Papers by Keyword: Activation

Abstract: Bulk mobility and dopant activation of implanted species into 4H-SiC plays a crucial role in the carrier conduction, blocking behavior, and channel properties of a 4H-SiC vertical power MOSFET. Nitrogen and phosphorus ion implantation became the norm as n-type dopants for 4H-SiC. Therefore, the doping and temperature behavior of both species in 4H-SiC needs to be well characterized. In this study, we report a comparison in electrical characteristics between nitrogen and phosphorus implanted 4H-SiC as a function of temperature for various doping levels. For this purpose, 4-point van der Pauw samples are prepared, resistivity and Hall measurements are conducted. We found that resistivities drop as temperature increases from 140 K with phosphorus having higher resistivities at all implanted doping concentrations. The carrier concentrations increase with increase of temperature, indicating incomplete ionization of dopants. Mobilities drop at low temperature due to increased impurity scattering, reaches a peak near 300 K and drops at higher temperature due to increased phonon scattering. From the obtained data, using a two-level charge neutrality equation, the activation percentage and ionization energies of dopants in hexagonal and cubic sites for both species are extracted and compared.

Abstract: Activated carbon (AC) is an adsorbent material used for the removal of pollutants from wastewater. Unfortunately, these materials used by the industry are very expensive. This is why research is being conducted to produce low-cost activated carbons from natural biomass. The objective of this work is to study the effect of activation by orthophosphoric acid on the quality of activated carbons. The different techniques used for the characterization are: the Iodine number and the Methylene Blue Index. For activated carbons prepared in a single activation step, iodine number of 609.12 and methylene blue value of 102.48 mg/g were obtained. For those prepared in two activation steps, iodine number of 951.75 mg/g and methylene blue value of 115.14 mg/g were obtained.

Abstract: Biorecycling of wood includes many different processes aimed at the complete utilization of the main and by-products. The complete isolation of C5 and C6 sugars from wood and their further use is currently attracting attention worldwide. The C5 sugars can be catalytically converted directly into furfural or into monosaccharides’ aqueous solution for further hydrolytic treatment. The resulting lignocellulose can be used in thermochemical pyrolysis (350-400°C) for the synthesis of levoglucosan. The biochar formed during pyrolysis and the liquid residue after the isolation of levoglucosan are by-products and can be used as precursors to obtain valuable products – activated carbon composites for supercapacitor electrodes and catalysts in fuel cells.

Abstract: This article presents the results of experimental processing of hydrocarbons (petroleum and mixtures based on them) on a laboratory stand. Cavitation treatment was carried out in flow-type rotary-pulsation apparatus with different impeller diameters and rotor rotation frequencies. The aim of the work was to determine the most effective processing mode for oil blends and distillates within the framework of laboratory experiments.

Abstract: This study aimed to determine the characteristics of activated charcoal from mangroves resulting from pyrolysis and activation with 3M KCl using Fourier Transform Infra-Red (FTIR), X-Ray Diffraction (XRD) and ash content analysis and to determine the ratio of Pb, Fe and Cd metal content in river water before and after filtered with activated charcoal. The results of the FTIR test for charcoal from mangroves resulting from pyrolysis and activation with KCl showed the presence of O-H, C=C, C-H, C-N and C-Cl groups as additional groups that appeared after the activation process. The results of XRD analysis show that the lattice parameter (α) can be calculated, namely in pyrolysis mangrove charcoal = 5.79 and charcoal from pyrolysis and activation mangrove wood = 5.88. The results show that there is a change in the distance between the crystal planes after activation, with the known value of, the results of d-spacing 3 strong peaks are 3.39 , 2.94 and 5.88 . The results of the analysis of the ash content are 15.4% and exceed the maximum percentage that has been determined, because there are still impurities attached to the carbon surface. The results of the analysis using Atomic Absorbtion Spectrophotometry (AAS) showed that there were differences in the levels of Pb, Fe and Cd in river water before and after being filtered with activated charcoal. There was a decrease in Pb levels from points 1,2 and 3 as much as 73%, 49% and 55.23%. Meanwhile, Fe metal decreased from points 1, 2 and 3 as much as 58%, 66% and 81%. And on Cd there was a decrease of 44%, 61% and 92%. From these percentage results, activated charcoal from mangroves can be said to be effective because it can absorb metals in river water. Pb metal in river water in East Kombos Manado City has passed the concentration specified in Government Regulation of the Republic of Indonesia No. 22 of 2021, Class II Water Quality Standards.

