精密氧化鋯射出胚料性質及 其強度性質之研究

吳榮源(Rong-Yuan Wu)

指導教授 ： 韋文誠

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.01766

摘要

本研究採用氧化鎂添加氧化鋯(Mg-PSZ)及氧化釔添加之氧化鋯(3Y-TZP)之兩種粉體，利用混煉、射出成形、溶脫、熱脫與燒結後，製備射出精密樣品。本研究要發展一套胚料均勻度的量化程序，研究範圍分為四個部分：一.選擇適當界面劑，提升Mg-PSZ射出胚料穩定性，得到最佳射出件性質。二.建立胚料均勻分析技術，分析胚料均勻度與混煉能量關係。三.根據能量消耗圖關係，監控混煉過程中胚料性質的變化，分析胚料均勻度與混煉時間關係，找出最適當混煉過程。四.使用不同混煉設備製備均勻射出胚料，進行造粒，觀察胚料均勻度與射出件燒結體尺寸變異與破壞強度關係。
第一部份藉由界面劑之路易酸鹼吸附理論來說明界面劑（包含潤滑與分散劑）之功能，選擇適當界面劑種類，提高Mg-PSZ射出胚料穩定性。懸浮漿體中添加不同界面劑，觀察粉體在正庚烷或熔融石蠟中之沈降行為，利用扭矩流變儀與毛隙流變儀觀察胚料之流變行為，再將胚料進行射出成形，觀察其尺寸變化與燒結性質。研究初步發現具有酯類功能鍵之F1界面劑，對於氧化鋯粉體不管在正庚烷中或熔融石蠟中皆可以得到良好分散行為，且讓潤濕粉體效果變佳，但所得射出胚料黏度略高。若採用兩種F1/SA混合界面劑，胚料所得流變性質較為穩定，且射出件之物理與機械性質變異較小。
第二部分研究則是利用毛隙流變儀、穿透性光學顯微鏡及扭矩流變儀，進行氧化鋯胚料均勻度之定量化分析。經由收集胚料混煉過程所產生扭矩力變化，計算胚料能量消耗圖（Np-Re），分析輸入混煉能量、雷諾數與溫度及轉數關係。由觀察胚料微結構之粉體聚結狀態，探討此混煉狀態與前各項因素之關係。最後使用定量化之分散指數（Ds）代表胚料均勻性質，提出混煉能量(P)與胚料均勻度之關係，進而瞭解施於胚料之混煉能量多寡影響胚料均勻度之行為。
第三部分的研究，利用扭矩流變儀及穿透性光學顯微鏡，進行釔-氧化鋯胚料混煉行為分析，找出胚料均勻度與時間關係，得到均勻胚料，進行射出、脫脂與燒結。收集胚料混煉過程所產生扭矩力變化，觀察胚料微結構之粉體聚結狀態，探討不同混煉條件下胚料均勻度與時間關係，其最佳混煉曲線為170oC/30 rpm/60 min，然後再以150oC/30 rpm/90min，即可製備出均勻胚料。將胚料進行射出、脫脂與燒結。結果顯示當胚料均勻度提高，射出件燒結體之破壞強度也會提高。
第四部分研究，利用高分佈機構之Z-blade混煉機混煉胚料，再依序利用高分散機構之雙滾筒或扭矩流變儀製備出均勻氧化鋯胚料，進行射出、脫脂與燒結成形後，量測燒結體尺寸變化與破壞強度。兩種高分散機構之雙滾筒與扭矩流變儀之分散剪應力分別為50 kPa與9.6 kPa進行混煉，利用均勻指數（homogenous index, Ha）與分散指數(dispersive index,Ds)顯示胚料均勻度，將胚料內粉體聚結分散到小於1 %後，再利用單螺桿擠出機進行造粒。均勻胚料製備出射出件燒結體，其最小尺寸變化的標準差百分比小於千分之1，且提高射出件燒結體破壞強度，韋伯模數從m= 8提高到m=12。

