The manufacture process of 8mol% Y-2O-3 stabilized ZrO-2(YSZ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increase...The manufacture process of 8mol% Y-2O-3 stabilized ZrO-2(YSZ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increases lineally with the forming press,and the sintering linear shrinkage of YSZ to the forming press compiles to the parabola trend. When the forming press exceeding 500MPa, the samples with lower shrinkage and high density were obtained. The sintering temperature of YSZ decreases greatly because of the small size and high active surface of YSZ powders. As a result, the beginning sintering temperature of YSZ made in the experiment is as low as 825℃, and the end sintering temperature is 1300-1350℃. The relative density of YSZ ceramic by solid sintering at 1300-1350℃ is more than 97%, with little and small pores in the uniform microstructure.展开更多
This paper reports the preparation of nano-TiO2 (about 10 nm) powder by the method of precipitation. In detail, some breparation conditions were investigated in order to find out how to control the grain size and redu...This paper reports the preparation of nano-TiO2 (about 10 nm) powder by the method of precipitation. In detail, some breparation conditions were investigated in order to find out how to control the grain size and reduce the agglomeration of powders. Also, the reflex spectra of nano-scale powders with different grain size were studied. It tvas found that the wave length and width of reflex spectra are connected with the grain size of nano-TiO2 powders展开更多
Chemical coprecipitation was used to produce ultrafine and easily sinterable Y2O3-stabilized and （Y2O3,MgO）-stabilized ZrO2 powders. Six precipitation processes for preparation of ZrO2-based ultrafine powders were d...Chemical coprecipitation was used to produce ultrafine and easily sinterable Y2O3-stabilized and （Y2O3,MgO）-stabilized ZrO2 powders. Six precipitation processes for preparation of ZrO2-based ultrafine powders were designed separately, meanwhile different techniques used to control the agglomeration formation were proposed. By means of TEM, SEM, Raman spectroscopy and IR spectroscopy, the mechanisms of agglomeration control in the precipitation processes and post-precipitation and drying process were investigated. The experimental results show that adding appropriate anion surface active agents （such as PAA1460） or polymer （PEG1540 matching with PEG200） in aqueous solution systems during precipitation processes could reinforce charge effect and location effect for gel particles interface. Adding wetting agents to wet gels washing with distilled water during drying process could change interface structure of gel particles and decrease surface tension between gel particles. The agglomeration control in the precipitation, post-precipitation and drying processes had remarkable influence on the characteristics of powders. By adding various macromolecules in the processes, the agglomeration state could be controlled efficiently, and the characteristics of powders were improved.展开更多
With zirconium oxychloride, nitrate of lime and ammonia as raw materials, nano powder of CaO ZrO 2 was prepared by chemical coprecipitation method. By use of azeotropic distillation processing, chemical coprecipitatio...With zirconium oxychloride, nitrate of lime and ammonia as raw materials, nano powder of CaO ZrO 2 was prepared by chemical coprecipitation method. By use of azeotropic distillation processing, chemical coprecipitation precursor was obtained. Phase transformation of the precursor was observed at the temperature of 593.81 ℃ and 1 234.56 ℃ respectively with DTA analyses. Phase structure was analyzed through XRD and Raman spectra. The average particle size of tetragonal zirconium oxide powder was 9.8 and 43.7 nm after calcination at 600 and 1 100 ℃ respectively which was tested by TEM and BET analyses. Furthermore, the influences of the doping of nitrate of lime and the average particle size of zirconium oxide on the stability of tetragonal zirconium oxide were also discussed.展开更多
TiO2 nano powders with Mn concentration of 0 at%-12 at% were synthesized by the sol-gel process, and were annealed at 500 ℃ and 800 ℃ in air for 2 hrs. X-ray diffraction （XRD） measurements indicate that the Mn-TiO...TiO2 nano powders with Mn concentration of 0 at%-12 at% were synthesized by the sol-gel process, and were annealed at 500 ℃ and 800 ℃ in air for 2 hrs. X-ray diffraction （XRD） measurements indicate that the Mn-TiO2 nano powders with Mn concentration of 1 at% and 2 at% annealed at 500 and 800 ℃ are of pure anatase and rutile, respectively. The scanning electron microscope （SEM） observations reveal that the crystal grain size increases with the annealing temperature, and the high resolution transmission electron microscopy （HRTEM） investigations further indicate that the samples are well crystallized, confirming that Mn has doped into the TiO2 crystal lattice effectively. The room temperature ferromagnetism, which could be explained within the scope of the bound magnetic polaron （BMP） theory, is detected in the Mn-TiO2 samples with Mn concentration of 2 at%, and the magnetization of the powders annealed at 500 ℃ is stronger than that of the sample treated at 800 ℃. The UV-VIS diffuse reflectance spectra results demonstrate that the absorption of the TiO2 powders could be enlarged by the enhanced trapped electron absorption caused by Mn doping.展开更多
Both green and residual bending strength of the dip-coat layer composed of ZrO2 (CaO) powder and colloi-dal zirconiz sol binder are sutdied and the effects of process factrs on the strength of dip-coat layer are inter...Both green and residual bending strength of the dip-coat layer composed of ZrO2 (CaO) powder and colloi-dal zirconiz sol binder are sutdied and the effects of process factrs on the strength of dip-coat layer are interpreted,using the results of TG-DTA ,TMA and SEM analyses of the fracture morphology of the coating layer and following the strength theory for porous body.展开更多
Cyanoacrylate adhesive and its composites have been widely used in industry and dentistry. According to literature survey done by the authors, there are few papers concentrated on role of nano-sized particles on wear ...Cyanoacrylate adhesive and its composites have been widely used in industry and dentistry. According to literature survey done by the authors, there are few papers concentrated on role of nano-sized particles on wear behavior of cyanoacrylate glue. Thus the main goal of current research focused on clarifying the role of nano-sized SiO2 on wear behavior of cyanoacrylate. Pin-on-disk wear test, SEM imaging and microhardness test was utilized to investigate wear performance of cyanoacrylate and its nanocomposites with SiO2. The results indicated that SiO2 nano powders can reduce wear rate of cyanoacrylate and change its wear mechanism. It was also shown that surface hardness of cyanoacrylate is increased by addition of nano-sized SiO2.展开更多
文摘The manufacture process of 8mol% Y-2O-3 stabilized ZrO-2(YSZ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increases lineally with the forming press,and the sintering linear shrinkage of YSZ to the forming press compiles to the parabola trend. When the forming press exceeding 500MPa, the samples with lower shrinkage and high density were obtained. The sintering temperature of YSZ decreases greatly because of the small size and high active surface of YSZ powders. As a result, the beginning sintering temperature of YSZ made in the experiment is as low as 825℃, and the end sintering temperature is 1300-1350℃. The relative density of YSZ ceramic by solid sintering at 1300-1350℃ is more than 97%, with little and small pores in the uniform microstructure.
