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
Based on thelow temperaturecombustion synthesisof α Al2 O3 from aluminum nitrate,the effectsofthe additives on the formation and particle properties of α Al2 O3 werestudied by XRDand SEM,theinitialstudy on the manom...Based on thelow temperaturecombustion synthesisof α Al2 O3 from aluminum nitrate,the effectsofthe additives on the formation and particle properties of α Al2 O3 werestudied by XRDand SEM,theinitialstudy on the manometer α Al2 O3 synthesisby LCSwas done, α Al2 O3 withtheparticlesize50 ～80 NM wasgot under properconditions.展开更多
The self-propagating combustion reaction（SPCR）method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as fuel.Thermal decomposition behavior of dried gels,phase identification and c...The self-propagating combustion reaction（SPCR）method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as fuel.Thermal decomposition behavior of dried gels,phase identification and crystallinity of synthesized C4AF,and impact of urea to metal nitrates（UR/MN）molar ratio on synthesis effect were investigated with the aid of differential thermogravimetric analysis,X-ray diffraction and Fourier transform inferred spectrometry.It is found that pure C4AF can be prepared by the SPCR method in 2 h at 500℃.The UR/MN molar ratio plays a significant role in the thermal decomposition behavior of dried gel,purity,crystallinity and crystallite size of synthesized C4AF.Ignition temperature should be not lower than 500℃but higher temperatures were unnecessary.No trace of free lime in synthesized C4AF is detected and calcium carbonate is the transition phase.Further calcining the synthesized C4AF at high temperatures is beneficial for increasing crystallinity,purity and crystallite size.Reaction activation energy of the further calcination process is 119.6 kJ/mol.It is more efficient to improve the synthesis effect by increasing UR/MN molar ratio than further calcination at high temperatures.展开更多
Nanometer α-Al2O3 powders were synthesized by the method of low-temperature combustion synthesis （LCS） with aluminum nitrate nonahydrate and urea as raw materials. The prepared powders were studied by XRD, TG-DTA, ...Nanometer α-Al2O3 powders were synthesized by the method of low-temperature combustion synthesis （LCS） with aluminum nitrate nonahydrate and urea as raw materials. The prepared powders were studied by XRD, TG-DTA, FT-IR and TEM. It is found that the average size of particles is 6080nm. The optimal synthetic conditions are obtained, i.e., the suitable fuel is urea; the molar ratio of oxidizer to fuel is 1∶2 and the igniting temperature is 700℃. The results show that the size of particles is governed by synthesizing temperature, the fuel and the molar ratio of oxidizer to fuel. TEM image of the particles collected shows that the crystal habits of particles have a spheric structure and particles are polycrystal.展开更多
Homogeneous HA coating materials were prepared on porous titanium by the low-temperature combustion synthesis. It was found that the mechanical properties of the specimen depend on the coating process and the heat tre...Homogeneous HA coating materials were prepared on porous titanium by the low-temperature combustion synthesis. It was found that the mechanical properties of the specimen depend on the coating process and the heat treatment, and the bending strength would be reduced during the coating process but could be improved by heat treatment. The effects of the temperature during heat- treatment on the phase composition and microstructure of the as-prepared coating, and the bending strength of the specimen were investigated by XRD and SEM. The experimental results show that in the coating process, slight oxidation of the substrate may give rise to a drop in bending strength ; however, it could be increased by the reaction of HA and TiO2 , and the sintering of the coating during heat treatment. The HA particles in the coating, with very fine sized particles. were pretty active and would decompose at 800℃.展开更多
A novel process termed low-temperature combustion-synthesis (LCS) ofBa(NO_3)_2-TiO_2-C_6H_8O_7.centre dot H_2O system was investigated at the initial temperature of 600deg C and ultrafine BaTiO_3 powders with a partic...A novel process termed low-temperature combustion-synthesis (LCS) ofBa(NO_3)_2-TiO_2-C_6H_8O_7.centre dot H_2O system was investigated at the initial temperature of 600deg C and ultrafine BaTiO_3 powders with a particle size of 200-350 nm were prepared. It was foundthat the molar ratio of NO_3^- / citric acid and the homogeneity of combustion have remarkableeffect on the characteristics of the powder. The reaction mechanism of LCS BaTiO_3 powders wasproposed on the basis of thermodynamic analysis.展开更多
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.
