添加陶瓷粉末高分子複合材料在兆赫波範圍之光學特性與應用研究

Abstract

由於兆赫波(THz)技術的快速發展，同時也需要進一步探索兆赫波系統各種應用的前瞻性，相關的元件及設備將不可或缺。為了尋找最適合用於兆赫波技術的材料，在本研究中選用3D列印常用的材料分別為Acrylonitrile butadiene styrene(ABS)、Polyamide(PA)、Poly Lactic Acid(PLA)及光固化樹脂，將其分別與不同重量百分比的陶瓷粉末混合，並藉由量測兆赫波時域光譜(THz-TDS)觀察在不同添加比例陶瓷粉末時吸收係數與折射率的改變。本實驗嘗試固定高分子粉末探討改變添加陶瓷粉末比例對兆赫波光學特性的影響。以PLA、PA粉末和光固化樹脂為基底分別混和10 wt%、20 wt%、30 wt %、40 wt%和50 wt%石英粉末，隨著添加的石英粉末比例提高，吸收係數會隨之下降，折射率也隨之提升；其中添加50 wt%石英粉末的樣品降低最多吸收係數，提升最多的折射率。為探討高分子材料添加不同陶瓷粉末後，其兆赫波光學常數的改變，本研究固定以ABS粉末為基底，混合不同陶瓷粉末。此部分分為兩組實驗，一組實驗使用鍛燒稻殼灰質(RHA)還原的SiO2，探討不同溫度製備的RHA其兆赫波光學特性的差異。本研究將ABS粉末混合50 wt%不同溫度製備的稻殼灰質樣品量測兆赫波時域光譜。另一組實驗則將ABS粉末分別與鍛燒1000℃前後Al2O3、SiO2、ZrSiO4和石英粉末混合，在0.5 THz時，混合50 wt%鍛燒後的Al2O3粉末樣品有最低的吸收係數3.40，在1 THz時，混合50 wt%鍛燒後的石英粉末樣品有最低的吸收係數9.17。混合50 wt% ZrSiO4粉末有最高的折射率，在0.5和1 THz時分別為1.81和1.80。為實現將陶瓷粉末添加於3D列印材料之中，在分析各3D列印技術的優缺點後，選用以光固化之技術製作透鏡。依據兆赫波時域光譜量測的結果，考量其可列印性及列印後的表面粗糙度，最後以光固化樹脂混合30 wt% Al2O3為材料來設計與製作兆赫光學透鏡。本研究分別製作了直徑50 mm焦距50 mm和100 mm的平凸透鏡，並以VDI公司開發的商用成套系統量測自製透鏡的聚焦效果與光斑大小，量測結果顯示其透鏡具有聚焦功能且符合焦距較短的透鏡光通過後發散較快的趨勢。以刀口法量測光斑大小，焦距50 mm的透鏡x方向的直徑為4.08 mm，y方向為3.89 mm；焦距100 mm的透鏡x方向直徑則為4.24 mm，y方向為4.05 mm。因此，添加陶瓷粉末於3D列印材料為提升折射率及降低吸收係數有效的方式，且可應用於3D列印技術，改善以3D列印技術製作THz的元件效能。

With the rapid development of terahertz (THz) technology comes the need to further explore the prospects for various applications of THz systems. For further study, components and equipment involving are indispensable. In order to find out the most suitable material for THz technology, we selected some common materials for different 3D printing techniques—acrylonitrile butadiene styrene (ABS), polyamide (PA), polylactic acid (PLA), and light-curable resin. After mixing each material with a ceramic powder of a different weight percentage, we observed the change in absorption coefficients and refractive indices of the mixtures by THz time-domain spectroscopy (THz-TDS).In this study, the impact of different percentage of a ceramic powder added in polymer powders on the optical characters of THz was tested. The base polymer powders including PLA, PA and light-curable resin were mixing with 10 wt%, 20 wt%, 30 wt %, 40 wt% , and 50 wt% of quartz powder. With higher percentage of quartz powder, the absorption coefficient became significantly lower following with higher refractive index. Hence, among all the samples, the powder mixture with 50 wt% quartz powder had the lowest absorption coefficient and highest refractive index.In order to explore the changes of optical constant of THz caused by different ceramic powders, we used a single polymer material, ABS powder, as base mixing with various ceramic powders. In this part, two sets of experiment were conducted. In the first set of the experiment, 50 wt% SiO2 (rice husk ash, RHA burnt at different temperatures) mixed with ABS powder were applied to find out the impact of RHA on the THz-TDS. The other experiment mixed Al2O3, SiO2, ZrSiO4 and quartz powder burnt at 1000 ℃ with ABS base. At 0.5 THz, the powder mixture with 50 wt% Al2O3 sample had the lowest absorption coefficient, 3.40. At 1.0 THz, the lowest absorption coefficient (9.17) was from the sample with 50 wt% quartz powder. Among all the samples, the mixture with 50 wt% ZrSiO4 powder had the highest refractive index at both 0.5 and 1.0 THz which were 1.81 and 1.80.After analyzing the advantages and disadvantages of each 3D printing techniques, the lens created by light curing techniques was selected. According to the results of THz-TDS and considering the printability and surface roughness after printing, the material we chose to design and 3D print was 30 wt% Al2O3 mixed with photocurable resin. The 50mm diameter plane-convex lenses with a focal length of 50mm and 100mm were produced in this study and the focusing effects and spot-size were measured by measuring system developed by VDI. Based on the tested results, the lenses have focus function and the trends of speedy divergence of light corresponding with the characters of those lenses with shorter focus. Using the knife edge method to measure the spot size, the lens with a focal length of 50 mm has a diameter of 4.08 mm in the x-direction and 3.89 mm in the y-direction; the lens with a focal length of 100 mm has a diameter of 4.24 mm in the x-direction and 4.05 mm in the y-direction. Since mixing ceramics powders into materials is an effective way to increase refractive indices and decrease absorption coefficients, this method could be applied to 3D printing technology to enhance the efficiency of 3D-printed THz components.