Y. Kianinia, A. K. Darban, E. Taheri-Nassaj, B. Rahnama, A. Foroutan,
Volume 12, Issue 1 (march 2015 2015)
Abstract
A method for producing high surface area nano-sized mesoporous alumina from inexpensive Iranian kaolin
as raw material is proposed. In this method, first, kaolin was purified for purifying Kaolin, High Grade Magnetic
Separation and leaching with HCl and chemical bleaching treatment by using sodium dithionite (Na
2
S
2O4
) as reducing
agent in acidic media (H
2SO
4
) were used. Purified kaolin was calcined. After that, Al (hydr) oxide from acid -leachates of calcined kaolin was precipitated with ammonia, in presence of polyethylene glycol. Finally, a white
powder of nano-sized alumina particles was obtained after calcination. BET surface area, X-ray diffraction (XRD),
Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize
the sample. The resulting alumina with relatively high surface area (201.53 m
2
g
-1
) and narrow mean pore diameter
(6.91 nm), consists of a particle size distribution ranging from 22 to 36 nm.
M. Soltanieh, M. Kiani, M. Hasheminiasari,
Volume 14, Issue 2 (June 2017)
Abstract
- The mechanism of diffusion layer growth in plasma nitrided coatings applied on a St52 steel using an active screen is investigated. The nitriding was performed at 450,500 and 550 ◦C temperature nitriding times of 5, 10 and 15 h, in a gas mixture containing 20 vol. % H2: 80 vol. % N2 and DC-pulsed plasma nitriding unit.
The surface, cross section and the thickness of diffusion of specimens was studied in terms of optical and scanning electron microscopy. According to the measurements of diffusion layer thickness, values of Q and D0 for nitrogen diffusion in substrate were calculated as 50585 (j/mol) and 4.11×10-10 (m2/s)respectively. The variations of depth of hardness during nitriding period was determined
