14 research outputs found
Characterization And Alkaline Fusion Recovery Process Of Rare Earths And Thorium From Malaysian Monazite
Full text linkThe use of edges to determine an optimal region of interest (ROI) location is
increasingly becoming popular for image deblurring. Recent studies have shown that
regions with strong edges tend to produce better deblurring results. In this study, a
direct method for ROI localization based on edge refinement filter and entropy-based
measurement is proposed. Using this method, the randomness of grey level distribution
is quantitatively measured, from which the ROI is determined. This method has low
computation cost since it contains no matrix operations. The proposed method has
been tested using three sets of test images - Dataset I, II and III. Empirical results
suggest that the improved edge refinement filter is competitive when compared to the
established edge detection schemes and achieves better performance in the Pratt's
figure-of-merit (PFoM) and the twofold consensus ground truth (TCGT); averaging at
15.7 % and 28.7 %, respectively. The novelty of the proposed approach lies in the use
of this improved filtering strategy for accurate estimation of point spread function
(PSF), and hence, a more precise image restoration. As a result, the proposed solutions
compare favourably against existing techniques with the peak signal-to-noise ratio
(PSNR), kernel similarity (KS) index, and error ratio (ER) averaging at 24.8 dB, 0.6
and 1.4, respectively. Additional experiments involving real blurred images
demonstrated the competitiveness of the proposed approach in performing restoration
in the absent of PSF
An Innovative Approach to Silicon-integrated Surface Modification of High Carbon Steels: Leveraging Waste Silicon and Carbon Sources
No full textThe alarming increase in waste is directly linked to development, as growing populations and expanding economies lead to higher levels of consumption and waste generation. The current "take-make-dispose" model of consumption is unsustainable, depletes natural resources, and contributes to concerning levels of environmental degradation. There is a need for a paradigm shift in waste management, which flips the perspective of the traditional linear model, recognising that one industry’s waste can be another’s raw material. This research is premised on the concept of ‘industrial symbiosis,’ as it presents a detailed investigation of the feasibility of utilising waste materials to enhance the surface properties of carbon steels, addressing the growing need for sustainable materials processing and waste valorisation.
The study focuses on employing waste-derived materials, such as mixed waste plastics (MWPs), spent coffee grounds (SCGs) as alternative reductants, and waste glass as silicon (Si) sources for surface modification. In essence, this project advocates the concept of extracting value from waste, transforming discarded materials into valuable resources for enhancing the properties and extending the lifetime of high-carbon steels. The investigation begins with a comprehensive characterisation of the waste materials using elementary and advanced analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), CHNS elemental analysis, thermogravimetric analysis coupled with differential thermal analysis (TGA-DTG), and off-gas analysis. This detailed characterisation provides valuable insights into the chemical composition, structure, and thermal behaviour of the waste materials, enabling a thorough assessment of their suitability and evaluate their potential as reductants in metallurgical processes. The effectiveness of these waste materials in reducing iron oxide (Fe2O3) to iron (Fe) is systematically assessed using hematite as a model raw material. This comparative evaluation reveals the potential of waste materials as reductants in pyrometallurgical processes, compared to conventional options and establishing their potential for complementing or even replacing traditional carbon sources. The study importantly showcases the synergistic effects of blending different waste materials, realistically imitating a real-time availability of accumulated wastes. It was observed that a combination of MWPs and metallurgical coke (MC) exhibits enhanced reducing capabilities compared to either material alone. This finding emphasises the potential for optimising waste utilisation by strategically combining different waste streams to maximise their synergistic effects.
The research then examines the diffusion behaviour of Si from different sources into high-carbon steel, investigating the impact of the presence or absence of a solid carbon source on the diffusion process. The effects of temperature, carbon source, and their interactions with Si diffusion are analysed, providing a broader understanding of the underlying mechanisms and the factors influencing Si uptake by the steel. Based on the conditions evaluated for Si diffusion into high carbon steel, the research explores the reduction of silica from different sources, including waste glass and SiO₂ powder, using various alternate reductant combinations of MWPs, SCGs, and MC. The influence of different reductant combinations and ratios on the efficiency of Si reduction is studied to determine the optimal conditions for Si formation. The reduction of silica by carbonaceous reductants was achieved through the creation of non-equilibrium reaction conditions facilitated by elevated partial pressures of reducing gases and synergistic effects between waste materials. Compared to their individual usage, a combination of MWP and SCG reductant systems favoured Si formation, as confirmed by phase analyses, emphasising the importance of synergistic effects in waste utilisation. Notably, the study revealed enhanced reduction efficiency to Si from waste glass compared to pure SiO₂ powder when employing the combination of MWPs and SCGs as reductants.
