bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Developments in Atom Probe Techniques and Potential Applications to Materials Science
Authors: Blavette Didier , Menand Alain 
Published: August 2016

The emergence of the field ion microscope, invented by E.W. Müller in 1951, allowed, for the first time, direct observation of metallic materials in real space on an atomic scale. Field ionization of rare gas atoms near the surface of the material allowed production of an atomic resolution image of the material; field evaporation of surface atoms allowed observation into the depth of the sample.Field ion microscopy (FIM) has produced numerous impressive results, one of them being three-dimensional reconstruction of defect cascades produced by heavy ion irradiation in metals. FIM techniques have also contributed in a spectacular way to the knowledge of the crystallographic structure of grain boundaries. Surface diffusion as well as surface reconstruction phenomena are applications where, again, FIM gave surprisingly detailed information. This overview of applications of FIM in materials science emphasizes recent work. Detailed information and descriptions of earlier work can be found elsewhere.During the development of FIM techniques, the basic shortcomings of the instrument for investigating metallic alloys were rapidly recognized. In Cu3Pd alloys, for instance, Cu atoms are darkly imaged and therefore appear as vacancies similar to Co atoms in PtCo and Pt3Co. It is thus impossible to distinguish vacancies from solute atoms. This clearly limited the quantitative use of FIM to study short-rangeorder in dilute alloys or to investigate long-range order (Figure 1). Similarly, in two-phase materials, precipitates often give rise to quite visible contrast. For instance, in nickel-based alloys, aluminum-enriched precipitates appear in bright contrast. It is therefore possible to find the size and also the number density of particles present in the material. However, FIM does not provide any composition data.
A Unified Approach to Solid-State Amorphization and Melting
Authors: Lam Nghi Q. , Okamoto Paul R. 
Published: August 2016

The crystalline-to-amorphous (c-a) phase transformation can be induced by a variet of solid-state processes ranging from energetic particle irradiation, interface inter diffusion reactions, hydrogen charging and mechanical deformation to the application of high pressures. During the past decade, such transformations have become the focus of considerable research not only because of their potential technological applications, but also because of strong scientific interest in the relationship between the c-a transition and the melting process.A common feature underlies all solid state amorphization processes: The atomic disorder created in the crystalline lattice in the form of static atomic displacement can induce volume change and elastic softening of the lattice. A particularly striking example of the softening effect is shown in Figure 1 for the case of radiation-induced amorphization of the intermetallic compound Zr3Al. The compound, which has the Ll2 (Cu3Au)-type superlattice structure, was irradiated with energetic ion at room temperature in a high-voltage electron microscope interfaced to a tandem ion accelerator. The rapid decrease in the intensities of both fundamental and superlattice reflections show that irradiation introduces antisite defects (chemical disorder) as well as static atomic displacements. The disordering of the long-range ordered structure, which occurs prior to the onset of amorphization, is accompanied by a volume expansion of about 2.5% and a ~25% decrease in the average velocity of sound. This decrease in sound velocity corresponds to a ~50% decrease in the average shear modulus, which is comparable to that observed for many metals during heating to melting. The volume dependence of this disorder-induced elastic softening is also similar to that associated with heating. In both cases, the shear modulus is a linearly decreasing function of volume expansion. However, for a given amount of expansion, the softening associated with static atomic displacements is nearly twice as large as that associated with increasing anharmonic lattice vibrations.
Microstructure and Processing of Ice Cream
Authors: Kilara Arun , Sharkasi Tawfik 
Published: August 2016

Ice cream and frozen desserts are popular throughout the world, but the United States is the largest consumer of ice cream. In the United States it is estimated that 46.8 pints per capita of ice cream and frozen desserts were consumed in 1992.Physically, ice cream is a foam in which the continuous phase is a partially frozen emulsion. Foams are also important for foods such as whipped toppings, souffle, mousse, meringue, and angel food cake. The structure of the foam affects the appearance, texture, consistency, lightness, and mouthfeel of these foods. A foam is mostly air and is characterized by high viscosity, low density, high surface area, and high surface energy. Food foams such as ice cream have an air content of 40-50% by volume. The continuous phase is a concentrated, unfrozen aqueous solution containing soluble milk salts, lactose, and added sugars. The dispersed solids (i.e., proteins, salts, stabilizer, and fat) are in the colloidal state and in the form of an emulsion. The ice crystals exist in the coarsely dispersed phase, occupying a major portion of the space between air cells.
Chemical Vapor Deposition of Copper for Advanced On-Chip Interconnects
Authors: Gelatos A.V. , Jain A. , Marsh R. , Mogab C.J. 
Published: August 2016

