添加氧化铝烧结助剂的碳化硼陶瓷无压烧结工艺研究

采用无压烧结工艺,通过添加质量分数为5%的氧化铝烧结助剂,制备得到了碳化硼陶瓷,其中烧结温度从2000℃到2250℃,保温时间为1、2和3 h。对烧结试样进行了体积密度、显气孔率、维氏硬度、显微形貌和晶体结构测试,并与2250℃下烧结得到的不添加烧结助剂碳化硼试样进行了比较。实验结果表明:由于烧结助剂与碳化硼在扩散运动中的相互作用,导致添加氧化铝助剂无压烧结碳化硼晶粒的形态变化具有温度选择性;氧化铝助剂所体现的液相扩散作用和钉扎作用,既可阻碍碳化硼晶粒长大,又可大幅度降低碳化硼的气孔率;通过烧结工艺控制氧化铝助剂成分在晶粒烧结体中的比例,可以将氧化铝成分完全包裹在碳化硼晶粒内部,有利于碳化硼烧结中的晶粒控制和空隙调整,从而避免助剂成分对烧结碳化硼可能造成的不利影响。     

多金属结核金属化还原多元合金磁性能

用自动矿物分析仪、金相显微镜和扫描电镜,从多元合金颗粒尺寸、锰含量、金相组织结构等进行研究,以饱和磁感应强度Ms和剩磁Mr来衡量合金磁性能变化规律,研究多金属结核金属化还原工艺中多元合金磁性能。结果表明,多金属结核金属化还原多元合金磁性能主要受合金颗粒尺寸和锰含量影响,多元合金晶粒尺寸越大,锰含量越低,合金颗粒磁性能越强。因此,工艺过程中应该尽可能增大多元合金晶粒尺寸,抑制锰的还原。     

MAGNETIC FLOCCULATION OF MINERAL FINES IN AN EXTERNAL MAGNETIC FIELD

This article highlights the magnetic flocculation of mineral fines in aqueous suspensions, including ferromagnetic and weakly magnetic minerals. The magnetic attraction between magnetic mineral particles in an external magnetic field, the stability of magnetic mineral fines in aqueous suspensions, kinetics of magnetic flocculation, and the main parameters of magnetic flocculation are discussed and summarized. Some of the experimental results are presented and the applications of magnetic flocculation to fine mineral beneficiation are briefly described.     

烧结法制备磁性磨料的研究进展

制备性能优良而成本低廉的磁性磨料是制约磁力研磨技术发展的关键所在.介绍了磁性磨料的基本组成和性能要求,通过总结几种烧结制备技术的研究进展,概述了磁性磨料的烧结工艺、微观分布、组织组成及表面处理,对比了不同烧结方法和不同体系磁性磨料的研磨性能并提出了今后的研究方向.     

磁场对水热法制备锰锌铁氧体的影响

在磁场条件下用水热法制备了尖晶石型锰锌铁氧体粉末。利用X-射线衍射、X-射线光电子能谱和高锰酸钾分光光度法对铁氧体粉末的微观结构、表面原子信息和锰的平均价态进行了研究。研究表明，在磁场条件下制备得到的物质没有新相的产生，磁场对锰锌铁氧体锰的平均价态有影响，且内加磁晶使锰的平均价态升高，而外加磁场使锰的平均价态降低。在内加磁晶和外加磁场的条件下得到的铁氧体样品，可能有一部分的锌进入了尖晶石的B位。     

凹凸棒石纳米纤维用作润滑油添加剂的摩擦学性能

采用天然凹凸棒石黏土作为添加剂加入到CD15W-40润滑油中,在Optimal SRV-IV摩擦磨损实验机上测试摩擦学性能,借助扫描电镜(SEM)及其附带的能量色散谱仪(EDS)分析摩擦副的表面形貌及表面元素组成。结果表明,CD15W-40润滑油中凹凸棒石黏土的质量分数为0.4%时平均摩擦因数较基础油润滑条件下降低14.29%,体积磨损率降低59.94%;凹凸棒石黏土的加入使得磨损表面更加光滑平整,同时磨损表面氧元素含量升高。凹凸棒石黏土层链状的晶体结构和摩擦过程中复杂的理化过程是实现减磨抗磨的原因。     

