臺灣博碩士論文加值系統

摘要
氫氣是二十一世紀最具潛力的環保能源。雖然它可以藉由太陽光或是電力來製造，但是要純化並分離出高純度的氫氣卻需要大量資金的投入。為了要減少費用並且得到大量高純度的氫氣，支撐式的鈀銀合金膜被導入氫氣純化的製程。鈀銀合金膜在氫氣滲透的過程中，能避開α/β相變化而產生的氫脆現象，因此近年來在能源科技被廣泛地研究。此具備超高純度氫氣分離效果的薄膜除了可應用於石化工業的氫器純化及回收，在燃料電池的氫氣反應器及重組反應製程，均有廣泛的運用。
本實驗係選用銀粉的團塊燒結成多孔性的銀板及銀管，銀基材不但提供良好的附著力及機械強度，並且降低成本，對實際應用於工業甚有助益。在鍍膜之前，先利用鈀銀奈米粒子填充孔洞來做表面改質並提供薄膜良好的支撐力，再利用丙酮將表面的殘餘粉粒清除，然後經由磁控濺鍍可成功地在銀板及銀管施鍍一層5μm鈀銀合金薄膜作為氫氣分離膜。以掃瞄式電子顯微鏡觀察基材和薄膜的表面及斷面，並經由X光繞射分析薄膜的成分，再藉由氫氣滲透裝置量測氫氣及氫/氮混合氣體在高溫下對鍍膜的滲透率。
根據SEM的觀察，除了表面填孔的步驟外，清潔表面也是影響鍍膜品質的重要因素。經由表面改質，緻密且連續的鈀銀合金膜可以均勻施鍍在2cm的銀管上。銀管上的膜最高可承受2.5kg/cm2的氫氣壓力，即使經過48次不同壓力的循環測試，其熱穩定度仍然相當好。本實驗中，氫氣的滲透通量隨壓力的增加，與壓力成一次方正比，偏離了Sievert’s law。

Abstract
Hydrogen is one of the most potential clean energies in the 21st century. Although it can be produced by solar light, electricity, etc., the purification process is still very costly step. To lower the cost and get higher purity and large amount of hydrogen, palladium-silver membrane supported on the porous substrate is used in hydrogen purification. The palladium-silver alloy membrane has been extensively studied in recent years due to the absence of α/β phase transition and embrittlement associated with hydrogen permeation. In addition to the application for ultra high purity hydrogen separation, it is also widely utilized in recovery or purification of hydrogen in petroleum industry, hydrogen reactor in fuel cells, and methane-steam reforming.
In this study, silver powder agglomerate was used to prepare porous substrate. The porous silver substrate was obtained by uniaxial mechanical pressing and sintering at 350℃ in air for 1 hr. Prior to sputter deposition, the surface was modified by filling with Pd70Ag30 nanoparticles to reduce the pore size and cleaning with acetone to remove the residual particles. After the surface modification, a 5μm-thick Pd-Ag membrane was deposited on the surface by dc magnetron sputtering. For the tube substrate, the membrane was deposited with a rotating design. The surface and cross-section morphologies of the substrate and membrane were examined by scanning electron microscopy. The compositions of the membrane were calibrated by X-ray diffraction. Besides, the permeation rate of hydrogen at 250℃ was measured by a gas permeation apparatus.
It was observed that cleaning surface with acetone was very important for the modification process. A dense and continuous Pd-Ag membrane could be uniformly prepared on the modified tube surface. A 5μm-thick membrane was successfully deposited on the 2cm-long silver tube surface. The maximum hydrogen pressure the tube membrane could support was 2.5 kg/cm2. The thermal stability and durability at different pressures was very good even after 48 cycles of test. The Sievert’s law was not obeyed in this study.

Table of Contents
中文摘要
Abstract
誌謝
Chapter I Introduction 1
1.Hydrogen and Its Application 1
2.Background of the Study 2
3.Principle of Hydrogen Separation through Palladium Membrane 5
4.Palladium-Silver System 10
5.Preparation of Pd-Ag Membrane on the Porous Substrate 11
Chapter II Experimental 23
1.Preparation of Porous Ag Substrates 23
(1) Synthesis of Nanocrystalline Silver Powder 25
(2) Preparation of Porous Silver Substrates 25
a. Silver Disc 25
b. Silver Tube 27
2.Surface Modification of the Porous Silver Substrate 27
(1) Synthesis of Nanocrystalline Pd70Ag30 Particles 30
(2) Surface Modification 30
3.Sputtering Deposition 33
4.Characterization of Membrane and Gas Permeation 39
Chapter III Results and Discussion 43
1.Characterization of the Ag Substrate and Pd-Ag Membrane 43
(1) Silver Disc 43
(2) Silver Tube 43
2.Hydrogen Permeation 55
(1) Silver Disc 58
(2) Silver Tube 58
Chapter IV Conclusions 82
References 83

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