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研究生：	吳采蓉 Wu, Tsai-Jung
論文名稱：	樹脂與碳纖維布被覆對高溫超導塊材YBCO機械性質的影響 Effects of coating resin and carbon fabric on the mechanical property of high temperature superconductor YBCO
指導教授：	陳引幹 Chen, I.G.
學位類別：	碩士 Master
系所名稱：	工學院 - 材料科學及工程學系 Department of Materials Science and Engineering
論文出版年：	2004
畢業學年度：	92
語文別：	中文
論文頁數：	110
中文關鍵詞：	YBCO 、碳纖維、三點彎曲試驗、樹脂
外文關鍵詞：	carbon fiber, YBCO, three-point bending test, resin
相關次數：	點閱：88 下載：1
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　　超導體在成長及充氧退火階段，因熱應力及熱膨脹係數的差異，內部會存在一定數量的裂縫及孔洞，在於實際應用時，外加磁場與超導體內部的電流造成強大的電磁應力，當磁場大於10T以上時，過大的應力會對超導體造成破壞，因此本實驗的目的在於提升超導體的機械性質，使超導體能應用於更大的磁場環境下。
　　本實驗使用商用環氧樹脂及碳纖維被覆於超導體上，藉由外在包覆的方式來提升超導體的機械性質：在大氣下塗膠時，樹脂與塊材的接合情形不佳；於真空狀態下塗膠，可提升塊材與樹脂及碳纖維的接合力。
　　對於未被覆前的塊材，原始塊材尺寸較大時，燒結時塊材內部不均勻的收縮導致孔洞的聚集，導致強度下降；低溫下(77K)塊材各試片間的彎曲強度差異較大，就平均而言約為常溫下的1.4倍，但彎曲模數卻較常溫為低。
　　在常溫下被覆樹脂對塊材的機械強度無明顯幫助，但卻大幅影響塊材的彎曲模數；在低溫時，若能改善塊材與樹脂的接合，被覆樹脂應能有效提高超導體的強度。
　　被覆碳纖維的試片彎曲強度最大，而由於碳纖維具有方向性，當被覆碳纖維方向平行於塊材受力方向時，彎曲強度提升的幅度最大；低溫下被覆碳纖維試片的彎曲強度達253.8MPa，為未被覆塊材低溫強度的2.4倍，但在應力應變圖中有數個數據振盪的區域，顯示此時塊材與樹脂或樹脂與碳纖維已開始脫離。
　　無論在室溫或低溫下，彎曲模數的大小依序為：未被覆塊材>被覆碳纖維試片>被覆樹脂試片。

　　There were cracks and voids exist in the single grained superconductors as growth and annealing process due to its difference in thermal expansion coefficients and thermal stresses. In practice, the Lorentz force resulting from the interaction between the current inside the superconductors and the external field results in strong stresses. The superconductors usually fractured when the external magnetic field exceeds 10 Tesla because of the huge stresses. The purpose of this experiment is to enhance the mechanical properties of YBCO-superconductors and capable of high external field.
　　In this experiment, the improvement of the mechanical properties of YBCO-superconductors is fulfilled by coating the commercial resins and carbon fabrics. When the coating process was operated in the atmosphere, the binding strength between the resins and the superconductor was poor. However, the operation in vacuum will enhance the binding strength.
　　For the un-coated samples, diminished flexural strength reveals while the size of the bulks are larger than the other small ones because of the un-uniform shrinkages occurring inside them. The flexural strength of the samples at 77K is about 140% of that at 300K, but the flexural modulus at low temperature is lower than that of high temperature.
　　At room temperature, coating resin on bulks was not good for samples at flexural strength, but decreases the flexural modulus. At low temperature, if we can improve the binding strength of the resin and the bulk, coating resin should be good for the strength of YBCO.
　　The highest flexural strength was obtained by coating the CF-coatings on the samples. Because the carbon fabrics have anisotropism, as the direction of the carbon fabrics are parallel to the external force, the resulting strength of the sample is the highest. At 77K, the flexural strength of the samples with CF-coatings reaches 253.8MPa, which is about 240% of that of the un-coated ones. Some oscillations were observed on the stress vs. strain curve, it means that some disjoint appeared between the bulk and the resin or between the resin and the carbon fabrics.
　　The samples at both room temperature and low temperature, the sequence of flexural modulus was in the following sequence of the un-coated samples, CF-coatings, and then the ones with resin-coatings.

