Materials Science Forum Vol. 998

Abstract: This paper introduces a study on multi-criteria optimization of the dressing parameters in surface grinding for 90CrSi tool steel. The aim of the study is to minimize the surface roughness, the normal shear force and maximize the grinding wheel life by using Taguchi method and Grey Relational Analysis (GRA). This multi-objective optimization is obtained by optimizing four four-level and two two-level dressing parameters in sixteen experiments based on an orthogonal array L₁₆(4⁴×2²). From the results of the study, the optimum dressing parameters were proposed. Also, to evaluate the optimum dressing model, an experiment was performed. The results of the comparison between the predicted model and the experiment show that the proposed model has been proven and it can be used for further applying of surface grinding.

Abstract: Herein, Ag-anatase photocatalysts were synthesized though chemical reduction method under room temperature by using PVP and NaBH₄ as stabilizer and strong reducing agent, respectively. The prepared photocatalysts were characterized by the following technique: XRD, SEM, HR-TEM, EDX, and UV-Vis-NIR. The photocatalytic performance of 0.05 g of photocatalysts were performed under UV irradiation within 1 h by using 10 mg/L of rhodamine B as the representative of organic pollutant. The results demonstrated that the optimum Ag loading contents were 2 %wt (2-ST) which can degrade rhodamine B up to 98.54%. Therefore, the photocatalytic performance of bare anatase could be enhanced by deposited Ag nanoparticles. Further, this prepared Ag-anatase could be suitable for environmental application.

Abstract: Titanium dioxide (TiO₂) is known as one of the widely used catalysts in photocatalysis process. Recently, the photocatalysis of TiO₂ has been implied in water purification and treatment, particularly dyes and organic compounds degradations. Naturally, the TiO₂ can be found in three phases including anatase, rutile and brookite; each phase has its own specific properties such as grain size, stability and band gap energy. In this work, the effect of calcination temperature on the structure, morphology and photocatalytic activity were investigated. The data suggested that the anatase/rutile ratio of TiO₂ can be controlled through the calcination process. The phase transformation data strongly indicated the liner function between percentage of rutile phase and calcination temperature. The BET analysis provided the consistent data with XRD patterns by showing that the specific surface area was decreased by increasing calcination temperature. The photodegradation of methylene blue under UV irradiation proved that the mixed phase of anatase/rutile ratio at 78.5/21.5 provided the highest photocatalytic activity. The phase composition ratio can influence the nanoparticles properties including band gap, specific surface area and energy band structure. Therefore, the control of anatase/rutile ratio was an alternative to enhance the photocatalytic activity of TiO₂ nanoparticles for dyes and organic compounds degradations.

Abstract: The dye-pigments and organic compounds are known as significant pollutants in wastewater of textile industrial. Among of treatment technologies, the photocatalysis using TiO₂ nano particles has potential on-site process for removing the dye-pigments and organic compounds, due to no hazardous waste and inexpensive. In this work, the TiO₂ nanoparticles were synthesized by two different methods of hydrothermal and sol-gel. Nanoparticle of TiO₂ synthesized by hydrothermal method contained pure anatase phase as similar as the TiO₂ nanoparticles synthesized by sol-gel method. However, the TiO₂ synthesized by hydrothermal method provided the higher specific surface area and pore volume rather than the another TiO₂. Further, the high efficiency 86% of methylene blue photodegradation was observed during the by using TiO₂ synthesized by hydrothermal method as photocatalyst, whereas the efficiency was only 72% for TiO₂ synthesized by sol-gel method.

Abstract: Surface area and particle size are significant properties of a catalyst that determine the reaction rate of the heterogeneous catalyst. In this research, calcium oxide derived from industrial eggshell waste was synthesized by thermal decomposition method under air-atmosphere. The obtained eggshell waste was washed, dried, and ground to 420 μm followed by calcination of the ground eggshell in different conditions including calcination temperature (800 to 900 °C) and holding time (1 to 4 hours). Changes of pore structure and the median particle size diameter of the obtained calcium oxides were systematically investigated by various scientific instruments. Results from powder X-ray diffractometer (PXRD) indicated that the calcium oxide can be obtained after calcination at both 800 and at 900°C. Laser diffractometer shows that median particle size diameter of calcium oxide significantly decreased by about 76-95 % with increasing of both calcination temperature and holding time. Additionally, specific surface area of calcium oxides determined by N₂ adsorption experiment at-195 °C shows that surface area of calcium oxide dramatically decreased (37-84 %) with increasing both calcination temperature from 800 to 900 °C and calcination time from 1 to 4 hours. These results indicated that both calcination temperature and time play an important role in the shrinkage of pores of calcium oxide. Higher calcination temperature and longer holding time induce more shrinkage of pore leading to smaller particle size diameter and lower surface area of the calcium oxide catalyst.

Abstract: In this research, titanium dioxide (TiO₂) nanoparticles were immobilized into polyvinyl alcohol (PVA) matrix without and with surfactants via solution casting film combined with thermal treatment method. The dispersion and distribution of TiO₂ nanoparticles presented by scanning electron microscopy (SEM) showed the uniform distribution of TiO₂ nanoparticles in PVA matrix with surfactant. Fourier-transform infrared spectroscopy (FTIR) showed increasing intensity peak at 560-800 cm^-1 corresponding to Ti-O stretching vibration indicating interaction between PVA and TiO₂ after thermal treatment. X-ray diffraction (XRD) result showed peak of PVA crystal structure due to the thermal treatment, and the addition of surfactant could decrease the average crystallite size of TiO₂ in PVA/TiO₂ nanocomposite films. Photocatalytic activity was determined from the film efficiency on removal of methylene blue (MB) under ultraviolet (UV). The results showed the greater MB removal efficiency of the PVA/TiO₂ nanocomposite films with surfactant and thermal treatment than those without surfactant and thermal treatment.

