Laser powder bed fusion(L-PBF) has attracted significant attention in both the industry and academic fields since its inception, providing unprecedented advantages to fabricate complex-shaped metallic components. The ...Laser powder bed fusion(L-PBF) has attracted significant attention in both the industry and academic fields since its inception, providing unprecedented advantages to fabricate complex-shaped metallic components. The printing quality and performance of L-PBF alloys are infuenced by numerous variables consisting of feedstock powders, manufacturing process,and post-treatment. As the starting materials, metallic powders play a critical role in infuencing the fabrication cost, printing consistency, and properties. Given their deterministic roles, the present review aims to retrospect the recent progress on metallic powders for L-PBF including characterization, preparation, and reuse. The powder characterization mainly serves for printing consistency while powder preparation and reuse are introduced to reduce the fabrication costs.Various powder characterization and preparation methods are presented in the beginning by analyzing the measurement principles, advantages, and limitations. Subsequently, the effect of powder reuse on the powder characteristics and mechanical performance of L-PBF parts is analyzed, focusing on steels, nickel-based superalloys, titanium and titanium alloys, and aluminum alloys. The evolution trends of powders and L-PBF parts vary depending on specific alloy systems, which makes the proposal of a unified reuse protocol infeasible. Finally,perspectives are presented to cater to the increased applications of L-PBF technologies for future investigations. The present state-of-the-art work can pave the way for the broad industrial applications of L-PBF by enhancing printing consistency and reducing the total costs from the perspective of powders.展开更多
In this study,the effects of reaction parameters on the deep-reduction and carbonization process of WO_(2)-Co to WC-Co were studied.The results indicate that the oxygen loss rate of WO_(2) is positively correlated wit...In this study,the effects of reaction parameters on the deep-reduction and carbonization process of WO_(2)-Co to WC-Co were studied.The results indicate that the oxygen loss rate of WO_(2) is positively correlated with temperature and methane partial pressure.The partial pressure of methane has no significant effect on the formation rate of WC.The carbon content and particle size of the product increase with the increase of CH_(4) partial pressure.By synergistically regulating the reaction temperature to 950℃,the CH_(4) partial pressure to 1.25%,and the reaction time to 60 min,ultrafine WC-Co powder without h phase can be obtained.The particle size of the composite powder is 128 nm,with total carbon content of 6.16%,free carbon content of 0.4%,and residual oxygen content of 0.05%,respectively.The growth rate relationship of tungsten carbide is as follows:δ(t)=1.21×10^(-13)exp(-12809.72/T)√t.展开更多
Boron has high mass and volume calorific values,but it is difficult to ignite and has low combustion efficiency.This literature review summarizes the strategies that are used to solve the above-mentioned problems,whic...Boron has high mass and volume calorific values,but it is difficult to ignite and has low combustion efficiency.This literature review summarizes the strategies that are used to solve the above-mentioned problems,which include coatings of boron by using fluoride compounds,energetic composites,metal fuels,and metal oxides.Coating techniques include recrystallization,dual-solvent,phase transfer,electrospinning,etc.As one of the effective coating agents,the fluorine compounds can react with the oxide shell of boron powder.In comparison,the energetic composites can effectively improve the flame temperature of boron powder and enhance the evaporation efficiency of oxide film as a condensed product.Metals and metal oxides would react with boron powder to form metal borides with a lower ignition point,which could reduce its ignition temperature.展开更多
