27SiMn轧制表面裂纹缺陷原因分析

通过采用化学成分分析、光学显微镜、扫描电镜和能谱仪等分析手段对27SiMn轧制开坯表面出现的裂纹缺陷原因进行分析,结果表明;27SiMn轧制开坯表面出现大量的裂纹缺陷主要是由于钢锭表层夹杂物聚集形成夹杂物铁素体带状组织缺陷,轧制开坯产生表面裂纹。     

Properties of NixZn(1−x)Fe2O4 thick films at microwave frequencies

The thick film Ni_xZn_(1−x)Fe₂O₄ on alumina substrate was prepared by screen printing of the ferrite powder synthesized by chemical co-precipitation method using nitrate precursors. These Ni_xZn_(1−x)Fe₂O₄ thick films of varying x were characterized by X-ray diffraction, FTIR spectroscopy and SEM (scanning electron microscopy). The permittivity and permeability were measured by overlay technique. Voltage standing wave ratio method was also used to measure the dielectric constant. The permittivity was found to increase with Ni content varying between 13 and 18. The permeability was ∼3.01. The overlay technique provides an easy method for measurement of permittivity and permeability of ferrite thick film.     

The use of ferrites as highly active oxygen storage materials for chemical looping hydrogen production under intermediate temperature

Shifting chemical looping from high temperatures to intermediate temperatures could mitigate the materials from sintering and benefit for longer durability as well as process economy. However, oxygen carriers cannot perform sufficiently due to the degrading effect at lower temperatures, resulting in the decrease of hydrogen production ability. Although doping precious metals can improve the poor performance at intermediate temperatures, the high cost impeded their large-scale application. In this paper, a range of oxygen carrier materials consisted of earth abundant elements were prepared for chemical looping hydrogen production. The results indicated that CoFe₂O₄ exhibited the highest hydrogen yield of 11.9 mmol·g⁻¹ and hydrogen production rate of 0.051 mmol g⁻¹·s⁻¹ at 650 °C, which was 1.7 times higher than that of Fe₂O₃. A combined experimental and DFT calculation method was used to understand the mechanism behind the performance. The results indicated that the synergistic effect between Co and Fe increased the reactivity of the ferrite materials. The enhanced hydrogen production performance was attributed to the high reduction degree and reversible phase change. This study can be also extended to develop more active oxygen carrier for chemical looping processes at intermediate temperatures.     

EBSD analysis of a Ti-IF steel subjected to hot torsion in the ferritic region

The effect of grain size on the warm deformation behaviour of a titanium stabilized interstitial free steel was investigated using hot torsion. Tests were performed at temperatures between 765 °C and 850 °C at strain rates between 0.003 s⁻¹ and 1 s⁻¹ for samples with grain sizes of 25 μm, 75 μm and 150 μm. The structures were observed using EBSD analysis and are consistent with those expected for materials dominated by dynamic recovery. Some evidence was found for small amounts of thermally induced migration of pre-existing boundary (bulging) and for the generation of new segments of high angle boundaries by continuous dynamic recrystallization. The early onset of a steady-state flow stress in the finer grained samples is attributed to one or a combination of thermally induced boundary migration and enhanced rates of recovery near subgrain (and grain) boundaries.     

Magnetic Properties of Y3Fe5O12 Nanoparticles Doped Bi and Ce Ions

Y_2.9-xCe_0.1Bi_xFe₅O₁₂ (x = 0-0.5) nanoparticles ranging from 58 to 63 nm were fabricated by a sol-gel method, and their crystallite structures and magnetic properties were investigated by X-ray diffraction (XRD), IR spectroscopy, and vibrating sample magnetometer (VSM). Results of VSM show that the saturation magnetization intensity increased with increase in Ce content (0.1), decrease in Bi concentration (x), and increase in particle size of the formulation.     

Effect of Chromium on Magnetic Properties of Y2.9Ce0.1Fe5-xCrxO12 Nanoparticles

Y_2.9Ce_0.1Fe_5-xCr_xO₁₂ (x = 0-0.5) nanoparticles were fabricated by a sol-gel method. Samples with particle size ranging from 60 to 64 nm were obtained and their crystalline structures and magnetic properties were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Results of VSM show that the saturation magnetization is increased firstly, after decreased with the Cr concentration (x). The saturation magnetization is increased with increasing the particle size.     

锶与二溴对甲偶氮羧显色反应的研究及其分析应用

研究了二溴对甲偶氮羧与锶（Ⅱ）的显色反应,考察了反应条件和分析特性。在Ｈ_３ＢＯ_３-Ｎａ_２Ｂ_４Ｏ_７缓冲溶液中,试剂与 Ｓｒ~(２＋)形成２：１的络合物,在 ６２０ｎｍ处的摩尔吸光系数 ε＝１．８９×１０~４。 Ｓｒ~(２＋)量在 ０．２５—１．２５μｇ／ｍＬ范围内,服从比尔定律。设计了测定铁氧体样品中锶的新方法,结果满意。     

铁氧体法处理含铬和镉废水的研究

用铁氧法处理含铬和镉废,在pH值为12、温度为70℃、滴加适量双氧水时,即可得磁性较强的铁氧体,同时,被处理后的废水中铬和镉的含量分别降低至0．008mg/L和0．041mg/L,均达到排放标准。     

钢的氧化物冶金技术

介绍了氧化物冶金技术的概念及发展现状,晶内铁素体的作用和形成机理,氧化物种类对晶内铁素体形成的影响及脱氧剂的选择;钢中氧浓度、凝固过程中冷却速度对氧化物夹杂尺寸和数量的影响。以钛脱氧钢为例,指出了有利于晶内针状铁素体形成的夹杂物尺寸、数量、奥氏体晶粒尺寸、氧浓度、铝浓度和氮浓度。     

Soft magnetic and high-frequency properties of Ni-Zn ferrite film with FeMn underlayer

Ni_0.45Zn_0.55Fe₂O₄ (40 nm) single-layer and Fe₅₀Mn₅₀ (25 nm)/Ni_0.45Zn_0.55Fe₂O₄ (40 nm) bilayer films were prepared on Si(111) substrates by radio frequency magnetron sputtering at room temperature, and the influence of FeMn underlayer on the microstructure and magnetic property of Ni-Zn ferrite film has been investigated. It was found that the introduction of Fe₅₀Mn₅₀ underlayer resulted in a decrease from 7.1 to 3.1 kA/m in coercivity and increase from 0.22 to 0.60 in residual magnetization ratio of the ferrite film. The complex permeability μ = μ′ − iμ″ values of the films were measured at a frequency of up to 5 GHz. An obvious resonance peak at about 1.65 GHz of the bilayer film appeared in the permeability spectrum. The reason has been researched preliminarily and was ascribed to the change of the film's microstructure with FeMn underlayer.