Si surface. In the case of the mixed solution by the aerosol OT and 4-cyanophenol, the aerosol OT controlled the surface oxidation on the hydrogen terminated Si against the 4-cyanophenol.
摘要:Magnesium (Mg) and its alloys are one of a novel kind of biodegradable metallic implants which attracted much fundamental research to develop its clinical application. Nevertheless, it has more restrictions in biomedical applications because it degrades too fast at the early stage after implantation, thus commonly leading to some problems such as early fast mechanical loss, hydric bubble aggregation, gap formation between the implants and the tissue. This work aims to study the effect of 0.5 wt% Sb addition on the microstructure, mechanical properties and degradation behavior of as cast Mg-4wt% Zn alloy. The evaluation process was conducted using optical and scanning electron microscopy, X-ray diffraction, tensile and compression tests, in addition to a corrosion study by immersing in simulated body fluid (SBF). Results showed that Sb refines the grain size of the base alloy and also enhances its mechanical properties and degradation rate as well. These were due to the formation of the secondary phase of Mg3Sb2. To get better degradation rate, the Mg-4wt% Zn and Mg-4wt% Zn-0.5wt% Sb alloys are coated with Ca-P using autocatalytic technique. The results demonstrated that the formed coat layer improves the degradation rate of samples under the condition of this study. The current study shows that Mg-4wt% Zn-0.5wt% Sb alloy has good mechanical properties and when it coated by Ca-P, it gave a better corrosion resistance that makes it ideal for biodegradable medical application.
摘要:This work focuses on the updating-based identification of the three-dimensional orthotropic elastic behavior of a thin carbon fiber reinforced plastic multilayer composite plate. This consists in identifying the engineering constants that minimize the relative deviations between the first eight experimental and three-dimensional finite element frequencies of the vibrating free plate. For this purpose, a multi-objective optimization procedure is applied;it exploits a Particle Swarm Optimizer algorithm (PSO) that is coupled to a metamodeling by the new response surfaces method procedure (NRSMP);the latter is based on numerical design experiments. The conducted sensitivity analyses indicate that the four engineering constants of the two-dimensional elasticity are the most influent.
摘要:The titanium implant surface plays a crucial role for implant incorporation into bone. A new strategy to improve implant integration in a bone is to develop surface nanocoatings with plant-derived polysaccharides able to increase adhesion of bone cells to the implant surface. The aim of the present study was to physically characterize and compare polystyrene and titanium surfaces nanocoated with different Rhamnogalacturonan-Is (RG-I) and to visualize RG-I nanocoatings. RG-Is from potato and apple were coated on aminated surfaces of polystyrene, titianium discs and titanium implants. To characterize, compare and visualize the surface nanocoatings measurements of contact angle measurements and surface roughness with atomic force microscopy, scanning electron microscopy, and confocal microscopy was performed. We found that, both unmodified and enzymatic modified RG-Is influenced surface wettability, without any major effect on surface roughness (Sa, Sdr). Furthermore, we demonstrated that it is possible to visualize the pectin RG-Is molecules and even the nanocoatings on titanium surfaces, which have not been presented before. The comparison between polystyrene and titanium surface showed that the used material affected the physical properties of non-coated and coated surfaces. RG-Is should be considered as a candidate for new materials as organic nanocoatings for biomaterials in order to improve bone healing.
摘要:Composites of Maghnite-H, a Montmorillonite sheet silicate clay, exchanged with protons, and Poly(3,4-ethylenedioxythiophene) (PEDOT) were prepared by in situ chemical polymerization of the 3,4-ethylenedioxythiophene, without the use of solvent or oxidant. The effect of changing monomer/clay ratio was studied and the resultant composite structures were characterized by Inferred spectroscopy, 27Al and 13CSolid-State NMR spectroscopy, scanning electron microscopy and powder X-ray diffraction. All analyses are consistent with a structure were the polymer is (partially) intercalated into the clay structure, which in favourable cases lead to exfoliation. The presence of the clay in the polymer leads to a desired increase in thermal stability as witnessed by thermogravimetry.
