High-temperature Heating Process Research Articles

Cracking resistance of crumb rubber modified green asphalt mixtures, using calcium carbonate nanoparticles and two by-product wax-based warm mix additives

Common procedures to incorporate the recycled crumb rubber (CR) in asphalt binders take a long time and use a high-temperature heating process, which makes these rubberized mixtures even more expensive and environment-unfriendly than conventional mixtures. In trying to make a cheaper and greener asphalt mixture, in this paper, the CR incorporation heating process and its duration were lowered (140–150°C in 15 minutes), and the effect of these changes was studied on the pavement's tensile/shear cracking resistance. Because the main disadvantage of using CR is the increase of viscosity, two by-products, slack wax (SW) and polypropylene wax (PPW) were used to correct the viscosity; also their effect on fracture toughness (Keff) and fracture energy (Gf) was assessed. As results showed that the following process decreases the cracking resistance, calcium carbonate nanoparticles (CCN) in different contents were added. Results show that adding 15% CR reduces Keff and Gf by about 18 and 16%, respectively. Adding the SW and PPW further reduces them by about 8 and 16%, respectively. In this condition, adding CCN in optimal content (about 5%) compensates for these reductions. Although these greener asphalts have the same cracking resistance as the control mixture, the environmental and cost-effectiveness analysis shows the developed materials are greener and cheaper.

Effect of sintering temperatures on the physical, structural properties and microstructure of mullite-based ceramics

<abstract> <p>This study explored the impact of sintering temperature variations on the synthesis and characteristics of mullite ceramics derived from a composite blend of kaolinite clay, silica (silicon dioxide), and feldspar. Sintering temperatures ranging from 1100 to 1200 ℃ were systematically examined to analyze alterations in shrinkage, density, microstructure, elemental composition, and phase formation. The study revealed that an increase in sintering temperature led to decreased shrinkage due to improved particle packing and reduced porosity. Ceramic density showed a direct relation with sintering temperature, reaching the optimal density at 1175 ℃ and indicating efficient particle packing and compaction. Analysis through field emission scanning electron microscopy (FESEM) provided insights into microstructural changes, including alterations in grain morphology, porosity, and connectivity. Energy dispersive X-ray spectroscopy (EDS) clarified element distribution within the microstructure, offering valuable information on compositional variations. X-ray diffraction (XRD) examinations unveiled temperature-dependent phase transformations, which confirmed the successful formation of mullite during the sintering process. A sintering temperature of 1175 ℃ yielded the optimal ceramic quality and cost-effectiveness for high-temperature heating processes.</p> </abstract>

Formulation of Malaysian clay into inert ceramic balls: Effect of sintering temperature

Ceramic ball support bed materials are used in multiple industries with the aim of providing support for the catalytic materials and assisting the reaction. The majority of ceramic ball products used in Malaysia are either imported as finished products or domestically produced using an imported formulated powder. Besides, the characteristics of sintered ceramic balls depend on the specific powder metallurgy route, including the material composition, range of particle size, and sintering process. Thus, this study focuses on producing inert ceramic balls from local Malaysian raw materials and optimising the sintering temperature with the aim of fulfilling the Universal Oil Products (UOP) standard requirements. The research utilises local clay raw material originating from Trong, Perak, Malaysia. The formulation of each ball was formulated based on a mixture of kaolinite clay, potash feldspar, and silica sand. The sintering process was then varied between 1250 and 1350 °C to tune the character of the finished ceramic ball product. The characterization of the ceramic ball was carried out based on the UOP standard and complemented with X-ray Diffractometer (XRD), Scanning Electron Microscope – Energy Dispersive X-ray (SEM-EDX), and X-ray Fluorescence (XRF) analysis. All tested ceramic balls meet the requirements of the UOP standard. In fact, locally formulated samples had approximately twice the crushing strength of required standards. Different sintering temperatures affect the quartz phase, kaolinite dehydroxylation, mullite formation, and feldspar fusion, thus controlling the final physical–mechanical properties of ceramic balls. Overall, the sintering temperature of 1300 °C provides the most promising output in terms of the quality of ceramic balls and the cost consideration involving the high-temperature heating process.

