磁性TiO2空心球的制备及其光催化性能

分别制备Fe3O4和ZnFe2O4粉体并以它们作为磁芯,葡萄糖为模板剂,氟钛酸铵为钛源,通过水热法制备出Fe3O4/C/TiO2和ZnFe2O4/C/TiO2前驱体,煅烧后获得磁性Fe3O4/TiO2和ZnFe2O4/TiO2空心球。采用扫描电子显微镜、X射线衍射仪、X射线光电子能谱仪分析了产物的形貌、结构和化学组成,用振动样品磁强计测试了样品的磁化强度。结果表明,以Fe3O4为磁芯得到的Fe3O4/TiO2空心球的比饱和磁化强度是ZnFe2O4为磁芯得到的ZnFe2O4/TiO2空心球的20倍。以亚甲基蓝溶液为降解模型,考察了磁芯Fe3O4添加量对Fe3O4/TiO2空心球在紫外光下的催化降解能力。结果显示,Fe3O4的添加量对Fe3O4/TiO2空心球的光降解性能影响较小,且Fe3O4/TiO2空心球的紫外光降解能力均比纯TiO2空心球略低,但Fe3O4/TiO2空心球具有在外加磁场下易于回收的优势,具有潜在的应用前景。     

球磨时间对Al2O3/Mo复合材料组织与性能的影响

采用溶胶-凝胶法制备Al2O3/Mo混合粉体,利用高能球磨法细化Al2O3/Mo复合材料中氧化铝和钼的晶粒尺寸,研究了球磨时间对Al2O3/Mo复合材料组织与性能的影响,利用XRD和扫描电镜对复合粉末形貌和复合材料进行了物相和形貌分析。研究表明:随着球磨时间的延长,复合粉末的形貌经历了球状到层片状再到球状的变化,粉末粒度逐渐减小,经粉末冶金烧结后的复合材料中,氧化铝和钼的粒径逐渐减小,经过60h的球磨,氧化铝颗粒的尺寸达到500nm左右;复合材料的密度呈现先增加后减小的趋势,显微硬度则逐渐上升至403.2HV。     

超细Fe2O3粉末的结构及热稳定性

采用差示扫描量热仪(DSC)和X射线衍射分析(XRD),研究超细Fe2O3粉末的热稳定性及晶体结构随颗粒尺寸的变化关系。研究结果表明:超细Fe2O3粉末在1 000~1 400℃之间会发生分解反应,生成Fe3O4。随Fe2O3颗粒粒径减小,此分解过程产生的热量减小;反应的起始温度也随颗粒粒径的减小逐渐降低,但降低的幅度渐小;晶粒粒径越小,晶格内的相关点阵参量越易发生微小变化,使晶胞出现略微膨胀的现象。Fe2O3粉末加热时因颗粒粘结引发颗粒粒径长大,但对晶粒粒径的影响不大。     

球磨工艺对Al2O3/Mo复合材料组织的影响

针对原位自生Al2O3增强钼基复合材料晶粒较大的问题,采用溶胶-凝胶与高能球磨相结合的方法细化复合材料晶粒,并利用SEM、XRD对不同球磨工艺所制备Al2O3/Mo复合粉末及复合材料的组织进行了观察和分析。结果表明:随着球磨时间的延长,Al2O3/Mo复合粉末颗粒由球状变为层片状再成为细小的球状,颗粒大小由约1.5μm细化为约500nm,其中的钼晶粒不断细化;高球料比所得粉末的分散性和破碎细化程度较好;转速提高使得粉末颗粒的尺寸均匀程度降低,且伴有结块现象,不利于粉末的细化。在球料比5∶1、转速300r/min、球磨时间60h条件下获得的复合粉末,经压坯烧结可制备出Al2O3颗粒为纳米级的钼基复合材料。     

不同退火温度对Mo-La2O3板材微观组织及力学性能的影响

本文研究了不同退火温度对Mo-La2O3板材微观组织及力学性能的影响。通过金相显微镜、扫描电镜观察了钼合金显微组织及断口形貌,利用透射电镜研究了La2O3对位错分布的影响规律。结果表明,随着退火温度的升高,钼合金晶粒长大,拉伸性能、断裂韧性及显微硬度显著降低。对于退火后的试样,当La2O3粒径较大时,这种颗粒位于晶界处,在颗粒及晶界处形成位错塞积;在退火后的钼合金中,La2O3粒径较小时,绝大多数颗粒位于晶粒内部,位错越过这些颗粒,在晶界或亚晶界上形成位错塞积。     

