Papers by Keyword: Chemical Etching

Abstract: The textile industry has been weaving polymer optical fibers (POFs) into plane fabric for many years for lighting and decoration. To apply POF-incorporated fabrics in a larger field of application, it is necessary to improve the side illumination of POF-incorporated fabrics. It has been reported that the chemical etching method is one method to enhance the illumination of POFs, while there is little research related to the application of chemical etching to enhance the illumination of POF-incorporated fabrics. In this work, the end emitting POFs (EEPOFs) were used as weft yarns, and polyethylene terephthalate (PET) yarns were used as warp yarns. The POF-incorporated woven PET fabrics were successfully fabricated with a 1/3 twill structure and then treated with a mixture of acetone and methanol (volume ratio: 1:1) for 1 min. The morphology and side illumination of etched POF-incorporated PET fabrics were investigated. As a result, the acetone/methanol mixture destroyed the cladding layer of EEPOFs, and the luminance of etched POF-incorporated PET fabrics was increased by more than 50 %. Besides, acetone/methanol etching resulted in a higher side illumination attenuation behavior.

Abstract: The solid – state nuclear track detector (SSNTDs) CR-39 can be used to study the different factors for alpha particle. Alpha particle is very dangerous inside the human body so the study its very important. In this article, we investigated the impact of two different etching solutions (NaOH and KOH)) on registrations properties, diameter D, track Diameter growth velocity VD, number of tracks and removal layer thickness of CR-39 nuclear track detector. The two types NaOH and KOH were dissolved in water with varied normality (3,5,7,9,11)N under a temperature of (70±1)°C to create the solution. During the experiment, a source of (α-particles) with a 4MeV energy was used to bombard all detectors (30 Sec). It was found the values of the diameter, number of tracks, removal layer thickness, track Diameter growth velocity VD by using the etching solution (NaOH +water) Solution greater than the values in (KOH + water) solution. the results showed excellent agreement with the outcomes of others who utilized different normalities.

Abstract: Chemical etching is an integral part of metallographic sample preparation. Maintaining precise etch times can be difficult and therefore repeatability is limited. The aim of this work is to improve the repeatability of sample preparation using robotization. Prior to etching, metallographic samples of S355J2 (1.0577) structural steel were finely mechanically polished. For verification, 15 specimens were prepared using an in-house designed automated etching machine with a built-in 5-axis robotic arm and 15 specimens prepared manually by an expert metallographer. The samples were etched with Kourbatoff no. 4 reagent for 8 seconds in a beaker placed in an ultrasonic cleaner at 80 kHz. The samples were then cleaned in 7 beakers of cleaning fluid also placed in the ultrasonic cleaner. The robotic etching and cleaning process was optimized and the quality of the resulting surface is at least as good as that of the samples prepared by an expert metallographer. The surfaces were compared using a light optical microscope (LOM) and a confocal laser scanning microscope (CLSM). The repeatability of the preparation process is a key aspect for obtaining a large dataset of steel microphotographs for training a deep neural network that will be used in future research.

Abstract: The mechanical properties of grinding-tools relies highly on adhesion between the abrasive particles and the bonding phase, generally composed of organic rubber or resin materials. The surface modification of abrasive particles represents an industrial alternative to improve the connection with the bonding phase material. However, increasing the roughness of abrasive particles is a challenging process because of their high chemical stability. In the present study, three different approaches are investigated to modify the surface of industrially used alumina abrasive particles. Chemical erosion under harsh acidic and alkaline conditions, and hydrothermal deposition of aluminium-based coatings were used for the surface modification of the abrasive particles. The chemical stability of alumina particles was demonstrated by the chemical etching while the succesufull surface deposition of AlOOH crystals modified the apparent roughness of the processed powder particles. Morphological changes after each treatment were studied by scanning electron microscopy and the phase composition was confirmed by X-ray diffraction.

Abstract: Various novel 3D micro machining technologies were researched and developed for silicon micro mechanical system fabrication. Micro EDM is one of them. The material removal mechanism is thermal sparking erosion and is completely independent with regards to the crystalline orientation of silicon, therefore there is no orientation constraint in processing the complex 3D geometry of silicon wafers. As thermal sparking implied, the process features local area high temperature melting and evaporating, and this characteristic has an adverse side-effect on the sparked surface integrity. One important concern is the generation of micro cracks, which would provide an adverse effect on the fatigue life of the micro feature element made of silicon. For this consideration, in this paper, with the experiment and SEM picture analysis approach, the author explored the micro crack generation characteristics on mono crystalline silicon wafers under micro EDM with available sparking energies and on the different crystal orientation surface machining. The generation of micro cracking is not only related with the sparking energy but also related with the crystalline orientation. The {100} orientation is the strongest surface to resist crack generation. For a strong-doped P type silicon wafer, there exists a maximum crack energy threshold. If single sparking energy is over this threshold, micro cracks unavoidably would be generated on any orientation surface. Two types of chemical etching post processes that can remove cracks on sparked surfaces are also tested and discussed.