Conversion of food waste to renewable energy: A techno-economic and environmental assessment

Increasing quantities of food waste have become a concern due to high disposal costs in landfills and high greenhouse gas emissions. With this increase in food waste generation, there is also an increasing demand for renewable natural gas to supplement traditional fossil fuel combustion and offset the impacts of climate change. Collecting food waste from landfills and turning it into renewable natural gas using anaerobic digestion could be a win-win option for both food waste disposal and renewable energy production. While some literature exists on the energy potential, economic feasibility, and environmental benefit of food waste disposal via anaerobic digestion, no existing study simultaneously evaluates the energy, economic and environmental effect of food waste to renewable energy via anaerobic digestion, especially on a plant and city scale. This study is focused on the techno-economic and environmental assessment of food waste to energy via anaerobic digestion in order to fill this gap. Four anaerobic digestion pathways are considered in this study: flare, pipeline natural gas, combined heat and power, and combined cycle for efficient power generation. Using a city of 1 M people the results show that renewable natural gas from food waste could supply the natural gas usage for 1.9% of residential use, 2.7% of commercial use, 1.1% of industrial use, 167.5% of the compressed natural gas vehicle fleet, 0.7% of electric power generation, or 2.5% of industrial high-temperature heating processes. All pathways except pipeline natural gas will have a positive net present value in the baseline scenario, and the pipeline natural gas pathway will become economically viable with a net present value of 31 USD/t of food waste with renewable energy credits. Lastly, all of the pathways achieve negative greenhouse gas emissions, which indicates that anaerobic digestion is a more environmentally friendly method for the handling of food waste than landfills.

Ultrafast high-temperature heating in air

Ultrafast high-temperature heating methods based on the Joule heating of carbon heaters can dramatically shorten the time required for material synthesis/sintering. However, commonly used porous carbon heaters cannot provide stable high temperatures in air, limiting their applicability to the processing of atmosphere-sensitive materials. In this study, we present a novel configuration for ultrafast high-temperature heating in air using commercial graphite paper. This configuration enables stable high temperatures of ~1330–2230 °C in air, on the time-scale of minutes, and ultrafast heating rates, reaching ~104 oC/min. We describe the mechanism behind the excellent performance of our proposed configuration, and further demonstrate its flexibility and controllability by considering ultrafast high-temperature sintering of ZnO ceramics with tunable microstructures using different heating profiles. Our configuration provides a complementary approach to simplifying the ultrafast high-temperature heating process, reducing costs, and meeting the requirements of synthesis/sintering in air.

Comparison Between RunX2 and Osteocalcin Expression Following the Application of Demineralized Freeze-Dried Bone Xenograft (DBFX) and Bovine Hydroxyapatite (BHA) and Their Effect on Bone Defect (In vivo Laboratory Experiment)

The use of biomaterial such as bone graft material is highly needed in oral and maxillofacial surgery to overcome bone defect that happened due to various reasons. One of the bone graft that widely used is bovine hydroxyapatite (BHA). BHA is produced by means of deproteinizing by a high-temperature heating process so that inorganic material of bone is left where the bone architecture is preserved. This material has osteoconductive property because it induces osteoblast activity and new bone formation. DFDBX is a bone graft derived from bovine bone which has undergone the demineralization process and subsequently frozen. Then, it will be exposed to hydrochloric acid until the bone matrix component-related collagen fibril called BMPs. Runt-Related Transcription factor 2 (RUNX2) is a transcription factor which is needed for osteoblast differentiation and it is first detected at preosteoblast. Osteocalcin is exerted during the last stage of differentiation, started at the early stage of mineralization. Objectives to compare the expression of RUNX2 and Osteocalcin following the application of DFDBX and BHA to the bone defect. Methode 30 male New Zealand White Rabbit, 6- months old, 3-3,5kg, divided into 3 groups comprising of 10 animals each, bone defect is created on each animal model. On group 1, DFDBX is applicated, BHA is on group 2, and control group with no graft application. After 2 weeks and 4 weeks following the animal model is terminated to retrieve a bone specimens for Immunohystochemistry examination. Result The expression of RUNX2 following the application of DFDBX and BHA showed a significant difference at week 2 but not showed at week 4. This research also found that the expression of osteocalcin did not show a significant difference at week 2 but showed a significant difference at week 4. Conclussion This study demonstrate that bone healing process in DFDBX group is more effective than BHA.

