Synthesis of nanowires and nanoparticles of cubic aluminium nitride

NASA Astrophysics Data System (ADS)

Balasubramanian, C.; Godbole, V. P.; Rohatgi, V. K.; Das, A. K.; Bhoraskar, S. V.

2004-03-01

Nanostructures of cubic aluminium nitride were synthesized by DC arc-plasma-induced melting of aluminium in a nitrogen-argon ambient. The material flux ejected from the molten aluminium surface was found to react with nitrogen under highly non-equilibrium conditions and subsequently condense on a water-cooled surface to yield a mixture of nanowires and nanoparticles of crystalline cubic aluminium nitride. Both x-ray diffraction and electron diffraction measurements revealed that the as-synthesized nitrides adopted the cubic phase. Fourier transform infrared spectroscopy was used to understand the bonding configuration. Microstructural features of the synthesized material were best studied by transmission electron microscopy. From these analyses cubic aluminium nitride was found to be the dominating phase for both nanowires and nanoparticles synthesized at low currents. The typical particle size distribution was found to range over 15-80 nm, whereas the wires varied from 30 to 100 nm in diameter and 500 to 700 nm in length, depending upon the process parameters such as arc current and the nitrogen pressure. The reaction products inside the plasma zone were also obtained theoretically by minimization of free energy and the favourable zone temperature necessary for the formation of aluminium nitride was found to be {\\sim } 6000 K. Results are discussed in view of the highly non-equilibrium conditions that prevail during the arc-plasma synthesis.

METHOD OF COATING GRAPHITE WITH STABLE METAL CARBIDES AND NITRIDES

DOEpatents

Gurinsky, D.H.

1959-10-27

A method is presented for forming protective stable nitride and carbide compounds on the surface of graphite. This is accomplished by contacting the graphite surface with a fused heavy liquid metal such as bismuth or leadbismuth containing zirconium, titanium, and hafnium dissolved or finely dispersed therein to form a carbide and nitride of at least one of the dissolved metals on the graphite surface.

Back scattering involving embedded silicon nitride (SiN) nanoparticles for c-Si solar cells

NASA Astrophysics Data System (ADS)

Ghosh, Hemanta; Mitra, Suchismita; Siddiqui, M. S.; Saxena, A. K.; Chaudhuri, Partha; Saha, Hiranmay; Banerjee, Chandan

2018-04-01

A novel material, structure and method of synthesis for dielectric light trapping have been presented in this paper. First, the light scattering behaviour of silicon nitride nanoparticles have been theoretically studied in order to find the optimized size for dielectric back scattering by FDTD simulations from Lumerical Inc. The optical results have been used in electrical analysis and thereby, estimate the effect of nanoparticles on efficiency of the solar cells depending on substrate thickness. Experimentally, silicon nitride (SiN) nanoparticles have been formed using hydrogen plasma treatment on SiN layer deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD). The size and area coverage of the nanoparticles were controlled by varying the working pressure, power density and treatment duration. The nanoparticles were integrated with partial rear contact c-Si solar cells as dielectric back reflector structures for the light trapping in thin silicon solar cells. Experimental results revealed the increases of current density by 2.7% in presence of SiN nanoparticles.

Preparation of Boron Nitride Nanoparticles with Oxygen Doping and a Study of Their Room-Temperature Ferromagnetism.

PubMed

Lu, Qing; Zhao, Qi; Yang, Tianye; Zhai, Chengbo; Wang, Dongxue; Zhang, Mingzhe

2018-04-18

In this work, oxygen-doped boron nitride nanoparticles with room-temperature ferromagnetism have been synthesized by a new, facile, and efficient method. There are no metal magnetic impurities in the nanoparticles analyzed by X-ray photoelectron spectroscopy. The boron nitride nanoparticles exhibit a parabolic shape with increase in the reaction time. The saturation magnetization value reaches a maximum of 0.2975 emu g -1 at 300 K when the reaction time is 12 h, indicating that the Curie temperature ( T C ) is higher than 300 K. Combined with first-principles calculation, the coupling between B 2p orbital, N 2p orbital, and O 2p orbital in the conduction bands is the main origin of room-temperature ferromagnetism and also proves that the magnetic moment changes according the oxygen-doping content change. Compared with other room temperature ferromagnetic semiconductors, boron nitride nanoparticles have widely potential applications in spintronic devices because of high temperature oxidation resistance and excellent chemical stability.

Atomic Layer Deposition of HfO2 and Si Nitride on Ge Substrates

NASA Astrophysics Data System (ADS)

Zhu, Shiyang; Nakajima, Anri

2007-12-01

Hafnium oxide (HfO2) thin films were deposited on Ge substrates at 300 °C using atomic layer deposition (ALD) with tetrakis(diethylamino)hafnium (termed as TDEAH) as a precursor and water as an oxidant. The deposition rate was estimated to be 0.09 nm/cycle and the deposited HfO2 films have a smooth surface and an almost stoichiometric composition, indicating that the growth follows a layer-by-layer kinetics, similarly to that on Si substrates. Si nitride thin films were also deposited on Ge by ALD using SiCl4 as a precursor and NH3 as an oxidant. Si nitride has a smaller deposition rate of about 0.055 nm/cycle and a larger gate leakage current than HfO2 deposited on Ge by ALD.

Highly nonlinear sub-micron silicon nitride trench waveguide coated with gold nanoparticles

NASA Astrophysics Data System (ADS)

Huang, Yuewang; Zhao, Qiancheng; Sharac, Nicholas; Ragan, Regina; Boyraz, Ozdal

2015-05-01

We demonstrate the fabrication of a highly nonlinear sub-micron silicon nitride trench waveguide coated with gold nanoparticles for plasmonic enhancement. The average enhancement effect is evaluated by measuring the spectral broadening effect caused by self-phase-modulation. The nonlinear refractive index n2 was measured to be 7.0917×10-19 m2/W for a waveguide whose Wopen is 5 μm. Several waveguides at different locations on one wafer were measured in order to take the randomness of the nanoparticle distribution into consideration. The largest enhancement is measured to be as high as 10 times. Fabrication of this waveguide started with a MEMS grade photomask. By using conventional optical lithography, the wide linewidth was transferred to a <100> wafer. Then the wafer was etched anisotropically by potassium hydroxide (KOH) to engrave trapezoidal trenches with an angle of 54.7º. Side wall roughness was mitigated by KOH etching and thermal oxidation that was used to generate a buffer layer for silicon nitride waveguide. The guiding material silicon nitride was then deposited by low pressure chemical vapor deposition. The waveguide was then patterned with a chemical template, with 20 nm gold particles being chemically attached to the functionalized poly(methyl methacrylate) domains. Since the particles attached only to the PMMA domains, they were confined to localized regions, therefore forcing the nanoparticles into clusters of various numbers and geometries. Experiments reveal that the waveguide has negligible nonlinear absorption loss, and its nonlinear refractive index can be greatly enhanced by gold nano clusters. The silicon nitride trench waveguide has large nonlinear refractive index, rendering itself promising for nonlinear applications.

Slow DNA Transport through Nanopores in Hafnium Oxide Membranes

PubMed Central

Bell, David C.; Cohen-Karni, Tzahi; Rosenstein, Jacob K.; Wanunu, Meni

2016-01-01

We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2–7 nm thick) free-standing hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore. PMID:24083444

Expression of genes encoding IGFBPs, SNARK, CD36, and PECAM1 in the liver of mice treated with chromium disilicide and titanium nitride nanoparticles.

PubMed

Minchenko, Dmytro O; Tsymbal, D O; Yavorovsky, O P; Solokha, N V; Minchenko, O H

2017-04-25

The aim of the present study was to examine the effect of chromium disilicide and titanium nitride nanoparticles on the expression level of genes encoding important regulatory factors (IGFBP1, IGFBP2, IGFBP3, IGFBP4, IGFBP5, SNARK/NUAK2, CD36, and PECAM1/CD31) in mouse liver for evaluation of possible toxic effects of these nanoparticles. Male mice received 20 mg chromium disilicide nanoparticles (45 nm) and titanium nitride nanoparticles (20 nm) with food every working day for 2 months. The expression of IGFBP1, IGFBP2, IGFBP3, IGFBP4, IGFBP5, SNARK, CD36, and PECAM1 genes in mouse liver was studied by quantitative polymerase chain reaction. Treatment of mice with chromium disilicide nanoparticles led to down-regulation of the expression of IGFBP2, IGFBP5, PECAM1, and SNARK genes in the liver in comparison with control mice, with more prominent changes for SNARK gene. At the same time, the expression of IGFBP3 and CD36 genes was increased in mouse liver upon treatment with chromium disilicide nanoparticles. We have also shown that treatment with titanium nitride nanoparticles resulted in down-regulation of the expression of IGFBP2 and SNARK genes in the liver with more prominent changes for SNARK gene. At the same time, the expression of IGFBP3, IGFBP4, and CD36 genes was increased in the liver of mice treated with titanium nitride nanoparticles. Furthermore, the effect of chromium disilicide nanoparticles on IGFBP2 and CD36 genes expression was significantly stronger as compared to titanium nitride nanoparticles. The results of this study demonstrate that chromium disilicide and titanium nitride nanoparticles have variable effects on the expression of IGFBP2, IGFBP3, IGFBP4, IGFBP5, SNARK, CD36, and PECAM1 genes in mouse liver, which may reflect the genotoxic activities of the studied nanoparticles.

Platinum nanoparticles on gallium nitride surfaces: effect of semiconductor doping on nanoparticle reactivity.

PubMed

Schäfer, Susanne; Wyrzgol, Sonja A; Caterino, Roberta; Jentys, Andreas; Schoell, Sebastian J; Hävecker, Michael; Knop-Gericke, Axel; Lercher, Johannes A; Sharp, Ian D; Stutzmann, Martin

2012-08-01

Platinum nanoparticles supported on n- and p-type gallium nitride (GaN) are investigated as novel hybrid systems for the electronic control of catalytic activity via electronic interactions with the semiconductor support. In situ oxidation and reduction were studied with high pressure photoemission spectroscopy. The experiments revealed that the underlying wide-band-gap semiconductor has a large influence on the chemical composition and oxygen affinity of supported nanoparticles under X-ray irradiation. For as-deposited Pt cuboctahedra supported on n-type GaN, a higher fraction of oxidized surface atoms was observed compared to cuboctahedral particles supported on p-type GaN. Under an oxygen atmosphere, immediate oxidation was recorded for nanoparticles on n-type GaN, whereas little oxidation was observed for nanoparticles on p-type GaN. Together, these results indicate that changes in the Pt chemical state under X-ray irradiation depend on the type of GaN doping. The strong interaction between the nanoparticles and the support is consistent with charge transfer of X-ray photogenerated free carriers at the semiconductor-nanoparticle interface and suggests that GaN is a promising wide-band-gap support material for photocatalysis and electronic control of catalysis.

Hafnium radioisotope recovery from irradiated tantalum

DOEpatents

Taylor, Wayne A.; Jamriska, David J.

2001-01-01

Hafnium is recovered from irradiated tantalum by: (a) contacting the irradiated tantalum with at least one acid to obtain a solution of dissolved tantalum; (b) combining an aqueous solution of a calcium compound with the solution of dissolved tantalum to obtain a third combined solution; (c) precipitating hafnium, lanthanide, and insoluble calcium complexes from the third combined solution to obtain a first precipitate; (d) contacting the first precipitate of hafnium, lanthanide and calcium complexes with at least one fluoride ion complexing agent to form a fourth solution; (e) selectively adsorbing lanthanides and calcium from the fourth solution by cationic exchange; (f) separating fluoride ion complexing agent product from hafnium in the fourth solution by adding an aqueous solution of ferric chloride to obtain a second precipitate containing the hafnium and iron; (g) dissolving the second precipitate containing the hafnium and iron in acid to obtain an acid solution of hafnium and iron; (h) selectively adsorbing the iron from the acid solution of hafnium and iron by anionic exchange; (i) drying the ion exchanged hafnium solution to obtain hafnium isotopes. Additionally, if needed to remove residue remaining after the product is dried, dissolution in acid followed by cation exchange, then anion exchange, is performed.

Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts

DOE PAGES

Garg, Aaron; Milina, Maria; Ball, Madelyn; ...

2017-05-25

Core–shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. In conclusion, the ability to control shell coveragemore » and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.« less

Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garg, Aaron; Milina, Maria; Ball, Madelyn

Core–shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. In conclusion, the ability to control shell coveragemore » and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.« less

Platinum Nanoparticle Loading of Boron Nitride Aerogel and Its Use as a Novel Material for Low-Power Catalytic Gas Sensing

DOE PAGES

Harley-Trochimczyk, Anna; Pham, Thang; Chang, Jiyoung; ...

2015-12-09

We report that a high-surface-area, highly crystalline boron nitride aerogel synthesized with nonhazardous reactants has been loaded with crystalline platinum nanoparticles to form a novel nanomaterial that exhibits many advantages for use in a catalytic gas sensing application. The platinum nanoparticle-loaded boron nitride aerogel integrated onto a microheater platform allows for calorimetric propane detection. The boron nitride aerogel exhibits thermal stability up to 900 °C and supports disperse platinum nanoparticles, with no sintering observed after 24 h of high-temperature testing. The high thermal conductivity and low density of the boron nitride aerogel result in an order of magnitude faster responsemore » and recovery times (<2 s) than reported on alumina support and allow for 10% duty cycling of the microheater with no loss in sensitivity. Lastly, the resulting 1.5 mW sensor power consumption is two orders of magnitude less than commercially available catalytic gas sensors and unlocks the potential for wireless, battery-powered catalytic gas sensing.« less

High-Performance Core–Shell Catalyst with Nitride Nanoparticles as a Core: Well-Defined Titanium Copper Nitride Coated with an Atomic Pt Layer for the Oxygen Reduction Reaction

DOE PAGES

Tian, Xinlong; Tang, Haibo; Luo, Junming; ...

2017-04-25

A class of core–shell structured low-platinum catalysts with well-dispersed inexpensive titanium copper nitride nanoparticles as cores and atomic platinum layers as shells exhibiting high activity and stability for the oxygen reduction reaction is successfully developed. In using nitrided carbon nanotubes (NCNTs) as the support greatly improved the morphology and dispersion of the nitride nanoparticles, resulting in significant enhancement of the performance of the catalyst. The optimized catalyst, Ti 0.9Cu 0.1N@Pt/NCNTs, has a Pt mass activity 5 times higher than that of commercial Pt/C, comparable to that of core–shell catalysts with precious metal nanoparticles as the core, and much higher thanmore » that the latter if we take into account the mass activity of all platinum group metals. Furthermore, only a minimal loss of activity can be observed after 10000 potential cycles, demonstrating the catalyst’s high stability. After durability testing, atomic-scale elemental mapping confirmed that the core–shell structure of the catalyst remained intact. This approach may open a pathway for the design and preparation of high-performance inexpensive core–shell catalysts for a wide range of applications in energy conversion processes.« less

High-Performance Core–Shell Catalyst with Nitride Nanoparticles as a Core: Well-Defined Titanium Copper Nitride Coated with an Atomic Pt Layer for the Oxygen Reduction Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Xinlong; Tang, Haibo; Luo, Junming

A class of core–shell structured low-platinum catalysts with well-dispersed inexpensive titanium copper nitride nanoparticles as cores and atomic platinum layers as shells exhibiting high activity and stability for the oxygen reduction reaction is successfully developed. In using nitrided carbon nanotubes (NCNTs) as the support greatly improved the morphology and dispersion of the nitride nanoparticles, resulting in significant enhancement of the performance of the catalyst. The optimized catalyst, Ti 0.9Cu 0.1N@Pt/NCNTs, has a Pt mass activity 5 times higher than that of commercial Pt/C, comparable to that of core–shell catalysts with precious metal nanoparticles as the core, and much higher thanmore » that the latter if we take into account the mass activity of all platinum group metals. Furthermore, only a minimal loss of activity can be observed after 10000 potential cycles, demonstrating the catalyst’s high stability. After durability testing, atomic-scale elemental mapping confirmed that the core–shell structure of the catalyst remained intact. This approach may open a pathway for the design and preparation of high-performance inexpensive core–shell catalysts for a wide range of applications in energy conversion processes.« less

Ablation Resistant Zirconium and Hafnium Ceramics

NASA Technical Reports Server (NTRS)

Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

1998-01-01

High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

Hafnium isotope stratigraphy of ferromanganese crusts

PubMed

Lee; Halliday; Hein; Burton; Christensen; Gunther

1999-08-13

A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in (87)Sr/(86)Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.

SEPARATION OF HAFNIUM FROM ZIRCONIUM

DOEpatents

Overholser, L.B.; Barton, C.J. Sr.; Ramsey, J.W.

1960-05-31

The separation of hafnium impurities from zirconium can be accomplished by means of organic solvent extraction. The hafnium-containing zirconium feed material is dissolved in an aqueous chloride solution and the resulting solution is contacted with an organic hexone phase, with at least one of the phases containing thiocyanate. The hafnium is extracted into the organic phase while zirconium remains in the aqueous phase. Further recovery of zirconium is effected by stripping the onganic phase with a hydrochloric acid solution and commingling the resulting strip solution with the aqueous feed solution. Hexone is recovered and recycled by means of scrubbing the onganic phase with a sulfuric acid solution to remove the hafnium, and thiocyanate is recovered and recycled by means of neutralizing the effluent streams to obtain ammonium thiocyanate.

Zirconium and hafnium

USGS Publications Warehouse

Jones, James V.; Piatak, Nadine M.; Bedinger, George M.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

Zirconium and hafnium are corrosion-resistant metals that are widely used in the chemical and nuclear industries. Most zirconium is consumed in the form of the main ore mineral zircon (ZrSiO4, or as zirconium oxide or other zirconium chemicals. Zirconium and hafnium are both refractory lithophile elements that have nearly identical charge, ionic radii, and ionic potentials. As a result, their geochemical behavior is generally similar. Both elements are classified as incompatible because they have physical and crystallochemical properties that exclude them from the crystal lattices of most rock-forming minerals. Zircon and another, less common, ore mineral, baddeleyite (ZrO2), form primarily as accessory minerals in igneous rocks. The presence and abundance of these ore minerals in igneous rocks are largely controlled by the element concentrations in the magma source and by the processes of melt generation and evolution. The world’s largest primary deposits of zirconium and hafnium are associated with alkaline igneous rocks, and, in one locality on the Kola Peninsula of Murmanskaya Oblast, Russia, baddeleyite is recovered as a byproduct of apatite and magnetite mining. Otherwise, there are few primary igneous deposits of zirconium- and hafnium-bearing minerals with economic value at present. The main ore deposits worldwide are heavy-mineral sands produced by the weathering and erosion of preexisting rocks and the concentration of zircon and other economically important heavy minerals, such as ilmenite and rutile (for titanium), chromite (for chromium), and monazite (for rare-earth elements) in sedimentary systems, particularly in coastal environments. In coastal deposits, heavy-mineral enrichment occurs where sediment is repeatedly reworked by wind, waves, currents, and tidal processes. The resulting heavy-mineral-sand deposits, called placers or paleoplacers, preferentially form at relatively low latitudes on passive continental margins and supply 100 percent of

Hafnium Oxide Film Etching Using Hydrogen Chloride Gas

NASA Astrophysics Data System (ADS)

Habuka, Hitoshi; Yamaji, Masahiko; Kobori, Yoshitsugu; Horii, Sadayoshi; Kunii, Yasuo

2009-12-01

Hydrogen chloride gas removes the hafnium oxide film formed by atomic layer deposition at the etch rate of about 1 nm/min. A 100 nm-thick hafnium oxide film was perfectly etched off at 1173 K for 60 min by 100% hydrogen chloride gas at 100 sccm. A weight decrease in the hafnium oxide film was observed at temperatures higher than ca. 600 K, which corresponds to the sublimation point of hafnium tetrachloride. The etching by-product is considered to be hafnium tetrachloride. The etching technique developed in this study is expected to be applicable to various processes, such as the cleaning of a hafnium oxide film deposition reactor.

Nanocomposites based on hierarchical porous carbon fiber@vanadium nitride nanoparticles as supercapacitor electrodes.

PubMed

Ran, Fen; Wu, Yage; Jiang, Minghuan; Tan, Yongtao; Liu, Ying; Kong, Lingbin; Kang, Long; Chen, Shaowei

2018-03-28

In this study, a hybrid electrode material for supercapacitors based on hierarchical porous carbon fiber@vanadium nitride nanoparticles is fabricated using the method of phase-separation mediated by the PAA-b-PAN-b-PAA tri-block copolymer. In the phase-separation procedure, the ionic block copolymer self-assembled on the surface of carbon nanofibers, and is used to adsorb NH 4 VO 3 . Thermal treatment at controlled temperatures under an NH 3  : N 2 atmosphere led to the formation of vanadium nitride nanoparticles that are distributed uniformly on the nanofiber surface. By changing the PAN to PAA-b-PAN-b-PAA ratio in the casting solution, a maximum specific capacitance of 240.5 F g -1 is achieved at the current density of 0.5 A g -1 with good rate capability at a capacitance retention of 72.1% at 5.0 A g -1 in an aqueous electrolyte of 6 mol L -1 KOH within the potential range of -1.10 to 0 V (rN/A = 1.5/1.0). Moreover, an asymmetric supercapacitor is assembled by using the hierarchical porous carbon fiber@vanadium nitride as the negative electrode and Ni(OH) 2 as the positive electrode. Remarkably, at the power density of 400 W kg -1 , the supercapacitor device delivers a better energy density of 39.3 W h kg -1 . It also shows excellent electrochemical stability, and thus might be used as a promising energy-storage device.

Hafnium Films and Magnetic Shielding for TIME, A mm-Wavelength Spectrometer Array

NASA Astrophysics Data System (ADS)

Hunacek, J.; Bock, J.; Bradford, C. M.; Butler, V.; Chang, T.-C.; Cheng, Y.-T.; Cooray, A.; Crites, A.; Frez, C.; Hailey-Dunsheath, S.; Hoscheit, B.; Kim, D. W.; Li, C.-T.; Marrone, D.; Moncelsi, L.; Shirokoff, E.; Steinbach, B.; Sun, G.; Trumper, I.; Turner, A.; Uzgil, B.; Weber, A.; Zemcov, M.

2018-04-01

TIME is a mm-wavelength grating spectrometer array that will map fluctuations of the 157.7-μm emission line of singly ionized carbon ([CII]) during the epoch of reionization (redshift z ˜ 5-9). Sixty transition-edge sensor (TES) bolometers populate the output arc of each of the 32 spectrometers, for a total of 1920 detectors. Each bolometer consists of gold absorber on a ˜ 3 × 3 mm silicon nitride micro-mesh suspended near the corners by 1 × 1 × 500 μm silicon nitride legs targeting a photon-noise-dominated NEP ˜ 1 × 10^{-17} W/√{Hz} . Hafnium films are explored as a lower-T_c alternative to Ti (500 mK) for TIME TESs, allowing thicker support legs for improved yield. Hf T_c is shown to vary between 250 and 450 mK when varying the resident Ar pressure during deposition. Magnetic shielding designs and simulations are presented for the TIME first-stage SQUIDs. Total axial field suppression is predicted to be 5 × 10^7.

Dispersion engineering of thick high-Q silicon nitride ring-resonators via atomic layer deposition.

PubMed

Riemensberger, Johann; Hartinger, Klaus; Herr, Tobias; Brasch, Victor; Holzwarth, Ronald; Kippenberg, Tobias J

2012-12-03

We demonstrate dispersion engineering of integrated silicon nitride based ring resonators through conformal coating with hafnium dioxide deposited on top of the structures via atomic layer deposition. Both, magnitude and bandwidth of anomalous dispersion can be significantly increased. The results are confirmed by high resolution frequency-comb-assisted-diode-laser spectroscopy and are in very good agreement with the simulated modification of the mode spectrum.

SEPARATING HAFNIUM FROM ZIRCONIUM

DOEpatents

Lister, B.A.J.; Duncan, J.F.

1956-08-21

A dilute aqueous solution of zirconyl chloride which is 1N to 2N in HCl is passed through a column of a cation exchange resin in acid form thereby absorbing both zirconium and associated hafnium impurity in the mesin. The cation exchange material with the absorbate is then eluted with aqueous sulfuric acid of a O.8N to 1.2N strength. The first portion of the eluate contains the zirconium substantially free of hafnium.

Free-Standing Self-Assemblies of Gallium Nitride Nanoparticles: A Review

DOE PAGES

Lan, Yucheng; Li, Jianye; Wong-Ng, Winnie; ...

2016-08-23

Gallium nitride (GaN) is an III-V semiconductor with a direct band-gap of 3.4eV . GaN has important potentials in white light-emitting diodes, blue lasers, and field effect transistors because of its super thermal stability and excellent optical properties, playing main roles in future lighting to reduce energy cost and sensors to resist radiations. GaN nanomaterials inherit bulk properties of the compound while possess novel photoelectric properties of nanomaterials. The review focuses on self-assemblies of GaN nanoparticles without templates, growth mechanisms of self-assemblies, and potential applications of the assembled nanostructures on renewable energy.

Taming interfacial electronic properties of platinum nanoparticles on vacancy-abundant boron nitride nanosheets for enhanced catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Wenshuai; Wu, Zili; Foo, Guo Shiou

Taming interfacial electronic effects on Pt nanoparticles modulated by their concomitants has emerged as an intriguing approach to optimize Pt catalytic performance. Here, we report Pt nanoparticles assembled on vacancy-abundant hexagonal boron nitride nanosheets and their use as a model catalyst to embrace an interfacial electronic effect on Pt induced by the nanosheets with N-vacancies and B-vacancies for superior CO oxidation catalysis. Experimental results indicate that strong interaction exists between Pt and the vacancies. Bader charge analysis shows that with Pt on B-vacancies, the nanosheets serve as a Lewis acid to accept electrons from Pt, and on the contrary, whenmore » Pt sits on N-vacancies, the nanosheets act as a Lewis base for donating electrons to Pt. The overall-electronic effect demonstrates an electron-rich feature of Pt after assembling on hexagonal boron nitride nanosheets. Such an interfacial electronic effect makes Pt favour the adsorption of O 2, alleviating CO poisoning and promoting the catalysis.« less

Taming interfacial electronic properties of platinum nanoparticles on vacancy-abundant boron nitride nanosheets for enhanced catalysis

DOE PAGES

Zhu, Wenshuai; Wu, Zili; Foo, Guo Shiou; ...

2017-06-09

Taming interfacial electronic effects on Pt nanoparticles modulated by their concomitants has emerged as an intriguing approach to optimize Pt catalytic performance. Here, we report Pt nanoparticles assembled on vacancy-abundant hexagonal boron nitride nanosheets and their use as a model catalyst to embrace an interfacial electronic effect on Pt induced by the nanosheets with N-vacancies and B-vacancies for superior CO oxidation catalysis. Experimental results indicate that strong interaction exists between Pt and the vacancies. Bader charge analysis shows that with Pt on B-vacancies, the nanosheets serve as a Lewis acid to accept electrons from Pt, and on the contrary, whenmore » Pt sits on N-vacancies, the nanosheets act as a Lewis base for donating electrons to Pt. The overall-electronic effect demonstrates an electron-rich feature of Pt after assembling on hexagonal boron nitride nanosheets. Such an interfacial electronic effect makes Pt favour the adsorption of O 2, alleviating CO poisoning and promoting the catalysis.« less

Effect of nitrogen on tensile properties and structures of T-111 (tantalum, 8 percent tungsten, 2 percent hafnium) tubing

NASA Technical Reports Server (NTRS)

Buzzard, R. J.; Metroka, R. R.

1973-01-01

The effect of controlled nitrogen additions was evaluated on the mechanical properties of T-111 (Ta-8W-2Hf) fuel pin cladding material proposed for use in a lithium-cooled nuclear reactor concept. Additions of 80 to 1125 ppm nitrogen resulted in increased strengthening of T-111 tubular section test specimens at temperatures of 25 to 1200 C. Homogeneous distributions of up to 500 ppm nitrogen did not seriously decrease tensile ductility. Both single and two-phase microstructures, with hafnium nitride as the second phase, were evaluated in this study.

Formulation and method for preparing gels comprising hydrous hafnium oxide

DOEpatents

Collins, Jack L; Hunt, Rodney D; Montgomery, Frederick C

2013-08-06

Formulations useful for preparing hydrous hafnium oxide gels contain a metal salt including hafnium, an acid, an organic base, and a complexing agent. Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including hafnium, an acid, an organic base, and a complexing agent.

