铅铁团簇的计算机模拟计算

铁作为著名的磁性材料及应用广范的催化材料,铁团簇已经在实验和理论上被研究了多年。铅具有高导热性、化学惰性以及高沸点等特点,且作为目前我国应用最广的铅酸电池的主要材料,铅团簇的理论研究也一直是一个热点。随着计算机运行速度以及计算机模拟技术的发展,应用密度泛函理论对其结构以及电子性质的研究日益增多。为了研究铅铁合金团簇的内部结构,探明铅与铁间相互作用的机理,进一步提高铅铁合金团簇的稳定性,综述了近年来国内外应用密度泛函理对铅铁团簇的研究现状,同时重点介绍了铅与铁单原子团簇目前的研究进展,旨在为研究铅铁合金团簇间的相互作用行为提供理论依据。

铁基氧化物团簇催化CO还原NO反应模拟

固定床实验表明,在深度欠氧的条件下,铁基氧化物对CO还原NO的反应具有催化作用.为进一步理解脱销催化反应机理,本文利用量化软件Gaussian模拟了铁及其三种不同价态氧化物团簇:Fe_(2)团簇、Fe_(2)O_(2)团簇、Fe_(2)O_(3)团簇催化CO还原NO的反应路径,为进一步改进脱硝反应提供理论基础.本文分析了反应过程的各阶段能量壁垒,三种团簇中最容易发生催化反应的团簇为Fe_(2),整个反应过程中的决速步为NO在Fe_(2)团簇上的解离吸附过程.

Fe_(55)团簇预熔化的分子动力学研究

本文运用分子动力学模拟小尺寸铁团簇在熔点附近的预熔化现象,根据均方根键长涨落判断出预熔化现象发生的温度区间并讨论在此温度区间内能量和结构的关系.结果表明,在团簇体系预熔化过程中,表面原子是先于内部熔化,随着温度的增加,两部分原子在熔点附近相互扩散,趋于无序并最终完全熔化.

Flavanoids from Clematis hexapetala

Aim To study the chemical constituents from the roots and rhizomes of Clematis hexapetala Pall.. Methods The components were isolated by means of solvent extraction, repeated chromatography with silica gel, sephadex LH-20 and prep-HPLC. The structures were determined by spectrum analysis. Results Twelve flavonoids were isolated and their structures were identified as 3, 5, 6, 7, 8, 3＇, 4＇-heptamethoxyflavone （1）, nobiletin （2）, liquiritigenin （3）, hesperetin （4）, naringenin （5）, liquiritigen-7-O-β-D-glucopyranoside （6）, 5,7, 4＇ -trihydroxy-3＇- methoxyflavanone -7-O-α-L-rhamnopyranosyl （ 1→6 ） -β-D-glucopyranoside （7）, 6-hydroxybiochain A （ 8）, formononetin （9）, daidzein （10）, genistein （11）, and tectoridin （12）. Conclusion All the said compounds were isolated from the plant for the first time.

Fen（n=2～20）团簇的结构、电子和磁性对大小的依赖

使用紧束缚(TB)多体势和遗传算法(GA),计算了Fen (n=2-20)团簇的基态结构.从优化结构出发,使用自洽的紧束缚3d、4s、4p模型哈密顿,计算了每原子平均磁矩(μ)n和向上与向下自旋电子态密度DOS.对小(n≤6)的团簇,Fen的平衡结构非常类似于惰性气体团簇,与硬球堆积相一致.7～12个原子团簇的结构由二十面体的骨架棗五角环组成.14～19个原子团簇形成六角环形结构.所计算的所有团簇的(μ)n都大于块体值,并随着团簇增大缓慢地非单调性地减小.平均配位数、团簇中局域配位数的分布和spd杂化都是影响电子和磁学特性的重要因素.

Effect of Na_2CO_3 on reduction and melting separation of ludwigite/coal composite pellet and property of boron-rich slag

The effects of Na_2CO_3 on the reduction and melting separation behavior of ludwigite/coal composite pellet, the desulfurization ratio and the property of the separated boron-rich slag were investigated at laboratory scale in the present work. Na_2CO_3 could improve the reduction rate of the composite pellet to some extent. The melting separation of the composite pellet became increasingly difficult with the increase of Na_2CO_3 in the pellet due to the sharply increasing of the melting point of slag. The sulfur content of the iron nugget gradually decreased from 0.27% to 0.084%（mass fraction） with the Na_2CO_3 content in the pellet increasing from 0 to 6%. The efficiency of extraction of boron（EEB） of the slow cooled boron-rich slag decreased from 86.46% to 59.52% synchronously. Na_2CO_3 had obviously negative effect on melting separation of the composite pellet and boron extraction of the boron-rich slag.

