In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal ch...In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal channel angular pressing and torsion（ECAPT） was conducted via three-dimensional（3D） finite element simulation,experimental investigation and theoretical analysis.Simulation results revealed that during the consolidation of aluminum powder particles by ECAPT,TE process played a significant role of back pressure.Due to the torsional shear and high hydrostatic pressure exerted by twist channel,both the magnitude and homogeneity of the effective strain were increased markedly.After one pass of ECAPT process using a square channel with an inner angle of 90° and a twist slope angle of 36.5° at 200℃,commercial pure aluminum powder particles were successfully consolidated to nearly full density.Simulation and experimental results showed good agreement.In the microstructure observations,grains were greatly refined.At the same time,porosities were effectively eliminated by shrinking in size and breaking into small ones.Microhardness test indicated that strain distribution of ECAPT-processed billet was more homogeneous with respect to the ECAP-processed one.All these improvements may be attributed to the extreme intense shear strain induced during ECAPT and the increase in self-diffusion coefficient of aluminum due to the back pressure exerted by TE process.展开更多
This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by...This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.展开更多
The combustion mechanism of aluminum particles in a detonation environment characterized by high temperature(in unit 10^(3)K),high pressure(in unit GPa),and high-speed motion(in units km/s)was studied,and a combustion...The combustion mechanism of aluminum particles in a detonation environment characterized by high temperature(in unit 10^(3)K),high pressure(in unit GPa),and high-speed motion(in units km/s)was studied,and a combustion model of the aluminum particles in detonation environment was established.Based on this model,a combustion control equation for aluminum particles in detonation environment was obtained.It can be seen from the control equation that the burning time of aluminum particle is mainly affected by the particle size,system temperature,and diffusion coefficient.The calculation result shows that a higher system temperature,larger diffusion coefficient,and smaller particle size lead to a faster burn rate and shorter burning time for aluminum particles.After considering the particle size distribution characteristics of aluminum powder,the application of the combustion control equation was extended from single aluminum particles to nonuniform aluminum powder,and the calculated time corresponding to the peak burn rate of aluminum powder was in good agreement with the experimental electrical conductivity results.This equation can quantitatively describe the combustion behavior of aluminum powder in different detonation environments and provides technical means for quantitative calculation of the aluminum powder combustion process in detonation environment.展开更多
A layered charge composed of the JH-2 explosive enveloped by a thick-walled cylindrical casing(active aluminum/rubber and inert lithium fluoride/rubber composites) was designed and explosion experiments were conducted...A layered charge composed of the JH-2 explosive enveloped by a thick-walled cylindrical casing(active aluminum/rubber and inert lithium fluoride/rubber composites) was designed and explosion experiments were conducted in a 1.3 m3tank and a 113 m3bunker.The blast parameters,including the quasistatic pressure(ΔpQS),special impulse(I),and peak overpressure(Δpmax),and images of the explosion process were recorded,and the influence of the Al content(30% and 50%) and Al particle size(1,10,and 50 μm) on the energy release of aluminum/rubber composites were investigated.The results revealed that the use of an active layer increased the peak overpressure generated by the primary blast wave,as well as the quasistatic pressure and special impulse related to fuel burning within tens of milliseconds after detonation.When the Al content was increased from 30% to 50%,the increases of ΔpQS and I were not obvious,and Δpmaxeven decreased,possibly because of decreased combustion efficiency and greater absorption of the blast wave energy for layers with 50% Al.Compared with the pure JH-2charge,the charge with 1 μm Al particles produced the highest Δpmax,indicating that better transient blast performance was generated by smaller Al particles.However,the charge with 10 μm Al particles showed the largest ΔpQSand I,suggesting that a stronger destructive effect occurred over a longer duration for charges that contained moderate 10 μm Al.展开更多