YMn_6Sn_(6-x)M_x(M=Ga,Ti)化合物的结构和磁性研究

:制备了 YMn6 Sn6 - x Gax( x =0 .3,0 .6 ,0 .9,1.2 ,1.5 ,1.8)和 YMn6 Sn6 - x Tix( x=0 ,0 .2 ,0 .4,0 .6 ,0 .8,1.0 )化合物 ,通过 X射线衍射和磁性测量手段对其结构和磁性进行了研究 ,实验表明 ,所有这些化合物均为 Ca Cu5型六方结构。对 YMn6 Sn6 - x Gax 研究表明 ,晶格参数和晶胞体积均随 Ga含量的增加而线性减小 ,磁性测量表明 :当x≥ 0 .3时 ,化合物由反铁磁性转变为铁磁性或亚铁磁性 ,随 Ga含量增加 ,该化合物的居里温度先增高 ,在 x=0 .6达到最大值 ,然后居里温度又逐渐降低。饱和磁化强度开始随 Ga含量的增加而增大 ,当 x>1.2时 ,随 Ga含量的增加而减小。对 YMn6 Sn6 - x Tix 研究表明 ,晶格参数和晶胞体积均随 Ti含量的增加而线性增大 ,磁性测量表明 ,当 x≥ 0 .6时 ,化合物由反铁磁性转变为铁磁性或亚铁磁性 ,随 Ti含量增加居里温度 (或奈耳温度 )呈线性下降 ,饱和磁化强度开始随 Ti含量的增加而增大 ,当 x>0 .6时 ,随 Ti含量的增加而减小     

六偏磷酸钠对磁性复合流体分散性及光学玻璃抛光性能的影响

为了提高磁性复合流体(Magnetic Compound Fluid,MCF)的抛光性能,通过实验调查无机电解质分散剂六偏磷酸钠(Sodium Hexametaphosphate,SHMP)对MCF颗粒团聚的影响,研究MCF抛光液颗粒分散性与BK7光学玻璃抛光材料去除率和表面粗糙度的变化关系。在MCF中添加不同质量分数的SHMP,测试MCF中颗粒的粒径分布和中值粒径D50的变化,并采用扫描电镜观察MCF中颗粒分散性;利用不同含量SHMP的MCF对BK7光学玻璃进行抛光加工,研究SHMP含量变化对光学玻璃抛光材料去除率和表面粗糙度的影响规律。实验表明,在MCF中添加适量SHMP能够减少抛光液颗粒的团聚,提高MCF抛光液的颗粒分散性,改善BK7光学玻璃的材料去除率和表面质量。当SHMP质量分数为3%时,中值粒径D50达到最小值7.023μm,并且MCF抛光液的分散性最佳,材料去除率达到最大值22.6×10^-4 g/min,表面粗糙度达到最小值15.78 nm。     

一种磁性内核锐钛型TiO2光催化剂的制备与研究

在水处理技术领域,TiO2光催化水处理技术因具有效率高、能耗低、适用范围广、反应条件温和等优点而被认为是最有前景的有机污染废水处理技术之一。直接应用TiO2悬浮体系处理污水要比基体负载固定TiO2体系有更高的处理效率,但是悬浮态的TiO2存在着回收困难的问题。对此,首先采用了共沉淀-水浴法制备了具有较好形貌的MnxZn1-xFe2O4软磁体颗粒,该软磁体颗粒能够在700℃以内保持良好的磁响应性;采用溶胶-凝胶法在颗粒上包覆SiO2中间层,得到了单分散球形的SiO2/MnxZn1-xFe2O4;采用水热法在其上包覆纳米锐钛型TiO2,最终得到了TiO2/SiO2/(MnxZn1-xFe2O4)磁性光催化剂,采用XRD、SEM、VSM等对其分析,结果表明:该催化剂呈单分散球形,粒径约在500 nm左右,具有明显的壳-核结构,磁性内核被SiO2严密包覆,锐钛型TiO2均匀负载其上,有灵敏的磁响应性。对毛用活性黄废水的降解实验证明了其较高的光催化活性。     

Motion of Crystal Particles by the Electromagnetic Vibrations in Mg-Cu-Y Bulk Metallic Glasses

