Periodic Bicontinuous Composites for High Specific Energy Absorption

We report on the mechanical behavior of an interpenetrating carbon/epoxy periodic submicrometer-scale bicontinuous composite material fabricated following the design principles deduced from biological composites. Using microscopic uniaxial compressive tests, the specific energy absorption is quantitatively evaluated and compared with the epoxy/air and carbon/air precursors. The carbon/epoxy material demonstrates extremely high specific energy absorption up to 720 kJ/kg and shear-dominant interphase interactions from the interlocked hard (carbon) and soft (epoxy) phases. Such bicontinuous nanocomposites are a new type of structural metamaterial with designed cell topology and mechanical anisotropy. Their inherent small length scale can play a critical role in prohibiting segregated mechanical responses leading to flaw tolerance

Extreme Mechanical Behavior of Nacre-Mimetic Graphene-Oxide and Silk Nanocomposites

Biological materials have the ability to withstand extreme mechanical forces due to their unique multilevel hierarchical structure. Here, we fabricated a nacre-mimetic nanocomposite comprised of silk fibroin and graphene oxide that exhibits hybridized dynamic responses arising from alternating high-contrast mechanical properties of the components at the nanoscale. Dynamic mechanical behavior of these nanocomposites is assessed through a microscale ballistic characterization using a 7.6 μm diameter silica sphere moving at a speed of approximately 400 m/s. The volume fraction of graphene oxide in these composites is systematically varied from 0 to 32 vol % to quantify the dynamic effects correlating with the structural morphologies of the graphene oxide flakes. Specific penetration energy of the films rapidly increases as the distribution of graphene oxide flakes evolves from noninteracting, isolated sheets to a partially overlapping continuous sheet. The specific penetration energy of the nanocomposite at the highest graphene oxide content tested here is found to be significantly higher than that of Kevlar fabrics and close to that of pure multilayer graphene. This study evidently demonstrates that the morphologies of nanoscale constituents and their interactions are critical to realize scalable high-performance nanocomposites using typical nanomaterial constituents having finite dimensions

Three-Dimensional Networked Nanoporous Ta₂O_5–<i>x</i> Memory System for Ultrahigh Density Storage

Oxide-based resistive memory systems have high near-term promise for use in nonvolatile memory. Here we introduce a memory system employing a three-dimensional (3D) networked nanoporous (NP) Ta₂O_5–<i>x</i> structure and graphene for ultrahigh density storage. The devices exhibit a self-embedded highly nonlinear <i>I–V</i> switching behavior with an extremely low leakage current (on the order of pA) and good endurance. Calculations indicated that this memory architecture could be scaled up to a ∼162 Gbit crossbar array without the need for selectors or diodes normally used in crossbar arrays. In addition, we demonstrate that the voltage point for a minimum current is systematically controlled by the applied set voltage, thereby offering a broad range of switching characteristics. The potential switching mechanism is suggested based upon the transformation from Schottky to Ohmic-like contacts, and <i>vice versa</i>, depending on the movement of oxygen vacancies at the interfaces induced by the voltage polarity, and the formation of oxygen ions in the pores by the electric field

Wavelength-Selective Three-Dimensional Thermal Emitters via Imprint Lithography and Conformal Metallization

Metallic photonic crystals (MPCs) exhibit wavelength-selective thermal emission enhancements and are promising thermal optical devices for various applications. Here, we report a scalable fabrication strategy for MPCs suitable for high-temperature applications. Well-defined double-layer titanium dioxide (TiO₂) woodpile structures are fabricated using a layer-by-layer soft-imprint method with TiO₂ nanoparticle ink dispersions, and the structures are subsequently coated with high purity, conformal gold films via reactive deposition from supercritical carbon dioxide. The resulting gold-coated woodpile structures are effective MPCs and exhibit emissivity enhancements at a selective wavelength. Gold coatings deposited using a cold-wall reactor are found to be smoother and result in a greater thermal emission enhancement compared to those deposited using a hot-wall reactor

