鐵電性(ferroelectric)和鐵彈性(ferroelastic)相變化材料，如二氧化釩(VO2)和鈦酸鋇(BaTiO3)，可以藉溫度或是其他外部的力場，如電磁輻射或應力場，進行固態-固態相變化(solid-solid phase transformation)。Landau的相變唯象理論(phenomenological theory of phase transformation)預測，當材料系統在相變化的附近，會處於一個相對高的能量狀態。本研究探討奈米尺度下具有層狀微結構的高阻尼及高勁度(high damping and high stiffness, HDHS)的複合材料。HDHS顆粒狀的複合材料已經被證明具有非常高的整體阻尼及勁度，唯其穩定性仍待進一步研究。本研究間接提供HDHS層狀複合材料的穩定性。
在實驗試體的準備上，多層薄膜藉由磁控濺鍍(magnetron sputter deposition)的方式將材料鍍在矽(Si)基板上面。至於微米柱則是使用了雙束型聚焦離子束(DB-FIB)來製作，使得薄膜或是矽基板上產生了微米柱的結構。再運用壓痕試驗(nanoindentation)及微壓試驗(micro-compression)量測薄膜和微米柱的力學性質。本研究試體包含鈦酸鋇薄膜(1μm厚)，銅/鈦酸鋇/銅(Cu/BaTiO3/Cu)的多層薄膜(總共30nm厚)和它們的微米柱。此外，矽基板微米柱提供了基材性質。研究鈦酸鋇在不同的溫度下，晶格結構由tetragonal到cubic之間的相變化。最後從單層材料的相變化延伸到量測多層薄膜，銅/鈦酸鋇/銅在升溫過程中微結構發生的變化情形。此外由奈米壓痕試驗，探討了MTS G200奈米壓痕試驗機在高溫下的穩定性和準確性。藉由奈米壓痕試驗我們也得到BaTiO3 單層膜之硬度及楊氏模數分別為 11 GPa 和 170 GPa。此外，高溫下量測SiO2的性質與常溫下量測到的相符合，硬度及楊氏模數分別是 9 GPa 和 70 GPa。
因為溫度引起的相變化，Cu/BaTiO3/Cu微米柱的力與位移關係產生不尋常的跳躍，本文驗證此跳躍之實驗重覆性，且發現純銅對照組並無此現象。對於微壓實驗後的試體進行TEM分析，發現鈦酸鋇薄膜產生局部結晶。本研究量測得的相變溫度範圍落在 40°C (313K) 到 80°C (353K)之間，低於由文獻鈦酸鋇塊體的600°C (873K)，原因可能為應力導致相變溫度降低。此外相變化發生的時間總共為0.6秒。

Phase-transforming materials, such as vanadium dioxide (VO2) or barium titanate (BaTiO3), are known to be ferroelectric and ferroelastic. Solid-solid phase transformation from one crystal symmetry to another upon varying temperature or external electromagnetic radiation or mechanical stress fields can be triggered. As predicted by Landau’s phenomenological theory of phase transition, the material system is at a high energy state in the vicinity of phase transition. The intent of this study was to determine if high damping and high stiffness (HDHS) composites with nano-scale microstructures could be fabricated and realized with phase-transforming inclusions. Bulk particulate composites composed of similar constituents have been shown to possess extremely high damping and high viscoelastic stiffness, and it is expected that composite with nano-scale microstructure may behave in a similar manner.
Micro-pillars were made using Dual Beam Focused Ion Beam (DB-FIB) out of multilayer thin films, and the films were made by sputtering deposition. Nanoindentation and micro-compression experiments were performed on copper thin films, barium titanate (BaTiO3) thin films, Cu/BaTiO3/Cu multi-layered thin films and micro-pillars. Silicon substrates and silicon micro-pillars were also tested for baseline comparison. High temperature, isothermal and heating nanoindentation tests were conducted on fused silica (amorphous SiO2) to verify the capabilities and isothermal of the MTS G200 nanoindenter. To study the tetragonal to cubic phase transformation in BaTiO3, both isothermal and heating experiments were conducted to investigate the phase transformation of single BaTiO3 layers and related Cu/BaTiO3/Cu multilayers. Nanoindentation tests at high temperature for SiO2 showed its hardness was 9 GPa, and Young’s modulus was 70 GPa. From nanoindentation tests, it was found that the hardness and modulus of BaTiO3 single layer thin films were 11 GPa and 170 GPa, respectively.
Temperature-induced anomalies in load and displacement signals were observed from the micro-pillar experiments, but not clearly from nanoindentation tests. The phase transformation of the confined barium titanate layer may be responsible for the anomalies. These results provide basic understandings of phase transformation in confined environments. Through TEM analysis, we found crystalline BaTiO3 phases after heating and micro-compression, which may be form due to phase transformation or grain growth. TEM studies of the as-deposited barium titanate films did not show crystalline phases, but the films may still possibly contain a small amount of nanoscale crystalline grains. In addition, it was found that phase transformation temperature was between 40°C (313K) to 80°C (353K), different from the transformation temperature of bulk barium titanate, which is about 600°C (873K). The shift in transformation temperature may be due to stress-induced mechanisms from the geometry and loading conditions. As for stability of the phenomena, it was found that the process took about 0.6 sec. It is possible that phase transformations were occurred in some regions but not detected due to the amount of materials being transformed is not enough to change mechanical loading and displacements.

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