Kirkham Melanie, Heroux Luke, Ruiz-Rodriguez Mariano, Huq Ashfia
Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Rev Sci Instrum. 2018 Sep;89(9):092904. doi: 10.1063/1.5031432.
High fluxes available at modern neutron and synchrotron sources have opened up a wide variety of and studies of real processes using scattering techniques. This has allowed the user community to follow chemistry in the beam, which often requires high temperatures, gas flow, etc. In this paper, we describe an integrated gas handling system for the general-purpose powder diffraction beamline Powgen at the Spallation Neutron Source. The Automated Gas Environment System (AGES) allows control of both gas flow and temperature (room temperature to 850 °C), while measuring the partial pressure of oxygen and following the effluent gas by mass spectrometry, concurrent with neutron powder diffraction, in order to follow the structural evolution of materials under these conditions. The versatility of AGES is illustrated by two examples of experiments conducted with the system. In solid oxide fuel cell electrode materials, oxygen transport pathways in double perovskites PrBaCoO and NdBaCoO were elucidated by neutron diffraction measurements under atmosphere with oxygen partial pressures (pO) of 10 to 10 (achieved using mixtures of nitrogen and oxygen) and temperatures from 575 to 850 °C. In another example, the potential oxygen storage material LaSrFeO was measured under alternating flows of 15% CH in N and air (20% O in N) at temperatures from 135 to 835 °C. From the oxygen stoichiometry, the optimal composition for oxygen storage was determined.
现代中子源和同步辐射源所具备的高通量，开启了利用散射技术对实际过程进行广泛多样研究的大门。这使得用户群体能够在束流中追踪化学反应，而这往往需要高温、气流等条件。在本文中，我们描述了一种用于散裂中子源通用粉末衍射束线Powgen的集成气体处理系统。自动化气体环境系统（AGES）能够控制气体流量和温度（室温至850°C），同时测量氧气分压，并在进行中子粉末衍射的同时通过质谱法追踪废气，以便在这些条件下追踪材料的结构演变。通过该系统进行的两个实验示例展示了AGES的多功能性。在固体氧化物燃料电池电极材料中，通过在氧气分压（pO）为10至10（使用氮气和氧气的混合物实现）且温度为575至850°C的气氛下进行中子衍射测量，阐明了双钙钛矿PrBaCoO和NdBaCoO中的氧传输途径。在另一个示例中，在135至835°C的温度下，对潜在的氧储存材料LaSrFeO在15% CH于N和空气（20% O于N）的交替气流下进行了测量。根据氧化学计量比，确定了最佳的氧储存组成。
