In Situ Measurement of Submicron Particles During Synthesis from Gaseous Precursors

表征气溶胶反应器内的颗粒大小分布、浓度和温度对于正确理解和控制该过程是至关重要的。第一阶段的研究展示了一种新的傅立叶变换红外(FT-IR)发射/传输(E/T)技术来解决上述问题，用于合成二氧化钛颗粒。二氧化钛颗粒在波数小于1000/cm时有很强的吸收，因此测量的消光与颗粒质量成正比。相反，超过1000/cm的消光是由散射引起的，并且是颗粒尺寸分布的强烈函数。利用Mie理论，人们可以解卷积消光光谱来估计几何平均直径，其值在其实际值的10%以内。除了颗粒质量和大小外，E/T FT-IR还可以同时测量颗粒温度以及气体浓度和温度。这一二期项目将开发一种在线原位分析亚微米级颗粒的仪器。这项研究将(1)改进FT-IR和优化传输和发射数据的获取程序，(2)改进和扩展测量的透射谱与颗粒大小之间的理论，(3)通过将红外反卷积与其他颗粒测量技术进行比较来评估仪器和分析软件，以及(4)在商业二氧化钛生产设施上对该仪器和软件进行现场测试。这一建议结合了三个关键组织的专业知识：(1)高级燃料研究提供了其丰富的FT-IR技术知识；(2)海曼特·彭德斯教授(缅因州大学)是从衰减光谱中反卷积颗粒尺寸分布的专家；(3)辛辛那提大学的Sotiris Pratsinis教授将评估FT-IR结果，并将其与传统的颗粒测量技术进行比较。上述仪器将进行气溶胶的尺寸测量以及粒子质量、粒子温度、气体成分和气体温度的测量。该仪器将坚固耐用、用户友好、便携且相对便宜。这种仪器的应用包括合成催化剂载体、可烧结陶瓷、金属颗粒、光学材料和电子材料。

Characterizing the particle size distribution, concentration, and temperature within an aerosol reactor is essential to the proper understanding and control of the process. Phase I research has demonstrated a novel Fourier transform infrared (FT-IR) emission/transmission (E/T) techniques to address the above problems for the synthesis of TiO particles. TiO particles strongly absorb at wavenumbers less than 1000/cm, and thus the measured extinction is directly proportional to the particle mass. In contrast, extinction above 1000/cm is due to scattering and is a strong function of the particle size distribution. Using Mie theory, one can deconvolute extinction spectra to estimate the geometric mean diameter within 10% of its actual value. In addition to particle mass and size, E/T FT-IR can also simultaneously measure particle temperature as well as gas concentrations and temperature. This Phase II project will develop an instrument for on-line in- situ analysis of submicron sized particles. This research will (1) develop improvements to the FT-IR and procedures to optimize the acquisition of transmission and emission data, (2) improve and extend the theory relating measured transmission spectra to particle size, (3) evaluate the instrument and analysis software by comparing the IR deconvolution to other particle sizing techniques, and (4) field test the instrument and software on a commercial TiO2 production facility. This proposal combines the expertise of three key organizations: (1) Advanced Fuel Research provides its extensive knowledge of FT-IR technology; (2) Prof. Hemant Pendse (University of Maine) is an expert in the deconvolution of particle size distributions from attenuation spectra; and (3) Prof. Sotiris Pratsinis (University of Cincinnati) will evaluate the FT-IR results and compare them to conventional particle sizing techniques. The above instrument will perform size measurements of aerosols as well as measuring particle mass, particle temperature, gas composition, and gas temperature. The instrument will be rugged, user friendly, portable, and relatively inexpensive. The applications for such an instrument include the synthesis of catalyst supports, sinterable ceramics, metal particles, optical materials, and electronic materials.