- 學位論文
以一步水熱法合成包覆金屬氧化物之碳微球的電導與熱導係數之研究
Electrical and Thermal Conductivity of Carbon Microspheres Encapsulating Metal Oxide and Synthesized by a One-Step Hydrothermal Method
摘要
碳球(CSs)於科學界已得到了較多的關注。近年來研究表示，其具備成本低、合成簡易、有生物相容性、較環保、且表面具許多功能性等優勢。本論文所研究的碳球是使用抗壞血酸(AsA)作為碳源，且是經由水熱或溶熱法等過程合成。首先，使用D-AsA作為碳源且利用二次水為溶劑合成碳球，而其之對照組則是L-AsA為碳源，兩組的反應條件都為180 ℃3小時。所合成出之碳球直徑約為1〜10微米且其在水中具高分散性，所以由上述可證實此碳球含高濃度的羥基和羧基於表面上。其次，使用L-AsA作為碳源並利用異丙醇（IPA）為溶劑合成碳球，反應溫度為180 º C，反應時間為3、12小時。其於反應時間3、12小時後所合成出的碳球直徑分別約為40〜60和20〜30 nm。由上述結果證實於溶熱法（IPA）下所合成之碳球比（H2O）下尺寸較小。第三，利用L-AsA為碳源合成碳球且同時加入金屬錯合物，如硝酸鈰Ce(NO3)3與氯化亞錫SnCl2，所合成出的複合粉體其結構可為核/殼結構或填充/載體結構。 所合成出碳球與複合粉體產物均經由 SEM、FE- SEM、EDX、TEM、XRD和FTIR進行鑑定。另外，本團隊準備已經過熱處理（在氦氣中或空氣中，產物代號會加上*字）後的產物並進行電導率和熱導率（分別為σ與k）量測，量測系統則是使用了自製之模組與實驗室之儀器。原本所合成出的碳球經電導係數量測（10-14 S/cm）後顯示出其導電性較差。經由熱處理後，σ值有很大程度的成長了至少108倍。不過，熱處理後之產物其熱導係數k之表現並不如電導係數σ。測量樣品CS*- isoV之σ與k值分別為 1.08×10-6 S/cm和2.341 W/m K，。測量樣品 CS#-V-SnO2之σ值為6.465×10-5 S/cm（H2O）和8.157×10-3 S/cm（IPA）。k值則為3.9312 W/m K（H2O）和4.2148 W/m K（IPA）。測量樣品 CS#-V-CeOx（H2O）之σ與k值分別為1.059×10-14 S/cm和8.8420 W/m K。測量樣品CS#-V-CeO2（IPA）之σ與k值分別為1.314×10-14 S/cm和2.8519 W/m K。最後之研究結果顯示，金屬氧化物空心球可經由在空氣下或氦氣下熱處理複合碳球/金屬氧化物粉體所製備出。此類空心球可以應用在催化、感測器或於層析柱中作為催化劑載體，電極材料和吸附劑等。
並列摘要
Carbon spheres (CSs) have received wide attention in recent years due to their advantages in low cost, easy preparation, biocompatibility, environmental benignity, and versatile surface functionalization. The thesis reports the synthesis of CSs using ascorbic acid (AsA) as carbon source to undergo a hydrothermal or solvothermal process. Firstly, a sample of CSs was produced using D-AsA as carbon source and water as solvent, an enantiomer of L-AsA, at 180ºC for 3 h. The produced CSs are 1~10 μm in diameter and highly dispersible in water, indicating of a high concentration of hydroxyl and carboxyl groups over the surface. Secondly, a sample of CSs was produced using L-AsA as carbon source and isopropyl alcohol (IPA) as solvent at 180ºC for 3 and 12 h.. The obtained CSs have diameters of 40~60 and 20~30 nm after reaction for 3 and 12 h, respectively. The sizes of the CSs synthesized in IPA are both smaller than that in water. Thirdly, Composite CSs were produced from L-AsA in the presence of metal complexes such as cerium nitrate Ce(NO3)3 and stannous chloride SnCl2 to give structures in core/shell or filler/matrix. The synthesized CSs were characterized by SEM, FE-SEM, EDX, TEM, XRD, and FTIR. Electrical and thermal conductivity (σ and κ, respectively) of the as-prepared and heated (in helium or air, marked by *) samples were also measured by self-made fixtures, the electrical multimeter, and other laboratory apparatus. The as-prepared CSs all show poor electrical conductivity on the order of 10-14 S/cm. By calcination, the σ was largely enhanced by at least 8 orders. However, heat treatment did not increase κ as much as σ. The measured σ and κ of sample CS*-isoV is 1.08×10-6 S/cm and 2.341 W/m K, respectively. The measured σ of sample CS#-V-SnO2 are 6.465×10-5 S/cm and 8.157×10-3 S/cm for H2O and IPA, respectively. The measured κ are 3.9312 W/m K and 4.2148 W/m K for H2O and IPA, respectively. The measured σ and κ of sample CS#-V-CeOx (H2O) are 1.059×10-14 S/cm and 8.8420 W/m K, respectively. The measured σ and κ of sample CS#-V-CeO2 (IPA) are 1.314×10-14 S/cm and 2.8519 W/m K, respectively. The results also show that hollow spheres were produced by calcining the composite CSs in helium and air. Such hollow spheres can be used in catalysis, sensor, and column chromatography as catalyst support, electrode material, and adsorbent.