The method for producing Mg-Cu-Y and Fe-Co-B-Si-Nb bulk metallic glasses using electromagnetic vibrations is effective in forming the metallic glass phase. Disappearance or decrement of clusters by the electromagnetic vibrations applied to the liquid state is considered to cause suppression of crystal nucleation, because the electromagnetic vibrations vibrate the clusters vigorously in the melt. The purpose of this study was to investigate motion of the crystal particles by the electromagnetic vibrations in Mg-Cu-Y bulk metallic glasses. The electromagnetic vibration force vibrated the crystal particles or the clusters that become crystal nuclei in the melt, because the electric current for the electromagnetic vibrations concentrates in those. Thus, the electromagnetic vibrations were found to select vibration particles from the melt. Moreover, it was considered that composites for which second phases or other compounds are dispersed into the metallic glass phase or a nanostructure phase can be produced by the electromagnetic vibration process. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.     

Rheological Properties of a Powder Magnetic Abrasive Tool

Specific frictional forces have been examined for a magnetic abrasive tools as affected by the parameters of the machining in wide magnetic gaps. Such a tools have liquid characteristics and can be considered as viscoplastic medium. The viscosity varies with the cutting speed and when there is any change between laminar and turbulent behavior of the magnetic abrasive particles, in accordance with the Reynolds number. A model representation is used for the tools which forms in large working gaps in the form of conical and spindle-shaped macroformations.     

硅橡胶/黏土可瓷化复合材料的热行为及微观结构

添加无机填料可改善硅橡胶烧蚀陶瓷残余物的强度,从而加强其结构完整性和高温稳定性。以甲基乙烯基硅橡胶为基体,以黏土矿物为填料制备硅橡胶/黏土可瓷化高分子复合材料,利用TG/DSC等热分析技术研究该材料的热稳定性。结果表明,添加黏土矿物可以改善硅橡胶的热稳定性,使其分解温度提高100℃左右。通过XRD分析和SEM观察发现:除少量杂质相之外,硅橡胶经600℃烧蚀后的物相主要为方石英,1 200℃烧蚀后的物相为莫来石和方石英,微观形貌特征分别为不致密絮状结构(600℃烧蚀后)和液相桥连的多孔结构(1 200℃烧蚀后)。根据试验结果分析复合材料的瓷化机理。     

离子型稀土矿土壤粒度分布特征研究——以赣县姜窝子稀土矿山为例

颗粒粒度分布对土壤水分运动和溶质迁移,以及水土流失有重要影响. 利用水洗分筛和激光粒度分析技术研究了江西赣县姜窝子稀土矿土壤颗粒粒度并探讨了土壤颗粒粒度在垂直方向的分布规律. 研究表明,姜窝子稀土矿山土壤颗粒粒度分布受风化程度、颗粒垂向迁移因素的影响,呈如下分布:①离子型稀土矿土壤颗粒按直径分为粗、细、粉、黏粒结构,且土壤粗颗粒以石英为主,稀土矿土壤颗粒粒度呈驼峰式分布,即粒径在粗颗粒（ > 2 mm） 和黏粒（ < 0.075 mm）含量较高,粒径在细、粉粒（0.075~2 mm）含量相对较低;②受风化程度和颗粒垂向迁移的影响,稀土矿土壤细、黏粒组分的含量随深度增大呈先升后降的曲线形态;③黏粒（ < 0.075 mm）激光粒度分析表明,颗粒分布随粒径的大小变化与粒径大于0.075 mm的颗粒在深度上的分布相似.      

褐铁矿致密化烧结技术试验研究

分析了褐铁矿的烧结特性及成矿机理,根据性能优势互补配矿理论,通过试验将褐铁矿与镜铁矿合理搭配进行烧结.试验结果表明：褐铁矿烧结性能得到强化,烧结矿指标明显改善,主要是镜铁矿液相生成温度高、流动性差,褐铁矿颗粒被镜铁矿包裹,使得褐铁矿颗粒在与液相接触之前得到致密,避免了脆化结构的形成.褐铁矿致密化烧结使得烧结矿的矿物结构发生变化,多孔薄壁结构减少,有利于改善烧结矿高温性能.     

