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In the pursuit of achieving zero emissions, exploring the concept of recycling metal waste from industries and workshops (i.e., waste-free) is essential. This is because metal recycling not only helps conserve natural resources but also requires less energy as compared to the production of new products from virgin raw materials. The use of metal scrap in rapid tooling (RT) for injection molding is an interesting and viable approach. Recycling methods enable the recovery of valuable metal powders from various sources, such as electronic, industrial, and automobile scrap. Mechanical alloying is a potential opportunity for sustainable powder production as it has the capability to convert various starting materials with different initial sizes into powder particles through the ball milling process. Nevertheless, parameter factors, such as the type of ball milling, ball-to-powder ratio (BPR), rotation speed, grinding period, size and shape of the milling media, and process control agent (PCA), can influence the quality and characteristics of the metal powders produced. Despite potential drawbacks and environmental impacts, this process can still be a valuable method for recycling metals into powders. Further research is required to optimize the process. Furthermore, ball milling has been widely used in various industries, including recycling and metal mold production, to improve product properties in an environmentally friendly way. This review found that ball milling is the best tool for reducing the particle size of recycled metal chips and creating new metal powders to enhance mechanical properties and novelty for mold additive manufacturing (MAM) applications. Therefore, it is necessary to conduct further research on various parameters associated with ball milling to optimize the process of converting recycled copper chips into powder. This research will assist in attaining the highest level of efficiency and effectiveness in particle size reduction and powder quality. Lastly, this review also presents potential avenues for future research by exploring the application of RT in the ball milling technique.

Graphitic carbon is a valuable material that can be utilized in many fields, such as electronics, energy storage and wastewater filtration. Due to the high demand for commercial graphite, an alternative raw material with lower costs that is environmentally friendly has been explored. Amongst these, an agricultural bio-waste material has become an option due to its highly bioactive properties, such as bioavailability, antioxidant, antimicrobial, in vitro and anti-inflammatory properties. In addition, biomass wastes usually have high organic carbon content, which has been discovered by many researchers as an alternative carbon material to produce graphite. However, there are several challenges associated with the graphite production process from biomass waste materials, such as impurities, the processing conditions and production costs. Agricultural bio-waste materials typically contain many volatiles and impurities, which can interfere with the synthesis process and reduce the quality of the graphitic carbon produced. Moreover, the processing conditions required for the synthesis of graphitic carbon from agricultural biomass waste materials are quite challenging to optimize. The temperature, pressure, catalyst used and other parameters must be carefully controlled to ensure that the desired product is obtained. Nevertheless, the use of agricultural biomass waste materials as a raw material for graphitic carbon synthesis can reduce the production costs. Improving the overall cost-effectiveness of this approach depends on many factors, including the availability and cost of the feedstock, the processing costs and the market demand for the final product. Therefore, in this review, the importance of biomass waste utilization is discussed. Various methods of synthesizing graphitic carbon are also reviewed. The discussion ranges from the conversion of biomass waste into carbon-rich feedstocks with different recent advances to the method of synthesis of graphitic carbon. The importance of utilizing agricultural biomass waste and the types of potential biomass waste carbon precursors and their pre-treatment methods are also reviewed. Finally, the gaps found in the previous research are proposed as a future research suggestion. Overall, the synthesis of graphite from agricultural bio-waste materials is a promising area of research, but more work is needed to address the challenges associated with this process and to demonstrate its viability at scale.

In this paper, we report the results of our investigation on the possibility of producing foam concrete by using a geopolymer system. Class C fly ash was mixed with an alkaline activator solution (a mixture of sodium silicate and NaOH), and foam was added to the geopolymeric mixture to produce lightweight concrete. The NaOH solution was prepared by dilute NaOH pellets with distilled water. The reactives were mixed to produce a homogeneous mixture, which was placed into a 50 mm mold and cured at two different curing temperatures (60 °C and room temperature), for 24 hours. After the curing process, the strengths of the samples were tested on days 1, 7, and 28. The water absorption, porosity, chemical composition, microstructure, XRD and FTIR analyses were studied. The results showed that the sample which was cured at 60 °C (LW2) produced the maximum compressive strength for all tests, (11.03 MPa, 17.59 MPa, and 18.19 MPa) for days 1, 7, and 28, respectively. Also, the water absorption and porosity of LW2 were reduced by 6.78% and 1.22% after 28 days, respectively. The SEM showed that the LW2 sample had a denser matrix than LW1. This was because LW2 was heat cured, which caused the geopolymerization rate to increase, producing a denser matrix. However for LW1, microcracks were present on the surface, which reduced the compressive strength and increased water absorption and porosity.

