EAGER: Developing atom probe tomography (APT) for the characterization of carbonate minerals

这一热切的奖项支持一名博士后，帮助开发使用聚焦离子束(FIB)制造适当形状的纳米级非生物和生物碳酸盐尖端的方法，以便随后使用原子探针断层扫描(APT)进行成分分析。APT被开发用于半导体工业中用于过程控制的合成导电材料的分析，以及对其他合成材料(例如陶瓷)中元素分布的亚纳米级/原子尺度的空间分辨分析。PI是一位专门研究生物成矿过程的矿物学家/地球化学家，他试图使用阿拉巴马大学中央分析设施(CAF)现有的FIB-SEM和APT仪器。APT技术使用脉冲激光蒸发极其精细的纳米材料尖端，然后使用飞行时间质谱仪(TOF-MS)来成像样品尖端中的单个原子分布。APT在碳酸盐研究中的应用还处于初级阶段，对于在原子尺度上理解矿化和成岩过程的潜在应用而言，对成功的分析提出了重大挑战。从脆性的生物碳酸盐矿物制造尖端需要非常小心地将离子研磨和尖端加载到APT仪器中，到目前为止，PI只成功地对生物碳酸盐尖端进行了一次成功的分析，分析精度有限。这项研究的一个目标是首先尝试改进非生物成因碳酸盐离子磨尖的方法，以便随后进行APT分析，然后尝试将这些过程外推到天然生物碳酸盐矿物的离子研磨。第二个目标是开发最佳分析方案，以确定碳酸盐矿物中主要、次要和微量元素的相对丰度是否能够在原子尺度上成功地成像。如果这项技术成功，它可能会对微生物介导的碳酸盐成矿过程的研究和古记录研究产生革命性的影响，但它存在相当大的风险，因此迫切需要提出机制。碳酸盐岩石存在于地球的大部分沉积陆壳中，因此在地质研究中具有重要意义。此外，目前地球化学技术和应用的大部分发展是为了研究古气候和古环境重建，其中生物成因碳酸盐矿物的分析起着至关重要的作用。原子探针的潜在应用可以提供以下方面的先进知识：1)扩散动力学(体积、晶界、微量元素等)；2)元素分配；3)矿物溶解和再结晶；以及4)瞬时非晶相向晶态相的转变。拟议的新的分析发展可以鼓励对地球化学研究和矿物分析采取新的方法，并促进跨学科研究。如果技术开发被证明是成功的，阿拉巴马大学中央分析设施(CAF)的APT和FIB仪器可以开放给外部社区使用。该提案将聘请一名博士后科学家，并将通过专题研讨会、科学会议和学术出版物的演讲来传播结果。

This EAGER award supports a postdoctoral student to assist in the development of methods to fabricate appropriately shaped, nanometer scale, tips of abiogenic and biogenic carbonates using a focused ion beam (FIB) for subsequent compositional analysis using atom probe tomography (APT). APT was developed for the analysis of synthesized conducting materials for process control in the semiconductor industry and sub-nanoscale/atomic scale spatially resolved analysis of elemental distributions in other synthesized materials (e.g., ceramics). The PI, a mineralogist/geochemist who specializes in studies of biogenic mineralization processes seeks to employ the extant FIB-SEM and APT instruments housed in the Central Analytical Facility (CAF) at the University of Alabama. APT technology uses pulsed laser evaporation of extremely delicate nanoscale materials tips followed by time-of-flight mass spectrometry (TOF-MS) to image individual atom distributions in sample tips. Application of APT to studies of carbonates is in its infancy and presents major challenges to successful analysis for potential application to understanding mineralization and diagenetic processes at the atomic scale. Fabrication of tips from brittle biogenic carbonates minerals requires extremely careful ion milling and tip loads into the APT instrument and the PI has thus far only achieved a single successful analysis of a biogenic carbonate tip with limited analytical precision. A goal of this EAGER is to first try to improve methods to ion mill tips of abiogenic carbonates for subsequent APT analysis and then to attempt to extrapolate those processes to ion milling of natural biogenic carbonate minerals. A second goal is develop optimal analysis protocols to determine if the relative abundances of major, minor, and trace elements of carbonate minerals can be successfully imaged at the atomic scale. The technique, should it be successful, could prove transformative for studies of microbially mediated carbonate mineralization processes and paleorecords research but it presents considerable risk, hence the EAGER proposal mechanism.Carbonate rocks are present in large parts of the sedimentary continental crust of the Earth and thus are of great significance in geological studies. Furthermore, much of the current development of geochemical techniques and applications is for studies in paleoclimate and paleoenvironmental reconstructions in which the analysis of biogenic carbonate minerals plays a crucial role. The potential use of atom probe could contribute advanced knowledge of: 1) diffusion kinetics (volume, grain-boundary, trace elements, etc.); 2) element partitioning; 3) mineral dissolution and recrystallization; and 4) transformation of transient amorphous phases into crystalline counterparts. Proposed new analytical developments could encourage new approaches to geochemistry research and mineral analysis and promote interdisciplinary research. Should the technique development prove successful, the APT and FIB instruments in the Central Analytical Facility (CAF) of The University of Alabama could be opened for outside community use. The proposal will engage a postdoctoral scientist and results will be disseminated through talks at topical workshops, scientific conferences and through scholarly publication.