Recovery Improvement of Fine Magnetic Particles by Floc Magnetic Separation

The performance of floc magnetic separation (FMS) has been compared with wet high-intensity magnetic separator (WHIMS). This study was performed on low-grade iron ore slime contained 59.58% Fe with 4.57% silica and 3.78% alumina. Detailed characterization data indicated that a substantial amount of the slime was below 20 µm in size. Beneficiation studies indicated that the FMS process is effective to recover fine hematite and goethite particles, compared with the conventional magnetic separation. In conventional magnetic separation, the extent of the fluid drag force exceeds the magnetic force exerted on ultrafine particles. Thus, ultrafine magnetic particles were usually not recovered effectively by magnetic separators, resulting in the loss of valuable ultrafine slime particles. The FMS process significantly increases the magnetic force on the ultrafine iron ore in the form of hydrophobic flocs in a magnetic field, thus the ultrafine particles can be picked up effectively as magnetic concentrates. The FMS process improved the Fe recovery from 37.35% to 79.60%.     

Structural aspect of the problem of designing superconducting materials based on Bi-2212 ion-plasma coatings for operation in strong magnetic fields

The Bi-2212 crystal structure parameters and the structural states of the material of thick ion-plasma coatings are analyzed during their production. These structural states include the amorphization of the coating material; changes in the modulated structure of Bi-2212; the formation of a basal texture, which characterizes oriented grain growth during heat treatment; and the improvement of integrain contacts. Problems related to the creation of high-current superconducting Bi-2212-based composites and those related to Chevrel phases, which began to be studied a decade earlier, are considered to be common. The differences in the changes of the critical currents of these materials in an applied magnetic field are associated with the difference in the superconducting fragments in their crystal structures. The development of studies dealing with the creation of superconducting composites containing ion-plasma coatings and intended for operation in strong magnetic fields is considered.     

SLon高梯度磁选机分选刚果（金）某氧化钴矿的试验研究

刚果（金）某氧化钴矿属于风化壳型钴土矿床,虽然钴品位高达1．64％,但是矿物组成复杂,大量钴以吸附嵌晶态赋存于黏土矿物含锰混晶中。试料采用预先擦洗分级,脱除大量低品位细粒（0．125mm）后,应用SLon高梯度磁选机磁选工艺,经小型试验获得了可直接用于湿法冶炼的钴粗精矿。粗精矿含钴7．82％,钴的总回收率达59．43％,磁选作业回收率达81．16％。     

Ni掺杂TiO_2电子和几何结构的第一性原理研究

利用密度泛函理论框架下的第一性原理方法,对不同掺杂量、不同方式的Ni掺杂锐钛矿相TiO_2(anatase TiO_2:A-TiO_2)的晶胞结构、缺陷形成能和态密度图像等进行了研究,并着重讨论了掺杂Ni离子周围配位场改变对体系电子结构的影响.结果表明,掺杂方式的不同对Ni-TiO_2超晶胞的几何结构有较大影响.正是几何结构的变化导致掺杂Ni离子处于不同类型的晶体配位场之中,这是掺杂体系电子结构差异的本质原因.通过对掺杂体系形成能的比较,发现Ni掺杂TiO_2的具体方式取决于晶体生长过程中的氧环境.通过对体系电子结构的研究,发现各种掺杂体系的禁带中都出现由Ni 3d-O2p轨道杂化形成的杂质能级.Ni离子替代晶格Ti掺杂会使吸收光谱红移,而Ni的晶隙掺杂则使吸收光谱蓝移,且这种光谱吸收带边的差异会随掺杂浓度的增加而增大.     

某地铁矿体选矿工艺矿物学和选矿试验研究

文章介绍了湖南某地铁矿体的选矿工艺矿物学和选矿试验研究。研究结果表明,采用弱磁选一强磁选试验流程可从含铁为30．17％的试样中获得弱磁选铁精矿产率为20．81％,含铁67．42％,铁回收率为46．50％;强磁选铁精矿产率为15．50％,含铁59．71％,铁回收率为30．68％。铁总回收率为77．18％的良好指标。     

Fabrication and Mechanical Properties of Sm2O3 Doped CeO2 Reinforced Ti3AlC2 Nano Composite

The fabrication process of Sm2O3 doped CeO2 reinforced Ti3AlC2 nano composites including the nano particle dispersion process by a hetero-coagulation process was developed using in-situ synthesis and densification process of Ti3AlC2. The effects of Sm2O2 doped CeO2 nano particles on mechanical properties of Ti3AlC2 were investigated. It was found that the presence of 20SDC nano particles in Ti3AlC2 was very effective to improve the mechanical properties of Ti3AlC2 without spoiling the unique characteristics of Ti3AlC2temary carbide.