The role of the reaction medium in the self propagating high temperature synthesis of nanosized tantalum powder

The high temperature combustion of the mixture Ta₂O₅ + 5 Mg has been investigated using a microthermocouple in the medium MgO and molten NaCl. The effect of varying the amounts of these two inorganic agents (MgO and NaCl) was examined. It was shown that using MgO as the reaction medium produces the complex oxide Mg_xTa_yO_z as an impurity in the Ta powder, whereas unagglomerated single-phase powder (particle size of 20-90 nm) of Ta was formed in the presence of NaCl. The approximate mechanism for forming the final product is discussed. The distributions of temperature, the rate of heat generation and degree of conversion in the combustion wave of the mixture Ta₂O₅ + 5Mg + NaCl were measured. The sizes of the combustion zones and the kinetics of reaction were derived.     

Low temperature synthesis of Yb doped SrCeO3 powders by gel combustion process

In this work, SrCe_0.9Yb_0.1O_3−δ powders were synthesized by a gel combustion method which combined gel process and combustion process. The effect of ratio of citric acid to metal cations (C/M), oxidizer and calcination temperature on the properties of powders was investigated in detail. It was found that the extra oxidizer NH₄NO₃ increased the flame temperature of combustion and thus promoted the formation of SrCeO₃. The relative amount of SrCeO₃ in powder increased as the C/M ratio increased. The as-ignited powder at 250 °C mainly consisted of the perovskite SrCeO₃, i.e. relative amount of 95.2 wt%. The adiabatic flame temperature of the combustion reaction was calculated to be 1903.1 °C, higher than the required formation temperature of 787.2 °C for SrCeO₃. Furthermore, the pure perovskite phase powder with agglomerated microstructure and average grain size of 2 μm was obtained after calcination at 1200 °C for 5 h. This heat-treatment temperature is 200 °C lower than the conventional solid state reaction method for SrCe_0.9Yb_0.1O_3−δ preparation.     

Toward design of the pre-stressed nano- and microscale aluminum particles covered by oxide shell

Prediction based on the recently developed melt-dispersion mechanism of reaction for nanometric (nano) and micrometer (micron) scale aluminum (Al) particles suggests a possible increase in particle reactivity if the alumina shell is pre-compressed and the Al core is pre-expanded. This prediction was checked experimentally by measuring the flame speed for Al and molybdenum trioxide (MoO₃) thermites in a semi-confined tube. Pre-stressing was produced by heating particles to several elevated temperatures, holding them at a temperature for 10 min to relax thermal stresses, and cooling them at several rates to room temperature. For the optimal thermal treatment conditions (heating to 105 °C and cooling at 0.13 °C/s), flame propagation speed increased by 31% for nanoparticles and for 41% for micron particles. Cooling at 0.06 °C/s after heating to 105 °C and cooling at 0.06 °C/s and 0.13 °C/s after heating to 170 °C either did not change the flame speed or increased it significantly less. Results are quantitatively consistent with the theoretical predictions based on the melt-dispersion mechanism.     

Structural and thermal properties of boron nanoparticles synthesized from B2O3 + 3Mg + kNaCl mixture

Amorphous boron nanoparticles were synthesized by heating a B₂O₃ + 3 Mg + kNaCl (k is the number of moles of NaCl) exothermic mixture in a laboratory oven at 800 °C under argon flow. NaCl was used as inert material to decrease the maximum combustion temperature of the reaction mixture when it was self-ignited after the melting of Mg at 650 °C. The size of the boron nanoparticles extracted from the final product by acid leaching ranged between 30 and 300 nm for k values ranging from 1 to 5. Moreover, increasing the value of k from 1 to 5 resulted in an increase in the specific surface area of the nanoparticles from 40 to 74 m² g⁻¹. However, at k = 10, a decrease in the specific surface area to 47.56 m² g⁻¹ was recorded due to incomplete reduction of B₂O₃. The ignition point of boron nanoparticles in air as estimated using a thermocouple was approximately 300 °C. Digital camera recording of the combustion process of boron nanoparticles in air revealed that the burning speed of the nanoparticles increased significantly from 0.3 to 15 cm/s when k increased from 1 to 5.     