A phototactic micromotor based on platinum nanoparticle decorated carbon nitride.

PubMed

Ye, Zhenrong; Sun, Yunyu; Zhang, Hui; Song, Bo; Dong, Bin

2017-11-30

In this paper, we report a unique phototactic (both positive and negative) micromotor based on platinum nanoparticle decorated carbon nitride. The phototaxis relies on the self-diffusiophoretic mechanism and different surface modifications. The micromotor reported in the current study does not require the addition of any external fuels and shows versatile motion behaviour, i.e. start, stop, directional and programmable motion, which is controlled by light. In addition, since the actuation of the precipitated micromotors at the bottom of a solution using light results in the opacity changes from transparent to translucent, we anticipate that the current micromotor may have potential application in the field of smart windows.

Boron nitride encapsulated copper nanoparticles: a facile one-step synthesis and their effect on thermal decomposition of ammonium perchlorate.

PubMed

Huang, Caijin; Liu, Qiuwen; Fan, Wenjie; Qiu, Xiaoqing

2015-11-16

Reactivity is of great importance for metal nanoparticles used as catalysts, biomaterials and advanced sensors, but seeking for high reactivity seems to be conflict with high chemical stability required for metal nanoparticles. There is a subtle balance between reactivity and stability. This could be reached for colloidal metal nanoparticles using organic capping reagents, whereas it is challenging for powder metal nanoparticles. Here, we developed an alternative approach to encapsulate copper nanoparticles with a chemical inertness material--hexagonal boron nitride. The wrapped copper nanoparticles not only exhibit high oxidation resistance under air atmosphere, but also keep excellent promoting effect on thermal decomposition of ammonium perchlorate. This approach opens the way to design metal nanoparticles with both high stability and reactivity for nanocatalysts and their technological application.

Boron nitride encapsulated copper nanoparticles: a facile one-step synthesis and their effect on thermal decomposition of ammonium perchlorate

PubMed Central

Huang, Caijin; liu, Qiuwen; Fan, Wenjie; Qiu, Xiaoqing

2015-01-01

Reactivity is of great importance for metal nanoparticles used as catalysts, biomaterials and advanced sensors, but seeking for high reactivity seems to be conflict with high chemical stability required for metal nanoparticles. There is a subtle balance between reactivity and stability. This could be reached for colloidal metal nanoparticles using organic capping reagents, whereas it is challenging for powder metal nanoparticles. Here, we developed an alternative approach to encapsulate copper nanoparticles with a chemical inertness material—hexagonal boron nitride. The wrapped copper nanoparticles not only exhibit high oxidation resistance under air atmosphere, but also keep excellent promoting effect on thermal decomposition of ammonium perchlorate. This approach opens the way to design metal nanoparticles with both high stability and reactivity for nanocatalysts and their technological application. PMID:26567862

Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

NASA Technical Reports Server (NTRS)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2009-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Methods of repairing a substrate

NASA Technical Reports Server (NTRS)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2011-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium boride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Hafnium-Based Contrast Agents for X-ray Computed Tomography.

PubMed

Berger, Markus; Bauser, Marcus; Frenzel, Thomas; Hilger, Christoph Stephan; Jost, Gregor; Lauria, Silvia; Morgenstern, Bernd; Neis, Christian; Pietsch, Hubertus; Sülzle, Detlev; Hegetschweiler, Kaspar

2017-05-15

Heavy-metal-based contrast agents (CAs) offer enhanced X-ray absorption for X-ray computed tomography (CT) compared to the currently used iodinated CAs. We report the discovery of new lanthanide and hafnium azainositol complexes and their optimization with respect to high water solubility and stability. Our efforts culminated in the synthesis of BAY-576, an uncharged hafnium complex with 3:2 stoichiometry and broken complex symmetry. The superior properties of this asymmetrically substituted hafnium CA were demonstrated by a CT angiography study in rabbits that revealed excellent signal contrast enhancement.

40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... zirconium-hafnium forming subcategory. 471.90 Section 471.90 Protection of Environment ENVIRONMENTAL... POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This subpart applies to discharges of pollutants to waters of the...

Strong light extraction enhancement using TiO2 nanoparticles-based microcone arrays embossed on III-Nitride light emitting diodes

NASA Astrophysics Data System (ADS)

Désières, Yohan; Chen, Ding Yuan; Visser, Dennis; Schippers, Casper; Anand, Srinivasan

2018-06-01

Colloidal TiO2 nanoparticles were used for embossing of composite microcone arrays on III-Nitride vertical-thin-film blue light emitting diodes (LEDs) as well as on silicon, glass, gallium arsenide, and gallium nitride surfaces. Ray tracing simulations were performed to optimize the design of microcones for light extraction and to explain the experimental results. An optical power enhancement of ˜2.08 was measured on III-Nitride blue LEDs embossed with a hexagonal array of TiO2 microcones of ˜1.35 μm in height and ˜2.6 μm in base width, without epoxy encapsulation. A voltage increase in ˜70 mV at an operating current density of ˜35 A/cm2 was measured for the embossed LEDs. The TiO2 microcone arrays were embossed on functioning LEDs, using low pressures (˜100 g/cm2) and temperatures ≤100 °C.

Graphitic carbon nitride nanosheet@metal-organic framework core-shell nanoparticles for photo-chemo combination therapy

NASA Astrophysics Data System (ADS)

Chen, Rui; Zhang, Jinfeng; Wang, Yu; Chen, Xianfeng; Zapien, J. Antonio; Lee, Chun-Sing

2015-10-01

Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX and the PDT effect of g-C3N4 nanosheets can lead to considerably enhanced efficacy. Furthermore, the red fluorescence of DOX and the blue fluorescence of g-C3N4 nanosheets provide the additional function of dual-color imaging for monitoring the drug release process.Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX

40 CFR 421.330 - Applicability: Description of the primary zirconium and hafnium subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... primary zirconium and hafnium subcategory. 421.330 Section 421.330 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Zirconium and Hafnium Subcategory § 421.330 Applicability: Description of the primary zirconium and hafnium subcategory. The provisions of this subpart are applicable to discharges resulting...

Hafnium silicate and hafnium silicon oxynitride gate dielectrics for strained Si_xGe_1-x: Interface stability

NASA Astrophysics Data System (ADS)

Addepalli, Swarna; Sivasubramani, Prasanna; El-Bouanani, Mohamed; Kim, Moon; Gnade, Bruce; Wallace, Robert

2003-03-01

Strained Si_xGe_1-x layers have gained considerable attention due to hole mobility enhancement, and ease of integration with Si-based CMOS technology. The deposition of stable high-κ dielectrics [1] such as hafnium silicate and hafnium silicon oxynitride in direct contact with SiGe would simultaneously improve the capacitance of the gate stack and lower the leakage current for high performance SiGe devices. However, the oxidation of the Si_xGe_1-x substrate either during dielectric deposition or post-deposition processing would degrade device performance due to the thermodynamic instability of germanium oxide [2,3]. Results from XPS, HR-TEM, and C-V, and I-V analyses after various annealing treatments will be presented for hafnium silicate and hafnium silicon oxynitride films deposited on strained Si_xGe_1-x(100), and correlated with dielectric-Si_xGe_1-x(100) interface stability. Implications to the introduction of these oxides as viable gate dielectric candidates for SiGe-based CMOS technology will be discussed. This work is supported by DARPA through SPAWAR Grant No. N66001-00-1-8928, and the Texas Advanced Technology Program. References: [1] G. D. Wilk, R. M. Wallace and J. M. Anthony, Journal of Applied Physics, 89, 5243 (2001) [2] W. S. Liu, J .S. Chen, M.-A. Nicolet, V. Arbet-Engels, K. L. Wang, Journal of Applied Physics, 72, 4444 (1992), and, Applied Physics Letters, 62, 3321 (1993) [3] W. S. Liu, M. -A. Nicolet, H. -H. Park, B. -H. Koak, J. -W. Lee, Journal of Applied Physics, 78, 2631 (1995)

Nanopillar arrays of amorphous carbon nitride

NASA Astrophysics Data System (ADS)

Sai Krishna, Katla; Pavan Kumar, B. V. V. S.; Eswaramoorthy, Muthusamy

2011-07-01

Nanopillar arrays of amorphous carbon nitride have been prepared using anodic aluminum oxide (AAO) membrane as a template. The amine groups present on the surface of these nanopillars were exploited for functionalization with oleic acid in order to stabilize the nanostructure at the aqueous-organic interface and also for the immobilization of metal nanoparticles and protein. These immobilised nanoparticles were found to have good catalytic activity.

Concise N-doped Carbon Nanosheets/Vanadium Nitride Nanoparticles Materials via Intercalative Polymerization for Supercapacitors.

PubMed

Tan, Yongtao; Liu, Ying; Tang, Zhenghua; Wang, Zhe; Kong, Lingbin; Kang, Long; Liu, Zhen; Ran, Fen

2018-02-13

N-doped carbon nanosheets/vanadium nitride nanoparticles (N-CNS/VNNPs) are synthesized via a novel method combining surface-initiated in-situ intercalative polymerization and thermal-treatment process in NH 3 /N 2 atmosphere. The pH value of the synthesis system plays a critical role in constructing the structure and enhancing electrochemical performance for N-CNS/VNNPs, which are characterized by SEM, TEM, XRD, and XPS, and measured by electrochemical station, respectively. The results show that N-CNS/VNNPs materials consist of 2D N-doped carbon nanosheets and 0D VN nanoparticles. With the pH value decreasing from 2 to 0, the sizes of both carbon nanosheets and VN nanoparticles decreased to smaller in nanoscale. The maximum specific capacitance of 280 F g -1 at the current density of 1 A g -1 for N-CNS/VNNPs is achieved in three-electrode configuration. The asymmetric energy device of Ni(OH) 2 ||N-CNS/VNNPs offers a specific capacitance of 89.6 F g -1 and retention of 60% at 2.7 A g -1 after 5000 cycles. The maximum energy density of Ni(OH) 2 ||N-CNS/VNNPs asymmetric energy device is as high as 29.5 Wh kg -1 .

A simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys

NASA Technical Reports Server (NTRS)

Dupraw, W. A.

1972-01-01

A simple analytical procedure is described for accurately and precisely determining the zirconium or hafnium content of molybdenum-base alloys. The procedure is based on the reaction of the reagent Arsenazo III with zirconium or hafnium in strong hydrochloric acid solution. The colored complexes of zirconium or hafnium are formed in the presence of molybdenum. Titanium or rhenium in the alloy have no adverse effect on the zirconium or hafnium complex at the following levels in the selected aliquot: Mo, 10 mg; Re, 10 mg; Ti, 1 mg. The spectrophotometric measurement of the zirconium or hafnium complex is accomplished without prior separation with a relative standard deviation of 1.3 to 2.7 percent.

Hafnium(IV) chloride complexes with chelating β-ketiminate ligands: Synthesis, spectroscopic characterization and volatility study

NASA Astrophysics Data System (ADS)

Patil, Siddappa A.; Medina, Phillip A.; Antic, Aleks; Ziller, Joseph W.; Vohs, Jason K.; Fahlman, Bradley D.

2015-09-01

The synthesis and characterization of four new β-ketiminate hafnium(IV) chloride complexes dichloro-bis[4-(phenylamido)pent-3-en-2-one]-hafnium (4a), dichloro-bis[4-(4-methylphenylamido)pent-3-en-2-one]-hafnium (4b), dichloro-bis[4-(4-methoxyphenylamido)pent-3-en-2-one]-hafnium (4c), and dichloro-bis[4-(4-chlorophenylamido)pent-3-en-2-one]-hafnium (4d) are reported. All the complexes (4a-d) were characterized by spectroscopic methods (1H NMR, 13C NMR, IR), and elemental analysis while the compound 4c was further examined by single-crystal X-ray diffraction, revealing that the complex is monomer with the hafnium center in octahedral coordination environment and oxygens of the chelating N-O ligands are trans to each other and the chloride ligands are in a cis arrangement. Volatile trends are established for four new β-ketiminate hafnium(IV) chloride complexes (4a-d). Sublimation enthalpies (ΔHsub) were calculated from thermogravimetric analysis (TGA) data, which show that, the dependence of ΔHsub on the molecular weight (4a-c) and inductive effects from chlorine (4d).

Hafnium transistor process design for neural interfacing.

PubMed

Parent, David W; Basham, Eric J

2009-01-01

A design methodology is presented that uses 1-D process simulations of Metal Insulator Semiconductor (MIS) structures to design the threshold voltage of hafnium oxide based transistors used for neural recording. The methodology is comprised of 1-D analytical equations for threshold voltage specification, and doping profiles, and 1-D MIS Technical Computer Aided Design (TCAD) to design a process to implement a specific threshold voltage, which minimized simulation time. The process was then verified with a 2-D process/electrical TCAD simulation. Hafnium oxide films (HfO) were grown and characterized for dielectric constant and fixed oxide charge for various annealing temperatures, two important design variables in threshold voltage design.

Electrostatic Self-Assembly of Diamond Nanoparticles onto Al- and N-Polar Sputtered Aluminum Nitride Surfaces.

PubMed

Yoshikawa, Taro; Reusch, Markus; Zuerbig, Verena; Cimalla, Volker; Lee, Kee-Han; Kurzyp, Magdalena; Arnault, Jean-Charles; Nebel, Christoph E; Ambacher, Oliver; Lebedev, Vadim

2016-11-17

Electrostatic self-assembly of diamond nanoparticles (DNPs) onto substrate surfaces (so-called nanodiamond seeding) is a notable technique, enabling chemical vapor deposition (CVD) of nanocrystalline diamond thin films on non-diamond substrates. In this study, we examine this technique onto differently polarized (either Al- or N-polar) c -axis oriented sputtered aluminum nitride (AlN) film surfaces. This investigation shows that Al-polar films, as compared to N-polar ones, obtain DNPs with higher density and more homogeneously on their surfaces. The origin of these differences in density and homogeneity is discussed based on the hydrolysis behavior of AlN surfaces in aqueous suspensions.

Electrostatic Self-Assembly of Diamond Nanoparticles onto Al- and N-Polar Sputtered Aluminum Nitride Surfaces

PubMed Central

Yoshikawa, Taro; Reusch, Markus; Zuerbig, Verena; Cimalla, Volker; Lee, Kee-Han; Kurzyp, Magdalena; Arnault, Jean-Charles; Nebel, Christoph E.; Ambacher, Oliver; Lebedev, Vadim

2016-01-01

Electrostatic self-assembly of diamond nanoparticles (DNPs) onto substrate surfaces (so-called nanodiamond seeding) is a notable technique, enabling chemical vapor deposition (CVD) of nanocrystalline diamond thin films on non-diamond substrates. In this study, we examine this technique onto differently polarized (either Al- or N-polar) c-axis oriented sputtered aluminum nitride (AlN) film surfaces. This investigation shows that Al-polar films, as compared to N-polar ones, obtain DNPs with higher density and more homogeneously on their surfaces. The origin of these differences in density and homogeneity is discussed based on the hydrolysis behavior of AlN surfaces in aqueous suspensions. PMID:28335345

Thermochemistry of amorphous and crystalline zirconium and hafnium silicates.

NASA Astrophysics Data System (ADS)

Ushakov, S.; Brown, C. E.; Navrotsky, Alexandra; Boatner, L. A.; Demkov, A. A.; Wang, C.; Nguyen, B.-Y.

2003-03-01

Calorimetric investigation of amorphous and crystalline zirconium and hafnium silicates was performed as part of a research program on thermochemistry of alternative gate dielectrics. Amorphous hafnium and zirconium silicates with varying SiO2 content were synthesized by a sol-gel process. Crystalline zirconium and hafnium silicates (zircon and hafnon) were synthesized by solid state reaction at 1450 °C from amorphous gels and grown as single crystals from flux. High temperature oxide melt solution calorimetry in lead borate (2PbO.B2O3) solvent at 800 oC was used to measure drop solution enthalpies for amorphous and crystalline zirconium and hafnium silicates and corresponding oxides. Applying appropriate thermochemical cycles, formation enthalpy of crystalline ZrSiO4 (zircon) from binary oxides (baddeleite and quartz) at 298 K was calculated as -23 +/-2 kJ/mol and enthalpy difference between amorphous and crystalline zirconium silicate (vitrification enthalpy) was found to be 61 +/-3 kJ/mol. Crystallization onset temperatures of amorphous zirconium and hafnium silicates, as measured by differential scanning calorimetry (DSC), increased with silica content. The resulting crystalline phases, as characterized by X-ray diffraction (XRD), were tetragonal HfO2 and ZrO2. Critical crystallite size for tetragonal to monoclinic transformation of HfO2 in the gel was estimated as 6 +/-2 nm from XRD data Crystallization enthalpies per mole of hafnia and zirconia in gels decrease slightly together with crystallite size with increasing silica content, for example from -22 to -15 +/-1 kJ per mol of HfO2 crystallized at 740 and 1006 °C from silicates with 10 and 70 mol Applications of thermal analyses and solution calorimetry techniques together with first-principles density functional calculations to estimate interface and surface energies are discussed.

Simultaneous determination of tantalum and hafnium in silicates by neutron activation analysis

USGS Publications Warehouse

Greenland, L.P.

1968-01-01

A neutron activation procedure suitable for the routine determination of tantalum and hafnium in silicates is described. The irradiated sample is fused with sodium peroxide and leached, and the insoluble hydroxides are dissolved in dilute hydrofluoric acid-hydrochloric acid. After LaF3 and AgCl scavenges, tantalum and hafnium are separated by anion exchange. Tantalum is obtained radiochemically pure; 233Pa and 95Zr contaminants in the hafnium fraction are resolved by ??-ray spectrometry. The chemical yield of the procedure is detemined after counting by re-irradiation. Values for the 8 U.S. Geological Survey standard rocks are reported. ?? 1968.

Preparation of refractory cermet structures for lithium compatibility testing

NASA Technical Reports Server (NTRS)

Heestand, R. L.; Jones, R. A.; Wright, T. R.; Kizer, D. E.

1973-01-01

High-purity nitride and carbide cermets were synthesized for compatability testing in liquid lithium. A process was developed for the preparation of high-purity hafnium nitride powder, which was subsequently blended with tungsten powder or tantalum nitride and tungsten powders and fabricated into 3 in diameter billets by uniaxial hot pressing. Specimens were then cut from the billets for compatability testing. Similar processing techniques were applied to produce hafnium carbide and zirconium carbide cermets for use in the testing program. All billets produced were characterized with respect to chemistry, structure, density, and strength properties.

The Hot-Pressing of Hafnium Carbide (Melting Point, 7030 F)

NASA Technical Reports Server (NTRS)

Sanders, William A.; Grisaffe, Salvatore J.

1960-01-01

An investigation was undertaken to determine the effects of the hot-pressing variables (temperature, pressure, and time) on the density and grain size of hafnium carbide disks. The purpose was to provide information necessary for the production of high-density test shapes for the determination of physical and mechanical properties. Hot-pressing of -325 mesh hafnium carbide powder was accomplished with a hydraulic press and an inductively heated graphite die assembly. The ranges investigated for each variable were as follows: temperature, 3500 to 4870 F; pressure, 1000 to 6030 pounds per square inch; and time, 5 to 60 minutes. Hafnium carbide bodies of approximately 98 percent theoretical density can be produced under the following minimal conditions: 4230 F, 3500 pounds per square inch, and 15 minutes. Further increases in temperature and time resulted only in greater grain size.

High-energy X-ray detection by hafnium-doped organic-inorganic hybrid scintillators prepared by sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yan; Koshimizu, Masanori, E-mail: koshi@qpc.che.tohoku.ac.jp; Yahaba, Natsuna

2014-04-28

With the aim of enhancing the efficiency with which plastic scintillators detect high-energy X-rays, hafnium-doped organic-inorganic hybrid scintillators were fabricated via a sol-gel method. Transmission electron microscopy of sampled material reveals the presence of Hf{sub x}Si{sub 1−x}O{sub 2} nanoparticles, dispersed in a polymer matrix that constitutes the active material of the X-ray detector. With Hf{sub x}Si{sub 1−x}O{sub 2} nanoparticles incorporated in the polymer matrix, the absorption edge and the luminescence wavelength is shifted, which we attribute to Mie scattering. The detection efficiency for 67.4-keV X-rays in a 0.6-mm-thick piece of this material is two times better than the same thicknessmore » of a commercial plastic scintillator-NE142.« less

Zirconium and hafnium in the southeastern Atlantic States

USGS Publications Warehouse

Mertie, J.B.

1958-01-01

The principal source of zirconium and hafnium is zircon, though a minor source is baddeleyite, mined only in Brazil. Zircon is an accessory mineral in igneous, metamorphic, and sedimentary rocks, but rarely occurs in hardrock in minable quantities. The principal sources of zircon are therefore alluvial deposits, which are mined in many countries of five continents. The principal commercial deposits in the United States are in Florida, though others exist elsewhere in the southeastern Coastal Plain. The evidence indicates that conditions for the accumulation of workable deposits of heavy minerals were more favorable during the interglacial stages of the Pleistocene epoch than during Recent time. Therefore detrital ores of large volume and high tenor are more likely to be found in the terrace deposits than along the present beaches. Other concentrations of heavy minerals, however, are possible at favored sites close to the Fall Line where the Tuscaloosa formation rests upon the crystalline rocks of the Piedmont province. A score of heavy and semiheavy minerals occur in the detrital deposits of Florida, but the principal salable minerals are ilmenite, leucoxene, rutile, and zircon, though monazite and staurolite are saved at some mining plants. Commercial deposits of heavy minerals are generally required to have a tenor of 4 percent, though ores with a lower tenor can be mined at a profit if the content of monazite is notably high. The percentages of zircon in the concentrates ranges from 10 to 16 percent, and in eastern Florida from 13 to 15 percent. Thus the tenor in zircon of the ore-bearing sands ranges from 0.4 to 0.6 percent. The content of hafnium in zircon is immaterial for many uses, but for some purposes very high or very low tenors in hafnium are required. Alluvial zircon cannot be separated into such varieties, which, if needed, must be obtained from sources in bedrock. It thus becomes necessary to determine the Hf : Zr ratios in zircon from many kinds of

Erbium doped aluminum nitride nanoparticles for nano-thermometer applications

NASA Astrophysics Data System (ADS)

Pandya, Sneha G.; Kordesch, Martin E.

2015-06-01

We have synthesized nanoparticles (NPs) of aluminum nitride (AlN) doped in situ with erbium (Er) using the inert gas condensation technique. These NPs have optical properties that make them good candidates for nanoscale temperature sensors. The photoluminescence (PL) spectrum of Er3+ in these NPs shows two emission peaks in the green region at around 540 and 560 nm. The ratio of the intensities of these luminescence peaks is related to temperature. Using Boltzmann’s distribution, the temperature of the NP and its surrounding can be calculated. The NPs were directly deposited on (111) p-type silicon wafers, transmission electron microscope grids and glass cover slips. XRD and HRTEM study indicates that most of the NPs have crystalline hexagonal AlN structure. An enhancement of the luminescence from these NPs was observed after heating in-air at 770 K for 3 h. The sample was then heated in air using a scanning optical microscope laser. The corresponding change in PL peak intensities of the NPs was recorded for laser powers ranging from 0.2 to 15.1 mW. Temperature calculated using the Boltzmann’s distribution was in the range of 300-470 K. This temperature range is of interest for semiconductor device heating and for thermal treatment of cancerous cells, for example.

Deep eutectic solvent approach towards nickel/nickel nitride nanocomposites

DOE PAGES

Gage, Samuel H.; Ruddy, Daniel A.; Pylypenko, Svitlana; ...

2016-12-15

Nickel nitride is an attractive material for a broad range of applications including catalysis. However preparations and especially those targeting nanoscale particles remain a major challenge. Herein, we report a wet-chemical approach to produce nickel/nickel nitride nanocomposites using deep eutectic solvents. A choline chloride/urea deep eutectic solvent was used as a reaction medium to form gels containing nickel acetate tetrahydrate. Heat treatment of the gel in inert atmosphere forms nanoparticles embedded within a nitrogen-doped carbon matrix. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to understand the decomposition profile of the precursors and to select pyrolysis temperatures locatedmore » in regions of thermal stability. X-ray diffraction (XRD) confirmed the presence of metallic nickel, whereas X-ray photoelectron spectroscopy (XPS) suggested the existence of a nickel nitride surface layer. According to transmission electron microscopy (TEM) analysis these mixed phase, possibly core-shell type nanoparticles, have very defined facets. Furthermore, these materials represent a unique opportunity to tune catalytic properties of nickel-based catalysts through control of their composition, surface structure, and morphology; in addition to employing potential benefits of a nitrogen-doped carbon support.« less

Separation of Zirconium and Hafnium: A Review

NASA Astrophysics Data System (ADS)

Xu, L.; Xiao, Y.; van Sandwijk, A.; Xu, Q.; Yang, Y.

Zirconium is an ideal material for nuclear reactors due to its low absorption cross-section for thermal neutrons, whereas the typically contained hafnium with strong neutron-absorption is very harmful for zirconium. This paper provides an overview of the processes for separating hafnium from zirconium. The separation processes are roughly classified into hydro- and pyrometallurgical routes. The current dominant zirconium production route involves pyrometallurgical ore cracking, multi-step hydrometallurgical liquid-liquid extraction for hafnium removal and the reduction of zirconium tetrachloride to the pure metal by the Kroll process. The lengthy hydrometallurgical Zr-Hf separation operations leads to high production cost, intensive labour and heavy environmental burden. Using a compact pyrometallurgical separation method can simplify the whole production flowsheet with a higher process efficiency. The known separation methods are discussed based on the following reaction features: redox characteristics, volatility, electrochemical properties and molten salt extraction. The commercially operating extractive distillation process is a significant advance in Zr-Hf separation technology but it suffers from high process maintenance cost. The recently developed new process based on molten salt-metal equilibrium for Zr-Hf separation shows a great potential for industrial application, which is compact for nuclear grade zirconium production starting from crude ore. In the present paper, the available separation technologies are compared. The advantages and disadvantages as well as future directions of research and development for nuclear grade zirconium production are discussed.

Parallel fabrication of sub-50-nm uniformly sized nanoparticles by deposition through a patterned silicon nitride nanostencil.

PubMed

Yan, X-M; Contreras, A M; Koebel, M M; Liddle, J A; Somorjai, G A

2005-06-01

Using low-pressure chemical vapor deposition of silicon dioxide, we have reduced the size of 56-nm features in a silicon nitride membrane, called a stencil, down to 36 nm. Sub-50-nm uniformly sized nanoparticles are fabricated by electron-beam deposition of Pt through the stencil mask. A self-assembled monolayer (SAM) of tridecafluoro-1,1,2,2-tetrahydrooctyl-1-trichlorosilane was used to reduce Pt clogging of the nanosize holes during deposition as well as to protect the stencil during the postdeposition Pt removal. X-ray photoelectron spectroscopy shows that the SAM protects the stencil efficiently during this postdeposition removal of Pt.

High P-T phase transitions and P-V-T equation of state of hafnium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hrubiak, Rostislav; Drozd, Vadym; Karbasi, Ali

2016-07-29

We measured the volume of hafnium at several pressures up to 67 GPa and at temperatures between 300 to 780 K using a resistively heated diamond anvil cell with synchrotron x-ray diffraction at the Advanced Photon Source. The measured data allows us to determine the P-V-T equation of state of hafnium. The previously described [Xia et al., Phys. Rev. B 42, 6736-6738 (1990)] phase transition from hcp ({alpha}) to simple hexagonal ({omega}) phase at 38 GPa at room temperature was not observed even up to 51 GPa. The {omega} phase was only observed at elevated temperatures. Our measurements have alsomore » improved the experimental constraint on the high P-T phase boundary between the {omega} phase and high pressure bcc ({beta}) phase of hafnium. Isothermal room temperature bulk modulus and its pressure derivative for the {alpha}-phase of hafnium were measured to be B{sub 0} = 112.9{+-}0.5 GPa and B{sub 0}'=3.29{+-}0.05, respectively. P-V-T data for the {alpha}-phase of hafnium was used to obtain a fit to a thermodynamic P-V-T equation of state based on model by Brosh et al. [CALPHAD 31, 173-185 (2007)].« less

Hafnium transistor design for neural interfacing.