Magnetic properties of small Fe clusters: a nonorthogonal Hamiltonian study

We calculate the magnetic properties of small Fe N clusters( N =2～7,9,13,15) by using a parameterized Hubbard tight binding spd band model Hamiltonian, with the parameters obtained from nonorthogonal Hamiltonian parameters. the average magnetic moments, and the spin polarized charge distribution within clusters are in agreement with those obtained by first principle and tight binding calculations. The effect of the nonorthogonal basis is discussed.

陈毅的思想政治教育艺术

1927年8月上旬,从武汉中央军事政治学校出发的陈毅,在江西宜黄追上了正南下广东的南昌起义军,被分配到号称'铁团'的第11军第25师73团任政治指导员。当时的73团作战勇猛,但有不少官兵却对政工干部持保留态度,认为他们不善打仗又满嘴空话。为了打开工作局面,陈毅决心以身作则,从而感染带动身边的人。

Effect of pyroxenite and olivine minerals as source of MgO in hematite pellet on improvement of metallurgical properties

Pelletization of hematite ore requires high fineness and very high induration temperature（~1325 ℃） owing to its poor diffusion bonding unlike magnetite ore. Further, high-alumina hematite pellets show very high reduction degradation index（RDI） during low temperature（500-650 ℃） reduction due to their volume expansion and lattice distortion. Noamundi（India） hematite ore contains very high Al2O3（2.3%） with adverse ratio of alumina to silica（~2） for which, it shows very high RDI. In this work, the acid pellets prepared from Noamundi ore fines of optimum Blaine fineness show good cold crushing strength（CCS）. However, it shows very high RDI（77%）. In order to reduce RDI, Mg O in form of two different gangue-containing fluxes, such as pyroxenite and olivine in varying quantities has been added. The optimum requirement and performance of these fluxes has been examined and compared. Both pyroxenite and olivine fluxed pellets show significant lowering of RDI（26% and 23%, respectively） and improvement of other properties, viz CCS, swelling indices etc with good reducibility（70%-77%）. Finally, a good quality acidic hematite pellet was developed from high-alumina ore without using any lime which is very important charge material in combination of basic sinter in blast furnace.

Mathematical models and expert system for grate-kiln process of iron ore oxide pellet production.Part Ⅱ:Rotary kiln process control

Rotary kiln process for iron ore oxide pellet production is hard to detect and control.Construction of one-dimensional model of temperature field in rotary kiln was described.And the results lay a solid foundation for online control.Establishment of kiln process control expert system was presented,with maximum temperature of pellet and gas temperature at the feed end as control cores,and interval estimate as control strategy.Software was developed and put into application in a pellet plant.The results show that control guidance of this system is accurate and effective.After production application for nearly one year,the compressive strength and first grade rate of pellet are increased by 86 N and 2.54%,respectively,while FeO content is 0.05% lowered.This system can reveal detailed information of real time kiln process,and provide a powerful tool for online control of pellet production.

Self-magnetization of pyrite and its application in flotation

Pyrite is a special weakly magnetic mineral containing Fe(II). Its self-magnetization only by adjusting slurry temperatureand pH value was able to enhance its magnetism, producing the so-called the magnetized pyrite, which was further used as magneticseeds in the flotation of pyrite ore to promote flotation recovery. Tests, such as self-magnetization, vibrating sample magnetometer(VSM), XPS, size analysis and flotation were carried out. The optimal conditions of the pyrite self-magnetization were pulp pH of11.81 and temperature of 65 °C. The magnetized pyrite was characteristic of the valence change of elemental iron, resulting instronger magnetism of the magnetized pyrite than that of the original pyrite. Then, this magnetized pyrite was applied to the magneticseeding flotation (MSF) of pyrite ore. It was found that the recovery of pyrite flotation grew with the increase of magneticsusceptibility of the magnetic seeds?the magnetized pyrite; and the proper dosage of the magnetized pyrite was 100 g/t. The reasonbehind the increased recovery lies in that the magnetized pyrite promoted the magnetic agglomeration between fine pyrite particles;and the fact that the stronger the magnetism of the magnetized pyrite, the larger the aggregate size, indicates that the agglomeration issomewhat in line with the flotation, also confirming that the MSF is more suitable for fine particles than traditional flotation.

