Superalloys based on platinum-group metals are being developed for high-temperature applications. These alloys have two-phase structures comprising either ordered precipitates in a matrix analogous to the nickel-based superalloys or a fine dispersion of oxide particles in a matrix analogous to oxide-dispersion-strengthened nickel-based alloys. Currently, alloys based on iridium, rhodium, and platinum have been obtained. This article reviews the rationale of developments and the progress made in this area. Oxidation and compression tests as well as characterization with scanning electron microscopy and transmission electron microscopy were undertaken. These tests showed encouraging results, and further work is being done on new alloying additions and tensile testing.

This article reviews two topics related to the stability of hard coatings composed of nanometer-thick layers: epitaxial stabilization and high-temperature stability. Early work on nanolayered hard coatings demonstrated large hardness increases as compared with monolithic coatings, but it was subsequently found that the layers interdiffused at elevated temperatures. More recently, it has been shown that nanolayers exhibit good stability at elevated temperatures if the layer materials are thermodynamically stable with respect to each other and are able to form low-energy coherent interfaces. This article discusses metal/nitride, nitride/nitride, and nitride/boride nanolayers that exhibit good high-temperature stability and hardness values that are maintained (or even increase) after high-temperature annealing. Epitaxial stabilization of nonequilibrium structuresin thin layers is a well-known phenomenon that has been applied to hard nitride materials. In particular, AlN, which crystallizes in the hexagonal wurtzite structure in bulk form, was stabilized in the rock-salt cubic structure in nitride/nitride nanolayers (e.g., AlN/TiN). These results and the current understanding of epitaxial stabilization in hard nanolayers are discussed.

We review the current understanding of single-event upsets (SEUs) in microelectronic devices. In recent years, SEUs have been recognized as one of the key reliability concerns for both current and future technologies. We identify the major sources of SEUs that impact many commercial products: (1) alpha particles in packaging materials, (2) background radiation due to cosmic rays, and (3) thermal neutrons in certain device materials. The origins of SEUs are examined from the standpoint of the fundamental atomic and nuclear interactions between the intruding particles (alpha particles, cosmic rays, and thermal neutrons) and semiconductor materials. We analyze field funneling, which is a key mechanism of charge collection in a device struck by an ionizing particle. Next, we formulate how SEU cross sections and SEU rates are calculated and discuss how these basic quantities are related to experiments. Finally, we summarize the major SEU issues regarding modeling, bulk complementary metal oxide semiconductor technologies, and research on future, exploratory technologies.

The following article is an edited transcript based on the MRS Medalist presentation given by Charles M. Lieber of Harvard University on December 4, 2002, at the Materials Research Society Fall Meeting in Boston. Lieber received the Medal “for controlled synthesis of nanowire and nanotube materials.” This presentation begins with an introduction to the bottom-up paradigm of nanoscience and nanotechnology. The key concepts of this paradigm are explored through studies outlining progress toward meeting the challenge of nanocomputing through the assembly of functional nanowire elements. The richness of the bottom-up paradigm and nanowire building blocks is then illustrated with the development of chemical and biological nanosensors. Finally, the uniqueness of nanowires is exemplified through discussion of the assembly of nanophotonic devices, including the demonstration of multicolor and addressable nanoscale light-emitting diodes, nanowire injection lasers, and assembled arrays of these nanophotonic sources. Challenges and goals for realizing nanotechnologies in the future are discussed in the conclusion.

This article discusses three main points. First, ultrahigh-temperature materials offer a large return to the propulsion community and to the economy, but replacing Ni-based alloys is a very difficult problem for both technical and financial reasons. Second, the oxidation resistance of selected Mo-Si-B alloys and the prospects for combining this with useful structural properties are remarkable, given the nature of conventional Mo alloys; however, there are nagging issues associated with their low-temperature (∼700°C) behavior. Third, further advances in the processing of such materials, together with assessments of their affordability and reliability, are vital for achieving a successful engineering technology.

Soft reactive adhesives (SRAs) are polymer-based materials (e.g., polyurethanes, polysiloxanes, polydienes) designed to be further vulcanized or slightly cross-linked through external activation (heat, moisture, oxygen, UV–visible irradiation, etc.), either at the time of their application or within a subsequent predefined period. They are used mainly as mastics, or sealing compounds, in a wide range of industrial and commercial fields such as construction, footwear, and the automotive industry. Generally deposited as thick films, SRAs behave as structural adhesives; their low elastic moduli accommodate large strains between the bonded parts without incurring permanent damage. Other outstanding attributes of SRAs are their resistance to solvents, their ability to withstand aggressive environments, and their ease of use. This article discusses examples of SRAs and, more specifically, shows how the cross-linking chemistry, mainly through step-growth polymerization, provides their primary advantages.

