Electrophoresis deposition, Gel electrolyte, Multilayer, PMMA, Stainless-steel mesh, Surface treatment, Electrical engineering. Electronics. Nuclear engineering, and TK1-9971
Abstract
In this paper, a dye-sensitized solar cell based on organic MK2 dye, a quasi-solid electrolyte, and a flexible counter electrode was investigated. Two types of TiO2 nanoparticles with different sizes were used to make the photoanode with a bi-layer structure. The quasi-solid electrolyte was made based on polymethylmethacrylate (PMMA) and iodide/triiodide couple. The counter electrode was fabricated by electrophoresis deposition of carbon nanotube (CNT) mixed with diallyl dimethylammonium chloride (PDDA) on a flexible stainless-steel mesh. A cellulose separator was used to improve the stability of the solar cell. A simple and low-cost sealing method using polypropylene-based tape has been proposed and used for conducting the stability test. The maximum conversion efficiency of 2.5% (under simulated AM 1.5) was obtained with the fabricated quasi-solid dye-sensitized solar cells.
The scope of this current work is to investigate, Coccinia Indica (CI) fiber which is used as a reinforcement to study and analyze the potential improvement in wear resistant property of epoxy matrix composites. For the first time, this finds applications, especially in brake pad where friction exists. Thus, it can be prepared with non-toxic and locally available cheap fibers to produce a prospective tribo-material. CI fiber reinforced with epoxy composites was prepared with untreated fiber and two different surface treatment was carried out namely 5 wt.% sodium hydroxide treatment and 3 wt.% silane treatment. The composite was prepared by hand layup and open mould technique with fiber length of 30 mm and fiber percentage of 35 wt.% for all kinds of samples. Computerized pin-on-disc machine was used to test tribological properties of the composites and the test was conducted with various parameters namely type of treatment, applied normal loads (15, 20, 25 and 30 N) and sliding speed (1.413, 1.884 and 2.356 m/s) for a constant sliding time of 15 min under dry condition. From the result, it was concluded that weight loss of NaOH and silane treated composites got reduced by 15% and 39%, while coefficient of friction was also decreased by 41% and 39% respectively. Scanning electron microscope (SEM) was used to observe the worn surface and wreckage in the tested composite samples. As a conclusion, experiment results and microscope observation indicate that 3 wt.% silane treated fiber composites exhibited good wear resistance compared to other.
Due to their capability of fabricating geometrically complex structures, additive manufacturing (AM) techniques have provided unprecedented opportunities to produce biodegradable metallic implants—especially using Mg alloys, which exhibit appropriate mechanical properties and outstanding biocompatibility. However, many challenges hinder the fabrication of AM-processed biodegradable Mg-based implants, such as the difficulty of Mg powder preparation, powder splash, and crack formation during the AM process. In the present work, the challenges of AM-processed Mg components are analyzed and solutions to these challenges are proposed. A novel Mg-based alloy (Mg–Nd–Zn–Zr alloy, JDBM) powder with a smooth surface and good roundness was first synthesized successfully, and the AM parameters for Mg-based alloys were optimized. Based on the optimized parameters, porous JDBM scaffolds with three different architectures (biomimetic, diamond, and gyroid) were then fabricated by selective laser melting (SLM), and their mechanical properties and degradation behavior were evaluated. Finally, the gyroid scaffolds with the best performance were selected for dicalcium phosphate dihydrate (DCPD) coating treatment, which greatly suppressed the degradation rate and increased the cytocompatibility, indicating a promising prospect for clinical application as bone tissue engineering scaffolds.
Ultrasonic nanocrystal surface modification (UNSM) technology can be used for the surface treatment of specimens produced by additive manufacturing using directed energy deposition. We investigated the change in the surface quality characteristics of the treated specimens with respect to the UNSM process variables. The roughness and waviness of the deposited surface were adopted as the objective functions and the optimal process conditions were determined by the response surface method (RSM). The surface waviness and roughness were determined to be most affected by the static load, with the scanning speed having the least effect. It was observed that a smaller inter-path interval decreased the surface waviness and roughness, and an excessively large or small static load deteriorated the surface modification results. The finally optimized conditions consisted of a static load of 45 N, inter-path interval of 10 μm, and scanning speed of 2600 mm/min. These conditions produced a surface waviness of 1.8097 μm and roughness of 0.3297 μm, which represent improvements of 80% and 72%, respectively, compared with the untreated specimen. It was further observed that UNSM significantly refined the material grains and considerably increased the martensite. This resulted in a surface microhardness increase of up to 71.2%.
