Papers by Author: Hai Li Yang

Abstract: Magnetic properties of silicon steel mainly depend on the internal organizational structure and chemical composition. The main factors affecting magnetic properties of silicon steel are analyzed and summarized, including grain size, inclusions (size, type, quantity, and morphology), crystal texture, internal stress, dimensional accuracy, the surface quality of steels, and chemical composition. The impact mechanism of the factors influencing silicon steel magnetic property is explained and these influence factors are interrelated.

Abstract: The General Status of the Refractory Metal was Reviewed Including its Characteristics and Application. the New Technology Research of Directly Prepared Refractory Metal from Refractory Metal Oxide was Discussed. FFC, OS and SOM Methods were Mainly Introduced. at the same Time, their Advantages and Disadvantages and the Difference between each other were also Pointed out. the Development Trends and Application Prospect of the Refractory Metal in Future were Prospected.

Abstract: Boronized layer was prepared on silicon steel substrate by pulse electrodeposition in KCl-NaCl-NaF-Na2B4O7 molten salts with different current density. The effect of current density on composition and microstructure of boronized layer was studied. The phase, the cross-sectional morphology and the compositional depth profile of the layer were studied by X-ray diffraction analysis (XRD), optical microscopy (OM) and glow discharge spectrometry (GDS). The presence of FeB on the surface of the boronizied steel was confirmed by XRD analysis. Cross sectional observation revealed that the boronized layer consisted of the outer layer FeB and the sublayer Fe2B. In addition, the low current density produced more proportion of Fe2B and bigger saw-tooth grains.

Abstract: The siliconized layers were formed on the surface of hot rolled grain oriented silicon steel using a molten salt pulse electrodeposition method. The process was performed in the temperature range 1023-1123 K and with varying deposition time (60-180 min). The profile distribution of Si in the siliconized layer was measured using the glow discharge spectrometry (GDS) and the depth from the surface to the substrate was taken as the layer thickness. The morphology and structure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that a longer deposition time tended to produce a larger grain and a looser, rougher layer. The phase structure of the layer was composed of Fe3Si with (110) preferred orientation in the experimental range. The longer deposition time resulted in an increase in thickness layer and the thickness of the layers ranged from 17 to 165m. Kinetic studies showed that the siliconized layer grew with a parabolic rate law, indicating the diffusion controlled growth. The activation energy for growth of siliconized layer was about 242 kJ/mol.

Abstract: The siliconized layer on low silicon steel substrate was produced under pulse current conditions from KCl-NaCl-NaF-SiO₂ molten salt and the effects of frequency on the composition and microstructure were investigated. The results showed that at the same average current density and other experimental conditions, Si content in the surface and the layer thickness decreased with increasing frequency. Low pulse frequency (500 Hz) and high frequencies (1500, 2000Hz) produced coarse grain and bigger surface roughness. There was a flat fine grain structure and a relatively thick (30m) layer when the frequency was 1000Hz. However, the effect of pulse frequency on the structure of the layer was not obvious. The phase structure of the layer was composed of Fe₃Si with (110) preferred orientation at all experimental frequencies.

Abstract: Boronizing of silicon steel is performed by electrodeposition in KCl-NaCl-NaF-Na2B4O710H2O molten salts with different amounts of borax. The effect of borax content on composition and microstructure of boride layer is studied. The compositional depth profile of boride layer is measured using the glow discharge spectrometry (GDS) and the depth from the surface to the substrate is taken as the layer thickness. The surface morphology is studied by atomic force microscopy (AFM). It is found that the thickness of the boride layer reached maximum values when the borax content is 0.05mol. The roughness decreases with raising borax content from 0.01 to 0.05mol while the further increase of borax content from 0.05 to 0.1mol results in increase of roughness. The boride layer formed at borax content 0.05 mol shows smallest values of surface roughness.

Abstract: The siliconized layer was pulse electrodeposited on grain oriented low-silicon steel sheet substrate in KCl-NaCl-NaF-SiO2 molten salts and the influence of duty cycle on the composition and microstructure of the siliconized layer was investigated. The results showed that when the duty cycle was in the range of 10% to 50% at average current density 30mA/cm2, Si content of siliconized layers was similar and the thickness of the layer was did not change much with different duty cycle. Cross sectional observation revealed that the siliconized layers had a two-layer structure. The top layer composed of columnar grains and a transition layer with equiaxed grains was close to the substrate. The layer was unsmooth when the duty cycle was 10%. While the surface appeared smooth and dense and the grains were fine when the duty cycle were 20% and 30%. The layer became more porous as the duty cycle increased to 40% and 50%.

Abstract: Fe3Si layer was prepared by pulse eletrodeposition of Si on the surface of non-oriented steel in molten salts. With an orthogonal test the optimal process parameters were determined: the formulation of salts was NaCl:KCl:NaF:SiO2=1:1:3:0.3(mole ratio), current density of 60 mA/ cm2, duty cycle of 30%, pulse period of 1000 s and a deposition time of 50 min, respectively. The compositional depth profile, the structure, the surface morphology and cross sectional micrograph of the layer were studied by glow discharge spectrometry (GDS), X ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscope (OM). The results showed that Si in the layer existed in the form of the gradient distribution. The phase structure of the layer was composed of the single-phase Fe3Si. The layer composed of equiaxed grains. The surface appeared smooth and dense, and with uniform thickness.

Abstract: A Si diffusion layer on grain-oriented low-silicon steel substrates was produced by pulse electrodeposition in KCl-NaCl-NaF-SiO2 molten salt and the effect of current density upon the composition and microstructure of the siliconized layer was investigated. The results showed that by glow discharge spectrometry (GDS), the change of Si content of siliconized layers was similar in the range of 20-60 mA/cm2. Si content in the surface was maximum, and then dropped sharply within the surface layer (< 7 m). The Si content remained nearly constant in the middle part of the siliconized layer. The content of Si near to the substrate decreased relatively slowly. The Si content in the surface and the layer thickness increased with increasing current density. Cross-sectional observations revealed that the Si diffusion layers had a two-layer structure: the top layer composed of columnar grains grown perpendicularly to the substrate surface and a transition layer with equiaxed grains was close to the substrate. In addition, the thickness of the layer was too small when the current density was 20 mA/cm2, while the layer became more porous as the current increased from 40 to 60 mA/cm2 according to SEM observations. The optimum current density for deposition was 30 mA/cm2.

Abstract: Nano-TiO2 was modified with a titanate coupling agent, LICA38 [neopentyl (dially) oxy, tri (-dioctyl) pyrophosphate titanate]. X-ray photoelectron spectroscopy (XPS) was used to evaluate the surface characteristics of the bare and the modified nano-TiO2. It was demonstrated that the carbon content of the bare TiO2 is 37.9 atm. %, and that of the modified TiO2 is 47.2 atm. %. Moreover, the density of the -C-H (-C-C) and -C-O groups increases due to modification, and the atomic percentage of C=O and -OH groups reduces. These results indicate that the -C-H (-C-C) and -C-O groups from LICA38 have been introduced to the surface of nano-TiO2 by coupling reaction with the hydroxyl groups.