摘要:Flame Thermal Spray (FTS) coatings frequently show some porosity and reduced adherence to substrate, which affect its properties, especially its corrosion resistance. In this work, the corrosion resistance of AISI 1018 carbon steel coated by different methods is compared: electroless nickel (EN) coating, NiCrFeBSi obtained by FTS, duplex coatings of an EN deposit on a layer of NiCrFeBSi obtained by FTS and a layer of NiCrFeBSi on an EN deposit. The coatings were characterized using optical microscopy and scanning electron microscopy techniques, EDS microprobe microanalysis, roughness as well as electrochemical polarization tests to obtain the corrosion rate. The results show the enhancement in the corrosion resistance in saline medium of the duplex coatings, especially of the EN coating on FTS layer.
摘要:Studies on surface analysis of carbon steel protected from corrosion in low chloride and nearly neutral aqueous environment by a synergistic mixture containing N,N-bis(phosphonomethyl) glycine (BPMG), zinc ions and citrate ions are presented. The effect of addition of citrate to the binary system, BPMG-Zn2+, is quite significant and is well explored through various studies. The surface protective nature is maintained in the pH range 5 - 9. Potentiodynamic polarization studies inferred that the ternary inhibitor is a mixed inhibitor. Impedance studies of the metal/solution interface indicated that the surface film is highly protective against the corrosion of carbon steel in the chosen environment. X-ray photoelectron spectroscopic (XPS) analysis of the surface film showed the presence of the elements namely iron, phosphorus, nitrogen, carbon, oxygen and zinc. Deconvolution spectra of these elements in the surface film inferred the presence of oxides/hydroxides of iron(III), Zn(OH)2 and [Fe(III), Zn(II)-BPMG-citrate] heteropolynuclear multiligand complex. This inference is further supported by the reflection absorption Fourier transform infrared spectrum of the surface film. Analysis by scanning electron microscopy (SEM) is presented for both the corroded and protected metal surfaces. Based on all these results, a plausible mechanism of corrosion inhibition is proposed.
摘要:A reflecting diffraction grating has been etched onto the backside of a standard cantilever for atomic force microscopy, and the diffracted light has been used to monitor the angular position of the cantilever. It is shown experimentally that for small angles of incidence and for large reflection angles, the force sensitivity can be improved by few times when an appropriate detection scheme based on the position sensitive (duolateral) detector is used. The first demonstration was performed with a one micron period amplitude diffraction grating onto the backside of an Al-coated cantilever etched by a focused ion beam milling for the experiments in air and an analogous 600 nm-period grating for the experiments in air and in water.
摘要:In our previous study, the specific interaction between P-factor, a peptide pheromone and its receptor, Mam2, on the cell surface of the fission yeast Schizosaccharomyces pombe was investigated by two methods, an atomic force microscope (AFM) and a GFP reporter assay. The removal of Leu at C-terminal of P-factor resulted in an inactivation of P-factor function to bind Mam2 and induce the signal transduction pathway. Here, we used truncated P-factor derivatives lacking N-terminal of P-factor (P12 ~ P22: 12 ~ 22 amino acid residues from C-terminal) as ligands for Mam2. From the dose-dependent analysis of the GFP reporter assay ranging from 1 nM to 100 μM of the peptide concentration, the peptides can be classified into three groups based on EC50 and maximal GFP production level, group1 (P-factor), group2 (P17 ~ 22), and group3 (P12 ~ P16). At 0.1 μM, only P-factor induced the signal transduction pathway. At 1 μM, peptides from group2 partially induced the pathway and peptides from group3 induced the pathway a little. At 10 μM, all peptides induced the pathway mostly depending on the length of peptides. We also performed AFM experiments using P-factor and peptides from group3 to investigate the interaction between the peptides and Mam2 for comparison between the two methods.
摘要:Cadmium sulphide thin films were deposited on the glass substrate via simple spray pyrolysis technique. The substrate temperatures (Ts) have been varied from 250℃ to 350℃ and concentration of precursor’s solution of cadmium chloride and thiourea was optimized. The X-ray patterns and morphological studies of CdS thin films indicated that films are crystalline in nature with hexagonal crystal structure. The grain size calculated and found to be 250.12 to 349.61 nm. The optical spectra exhibited high transmittance and band gap varied from 2.41 eV to 2.39 eV. The angle of contact measured and found to be hydrophilicity behaviour. The electrical conductivity and thermoelectric power have been measured with two probe method. It was found that CdS thin films were semiconducting in nature with n-type.
表面工程材料与先进技术期刊(英文)的期刊信息
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创刊时间:2011
地区:CN
语言:中文
热门主题:LT
SUB
COATINGS
WEAR
CORROSION
SURFACE
NANOTUBES
TITANIUM
LASER
MICROSCOPY