The epoxy composites reinforced with flax/cotton fibers subjected to two surface treatments were prepared by hand lay-up method. Flax/cotton fabrics were subjected to bleaching using hydrogen peroxide, silanization, and two-step modification consisting of both methods. The effects of these treatments were assessed by Fourier Transform Infrared Spectroscopy (FTIR) and the fabric color was examined with accordance to CIELab method. The produced composites were subjected to the assessment of mechanical properties using static tensile and flexural tests. Moreover, impact resistance was evaluated by drop impact tests and the Charpy method. The effect of surface treatment of flax/cotton fabrics on epoxy-based composites thermomechanical properties were studied using dynamic thermomechanical analysis (DMTA) and related to structural changes investigated with scanning electron microscopy (SEM). The realized research showed that the use of a two-stage surface modification of fibers allows the production of composites with increased interfacial adhesion, as well as enhanced mechanical properties in comparison to materials manufactured using unmodified fabrics.
Hydrogen peroxide treatment is a cost-effective and simple method to improve the bioactivity of titanium implants. In this study, the effects of chloride ion concentration and temperature of hydrogen peroxide on the surface treatment of titanium were investigated using X-ray diffractometry (XRD), Field Emission-Scanning Electron Microscopy (FESEM), and tests in order to determine wettability and apatite forming ability. The results showed that at the lower temperatures of treatment (60 °C), hydrogen peroxide corroded the formed titania layer and the post-heat treatment resulted in rutile formation on the surface of titanium. At higher temperatures of treatment (100 °C), a uniform and crack-free anatase layer was formed on the surface of titanium, leading to the improvement of superhydrophilicity and the apatite forming ability of titanium. However, these properties were affected by increasing the chloride concentration of hydrogen peroxide. At appropriate conditions, titanium dental implant surfaces could be treated effectively using hydrogen peroxide, such that the time of treatment could be reduced to 5 h.
Surface-treated steel fibers were developed for enhancing the dynamic pullout performance from ultra-high-performance cement composites (UHPCC). To this end, three types of straight steel fibers with a smooth surface (plain) and longitudinal and transverse abrasions were prepared and tested in impact loading conditions. Sandpapers with various grits were used to abrade the fiber surface; hence, various surface roughness parameters could be achieved. Test results indicated that the surface of smooth steel fiber became much rougher upon abrading it using the sandpapers. The pullout resistance of the abraded steel fibers from UHPCC was better than that of the smooth fiber from the same matrix under the static and impact loads. Some of the transversely abraded steel fibers demonstrated a slip-hardening response, which has been rarely observed in commercial smooth, straight steel fiber products. Considering the pullout resistance and rate sensitivity, the transversely abraded steel fiber was the most effective reinforcement for UHPCC subjected to high loading rates, and these fibers could achieve approximately three times greater equivalent bond strength than the plain fiber. The static and dynamic bond strengths increased almost linearly with the surface roughness of the fiber, whereas the pullout energy had no apparent relation with the roughness.
A novel application for conical wire array Z-pinches to surface science is presented. The axial outflows emitted by a tungsten conical wire array in the form of both a dense plasma jet and energetic ions are used to produce morphological modification of substrate surfaces without using any kind of chemical treatment. In particular, surface modifications of (100) oriented Si substrates in the form of micropores and stripes-like formations after a single interaction of the Si to the axial outflows are obtained. It is found that the prevalence of each kind of formation, either micropores or stripes, on the treated substrate depends on the relative position of the target with respect to the wire array. The results indicate that at distances of 11 cm over the array there is still effect of the dense plasma jet outflow since both micropores and stripes are found. On the contrary, solely stripe-like patterns are found at greater distances where the effect of the dense plasma outflow is minimal or null, and only the ion outflow irradiates the surface. The description of the method and future perspectives of this novel application of surface treatment are shown and discussed.