PubMed

Parent, David W; Basham, Eric J

2008-01-01

A design methodology is presented that uses the EKV model and the g(m)/I(D) biasing technique to design hafnium oxide field effect transistors that are suitable for neural recording circuitry. The DC gain of a common source amplifier is correlated to the structural properties of a Field Effect Transistor (FET) and a Metal Insulator Semiconductor (MIS) capacitor. This approach allows a transistor designer to use a design flow that starts with simple and intuitive 1-D equations for gain that can be verified in 1-D MIS capacitor TCAD simulations, before final TCAD process verification of transistor properties. The DC gain of a common source amplifier is optimized by using fast 1-D simulations and using slower, complex 2-D simulations only for verification. The 1-D equations are used to show that the increased dielectric constant of hafnium oxide allows a higher DC gain for a given oxide thickness. An additional benefit is that the MIS capacitor can be employed to test additional performance parameters important to an open gate transistor such as dielectric stability and ionic penetration.

Etude de la nitruration carbothermique du dioxyde de hafnium par diffraction X à haute température

NASA Astrophysics Data System (ADS)

Pialoux, A.

1993-03-01

The carbothermal reduction of hafnium dioxide under atmospheric level nitrogen pressure has been investigated using a graphite resistance high temperature X-ray diffractometer up to around 2300 K. A carbon transfer reaction through the gaseous phase (N 2, CO/CO 2) is shown to precede, then to compete the direct reduction of the hafnium oxide by the graphite in pure nitrogen. A complex mechanism has been found that accounts for the formation of hafnium dioxynitride and possibly of three other hafnium oxynitrides, then of hafnium mononitride and hafnium monocarbonitride, along two different steps between 1613 and 1923 K. An evaluation has been made concerning the composition of these γ 1- HfO 2-xN x/2□ x/2 (CaF 2-type structure), γ 2- Hf 7O 11N 2, γ 3- Hf 7O 8N 4 (rhombohedral), γ 4- Hf 2ON 2 (Mn 2O 3-type structure), HfN and HfN 1-zC z (NaCl-type structure) phases, considering the variations of their lattice parameters and the available data in the literature, especially on the isomorphous compounds of zirconium. It must be emphasized the new γ 1- HfO 2-xN x/2 phase, the dilatation of which is linear ( overlineα = 12×10 -6K -1), shows a constant composition from 2158 down to 1473 K (x ≈ 0,2). But under 1473 K, inevitably, the hafnium dioxynitride disappears, and poorly crystallized monoclinic αHfO 2 and rhombohedral γ 2- Hf 7O 11N 2 are formed.

Structure refinement for tantalum nitrides nanocrystals with various morphologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Lianyun; School of Science, Beijing Jiaotong University, 3 Shang Yuan Cun, Haidian District, Beijing 100044; Huang, Kai

2012-07-15

Graphical abstract: Tantalum nitrides nanocrystals with various phases and morphologies for the first time have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. Highlights: ► The spherical TaN, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. ► The crystal structures of different tantalum nitrides were determined by Rietveld refinement on the X-ray diffraction data and the examinations of electron microcopies. ► The specific surface area of the tantalum nitrides powders was around 10 m{supmore » 2} g{sup −1}. ► Tantalum nitrides powders could be suitable for capacitor with high specific capacitance. -- Abstract: Tantalum nitrides (TaN{sub x}) nanocrystals with different phase and morphology have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. The crystal structures of tantalum nitrides were determined by Rietveld refinement based on the X-ray diffraction data. The morphologies of various tantalum nitrides nanocrystals in high quality were analyzed through the electron microcopies examinations. The spherical TaN nanoparticles, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been selectively prepared at different annealing temperatures. In addition, the specific surface areas of the tantalum nitrides nanocrystals measured by BET method were around 9.87–11.64 m{sup 2} g{sup −1}, indicating that such nano-sized tantalum nitrides could be suitable for capacitor with high specific capacitance.« less

Strategies to indium nitride and gallium nitride nanoparticles: Low-temperature, solution-phase and precursor routes

NASA Astrophysics Data System (ADS)

Dingman, Sean Douglas

I present new strategies to low-temperature solution-phase synthesis of indium and gallium nitride (InN and GaN) ceramic materials. The strategies include: direct conversion of precursor molecules to InN by pyrolysis, solution-phase synthesis of nanostructured InN fibers via molecular precursors and co-reactants, and synthesis of powders through reactions derived from molten-salt chemistry. Indium nitride powders are prepared by pyrolysis of the precursors R 2InN3 (R = t-Bu (1), i-Amyl(2), Et(3), i-Pr( 4)). The precursors are synthesized via azide-alkoxide exchange of R2InOMe with Me3SiN3. The precursors are coordination polymers containing five-coordinate indium centers. Pyrolysis of 1 and 2 under N2 at 400°C yields powders consisting primarily of InN with average crystal sizes of 15--35 nm. 1 yields nanocrystalline InN with average particle sizes of 7 nm at 250°C. 3 and 4 yield primarily In metal from pyrolysis. Refluxing 1 in diisopropylbenzene (203°C) in the presence of primary amines yields InN nanofibers 10--100 nm in length. InN nanofibers of up to 1 mum can be synthesized by treating 1 with 1,1-dimethylhydrazine (DMHy) The DMHy appears to control the fiber length by acting as a secondary source of active nitrogen in order to sustain fiber growth. The resulting fibers are attached to droplets of indium metal implying a solution-liquid-solid growth mechanism. Precursor 4 yields crystalline InN whiskers when reacted with DMHy. Reactions of 4 with reducing agents such as HSnBu3, yield InN nanoparticles with an average crystallite size of 16 nm. Gallium precursors R2GaN3 (R = t-Bu( 5), Me3SiCH2(6) and i-Pr( 7)), synthesized by azide-alkoxide exchange, are found to be inert toward solution decomposition and do not yield GaN. These compounds are molecular dimers and trimers unlike the indium analogs. Compound 6 displays a monomer-dimer equilibrium in benzene solution, but exists as a solid-state trimer. InN powders are also synthesized by reactions of InCl3 and

Tensile and stress-rupture behavior of hafnium carbide dispersed molybdenum and tungsten base alloy wires

NASA Technical Reports Server (NTRS)

Yun, Hee Mann; Titran, Robert H.

1993-01-01

The tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 microns in diameter, were determined over the temperature range from 1200 K to 1600 K. Three molybdenum alloy wires; Mo + 1.1w/o hafnium carbide (MoHfC), Mo + 25w/o W + 1.1w/o hafnium carbide (MoHfC+25W) and Mo + 45w/o W + 1.1w/o hafnium carbide (MoHfC+45W), and a W + 0.4w/o hafnium carbide (WHfC) tungsten alloy wire were evaluated. The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress rupture strength at temperatures above 1400 K. Theoretical calculations indicate that the strength and ductility advantage of the HfC dispersed alloy wires is due to the resistance to recrystallization imparted by the dispersoid.

Nanostructured silicon nitride from wheat and rice husks

NASA Astrophysics Data System (ADS)

Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.; Wollmershauser, J. A.; Feng, C. R.

2016-04-01

Nanoparticles, submicron-diameter tubes, and rods of Si3N4 were synthesized from the thermal treatment of wheat and rice husks at temperatures at and above 1300 °C in a nitrogen atmosphere. The whole pattern Rietveld analysis of the observed diffraction data from treatments at 1300 °C showed the formation of only hexagonal α-phase of Si3N4 with an R-factor of 1%, whereas samples treated at 1400 °C and above showed both α- and β-phases with an R-factor of 2%. Transmission electron microscopy showed the presence of tubes, rods, and nanoparticles of Si3N4. In a two-step process, where pure SiC was produced first from rice or wheat husk in an argon atmosphere and subsequently treated in a nitrogen atmosphere at 1450 °C, a nanostructured composite material having α- and β-phases of Si3N4 combined with cubic phase of SiC was formed. The thermodynamics of the formation of silicon nitride is discussed in terms of the solid state reaction between organic matter (silica content), which is inherently present in the wheat and rice husks, with the nitrogen from the furnace atmosphere. Nanostructures of silicon nitride formed by a single direct reaction or their composites with SiC formed in a two-step process of agricultural byproducts provide an uncomplicated sustainable synthesis route for silicon nitride used in mechanical, biotechnology, and electro-optic nanotechnology applications.

Waste conversion into high-value ceramics: Carbothermal nitridation synthesis of titanium nitride nanoparticles using automotive shredder waste.

PubMed

Mayyas, Mohannad; Pahlevani, Farshid; Maroufi, Samane; Liu, Zhao; Sahajwalla, Veena

2017-03-01

Environmental concern about automotive shredder residue (ASR) has increased in recent years due to its harmful content of heavy metals. Although several approaches of ASR management have been suggested, these approaches remain commercially unproven. This study presents an alternative approach for ASR management where advanced materials can be generated as a by-product. In this approach, titanium nitride (TiN) has been thermally synthesized by nitriding pressed mixture of automotive shredder residue (ASR) and titanium oxide (TiO 2 ). Interactions between TiO 2 and ASR at non-isothermal conditions were primarily investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry. Results indicated that TiO 2 influences and catalyses degradation reactions of ASR, and the temperature, at which reduction starts, was determined around 980 °C. The interaction between TiO 2 and ASR at isothermal conditions in the temperature range between 1200 and 1550 °C was also studied. The pressed mixture of both materials resulted in titanium nitride (TiN) ceramic at all given temperatures. Formation kinetics were extracted using several models for product layer diffusion-controlled solid-solid and solid-fluid reactions. The effect of reactants ratio and temperature on the degree of conversion and morphology was investigated. The effect of reactants ratio was found to have considerable effect on the morphology of the resulting material, while temperature had a lesser impact. Several unique structures of TiN (porous nanostructured, polycrystalline, micro-spherical and nano-sized structures) were obtained by simply tuning the ratio of TiO 2 to ASR, and a product with appreciable TiN content of around 85% was achieved after only one hour nitridation at 1550 °C. Copyright © 2016 Elsevier Ltd. All rights reserved.

Carbon nitride supported copper nanoparticles: light-induced electronic effect of the support for triazole synthesis

NASA Astrophysics Data System (ADS)

Nandi, Debkumar; Taher, Abu; Ul Islam, Rafique; Siwal, Samarjeet; Choudhary, Meenakshi; Mallick, Kaushik

2016-11-01

The composite framework of graphitic carbon nitride (gCN) supported copper nanoparticle can act as a high-performance photoreactor for the synthesis of 1,2,3-triazole derivatives under light irradiation in the absence of alkaline condition. The photoactivity of gCN originates from an electron transition from the valence band to the conduction band, in the presence of photon energy, and the hot electron acts as a scavenger of the terminal proton of the alkyne molecule to facilitate the formation of copper acetanilide complex. In this study, we have performed the experiment under a different photonic environment, including dark condition, and in the presence and absence of base. A comparative study was also executed using Cu-TiO2 system, as a reference material, in the support of our proposed mechanism. The recycling performance and the photocorrosion effect of the catalyst have also been reported in this study.

Mineral resource of the month: zirconium and hafnium

USGS Publications Warehouse

Gambogi, Joseph

2007-01-01

Zirconium and hafnium are corrosion-resistant metals that are grouped in the same family as titanium on the periodic table. The two elements commonly occur in oxide and silicate minerals and have significant economic importance in everything from ink, ceramics and golf shoes to nuclear fuel rods.

Synthesis of Spherical Carbon Nitride-Based Polymer Composites by Continuous Aerosol-Photopolymerization with Efficient Light Harvesting.

PubMed

Poostforooshan, Jalal; Badiei, Alireza; Kolahdouz, Mohammadreza; Weber, Alfred P

2016-08-24

Here we report a novel, facile, and sustainable approach for the preparation of spherical submicrometer carbon nitride-based polymer composites by a continuous aerosol-photopolymerization process. In this regard, spherical mesoporous carbon nitride (SMCN) nanoparticles were initially prepared via a nanocasting approach using spray-drying synthesized spherical mesoporous silica (SMS) nanoparticles as hard templates. In addition to experimental characterization, the effect of porosity on the light absorption enhancement and consequently the generation rate of electron-hole pairs inside the SMCN was simulated using a three-dimensional finite difference time-domain (FDTD) method. To produce the carbon nitride-based polymer composite, SMCN nanoparticles exhibit excellent performance in photopolymerization of butyl acrylate (PBuA) monomer in the presence of n-methyldiethanolamine (MDEA) as a co-initiator in a continuous aerosol-based process. In this one-pot synthesis, SMCN nanoparticles act not only as photoinitiators but at the same time as fillers and templates. The average aerosol residence time in the photoreactor is about 90 s. The presented aerosol-photopolymerization process avoids the need for solvent and surfactant, operates at room temperature, and, more importantly, is suitable to produce the spherical composite with hydrophobic polymers. Furthermore, we simulated the condition of SMCN nanoparticles during illumination in the gas phase process, which can freely rotate. The results demonstrated that the hole (h(+)) density is almost equally distributed in the whole part of the SMCN nanoparticles due to their rotation, leading to efficient light harvesting and more homogeneous photoreaction. The combination of the outstanding features of environmentally friendly SMCN, photopolymerization, and aerosol processing might open new avenues, especially in green chemistry, to produce novel polymer composites with multifunctional properties.

SEPARATING HAFNIUM FROM ZIRCONIUM

DOEpatents

Lister, B.A.J.; Duncan, J.F.; Hutcheon, J.M.

1956-08-21

Substantially complete separation of zirconium from hafnium may be obtained by elution of ion exchange material, on which compounds of the elements are adsorbed, with an approximately normal solution of sulfuric acid. Preferably the acid concentration is between 0.8 N amd 1.2 N, amd should not exceed 1.5 N;. Increasing the concentration of sulfate ion in the eluting solution by addition of a soluble sulfate, such as sodium sulfate, has been found to be advantageous. The preferred ion exchange materials are sulfonated polystyrene resins such as Dowex 50,'' and are preferably arranged in a column through which the solutions are passed.

Effect of cathode cooling efficiency and oxygen plasma gas pressure on the hafnium cathode wall temperature

NASA Astrophysics Data System (ADS)

Ashtekar, Koustubh; Diehl, Gregory; Hamer, John

2012-10-01

The hafnium cathode is widely used in DC plasma arc cutting (PAC) under an oxygen gas environment to cut iron and iron alloys. The hafnium erosion is always a concern which is controlled by the surface temperature. In this study, the effect of cathode cooling efficiency and oxygen gas pressure on the hafnium surface temperature are quantified. The two layer cathode sheath model is applied on the refractive hafnium surface while oxygen species (O2, O, O+, O++, e-) are considered within the thermal dis-equilibrium regime. The system of non-linear equations comprising of current density balance, heat flux balance at both the cathode surface and the sheath-ionization layer is coupled with the plasma gas composition solver. Using cooling heat flux, gas pressure and current density as inputs; the cathode wall temperature, electron temperature, and sheath voltage drop are calculated. Additionally, contribution of emitted electron current (Je) and ions current (Ji) to the total current flux are estimated. Higher gas pressure usually reduces Ji and increases Je that reduces the surface temperature by thermionic cooling.

Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.

PubMed

Yun, Dong-Jin; Lee, Seunghyup; Yong, Kijung; Rhee, Shi-Woo

2012-04-01

The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 Å/s and R.T.) showed the largest grain size (0.8-1.0 μm) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (<5 V) pentacene thin film transistor (μ: ~2 cm(2)/(V s), on/off ratio, >1 × 10(4)) and complementary inverter (DC gains, ~20) could be fabricated.

Superconducting structure with layers of niobium nitride and aluminum nitride

DOEpatents

Murduck, James M.; Lepetre, Yves J.; Schuller, Ivan K.; Ketterson, John B.

1989-01-01

A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources.

Atomic layer deposition and characterization of hafnium oxide grown on silicon from tetrakis(diethylamino)hafnium and water vapor

NASA Astrophysics Data System (ADS)

Deshpande, Anand; Inman, Ronald; Jursich, Gregory; Takoudis, Christos

2004-09-01

In this work thin films of hafnium oxide are deposited on Si(100) substrates by means of atomic layer deposition (ALD) using tetrakis(diethylamino)hafnium and water vapor at substrate temperatures of 250-350ºC. Our system capabilities include fast transient delivery of reactive fluids, real-time vapor phase detection (in situ tunable diode laser hygrometer), precursor thermochemical capabilities, and ppt level elemental analysis by inductive coupling plasma mass spectrometry. The composition, purity, and other properties of the films and resulting interfaces are determined using x-ray and Fourier transform infrared spectroscopies, Z-contrast imaging and electron energy loss spectroscopy in a scanning transmission electron microscope with A˚ scale resolution, and spectroscopic ellipsometry. The observed ALD rate is ~1.4 A˚ per cycle. The nonuniformity across the film is less than 4%. Negligible carbon contamination is found in the resulting stoichiometric films under all conditions studied. The pulse sequence was optimized to prevent disastrous particulate problems while still minimizing purge times. The film deposition is investigated as a function of substrate temperature and reagent pulsing characteristics. A mild inverse temperature dependence of the ALD rate is observed. The initial stage of the HfO2 growth is investigated in detail.

Plasma synthesis and HPHT consolidation of BN nanoparticles, nanospheres, and nanotubes to produce nanocrystalline cubic boron nitride

NASA Astrophysics Data System (ADS)

Stout, Christopher

Plasma methods offer a variety of advantages to nanomaterials synthesis. The process is robust, allowing varying particle sizes and phases to be generated simply by modifying key parameters. The work here demonstrates a novel approach to nanopowder synthesis using inductively-coupled plasma to decompose precursor, which are then quenched to produce a variety of boron nitride (BN)-phase nanoparticles, including cubic phase, along with short-range-order nanospheres (e.g., nano-onions) and BN nanotubes. Cubic BN (c-BN) powders can be generated through direct deposition onto a chilled substrate. The extremely-high pyrolysis temperatures afforded by the equilibrium plasma offer a unique particle growth environment, accommodating long deposition times while exposing resulting powders to temperatures in excess of 5000K without any additional particle nucleation and growth. Such conditions can yield short-range ordered amorphous BN structures in the form of 20nm diameter nanospheres. Finally, when introducing a rapid-quenching counter-flow gas against the plasma jet, high aspect ratio nanotubes are synthesized, which are collected on substrate situated radially. The benefits of these morphologies are also evident in high-pressure/high-temperature consolidation experiments, where nanoparticle phases can offer a favorable conversion route to super-hard c-BN while maintaining nanocrystallinity. Experiments using these morphologies are shown to begin to yield c-BN conversion at conditions as low as 2.0 GPa and 1500°C when using micron sized c-BN seeding to create localized regions of high pressures due to Hertzian forces acting on the nanoparticles.

Superconducting structure with layers of niobium nitride and aluminum nitride

DOEpatents

Murduck, J.M.; Lepetre, Y.J.; Schuller, I.K.; Ketterson, J.B.

1989-07-04

A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources. 8 figs.

Review of anhydrous zirconium-hafnium separation techniques. Information circular/1984

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skaggs, R.L.; Rogers, D.T.; Hunter, D.B.

1983-12-01

Sixteen nonaqueous techniques conceived to replace the current aqueous scheme for separating hafnium and zirconium tetrachlorides were reviewed and evaluated by the Bureau of Mines. The methods are divided into two classes: separation by fractional volatilization of the tetrachlorides, which takes advantage of the higher volatility of hafnium tetrachloride; and separation by chemical techniques, based on differences in chemical behavior of the two tetrachlorides. The criteria used to evaluate separation methods were temperature, pressure, separation factor per equilibrium stage, complexity, compatibility with existing technology, and potential for continuous operation. Three processes were selected as being most promising: (1) high-pressure distillation,more » (2) extractive distillation from a molten salt, and (3) preferential reduction of gaseous ZrCl4. Any of the proposed nonaqueous Hf-Zr separation schemes must be supplemented with additional purification to remove trace impurities.« less

Functionalized boron nitride nanotubes

DOEpatents

Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

2014-04-22

A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

Interfacial phenomena in high-kappa dielectrics

NASA Astrophysics Data System (ADS)

Mathew, Anoop

The introduction of novel high-kappa dielectric materials to replace the traditional SiO2 insulating layer in CMOS transistors is a watershed event in the history of transistor development. Further, replacement of the traditional highly-doped polycrystalline silicon gate electrode with a new set of materials for metal gates complicates the transition and introduces further integration challenges. A whole variety of new material surfaces and interfaces are thus introduced that merit close investigation to determine parameters for optimal device performance. Nitrogen is a key component that improves the performance of a variety of materials for the next generation of these CMOS transistors. Nitrogen is introduced into new gate dielectric materials such as hafnium silicates as well as in potential metal gate materials such as hafnium nitride. A photoemission study of the binding energies of the various atoms in these systems using photoemission reveals the nature of the atomic bonding. The current study compares hafnium silicates of various compositions which were thermally nitrided at different temperatures in ammonia, hafnium nitrides, and thin HfO2 films using photoelectron spectroscopy. A recurring theme that is explored is the competition between oxygen and nitrogen atoms in bonding with hafnium and other atoms. The N 1s photoemission peak is seen to have contributions from its bonding with hafnium, oxygen, and silicon atoms. The Hf 4f and O 1s spectra similarly exhibit signatures of their bonding environment with their neighboring atoms. Angle resolved photoemission and in-situ annealing/argon sputtering experiments are used to elucidate the nature of the bonding and its evolution with processing. A nondestructive profilitng of nitrogen distribution as a function of composition in nitrided hafnium silicates is also constructed using angle resolved photoemission as a function of the take-off angle. These results are corroborated with depth reconstruction obtained

Aqueously Dispersed Silver Nanoparticle-Decorated Boron Nitride Nanosheets for Reusable, Thermal Oxidation-Resistant Surface Enhanced Raman Spectroscopy (SERS) Devices

NASA Technical Reports Server (NTRS)

Lin, Yi; Bunker, Christopher E.; Fernandos, K. A. Shiral; Connell, John W.

2012-01-01

The impurity-free aqueous dispersions of boron nitride nanosheets (BNNS) allowed the facile preparation of silver (Ag) nanoparticle-decorated BNNS by chemical reduction of an Ag salt with hydrazine in the presence of BNNS. The resultant Ag-BNNS nanohybrids remained dispersed in water, allowing convenient subsequent solution processing. By using substrate transfer techniques, Ag-BNNS nanohybrid thin film coatings on quartz substrates were prepared and evaluated as reusable surface enhanced Raman spectroscopy (SERS) sensors that were robust against repeated solvent washing. In addition, because of the unique thermal oxidation-resistant properties of the BNNS, the sensor devices may be readily recycled by short-duration high temperature air oxidation to remove residual analyte molecules in repeated runs. The limiting factor associated with the thermal oxidation recycling process was the Ostwald ripening effect of Ag nanostructures.

Multifunctional cyanate ester nanocomposites reinforced by hexagonal boron nitride after noncovalent biomimetic functionalization.

PubMed

Wu, Hongchao; Kessler, Michael R

2015-03-18

Boron nitride (BN) reinforced polymer nanocomposites have attracted a growing research interest in the microelectronic industry for their uniquely thermal conductive but electrical insulating properties. To overcome the challenges in surface functionalization, in this study, hexagonal boron nitride (h-BN) nanoparticles were noncovalently modified with polydopamine in a solvent-free aqueous condition. The strong π-π interaction between the hexagonal structural BN and aromatic dopamine molecules facilitated 15 wt % polydopamine encapsulating the nanoparticles. High-performance bisphenol E cyanate ester (BECy) was incorporated by homogeneously dispersed h-BN at different loadings and functionalities to investigate their effects on thermo-mechanical, dynamic-mechanical, and dielectric properties, as well as thermal conductivity. Different theoretical and empirical models were successfully applied to predict thermal and dielectric properties of h-BN/BECy nanocomposites. Overall, the prepared h-BN/BECy nanocomposites exhibited outstanding performance in dimensional stability, dynamic-mechanical properties, and thermal conductivity, together with the controllable dielectric property and preserved thermal stability for high-temperature applications.

Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

NASA Astrophysics Data System (ADS)

Singh, Bikramjeet; Singh, Paviter; Kumar, Manjeet; Thakur, Anup; Kumar, Akshay

2015-05-01

Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H3BO3). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT).

Evidence for oxygen vacancies movement during wake-up in ferroelectric hafnium oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Starschich, S.; Böttger, U.; Menzel, S.

The wake-up effect which is observed in ferroelectric hafnium oxide is investigated in yttrium doped hafnium oxide prepared by chemical solution deposition. It can be shown that not the amount of cycles but the duration of the applied electrical field is essential for the wake-up. Temperature dependent wake-up cycling in a range of −160 °C to 100 °C reveals a strong temperature activation of the wake-up, which can be attributed to ion rearrangement during cycling. By using asymmetrical electrodes, resistive valence change mechanism switching can be observed coincident with ferroelectric switching. From the given results, it can be concluded that redistribution ofmore » oxygen vacancies is the origin of the wake-up effect.« less

Boron nitride composites

DOEpatents

Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

2017-02-21

According to one embodiment, a composite product includes: a matrix material including hexagonal boron nitride and one or more borate binders; and a plurality of cubic boron nitride particles dispersed in the matrix material. According to another embodiment, a composite product includes: a matrix material including hexagonal boron nitride and amorphous boron nitride; and a plurality of cubic boron nitride particles dispersed in the matrix material.

Method and device to synthesize boron nitride nanotubes and related nanoparticles

DOEpatents

Zettl, Alexander K.

2016-07-19

Methods and apparatus for producing chemical nanostructures having multiple elements, such as boron and nitride, e.g. boron nitride nanotubes, are disclosed. The method comprises creating a plasma jet, or plume, such as by an arc discharge. The plasma plume is elongated and has a temperature gradient along its length. It extends along its length into a port connector area having ports for introduction of feed materials. The feed materials include the multiple elements, which are introduced separately as fluids or powders at multiple ports along the length of the plasma plume, said ports entering the plasma plume at different temperatures. The method further comprises modifying a temperature at a distal portion of or immediately downstream of said plasma plume; and collecting said chemical nanostructures after said modifying.

Effect of hafnium doping on density of states in dual-target magnetron co-sputtering HfZnSnO thin film transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Chuan-Xin; Li, Jun, E-mail: SHUniverjunli@163.com; Fu, Yi-Zhou

2015-11-23

This study investigates the effect of hafnium doping on the density of states (DOSs) in HfZnSnO thin film transistors fabricated by dual-target magnetron co-sputtering system. The DOSs is extracted by temperature-dependent field-effect measurements, and they decrease from 1.1 × 10{sup 17} to 4.6 × 10{sup 16 }eV/cm{sup 3} with increasing the hafnium concentrations. The behavior of DOSs for the increasing hafnium concentration HfZnSnO thin film transistors can be confirmed by both the reduction of ΔV{sub T} under bias stress and the trapping charges calculated by capacitance voltage measurements. It suggests that the reduction in DOSs due to the hafnium doping is closely related with themore » bias stability and thermal stability.« less

Hafnium germanosilicate thin films for gate and capacitor dielectric applications: thermal stability studies

NASA Astrophysics Data System (ADS)

Addepalli, Swarna; Sivasubramani, Prasanna; El-Bouanani, Mohamed; Kim, Moon; Gnade, Bruce; Wallace, Robert

2003-03-01

The use of SiO_2-GeO2 mixtures in gate and capacitor dielectric applications is hampered by the inherent thermodynamic instability of germanium oxide. Studies to date have confirmed that germanium oxide is readily converted to elemental germanium [1,2]. In sharp contrast, germanium oxide is known to form stable compounds with transition metal oxides such as hafnium oxide (hafnium germanate, HfGeO_4) [3]. Thus, the incorporation of hafnium in SiO_2-GeO2 may be expected to enhance the thermal stability of germanium oxide via Hf-O-Ge bond formation. In addition, the introduction of a transition metal would simultaneously enhance the capacitance of the dielectric thereby permitting a thicker dielectric which reduces leakage current [4]. In this study, the thermal stability of PVD-grown hafnium germanosilicate (HfGeSiO) films was investigated. XPS, HR-TEM, C-V and I-V results of films after deposition and subsequent annealing treatments will be presented. The results indicate that the presence or formation of elemental germanium drastically affects the stability of the HfGeSiO films. This work is supported by DARPA through SPAWAR Grant No. N66001-00-1-8928, and the Texas Advanced Technology Program. References: [1] W. S. Liu, J .S. Chen, M.-A. Nicolet, V. Arbet-Engels, K. L. Wang, Journal of Applied Physics, 72, 4444 (1992), and, Applied Physics Letters, 62, 3321 (1993) [2] W. S. Liu, M. -A. Nicolet, H. -H. Park, B. -H. Koak, J. -W. Lee, Journal of Applied Physics, 78, 2631 (1995) [3] P. M. Lambert, Inorganic Chemistry, 37, 1352 (1998) [4] G. D. Wilk, R. M. Wallace and J. M. Anthony, Journal of Applied Physics, 89, 5243 (2001)

Highly efficient hydrogen release from formic acid using a graphitic carbon nitride-supported AgPd nanoparticle catalyst

NASA Astrophysics Data System (ADS)

Yao, Fang; Li, Xiao; Wan, Chao; Xu, Lixin; An, Yue; Ye, Mingfu; Lei, Zhao

2017-12-01

Bimetallic AgPd nanoparticles with various molar ratios immobilized on graphitic carbon nitride (g-C3N4) were successfully synthesized via a facile co-reduction approach. The powder XRD, XPS, TEM, EDX, ICP-AES and BET were employed to characterize the structure, size, composition and loading metal electronic states of the AgPd/g-C3N4 catalysts. The catalytic property of as-prepared catalysts for the dehydrogenation of formic acid (FA) with sodium formate (SF) as the additive was investigated. The performance of these catalysts, as indicated by the turnover frequency (TOF), depended on the composition of the prepared catalysts. Among all the AgPd/g-C3N4 catalysts tested, Ag9Pd91/g-C3N4 was found to be an exceedingly high activity for decomposing FA into H2 with TOF up to 480 h-1 at 323 K. The prepared catalyst is thus a potential candidate for triggering the widespread use of FA for H2 storage.