电刷镀Ni-Co-W/Y2O3复合镀层的组织与摩擦磨损特性

采用复合电刷镀工艺在45钢基材上制备了含微米Y2O3颗粒的Ni-Co-W基复合刷镀层,采用扫描电镜、X射线衍射仪、显微硬度计、摩擦磨损试验机等对镀层的表面形貌、截面组织、结构、硬度及耐磨性进行了测定,与Ni-Co-W镀层进行了对比分析。结果表明:Ni-Co-W/Y2O3复合镀层厚度均匀,与基体之间呈凸凹镶嵌,结合紧密;与Ni-Co-W合金镀层相比,Ni-Co-W/Y2O3复合镀层的表面更加平整、光滑,组织更为致密,微裂纹明显减少;硬度较Ni-Co-W合金镀层更高,摩擦系数较低,Y2O3颗粒在镀层与摩擦副相互作用的过程中起支撑作用,减弱了磨损面的犁削效应和黏结效应,耐磨性显著优于Ni-Co-W合金镀层。XRD分析结果表明:此两种镀层均存在非晶态结构,微米Y2O3颗粒的加入促进镀层结构由非晶态向微晶态转变。     

系列层状K2La2Ti3O10的制备及光催化性能

通过固相反应法合成了一系列不同尺寸的K2La2Ti3O10,考察了原料TiO2粒径对固相反应速率及产物尺寸、形貌的影响,得到了不同粒径下原料的最佳配比;以降解甲基橙为探针考察其光催化性能.结果表明减小原料粒径,反应温度降低、速率加快;有利于合成小尺寸、大比表面积(可达11.83 m2·g-1)的层状K2La2Ti3O10,而且光催化性能提高.     

Al_2O_3掺杂钼合金粉末的形貌变化

采用水热合成法结合低温煅烧及两次还原工艺制备了Al2O3质量分数分别为0、0.25%、0.5%、0.75%、1.0%的钼合金粉末。通过SEM观察了混合钼合金粉末的形貌,采用XRD分析了钼合金粉末的相组成,研究了不同制备阶段Al2O3掺杂量对钼合金粉末的影响。结果表明:Al2O3掺杂量对钼合金粉末的均匀性、颗粒分布、粒径大小有一定影响,Al2O3掺杂量的增加对钼合金粉末的团聚有分散作用。经两次氢气还原,片状的MoO3颗粒完全被还原为球状的Mo颗粒,混合粉末主要由Mo和α-Al2O3相组成,不含其他相。α-Al2O3能细化还原后的Mo颗粒,且Al2O3掺杂量越大,Mo颗粒的细化效果越显著。     

纳米ZrO_2粉末感应等离子体球化处理工艺研究

采用液体送粉技术及感应等离子体球化技术对纳米YSZ(6%~8%Y2O3-ZrO2)粉末进行了团聚、球化处理,研究了感应等离子体球化处理工艺参数对于粉体球化率的影响,采用三维景深显微镜、场发射扫描电镜、X射线衍射(XRD)研究了球化处理前后纳米YSZ粉末的表面形貌、截面形貌及其相结构。结果表明,采用液体送粉感应等离子球化处理技术,可同时对纳米YSZ粉末进行团聚及其致密化处理,得到的粉末为表面光洁、致密的实心球或空心球粉末,其粒径分布范围为40~100μm;YSZ粉末的相结构在处理前后没有发生变化。     

钛铁矿氧化过程中的离子竞争扩散机制

在600～750℃的温度范围、空气气氛下焙烧攀枝花钛铁矿,通过观察分析钛铁矿氧化后的微观形貌、物相组成以及氧化动力学,对钛铁矿的氧化机理进行了详细地研究。试验结果表明钛铁矿的氧化机制是一种Fe、O离子相互竞争扩散的反应机制。在反应初期,钛铁矿的氧化是通过Fe离子的向外扩散完成,氧化产物是Fe2O3和Fe2Ti3O9,其中Fe2O3会在颗粒表面富集;当反应进行到一定程度后(表面Fe2O3层厚度达到1～2μm),O离子的向内扩散在反应中占主导,颗粒内部逐渐形成Fe2O3和TiO2。由于从Fe离子扩散转变到O离子扩散均发生在表面氧化铁层厚度达到1～2μm时,这一转变时间与温度和钛铁矿颗粒粒径无关,所以Fe离子扩散在整个氧化过程中所占的比重会随着钛铁矿颗粒粒径的减小而增大,而O离子扩散则相反。     

加料方式对葡萄糖还原法制备的氧化亚铜形貌和粒度的影响

研究不同温度下,并流和分步加料方式对葡萄糖还原法制备的氧化亚铜形貌及粒度的影响.结果表明:采用并流加料制备氧化亚铜,其粒度随温度升高而减小,而分步加料方式与之相反.采用NaOH和C6H12O6溶液并流加料方式下,所得氧化亚铜为晶粒直径10～30 nm的规则球形颗粒,反应温度对形貌影响不大,且粒度随温度升高而减小;而分步加料方式下,50℃所得氧化亚铜颗粒形貌为类球形;随温度升高逐渐转变为立方堆积体,但颗粒粒度却随温度升高而增大.     

