Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk, which were first treated at 900?1 000 ℃ for nucleation, then treated at higher temperature for crystallization to obtain ultra-fine zirconia-mullite composite ceramics. The effects of treating temperature and ZrO_2 addition on mechanical properties and microstructure were analyzed. A unique structure in which there are a lot of near equiaxed t-ZrO_2 grains and fine yield-cracks has been developed in the samples with 15% zirconia addition treated at 1 150 ℃. This specific microstructure is much more effective in toughening ceramics matrix and results in the best mechanical properties. The flexural strength and fracture toughness are 520 MPa and 5.13 MPa?m~(1/2), respectively. Either higher zirconia addition or higher crystallization temperature will produce large size rod-like ZrO_2 and mullite grains, which are of negative effect on mechanical properties of this new composite ceramics.
MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that the sample with 0.2% La3+(mass fraction) or without La3+ has only spinel phase, but the sample with mass fraction of La3+ exceeding 0.4% posses second phase besides the spinel one; and the nano-MnZn ferrites change from cube to hexagon when the mass fractions of La3+ is up to 1.2%. TEM image of the sample with 1.2% La3+ indicates that the homogeneous hexagonal crystal is obtained and the particles are larger than those of undoped; the addition of La3+ has great influence on the crystallization of hydrothermal process and can change the shape of particles and improve their growth. The saturation magnetization of the sample with 1.2% La3+ (2.64 A·m2·kg-1) is lower than that of undoped (17.54 A·m2·kg-1) and it behaves superparamagnetically.
Transactions of Nonferrous Metals Society of China,2002年12(6):1020-1023 ISSN：1003-6326
Cent S Univ, Natl Key Lab Powder Met, Changsha 410083, Peoples R China.;Cent S Univ, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.;[Liang Shuquan; Huang Baiyun] National Key Laboratory for Powder Metallurgy, Central South University,Changsha 410083, China;[Liang Shuquan] School of Materials Science and Engineering, Central South University,Changsha 410083, China;[Li Weizhou] 中南大学
Lab. for Powder Metall., Central South Univ., China
suspension system;rheology;Einsteins viscose law
The viscose models for powder suspension system was reviewed and analysed. It is found that by introducing modification function f(φ) in the differential form of classical Einsteins viscosity law, all of viscose models can be unified if f(φ) takes suitable form . Some rational forms of the function f(φ) were discussed according to functional approximation method, and a new rheological model contained two undetermined parameters was consequently developed, more suitable for high particle concentration dispersing system. The experimental results show that this new model is of better consistence.
Transactions of Nonferrous Metals Society of China,2004年14(4):762-768 ISSN：1003-6326
[梁叔全] Cent S Univ, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.;Cent S Univ, State Key Lab Powder Met, Changsha 410083, Peoples R China.
[Liang, SQ] Cent S Univ, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.
binder;chemistry;powder injection molding
The polymer binder selection is one of the very important aspects for the powder injection molding.However, even nowadays the binder selection is still mainly performed by try and error method. Six commercial or intensive studied binder formulas were analyzed according to state diagram and chemical characteristics of ingredients in each binder formula. In addition, the interactions between the binder components and additives were also taken into account. Based on the analysis, the optimum binder formula was selected and some selection criterions were put forward for the binder and additives.
Liang Shuquan（梁叔全）;Tang Yan*;Zhang Yong;Zhong Jie
[Liang Shuquan; Tang Yan; Zhang Yong; Zhong Jie] Cent S Univ, Sch Mat Sci & Engn, Changsha 410083, Hunan, Peoples R China.
2nd International Conference on Multi-Functional Materials and Structures
OCT 09-12, 2009
Qingdao, PEOPLES R CHINA
[Liang Shuquan;Tang Yan;Zhang Yong;Zhong Jie] Cent S Univ, Sch Mat Sci & Engn, Changsha 410083, Hunan, Peoples R China.
Advanced Materials Research
metal powder injection molding;carbon nanotube;feedstock;rheology properties
Carbon nanotubes/ iron compound powder was prepared by high energy ball milling after purified and activated the CNTs. Then, the compound powder and paraffin wax based-binders were mixed to prepare feedstock and the rheological behavior was evaluated by SEM, rheometer and infrared spectrum analysis. By changing the CNTs content and powder loading, the viscosity, shear rate sensitive factor and viscos-activation energy were calculated. 0.2wt% of CNTs, the feedstock can disperse in the binders uniformly without the flowability affecting. Meanwhile, adding proper ratio of CNTs can increase the powder loading of MIM feedstock about 10%, which can optimize the following process conditions and the properties of MIM product.
[Liang, Shuquan; Tan, Xiaoping] Cent South Univ Technol, Sch Mat Sci & Engineer, Key Lab Nonferrous Met Mat, Minist Educ, Changsha 410083, Hunan, Peoples R China.;[Tan, Xiaoping; Chai, LiYuan] Cent South Univ Technol, Coll Metallurg Sci & Engn, Changsha 410083, Hunan, Peoples R China.
2011 International Conference on Intelligent Materials, Applied Mechanics and Design Science, IMAMD2011
December 24, 2011 - December 25, 2011
(1) Key Laboratory for Nonferrous Metal Materials of the Ministry of Education, School of Materials Science and Engineer, Central South University, Changsha Hunan 410083, China; (2) College of Metallurgical Science and Engineering, Central South University, Changsha Hunan 410083, China
Zirconia-mullite nanocomoposites were prepared from Si-Al-Zr-O amorphous bulk with diffrent content of CaO and MgO by two-step thermal treatment between 900 and 1200 degrees C. The effects of the additives on the phase and microsturcture were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy(TEM). The results show that the addition of CaO promotes cristobalite phase formation and the anisotropic growth of mullite grains. An indention micro-crack method was used to measure the fracture toughness of zirconia-mullite nanocomoposites. The results demonstrate that the fracture toughness increases with higher concentration of CaO. The improvement of fracture toughness is attributed to the anisotropic growth of grains.