Rapid development of advanced technology in Malaysia gave impact increasing in the accumulation of heavy metal every day in our daily life through wastewater. Long term exposure of human bodies to heavy metals susceptible to receives various infections and diseases. From an environmental and economic perspective, adsorption is acceptable process that can be applied in wastewater treatment. However, usage of activated carbon most acknowledged and costly adsorbents lead people to find an alternative to activated carbon. Several studies of physical properties of geopolymer make them gain attention to replace an activated carbon in the treatment of heavy metal. This paper review adsorption of heavy metal by using geopolymer.

Iron Ore Tailings (IoTs) were mainly released from ore concentrating processes, which caused serious environmental problems and resulted in a large number of emissions detrimental to the ecological balance. The wise application of IoTs served the purpose of environmental protection and sustainable development. Therefore, the objective of this study was to perform a comprehensive and extensive examination of IoTs’ application as ternary supplementary cementitious materials (SCMs), by combining FA with RHA for sustainable foamed concrete (FC) production. Five batches of FC mix were prepared with varying amounts of ternary SCMs, including the control mix. IoTs, RHA, and FA were used as partial replacements for cement, with weight fractions of 0%, 12%, 24%, 36%, 48%, and 60%. The ternary SCMs system consisted of IoTs, FA, and RHA, with a weight ratio of 1:1:1. The freshness, pore structure, transport, and strength properties were evaluated. The test results showed that FC’s setting time and hardened density increased, while the mix workability decreased with increasing ternary SCMs substitutes. Substituting 24% SCMs improved porosity, water absorption, sorptivity, intrinsic permeability, chloride ion diffusion, and resulted in a denser microstructure. This significantly improved the compactness of the FC mixture, resulting in the best strength properties. The test findings indicated a significant improvement of 14.62%, 24.20%, and 28.84% in compressive, flexural, and splitting tensile strength, respectively, compared to the control mix by substituting 24% SCMs. The research findings enhanced the sustainable utilization of IoTs as an eco-friendly ingredient for substituting cement in FC production.

Persistent research work has aided the development of supplementary cementitious materials, contributing to both sustainable development and mitigating environmental impacts. This study utilized Tianqi aluminosilicate (TAS) as partial replacement for Ordinary Portland Cement (OPC) in foamed concrete (FC) mix. The mechanical, transport, and microstructural characteristics of the concrete were explored. The formed concrete mixes were developed by varying TAS from 0 to 40%, in steps of 10% for OPC to identify optimal performance. The mechanical characteristics (compressive, flexural, splitting tensile, and elastic modulus) improved by 18–25% over control and peaked at 20% TAS. At 20% TAS substitution, the transport properties (water absorption and permeability) improved significantly, which corresponds to 35% and 28%, reduction, respectively. SEM analysis revealed that TAS refined pore structure, yielding a denser matrix with homogeneous hydration product distribution. The result revealed foam stability and uniformity in mixes containing TAS, and an improvement in mechanical and durability of the concrete. Filler effect and pozzolanic activities of TAS were identified as two key factors responsible for the observed results. There was pore refinement improved secondary hydration in the concrete matrix. The results show that 20% TAS substitution improves strength and durability while lowering OPC use and striking the ideal performance balance. From the results, TAS proved to be a sustainable supplementary cementitious material aiding the durability of the mixes. This work advances eco-friendly construction practices by demonstrating TAS’s viability in high-performance FC applications.