Protective clothing provides laboratory and hazardous-materials workers, firefighters, military personnel, and others with the means to control their exposure to chemicals, biological materials, and heat sources. Depending on the specific application, the textile materials used in protective clothing must provide high performance in a number of areas, for example, impermeability to hazardous chemicals, breathability, light weight, low cost, and durability. Models based on computational fluid dynamics have been developed to predict the performance of protective clothing materials. Such models complement testing by enabling property data from laboratory materials tests to be used in predictions of the performance of integrated multilayer garments under varying environmental conditions.

Scale effects in cellular metals can develop when the specimen size is of the order of the cell size. Decreasing the relevant specimen dimensions—height, width, and ligament size (the region between notches in notched specimens)—leads to material strengthening in shear, in indentation, and in notched specimens and to reduced strength and stiffness in uniaxial compression. Experimental size-effect studies were reviewed, and it was concluded from discrete modeling results that scale effects are caused by two different microstructural mechanisms: boundary-layer effects and constraint effects. The first mechanism is active in shear (strong boundary layers) and uniaxial compression (weak boundary layers) and vanishes for specimens larger than two cell sizes and seven cell sizes, respectively. The second mechanism is active in indentation and in notched specimens, leading to a strengthening behavior that is inversely proportional to indenter and ligament size.

Inkjet printing is an attractive method for patterning and fabricating objects directly from design or image files without the need for masks, patterns, or dies. In order to achieve this with metals or ceramics, it is often necessary to print them as highly concentrated suspensions of powders in liquids. Such liquid suspensions must have physical properties appropriate to the inkjet delivery mechanism. These properties are presented using a nondimensional formalism to illustrate the requirements for both drop formation and spreading on impact. Further critical issues relevant to inkjet printing of particulate suspensions are discussed and illustrated with experiments on a model alumina-containing colloidal suspension.

Knowledge of the dynamic dimension of materials is an extremely important ingredient for understanding their properties. Neutron scattering is uniquely capable of revealing aspects of the atomic and molecular geometry of motions over a wide range of time scales. To illustrate this fact, we give a number of examples from different areas of materials science. We discuss the diffusion of hydrogen in protonic conductors; the hydration of portland cement; and aspects of the molecular rheology of polymers, emphasizing in particular the effect of branching. All of these experiments have added important basic information to the understanding of the respective systems. With the advent of the new megawatt neutron spallation sources, the role of neutron scattering in revealing the dynamical properties of materials is expected to increase substantially.

Advanced three-dimensional (3D) packaging techniques for electronic components are promising for the realization of “systems-in-packages.” Three-dimensional packages require the use of a variety of materials within a small physical size range. Materials selection is therefore critical from electrical, optical, mechanical, structural, thermal, and manufacturability viewpoints. The materials combination depends also on the intended application for the 3D packaged modules. This article reviews 3D packaging approaches, materials classes, and examples. Three-dimensional packaged systems using judiciously selected materials offer performance advantages that cannot be provided by planar implementation.

This article is based on a presentation on organic-based magnets given as part of Symposium X—Frontiers of Materials Research on December 4, 2002, at the 2002 Materials Research Society Fall Meeting in Boston. The advent of organic-based magnets opened the opportunity for tuning magnetic properties by molecular design and the discovery of new phenomena that rely on the internal structure of the molecules that make up these magnets. In the past 18 years, numerous classes of organic-based ferromagnets, ferrimagnets, and spin glasses (spins essentially frozen in place without long-range order) have been reported. These materials have magnetic ordering temperatures ranging from <1 K to above room temperature and demonstrate many of the magnetic properties associated with conventional magnets. This article concentrates on new phenomena that are unique to organic-based magnets. Three of these effects—“high-temperature” light-induced magnetism, spin-polarized magnetic organic semiconductors with the potential for spintronics, and the development of fractal magnetic order—are discussed to illustrate the richness of opportunity in organic-based magnets.

Half-metals are unusual ferromagnets that have electrons at the Fermi level in a single spin state, either spin up or spin down. Of potential interest as sources and analyzers of polarized electrons in spintronic devices, they are usually identified from spin-dependent band-structure calculations. We present a classification scheme for half-metals and then discuss methods for measuring spin polarization based on point contacts or tunnel junctions with ferromagnetic or superconducting counter electrodes. Oxide examples include CrO2, the best-studied half-metal. The half-metallicity tends to be destroyed by increasing temperature and by structural defects. The half-metals that currently offer the best prospects for spintronics applications are those with the highest Curie temperatures, such as magnetite, Fe3O4, and perhaps oxide semiconductors such as Co-doped ZnO.