The effect of FeS film on the surface of iron powder particles on mechanical properties and fracture of Fe–Cu–C alloys

This article provides a new kind of P/M processing by designing thin-layered FeS film coated on the surface of iron powder particles for preparing high density Fe–Cu–C materials. Experimental results showed that FeS lubricating coating on the surface of iron powder particles was significant as a means of reducing friction in the pressing process of Fe–Cu–C alloys. After being pressed, the green density increased from 7.18 to 7.42?g?cm^?3. The sintered density increased from 7.10 to 7.37?g?cm^?3. In the sintering process, the FeS was liquid, and useful in purifying particle surface and strengthening grain boundaries to improve the mechanical properties. The hardness and tensile strength of the Fe–2.0Cu–0.9C–0.5FeS₂ material were 80.5 HRB and 590?MPa. Analysis of fracture showed the main fracture was transgranular fracture. And FeS spherical particles gathered in the pores of the Fe–Cu–C alloys.     

纳米氧化铁的制备及形貌分析

以九水硝酸铁（Fe（NO₃）₃·9H₂O）为铁源,无水乙醇和乙二胺为表面活性剂,采用水热法制备了纳米氧化铁（Fe₂O₃纳米棒）,通过扫描电子显微镜观察分析了Fe₂O₃纳米棒形貌,研究了（Fe（NO₃）₃·9H₂O）质量分数及反应温度对Fe₂O₃纳米棒颗粒尺寸的影响。结果表明,纳米棒的长度和宽度分别约为500～600 nm和50～60 nm;在160～220 ℃范围内,温度对Fe₂O₃纳米棒形貌的影响不显著;在一定范围内提高铁源质量分数可使纳米棒颗粒尺寸变小。Fe₂O₃纳米棒的形成机理为:铁源在强碱性的溶液中反应生成棕黄色絮状沉淀α-FeOOH,该沉淀在高温高压的环境中,在乙二胺作用下脱水形成Fe₂O₃纳米棒。     

铁粉矿在HIsarna工艺中预还原行为的研究

通过高温实验与理论分析研究了铁粉矿颗粒在高温下的热分解和熔化行为,以及熔化后气体与熔融粉矿液滴之间的还原动力学.当温度高于FeO熔点且产物层中有FeO生成时,铁粉矿颗粒会出现熔化现象.还原反应前210 ms伴随着剧烈的热分解反应,主要是Fe_2O_3分解成Fe_3O_4.熔化后的铁粉矿颗粒产物层是液态的FeO,颗粒中心是未反应的固态Fe_3O_4,还原反应发生在颗粒表面.Fe~(3+)在产物层中的扩散是还原反应的限制性环节,通过计算得到气体与熔融铁粉矿颗粒还原反应的表观活化能约为141 kJ/mol.     

Structure of fullerene-containing deformed powder steels

The effect of dynamic hot compaction (DHC) and intensive plastic torsional deformation (IPTD) on the structure and properties fullerene-containing powdered compositions of Fe graphite and Fe cast iron has been investigated. It is found that sintering Fe graphite samples results in the synthesis of fullerenes in their surface layer and a fullerene-containing phase is observed in their body after DHC as well. DHC results in an increase in the wear resistance of the Fe graphite composition. It is shown that a 6.16 Å line appears on diffractograms of all examined samples (both Fe graphite and Fe cast iron) as a result of IPTD. Scanning probe microscopy found that the elasticity modulus of samples of iron graphite increases from 50–58 to 67–91 GPa and local hardness increases from 10–19 to 137–155 GPa because of IPTD. The elasticity modulus of iron-pig-iron samples also increases from 63 GPa before IPTD to 55–109 GPa afterwards. A wide scatter in values of this index testifies to the inhomogeneity of the structure formed in the course of deformation.     

