【摘要】：孔隙率和力學(xué)性能的預(yù)測(cè)問(wèn)題是泡沫鈦所有制備方法都面臨的重大難題,特別是當(dāng)前泡沫鈦的研究還停留在實(shí)驗(yàn)室階段,使得這一問(wèn)題變得尤其重要。目前,國(guó)內(nèi)外尤其是美歐日等發(fā)達(dá)國(guó)家雖對(duì)此問(wèn)題已有所重視,但還處于初步研究階段。本文對(duì)此進(jìn)行了有益的嘗試,在文獻(xiàn)綜述的基礎(chǔ)上,研究了造孔劑的不同參數(shù)下所獲得的孔隙率和力學(xué)性能及它們的重復(fù)性,深入分析了孔隙率與造孔劑含量之間的關(guān)系,得到了一些有價(jià)值的成果。本文的主要研究貢獻(xiàn)如下:(1)綜述了泡沫鈦的制備進(jìn)展。本文全面總結(jié)了2004年以來(lái)新出現(xiàn)的泡沫鈦制備方法,并進(jìn)行了分類(lèi)介紹。通過(guò)比較這些方法的技術(shù)特點(diǎn),提出了泡沫鈦制備方法的發(fā)展趨勢(shì)。(2)綜述了造孔劑技術(shù)制備泡沫鈦的研究現(xiàn)狀與進(jìn)展。本文全面總結(jié)了制備泡沫鈦用的所有造孔劑。通過(guò)分類(lèi)介紹這些造孔劑的特點(diǎn),指出了造孔劑技術(shù)制備泡沫鈦領(lǐng)域的發(fā)展方向。(3)針對(duì)高孔隙率泡沫鈦制備困難的特點(diǎn),提出了基于造孔劑的熱分析實(shí)驗(yàn)結(jié)果來(lái)選擇合適的脫除工藝的思想。本文采用熱分析儀來(lái)測(cè)定尿素的熱重和差示掃描量熱曲線,根據(jù)這些曲線來(lái)選擇尿素的脫除氣氛、加熱速率和終止溫度,由此解決了制備高孔隙率泡沫鈦的坍塌問(wèn)題。再將造孔劑的脫除和鈦粉的高溫?zé)Y(jié)分兩步單獨(dú)進(jìn)行,有效的避免了鈦粉表面的氧化問(wèn)題。在造孔劑含量超過(guò)60%的情況下,制備出了孔隙率介于50.2-71.4%的泡沫鈦。結(jié)果表明,孔隙率小于造孔劑含量。(4)給出了造孔劑的粒徑大小影響孔隙率的理論解釋。本文通過(guò)篩分獲得了3個(gè)不同粒徑分布的造孔劑顆粒。在造孔劑含量相同的情況下,結(jié)果表明孔隙率一方面全部小于造孔劑含量,另一方面隨著造孔劑粒徑的減小而微弱的減小。通過(guò)假設(shè)宏觀大孔在燒結(jié)過(guò)程發(fā)生體積收縮,分析表明宏觀大孔在燒結(jié)過(guò)程的體積收縮量隨著造孔劑粒徑的減小而微弱的增大。(5)提出了孔隙率和力學(xué)性能的重復(fù)性概念。結(jié)果表明,孔隙率具有重復(fù)性,而力學(xué)性能重復(fù)性比較差,但可通過(guò)增大造孔劑的含量或減小造孔劑的粒徑大小來(lái)提高力學(xué)性能的重復(fù)性。通過(guò)討論,力學(xué)性能重復(fù)性差主要?dú)w因于宏觀大孔分布的不可控性等因素造成的。(6)論證了宏觀大孔在燒結(jié)過(guò)程的體積變化。通過(guò)理論聯(lián)系實(shí)際,證明得到宏觀大孔在燒結(jié)過(guò)程發(fā)生體積收縮現(xiàn)象。當(dāng)宏觀大孔的體積減小量大于骨架上微觀小孔的體積時(shí),會(huì)導(dǎo)致孔隙率小于造孔劑含量。(7)建立了孔隙率與造孔劑含量的數(shù)學(xué)模型。通過(guò)理論聯(lián)系實(shí)際,證明得到孔隙率與造孔劑含量呈線性關(guān)系,實(shí)現(xiàn)了孔隙率的預(yù)測(cè)。再結(jié)合Gibson-Ashby模型方程,實(shí)現(xiàn)了通過(guò)造孔劑含量來(lái)預(yù)測(cè)力學(xué)性能。
[Abstract]:The prediction of porosity and mechanical properties is an important problem in the preparation of titanium foams. Especially, the research of titanium foams is still in the laboratory stage, which makes this problem more and more important. At present, the developed countries, especially the United States, Europe and Japan, have paid attention to this problem, but they are still in the preliminary research stage. On the basis of literature review, the porosity, mechanical properties and repeatability of pore-forming agent under different parameters were studied, and the relationship between porosity and content of pore-forming agent was analyzed. Some valuable results have been obtained. The main contributions of this paper are as follows: (1) the progress in the preparation of titanium foams is reviewed. In this paper, the preparation methods of titanium foams have been summarized and classified. By comparing the technical characteristics of these methods, the development trend of preparation methods of titanium foam was put forward. (2) the research status and progress of preparation of titanium foam by pore-forming agent technology were reviewed. All the pore-forming agents used in the preparation of titanium foam are summarized in this paper. This paper introduces the characteristics of these pore-forming agents and points out the direction of development in the preparation of titanium foam by pore-forming technology. (3) in view of the difficult preparation of titanium foam with high porosity, it is pointed out that it is difficult to prepare titanium foam with high porosity. The idea of selecting the appropriate removal process based on the experimental results of thermal analysis of pore-forming agent was put forward. In this paper, thermogravimetric and differential scanning calorimetry curves of urea are measured by thermal analyzer. According to these curves, the atmosphere of urea removal, heating rate and termination temperature are selected to solve the collapse problem of preparing titanium foam with high porosity. The removal of pore-forming agent and high-temperature sintering of titanium powder are carried out separately in two steps, thus effectively avoiding the oxidation of titanium powder surface. When the content of pore-forming agent is more than 60%, titanium foams with porosity between 50.2 and 71.4% have been prepared. The results show that the porosity is less than the content of pore-forming agent. (4) the theoretical explanation of the effect of pore-forming agent size on porosity is given. In this paper, three pore-forming agent particles with different particle size distribution were obtained by sieving. When the content of pore-forming agent is the same, the porosity is lower than that of pore-forming agent on the one hand, on the other hand, the porosity decreases slightly with the decrease of pore-forming agent particle size. The volume shrinkage of macropores during sintering process is assumed to increase slightly with the decrease of pore size. (5) the concept of repeatability of porosity and mechanical properties is put forward. The results show that the porosity has repeatability, but the mechanical property repeatability is poor. However, the repeatability of mechanical properties can be improved by increasing the content of pore-forming agent or decreasing the particle size of pore-forming agent. It is discussed that the poor repeatability of mechanical properties is mainly due to the uncontrollability of macro-pore distribution and other factors. (6) the volume change of macro-pore in sintering process is demonstrated. According to the theory and practice, it is proved that the macro-pore shrinkage occurs in the sintering process. When the volume reduction of macropores is larger than that of micropores on the skeleton, the porosity will be smaller than the content of pore-forming agent. (7) A mathematical model of porosity and pore-forming agent content has been established. According to the theory and practice, it is proved that the porosity is linearly related to the content of pore-forming agent, and the prediction of porosity is realized. Combined with the Gibson-Ashby model equation, the mechanical properties can be predicted by the content of pore-forming agent.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG146.23

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