Aluminum particles 15-25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a hi...Aluminum particles 15-25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size（15-25 μm, 74-105 μm, and 2.38 mm） and oxidizer（air, CO2, and argon）, the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry （TGA/DSC） enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.展开更多
A wide range of wastes can potentially be used to generate thermal and electrical energy.The co-combustion of several types of waste as part of water-containing waste-derived fuels is a promising method for their reco...A wide range of wastes can potentially be used to generate thermal and electrical energy.The co-combustion of several types of waste as part of water-containing waste-derived fuels is a promising method for their recovery.In this research,we use thermogravimetric analysis and differential scanning calorimetry to study the thermal behavior and kinetics of coal slime,biomass,waste oils,and blends on their basis.We also analyze the concentrations of gaseous emissions.The results show that biomass,oils,and coal slime significantly affect each other in the course of their co-combustion when added to slurry fuels.The preparation of coal-water slurry based on slime and water reduced the ignition and burnout temperature by up to 16%.Adding biomass and waste oils additionally stimulated the slurry ignition and burnout,which occurred at lower temperatures.Relative to dry coal slime,threshold ignition temperatures and burnout temperatures decreased by 6%–9%and 17%–25%,respectively.Also,the use of biomass and waste oils as part of slurries inhibited NOхand SO_(2)emission by 2.75 times.According to the kinetic analysis,added biomass and waste turbine oil provide a 28%–51%reduction in the activation energy as compared to a coal-water slurry without additives.展开更多
Thermogravimetric analysis/differential scanning calorimeter(TGA/DSC)technique along with basic coal characteristics study is carried out for eighty coal samples of Indian coalfields,to determine spontaneous combustio...Thermogravimetric analysis/differential scanning calorimeter(TGA/DSC)technique along with basic coal characteristics study is carried out for eighty coal samples of Indian coalfields,to determine spontaneous combustion propensity behaviour of coal.TGA study of coal samples indicates that there is an increase in the mass of coal samples in the temperature range 150-350℃,which may be due to oxygen adsorption and absorption.The correlation and principal component analysis states that the component of proximate analysis(M_(ad),VM_(d),FR,and VR)have an acceptable correlation with the TGA experiments results i.e.,Tgsh and Tgign.Multiple fixed nonlinear regression analysis shows that thermogravimetry(TG)experiment results Tgign may be the best index to categorise/classify the coal as per their susceptibility towards spontaneous combustion.The authors proposed four groups of classification as per their propensity towards spontaneous combustion depending upon the moisture(M_(ad)),volatile matter(VM_(d)),and TG ignition temperature from differential thermogravimetric(DTG)curve(Tgign)using hierarchal clustering analysis.The coal samples of different seams from Indian coalfield may be classified into four different clusters,viz.very highly/extremely susceptible(Tgign<260℃),highly susceptible(260℃≤Tgign<290℃),moderately susceptible(290℃≤Tgign≤320℃),and poorly susceptible(Tgign>320℃).The field observations and TGA/DSC experiment results with the following statistical analysis substantiate a similar assessment.展开更多
Studies of thermodynamic, electric and magnetic properties were conducted on the （KxSr1-x）CrOz, x = 0.10, 0.15 and 0.50system; adjusted for different crystal sizes （polycrystalline, nano-crystalline and single crys...Studies of thermodynamic, electric and magnetic properties were conducted on the （KxSr1-x）CrOz, x = 0.10, 0.15 and 0.50system; adjusted for different crystal sizes （polycrystalline, nano-crystalline and single crystals）. For polycrystals, a solid-statereaction method was used （room temperature, TR, up to 665 °C）. Nano-crystals, a crushing technique with a mechanical mortar wereprocessed at TR. Single crystals were acquired, through fusion method starting from polycrystals pre-manufactured （665 °C） over900 °C. For the methods described above, they all were worked at atmospheric pressure. Studying the thermodynamic in the crystalsmixture were obtained by TGA （thermogravimetric analysis） and DSC （differential scanning calorimetry）. Powder XRD （X-raydiffraction） in the manual grinding mixture a SrCO3 solid solution, at TR was detected. When increasing the temperature, a solidsolution of K2Sr（CrO4）2 is formed. By HRTEM （high-resolution transmission electronic microscope）, crystal sizes 4-12 nm were seen.（K0.50Sr0.50）CrOz composition presents a weak ferromagnetic and an insulating behavior.展开更多
基金Supported by Defense Acquisition Program Administration and Agency for Defense Development(Grant Nos.UD110095CD,UD130038GD)
文摘Aluminum particles 15-25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size（15-25 μm, 74-105 μm, and 2.38 mm） and oxidizer（air, CO2, and argon）, the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry （TGA/DSC） enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.