Age-hardening characteristics of aluminum alloy-hollow fly ash composites

The aging characteristics of aluminum alloy A356 and an aluminum alloy A356 containing hollow spherical fly ash particles were studied using optical microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, hardness tests, and compressive tests. The variation of hardness and compressive strength as a function of aging time for the composite have been reported. Since the density of the composite is lower than that of the base alloy due to the presence of hollow particles, the composites have a higher specific strength and specific hardness compared to the matrix. Even though the hardness of the as-cast composite was higher than that of the base alloy, no significant change in the aging kinetics was observed, due to the presence of spherical fly ash particles in the matrix. Aging times of the order of 10⁴ to 10⁵ seconds were required to reach the peak hardness (92 HRF) and compressive strength (376 MPa) in both the A356-5 wt pct fly ash composite and the matrix alloy. The possible effects of shape and hollowness of particles, the interface between the matrix and the particles, the low modulus of the particles, and the microcracks formed on the surface of hollow fly ash particles on the kinetics of the age hardening of aluminum alloy A356 are discussed.     

超细铁粉的制备及其对硝酸盐的降解

分别采用液相还原改性法和微乳液法制备超细铁颗粒,用乙醇-水体系制备镍包覆铁颗粒的Fe/Ni双金属颗粒,用来进行硝酸盐的降解实验,并用扫描电镜(SEM)和X射线衍射(XRD)分析超细粉末的物相结构及形貌.结果表明:通过液相还原改性法制备的超细铁粉,颗粒形状不规则,颗粒大小在0.2～0.3 μm之间;而用乙醇-水体系制备的铁/镍粉颗粒为等轴晶粒,颗粒大小也在0.2～0.3 μm之间;加入PEG-6000可改善液相改性法和醇-水法制备的铁粉的分散性.微乳液法制备的铁粉为球形颗粒,存在较明显的团聚现象,颗粒大小在0.5～ 1μm之间.在相同条件下,不同方法制备的超细铁粉降解硝酸盐的能力由高到低依次为:微乳液法制备的铁粉＞乙醇-水体系法制备的Fe/Ni双金属粉＞液相还原改性制备的铁粉＞不加PEG的乙醇-水体系制备的铁粉.     

Spheroidization of Iron Powder in Microwave and Hybrid Plasma Torches

The process of porous iron powder spheroidization with a particle size from 45 to 85 μm is investigated in the microwave discharge and joint microwave and DC discharge modes in nitrogen and helium plasma. The powder was prepared by air spraying and annealed in hydrogen. Spraying in plasma results in hollow spheroidized particles with a wall thickness from 1 to 10 μm. The fraction of spheroidized powder particles in their total number is determined. It is revealed that the degree of spheroidization of iron powder particles linearly increases with an increase in the microwave radiation power from 1.5 to 5 kW. The combination of operational conditions of the microwave radiation with the arc discharge is observed when using the hybrid plasmatron mode, which makes it possible to increase the plasma temperature. An almost 100% spheroidization of iron powder is attained with the power ratio of microwave and arc discharges of 1 : 1. The metallographic investigation of spheroidized particles showed that their finite size differs from the initial one approximately tenfold. It is established that, irrespective of the spheroidization mode, the iron powder oxidizes, which is caused by an insufficient degree of purification of plasma-forming gases. The structure of the particle surface when using nitrogen or helium as a plasma-forming gas is different. The experiments show that the application of helium is preferential because the particles have only insignificant roughness in this case when compared with the particle structure when performing spheroidization with the use of nitrogen.

     

约束弧等离子体制备铝纳米粉体的研究

利用自行研制的约束弧等离子体制备金属纳米粉试验装置,成功制备了平均粒度为44nm的铝纳米粉体。利用X射线衍射(XRD)、BET吸附法、透射电子显微镜(TEM)和相应选区电子衍射(SAED)等测试手段对所制备样品的晶体结构、形貌、粒度及其分布、比表面积进行性能表征。试验结果表明:约束弧等离子体法制备的铝纳米粉晶体结构为fcc结构的晶态,与体材料相比晶格常数发生膨胀。比表面积为41m2.g-1,粒径范围分布在20~70nm之间,平均粒径为44nm,粒度均匀,分散性好,呈规则球形链状分布。     

喷雾干燥法制备PSZ—3Y粉末的粒度研究

用激光衍射法和BET法（Brunner-Emmett-Teller Method)研究了用喷雾干燥法制备的PSZ－3Y粉末的粒度性能。用喷雾干燥法能制得粒度均匀性好的球状PSZ－3Y粉末。影响粒度的主要因素是料液中（ZrO2 Y2O3)的浓度,其次是送料速度。从颗粒形貌图看出,颗粒表面布满了裂纹,所以这样的粉末经二次处理后,可获得超细粉末。