M.K. Miller

Invited review article: Atom probe tomography.

The technique of atom probe tomography (APT) is reviewed with an emphasis on illustrating what is possible with the technique both now and in the future. APT delivers the highest spatial resolution (sub-0.3-nm) three-dimensional compositional information of any microscopy technique. Recently, APT has changed dramatically with new hardware configurations that greatly simplify the technique and improve the rate of data acquisition. In addition, new methods have been developed to fabricate suitable specimens from new classes of materials. Applications of APT have expanded from structural metals and alloys to thin multilayer films on planar substrates, dielectric films, semiconducting structures and devices, and ceramic materials. This trend toward a broader range of materials and applications is likely to continue.

Review of atom probe FIB-based specimen preparation methods.

Several FIB-based methods that have been developed to fabricate needle-shaped atom probe specimens from a variety of specimen geometries, and site-specific regions are reviewed. These methods have enabled electronic device structures to be characterized. The atom probe may be used to quantify the level and range of gallium implantation and has demonstrated that the use of low accelerating voltages during the final stages of milling can dramatically reduce the extent of gallium implantation.

Atom Probe Tomography of Nanoscale Particles in ODS Ferritic Alloys

An atom probe tomography characterization of the microstructure of as-processed and crept mechanically-alloyed, oxide-dispersion-strengthened (MA/ODS) ferritic alloys has been performed. The significant enrichments of Cr, W, Ti, Y, O, C and B in the vicinity of dislocations and the presence of ultrastable 4-nm-diameter Ti-, Y- and O-enriched particles appears to be responsible for their improved high temperature mechanical properties.

Oxygen impurity and microalloying effect in a Zr-based bulk metallic glass alloy

A Zr-base bulk metallic glass (BMG) alloy withthe base composition Zr–10 at.%Al–5% Ti–17.9% Cu–14.6% Ni (BAM-11) was used to study the effects of oxygen impurities and microalloying on the microstructure and mechanical properties. Oxygen impurity at a level of 3000 appm dramatically reduced the glass forming ability and embrittled BAM-11 at room temperature. The embrittlement was due to the formation of oxygen-induced Zr4Ni2O nuclei that triggered near complete crystallization of the metallic glass. Microalloying with 0.1 at.%B+0.2%Si+0.1%Pb was effective in suppressing the crystalline phase formation and alleviating the detrimental effect of oxygen. Microstructural analyses indicate that the beneficial effect of the optimum dopants was mainly due to stabilization of the glass-phase matrix even though it contained high levels of oxygen. Thus, microalloying is effective in reducing the production cost and is very useful for manufacturing good-quality Zr-based BMGs from impure charge materials. # 2002 Published by Elsevier Science Ltd.

Spinodal decomposition in Fe-Cr alloys: Experimental study at the atomic level and comparison with computer models—I. Introduction and methodology

Abstract A three-part series of papers is presented concerning the atomic scale analysis of spinodal decomposition in Fe-Cr alloys. This first part deals with the experimental techniques and computer simulations, the second part discusses the dynamics of early stage phase separation, and the third part describes the morphological and structural characterization of spinodal microstructures. In this first paper, three-dimensional reconstructions of the atomic structure of a series of thermally aged Fe-Cr alloys are shown. Two methods for computer simulation of the decomposition process are described. The first is an atomistic simulation based on the Monte Carlo algorithm and the second is a numerical solution to the Cahn—Hilliard—Cook theory. The three-dimensional atomic scale structures resulting from decomposition within the low temperature miscibility gap are reconstructed. It is shown that both models generate microstructures which are qualitatively similar to those observed experimentally.

Effects of focused ion beam milling on the nanomechanical behavior of a molybdenum-alloy single crystal

Nanoindentation was performed on a Mo-alloy single crystal to investigate effects of focused ion beam (FIB) milling on mechanical behavior. On a non-FIB-milled surface, pop-ins were observed on all load-displacement curves corresponding to a transition from elastic to plastic deformation. Similar pop-ins were not detected on surfaces subjected to FIB milling. This difference indicates that FIB milling introduces damage that obviates the need for dislocation nucleation during subsequent deformation. A second effect of FIB milling is that it increased the surface hardness. Together, these effects could be the source of the size effects reported in the literature on micropillar tests.

Atom Probe Tomography: A Technique for Nanoscale Characterization

Atom probe tomography is a technique for the nanoscale characterization of microstructural features. Analytical techniques have been developed to estimate the size, composition, and other parameters of features as small as 1 nm from the atom probe tomography data. These methods are outlined and illustrated with examples of yttrium-, titanium-, and oxygen-enriched particles in a mechanically alloyed, oxide-dispersion-strengthened steel.

Understanding Pressure Vessel Steels: An Atom Probe Perspective

A review of the contributions of the atom probe field-ion microscopy (APFIM) technique to the microstructural characterization of pressure vessel steels and to the understanding of the embrittlement of these materials during neutron irradiation is presented. Atom probe studies have revealed that the microstructure contains a variety of ultrafine clusters and precipitates some of which are only formed during neutron irradiation. Furthermore, there is a complex pattern of segregation of various solutes (including phosphorus, nickel, manganese, or molybdenum) to grain boundaries in some pressure vessel materials, and there may also be additional intergranular precipitation in these materials. Published by Elsevier Science Inc.

The Oak Ridge Polycystic Kidney mouse: Modeling ciliopathies of mice and men

The Oak Ridge Polycystic Kidney (ORPK) mouse was described nearly 14 years ago as a model for human recessive polycystic kidney disease. The ORPK mouse arose through integration of a transgene into an intron of the Ift88 gene resulting in a hypomorphic allele (Ift88Tg737Rpw). The Ift88Tg737Rpw mutation impairs intraflagellar transport (IFT), a process required for assembly of motile and immotile cilia. Historically, the primary immotile cilium was thought to have minimal importance for human health; however, a rapidly expanding number of human disorders have now been attributed to ciliary defects. Importantly, many of these phenotypes are present and can be analyzed using the ORPK mouse. In this review, we highlight the research conducted using the OPRK mouse and the phenotypes shared with human cilia disorders. Furthermore, we describe an additional follicular dysplasia phenotype in the ORPK mouse, which alongside the ectodermal dysplasias seen in human Ellis‐van Creveld and Sensenbrenners syndromes, suggests an unappreciated role for primary cilia in the skin and hair follicle. Developmental Dynamics 237:1960–1971, 2008.

An atom probe field ion microscopy study of neutron-irradiated pressure vessel steels

Abstract Atom probe field ion microscopy has revealed that the microstructure of commercial pressure vessel steels that have been neutron-irradiated is extremely complex and involves many different types of features. These features include ultrafine distributions of copper atmospheres, clusters and precipitates, phosphorus clusters, molybdenum carbides and nitrides, and vanadium carbo-nitrides in the matrix. In addition to these ultrafine features, coarse alloy cementite, molybdenum carbides, and copper-manganese precipitates have been observed at grain boundaries. The grain boundaries were also found to be coated with an ultrathin film of molybdenum carbides and nitrides and were enriched in phosphorus, nickel and manganese.