The fractured surrounding rocks of roadways pose major challenges to safe mining.Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks.The aim of ...The fractured surrounding rocks of roadways pose major challenges to safe mining.Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks.The aim of this study is to develop highly efficient composite ultrafine cement(CUC)grouts to reinforce the roadway in fractured surrounding rocks.The materials used are ultrafine cement(UC),ultrafine fly ash(UF),ultrafine slag(US),and additives(superplasticizer[SUP],aluminate ultrafine expansion agent[AUA],gypsum,and retarder).The fluidity,bleeding,shrinkage,setting time,chemical composition,microstructure,degree of hydration,and mechanical property of grouting materials were evaluated in this study.Also,a suitable and effective CUC grout mixture was used to reinforce the roadway in the fractured surrounding rock.The results have shown that the addition of UF and US reduces the plastic viscosity of CUC,and the best fluidity can be obtained by adding 40%UF and 10%US.Since UC and UF particles are small,the pozzolanic effect of UF promotes the hydration reaction,which is conductive to the stability of CUC grouts.In addition,fine particles of UC,UF,and US can effectively fill the pores,while the volumetric expansion of AUA and gypsum decreases the pores and thus affects the microstructure of the solidified grout.The compressive test results have shown that the addition of specific amounts of UF and US can ameliorate the mechanical properties of CUC grouts.Finally,the CUC22‐8 grout was used to reinforce the No.20322 belt roadway.The results of numerical simulation and field monitoring have indicated that grouting can efficaciously reinforce the surrounding rock of the roadway.In this research,high‐performance CUC grouts were developed for surrounding rock reinforcement of underground engineering by utilizing UC and some additives.展开更多
The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.O...The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.展开更多
High purity and ultrafine DAAF(u-DAAF)is an emerging insensitive charge in initiators.Although there are many ways to obtain u-DAAF,developing a preparation method with stable operation,accurate control,good quality c...High purity and ultrafine DAAF(u-DAAF)is an emerging insensitive charge in initiators.Although there are many ways to obtain u-DAAF,developing a preparation method with stable operation,accurate control,good quality consistency,equipment miniaturization,and minimum manpower is an inevitable requirement to adapt to the current social technology development trend.Here reported is the microfluidic preparation of u-DAAF with tunable particle size by a passive swirling microreactor.Under the guidance of recrystallization growth kinetics and mixing behavior of fluids in the swirling microreactor,the key parameters(liquid flow rate,explosive concentration and crystallization temperature)were screened and optimized through screening experiments.Under the condition that no surfactant is added and only experimental parameters are controlled,the particle size of recrystallized DAAF can be adjusted from 98 nm to 785 nm,and the corresponding specific surface area is 8.45 m^(2)·g^(-1)to 1.33 m^(2)·g^(-1).In addition,the preparation method has good batch stability,high yield(90.8%-92.6%)and high purity(99.0%-99.4%),indicating a high practical application potential.Electric explosion derived flyer initiation tests demonstrate that the u-DAAF shows an initiation sensitivity much lower than that of the raw DAAF,and comparable to that of the refined DAAF by conventional spraying crystallization method.This study provides an efficient method to fabricate u-DAAF with narrow particle size distribution and high reproducibility as well as a theoretical reference for fabrication of other ultrafine explosives.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
Improving the application of nanomaterials has always been a research hotspot in the field of energetic materials(EMs)due to their obvious catalytic effect on the EMs,especially the uniformly dispersed nanomaterials.H...Improving the application of nanomaterials has always been a research hotspot in the field of energetic materials(EMs)due to their obvious catalytic effect on the EMs,especially the uniformly dispersed nanomaterials.However,few studies have reported the dispersion of nanomaterials.In this study,the dispersity and mixing uniformity of nano-CuCr_(2)O_(4)was evaluated based on the difference of solid UV light absorption between the nano-catalytic materials and EMs.The nano-CuCr_(2)O_(4)/ultrafine AP composites with different dispersity of nano-CuCr_(2)O_(4)were prepared by manual grinding and mechanical grinding with different grinding strength and griding time.And then,the absorbance of different samples at 212 nm was obtained by solid UV testing due to the high repeatability of the absorbance at 210-214 nm for three parallel experiments,and the dispersity of