Nanoporous Silicon Oxide Memory

Oxide-based two-terminal resistive random access memory (RRAM) is considered one of the most promising candidates for next-generation nonvolatile memory. We introduce here a new RRAM memory structure employing a nanoporous (NP) silicon oxide (SiO_<i>x</i>) material which enables unipolar switching through its internal vertical nanogap. Through the control of the stochastic filament formation at low voltage, the NP SiO_<i>x</i> memory exhibited an extremely low electroforming voltage (∼1.6 V) and outstanding performance metrics. These include multibit storage ability (up to 9-bits), a high ON–OFF ratio (up to 10⁷ A), a long high-temperature lifetime (≥10⁴ s at 100 °C), excellent cycling endurance (≥10⁵), sub-50 ns switching speeds, and low power consumption (∼6 × 10^–5 W/bit). Also provided is the room temperature processability for versatile fabrication without any compliance current being needed during electroforming or switching operations. Taken together, these metrics in NP SiO_<i>x</i> RRAM provide a route toward easily accessed nonvolatile memory applications

Structurally Engineered Nanoporous Ta₂O_5–<i>x</i> Selector-Less Memristor for High Uniformity and Low Power Consumption

A memristor architecture based on metal-oxide materials would have great promise in achieving exceptional energy efficiency and higher scalability in next-generation electronic memory systems. Here, we propose a facile method for fabricating selector-less memristor arrays using an engineered nanoporous Ta₂O_5–<i>x</i> architecture. The device was fabricated in the form of crossbar arrays, and it functions as a switchable rectifier with a self-embedded nonlinear switching behavior and ultralow power consumption (∼2.7 × 10^–6 W), which results in effective suppression of crosstalk interference. In addition, we determined that the essential switching elements, such as the programming power, the sneak current, the nonlinearity value, and the device-to-device uniformity, could be enhanced by in-depth structural engineering of the pores in the Ta₂O_5–<i>x</i> layer. Our results, on the basis of the structural engineering of metal-oxide materials, could provide an attractive approach for fabricating simple and cost-efficient memristor arrays with acceptable device uniformity and low power consumption without the need for additional addressing selectors

THE DEVELOPMENT OF THE TECHNOLOGICAL BASES FOR OBTAINING AND PROCESSING OF THE BASE THERMOPLASTIC BUTADIEN-NITRIL ELASTOMERS

The object of investigation: the butadien-nitril rubber, polyvinylchloride, polystirol, polycarbonate, ABC-plastics, polyamide, acetylcellulose, polypropylene. The theoretical justification has been given, the mathematical model of the quality of the base materials, the mathematical model of optimization of the modified thermoplastic elastomers recipe have been developed, the influence of the fillers and plastificators of the different nature on the consumers properties of the base materials has been developed, the method of prognosing of the materials technological properties has been developed. Offered has been the method of the &quot;dynamic&quot; vulcanization, with the aid of which the base materials have been received, and it allows to reduce the time of the vulcanization by 5 times and to reduce the electric power consumption. The recipes of the cast compositions, posessing the improved values of the operating and consumer properties, the modes and the parameters of the processing of the base materials, the multiple use of the obtained alloys have been offered. The base polymer materials of the new type for casting under pressure have been introduced in practiceAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Carbon Nanotube Core Graphitic Shell Hybrid Fibers

A carbon nanotube yarn core graphitic shell hybrid fiber was fabricated <i>via</i> facile heat treatment of epoxy-based negative photoresist (SU-8) on carbon nanotube yarn. The effective encapsulation of carbon nanotube yarn in carbon fiber and a glassy carbon outer shell determines their physical properties. The higher electrical conductivity (than carbon fiber) of the carbon nanotube yarn overcomes the drawbacks of carbon fiber/glassy carbon, and the better properties (than carbon nanotubes) of the carbon fiber/glassy carbon make up for the lower thermal and mechanical properties of the carbon nanotube yarn <i>via</i> synergistic hybridization without any chemical doping and additional processes