Pre-alloyed powder of Ti2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into fi ve kinds of powder size distribution. Fully dense Ti2AlNb alloy was prepared by powde...Pre-alloyed powder of Ti2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into fi ve kinds of powder size distribution. Fully dense Ti2AlNb alloy was prepared by powder metallurgy(PM) using hot isostatic pressing. The properties of pre-alloyed powder and PM Ti2AlNb alloy were tested. Results show that mean grain size of PM Ti2AlNb alloy is infl uenced by powder particle size, but particle size has no signifi cant infl uence on tensile properties. Finer Ti2AlNb powder has low Argon gas bubble ratio and high oxygen content, and poor fl owability of fi ner powder increases the degree of diffculty during degassing. As a result, big pores(> 50 μm) are observed in PM Ti2AlNb alloy prepared by fi ner powder and cause plasticity loss of tensile properties. In order to get a better comprehensive properties of PM Ti2AlNb alloy, powder with an average size(~ 100 μm) is suggested.展开更多
The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of...The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of grains, the one with black cores surrounded by obvious rim structures, and the other whose cores were white with unconspicuous rim structures and adhesive phase. In the cermet made from fine powders, the amount of grains with white cores was much more than that in cermet made from coarse powders. In addition, their properties were also much better.展开更多
Cu(NO3)(2) and (NH4)(6)H(2)W(12)O(40)center dot 4H(2)O were used to prepare W/Cu nanosized composite powder by sol-gel technique. The influences of heat treatment process, pH value of the solution and the amount of an...Cu(NO3)(2) and (NH4)(6)H(2)W(12)O(40)center dot 4H(2)O were used to prepare W/Cu nanosized composite powder by sol-gel technique. The influences of heat treatment process, pH value of the solution and the amount of an addition agent on particle size were investigated by DSC, XRD and TEM. The results show that, at a certain heat treatment temperature, the W/Cu nanoparticle size increases with the pH value or the amount of the addition agent increasing.展开更多
The nano-sized BaTiO3:La3+ powders were prepared by sol-gel process using butyl phthalate, barium acetate and lanthanum oxide as raw material, and these samples were tested by means of TG-DTA, XRD and SEM. The results...The nano-sized BaTiO3:La3+ powders were prepared by sol-gel process using butyl phthalate, barium acetate and lanthanum oxide as raw material, and these samples were tested by means of TG-DTA, XRD and SEM. The results indicate that with the annealing temperature and the doped concentration rising, the powders' particle sizes will increase and decrease respectively. When annealing temperature is 900℃and doped concentration is 7%, the phase is cubic without other phases, and the particle size of power is 43 .34 nm.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
Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4....Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4.5：1, total feed of 4.9 m3/h, and plasma power of 25 kW. The samples were analyzed by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, and inductively coupled plasma - mass spectrometry （ICP-MS）, inductively coupled plasma - atomic emission spectrometry （ICP-AES）, inductive combustion infrared absorption （ICIA） and infrared thermal conductivity of oxygen and nitrogen analyzer （ITCA）. The results show that the boron powders have different crystal structures with higher dispersion and purity. The average diameter is about 50 nm, and the purity is 90.29% or so. This new technology can use simple process to produce high quality boron powders, and is feasible for industrial production.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
A trajectory imaging based method for measuring the velocity and diameter of coal particles was presented.By using an industrial charge-coupled device(CCD)camera and a low power semiconductor laser,the images of coal ...A trajectory imaging based method for measuring the velocity and diameter of coal particles was presented.By using an industrial charge-coupled device(CCD)camera and a low power semiconductor laser,the images of coal particles under relatively long exposure time were recorded and then processed to yield both the velocities and sizes.Fundamental research on this method with special attention to recording parameters,e.g.,magnification factor and exposure time,was carried out.For most of the test cases,the results agree with those obtained by particle image velocimetry(PIV)and shadow imaging method.Measurements with good accuracy can be obtained when the imaging magnification factor and exposure time are set appropriately,making N be larger than 3.5,and R between 5-7,where N and R are the number of pixels occupied by the average width and the ratio of length to width of particle trajectory on the image,respectively.The work indicates the feasibility and potential application of the present measurement method for online measurement of coal powder in pipes in industrial power plants.展开更多
Effects of particle size （A：d50 = 336. 9 μm, B：d50 =123.5μm, C： d50=19.5 μm, D： dso=2.21μm） and content （1 wt% , 3 wt% , 5 wt% , 7 wt% ） of silicon powder on cold crushing strength （CCS） , pore size dis...Effects of particle size （A：d50 = 336. 9 μm, B：d50 =123.5μm, C： d50=19.5 μm, D： dso=2.21μm） and content （1 wt% , 3 wt% , 5 wt% , 7 wt% ） of silicon powder on cold crushing strength （CCS） , pore size distribution and microstructure of Al2O3 - ZrO2 - C refractories coked at high temperature had been investigated by means of mercury porosimeter, SEM, EDS, tic. The results indicated that particle size and content of silicon powder affected the cold crushing strength of coked specimens. It increased with the addition of silicon powder and its finer particle size. However, it decreased greatly when using too fine silicon powder. The particle size and content of silicon powder also impacted the phase evolution and microstructure of coked specimens, much more β-SiC whiskers constituted network structure and well distributed in specimens with reduction of their slenderness ratios when finer silicon powder was added, corresponding to that, the specimens＇ pore size distribution range became narrower with smaller pore diameter, but β-SiC whiskers were distributed sparsely and the specific pore volume of small pores increased when much finer powder was added. It was worthly mentioned that some nitride could form in specimens with addition of appropriate particle size and content of silicon powder.展开更多