different samples was calculated through the established difference equation.Furthermore,the samples were characterized by XRD,IR,SEM,EDS,DSC and TG-MS,which confirmed that different mixing methods did not change the structure of the samples(XRD and IR),and the mixing uniformity improved with the increase of grinding strength and grinding time(SEM and EDS).The scientificity and feasibility of the difference equation were further verified by DSC.The dispersity of nano-CuCr_(2)O_(4)exhibits a positive intrinsic relationship with its catalytic performance,and the uniformly dispersed nano-CuCr_(2)O_(4)significantly reduces the thermal decomposition temperature of ultrafine AP from 367.7 to 338.8℃.The TG-MS patterns show that the dispersed nano-CuCr_(2)O_(4)advanced the thermal decomposition process of ultrafine AP by about 700 s,especially in the high temperature decomposition stage,and the more concentrated energy release characteristic is beneficial to further enhance the energy performance of AP-based propellants.The above conclusions show that the evaluation method of dispersity based on solid UV curves could provide new ideas for the dispersity characterization of nano-catalytic materials in EMs,which is expected to be widely used in the field of EMs.展开更多
A novel CVD process for the preparation of ultrafine rhenium powders was investigated using ammonium perrhenate as starting materials. In the process, volatile rhenium oxides, such as ReO4 and Re2O7, were vaporized un...A novel CVD process for the preparation of ultrafine rhenium powders was investigated using ammonium perrhenate as starting materials. In the process, volatile rhenium oxides, such as ReO4 and Re2O7, were vaporized under a controlled oxidizing atmosphere via the pyrolysis of ammonium perrhenate, and carried into reduction zone by carrier gas, and there reduced into rhenium powders by hydrogen gas. Thermodynamic calculations indicated that Re207 could be prevented from further decomposition through controlling the oxygen partial pressure higher than 10 1.248 Pa in the pyrolysis of ammonium perrhenate. This result was further validated via DSC-TGA analysis of ammonium perrhenate. The typical rhenium powders prepared by the CVD method proposed show irregular polyhedron morphology with particle size in the range of 100-800 nm and a Ds0 of 308 nm. The specific surface area and oxygen content were measured to be 4.37 m^2/g and 0.45%, respectively.展开更多
The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymeri...The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization of YBa2Cu3O7-x in the Sol-Gel synthetic reaction has bee studied. The particle size ,pruity, sintering activity and superconducting properties of YBa2Cu3O7-x prepared by Sol-Gel method are better than by solid state reaction.展开更多
The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders...The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders were investigated.It is found that Arabic gum can better adsorb on silver particles via chemical adsorption,and it shows the best dispersive effect among all the selected dispersants.The particle size of silver powders can be finely tuned from 0.34 to 4.09μm by adjusting pH values,while the morphology of silver powders can be tuned by changing the temperature.The silver powders with high tap density higher than 4.0 g/cm3 were successfully prepared in a wide temperature range of 21.8-70°C.Especially,the tap density is higher than 5.0 g/cm3 when the temperature is optimized to be 50°C.The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste.展开更多
The Williamson-Hall and uniaxial compression methods were used to study the variations of the micro-strain and stress-strain relations in WC powders after jet milling and ball milling, respectively. The rupture behavi...The Williamson-Hall and uniaxial compression methods were used to study the variations of the micro-strain and stress-strain relations in WC powders after jet milling and ball milling, respectively. The rupture behavior of agglomerates in WC powders was investigated. Meanwhile, the as-obtained WC powders treated by different milling methods were used to fabricate WC-10%Co cemented carbides, followed by the performance assessment of cemented carbides. The results show that the micro-strain of the jet-milled WC powders decreases significantly compared with that of the ball-milled WC powders, and that the cemented carbides prepared by jet-milled WC powders exhibit excellent properties with a transverse-rupture strength of 4260 MPa, due to the elimination of agglomerates and the reduction of lattice strain.展开更多
