Advanced Materials Research Vol. 454

Abstract: In this paper, the recent studies of our lab in Tsinghua University are reviewed in detail with regard to methods of preparing Nano-powders, Micron/Nano composite and Nanostructure surface; Ways to characterize the properties of Nano particle and Nano surface are summarized. And in addition, the industrial applications of powder technology are also introduced.

Abstract: Honghua has been demonstrated useful for promoting blood circulation and stopping pain. The physicochemical characterization of Honghua powders was greatly influenced by ultrafine pulverization. To study the physicochemical characterization of Honghua, the raw plant material of Honghua was ground to powders by high speed centrifugal sheering (HSCS) pulverizer. The micron powders were characterized by laser scattering granulometric analyzer and scanning electron microscope (SEM). Hydroxysafflor yellow A is one of active ingredients of Honghua, and its dissolution speed was determined to evaluate the chemical characterization of Honghua powder. The results showed that after ultrafine pulverization, dissolution speed of hydroxysafflor yellow A was increased by 28.6% compared with the normal powders

Abstract: The poly(phenlene sulfide)(PPS)/carbon nanotubes (CNTs) composite was prepared by plastic pressure moulding of mixture of PPS and CNTs mixed by ball mill. The structure, elcctrical conductivity and mechanical properties of the composite were studied in detail. The effect of content of CNT on mechanic properties and conductivity of composite was carried out, repectivly. The SEM characterization indicates that CNTs were dispersed uniformly in the PPS matrix, which leads to a remarkable improvement in mechanical properties of composite. Compared with the those of neat PPS, both the tensile strength and impact strength of the composite increase with content of CNTs. and the addition of CNT increases the conductivity of the composites dramatically.

Abstract: Single-walled carbon nanotubes (SWNTs) have been successfully prepared from starch by arc discharge technique. The SWNTs products were characterized by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The growth mechanism of the SWNTs was discussed in terms of the starch. The results demonstrate that starch is one of the suitable precursor for making SWNTs by arc discharge method.

Abstract: Composite particles with ultra-high molecular polyethylene (UHMWPE) core and carbon nanotube (CNT) shell were produced by an impact coating process, and molded into conductive polymer composites. Morphology of these composite particles was observed and the electrical behavior of these molded composites was measured. UHMWPE particles were very well coated by CNT, and conductive networks of CNT were formed after molding. These conductive polymer composites with low loadings of conductive filler exhibit lower room-temperature resistivity, and volume resistivity decreases with temperature on the whole. This is because of the CNT distribution is uniform in a macroscopic view but is oriented in a mesoscopic view. Thermionic emission of CNT is strong in polymer composites produced by this process. A related mechanism is discussed.

Abstract: This article describes the alumina ceramic mixed with two kinds of additives in order to improve the performance of ceramic, such as mixed with submicron ZrO₂ and Nano-SiC. The main use of monoclinic zirconia (m-ZrO₂) and tetragonal zirconia (t-ZrO₂) of reversible phase transition of volume change and use of nano-SiC particle dispersion toughening mechanism to improve the toughness and wear resistance of composite alumina ceramic. Through doing various tests about fired products, including hardness testing, SEM test and bulk density measurement, we can understand the microstructure and mechanical properties of some of the products for analysis.

Abstract: The blast-furnace slag （BFS）has been characterized by chemical and phase composition to evaluate its hydration reactivity. It has high potential activity for its glassy structure, so its use to prepare new filling cementation material is possible. New backfilling cementation material composition has been formulated and optimized by activation of BFS. The optimal formula of new backfilling cementation material SL(Slag activated by lime) and SLC(Slag activated by lime and calcium chloride) was 87% BFS ,13% lime and 86.84% BFS, 13.02% lime, 0.14% calcium chloride respectively. Finally, the feature of cementing properties was analyzed through comparison between new cementation material and ordinary Portland cement with compressive strength, water requirement of normal consistence, setting time, bleeding water and slump. The result showed that material SL and SLC have superior performance to ordinary Portland cement used to mining cemented filling.

Abstract: Sepoilite was surface-modified by the mixture of ethanolamine and n, n-dimethyl ethanolamine. The XRD, SEM, FT-IR, BET and TGA were used to characterize the material structure and the adsorption property in CO2. The results showed that the weight percentage of CO2 adsorption rose from 4.01% for pure sepoilite to 19.28% for the modified sepoilite at room temperature.

Abstract: The mineral composition and microstructure of slag film of medium carbon steel are studied systematically with the methord of the technological mineralogy. The result shows that: The main mineral compositions of slag film are melilite and glass phase, and the texture of slag film is of two-layer or three, in which glassy-layer and crystallizing-layer appear alternately, the crystallization rate is from 2% to 5%. The melilite in slag film is good for improving lubrication and controlling heat transfer, so melilite can be promote in slag film for improving the quality of medium carbon steel.

Abstract: The magnesium hydroxide (MH) whisker/PE composites were prepared by melt-extrusion with modified whiskers and unmodified whiskers as fillers respectively. The flame retardant property of composites was tested by the oxygen index machine. The magnesium hydroxide whiskers could improve the flame retardant property of the composites. When the contents of the modified and unmodified whiskers increased from 10% to 60%, the oxygen index of the composites increased from 24.4% to 43.4%, 23.2% to 40.2% respectively. The flame retardant of the modified whiskers/PE composites was better than the unmodified. The morphology of fracture was analyzed by SEM: the modified whisker could be more evenly divided into PE matrix with better dispersibility and compatibility, for that there occurred organic molecule membranes on the surface of the crystal whiskers after being modified, which lowered the interfacial energy of whiskers.