不同奈米粉體的分散方式產生的奈米微粒特性

Abstract

本研究以旋轉腔體試驗機(rotating drum dustiness tester)、漩渦振盪器(vortex shaker)和微小粉末分散器 (small-scale powder disperser, SSPD)進行奈米粉體的逸散特性之研究，並比較三者的實驗結果，以了解不同粉體經不同分散方法產生的微粒質量及粒徑分佈特性。奈米二氧化鈦、氧化鋅和二氧化矽為本研究選用的奈米粉體，奈米粉體逸散的微粒使用掃描式電移動度粒徑分析儀(Scanning Mobility Particle Sizer, SMPS) 、氣動微粒分析儀(Aerodynamic Particle Sizer, APS)及微孔均勻衝擊採樣器(Micro-Orifice Uniform Deposit Impactor, MOUDI)進行量測，得到的數據以單位粉體重量產生的微粒數目或質量濃度表示之。實驗結果顯示，以不同方式分散出微粒的質量中間氣動直徑 (mass median aerodynamic diameters, MMADs)大致皆落在1~6 μm之間，0.1 μm以下的奈米微粒質量濃度很低。以SSPD分散奈米二氧化鈦的MMAD與GSD值為1.1 μm與2.1，為三種奈米粉體中MMAD最小的。逸散的微粒比質量濃度在三種不同方式的分散下皆以奈米二氧化鈦最高，奈米二氧化矽最低。NMD方面，以SSPD分散奈米二氧化矽的NMD與GSD為164 nm與2.2，為三種奈米粉體中MND最小的。由SSPD和漩渦振盪法的得到的逸散總微粒比數目濃度，以奈米二氧化鈦的最高，奈米氧化鋅次之，奈米二氧化矽最低；由旋轉腔體試驗機法得到的逸散總微粒比數目濃度，則以奈米氧化鋅最高，奈米二氧化鈦最低，造成此排序結果的差異主要與實驗系統施予粉體的分散能量不同所致，且根據實驗的NMD及MMAD結果與分散系統阻力計算的結果，皆指出SSPD為本研究粉體分散能量最高的方法。 奈米粉體以SSPD分散後的數目濃度結果，利用計算得到的微粒有效密度與奈米粉體的顯在密度，分別將SMPS與APS的數目濃度轉換成質量濃度，發現兩者轉換的質量濃度分佈結果與MOUDI的量測結果相近。本研究以AerotrakTM 9000量測沉積肺部的微粒表面積濃度，並與SSPD逸散實驗的SMPS和APS之量測數據乘上ICRP(International Commission on Radiological protection)呼吸系統的沉積模式因子所推算的肺部沉積之表面積濃度進行比較，可知奈米二氧化鈦具有最高的肺部沉積表面積濃度，奈米氧化鋅次之，奈米二氧化矽最低。三種奈米粉體在肺泡區及氣管與支氣管區的量測值與計算值之誤差百分比範圍分別為+10~+32 %與+7~−17 %，故在氣管與支氣管區所計算的肺部沉積表面積濃度結果較肺泡區的計算結果佳。

In the present work, the standard rotating drum with a modified sampling train, vortex shaker and the SSPD (Small-Scale Powder Disperser) were used to investigate the emission characteristics of nanopowders. The experimental data of mass and number distributions of generated nanoparticles were compared among three dispersion methods. Nano-titanium dioxide, nano-zinc oxide and nano-silicon dioxide were used as the test nanopowders. A TSI SMPS (Scanning Mobility Particle Sizer), a TSI APS (Aerodynamic Particle Sizer) and a MSP MOUDI (Micro-Orifice Uniform Deposit Impactor) were used to measure number and mass distributions of the generated nanoparticles. Results showed that the mass median aerodynamic diameters (MMADs) measured by using SSPD、vortex shaker and rotating drum for three nanopowders were found to fall in between 1~6 μm. The MOUDI data showed that the mass concentrations of nanoparticles (diameter is less than 100 nm) were negligible. The MMAD and geometric standard deviation (GSD) of nano-TiO2 was 1.1 μm and 2.1 by using SSPD dispersion method, which was the smallest among three nanopowders. Nano-TiO2 has the highest total specific mass concentration among all nanopowders in every different dispersion method. The NMD and GSD of nano-SiO2 was 164 nm and 2.2 by using the SSPD dispersion method, which was the smallest among all three nanopowders. From the total specific number concentration data of SSPD and vortex shaker, nano-TiO2 was found to have the highest specific number concentration than other nanopowder, followed by nano-ZnO and nano-SiO2. For the total specific number concentration data of rotating drum, nano-ZnO was found to have the highest value, followed by nano-SiO2 and nano-TiO2. Different dispersion methods have different dispersion energy exerted on nanopowders. The SSPD is the most energetic dispersion method and produces the smallest NMD and MMAD among three different dispersion methods. The number concentration distributions of the SSPD method was converted to mass concentration distributions using the effective density and the apparent density of nanopowders for SMPS and APS, respectively. It was found that the converted mass distributions agreed with those measured by the MOUDI. Based on the ICRP (International Commission on Radiological protection) lung deposition model, calculated lung deposited surface area concentration from the number distribution data of the SSPD experiments were compared with those by a TSI AerotrakTM 9000. It was found that the difference for the alveolar and tracheobronchial deposited surface area concentration was +10~+32 % and +7~−17 %, respectively.