Nitride alloy layer formation of duplex stainless steel using nitriding process

NASA Astrophysics Data System (ADS)

Maleque, M. A.; Lailatul, P. H.; Fathaen, A. A.; Norinsan, K.; Haider, J.

2018-01-01

Duplex stainless steel (DSS) shows a good corrosion resistance as well as the mechanical properties. However, DSS performance decrease as it works under aggressive environment and at high temperature. At the mentioned environment, the DSS become susceptible to wear failure. Surface modification is the favourable technique to widen the application of duplex stainless steel and improve the wear resistance and its hardness properties. Therefore, the main aim of this work is to nitride alloy layer on the surface of duplex stainless steel by the nitriding process temperature of 400°C and 450°C at different time and ammonia composition using a horizontal tube furnace. The scanning electron microscopy and x-ray diffraction analyzer are used to analyse the morphology, composition and the nitrided alloy layer for treated DSS. The micro hardnesss Vickers tester was used to measure hardness on cross-sectional area of nitrided DSS. After nitriding, it was observed that the hardness performance increased until 1100 Hv0.5kgf compared to substrate material of 250 Hv0.5kgf. The thickness layer of nitride alloy also increased from 5μm until 100μm due to diffusion of nitrogen on the surface of DSS. The x-ray diffraction results showed that the nitride layer consists of iron nitride, expanded austenite and chromium nitride. It can be concluded that nitride alloy layer can be produced via nitriding process using tube furnace with significant improvement of microstructural and hardness properties.

In situ self-sacrificed template synthesis of vanadium nitride/nitrogen-doped graphene nanocomposites for electrochemical capacitors.

PubMed

Liu, Hong-Hui; Zhang, Hong-Ling; Xu, Hong-Bin; Lou, Tai-Ping; Sui, Zhi-Tong; Zhang, Yi

2018-03-15

Vanadium nitride and graphene have been widely used as pseudo-capacitive and electric double-layer capacitor electrode materials for electrochemical capacitors, respectively. However, the poor cycling stability of vanadium nitride and the low capacitance of graphene impeded their practical applications. Herein, we demonstrated an in situ self-sacrificed template method for the synthesis of vanadium nitride/nitrogen-doped graphene (VN/NGr) nanocomposites by the pyrolysis of a mixture of dicyandiamide, glucose, and NH 4 VO 3 . Vanadium nitride nanoparticles of the size in the range of 2 to 7 nm were uniformly embedded into the nitrogen-doped graphene skeleton. Furthermore, the VN/NGr nanocomposites with a high specific surface area and pore volume showed a high specific capacitance of 255 F g -1 at 10 mV s -1 , and an excellent cycling stability (94% capacitance retention after 2000 cycles). The excellent capacitive properties were ascribed to the excellent conductivity of nitrogen-doped graphene, high surface area, high pore volume, and the synergistic effect between vanadium nitride and nitrogen-doped graphene.

Article having an improved platinum-aluminum-hafnium protective coating

NASA Technical Reports Server (NTRS)

Nagaraj, Bangalore Aswatha (Inventor); Williams, Jeffrey Lawrence (Inventor)

2005-01-01

An article protected by a protective coating has a substrate and a protective coating having an outer layer deposited upon the substrate surface and a diffusion zone formed by interdiffusion of the outer layer and the substrate. The protective coating includes platinum, aluminum, no more than about 2 weight percent hafnium, and substantially no silicon. The outer layer is substantially a single phase.

Preparation of carbon nanoparticles and carbon nitride from high nitrogen compound

DOEpatents

Huynh, My Hang V [Los Alamos, NM; Hiskey, Michael A [Los Alamos, NM

2009-09-01

The high-nitrogen compound 3,6-di(azido)-1,2,4,5-tetrazine (DiAT) was synthesized by a relatively simple method and used as a precursor for the preparation of carbon nanospheres and nanopolygons, and nitrogen-rich carbon nitrides.

Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) Nanorods Superlattice (SL)

DTIC Science & Technology

2006-03-29

Final Report (Technical) 3. DATES COVERED 29-03-2005 to 29-05-2006 4. TITLE AND SUBTITLE Indium Gallium Nitride/ Gallium Nitride (InGaN/GaN...Institution: Quantum functional Semiconductor Research Center (QSRC), Dongguk University - Title of project: Indium Gallium Nitride/ Gallium Nitride...Accepted with minor revision Indium Gallium Nitride / Gallium Nitride (InGaN/ GaN) Nanorods Superlattice (SL) Abstract The growth condition, electrical

Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Bikramjeet; Singh, Paviter; Kumar, Akshay, E-mail: akshaykumar.tiet@gmail.com

2015-05-15

Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H{sub 3}BO{sub 3}). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications asmore » well boron neutron capture therapy (BNCT)« less

Synthesis of transparent nanocomposite monoliths for gamma scintillation

NASA Astrophysics Data System (ADS)

Liu, Chao; Hajagos, Tibor J.; Kishpaugh, David; Jin, Yunxia; Hu, Wei; Chen, Qi; Pei, Qibing

2015-08-01

During the past decade, inorganic nanoparticles/polymer nanocomposites have been intensively studied to provide a low cost, high performance alternative for gamma scintillation. However, the aggregation of nanoparticles often occurs even at low nanoparticle concentrations and thus deteriorates the transparency and performance of these nanocomposite scintillators. Here we report an efficient fabrication protocol of transparent nanocomposite monoliths based on surface modified hafnium oxide nanoparticles. Using hafnium oxide nanoparticles with surface-grafted methacrylate groups, highly transparent bulk-size nanocomposite monoliths (2 mm thick, transmittance at 550 nm >75%) are fabricated with nanoparticle loadings up to 40 wt% (net hafnium wt% up to 28.5%). These nanocomposite monoliths of 1 cm diameter and 2 mm thickness are capable of producing a full energy photopeak for 662 keV gamma rays, with the best deconvoluted photopeak energy resolution reaching 8%.

Visible-light-driven dynamic cancer therapy and imaging using graphitic carbon nitride nanoparticles.

PubMed

Heo, Nam Su; Lee, Sun Uk; Rethinasabapathy, Muruganantham; Lee, Eun Zoo; Cho, Hye-Jin; Oh, Seo Yeong; Choe, Sang Rak; Kim, Yeonho; Hong, Won G; Krishnan, Giribabu; Hong, Won Hi; Jeon, Tae-Joon; Jun, Young-Si; Kim, Hae Jin; Huh, Yun Suk

2018-09-01

Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesized and evaluated for photodynamic therapy (PDT) and cell imaging applications. NP-g-CN particles were prepared through an intercalation process using a rod-like melamine-cyanuric acid adduct (MCA) as the molecular precursor and a eutectic mixture of LiCl-KCl (45:55 wt%) as the reaction medium for polycondensation. The nano-dimensional NP-g-CN penetrated the malignant tumor cells with minimal hindrance and effectively generated reactive oxygen species (ROS) under visible light irradiation, which could ablate cancer cells. When excited by visible light irradiation (λ > 420 nm), NP-g-CN introduced to HeLa and cos-7 cells generated a significant amount of ROS and killed the cancerous cells selectively. The cytotoxicity of NP-g-CN was manipulated by altering the light irradiation and the BP-g-CN caused more damage to the cancer cells than normal cells at low concentrations. As a potential non-toxic organic nanomaterial, the synthesized NP-g-CN are biocompatible with less cytotoxicity than toxic inorganic materials. The combined effects of the high efficacy of ROS generation under visible light irradiation, low toxicity, and bio-compatibility highlight the potential of NP-g-CN for PDT and imaging without further modification. Copyright © 2018 Elsevier B.V. All rights reserved.

Hexagonal boron nitride nanoparticles decorated halloysite clay nanotubes as a potential hydrogen storage medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muthu, R. Naresh, E-mail: rnaresh7708@gmail.com; Rajashabala, S.; Kannan, R.

2016-05-23

The light weight and compact hydrogen storage materials is still prerequisite for the carbon free hydrogen fuel cell technology. In this work, the hydrogen storage performance of acid treated halloysite clay nanotubes (A-HNTs) and hexagonal boron nitride (h-BN) nanoparticles decorated acid treated halloysite nanoclay composite (A-HNT-h-BN) are demonstrated, where facile ultrasonic technique is adopted for the synthesis of A-HNT-h-BN nanoclay composite. Hydrogen storage studies were carried out using Sieverts-like hydrogenation setup. The A-HNTs and A-HNT-h-BN nanoclay composite were analyzed by XRD, FTIR, HRTEM, EDX, CHNS-elemental analysis and TGA. The A-HNT-h-BN nanoclay composite shows superior storage capacity of 2.19 wt% atmore » 50 °C compared to the A-HNTs (0.58 wt%). A 100% desorption of stored hydrogen is noted in the temperature range of 138–175 °C. The average binding energy of hydrogen was found to be 0.34 eV for the prepared A-HNT-h-BN nanoclay composite. The excellent storage capability of A-HNT-h-BN nanoclay composite towards hydrogen at ambient temperature may find bright perspective in hydrogen fuel cell technology in near future.« less

Hafnium-Based Bulk Metallic Glasses for Kinetic Energy Penetrators

DTIC Science & Technology

2004-12-01

uranium -based (DU) and tungsten- nickel -iron (W-Ni-Fe) composite kinetic energy (KE) munitions is primarily ascribed to their high densities (U: ρ...based on an invariant point identified in the hafnium- copper- nickel ternary system. They are denser than zirconium-based glass-forming compositions...depleted- uranium penetrators. 1. INTRODUCTION 1.1 Criterion for Effective Kinetic Energy Penetrator Performance The lethality of depleted

Targeting Endothelial Cells with Multifunctional GaN/Fe Nanoparticles

NASA Astrophysics Data System (ADS)

Braniste, Tudor; Tiginyanu, Ion; Horvath, Tibor; Raevschi, Simion; Andrée, Birgit; Cebotari, Serghei; Boyle, Erin C.; Haverich, Axel; Hilfiker, Andres

2017-08-01

In this paper, we report on the interaction of multifunctional nanoparticles with living endothelial cells. The nanoparticles were synthesized using direct growth of gallium nitride on zinc oxide nanoparticles alloyed with iron oxide followed by core decomposition in hydrogen flow at high temperature. Using transmission electron microscopy, we demonstrate that porcine aortic endothelial cells take up GaN-based nanoparticles suspended in the growth medium. The nanoparticles are deposited in vesicles and the endothelial cells show no sign of cellular damage. Intracellular inert nanoparticles are used as guiding elements for controlled transportation or designed spatial distribution of cells in external magnetic fields.

Designing nanoscale constructs from atomic thin sheets of graphene, boron nitride and gold nanoparticles for advanced material applications

NASA Astrophysics Data System (ADS)

Jasuja, Kabeer

2011-12-01

Nanoscale materials invite immense interest from diverse scientific disciplines as these provide access to precisely understand the physical world at their most fundamental atomic level. In concert with this aim of enhancing our understanding of the fundamental behavior at nanoscale, this dissertation presents research on three nanomaterials: Gold nanoparticles (GNPs), Graphene and ultra-thin Boron Nitride sheets (UTBNSs). The three-fold goals which drive this research are: incorporating mobility in nanoparticle based single-electron junction constructs, developing effective strategies to functionalize graphene with nano-forms of metal, and exfoliating ultrathin sheets of Boron Nitride. Gold nanoparticle based electronic constructs can achieve a new degree of operational freedom if nanoscale mobility is incorporated in their design. We achieved such a nano-electromechanical construct by incorporating elastic polymer molecules between GNPs to form 2-dimensional (2-D) molecular junctions which show a nanoscale reversible motion on applying macro scale forces. This GNP-polymer assembly works like a molecular spring opening avenues to maneuver nano components and store energy at nano-scale. Graphene is the first isolated nanomaterial that displays single-atom thickness. It exhibits quantum confinement that enables it to possess a unique combination of fascinating electronic, optical, and mechanical properties. Modifying the surface of graphene is extremely significant to enable its incorporation into applications of interest. We demonstrated the ability of chemically modified graphene sheets to act as GNP stabilizing templates in solution, and utilized this to process GNP composites of graphene. We discovered that GNPs synthesized by chemical or microwave reduction stabilize on graphene-oxide sheets to form snow-flake morphologies and bare-surfaces respectively. These hybrid nano constructs were extensively studied to understand the effect and nature of GNPs

Methods of forming boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J

A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boronmore » nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.« less

Direct electrochemistry of cytochrome c immobilized on titanium nitride/multi-walled carbon nanotube composite for amperometric nitrite biosensor.

PubMed

Haldorai, Yuvaraj; Hwang, Seung-Kyu; Gopalan, Anantha-Iyengar; Huh, Yun Suk; Han, Young-Kyu; Voit, Walter; Sai-Anand, Gopalan; Lee, Kwang-Pill

2016-05-15

In this report, titanium nitride (TiN) nanoparticles decorated multi-walled carbon nanotube (MWCNTs) nanocomposite is fabricated via a two-step process. These two steps involve the decoration of titanium dioxide nanoparticles onto the MWCNTs surface and a subsequent thermal nitridation. Transmission electron microscopy shows that TiN nanoparticles with a mean diameter of ≤ 20 nm are homogeneously dispersed onto the MWCNTs surface. Direct electrochemistry and electrocatalysis of cytochrome c immobilized on the MWCNTs-TiN composite modified on a glassy carbon electrode for nitrite sensing are investigated. Under optimum conditions, the current response is linear to its concentration from 1 µM to 2000 µM with a sensitivity of 121.5 µA µM(-1)cm(-2) and a low detection limit of 0.0014 µM. The proposed electrode shows good reproducibility and long-term stability. The applicability of the as-prepared biosensor is validated by the successful detection of nitrite in tap and sea water samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Transition metal nitride coated with atomic layers of Pt as a low-cost, highly stable electrocatalyst for the oxygen reduction reaction

DOE PAGES

Tian, Xinlong; Adzic, Radoslav R.; Luo, Junming; ...

2016-02-10

Here, the main challenges to the commercial viability of polymer electrolyte membrane fuel cells are (i) the high cost associated with using large amounts of Pt in fuel cell cathodes to compensate for the sluggish kinetics of the oxygen reduction reaction, (ii) catalyst degradation, and (iii) carbon-support corrosion. To address these obstacles, our group has focused on robust, carbon-free transition metal nitride materials with low Pt content that exhibit tunable physical and catalytic properties. Here, we report on the high performance of a novel catalyst with low Pt content, prepared by placing several layers of Pt atoms on nanoparticles ofmore » titanium nickel binary nitride. For the ORR, the catalyst exhibited a more than 400% and 200% increase in mass activity and specific activity, respectively, compared with the commercial Pt/C catalyst. It also showed excellent stability/durability, experiencing only a slight performance loss after 10,000 potential cycles, while TEM results showed its structure had remained intact. The catalyst’s outstanding performance may have resulted from the ultrahigh dispersion of Pt (several atomic layers coated on the nitride nanoparticles), and the excellent stability/durability may have been due to the good stability of nitride and synergetic effects between ultrathin Pt layer and the robust TiNiN support.« less

Inter-diffusion of copper and hafnium as studied by x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Pearson, Justin; Chourasia, A. R.

The Cu/Hf interface has been characterized by x-ray photoelectron spectroscopy. Thin films (thicknesses ranging from 100 nm to 150 nm) of hafnium were deposited on a silicon substrate. About 80 nm of copper was then deposited on such samples. The e-beam method was used for the deposition. The samples were annealed for 30 min at temperatures of 100, 200, 300, 400, and 500°C. The inter-diffusion of copper and hafnium was investigated by sequential sputter depth profiling and x-ray photoelectron spectroscopy. The interdiffusion in each case was analyzed by the Matano-Boltzmann's procedure using the Fick's second law. The interdiffusion coefficients and the width of the interface as determined from the data have been correlated with the annealing temperature. Supported by Organized Research, TAMU-Commerce.

The performance of hafnium and gadolinium self powered neutron detectors in the TREAT reactor

NASA Astrophysics Data System (ADS)

Imel, G. R.; Hart, P. R.

1996-05-01

The use of gadolinium and hafnium self powered neutron detectors in a transient reactor is described in this paper. The detectors were calibrated to the fission rate of U-235 using calibrated fission chambers; the calibration factors were tested in two reactors in steady state and found to be consistent. Calibration of the detectors in transient reactor conditions was done by using uranium wires that were analyzed by radiochemistry techniques to determine total fissions during the transient. This was correlated to the time-integrated current of the detectors during the transient. A temperature correction factor was derived to account for self-shielding effects in the hafnium and gadolinium detectors. The dynamic response of the detectors under transient conditions was studied, and found to be excellent.

Crystalline boron nitride aerogels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.

This disclosure provides methods and materials related to boron nitride aerogels. For example, one aspect relates to a method for making an aerogel comprising boron nitride, comprising: (a) providing boron oxide and an aerogel comprising carbon; (b) heating the boron oxide to melt the boron oxide and heating the aerogel; (c) mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide; and (d) converting at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride. Another aspect relates to a method for making an aerogel comprising boron nitride, comprising heating boron oxidemore » and an aerogel comprising carbon under flow of a nitrogen-containing gas, wherein boron oxide vapor and the nitrogen-containing gas convert at least a portion of the carbon to boron nitride to obtain the aerogel comprising boron nitride.« less

Cellulose nanobiocomposites with reinforcement of boron nitride: study of thermal, oxygen barrier and chemical resistant properties.

PubMed

Swain, Sarat K; Dash, Satyabrata; Behera, Chandini; Kisku, Sudhir K; Behera, Lingaraj

2013-06-20

A series of cellulose based nanobiocomposites (cellulose/BN) were prepared with incorporation of various percentage of nano boron nitride (BN). The interaction between cellulose and boron nitride was studied by Fourier transform infrared spectroscopy (FTIR). The structure of cellulose/BN nanobiocomposites was investigated by XRD, FESEM, and HRTEM. It was observed that the boron nitride nanoparticles were dispersed within cellulose matrix due to intercalation and partial exfoliation. The quantitative identification of nanobiocomposites was investigated by selected area electron diffraction (SAED). Thermal stabilities of the prepared nanobiocomposites were measured by thermo gravimetric analysis (TGA) and it was found that thermal stability of the nanobiocomposites was higher than the virgin cellulose. The oxygen barrier property of cellulose/BN nanobiocomposites was measured using a gas permeameter and a substantial reduction in oxygen permeability due to increase in boron nitride loading was observed. Further it was noticed that the chemical resistance of the nanobiocomposites was more than the virgin cellulose. Hence, the prepared nanobiocomposite may be widely used for insulating and temperature resistant packaging materials. Copyright © 2013 Elsevier Ltd. All rights reserved.

"Decarbonization" of an imino N-heterocyclic carbene via triple benzyl migration from hafnium

USDA-ARS?s Scientific Manuscript database

An imino N-heterocyclic carbene underwent three sequential benzyl migrations upon reaction with tetrabenzylhafnium, resulting in complete removal of the carbene carbon from the ligand. The resulting eneamido-amidinato hafnium complex showed alkene polymerization activity comparable to that of a prec...

Ni nanoparticles@Ni-Mo nitride nanorod arrays: a novel 3D-network hierarchical structure for high areal capacitance hybrid supercapacitors.

PubMed

Ruan, Yunjun; Lv, Lin; Li, Zhishan; Wang, Chundong; Jiang, Jianjun

2017-11-23

Because of the advanced nature of their high power density, fast charge/discharge time, excellent cycling stability, and safety, supercapacitors have attracted intensive attention for large-scale applications. Nevertheless, one of the obstacles for their further development is their low energy density caused by sluggish redox reaction kinetics, low electroactive electrode materials, and/or high internal resistance. Here, we develop a facile and simple nitridation process to successfully synthesize hierarchical Ni nanoparticle decorated Ni 0.2 Mo 0.8 N nanorod arrays on a nickel foam (Ni-Mo-N NRA/NF) from its NiMoO 4 precursor, which delivers a high areal capacity of 2446 mC cm -2 at a current density of 2 mA cm -2 and shows outstanding cycling stability. The superior performance of the Ni-Mo-N NRA/NF can be ascribed to the metallic conductive nature of the Ni-Mo nitride, the fast surface redox reactions for the electrolyte ions and electrode materials, and the low contacted resistance between the active materials and the current collectors. Furthermore, a hybrid supercapacitor (HSC) is assembled using the Ni-Mo-N NRA/NF as the positive electrode and reduced graphene oxide (RGO) as the negative electrode. The optimized HSC exhibits excellent electrochemical performance with a high energy density of 40.9 W h kg -1 at a power density of 773 W kg -1 and a retention of 80.1% specific capacitance after 6000 cycles. These results indicate that the Ni-Mo-N NRA/NF have a promising potential for use in high-performance supercapacitors.

Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

NASA Astrophysics Data System (ADS)

Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

2017-02-01

This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' }) and imaginary (ɛ ^' ' }) parts of the complex permittivity (ɛ ^*) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

Crystalline boron nitride aerogels

DOEpatents

Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

2017-04-04

This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

Nanoparticle radio-enhancement: principles, progress and application to cancer treatment

NASA Astrophysics Data System (ADS)

Kuncic, Zdenka; Lacombe, Sandrine

2018-01-01

Enhancement of radiation effects by high-atomic number nanoparticles (NPs) has been increasingly studied for its potential to improve radiotherapeutic efficacy. The underlying principle of NP radio-enhancement is the potential to release copious electrons into a nanoscale volume, thereby amplifying radiation-induced biological damage. While the vast majority of studies to date have focused on gold nanoparticles with photon radiation, an increasing number of experimental, theoretical and simulation studies have explored opportunities offered by other NPs (e.g. gadolinium, platinum, iron oxide, hafnium) and other therapeutic radiation sources such as ion beams. It is thus of interest to the research community to consolidate findings from the different studies and summarise progress to date, as well as to identify strategies that offer promising opportunities for clinical translation. This is the purpose of this Topical Review.

PROCESS OF RECOVERING ZIRCONIUM VALUES FROM HAFNIUM VALUES BY SOLVENT EXTRACTION WITH AN ALKYL PHOSPHATE

DOEpatents

Peppard, D.F.

1960-02-01

A process of separating hafnium nitrate from zirconium nitrate contained in a nitric acid solution by selectively. extracting the zirconium nitrate with a water-immiscible alkyl phosphate is reported.

Toward Edge-Defined Holey Boron Nitride Nanosheets

NASA Technical Reports Server (NTRS)

Lin, Yi; Liao, Yunlong; Chen, Zhongfan; Connell, John W.

2015-01-01

"Holey" two-dimensional (2D) nanosheets with well-defined holy morphology and edge chemistry are highly desirable for applications such as energy storage, catalysis, sensing, transistors, and molecular transport/separation. For example, holey grapheme is currently under extensive investigation for energy storage applications because of the improvement in ion transport due to through the thickness pathways provided by the holes. Without the holes, the 2D materials have significant limitations for such applications in which efficient ion transport is important. As part of an effort to apply this approach to other 2D nanomaterials, a method to etch geometrically defined pits or holes on the basal plane surface of hexagonal boron nitride (h-BN) nanosheets has been developed. The etching, conducted via heating in ambient air using metal nanoparticles as catalysts, was facile, controllable, and scalable. Starting h-BN layered crystals were etched and subsequently exfoliated into boron nitride nanosheets (BNNSs). The as-etched and exfoliated h-BN nanosheets possessed defined pit and hole shapes that were comprised of regulated nanostructures at the edges. The current finding are the first step toward the bulk preparation of holey BNNSs with defined holes and edges.

Ferroelectric memory based on molybdenum disulfide and ferroelectric hafnium oxide

NASA Astrophysics Data System (ADS)

Yap, Wui Chung; Jiang, Hao; Xia, Qiangfei; Zhu, Wenjuan

Recently, ferroelectric hafnium oxide (HfO2) was discovered as a new type of ferroelectric material with the advantages of high coercive field, excellent scalability (down to 2.5 nm), and good compatibility with CMOS processing. In this work, we demonstrate, for the first time, 2D ferroelectric memories with molybdenum disulfide (MoS2) as the channel material and aluminum doped HfO2 as the ferroelectric gate dielectric. A 16 nm thick layer of HfO2, doped with 5.26% aluminum, was deposited via atomic layer deposition (ALD), then subjected to rapid thermal annealing (RTA) at 1000 °C, and the polarization-voltage characteristics of the resulting metal-ferroelectric-metal (MFM) capacitors were measured, showing a remnant polarization of 0.6 μC/cm2. Ferroelectric memories with embedded ferroelectric hafnium oxide stacks and monolayer MoS2 were fabricated. The transfer characteristics after program and erase pulses revealed a clear ferroelectric memory window. In addition, endurance (up to 10,000 cycles) of the devices were tested and effects associated with ferroelectric materials, such as the wake-up effect and polarization fatigue, were observed. This research can potentially lead to advances of 2D materials in low-power logic and memory applications.

Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

NASA Astrophysics Data System (ADS)

Gaballa, Osama Gaballa Bahig

Carbides, nitrides, and borides ceramics are of interest for many applications because of their high melting temperatures and good mechanical properties. Wear-resistant coatings are among the most important applications for these materials. Materials with high wear resistance and high melting temperatures have the potential to produce coatings that resist degradation when subjected to high temperatures and high contact stresses. Among the carbides, Al4SiC4 is a low density (3.03 g/cm3), high melting temperature (>2000°C) compound, characterized by superior oxidation resistance, and high compressive strength. These desirable properties motivated this investigation to (1) obtain high-density Al4SiC4 at lower sintering temperatures by hot pressing, and (2) to enhance its mechanical properties by adding WC and TiC to the Al4SiC4. Also among the carbides, tantalum carbide and hafnium carbide have outstanding hardness; high melting points (3880°C and 3890°C respectively); good resistance to chemical attack, thermal shock, and oxidation; and excellent electronic conductivity. Tantalum hafnium carbide (Ta4HfC 5) is a 4-to-1 ratio of TaC to HfC with an extremely high melting point of 4215 K (3942°C), which is the highest melting point of all currently known compounds. Due to the properties of these carbides, they are considered candidates for extremely high-temperature applications such as rocket nozzles and scramjet components, where the operating temperatures can exceed 3000°C. Sintering bulk components comprised of these carbides is difficult, since sintering typically occurs above 50% of the melting point. Thus, Ta4 HfC5 is difficult to sinter in conventional furnaces or hot presses; furnaces designed for very high temperatures are expensive to purchase and operate. Our research attempted to sinter Ta4HfC5 in a hot press at relatively low temperature by reducing powder particle size and optimizing the powder-handling atmosphere, milling conditions, sintering

PECVD silicon-rich nitride and low stress nitride films mechanical characterization using membrane point load deflection

NASA Astrophysics Data System (ADS)

Bagolini, Alvise; Picciotto, Antonino; Crivellari, Michele; Conci, Paolo; Bellutti, Pierluigi

2016-02-01

An analysis of the mechanical properties of plasma enhanced chemical vapor (PECVD) silicon nitrides is presented, using micro fabricated silicon nitride membranes under point load deflection. The membranes are made of PECVD silicon-rich nitride and low stress nitride films. The mechanical performance of the bended membranes is examined both with analytical models and finite element simulation in order to extract the elastic modulus and residual stress values. The elastic modulus of low stress silicon nitride is calculated using stress free analytical models, while for silicon-rich silicon nitride and annealed low stress silicon nitride it is estimated with a pre-stressed model of point-load deflection. The effect of annealing both in nitrogen and hydrogen atmosphere is evaluated in terms of residual stress, refractive index and thickness variation. It is demonstrated that a hydrogen rich annealing atmosphere induces very little change in low stress silicon nitride. Nitrogen annealing effects are measured and shown to be much higher in silicon-rich nitride than in low stress silicon nitride. An estimate of PECVD silicon-rich nitride elastic modulus is obtained in the range between 240-320 GPa for deposited samples and 390 GPa for samples annealed in nitrogen atmosphere. PECVD low stress silicon nitride elastic modulus is estimated to be 88 GPa as deposited and 320 GPa after nitrogen annealing.

