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|Title: ||PZT 壓電纖維製備與機電能源轉換研究|
Study on Preparation and Electromechanical Energy Conversion of PZT Piezoelectric Fibers
|Authors: ||Chung-Hao Yi|
|Contributors: ||NTOU:Department of Marine Engineering|
lead zirconate titanate fibers;extrusion method;boric acid condensation;1-3 type of composite;electron spinning
|Issue Date: ||2013-10-07T03:00:41Z
|Abstract: ||鋯鈦酸鉛(PZT)材料壓電性源於其不對稱性的結晶結構，容易受摻雜和溫度與組成的影響。當材料尺度降至微米甚至奈米等級時，其晶粒尺寸與晶格將受到幾何應力的影響，極可能改變壓電特性。本論文探討一維PZT纖維製備及其相關性質，並與高分子樹脂形成1-3型可撓的PZT壓電纖維複合材料，提升壓電常數及能量密度。當以靜電抽絲法 (electro-spinning) 製備奈米級纖維時，可形成單晶粒排列之奈米纖維。 在本研究中，利用縮合水浴法配合擠出成型製作PZT纖維，減少了大量有機添加物，讓PZT燒結後更加緻密，而且降低擠出成型的壓力讓模具擠出口壽命延長，擠出的纖維在水浴中快速反應，適合連續大量的生產。經過調整PVA分子量及水浴中硼酸的濃度，纖維的直徑可從200μm-1mm，並維持一定的真圓性。加工成1-3型複材後，介電常數(εr)及飽合極化量(Ps)隨著PZT的填充率增加而增加，最高78%的填充率讓介電常數提高至2400 (1kHz)，飽合極化量在21 μC/cm2，壓電係數d33隨著纖維粗細、試片厚度及PZT的填充率不同，最高也達到650 pC/N，總合來說，均勻的纖維排列成1-3型複材，能夠讓複材的PZT填充率更高，能更接近塊材的特性且又兼具複材的可撓性。 小於50 μm直徑的纖維難以擠出成型法製備，以靜電抽絲法製備 50-400奈米直徑的PZT纖維，從SEM及HRTEM分析，了解奈米纖維在800°C熱處理後，晶粒明顯成長，其大小超過了纖維的直徑。配合XRD的分析，晶格常數c/a的長方性(tetragonality)隨著溫度增加而逐漸變小，說明奈米級超細纖維的幾何尺寸限制極有可能讓PZT的不對稱晶格變成對稱，降低壓電特性，如何兼顧奈米尺度與高結晶異方性維持PZT纖維壓電性？為材料科學與工程極待突破的課題。|
The piezoelectric properties of lead zirconate titanate (PZT) originate from the asymmetrical crystal structure, which are affected by dopants, temperatures and compositions. When the PZT material size reduced to micron- or even nano-meter scale, the grain size and lattice would be varied due to the generated geometrical stress and the obtained results possibly affected the piezoelectric properties. This thesis studies the one-dimensional PZT fiber preparation and its related properties. Such prepared PZT fibers were arrayed and combined with polymer resin to form a 1-3 flexible PZT piezoelectric fiber composite so as to enhancing the piezoelectric constant and power density. The single grain stacking nanofibers were prepared by electro-spinning method and then characterized. In this study, we produced PZT fibers by extruding PZT fibers in which PVA condensation reacted with boric acid in an aqueous bath. The advantages of this innovated method are reduction of the amount of organic additives, sintering PZT fibers densely, and dropping the extrusion pressure as to increasing the lifetime of the extruding orifice. The condensation reaction was very quickly when the extruded fiber paste in an aqueous bath containing boric acid. This extruding process is suitable for continuous mass production. By adjusting PVA molecular weight and concentration of boric acid in aqueous bath, uniform PZT fibers with true roundness were fabricated successfully with diameter of 200 μm-1 mm. The dielectric constant (εr) and saturated polarization (Ps) increased with PZT fibers volume fraction increase for 1-3 type of PZT-epoxy composite. The dielectric constant 2400 (at 1 kHz) and saturated polarization 21 μC/cm2 were obtained when the PZT fiber volume fraction was up to 78%. The piezoelectric coefficient d33 was sensitive with the diameter of the PZT fiber, the composite thickness and the PZT fiber volume fraction in composite. The maximum d33 value was 650 pC/N. Uniform PZT fiber arrays in 1-3 composite allowed the higher PZT volume fraction in composite and then achieved high piezoelectric properties close to bulk characteristics and behaved a flexible feature. The PZT fiber with diameter less than 50 μm is difficult to prepare by extrusion method. The nano-PZT fibers with 50-400 nm diameter were synthesized by electro-spinning method. The abnormal grain growth occurred after 800°C post-heat treatment from the SEM/HRTEM observation. The lattice constant ratio of c/a (tetragonality) decreased with the post-heat treated temperature from 600 to 800°C analyzed by XRD. This result indicated that the piezoelectric characteristics may disappear due to a transition from asymmetrical tetragonal lattice to symmetrical pseudo-cubic lattice resulted from nanofiber surface confined stress. How to synthesize nano-PZT fibers and to maintain the high piezoelectric properties with anisotropic crystal lattice will be a breakthrough issue for materials scientists.
|Appears in Collections:||[輪機工程學系] 博碩士論文|
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