Abstract: Commercial activated carbon (CAC) was modified using low-pressure radio frequency nitrogen plasma discharge (NPD) operating at 0.3 mbar and 40 kHz. The surface chemistry of CAC was modified using HNO₃ pre-oxidation to possibly influence the reactivity of NPD. The results of x-ray photoelectron spectroscopy (XPS) suggested that pre-oxidation reduces aromaticity, generates aliphatic carbons (C-C and C-H), and increases carboxylic functional groups (COOH) which probably enhances the nitrogen plasma functionalization based on the N/C ratio for CAC-O-P (4.29 %) compared to CAC-P (2.88 %). FTIR was used to confirm such effects of pre-oxidation from the functional groups present on the carbon surface. The total surface area was identified using Langmuir and Brunauer–Emmett–Teller (BET) N₂ adsorption isotherms at 77 K. Both pre-oxidation and plasma treatment caused an increase in the surface area of CAC up to 150 percent. Carbon t-plot method was used to determine the micropore volume, micropore area, and external surface area. The total surface area of each activated carbon was mostly constituted of micropore area which was identified to be directly proportional to the micropore volume. Scanning electron microscope (SEM) confirms the destruction of the surface morphology for CAC-O that might have caused the increase in surface area. Development of surface threadlike structures were observed for the NPD treated CAC-O. NPD favors the development of NH₂ functionalities and reduces the aromaticity of activated carbons while enhancing the surface morphology and the surface area.

Abstract: The present work is aim to study the adsorption/desorption properties of the Ag-modified Y zeolite towards toluene as well as its high temperature behavior under the prompt thermal aging conditions. The Ag/Y samples were obtained by an ion exchange technique and mixed with pure alumina used as a binder. The reference samples were prepared by an incipient wetness impregnation of alumina with a solution of silver nitrate and mixed with pure HY zeolite. The initial and aged samples were characterized by TEM and XRD methods. It was found that the Ag-modified Y zeolite strongly adsorbs toluene. Irreversible sorption of toluene over the most active silver sites was shown to exclude them from the participation in oxidation processes, thus diminishing the overall efficiency of the adsorption-catalytic system.

Abstract: Plastic is materials that are not easily broken down, so it can cause a variety of complex problems such as loss of natural resources, environmental pollution, and depletion of landfill space. Plastic favored by the public is Polypropylene (PP) and High Density Polyethylene (HDPE) for example, food storage, transparent drinking glasses and drinking bottles for babies. This will be a problem in the future. Some alternatives used to reduce the volume of plastic waste are the thermal transformation process which is divided into three types of processing, namely combustion, gasification, and pyrolysis. Pyrolysis is a process of thermal degradation of long chains into smaller molecules. The process of pyrolysis in this study used a variety of catalysts (without catalyst, 5%, 10%, 15%, and 20%) and used variations in particle size, namely size I (30 cm³); size II (7.5 cm³); size III (1,875 cm³) weighing 350 grams of plastic cups and 350 grams of bottle caps. Pyrolysis run for 100 minutes and took the result of pyrolysis every 20 minutes interval. The test carried out by using proximate analysis, fuel specification analysis, and GC-MS. Based on the result of research conducted on the pyrolysis process of a mixture of HDPE and PP variations of catalysts, it obtained optimum liquid and gas yields of 98.57% and 1.43%. Besides, in the size variation, the optimum liquid and gas yield was 96.57% and 3.43%. The proximate result has fulfilled the conditions set by the value of ash content, fly substance, and carbon bound 0.15%; 99.57%; 0.28%. In the GC-MS (Gas Chromatography-Mass Spectrometry) test the highest % area was 39.18% with C₉H₁₈ or 2,4-dimethyl-1-heptane compounds. The best simulation result obtained the value of activation energy and reaction speed for liquid and gas in the variation of the catalyst of (87,930.07; 101,527.17) J/mol and (2.03 x 10²; 3.74 x 10³).

Abstract: Understanding the process of water oxidation, especially intermediate species, represents an important step toward gaining a mechanistic understanding of new emerging catalysts. The aim of this study is exploring the process of water oxidation and electrolyte orientation under external potential when using an emerging water oxidation catalyst, CoB_i, in sodium borate (NaBi) buffer using in situ attenuated–total-reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy. CoB_i is generated via electrodeposition from aqueous solutions containing borate and Co²⁺. IR spectra were obtained for CoB_i films under applied potentials supporting water oxidation catalysis. The spectra of water and CoB_i on ZnSe/Cr/Au electrode surfaces change in intensity and their slope depends on the potential, which is rarely reported. The appearance of new bands at certain potentials is interpreted in terms of the potential-dependent re-alignment of water and borate molecules both from the film and electrolyte. A superoxide surface intermediate at 1027 cm^-1 was observed in both thin and thick films. It is proposed to be Co (III)OO*H bridging and relates to a fast water oxidation process. The chemical structure of the intermediate species is proposed finally.