Continued dimensional scaling of the elements of integrated circuits places significant restrictions on the width, density, and current carrying capability of metallic interconnects. It is expected that, by the year 2000, the transistor channel length will be at 0.18 μm, while microprocessors will pack more than 15 million transistors over an area ~700 mm. To conserve area, interconnects will continue to be stacked at an increasing number of levels (six by the year 2000, versus four in today's leading microprocessors), and the minimum spacing and width within an interconnect layer will shrink to 0.3 μm. In addition, it is expected that future interconnects will need to sustain increasingly higher current densities without electromigration failures.Aluminum alloys are the conductors of choice in present-day interconnects, and much effort is focused on means to extend the usefulness of aluminum through improvements in reliability, either by new alloy formulations or by the development of complicated multimetal stacks. A more radical approach, which is gaining increased attention, is the replacement of aluminum altogether by copper. The bulk resistivity of copper is significantly lower than that of aluminum (1.7 μΩ cm for Cu versus 3.0 μΩ cm for Al-Cu), which is expected to translate to interconnects of higher performance because of reduction in signal propagation delay. In addition, the significantly higher melting temperature of copper (~1100°C versus ~600°C for Al-Cu alloys) and its higher atomic weight are expected to translate to improved resistance to electromigration.
Electroless Copper Deposition on Metals and Metal Silicides
Authors: Mak Cecilia Y. 
Published: August 2016

Chemical plating techniques have been used in silicon processing for many years for junction delineation and ohmic contact formation. In recent years, interest in this area has been renewed because of the potential use of electroless copper deposition for ultra-large-scale integration (ULSI) metallization and for the formation of thin metal etch masks for deep-ultraviolet lithography. Good deposition selectivity, low operating temperature, high copper purity, good filling characteristics, and planar topography have been among the many advantageous attributes reported from early investigations.In the June 1993 issue of theMRS Bulletinon Copper Metallization, Cho et al. gave an exposition on the use of electroless copper for VLSI. More comprehensive reviews of the electrochemical fundamentals can be found in References 8,9, and 10. This article summarizes the current understanding of various chemical and material aspects of this deposition method in an attempt to give an overview of the film growth characteristics for thin film applications. Because of length limitations, only selected topics are included. The emphasis is on the initiation conditions and the resultant microstructure and properties obtained. We also discuss special considerations for fine pattern formation.The information presented here applies primarily to electroless copper deposition on metals and metal silicides since these are the typical substrate surfaces for metallization in contact vias of ULSI circuits. Strictly speaking, metallization of upper-level interconnects occurs mostly on a dielectric base. However, since copper systems usually require a diffusion barrier to shield the copper from diffusing into the silicon, we can treat the deposition process startingfrom this layer onward.
Why Crystal Engineering of Oxides?
Authors: Koinuma Hideomi 
Published: August 2016

This issue of the MRS Bulletin, on the crystal engineering of high Tc and related oxide films, essentially responds to four questions. The first three are∎ Why has a high Tc superconducting tunnel junction not yet been fabricated?∎ Is it possible to fabricate a high Tc tunnel junction and if so, how?∎ How can thin-film technology contribute to the progress of high Tc superconductor research beyond the fabrication of electronic devices?Experimental efforts to answer these questions and solve associated problems must focus on atomic-scale control and characterization of surfaces and interfaces, which we designate here as crystal engineering of high Tc and related oxide films. Meanwhile, we have started to realize that the crystal engineering technology of oxides need not be limited to high Tc super-conductor research; it can be extended to electronic materials research, where it may have a somewhat more profound significance. In this light, I would like to pose the fourth question, one that may be especially relevant to this particular topic in the near future:∎ Will we find or develop an electronic material superior to silicon?Ever since the first success in superconducting La-Sr-Cu-O film deposition in early 1987, extensive studies have been conducted on the fabrication of high Tc oxide films and devices. Success has been achieved to some extent in relatively simple devices using plain superconducting films or grain boundary and step edge junctions. Nobody, however, has succeeded in fabricating an SIS (superconductor-insulator-superconductor) runnel junction that shows a clear hysteresis in I-V characteristics at a temperature above 77 K. Such a junction is presumably the key to the wide electronic device application of high Tc superconductors, for example, for switching devices expected to work much faster than conventional semiconductor transistors.
Up Close: Center for Electron Microscopy of Materials Science at the University of Antwerp
Authors: Van Tendeloo G. , Schryvers D. , Van Dyck D. , Van Landuyt J. , Amelinckx S. 
Published: August 2016

