論文提要（中）：
本實驗使用雷射剝蝕凝聚（laser ablation condensation）與高溫退火(high temperature annealing)的方式形成(Ni,Ti)O2， (Ni,Co)O與(Co,Mg)O等固溶凝聚物，並使用掃瞄式(SEM)與解析式(AEM)電子顯微鏡來研究其凝聚、形狀、聚簇、缺陷、與相變化的行為。
在(Ni,Ti)O2的系統中，我們使用Nd-YAG脈衝雷射，剝蝕金屬鎳與鈦的複合靶材，於特定雷射功率密度及氧流量，和急熱急冷所產生壓力效應的情況下，製造出含鎳並屬於金紅石結構的二氧化鈦奈米球，在經過電子束照射後，表面開始產生Ni2(1+x)Ti1-xO4尖晶石(spinel)顆粒析出，並與金紅石(rutile)之間的晶向關係為[111]r//[012]s; (10 )r//(200)s。在經過更長時間的電子束照射下，奈米球表面產生快速的動態分解過程(decomposition)，使得NiTiO3的奈米顆粒於非晶(amorphous)區域生成。
此外，利用同樣的方式可以合成出含鎳螢石態(fluorite-type)的二氧化鈦高壓相。當奈米凝聚物的尺寸小於20nm，則其形狀接近立方八面體(cubo-octahedral)，並依循(100)f//(110)m; [001]f//[001]m的晶向關係麻田散鐵相變(martensitic transformation)成斜鋯石（baddeleyite）結構。當凝聚物尺寸兩倍於20nm，並受基材制約下，其形狀接近球形，且存在馬賽克雙晶(mosaic twin)，並依循(010)f//( 20)m; [001]f//[001]m的晶向關係。又由於氧化鎳溶入緻密的二氧化鈦凝聚物中，所產生體積與電荷補償效應(charge and volume compensating)的氧空缺，並輔以電子束照射下，會促進鬆弛(relaxation)與非晶(amorphization)過程進行。
再更進一步利用脈衝雷射剝蝕金屬鎳、金屬鈷與鎳鈷或鈷鎳的複合靶材在充滿氧的氣氛下，可以合成出具岩鹽結構(rock-salt type)的凝聚物。在解析式電鏡的觀察中，氧化鎳奈米顆粒的形狀為立方體(cube)，而氧化鈷與Ni1-xCoxO奈米顆粒為立方八面體(cubo-octahedral)，這些奈米晶體多以{100} 或 {111}的晶癖面聚合(coalescence)形成奈米鏈狀聚簇(nano chain aggregates)或最密堆積(closer packed manner)的情形。此外，少量岩鹽結構的氧化鈷會氧化成Co3-δO4尖晶石結構，並由電子繞射的證據可知，其中具有調節性分佈(modulated distribution)的缺陷聚簇(defect cluster)存在。
最後，我們利用氧化鈷有或沒有參雜20mol%氧化鎂，在大氣下作400-1500 oC的退火，並以掃瞄式電鏡觀察表面形貌的改變，發現氧化鎂成分如預期地相當抑制了熱腐蝕與富鎳尖晶石的成核。令人驚訝地，在1500 oC更長時間退火的情況下，立方晶系產生非等向性(anisotropic)以{100} 與 {111}晶癖面開展的溶蝕坑(etch pits)/溶蝕丘(hillocks)，可歸因於<110>方向差排露頭於{111}的晶癖面上。在此同時，昇華凝聚(sublimination-condensation)所產生的氧化鈷立方晶體，可藉由布朗運動與其母材產生平行和45度的晶向關係。

Abstract

This research is focused on the condensation and phase transformation of NiO-TiO2, Co1-XO-NiO, and Co1-XO-MgO solid solution via dynamic laser ablation condensation and high temperature annealing.

TiO2 rutile nanospheres with enhanced solid solution of NiO were synthesized via very energetic pulse laser ablation on clamped Ni/Ti target in oxygen for a very rapid heating/cooling, and hence pressure effect. Upon electron irradiation, the NiO-dissolved rutile (r) were partially transformed into 2(01 ) commensurate superstructure and Ni2(1+x)Ti1-xO4 spinel (s) following the crystallographic relationship [111]r//[012]s; (10 )r//(200)s. Alternatively, random NiTiO3 nanodomains were formed from amorphous regions in such a rapid decomposition process.