Kinetic model research on drying characteristics of artificial magnetite green pellet

In this study,the effects of drying temperature,hot airflow speed and diameter of green pellet on drying rate of artificial magnetite pellet were deeply investigated to clarify the drying characteristics of artificial magnetite green pellet.The results show that the drying process of artificial magnetite green pellet has three stages,accelerated drying stage,constant drying stage and decelerated drying stage.And drying temperature and hot airflow speed both have significant reciprocal effects on moisture ratio and drying rate of green pellet during the drying process.However,the diameter of green pellet has little effect on drying process of green pellet.Then the drying fitting models of Correction Henderson and Pabis,Lewis,Correction Page(III),Wang and Singh are used to describe the drying kinetics of artificial magnetite green pellet.The fitting results indicate that the drying process of artificial magnetite pellet can be described by Correction Page(III)model accurately.Finally,the contrast experiments demonstrate that the fitting model can well describe the actual drying process.

Effect of B2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP were also examined using the simulated coke oven gas (COG). The results suggested that the CS of CVTP was increased from 2448 to 3819.2 N, while the porosity of CVTP was decreased from 14.86% to 10.03% with the increase in B2O3 addition amounts. Moreover, the B2O3 mainly existed in the forms of TiB0.024O2 and Fe3BO5 in both CVTP and the reduced CVTP. Specifically, the CS of the reduced CVTP was elevated from 901 to 956.2 N, while the RSI was reduced from 5.87% to 3.81% as the B2O3 addition amounts were increased. Taken together, B2O3 addition would facilitate the aggregation and diffusion of metallic iron particles, which contributed to reducing the formation of metal iron whiskers and weakening the reduction swelling behavior.

Influence of flux additives on iron ore oxidized pellets

Six additives,i.e.,limestone,lime,magnesite,magnesia,dolomite and light-burned-dolomite,were added for investigating their influences on the pellet quality.For green balls,adding lime and light-burned-dolomite makes the wet drop strength decrease firstly,and then increase with further increase of additive dosage.Ca(OH)2 affects the bentonite properties at the beginning,but the binding property of Ca(OH)2 will be main when the dosage is higher.The other four additives decrease the drop strength for their disadvantageous physical properties.For preheated pellets,no mater what kind of additive is added,the compressive strength will be decreased because of unmineralized additives.For roasted pellets,calcium additives can form binding phase of calcium-ferrite,and suitable liquid phase will improve recrystallization of hematite,but excessive liquid will destroy the structure of pellets,so the compressive strength of pellet increases firstly and then drops.When adding magnesium additives,the strength will be decreased because of the oxidation of magnetite retarded by MgO.

Oxidation and roasting characteristics of artificial magnetite pellets

Compared with natural magnetite concentrate, artificial magnetite with more lattice defects and higher activity tends to be oxidized. And the artificial magnetite pellet at the temperature of 400℃ has the oxidation degree approaching to natural magnetite concentrate pellet fired at 1000℃. Besides, two kinds of pellets displayed quite different roasting characteristics. When preheated at the same temperature for the same period of time, natural magnetite concentrate pellet and artificial magnetite concentrate pellet need to be roasted at the temperature of 1100℃ and 1250℃, respectively, for 25 min to reach the compressive strength of 3000 N per pellet. When roasted at the same temperature of 1200℃, natural magnetite pellet and artificial magnetite pellet need to be roasted for 15 min and 30 min, respectively, to reach the compressive strength over 3000 N per pellet. It can be seen from the test that artificial magnetite pellet has a faster oxidation, resulting in the high porosity in the produced pellet, and it requires a roasting process at higher temperature for a longer time to reach the desired compressive strength for industrial production.