The Center for Electron Microscopy of Materials Science (EMAT) at the University of Antwerp, Belgium, started in 1967 under the initiative of S. Amelinckx. While most materials science laboratories choose a particular research theme (e.g., superconducting materials) and study it through several available techniques, the EMAT group at Antwerp has taken a different approach. From the beginning, EMAT has concentrated on a single technique: transmission electron microscopy. Since the laboratory, as well as the university, is very small, we felt it would be better to be excellent in a single technique than to have limited proficiency in several techniques. Until recently, EMAT has been able to maintain this strategy, although the group has grown considerably; at present it consists of four academic staff members, four postdocs, and 12 PhD students, supported by a technical and administrative staff of eight people.Instrumentation at EMATThe range of electron microscopes and related instruments in the EMAT laboratory is quite extensive and includes several instruments dedicated to specific techniques. The instruments include:∎ A 1,250 kV high-voltage electron microscope, used mainly for studying processed semiconductor devices and for in situ radiation experiments.∎ A 400 kV and a 200 kV high-resolution electron microscope with resolving powers of 1.7 Å and 2.5 Å, respectively. Both instruments are equipped with a TV imaging system and a video camera.∎ A 200 kV and a 100 kV analytical electron microscope with large tilting possibilities, cooling and heating facilities, and capability for energy dispersive x-ray analysis for measuring the local composition.
Carbon Nanotubes
Authors: Iijima Sumio 
Published: August 2016

Nanostructured materials have recently attracted the attention of some materials scientists. Because of their unique properties occurring in low-dimensional structures, nanostructured materials are sought for their possible industrial applications. This article introduces a specific nanostructured material, the carbon nanorube—an extremely thin filaments of graphite considered to be a quasi one-dimensional structure, with a simple well-understood atomic structure. Because of these qualities, the carbon nanorube has elicited great interest from diverse fields of basic and technological research. My discovery of carbon nanotubes was inspired by the discovery of C60 and its family and their mass production. The carbon nanotubes were serendipitously found during the examination of fullerene materials by a high-resolution transmission electron microscope (HRTEM). Since introducing this technique in 1971, I have been employing HRTEM to characterize the microscopic structural details of a variety of materials, including carbonaceous materials. So far, only nanotubes have been revealed with HRTEM.Interest in the carbon nanorube is multifold. Academically the nanotube is an ideal model structure for a quasi one-dimensional structure since its known atomic structure makes computer simulations more reliable. It is worthwhile to study both rare structures of graphite—cylindrical forms with a helical arrangement of carbon atom hexagons and flexible graphitic sheets containing topological surface defects. These materials may find practical uses as tough graphite fibers, molecular wires, catalyst supports, molecular adsorbers, and so on.
New Horizons in Carbon Chemistry and Materials Science
Authors: Kroto H.W. , Hare J.P. , Sarkar A. , Hsu K. , Terrones M. , Abeysinghe J.R. 
Published: August 2016

The discovery that C60 Buckminsterfullerene may be created spontaneously in high yield when carbon vapor condenses indicates that graphene sheet curvature and closure is a common occurrence during carbon nucleation to form extended networks. As a consequence, a net microscopic perspective on graphitelike carbonaceous materials has evolved. This perspective is summarized here because the net observations relate to various types of nonplanar graphitic structures that promise to be useful as viable nanoscale engineering materials.C60 Buckminsterfullerene was discovered in 1985 among the products of chemical nucleation of carbon in the gas phase. The faint whisper, embedded in the helium wind that blew a laser-initiated carbon plasma into a mass spectrometer, was interpreted as the possible signature of the elegant soccer-ball-shaped molecule. That noticed signal, which indicated that a pure 60-carbon-atom molecule might be very stable, was quite unexpected and thus a truly serendipitous discovery. The original aim of the experiments was to simulate the conditions in a red giant carbon star and particularly to probe an earlier proposal that long carbon-chain molecules might have originated in such celestial objects and might have been subsequently ejected into interstellar space. The carbon chains themselves had been discovered to be abundant in certain regions of the interstellar medium by a radioastronomy search program in the late 1970s. The molecular rotational frequencies, which formed the basis for the radio search, resulted from a spectroscopic study of cyanopolyynes that had been synthesized in the laboratory.
Metal Container Materials for Nuclear Waste
Authors: McCright R. Daniel 
Published: August 2016

Selecting materials to contain high-level nuclear waste presents an unparalleled challenge to materials scientists and engineers because of the very long times required for containing the waste and the high degree of certainty required when predicting a container's long-term performance. Material endurance without severe degradation is the primary property sought in container materials. There are, of course, additional factors related to mechanical properties, fabricability and weldability, and economics, but these factors are usually secondary to the chemical properties of the material. Metals and alloys have been given prime consideration as container materials because metal materials are ductile and tough, they can be easily fabricated in mass quantities and large container sizes, and they can be readily joined to create intact gas-tight seals between parts.In selecting a suitable container material, the container's environment is the most important consideration. Several geological formations and resulting geochemical environments are under consideration as disposal sites in different countries. This short review will discuss the principles governing corrosion of the primary container materials being considered in various national nuclear waste disposal programs and will show how this background can guide materials selection. Important candidate materials are then considered along with examples of how these materials will be expected to perform under repository conditions existing in a range of national programs.
Functionally Gradient Materials
Authors: Rabin B.H. , Shiota I. 
Published: August 2016