High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Park, Cheol (Inventor); Bryant, Robert George (Inventor); Lowther, Sharon E. (Inventor)

2015-01-01

Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

Fabrication of Antireflective Sub-Wavelength Structures on Silicon Nitride Using Nano Cluster Mask for Solar Cell Application

PubMed Central

2009-01-01

We have developed a simple and scalable approach for fabricating sub-wavelength structures (SWS) on silicon nitride by means of self-assembled nickel nanoparticle masks and inductively coupled plasma (ICP) ion etching. Silicon nitride SWS surfaces with diameter of 160–200 nm and a height of 140–150 nm were obtained. A low reflectivity below 1% was observed over wavelength from 590 to 680 nm. Using the measured reflectivity data in PC1D, the solar cell characteristics has been compared for single layer anti-reflection (SLAR) coatings and SWS and a 0.8% improvement in efficiency has been seen. PMID:20596409

Method for preparing actinide nitrides

DOEpatents

Bryan, G.H.; Cleveland, J.M.; Heiple, C.R.

1975-12-01

Actinide nitrides, and particularly plutonium and uranium nitrides, are prepared by reacting an ammonia solution of an actinide compound with an ammonia solution of a reactant or reductant metal, to form finely divided actinide nitride precipitate which may then be appropriately separated from the solution. The actinide nitride precipitate is particularly suitable for forming nuclear fuels.

Decorating CoP and Pt Nanoparticles on Graphitic Carbon Nitride Nanosheets to Promote Overall Water Splitting by Conjugated Polymers.

PubMed

Pan, Zhiming; Zheng, Yun; Guo, Fangsong; Niu, Pingping; Wang, Xinchen

2017-01-10

The splitting of water into H 2 and O 2 using solar energy is one of the key steps in artificial photosynthesis for the future production of renewable energy. Here, we show the first use of CoP and Pt nanoparticles as dual co-catalysts to modify graphitic carbon nitride (g-C 3 N 4 ) polymer to achieve overall water splitting under visible light irradiation. Our findings demonstrate that loading dual co-catalysts on delaminated g-C 3 N 4 imparts surface redox sites on the g-C 3 N 4 nanosheets that can not only promote catalytic kinetics but also promote charge separation and migration in the soft interface, thus improving the photocatalytic efficiency for overall water splitting. This robust, abundant, and stable photocatalyst based on covalent organic frameworks is demonstrated to hold great promise by forming heterojunctions with CoP and Pt for catalyzing the direct splitting of water into stoichiometric H 2 and O 2 using energy from photons. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

NASA Technical Reports Server (NTRS)

Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

1983-01-01

A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

One-step route to a hybrid TiO2/Ti x W1-x N nanocomposite by in situ selective carbothermal nitridation.

PubMed

Schnepp, Zoë; Hollamby, Martin J; Tanaka, Masahiko; Matsushita, Yoshitaka; Katsuya, Yoshio; Sakka, Yoshio

2012-06-01

Metal oxide/nitride nanocomposites have many existing and potential applications, e.g. in energy conversion or ammonia synthesis. Here, a hybrid oxide/nitride nanocomposite (anatase/Ti x W 1- x N) was synthesized by an ammonia-free sol-gel route. Synchrotron x-ray diffraction, complemented with electron microscopy and thermogravimetric analysis, was used to study the structure, composition and mechanism of formation of the nanocomposite. The nanocomposite contained nanoparticles (<5 nm diameter) of two highly intermixed phases. This was found to arise from controlled nucleation and growth of a single oxide intermediate from the gel precursor, followed by phase separation and in situ selective carbothermal nitridation. Depending on the preparation conditions, the composition varied from anatase/Ti x W 1- x N at low W content to an isostructural mixture of Ti-rich and W-rich Ti x W 1- x N at high W content. In situ selective carbothermal nitridation offers a facile route to the synthesis of nitride-oxide nanocomposites. This conceptually new approach is a significant advance from previous methods, which generally require ammonolysis of a pre-synthesized oxide.

Optical Properties and Plasmonic Performance of Titanium Nitride

PubMed Central

Patsalas, Panos; Kalfagiannis, Nikolaos; Kassavetis, Spyros

2015-01-01

Titanium nitride (TiN) is one of the most well-established engineering materials nowadays. TiN can overcome most of the drawbacks of palsmonic metals due to its high electron conductivity and mobility, high melting point and due to the compatibility of its growth with Complementary Metal Oxide Semiconductor (CMOS) technology. In this work, we review the dielectric function spectra of TiN and we evaluate the plasmonic performance of TiN by calculating (i) the Surface Plasmon Polariton (SPP) dispersion relations and (ii) the Localized Surface Plasmon Resonance (LSPR) band of TiN nanoparticles, and we demonstrate a significant plasmonic performance of TiN.

Structural stability and electronic structure of transition metal compound: HfN

NASA Astrophysics Data System (ADS)

Sarwan, Madhu; Shukoor, V. Abdul; Singh, Sadhna

2018-05-01

The structural stability of transition metal nitride (HfN) has been investigated using density functional theory (DFT) with the help of Quantum-espresso codes. Our calculations confirm that the hafnium nitride (HfN) is stable in zinc-blende (B3) and rock-salt (B1) type structure. We have also reported the structural and electronic properties of HfN compound. These structural properties have been compared with experimental and theoretical data available on this compound.

Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2 Gyr ago.

PubMed

Næraa, T; Scherstén, A; Rosing, M T; Kemp, A I S; Hoffmann, J E; Kokfelt, T F; Whitehouse, M J

2012-05-30

Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature. Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time, with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon. Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics. In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago, suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record. Here we report in situ uranium-lead, hafnium and oxygen isotope data from zircons of basement rocks in southern West Greenland across the critical time period during which modern-like tectonic regimes could have initiated. Our data show pronounced differences in the hafnium isotope-time patterns across this interval, requiring changes in the characteristics of the magmatic protolith. The observations suggest that 3.9-3.5-Gyr-old rocks differentiated from a >3.9-Gyr-old source reservoir with a chondritic to slightly depleted hafnium isotope composition. In contrast, rocks formed after 3.2 Gyr ago register the first additions of juvenile depleted material (that is, new mantle-derived crust) since 3.9 Gyr ago, and are characterized by striking shifts in hafnium isotope ratios similar to those shown by Phanerozoic subduction-related orogens. These data suggest a transitional period 3.5-3.2 Gyr ago from an ancient (3.9-3.5 Gyr old) crustal evolutionary regime unlike that of modern plate tectonics to a geodynamic setting after 3.2 Gyr ago that involved juvenile crust generation by plate

The elevated temperature mechanical properties of silicon nitride/boron nitride fibrous monoliths

NASA Astrophysics Data System (ADS)

Trice, Rodney Wayne

A unique, all-ceramic material capable of non-brittle fracture via crack deflection has been characterized from 25sp°C through 1400sp°C. This material, called fibrous monoliths (FMs), was comprised of unidirectionally aligned 250 mum diameter cells of silicon nitride surrounded by 10 mum thick cell boundaries of boron nitride. Six weight percent yttria and two weight percent alumina were added to the silicon nitride to aid in densification. TEM experiments revealed that the sintering aids used to densify the silicon nitride cells were migrating into the boron nitride cell boundary during hot-pressing and that a fine network of micro-cracks existed between basal planes of boron nitride. Elevated temperature four point bending tests were performed on fibrous monolith ceramics from room temperature through 1400sp°C. Peak strengths of FMs averaged 510 MPa for specimens tested at room temperature through 176 MPa at 1400sp°C. Work of fractures ranged from 7300 J/msp2 to 3200 J/msp2 under the same temperature conditions. The interfacial fracture energy of boron nitride, GammasbBN, as a function of temperature has been determined using the Charalambides method. The fracture energy of boron nitride is approximately 40 J/msp2 and remained constant from 25sp°C through 950sp°C. A sharp increase in GammasbBN, to about 60 J/msp2, was observed at 1000sp°C-1050sp°C. This increase in GammasbBN was attributed to interactions of the crack tip with the cell boundary glassy phase. Subsequent measurements at 1075sp°C indicated a marked decrease in GammasbBN to near 40 J/msp2 before plateauing at 17-20 J/msp2 in the 1200sp°C-1300sp°C regime. The Mode I fracture toughness of silicon nitride was also determined using the single edge precracked beam method as a function of temperature. The He and Hutchinson model relating crack deflection at an interface to the Dundurs' parameter was applied to the current data set using the temperature dependent fracture energies of the boron

Ion-beam nitriding of steels

NASA Technical Reports Server (NTRS)

Salik, J.

1984-01-01

The application of the ion beam technique to the nitriding of steels is described. It is indicated that the technique can be successfully applied to nitriding. Some of the structural changes obtained by this technique are similar to those obtained by ion nitriding. The main difference is the absence of the iron nitride diffraction lines. It is found that the dependence of the resultant microhardness on beam voltage for super nitralloy is different from that of 304 stainless steel.

Gallium nitride optoelectronic devices

NASA Technical Reports Server (NTRS)

Chu, T. L.; Chu, S. S.

1972-01-01

The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

Cathodoluminescence Study of Hafnium Oxide

NASA Astrophysics Data System (ADS)

Purcell, Emily; Hengehold, Robert; McClory, John

2011-10-01

Hafnium dioxide (HfO2) is increasingly being used in place of silicon oxide as a gate insulator in field effect transistors. This is primarily due to its high dielectric constant, κ, of 25. Samples of HfO2 were grown by either atomic layer deposition (ALD) or pulsed laser deposition (PLD), with the PLD samples having assorted substrate temperatures during deposition (300 C, 500 C, and 750 C). Cathodoluminescence (CL) was chosen as the technique used for studying these HfO2 samples. The CL system used was capable of beam energies ranging from 1 keV to 20 keV and beam currents ranging from 10 μA to 50 μA. A Monte Carlo calculation using CASINO software was performed in order to determine the beam energy for the desired depth of penetration. Measurements were taken at sample temperatures ranging from 7K (closed cycled cryostat) to 300K (room temperature), as well as at various beam energies and beam currents. Comparison will be made between the PLD and ALD spectra.

Boron Nitride Nanoribbons from Exfoliation of Boron Nitride Nanotubes

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh; Hurst, Janet; Santiago, Diana

2017-01-01

Two types of boron nitride nanotubes (BNNTs) were exfoliated into boron nitride nanoribbons (BNNR), which were identified using transmission electron microscopy: (1) commercial BNNTs with thin tube walls and small diameters. Tube unzipping was indicated by a large decrease of the sample's surface area and volume for pores less than 2 nm in diameter. (2) BNNTs with large diameters and thick walls synthesized at NASA Glenn Research Center. Here, tube unraveling was indicated by a large increase in external surface area and pore volume. For both, the exfoliation process was similar to the previous reported method to exfoliate commercial hexagonal boron nitride (hBN): Mixtures of BNNT, FeCl3, and NaF (or KF) were sequentially treated in 250 to 350 C nitrogen for intercalation, 500 to 750 C air for exfoliation, and finally HCl for purification. Property changes of the nanosized boron nitride throughout this process were also similar to the previously observed changes of commercial hBN during the exfoliation process: Both crystal structure (x-ray diffraction data) and chemical properties (Fourier-transform infrared spectroscopy data) of the original reactant changed after intercalation and exfoliation, but most (not all) of these changes revert back to those of the reactant once the final, purified products are obtained.

Preparation of the highly dispersed powder of titanium carbonitride by SHS azide technology with previous partial nitriding

NASA Astrophysics Data System (ADS)

Amosov, A. P.; Markov, Yu M.; Dobrovolskaya, R. A.; Nikolaeva, E. N.

2017-02-01

It is shown that the powder of very hard refractory titanium carbonitride (TiC0.5N0.5) is the basis of tungsten-free hard alloys which are prospective for application as inexpensive cutting tools. The finer the powder of titanium carbonitrideis, the moreenhanced properties of hard alloys, sintered from the powder, are. An opportunity to reduce the particle size of the titanium carbonitride powder obtained by energy-saving azide technology of self-propagating high-temperature synthesis at the cost of reducing the particle size of the initial titanium powderwas investigated. To ensure the safety of the grinding process of the initial metal titanium powder, it was offered to nitride a Ti powder partially into a TiN0.2 compound. Such partial nitriding was performed by the azidetechnology with lack of sodium azide (NaN3) as a nitriding reagent. After intensive grinding in the planetary ball mill, the TiN0.2 powder turned into a superfine powder with an ultrafine structure. This powder was capable of nitriding and carburizing in the azide technology with formation of superfine pure powder agglomerates which are composed of ultrafine and nano-particles of TiC0.5N0.5.

Self-cleaning and surface chemical reactions during hafnium dioxide atomic layer deposition on indium arsenide.

PubMed

Timm, Rainer; Head, Ashley R; Yngman, Sofie; Knutsson, Johan V; Hjort, Martin; McKibbin, Sarah R; Troian, Andrea; Persson, Olof; Urpelainen, Samuli; Knudsen, Jan; Schnadt, Joachim; Mikkelsen, Anders

2018-04-12

Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor-oxide interface. Here, we directly observe the chemical reactions at the surface during the first cycle of hafnium dioxide deposition on indium arsenide under realistic synthesis conditions using photoelectron spectroscopy. We find that the widely used ligand exchange model of the ALD process for the removal of native oxide on the semiconductor and the simultaneous formation of the first hafnium dioxide layer must be significantly revised. Our study provides substantial evidence that the efficiency of the self-cleaning process and the quality of the resulting semiconductor-oxide interface can be controlled by the molecular adsorption process of the ALD precursors, rather than the subsequent oxide formation.

Stable tetragonal phase and magnetic properties of Fe-doped HfO2 nanoparticles

NASA Astrophysics Data System (ADS)

Sales, T. S. N.; Cavalcante, F. H. M.; Bosch-Santos, B.; Pereira, L. F. D.; Cabrera-Pasca, G. A.; Freitas, R. S.; Saxena, R. N.; Carbonari, A. W.

2017-05-01

In this paper, the effect in structural and magnetic properties of iron doping with concentration of 20% in hafnium dioxide (HfO2) nanoparticles is investigated. HfO2 is a wide band gap oxide with great potential to be used as high-permittivity gate dielectrics, which can be improved by doping. Nanoparticle samples were prepared by sol-gel chemical method and had their structure, morphology, and magnetic properties, respectively, investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with electron back scattering diffraction (EBSD), and magnetization measurements. TEM and SEM results show size distribution of particles in the range from 30 nm to 40 nm with small dispersion. Magnetization measurements show the blocking temperature at around 90 K with a strong paramagnetic contribution. XRD results show a major tetragonal phase (94%).

Method to synthesize bulk iron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monson, Todd; Lavernia, Enrique J.; Zheng, Baolong

Bulk iron nitride can be synthesized from iron nitride powder by spark plasma sintering. The iron nitride can be spark plasma sintered at a temperature of less than 600°C. and a pressure of less than 600 MPa, with 400 MPa or less most often being sufficient. High pressure SPS can consolidate dense iron nitrides at a lower temperature to avoid decomposition. The higher pressure and lower temperature of spark discharge sintering avoids decomposition and limits grain growth, enabling enhanced magnetic properties. The method can further comprise synthesis of nanocrystalline iron nitride powders using two-step reactive milling prior to high-pressure sparkmore » discharge sintering.« less

Surface modification of 17-4PH stainless steel by DC plasma nitriding and titanium nitride film duplex treatment

NASA Astrophysics Data System (ADS)

Qi, F.; Leng, Y. X.; Huang, N.; Bai, B.; Zhang, P. Ch.

2007-04-01

17-4PH stainless steel was modified by direct current (DC) plasma nitriding and titanium nitride film duplex treatment in this study. The microstructure, wear resistance and corrosion resistance were characterized by X-ray diffraction (XRD), pin-on-disk tribological test and polarization experiment. The results revealed that the DC plasma nitriding pretreatment was in favor of improving properties of titanium nitride film. The corrosion resistance and wear resistance of duplex treatment specimen was more superior to that of only coated titanium nitride film.

Aminopyridinate-FI hybrids, their hafnium and titanium complexes, and their application in the living polymerization of 1-hexene.

PubMed

Haas, Isabelle; Dietel, Thomas; Press, Konstantin; Kol, Moshe; Kempe, Rhett

2013-10-11

Based on two well-established ligand systems, the aminopyridinato (Ap) and the phenoxyimine (FI) ligand systems, new Ap-FI hybrid ligands were developed. Four different Ap-FI hybrid ligands were synthesized through a simple condensation reaction and fully characterized. The reaction of hafnium tetrabenzyl with all four Ap-FI hybrid ligands exclusively led to mono(Ap-FI) complexes of the type [(Ap-FI)HfBn2 ]. The ligands acted as tetradentate dianionic chelates. Upon activation with tris(pentafluorophenyl)borane, the hafnium-dibenzyl complexes led to highly active catalysts for the polymerization of 1-hexene. Ultrahigh molecular weights and extremely narrow polydispersities support the living nature of this polymerization process. A possible deactivation product of the hafnium catalysts was characterized by single-crystal X-ray analysis and is discussed. The coordination modes of these new ligands were studied with the help of model titanium complexes. The reaction of titanium(IV) isopropoxide with ligand 1 led to a mono(Ap-FI) complex, which showed the desired fac-mer coordination mode. Titanium (IV) isopropoxide reacted with ligand 4 to give a complex of the type [(ApH-FI)2 Ti(OiPr)2 ], which featured the ligand in its monoanionic form. The two titanium complexes were characterized by X-ray crystal-structure analysis. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Boron nitride composites

DOEpatents

Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

2016-02-16

According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

Method of manufacture of atomically thin boron nitride

DOEpatents

Zettl, Alexander K

2013-08-06

The present invention provides a method of fabricating at least one single layer hexagonal boron nitride (h-BN). In an exemplary embodiment, the method includes (1) suspending at least one multilayer boron nitride across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure. The present invention also provides a method of fabricating single layer hexagonal boron nitride. In an exemplary embodiment, the method includes (1) providing multilayer boron nitride suspended across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure.

Thermal conversion of an iron nitride-silicon nitride precursor into a ferromagnetic nanocomposite

NASA Astrophysics Data System (ADS)

Maya, L.; Thompson, J. R.; Song, K. J.; Warmack, R. J.

1998-01-01

Iron nitride films, FeN, in a pure form and in the form of a nanocomposite in silicon nitride were prepared by reactive sputtering using iron or iron disilicide, respectively, as targets in a nitrogen plasma. Iron nitride decomposes into the elements by heating in vacuum to 800 °C. Intermediate phases such as Fe2N or Fe4N form at lower temperatures. The nanocomposites contain the iron phases as particles with an average size of ˜5 nm dispersed in the amorphous silicon nitride matrix. The magnetic properties of the nanocomposites were established. The precursor FeN-Si3N4 film is paramagnetic, while the Fe-Si3N4, obtained by heating in vacuum, is ferromagnetic and shows typical superparamagnetic behavior. These films are of interest as recording media with superior chemical and mechanical stability and may be encoded by localized heating.

Processing and characterization of boron carbide-hafnium diboride ceramics

NASA Astrophysics Data System (ADS)

Brown-Shaklee, Harlan James

Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB2 sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB2 powder in part by removing oxides at the HfB2 surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB2 by 150°C compared to carbon, which reduced the hot pressing temperature by ˜50°C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated. Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB2. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB2. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B6.5 C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB2, respectively, which facilitate densification. Evaluation of the thermal conductivity (kth) between room temperature and 2000°C suggested that the stoichiometry of the boron carbide additives did not significantly affect kth of HfB2-BxC composites. The improved sinterability and the high kth (˜110 W/m-K at 300K and ˜90 W/m-K at 1000°C ) of HfB2-BxC ceramics make them excellent candidates for isotopically enriched reactor control materials.

Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates

DTIC Science & Technology

2013-02-01

Nord, J.; Albe, K.; Erhart, P.; Nordlund, K. Modelling of Compound Semiconductors: Analytical Bond-order Potential for Gallium , Nitrogen and Gallium ...Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates by Iskander G. Batyrev, Chi-Chin Wu...Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates Iskander G. Batyrev and N. Scott Weingarten Weapons and

Hard carbon nitride and method for preparing same

DOEpatents

Haller, Eugene E.; Cohen, Marvin L.; Hansen, William L.

1992-01-01

Novel crystalline .alpha. (silicon nitride-like)-carbon nitride and .beta. (silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate.

Laser pyrolysis fabrication of ferromagnetic gamma'-Fe4N and FeC nanoparticles

NASA Technical Reports Server (NTRS)

Grimes, C. A.; Qian, D.; Dickey, E. C.; Allen, J. L.; Eklund, P. C.

2000-01-01

Using the laser pyrolysis method, single phase gamma'-Fe4N nanoparticles were prepared by a two step method involving preparation of nanoscale iron oxide and a subsequent gas-solid nitridation reaction. Single phase Fe3C and Fe7C3 could be prepared by laser pyrolysis from Fe(CO)5 and 3C2H4 directly. Characterization techniques such as XRD, TEM and vibrating sample magnetometer were used to measure phase structure, particle size and magnetic properties of these nanoscale nitride and carbide particles. c2000 American Journal of Physics.

Hard carbon nitride and method for preparing same

DOEpatents

Haller, E.E.; Cohen, M.L.; Hansen, W.L.

1992-05-05

Novel crystalline [alpha](silicon nitride-like)-carbon nitride and [beta](silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate. 1 figure.

P-type gallium nitride

DOEpatents

Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

1997-08-12

Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

P-type gallium nitride

DOEpatents

Rubin, Michael; Newman, Nathan; Fu, Tracy; Ross, Jennifer; Chan, James

1997-01-01

Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5.times.10.sup.11 /cm.sup.3 and hole mobilities of about 500 cm.sup.2 /V-sec, measured at 250.degree. K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.

Experimental observation of boron nitride chains.

PubMed

Cretu, Ovidiu; Komsa, Hannu-Pekka; Lehtinen, Ossi; Algara-Siller, Gerardo; Kaiser, Ute; Suenaga, Kazu; Krasheninnikov, Arkady V

2014-12-23

We report the formation and characterization of boron nitride atomic chains. The chains were made from hexagonal boron nitride sheets using the electron beam inside a transmission electron microscope. We find that the stability and lifetime of the chains are significantly improved when they are supported by another boron nitride layer. With the help of first-principles calculations, we prove the heteroatomic structure of the chains and determine their mechanical and electronic properties. Our study completes the analogy between various boron nitride and carbon polymorphs, in accordance with earlier theoretical predictions.

Metal–Organic Nanosheets Formed via Defect-Mediated Transformation of a Hafnium Metal–Organic Framework

PubMed Central

2017-01-01

We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed “double cluster” (Hf12O8(OH)14), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal–organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal–organic nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions, suggesting that defect-ordered MOFs could be a productive route to porous two-dimensional materials. PMID:28343394

Metal-Organic Nanosheets Formed via Defect-Mediated Transformation of a Hafnium Metal-Organic Framework.

PubMed

Cliffe, Matthew J; Castillo-Martínez, Elizabeth; Wu, Yue; Lee, Jeongjae; Forse, Alexander C; Firth, Francesca C N; Moghadam, Peyman Z; Fairen-Jimenez, David; Gaultois, Michael W; Hill, Joshua A; Magdysyuk, Oxana V; Slater, Ben; Goodwin, Andrew L; Grey, Clare P

2017-04-19

We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed "double cluster" (Hf 12 O 8 (OH) 14 ), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal-organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal-organic nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions, suggesting that defect-ordered MOFs could be a productive route to porous two-dimensional materials.

X-ray detection capabilities of plastic scintillators incorporated with hafnium oxide nanoparticles surface-modified with phenyl propionic acid

NASA Astrophysics Data System (ADS)

Hiyama, Fumiyuki; Noguchi, Takio; Koshimizu, Masanori; Kishimoto, Shunji; Haruki, Rie; Nishikido, Fumihiko; Yanagida, Takayuki; Fujimoto, Yutaka; Aida, Tsutomu; Takami, Seiichi; Adschiri, Tadafumi; Asai, Keisuke

2018-01-01

We synthesized plastic scintillators incorporated with HfO2 nanoparticles as detectors for X-ray synchrotron radiation. Nanoparticles with sizes of less than 10 nm were synthesized with the subcritical hydrothermal method. The detection efficiency of high-energy X-ray photons improved by up to 3.3 times because of the addition of the nanoparticles. Nanosecond time resolution was successfully achieved for all the scintillators. These results indicate that this method is applicable for the preparation of plastic scintillators to detect X-ray synchrotron radiation.

Molecular Beam Epitaxial Growth of Iron Nitrides on Zinc-Blende Gallium Nitride(001)

NASA Astrophysics Data System (ADS)

Pak, Jeongihm; Lin, Wenzhi; Chinchore, Abhijit; Wang, Kangkang; Smith, Arthur R.

2008-03-01

Iron nitrides are attractive materials for their high magnetic moments, corrosion, and oxidation resistance. We present the successful epitaxial growth of iron nitride on zinc-blende gallium nitride (c-GaN) in order to develop a novel magnetic transition metal nitride/semiconductor system. First, GaN is grown on magnesium oxide (MgO) substrates having (001) orientation using rf N2-plasma molecular beam epitaxy. Then we grow FeN at substrate temperature of ˜ 210 ^oC up to a thickness of ˜ 10.5 nm. In-situ reflection high-energy electron diffraction (RHEED) is used to monitor the surface during growth. Initial results suggest that the epitaxial relationship is FeN[001] || GaN[001] and FeN[100] || GaN[100]. Work in progress is to investigate the surface using in-situ scanning tunneling microscopy (STM) to reveal the surface structure at atomic scale, as well as to explore more Fe-rich magnetic phases.

Boron nitride housing cools transistors

NASA Technical Reports Server (NTRS)

1965-01-01

Boron nitride ceramic heat sink cools transistors in r-f transmitter and receiver circuits. Heat dissipated by the transistor is conducted by the boron nitride housing to the metal chassis on which it is mounted.

Silicon nitride/silicon carbide composite powders

DOEpatents

Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

1996-06-11

Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Viability and proliferation of endothelial cells upon exposure to GaN nanoparticles.

PubMed

Braniste, Tudor; Tiginyanu, Ion; Horvath, Tibor; Raevschi, Simion; Cebotari, Serghei; Lux, Marco; Haverich, Axel; Hilfiker, Andres

2016-01-01

Nanotechnology is a rapidly growing and promising field of interest in medicine; however, nanoparticle-cell interactions are not yet fully understood. The goal of this work was to examine the interaction between endothelial cells and gallium nitride (GaN) semiconductor nanoparticles. Cellular viability, adhesion, proliferation, and uptake of nanoparticles by endothelial cells were investigated. The effect of free GaN nanoparticles versus the effect of growing endothelial cells on GaN functionalized surfaces was examined. To functionalize surfaces with GaN, GaN nanoparticles were synthesized on a sacrificial layer of zinc oxide (ZnO) nanoparticles using hydride vapor phase epitaxy. The uptake of GaN nanoparticles by porcine endothelial cells was strongly dependent upon whether they were fixed to the substrate surface or free floating in the medium. The endothelial cells grown on surfaces functionalized with GaN nanoparticles demonstrated excellent adhesion and proliferation, suggesting good biocompatibility of the nanostructured GaN.

Photodetectors using III-V nitrides

DOEpatents

Moustakas, Theodore D.; Misra, Mira

1997-01-01

A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector.