文摘This paper reports the preparation of nano-TiO2 (about 10 nm) powder by the method of precipitation. In detail, some breparation conditions were investigated in order to find out how to control the grain size and reduce the agglomeration of powders. Also, the reflex spectra of nano-scale powders with different grain size were studied. It tvas found that the wave length and width of reflex spectra are connected with the grain size of nano-TiO2 powders
文摘Chemical coprecipitation was used to produce ultrafine and easily sinterable Y2O3-stabilized and （Y2O3,MgO）-stabilized ZrO2 powders. Six precipitation processes for preparation of ZrO2-based ultrafine powders were designed separately, meanwhile different techniques used to control the agglomeration formation were proposed. By means of TEM, SEM, Raman spectroscopy and IR spectroscopy, the mechanisms of agglomeration control in the precipitation processes and post-precipitation and drying process were investigated. The experimental results show that adding appropriate anion surface active agents （such as PAA1460） or polymer （PEG1540 matching with PEG200） in aqueous solution systems during precipitation processes could reinforce charge effect and location effect for gel particles interface. Adding wetting agents to wet gels washing with distilled water during drying process could change interface structure of gel particles and decrease surface tension between gel particles. The agglomeration control in the precipitation, post-precipitation and drying processes had remarkable influence on the characteristics of powders. By adding various macromolecules in the processes, the agglomeration state could be controlled efficiently, and the characteristics of powders were improved.
文摘With zirconium oxychloride, nitrate of lime and ammonia as raw materials, nano powder of CaO ZrO 2 was prepared by chemical coprecipitation method. By use of azeotropic distillation processing, chemical coprecipitation precursor was obtained. Phase transformation of the precursor was observed at the temperature of 593.81 ℃ and 1 234.56 ℃ respectively with DTA analyses. Phase structure was analyzed through XRD and Raman spectra. The average particle size of tetragonal zirconium oxide powder was 9.8 and 43.7 nm after calcination at 600 and 1 100 ℃ respectively which was tested by TEM and BET analyses. Furthermore, the influences of the doping of nitrate of lime and the average particle size of zirconium oxide on the stability of tetragonal zirconium oxide were also discussed.
基金Project supported by the Innovation Foundation of BUAA for PhD Graduates (Grant No. 292122)Equipment Research Foundation of China
文摘TiO2 nano powders with Mn concentration of 0 at%-12 at% were synthesized by the sol-gel process, and were annealed at 500 ℃ and 800 ℃ in air for 2 hrs. X-ray diffraction （XRD） measurements indicate that the Mn-TiO2 nano powders with Mn concentration of 1 at% and 2 at% annealed at 500 and 800 ℃ are of pure anatase and rutile, respectively. The scanning electron microscope （SEM） observations reveal that the crystal grain size increases with the annealing temperature, and the high resolution transmission electron microscopy （HRTEM） investigations further indicate that the samples are well crystallized, confirming that Mn has doped into the TiO2 crystal lattice effectively. The room temperature ferromagnetism, which could be explained within the scope of the bound magnetic polaron （BMP） theory, is detected in the Mn-TiO2 samples with Mn concentration of 2 at%, and the magnetization of the powders annealed at 500 ℃ is stronger than that of the sample treated at 800 ℃. The UV-VIS diffuse reflectance spectra results demonstrate that the absorption of the TiO2 powders could be enlarged by the enhanced trapped electron absorption caused by Mn doping.
文摘Both green and residual bending strength of the dip-coat layer composed of ZrO2 (CaO) powder and colloi-dal zirconiz sol binder are sutdied and the effects of process factrs on the strength of dip-coat layer are interpreted,using the results of TG-DTA ,TMA and SEM analyses of the fracture morphology of the coating layer and following the strength theory for porous body.
文摘Cyanoacrylate adhesive and its composites have been widely used in industry and dentistry. According to literature survey done by the authors, there are few papers concentrated on role of nano-sized particles on wear behavior of cyanoacrylate glue. Thus the main goal of current research focused on clarifying the role of nano-sized SiO2 on wear behavior of cyanoacrylate. Pin-on-disk wear test, SEM imaging and microhardness test was utilized to investigate wear performance of cyanoacrylate and its nanocomposites with SiO2. The results indicated that SiO2 nano powders can reduce wear rate of cyanoacrylate and change its wear mechanism. It was also shown that surface hardness of cyanoacrylate is increased by addition of nano-sized SiO2.