The core of the study lies in investigating the surface modification of low-alloy, high-carbon steels through Si diffusion using waste-derived alternate reductants and Si sources. The effects of different process parameters, such as temperature, reductant ratios, and Si source, are investigated. This systematic investigation aimed to understand the surface modification process with the highest level of Si diffusion into the subsurface of steel. The extent of Si reduction achieved was directly influenced by the quantity, and combination of reductants employed. The liberation of Si was effective in the presence of the combination of reductants- MWP and SCG, MWP and MC. Also, the carbon content within the chosen reductant directly affected the melting behaviour of the steel during the process. The carbon served as a reducing agent, but a significant role was also played in the subsequent incorporation of Si into the steel matrix, likely affecting the final properties of the steel product. Optimisation of the reductants, both in quantity and nature, especially carbon content, was critical for controlling the reduction and Si integration into the steel.
The performance of the Si-integrated steel surfaces is evaluated through a series of functional characterisation tests, including corrosion and wear tests and hardness measurements. The impact of the surface modification on the material’s properties is assessed, and the performance of steels treated with different waste-derived materials is compared. Silicon incorporation onto steel surfaces reasonably improved tribological properties and corrosion resistance. The silicon-modified steel exhibited reduced friction and wear due to the formation of hard and soft phases and demonstrated enhanced oxidative resistance. A substantial increase in corrosion protection efficiency compared to untreated steel was exhibited by the treated steel. This comprehensive evaluation provides a valuable understanding of the functional effectiveness of the waste-driven surface modification approach in enhancing the properties of the steel, demonstrating its potential for improving corrosion resistance, wear resistance, and hardness. By extracting value from waste materials and applying them to enhance the surface properties of high-carbon steels, this research offers a compelling example of how sustainable practices can be integrated into industrial processes. The insights gained from this study pave the way for developing more sustainable and resource-efficient surface modification techniques, offering a promising avenue for the metal industries to reduce their environmental footprint and enhance the performance of their products
Degradation Kinetics of Automotive Shredder Residue and Waste Automotive Glass for SiC Synthesis: An Energy-Efficient Approach
No full textGenerally, fossil carbon materials (coal, coke/char, and petroleum coke), biological carbon materials (charcoal, woodchips), and quartz from the earth’s crust are sources of carbon and silica to synthesise silicon carbide (SiC) at temperatures between 2000 and 2200 °C. The study investigated the isothermal and non-isothermal kinetics of synthesising SiC from automotive shredder residues (ASR) and windshield glass of end-of-life-vehicle (ELVs) at 1300 °C, 1400 °C, and 1500 °C for 30 min. The kinetics of ASR and waste glass degradation were studied by relating the thermogravimetric data via the Coats–Redfern model. The reaction mechanism includes the rapid formation of a gaseous SiO intermediate, and carbon reduction of the SiO to SiC is reaction-rate-controlling. The understanding of kinetics inferred that the optimisation of SiC formation is entirely associated with the conversion of SiO2 to SiO vapour and their reaction with CO and carbon particles. The kinetic parameters of the degradation of mixed ASR and waste glass were determined, and the activation energy of mixed ASR and glass for non-isothermal conditions are 22.48 kJ mol−1, 2.97 kJ mol−1, and 6.5 kJ mol−1, and for the isothermal study to produce SiC is 225.9 kJ mol−1, respectively. The results confirmed that this facile way of synthesising SiC would conserve about 50% of chemical energy compared to the traditional way of producing SiC. A beneficial route of transforming the heterogenous ASR and glass wastes into SiC with economic and environmental benefits is recognised
Review-Phosphor Plates for High-Power LED Applications: Challenges and Opportunities toward Perfect Lighting
