Non-isothermal crystallization kinetics of a rapidly solidified as-cast TiZrHfNiCu high entropy bulk metallic glass

This paper aims to investigate the thermal behavior and crystallization kinetics of TiZrHfNiCu high entropy bulk metallic glass (HE-BMG) alloy using the standard procedure of Differential Scanning Calorimetric (DSC) annealing technique. The alloy was produced using an arc melting machine with a critical diameter of 1.5 mm. The crystallization kinetics and phase transformation mechanism of TiZrHfNiCu HE-BMG was investigated under the isochronal condition at a single heating run based on the Johnson-Mehl- Avrami (JMA) theory. In isochronal heating, the apparent activation energy for glass transition and crystallization events was analyzed by Kissinger and Ozawa methods. The average activation energy value for crystallization of TiZrHfNiCu amorphous alloys in isochronal modes was 226.41 kJ/mol for the first crystallization and 297.72 kJ/mol for second crystallization stages. The crystallization mechanism of the first step was dominated by two- and three-dimensional growth with increasing nucleation rate, while the crystallization mechanism in the second stage was dominated by two-dimensional crystallization growth with a constant nucleation rate. The diffusion mechanism result proved the theory of sluggish atomic diffusion of HEA at elevated temperature

Composition of fatty acid methyl ester in microalgae Chlorella vulgaris : Comparison between various methods of harvesting, extraction and transesterification

The aim of the study was to identify which of methods produces the highest yield of fatty acid methyl ester (FAME) from microalgae. Different methods of harvesting (centrifugation, Cen & coagulation, Co), extraction (Test Tube, TT & Soxhlet, Sox) and transesterification (direct transesterification, d-trans & extraction transesterification, ext-trans) were considered. The procedures of this research consists of microalgae cultivation, harvesting of biomass and extraction of oil to obtain the lipid. The further process of converting lipid into FAME is followed by transesterification process. The FAME compositions of Chlorella vulgaris were analyzed using Gas chromatography mass spectrometry (GC–MS). The main components were consists of palmitic, stearic and oleic acids for both transesterification methods. However, FAME extracted from d-trans contained more components (linoleic and linolenic acid) than ext-trans. Furthermore, the highest amount of FAME gained by ext-trans was produced by the method of centrifugation-test tube (Cen-TT). Although Cen-TT produced the highest amount of FAME for ext-trans, it still cannot meet the highest amount of FAME produced by d-trans. Therefore, the Cen-TT method was selected to be the best microalgae harvesting and extraction method in ext-trans meanwhile the most efficient transesterification method was d-trans

Enhancement of fenton process using high entropy alloy powder as catalyst

The Fenton process is one of the chemical oxidation degradation processes widely used in wastewater management due to being environmentally safe. The Fenton process is a reaction in which iron-catalyzed hydrogen peroxide to generate hydroxyl radical. Even though the Fenton process can degrade the azo dye solution, there are still substantial limitations, such as high sludge production and limited catalytic activity. This study focus on improving the azo dye degradation process in the Fenton process. Thus, a novel alloy material known as High Entropy Alloy (HEA) powder has been proposed for use as a catalytic material in the Fenton process. Mechanical alloying method was used to produce HEA powder, which is expected to considerably improve its efficiency in the degradation of azo dyes. The result shows the presence of HEA as catalyst improves the Fenton reaction by providing additional actives sites. This research contributed to the development of an appealing, low-cost, and efficient approach for HEA functional applications in wastewater management

Assisting Liquid Phase Sintering of Pure Aluminum (Al) by the Tin Addition

In the present study, the addition of tin (Sn) to the pure Al system was done, and its effects on the morphology, density, and compressive yield strength of pure Al were analyzed systematically. In this context, the morphology of sintered Al revealed enhanced wettability and sintering response between Al particles with increased Sn content. Moreover, physical characteristics of sintered Al alloys demonstrated oxidation phenomenon (black color specimen) with the lowest Sn content of 1.5 weight percent (wt.%), in which a higher Sn content of 2 and 2.5 wt.% produced silver color specimens, implying a reduction in oxidation. Additionally, densification of sintered Al alloys was greatly promoted with increased Sn contents, suggesting effective wetting as confirmed by the previous morphological observations. Similarly, the compressive yield strength of sintered Al alloys improved with increased Sn content which might be due to the enhanced inter-particle contacts between Al particles and sufficient wetting by molten Sn. Based on the results obtained, the introduction of Sn powder at various contents improved the sintering response of pure Al powder by providing sufficient liquid-phase sintering. Therefore, the sintered Al alloys had enhanced the morphological, densification, physical characteristics, and compressive yield strength