High velocity compaction process of atomized Al powders was studied. The green density, the maximal force and the withdraw force of specimen were investigated. The green density of atomized aluminum powder was obtaine...High velocity compaction process of atomized Al powders was studied. The green density, the maximal force and the withdraw force of specimen were investigated. The green density of atomized aluminum powder was obtained to be 2.68 g/cm3 and its relative density is about 99%. The maximal force increased proximately linearly with the compaction energy. The withdraw force was observed ranging between 30 and 70 kN. The radial spring back was less than 0.1%.展开更多
High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch...High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.展开更多
The MIG welding of in-situ generated nano-Al_(2)O_(3)powder metallurgy 7A52(PM 7A52)aluminum alloy was investigated.The microstructure was characterized using EBSD and TEM,while macrotexture and internal residual stre...The MIG welding of in-situ generated nano-Al_(2)O_(3)powder metallurgy 7A52(PM 7A52)aluminum alloy was investigated.The microstructure was characterized using EBSD and TEM,while macrotexture and internal residual stresses were analyzed with a self-developed SWXRD technique.The results revealed that PM 7A52 aluminum alloy effectively reduced the grain size,dislocation density,and texture strength in the post-weld microstructure.Furthermore,the residual stress in the weld zone(WZ)of PM 7A52 aluminum alloy was reduced by 38 MPa compared to that of the conventional melt-cast 7A52(CM 7A52)aluminum alloy.Notably,the tensile strength and elongation of welded joints in PM 7A52 aluminum alloy were increased by approximately 15%and 26%,respectively.The improvement in joint tensile strength was primarily attributed to grain boundary strengthening and dispersion strengthening caused byγ-Al_(2)O_(3)particles entering the WZ.展开更多
Aiming at improving the properties of magnesia carbon materials,silicon aluminum carbide(Al_(4)SiC_(4))containing materials were prepared using industrial aluminum powder,silicon carbide powder,and graphite as raw mat...Aiming at improving the properties of magnesia carbon materials,silicon aluminum carbide(Al_(4)SiC_(4))containing materials were prepared using industrial aluminum powder,silicon carbide powder,and graphite as raw materials,and activated alumina powder as an additive,mixing thoroughly,pressing into cylinders and then firing at 1200℃for 30 min in a carbon embedded atmosphere by the microwave method.The effects of the aluminum powder addition(20%and 24%,by mass)and activated alumina powder addition(0,3%,5%and 7%,by mass)on the microwave synthesis of Al_(4)SiC_(4) as well as the effect of the obtained Al_(4)SiC_(4) containing material on the properties of magnesia carbon bricks were studied.The results show that:compared with the samples with 20%aluminum powder,those with 24%aluminum powder generate more Al_(4)SiC_(4).With the activated alumina powder addition increasing from 0 to 7%,the amount of Al_(4)SiC_(4) generated increases first and then decreases.Compared with the sample without activated alumina powder,the samples with activated alumina powder show lower bulk density and higher apparent porosity.With the activated alumina powder addition increasing from 3%to 7%,the bulk density of the samples increases first and then decreases,while the apparent porosity of the samples shows an opposite trend.The optimal additions are 24%aluminum powder and 5%activated alumina powder,and Al_(4)SiC_(4) synthesized in this sample has a hexagonal plate structure.With the synthesized Al_(4)SiC_(4) containing material added,the magnesia carbon brick has slightly increased cold modulus of rupture,basically the same modulus of elasticity and improved oxidation resistance.展开更多
Though silanization of aluminum powder is currently used to improve its flow properties,for use as an alternative fuel source,there are a wide range of experimental parameters for the process and not all of them have ...Though silanization of aluminum powder is currently used to improve its flow properties,for use as an alternative fuel source,there are a wide range of experimental parameters for the process and not all of them have been thoroughly explored.Until this is complete,it is unknown if the process is optimized in terms of time,efficiency,and effect.Herein,we report on a study into the effects of changes in humidity,degree of agitation,reaction temperature,and curing time upon the deposition of phenyl triethoxysilane into 20μm(d50)aluminum particles.We confirm the deposition of the coating via diffuse reflectance infrared spectroscopy and x-ray photoelectron spectroscopy.We then characterize the coated particles using apparent density measurements and Carney flow methods.Using analysis of variance,we find that,of the parameters explored,only changes in cure time and reaction temperature provide meaningful changes to the apparent density,while none of our parameters produced statistically significant changes in Carney flow values.Thus,we conclude that,when optimizing silanization of aluminum particles,environmental control of humidity is unneeded and that the reaction can be run with minimal agitation.The ability to largely ignore these parameters is a benefit to large-scale processing.展开更多
