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The solid-state recycling technique has gained significant attention for its ability to reduce metal losses, energy consumption, and solid waste. This study introduced solid-state recycling method to develop zirconia-reinforced AA7075/AA7050 aluminum chip-based matrix composite via a hot press forging process (HPF). The chips were cold-compacted at 35 tons and then hot-forged through a dog bone-shaped die. Full factorial and response surface methodology (RSM) designs were applied using Minitab 18 software. The Face Centred Composite (CCF) of RSM was adopted to rank each factor's effect and analyze interactions between input factors and output responses, followed by process optimization. The selected factors of temperature (Tp) and volume fraction of zirconia (ZrO2) nanoparticles (Vf) were set at 450, 500, and 550 °C with 5, 10, and 15 wt %, respectively. The analyzed responses were ultimate tensile strength (UTS) and microhardness (MH). SEM micrograph revealed a slightly uniform distribution of ZrO2 particles in the matrix. The developed composite gained the maximum strength of 262.52 MPa, a microhardness of 135.5 HV and a density of 2.828 g/cm³ at 550 °C and 10 wt % setting. RSM optimization results suggested 550 °C and 10.15 wt % as optimal conditions for maximum UTS and MH. The preheating temperature exhibited a more significant influence than the ZrO2 volume fraction on the composite's mechanical properties; however, both had a slight effect on grain size. The future prospects of this work are briefly addressed at the end. In conclusion, the HPF process was found to be an efficient recycling method for mitigating environmental impacts by conserving energy and materials. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: Air pollution is associated with population growth and economic advancement. Severe cardiovascular complications that require extensive medical service are aggravated by air pollutants. This study illustrates the trend and correlation of cardiovascular disease hospital admission with air pollutants in Sabah for the past 9 years (2010-2019). The additional information obtained from this study will be useful to enhance proper environmental management and reduce air pollution in the cities of Sabah. METHODS: Ecological study design was utilized with cardiovascular disease hospital admission and ambient air pollutants in Sabah retrospective data. Data were collected from four districts with established continuous air quality monitoring stations. Collected data were analysed spatially and statistically. Autoregressive integrated moving average modelling was implemented to forecast the cardiovascular disease hospital admission. FINDINGS: Kota Kinabalu recorded the highest hospital admissions for cardiovascular disease, followed by Sandakan, Tawau and Keningau. The cardiovascular disease hospital admission prevalence rate in Kota Kinabalu was 12.45 per 1,000 population, followed by Sandakan, Tawau and Keningau (4.54; 4.18; and 5.88 per 1,000 population) in 2019. The cardiovascular hospital admissions increased in Kota Kinabalu, Sandakan and Tawau. The nitrogen dioxide (<0.04 ppm), carbon monoxide (<9 ppm), ozone (<0.05 ppm) and PM10 (<100 µg/m3) gases detected are below the national standard limit levels. In the later years of the series, the ozone and fine particulate gases intensify. Carbon monoxide has the highest positive correlation with cardiovascular disease hospital admission compared to other air pollutants. The autoregressive integrated moving average (0,1,1) with carbon monoxide and ozone as external regressors is the model with minimum Akaike information criterion. CONCLUSION: The carbon monoxide concentration in ambient air illustrates a potential risk for the increasing cardiovascular disease hospital admission number in Sabah. The study findings provide evidence-based source for the healthcare management team, policymakers, and community to sustain clean and safe ambient air. [ABSTRACT FROM AUTHOR]

Solid-state recycling of light metals reinforced inclusions through hot Equal Channel Angular Pressing (ECAP) is performed to directly recycle metal scraps and reduce cost of material in engineering applications. The ECAP is one of the most important method in severe plastic deformation (SPD) that can convert light metals into finished products. This paper reviews several experimental and numerical works that have been done to investigate the effects of the ECAP parameters such as die angles, material properties, outer corner angle, friction coefficient, temperature, size of chips, pressing force, ram speed and direct effects of number of passes on the strain distributions. It also includes the performance enhancement of aluminium matrix composite reinforced ceramic-based particles that derived from direct recycled aluminium chips for sustainable manufacturing practices.

In common practice, tools for EDM have traditionally been made by machining copper or graphite to the required profile using CNC machines. Increasing the degree of complexity of any tooling design for any operations results in a corresponding increase in time and cost required. With the advent of rapid prototyping techniques, the problem of making tools with complex shapes becomes much simpler and easy. The main aim of this research was to develop new EDM electrode material through a novel approach by rapid prototyping (RP) technique. In this study, the potential application of copper (Cu) reinforced alumina (Al2O3) fabricated with various compositions as an EDM electrode was investigated. The electrodes were fabricated by Canon PIXMA IP 1800 printer and underwent sintering temperature at 85 % and 95 % melting point of copper. The EDMed workpiece was aluminium and the electrodes surface was analyzed through scanning electron microscope (SEM). Findings showed that the electrode with Cu - 0 vol. %Al2O3 composite and sintered at temperature 977 °C resulted in highest metal removal rate (MRR) and lowest electrode wear rate (EWR) while Cu – 10 vol. %Al2O3 composite and sintered at temperature 977 °C revealed a better surface finish than other electrodes. An increase in Al2O3 content in general will increase the hardness of tool, as a trade-off, the conductivity was reduced.

The self-healing of bio-concrete cracks and pores have been utilised worldwide to improve the properties of bio-concrete using different types of bacteria. Meanwhile, no published research was conducted to heal bio-foamed concrete bricks (B-FCB) pores using Bacillus tequilensis. Previous studies focused on the concentration of bacteria and neglect other factors that could affect the healing process. This research aimed to optimise the healing ratio of B-FCB pores using four factors: B. tequilensis concentration, concrete density, temperature and CO2 concentration. Initial water absorption (IWA) and water absorption (WA) were used as responses in statistical methods, namely, factorial and response surface methodology (RSM). B. tequilensis species was isolated from cement kiln dust, produced in a powder form, then subjected to simulate test using a special medium consisting of foamed concrete materials to check the survival ability in B-FCB. SEM, EDX, and XRD were used to investigate the healing process of B-FCB pores. The results revealed that the decrement ratios of IWA and WA of B-FCB were 52.8% and 29.1% compared to FCB, respectively. SEM results reflect the healing that occurred in B-FCB pores, mostly healed via precipitation of CaCO3 as demonstrated on the XRD results. [ABSTRACT FROM AUTHOR]

The paper reviewed the current perspectives on the development of carbon dioxide (CO2) sequestration through its process conversion into calcite. The process occurs in either geological or biological systems. However, geological sequestration is an expensive process, which is slow in comparison to bio-sequestration. Recently, the bio-sequestration of atmospheric CO2 into the soil using microorganisms such as algae has been investigated. However, the algae cannot be used in the bio-concrete due to their nature as phototrophic organisms. In contrast, bacteria are the most potent organisms in bio-concrete technology. The use of bacterial species in the bio-aerated concrete bricks (B-ACB) and its potential to bio-sequestrate CO2 represents a future strategy to reduce high CO2 pollution. Bacterial cells can capture CO2 by accelerating the carbonation processes, which convert CO2 into calcium carbonate (CaCO3) via carbon anhydrase and urease enzymes. The present paper aimed to highlight and discuss the applicability of bacteria in the B-ACB for capturing and storing CO2. It is evident from the literature that the new trends to use bio-concrete might contribute to the reduction of CO2 by accelerating the carbonation process and strengthening the B-ACB. [ABSTRACT FROM AUTHOR]