The hexagonal BaGd x Fe 12- x O 19 ( x =0.1～1.0) nano sized powders with M type structure were synthesized by the sol gel auto combustion high temperature synthesis method. The effects of pH of...The hexagonal BaGd x Fe 12- x O 19 ( x =0.1～1.0) nano sized powders with M type structure were synthesized by the sol gel auto combustion high temperature synthesis method. The effects of pH of the solution, the molar ratio of nitrate/citric acid and the calcination temperature on the synthesis of the ferrites were investigated. The crystal structure, grain size, shape and magnetic properties were studied by means of XRD, TEM and vibrating sample magnetometer.The results show that under the conditions of pH 7.0 or so, mole ratio of citrate/nitrate (1～3) and calcination temperature of 850 ℃ for 1 h, M type BaGd x Fe 12- x O 19 ultrafine powders with a particle size of less than 100 nm can be obtained, and the coercive force reaches 430 kA·m -1 at x =1.0, which is far greater than that of barium ferrite (BaFe 12 O 19 ).展开更多
The continuously dynamic-controlled combustion synthesis （CDCCS） was developed based on the continuous fluidization and combustion synthesis technologies. CoC2O4·2H2O powders were transformed to Co3O4 in a gas-...The continuously dynamic-controlled combustion synthesis （CDCCS） was developed based on the continuous fluidization and combustion synthesis technologies. CoC2O4·2H2O powders were transformed to Co3O4 in a gas-solid fluid bed unit designed and build independently, where the reactant of CoC2O4·2H2O powders and the reactant of air were poured and introduced from the top and the bottom of the bed at a certain rates respectively. The reagents met in the bed and ignited at a given low temperature, resulting in formation of Co3O4. The results show a significant difference in combustion wave models. In the case of CDCCS, there was an immobile combustion wave, floating in the combustion zone located in the middle of the bed, instead of propagating of the combustion wave. The temperature of the combustion wave can be controlled by adjusting the flow rate of carrier gas. The resultant Co3O4 powders （diameter size ≤0.8 μm） have a narrow particle size distribution and spherical or quasi-spherical shape. This novel technique has many advantages, such as continuation, efficiency, energy conservation and environmental friendly and has been used in mass production.展开更多
An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has be...An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.展开更多
A simple and rapid process for synthesizing lead zirconate titanate,Pb（Zr0.52Ti0.48）O3（PZT）,ferroclectric powders was developed.This process,combining the sol-gel and combustion process.offers several advantages o...A simple and rapid process for synthesizing lead zirconate titanate,Pb（Zr0.52Ti0.48）O3（PZT）,ferroclectric powders was developed.This process,combining the sol-gel and combustion process.offers several advantages over conventional methods.including rapid solution synthesis,use of commercially available materials lower synthesis temperature and ease of obtaining ultrafine powders.The precursor solution for synthesizing powders was prepared from lead nitrate.zireonium nitrate.titanium oxynitrate,citric acid and deionized water.The precarsor was investigated by DSC-TG,and the PZT powders were investigated by powder-XRD,IR spectra and TEM.XRD analysis shous that the powders possess a single phase perovskite type structure,no pyrochlore phase exists.and TEM image shows that the grain size of the powders is about 40nm.展开更多
Using 9200 laser particle size analyzer and KYKY-2800 scanning electron microscope, particle sizes and cellular morphology of Radix Astragalus and Radix Isatidis ultrafine powders were observed. According to the resu...Using 9200 laser particle size analyzer and KYKY-2800 scanning electron microscope, particle sizes and cellular morphology of Radix Astragalus and Radix Isatidis ultrafine powders were observed. According to the results, the particle size of 89. 1 % of Radix Astragalus ultrafine powders ranged from 1.729 [xm to 44.938 ｜xm, Z ）50 =4.368 ｜xm; the particle size of 93.411% of Radix Isatidis ultrafine powders ranged from 1.510 [xm to 44.938 ｜xm, Z ）50 = 8 .7 2 6 [xm. Radix As-tragalus and Radix Isatidis ultrafine powders were pulverized completely without intact cellular morphology. The antibacterial activity of Radix Astragalus and Radix Isatidis ultrafine powders against chicken-derived E. coli （078） was investigated. The results indicated that Radix Astragalus and Radix Isatidis ultrafine powders exhibited higher antibacterial activity against chicken-derived E. coli （078 ） compared with the corresponding coarse powders. This study laid a solid foundation for the development and application of Chinese medicine ultrafine powder preparations.展开更多