This issue of the MRS Bulletin provides an up-to-date look at ongoing research activities within the field of functionally gradient materials (FGM). The term FGM, now widely used by the materials community, originated in Japan in the late 1980s as a description for a class of engineering materials exhibiting spatially inhomogeneous microstructures and properties. Of course, gradient materials are not something new. It must be recognized that humans have extensively utilized materials containing microstructural gradients (either those found in nature or those created through processing) since the earliest days of craftsmanship and engineering construction. Indeed, there are examples of graded materials developed long ago, such as case-hardened steel, which are still in common use today. Contemporary examples of these materials serve in technologically significant applications, as, for example, in thermal-barrier coatings for gas turbines. Nevertheless, what is new and exciting about FGMs is the realization that gradients can be designed at the microstructural level to tailor a material for the specific functional and performance requirements of an intended application. In addition, recent advances in processing are opening the possibility for the extension of the gradient materials concept to new materials systems and engineering problems.The recent resurgence of interest in gradient materials has been driven by the need for improved materials, capable of meeting the demanding performance requirements established by emerging technologies such as the aerospace plane, ceramic engines, and nuclear fusion.
Grain Growth in Si3 N4-Based Materials
Authors: L.|Kang Suk-Joong , Han Sang-Moo 
Published: August 2016

The growth of Si3N4 grains in the usual sintering process occurs in an oxynitride liquid formed by reactions between sintering additives, impurity SiO2, and Si3N4. The shape of an Si3N4 grain in the liquid matrix is a hexagonal rod, although the aspect ratio (c/a) varies considerably, depending on the processing conditions and final crystalline forms of α or β. Figure 1 shows two types of microstructures observed in sintered Si3N4-based materials. The microstructure shown in Figure la is normal with unimodal grain-size distribution and that of Figure 1b is abnormal with a microstructure of exceptionally large elongated grains within fine matrix grains. When normal grain growth occurs, the microstructure varies little with sintering time, and the development may be described by a simple law. But, when abnormal grain growth occurs, a duplex grain structure with a bimodal grainsize distribution results; then no simple kinetic law can describe the microstructure development.The grain growth in the microstructures shown in Figure 1 exemplifies the growth of faceted grains in a liquid matrix. The grain growth in a matrix occurs via growth of larger grains and dissolution of smaller ones by material transport through the liquid phase. The driving force of the material transport for an individual grain is determined by the difference between its size and the critical grain size, which is invariant at the moment of observation. Since the driving force is usually low, the volume change of each grain is relatively slow and analogous to the crystal growth or dissolution in a liquid matrix under low super- or undersaturation. Therefore, knowledge of the growth behavior of faceted crystals under low supersaturation in a liquid may provide fundamental understanding of the grain growth in Si3N4-based materials.
Dislocation-Based Deformation Mechanisms in Metallic Nanolaminates
Authors: Anderson P.M. , Foecke T. , Hazzledine P.M. 
Published: August 2016

The appeal of nanolayered materials from a mechanical viewpoint is that, in principle, plastic deformation can be confined to small volumes of material by Controlling both the frequency and magnitude of obstacles to dislocation motion. As we shall see, the spacing of obstacles can be used to impart large plastic anisotropy and work hardening. However, how strong can such materials be made as layer thickness (and therefore obstacle spacing) is decreased to the nanoscale level? In perspective, large, micron-scale, polycrystalline materials generally display improved yield strength (and fracture toughness) as grain size is decreased. This behavior at the micron scale can be explained via modeis that are built on two assumptions: (1) the strength of obstacles to crystal slip is sufficiently large to require pileups of numerous dislocations in order to slip past them; and (2) the strength of such obstacles does not change, even if their spacing is decreased. The modeling presented here shows that these assumptions may break down at the nanometer scale. The result is that there is a critical layer thickness in the nanometer range, below which improvement in strength does not occur.Our discussion to follow briefly outlines a more macroscopic, micron-scale approach to determine yield strength, and then contrasts that with a sequence of events leading up to yield in nanolayered materials. We also address whether nanoscale materials are expected to exhibit more uniform or coarse slip than micron-scale materials. Finally, a semi-quantitative model of yield strength is developed which requires, as input, the strength of an interface to crystal slip transmission across it. We discuss several contributions to the interfacial strength and apply the theory to demonstrate a peak in strength for a 50 vol% Cu-50 vol% Ni multilayered sample.