Wear-resistant laser-induced thermite reaction Al2O3 ceramic coatings can be fabricated on pure Al and AA7075 aluminum alloy by laser cladding (one-step method) and laser cladding followed by laser re-melting (two-...Wear-resistant laser-induced thermite reaction Al2O3 ceramic coatings can be fabricated on pure Al and AA7075 aluminum alloy by laser cladding (one-step method) and laser cladding followed by laser re-melting (two-step method) using mixed powders CuO-Al-SiO2 in order to improve the wear properties of aluminum and aluminum alloy, respectively. The microstructure of the coatings was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The wear resistance of the coatings was evaluated under dry sliding wear test condition at room temperature. Owing to the presence of hard α-Al2O3 and γ-Al2O3 phases, the coatings exhibited excellent wear resistance. In addition, the wear resistance of the coatings fabricated by two-step method is superior to that of the coatings fabricated by one-step method.展开更多
In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite (IMC) reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuou...In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite (IMC) reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling (DMM) instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-α-Al2O3 IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for γ-TLA1 as well as Al2Ti and Al2O3 are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.展开更多
The microstructure and wear behaviour of the thermite reaction coating produced by the hybrid laser claddingremelting on AA7075 aluminum alloy for the systems of Al-CuO-SiO2, Al-Cr2O3-SiO2, Al-Fe2O3-SiO2, and Al-TiO2-...The microstructure and wear behaviour of the thermite reaction coating produced by the hybrid laser claddingremelting on AA7075 aluminum alloy for the systems of Al-CuO-SiO2, Al-Cr2O3-SiO2, Al-Fe2O3-SiO2, and Al-TiO2-SiO2 were studied. The results of the X-ray diffraction (XRD) analysis show that in all the four reaction coatings, α-Al2O3 and γ-Al2O3 phases were present at the top surface, together with various intermetallic phases, the corresponding reduced metal and Al phase in the fusion zone. Under the dry sliding condition, the wear resistance, in terms of weight loss, of the laser-clad specimens was considerably higher than that of the untreated specimen. The predominant wear mechanism of the former specimens was abrasive wear, while for the latter, it was the adhesive wear that prevailed.展开更多
NiAl/Al2O3 composite were synthesized by thermite reaction of nickel oxide and aluminum powder mixtures.The phase,the microstructure of the composite,as well as the thermite reaction mechanism,were investigated by X-r...NiAl/Al2O3 composite were synthesized by thermite reaction of nickel oxide and aluminum powder mixtures.The phase,the microstructure of the composite,as well as the thermite reaction mechanism,were investigated by X-ray diffractomety(XRD0,scanning electron microscopy(SEM) combined with differential scanning calorimetry(DSC).The experimental results show that the thermite reaction leads to the interpenetrating network structure of NiAl/Al2O3 at 1223K for 60min and the chemical reaction apparent activation energy is Eap=166.960±13.496kJ·mol^-1 in the NiO/Al system.展开更多
Energetic metal-organic complexes have been involved in nanothermites as novel oxidants.However,the existing preparation methods often lead to mixing inhomogeneity and small contact area of ingredients,the reactivity ...Energetic metal-organic complexes have been involved in nanothermites as novel oxidants.However,the existing preparation methods often lead to mixing inhomogeneity and small contact area of ingredients,the reactivity and functionality of the novel energetic nanocomposites are still limited.In this work,spray crystallization(SC)method was used to prepare novel energetic nanocomposites,the high-energy metal-organic complex[Ni(CHZ)_(3)](ClO_(4))_(2)(CHZ=1,3-diaminourea)was composited with nanoaluminum(n-Al).Results showed that n-Al/[Ni(CH_(2))_(3)](ClO_(4))_(2)energetic nanocomposites prepared by SC method increased heat release to 2977.6 J/g and peak pressure to 3.91 MPa with higher pressurization rate(1324.06 MPa/s),decreased sensitivity thresholds(>100 mJ)to electrostatic discharge(ESD)and enhanced detonation ability compared with[Ni(CHZ)_(3)](ClO_(4))_(2)alone and physically mixed(PM)n-Al/[Ni(CHZ)_(3)](ClO_(4))_(2).These results proved that it is significant to introduce energetic metal-organic complexes with inherent high energy in new-concept n-Al/energetic metal-organic complexes nanocomposites through SC method for a better performance of its application.展开更多
In order to get high quality of products, the combustion of aluminium-ironoxide thermite in SHS-gravitational process must be under control. The effects of thermite fillingdensity, hole in thermite and inclined angle ...In order to get high quality of products, the combustion of aluminium-ironoxide thermite in SHS-gravitational process must be under control. The effects of thermite fillingdensity, hole in thermite and inclined angle of pipe on combustion rate were studied. It shows thatthe combustion rate decreases with the decrease of filling density. The thermite combusts downwardsthe pipe much more quickly if there are holes in the thermite. And the combustion rate increaseswith the increase of the inclined angle of pipe. The experiment results show that the combustion ofthermite is predominantly controlled by gas phase reaction, which is attributed to the hightemperature of the thermite combustion.展开更多
基金the Open Fund of the State Key Laboratory of Plastic Forming Simulation and Mould Technology in Huazhong University of Science and Technology(No.05-14)the Open Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnic University(No.05-10)
文摘Wear-resistant laser-induced thermite reaction Al2O3 ceramic coatings can be fabricated on pure Al and AA7075 aluminum alloy by laser cladding (one-step method) and laser cladding followed by laser re-melting (two-step method) using mixed powders CuO-Al-SiO2 in order to improve the wear properties of aluminum and aluminum alloy, respectively. The microstructure of the coatings was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The wear resistance of the coatings was evaluated under dry sliding wear test condition at room temperature. Owing to the presence of hard α-Al2O3 and γ-Al2O3 phases, the coatings exhibited excellent wear resistance. In addition, the wear resistance of the coatings fabricated by two-step method is superior to that of the coatings fabricated by one-step method.
