Papers by Author: Ming Li Qin

Abstract: By the use of YH₂ and NiO, oxide particles were introduced in Ni-base ODS alloys through reactive ball milling, which shows the advantages of energy-saving and uniform distribution of the oxide dispersion. The mophological and size evolution of ball milled powder were investigated, and the synthesized oxides were characterized. The results shows that the ball milled powder exhibits the feather of severe deformation. The disintegration of particles occurs after 10 h, and the balance of powder welding and fracturing is achieved around 25 h. the formation of Y₂O₃ with the size of 20~50 nm was confirmed by XRD and TEM results.

Abstract: The CuS flower-like superstructures were selectively and facilely synthesized by a hydrothermal method at 120 °C. The EDS, SEM, HRTEM and FFT results show that the CuS superstore has a well-defined uniform 3-dimensional flower-like morphology. These superstructures have sizes of about 500 nm and are built from several intersectional nanoplates, which have a mean length of about 500 nm and an average thickness of about 50 nm. Optical absorption spectrum of the CuS superstructure shows it has good absorption in the near-IR region and the band gap is 2.08 eV.

Abstract: Nb-5 at.% W-5 at.% Mo-2 at.%Zr-2 at.% C (Nb5522) bulk alloys were prepared using blended powders or ball-milled powders via spark plasma sintering. The differences between blended powder compacts and ball milled powder compacts with respect to their density, microstructure and mechanical properties were studied. The results showed that ball milling enhances the sinterability of Nb5522 powders. After sintered by SPS at 1873 K, the milled powders achieved a near-full densification density. The SPS process favors the precipitation of (Nb, Zr)C particles.

Abstract: Co-based ODS alloys strengthened by γ΄ precipitates and nanosized oxides are promising high-temperature structural materials. Single solid solution of Al and W in the matrix can not be achieved after mechanical alloying, resulting in the formation of low volume fraction of γ΄ phase and several kinds of secondary phases. The addition of Ni promotes the precipitation of γ΄ phase and reduces the amount of secondary phases by the enlargement of the solid solution limit of Al and W within the matrix. In comparison with the lower fracture strength and cleavage fracture mode of the alloy without the addition of Ni, Ni-containing Co-base ODS alloys exhibit much higher fracture strength and obvious ductile facture mode.

Abstract: The effect of ball-to-powder weight ratio on the fabrication of Nb-base powder via ball milling was studied. The structural evolution and morphology of the powders were investigated using LPSA, XRD and SEM techniques. The results indicate that increasing the BPR leads to decreases in particle size and grain size of powders. For a given milling time of 18 h and rotational speed of 250 rpm, ball milling with BPR of 20:1 produces an ultrafine powder with a mean particle size of about 2 μm and a grain size of about 20 nm. A 30:1 of BPR increases the useless collision frequency during ball milling, leads to a serious fraying of milling balls.

Abstract: Abstract. Aluminum nitride(AlN) powders were synthesized by carbonthermal reduction of Ammonium aluminum carbonate hydroxide(AACH). The AACH were prepared from ammonium alum and ammonium hydrogen carbonate by precipitation method and AACH adhere to carbon black during precipitation. The precursor has a high reaction activity (near 100% of nitridation ratio after heated in flow nitrogen at 1400°C, 2h). After carbon remove in muffle furnace at 700 °C, white color Aluminum nitride (AlN) powder attained and mean size is 100 nm. The specific surface area of the powders decreased with increasing of concentration of ammonium alum and ammonium hydrogen carbonate, which range from 22 m2/g to 7 m2/g, particle size vary from 58 to 120 nm. Phase presents in the products during heating in flowed nitrogen were observed by X-ray diffraction. The -Al2O3 formed when the precursor heated to 1200°C, AlN was founded at 1300°C and the reaction ended at 1400°C, the reaction temperature and annealing time were much lower than nitridate the mixture of Al2O3 and carbon black. Particle size was increased when reaction temperature increased from 1400°C to 1550°C.