Abstract: Titanium and its alloys are standard for orthopedic prosthetic devices, due to their good mechanical properties and biocompatibility. However, bioactivity on the implant surface needs to be improved to achieve an optimal osseointegration process. Metal implants are often coated by hydroxyapatite because they have a chemical composition and crystal structure similar to apatite in the human skeletal that suitable for bone reconstruction. The focus of this research is on surface treatment designed to promote better biological responses through hydroxyapatite layers. Also combining the acid etching treatment of Ti-6Al-4V and the electrophoretic coating process of the hydroxyapatite to obtain stronger mechanical interlocking interface. Hydrofluoric-Acid treatment conducted in various time. Then, coated with nanosized hydroxyapatite through electrophoretic deposition at 15V voltage for 10 minutes. Scanning Electron Microscopy and Contour measurements were performed to show the surface topography indicating the formation of surface contours with increasing surface roughness parameters in accordance with the time of the etching process. The contours on the surface of the substrate induce the mechanical interlocking of the surface so that the results of hydroxyapatite deposition optimal at the time of etching 5 minutes

Abstract: Leaves of an obscure plant “oxalis deppei” are so hydrophobic that showered water droplets are almost completely repelled and hardly remained on their surfaces. For this reason, surface configurations were investigated. On the live leaves, there formed protrusions somewhat similar to those observed on lotus leaves which are well known as super hydrophobic leaves. However, in winter, it was found that even dead leaves were hydrophobic also. Because leaf tissues were shriveled and dried half, heights of protrusions with sizes of 20-50 μm were low, and undulations of surfaces were gentle and smooth, and pitches of undulations were as large as 30-70 μm. It was thought that such gentle lens-like protrusions would be probably formed on versatile stainless-steel plates using lithography and wet chemical etching. For this reason, arrays of protrusions with a size of 20 μm, a pitch of 35 μm, and heights of 6-7 μm were formed, and change of hydrophobic properties were investigated. As a result, the hydrophobic properties were effectively improved by forming even such gentle and smooth protrusions. It was also clarified that contact angles were improved almost in proportion to etched depths.

Abstract: Titanium implants with porous surface arranged orderly were fabricated by micromachining through photolithography and chemical etching. The titanium discs were implanted into the canine mandible alveolar bone for 3 and 21 days, for animal experiments. Neogenetic bone was observed onto porous surface after 7 days‘ implantation. This result allows us to expect application of titanium with porous surface as biomaterials.

Abstract: Compared to perfect crystal lattice, typical edge dislocation structure has been modeled by quantum chemistry simulation in order to analyze the influence of crystal structure defects on removal process in atmospheric pressure plasma polishing (APPP). The Partial density of states (PDOS), number of states, average number of bonding electrons and energy have been calculated and analyzed further for these models. The analysis results reveal that silicon crystal with edge dislocation can be etched more easily than that of perfect crystal lattice. It is also found that the removal rate of sample with higher dislocation density is larger than that of lower dislocation density in the same experiment conditions. Thus, theoretical simulation demonstrates that structure dislocation is helpful for raising the etching rate, which accords well with testifying experiments results. But maybe structure dislocation could deteriorate surface roughness to some extent in initial stage of machining, as the dislocation structure is usually etched unevenly, although this is just a transition period.

Abstract: Silicon wafers are the most widely used semiconductor substrates. It has been considered that silicon wafers after chemomechanical polishing (CMP) have no subsurface defects. However, in fact, defects such as dislocation and latent microcracks will remain in the wafers if CMP is performed under unsuitable conditions. In this study, we confirmed the existence of subsurface damages at a depth of submicron level in a silicon wafer after CMP, then used a nanosecond pulsed Nd:YAG laser to repair the subsurface damages. It was found that subsurface defects were recovered to a single crystalline structure by laser irradiation without changing the surface topography. The phase transformation of silicon before and after laser irradiation was confirmed by laser Raman spectroscopy and chemical etching using saturated aqueous solution of Ca(OH)₂. The findings from this study contributes to improve the quality of silicon wafers for high-performance semiconductors.