Scalable Synthesis of High Entropy Alloy Nanoparticles by Microwave Heating

High entropy alloy nanoparticles (HEA-NPs) are reported to have superior performance in catalysis, energy storage, and conversion due to the broad range of elements that can be incorporated in these materials, enabling tunable activity, excellent thermal and chemical stability, and a synergistic catalytic effect. However, scaling the manufacturing of HEA-NPs with uniform particle size and homogeneous elemental distribution efficiently is still a challenge due to the required critical synthetic conditions where high temperature is typically involved. In this work, we demonstrate an efficient and scalable microwave heating method using carbon-based materials as substrates to fabricate HEA-NPs with uniform particle size. Due to the abundant functional group defects that can absorb microwave efficiently, reduced graphene oxide is employed as a model substrate to produce an average temperature reaching as high as ∼1850 K within seconds. As a proof-of-concept, we utilize this rapid, high-temperature heating process to synthesize PtPdFeCoNi HEA-NPs, which exhibit an average particle size of ∼12 nm and uniform elemental mixing resulting from decomposition nearly at the same time and liquid metal solidification without diffusion. Various carbon-based materials can also be employed as substrates, including one-dimensional carbon nanofibers and three-dimensional carbonized wood, which can achieve temperatures of >1400 K. This facile and efficient microwave heating method is also compatible with the roll-to-roll process, providing a feasible route for scalable HEA-NPs manufacturing.

Nucleation Control in Physical Vapor Transport Growth of AlN Single Crystals on Polycrystal Tungsten Substrates

The improved resistively-heated furnace with two heaters established a vertical thermal gradient to control nucleation during AlN single crystals Physical Vapor Transport (PVT) growth on polycrystal tungsten substrates. During the high temperature (> 1850 °C) heating process, the reverse temperature field (i.e., the temperature difference between the sublimation zone and the crystalline zone ΔT < 0) was obtained to reduce the number of nuclei on the tungsten substrate. During growth, the proper positive values of ΔT T were chosen to content the supersaturation values (0.25 < S < 0.3). The reverse temperature condition during high temperature (> 1850 °C) cooling was fulfilled to avoid recrystallization on grown AlN crystal. AlN single crystals made through the method were characterized by X-ray diffractions (XRD) and Raman spectroscopy.

Effects of high-temperature oxygen-deficient oxidation on the surface properties of sub-bituminous coal

ABSTRACTThe air oxidation of coal releases heat which increases coal temperature, as a result, the spontaneous combustion of coal happens. Generally, coal spontaneous combustion needs to be prevented artificially, however, most of the coal particles still suffer a high-temperature heating process under the oxygen-deficient condition. This paper aims to investigate the effect of high temperature (500°C, 600°C, and 700°C) oxygen-deficient (3% oxygen and 97% nitrogen) oxidation on the surface properties of sub-bituminous coal. SEM and XPS were applied to show the changes of surface properties of sub-bituminous coal. SEM results showed the number of pores and cracks on coal surface increased with the increasing heating temperature, and XPS results showed the content of hydrophobic functional groups on coal surface reduced whereas the content of hydrophilic oxygen-containing functional groups increased after the oxygen-deficient oxidation.