Abstract: Iron is a major impurity in many water resources and leads to contamination in drinking water. One technology that can be used to reduce the iron content is adsorption using activated carbon. Activated carbon can be derived from biomass including forestry and agricultural waste. To produce an economic adsorbent, the researcher used bengkirai wood sawdust waste which contains 52.9% cellulose and 24% lignin. This material is treated by physical and chemical activation to produce activated carbon. However, there is no information on the effect of the type and concentration of activator on the performance of bengkirai wood activated carbon in reducing iron content. Thus, the purpose of this research is to understand the effect of activator type and concentration on the performance of activated carbon from bengkirai wood to adsorb iron content. There are five steps in this research which are preparation, carbonization, chemical activation, characterization and performance test. The raw material is prepared by screening to get an uniform size of bengkirai wood sawdust. Then, the uniformed bengkirai sawdust is physically activated in the carbonization step by heating it in the furnace at 600°C for 2 hours. After that, the carbon is activated using acid which are HCl, HNO₃, and H₂SO₄ with concentrations of 0.1 M, 0.3 M and 0.5 M. The characterization done in this study are iodine number test and functional group test using Fourier Transform Infrared Spectroscopy (FTIR). The final step is performance test of activated carbon to adsorb iron in the water by contacting the activated carbon into water containing iron for 1 hour. The concentration of iron in the water is measured using Uv vis spectofometry. The result shows that the carbon activation with H₂SO₄ 0.1 M produce activated carbon with the highest iodine number compared to the other type of activator and concentration. The iodine number for this activated carbon is 839.76 mg/g. However, the activated carbon treated using HNO₃ shows the best performance to adsorb iron in water.

Abstract: Local date palm (Phoenix dactylifera) waste stems were used to prepare activated carbon (AC) using KOH, NaCl and ZnCl₂ as activation agents. Carbonization was conducted at 600 °C for 2hr under nitrogen flow, followed by activation at 750 °C for 2 hr under carbon dioxide flow. AC was characterized using a scanning electron microscope (SEM), Attenuated total reflectance Fourier transform infrared (ATR FT-IR), Thermogravimetric analysis (TGA), Iodine adsorption, BET, micropores, and mesopores surface areas at different carbon-to-activation-agent-ratios (1:1, 1:2, 1:3). FT-IR spectra results showed a reduction in AC-NaCl bands compared to other AC, which indicates less functional surface groups. At 750 °C, the TGA analysis showed the carbon yield as AC-ZnCl₂ > AC-NaCl > AC-KOH, however, among all samples, AC-NaCl at 1:2 ratio was the best in terms of iodine removal. This treated AC sample exhibited about 18.3 % maximum iodine removal, which indicates the high surface area and porosity with 550.4380 m²/g, 348.7432 m²/g, and 201.6947 m²/g BET, micropores and mesopores surface areas, respectively. In conclusion, the local Omani date palm waste stems can be used for AC production with a well porous structure using cheap and environmentally friendly salts as activation agents. In addition, the produced AC attained better adsorption characteristics among other alternatives.

Abstract: The article presents the results of the evaluation of the strength of fine-grained concrete of ordinary grades on mixed cement binders with ash and slag waste of thermal power plants. To ensure the required strength, the preliminary activation of the mixed binder was envisaged, which is one of the main techniques for reducing cement consumption. Experimental-statistical models of the strength properties of fine-grained concrete was obtained, which make it possible to predict the required strength with a minimum consumption of cement and the optimal concentration of ash in the binder.

Abstract: The possibility of increasing crack resistance, strength and elastic modulus of polymer-containing compositions due to the directed organization of their structure by internal, external and complex activation is investigated. Filled polymer compositions are presented as open complex dynamic systems. This made it possible to use rational fillers and special matrix-transformer of external electromagnetic influences as factors for controlling the processes of their structure formation and hardening to obtain materials with the required properties.

Abstract: Plastic pollution is an environmental problem that has not resolved until now. Pyrolysis is able to be a solution to reduce plastic waste. The use of catalysts will reduce heating temperatures, speed up processing time, and increase product yield. Natural zeolite has the potency as a catalyst in pyrolysis process due to its micropore structure, high acidity and thermal stability. The purpose of this research is to determine the effect of active zeolite catalyst on the polypropylene pyrolysis. The main process of this study is pyrolysis of polypropylene (PP) plastic waste without catalysts and with natural zeolite catalysts which were non-activated and activated. Natural zeolites were activated by HF, HCl and NH₄Cl. The well result of this research is represented by the yield, viscosity, calorific value, FTIR and GC-MS analysis. Based on the results of diffractogram analysis, natural zeolites catalyst in this study is included in modernite minerals crystalline. The ratio of Si/Al in zeolite before activation was 7.07 and the acidity was 0.697 g/mmol. After the activation process, the ratio of Si/Al and zeolite acidity increased by 62.181% and 43.84%. The use of active natural zeolite catalysts in pyrolysis PP could reduce the total reaction time by 57.14%. Pyrolysis products with active zeolite catalyst compared to without catalysts had clearer color and higher heating value, compared to pirolysis without catalyst. Based on function group analysis with FTIR, the mixture of hydrolyzed compounds containing successive functional groups are-C-H (alkanes), double bond of C=C, hydroxyl-OH group which can be determined as phenol (ArOH), alcohol (ROH), and carboxylic acid (RCOOH). The GC-MS analysis showed that pyrolysis products are composed of a mixture of alkanes, cycloalkanes, alkenes, carboxylic acids with aromatic rings, and ketones. The pyrolysis products without catalysts consist of 5-11 (C5-C11) carbon atoms, whereas the range of carbon atoms of pyrolysis products with active zeolite catalysts was 6-24 (C6-C24).