The processes of the coupling graft of -Si(OCH3)3 groups between 7-aminopropyl trimethoxysilane molecules and iron microparticles and the preparation of Fe/SiO2 core-shell composite particles in the alcohol-alkali-wat...
详细信息
The processes of the coupling graft of -Si(OCH3)3 groups between 7-aminopropyl trimethoxysilane molecules and iron microparticles and the preparation of Fe/SiO2 core-shell composite particles in the alcohol-alkali-water solution were investigated in the paper. The as-prepared and heat-treated composite particles were characterized with XRD, SEM, and pickling tests. The results showed that the formation of free SiO2 could be effectively prevented by decreasing the rate of adding ammonia, and that Fe/SiO2 core-shell composite particles almost without free SiO2 were successfully fabricated with a controlling rate about 5 drops of ammonia per minute. The optimal temperature range for the densification of SiO2 nanoshell is about 600 [similar to] 700 °C. The SiO2 nanoshells were badly melt and dropped off when the composite particles were heat-treated at 900 °C. The acid resistance of the composite particles increases as the temperature rose from 200 °C to 700 °C.
TiB2-Si3N4-BN composite was fabricated by hot press, and the influence of the content of additive and sintering temperature on the property is also discussed. The results show that content of the additive and the sint...
详细信息
TiB2-Si3N4-BN composite was fabricated by hot press, and the influence of the content of additive and sintering temperature on the property is also discussed. The results show that content of the additive and the sintering temperature play an important role on the materials properties, TiB2-Si3N4-BN composite is of better properties at sintering temperature 2073 K with the additive of 1 wt%.
Mullite-based nanocomposite powders with embedded iron nanoparticles were synthesized by reduction of sol-gel prepared Al5.4Fe 0.6Si2O13 solid solution in hydrogen. Structural characterization studied by TEM revealed ...
详细信息
ISBN:
(纸本)0470080337
Mullite-based nanocomposite powders with embedded iron nanoparticles were synthesized by reduction of sol-gel prepared Al5.4Fe 0.6Si2O13 solid solution in hydrogen. Structural characterization studied by TEM revealed that the intra-granular iron nanoparticles along with inter-type iron grains were obtained in mullite matrix. The magnetic properties of nanocomposite powders after reduction at 1200°C were measured by SQUID. It suggests that the intergranular and intragranular α-iron nanoparticles had the ferromagnetic and superparamagnetic behavior at room temperature, respectively. Dense Mullite-based iron composites were prepared from the nanocomposite powders reduced at different temperatures by hot pressing. The mechanical and magnetic properties were strongly affected by the reduction temperature. Flexural strength of mullite based iron nanocomposite reduced at 1200°C and successively hot pressed at 1650°C is one times higher than monothetic mullite. Furthermore, dense composites also behave ferromagnetic property at room temperature.
SiCp/Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering (SPS), and their thermophysical properties, such as thermal conductivity (TC) and coefficient of thermal ex...
详细信息
ISBN:
(纸本)0470081562
SiCp/Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering (SPS), and their thermophysical properties, such as thermal conductivity (TC) and coefficient of thermal expansion (CTE), were characterized. The principle of the fabrication was analyzed. Spark can be generated by electric field if the cavity in the green body is large enough. The melted Al by spark densify the compact which is similar to the pressure infiltration but with simple method. High relative density (R-D) of composites was successfully achieved through the optimization of sintering parameters. The measured TCs of SiCp/Al composites fabricated by SPS are higher than 195W/m·k.
Aluminum borate whiskers with TiB2 as borate source were prepared in this paper. The phase transformation process was analyzed by XRD and TG-DSC. The results indicate that TiB2 was decomposed into TiO 2 and B2O3 in th...