Low-temperature combustion waves in low-energy K2TaF7–Si-additive systems

This work presents the use of a thermocouple technique for measuring temperature profiles in a condensed K₂TaF₇–Si system blended with a small amount of Teflon [(C₂F₄)_n] or potassium chlorate (KClO₃). A base experiment is described in detail to demonstrate the ability of the system to react under a low-rate self-sustaining mode at ambient temperature. The ignition temperatures, temperature–time profiles, combustion parameters, and final products are presented with respect to the additive concentration. The combustion processes begin at 340 and 450 °C for the KClO₃ and (C₂F₄)_n-containing mixtures, respectively. The maximum temperatures of both KClO₃ and (C₂F₄)_n-containing mixtures range from 470 to 960 °C and the combustion self-propagates along the sample at a speed of 0.01–0.08 cm/s. The solid combustion products produced under the optimized conditions include fine powders of tantalum, tantalum carbide, and tantalum silicides. The chemical mechanism of the combustion process and reaction parameters responsible for low-speed wave propagation are presented and discussed.     

Numerical analysis on combustion process and sodium transformation behavior in a 660 MW supercritical face-fired boiler purely burning high sodium content Zhundong coal

CHEMKIN software was used to optimize the reaction mechanism of sodium in flue gas to study the influence of targeted design for purely burning Zhundong (ZD) coal on boiler characteristics. Then, the optimized 32-step elemental reaction was combined with CFD software. An eddy-dissipation concept model considering detailed chemical reactions was used to simulate the transformation behavior of sodium-containing substances. The combustion characteristics of the 660 MW face-fired boiler under various loads were also simulated. The field distribution in the furnace and the migration path of sodium along the track of pulverized coal particles were obtained. The results show that the interference between each burner in the furnace is small at the BMCR load, and the phenomenon of “wind wrapping fire” is distinctly clear. The temperature at furnace outlet is approximately 970.98 °C. At a low load, the combustion in the furnace is stable, and the temperature at the furnace outlet reaches the design value. The sodium present in ZD coal is involved in the reaction after it is released in the form of Na and NaCl. Sodium is present in different forms in the main burner zone, mainly NaCl (67%), NaOH (12%), Na (9%), and Na₂SO₄ (7%). The forms of sodium at the furnace outlet are NaCl (50%), Na₂SO₄ (37%), Na₂Cl₂ (9%) and NaHSO₄ (4%). A small amount of Na₂SO₄ is formed by NaHSO₄ reaction in the main burner zone. It then reacts to form NaSO₄, wherein NaHSO₄ is formed by path 2. Na₂SO₄ is mainly generated in the burnout zone through path 1, and paths 2, 3, and 4 are hardly observed. The findings of this research can provide reference for the design of a purely fired ZD coal boiler and further studies on slagging observed on the heating surface.     

Reactivity deterioration of NiO/Al2O3 oxygen carrier for chemical looping combustion of coal in a 10 kWth reactor

A relatively long-term experiment for chemical looping combustion of coal with NiO/Al₂O₃ oxygen carrier was carried out in a 10 kW_th continuous reactor of interconnected fluidized beds, and 100 h of operation was reached with the same batch of the oxygen carrier. The reactivity deterioration of the oxygen carriers was present during the experimental period. The reactivity deterioration of reacted oxygen carriers at different experimental stages was evaluated using X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray fluorescence spectrometer. SEM analysis showed no significant change in the morphology of the nickel-based oxygen carrier at the fuel reactor temperature ?940 °C, but loss of surface area and porosity of reacted oxygen carriers was observed when the fuel reactor temperature exceeded 960 °C. The results show that the sintering effect have mainly contributed to the reactivity deterioration of reacted oxygen carriers in the CLC process for coal, while the effects of coal ash and sulfur can be ignored. The oxidization of reduced oxygen carrier with air was an intensive exothermic process, and the high temperature of oxygen carrier particles led to sintering on the surface of oxygen carrier particles in the air reactor. Attention must be paid to control the external circulation of oxygen carrier particles in the interconnected fluidized beds in order to efficiently transport heat from the air reactor to the fuel reactor, and reduce the temperature of oxygen carrier particles in the air reactor. Improvement of reactivity deterioration of reacted oxygen carriers was achieved by the supplement of steam into the fuel reactor. Nevertheless, NiO/Al₂O₃ is still one of the optimal oxygen carriers for chemical looping combustion of coal if the sintering of oxygen carrier is minimized at the suitable reactor temperature.     