Tensile strength of aluminium nitride films

NASA Astrophysics Data System (ADS)

Zong, Deng Gang; Ong, Chung Wo; Aravind, Manju; Tsang, Mei Po; Loong Choy, Chung; Lu, Deren; Ma, Dejun

2004-11-01

Two-layered aluminium nitride (AlN)/silicon nitride microbridges were fabricated for microbridge tests to evaluate the elastic modulus, residual stress and tensile strength of the AlN films. The silicon nitride layer was added to increase the robustness of the structure. In a microbridge test, load was applied to the centre of a microbridge and was gradually increased by a nano-indenter equipped with a wedge tip until the sample was broken, while displacement was recorded coherently. Measurements were performed on single-layered silicon nitride microbridges and two-layered AlN/silicon nitride microbridges respectively. The data were fitted to a theory to derive the elastic modulus, residual stress and tensile strength of the silicon nitride films and AlN films. For the AlN films, the three parameters were determined to be 200, 0.06 and 0.3 GPa, respectively. The values of elastic modulus obtained were consistent with those measured by conventional nano-indentation method. The tensile strength value can be used as a reference to reflect the maximum tolerable tensile stress of AlN films when they are used in micro-electromechanical devices.

Alloy Effects on the Gas Nitriding Process

NASA Astrophysics Data System (ADS)

Yang, M.; Sisson, R. D.

2014-12-01

Alloy elements, such as Al, Cr, V, and Mo, have been used to improve the nitriding performance of steels. In the present work, plain carbon steel AISI 1045 and alloy steel AISI 4140 were selected to compare the nitriding effects of the alloying elements in AISI 4140. Fundamental analysis is carried out by using the "Lehrer-like" diagrams (alloy specific Lehrer diagram and nitriding potential versus nitrogen concentration diagram) and the compound layer growth model to simulate the gas nitriding process. With this method, the fundamental understanding for the alloy effect based on the thermodynamics and kinetics becomes possible. This new method paves the way for the development of new alloy for nitriding.

Finishing Techniques for Silicon Nitride Bearings

DTIC Science & Technology

1976-03-01

finishing procedures. Rolling contact fatigue lives of silicon nitride with selected smoother finishes tested at 800 ksi Hertz stress were an order...grinding. Rolling contact fatigue lives of silicon nitride with selected smoother finishes tested at 800 ksi Hertz stress were an order of magnitude...lives of silicon nitride with selected smoother finishes tested at 800 ksi Hertz stress were an order of magnitude longer than those

Evidence for the Formation of Nitrogen-Rich Platinum and Palladium Nitride Nanoparticles

DOE PAGES

Veith, Gabriel M.; Lupini, Andrew R.; Baggetto, Loïc; ...

2013-12-03

Here, we report evidence for the formation of nitrogen-rich precious metal nanoparticles (Pt, Pd) prepared by reactive sputtering of the pure metal in a N 2 plasma. The composition of the nanoparticles varies as a function of particle size and growth conditions. For the smallest particles the nitrogen content appears to be as high as 6.7 N atoms for each Pd atom or 5.9 N atoms for each Pt atom whereas bulk films have nominal compositions of Pt 7.3N and Pd 2.5N. The nanoparticles are metastable in air and moisture, slowly decomposing over several years. This paper describes the synthesismore » of these materials along with experimental evidence of the composition, oxidation state, and growth modes. Moreover, the catalytic properties of these N-rich nanoparticles were accessed by rotating disk electrode electrochemical studies, the liquid phase oxidation of benzyl alcohol and gas phase CO oxidation and support the experimental evidence for the materials composition.« less

Photodetectors using III-V nitrides

DOEpatents

Moustakas, T.D.; Misra, M.

1997-10-14

A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector. 24 figs.

The role of nano-particles in the field of thermal spray coating technology

NASA Astrophysics Data System (ADS)

Siegmann, Stephan; Leparoux, Marc; Rohr, Lukas

2005-06-01

Nano-particles play not only a key role in recent research fields, but also in the public discussions about health and safety in nanotechnology. Nevertheless, the worldwide activities in nano-particles research increased dramatically during the last 5 to 10 years. There are different potential routes for the future production of nano-particles at large scale. The main directions envisaged are mechanical milling, wet chemical reactions or gas phase processes. Each of the processes has its specific advantages and limitations. Mechanical milling and wet chemical reactions are typically time intensive and batch processes, whereas gas phase productions by flames or plasma can be carried out continuously. Materials of interest are mainly oxide ceramics, carbides, nitrides, and pure metals. Nano-ceramics are interesting candidates for coating technologies due to expected higher coating toughness, better thermal shock and wear resistance. Especially embedded nano-carbides and-nitrides offer homogenously distributed hard phases, which enhance coatings hardness. Thermal spraying, a nearly 100 years old and world wide established coating technology, gets new possibilities thanks to optimized, nano-sized and/or nano-structured powders. Latest coating system developments like high velocity flame spraying (HVOF), cold gas deposition or liquid suspension spraying in combination with new powder qualities may open new applications and markets. This article gives an overview on the latest activities in nano-particle research and production in special relation to thermal spray coating technology.

Molten-Salt-Based Growth of Group III Nitrides

DOEpatents

Waldrip, Karen E.; Tsao, Jeffrey Y.; Kerley, Thomas M.

2008-10-14

A method for growing Group III nitride materials using a molten halide salt as a solvent to solubilize the Group-III ions and nitride ions that react to form the Group III nitride material. The concentration of at least one of the nitride ion or Group III cation is determined by electrochemical generation of the ions.

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharlamov, Alexey; Bondarenko, Marina, E-mail: mebondarenko@ukr.net; Kharlamova, Ganna

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists ofmore » weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets. - Graphical abstract: XRD pattern and schematic atomic model of one layer of reduced carbon nitride, carbon nitride oxide and synthesized carbon nitride. For the first time at the reduction by hydroquinone of the water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O is obtained the reduced carbon nitride (or reduced multi-layer azagraphene). Display Omitted - Highlights: • First the reduced carbon nitride (RCN) at the reduction of the carbon nitride oxide was obtained. • Water-soluble carbon nitride oxide was reduced by hydroquinone. • The chemical bonds in a heteroatomic plane of RCN correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. • Reduced carbon nitride consists of poorly connected heteroatomic azagraphene layers.« less

High spatial resolution mapping of surface plasmon resonance modes in single and aggregated gold nanoparticles assembled on DNA strands

NASA Astrophysics Data System (ADS)

Diaz-Egea, Carlos; Sigle, Wilfried; van Aken, Peter A.; Molina, Sergio I.

2013-07-01

We present the mapping of the full plasmonic mode spectrum for single and aggregated gold nanoparticles linked through DNA strands to a silicon nitride substrate. A comprehensive analysis of the electron energy loss spectroscopy images maps was performed on nanoparticles standing alone, dimers, and clusters of nanoparticles. The experimental results were confirmed by numerical calculations using the Mie theory and Gans-Mie theory for solving Maxwell's equations. Both bright and dark surface plasmon modes have been unveiled.

Boron Nitride Nanotubes

NASA Technical Reports Server (NTRS)

Jordan, Kevin (Inventor); Smith, Michael W. (Inventor); Park, Cheol (Inventor)

2012-01-01

Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

Boron nitride nanotubes

DOEpatents

Smith, Michael W [Newport News, VA; Jordan, Kevin [Newport News, VA; Park, Cheol [Yorktown, VA

2012-06-06

Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

Growth of gallium nitride and indium nitride nanowires on conductive and flexible carbon cloth substrates.

PubMed

Yang, Yi; Ling, Yichuan; Wang, Gongming; Lu, Xihong; Tong, Yexiang; Li, Yat

2013-03-07

We report a general strategy for synthesis of gallium nitride (GaN) and indium nitride (InN) nanowires on conductive and flexible carbon cloth substrates. GaN and InN nanowires were prepared via a nanocluster-mediated growth method using a home built chemical vapor deposition (CVD) system with Ga and In metals as group III precursors and ammonia as a group V precursor. Electron microscopy studies reveal that the group III-nitride nanowires are single crystalline wurtzite structures. The morphology, density and growth mechanism of these nanowires are determined by the growth temperature. Importantly, a photoelectrode fabricated by contacting the GaN nanowires through a carbon cloth substrate shows pronounced photoactivity for photoelectrochemical water oxidation. The ability to synthesize group III-nitride nanowires on conductive and flexible substrates should open up new opportunities for nanoscale photonic, electronic and electrochemical devices.

Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions.

PubMed

Yang, Sungeun; Kim, Jiwhan; Tak, Young Joo; Soon, Aloysius; Lee, Hyunjoo

2016-02-05

As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. Herein, a single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with the aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as formic acid and methanol, also exhibited unique selectivity on the single-atom platinum catalyst. A lack of platinum ensemble sites changed the reaction pathway for the oxygen-reduction reaction toward a two-electron pathway and formic acid oxidation toward direct dehydrogenation, and also induced no activity for the methanol oxidation. This work demonstrates that single-atom platinum can be an efficient electrocatalyst with high mass activity and unique selectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Raman scattering in HfxZr1-xO2 nanoparticles

NASA Astrophysics Data System (ADS)

Robinson, Richard D.; Tang, Jing; Steigerwald, Michael L.; Brus, Louis E.; Herman, Irving P.

2005-03-01

Raman spectroscopy demonstrates that ˜5nm dimension HfxZr1-xO2 nanocrystals prepared by a nonhydrolytic sol-gel synthesis method are solid solutions of hafnia and zirconia, with no discernable segregation within the individual nanoparticles. Zirconia-rich particles are tetragonal and ensembles of hafnia-rich particles show mixed tetragonal/monoclinic phases. Sintering at 1200 °C produces larger particles (20-30 nm) that are monoclinic. A simple lattice dynamics model with composition-averaged cation mass and scaled force constants is used to understand how the Raman mode frequencies vary with composition in the tetragonal HfxZr1-xO2 nanoparticles. Background luminescence from these particles is minimized after oxygen treatment, suggesting possible oxygen defects in the as-prepared particles. Raman scattering is also used to estimate composition and the relative fractions of tetragonal and monoclinic phases. In some regimes there are mixed phases, and Raman analysis suggests that in these regimes the tetragonal phase particles are relatively rich in zirconium and the monoclinic phase particles are relatively rich in hafnium.

Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Semaltianos, N. G., E-mail: nsemaltianos@yahoo.com; Friedt, J.-M.; Blondeau-Patissier, V.

2016-05-28

Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO{sub 2}) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter inmore » the range of 4.3–5.3 nm. Nanoparticles synthesized in DI water have band gaps of 5.6 and 5.4 eV, in ethanol 5.72 and 5.65 eV (using low and high pulse energy), and in toluene 3 eV. The values for the relative permittivity in the range of 7.74–8.90 were measured for hafnia nanoparticles' thin films deposited on substrates by drop-casting (self-assembled layers) in parallel plate capacitor structures.« less

Low temperature route to uranium nitride

DOEpatents

Burrell, Anthony K.; Sattelberger, Alfred P.; Yeamans, Charles; Hartmann, Thomas; Silva, G. W. Chinthaka; Cerefice, Gary; Czerwinski, Kenneth R.

2009-09-01

A method of preparing an actinide nitride fuel for nuclear reactors is provided. The method comprises the steps of a) providing at least one actinide oxide and optionally zirconium oxide; b) mixing the oxide with a source of hydrogen fluoride for a period of time and at a temperature sufficient to convert the oxide to a fluoride salt; c) heating the fluoride salt to remove water; d) heating the fluoride salt in a nitrogen atmosphere for a period of time and at a temperature sufficient to convert the fluorides to nitrides; and e) heating the nitrides under vacuum and/or inert atmosphere for a period of time sufficient to convert the nitrides to mononitrides.

Synthesis and characterization of Ag embedded graphitic carbon nitride

NASA Astrophysics Data System (ADS)

Patra, P. C.; Mohapatra, Y. N.

2018-05-01

Silver embedded graphitic carbon nitride (g-C3N4:Ag) was prepared by a simple wet chemical pathway using dimethylformamide (DMF) as a common solvent which facilitate homogenous distribution of Ag nanoparticles under ambient conditions. The phase, chemical structure and thermal stability of the as prepared g-C3N4:Ag composite was characterized by X-ray diffraction (XRD), Fourier transmission infrared (FTIR) spectroscopy and Thermo gravimetric analysis (TGA). The optical properties of g-C3N4:Ag were investigated by diffuse reflectance UV/vis spectroscopy and steady state photoluminescence (PL) spectroscopy. The bandgap of g-C3N4:Ag is determined to be 2.72 eV compared to 2.85 eV for that of pure g-C3N4 using Kubelka-Monk function. Comparing the UV/vis spectra, there is a broad spectrum in the region 2.3 to 2.6 eV in the case of g-C3N4:Ag, which is attributed to the presence of Ag nanoparticles. The emission peak of g-C3N4:Ag is slightly broadened and quenched in intensity to that of pure g-C3N4.

Viability and proliferation of endothelial cells upon exposure to GaN nanoparticles

PubMed Central

Braniste, Tudor; Tiginyanu, Ion; Horvath, Tibor; Raevschi, Simion; Cebotari, Serghei; Lux, Marco; Haverich, Axel

2016-01-01

Summary Nanotechnology is a rapidly growing and promising field of interest in medicine; however, nanoparticle–cell interactions are not yet fully understood. The goal of this work was to examine the interaction between endothelial cells and gallium nitride (GaN) semiconductor nanoparticles. Cellular viability, adhesion, proliferation, and uptake of nanoparticles by endothelial cells were investigated. The effect of free GaN nanoparticles versus the effect of growing endothelial cells on GaN functionalized surfaces was examined. To functionalize surfaces with GaN, GaN nanoparticles were synthesized on a sacrificial layer of zinc oxide (ZnO) nanoparticles using hydride vapor phase epitaxy. The uptake of GaN nanoparticles by porcine endothelial cells was strongly dependent upon whether they were fixed to the substrate surface or free floating in the medium. The endothelial cells grown on surfaces functionalized with GaN nanoparticles demonstrated excellent adhesion and proliferation, suggesting good biocompatibility of the nanostructured GaN. PMID:27826507

Non-carbon titanium cobalt nitride nanotubes supported platinum catalyst with high activity and durability for methanol oxidation reaction

NASA Astrophysics Data System (ADS)

Chen, Xiaoxiang; Li, Wuyi; Pan, Zhanchang; Xu, Yanbin; Liu, Gen; Hu, Guanghui; Wu, Shoukun; Li, Jinghong; Chen, Chun; Lin, Yingsheng

2018-05-01

Titanium cobalt nitride nanotubes (Ti0.95Co0.05N NTs) hybrid support, a novel robust non-carbon support material prepared by solvothermal and post-nitriding processes, is further decorated with Pt nanoparticles for the electrooxidation of methanol. The catalyst is characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The morphology, structure and composition of the synthesized Ti0.95Co0.05N NTs suggest that the nanotube wall is porous and consists of homogeneous cohesively attached nitrides nanocube particles. Notable, Ti0.95Co0.05N NTs supported Pt catalyst exhibits significantly improved catalytic activity and durability for methanol electrooxidation compared with the conventional JM Pt/C catalyst. The experimental data indicate that enhanced catalytic activity and stability of Pt/Ti0.95Co0.05N NTs towards methanol electrooxidation might be mainly attributed to the tubular nanostructures and synergistic effect introduced by the Co doping. Both of them are playing an important role in improving the activity and durability of the Ti0.95Co0.05N NTs catalyst.

The prospect of uranium nitride (UN) and mixed nitride fuel (UN-PuN) for pressurized water reactor

NASA Astrophysics Data System (ADS)

Syarifah, Ratna Dewi; Suud, Zaki

2015-09-01

Design study of small Pressurized Water Reactors (PWRs) core loaded with uranium nitride fuel (UN) and mixed nitride fuel (UN-PuN), Pa-231 as burnable poison, and Americium has been performed. Pa-231 known as actinide material, have large capture cross section and can be converted into fissile material that can be utilized to reduce excess reactivity. Americium is one of minor actinides with long half life. The objective of adding americium is to decrease nuclear spent fuel in the world. The neutronic analysis results show that mixed nitride fuel have k-inf greater than uranium nitride fuel. It is caused by the addition of Pu-239 in mixed nitride fuel. In fuel fraction analysis, for uranium nitride fuel, the optimum volume fractions are 45% fuel fraction, 10% cladding and 45% moderator. In case of UN-PuN fuel, the optimum volume fractions are 30% fuel fraction, 10% cladding and 60% coolant/ moderator. The addition of Pa-231 as burnable poison for UN fuel, enrichment U-235 5%, with Pa-231 1.6% has k-inf more than one and excess reactivity of 14.45%. And for mixed nitride fuel, the lowest value of reactivity swing is when enrichment (U-235+Pu) 8% with Pa-231 0.4%, the excess reactivity value 13,76%. The fuel pin analyze for the addition of Americium, the excess reactivity value is lower than before, because Americium absorb the neutron. For UN fuel, enrichment U-235 8%, Pa-231 1.6% and Am 0.5%, the excess reactivity is 4.86%. And for mixed nitride fuel, when enrichment (U-235+Pu) 13%, Pa-231 0.4% and Am 0.1%, the excess reactivity is 11.94%. For core configuration, it is better to use heterogeneous than homogeneous core configuration, because the radial power distribution is better.

The influence of interfacial defects on fast charge trapping in nanocrystalline oxide-semiconductor thin film transistors

NASA Astrophysics Data System (ADS)

Kim, Taeho; Hur, Jihyun; Jeon, Sanghun

2016-05-01

Defects in oxide semiconductors not only influence the initial device performance but also affect device reliability. The front channel is the major carrier transport region during the transistor turn-on stage, therefore an understanding of defects located in the vicinity of the interface is very important. In this study, we investigated the dynamics of charge transport in a nanocrystalline hafnium-indium-zinc-oxide thin-film transistor (TFT) by short pulse I-V, transient current and 1/f noise measurement methods. We found that the fast charging behavior of the tested device stems from defects located in both the front channel and the interface, following a multi-trapping mechanism. We found that a silicon-nitride stacked hafnium-indium-zinc-oxide TFT is vulnerable to interfacial charge trapping compared with silicon-oxide counterpart, causing significant mobility degradation and threshold voltage instability. The 1/f noise measurement data indicate that the carrier transport in a silicon-nitride stacked TFT device is governed by trapping/de-trapping processes via defects in the interface, while the silicon-oxide device follows the mobility fluctuation model.

Cubic nitride templates

DOEpatents

Burrell, Anthony K; McCleskey, Thomas Mark; Jia, Quanxi; Mueller, Alexander H; Luo, Hongmei

2013-04-30

A polymer-assisted deposition process for deposition of epitaxial cubic metal nitride films and the like is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures under a suitable atmosphere to yield metal nitride films and the like. Such films can be used as templates for the development of high quality cubic GaN based electronic devices.

Blueish green photoluminescence from nitrided GaAs(100) surfaces

NASA Astrophysics Data System (ADS)

Shimaoka, Goro; Udagawa, Takashi

1999-04-01

Optical and structural studies were made on the Si-doped (100)GaAs surfaces nitrided at a temperature between 650° and 750°C for 15 min in the flowing NH 3 gas. The wavelength of photoluminescence (PL) spectra were observed to be shortened from 820 nm of the GaAs nitrided at 650°C with increasing nitridation temperature. Blueish green PL with wavelengths of approx. 490 nm and 470 nm were emitted from the nitrided surfaces at 700° and 750°C, respectively. Results of AES and SIMS indicated that the surfaces are nitrided as GaAs 1- xN x, (0< x≤1) alloy layer, and the nitrided region also tended to increase as the temperature raised. High-resolution transmission electron microscopic (HRTEM), transmission electron diffraction (TED) and energy dispersive X-ray (EDX) results showed that films peeled off from the nitrided surfaces consisted mainly of hexagonal, wurtzite-type gallium nitride (GaN) with stacking faults and microtwins.

Hexagonal Ag nanoarrays induced enhancement of blue light emission from amorphous oxidized silicon nitride via localized surface plasmon coupling.

PubMed

Ma, Zhongyuan; Ni, Xiaodong; Zhang, Wenping; Jiang, Xiaofan; Yang, Huafeng; Yu, Jie; Wang, Wen; Xu, Ling; Xu, Jun; Chen, Kunji; Feng, Duan

2014-11-17

A significant enhancement of blue light emission from amorphous oxidized silicon nitride (a-SiNx:O) films is achieved by introduction of ordered and size-controllable arrays of Ag nanoparticles between the silicon substrate and a-SiNx:O films. Using hexagonal arrays of Ag nanoparticles fabricated by nanosphere lithography, the localized surface plasmons (LSPs) resonance can effectively increase the internal quantum efficiency from 3.9% to 13.3%. Theoretical calculation confirms that the electromagnetic field-intensity enhancement is through the dipole surface plasma coupling with the excitons of a-SiNx:O films, which demonstrates a-SiNx:O films with enhanced blue emission are promising for silicon-based light-emitting applications by patterned Ag arrays.

Process for making transition metal nitride whiskers

DOEpatents

Bamberger, Carlos E.

1989-01-01

A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites.

Precipitation Modeling in Nitriding in Fe-M Binary System

NASA Astrophysics Data System (ADS)

Tomio, Yusaku; Miyamoto, Goro; Furuhara, Tadashi

2016-10-01

Precipitation of fine alloy nitrides near the specimen surface results in significant surface hardening in nitriding of alloyed steels. In this study, a simulation model of alloy nitride precipitation during nitriding is developed for Fe-M binary system based upon the Kampmann-Wagner numerical model in order to predict variations in the distribution of precipitates with depth. The model can predict the number density, average radius, and volume fraction of alloy nitrides as a function of depth from the surface and nitriding time. By a comparison with the experimental observation in a nitrided Fe-Cr alloy, it was found that the model can predict successfully the observed particle distribution from the surface into depth when appropriate solubility of CrN, interfacial energy between CrN and α, and nitrogen flux at the surface are selected.

Low pressure growth of cubic boron nitride films

NASA Technical Reports Server (NTRS)

Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

1997-01-01

A method for forming thin films of cubic boron nitride on substrates at low pressures and temperatures. A substrate is first coated with polycrystalline diamond to provide a uniform surface upon which cubic boron nitride can be deposited by chemical vapor deposition. The cubic boron nitride film is useful as a substitute for diamond coatings for a variety of applications in which diamond is not suitable. any tetragonal or hexagonal boron nitride. The cubic boron nitride produced in accordance with the preceding example is particularly well-suited for use as a coating for ultra hard tool bits and abrasives, especially those intended to use in cutting or otherwise fabricating iron.

Hierarchical TiN nanoparticles-assembled nanopillars for flexible supercapacitors with high volumetric capacitance.

PubMed

Qin, Ping; Li, Xingxing; Gao, Biao; Fu, Jijiang; Xia, Lu; Zhang, Xuming; Huo, Kaifu; Shen, Wenli; Chu, Paul K

2018-05-10

Titanium nitride (TiN) is an attractive electrode material in fast charging/discharging supercapacitors because of its excellent conductivity. However, the low capacitance and mechanical brittleness of TiN restricts its further application in flexible supercapacitors with high energy density. Thus, it is still a challenge to rationally design TiN electrodes with both high electrochemical and mechanical properties. Herein, the hierarchical TiN nanoparticles-assembled nanopillars (H-TiN NPs) array as binder free electrodes were obtained by nitriding of hierarchical titanium dioxide (TiO2) nanopillars, which was produced by a simple hydrothermal treatment of anodic TiO2 nanotubes (NTs) array in water. The porous TiN nanoparticles connected to each other to form ordered nanopillar arrays, effectively providing larger specific surface area and more active sites for charge storage. The H-TiN NPs delivered a high volumetric capacitance of 120 F cm-3 at 0.83 A cm-3, which is better than that of TiN NTs arrays (69 F cm-3 at 0.83 A cm-3). After assembling into all-solid-state devices, the H-TiN NPs based supercapacitors exhibited outstanding volumetric capacitance of 5.9 F cm-3 at 0.02 A cm-3 and a high energy density of 0.53 mW h cm-3. Our results reveal a new strategy to optimize the supercapacitive performance of metal nitrides.

Process for making transition metal nitride whiskers

DOEpatents

Bamberger, C.E.

1988-04-12

A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites. 1 fig., 1 tab.

Exploring electrolyte preference of vanadium nitride supercapacitor electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Bo; Chen, Zhaohui; Lu, Gang

Highlights: • Hierarchical VN nanostructures were prepared on graphite foam. • Electrolyte preference of VN supercapacitor electrodes was explored. • VN showed better capacitive property in organic and alkaline electrolytes than LiCl. - Abstract: Vanadium nitride hierarchical nanostructures were prepared through an ammonia annealing procedure utilizing vanadium pentoxide nanostructures grown on graphite foam. The electrochemical properties of hierarchical vanadium nitride was tested in aqueous and organic electrolytes. As a result, the vanadium nitride showed better capacitive energy storage property in organic and alkaline electrolytes. This work provides insight into the charge storage process of vanadium nitride and our findings canmore » shed light on other transition metal nitride-based electrochemical energy storage systems.« less

Modeling the Gas Nitriding Process of Low Alloy Steels

NASA Astrophysics Data System (ADS)

Yang, M.; Zimmerman, C.; Donahue, D.; Sisson, R. D.

2013-07-01

The effort to simulate the nitriding process has been ongoing for the last 20 years. Most of the work has been done to simulate the nitriding process of pure iron. In the present work a series of experiments have been done to understand the effects of the nitriding process parameters such as the nitriding potential, temperature, and time as well as surface condition on the gas nitriding process for the steels. The compound layer growth model has been developed to simulate the nitriding process of AISI 4140 steel. In this paper the fundamentals of the model are presented and discussed including the kinetics of compound layer growth and the determination of the nitrogen diffusivity in the diffusion zone. The excellent agreements have been achieved for both as-washed and pre-oxided nitrided AISI 4140 between the experimental data and simulation results. The nitrogen diffusivity in the diffusion zone is determined to be constant and only depends on the nitriding temperature, which is ~5 × 10-9 cm2/s at 548 °C. It proves the concept of utilizing the compound layer growth model in other steels. The nitriding process of various steels can thus be modeled and predicted in the future.

Synthesis, Properties, and Applications Of Boron Nitride

NASA Technical Reports Server (NTRS)

Pouch, John J.; Alterovitz, Samuel A.

1993-01-01

Report describes synthesis, properties, and applications of boron nitride. Especially in thin-film form. Boron nitride films useful as masks in x-ray lithography; as layers for passivation of high-speed microelectronic circuits; insulating films; hard, wear-resistant, protective films for optical components; lubricants; and radiation detectors. Present status of single-crystal growth of boron nitride indicates promising candidate for use in high-temperature semiconductor electronics.

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O

NASA Astrophysics Data System (ADS)

Kharlamov, Alexey; Bondarenko, Marina; Kharlamova, Ganna; Fomenko, Veniamin

2016-09-01

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C3N4)O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C3N4. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets.

Electrochemical Solution Growth of Magnetic Nitrides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monson, Todd C.; Pearce, Charles

Magnetic nitrides, if manufactured in bulk form, would provide designers of transformers and inductors with a new class of better performing and affordable soft magnetic materials. According to experimental results from thin films and/or theoretical calculations, magnetic nitrides would have magnetic moments well in excess of current state of the art soft magnets. Furthermore, magnetic nitrides would have higher resistivities than current transformer core materials and therefore not require the use of laminates of inactive material to limit eddy current losses. However, almost all of the magnetic nitrides have been elusive except in difficult to reproduce thin films or asmore » inclusions in another material. Now, through its ability to reduce atmospheric nitrogen, the electrochemical solution growth (ESG) technique can bring highly sought after (and previously inaccessible) new magnetic nitrides into existence in bulk form. This method utilizes a molten salt as a solvent to solubilize metal cations and nitrogen ions produced electrochemically and form nitrogen compounds. Unlike other growth methods, the scalable ESG process can sustain high growth rates (~mm/hr) even under reasonable operating conditions (atmospheric pressure and 500 °C). Ultimately, this translates into a high throughput, low cost, manufacturing process. The ESG process has already been used successfully to grow high quality GaN. Below, the experimental results of an exploratory express LDRD project to access the viability of the ESG technique to grow magnetic nitrides will be presented.« less

Cubic phase stabilization in nanoparticles of hafnia-zirconia oxides: Particle-size and annealing environment effects

NASA Astrophysics Data System (ADS)

Lu, Chih-Hsin; Raitano, Joan M.; Khalid, Syed; Zhang, Lihua; Chan, Siu-Wai

2008-06-01

Amorphous hafnia (HfO2-y), zirconia (ZrO2-y), and hafnia-zirconia (xHfO2-y-(1-x)(ZrO2-y)) nanoparticles were prepared by combining aqueous solutions of hexamethylenetetramine (HMT) with hafnium dichloride oxide (HfOCl2ṡ8H2O), zirconium dichloride oxide (ZrOCl2ṡ8H2O), or a mixture of these two salts at room temperature. For pure hafnia, transmission electron microscopy showed that the lower cation concentration (0.01M) resulted in the precipitation of smaller amorphous nanoparticles relative to higher concentrations (0.015M-0.04M). Consequently, the lower concentration preparation route coupled with a reducing environment (H2:N2=9:91) during annealing at temperatures between 650 and 850°C allowed for nanoparticles with a cubic structure to be prepared as determined by x-ray diffraction. The structurally cubic hafnia nanoparticles were 6nm or less in diameter and equiaxed. Using the same method (0.01M total metal cation concentration and reducing environment during annealing), nanoparticles of cubic structure were prepared across the entire hafnia-zirconia compositional spectrum, with a critical particle size for the cubic structure of about 6nm. Nanoparticles of tetragonal and monoclinic structure were prepared by increasing the annealing temperature and/or using a less reducing environment. The unique role of HMT in sample preparation is discussed as well.