详细信息
Aluminum borate whiskers with TiB2 as borate source were prepared in this paper. The phase transformation process was analyzed by XRD and TG-DSC. The results indicate that TiB2 was decomposed into TiO 2 and B2O3 in the calcining process in the active [O] atmosphere. 2Al2O3.B2O3 was formed in the lower temperature with reaction of Al2O3 and B2O3, while 9Al2O3.2B 2O3 whiskers were grown by compensation of 2Al 2O3.B2O3 at higher temperature (above 1050°C).
The paper presents results on the mechanism of spark plasma sintering (SPS). First, the temperature distribution in the sample and the die in SPS were studied. Under certain conditions, the difference may reach a few ...
详细信息
ISBN:
(纸本)0470081562
The paper presents results on the mechanism of spark plasma sintering (SPS). First, the temperature distribution in the sample and the die in SPS were studied. Under certain conditions, the difference may reach a few hundreds of degrees of centigrade. Controlling of processing parameters can decrease the temperature difference. Second, the process of atomic diffusion due to the effect of the current was also studied. It was found that the atomic diffusion is enhanced at the interface between specimens in the SPS relative to hot pressing (HP). Third, we have utilized the SPS process to form transparent ceramics, porous metals and ceramics, and to effect welding of alloys.
Aluminum borate whisker with TiB2 as borate source was prepared in this paper. The phase transformation process and whisker growth mechanism were analyzed. The results indicate that TiB2 is oxidized by active [O] rele...
详细信息
Aluminum borate whisker with TiB2 as borate source was prepared in this paper. The phase transformation process and whisker growth mechanism were analyzed. The results indicate that TiB2 is oxidized by active [O] released from the decomposition of (NH4)2SO4. B2O3 released from TiB2 oxidation provide borate source for whisker growing. Al/B ratio has influence on whisker morphology. Surplus B2O3 is needed during aluminum borate whisker growth because liquid B2O3 is a medium to transport Al2O3 to the tiny whisker nearby.
High-energy ball mill method was used to treat the stainless steel powder;the effects of treat parameters (ball-raw materials rate, treatment time) on the microstructure and phase composite were studied. X- ray diffra...
详细信息
High-energy ball mill method was used to treat the stainless steel powder;the effects of treat parameters (ball-raw materials rate, treatment time) on the microstructure and phase composite were studied. X- ray diffraction, SEM and the BET method were used to evaluate the microstructure of treated samples. The results showed that with increasing in ball mill time, the particle size of stainless steel powder decreases obviously;surface features of powder were changed significantly. X-ray diffraction calculation results showed that the particle size of stainless steel powder have been 28 nm after 120 h ball mill treatment, the BET analysis results agree with the X-ray diffraction calculation results.
In situ reaction method was undertaken to fabricate A1N-BN composites in this paper. Factors including temperature, heat preservation time, and the ratio of Al to BN were investigated in this system. DTA and XRD were ...
详细信息
In situ reaction method was undertaken to fabricate A1N-BN composites in this paper. Factors including temperature, heat preservation time, and the ratio of Al to BN were investigated in this system. DTA and XRD were employed to character the phases of production. SEM was conducted to observe the microstructure of the samples. The results showed that the grains tended to perfect with the increasing of the sintering temperature and soaking time. Optimum parameters were temperature of 1000°C and 1.5 h for soaking time.
AlN was synthesized by in situ reaction with Al and BN in this paper. AlN-BN composites were fabricated by hot-pressed sintering without additives. The relationship between the ratio of Al to BN and microstructure and...
详细信息
AlN was synthesized by in situ reaction with Al and BN in this paper. AlN-BN composites were fabricated by hot-pressed sintering without additives. The relationship between the ratio of Al to BN and microstructure and properties were studied. The results show that the content of AlN increases with the ratio of Al to BN increasing, and the density, hardness, bending strength, thermal conductivity and dielectric constant also increase with the ratio of Al to BN increasing. The results show that the samples with thermal conductivity 63.5 W/m·K and dielectric constant 8.76 are acquired by hot-pressed sintering under nitrogen atmosphere and two hours soaking time.
暂无评论