Hydrogen release from a mixture of NaBH4 and Mg(OH)2

Hydrogen generating reaction between sodium borohydride, NaBH₄, and magnesium hydroxide, Mg(OH)₂ (brucite), was studied. Reaction rate was found to depend on the degree of reactants homogenization and/or their particle size. Kinetic of the reaction was studied in isothermal approach in the temperature range of 240–360 °C. It is shown that the reaction obeys 2D diffusion mechanism and its activation energy is 155.9 kJ/mol. Powder XRD analysis and Raman spectroscopy reveal that mechanically activated mixture of NaBH₄ and Mg(OH)₂ reacts yielding MgO as the only crystalline phase in the temperature range of 240–318 °C. At higher temperatures a new crystalline tetragonal phase of as yet undetermined composition is developed.     

Site density effect of Ni particles on hydrogen desorption of MgH2

Fine Ni particles are effective in catalyzing hydrogen sorption of MgH₂, but there is confusion about the extent of this effect in relation to Ni particle size and content. Here, effects of Ni particles of different sizes on hydrogen desorption of MgH₂ were comparatively investigated. MgH₂ mixed with only 2 at% of fine Ni particles rapidly desorbs hydrogen up to 6.5 wt% around 200–340 °C, but there is no significant difference in the desorption temperature of the mixture when Ni particles vary from 90 to 200 nm. Increasing the content of Ni to 4 at%, or a combined (2 at% Ni + 2 at% Fe), leads to hydrogen desorption starting from 160 °C. Further analyses of the literature suggest that the effectiveness of Ni catalysis largely depends on its site density over MgH₂ surface, i.e., an optimal site density of catalytic particles is important in balancing the sorption properties of MgH₂. The projected trend suggests that MgH₂ can desorb hydrogen from 100 °C, the targeted temperature for fuel cells, if the number of catalyst sites is around 4 × 10¹⁴ per m² of MgH₂, or the number ratio of Ni to MgH₂ particles is about a million to one.     

The influence of the addition of sodium on the transformation of alkali and alkaline-earth metals during oxy-fuel combustion

Alkali and alkaline-earth metals (AAEM) of coal directly affect the coal combustion properties and ash formation during coal oxy-fuel combustion. To further understand the influence of adding sodium on the transformation of AAEM, sodium chloride (NaCl) and sodium acetate (NaAc) were added to Shenmu coal in this study. A drop-tube reactor and ion chromatography were adopted in this study and a serial dissolution method was used to clarify the occurrence modes of the AAEM. The results showed that all types of AAEM can release and the release rates were increased with an increase in temperature during oxy-fuel combustion. Water-soluble (W-type) alkali metals react with SiO₂ and Al₂O₃ in coal and are converted into acid-soluble (H-type) silicate or acid-insoluble (I-type) aluminosilicate under certain experimental conditions. The addition of sodium can promote the release of AAEM via promoting coal combustion; the promotion effect was significant at 600 °C, and the effect of NaCl was more noticeable than that of NaAc. Furthermore, the promoting effect on alkali metals was more noticeable than that on alkali-earth metals. The added sodium can also react with SiO₂ and Al₂O₃ to form H-type sodium silicate or I-type sodium aluminosilicate.     

Slagging behavior and mechanism of high-sodium–chlorine coal combustion in a full-scale circulating fluidized bed boiler

The contents of chlorine and sodium in Xinjiang Shaerhu (SEH) coal are extremely high, leading to severe slagging. In this paper, the slag was sampled from a circulating fluidized bed (CFB) boiler purely burning SEH coal, to analyze the slagging mechanism based on the characterization of morphology and composition. The results show a three-layer structure for the slag sampled from the buried heat-exchanger in the dense-phase zone of the CFB boiler. The inner layer close to the heat-exchanger is NaCl, which enhances the adhesion of ash particles, while the middle layer and the outer layer are mainly composed of Ca₂Al₂SiO₇ and other Si–Al materials. In comparison, the slag sampled from the refractory wall shows a molten state without a layered structure and mainly composed of NaCl, NaAlSiO₄, Ca₂Al₂SiO₇, and CaSiO₃. The effect of mixing bed material, on the ash melting and release of chlorine and sodium was further conducted, which indicates that the mixing of bed material has no significant effect on the release of chlorine(Cl) and sodium(Na) but highly affects the melting temperature and compositions. The ash fusion temperature reaches the lowest with a 50% mixing ratio of bed material, which is 120 °C lower than that of SEH coal ash. This study can provide better guidance for controlling severe slagging, from the combustion of high Na and Cl coal in industrial furnaces.     

