| 摘要: | 隨著環保意識抬頭，將農業廢棄的鳳梨葉回收纖維，水熱轉化成奈米碳材料，兼具減廢與高值化再利用之效。本研究利用回收鳳梨葉纖維於稀酸中水熱碳化形成微米碳球，並添加銅離子與甘油或是與尿素跟氨水以一步水熱法製備銅/碳微米球。SEM觀察到鳳梨纖維經190℃水熱後，形成直徑約0.2~8.6 μm的微米碳球，其數量隨著時間而增加，220℃水熱後，由於反應速度提高，碳球成長較快，得到直徑0.4~10.0 μm。由XRD結果得知所製備的微球為富含碳的非晶結構，Raman光譜測得典型碳材料的G-band與D-band訊號，隨著水熱時間增加，D-band峰逐漸消失，顯示碳原子排列變得規則，TGA熱重量損失測得纖維素以及碳殘留的損失溫度。當鳳梨纖維與銅離子和甘油共水熱後，成功製得產量更高的銅/碳微米球，直徑為0.6~6.1 μm與純碳球相近。XRD測得明顯銅的FCC (Face-centered Cubic)繞射峰，碳仍為非晶結構。由Raman光譜得知少量銅的存在，並不影響碳原子排列，隨著水熱時間增加，碳原子排列變得規則。然而，增加銅的含量後，反而使碳的D-band增強。銅/碳微米球的水熱反應機制為銅離子在甘油作用下還原成銅，同時鳳梨纖維被稀酸水解產生葡萄糖，並脫水形成羥基甲基糠醛，最後在銅表面聚合形成碳球。TGA測得在200℃~300℃為纖維素的裂解，300℃~400℃為鹼式碳酸銅裂解，400℃~500℃為氧化銅和碳氧化的裂解，600℃~700℃為氧化亞銅的裂解。將碳球與銅/碳材料與水性聚氨酯均勻混和製成薄膜，發現薄膜的導電率隨著水熱溫度與銅的含量而增加，220℃的C、1Cu/C和2Cu/C所得到的導電率分為是1.78×10-9 S/m、1.87×10-9 S/m以及3.11×10-9 S/m，在電熱實驗下溫度分別上升1.9℃、2.9℃和4.5℃，顯示本研究之碳球與銅/碳材料之導電性質與電熱性質優於市售碳粉。
With the rise of environmental awareness, recycling pineapple leaves of agricultural waste into fibers and converting them into nano-carbon materials through hydrothermal treatment achieves both waste reduction and high-value reuse. In this study, recycled pineapple fibers were subjected to hydrothermal carbonization in dilute acid to form carbon microspheres. Copper ions were then added along with glycerol, urea or ammonia solution using one-step hydrothermal method to prepare copper/carbon microspheres. SEM observations revealed that pineapple fibers underwent hydrothermal treatment at 190℃, forming microcarbon spheres with a diameter of 0.2-8.6 μm. The quantity of microspheres increased over time. After hydrothermal treatment at 220℃, the reaction rate increased, leading to faster growth of carbon spheres with a diameter of 0.4-10.0 μm. XRD results indicated that the prepared microspheres consisted of carbon-rich amorphous structures. Raman spectroscopy showed characteristic G-band and D-band signals of typical carbon materials, with the D-band peak gradually disappearing as hydrothermal time increased, indicating a more regular arrangement of carbon atoms. TGA curves revealed that the residual cellulose and carbon degraded with the increasing temperature. When pineapple fibers were hydrothermally treated with copper ions and glycerol, copper/carbon microspheres with higher yields were successfully obtained, with diameters similar to those of pure carbon microspheres. XRD analysis revealed distinct FCC (Face-Centered Cubic) diffraction peaks of copper, while carbon remained in an amorphous structure. Raman spectroscopy indicated that the presence of a small amount of copper did not affect the arrangement of carbon atoms, which became more regular with increasing hydrothermal time. However, increasing the copper content resulted in enhanced D-band intensity in carbon. The hydrothermal reaction mechanism of copper/carbon microspheres is speculated to involve the reduction of copper ions to copper under the action of glycerol, simultaneous hydrolysis of pineapple fibers by dilute acid to produce glucose, and dehydration to form hydroxymethyl furfural, followed by polymerization on the surface of copper to form carbon microspheres. The TGA analysis showed that the degradation of cellulose occurs between 200°C and 300°C, basic copper carbonate decomposes between 300°C and 400°C, copper oxide and carbon oxidizes and degrades between 400°C and 500°C, and cuprous oxide decomposes between 600°C and 700°C. The conductive films were prepared by uniformly mixing carbon microspheres with copper/carbon materials and waterborne polyurethane (WPU). It was observed that the conductivity of the films increased with the hydrothermal temperature and copper content. The conductive films produced from hydrothermal products of C, 1Cu/C and 2Cu/C at 220°C exhibited conductivities of 1.78×10-9 S/m, 1.87×10-9 S/m and 3.11×10-9 S/m, respectively. Afterelectrothermal experiments, the temperatures of C, 1Cu/C and 2Cu/C films increased by 1.9°C, 2.9°C and 4.5°C, respectively, which were superior to films made from commercial carbon powders. It indicates that the conductive properties and electrothermal properties of the carbon microspheres and copper/carbon materials in this study are superior to those of commercial carbon powders. |