Method of nitriding refractory metal articles

DOEpatents

Tiegs, Terry N.; Holcombe, Cressie E.; Dykes, Norman L.; Omatete, Ogbemi O.; Young, Albert C.

1994-01-01

A method of nitriding a refractory-nitride forming metal or metalloid articles and composite articles. A consolidated metal or metalloid article or composite is placed inside a microwave oven and nitrogen containing gas is introduced into the microwave oven. The metal or metalloid article or composite is heated to a temperature sufficient to react the metal or metalloid with the nitrogen by applying a microwave energy within the microwave oven. The metal or metalloid article or composite is maintained at that temperature for a period of time sufficient to convert the article of metal or metalloid or composite to an article or composite of refractory nitride. In addition, a method of applying a coating, such as a coating of an oxide, a carbide, or a carbo-nitride, to an article of metal or metalloid by microwave heating.

Method of nitriding refractory metal articles

DOEpatents

Tiegs, T.N.; Holcombe, C.E.; Dykes, N.L.; Omatete, O.O.; Young, A.C.

1994-03-15

A method of nitriding a refractory-nitride forming metal or metalloid articles and composite articles. A consolidated metal or metalloid article or composite is placed inside a microwave oven and nitrogen containing gas is introduced into the microwave oven. The metal or metalloid article or composite is heated to a temperature sufficient to react the metal or metalloid with the nitrogen by applying a microwave energy within the microwave oven. The metal or metalloid article or composite is maintained at that temperature for a period of time sufficient to convert the article of metal or metalloid or composite to an article or composite of refractory nitride. In addition, a method of applying a coating, such as a coating of an oxide, a carbide, or a carbo-nitride, to an article of metal or metalloid by microwave heating.

Uranium nitride behavior at thermionic temperatures

NASA Technical Reports Server (NTRS)

Phillips, W. M.

1973-01-01

The feasibility of using uranium nitride for in-core thermionic applications was evaluated in electrically heated thermal gradient tests and in flat plate thermionic converters. These tests indicated that grain boundary penetration of uranium nitride into both tungsten and rhenium will occur under thermal gradient conditions. In the case of the tungsten thermionic converter, this led to grain boundary rupture of the emitter and almost total loss of electrical output from the converter. It appears that uranium nitride is unsuitable for thermionic applications at the 2000 K temperatures used in these tests.

Application of hard coatings to substrates at low temperatures

NASA Technical Reports Server (NTRS)

Sproul, William D.

1993-01-01

BIRL, the industrial research laboratory of Northwestern University, has conducted unique and innovative research, under sponsorship from the NASA Marshall Space Flight Center (MSFC), in the application of hard, wear resistant coatings to bearing steels using the high-rate reactive sputtering (HRRS) process that was pioneered by Dr. William Sproul, the principal investigator on this program. Prior to this program, Dr. Sproul had demonstrated that it is possible to apply hard coatings such as titanium nitride (TiN) to alloy steels at low temperatures via the HRRS process without changing the metallurgical properties of the steel. The NASA MSFC program at BIRL had the specific objectives to: apply TiN to 440C stainless steel without changing the metallurgical properties of the steel; prepare rolling contact fatigue (RCF) test samples coated with binary hard coatings of TiN, zirconium nitride (ZrN), hafnium nitride (HfN), chromium nitride (CrN), and molybdenum nitride (MoN), and metal coatings of copper (Cu) and gold (Au); and develop new alloyed hard coatings of titanium aluminum nitride (Ti(0.5)Al(0.5)N), titanium zirconium nitride (Ti(0.5)Zr(0.5)N), and titanium aluminum vanadium nitride.

Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Wenhao; Holder, Aaron; Orvañanos, Bernardo

Compared to oxides, the nitrides are relatively unexplored, making them a promising chemical space for novel materials discovery. Of particular interest are nitrogen-rich nitrides, which often possess useful semiconducting properties for electronic and optoelectronic applications. However, such nitrogen-rich compounds are generally metastable, and the lack of a guiding theory for their synthesis has limited their exploration. Here, we review the remarkable metastability of observed nitrides, and examine the thermodynamics of how reactive nitrogen precursors can stabilize metastable nitrogen-rich compositions during materials synthesis. We map these thermodynamic strategies onto a predictive computational search, training a data-mined ionic substitution algorithm specifically formore » nitride discovery, which we combine with grand-canonical DFT-SCAN phase stability calculations to compute stabilizing nitrogen chemical potentials. We identify several new nitrogen-rich binary nitrides for experimental investigation, notably the transition metal nitrides Mn3N4, Cr3N4, V3N4, and Nb3N5, the main group nitride SbN, and the pernitrides FeN2, CrN2, and Cu2N2. By formulating rational thermodynamic routes to metastable compounds, we expand the search space for functional technological materials beyond equilibrium phases and compositions.« less

Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

DOE PAGES

Sun, Wenhao; Holder, Aaron; Orvañanos, Bernardo; ...

2017-07-17

Compared to oxides, the nitrides are relatively unexplored, making them a promising chemical space for novel materials discovery. Of particular interest are nitrogen-rich nitrides, which often possess useful semiconducting properties for electronic and optoelectronic applications. However, such nitrogen-rich compounds are generally metastable, and the lack of a guiding theory for their synthesis has limited their exploration. Here, we review the remarkable metastability of observed nitrides, and examine the thermodynamics of how reactive nitrogen precursors can stabilize metastable nitrogen-rich compositions during materials synthesis. We map these thermodynamic strategies onto a predictive computational search, training a data-mined ionic substitution algorithm specifically formore » nitride discovery, which we combine with grand-canonical DFT-SCAN phase stability calculations to compute stabilizing nitrogen chemical potentials. We identify several new nitrogen-rich binary nitrides for experimental investigation, notably the transition metal nitrides Mn3N4, Cr3N4, V3N4, and Nb3N5, the main group nitride SbN, and the pernitrides FeN2, CrN2, and Cu2N2. By formulating rational thermodynamic routes to metastable compounds, we expand the search space for functional technological materials beyond equilibrium phases and compositions.« less

Electrochemical nitridation of metal surfaces

DOEpatents

Wang, Heli; Turner, John A.

2015-06-30

Electrochemical nitridation of metals and the produced metals are disclosed. An exemplary method of electrochemical nitridation of metals comprises providing an electrochemical solution at low temperature. The method also comprises providing a three-electrode potentiostat system. The method also comprises stabilizing the three-electrode potentiostat system at open circuit potential. The method also comprises applying a cathodic potential to a metal.

As-Received, Ozone Cleaned and Ar+ Sputtered Surfaces of Hafnium Oxide Grown by Atomic Layer Deposition and Studied by XPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engelhard, Mark H.; Herman, Jacob A.; Wallace, Robert

2012-06-27

In this study, X-ray photoelectron spectroscopy (XPS) characterization was performed on 47 nm thick hafnium oxide (HfO{sub 2}) films grown by atomic layer deposition using TEMA-Hf/H{sub 2}O at 250 C substrate temperature. HfO{sub 2} is currently being studied as a possible replacement for Silicon Oxide (SiO{sub 2}) as a gate dielectric in electronics transistors. XPS spectra were collected on a Physical Electronics Quantum 2000 Scanning ESCA Microprobe using a monochromatic Al K{sub a} X-ray (1486.7 eV) excitation source. The sample was analyzed under the following conditions: as received, after UV irradiation for five minutes, and after sputter cleaning with 2more » kV Ar{sup +} ions for 180 seconds. Survey scans showed carbon, oxygen, and hafnium as the major species in the film, while the only minor species of argon and carbide was detected after sputtering. Adventitious carbon initially composed approximately 18.6 AT% of the surface, but after UV cleaning it was reduced to 2.4 AT%. This demonstrated that that the majority of carbon was due to adventitious carbon. However, after 2 kV Ar{sup +} sputtering there was still only trace amounts of carbon at {approx}1 AT%, Some of this trace carbon is now in the form of a carbide due to the interaction with Ar{sup +} used for sputter cleaning. Furthermore, the stoiciometric ratio of oxygen and hafnium is consistent with a high quality HfO{sub 2} film.« less

Cytocompatibility evaluation of gum Arabic-coated ultra-pure boron nitride nanotubes on human cells.

PubMed

Ciofani, Gianni; Del Turco, Serena; Rocca, Antonella; de Vito, Giuseppe; Cappello, Valentina; Yamaguchi, Maho; Li, Xia; Mazzolai, Barbara; Basta, Giuseppina; Gemmi, Mauro; Piazza, Vincenzo; Golberg, Dmitri; Mattoli, Virgilio

2014-05-01

Boron nitride nanotubes (BNNTs) are tubular nanoparticles with a structure analogous to that of carbon nanotubes, but with B and N atoms that completely replace the C atoms. Many favorable results indicate BNNTs as safe nanomaterials; however, important concerns have recently been raised about ultra-pure, long (~10 µm) BNNTs tested on several cell types. Here, we propose additional experiments with the same BNNTs, but shortened (~1.5 µm) with a homogenization/sonication treatment that allows for their dispersion in gum Arabic aqueous solutions. Obtained BNNTs are tested on human endothelial and neuron-like cells with several independent biocompatibility assays. Moreover, for the first time, their strong sum-frequency generation signal is exploited to assess the cellular uptake. Our data demonstrate no toxic effects up to concentrations of 20 µg/ml, once more confirming biosafety of BNNTs, and again highlighting that nanoparticle aspect ratio plays a key role in the biocompatibility evaluation.

Feasibility study of silicon nitride regenerators

NASA Technical Reports Server (NTRS)

Fucinari, C. A.; Rao, V. D. N.

1979-01-01

The feasibility of silicon nitride as a regenerator matrix material for applications requiring inlet temperatures above 1000 C is examined. The present generation oxide ceramics are used as a reference to examine silicon nitride from a material characteristics, manufacturing, thermal stress and aerothermodynamic viewpoint.

Fabrication of gallium nitride nanowires by metal-assisted photochemical etching

NASA Astrophysics Data System (ADS)

Zhang, Miao-Rong; Jiang, Qing-Mei; Zhang, Shao-Hui; Wang, Zu-Gang; Hou, Fei; Pan, Ge-Bo

2017-11-01

Gallium nitride (GaN) nanowires (NWs) were fabricated by metal-assisted photochemical etching (MaPEtch). Gold nanoparticles (AuNPs) as metal catalyst were electrodeposited on the GaN substrate. SEM and HRTEM images show the surface of GaN NWs is smooth and clean without any impurity. SAED and FFT patterns demonstrate GaN NWs have single crystal structure, and the crystallographic orientation of GaN NWs is (0002) face. On the basis of the assumption of localized galvanic cells, combined with the energy levels and electrochemical potentials of reactants in this etching system, the generation, transfer and consumption of electron-hole pairs reveal the whole MaPEtch reaction process. Such easily fabricated GaN NWs have great potential for the assembly of GaN-based single-nanowire nanodevices.

High efficiency III-nitride light-emitting diodes

DOEpatents

Crawford, Mary; Koleske, Daniel; Cho, Jaehee; Zhu, Di; Noemaun, Ahmed; Schubert, Martin F; Schubert, E. Fred

2013-05-28

Tailored doping of barrier layers enables balancing of the radiative recombination among the multiple-quantum-wells in III-Nitride light-emitting diodes. This tailored doping enables more symmetric carrier transport and uniform carrier distribution which help to reduce electron leakage and thus reduce the efficiency droop in high-power III-Nitride LEDs. Mitigation of the efficiency droop in III-Nitride LEDs may enable the pervasive market penetration of solid-state-lighting technologies in high-power lighting and illumination.

Hafnium, Tungsten, and the Differentiation of the Moon and Mars

NASA Astrophysics Data System (ADS)

Taylor, G. J.

2003-11-01

Measurements of the isotopic composition of tungsten (W) show that lunar samples and Martian meteorites have an excess of W-182. This was produced by the decay of hafnium-182 (Hf-182), an isotope with a half-life of only 9 million years. Because tungsten dissolves enthusiastically in metallic iron and hafnium does not, it is possible to use the abundance of W-182 in rocks formed by melting of the silicate mantle as an indicator of the timing of core formation. However, the concentrations of Hf and W in rocky material can be affected by melting and crystallization, so we also need to know how each element concentrates in common minerals in the mantles of the Moon and Mars. The behavior of Hf has been studied experimentally, but this is not true of W. Kevin Righter (Johnson Space Center) and Charles (Chip) Shearer (University of New Mexico) have filled this knowledge void by determining how W partitions between olivine, high- and low-calcium pyroxene, plagioclase feldspar, and garnet. The new data allowed Righter and Shearer to reexamine available measurements of the isotopic composition of W in lunar samples and Martian meteorites. Their analysis suggests that the lunar magma ocean, a huge magma system that surrounded the Moon when it formed, solidified in less than 30 million years. This is shorter than many theoretical calculations suggest. Pathfinder data and chemical data from Martian meteorites suggest that the core of Mars makes up about 20% of the planet. Core formation and subsequent melting of a region of the mantle containing garnet and high-calcium pyroxene took place less than 20-30 million years after the formation of the first solids in the solar system. This type of research shows the importance of measurements of isotopic compositions of radioactive elements or their decay products and laboratory experiments on the geochemical behavior of those elements.

Method of preparation of uranium nitride

DOEpatents

Kiplinger, Jaqueline Loetsch; Thomson, Robert Kenneth James

2013-07-09

Method for producing terminal uranium nitride complexes comprising providing a suitable starting material comprising uranium; oxidizing the starting material with a suitable oxidant to produce one or more uranium(IV)-azide complexes; and, sufficiently irradiating the uranium(IV)-azide complexes to produce the terminal uranium nitride complexes.

Nanotechnology Support for Memristor Nanoelectronics

DTIC Science & Technology

2012-03-01

hafnium oxide; 2) investigation of a conductive atomic force microscopy (cAFM) approach for measuring nanoparticle electrical properties , which was...films; and 4) successful measurement of memristive properties of nanoparticle -loaded insulating films. These results lay the groundwork for follow-on...a cAFM strategy for measuring nanoparticle electrical properties . Our initial approach to measuring nanoparticles was to attempt electrical

Feasibility study of silicon nitride protection of plastic encapsulated semiconductors

NASA Technical Reports Server (NTRS)

Peters, J. W.; Hall, T. C.; Erickson, J. J.; Gebhart, F. L.

1979-01-01

The application of low temperature silicon nitride protective layers on wire bonded integrated circuits mounted on lead frame assemblies is reported. An evaluation of the mechanical and electrical compatibility of both plasma nitride and photochemical silicon nitride (photonitride) passivations (parallel evaluations) of integrated circuits which were then encapsulated in plastic is described. Photonitride passivation is compatible with all wire bonded lead frame assemblies, with or without initial chip passivation. Plasma nitride passivation of lead frame assemblies is possible only if the chip is passivated before lead frame assembly. The survival rate after the environmental test sequence of devices with a coating of plasma nitride on the chip and a coating of either plasma nitride or photonitride over the assembled device is significantly greater than that of devices assembled with no nitride protective coating over either chip or lead frame.

Method for producing refractory nitrides

DOEpatents

Quinby, Thomas C.

1989-01-24

A process for making fine, uniform metal nitride powders that can be hot pressed or sintered. A metal salt is placed in a solvent with Melamine and warmed until a metal-Melamine compound forms. The solution is cooled and the metal-Melamine precipitate is calcined at a temperature below 700.degree. C. to form the metal nitrides and to avoid formation of the metal oxide.

Study of bulk Hafnium oxide (HfO2) under compression

NASA Astrophysics Data System (ADS)

Pathak, Santanu; Mandal, Guruprasad; Das, Parnika

2018-04-01

Hafnium oxide (HfO2) is a technologically important material. This material has K-value of 25 and band gap 5.8 eV. A k value of 25-30 is preferred for a gate dielectric [1]. As it shows good insulating and capacitive properties, HfO2 is being considered as a replacement to SiO2 in microelectronic devices as gate dielectrics. On the other hand because of toughening mechanism due to phase transformation induced by stress field observed in these oxides, HFO2 has been a material of investigations in various configurations for a very long time. However the controversies about phase transition of HfO2 under pressure still exists. High quality synchrotron radiation has been used to study the structural phase transition of HfO2 under pressure.

Liquid flow cells having graphene on nitride for microscopy

DOEpatents

Adiga, Vivekananda P.; Dunn, Gabriel; Zettl, Alexander K.; Alivisatos, A. Paul

2016-09-20

This disclosure provides systems, methods, and apparatus related to liquid flow cells for microscopy. In one aspect, a device includes a substrate having a first and a second oxide layer disposed on surfaces of the substrate. A first and a second nitride layer are disposed on the first and second oxide layers, respectively. A cavity is defined in the first oxide layer, the first nitride layer, and the substrate, with the cavity including a third nitride layer disposed on walls of the substrate and the second oxide layer that define the cavity. A channel is defined in the second oxide layer. An inlet port and an outlet port are defined in the second nitride layer and in fluid communication with the channel. A plurality of viewports is defined in the second nitride layer. A first graphene sheet is disposed on the second nitride layer covering the plurality of viewports.

Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

PubMed Central

2014-01-01

Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

Method of densifying an article formed of reaction bonded silicon nitride

NASA Technical Reports Server (NTRS)

Mangels, John A. (Inventor)

1982-01-01

A method of densifying an article formed of reaction bonded silicon nitride is disclosed. The reaction bonded silicon nitride article is packed in a packing mixture consisting of silicon nitride powder and a densification aid. The reaction bonded silicon nitride article and packing powder are sujected to a positive, low pressure nitrogen gas treatment while being heated to a treatment temperature and for a treatment time to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed. Thereafter, the reaction bonded silicon nitride article and packing powder are subjected to a positive high pressure nitrogen gas treatment while being heated to a treatment temperature and for a treatment time to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.

Nano-particulate Aluminium Nitride/Al: An Efficient and Versatile Heterogeneous Catalyst for the Synthesis of Biginelli Scaffolds

NASA Astrophysics Data System (ADS)

Tekale, S. U.; Tekale, A. B.; Kanhe, N. S.; Bhoraskar, S. V.; Pawar, R. P.

2011-12-01

Nano-particulate aluminium nitride/Al (7:1) is reported as a new heterogeneous solid acid catalyst for the synthesis of 3, 4-dihydroxypyrimidi-2-(1H)-ones and their sulphur analogues using the Biginelli reaction. This method involves short reaction time, easy separation, high yields and purity of products.

Nanotribological response of a plasma nitrided bio-steel.

PubMed

Samanta, Aniruddha; Chakraborty, Himel; Bhattacharya, Manjima; Ghosh, Jiten; Sreemany, Monjoy; Bysakh, Sandip; Rane, Ramkrishna; Joseph, Alphonsa; Jhala, Ghanshyam; Mukherjee, Subroto; Das, Mitun; Mukhopadhyay, Anoop K

2017-01-01

AISI 316L is a well known biocompatible, austenitic stainless steel (SS). It is thus a bio-steel. Considering its importance as a bio-prosthesis material here we report the plasma nitriding of AISI 316L (SS) followed by its microstructural and nanotribological characterization. Plasma nitriding of the SS samples was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as SSPN. The experimental results confirmed the formations of an embedded nitrided metal layer zone (ENMLZ) and an interface zone (IZ) between the ENMLZ and the unnitrided bulk metallic layer zone (BMLZ) in the SSPN sample. These ENMLZ and IZ in the SSPN sample were richer in iron nitride (FeN) chromium nitride (CrN) along with the austenite phase. The results from nanoindentation, microscratch, nanoscratch and sliding wear studies confirmed that the static contact deformation resistance, the microwear, nanowear and sliding wear resistance of the SSPN samples were much better than those of the SS samples. These results were explained in terms of structure-property correlations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Boron nitride converted carbon fiber

DOEpatents

Rousseas, Michael; Mickelson, William; Zettl, Alexander K.

2016-04-05

This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.

Mesoporous coaxial titanium nitride-vanadium nitride fibers of core-shell structures for high-performance supercapacitors.

PubMed

Zhou, Xinhong; Shang, Chaoqun; Gu, Lin; Dong, Shanmu; Chen, Xiao; Han, Pengxian; Li, Lanfeng; Yao, Jianhua; Liu, Zhihong; Xu, Hongxia; Zhu, Yuwei; Cui, Guanglei

2011-08-01

In this study, titanium nitride-vanadium nitride fibers of core-shell structures were prepared by the coaxial electrospinning, and subsequently annealed in the ammonia for supercapacitor applications. These core-shell (TiN-VN) fibers incorporated mesoporous structure into high electronic conducting transition nitride hybrids, which combined higher specific capacitance of VN and better rate capability of TiN. These hybrids exhibited higher specific capacitance (2 mV s(-1), 247.5 F g(-1)) and better rate capability (50 mV s(-1), 160.8 F g(-1)), which promise a good candidate for high-performance supercapacitors. It was also revealed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) characterization that the minor capacitance fade originated from the surface oxidation of VN and TiN.

Aluminum nitride insulating films for MOSFET devices

NASA Technical Reports Server (NTRS)

Lewicki, G. W.; Maserjian, J.

1972-01-01

Application of aluminum nitrides as electrical insulator for electric capacitors is discussed. Electrical properties of aluminum nitrides are analyzed and specific use with field effect transistors is defined. Operational limits of field effect transistors are developed.

77 FR 51825 - Ferrovanadium and Nitrided Vanadium From Russia

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-27

... Nitrided Vanadium From Russia Determination On the basis of the record \\1\\ developed in the subject five... order on ferrovanadium and nitrided vanadium from Russia would not be likely to lead to continuation or... in USITC Publication 4345 (August 2012), entitled Ferrovanadium and Nitrided Vanadium from Russia...

Low-loss binder for hot pressing boron nitride

DOEpatents

Maya, Leon

1991-01-01

Borazine derivatives used as low-loss binders and precursors for making ceramic boron nitride structures. The derivative forms the same composition as the boron nitride starting material, thereby filling the voids with the same boron nitride material upon forming and hot pressing. The derivatives have a further advantage of being low in carbon thus resulting in less volatile byproduct that can result in bubble formation during pressing.

Spherical boron nitride particles and method for preparing them

DOEpatents

Phillips, Jonathan; Gleiman, Seth S.; Chen, Chun-Ku

2003-11-25

Spherical and polyhedral particles of boron nitride and method of preparing them. Spherical and polyhedral particles of boron nitride are produced from precursor particles of hexagonal phase boron nitride suspended in an aerosol gas. The aerosol is directed to a microwave plasma torch. The torch generates plasma at atmospheric pressure that includes nitrogen atoms. The presence of nitrogen atoms is critical in allowing boron nitride to melt at atmospheric pressure while avoiding or at least minimizing decomposition. The plasma includes a plasma hot zone, which is a portion of the plasma that has a temperature sufficiently high to melt hexagonal phase boron nitride. In the hot zone, the precursor particles melt to form molten particles that acquire spherical and polyhedral shapes. These molten particles exit the hot zone, cool, and solidify to form solid particles of boron nitride with spherical and polyhedral shapes. The molten particles can also collide and join to form larger molten particles that lead to larger spherical and polyhedral particles.

The Hardest Superconducting Metal Nitride

NASA Astrophysics Data System (ADS)

Wang, Shanmin; Antonio, Daniel; Yu, Xiaohui; Zhang, Jianzhong; Cornelius, Andrew L.; He, Duanwei; Zhao, Yusheng

2015-09-01

Transition-metal (TM) nitrides are a class of compounds with a wide range of properties and applications. Hard superconducting nitrides are of particular interest for electronic applications under working conditions such as coating and high stress (e.g., electromechanical systems). However, most of the known TM nitrides crystallize in the rock-salt structure, a structure that is unfavorable to resist shear strain, and they exhibit relatively low indentation hardness, typically in the range of 10-20 GPa. Here, we report high-pressure synthesis of hexagonal δ-MoN and cubic γ-MoN through an ion-exchange reaction at 3.5 GPa. The final products are in the bulk form with crystallite sizes of 50 - 80 μm. Based on indentation testing on single crystals, hexagonal δ-MoN exhibits excellent hardness of ~30 GPa, which is 30% higher than cubic γ-MoN (~23 GPa) and is so far the hardest among the known metal nitrides. The hardness enhancement in hexagonal phase is attributed to extended covalently bonded Mo-N network than that in cubic phase. The measured superconducting transition temperatures for δ-MoN and cubic γ-MoN are 13.8 and 5.5 K, respectively, in good agreement with previous measurements.

Safety Assessment of Boron Nitride as Used in Cosmetics.

PubMed

Fiume, Monice M; Bergfeld, Wilma F; Belsito, Donald V; Hill, Ronald A; Klaassen, Curtis D; Liebler, Daniel C; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

2015-01-01

The Cosmetic Ingredient Review Expert Panel (Panel) assessed the safety of boron nitride which functions in cosmetics as a slip modifier (ie, it has a lubricating effect). Boron nitride is an inorganic compound with a crystalline form that can be hexagonal, spherical, or cubic; the hexagonal form is presumed to be used in cosmetics. The highest reported concentration of use of boron nitride is 25% in eye shadow formulations. Although boron nitride nanotubes are produced, boron nitride is not listed as a nanomaterial used in cosmetic formulations. The Panel reviewed available chemistry, animal data, and clinical data and concluded that this ingredient is safe in the present practices of use and concentration in cosmetic formulations. © The Author(s) 2015.

Multimode resistive switching in nanoscale hafnium oxide stack as studied by atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Y., E-mail: houyi@pku.edu.cn, E-mail: lfliu@pku.edu.cn; IMEC, Kapeldreef 75, B-3001 Heverlee; Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Heverlee

2016-07-11

The nanoscale resistive switching in hafnium oxide stack is investigated by the conductive atomic force microscopy (C-AFM). The initial oxide stack is insulating and electrical stress from the C-AFM tip induces nanometric conductive filaments. Multimode resistive switching can be observed in consecutive operation cycles at one spot. The different modes are interpreted in the framework of a low defect quantum point contact theory. The model implies that the optimization of the conductive filament active region is crucial for the future application of nanoscale resistive switching devices.

Composition effects on mechanical properties of tungsten-rhenium-hafnium-carbon alloys

NASA Technical Reports Server (NTRS)

Witzke, W. R.

1973-01-01

The mechanical properties of rod and sheet fabricated from arc melted W-4Re-Hf-C alloys containing up to about 0.8 mol percent hafnium carbide (HfC) were evaluated in the as-worked condition. The DBTT's of electropolished bend and tensile specimens were independent of HfC content in this range but dependent on excess Hf or C above that required for stoichiometric HfC. Low temperature ductility was a maximum at Hf contents slightly in excess of stoichiometric. Variations in high temperature strength were also dependent on excess Hf and C. Maximum creep strengthening also occurred at Hf contents in excess of stoichiometric. Analysis of extracted second phase particles indicated that creep strength was reduced by increasing WC content in the HfC particles.

Additive Manufacturing of Dense Hexagonal Boron Nitride Objects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marquez Rossy, Andres E.; Armstrong, Beth L.; Elliott, Amy M.