The effect of particle size and distribution of rapidly quenching NdFeB magnetic powder on the magnetic properties of polymerbonded NdFeB permanent magnet was studied. The results show that the particle size and the d...The effect of particle size and distribution of rapidly quenching NdFeB magnetic powder on the magnetic properties of polymerbonded NdFeB permanent magnet was studied. The results show that the particle size and the distribution of rapidly quenching NdFeB magnetic powder have significant effects on the magnetic properties of polymerbonded NdFeB permanent magnet. As long as the size and the distribution of rapidly quenching NdFeB powder are within the right range, high magnetic properties of polymerbonded NdFeB permanent magnet can be obtained. This is mainly because the rapidly quenching NdFeB magnetic powder has high hardness and is scaleshaped. The larger the size of rapidly quenching NdFeB particles is, the more difficult it is to obtain high density of bonded NdFeB magnet. However the structure will be destroyed if the size is too small. It results in the deterioration of magnetic properties. The mechanism is also discussed.展开更多
The usage of powder metallurgy aluminium compacts in lieu of ferrous components in automotives helps to lower vehicle weight. The major drawback in the commercially available press sintered aluminium alloy is porosity...The usage of powder metallurgy aluminium compacts in lieu of ferrous components in automotives helps to lower vehicle weight. The major drawback in the commercially available press sintered aluminium alloy is porosity which is mainly dependent on the powder metallurgical process parameters such as compaction pressure, sintering temperature and cooling rate after sintering. In this paper the effect of particle size and furnace controlled cooling after sintering on porosity level and micro hardness of an elemental 6061 aluminium alloy has been investigated. Aluminium particle sizes of 20 μm and 150 μm were used. The elemental 6061 aluminium alloy powders are warm compacted at 175 MPa. After sintering for about one hour at 600°C, the aluminium compacts were furnace cooled at the rate of 1°C /min to different temperatures of 500°C, 400°C, 300°C and 200?C. When the cooling temperature after sintering inside the furnace is effected at various temperatures from 600°C to 200°C, for a precipitate hardened aluminium compacts with aluminium particle size of 20 μm, the porosity level reduced by 26% and that for aluminium particle size of 150μm, the porosity level reduced by 23%. Marked improvement in micro hardness value is also observed correspondingly.展开更多
Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100...Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100 nm, 0.4-0.6μm and 1μm in size were obtained respectively by changing the hydrothermal precursors and the pH value of hydrothermal slurry. Calcination of boehmite powders of 30-100 nm at 1250℃ for 1h resulted in the formation of single-phase α-Al2O3 , and the products consisted of vermicular particles. The boehmite powders of 0.4-0.6μm were also fully converted to α-Al2O3 at 1250℃, and the products consisted of plate-like particles with the same size of 0.4-0.6μm. The boehmite powders of 1μm calcined at 1350℃ for 2h were still composed of a little proportions of transition aluminas besides α-Al2O3, and the particles sintered severely. The reaction processes for the formation of crystalline boehmites under hydrothermal conditions and α-Al2O3 powders during calcination have been discussed.展开更多
Polypropylene composites of snail shell powder were prepared at filler contents, 0 to 40 wt%. The particle sizes of the snail shell powder investigated were 0.150, 0.30, and 0.42 μm. Talc, of particle size, 0.150 μm...Polypropylene composites of snail shell powder were prepared at filler contents, 0 to 40 wt%. The particle sizes of the snail shell powder investigated were 0.150, 0.30, and 0.42 μm. Talc, of particle size, 0.150 μm was used as the reference filler. The polypropylene composites were prepared in an injection moulding machine and the resulting composites were extruded as sheets. Some mechanical and end-use properties of the prepared composites were determined. Results showed that the snail shell powder improved the tensile modulus, flexural strength, and impact strength of polypropylene and these properties increased with increases in the filler content and decreases in the filler particle size. The elongation at break of the composites was however observed to decrease with increases in the filler content, and particle size. The elongation at break of talc filled polypropylene was zero, an indication of the brittle nature of polypropylene composites of talc. The hardness, water sorption (24-hr) and specific gravity of the composites were found to increase with increases in the filler content, and decreases in the filler particle size. The level of water absorbed by snail shell powder composites of polypropylene is considerably higher than that of talc filled polypropylene. The flame retardant properties of the prepared composites were however found to decrease with increases in the filler content, and particle size. Generally, snail shell powder was found to show greater property improvement over talc in the prepared composites.展开更多
文摘Pre-alloyed powder of Ti2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into fi ve kinds of powder size distribution. Fully dense Ti2AlNb alloy was prepared by powder metallurgy(PM) using hot isostatic pressing. The properties of pre-alloyed powder and PM Ti2AlNb alloy were tested. Results show that mean grain size of PM Ti2AlNb alloy is infl uenced by powder particle size, but particle size has no signifi cant infl uence on tensile properties. Finer Ti2AlNb powder has low Argon gas bubble ratio and high oxygen content, and poor fl owability of fi ner powder increases the degree of diffculty during degassing. As a result, big pores(> 50 μm) are observed in PM Ti2AlNb alloy prepared by fi ner powder and cause plasticity loss of tensile properties. In order to get a better comprehensive properties of PM Ti2AlNb alloy, powder with an average size(~ 100 μm) is suggested.
