Advanced Materials Research Vols. 557-559

Abstract: This article aims to show the effects of the EDM process that influences the surface hardness by comparing the hardness values before and after the spark on the plastic mould steel AISI P20. Divided by the heat treatment, there were three different hardness levels: 1) the plastic mould steel AISI P20 through the process of quenching with the hardness value in the range of 690-710 HV; 2) the steel through the process of quenching and then annealing with the hardness value in the range of 470-490 HV; and 3) the non-heat treatment steel (raw material) with the hardness value in the range of 300-320 HV. The condition of EDM spark on the surface workpiece was 3 mm of depth and 10 mm of diameter copper electrode. The experiment was carried out under the cover of hydrocarbon, using dielectric cooling, and removing debris by the side flushing through the 6 mm of diameter pipe with the flow rate of 15 liters per minute. The experiment parameters included on-time duty factor variable, off-time duty factor variable, and current. Based on the experiment, it was found that when the duty factor increased, the hardened workpiece showed the less surface hardness value. At the same time, the annealed, and the non-heat treatment workpieces showed that the hardness values were proportional to the duty factor and the current of the EDM process.

Abstract: Hybrid sols were synthesized through a combination of hydrolysis and condensation reactions of tetraetoxysilane and γ-Methacryloxypropyltrimethoxysilane together with the addition of a colloidal silica suspension. A transparent, hard UV-curable hybrid coatings based on hybrid sols were prepared in order to improve the scratch and abrasion resistance of PMMA substrate. The effects of the content of colloidal silica suspension on pencil hardness, transmittance, and haze were investigated. The pencil hardness of all coating films in this study can be tuned from 4H to 9H, whereas that of uncoated PMMA substrate is 1H. The higher hardness of the coatings can be attributed to the dense structure induced by the increase of network density with the addition of colloidal silica suspension. Furthermore, it is found that the transmittance of coatings slightly fluctuates between 91.8% and 93.6% with increasing colloidal silica content. These results indicate the good compatibility of the organic and inorganic components.

Abstract: Polyaniline thin layers were successfully coated on the surface of graphene sheets through in situ chemical oxidative polymerization. By integrating into a resistive sensor design, the sensing properties of the nanocomposites were evaluated. It is found that the nanocomposite sensors exhibited high sensitivity with fast response and recovery time, and good reproducibility charactics for ammonia gas at room temperature even exposed to low concentration of 10 ppm, implying that the nanocomposite could be a promising candidate as a gas sensor for ammonia gas.

Abstract: A superhydrophobic nickel oxide (NiO) surface with hierarchical micro- and nanostructures was obtained by a novel and facile method. The water contact angle and sliding angle of the superhydrophobic NiO surface were 156±1.9º and 3º, respectively. The superhydrophobic NiO surface made the substrate float on the water surface and showed high buoyancy. Execept for pure water, the superhydrophobicity of the superhydrophobic NiO surface remained unchanged when contacting with salt aqueous solutions. After being stored in ambient environment for 8 months, the superhydrophobic property remained constant, and no contamination was observed on the superhydrophobic NiO surface.

Abstract: Thermoelectric bismuth-telluride films were successfully prepared from nitric acid aqueous solution with ethylene glycol on Ti-sputtered silicon substrates by electrochemical deposition techniques. Cyclic voltammograms (CV), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were used to investigate nucleation process, the crystal structures, morphologies and compositions of the bismuth-telluride films. The results show that the materials are Bi-rich, exhibiting preferred (110) orientation with rhombohedral structure. The crystallite size of films was calculated based on Scherrer’s equation and found to be 18-20 nm.

Abstract: In this work, La₂O₃ gate dielectric film was deposited by plasma enhanced atomic layer deposition. we investigate the effect of surface preparation of GaAs substrate, for example, native oxide, S-passivation, and NH₃ plasma in situ treatment. The interfacial reaction mechanisms of La₂O₃ on GaAs is studied by means of X-ray photoelectron spectroscopy(XPS), high-resolution transmission electron microscopy(HRTEM) and atomic force microscope (AFM). As-O bonding is found to get effectively suppressed in the sample GaAs structures with both S-passivation and NH3 plasma surface treatments.

Abstract: The zinc coating was immersed into a rare-earth conversion coating treatment liquid, with Ce(NO3)3•6H2O as the main salt and 30% H2O2 as the oxidizing agent. A Ce-H2O series potential-pH diagram and a Zn-H2O series potential-pH diagram were then established by calculating the maximum pH value obtainable on the interface. Therefore, the cerium conversion coating was deduced to be composed of ZnO, CeO2, Ce2O3, Ce(OH)3, and Ce(OH)4, In addition, XPS and XRD was used to analyze the appearance and phase of the cerium-based conversion coating in terms of the rare-earth conversion coating obtained in the experiment. The results reveal that the cerium-based conversion coating is the compound coating mainly consists of ZnO, CeO2, Ce2O3, Ce(OH)3 and Ce(OH)4, which is in line with the theoretical analysis.

Abstract: A kind of nanoparticles modified Na2SiO3 adhesive was prepared from Na2SiO3 aqueous solution with nano-silica and nano-magnesia as curing agent, and nano attapulgite as skeleton material. The chemical structure, surface morphology and thermal properties of nanoparticles modified Na2SiO3 adhesive were characterized by Fourier transform infrared spectrometer, scanning electron microscope, and thermo-gravimetric analyzer. As the two main measures of adhesion properties, the bonding strength and water resistance were also determined. The results showed that nanoparticles uniformly dispersed in Na2SiO3 matrix in the state of grain, so the homogenous morphology of cured adhesive was formed and bonding strength of Na2SiO3 adhesive was improved. Nanoparticles modified Na2SiO3 adhesive have good thermal stability in the range of 30~800 °C. The bonding strength and 24h water absorption rate of poplar plywood glued by the nanoparticles modified Na2SiO3 adhesive is 0.8 MPa and 23.7%, respectively, reaching the type-two plywood performance standards.

Abstract: A series of lanthanum ion-doped titanium dioxide coatings have been prepared on the surface of 304 stainless steel by using sol-gel and dip-coating technology. The corrosion protection properties of the coatings were investigated by electrochemical measurements. It is found that the photogenerated cathodic protection property of the TiO₂ coating is enhanced under illumination by doping with an appropriate amount of lanthanum ions. The results also indicate that the presence of lanthanum ions improves the corrosion protection property of the TiO₂ coating without the photo effect attributed to the self-healing properties of lanthanum ions.

Abstract: A superhydrophobic LDPE film was obtained by a simple method in atmosphere without addition of low-surface-energy materials. The water contact angle of the superhydrophobic LDPE film are 155±1.9º. SEM shows that compared with common smooth LDPE film, a porous structure was obviously observed on the superhydrophobic LDPE film. Such a special surface microstructure may result in the superhydrophobic property. The effect of drying temperature and concentration on water contact angle were studied.