Effect of nickel oxide additive on smelting mechanism of chromium-bearing vanadium titanomagnetite pellets

The effect of nickel oxide additive on the smelting behaviors of chromium-bearing vanadium titanomagnetite pellets(CVTP)was investigated while analyzing the transfer behavior of nickel in iron and slag.The results show that when NiO added to CVTP increases from 0 to 6 wt.%,softening start temperature increases from 1148 to 1212℃,and the softening end temperature increases from 1280 to 1334℃;the melting start temperature increases from 1318 to 1377℃,and the dripping temperature decreases from 1558 to 1521℃.The pig iron comprises a compound of Fe-Ni-C.The slag structure depolymerizes with increasing nickel addition.The softening-melting behaviors of CVTP,the reduction of nickel into pig iron,and the depolymerization of slag structure indicate the feasibility of producing nickel-iron alloy through the blast furnace process.

Concentrations and Sources of Polycyclic Aromatic Hydrocarbons in Topsoil of Benxi City, Northeast China

Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study, and sampling sites were located in industrial area and residential area. Results demonstrate that there is high variability in the total PAHs concentrations, ranging from 783.00 ng/g to 729 076.29 ng/g dry weight in the topsoil of Benxi City and the pollution in industrial area is the most serious. The results also present that higher molecular weight PAHs (4–6 rings) contribute substantially (79.03%) to the overall content of PAHs. The PAHs sources were determined with factor analysis by nonnegative constraints, and the results show that PAHs originating from traffic tunnel, power plant, coke oven and residential emission sources, account for 27.10%, 40.81%, 20.11% and 11.98%, respectively, of the total. The PAHs pollution is the most serious around Benxi Iron and Steel Group Corporation, and the PAHs mainly originate from coke oven and traffic tunnel, with the average contribution rate of 57.40% and 42.60%, respectively. The source apportionment results are basically consistent with the industry distribution, and the geographical and climatic characteristics of the study area.

Effect of modified humic acid binder on pelletisation of specularite concentrates

A modified humic acid(MHA) binder was tested as a substitute for bentonite to prepare qualified specularite pellets. The results show that there is stronger chemisorption between organic functional groups in MHA binder molecular and specularite particles, improving the green pellet strength. MHA binder has obvious effect on the strength and microstructure of preheated pellets due to the thermal decomposition of organic matters in MHA binder. Appropriately increasing preheating temperature or time can eliminate the adverse impact of organic matters on the preheated pellet strength. Compared with the bentonite pellets, the roasted pellets with MHA binder have a more compact microstructure, and the recrystallization of the Fe2O3 crystal grains is better.Consequently, under optimal conditions, 0.75%(mass fraction) MHA binder pellets have equal or better pellet strengths and contain1.06% more total iron than 2 % bentonite pellets. The testing results indicate that MHA binder is a promising and effective alternative to bentonite for the specularite pellets.

Vanadium recovery from Na_(2)SO_(4)-added V-Ti magnetite concentrate via grate-kiln process

Pilot experiments on Na;SO;-roasting of V-Ti magnetite(VTM) concentrate pellets were performed to activate vanadium with simulated grate-kiln machines. Combined with thermodynamic calculation, X-ray diffraction(XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM-EDS), and inductively coupled plasma-atomic emission spectrometry(ICP-AES) analyses, process parameters of pellet making were optimized, and the enhancement of vanadium oxidation and conversion was realized. The results show that, in balling stage, adding Na;SO;can promote the thermal decrepitation resistance of green pellets;in the drying stage, higher wind temperature can improve the dispersion of sodium salt in pellets;in preheating stage, using O;-rich hot gas can promote more thorough oxidation of vanadium;in roasting stage, the effect of vanadium conversion to sodium vanadate is better when the liquid amount is 15.5%-22.5%. Based on the above measures, the vanadium conversion rate achieved in the roasted pellets is 85.6%, proving the feasibility of vanadium recovery using an existing pellet production line.

Sticking of iron ore pellets in direct reduction with hydrogen and carbon monoxide:Behavior and prevention

A series of reduction experiments of iron ore pellets with hydrogen,carbon monoxide and their mixture were carried out in a laboratory scale shaft furnace.The sticking behavior accompanying reduction of iron ore pellets was investigated.And morphology of the sticking interface forming during reduction was analyzed by SEM equipped with EDS.In order to evaluate the effects of the temperature and gas composition on sticking properties,reduction of iron ore pellets were conducted at 800-1000 ℃.The results show that the sticking strength of the pellets increases with temperature,however,decreases with hydrogen content in reducing gas.For an efficient shaft furnace operation in direct reduction(DR),relative prevention of sticking such as coating of pellets was also developed to solve sticking problem.The results show that CaO is a suitable material for the coating method.