Nanoscale multilayered (superlattice) hard coatings can be manufactured in a plastic hardness range (HP) between 25GPa and 55 GPa by a combination of cathodic arc evaporation and unbalanced magnetron sputtering (arc bond sputter technology). Using large-scale industrial physical vapor deposition (PVD) equipment and a sufficiently high pumping speed, multilayered coatings can be deposited by simultaneously operating cathodes without special shutter and shielding facilities in a common reactive-gas atmosphere. The efficiency of the process is in many cases identical to that of TiN and CrN. Temperature-resistant, wear-resistant, and corrosion-resistant coatings of various compositions have been produced under industrial conditions. So far, the main applications concentrate on metal-forming and on cutting die steel, Inconel, stainless steel, and titanium. Applications have also been found in the chemical, textile, medical, and automotive industries.

With the advent of bright-blue light-emitting diodes in 1994, violet laser diodes in 1996, and vertical-cavity surface-emitting lasers at telecommunications wavelengths in 2000, all based on nitride-containing III–V compounds, a new age for optoelectronics began. Despite their technological success, III-nitride materials still hold some mysteries. Compared with conventional III–V semiconductors, even commercial nitride devices are of poor material quality. Due to their heteroepitaxial origin, their crystals are full of dislocations. Electrical properties, particularly in the case of p-type material, are fairly unsatisfactory. Still, light-emitting diodes with extremely high brightness and lasers with high power and good lifetime can be produced with III–V nitride compounds. In this review, we will give an overview of the essential properties of nitride materials for optoelectronic devices, their current development status, open questions, and recent device achievements.

The once-ephemeral soft error phenomenon has recently caused considerable concern for manufacturers of advanced silicon technology. Soft errors, if unchecked, now have the potential for inducing a higher failure rate than all of the other reliability-failure mechanisms combined. This article briefly reviews the three dominant radiation mechanisms responsible for soft errors in terrestrial applications and how soft errors are generated by the collection of radiation-induced charge. Scaling trends in the soft error sensitivity of various memory and logic components are presented, along with a consideration of which applications are most likely to require intervention. Some of the mitigation strategies that can be employed to reduce the soft error rate in these devices are also discussed.

Military, firefighter, law enforcement, and medical personnel require high-level protection when dealing with chemical and biological threats in many environments ranging from combat to urban, agricultural, and industrial. Current protective clothing is based on full barrier protection, such as hazardous materials (HAZMAT) suits, or permeable adsorptive protective overgarments, such as those used by the U.S. military. New protective garment systems are envisioned that contain novel features, such as the capability to selectively block toxic chemicals, to chemically destroy toxic materials that contact the fabric, and to detect hazardous agents on the surface of the fabric. New technologies being built into advanced fabrics for enhanced chemical and biological protection include selectively permeable membranes, reactive nanoparticles, reactive nanofibers, biocidal fabric treatments, and conductive-polymer indicators on optical fibers.

Nanocomposite thin films successfully promote hardness, oxidation resistance, improved wear behavior, and other properties relevant for wear-reducing coatings. Such coatings are composed of nanocrystalline grains of transition-metal nitrides or carbides surrounded by an amorphous hard matrix. The properties of nanocomposite coatings, especially hardness, are directly linked to nanostructure. The codeposition of the amorphous and nanocrystalline phases of different compositions results in different morphologies, which in turn affect the coating's properties. A maximum hardness ranging from 30 GPa to reported values above 60 GPa has been observed for most nanocomposite coatings. To obtain enhanced hardness, the domain size of the nanocrystalline phase must be below 10 nm, while the thickness of the amorphous layer separating the nanocrystals must be maintained at only a few atomic bond lengths. The prime reason for the hardness enhancement is the absence of dislocation activity.

Packaging of solid-state power electronics is a highly interdisciplinary process requiring knowledge of electronics, heat transfer, mechanics, and materials science. Consequently, there are numerous opportunities for innovations at the interfaces of these complementary fields. This article offers a perspective of the current state of the art and identifies six specific areas for materials-based research in power electronics packaging. The emphasis is on identifying the underlying physical relationships that link the performance of the power electronics system to the microstructure and architectural arrangement of the constituents.

Although adhesives, particularly those based on epoxy resins, are finding increasing use in structural applications, their utilization at elevated temperature (>150°C) has been limited by their relatively poor thermal and thermo-oxidative stability. As a result, significant effort has been directed in recent years toward the development of polymers exhibiting increased thermal resistance. Although a wealth of research conducted over several decades has resulted in a myriad of polymer types exhibiting, in some cases, impressive high-temperature performance, many systems have demonstrated poor processability Thus, much emphasis has been placed on developing high-temperature performance while providing processability characteristics that are similar, if not identical, to epoxies. This article considers the various approaches that have been shown to offer such dual capabilities. In addition, the results of various studies undertaken to investigate the effects of elevated temperature on the strength and fatigue resistance of bonded joints are reported.