發(fā)布時間：2018-04-04 20:54

  本文選題：六硼化鑭　切入點(diǎn)：納米粉末　出處：《電子科技大學(xué)》2015年碩士論文

【摘要】：六硼化鑭(La B6)具有電導(dǎo)率高、熱蒸發(fā)率低、發(fā)射電流密度大和良好的熱穩(wěn)定性等優(yōu)異性能。本論文旨在研究高純度、小顆粒、粒度分布均勻且具有優(yōu)異電子發(fā)射性能的納米LaB6粉末的制備工藝,用于改善PDP的顯示性能。本論文采用固相合成法進(jìn)行LaB6納米粉末的制備,借助X射線衍射圖譜分析、沉降分析、掃描電子顯微鏡等分析技術(shù)研究了LaCl3和KBH4為原料的固相合成反應(yīng)的機(jī)理,對合成制備工藝參數(shù)進(jìn)行了優(yōu)化,同時還研究了合成產(chǎn)物的清洗和分散技術(shù),并對制備的LaB6納米粉末進(jìn)行了組織形貌表征和性能測試。通過自然沉降分析和掃描電鏡觀察分析了LaB6納米粉末分散體系的穩(wěn)定性,探索LaB6納米粉末的有效的分散方法及粒度的分析手段。不同分散劑和分散方法對LaB6納米粉末的分散效果有明顯的差異,PEI陽離子型表面活性劑對其分散作用不明顯,非離子型的表面活性劑PEG2000一定程度上起到了分散作用,但不夠穩(wěn)定,DBS陰離子型表面活性劑配制的分散液穩(wěn)定性良好,但在過濾烘干后仍然不利于形貌觀測;磷酸對La B6納米粉末的改性效果明顯,穩(wěn)定性優(yōu)于DBS,在過濾并干燥處理后,顆粒團(tuán)聚情況明顯優(yōu)于未分散的顆粒。通過對不同溫度下反應(yīng)產(chǎn)物的成分分析探索反應(yīng)機(jī)理。該反應(yīng)的主要產(chǎn)物除LaB6外,還有大量的KCl和少量的LaBO3、La3BO6。600℃時開始產(chǎn)生LaB6,700℃時反應(yīng)得到充分的進(jìn)行,800℃時產(chǎn)物中的KCl開始熔融并蒸發(fā),隨著溫度的繼續(xù)升高,900℃時有單質(zhì)K析出,在溫度升高到1000℃以后,KCl和LaBO3等雜質(zhì)氣化和分解殆盡,產(chǎn)物為較純凈的LaB6。借助XRD、掃描電鏡和沉降分析等方法,對制備工藝參數(shù)進(jìn)行探索研究。結(jié)果表明,反應(yīng)溫度越高,生成的LaB6晶粒越大,保溫時間越長,越有助于LaB6的生成和晶粒的長大,提高B元素的配料比有助于LaB6的生成,但生成物的團(tuán)聚狀況嚴(yán)重,加入反應(yīng)助劑Mg后可以有效的避免B元素和La元素與O的結(jié)合。對LaB6納米粉末進(jìn)行精細(xì)組織表征和性能測試。固相合成的LaB6納米粉末結(jié)晶良好,顆粒分散均勻,晶粒尺寸在10~50nm的范圍內(nèi),優(yōu)化工藝參數(shù)后制備出了純度約為97.52%的LaB6納米粉末,其平均晶粒尺寸為D=19.53nm,晶格常數(shù)a=4.153?,通過理查森直線法算得其逸出功為2.45eV。
[Abstract]:Lanthanum hexaboride (La B 6) has excellent properties such as high conductivity, low thermal evaporation rate, high emission current density and good thermal stability.The purpose of this paper is to study the preparation process of high purity, small particle size, uniform particle size distribution and excellent electron emission properties of nano-sized LaB6 powder, which can be used to improve the display performance of PDP.In this paper, solid state synthesis method was used to prepare LaB6 nanometer powder. The mechanism of solid state synthesis of LaCl3 and KBH4 was studied by means of X-ray diffraction pattern analysis, sedimentation analysis and scanning electron microscope.The preparation process parameters were optimized, the cleaning and dispersion techniques of the synthesized products were studied, and the microstructure and properties of the prepared LaB6 nano-powders were characterized.The stability of LaB6 nano-powder dispersion system was analyzed by natural sedimentation analysis and scanning electron microscope, and the effective dispersion method and particle size analysis method of LaB6 nano-powder were explored.The dispersion effects of different dispersants and methods on LaB6 nano-powders were obviously different. The dispersion effect of LaB6 cationic surfactants was not obvious, and that of non-ionic surfactants PEG2000 played a dispersing role to some extent.However, the dispersion prepared by DBS anion surfactant has good stability, but it is not good for morphology observation after filtration and drying, the modification effect of phosphoric acid on La B6 nanometer powder is obvious, the stability is better than that of DBS, and after filtration and drying, the dispersion is better than DBS.The agglomeration of particles is better than that of undispersed particles.The reaction mechanism was explored by analyzing the composition of the reaction products at different temperatures.In addition to LaB6, a large number of KCl and a small amount of LaBO _ 3B _ 3BO _ (6.600 鈩，

本文編號：1711650