Migration and transformation of sodium and chlorine in high-sodium high-chlorine Xinjiang lignite during circulating fluidized bed combustion

The Xinjiang lignite mined from Shaerhu coalfield (SEHc) easily causes severe fouling and corrosion because of its high sodium and chlorine contents. Therefore, it is necessary to study the migration and transformation behavior of sodium and chlorine during combustion in order to reveal the mechanisms of fouling and corrosion, and propose the effective solutions of above problems. In this study, based on the 0.4 T/D circulating fluidized bed (CFB) test system, the migration and transformation behavior of sodium and chlorine in SEHc during combustion at 950 °C was explored. The migration and transformation paths of sodium and chlorine were proposed through the chemical characterization of ash samples along the flue gas flow direction, as well as the thermodynamic equilibrium calculation by the software of Factsage 6.1. The experimental studies show the sodium and chlorine mainly in the form of NaCl crystal in raw coal underwent a series of physical and chemical changes during combustion, and subsequently distributed in bottom ash/circulating ash, fly ash and gas phase in various forms including sodium aluminosilicates, chlorides and sodium oxides. Sodium was more inclined to be resided in ash in the form of aluminosilicates through the reactions with other minerals (SiO₂ and Al₂O₃), while chlorine was easily released into the flue gas in forms of HCl, Cl₂, NaCl, etc. The Cl-based species might result in the corrosion of metal heating surfaces because of the presence of corrosion products (metal chlorides) in fly ash. As temperature decreased, the sodium or chlorine vapors would successively deposit in fly ash via physical condensation or chemical reaction. At 840～570 °C, the sodium-based species (Na₂O and NaCl) would first deposit in fly ash, then gaseous chlorine species (NaCl, FeCl₃ and so on) primarily deposited at 570～180 °C.     

Electrochemical performance of a solid oxide fuel cell based on Ce0.8Sm0.2O2−δ electrolyte synthesized by a polymer assisted combustion method

A polyvinyl alcohol assisted combustion synthesis method was used to prepare Ce_0.8Sm_0.2O_2−δ (SDC) powders for an intermediate temperature solid oxide fuel cell (IT-SOFC). The XRD results showed that this combustion synthesis route could yield phase-pure SDC powders at a relatively low calcination temperature. A thin SDC electrolyte film with thickness control was produced by a dry pressing method at a lower sintering temperature of 1250 °C. With Sm_0.5Sr_0.5Co₃-SDC as the composite cathode, a single cell based on this thin SDC electrolyte was tested from 550 to 650 °C. The maximum power density of 936 mW cm⁻² was achieved at 650 °C using humidified hydrogen as the fuel and stationary air as the oxidant.     

Combustion of polymer pellets in a bubbling fluidised bed

Single pellets (≈3 mm diameter) of high density polyethylene (HDPE) have been burned in an electrically heated bed of silica sand, fluidised by air or mixtures of N₂ and O₂ at atmospheric pressure. During the combustion of single pellets, measurements were made of the concentrations of CO and CO₂ in the off-gas, enabling burnout-times to be derived. This was done for different temperatures (400–900 °C) in a bubbling fluidised bed and a range of masses for the HDPE pellets. In addition, the size of the sand, the fluidising velocity and the concentration of O₂ in the fluidising gas were all varied. In a bed above 400 °C, a polymer pellet melted on entering the hot sand, which was wetted to form a small aggregate (or “blob” ∼5 mm in diameter) of sand particles held together by molten polymer. Next, the blob sank and volatilisation and thermal decomposition of the polymer produced hydrocarbon vapours, which burned mainly above the sand. It was deduced that there are actually three ranges of temperature, each with a different mechanism of combustion. With the bed in the high temperature regime at 640–900 °C, burnout was controlled by mass transfer of hydrocarbon vapour (deduced to have a mean composition of approximately (C₂H₄)₅) away from such a blob of sand and molten polymer. When the bed was between 485 and 640 °C (the medium temperature regime), radiative heat transfer to a blob of polymer controlled burnout. At 400–485 °C (the low temperature region) the burnout-time was controlled by the volatilisation (gasification) of a polymer pellet to produce a combustible hydrocarbon vapour. The activation energy for this gasification was ∼58 kJ/mol. This is the same as that characterising the ignition delay, which was also measured. The measured rates of burning indicate an enthalpy of gasification of ≈450 J/g. The total yield of CO and CO₂ was found to depend on the bed’s temperature and was low enough to indicate that soot, together with unburned hydrocarbons, can be important products from such a bed.     