Low-intensity ultrasound was applied to the pressureless consolidation of AlSi10Mg powders in a broad temperature range from 600 to 860℃.Under static conditions,the consolidation of AlSi10Mg powders can only be achie...Low-intensity ultrasound was applied to the pressureless consolidation of AlSi10Mg powders in a broad temperature range from 600 to 860℃.Under static conditions,the consolidation of AlSi10Mg powders can only be achieved at 860℃,but still with the presence of some residual unconsolidated regions.The introduction of low-intensity ultrasound at this temperature eliminates the unconsolidated regions and transforms the columnar grains observed in original directional solidification into equiaxed or globular grains.Remarkably,the application of low-intensity ultrasound significantly reduces the consolidation temperature to 620℃,without compromising the microhardness of the resulting samples when compared to static conditions.Furthermore,by lowering the temperature to 600℃,a well-sintered porous material is obtained through the assistance of the low-intensity ultrasound.展开更多
Coating modification is an important way to enhance the reactivity of aluminum powder.In this paper,ammonium perchlorate and aluminum powder were assembled into energetic microunits by liquid deposition method.Spheric...Coating modification is an important way to enhance the reactivity of aluminum powder.In this paper,ammonium perchlorate and aluminum powder were assembled into energetic microunits by liquid deposition method.Spherical particles with AP as shell and ultrafine aluminum powder as the core(Al@AP)were gained.The micromorphology results show that the coated particles are about 5μm,and the coating layer is evenly distributed on the outer surface of aluminum powder,indicating a complete coating.The energetic microunits were implanted into the nitrate ester plasticizing adhesive system(NEPE)as solid phase fillers.The effect of filler on the rheological properties,safety,mechanical properties,thermal reaction and energy properties of the system was analyzed by comparing with the raw aluminum filler.The test results show that the rheological properties,mechanical properties and pressure index of NEPE containing system Al@AP meets the requirements of solid propellant charging.Compared with Al based propellant,the mechanical sensitivity and thermal sensitivity are decreased,the safety is better,and the explosion heat of the propellant is increased by 7.8%.The engine test shows that the specific impulse is increased by 1.2 s.Al@AP can improve the energy output and safety of NEPE propellant,and has potential application prospects in high-energy propellants.展开更多
Baded on the study of nickel electroplating technology at room temperature, the plated sheet containing rapidly solidified Al-Fe-Cu- V-Si-Ni-Ce-Zr aluminum alloy powders is constructed successfully. The powders and ni...Baded on the study of nickel electroplating technology at room temperature, the plated sheet containing rapidly solidified Al-Fe-Cu- V-Si-Ni-Ce-Zr aluminum alloy powders is constructed successfully. The powders and nickel matrix are combined well in the sheet. It can be used to prepare the observation specimen for TEM and determine the hardness of single powder particle as solidified and after heat-treated. The advantages of this method are the realization of heat treatment of powders and the TEM observation of non-interfered microstructure of powders in the size of several microns.展开更多
A new technique, powder compact foaming process for the production of aluminumfoams has been studied in this article. According to this method, the aluminum pow-der is mixed with a powder foaming agent (TiH_2). Subseq...A new technique, powder compact foaming process for the production of aluminumfoams has been studied in this article. According to this method, the aluminum pow-der is mixed with a powder foaming agent (TiH_2). Subsequent to mixing, the powderblend is hot compacted to obtain a dense semi--finished product. Upon heating to tem-peratures within the range of the melting point, the foaming agent decomposes to evolvegas and the semi--finished product expands into a porous cellular aluminum. Foamingprocess is the key in this method. Based on experiments, the foaming characteris-tics were mainly analyzed and discussed. Experiments show that the aluminum--foamwith closed pores and a uniform cell structure of high porosity can be obtained usingthis method by adjusting the foaming parameters: the content of foaming agent andfoaming temperature.展开更多
AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challe...AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challenge. In this article, a flexile powder metallurgy processing was used to produce a fully dense AI-4.0Cu （wt%） alloy composite reinforced with 65 vol.% Si particles. In this composite, Si particles were homogenously distributed, and the particle size was refined to the range of 3-15 μm. Tensile and flexural strength of the composite were 282 and 455 MPa, respectively, about 100% and 50% higher than the best properties reported in literature. The measured fracture toughness of the composite was 4.90 MPa m1/2. The improved strength of 65%Si/AI was attributed to the optimized particle characteristics and matrix properties. This investigation is expected to provide a primary understanding of the mechanical behaviors of Si/AI composites, and also promote the structural applications of this low-thermal-expansion material.展开更多
Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-pre...Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray ...展开更多
In this paper, Al/Ni/TiC powders were mixed on the surface of A380 aluminum alloy, by selecting appropriate laser parameters;the cladding layer with good adhesion to the substrate was obtained. The microstructure and ...In this paper, Al/Ni/TiC powders were mixed on the surface of A380 aluminum alloy, by selecting appropriate laser parameters;the cladding layer with good adhesion to the substrate was obtained. The microstructure and properties of the cladding layer under different laser parameters were analyzed. The results show that: the phase composition of the cladding layer is mainly composed of TiC, Al, Ni, C and Ti phases. The hardness of the cladding region is up to 173.3 HV, which is about 2.9 times the matrix (–59.1 HV). The corrosion voltage (–1.8 V) of the cladding layer shifted significantly from the corrosion potential (–1.18 V), the corrosion current density increased, the resistance value decreased and the diameter of the capacitor arc decreased;all these phenomena indicate that the corrosion resistance of the cladding layer is decreased.展开更多
By nickel electroplating at room temperature, the specimen preparation of ultra sonic gas atomized aluminum alloy powders for observation in transmission electron microscope was carried out. The advantages of this tec...By nickel electroplating at room temperature, the specimen preparation of ultra sonic gas atomized aluminum alloy powders for observation in transmission electron microscope was carried out. The advantages of this technique are simple technologically and convenient practically. The nickel and the powders combine well in the plated sheet which can be thinned by ion milling. The powders in the thinned sheet possess large thinned area and can be examined in common TEM for the studies of their microstructure.展开更多
High-velocity compaction （HVC） provides an effective means in the field of powder metallurgy （P/M） to reduce the porosity as well as to ameliorate the mechanical properties of products. In this study, the green de...High-velocity compaction （HVC） provides an effective means in the field of powder metallurgy （P/M） to reduce the porosity as well as to ameliorate the mechanical properties of products. In this study, the green density of an aluminum alloy is found to be 2.783 g cm 3. The ejection force for the aluminum alloy is in the range of 23 to 80 kN and the spring back is found to be less than 0.40%. The hardness of the green body is in the range of HRB 30 to 70. The bending strength of the green body is in the range of 6 to 26 MPa, which are higher than that of other aluminum alloys prepared by the traditional compaction method.展开更多
The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as ...The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.展开更多
基金Project(51401177)supported by the National Natural Science Foundation of ChinaProject(13KJD430005)supported by the Natural Science Foundation of Jiangsu Higher Education Institutions of ChinaProject(JSKLEDC201309)supported by Jiangsu Key Laboratory of Large Engineering Equipment Detection and Control,China
文摘In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal channel angular pressing and torsion（ECAPT） was conducted via three-dimensional（3D） finite element simulation,experimental investigation and theoretical analysis.Simulation results revealed that during the consolidation of aluminum powder particles by ECAPT,TE process played a significant role of back pressure.Due to the torsional shear and high hydrostatic pressure exerted by twist channel,both the magnitude and homogeneity of the effective strain were increased markedly.After one pass of ECAPT process using a square channel with an inner angle of 90° and a twist slope angle of 36.5° at 200℃,commercial pure aluminum powder particles were successfully consolidated to nearly full density.Simulation and experimental results showed good agreement.In the microstructure observations,grains were greatly refined.At the same time,porosities were effectively eliminated by shrinking in size and breaking into small ones.Microhardness test indicated that strain distribution of ECAPT-processed billet was more homogeneous with respect to the ECAP-processed one.All these improvements may be attributed to the extreme intense shear strain induced during ECAPT and the increase in self-diffusion coefficient of aluminum due to the back pressure exerted by TE process.
基金supported by the National Natural Science Foundation of China(Nos.52176099,51376007 and 51806001)the Project of Jiangsu Provincial Six Talent Peak,China(No.JNHB-097)。
文摘This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.
