金属粉末颗粒整形及在多孔材料制备中的应用

发布时间：2018-05-06 04:25

  本文选题：金属多孔材料 + 复合粉体　； 参考：《北京科技大学》2015年博士论文

【摘要】：金属多孔材料具有密度小、比表面积大、抗冲击性能高、通透性好等优点,因此成为当今研究的热点之一。我们通过两种方式来改善现有的制备金属多孔材料存在的问题：一是制备复合粉末颗粒,二是改进成形和烧结方式。本文主要研究内容包括：CuSn10复合粉体、球形钨粉的制备和机理分析；材料的不同成形方式和烧结方式；探讨了材料的组织与性能之间的关系： 1)颗粒的复合化和球形化 本文采用颗粒复合化(particle composite system)设备制备锡包铜复合粉体和球形钨粉。(1)复合铜锡粉末的制备,采用PCS制备出锡均匀包覆在铜粉表面的复合粉体,原料分别采用电解铜粉／锡粉和雾化铜粉／锡粉,制备工艺为：粉末原料在三维球磨机中预混合20min,球料比为1：2；复合整形处理参数为转速3000r/min,时间15min。(2)球形化钨粉的制备,分别采用氧化钨粉和钨粉作为原料,整形处理的参数为4000r/min,时间45min,对于两种原料粉末都可以达到较好的处理效果。 对于粉末颗粒的整形效果表征引入分形维数分析。对于钨粉球形化过程,通过颗粒轮廓分形计算可知随着处理时间增加,轮廓分维值降低,球形度和表面光洁度提高。引入粒度分形维数,推导出粉末整形过程中整形模型(In(dt/do)=ktn)和整形分形模型((Dt-Do)In(dt/dmax)=k*tn),两种模型均取得了与试验数据较好的一致性。 2)烧结金属多孔材料的制备 本文分别采用模压法和凝胶注模法制备烧结金属材料。 对于模压法,随着球形化工艺转速提高或处理时间延长,制得的材料压溃强度提高,而烧结收缩率、密度和开孔孔隙率变化不同,采用转速3000r/min,时间15min的粉末做原料制备的材料综合性能较好：径向和轴向收缩率分别为0.56%和0.98%,密度为6.68g/cm3,开孔孔隙率为22.45%,压溃强度达到220.8MPa。 对于凝胶注模法,通过差热-热重-红外-质谱分析,建立了坯体固化、干燥和脱脂动力学方程,通过理论分析和实验研究确定有效的固化、干燥和脱脂机制,且确定了甲基丙烯酸-2-羟基乙酯—二乙二醇二丙烯酸酯(HEMA-DEDA)凝胶体系。对于固化过程,采用Kissinger法和Flynn-Wall-Ozawa法处理,得到反应活化能为2258KJ/mol,固化温度61.95℃,从而建立动力学方程对于热解过程,分别采用模型法和非模型法,得到的反应活化能为188.75～217.49KJ/mol之间。随固相含量增加,烧结体收缩率和孔隙率降低,布氏硬度和抗压强度增加,综合来说：坯体最大强度为12.76MPa,烧结体孔隙率在15.54%～28.17%之间,烧结收缩率最低为4.24%,布氏硬度在35～55之间,最大抗压强度为237.8MPa。 对于多孔钨材料,以普通钨粉和球形钨为原料,采用反应烧结法制备多孔钨材料,处理参数为：钨粉500℃氧化30min,然后添加质量分数为1%的铝粉混合,在氢气气氛1150℃烧结30min,从而制得多孔钨。通过实验结果可知：在压制压力为200MPa的时候,制备出的材料总孔隙率可达36.26%,开孔孔隙率为35.58%,抗弯强度为152.15MPa。 3)铜基多孔材料的摩擦磨损性能和热学性能 通过采用复合粉体制备多孔铜基复合材料,材料的孔隙连通度和储油性能较好,在摩擦试验中在很短的时间内达到摩擦动态平衡阶段。在干摩擦情况下,材料的摩擦因数随着孔隙的增加和加载载荷的增加而增大,孔隙率为18.74%时,材料的摩擦因数从0.257增加到0.331,对应的体积磨损率从14.41×10-14增加到30.25×10-14mJ；而在孔隙率为27.15%时,材料的摩擦因数从0.423增加到0.479,体积磨损率从52.41×10-14增加到75.54×10-14m/J。 对于不同转速下无油和含油摩擦存在着不同的规律。干摩擦状态下,随着转速的增加,平均动摩擦因数和体积磨损率均呈现降低趋势：孔隙率18.74%时摩擦因数从0.271降低到0.252,体积磨损率从32.32×10-14降低到18.63×10-14m/J；而在孔隙为27.15%时,摩擦因数从0.438降低到0.391,体积磨损率从68.25×10-14降低到51.60×10-14m/J。而在含油状态下,材料的摩擦状态表现出有低速的粘着磨损到高速时以剪切作用的转化过程,孔隙率为22.52%时,随转速的增加,材料的摩擦因数从0.091增加到0.102。 对于多孔材料热学性能,材料的热导率跟孔隙分布和形状有密切关系。采用几何平均法(GEM)进行分析,随着孔隙率的增加,热导率从32.96W/m·k降低到12.84W/m·k,材料的传热以基体导热为主,结构因子n值接近于0,说明通过复合颗粒制备的烧结铜基多孔材料,孔隙结构和孔隙分布均一。
[Abstract]:The metal porous material has the advantages of small density , large specific surface area , high impact resistance , good permeability and the like , thus being one of the hot spots in the present research .
the different forming modes and the sintering mode of the material ;
The relationship between the microstructure and properties of the material is discussed .

1 ) compounding and spheronization of particles

The composite powders of tin - clad copper and spherical tungsten powder were prepared by particle composite system .
The parameters of the composite shaping were 3000r / min and 15min . ( 2 ) Preparation of spherical tungsten powder , tungsten oxide powder and tungsten powder were used as raw materials , the parameters of shaping were 4000r / min and time 45min .

The fractal dimension of powder particles is characterized by fractal dimension analysis . It can be seen that the fractal dimension of the contour decreases , the spherical degree and the surface smoothness are improved by the fractal calculation of the particle contour for the spherical process of tungsten powder . In this paper , the fractal dimension of particle size is introduced , and the shaping model ( In ( dt / do ) = ktn ) and the shaping fractal model ( dt - Do ) In ( dt / dmax ) = k * tn ) are derived .

2 ) Preparation of sintered metal porous material

In this paper , sintered metal materials were prepared by compression molding and gel casting respectively .

The compression strength of the material is increased with the increase of the rotation speed or the processing time , but the sintering shrinkage , the density and the porosity of the opening are different . The material prepared from the powder with the rotating speed of 3000r / min and the time 15min is better : the radial and axial shrinkage is 0.56 % and 0.98 % , the density is 6.68g / cm3 , the porosity of the opening is 22.45 % , and the crushing strength is 220 . 8MPa .

The kinetic equation of solidification , drying and degrease was established by means of differential thermal - thermal gravimetric - infrared - mass spectrometry . The reaction activation energy was determined by Kissinger method and non - model method . The reaction activation energy was 188.75 锝，

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