Combustion characteristics of novel hybrid nanoenergetic formulations

This paper presents the combustion characteristics of various copper oxide (CuO) nanorods/aluminum (Al) nanothermite compositions and hybrid nanoenergetic mixtures formed by combining nanothermites with either ammonium nitrate (NH₄NO₃) or secondary explosives such as RDX and CL-20 in different weight proportions. The different types of nanorods prepared in this study are referred to as CuO-VD (dried under vacuum at 25 °C for 24 h), CuO-100 (at 100 °C for 16 h) and CuO-400 (short time (1 min) calcination at 400 °C). The physical and chemical characteristics of these different kinds of CuO nanorods were determined using a variety of analytical tools such as X-ray diffractometer, transmission electron microscope (TEM), Fourier transform infrared spectrometer (FTIR), surface area analyzer and simultaneous differential scanning calorimeter (DSC)/thermogravimetric analyzer (TGA). These measured characteristics were correlated with the combustion behavior of the nanoenergetic compositions synthesized in this work. The use of different drying and calcination parameters produced the synthesis of CuO nanorods with varying amount of hydroxyl (OH) and CH_n (n = 2, 3) functional groups. The experimental observations confirm that the presence of these functional groups on the surface of CuO nanorods enabled the formation of assembled nanoenergetic composite, upon mixed with Al nanoparticles. A facile one-step synthesis of assembled composite through surface functionalization is reported and it can be extended to large-scale preparation of assembled nanoenergetic mixtures. The combustion behavior was studied by measuring both combustion wave speed and pressure–time characteristics. Pressurization rate was determined by monitoring the pressure–time characteristics during the combustion reaction initiated by a hot wire in a fully-confined geometry. Different amounts of nanothermite powder were packed in the same volume of combustion chamber by applying different packing pressures and the pressure–time characteristics were measured as a function of varying percent theoretical maximum density (% TMD). The experimental setup used in this work enabled us to study the functional behavior of initiating explosives such as NH₄NO₃ nanoparticles, RDX and CL-20 using nanothermites under fully-confined test geometry. The dent tests performed on lead witness plates support the experimental observations obtained from pressure–time and combustion wave speed measurements of hybrid mixtures.     

Investigation of grain boundary formation in PtRu/C catalyst obtained in a polyol process with post-treatment

The grain boundary formation in PtRu/C catalyst obtained in a polyol process with post-treatment was investigated by scanning transmission electron microscopy, transmission electron microscopy (TEM) and High resolution TEM. The crystalline structure and surface composition of the PtRu/C catalysts were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical activities were evaluated by CO stripping voltammetry and linear sweep voltammetry measurements in combination with in situ IR reflection-absorption spectroscopy. As-prepared isolated spherical nanoparticles on the carbon support started to interconnect after washing procedure, and the interconnection between the particles was greatly promoted by reduction post-treatment at 80 °C; grain boundary formation occurred in the interconnected particles with increasing reduction temperature to 200 °C, and the particles reconstructed severely with further increasing reduction temperature to 400 °C. The defects at the grain boundary served as active sites for methanol electro-oxidation by weakening CO_ads adsorption on Pt sites and facilitating OH_ads formation, and the PtRu/C catalyst treated in 5% H₂/Ar at 200 °C for 10 h had the greatest catalytic activity for methanol electro-oxidation among the PtRu/C catalysts treated under various atmospheres and temperatures.     

Hydrogen generation from hydrolysis of aluminum/graphite composites with a core–shell structure

Hydrogen generated by hydrolysis of metal aluminum with water is promising for portable fuel cell applications. However aluminum would not react with water to yield hydrogen at ordinary conditions due to the passive oxide film formed on its surface. In the present investigation, the aluminum/graphite composite were prepared by a ball milling process in an attempt to improve the reactivity of aluminum, using sphere-shape aluminum particles and laminate graphite as the initial materials and 2 wt% NaCl as the milling-assisted agent. The TEM observation showed that the Al particles are covered by graphite to form a core–shell structure. Such a Al/graphite composite material exhibited a pronounced hydrolysis reactivity with tap water to generate hydrogen while Al alone did not react with water. The presence of graphite could lower the hydrogen generation reaction temperature below 45 °C. Increasing the reaction temperature could obtain an increased hydrogen generation rate and the maximum hydrogen generation rate of 40 cm³ min⁻¹ g⁻¹ Al was obtained when the reaction temperature was increased to 75 °C. Prolonging milling time could also improve the Al hydrolysis reactivity in the composite particularly at a relatively low temperature. The XRD results identified that the hydrolysis byproducts are bayerite (Al(OH)₃) and boehmite (AlOOH). The microstructure-related hydrolysis reaction mechanism was finally proposed.     