文摘Based on thelow temperaturecombustion synthesisof α Al2 O3 from aluminum nitrate,the effectsofthe additives on the formation and particle properties of α Al2 O3 werestudied by XRDand SEM,theinitialstudy on the manometer α Al2 O3 synthesisby LCSwas done, α Al2 O3 withtheparticlesize50 ～80 NM wasgot under properconditions.
基金Funded partly by the National "973" Program of China(No.2015CB655101)National Natural Science Foundation of China(No.51379163)
文摘The self-propagating combustion reaction（SPCR）method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as fuel.Thermal decomposition behavior of dried gels,phase identification and crystallinity of synthesized C4AF,and impact of urea to metal nitrates（UR/MN）molar ratio on synthesis effect were investigated with the aid of differential thermogravimetric analysis,X-ray diffraction and Fourier transform inferred spectrometry.It is found that pure C4AF can be prepared by the SPCR method in 2 h at 500℃.The UR/MN molar ratio plays a significant role in the thermal decomposition behavior of dried gel,purity,crystallinity and crystallite size of synthesized C4AF.Ignition temperature should be not lower than 500℃but higher temperatures were unnecessary.No trace of free lime in synthesized C4AF is detected and calcium carbonate is the transition phase.Further calcining the synthesized C4AF at high temperatures is beneficial for increasing crystallinity,purity and crystallite size.Reaction activation energy of the further calcination process is 119.6 kJ/mol.It is more efficient to improve the synthesis effect by increasing UR/MN molar ratio than further calcination at high temperatures.
文摘Nanometer α-Al2O3 powders were synthesized by the method of low-temperature combustion synthesis （LCS） with aluminum nitrate nonahydrate and urea as raw materials. The prepared powders were studied by XRD, TG-DTA, FT-IR and TEM. It is found that the average size of particles is 6080nm. The optimal synthetic conditions are obtained, i.e., the suitable fuel is urea; the molar ratio of oxidizer to fuel is 1∶2 and the igniting temperature is 700℃. The results show that the size of particles is governed by synthesizing temperature, the fuel and the molar ratio of oxidizer to fuel. TEM image of the particles collected shows that the crystal habits of particles have a spheric structure and particles are polycrystal.
文摘Homogeneous HA coating materials were prepared on porous titanium by the low-temperature combustion synthesis. It was found that the mechanical properties of the specimen depend on the coating process and the heat treatment, and the bending strength would be reduced during the coating process but could be improved by heat treatment. The effects of the temperature during heat- treatment on the phase composition and microstructure of the as-prepared coating, and the bending strength of the specimen were investigated by XRD and SEM. The experimental results show that in the coating process, slight oxidation of the substrate may give rise to a drop in bending strength ; however, it could be increased by the reaction of HA and TiO2 , and the sintering of the coating during heat treatment. The HA particles in the coating, with very fine sized particles. were pretty active and would decompose at 800℃.
文摘A novel process termed low-temperature combustion-synthesis (LCS) ofBa(NO_3)_2-TiO_2-C_6H_8O_7.centre dot H_2O system was investigated at the initial temperature of 600deg C and ultrafine BaTiO_3 powders with a particle size of 200-350 nm were prepared. It was foundthat the molar ratio of NO_3^- / citric acid and the homogeneity of combustion have remarkableeffect on the characteristics of the powder. The reaction mechanism of LCS BaTiO_3 powders wasproposed on the basis of thermodynamic analysis.
