Evolution of the composition and structure of PAN carbon fiber during preoxidation

Using scanning electronic microscope, X-ray diffraction analysis, PYR-GCMS and IR etc., we studied the evolving process of the composition and structure of PAN carbon fiber during preoxidation. In the initial stage of preoxidation, PAN filament tows disappear and become semi-thaw. At first, reactions happen between the copolymers and esters disappear. The molecules annularly crosslink and the index of cyclation slowly increases. It is easy to fix the structure and form defects during the initial and the medium stages, which are most reactive. More traction is advised in these stages to minimize the structural deficiencies. In the medium stage of preoxidation, the fiber was reshaped into new sheet stacks and gradually changed to sheet sectors, and this structure tends to be stable in the final stage. Induced by acid and ester copolymer, PAN fiber forms a very stable cycle structure in the final stage. Besides, monomer, dimmer and trimer obviously decrease. In the final stage of the preoxidation, there exi     

含砷金矿的磁场强化生物预氧化

生物氧化;浸金工艺;含砷金矿的磁场强化生物预氧化     

Corrosion product build-up on stainless steel and its influence on hydrazine decomposition.60Co deposition in loop tests using borated water at 300°C

The corrosion rate of stainless steel decreases with time of operation under conditions characteristic of the primary circuit of pressurized-water reactors. Due to this the concentration of corrosion products in solution rapidly increases during heating-up and decreases after reaching the operation product levels is up to about three orders of magnitude. By a preoxidation treatment using potassium dichromate, the corrosion product release can be essentially diminished. In order to describe the influence of corrosion products in solution we investigate the thermal decomposition of hydrazine as well as the deposition behavior of⁶⁰Co. the half life of the thermal N₂H₄ decomposition at 300°C in borated water increases from about 1 to about 60 minutes, starting with glossy loop surfaces. Without adding boric acid to the water, half lives between 1 and 120 minutes were found; with an activation energy for the decomposition being estimated in the temperature region 270–310°C. The deposition behavior of⁶⁰Co is characterized by a very fast primary step, followed by retarded secondary deposition steps. The primary deposition step can be described by half lives of about 5 seconds. The influence of preoxidation treatment and subsequent decrease of corrosion product concentration on decomposition of N₂H₄ and deposition of⁶⁰Co is discussed.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991.Deceased (April 23, 1991).     

预氧化固气法合成LiNiO2的研究

LiNiO₂ was prepared by reaction of stoichiometric amounts of thoroughly-mixed LiOH·H₂O and preoxidation nanometer-scale Ni₃O₂(OH)₄ powders in O₂ at the temperature of 700℃ for 6h. The products were tested by XRD， XPS， SEM and electrochemistry methods. It was shown that product was LiNiO₂ single-phase， and the valence of nickel was +3; the average size of it was 40nm; its initial charge specific capacity is 168mAh·g^-1 and the coulomb efficiency is 90%; the second charge specific capacity is 160mAh·g^-1 and the coulomb efficiency is 96%.     

PAN基中空纤维炭膜炭化条件的研究

研究了以ＰＡＮ其中空纤维膜为基质制备中空纤维央膜的过程。考察了ＰＡＮ厚膜的预氧化和炭化条件对中空纤维炭膜Ｈ２，Ｎ２气体渗透性和选择性的影响。结果表明，预氧化温度和时间对Ｈ２，Ｎ２气体的渗透速率有一定影响；