Natural carotenoid pigments of 6 chlorophyta freshwater green algae species

Nowadays, halal products are gaining wider recognition as a new benchmark for safety and quality assurance.As a consequence the commercial development of microalgae is established due to their high value chemicals, for examples, β-carotene, astaxanthin, phycobilin pigments and algal extracts for cosmaceutical products. Therefore, many researchers have gained interest to study the potential of microalgae as new valuable chemicals and other product sources. The aim of the research is to explore new sources of pigments to be used as halal food colorants. This quest is not only directed in finding natural alternatives for synthetic dyes, but also to discover new taxons for the carotenoid production. Thus, there is a solid need to investigate the potential of natural pigments, particularly carotenoids in microalgae to be fully utilised and commercialised especially in halal market, health advantages, food products and dye technology. A total of 6 species was evaluated for quantitative and qualitative carotenoid composition, namely, Chlorella fusca, Chlorella vulgaris, Selenastrum capricornutum, Pandorina morum, Botryococcus sudeticus and Chlorococcum sp.The main carotenoids identified in all species through HPLC analysis were lutein, β-cryptoxanthin and β-carotene. The ratio of these carotenoids varies between species. Lutein was detected substantially higher in Chlorella fusca (69.54±11.29 μg/g DW); β-cryptoxanthin in Pandorina morum species (1.24±0.33 μg/g DW) whereas β-carotene in Chlorella vulgaris (18.42±9.2 ug/g DW). The significant outcome of the research will be new findings of new natural carotenoid pigment sources as potential food colorants and bioactive compounds which can be beneficial to halal health promoting products industry

Response surface optimization of hydrogen-rich syngas production by the catalytic valorization of greenhouse gases (CH4 and CO2) over Sr-promoted Ni/SBA-15 catalyst

Dry reforming of methane (DRM) which utilizes CO2 and CH4, is a more efficient and environmentally friendly syngas production method. However, since the technique is endothermic, catalyst deactivation from sintering and carbon deposition has prevented its industrial implementation. This study investigated the effect of Strontium (Sr) promoter on Ni-based catalyst synthesized on SBA-15 support via the impregnation method. The incorporation of Sr as a promoter has demonstrated distinct advantages, primarily attributed to its remarkable capability to inhibit carbon formation. This property imparts a notable enhancement in the stability of the catalyst, thereby extending its operational lifespan and maintaining consistent catalytic performance. The physicochemical properties of the fresh catalyst were observed by using various characterization techniques such as X-Ray diffraction (XRD) analysis, N2 physisorption analysis, field emission scanning electron microscopy (FESEM), and temperature programmed reduction using hydrogen as the probing gas (TPR-H2). The catalysts were tested in DRM reaction using a tubular fixed bed reactor at 800 °C with an equimolar feed ratio. Overall, 1% Sr promoted Ni/SBA-15 showed enhanced performance having CO2 and CH4 initial conversions of 88.5% and 96.5%, respectively while remaining stable for 320 min on stream. Furthermore, the predicted optimal condition was 713.73 °C and a feed gas ratio (CH4:CO2) of 1.12, with CO2 and CH4 conversion rates of 69.59% and 84.83%, respectively, resulting in an H2:CO ratio of 1.00. Slight differences from the predicted values were considered insignificant, validating the Srb catalyst at a 95% confidence level with a 5% likelihood of error in the RSM model

Development of High Entropy Alloy (HEA) as catalyst for Azo dye degradation in Fenton process

Azo dye is widely used in the textile industry since it is cost effective and simple to use . However, it becomes a continuous source of environmental pollution due to its carcinogenicity and toxicity. Various methods had been used to remove the azo dye in solution. One of the famous and repeatedly used is Fenton process. The Fenton’s process is one of the advanced oxidation process where iron catalysed hydrogen peroxide to generate hydroxyl radical. Treating azo dyes in solution requires a catalyst to enhance the process of degradation. Herein, high entropy alloy (HEA) has been proposed as a catalytic material to enhance the performance of Fenton process for azo dye degradation. HEA has been reported as a promising catalyst due to its high surface area. The higher the number of active sites, the higher the rate of azo dye degradation as more active sites are available for adsorption of azo dyes. The results have shown that HEA can be used as a catalyst to fasten the Fenton’s reaction since the degradation time is proven to be shorter in the presence of HEA. The method derived from the result of this study will contribute in treating azo dyes for wastewater management in Fenton process