热等静压原位合成SiC–TiC复相陶瓷的微观组织与性能研究

采用纳米级β-SiC粉末、Si粉末、C粉末以及微米级TiH_2粉末为原料,利用热等静压原位合成工艺制备了SiC–TiC复相陶瓷,研究了不同原位合成反应和烧结工艺对复相陶瓷微观组织及力学性能的影响。结果表明:以SiC、TiH_2、C粉末为原料的原位合成反应,无明显副反应发生,更有益于制备成分符合预期、致密度良好且性能优秀的SiC–TiC复相陶瓷。在1600℃,120 MPa,4 h等静压烧结工艺下原位合成得到的体积分数为SiC–32%TiC复相陶瓷具有最好的致密度、硬度、三点弯曲强度以及良好的断裂韧性,分别达到98.7%、21.2 GPa、428 MPa和5.5 MPa·m1/2。提高热等静压压力有助于提高材料的烧结扩散活性,从而提高材料的致密度,有益于力学性能的提升。     

粉末特性对AlN陶瓷致密化的影响

以沉淀前驱物和低温燃烧合成前驱物为原料，利用碳热还原法制备出比表面积分别为4．26m^2／g和17．4m^2／g的两种AlN粉末，以该两种粉末为原料制备AlN陶瓷，研究了粉末比表面积对AlN陶瓷烧结行为的影响。结果表明：粉末比表面积是影响AlN烧结行为的关键因素之一，对于燃烧合成前驱物制备的AlN粉末试样，没有添加Y2O3烧结助剂时在1700℃获得致密，添加Y2O3烧结助剂后，试样的烧结致密化温度降低为1600℃；而对于沉淀前驱物合成的AlN粉末试样，添加烧结助剂后仍需要在高于1800℃才能获得致密。探讨了粉末比表面积对AlN陶瓷烧结行为的影响机理，并利用SEM对陶瓷烧结过程中的显微结构变化进行了表征。     

NiO掺杂对菱镁矿烧结性能的影响

以天然菱镁矿为原料,添加不同质量分数的NiO粉末,采用高温煅烧法制备了镁砂。利用显气孔体密测定仪、X射线衍射仪、扫描电子显微镜分析NiO粉末掺杂对镁砂熟料烧结性能、物相组成、微观结构的影响。结果表明,在菱镁矿中添加NiO粉末有利于提高镁砂烧结致密性,促进MgO晶粒长大。当不添加NiO粉末时,试样在1600℃烧结前后线变化率为8.72%,体积密度为2.96 g·cm-3,显气孔率为19.2%,MgO晶粒尺寸为1.36 μm;当加入质量百分数为0.75% NiO粉末时,试样烧结前后线变化率为18.06%,制备镁砂体积密度为3.29 g·cm-3,显气孔率为11.5%,MgO晶粒尺寸为3.81 μm。在1600℃对添加NiO粉末的菱镁矿进行烧结,NiO可以与MgO完全固溶,引起MgO晶格畸变,降低晶体活化能,提高MgO烧结致密性能。但添加过多NiO,在短时间内无法与MgO完全固溶,妨碍烧结相的直接接触,影响传质过程,导致样品烧结性能降低。     

渗碳处理对等离子喷涂 TaC 涂层结构和物相组成的影响

TaC 涂层在还原气氛下能耐酸、碱、盐等物质的腐蚀,是优异的表面防护涂层材料。本文结合喷雾干燥与等离子球化技术制备TaC粉体,并采用真空等离子喷涂技术制备TaC涂层。采用真空碳管炉对涂层进行渗碳处理,比较研究不同渗碳温度对涂层结构和物相组成的影响。结果发现,相较于喷雾造粒,等离子球化处理的 TaC 粉体呈致密球形,该粉体制备的涂层较为致密,孔隙率较低。此外,喷涂过程中 TaC 发生脱碳产生 Ta2C 相,而渗碳反应可以将喷涂过程中产生的 Ta2C 相转化成 TaC 相。Ta 2C 与 C 反应生成 TaC 的过程受动力学控制,当渗碳温度超过 900 ℃时,几乎完全转化为 TaC 相。     

原料B4C粉末粒度对多孔 TiB2-TiC复相陶瓷孔结构的影响

为了获得总孔隙度为(30±5)％的TiB2-TiC复相陶瓷,采用不同粒度的B4C与Ti粉为原料,通过反应烧结制备TiB2-TiC多孔复合材料.研究原料B4C粒度对样品的密度及孔结构性能的影响.实验结果表明:随着原料B4C粉末粒度的减小,样品的密度逐渐增大,总孔隙率和开孔隙率逐步减小;当采用中位径为2.62 μm的B4C...     