基金the National Natural Science Foundation of China, the Doctoral EducationFoundation of China, the State Key Laboratory of Powde
文摘The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of grains, the one with black cores surrounded by obvious rim structures, and the other whose cores were white with unconspicuous rim structures and adhesive phase. In the cermet made from fine powders, the amount of grains with white cores was much more than that in cermet made from coarse powders. In addition, their properties were also much better.
基金This Project was financially supported by the National Natural Science Foundation of China (No. 50471033).
文摘Cu(NO3)(2) and (NH4)(6)H(2)W(12)O(40)center dot 4H(2)O were used to prepare W/Cu nanosized composite powder by sol-gel technique. The influences of heat treatment process, pH value of the solution and the amount of an addition agent on particle size were investigated by DSC, XRD and TEM. The results show that, at a certain heat treatment temperature, the W/Cu nanoparticle size increases with the pH value or the amount of the addition agent increasing.
文摘The nano-sized BaTiO3:La3+ powders were prepared by sol-gel process using butyl phthalate, barium acetate and lanthanum oxide as raw material, and these samples were tested by means of TG-DTA, XRD and SEM. The results indicate that with the annealing temperature and the doped concentration rising, the powders' particle sizes will increase and decrease respectively. When annealing temperature is 900℃and doped concentration is 7%, the phase is cubic without other phases, and the particle size of power is 43 .34 nm.
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.
基金supported in part by the National Centre of Analysis and Testing for Nonferrous Metal & Electronic Material for Elementary Analysis, Beijing, China
文摘Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4.5：1, total feed of 4.9 m3/h, and plasma power of 25 kW. The samples were analyzed by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, and inductively coupled plasma - mass spectrometry （ICP-MS）, inductively coupled plasma - atomic emission spectrometry （ICP-AES）, inductive combustion infrared absorption （ICIA） and infrared thermal conductivity of oxygen and nitrogen analyzer （ITCA）. The results show that the boron powders have different crystal structures with higher dispersion and purity. The average diameter is about 50 nm, and the purity is 90.29% or so. This new technology can use simple process to produce high quality boron powders, and is feasible for industrial production.
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.
基金Project supported by the National Natural Science Foundation of China (Nos. 51176162 and 51276164)the National Basic Research Program (973) of China (No. 2009CB219802)+2 种基金the Zhejiang Provincial Science and Technology Project (No. 2012C21077)the Zhejiang Provincial Natural Science Foundation of China (No. Y1110642)the Program of Introducing Talents of Discipline to University (No. B08026),China
文摘A trajectory imaging based method for measuring the velocity and diameter of coal particles was presented.By using an industrial charge-coupled device(CCD)camera and a low power semiconductor laser,the images of coal particles under relatively long exposure time were recorded and then processed to yield both the velocities and sizes.Fundamental research on this method with special attention to recording parameters,e.g.,magnification factor and exposure time,was carried out.For most of the test cases,the results agree with those obtained by particle image velocimetry(PIV)and shadow imaging method.Measurements with good accuracy can be obtained when the imaging magnification factor and exposure time are set appropriately,making N be larger than 3.5,and R between 5-7,where N and R are the number of pixels occupied by the average width and the ratio of length to width of particle trajectory on the image,respectively.The work indicates the feasibility and potential application of the present measurement method for online measurement of coal powder in pipes in industrial power plants.
