Papers by Keyword: Surface Texturing

Abstract: This paper reports the temperature and the concentration dependence of anisotropic etching for (100) p-Silicon in an aqueous KOH solution etching rate of wet etching has been experimentally determined with varying concentrations and the temperature of the KOH solution. The texturing process was managed at different etching durations ( 20 min, 40 min, and 60 min). XRD test showed that the lowest value of grain size was 5.0 nm (obtained with the highest porosity percentage of 50% with 4.5% KOH concentration for 60 min). FESEM test showed that the pore diameter increased with increasing etching time. The lowest reflectance value was (2.8 % at 550 nm wavelengths for samples treated with 4.5% KOH concentration for 60 min etching time. The refractive index value was 1.8 for the same black Si sample, also Hall test is introduced.

Abstract: Osseointegration is a process consisting of the formation of bone tissue on the implant surface, so that the osseointegration process occurs, a surface with surface roughness (Ra) is required in isotropic microtopography with a size of 1-100 nm. The plasma treatment can be done to reach the Ra parameter. This study aims to discuss the treatment of Plasma Electrolytic Process (PEP) with the principle of physiochemical erosion using electrolytic cells on Ti-6Al-4V alloy implants, to form a plasma layer in the form of spark discharge and Vapour Gas Envelope (VGE). Samples made of Ti-6Al-4V are tested with several parameters including different electrolytes and different applied voltages are investigated, and the results of the formation of VGE which influences the surface characterization are evaluated. The results show that the process of PEP with electrolyte consist of 50% H₃PO₄ + 10% NaClO₄ + 1% HF and 10% ethylene glycol + 2% NH₄F at a voltage of 90-130 V produces VGE and non-homogeneous spark discharge resulting in a surface with microporous structures with increasing surface roughness and micro-hardness indicating the formation of an oxide layer.

Abstract: A new surface texturing technique, based on liquid plasma discharging in an aqueous electrolyte, is proposed to modify the surface morphology of grey cast iron. During the process, a grey cast iron sample serves as a cathode where the reduction of hydrogen from the aqueous electrolyte occurs and consequently plasma discharging is generated on the sample surface under applied high voltages (up to 480V). The formed hydrogen bubbles are exploded during the electrical discharging, leaving an irregular array of craters on the sample surface due to the high temperature and shockwaves of the plasma micro-arc discharging. After polishing the crater-like textured surface, surface roughness and oil retention are measured by a profilometer. Reciprocating tribotests are utilized to determine the coefficients of friction. The surface morphology of the polished and tested surface is studied by SEM. The same tests are also conducted for the cast iron with a cross-hatched surface. These two set of results are compared to determine the effects of the texturing and polishing on friction. The results show that the polishing of textured surface can decrease the roughness and coefficients of friction significantly at starved lubricating conditions. This method has potential to be applied on the cylinder bore surface of a cast iron liner for the internal combustion engine (ICE). By honing the textured bore surface, the friction between piston and cylinder bore is expected to decrease and the ICE efficiency to increase for environmental benefits.

Abstract: The aim of this study was to investigate the influence of laser surface texturing on fatigue life and tribological properties. Textures were introduced before and after hard TiAlN coating deposition in order to investigate the sequence of surface texturing process. It was found that the sequence of surface texturing has an effect on tribological and fatigue life behaviour. If laser texturing is done after coating deposition, friction is lower because of the better wettability of steel in comparison with coating, but suffers in fatigue life properties.

Abstract: In laser processing of surfaces, typically to impart some texture or to drill shallow holes, it is necessary to correlate pulse properties (wavelength, power, beam radius and quality, duration) and material properties (reflectivity, melting temperature, conductivity, diffusivity) mainly with the depth of the formed crater. Crater shape is assumed to be paraboloidal and its maximum diameter is assumed to be uniquely related to its depth. An empirical and an analytical model are suggested to this end. The former entails construction of Artificial Neural Networks from experimental measurements, whilst the latter entails modification of established models from literature. Both types of models are exemplified in this paper drawing on data from available literature.

Abstract: In this research, we focus on the improvement of frictional performance of piston ring achieved by Laser Surface Texturing. Five kinds of samples (non-texture, dimple 100μm, dimple120μm, groove 45 degrees to sliding direction and groove 90 degrees to sliding direction) were tested under reciprocating sliding condition. The results showed that the sample of groove 90 degrees to sliding condition has the maximum decrease on either average friction coefficient (26%) or friction coefficient at end points of stock (33%). And we think that under boundary lubrication regime, the uniformity of distribution of the texture and flow of oil in contact surface are the key factors which affect the friction coefficient.

Abstract: The reduced wear rate of hip-joint bearing components is the main issues in biotribology researches for the biomedical implants. Ultra-high molecular weight polyethylene (UHMWPE) is extensively used as a bearing material because of having its great properties of friction and wear. Surface texturing can be selected as a method of enhancing tribology properties of engineering surfaces. In this present study, surface texturing examination was performed by 3D finite element method under influence of normal load. Stress distribution of UHMWPE surface under the influence of texturing with the variation in diameter cavities and separation was investigated. The result showed that the surface texturing provided the higher stress distribution of the lower separation in the cylindrical cavities.

Abstract: Whirling electrical discharge texturing (WEDT) was developed to process microstructures on the inner surface of cylindrical parts made of high hardness materials. However, the minimum processable diameter of the cylindrical parts was φ 5 mm and the equipment could not feed the new tool electrodes. Therefore, the authors devised a novel method of WEDT using a straight wire tool electrode for a cylindrical surfaces with a small diameter. It was confirmed that microstructures could be created on the inner surface of a cylinder of φ 1.1 mm diameter, and that the texture-area ratio could be controlled by the workpiece feed speed. Moreover, new EDT equipment with a feeding system for a wire tool electrode and a bending system for the tip of a wire tool electrode was developed. As a result, the equipment that can process microstructures on the inner surface of a cylinder with a small diameter and feed a wire tool electrode during texturing was successfully developed.

Abstract: We investigate the effect of surface texturing on the light trapping properties of Silicon wafers as a function of reflection reduction and surface morphology. This was achieved by structuring a random square-based pyramids pattern on the surface of Silicon substrate using anisotropy etching. The light trapping effect was optimized for silicon solar cells by investigating the dependence of the silicon surface texturing on the process parameters such as etchant concentration, etching time and temperature. We study the surface morphology by analyzing the surface behaviour of the textured substrate using the atomic force microscope and scanning electron microscope. The results of roughness and optical reflection were obtained using the surface profiler and the UV/VIS the spectrometer respectively. In addition, an analytical modelling method was developed to determine the angles of incidence of light rays with each of the facets of the pyramids and the coordinate of the reflected light rays. The method used here is based on 3-D vector geometry of the pyramidal facets. The optimum parameters are found to be 40min, a temperature of 80^oC and with KOH/IPA/DI in the ratio [2:4:46] by volume, yielding a surface roughness over 600 nm and a relative optical reflectance in the visible spectrum less than 10%, using polished Si as reference. The results and analysis of both the modelled and measured reflectance, suggest that the performance of the light trapping technique has a big potential in silicon solar cells application.

Abstract: Technology for surface protection in contact with seawater has been studied. It mainly focuses on the capability of superhydrophobicity characteristic. Currently, the application of superhydrophobicity in controlling corrosion problem in the marine environment is still new. The development of superhydrophobicity on the materials surface can be achieved by designing a specific texture pattern in micro-or nanometer scale for producing high roughness surface. This review paper is mainly on the laser technology for producing superhydrophobicity characteristic of materials surface. This technique offers the most control and precision over the produced geometry.