Growing environmental concerns have intensified research into sustainable construction materials, such as natural fiber-reinforced concrete. Among these, lightweight foamed concrete (LFC) stands out for its reduced material consumption, improved thermal insulation, and lower environmental footprint. The integration of natural fibers, such as sugarcane bagasse fiber (SBF), into LFC has the potential to further enhance its performance. This study investigates the influence of varying SBF weight fractions (0%, 1%, 2%, 3%, 4%, and 5%) on the physical, mechanical, and durability properties of LFC with a target density of 1000 kg/m 3 . The primary objective was to determine the optimal SBF content for achieving superior material characteristics. Experimental results revealed that the inclusion of 4% SBF provided the best overall performance, improving compressive strength by 53%, increasing ultrasonic pulse velocity (UPV) by 17%, and reducing drying shrinkage by 58% compared to the control mix. Additionally, slump flow decreased progressively with higher fiber content, indicating enhanced cohesion. Water absorption and porosity were significantly reduced with increasing SBF, with the 5% mix showing up to a 19% decrease in water absorption. Thermal conductivity also declined slightly, suggesting improved insulation properties. Microstructural analysis confirmed better fiber-matrix bonding at the optimal fiber content, contributing to the observed improvements in performance. This study offers valuable insights into the mechanical, thermal, and durability characteristics of LFC-SBF composites, highlighting their potential as sustainable construction materials.

This investigative study aims to study the mechanical and morphological properties of fly ash (FA)-based geopolymer paste as a repair material when applied on ordinary Portland cement (OPC) overlay concrete. The first part of this study investigates the optimal mix design of FA-based geopolymer paste with various NaOH concentrations of 8, 10, 12, and 14 M, which were used later as a repair material. The second part studies the bonding strength using a slant shear test between the geopolymer repair material and OPC substrate concrete. The results showed that a shorter setting time corresponds to the higher NaOH molarity, within the range of 53 and 30 min at 8 and 14 M, respectively. The compressive strength of FA-based geopolymer paste was found to reach 92.5 MPa at 60 days. Also, from the slant shear test results, prism specimens with 125 mm length and 50 mm wide have a large bond strength of 11 MPa at 12 M. The scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) analysis showed that the OPC substrate has a significant effect on slant shear bond strength, where the presence of free cations of Ca2+ on the OPC substrate surface contributed to the formation of calcium alumina-silicate hydrate gel (C-A-S-H) by building various cross-links of Ca-O-Si.

High entropy alloy (HEA) involves the addition of five or more elements into the materials system. This provides a multidimensional configuration space that is limitless in terms of its properties and functions. Some high-entropy alloys have already been shown to have superior properties over conventional alloys, especially the CoCr-based HEA materials. Better high-entropy alloy applications may be discovered, especially in micro- and nano-level structures, hence the development of thin film/coating -based HEA materials. Therefore, in this review paper, we are aiming to provide recent studies on the thin film/coating-based high-entropy alloy on fundamental issues related to methods of preparation, phase formation and mechanical properties. We found that sputtering has been extensively used to grow thin-film-based HEAs as it allowed parameters to be controlled with homogeneous growth. The evolution from bulk to thin samples can also be observed with the mechanical properties has exceeded the bulk-based HEA expectations, which are high hardness, better interfacial bonding and tribological behaviour and higher corrosion resistant.

Nowadays, lead-free solder has been currently used in electronic packaging technology as part of soldering material. Since SnPb was detected to produce toxicity and might harm the consumers, the usage of Pb solder has been banned by WEE and RoHS. Therefore, various studies have been developed as alternatives to replace the usage of SnPb. Since lead-free solder might not perform as well as their traditional SnPb, researchers suggested to add some elemental reinforcement particles in matrix alloy. Previously, addition of ceramic reinforcement has been widely known in enhancing the properties of solder-substrate. This paper reviews about the presence studies of ceramic as solder reinforcement, the characteristics of geopolymer ceramic as potential solder reinforcement, and their properties in providing a superior solder joint. In this review, the characterization is divided into two stages; 1) characterization of geopolymers in terms of microstructural and crystallographic; 2) characterization of solder properties in terms of intermetallic layer growth (IMC), wettability, and its mechanical properties