本文選題：氮化碳 + 第一性原理��； 參考：《南京航空航天大學(xué)》2015年碩士論文

【摘要】：晶體氮化碳材料是一種在自然界未被發(fā)現(xiàn)的新型超硬材料,α、β、立方和準(zhǔn)立方相氮化碳的體彈性模量都能夠媲美甚至超過金剛石。另外,優(yōu)異的化學(xué)惰性和耐磨性也使得晶體氮化碳有望在刀具涂層方面有突出的表現(xiàn)。本文開展了等離子體CVD法制備氮化碳材料的理論與實(shí)驗(yàn)研究,主要內(nèi)容包括計(jì)算仿真、機(jī)理分析和實(shí)驗(yàn)驗(yàn)證三個(gè)部分。本文主要研究及結(jié)論如下:(1)利用Material Studio軟件進(jìn)行了第一性原理化學(xué)吸附仿真研究。研究表明:N2分子在金剛石過渡層和硬質(zhì)合金表面不產(chǎn)生化學(xué)吸附,N原子在其表面上產(chǎn)生化學(xué)吸附;N原子在硬質(zhì)合金表面吸附能比在金剛石過渡層上有更大的值;N原子在硬質(zhì)合金表面比在金剛石過渡層上更易于與基底成鍵,氮化碳更易于在其上直接形核和生長;若采用直流電弧等離子體噴射法制備晶體氮化碳膜,可以通過增大反應(yīng)氣體配比中N2分子量和提高電弧功率密度,產(chǎn)生更多活性N原子,以便提高氮化碳膜形核和生長效率。(2)對(duì)等離子體CVD法制備晶體氮化碳涂層的機(jī)理進(jìn)行了研究。有別于王季陶提出的CVD法制備金剛石膜的“化學(xué)泵”理論,提出了應(yīng)用于氮化碳涂層制備過程的新型“化學(xué)泵”模型;在金剛石過渡層上沉積氮化碳涂層時(shí),基底溫度對(duì)金剛石相和氮化碳相的刻蝕與沉積產(chǎn)生顯著影響,并提出了在適當(dāng)溫度下金剛石相刻蝕和氮化碳相沉積同時(shí)進(jìn)行的假設(shè)模型;當(dāng)?shù)?碳源配比在100:1~10:1時(shí),氮化碳膜才易于成核和生長,并且碳源濃度增長對(duì)氮化碳的晶形和晶粒大小影響很大;沉積氣壓與碳源濃度有交互作用,共同對(duì)氮化碳材料的形貌有顯著影響。(3)采用直流電弧等離子體噴射法分別在金剛石過渡層和硬質(zhì)合金上開展制備氮化碳實(shí)驗(yàn),并對(duì)實(shí)驗(yàn)結(jié)果與仿真結(jié)論和理論分析進(jìn)行對(duì)比研究。對(duì)在不同基底溫度下金剛石過渡層沉積的氮化碳涂層進(jìn)行SEM,XRD等測試,研究表明基底溫度對(duì)金剛石過渡層上制備的氮化碳涂層的晶形和晶粒大小產(chǎn)生顯著影響;首次在硬質(zhì)合金基底上直接制備出了晶形較為完好的氮化碳晶體涂層,并對(duì)在不同碳源濃度條件下于硬質(zhì)合金上沉積氮化碳涂層進(jìn)行SEM,XRD等測試,碳源濃度和基底選擇等對(duì)氮化碳制備的影響與機(jī)理分析、仿真結(jié)果相一致。
[Abstract]:Crystalline carbon nitride is a new superhard material that has not been found in nature. The bulk elastic modulus of 偽, 尾, cubic and quasi cubic carbon nitride is comparable to or even higher than that of diamond. In addition, the excellent chemical inertia and wear resistance also make the crystal carbon nitride has a promising performance in tool coating. In this paper, the theoretical and experimental studies on the preparation of carbon nitride materials by plasma CVD are carried out. The main contents include computer simulation, mechanism analysis and experimental verification. The main research and conclusions are as follows: (1) First-principle chemisorption simulation is carried out using material Studio software. The results show that no chemisorbed N atom is produced on diamond transition layer and cemented carbide surface by N 2 molecule. The adsorption energy of N atom on cemented carbide surface is higher than that on diamond transition layer. Atoms bond to the substrate more easily on the surface of the cemented carbide than on the diamond transition layer. It is easier for carbon nitride to nucleate and grow directly on it. If carbon nitride films are prepared by DC arc plasma jet method, more active N atoms can be produced by increasing the molecular weight of N 2 in the reaction gas ratio and increasing the arc power density. In order to improve the nucleation and growth efficiency of carbon nitride film. (2) the mechanism of preparing crystal carbon nitride coating by plasma CVD was studied. Different from the "chemical pump" theory proposed by Wang Jitao for the preparation of diamond films by CVD, a new "chemical pump" model applied to the preparation process of carbon nitride coatings was put forward, and the carbon nitride coating was deposited on the transition layer of diamond. The substrate temperature has a significant effect on the etching and deposition of diamond and carbon nitride phase, and a hypothetical model of diamond phase etching and carbon nitride deposition at appropriate temperature is proposed, when the ratio of nitrogen source to carbon source is 100: 1 / 10: 1, Nitride carbon film is easy to nucleate and grow, and the increase of carbon source concentration has a great influence on the crystal shape and grain size of carbon nitride, and the deposition pressure has interaction with carbon source concentration. (3) carbon nitride was prepared on diamond transition layer and cemented carbide by DC arc plasma jet method. The experimental results are compared with the simulation results and theoretical analysis. The carbon nitride coatings deposited at different substrate temperatures were tested by SEM XRD. The results show that the substrate temperature has a significant effect on the crystal shape and grain size of the carbon nitride coatings prepared on the diamond transition layer. For the first time, the crystalline carbon nitride crystal coating was prepared on cemented carbide substrate for the first time, and the carbon nitride coating deposited on cemented carbide with different carbon source concentration was tested by SEM XRD and so on. The effects of carbon source concentration and substrate selection on the preparation of carbon nitride were analyzed and the simulation results were consistent.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB306

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