超磁致伸縮復合材料的制備

材料科學論文編號:CL003  論文字數:22379,頁數:35

目  錄

摘要 
Abstract 
1  緒論  1
1.1 引言  1
1.2 超磁致伸縮材料性能及其研究現狀  1
1.2.1超磁致伸縮材料的性能特點  1
1.2.2超磁致伸縮復合材料的性能  2
1.2.3超磁致伸縮材料與超磁致伸縮復合材料綜合性能比較  2
1.2.4超磁致伸縮材料的研究現狀  3
1.2.4.1超磁致伸縮合金的研究現狀  3
1.2.4.2超磁致伸縮復合材料的研究現狀  3
1.3 稀土-鐵系超磁致伸縮材料的制備技術  3
1.3.1“一步法”新工藝  3
1.3.2粉末冶金法  4
1.3.3薄膜制備技術  5
1.4 工藝參數的優化選擇  5
1.4.1顆粒尺寸的選擇  5
1.4.2成型壓力的選擇  6
1.4.3樹脂含量的選擇  6
1.4.4其它    6
1.5超磁致伸縮材料的應用   6
1.6 GMM應用市場分析  7
1.6.1國內外市場需求  7
1.6.2GMM的市場前景  8
1.7 本課題的研究內容及意義   8
2  實驗準備工作   9
2.1 材料的準備    9
2.1.1合金的準備    9
2.1.2 樹脂粘結劑主要成份的選擇    9
2.1.2.1樹脂的選擇    9
2.1.2.2固化劑的選擇    9
2.2模具的設計、研制   10
2.3 測試方法  12
2.3.1分析測試方法  12
2.3.2 磁致伸縮系數(λ)的測量  12
2.3.3 GMM和GMPC密度的測量  13
3  合金的制備  14
3.1 GMM制備  14
3.1.1合金制備  14
3.1.2合金的XRD分析  14
3.1.3合金的SEM分析  15
3.1.4合金的磁致伸縮系數  16
4  超磁致伸縮復合材料的制備及性能測試  17
4.1 GMPC制備  17
4.2 GMPC性能測試與結果討論  17
4.2.1 GMM合金粉末粒度分析  17
4.2.2磁致伸縮常數的測量  18
4.2.3 組織形貌的觀測  19
4.2.4合金和復合材料的密度測定結果  19
4.2.5復合材料的電阻率測定結果  19
4.3 關于GMPC制備的總結  20
5  摻Ho超磁致伸縮材料合金退火后“蘑菇”狀析出物研究  21
5.1 摻Ho超磁致伸縮合金退火后“蘑菇”析出 21
5.2 基體棒和“蘑菇”分析 21
5.2.1組織形貌分析   21
5.2.2成分分析   22
5.2.3XRD物相及結構分析  23
5.3 磁致伸縮常數的測量   25
6  結論  22
謝辭   26
參考文獻   27

摘  要

超磁致伸縮材料作為一種新型功能材料，受到世界高技術領域專家們的極大關注，發展迅速。美國、日本等國家對其制備工藝、成分、相結構、磁結構和性能做了大量研究工作，技術已經日趨成熟。但是稀土超磁致伸縮材料是鐵磁導電物質，當外加磁場強度變化時，將在介質中產生渦流，使材料發熱，而且交變磁場頻率越高，渦流越強烈，從而限制了磁致伸縮材料在超聲技術中的應用。樹脂基稀土超磁致伸縮復合材料（Giant Magnetostrictive Powder Composite，GMPC）的出現，解決了這個問題。其上限頻率可達100kHz，這就大大擴充了超磁致伸縮材料在高頻超聲技術中的應用，具有極大的發展前景。
本論文旨在：（1）設計、研制一套適用于GMPC的制備成型模具，包括磁場的施加措施等；（2）采用手工破碎制粉技術和自行設計的成型模具、用粉末粘結法制備出性能良好的GMPC，對其磁致伸縮、電阻等性能進行綜合測試分析；（3）研究GMPC的磁場成型工藝對其磁性能的影響規律，從而探索出GMPC的最佳制備工藝。
實驗采用D8-ADVANCE型X射線衍射儀進行材料結構及物相分析，用JSM-5610LV型掃描電鏡觀察樣品組織及顆粒表面形貌，用4×BⅡ型（雙目）金相顯微鏡觀察試樣的金相顯微組織，采用OMEC SCF-106型激光粒度分析儀測試粉體的粒度，采用TG328A型分析天平測量合金和復合材料的密度，用Aglient4294A型動態阻抗分析儀測量GMPC的動態電阻率，采用直流電橋電阻應變片法測量樣品的磁致伸縮系數。
實驗得到如下結論：（1）采用非自耗電弧爐熔煉-燒鑄技術，通過控制熱流方向，制備出較高性能的稀土超磁致伸縮合金。實驗表明，所制備的合金棒具有明顯的Laves相結構的ReFe2相，合金組織均勻，且具有一定的擇優生長，磁致伸縮量在本實驗條件下最大可達782×10-6，是較理想的磁致伸縮合金；（2）采用手工破碎制粉技術和自行設計的成型模具、用粉末粘結法能夠制備性能良好的GMPC。所制備得的GMPC最大磁致伸縮量λm最高可達491.3×10-6，與原材料Terfenol-D的磁致伸縮量（近705.6×10-6）相比，λm只降低了約30％；（3）在其它制備工藝條件相同時，經磁場成型的GMPC其λm(最大磁場為400kA/m下的磁致伸縮)為491.3×10-6，而未經磁場成型的λm為402.6×10-6，說明在磁場下成型可以使晶粒有很好的定向，從而提高了復合材料的磁致伸縮性能；（4）GMPC電阻率測量結果表明，所制備的樣品電阻率約為32×10-2Ω·m，比合金Terfenol-D的電阻率約大四個數量級，說明制備的GMPC將具有較好的高頻磁性能，通過對GMPC組織形貌進行分析，發現GMPC組織均勻，很少有氣孔，致密度很高。
另外，對摻Ho合金制備過程中出現的蘑菇進行了研究。從實驗得到如下結論：（1）對摻Ho合金蘑菇析出物的研究發現：經退火處理后，隨著Ho含量的增加，“蘑菇”狀析出物越多，析出的“蘑菇”為多相組織，主要包括DyFe2相、RE(Tb,Dy)5Si3和稀土氧化物相，還存在少量其它雜質；（2）“蘑菇”的析出（過量稀土元素的析出），使得基體成分優化為Tb0.2234Dy0.678Ho0.354Fe2，從而具有較好的磁致伸縮性能，理論上，蘑菇的出現是由于能量最小化作用的結果；（3）隨著Ho含量的增加，合金的磁致伸縮系數先減小，含量為0.15時，達最小值213.5×10-6，隨后又漸漸升高，含量為0.25時， 達538.8×10-6。含量為0.25時，合金樣品中析出的“蘑菇” 磁致伸縮系數最小，為114.2×10-6。