ZnO压敏陶瓷的致密化过程

研究了用粒径为90～100 μm的ZnO粉末制备压敏陶瓷时的致密化过程,用TG-DTA技术测定了烧结过程中的有关特性,考察了烧结温度、掺杂氧化物的量等对烧结体收缩率、烧结密度、气孔率等的影响,结果表明:用大粒径的氧化锌粉末制备的氧化锌陶瓷体在825～900℃之间的收缩率、气孔含量的变化非常迅速,其陶瓷体内无明显的固相反应,而在900～1300℃之间的收缩率、气孔含量的变化不如前者明显,但其烧结体内部的固相反应却十分剧烈,该阶段是压敏陶瓷形成非线性特性的关键。     

钼合金表面Zr和B_4C反应烧结制备陶瓷涂层

以Zr和B_4C等粉末为原料,采用喷涂和反应烧结方法在钼合金表面形成陶瓷涂层,研究反应烧结工艺对涂层表面形貌、相组成和相结构的影响,再通过硅扩散反应形成抗氧化涂层,研究抗氧化涂层对钼合金在1 500℃静态抗氧化行为的影响。结果表明:钼合金表面Zr-B_4C在1 700℃反应烧结2h形成多孔陶瓷结构,烧结产物主要含ZrC及少量的Mo_2C和MoB等物相。涂层在1 500℃抗氧化寿命达10h以上,1 500℃氧化1 h,质量增加速率为1.175 mg/cm~2。     

热压工艺对硅掺杂碳复合靶材的性能影响研究

以碳粉、碳化硅粉体为原料,添加不同含量的硅粉为烧结助剂,在不同的热压工艺参数下制备C/Si 80%/20%(原子分数)复合靶材,通过扫描电镜(SEM)分析微观形貌、四探针测试电阻率、X射线衍射(XRD)分析晶体结构、压汞法测试气孔分布,分析Si粉的添加量、液相保温时间、原料预处理工艺对靶材致密化和均匀性的影响,优化硅碳复合(C/Si 80%/20%)靶材的热压烧结工艺。结果如下：(1)随着Si粉添加量增加,体系中液相含量增加,扩散传质速率加快,硅碳化合反应生成3C-SiC,体系中的Si元素全部以3C-SiC的形式存在,靶材的致密度逐渐增加,Si粉添加量为14%时,靶材的密度达到2.51 g·cm-3;开孔孔径分布随Si粉添加量的增加而逐渐减小至20 nm以下;靶材电阻率随Si粉添加量的增加而逐渐降低,Si粉添加量为14%时,电阻率降低50%。(2)在1350～1450℃,随着液相保温时间的增加,硅元素挥发并逸出,产生反致密化的现象,Si含量越高,反致密化越明显,密度降低至2.2 g·cm^-3。(3)采用SiC/C/Si 6%/74%/14%组分体系,C/Si预球磨...     

Mo2C增强M2高速钢球磨粉末的致密化及力学性能

采用高能球磨对M2高速钢粉末进行破碎,然后添加含量(质量分数,下同)为0～10%的碳化钼(Mo₂C)粉末,混合均匀后将混合粉末冷压成形,在真空下烧结得到M2钢与Mo₂C增强M2钢,研究烧结样品的致密化行为和力学性能,分析Mo₂C对M2钢粉末烧结致密化的影响。结果表明,高能球磨对原料粉末的细化可提高粉体的烧结活性,促进压坯在烧结中期的致密化。通过1180℃固相烧结获得近全致密(相对密度>98%)的M2钢与Mo₂C增强M2钢。烧结过程中,Mo₂C在950℃基本完全与Fe基体反应转变为M6C相,由此带来的反应烧结与活化烧结促进了烧结中期坯体致密度的提高。烧结中后期形成的大量弥散分布的M₆C与M₂C碳化物可抑制基体晶粒长大,提高烧结体的硬度和抗弯强度。添加10%Mo₂C烧结所得M2钢的抗弯强度达到3 135 MPa,硬度(HRC)达到59.6。通过原料粉末细化、Mo₂C的反应扩散以及金属颗粒的...     