Thermo-Fluid Characteristics of High Temperature Molten Salt Flowing in Single-Leaf Type Hollow Paddles.

A single-leaf type paddle heat exchanger with molten salt as the working fluid is a proper option in high temperature heating processes of materials. In this paper, based on computational fluid dynamics (CFD) simulations, we present the thermo-fluid characteristics of high temperature molten salt flowing in single-leaf type hollow paddles in the view of both the first law and the second law of thermodynamics. The results show that the heat transfer rate of the hollow paddles is significantly greater than that of solid paddles. The penalty of the heat transfer enhancement is additional pressure drop and larger total irreversibility (i.e., total entropy generation rate). Increasing the volume of the fluid space helps to enhance the heat transfer, but there exists an upper limit. Hollow paddles are more favorable in heat transfer enhancement for designs with a larger height of the paddles, flow rate of molten salt and material-side heat transfer coefficient. The diameter of the flow holes influences the pressure drop strongly, but their position is not important for heat transfer in the studied range. Other measures of modifying the fluid flow and heat transfer like internal baffles, more flow holes or multiple channels for small fluid volume are further discussed. For few baffles, their effects are limited. More flow holes reduce the pressure drop obviously. For the hollow paddles with small fluid volume, it is possible to increase the heat transfer rate with more fluid channels. The trade-off among fluid flow, heat transfer and mechanical strength is necessary. The thermo-fluid characteristics revealed in this paper will provide guidance for practical designs.

The influence of high-temperature heating on composition and thermo-oxidative stability of the oil extracted from Arabica coffee beans.

The aim of the present study was to establish the influence of high-temperature heating on the composition and thermal behavior of coffee oils obtained from Arabica green and roasted coffee beans, respectively. Morphological studies performed using scanning electron microscopy revealed the oil bodies uniformly distributed within the cells in both types of coffee beans analyzed. The obtained oils have a fatty acid composition rich in linoleic acid, palmitic acid, oleic acid, stearic acid, arachidic acid and linolenic acid. The total content of saturated fatty acids of investigated oils was 49.38 and 46.55%, the others being unsaturated fatty acids. The thermal behavior and thermo-oxidative stability of coffee oils extracted from green coffee beans and roasted coffee beans, the coffee oil high-temperature heated up to 200 °C, were investigated using simultaneous thermal analysis TG/DTG/DTA, in an oxidizing atmosphere. The data obtained for the analyzed samples depend mainly on the nature and compositions of fatty acids, and to a lesser extent on the roasting process of the coffee beans and the high-temperature heating process of the extracted oil. The chromatographic and TG/DTG/DTA data suggest that Arabica coffee oil has great potential for use in technological processes which require high-temperature heating (e.g. food industry or pastries).

Laboratory Investigation on Physical and Mechanical Properties of Granite After Heating and Water-Cooling Treatment

High-temperature treatment may cause changes in physical and mechanical properties of rocks. Temperature changing rate (heating, cooling and both of them) plays an important role in those changes. Thermal conductivity tests, ultrasonic pulse velocity tests, gas permeability tests and triaxial compression tests are performed on granite samples after a heating and rapid cooling treatment in order to characterize the changes in physical and mechanical properties. Seven levels of temperature (from 25 to 900 °C) are used. It is found that the physical and mechanical properties of granite are significantly deteriorated by the thermal treatment. The porosity shows a significant increase from 1.19% at the initial state to 6.13% for samples heated to 900 °C. The increase in porosity is mainly due to three factors: (1) a large number of microcracks caused by the rapid cooling rate; (2) the mineral transformation of granite through high-temperature heating and water-cooling process; (3) the rapid cooling process causes the mineral particles to weaken. As the temperature of treatment increases, the thermal conductivity and P-wave velocity decrease while the gas permeability increases. Below 200 °C, the elastic modulus and cohesion increase with temperature increasing. Between 200 and 500 °C, the elastic modulus and cohesion have no obvious change with temperature. Beyond 500 °C, as the temperature increases, the elastic modulus and cohesion obviously decrease and the decreasing rate becomes slower with the increase in confining pressure. Poisson’s ratio and internal frictional coefficient have no obvious change as the temperature increases. Moreover, there is a transition from a brittle to ductile behavior when the temperature becomes high. At 900 °C, the granite shows an obvious elastic–plastic behavior.