基金supported by a grant from the Ministry of Science and Higher Education of Russia,Agreement No 075-152020-806 (Contract No 13.1902.21.0014)。
文摘A wide range of wastes can potentially be used to generate thermal and electrical energy.The co-combustion of several types of waste as part of water-containing waste-derived fuels is a promising method for their recovery.In this research,we use thermogravimetric analysis and differential scanning calorimetry to study the thermal behavior and kinetics of coal slime,biomass,waste oils,and blends on their basis.We also analyze the concentrations of gaseous emissions.The results show that biomass,oils,and coal slime significantly affect each other in the course of their co-combustion when added to slurry fuels.The preparation of coal-water slurry based on slime and water reduced the ignition and burnout temperature by up to 16%.Adding biomass and waste oils additionally stimulated the slurry ignition and burnout,which occurred at lower temperatures.Relative to dry coal slime,threshold ignition temperatures and burnout temperatures decreased by 6%–9%and 17%–25%,respectively.Also,the use of biomass and waste oils as part of slurries inhibited NOхand SO_(2)emission by 2.75 times.According to the kinetic analysis,added biomass and waste turbine oil provide a 28%–51%reduction in the activation energy as compared to a coal-water slurry without additives.
基金M/s CIL R&D Board,Kolkata(CIL/R&D/01/60/2016)for their financial support.
文摘Thermogravimetric analysis/differential scanning calorimeter(TGA/DSC)technique along with basic coal characteristics study is carried out for eighty coal samples of Indian coalfields,to determine spontaneous combustion propensity behaviour of coal.TGA study of coal samples indicates that there is an increase in the mass of coal samples in the temperature range 150-350℃,which may be due to oxygen adsorption and absorption.The correlation and principal component analysis states that the component of proximate analysis(M_(ad),VM_(d),FR,and VR)have an acceptable correlation with the TGA experiments results i.e.,Tgsh and Tgign.Multiple fixed nonlinear regression analysis shows that thermogravimetry(TG)experiment results Tgign may be the best index to categorise/classify the coal as per their susceptibility towards spontaneous combustion.The authors proposed four groups of classification as per their propensity towards spontaneous combustion depending upon the moisture(M_(ad)),volatile matter(VM_(d)),and TG ignition temperature from differential thermogravimetric(DTG)curve(Tgign)using hierarchal clustering analysis.The coal samples of different seams from Indian coalfield may be classified into four different clusters,viz.very highly/extremely susceptible(Tgign<260℃),highly susceptible(260℃≤Tgign<290℃),moderately susceptible(290℃≤Tgign≤320℃),and poorly susceptible(Tgign>320℃).The field observations and TGA/DSC experiment results with the following statistical analysis substantiate a similar assessment.
文摘Studies of thermodynamic, electric and magnetic properties were conducted on the （KxSr1-x）CrOz, x = 0.10, 0.15 and 0.50system; adjusted for different crystal sizes （polycrystalline, nano-crystalline and single crystals）. For polycrystals, a solid-statereaction method was used （room temperature, TR, up to 665 °C）. Nano-crystals, a crushing technique with a mechanical mortar wereprocessed at TR. Single crystals were acquired, through fusion method starting from polycrystals pre-manufactured （665 °C） over900 °C. For the methods described above, they all were worked at atmospheric pressure. Studying the thermodynamic in the crystalsmixture were obtained by TGA （thermogravimetric analysis） and DSC （differential scanning calorimetry）. Powder XRD （X-raydiffraction） in the manual grinding mixture a SrCO3 solid solution, at TR was detected. When increasing the temperature, a solidsolution of K2Sr（CrO4）2 is formed. By HRTEM （high-resolution transmission electronic microscope）, crystal sizes 4-12 nm were seen.（K0.50Sr0.50）CrOz composition presents a weak ferromagnetic and an insulating behavior.