基金Project supported by the National Natural Science Foundation of China(Grant No.11772058)。
文摘The combustion mechanism of aluminum particles in a detonation environment characterized by high temperature(in unit 10^(3)K),high pressure(in unit GPa),and high-speed motion(in units km/s)was studied,and a combustion model of the aluminum particles in detonation environment was established.Based on this model,a combustion control equation for aluminum particles in detonation environment was obtained.It can be seen from the control equation that the burning time of aluminum particle is mainly affected by the particle size,system temperature,and diffusion coefficient.The calculation result shows that a higher system temperature,larger diffusion coefficient,and smaller particle size lead to a faster burn rate and shorter burning time for aluminum particles.After considering the particle size distribution characteristics of aluminum powder,the application of the combustion control equation was extended from single aluminum particles to nonuniform aluminum powder,and the calculated time corresponding to the peak burn rate of aluminum powder was in good agreement with the experimental electrical conductivity results.This equation can quantitatively describe the combustion behavior of aluminum powder in different detonation environments and provides technical means for quantitative calculation of the aluminum powder combustion process in detonation environment.
基金funded by the National Natural Science Foundation of China(Grant No.11972018)the Defense Pre-Research Joint Foundation of Chinese Ordnance Industry(Grant No.6141B012858)。
文摘A layered charge composed of the JH-2 explosive enveloped by a thick-walled cylindrical casing(active aluminum/rubber and inert lithium fluoride/rubber composites) was designed and explosion experiments were conducted in a 1.3 m3tank and a 113 m3bunker.The blast parameters,including the quasistatic pressure(ΔpQS),special impulse(I),and peak overpressure(Δpmax),and images of the explosion process were recorded,and the influence of the Al content(30% and 50%) and Al particle size(1,10,and 50 μm) on the energy release of aluminum/rubber composites were investigated.The results revealed that the use of an active layer increased the peak overpressure generated by the primary blast wave,as well as the quasistatic pressure and special impulse related to fuel burning within tens of milliseconds after detonation.When the Al content was increased from 30% to 50%,the increases of ΔpQS and I were not obvious,and Δpmaxeven decreased,possibly because of decreased combustion efficiency and greater absorption of the blast wave energy for layers with 50% Al.Compared with the pure JH-2charge,the charge with 1 μm Al particles produced the highest Δpmax,indicating that better transient blast performance was generated by smaller Al particles.However,the charge with 10 μm Al particles showed the largest ΔpQSand I,suggesting that a stronger destructive effect occurred over a longer duration for charges that contained moderate 10 μm Al.
基金National Nature Science Foundation of China (51033026)
文摘High velocity compaction process of atomized Al powders was studied. The green density, the maximal force and the withdraw force of specimen were investigated. The green density of atomized aluminum powder was obtained to be 2.68 g/cm3 and its relative density is about 99%. The maximal force increased proximately linearly with the compaction energy. The withdraw force was observed ranging between 30 and 70 kN. The radial spring back was less than 0.1%.
基金supported by the Defense Acquisition Program Administration and Agency for Defense Development under the contract UD110095CDsupported by the Advanced Research Center Program(NRF-2013R1A5A1073861) through the National Research Foundation of Korea(NRF) grant funded by the Korean government(MSIP) contracted through the Advanced Space Propulsion Research Center at Seoul National University
文摘High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.
基金supported by the National Key Research and Development Program of China(No.SQ2021YFF0600011)。
文摘The MIG welding of in-situ generated nano-Al_(2)O_(3)powder metallurgy 7A52(PM 7A52)aluminum alloy was investigated.The microstructure was characterized using EBSD and TEM,while macrotexture and internal residual stresses were analyzed with a self-developed SWXRD technique.The results revealed that PM 7A52 aluminum alloy effectively reduced the grain size,dislocation density,and texture strength in the post-weld microstructure.Furthermore,the residual stress in the weld zone(WZ)of PM 7A52 aluminum alloy was reduced by 38 MPa compared to that of the conventional melt-cast 7A52(CM 7A52)aluminum alloy.Notably,the tensile strength and elongation of welded joints in PM 7A52 aluminum alloy were increased by approximately 15%and 26%,respectively.The improvement in joint tensile strength was primarily attributed to grain boundary strengthening and dispersion strengthening caused byγ-Al_(2)O_(3)particles entering the WZ.
基金This work was funded by Luoyang Major Science and Technology Innovation Project(2301009A)Henan Province Key ResearchandDevelopment Project(231111230200).
