發(fā)布時(shí)間：2018-07-03 19:12

  本文選題：鈦酸鍶鋇陶瓷 + 放電等離子燒結(jié)　； 參考：《浙江大學(xué)》2017年博士論文

【摘要】：隨著脈沖功率系統(tǒng)小型化和輕量化的發(fā)展,開發(fā)具有更高儲(chǔ)能密度的電介質(zhì)材料成為當(dāng)前研究的熱點(diǎn)。本文選取鈦酸鍶鋇(Ba1-xSrxTiO3)基陶瓷作為研究對(duì)象,系統(tǒng)地研究了制備工藝、微觀結(jié)構(gòu)和相組成對(duì)材料儲(chǔ)能性能的影響。同時(shí),結(jié)合數(shù)值模擬,預(yù)測(cè)了鈦酸鍶鋇基陶瓷的介電擊穿過程和儲(chǔ)能密度。得到的主要結(jié)論如下:陶瓷的微觀結(jié)構(gòu)會(huì)直接影響其擊穿場(chǎng)強(qiáng),而微觀結(jié)構(gòu)又和制備工藝密切相關(guān)。傳統(tǒng)固相燒結(jié)(CM)制備的Ba0.4Sr0.6TiO3樣品致密度較低且微觀結(jié)構(gòu)不均勻。放電等離子燒結(jié)(SPS)制備的樣品相對(duì)致密度均在99%以上,陶瓷晶粒細(xì)小且粒徑分布均一。因此,相比于CM樣品,微結(jié)構(gòu)的改善使得SPS樣品的擊穿場(chǎng)強(qiáng)從180 kV/cm提高到260 kV/cm,最大儲(chǔ)能密度從0.61 J/cm3提高到1.20 J/cm3,儲(chǔ)能效率從72.6%提高到91.6%。為研究晶粒尺寸效應(yīng)對(duì)材料擊穿場(chǎng)強(qiáng)和儲(chǔ)能密度的影響,本文采用溶膠凝膠法結(jié)合放電等離子燒結(jié)制備了具有不同晶粒大小的Ba0.4Sr0.6TiO3致密陶瓷,結(jié)果表明,平均晶粒尺寸約為200 nm的樣品的儲(chǔ)能性能最佳,其擊穿場(chǎng)強(qiáng)高達(dá)240 kV/cm,最大儲(chǔ)能密度為1.23J/cm3,儲(chǔ)能效率為94.52%。在Ba0.4Sr0.6TiO3陶瓷中添加高絕緣性的MgO顆粒能有效地提高其擊穿場(chǎng)強(qiáng)。由于SPS燒結(jié)溫度低且燒結(jié)時(shí)間短,Ba0.4Sr0.6TiO3基體和MgO之間的擴(kuò)散和化學(xué)反應(yīng)被有效地抑制。結(jié)果顯示,性能最佳的復(fù)相陶瓷組分為95 wt%Ba0.4Sr0.6TiO3+5 wt%MgO,其擊穿場(chǎng)強(qiáng)達(dá)到300 kV/cm,最大儲(chǔ)能密度為1.50 J/cm3,儲(chǔ)能效率為88.5%。制備核殼結(jié)構(gòu)的復(fù)相陶瓷也是提高材料儲(chǔ)能性能的重要手段。本文采用液相法制備了具有不同摩爾分?jǐn)?shù)的Ba0.4Sr0.6TiO3@SiO2核殼結(jié)構(gòu)粉末,并結(jié)合放電等離子燒結(jié)獲得了致密的Ba0.4Sr0.6TiO3@SiO2復(fù)相陶瓷。結(jié)果表明,核殼結(jié)構(gòu)的界面處在750℃左右開始發(fā)生化學(xué)反應(yīng),原本均勻包覆在Ba0.4Sr0.6TiO3顆粒表面的無定型SiO2殼層結(jié)構(gòu)逐漸消失,取而代之的是反應(yīng)生成的Sr2TiSi2O8相。當(dāng)SiO2包覆量較少時(shí),生成的Sr2TiSi2O8納米顆粒均勻包覆在Ba0.4Sr0.6TiO3基體表面并顯著地提高復(fù)相陶瓷的擊穿場(chǎng)強(qiáng);隨著SiO2含量的增多,Sr2TiSi2O8納米顆粒聚集長(zhǎng)大,在Ba0.4Sr0.6TiO3晶界處形成微米顆粒,使得其擊穿場(chǎng)強(qiáng)有所下降。性能最佳的復(fù)相陶瓷組分為92 mol%Ba0.4Sr0.6TiO3 + 8 mol%Si02,其擊穿場(chǎng)強(qiáng)高達(dá)400kV/cm,最大儲(chǔ)能密度為1.60J/ccm3,儲(chǔ)能效率為90.9%。在Ba0.4Sr0.6TiO3/MgO復(fù)相陶瓷中,Ba0.4Sr0.6TiO3基體的介電常數(shù)約為950,而MgO的介電常數(shù)僅為10。根據(jù)靜電平衡方程,這種介電常數(shù)的巨大差異必然會(huì)導(dǎo)致局域電場(chǎng)的不均勻分布,從而影響介電擊穿過程。本文基于隨機(jī)模型,模擬了鈦酸鍶鋇基陶瓷和氧化鎂基陶瓷的擊穿路徑。結(jié)果表明,在Ba0.4Sr0.6TiO3基材料中,無論添加的MgO第二相是球狀還是棒狀,放電通道都會(huì)嘗試“繞過”MgO晶粒;而在MgO基材料中,放電通道總是傾向于“穿過”Ba0.4Sr0.6TiO3晶粒。最后,基于Landau-Devonshire唯象理論和Ginzburg-Landau方程,本文利用相場(chǎng)模型模擬了Ba1-xSrxTiO3單晶和多晶的鐵電性能,并通過模擬的電滯回線計(jì)算了其儲(chǔ)能密度。結(jié)果表明,隨著Sr含量的增加,其儲(chǔ)能密度先增加后減小,當(dāng)x=0.6時(shí)材料具有最佳的儲(chǔ)能性能。
[Abstract]:With the development of miniaturization and light weight of pulse power system, the development of dielectric materials with higher energy storage density has become a hot spot of current research. This paper selected barium strontium titanate (Ba1-xSrxTiO3) based ceramics as the research object, and systematically studied the preparation process, the effect of microstructure and phase composition on the energy storage performance of the material. The dielectric breakdown process and the energy storage density of barium strontium titanate ceramics are predicted by value simulation. The main conclusions are as follows: the microstructure of the ceramics will directly affect the breakdown field, and the microstructure is closely related to the preparation process. The Ba0.4Sr0.6TiO3 sample prepared by the traditional solid phase sintering (CM) has a low density and the microstructure is not uniform. The relative density of the samples prepared by electric plasma sintering (SPS) is above 99%, and the ceramic grain is fine and the particle size distribution is uniform. Therefore, compared to the CM sample, the breakdown strength of the SPS samples increases from 180 kV/cm to 260 kV/cm, the maximum energy storage density is increased from 0.61 J/ cm3 to 1.20 J/cm3, and the energy storage efficiency is increased from 72.6% to 91.6%.. In order to study the effect of grain size effect on material breakdown field