No full textIn the past decades, solid-state lighting based on phosphors as energy converters has been a fast-growing industry. Phosphorconverted white light-emitting diodes (pc-wLEDs) enable high-power applications and miniaturization; for this, the phosphor must have good stability and high efficiency. In order to satisfy this demand, phosphor plates have been proposed instead of conventional organic-based phosphor binders. In this review, such phosphor plates are categorized according to their synthesis methods, and the advantages and disadvantages of each category are detailed. In addition, we describe the major aspects of phosphor plates that require improvement for applications in high-power devices. For the fabrication of high-power LEDs, the phosphor configuration, color purity, porosity, and particle size of glass powders are key properties to enhance the luminescence efficiency and reduce the generation of heat inside wLED packages, thereby improving thermal stability. (c) The Author(s) 2017. Published by ECS. All rights reserved.This work was financially supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2017R1A2B3011967)
High-temperature carbothermal dephosphorization of Malaysian monazite
No full textHigh-temperature carbothermal reduction experiments with graphite powder were conducted to assess the dephosphorization behavior of Malaysian monazite concentrate. Thermodynamic analysis of the possible dephosphorization reactions was conducted to evaluate the feasibility of the carbothermal reduction of the monazite phases. The effects of temperature, particle size, and monazite to carbon ratio were then investigated under different conditions. The carbothermal reduction experiments were conducted based on the Taguchi design method, and up to 97% of phosphorous removal was achieved under optimized conditions. The optimal conditions for dephosphorization were determined as; a reduction temperature of 1350 °C, a particle size of -75 μm, and monazite to carbon molar ratio of 0.3. Microstructural and phase characterization of the dephosphorized products revealed that CeO2, Nd2O3, La2O3, and Pr2O3 oxide phases were prominent, and no residual peaks of monazite remained in the reduced products. The information gained from the study can aid in the design of a suitable post-dephosphorization hydrometallurgical treatment for exploiting Malaysian monazite as a local source of REEs
Economic evaluation of thorium oxide production from monazite using alkaline fusion method
No full textMonazite is a phosphate mineral that contains thorium (Th) and rare earth elements. The Th concentration in monazite can be as high as 500 ppm, and it has the potential to be used as fuel in the nuclear power system. Therefore, this study aimed to conduct the techno-economic analysis (TEA) of Th extraction in the form of thorium oxide (ThO2) from monazite. Th can be extracted from monazite through an alkaline fusion method. The TEA of ThO2 production studied parameters, including raw materials, equipment costs, total plant direct and indirect costs, and direct fixed capital cost. These parameters were calculated for the production of 0.5, 1, and 10 ton ThO2 per batch. The TEA study revealed that the highest production cost was ascribed to installed equipment. Furthermore, the highest return on investment (ROI) of 21.92% was achieved for extraction of 1 ton/batch of ThO2, with a payback time of 4.56 years. With further increase in ThO2 production to 10 ton/batch, the ROI was decreased to 5.37%. This is mainly due to a significant increase in the total capital investment with increasing ThO2 production scale. The minimum unit production cost was achieved for 1 ton ThO2/batch equal to 335.79 $/Kg ThO2
Thermal Transformation of Secondary Resources of Carbon-Rich Wastes into Valuable Industrial Applications
No full textCarbon-based materials have become an indispensable component in a myriad of domestic and industrial applications. Most of the carbon-based end-of-life products discussed in this review end up in landfills. Where recycling is available, it usually involves the production of lower-value products. The allotropic nature of carbon has been analysed to identify novel materials that could be obtained from used products, which also transform into a secondary carbon resource. Thermal transformation of carbon-rich wastes is a promising and viable pathway for adding value to waste that would otherwise go to landfills. The valorisation routes of four different carbon-rich wastes by thermal transformation are reviewed in the study—automotive shredder residue (ASR), textile wastes, leather wastes, and spent coffee grounds (SCGs). Textile wastes were thermally transformed into carbon fibres and activated carbon, while ASRs were used as a reductant to produce silicon carbide (SiC) from waste glass. The leather wastes and spent coffee grounds (SCGs) were employed as reductants in the reduction of hematite. This paper examines the possible routes of thermally transforming carbon-rich wastes into different industrial processes and applications. The transformation products were characterised using several techniques to assess their suitability for their respective applications. The strategy of valorising the wastes by thermal transformation has successfully prevented those wastes from ending up in landfills
Synthesis of Ziegler-Natta Catalyst using Malaysian Ilmenite Derived TiCl4 via Recrystallization Method: A Statistical Approach
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