A method is described for coating fine iron particles(~1 μm) with a uniform silica layer, produced by the hydrolysis of tetraethyl orthosilicate. The presence of a small amount of gelatin on the surface of the iron p...A method is described for coating fine iron particles(~1 μm) with a uniform silica layer, produced by the hydrolysis of tetraethyl orthosilicate. The presence of a small amount of gelatin on the surface of the iron particles facilitates this process. The X ray photoelectron measurements indicated that the gelatin interacted with the surface of the iron particles by means of both nitrogen(in —NH 2 groups) and oxygen(in —COOH groups) and then bound to the silica. The silica coating increases the resistance of the iron particles to oxidation on heating in air, which makes the temperature at which an observable oxidization occurs from 330 ℃ to 400 ℃ raised.展开更多
The structures and chemical states of SiO2/α-FeOOH and SiO2/α-Fe2O3 Ane particles haye been investigated by the technologies of HREM, XPS and CELS. The results show that a crystalline interface layer between SiO2 co...The structures and chemical states of SiO2/α-FeOOH and SiO2/α-Fe2O3 Ane particles haye been investigated by the technologies of HREM, XPS and CELS. The results show that a crystalline interface layer between SiO2 coating and α-FeOOH nucleus is formed, and its chethecal composition is infered to be α-Fe2O3. In view of this, a mechanism of its formation is presented. The results also show that the coating of SiO2/α-Fe2O3 obtained from SiO2/α-FeOOH by a thermal treatment is converted from an amorphous to crystal, line one and its mechanism is discussed. In addtion, the effects of the coating on the structuxe of vacant state above Fermi level of α-FeOOH fine particles have also been studied.展开更多
文摘A method is described for coating fine iron particles(~1 μm) with a uniform silica layer, produced by the hydrolysis of tetraethyl orthosilicate. The presence of a small amount of gelatin on the surface of the iron particles facilitates this process. The X ray photoelectron measurements indicated that the gelatin interacted with the surface of the iron particles by means of both nitrogen(in —NH 2 groups) and oxygen(in —COOH groups) and then bound to the silica. The silica coating increases the resistance of the iron particles to oxidation on heating in air, which makes the temperature at which an observable oxidization occurs from 330 ℃ to 400 ℃ raised.
文摘The structures and chemical states of SiO2/α-FeOOH and SiO2/α-Fe2O3 Ane particles haye been investigated by the technologies of HREM, XPS and CELS. The results show that a crystalline interface layer between SiO2 coating and α-FeOOH nucleus is formed, and its chethecal composition is infered to be α-Fe2O3. In view of this, a mechanism of its formation is presented. The results also show that the coating of SiO2/α-Fe2O3 obtained from SiO2/α-FeOOH by a thermal treatment is converted from an amorphous to crystal, line one and its mechanism is discussed. In addtion, the effects of the coating on the structuxe of vacant state above Fermi level of α-FeOOH fine particles have also been studied.