Improving steam-reforming performance by nanopowdering CuCrO2

In this study, the delafossite type CuCrO₂ nanopowder was used as a precursor for preparing Cu-based catalyst for steam reforming of methanol (SRM). The efficiency of hydrogen generation was greatly improved by reducing the size of CuCrO₂ to nanoscale. The reduction temperature of Cu metal particles from CuCrO₂ decreased from 600 °C to 200 °C due to this size effect. Additionally, because of lowered activation energy, CuCrO₂ nanopowder could be reduced by methanol vapor. Thus the CuCrO₂ nanopowder, prepared by GNP method, had much higher SRM efficiency than bulk CuCrO₂ and the commercial SRM catalyst, even without H₂ activation process. The SEM images revealed that the powder retained a cotton candy-like porous structure after reduction treatment. The TEM images showed that the Cu particles were about 5 nm in diameter and well dispersed on Cr₂O₃ after the reduction of CuCrO₂ nanopowder at 500 °C. The catalyst was evaluated by the generation rate with steam reforming of methanol, and the peak hydrogen generation rate read as high as 2550 ml/min g-cat at 360 °C with hydrogen activation. CuCrO₂ nanopowder showed high catalytic activity even without reduction treatment, and hydrogen generation rate read as high as 1740 ml/min g-cat at 360 °C.     

Sintering and electrical properties of Ce0.75Sm0.2Li0.05O1.95

Ceria-based electrolytes have been widely investigated in intermediate-temperature solid oxide fuel cell (SOFC), which might be operated at 500–600 °C. Samarium doped (20 mol%) ceria (20SDC) one of the most promising material in this class of compounds. In this work we report effect of lattice substitution of 5 mol % Li on Sm in (20SDC). It was prepared by citrate–nitrate auto combustion synthesis having a powder of average particle size ∼50 nm. The sintered density of more than 98% of the theoretical density at 950 °C has been achieved. Increased ionic conductivity (lattice) at 500 °C has also been achieved in Ce_0.75Sm_0.2Li_0.05O_1.95 compare to that of Ce_0.8Sm_0.2O_1.95. Corresponding activation energy of conduction ∼0.7 eV has been calculated in the temperature range of 200–600 °C. In reducing atmosphere the electrical conductivity has not been altered much. Thus Ce_0.75Sm_0.2Li_0.05O_1.95 has been found to be quite promising in terms of reducing the processing temperature as well as operating temperature of SOFC.     

Comparison of CuO and NiO as oxygen carrier in chemical looping combustion of a Victorian brown coal

Chemical looping combustion (CLC) is a novel process where an oxygen carrier, preferably oxides of metal, is used to transfer oxygen from the combustion air to the fuel. The outlet gas from the process reactor consists of CO₂ and H₂O, and concentrated stream of CO₂ is obtained for sequestration when water vapour is condensed. Chemical looping has been widely studied for combustion of natural gas; however its application to solid fuels, such as coal, is being studied relatively recently; no work has been done using Victorian brown coal which represents a very large resource, over 500 years at current consumption rate. In this study we carried out an experimental investigation pertaining to CLC of a Victorian brown coal from Loy Yang mine using NiO and CuO as oxygen carrier. The experiments were conducted using a thermogravimetric analyser (TGA) under CO₂ gasification environment with NiO and CuO. The reduction and re-oxidation of NiO in five repeated cycle operations were performed at 950 °C. However, the same cyclic operation for CuO was performed at 800 °C, as it was observed that at 950 °C CuO could not be re-oxidized to its original state due to sintering, which significantly altered the morphology. The extent of coal combustion and re-oxidation of metal oxides resulted in a 4.4-7.5% weight loss of NiO per cycle. No such weight loss was observed in case of CuO at 800 °C. The high reactivity of CuO was observed as compared to NiO during cyclic operation. The percentage of combustion at the end of the 5th cycle with CuO was 96% as compared to 67% with NiO. Fresh oxide particles and solid residues are characterized using SEM to understand surface morphological changes due to combustion. The energy dispersive X-rays (EDX) helped to get surface elemental information, albeit qualitative, of fresh and used metal oxide particles. The current study, for the first time, has generated practical information on the temperature range, approximate time, and percent combustion that can be achieved while using NiO and CuO as oxygen carriers during CLC with Loy Yang brown coal. Based on these results the ongoing work includes long duration experiments with Loy Yang and other Victorian brown coals.