文摘In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite (IMC) reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling (DMM) instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-α-Al2O3 IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for γ-TLA1 as well as Al2Ti and Al2O3 are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.
文摘The microstructure and wear behaviour of the thermite reaction coating produced by the hybrid laser claddingremelting on AA7075 aluminum alloy for the systems of Al-CuO-SiO2, Al-Cr2O3-SiO2, Al-Fe2O3-SiO2, and Al-TiO2-SiO2 were studied. The results of the X-ray diffraction (XRD) analysis show that in all the four reaction coatings, α-Al2O3 and γ-Al2O3 phases were present at the top surface, together with various intermetallic phases, the corresponding reduced metal and Al phase in the fusion zone. Under the dry sliding condition, the wear resistance, in terms of weight loss, of the laser-clad specimens was considerably higher than that of the untreated specimen. The predominant wear mechanism of the former specimens was abrasive wear, while for the latter, it was the adhesive wear that prevailed.
文摘NiAl/Al2O3 composite were synthesized by thermite reaction of nickel oxide and aluminum powder mixtures.The phase,the microstructure of the composite,as well as the thermite reaction mechanism,were investigated by X-ray diffractomety(XRD0,scanning electron microscopy(SEM) combined with differential scanning calorimetry(DSC).The experimental results show that the thermite reaction leads to the interpenetrating network structure of NiAl/Al2O3 at 1223K for 60min and the chemical reaction apparent activation energy is Eap=166.960±13.496kJ·mol^-1 in the NiO/Al system.
基金supported by National Natural Science Foundation of China(project no.51676100)。
文摘Energetic metal-organic complexes have been involved in nanothermites as novel oxidants.However,the existing preparation methods often lead to mixing inhomogeneity and small contact area of ingredients,the reactivity and functionality of the novel energetic nanocomposites are still limited.In this work,spray crystallization(SC)method was used to prepare novel energetic nanocomposites,the high-energy metal-organic complex[Ni(CHZ)_(3)](ClO_(4))_(2)(CHZ=1,3-diaminourea)was composited with nanoaluminum(n-Al).Results showed that n-Al/[Ni(CH_(2))_(3)](ClO_(4))_(2)energetic nanocomposites prepared by SC method increased heat release to 2977.6 J/g and peak pressure to 3.91 MPa with higher pressurization rate(1324.06 MPa/s),decreased sensitivity thresholds(>100 mJ)to electrostatic discharge(ESD)and enhanced detonation ability compared with[Ni(CHZ)_(3)](ClO_(4))_(2)alone and physically mixed(PM)n-Al/[Ni(CHZ)_(3)](ClO_(4))_(2).These results proved that it is significant to introduce energetic metal-organic complexes with inherent high energy in new-concept n-Al/energetic metal-organic complexes nanocomposites through SC method for a better performance of its application.
文摘In order to get high quality of products, the combustion of aluminium-ironoxide thermite in SHS-gravitational process must be under control. The effects of thermite fillingdensity, hole in thermite and inclined angle of pipe on combustion rate were studied. It shows thatthe combustion rate decreases with the decrease of filling density. The thermite combusts downwardsthe pipe much more quickly if there are holes in the thermite. And the combustion rate increaseswith the increase of the inclined angle of pipe. The experiment results show that the combustion ofthermite is predominantly controlled by gas phase reaction, which is attributed to the hightemperature of the thermite combustion.