文摘Aiming at improving the properties of magnesia carbon materials,silicon aluminum carbide(Al_(4)SiC_(4))containing materials were prepared using industrial aluminum powder,silicon carbide powder,and graphite as raw materials,and activated alumina powder as an additive,mixing thoroughly,pressing into cylinders and then firing at 1200℃for 30 min in a carbon embedded atmosphere by the microwave method.The effects of the aluminum powder addition(20%and 24%,by mass)and activated alumina powder addition(0,3%,5%and 7%,by mass)on the microwave synthesis of Al_(4)SiC_(4) as well as the effect of the obtained Al_(4)SiC_(4) containing material on the properties of magnesia carbon bricks were studied.The results show that:compared with the samples with 20%aluminum powder,those with 24%aluminum powder generate more Al_(4)SiC_(4).With the activated alumina powder addition increasing from 0 to 7%,the amount of Al_(4)SiC_(4) generated increases first and then decreases.Compared with the sample without activated alumina powder,the samples with activated alumina powder show lower bulk density and higher apparent porosity.With the activated alumina powder addition increasing from 3%to 7%,the bulk density of the samples increases first and then decreases,while the apparent porosity of the samples shows an opposite trend.The optimal additions are 24%aluminum powder and 5%activated alumina powder,and Al_(4)SiC_(4) synthesized in this sample has a hexagonal plate structure.With the synthesized Al_(4)SiC_(4) containing material added,the magnesia carbon brick has slightly increased cold modulus of rupture,basically the same modulus of elasticity and improved oxidation resistance.
基金the research project funded by the Office of Naval Research(Grant N3885NVONR).
文摘Though silanization of aluminum powder is currently used to improve its flow properties,for use as an alternative fuel source,there are a wide range of experimental parameters for the process and not all of them have been thoroughly explored.Until this is complete,it is unknown if the process is optimized in terms of time,efficiency,and effect.Herein,we report on a study into the effects of changes in humidity,degree of agitation,reaction temperature,and curing time upon the deposition of phenyl triethoxysilane into 20μm(d50)aluminum particles.We confirm the deposition of the coating via diffuse reflectance infrared spectroscopy and x-ray photoelectron spectroscopy.We then characterize the coated particles using apparent density measurements and Carney flow methods.Using analysis of variance,we find that,of the parameters explored,only changes in cure time and reaction temperature provide meaningful changes to the apparent density,while none of our parameters produced statistically significant changes in Carney flow values.Thus,we conclude that,when optimizing silanization of aluminum particles,environmental control of humidity is unneeded and that the reaction can be run with minimal agitation.The ability to largely ignore these parameters is a benefit to large-scale processing.
基金National Natural Science Foundation of China(Nos.52101051,52130405,51872241,52101142)Key Research Plan of Shaanxi Province,China(No.2020ZDLGY13-03)+1 种基金Key Research and Development Program of Shaanxi Province,China(No.2023-YBGY-439)Fundamental Research Funds for the Central Universities,China(No.5000210653)。
文摘Low-intensity ultrasound was applied to the pressureless consolidation of AlSi10Mg powders in a broad temperature range from 600 to 860℃.Under static conditions,the consolidation of AlSi10Mg powders can only be achieved at 860℃,but still with the presence of some residual unconsolidated regions.The introduction of low-intensity ultrasound at this temperature eliminates the unconsolidated regions and transforms the columnar grains observed in original directional solidification into equiaxed or globular grains.Remarkably,the application of low-intensity ultrasound significantly reduces the consolidation temperature to 620℃,without compromising the microhardness of the resulting samples when compared to static conditions.Furthermore,by lowering the temperature to 600℃,a well-sintered porous material is obtained through the assistance of the low-intensity ultrasound.
基金supported by Natural Science Foundation (Grant No.21975024)Natural Science Foundation of Inner Mongolia Autonomous Region (Grant No.2021BS05014)。
文摘Coating modification is an important way to enhance the reactivity of aluminum powder.In this paper,ammonium perchlorate and aluminum powder were assembled into energetic microunits by liquid deposition method.Spherical particles with AP as shell and ultrafine aluminum powder as the core(Al@AP)were gained.The micromorphology results show that the coated particles are about 5μm,and the coating layer is evenly distributed on the outer surface of aluminum powder,indicating a complete coating.The energetic microunits were implanted into the nitrate ester plasticizing adhesive system(NEPE)as solid phase fillers.The effect of filler on the rheological properties,safety,mechanical properties,thermal reaction and energy properties of the system was analyzed by comparing with the raw aluminum filler.The test results show that the rheological properties,mechanical properties and pressure index of NEPE containing system Al@AP meets the requirements of solid propellant charging.Compared with Al based propellant,the mechanical sensitivity and thermal sensitivity are decreased,the safety is better,and the explosion heat of the propellant is increased by 7.8%.The engine test shows that the specific impulse is increased by 1.2 s.Al@AP can improve the energy output and safety of NEPE propellant,and has potential application prospects in high-energy propellants.