摘  要	                                        I
Abstract	                                 II
目  錄	                                       IV
圖 目 錄	                                     VII
表 目 錄	                                      XI
第一章  緒論	                                     1
1-1  前言	                                        1
1-2  實驗目的	                              2
第二章  理論基礎與文獻回顧	                      3
2-1  超導體的機械性質及所承受的應力	           3
2-1.1  超導體的機械性質[1,2]	                  3
2-1.1.1  抗拉強度	                              3
2-1.1.2  抗壓強度	                              3
2-1.1.3  抗折強度	                              3
2-1.2  超導體在長晶過程所承受應力[3]	             4
2-1.3  磁場對超導體的破壞[4]	                 5
2-2  超導體表面裂縫及孔洞分佈型態	            8
2-2.1  a-b平面裂縫生成原因[5]                     8
2-2.2  c軸裂縫生成原因[6]	                   9
2-2.3  表面孔洞分佈型態[7,3]	                  9
2-3  環氧樹脂及碳纖維的基本性質	            10
2-3.1  環氧樹脂的基本性質[8]	                10
2-3.2  環氧樹脂與硬化劑的反應機構[9]	            10
2-3.3  碳纖維的歷史[10,11,12]	                   11
2-3.4  碳纖維的編織[12]	                   11
2-3.5  碳纖維的優點及應用[12]	                11
2-4  包覆環氧樹脂與碳纖維對機械性質的改善	       12
2-4.1  超導塊材被覆樹脂方式[13,14]	       12
2-4.2  被覆樹脂與碳纖維對於塊材機械性質的影響	 
                                                 12
2-4.2.1  彎曲強度[15]	                     12
2-4.2.2  拉伸強度[16]	                     13
2-4.3  被覆樹脂及碳纖維對於塊材超導性質的影響	 
                                                 13
2-4.3.1  施加反覆磁場對超導體造成的破壞[17]	  13
2-4.3.2  現今YBCO超導體可擄獲的最大磁場[14]	    14
第三章  實驗步驟	                          35
3-1  實驗材料	                             35
3-2  實驗步驟	                             35
3-2.1  塊材前處理	                            35
3-2.2  塗膠前塊材表面觀察	                36
3-2.3  塊材塗佈樹脂方式	                         36
3-2.3.1  在大氣下塗膠	                           36
3-2.3.2 真空包裝機塗膠步驟	                36
3-2.4  塊材包覆碳纖維布方式	               37
3-3  機械性質分析	                           37
3-3.1  常溫下的彎曲強度	                         37
3-3.2  低溫下的彎曲強度	                         37
3-4  儀器設備	                             38
3-5 試片條件	                             39
第四章  結果與討論	                         51
4-1  樹脂與塊材間的界面觀察	              51
4-1.1  塊材的表面觀察	                          51
4-1.2  塊材被覆樹脂方式	                         51
4-1.2.1  實驗初期	                             51
4-1.2.2  在真空狀態下被覆樹脂	               51
4-1.3  樹脂與塊材間的界面觀察	              52
4-1.3.1  塊材與樹脂的表面接合情形	             52
4-1.3.2  樹脂填入孔洞情形	                 53
4-1.3.3  樹脂滲入塊材深度	                 53
4-1.3.4  實驗室自製塊材與Murakami使用塊材橫截面的比較	                                        53
4-2  三點彎曲試驗	                           62
4-2.1  試片尺寸對受力方向的影響	             62
4-2.2  試片粗度的影響	                          62
4-2.3  數據的校正方式	                          63
4-3  常溫下超導體YBCO的機械性質	              65
4-3.1  不同尺寸塊材的強度	                65
4-3.2  被覆樹脂方式對於試片強度的影響	          66
4-3.2.1  被覆樹脂試片	                           66
4-3.2.2  被覆碳纖維試片	                  67
4-3.3  被覆樹脂對於試片強度的影響	            73
4-3.4  樹脂含量與碳纖維方向對於試片強度的影響                      
                                                 79
4-3.5  與Murakami的實驗相比較[15]	          86
4-3.6  綜合比較	                             86
4-4  低溫下(77K)超導體YBCO的機械性質	      91
4-4.1  未被覆的塊材強度	                         91
4-4.2  被覆樹脂的試片強度	                91
4-4.3  被覆碳纖維的試片強度	               92
4-4.4  應變值的校正	                           97
4-4.5  與Murakami的實驗相比較[15]	         100
4-4.6  綜合比較	                            100
第五章  結論         	                   106
參考文獻	                                    108


                                    

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校內：2005-07-26公開
校外：2005-07-26公開

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