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. AE89991/403)National Natural Science Foundation of China (Grant No. 52005262)+1 种基金Natural Science Foundation of Jiangsu Province (BK20202007)National Key Research and Development Program of China (2022YFB4600800)。
文摘Laser powder bed fusion(L-PBF) has attracted significant attention in both the industry and academic fields since its inception, providing unprecedented advantages to fabricate complex-shaped metallic components. The printing quality and performance of L-PBF alloys are infuenced by numerous variables consisting of feedstock powders, manufacturing process,and post-treatment. As the starting materials, metallic powders play a critical role in infuencing the fabrication cost, printing consistency, and properties. Given their deterministic roles, the present review aims to retrospect the recent progress on metallic powders for L-PBF including characterization, preparation, and reuse. The powder characterization mainly serves for printing consistency while powder preparation and reuse are introduced to reduce the fabrication costs.Various powder characterization and preparation methods are presented in the beginning by analyzing the measurement principles, advantages, and limitations. Subsequently, the effect of powder reuse on the powder characteristics and mechanical performance of L-PBF parts is analyzed, focusing on steels, nickel-based superalloys, titanium and titanium alloys, and aluminum alloys. The evolution trends of powders and L-PBF parts vary depending on specific alloy systems, which makes the proposal of a unified reuse protocol infeasible. Finally,perspectives are presented to cater to the increased applications of L-PBF technologies for future investigations. The present state-of-the-art work can pave the way for the broad industrial applications of L-PBF by enhancing printing consistency and reducing the total costs from the perspective of powders.
基金financial support from the National Natural Science Foundation of China(22078326,21878305).
文摘In this study,the effects of reaction parameters on the deep-reduction and carbonization process of WO_(2)-Co to WC-Co were studied.The results indicate that the oxygen loss rate of WO_(2) is positively correlated with temperature and methane partial pressure.The partial pressure of methane has no significant effect on the formation rate of WC.The carbon content and particle size of the product increase with the increase of CH_(4) partial pressure.By synergistically regulating the reaction temperature to 950℃,the CH_(4) partial pressure to 1.25%,and the reaction time to 60 min,ultrafine WC-Co powder without h phase can be obtained.The particle size of the composite powder is 128 nm,with total carbon content of 6.16%,free carbon content of 0.4%,and residual oxygen content of 0.05%,respectively.The growth rate relationship of tungsten carbide is as follows:δ(t)=1.21×10^(-13)exp(-12809.72/T)√t.
基金funded by Shaanxi Provincial Key Research and Development Program of China(Grant No.2021ZDLGY11)partially supported by NSAF Project of China(Grant No.U2030202)。
文摘Boron has high mass and volume calorific values,but it is difficult to ignite and has low combustion efficiency.This literature review summarizes the strategies that are used to solve the above-mentioned problems,which include coatings of boron by using fluoride compounds,energetic composites,metal fuels,and metal oxides.Coating techniques include recrystallization,dual-solvent,phase transfer,electrospinning,etc.As one of the effective coating agents,the fluorine compounds can react with the oxide shell of boron powder.In comparison,the energetic composites can effectively improve the flame temperature of boron powder and enhance the evaporation efficiency of oxide film as a condensed product.Metals and metal oxides would react with boron powder to form metal borides with a lower ignition point,which could reduce its ignition temperature.
基金supported by the National Natural Science Foundation of China(NSFC)(grant No.52074169,No.51704280)the China Postdoctoral Science Foundation(No.2023M732109)the Opening Foundation of Shandong Key Laboratory of Civil Engineering Disaster Prevention and Mitigation(No.CDPM2021FK02).