文摘Baded on the study of nickel electroplating technology at room temperature, the plated sheet containing rapidly solidified Al-Fe-Cu- V-Si-Ni-Ce-Zr aluminum alloy powders is constructed successfully. The powders and nickel matrix are combined well in the sheet. It can be used to prepare the observation specimen for TEM and determine the hardness of single powder particle as solidified and after heat-treated. The advantages of this method are the realization of heat treatment of powders and the TEM observation of non-interfered microstructure of powders in the size of several microns.
文摘A new technique, powder compact foaming process for the production of aluminumfoams has been studied in this article. According to this method, the aluminum pow-der is mixed with a powder foaming agent (TiH_2). Subsequent to mixing, the powderblend is hot compacted to obtain a dense semi--finished product. Upon heating to tem-peratures within the range of the melting point, the foaming agent decomposes to evolvegas and the semi--finished product expands into a porous cellular aluminum. Foamingprocess is the key in this method. Based on experiments, the foaming characteris-tics were mainly analyzed and discussed. Experiments show that the aluminum--foamwith closed pores and a uniform cell structure of high porosity can be obtained usingthis method by adjusting the foaming parameters: the content of foaming agent andfoaming temperature.
基金supported by the National Basic Research Program of China(973 Program)(No.2012CB619606)
文摘AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challenge. In this article, a flexile powder metallurgy processing was used to produce a fully dense AI-4.0Cu （wt%） alloy composite reinforced with 65 vol.% Si particles. In this composite, Si particles were homogenously distributed, and the particle size was refined to the range of 3-15 μm. Tensile and flexural strength of the composite were 282 and 455 MPa, respectively, about 100% and 50% higher than the best properties reported in literature. The measured fracture toughness of the composite was 4.90 MPa m1/2. The improved strength of 65%Si/AI was attributed to the optimized particle characteristics and matrix properties. This investigation is expected to provide a primary understanding of the mechanical behaviors of Si/AI composites, and also promote the structural applications of this low-thermal-expansion material.
文摘Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray ...
文摘In this paper, Al/Ni/TiC powders were mixed on the surface of A380 aluminum alloy, by selecting appropriate laser parameters;the cladding layer with good adhesion to the substrate was obtained. The microstructure and properties of the cladding layer under different laser parameters were analyzed. The results show that: the phase composition of the cladding layer is mainly composed of TiC, Al, Ni, C and Ti phases. The hardness of the cladding region is up to 173.3 HV, which is about 2.9 times the matrix (–59.1 HV). The corrosion voltage (–1.8 V) of the cladding layer shifted significantly from the corrosion potential (–1.18 V), the corrosion current density increased, the resistance value decreased and the diameter of the capacitor arc decreased;all these phenomena indicate that the corrosion resistance of the cladding layer is decreased.
文摘By nickel electroplating at room temperature, the specimen preparation of ultra sonic gas atomized aluminum alloy powders for observation in transmission electron microscope was carried out. The advantages of this technique are simple technologically and convenient practically. The nickel and the powders combine well in the plated sheet which can be thinned by ion milling. The powders in the thinned sheet possess large thinned area and can be examined in common TEM for the studies of their microstructure.
基金supported by the Major State Basic Research and Development Program of China (No.2006CB605207the MOE Program for Cheung Kong Scholars and Innovative Research Teams in Universities of China (No.I2P407)
文摘High-velocity compaction （HVC） provides an effective means in the field of powder metallurgy （P/M） to reduce the porosity as well as to ameliorate the mechanical properties of products. In this study, the green density of an aluminum alloy is found to be 2.783 g cm 3. The ejection force for the aluminum alloy is in the range of 23 to 80 kN and the spring back is found to be less than 0.40%. The hardness of the green body is in the range of HRB 30 to 70. The bending strength of the green body is in the range of 6 to 26 MPa, which are higher than that of other aluminum alloys prepared by the traditional compaction method.
文摘The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.
