Acquisition of an Advanced X-ray Diffractometer System, Equipped with an Area Detector

该合同通过材料研究部和多学科活动办公室提供部分支持，用于采购配备抛物面聚光镜和x射线区域探测器的多用户四圆x射线衍射仪。由于其结构，这种仪器提供了对各种材料进行重要的新颖、非传统表征的机会。该仪器将有利于材料研究、核工程、物理和化学工程的教师和学生，并将为学生提供培训。首先，四个旋转轴允许使用三个轴在实际空间中任意定位样品，同时使用第四个轴扫描衍射辐射分布。随着越来越多的物理各向异性被常规地设计成大块样品和薄膜，以及越来越多的单晶样材料被广泛应用，在三维空间中定向样品的能力变得至关重要。其次，抛物线渐变多层x射线光学元件允许从宽接受角度收集Cu， Ka辐射，然后转换成平行光束。与平面晶体光学相比，伴随的强度增加以及光束发散介于共聚焦或狭缝光学和多反射单色器之间的光束发散产生了准直的平行光束，非常适合在高定向但不是外延材料上进行的实验，以及利用非常低的入射光束角度的实验，即掠射x射线散射和小角度x射线散射。第三，散射辐射的区域检测有助于以极具时间效率的方式检查大面积的互易空间。这对于任何存在复杂互反空间结构的情况都具有重要的实用价值。例如，面积检测极大地简化了从纹理材料中收集极点图形和确定复杂微观结构的衍射峰形状。该设备是满足材料科学和工程中高级表征的一般需要所必需的。目前的材料研究计划将受到拟议仪器的重大影响。这些包括：(i)多组分氧化薄膜和异质结构的结构表征；（ii）嵌段共聚物复杂形态的研究；（iii）半导体薄膜异质结构的表征；（iv）研究织构对用于腐蚀性环境的金属和合金的蠕变、变形、断裂和降解的影响；(v)相鉴定、微观结构测定以及纳米粉末和粉末复合材料的转化研究。在这些领域都有巨大的科学和商业利益，新的衍射仪器提供的能力将大大扩展从现有资金来源获得的科学贡献。最后，对研究生和本科生的培训都强调了获得这种衍射仪所提供的最先进方法的重要性。＊＊＊

9704210 Streiffer This award provides partial support through the Division of Materials Research and the office of Multidisciplinary Activities for the acquisition of a multiuser, four-circle x-ray diffractometer equipped with parabolic condensing mirrors and an x-ray area detector. Such an instrument presents the opportunity to perform significant novel, nontraditional characterization of a wide variety of materials because of its configuration. This instrument will benefit faculty and students in Materials Research, Nuclear Engineering, Physics, and Chemical Engineering, and will provide training for students. First, four rotation axes allow a sample to be arbitrarily positioned in real space using three axes, while the diffracted radiation distribution is scanned with the fourth axis. The ability to orient a sample in three dimensions has become crucial as increasing physical anisotropy is routinely engineered into bulk specimens and thin films, and as more single-crystal-like materials are used in a wide range of applications. Second, parabolic, graded multilayer x-ray optical elements allow collection of Cu, Ka radiation from a wide acceptance angle followed by conversion into a parallel beam. The concomitant increase in intensity relative to flat crystal optics along with a beam divergence intermediate between that of parafocusing or slit optics and that of multi-bounce monochromators yields a collimated, parallel beam that is ideally suited for experiments performed on highly-oriented, but not epitaxial, materials, and for experiments utilizing very low incident beam angles, namely glancing incidence x-ray scattering and small angle x- ray scattering. Third, area detection of the scattered radiation facilitates examination of large areas of reciprocal space in an extremely time-efficient manner. This is of paramount utility for any case in which there is complicated reciprocal space structure. As examples, area detection great ly simplifies the collection of pole figures from textured materials and the determination of diffraction peak shapes for complex microstructures. This equipment is required to fulfill the general need for advanced characterization in materials science and engineering. Current materials research programs will be significantly impacted by the proposed instrumentation. These include: (i) structural characterization of multicomponent oxide thin films and heterostructures; (ii) investigation of complex morphologies in block copolymers; (iii) characterization of semiconductor thin film heterostructures; (iv) investigation of the effects of texture on creep, deformation, fracture, and degradation of metals and alloys targeted for use in aggressive environments, and (v) phase identification, microstructure determination, and investigation of transformations in nanosized powders and powder composites. There is great scientific and commercial interest in each of these areas, and the capabilities provided by new diffraction instrumentation will significantly extend the scientific contribution obtained from existing funding sources. Finally, the importance of access to state-of-the-art methodologies, as will be provided by such a diffractometer, is emphasized for both graduate and undergraduate training. ***