文摘Effects of particle size （A：d50 = 336. 9 μm, B：d50 =123.5μm, C： d50=19.5 μm, D： dso=2.21μm） and content （1 wt% , 3 wt% , 5 wt% , 7 wt% ） of silicon powder on cold crushing strength （CCS） , pore size distribution and microstructure of Al2O3 - ZrO2 - C refractories coked at high temperature had been investigated by means of mercury porosimeter, SEM, EDS, tic. The results indicated that particle size and content of silicon powder affected the cold crushing strength of coked specimens. It increased with the addition of silicon powder and its finer particle size. However, it decreased greatly when using too fine silicon powder. The particle size and content of silicon powder also impacted the phase evolution and microstructure of coked specimens, much more β-SiC whiskers constituted network structure and well distributed in specimens with reduction of their slenderness ratios when finer silicon powder was added, corresponding to that, the specimens＇ pore size distribution range became narrower with smaller pore diameter, but β-SiC whiskers were distributed sparsely and the specific pore volume of small pores increased when much finer powder was added. It was worthly mentioned that some nitride could form in specimens with addition of appropriate particle size and content of silicon powder.
文摘The effect of particle size and distribution of rapidly quenching NdFeB magnetic powder on the magnetic properties of polymerbonded NdFeB permanent magnet was studied. The results show that the particle size and the distribution of rapidly quenching NdFeB magnetic powder have significant effects on the magnetic properties of polymerbonded NdFeB permanent magnet. As long as the size and the distribution of rapidly quenching NdFeB powder are within the right range, high magnetic properties of polymerbonded NdFeB permanent magnet can be obtained. This is mainly because the rapidly quenching NdFeB magnetic powder has high hardness and is scaleshaped. The larger the size of rapidly quenching NdFeB particles is, the more difficult it is to obtain high density of bonded NdFeB magnet. However the structure will be destroyed if the size is too small. It results in the deterioration of magnetic properties. The mechanism is also discussed.
文摘The usage of powder metallurgy aluminium compacts in lieu of ferrous components in automotives helps to lower vehicle weight. The major drawback in the commercially available press sintered aluminium alloy is porosity which is mainly dependent on the powder metallurgical process parameters such as compaction pressure, sintering temperature and cooling rate after sintering. In this paper the effect of particle size and furnace controlled cooling after sintering on porosity level and micro hardness of an elemental 6061 aluminium alloy has been investigated. Aluminium particle sizes of 20 μm and 150 μm were used. The elemental 6061 aluminium alloy powders are warm compacted at 175 MPa. After sintering for about one hour at 600°C, the aluminium compacts were furnace cooled at the rate of 1°C /min to different temperatures of 500°C, 400°C, 300°C and 200?C. When the cooling temperature after sintering inside the furnace is effected at various temperatures from 600°C to 200°C, for a precipitate hardened aluminium compacts with aluminium particle size of 20 μm, the porosity level reduced by 26% and that for aluminium particle size of 150μm, the porosity level reduced by 23%. Marked improvement in micro hardness value is also observed correspondingly.
文摘Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100 nm, 0.4-0.6μm and 1μm in size were obtained respectively by changing the hydrothermal precursors and the pH value of hydrothermal slurry. Calcination of boehmite powders of 30-100 nm at 1250℃ for 1h resulted in the formation of single-phase α-Al2O3 , and the products consisted of vermicular particles. The boehmite powders of 0.4-0.6μm were also fully converted to α-Al2O3 at 1250℃, and the products consisted of plate-like particles with the same size of 0.4-0.6μm. The boehmite powders of 1μm calcined at 1350℃ for 2h were still composed of a little proportions of transition aluminas besides α-Al2O3, and the particles sintered severely. The reaction processes for the formation of crystalline boehmites under hydrothermal conditions and α-Al2O3 powders during calcination have been discussed.
文摘Polypropylene composites of snail shell powder were prepared at filler contents, 0 to 40 wt%. The particle sizes of the snail shell powder investigated were 0.150, 0.30, and 0.42 μm. Talc, of particle size, 0.150 μm was used as the reference filler. The polypropylene composites were prepared in an injection moulding machine and the resulting composites were extruded as sheets. Some mechanical and end-use properties of the prepared composites were determined. Results showed that the snail shell powder improved the tensile modulus, flexural strength, and impact strength of polypropylene and these properties increased with increases in the filler content and decreases in the filler particle size. The elongation at break of the composites was however observed to decrease with increases in the filler content, and particle size. The elongation at break of talc filled polypropylene was zero, an indication of the brittle nature of polypropylene composites of talc. The hardness, water sorption (24-hr) and specific gravity of the composites were found to increase with increases in the filler content, and decreases in the filler particle size. The level of water absorbed by snail shell powder composites of polypropylene is considerably higher than that of talc filled polypropylene. The flame retardant properties of the prepared composites were however found to decrease with increases in the filler content, and particle size. Generally, snail shell powder was found to show greater property improvement over talc in the prepared composites.
