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

这个EAGER奖项支持博士后学生协助开发方法，使用聚焦离子束（FIB）制造适当形状的纳米尺度的非生物和生物碳酸盐尖端，随后使用原子探针断层扫描（APT）进行成分分析。APT被开发用于分析半导体工业中用于过程控制的合成导电材料，以及亚纳米/原子尺度的空间分辨分析其他合成材料（如陶瓷）中的元素分布。PI是一位专门研究生物矿化过程的矿物学家/地球化学家，他试图使用阿拉巴马大学中央分析设施（CAF）中现存的FIB-SEM和APT仪器。APT技术使用脉冲激光蒸发极其精细的纳米级材料尖端，然后使用飞行时间质谱（TOF-MS）对样品尖端中的单个原子分布进行成像。APT在碳酸盐岩研究中的应用尚处于起步阶段，这对成功分析在原子尺度上理解成矿和成岩过程的潜在应用提出了重大挑战。从脆性生物碳酸盐矿物中制造尖端需要非常小心的离子研磨和尖端载荷到APT仪器中，到目前为止，PI只成功地分析了一次生物碳酸盐尖端，分析精度有限。本EAGER的目标是首先尝试改进离子磨非生物源碳酸盐尖端的方法，用于后续的APT分析，然后尝试将这些过程外推到天然生物源碳酸盐矿物的离子磨。第二个目标是开发最佳分析方案，以确定碳酸盐矿物的主要、次要和微量元素的相对丰度是否可以在原子尺度上成功成像。如果这项技术取得成功，可能会对微生物介导的碳酸盐矿化过程和古记录研究产生革命性的影响，但它存在相当大的风险，因此提出了EAGER建议机制。碳酸盐岩在地球的沉积大陆地壳中大量存在，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发展主要集中在古气候和古环境重建的研究中，其中生物成因碳酸盐矿物的分析起着至关重要的作用。原子探针的潜在用途可以促进：1)扩散动力学（体积，晶界，微量元素等）；2)元素划分；3)矿物溶解和再结晶；4)瞬态非晶相转变为晶相。拟议的新的分析发展可以鼓励地球化学研究和矿物分析的新方法，并促进跨学科研究。如果技术开发成功，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，结果将通过专题研讨会、科学会议和学术出版物传播。

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.