In addition, the dense fluorite-type (f) derived TiO2 condensates dissolved up to 5 at% Ni2+ of the cations were synthesized via the same route. The nanocondensates less than 20 nm in size are nearly cubo-octahedral in shape and tended to transform martensitically to monoclinic (m) baddeleyite-type following the crystallographic relationship (100)f//(110)m; [001]f//[001]m. The condensates twice larger in size, with considerable matrix constraint, are nearly spherical in shape and consist of mosaic m-twin variants following complicated crystallographic relationships with each other and with the relic f-phase: (010)f//( 20)m; [001]f//[001]m. The charge and volume compensating oxygen vacancies due to NiO dissolution in the dense TiO2 condensates could facilitate the relaxation and amorphization process.

Further more, pulse laser irradiation of Ni, Co, and Co-Ni (or Ni-Co) targets in an oxygen background gas produced nanocondensates with rock-salt type structure. Analytical electron microscopic observations indicated that such nanocrystals are cubic in shape for NiO and cubo-octahedral for Co1-xO and Ni1-xCoxO. The nanocrystals coalesced predominantly with {100} or {111} facets to form nano chain aggregates or closer packed manner. The Co1-xO was more or less oxidized as Co3-

Contents
誌謝 I
論文提要（中） IV
Abstract VII
Contents IX
List of Figures XII
List of Table and Appendix XXII
Chapter 1 Introduction
1.1 Alloying/dealloying in nanometer-sized particles 1
1.2 Condensation/phase transformation of dense TiO2 polymorphs 2
1.3 Shape and defect clusters of transition metal oxide solid solution with
rock salt-type structure……………………………………………………….. 3
1.4 Dissolution of ceramic single crystal and polycrystals………………………..4
1.5 Investigation scope 5

Chapter 2 Condensation and Decomposition of NiO-dissolved Rutile Nanospheres
2.1 Introduction 8
2.2 Experimental 9
2.3 Results 10
2.3.1 As-formed condensates
2.3.2 Phase and composition change upon electron irradiation
2.4 Discussion 12
2.4.1 Enhanced dissolution of NiO in rutile condensate
2.4.2 Retention of NiO in rutile condensates to ambient pressure
2.4.3 Anisotropic expelling of NiO from rutile by electron irradiation
2.4.4 Formation mechanism of Ni2TiO4 and NiTiO3 from NiO-oversaturated rutile
2.5 Conclusions 17

Chapter 3 On the Relxation/Transformation of NiO-Dissolved TiO2 Condensates with Fluorite-type derived Structures
3.1 Introduction 33
3.2 Experimental 34
3.3 Results 35
3.4 Discussion 36
3.4.1 Defect chemistry and transformation of NiO dissolved in fluorite-type structure
3.4.2 Implications
3.5 Conclusions 40

Chapter 4 Laser Ablation Condensation and Phase Change of Ni1-XCoXO Nanoparticles
4.1 Introduction 49
4.2 Experimental 51
4.3 Results 52
4.3.1 Ni target
4.3.2 Co target
4.3.3 Co-Ni target
4.3.4 Ni-Co target
4.4 Discussion 55
4.4.1 Composition rather than residual stress dependent shape of the nanocondensates
4.4.2 Phase selection of the nanocondensates
4.4.3 Defect chemistry of paracrystalline nanocondensates
4.4.4 {hkl}-specific coalescence of the nanocondensates
4.5 Conclusions…………………………………………………………………..61
Chapter 5 On the Surface Morphology of Solution Annealed Co1-XO-MgO – Effects of Directional Dislocation Exposure and Co1&#8722;XO Condensation
5.1 Introduction ………………80
5.2 Experimental 82
5.3 Results 82
5.3.1 Phase and defect identification
5.3.2 Surface morphology of thermally etched Co1-XO vs. C8M2 ceramics
5.3.3 Morphology of thermal etch pits and hillocks in C8M2 ceramics
5.3.4 Condensation of Co-rich crystallites on C8M2 ceramics
5.4 Discussion 86
5.4.1 Defect chemistry and spinel paracrystal formation in bulk material
5.4.2 Solute segregation and spinel paracrystal formation at line and planar defects
5.4.3 Dislocation exposure and the formation of thermal etch pits with spiral hillocks
5.4.4 Epitaxial condensation of Co1-XO on Co1-XO-MgO solid solution grain
5.5 Conclusions......................................................................................................92

References………………………………………………………………………….111

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