文摘The fractured surrounding rocks of roadways pose major challenges to safe mining.Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks.The aim of this study is to develop highly efficient composite ultrafine cement(CUC)grouts to reinforce the roadway in fractured surrounding rocks.The materials used are ultrafine cement(UC),ultrafine fly ash(UF),ultrafine slag(US),and additives(superplasticizer[SUP],aluminate ultrafine expansion agent[AUA],gypsum,and retarder).The fluidity,bleeding,shrinkage,setting time,chemical composition,microstructure,degree of hydration,and mechanical property of grouting materials were evaluated in this study.Also,a suitable and effective CUC grout mixture was used to reinforce the roadway in the fractured surrounding rock.The results have shown that the addition of UF and US reduces the plastic viscosity of CUC,and the best fluidity can be obtained by adding 40%UF and 10%US.Since UC and UF particles are small,the pozzolanic effect of UF promotes the hydration reaction,which is conductive to the stability of CUC grouts.In addition,fine particles of UC,UF,and US can effectively fill the pores,while the volumetric expansion of AUA and gypsum decreases the pores and thus affects the microstructure of the solidified grout.The compressive test results have shown that the addition of specific amounts of UF and US can ameliorate the mechanical properties of CUC grouts.Finally,the CUC22‐8 grout was used to reinforce the No.20322 belt roadway.The results of numerical simulation and field monitoring have indicated that grouting can efficaciously reinforce the surrounding rock of the roadway.In this research,high‐performance CUC grouts were developed for surrounding rock reinforcement of underground engineering by utilizing UC and some additives.
基金Funded by the Technology Innovation Leading Program of Shaanxi(No.2022QFY08-02)。
文摘The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.
基金the National Natural Science Foundation of China (Grant No.22105184)Research Fund of SWUST for PhD (Grant No.22zx7175)+1 种基金Sichuan Science and Technology Program (Grant No.2019ZDZX0013)Institute of Chemical Materials Program (Grant No.SXK-2022-03)for financial support。
文摘High purity and ultrafine DAAF(u-DAAF)is an emerging insensitive charge in initiators.Although there are many ways to obtain u-DAAF,developing a preparation method with stable operation,accurate control,good quality consistency,equipment miniaturization,and minimum manpower is an inevitable requirement to adapt to the current social technology development trend.Here reported is the microfluidic preparation of u-DAAF with tunable particle size by a passive swirling microreactor.Under the guidance of recrystallization growth kinetics and mixing behavior of fluids in the swirling microreactor,the key parameters(liquid flow rate,explosive concentration and crystallization temperature)were screened and optimized through screening experiments.Under the condition that no surfactant is added and only experimental parameters are controlled,the particle size of recrystallized DAAF can be adjusted from 98 nm to 785 nm,and the corresponding specific surface area is 8.45 m^(2)·g^(-1)to 1.33 m^(2)·g^(-1).In addition,the preparation method has good batch stability,high yield(90.8%-92.6%)and high purity(99.0%-99.4%),indicating a high practical application potential.Electric explosion derived flyer initiation tests demonstrate that the u-DAAF shows an initiation sensitivity much lower than that of the raw DAAF,and comparable to that of the refined DAAF by conventional spraying crystallization method.This study provides an efficient method to fabricate u-DAAF with narrow particle size distribution and high reproducibility as well as a theoretical reference for fabrication of other ultrafine explosives.
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.
基金the National Natural Science Foundation of China(Project Nos.21805139,21905023,12102194,22005144 and 22005145)the Joint Funds of the National Natural Science Foundation of China(Grant No.U2141202)+2 种基金Natural Science Foundation of Jiangsu Province(Grant No.BK20200471)the Fundamental Research Funds for the Central Universities(Grant Nos.30920041106,30921011203)Young Elite Scientists Sponsorship Program by CAST(Program,2021QNRC001).