放电等离子烧结制备NiFe2O4陶瓷的工艺优化及性能研究

以粒径为50 nm的NiFe₂O₄粉末作为原料,制备出单相NiFe₂O₄陶瓷,优化放电等离子烧结工艺,研究升温速率和保温时间对烧结块体物相、微观结构、致密度及磁性能的影响。结果表明,升温速率从30～60℃/min升高至60℃/min,致密度显著升高至97.7%。当升温速率升高100℃/min时,致密度升高至98.3%。且升温速率提高,块体的磁滞损耗下降;保温时间从4 min延长到12 min时,块体的磁导率和密度皆增大,但当保温时间超过12 min后,其密度及磁导率不升反降。并得出升温速率为100℃/min和保温时间12 min为最佳烧结工艺,所制备出的NiFe₂O₄陶瓷烧结体致密度为98.3%,磁导率为13 000 H/m。     

China's Major Non-ferrous Metals Imports & Exports

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Zinc Production by Province in 2014

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80% of Chinese Firms Purchasing Overseas Mines Ended up in the Red

<正>Minmetals Resources acquired the world’s largest copper mine under construction for USD5.85 billion.One after another,listed companies Jien Nickle,China Molybdenum and Chihong Zinc and Germanium raised money to get involved in overseas mining projects…SOEs and private enterprises are engaged in a frenzy of overseas mine purchasing.A reporter with Economic     

Copper Processing Profit Dropped Sharply,Copper Consumption Will Face Impact in the Second Half of the Year

正Judging from China’s copper consumption field,the biggest consumption unit is electric power,which accounts for 47%of total consumption;it is followed by light industry sector,including household electrical appliance,machinery,durable goods and hardware etc,which accounts for 22%of total consumption;followed by transportation field,     

Central Geological Prospecting Fund Newly Added 16.47 Million Tonnes of Bauxite in 2013

正In 2013,the Central Geological Prospecting Fund(CGPF)Project newly discovered 15 ore fields,including 3 large above ore fields,and 5medium sized ore fields.The reporter learned from the recently published"Annual Report of Central Geological Prospecting Fund Project(2013)"that,from 2006 to 2013 the CGPF     

Manufacturers of Copper Tube for Central Air Conditioner Use Face Mounting Pressure in the Final Quarter of the Year

正This year,the investment growth rate of real estate industry continued to slow down,sold area of commercial housing also dropped significantly,which brought huge pressure to the domestic air conditioning manufactures.In the first half of the year,by relying on high growth in national financial expenditure,along with investment in public infrastructure     

Xinjiang Ranks No.1 in Production of Primary Aluminum in China

正Kang Yi,Honorary Chairman of China Nonferrous Metals Industry Association,said recently at the Forum on Development of the Non-ferrous Metals Industry in Central and Western China held in Zhengzhou that,as more and more electrolytic aluminum factories in Xinjiang came into operation,the electrolytic aluminum output of Xinjiang had reached2,275,000 tons in the first 7 months this year,     

Shenhuo Coal Industry and Electricity Power Completed800,000 t/a Aluminum Project in Xinjiang

正"Xinjiang project has been completed according to schedule,but total completion and total start of production are two different concepts,after completion it still needs a gradual process of reaching production target."On the morning of November 3,Shenhuo Coal Industry and Electricity Power told investors the above statement on the investor interaction platform.     

Guangdong Metal Transaction Center has Become the Second Largest Precious Metal Transaction Platform Nationwide

正The reporter learned from Guangdong Province Precious Metal Transaction Center that in 2013the Center maintained healthy development momentum,and had become the second largest precious metal transaction platform in China in terms of market size;currently Guangdong is quickening steps of financial innovation for the Center,aiming to build a transaction center with international core competitiveness.     

Seven Rare Earth Projects Involving Close to 3 Billion Yuan Investment Landed In the HighTech Zone

正On May 22,Baotou Rare Earth Industry Cooperation Consultation MeetingProject Agreement-signing Ceremony was held in Ningbo,nearly 40 enterprises from Ningbo,Guangdong,Hunan,and Shanxi participated in project consultation.After multi-lateral communication,agreements were signed for a total of 7 rare earth projects successfully.