關鍵詞：Terfenol-D；磁致伸縮；復合材料；制備；摻Ho；蘑菇

Abstract

As a novel functional material ,magnetostrictive material has risen comprehensive attention by the experts in the high-tech fields and got momentum in the past few years.Much work has done on the preparation ,composition ,phase structure ,magnetic-structure and properties in U.S.A ,Japan and so on ,which make the technology mature gradually .But as a ferromagnetic electric conductor, when the magnetic field changes,eddy that makes material heat will produce. And when the reversal frequency of magnetic field is higher, the eddy is violent,those defects limit its application in ultrasonic technology. The appearance of polymer-bonded giant magnetostrictive composite(GMPC) solved this bottle-neck.The effective frequency of GMPC can reach to 100KHz ,which greatly extended the application of magnetostrictive materials in ultrasonic technology .GMPC has great developmental prospects .
 The main aims are:(1)a mould which applied to the fabrication of GMPC was designed and produced,the magnetic field was also considered;(2) excellent GMPC was fabricated with the technique of manual milling,mould,and powder felting, properties of magnetostriction,resistance and so on was also tested;(3)the magnetic properties which were influenced by the processing in the magnetic field were researched,the optimum technics was also explored.
 The properties of GMM and GMPC were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), standard resistance strain gauge technique , VSM and so on in this paper.
 The GMPC in this experiment was cured with GMM powder and resin under stress .We got optimum particle size of 112.5μm ,compaction pressure of 0.5GPa ,phenol content of 3.1～4wt%,and the direction of applied magnetic field according to the data essayes provided.The material was formed in that optimum condition.The results show as follows:(1)the GMM was fabricated by the technique of arc-melting-casting after controlling the direction of heat,result shows that the phase of the alloy was REFe2,struture was uniform and had some preferiation ,the maximum magnetostriction in the magnetic field provided in this experiment(λm) was 780×10-6 and turned to be ideal alloy;(2)the excellent GMPC was fabricated with the technique of manual milling,mould,and powder felting.λm was 491.3×10-6 which loses only 30% with respect to the magnetostriction of GMM(705.6×10-6 more or less);(3)the composites pressing in the magnetic field has the λm of 491.3×10-6 and those without 402.6×10-6,the composites pressing in the magnetic field have better property;(4)The gained composites are of uniform microstruture ,few air hole and high density,what's more,resistance of the sample is about 32×10-2Ω·m which is four orders of magnitude larger than GMM reported.
 The mushrooms that appeared in the processing of Ho dopping alloy were analysed ,which shows:(1)The alloy rods have the structure of obvious MgCu2 Laves cubic structure while mushrooms are phase of rare-earth oxidation ,RE(Tb,Dy)5Si3 and also Laves cubic;(2)the separating out of the mushroom(the seprating of excessive rare-earth elements) makes the component of Tb0.2234Dy0.678Ho0.354Fe2 which leads to good magnetostriction properties;in theory ,the appearing of the mushroom is the minimization of energy;(3)the magnetostriction of the alloy decreases with the increasing amount of Ho dopping,minimum occurs at x(ratio of Ho atom)=0.20 and increases gradually until x=0.25 with the magnetostriction of 538.8×10-6.

Key word: Terfenol-D; Magnetostriction; Composite;Ho dopping ;Mushroom