文摘Improving the application of nanomaterials has always been a research hotspot in the field of energetic materials(EMs)due to their obvious catalytic effect on the EMs,especially the uniformly dispersed nanomaterials.However,few studies have reported the dispersion of nanomaterials.In this study,the dispersity and mixing uniformity of nano-CuCr_(2)O_(4)was evaluated based on the difference of solid UV light absorption between the nano-catalytic materials and EMs.The nano-CuCr_(2)O_(4)/ultrafine AP composites with different dispersity of nano-CuCr_(2)O_(4)were prepared by manual grinding and mechanical grinding with different grinding strength and griding time.And then,the absorbance of different samples at 212 nm was obtained by solid UV testing due to the high repeatability of the absorbance at 210-214 nm for three parallel experiments,and the dispersity of different samples was calculated through the established difference equation.Furthermore,the samples were characterized by XRD,IR,SEM,EDS,DSC and TG-MS,which confirmed that different mixing methods did not change the structure of the samples(XRD and IR),and the mixing uniformity improved with the increase of grinding strength and grinding time(SEM and EDS).The scientificity and feasibility of the difference equation were further verified by DSC.The dispersity of nano-CuCr_(2)O_(4)exhibits a positive intrinsic relationship with its catalytic performance,and the uniformly dispersed nano-CuCr_(2)O_(4)significantly reduces the thermal decomposition temperature of ultrafine AP from 367.7 to 338.8℃.The TG-MS patterns show that the dispersed nano-CuCr_(2)O_(4)advanced the thermal decomposition process of ultrafine AP by about 700 s,especially in the high temperature decomposition stage,and the more concentrated energy release characteristic is beneficial to further enhance the energy performance of AP-based propellants.The above conclusions show that the evaluation method of dispersity based on solid UV curves could provide new ideas for the dispersity characterization of nano-catalytic materials in EMs,which is expected to be widely used in the field of EMs.
文摘A novel CVD process for the preparation of ultrafine rhenium powders was investigated using ammonium perrhenate as starting materials. In the process, volatile rhenium oxides, such as ReO4 and Re2O7, were vaporized under a controlled oxidizing atmosphere via the pyrolysis of ammonium perrhenate, and carried into reduction zone by carrier gas, and there reduced into rhenium powders by hydrogen gas. Thermodynamic calculations indicated that Re207 could be prevented from further decomposition through controlling the oxygen partial pressure higher than 10 1.248 Pa in the pyrolysis of ammonium perrhenate. This result was further validated via DSC-TGA analysis of ammonium perrhenate. The typical rhenium powders prepared by the CVD method proposed show irregular polyhedron morphology with particle size in the range of 100-800 nm and a Ds0 of 308 nm. The specific surface area and oxygen content were measured to be 4.37 m^2/g and 0.45%, respectively.
文摘The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization of YBa2Cu3O7-x in the Sol-Gel synthetic reaction has bee studied. The particle size ,pruity, sintering activity and superconducting properties of YBa2Cu3O7-x prepared by Sol-Gel method are better than by solid state reaction.
基金Project(2014DFA90520)supported by the International Cooperation Program of Ministry of Science and Technology of ChinaProject(2013A090100003)supported by the Production,Teaching and Research Program of Guangdong Province,ChinaProject(2013DY048)supported by the Science and Technology Cooperation Program of Daye Nonferrous Metals Group,China
文摘The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders were investigated.It is found that Arabic gum can better adsorb on silver particles via chemical adsorption,and it shows the best dispersive effect among all the selected dispersants.The particle size of silver powders can be finely tuned from 0.34 to 4.09μm by adjusting pH values,while the morphology of silver powders can be tuned by changing the temperature.The silver powders with high tap density higher than 4.0 g/cm3 were successfully prepared in a wide temperature range of 21.8-70°C.Especially,the tap density is higher than 5.0 g/cm3 when the temperature is optimized to be 50°C.The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste.
基金Project(2016GZ0290) supported by the Key Technology R&D Program of Sichuan Province,ChinaProject(2019CDXYCL0031) supported by the Fundamental Research Funds for the Central Universities,China
文摘The Williamson-Hall and uniaxial compression methods were used to study the variations of the micro-strain and stress-strain relations in WC powders after jet milling and ball milling, respectively. The rupture behavior of agglomerates in WC powders was investigated. Meanwhile, the as-obtained WC powders treated by different milling methods were used to fabricate WC-10%Co cemented carbides, followed by the performance assessment of cemented carbides. The results show that the micro-strain of the jet-milled WC powders decreases significantly compared with that of the ball-milled WC powders, and that the cemented carbides prepared by jet-milled WC powders exhibit excellent properties with a transverse-rupture strength of 4260 MPa, due to the elimination of agglomerates and the reduction of lattice strain.
