Please use this identifier to cite or link to this item:
Effect of liquid carbon-assisted synthesis on crystalline size of tetragonal zirconia room-temperature stabilization
|Authors: ||Yang, Zong-Syun|
|Contributors: ||NTOU:Institute of Materials Engineering|
zirconia;tetragonal;carbon-assistant;liquid carbon materials
|Issue Date: ||2017-05-24T08:17:42Z
|Abstract: ||本研究先利用溶膠凝膠法製備微米至次微米四方晶相氧化鋯(t-ZrO2)顆粒，並於離心過程後個別加入不同含量之液態碳物質，如：酚醛樹脂(phenolic resin)與果糖(fructose)，隨後分別於不同環境與溫度下進行煅燒，所得的結果與先前的研究(添加丙三醇(glycerol))進行比較，比較探討不同液態碳物質輔助下對合成四方晶相氧化鋯晶粒尺寸之影響。煅燒後氧化鋯之結晶晶粒尺寸以X光繞射儀(XRD)檢測其相組成並計算其晶粒尺寸，並利用掃描式電子顯微鏡(SEM)觀察其形貌與顆粒尺寸，此外，亦利用傅立葉轉換紅外光譜儀(FTIR)檢測樣品中存在何種官能基以及X射線電子能譜儀(XPS)檢測化學鍵結與氧離子空缺變化。 實驗結果顯示，於大氣800°C煅燒後，會有單斜晶相氧化鋯(m-ZrO2)形成，但於真空800°C煅燒後，氧化鋯仍以四方晶相穩定存在。添加5%酚醛樹脂或8%果糖的氧化鋯於真空800°C煅燒後t-ZrO2晶粒尺寸分別可達47奈米、50奈米，其明顯大於沒有碳輔助的結果(32奈米)。XPS分析結果顯示在有碳輔助煅燒後之試樣中，晶格中氧空缺所佔的比例會大於沒有碳輔助的結果，而且其隨著煅燒溫度(400°C ~800°C)提高而增加。顯然地，煅燒過程中液態碳物質的添加能夠幫助氧化鋯形成額外的氧離子空缺而有助於四方晶相穩定，使其晶粒尺寸成長而且大於未添加的結果。由於含碳物質不完全燃燒會產生一氧化碳(CO)，其為一還原性氣氛，因而在真空煅燒過程中，其有助於產生較多的氧空缺而促進四方晶相穩定。再者，依添加液態碳物質的類別，分別有一最適添加量，超過此添加量，液態碳物質輔助的增益效應降低。比較三種碳物質之添加效益後亦發現此增亦效應果糖最優、酚醛樹脂次之而丙三醇再次。原因可能是不同液態碳物質於煅燒時，分解出一氧化碳(CO)的能力不一所引起。三者中，果糖的裂解溫度最低，所以在真空煅燒過程中較容易產生一氧化碳，因而呈現四方相晶粒尺寸最佳的增益效應。|
The research first prepared tetragonal zirconia (t-ZrO2) particles with submicron size using the sol-gel method under carbon-assistant in which the assisted carbonaceous materials of phenolic resin and fructose were separately added into the gel after a centrifugal process. The dried powders were subsequently calcined under distinct atmospheres at various temperatures. The results were also used to compare with the previous study (with the addition of glycerol) to study the effect of liquid carbon-assisted synthesis on crystalline size enhancement and metastability of tetragonal zirconia (t-ZrO2). The calcined powders were examined by x-ray diffractometer (XRD) to evaluate the crystalline size of t-phase. The morphology and particle size were observed and measured by scanning electron microscope. Furthermore, Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) were employed to investigate the present functional groups of powders before and after being calcined, and to study the variation of oxygen vacancies ratio and chemical bonding in the calcined powders. The results show that monoclinic zirconia (m-ZrO2) formed after the calcination of 800C under atmosphere, but ZrO2 with the type of t-phase still stabilized after the calcination of 800C under the vacuum of approximately 10-6 torr. Following the calcination of 800C under the vacuum, the crystalline size of t-ZrO2 in the calcined specimens with the separated addition of 5% phenolic resin and 8% fructose can be achieved by 47 nm and 50 nm, respectively, which are both clearly larger than that (32 nm) without any addition. The analyzed results of XPS indicate that the oxygen vacancies ratio in the lattice of the calcined specimen with the addition of carbonaceous materials is more than that without any addition and increases with increasing the temperature of calcination. Apparently, the addition of liquid carbonaceous materials is helpful to the production of oxygen vacancies during calcination which facilitates the stability of t-ZrO2; the crystalline size of t-ZrO2 was enhanced and larger than that without any addition. Because the incomplete combustion of carbonaceous materials can produce carbon monoxide (CO) that is a reductive gas, the gas is beneficial to produce much more oxygen vacancies in zirconia during the calcination under vacuum which promotes the stability of t-ZrO2. Moreover, there is an optimum addition content to individual carbonaceous materials the effect of carbon assistant on the enhancement of crystalline size of t-ZrO2 decreased with increasing the addition content when the addition content of carbonaceous materials was more than the individual optimum addition content. Comparing the results of optimum addition of the three liquid carbonaceous materials also showed that the effect on the crystalline size enhancement of t-ZrO2 is: fructose > phenolic resin > glycerol. The phenomenon could be attributed to the discrepancy of ability of producing CO gas when the specimen with the addition of specific carbonaceous materials calcined under vacuum. The pyrolysis temperature of fructose among the three carbonaceous materials is the lowest, so it much easily produces CO during the calcination under vacuum and consequently exhibits the best enhancement of crystalline size of t-ZrO2.
|Appears in Collections:||[材料工程研究所] 博碩士論文|
Files in This Item:
All items in NTOUR are protected by copyright, with all rights reserved.