Effect of low-temperature pyrolysis on surface properties of sub-bituminous coal sample and its relationship to flotation response

Coal spontaneous combustion makes coal suffer a high-temperature heating process (similar to a low-temperature pyrolysis). Additionally, low rank coal is considered to be friendly utilized through two steps, i.e. low-temperature pyrolysis of low rank coal to gain gas/liquid components and then coal char forwarded to the burning or other chemical applications. Therefore, it is necessary to investigate the effect of low-temperature pyrolysis on the surface properties of low rank coal and its role in the floatability of coal particles because coal already suffering spontaneous combustion should be upgraded before usage. In this investigation, SEM, XPS, attachment time and flotation tests were employed to reveal the changes of surface properties and floatability of sub-bituminous coal before and after the pyrolysis. After the pyrolysis, a significant mass loss was observed and many pores/cracks were newly created as well as the content of hydrophobic functional groups on coal surface was increased whereas the content of hydrophilic oxygen-containing functional groups was reduced. The attachment time of coal-bubble was significantly decreased after the pyrolysis, which directly made an increase in the hydrophobicity and floatability of sub-bituminous coal. The findings of this paper may be useful for a better use of sub-bituminous coal resources because sub-bituminous coal is well known as difficult to float and sub-bituminous coal fines are usually wasted in coal preparation plants. This paper proposes that coal char from sub-bituminous coal may be forwarded to a further upgrading process (i.e. flotation) because the floatability of sub-bituminous coal is significantly improved by the pyrolysis.

Rapid, in Situ Synthesis of High Capacity Battery Anodes through High Temperature Radiation-Based Thermal Shock.

High capacity battery electrodes require nanosized components to avoid pulverization associated with volume changes during the charge-discharge process. Additionally, these nanosized electrodes need an electronically conductive matrix to facilitate electron transport. Here, for the first time, we report a rapid thermal shock process using high-temperature radiative heating to fabricate a conductive reduced graphene oxide (RGO) composite with silicon nanoparticles. Silicon (Si) particles on the order of a few micrometers are initially embedded in the RGO host and in situ transformed into 10-15 nm nanoparticles in less than a minute through radiative heating. The as-prepared composites of ultrafine Si nanoparticles embedded in a RGO matrix show great performance as a Li-ion battery (LIB) anode. The in situ nanoparticle synthesis method can also be adopted for other high capacity battery anode materials including tin (Sn) and aluminum (Al). This method for synthesizing high capacity anodes in a RGO matrix can be envisioned for roll-to-roll nanomanufacturing due to the ease and scalability of this high-temperature radiative heating process.

Phase formation and superconducting properties of mechanically alloyed Nb3(Al1−xGex) system

Mechanically alloyed Nb3(Al1−xGex) compounds with nominal composition x = 0%, 10%, 15%, 20%, 25% and 30% were synthesized using high-energy ball milling. The effects of Ge content and sintering temperature on the formation of the Nb3Al superconducting phase at a relatively low temperature without the extremely high-temperature rapid heating, quenching and transformation process were studied. The results revealed that Ge doping in Nb3Al improved the formation of the A15 phase at low temperatures, enhanced the superconducting transition temperature (Tc), and refined the grain structure, thus improving the overall superconducting properties. The pinning behavior was also studied for the optimized sample.

