Combustion reaction welding, one promising method to weld ceramies and metals, was used to weld TiB2 and Mo. The results showed that the reacted products through combustion reaction were TiB2 and MoB when the Mo contents in reactants were 20 wt pct and 40 wt pct while there was Mo besides MoB and TiB2 when there were 60 wt pct and 80 wt pct Mo in reactants. Diffusion of elements occurred at the interfaces of the two substrates. The interfaces between the reacted and the two substrates were indistinct after being welded. The welding temperature strongly affected properties of the samples. The value of bending strength of the sample with 80 wt pct Mo in reactant welded at 1500℃ was the highest, 368.52 MPa. The highest value of shear strength among all the samples was that of the one with 40 wt pct Mo in reactant vvelded at 1500℃, 50.97 MPa.
Daihua HE, Zhengyi FU and Qingjie ZHANGState Key Lab. of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
Porous alumina of regular spherical particles was fabricated with the spark plasma sintering （SPS） and then compared to those obtained through conventional hot pressing （HP）. The effects of the parameters of the heating process on porosity were also investigated, Microstructural studies suggest that porous ingots including regular pores be made out of regular spherical alumina particles due to the close sphere packages. A comparative study on the relative necks of the specimens produced by SPS and HP indicates an enhancement of neck growth with SPS. Contrasting the theoretical values to the experimental results over the relative necks indicates that a proper relationship between the relative necks and the porosity can be established by a sintering model.
WANG Kun FU Zheng-yi PENG Yong WANG Yu-cheng ZHANG Jin-yong ZHANG Qing-jie
Rhizama Chuanxiong is a kind of traditional medicinal herb used to promote blood circulation and eliminate wind to relieve pain. In this work, nano Rhizoma Chuanxiong particles were successfully prepared by high speed centrifugal sheering (HSCS) pulverizer. The influence of processing parameters on the size of Rhizama Chuanxiong particles and the different properties between nano Rhizoma Chuanxiong particles and original fine powder were systematically studied by ZetaPALS light scattering granulometric analyzer and optical microscope. The content of effective ingredient tetramethylpyrazine (TMP) was determined by high-performance liquid chromatography (HPLC). The results illustrate that general Rhizama Chuanxiong powder can be ultrafinely ground to nanometer within 50 min, and the cellular tissues of Rhizoma Chuanxiong are broken into pieces and dispersed stably and homogeneously after being ultrafinely ground. In addition, the active ingredients can dissolve out directly and fully, and the extraction ratio of TMP is increased 32.2% by HSCS processing.
The spores of Ganoderma lucidum were ground and broken to ultrafine particles by high speed centrifugal shearing（HSCS） pulverizer. The characteristics of Ganoderma lucidum spores were analyzed by scanning electron microscope （SEM）, Fourier transform infrared spectrophotometry （FTIR）. Ultraviolet-visible pectrophotometer was used to determine the extraction ratio of aqueous solubility polysaccharide between the raw and broken spores. The immunological function on the mice before and after the breaking of spores wan investigated. The experimental results show that after being ground, the sporoderm-broken ratio reachs 100%, the original active ingredients of ganoderma lucidum spores do not change, and the extraction ratio of aqueous solubility polysaccharide is greatly increased by 40.08%. The broken spores show much higher immunological activity comparing with original spores of Ganoderma lucidum.
The temperature field during the whole process of SPS sintering TiB2 -BN sample was numerically simulated based on the simplification of the temperature rising process. The result shows that the highest temperature is found in the punch and the heat flows from punch to sample and die in SPS sintering system. In the radial direction, the center temperature of the sample is much higher than the circumference temperature of the sampie. In the axial direction, the center temperature of the sample is lower than the border temperature of the sampie. The temperature difference in the sample is growing bigger in the sintering process and reaches the maximum at the end of the heating-up process.
Pulse current heating (PCH) was used to join Ti-6Al-4V alloy at two cases of with die and without die. Hot-pressing (HP) method was used to provide a comparison between the two methods. Microstructures near the contacting surfaces were observed in optical microscope. Temperature distribution was analyzed. After joining, the tensile properties of the samples were evaluated. Experimental results show that grains and phases grow transversely on contacting surfaces, which makes two parts into a whole with a certain of tensile strength. PCH joining is a different temperature joining method. The highest temperature is located at the interface. The comparison of tensile strengths of samples joined by the two methods indicates that joining temperature and holding time needed by PCH are lower and less than those needed for HP.
