發(fā)布時間：2018-05-06 04:25

  本文選題：金屬多孔材料 + 復合粉體�。� 參考：《北京科技大學》2015年博士論文

【摘要】：金屬多孔材料具有密度小、比表面積大、抗沖擊性能高、通透性好等優(yōu)點,因此成為當今研究的熱點之一。我們通過兩種方式來改善現(xiàn)有的制備金屬多孔材料存在的問題：一是制備復合粉末顆粒,二是改進成形和燒結(jié)方式。本文主要研究內(nèi)容包括：CuSn10復合粉體、球形鎢粉的制備和機理分析；材料的不同成形方式和燒結(jié)方式；探討了材料的組織與性能之間的關系： 1)顆粒的復合化和球形化 本文采用顆粒復合化(particle composite system)設備制備錫包銅復合粉體和球形鎢粉。(1)復合銅錫粉末的制備,采用PCS制備出錫均勻包覆在銅粉表面的復合粉體,原料分別采用電解銅粉／錫粉和霧化銅粉／錫粉,制備工藝為：粉末原料在三維球磨機中預混合20min,球料比為1：2；復合整形處理參數(shù)為轉(zhuǎn)速3000r/min,時間15min。(2)球形化鎢粉的制備,分別采用氧化鎢粉和鎢粉作為原料,整形處理的參數(shù)為4000r/min,時間45min,對于兩種原料粉末都可以達到較好的處理效果。 對于粉末顆粒的整形效果表征引入分形維數(shù)分析。對于鎢粉球形化過程,通過顆粒輪廓分形計算可知隨著處理時間增加,輪廓分維值降低,球形度和表面光潔度提高。引入粒度分形維數(shù),推導出粉末整形過程中整形模型(In(dt/do)=ktn)和整形分形模型((Dt-Do)In(dt/dmax)=k*tn),兩種模型均取得了與試驗數(shù)據(jù)較好的一致性。 2)燒結(jié)金屬多孔材料的制備 本文分別采用模壓法和凝膠注模法制備燒結(jié)金屬材料。 對于模壓法,隨著球形化工藝轉(zhuǎn)速提高或處理時間延長,制得的材料壓潰強度提高,而燒結(jié)收縮率、密度和開孔孔隙率變化不同,采用轉(zhuǎn)速3000r/min,時間15min的粉末做原料制備的材料綜合性能較好：徑向和軸向收縮率分別為0.56%和0.98%,密度為6.68g/cm3,開孔孔隙率為22.45%,壓潰強度達到220.8MPa。 對于凝膠注模法,通過差熱-熱重-紅外-質(zhì)譜分析,建立了坯體固化、干燥和脫脂動力學方程,通過理論分析和實驗研究確定有效的固化、干燥和脫脂機制,且確定了甲基丙烯酸-2-羥基乙酯—二乙二醇二丙烯酸酯(HEMA-DEDA)凝膠體系。對于固化過程,采用Kissinger法和Flynn-Wall-Ozawa法處理,得到反應活化能為2258KJ/mol,固化溫度61.95℃,從而建立動力學方程對于熱解過程,分別采用模型法和非模型法,得到的反應活化能為188.75～217.49KJ/mol之間。隨固相含量增加,燒結(jié)體收縮率和孔隙率降低,布氏硬度和抗壓強度增加,綜合來說：坯體最大強度為12.76MPa,燒結(jié)體孔隙率在15.54%～28.17%之間,燒結(jié)收縮率最低為4.24%,布氏硬度在35～55之間,最大抗壓強度為237.8MPa。 對于多孔鎢材料,以普通鎢粉和球形鎢為原料,采用反應燒結(jié)法制備多孔鎢材料,處理參數(shù)為：鎢粉500℃氧化30min,然后添加質(zhì)量分數(shù)為1%的鋁粉混合,在氫氣氣氛1150℃燒結(jié)30min,從而制得多孔鎢。通過實驗結(jié)果可知：在壓制壓力為200MPa的時候,制備出的材料總孔隙率可達36.26%,開孔孔隙率為35.58%,抗彎強度為152.15MPa。 3)銅基多孔材料的摩擦磨損性能和熱學性能 通過采用復合粉體制備多孔銅基復合材料,材料的孔隙連通度和儲油性能較好,在摩擦試驗中在很短的時間內(nèi)達到摩擦動態(tài)平衡階段。在干摩擦情況下,材料的摩擦因數(shù)隨著孔隙的增加和加載載荷的增加而增大,孔隙率為18.74%時,材料的摩擦因數(shù)從0.257增加到0.331,對應的體積磨損率從14.41×10-14增加到30.25×10-14mJ；而在孔隙率為27.15%時,材料的摩擦因數(shù)從0.423增加到0.479,體積磨損率從52.41×10-14增加到75.54×10-14m/J。 對于不同轉(zhuǎn)速下無油和含油摩擦存在著不同的規(guī)律。干摩擦狀態(tài)下,隨著轉(zhuǎn)速的增加,平均動摩擦因數(shù)和體積磨損率均呈現(xiàn)降低趨勢：孔隙率18.74%時摩擦因數(shù)從0.271降低到0.252,體積磨損率從32.32×10-14降低到18.63×10-14m/J；而在孔隙為27.15%時,摩擦因數(shù)從0.438降低到0.391,體積磨損率從68.25×10-14降低到51.60×10-14m/J。而在含油狀態(tài)下,材料的摩擦狀態(tài)表現(xiàn)出有低速的粘著磨損到高速時以剪切作用的轉(zhuǎn)化過程,孔隙率為22.52%時,隨轉(zhuǎn)速的增加,材料的摩擦因數(shù)從0.091增加到0.102。 對于多孔材料熱學性能,材料的熱導率跟孔隙分布和形狀有密切關系。采用幾何平均法(GEM)進行分析,隨著孔隙率的增加,熱導率從32.96W/m·k降低到12.84W/m·k,材料的傳熱以基體導熱為主,結(jié)構(gòu)因子n值接近于0,說明通過復合顆粒制備的燒結(jié)銅基多孔材料,孔隙結(jié)構(gòu)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，

本文編號：1850785