添加锰粉对铝碳耐火材料抗氧化性的影响

石墨和结合碳的氧化是铝碳耐火材料在使用中损坏的重要原因之一.研究了锰粉在铝碳耐火材料中的行为以及作为抗氧化剂的作用,并与仅添加Si或Al试样的性能相比,添加Mn试样的抗氧化性明显增大,且Mn的含量为3%左右,复合添加Si和Mn试样的抗氧化性均有大大提高.在高温下Mn在含碳材料中能促进易被氧化的石墨边棱活性炭、结合剂残碳形成难被氧化的C-C键结构,使含锰试样抗氧化大大提高,另外在高温下形成的硅酸锰熔体作为一道屏障也起到了延缓或阻止碳氧化的作用.     

Kinetics of reductive leaching of manganese oxide ore using cellulose as reductant

The kinetics of reductive leaching of manganese from a low-grade manganese oxide ore were studied using cellulose as reductant in dilute sulfuric acid medium.It was found that when the stirring speed was higher than 200 r/min,the effect of gas film diffusion on manganese extraction efficiency could be neglected,and the kinetic behavior was investigated under the condition of elimination of external diffusion influence on the leaching process.Effects of leaching temperature,mass ratio of cellulose and ore,and the sulfuric acid concentration on manganese extraction efficiency were discussed.The kinetic data were analyzed based on the shrinking core model,which indicated that the leaching process was dominated by both ash layer diffusion and chemical reaction at the initial stage,with the progress of leaching reaction,the rate-controlling step switched to the ash layer diffusion.It was also concluded that the sulfuric acid concentration had the most significant influence on the leaching rate,the reaction orders with respect to the sulfuric acid concentration were 2.102 in the first 60 min,and 3.642 in the later 90 min,while the reaction orders for mass ratio of cellulose and ore were 0.660 and 0.724,respectively.An Arrhenius relationship was used to relate the temperature to the rate of leaching,from which apparent activation energies were calculated to be 46.487 kJ/mol and 62.290 kJ/mol at the two stages,respectively.Finally,the overall leaching rate equations for the manganese dissolution reaction with cellulose in sulphuric acid solution were developed.The morphological changes and mineralogical forms of the ore before and after the chemical treatment were discussed with the support of SEM and XRD analyses.     

Mechanism of boron oxide as a phase regulator for modification of manganese slag

The current research focused on adjusting the low hydration activity of the metallurgical slag by phase reconstruction technique. Boron oxide was used as a phase regulator to improve the amorphous phase composition of the manganese slag, consequently enhancing its hydraulic activity. The effects of boron oxide dosage and calcination temperature on the manganese slag amorphous phase content were investigated. XRD and DTG were performed to analyze the hydration mechanism of the manganese slag powder and cement. Results show that, when boron oxide dosage is 15%, calcination temperature is 1 300 ℃, and holding time for 1 hour, the amorphous content of the modified manganese slag reaches 95% and its 28-day activity index reaches 81.7%. The manganese slag powder can then be used as cement or concrete admixtures for the building materials industry.     

40NiCrMo7钢表面锰系磷化膜的制备及耐蚀性

为了满足紧固件在工业中的实际应用,采用不同磷化工艺于40NiCrMo7钢表面制备了锰系磷化膜,并作为紧固件的表面腐蚀防护层.运用扫描电子显微镜、能谱仪、X射线衍射仪、盐雾腐蚀试验机与电化学测试系统对磷化膜的结晶组织、相结构及耐蚀性进行了研究.结果表明,磷化膜的主要相结构为MnHPO_4·2.25H_2O;在工艺Ⅱ条件下,锰系磷化膜组织均匀致密,且覆盖完整;磷化膜的腐蚀速率为0.018 mm/a,同时腐蚀防护率高达97.20%;经240h盐雾腐蚀试验后,磷化膜在工艺Ⅱ条件下的腐蚀面积仅为1%.     