關鍵字

尺寸變異 ； 複合界面劑 ； 破壞強度 ； 分散指數 ； 氧化鋯胚料 ； 能量消耗圖 ； 韋伯模數 ； 均勻指數

並列摘要

The process of ceramic injection molding consisted of kneading process, injection molding, debinding process and sintering process. In my study, feedstock homogeneity and physical properties of Mg-PSZ and 3Y-TZP is investigated for fabricating precise parts by micro-injection molding. The objectives of my research include: 1. How to select best appropriate surfactant is selected for get stable feedstock and best physical properties of injection parts. 2. How to quantitatively analysis technique of feedstock homogeneity is established. The relationship between feedstock homogeneity and kneading power is realized by power consumption diagram. 3. According to power consumption relationship the torque variation of feedstock is monitored by torque rheometer. The relationship between feedstock homogeneity and kneading time is analyzed to get appropriate kneading process. 4. The different zirconia feedstock is kneading and pelleting by kneaders. The feedstock homogeneity that is relative to dimensional stability and fracture strength of sintering part is observed.
Firstly, according to Lewis acid-base theory the appropriate surfactant is selected to get the stability of Mg-PSZ feedstock. The sedimentation behavior of solvents and melted waxes is observed by adding different surfactants. The flow properties of zirconia feedstocks are measured by torque and capillary rheometer. Then, the dimensional stability and fracture strength of sintering properties is observed the relationship of surfactant types. The zirconia suspension contained F1 surfactant of ester group get dispersive behavior in heptane or melted wax. The F1 surfactant improved wetting effect with zirconia and increased viscosity of Mg-PSZ feedstock. The zirconia feedstock that made up of F1/ SA duplex surfactants become more stability of flow properties and smallest variation of physical properties.
Secondly, the homogeneity of zirconia feedstock is analyzed quantitatively by torque rheometer, capillary rheometer and transmission optic microscopy. The quantitative indexes have homogenous index (Ha) and dispersive index (Ds). The dispersive index shows significantly feedstock homogeneity. Besides, calculating the power consumption diagram (Np-Re diagram) is due to torque variation of kneading process. The parameters of kneading power, Reynolds number are calculated with kneading temperature and speed of blade rotation. The kneading power (P) that calculated from Np-Re equation is critical value with feedstock homogeneity.
Thirdly, the kneading behavior of 3Y-TZP feedstock is investigated by torque rheometer and transmission optic microscopy. The optimum kneading process is determined to fully homogenous feedstock due to the relationship between feedstock homogeneity and kneading time. The physical properties of sintering parts are analyzed for injection molding, debinding and sintering. The different kneading conditions are selected to knead zirconia feedstock. The agglomerate fraction in feedstock is relative to kneading curve that involved temperature, rotation and time. The best kneading curve of 170oC/30 rpm/60 min and then 150oC/30 rpm/90 min fabricates zirconia feedstock that contained less than 1% agglomerate. The ceramic parts are fabricated from zirconia feedstock by the processes of injection molding, debinding and sintering. The dimensional stability and fracture strength of sintering parts are increased.
Finally, homogenous feedstock of zirconia is made up by Z-blade kneader with best distributive mixing, twin roller kneader and torque rheometer with dispersive mixing. The dispersive index of 3Y-TZP feedstock is 0.81 due to kneading by Z-blade kneader. Then, the dispersive index is less than 2% agglomerate due to kneading by two roller mixer or torque rheometer. The shear stresses of twin roller kneader and torque rheometer are 50 kPa and 9.6 kPa, respectively. The kneading time of twin roller kneader needs less than torque rheometer. The homogenous feedstock is fabricated to injection parts. The dimensional variation of sintering parts that made up homogenous feedstock is less than 0.1 % and fracture strength improves from 520 to 780 MPa. The Weibull modulus increase from m=8 to m=12.

並列關鍵字

Weibull modulus ； dispersive index, power consumption diagram ； homogenous index ； fracture strength ； duplex surfactants ； dimensional stability ； zirconia

參考文獻

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