文摘The hexagonal BaGd x Fe 12- x O 19 ( x =0.1～1.0) nano sized powders with M type structure were synthesized by the sol gel auto combustion high temperature synthesis method. The effects of pH of the solution, the molar ratio of nitrate/citric acid and the calcination temperature on the synthesis of the ferrites were investigated. The crystal structure, grain size, shape and magnetic properties were studied by means of XRD, TEM and vibrating sample magnetometer.The results show that under the conditions of pH 7.0 or so, mole ratio of citrate/nitrate (1～3) and calcination temperature of 850 ℃ for 1 h, M type BaGd x Fe 12- x O 19 ultrafine powders with a particle size of less than 100 nm can be obtained, and the coercive force reaches 430 kA·m -1 at x =1.0, which is far greater than that of barium ferrite (BaFe 12 O 19 ).
基金Project (2007BAE05B01) supported by the National Key Technologies R & D Program of China
文摘The continuously dynamic-controlled combustion synthesis （CDCCS） was developed based on the continuous fluidization and combustion synthesis technologies. CoC2O4·2H2O powders were transformed to Co3O4 in a gas-solid fluid bed unit designed and build independently, where the reactant of CoC2O4·2H2O powders and the reactant of air were poured and introduced from the top and the bottom of the bed at a certain rates respectively. The reagents met in the bed and ignited at a given low temperature, resulting in formation of Co3O4. The results show a significant difference in combustion wave models. In the case of CDCCS, there was an immobile combustion wave, floating in the combustion zone located in the middle of the bed, instead of propagating of the combustion wave. The temperature of the combustion wave can be controlled by adjusting the flow rate of carrier gas. The resultant Co3O4 powders （diameter size ≤0.8 μm） have a narrow particle size distribution and spherical or quasi-spherical shape. This novel technique has many advantages, such as continuation, efficiency, energy conservation and environmental friendly and has been used in mass production.
文摘An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.
文摘A simple and rapid process for synthesizing lead zirconate titanate,Pb（Zr0.52Ti0.48）O3（PZT）,ferroclectric powders was developed.This process,combining the sol-gel and combustion process.offers several advantages over conventional methods.including rapid solution synthesis,use of commercially available materials lower synthesis temperature and ease of obtaining ultrafine powders.The precursor solution for synthesizing powders was prepared from lead nitrate.zireonium nitrate.titanium oxynitrate,citric acid and deionized water.The precarsor was investigated by DSC-TG,and the PZT powders were investigated by powder-XRD,IR spectra and TEM.XRD analysis shous that the powders possess a single phase perovskite type structure,no pyrochlore phase exists.and TEM image shows that the grain size of the powders is about 40nm.
基金Oupported by Spark Program of the Ministry of Science and Technology of China(2015GA620002)Science and Technology Support Program of Science and Technology Department of Hebei Province(12220408D,14966610D)+2 种基金Post-award Grant Program from the Department of Science and Technology of Hebei Province(15926620H)Project of Shijiazhuang Municipal Science and Technology Bureau(141200603A)Project of Chengde Municipal Science and Technology Bureau(2015N0001)
文摘Using 9200 laser particle size analyzer and KYKY-2800 scanning electron microscope, particle sizes and cellular morphology of Radix Astragalus and Radix Isatidis ultrafine powders were observed. According to the results, the particle size of 89. 1 % of Radix Astragalus ultrafine powders ranged from 1.729 [xm to 44.938 ｜xm, Z ）50 =4.368 ｜xm; the particle size of 93.411% of Radix Isatidis ultrafine powders ranged from 1.510 [xm to 44.938 ｜xm, Z ）50 = 8 .7 2 6 [xm. Radix As-tragalus and Radix Isatidis ultrafine powders were pulverized completely without intact cellular morphology. The antibacterial activity of Radix Astragalus and Radix Isatidis ultrafine powders against chicken-derived E. coli （078） was investigated. The results indicated that Radix Astragalus and Radix Isatidis ultrafine powders exhibited higher antibacterial activity against chicken-derived E. coli （078 ） compared with the corresponding coarse powders. This study laid a solid foundation for the development and application of Chinese medicine ultrafine powder preparations.