添加锰粉对铝碳耐火材料抗侵蚀性的影响

石墨和结合碳的氧化是铝碳耐火材料在使用中损坏的重要原因之一．研究了锰粉在铝碳耐火材料中抗渣蚀性的作用，与仅添加Si或Al的试样相比，添加Mn的试样抗侵蚀性较低，复合添加Si和Mn的试样的抗侵蚀性均有提高．     

Influence of Cr2O3-Al2O3 composite oxide scale on oxidation resistance of ZG40Cr24

Test alloys ZG40Cr24 with alloying of 3 wt% aluminium were cast by intermediate frequency induction furnace. The oxidation resistance of test alloys at 1 000 ℃ for 500 hours was examined according to oxidation weight gain method. The scale morphology and composition were studied using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. By energy dispersive spectroscopy (EDS) studies, a kind of composite oxide scale compounded highly by Cr2O3, Al2O3 and spinel MCr2O4 in molecule scale came into being at high temperature. With flat and compact structure, fine and even grains, such composite scale granted complete oxidation resistance to alloy ZG40Cr24. The oxidation resistance mechanism was studied deeply in electrochemistry corrosion. The P+N semiconductor composite scale composed plenty of inner PN junctions, of which the unilateral conductive and the out-of-order arrangement endowed itself insulating in all directions. The positive and negative charges in scale could not move, and the mobile number and transferring rate of them both dropped enormously, as a result, the oxidation rate of the matrix metal was cut down greatly. So the composite scale presented excellent oxidation resistance.     

低品位锰矿制备硫酸锰的研究

以铁矿精选后的尾矿-硫精砂为还原剂,用硫酸直接浸出锰含量为15％左右的低品位锰矿,可得到较好技术指标的硫酸锰产品,锰的浸出率在97％以上,锰回收率可达92．39％．实验得出当锰矿粉、硫铁矿和硫酸三者的质量比为1：0．2：0．46,浸出时间为10h时,锰浸出效果较佳,且副产品酸性白土的产率为51％～72％．     

Evaluation of metal-doped manganese oxide octahedral molecular sieves in catalytic reduction of NOx from cigarette mainstream smoke

A series of Ag, Cu and Co-doped manganese oxide octahedral molecular sieves (OMS-2) were synthesized and evaluated to remove nitrogen oxides (NO _x ) from cigarette mainstream smoke. The three kinds of catalysts were added to cigarettes for studying the capabilities of reducing NO _x from cigarette mainstream smoke. The catalysis and reduction of NO in laboratory were studied. A mechanism for NO _x catalytic reduction from burning cigarettes with the catalysts adding to cigarettes was described. The catalysts show excellent catalytic activity for NO _x removal, especially the Ag-doped OMS-2 catalyst. 0.5% (mass fraction) Ag-doped OMS-2 catalyst has the best ability to remove NO _x from cigarette mainstream smoke. The use of Ag-doped OMS-2 as catalyst for removing carcinogenic compounds from cigarette smoke will be an effective strategy to protect the environment and public health.     

Influence of TiO<Subscript>2</Subscript> on the alkali resistance and structure of invert glass

Through measuring the alkali resistance of the invert glass and the quanity of SiO₂ and TiO₂ migrating fron the glass into the solution, the influence of TiO₂ on the alkali resistance of the glass is discussed and its structure is also analyzed by infrared spectroscopy. It is concluded that TiO₂ has double functions for the alkali resistance of the invert glass. On the one hand, both TiO₂ polarizing the secondary ions in glass and TiO₂ isomorphism replacement of SiO₂ make the alkali resitance of the glass decrease. On the ther hand, TiO₂ patching network and anti-erosion covering help to increase the alkali resistance. ZHAO Qing-lin: Born in 1972 Funded by the National Natural Science Foundation of China(No. 59372081)     

Influence of Impact Energy on Impact Corrosion-abrasion of High Manganese Steel

The impact corrosion-abrasion properties and mechanism of high manganese steel were investigated under different impact energies. The result shows that the wearability of the steel decreases with the increase of the impact energy. The dominant failure mechanism at a lower impact energy is the rupture of extrusion edge along root and a slight shallow-layer spalling. It transforms to shallow-layer fatigue flaking along with serious corrosion-abrasion when the impact energy is increased, and finally changes to bulk flaking of hardened laver caused by deeo work-hardening and heaw corrosion-abrasion.