Comparison of surface properties of anthracite coals before and after high temperature heating process

Surface property plays a very important role on coal hydrophobicity which determines flotation behavior of fine coals. However, coal spontaneous combustion makes coal suffer both oxidation and high temperature heating processes. Coals from the outside of coal piles primarily suffer oxidation process (or combustion process) while coals from the inside of coal piles primarily suffer high temperature heating process. It is necessary to investigate the changes in surface properties of coal before and after high temperature heating process. In this investigation, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), surface area (BET) and contact angle measurements were used to indicate the changes in surface properties of anthracite coal before and after high temperature heating process. Throughout this study, surface properties of coal can be changed significantly after high temperature heating process. Meanwhile, coal hydrophobicity can be also reduced after high temperature heating process.

Fe–Ni–Al pillared montmorillonite as a heterogeneous catalyst for the Catalytic Wet Peroxide Oxidation degradation of Orange Acid II: Preparation condition and properties study

The introduction of nickel in Fe–Al pillared montmorillonite was studied to enhance the catalytic performance of metal-pillared clays during Catalytic Wet Peroxide Oxidation (CWPO). Fe–Ni–Al pillared montmorillonite was synthesized by ion exchange method and tested by CWPO reaction. Catalysts were characterized by several methods: chemical composition analysis, X-ray diffraction analysis, N2 adsorption/desorption, Fourier Transformed Infrared Spectroscopy, H2 temperature-programmed reduction and thermal analysis. The results indicated the enhanced structural properties and catalytic performance of prepared clays could correspond to the introduction of active metal oxides as pillars supporting the interlayer space. Besides, the effects of active metal molar loading (AML), Fe/Ni molar ratio and calcination temperature on the pillared clays were measured and discussed. It was proposed the introduction of nickel to the pillaring solution may contribute to better active iron stability and catalytic performance. It turned out the iron presented in the clays as FeOOH form when nickel was introduced. Further, moderate calcination temperature would keep a modified clay structure and retain FeOOH as active sites in the clay, while high temperature (above 773K) heating process may damage the interlayer structure. Throughout this work, Fe(4)Ni(6)Al-MMT(773K), heated at 773K with 4:6 Fe/Ni molar ratio and 6% active metal loading, shows better catalytic behavior and stronger stability among all the prepared materials.

Changes in the hydrophobicity of anthracite coals before and after high temperature heating process

Coal spontaneous combustion can make coal suffer a high temperature heating process. This heating process can change physical and chemical properties of coal, but the changes in the hydrophobicity of coals before and after high temperature heating process have not been investigated adequately since the natural hydrophobicity of coal usually determines the flotation behavior of fine coals. Therefore, this paper is to investigate the changes in the hydrophobicity of coals before and after the high temperature heating process. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to indicate these changes. The heating temperature was 600°С. The heating times were 0 (original coal), 10, 20, 60, and 120min, respectively. An ultra-low-ash anthracite coal with ash content of 1.55% was used to conduct the high temperature heating process in the laboratory. Throughout this study, the hydrophobicity of anthracite coal can be reduced quickly after high temperature heating process since the content of hydrophilic functional groups on anthracite coal surface is increased while the content of hydrophobic functional groups is reduced by the high temperature heating process.

Volume Reduction Effect of Radioactive Contaminated Soil by High Temperature Heating Process

Volume Reduction Effect of Radioactive Contaminated Soil by High Temperature Heating Process

Mechanical and corrosion properties of Ta–Mo coatings by heating processes

In this research, substrate heating process has been used for the production of Ta–Mo high temperature protective coatings. The microstructures of the alloy coatings have been studied through X-ray diffraction and scanning electron microscopy. Mechanical and corrosion properties of different alloys have been investigated in both low and high temperature heating processes. Substrate heating processes (from 250 to 550°C) were expected to produce partially recrystallised and fully recrystallised microstructures. Higher heating temperature results in recrystallised microstructures, but adversely affects the density of atoms Vt and bond energy G. The behaviour of low and high temperature heating processes on corrosion and mechanical properties of Ta–Mo nanostructured coatings was studied.