Abstract: The microstructures, mechanical properties, deformation mechanism, and recrystallization behavior of Cu-Zn-Bi alloys for cartridge case application have been investigated in this research. Cu-28Zn-1.1Bi wt. % alloys were produced by gravity casting and subjected to a homogenization – cold rolling – annealing sequences with variations on reduction level and annealing temperature. Samples characterizations were done through optical emission spectroscopy, optical microscopy, SEM-EDS imaging, and X-ray mapping modes, while hardness measurements were performed using micro Vickers method. The presence of Bi was found to increase cartridge brass hardness through a dispersoid strengthening mechanism in which dislocation movements are rendered by Bi particles. Higher deformation levels resulted in higher microhardness of the alloy. Recrystallization took place at grain boundaries and areas surrounding Bi dispersoid at 400 °C, while further heating resulted in grain growth phenomenon. Bismuth addition accelerated the recrystallization process in cartridge brass by a particles stimulated nucleation (PSN) mechanism.
Abstract: In order to improve the anticorrosion ability of a Mg-5Zn-1.5Ca alloy used as a bone replacement material, this study prepared the MnCaP conversion coating, which was formed from a phosphating solution mixed with a MnCl2 solution of 0.05 molarity, on a magnesium (Mg) alloy. After forming a MnCaP conversion coating on a Mg alloy, micro-arc oxidation (MAO) proceeded for improving the anticorrosion ability of the sample. As a result, when the 0.05MnCaP coating on a Mg alloy was immersed in the simulated body fluid (SBF), the corrosion current, pH value change, and hydrogen evolution volume of the SBF solution are lower than a uncoated Mg alloy. From the SEM and EDS analyses for a corroded 0.05MnCaP coating on a Mg alloy, the manganese (Mn) phosphate in a lumpy-rock form and the calcium (Ca) phosphate in a flake form alternate to each other densely, so that the coating can effectively prevent a Mg alloy from corrosion.
Abstract: Cleft lip occurs due to incomplete joining of the tissue that forms the upper lip resulting in an opening in the upper lip. This opening is in the form of a slit and is large extending up to the nose. Many methods have been suggested in repairing the cleft lip. As a part of post-surgical treatment, the nasal deformity has been an issue. Nasal conformer is a post-surgical aid that helps the patients to keep their nasal deformity in control. The present work aims in design and manufacturing of this nasal conformer for the much needy poor patients. Computer Aided Design (CAD) techniques are used to model the nasal conformer by taking the dimensions of the various aged group people ranging from 6 months to 16 years old. Based on that, 5 such sizes have been arrived. These CAD models have been manufactured using Fused Deposition Modeling (FDM) technique to prepare the final pattern for molding process. Once the molds for the nasal conformer have been created, the final parts have been casted using Silicone material. The final casted nasal conformers are being proposed to be distributed to the needy.
Abstract: Dental applications like crowns, veneers or bridges require high accuracy to be fitted on the patient’s stump. Stereolithography is an additive manufacturing method, which offers high precision by using light exposure as the layer generating mechanism. In the LCM process, this precision is combined with a thermal post-processing step to achieve full ceramic restorations. The overall production of such ceramic parts in a reproducible way is a highly complex procedure. The first requirement is to find a slurry formulation, which is stable against sedimentation and segregation, that is also processable in a stereolithographic system. Such a formulation has been found by us, which could be shown by rheology measurements. During experiments with this formulation, it could be observed that there is a correlation between wet film thickness and resolution. Several adjustments to the machine have been made, to fully control this parameter. Namely, changes to the vat, the doctor blade and the building platform have been made. The improvement of the process and the quality of the final parts are validated by fabricating Siemens stars and by biaxial bending tests.
Abstract: Laser micromachining has become a hotspot in recent years due to its high precision, non-contact and adjustable parameter. In this paper, TC4 titanium alloy implant samples were conducted to obtain specific surface textures through picosecond laser. The laser parameters which directly influenced the microstructure and characteristic of surface textures were optimized within the context of laser power, scanning speed and scanning number via response surface methodology. The microstructure was evaluated using scanning electron microscope (SEM) while the feature size of the surface textures was measured through surface 3D profiler. In addition, endothelial cell culture was conducted to investigate the biofunctionalization of samples with specific surface textures. It demonstrated that well-structured textures played an important role in promoting cell adhesion and proliferation for titanium alloy implants.
Abstract: Zirconia (ZrO2) nanotubes were prepared by anodization of zirconium (Zr) foil in a glycerol-formamide electrolyte containing ammonium fluoride. The effects of anodizing voltage and temperature on the pore diameter and thickness of the resulting nanotube array were studied. ZrO2 nanotubes with larger pore diameter were formed at higher anodizing voltage and temperature. Additinally, the thickness of the oxide layer was also increased. The applicability of the ZrO2 nanotubes for adsorption of heavy metals in aqueous solution was evaluated using Pb (II) as the model ions. Generally, the uptake of Pb (II) was increased at longer adsorption time and higher initial concentration of the adsorbate.
Abstract: The energy materials such as titania (TiO2) and alumina (Al2O3) are the environmental friendly materials. In this paper the nanostructure of high surface area titania and alumina are fabricated by anodization process and assistance in electrochemical mold. In general, academic or research institutes can simply control the required experimental conditions in a small sample; however, it’s difficult to control the stable parameters in a large surface and a large number of nanostructural products in the industry production. In order to solve the problems of unstable current density and temperature we have designed a cooling functional electrochemical mold which can improve the nanostructural quality of energy materials during a large number production. The electrochemical mold is used for a local surface treatment at an isothermal temperature controlling. The mold limits sample for a specific treated area and current density in the electrolyte. The mold can be used for the assistance of electrolysis, electro-polishing, electro-deposition, anodization, etching, chemical deposition, pickling, and caustic processes. The mold structure includes fixture group, water-cooling electrode group, and electrode conductive group.
Abstract: We developed a one-pot method for the fabrication of hydrogel-based photonic crystal (PC) materials. An array of monodisperse colloids was self-assembled within a polymer solution, which generates a visible light diffractable photonic mixture. This mixture was molded and gelated into a hydrogel PC material by freeze-thaw treatment. Drug release as well as the structure colour changing properties of the PC hydrogels were discussed, and the experiment results revealed that our one-pot design and the associated modification approach has potential in efficient fabrication of PC materials.
Abstract: WO3 nanostructure with nanocube morphology was synthesized through acidification of Na2WO4·2H2O, which were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, the result of the present work implied that the sensor fabricated by nanocube WO3 could detect the level of 330 ppb H2S, which is much lower than the threshold limit value of 10 ppm. Compared with other results, the nanocube WO3 sensor shows higher sensitivity, excellent selectivity and faster response/recovery to H2S. Especially, the best operating temperature of this nanocube WO3 for H2S detection is 100 °C.
Abstract: This study describes the structural modifications of char electrodes and the resulting carbon nanoparticles using method of arc discharge in liquid method, an approach which is simpler and less expensive than other techniques such as CVD and laser vaporization. The nanoparticles are obtained from powder floating on the water surface during arc discharge between two electrodes submerged in water. X-ray diffraction analysis (XRD) profiles show peak formation at 24-26o 2Ѳ, associated with hexagonal graphite structure.Transmission electron microscopy (TEM) confirmed the presence of graphitic-structured nanoparticles after arc discharge; these nanoparticles have diameters ranging from 20 to 100 nm. In contrast, nanoparticles produced using graphite electrodes with current source variations show more complicated and varied stuctures, for example, structures such as nanoonions, graphene, and amorphous nanoparticles.