strength and energy storage density, the Ba0.4Sr0.6TiO3 compact ceramics with different grain sizes were prepared by sol-gel method and discharge plasma sintering. The results showed that the energy storage performance of the sample with an average size of 200 nm was the best, and the breakdown field strength was up to 240 kV/cm. The large energy storage density is 1.23J/cm3, and the energy storage efficiency of 94.52%. in Ba0.4Sr0.6TiO3 ceramics with high insulating MgO particles can effectively improve the breakdown field strength. The diffusion and chemical reaction between the Ba0.4Sr0.6TiO3 matrix and MgO is effectively suppressed because of the low sintering temperature and the short sintering time of SPS. The results show that the best complex phase ceramics have the best performance. The composition is 95 wt%Ba0.4Sr0.6TiO3+5 wt%MgO, the breakdown field strength is 300 kV/cm, the maximum energy storage density is 1.50 J/cm3, the energy storage efficiency is 88.5%. to prepare the shell structure complex phase ceramics is also an important means to improve the material storage performance. In this paper, the liquid phase method was used to prepare the Ba0.4Sr0.6TiO3@SiO2 nuclear shell powder with different mole fraction. The compact Ba0.4Sr0.6TiO3@SiO2 composite ceramics were obtained by spark plasma sintering. The results showed that the chemical reaction of the core shell structure began to occur at about 750 degrees C. The amorphous SiO2 shell structure which was originally coated on the surface of Ba0.4Sr0.6TiO3 particles gradually disappeared, and replaced by the reaction generated Sr2TiSi2O8 phase. When SiO2 When the coating amount is less, the Sr2TiSi2O8 nanoparticles are evenly coated on the surface of the Ba0.4Sr0.6TiO3 matrix and significantly improve the breakdown field strength of the composite ceramics. As the content of SiO2 increases, the Sr2TiSi2O8 nanoparticles gather and grow, and the micron particles are formed at the Ba0.4Sr0.6TiO3 grain boundary, which makes the breakdown field strength decrease. The ceramic component is 92 mol%Ba0.4Sr0.6TiO3 + 8 mol%Si02, the breakdown field strength is as high as 400kV/cm, the maximum energy storage density is 1.60J/ccm3, the energy storage efficiency is 90.9%. in the Ba0.4Sr0.6TiO3/MgO complex ceramics, the dielectric constant of the Ba0.4Sr0.6TiO3 matrix is about 950, and the dielectric constant of MgO is only 10. based on the electrostatic equilibrium equation, and the dielectric constant is huge. The difference inevitably leads to the inhomogeneous distribution of the local electric field, thus affecting the dielectric breakdown process. Based on the random model, the breakdown path of barium strontium titanate based ceramics and Magnesium Oxide based ceramics is simulated. The results show that in the Ba0.4Sr0.6TiO3 based materials, no matter the second phase of the addition of MgO is a ball or a rod, the discharge channel will try to "go around" In the MgO based material, the discharge channel is always inclined to "pass through" the Ba0.4Sr0.6TiO3 grain. Finally, based on the Landau-Devonshire phenomenological theory and the Ginzburg-Landau equation, the ferroelectric properties of the Ba1-xSrxTiO3 single crystal and the polycrystalline are simulated by the phase field model, and the energy storage density of the Ba0.4Sr0.6TiO3 is calculated by the simulated hysteresis loop. The results showed that with the increase of Sr content, the energy storage density first increased and then decreased. When x=0.6, the material had the best energy storage performance.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ174.1

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本文編號(hào)：2094714