The feasibility of manufacturing hexagonal boron nitride objects via additive manufacturing techniques was investigated. It was demonstrated that it is possible to hot-extrude thermoplastic filaments containing uniformly distributed boron nitride particles with a volume concentration as high as 60% and that these thermoplastic filaments can be used as feedstock for 3D-printing objects using a fused deposition system. Objects 3D-printed by fused deposition were subsequently sintered at high temperature to obtain dense ceramic products. In a parallel study the behavior of hexagonal boron nitride in aqueous solutions was investigated. It was shown that the addition of a cationic dispersant to anmore » azeotrope enabled the formulation of slurries with a volume concentration of boron nitride as high as 33%. Although these slurries exhibited complex rheological behavior, the results from this study are encouraging and provide a pathway for manufacturing hexagonal boron nitride objects via robocasting.« less

Nanowire-templated lateral epitaxial growth of non-polar group III nitrides

DOEpatents

Wang, George T [Albuquerque, NM; Li, Qiming [Albuquerque, NM; Creighton, J Randall [Albuquerque, NM

2010-03-02

A method for growing high quality, nonpolar Group III nitrides using lateral growth from Group III nitride nanowires. The method of nanowire-templated lateral epitaxial growth (NTLEG) employs crystallographically aligned, substantially vertical Group III nitride nanowire arrays grown by metal-catalyzed metal-organic chemical vapor deposition (MOCVD) as templates for the lateral growth and coalescence of virtually crack-free Group III nitride films. This method requires no patterning or separate nitride growth step.

Boron Nitride Nanotubes for Engineering Applications

NASA Technical Reports Server (NTRS)

Hurst, Janet; Hull, David; Gorican, Daniel

2005-01-01

Boron nitride nanotubes (BNNT) are of significant interest to the scientific and technical communities for many of the same reasons that carbon nanotubes (CNT) have attracted wide attention. Both materials have potentially unique and important properties for structural and electronic applications. However of even more consequence than their similarities may be the complementary differences between carbon and boron nitride nanotubes While BNNT possess a very high modulus similar to CNT, they also possess superior chemical and thermal stability. Additionally, BNNT have more uniform electronic properties, with a uniform band gap of 5.5 eV while CNT vary from semi-conductive to highly conductive behavior. Boron nitride nanotubes have been synthesized both in the literature and at NASA Glenn Research Center, by a variety of methods such as chemical vapor deposition, arc discharge and reactive milling. Consistent large scale production of a reliable product has proven difficult. Progress in the reproducible synthesis of 1-2 gram sized batches of boron nitride nanotubes will be discussed as well as potential uses for this unique material.

Solar selective performance of metal nitride/oxynitride based magnetron sputtered thin film coatings: a comprehensive review

NASA Astrophysics Data System (ADS)

Ibrahim, Khalil; Taha, Hatem; Mahbubur Rahman, M.; Kabir, Humayun; Jiang, Zhong-Tao

2018-03-01

Since solar-thermal collectors are considered to be the most direct way of converting solar energy into usable forms, in the last few years growing attention has been paid to the development of transition metal nitride and metal oxynitride based thin film selective surfaces for solar-thermal collectors, in order to harvest more solar energy. A solar-thermal energy system, generally, shows very high solar absorption of incident solar radiation from the solar-thermal collectors in the visible range (0.3 to 2.5 μm) and extremely low thermal losses through emission (or high reflection) in the infrared region (≥2.5 μm). The efficiency of a solar-thermal energy conversion system can be improved by the use of solar selective surfaces consisting of novel metallic nanoparticles embedded in metal nitride/oxynitride systems. In order to enhance the effectiveness of solar-thermal devices, solar selective surfaces with high thermal stability are a prerequisite. Over the years, substantial efforts have been made in the field of solar selective surfaces to attain higher solar absorptance and lower thermal emittance in high temperature (above 400 °C) applications. In this article, we review the present state-of-the-art transition metal nitride and/or oxynitride based vacuum sputtered nanostructured thin film coatings, with respect to their optical and solar selective surface applications. We have also summarized the solar selectivity data from recently published investigations, including discussion on some potential applications for these materials.

Mechanical properties of PEO-coatings on the surface of magnesium alloy MA8 modified by TiN nanoparticles

NASA Astrophysics Data System (ADS)

Imshinetsky, Igor M.; Mashtalyar, Dmitriy V.; Sunebryukhov, Sergey L.; Gnedenkov, Sergey V.

2017-09-01

The methods to form protective coatings by the plasma electrolytic oxidation method (PEO) in the electrolytic system containing nanosized particles of titanium nitride has been develoted. Tribological and morfological studies of the composite coatings have been carried out. It has been established that the microhardness of the coating with nanoparticles concentration of 3 g/l increases by 2 folds, while the wear resistance - by 2.2 fold, as compared to respective values for the PEO-coating formed in the electrolyte without nanoparticles.

Nitride microlens arrays for blue and ultraviolet wavelength applications

NASA Astrophysics Data System (ADS)

Oder, T. N.; Shakya, J.; Lin, J. Y.; Jiang, H. X.

2003-05-01

Nitride microlens arrays with sizes as small as 10 μm in diameter have been fabricated on GaN and AlN epilayers using the method of photoresist reflow and inductively coupled plasma dry etching. The focal lengths of the microlenses varied from 7-30 μm as determined by theoretical fitting as well as by the near-field scanning optical microscopy measurement. Scanning electron and atomic force microscopies were used to obtain the surface profile of the microlenses which were found to match very well with hemispherical fitting and a surface roughness value around 1 nm was obtained. Nitride microlens arrays would be naturally chosen for green/blue to deep ultraviolet wavelength applications. In addition, nitride microlenses offer the possibility of integrating nitride-based microsize photonic devices as well as of coupling light into, out of, and between arrays of III-nitride emitters for other applications, such as spatially resolved fluorescence spectroscopy studies of biological and medical systems and optical links, thereby further expanding the applications of III nitrides.

Plasmonic spectral tunability of conductive ternary nitrides

NASA Astrophysics Data System (ADS)

Kassavetis, S.; Bellas, D. V.; Abadias, G.; Lidorikis, E.; Patsalas, P.

2016-06-01

Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as TixTa1-xN, TixZr1-xN, TixAl1-xN, and ZrxTa1-xN share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400-700 nm) and UVA (315-400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementioned broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.

Dispersible shortened boron nitride nanotubes with improved molecule-loading capacity.

PubMed

Zhi, Chunyi; Hanagata, Nobutaka; Bando, Yoshio; Golberg, Dmitri

2011-09-05

The oxidation process of boron nitride nanotubes was thoroughly investigated, and a slow oxidation characteristic was clearly revealed. Subsequently, the controllable oxidation process was utilized to break the sturdy structure of the boron nitride nanotubes to fabricate shortened nanotubes. The shortened boron nitride nanotubes were found to possess good solubility in water and many organic solvents. Further experiments demonstrated remarkably improved molecule-loading capacity of the shortened boron nitride nanotubes. These dispersible shortened boron nitride nanotubes might have the potential to be developed as effective delivery systems for various molecules, which may find applications in bio-related fields. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Hardest Superconducting Metal Nitride

DOE PAGES

Wang, Shanmin; Antonio, Daniel; Yu, Xiaohui; ...

2015-09-03

Transition–metal (TM) nitrides are a class of compounds with a wide range of properties and applications. Hard superconducting nitrides are of particular interest for electronic applications under working conditions such as coating and high stress (e.g., electromechanical systems). However, most of the known TM nitrides crystallize in the rock–salt structure, a structure that is unfavorable to resist shear strain, and they exhibit relatively low indentation hardness, typically in the range of 10–20 GPa. Here, we report high–pressure synthesis of hexagonal δ–MoN and cubic γ–MoN through an ion–exchange reaction at 3.5 GPa. The final products are in the bulk form withmore » crystallite sizes of 50 – 80 μm. Based on indentation testing on single crystals, hexagonal δ–MoN exhibits excellent hardness of ~30 GPa, which is 30% higher than cubic γ–MoN (~23 GPa) and is so far the hardest among the known metal nitrides. The hardness enhancement in hexagonal phase is attributed to extended covalently bonded Mo–N network than that in cubic phase. The measured superconducting transition temperatures for δ–MoN and cubic γ–MoN are 13.8 and 5.5 K, respectively, in good agreement with previous measurements.« less

The synthesis and characterization of iron nanoparticles

NASA Astrophysics Data System (ADS)

Bennett, Tyler

Nanoparticle synthesis has garnered attention for technological applications for catalysts, industrial processing, and medical applications. The size ranges for these is in the particles nanostructural domain. Pure iron nanoparticles have been of particular interest for their reactivity and relative biological inertness. Applications include cancer treatment and carrying medicine to a relevant site. Unfortunately, because of their reactivity, pure iron nanoparticles have been difficult to study. This is because of their accelerated tendency to form oxides in air, due to the increased surface area to volume ratio. Using synthesis processes with polyphenols or long chain amines, air stable iron nanoparticles have been produced with a diameter size range of ~ 2 to about ~10 nm, but apparently have transformed due to internal pressure and crystallographic defects to the FCC phase. The FCC crystals have been seen to form icosahedral and decahedral shapes. This size is within the range for use as a catalyst for the growth of both carbon nanotubes and boron nitride nanotubes as well for biomedical applications. The advantages of these kinds of catalysts are that nanotube growth can be for the first time separated from the catalyst formation. Additionally, the catalyst size can be preselected for a certain size nanotube to grow. In summary: (1) we found the size distributions of nanoparticles for various synthesis processes, (2) we discovered the right size range for growth of nanotubes from the iron nanoparticles, (3) the nanoparticles are under a very high internal pressure, (4) the nanoparticles are in the FCC phase, (5) they appear to be in icosahedral and decahedral structures, (6) they undergo room temperature twinning, (7) the FCC crystals are distorted due to carbon in octahedral sites, (8) the iron nanoparticles are stable in air, (9) adding small amounts of copper make the iron nanoparticles smaller.

Advances and directions of ion nitriding/carburizing

NASA Technical Reports Server (NTRS)

Spalvins, Talivaldis

1989-01-01

Ion nitriding and carburizing are plasma activated thermodynamic processes for the production of case hardened surface layers not only for ferrous materials, but also for an increasing number of nonferrous metals. When the treatment variables are properly controlled, the use of nitrogenous or carbonaceous glow discharge medium offers great flexibility in tailoring surface/near-surface properties independently of the bulk properties. The ion nitriding process has reached a high level of maturity and has gained wide industrial acceptance, while the more recently introduced ion carburizing process is rapidly gaining industrial acceptance. The current status of plasma mass transfer mechanisms into the surface regarding the formation of compound and diffusion layers in ion nitriding and carbon build-up ion carburizing is reviewed. In addition, the recent developments in design and construction of advanced equipment for obtaining optimized and controlled case/core properties is summarized. Also, new developments and trends such as duplex plasma treatments and alternatives to dc diode nitriding are highlighted.

Dissolution of bulk specimens of silicon nitride

NASA Technical Reports Server (NTRS)

Davis, W. F.; Merkle, E. J.

1981-01-01

An accurate chemical characterization of silicon nitride has become important in connection with current efforts to incorporate components of this material into advanced heat engines. However, there are problems concerning a chemical analysis of bulk silicon nitride. Current analytical methods require the pulverization of bulk specimens. A pulverization procedure making use of grinding media, on the other hand, will introduce contaminants. A description is given of a dissolution procedure which overcomes these difficulties. It has been found that up to at least 0.6 g solid pieces of various samples of hot pressed and reaction bonded silicon nitride can be decomposed in a mixture of 3 mL hydrofluoric acid and 1 mL nitric acid overnight at 150 C in a Parr bomb. High-purity silicon nitride is completely soluble in nitric acid after treatment in the bomb. Following decomposition, silicon and hydrofluoric acid are volatilized and insoluble fluorides are converted to a soluble form.

Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Si, M. S.; Gao, Daqiang, E-mail: gaodq@lzu.edu.cn, E-mail: xueds@lzu.edu.cn; Yang, Dezheng

2014-05-28

Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstratemore » such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.« less

Group-III Nitride Field Emitters

NASA Technical Reports Server (NTRS)

Bensaoula, Abdelhak; Berishev, Igor

2008-01-01

Field-emission devices (cold cathodes) having low electron affinities can be fabricated through lattice-mismatched epitaxial growth of nitrides of elements from group III of the periodic table. Field emission of electrons from solid surfaces is typically utilized in vacuum microelectronic devices, including some display devices. The present field-emission devices and the method of fabricating them were developed to satisfy needs to reduce the cost of fabricating field emitters, make them compatible with established techniques for deposition of and on silicon, and enable monolithic integration of field emitters with silicon-based driving circuitry. In fabricating a device of this type, one deposits a nitride of one or more group-III elements on a substrate of (111) silicon or other suitable material. One example of a suitable deposition process is chemical vapor deposition in a reactor that contains plasma generated by use of electron cyclotron resonance. Under properly chosen growth conditions, the large mismatch between the crystal lattices of the substrate and the nitride causes strains to accumulate in the growing nitride film, such that the associated stresses cause the film to crack. The cracks lie in planes parallel to the direction of growth, so that the growing nitride film becomes divided into microscopic growing single-crystal columns. The outer ends of the fully-grown columns can serve as field-emission tips. By virtue of their chemical compositions and crystalline structures, the columns have low work functions and high electrical conductivities, both of which are desirable for field emission of electrons. From examination of transmission electron micrographs of a prototype device, the average column width was determined to be about 100 nm and the sharpness of the tips was determined to be characterized by a dimension somewhat less than 100 nm. The areal density of the columns was found to about 5 x 10(exp 9)/sq cm . about 4 to 5 orders of magnitude

Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

NASA Astrophysics Data System (ADS)

Czarnowska, Elżbieta; Borowski, Tomasz; Sowińska, Agnieszka; Lelątko, Józef; Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał; Wierzchoń, Tadeusz

2015-04-01

NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications.

Excellent electrical conductivity of the exfoliated and fluorinated hexagonal boron nitride nanosheets.

PubMed

Xue, Yafang; Liu, Qian; He, Guanjie; Xu, Kaibing; Jiang, Lin; Hu, Xianghua; Hu, Junqing

2013-01-24

The insulator characteristic of hexagonal boron nitride limits its applications in microelectronics. In this paper, the fluorinated hexagonal boron nitride nanosheets were prepared by doping fluorine into the boron nitride nanosheets exfoliated from the bulk boron nitride in isopropanol via a facile chemical solution method with fluoboric acid; interestingly, these boron nitride nanosheets demonstrate a typical semiconductor characteristic which were studied on a new scanning tunneling microscope-transmission electron microscope holder. Since this property changes from an insulator to a semiconductor of the boron nitride, these nanosheets will be able to extend their applications in designing and fabricating electronic nanodevices.

Structure and energetics of carbon, hexagonal boron nitride, and carbon/hexagonal boron nitride single-layer and bilayer nanoscrolls

NASA Astrophysics Data System (ADS)

Siahlo, Andrei I.; Poklonski, Nikolai A.; Lebedev, Alexander V.; Lebedeva, Irina V.; Popov, Andrey M.; Vyrko, Sergey A.; Knizhnik, Andrey A.; Lozovik, Yurii E.

2018-03-01

Single-layer and bilayer carbon and hexagonal boron nitride nanoscrolls as well as nanoscrolls made of bilayer graphene/hexagonal boron nitride heterostructure are considered. Structures of stable states of the corresponding nanoscrolls prepared by rolling single-layer and bilayer rectangular nanoribbons are obtained based on the analytical model and numerical calculations. The lengths of nanoribbons for which stable and energetically favorable nanoscrolls are possible are determined. Barriers to rolling of single-layer and bilayer nanoribbons into nanoscrolls and barriers to nanoscroll unrolling are calculated. Based on the calculated barriers nanoscroll lifetimes in the stable state are estimated. Elastic constants for bending of graphene and hexagonal boron nitride layers used in the model are found by density functional theory calculations.

Monolithic Gyroidal Mesoporous Mixed Titanium–Niobium Nitrides

PubMed Central

2015-01-01

Mesoporous transition metal nitrides are interesting materials for energy conversion and storage applications due to their conductivity and durability. We present ordered mixed titanium–niobium (8:2, 1:1) nitrides with gyroidal network structures synthesized from triblock terpolymer structure-directed mixed oxides. The materials retain both macroscopic integrity and mesoscale ordering despite heat treatment up to 600 °C, without a rigid carbon framework as a support. Furthermore, the gyroidal lattice parameters were varied by changing polymer molar mass. This synthesis strategy may prove useful in generating a variety of monolithic ordered mesoporous mixed oxides and nitrides for electrode and catalyst materials. PMID:25122534

Vertical III-nitride thin-film power diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wierer, Jr., Jonathan; Fischer, Arthur J.; Allerman, Andrew A.

2017-03-14

A vertical III-nitride thin-film power diode can hold off high voltages (kV's) when operated under reverse bias. The III-nitride device layers can be grown on a wider bandgap template layer and growth substrate, which can be removed by laser lift-off of the epitaxial device layers grown thereon.

Photoinduced doping in heterostructures of graphene and boron nitride.

PubMed

Ju, L; Velasco, J; Huang, E; Kahn, S; Nosiglia, C; Tsai, Hsin-Zon; Yang, W; Taniguchi, T; Watanabe, K; Zhang, Y; Zhang, G; Crommie, M; Zettl, A; Wang, F

2014-05-01

The design of stacks of layered materials in which adjacent layers interact by van der Waals forces has enabled the combination of various two-dimensional crystals with different electrical, optical and mechanical properties as well as the emergence of novel physical phenomena and device functionality. Here, we report photoinduced doping in van der Waals heterostructures consisting of graphene and boron nitride layers. It enables flexible and repeatable writing and erasing of charge doping in graphene with visible light. We demonstrate that this photoinduced doping maintains the high carrier mobility of the graphene/boron nitride heterostructure, thus resembling the modulation doping technique used in semiconductor heterojunctions, and can be used to generate spatially varying doping profiles such as p-n junctions. We show that this photoinduced doping arises from microscopically coupled optical and electrical responses of graphene/boron nitride heterostructures, including optical excitation of defect transitions in boron nitride, electrical transport in graphene, and charge transfer between boron nitride and graphene.

Investigation of Nitride Morphology After Self-Aligned Contact Etch

NASA Technical Reports Server (NTRS)

Hwang, Helen H.; Keil, J.; Helmer, B. A.; Chien, T.; Gopaladasu, P.; Kim, J.; Shon, J.; Biegel, Bryan (Technical Monitor)

2001-01-01

Self-Aligned Contact (SAC) etch has emerged as a key enabling technology for the fabrication of very large-scale memory devices. However, this is also a very challenging technology to implement from an etch viewpoint. The issues that arise range from poor oxide etch selectivity to nitride to problems with post etch nitride surface morphology. Unfortunately, the mechanisms that drive nitride loss and surface behavior remain poorly understood. Using a simple langmuir site balance model, SAC nitride etch simulations have been performed and compared to actual etched results. This approach permits the study of various etch mechanisms that may play a role in determining nitride loss and surface morphology. Particle trajectories and fluxes are computed using Monte-Carlo techniques and initial data obtained from double Langmuir probe measurements. Etched surface advancement is implemented using a shock tracking algorithm. Sticking coefficients and etch yields are adjusted to obtain the best agreement between actual etched results and simulated profiles.

Interface formation in monolayer graphene-boron nitride heterostructures.

PubMed

Sutter, P; Cortes, R; Lahiri, J; Sutter, E

2012-09-12

The ability to control the formation of interfaces between different materials has become one of the foundations of modern materials science. With the advent of two-dimensional (2D) crystals, low-dimensional equivalents of conventional interfaces can be envisioned: line boundaries separating different materials integrated in a single 2D sheet. Graphene and hexagonal boron nitride offer an attractive system from which to build such 2D heterostructures. They are isostructural, nearly lattice-matched, and isoelectronic, yet their different band structures promise interesting functional properties arising from their integration. Here, we use a combination of in situ microscopy techniques to study the growth and interface formation of monolayer graphene-boron nitride heterostructures on ruthenium. In a sequential chemical vapor deposition process, boron nitride grows preferentially at the edges of existing monolayer graphene domains, which can be exploited for synthesizing continuous 2D membranes of graphene embedded in boron nitride. High-temperature growth leads to intermixing near the interface, similar to interfacial alloying in conventional heterostructures. Using real-time microscopy, we identify processes that eliminate this intermixing and thus pave the way to graphene-boron nitride heterostructures with atomically sharp interfaces.

Exceptionally Slow Movement of Gold Nanoparticles at a Solid/Liquid Interface Investigated by Scanning Transmission Electron Microscopy.

PubMed

Verch, Andreas; Pfaff, Marina; de Jonge, Niels

2015-06-30

Gold nanoparticles were observed to move at a liquid/solid interface 3 orders of magnitude slower than expected for the movement in a bulk liquid by Brownian motion. The nanoscale movement was studied with scanning transmission electron microscopy (STEM) using a liquid enclosure consisting of microchips with silicon nitride windows. The experiments involved a variation of the electron dose, the coating of the nanoparticles, the surface charge of the enclosing membrane, the viscosity, and the liquid thickness. The observed slow movement was not a result of hydrodynamic hindrance near a wall but instead explained by the presence of a layer of ordered liquid exhibiting a viscosity 5 orders of magnitude larger than a bulk liquid. The increased viscosity presumably led to a dramatic slowdown of the movement. The layer was formed as a result of the surface charge of the silicon nitride windows. The exceptionally slow motion is a crucial aspect of electron microscopy of specimens in liquid, enabling a direct observation of the movement and agglomeration of nanoscale objects in liquid.

Tubes of rhombohedral boron nitride

NASA Astrophysics Data System (ADS)

Bourgeois, L.; Bando, Y.; Sato, T.

2000-08-01

The structure of boron nitride bamboo-like tubular whiskers grown from boron nitride powder is investigated by high-resolution transmission electron microscopy. Despite the relatively small size of the tubes (20-200 nm in diameter), they all exhibit rhombohedral-like ordering in their layer stacking. The tubular sheets also tend to have their [10 bar 1 0] direction parallel to the fibre axis. Particles of iron alloys are commonly found encapsulated inside or at the end of the filaments. It is suggested that iron plays an active role in the growth of the fibres.

Magnetoresistance measurements of superconducting molybdenum nitride thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baskaran, R., E-mail: baskaran@igcar.gov.in; Arasu, A. V. Thanikai; Amaladass, E. P.

2016-05-23

Molybdenum nitride thin films have been deposited on aluminum nitride buffered glass substrates by reactive DC sputtering. GIXRD measurements indicate formation of nano-crystalline molybdenum nitride thin films. The transition temperature of MoN thin film is 7.52 K. The transition width is less than 0.1 K. The upper critical field Bc{sub 2}(0), calculated using GLAG theory is 12.52 T. The transition width for 400 µA current increased initially upto 3 T and then decreased, while that for 100 µA current transition width did not decrease.

Hard and low friction nitride coatings and methods for forming the same

DOEpatents

Erdemir, Ali; Urgen, Mustafa; Cakir, Ali Fuat; Eryilmaz, Osman Levent; Kazmanli, Kursat; Keles, Ozgul

2007-05-01

An improved coating material possessing super-hard and low friction properties and a method for forming the same. The improved coating material includes the use of a noble metal or soft metal homogeneously distributed within a hard nitride material. The addition of small amounts of such metals into nitrides such as molybdenum nitride, titanium nitride, and chromium nitride results in as much as increasing of the hardness of the material as well as decreasing the friction coefficient and increasing the oxidation resistance.

Pyroelectricity of silicon-doped hafnium oxide thin films

NASA Astrophysics Data System (ADS)

Jachalke, Sven; Schenk, Tony; Park, Min Hyuk; Schroeder, Uwe; Mikolajick, Thomas; Stöcker, Hartmut; Mehner, Erik; Meyer, Dirk C.

2018-04-01

Ferroelectricity in hafnium oxide thin films is known to be induced by various doping elements and in solid-solution with zirconia. While a wealth of studies is focused on their basic ferroelectric properties and memory applications, thorough studies of the related pyroelectric properties and their application potential are only rarely found. This work investigates the impact of Si doping on the phase composition and ferro- as well as pyroelectric properties of thin film capacitors. Dynamic hysteresis measurements and the field-free Sharp-Garn method were used to correlate the reported orthorhombic phase fractions with the remanent polarization and pyroelectric coefficient. Maximum values of 8.21 µC cm-2 and -46.2 µC K-1 m-2 for remanent polarization and pyroelectric coefficient were found for a Si content of 2.0 at%, respectively. Moreover, temperature-dependent measurements reveal nearly constant values for the pyroelectric coefficient and remanent polarization over the temperature range of 0 ° C to 170 ° C , which make the material a promising candidate for IR sensor and energy conversion applications beyond the commonly discussed use in memory applications.

Plasmonic spectral tunability of conductive ternary nitrides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kassavetis, S.; Patsalas, P., E-mail: ppats@physics.auth.gr; Bellas, D. V.

2016-06-27

Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as Ti{sub x}Ta{sub 1−x}N, Ti{sub x}Zr{sub 1−x}N, Ti{sub x}Al{sub 1−x}N, and Zr{sub x}Ta{sub 1−x}N share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400–700 nm) and UVA (315–400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementionedmore » broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.« less

Nitridation of porous GaAs by an ECR ammonia plasma

NASA Astrophysics Data System (ADS)

Naddaf, M.; Hullavarad, S. S.; Ganesan, V.; Bhoraskar, S. V.

2006-02-01

The effect of surface porosity of GaAs on the nature of growth of GaN, by use of plasma nitridation of GaAs, has been investigated. Porous GaAs samples were prepared by anodic etching of n-type (110) GaAs wafers in HCl solution. Nitridation of porous GaAs samples were carried out by using an electron-cyclotron resonance-induced ammonia plasma. The formation of mixed phases of GaN was investigated using the grazing angle x-ray diffraction method. A remarkable improvement in the intensity of photoluminescence (PL) compared with that of GaN synthesized by direct nitriding of GaAs surface has been observed. The PL intensity of nitrided porous GaAs at the temperature of 380 °C was found to be about two orders of magnitude higher as compared with the directly nitrided GaAs at the temperature of 500 °C. The changes in the morphology of nitrided porous GaAs have been investigated using both scanning electron microscopy and atomic force microscopy.

Infrared bolometers with silicon nitride micromesh absorbers

NASA Technical Reports Server (NTRS)

Bock, J. J.; Turner, A. D.; DelCastillo, H. M.; Beeman, J. W.; Lange, A. E.; Mauskopf, P. D.

1996-01-01

Sensitive far infrared and millimeter wave bolometers fabricated from a freestanding membrane of low stress silicon nitride are reported. The absorber, consisting of a metallized silicon nitride micromesh thermally isolated by radial legs of silicon nitride, is placed in an integrating cavity to efficiently couple to single mode or multiple mode infrared radiation. This structure provides low heat capacity, low thermal conduction and minimal cross section to energetic particles. A neutron transmutation doped Ge thermister is bump bonded to the center of the device and read out with evaporated Cr-Au leads. The limiting performance of the micromesh absorber is discussed and the recent results obtained from a 300 mK cold stage are summarized.

Enhanced Electroluminescence from Silicon Quantum Dots Embedded in Silicon Nitride Thin Films Coupled with Gold Nanoparticles in Light Emitting Devices

PubMed Central

Muñoz-Rosas, Ana Luz; Alonso-Huitrón, Juan Carlos

2018-01-01

Nowadays, the use of plasmonic metal layers to improve the photonic emission characteristics of several semiconductor quantum dots is a booming tool. In this work, we report the use of silicon quantum dots (SiQDs) embedded in a silicon nitride thin film coupled with an ultra-thin gold film (AuNPs) to fabricate light emitting devices. We used the remote plasma enhanced chemical vapor deposition technique (RPECVD) in order to grow two types of silicon nitride thin films. One with an almost stoichiometric composition, acting as non-radiative spacer; the other one, with a silicon excess in its chemical composition, which causes the formation of silicon quantum dots imbibed in the silicon nitride thin film. The ultra-thin gold film was deposited by the direct current (DC)-sputtering technique, and an aluminum doped zinc oxide thin film (AZO) which was deposited by means of ultrasonic spray pyrolysis, plays the role of the ohmic metal-like electrode. We found that there is a maximum electroluminescence (EL) enhancement when the appropriate AuNPs-spacer-SiQDs configuration is used. This EL is achieved at a moderate turn-on voltage of 11 V, and the EL enhancement is around four times bigger than the photoluminescence (PL) enhancement of the same AuNPs-spacer-SiQDs configuration. From our experimental results, we surmise that EL enhancement may indeed be due to a plasmonic coupling. This kind of silicon-based LEDs has the potential for technology transfer. PMID:29565267

Single Nanoparticle Translocation Through Chemically Modified Solid Nanopore

NASA Astrophysics Data System (ADS)

Tan, Shengwei; Wang, Lei; Liu, Hang; Wu, Hongwen; Liu, Quanjun

2016-02-01

The nanopore sensor as a high-throughput and low-cost technology can detect single nanoparticle in solution. In the present study, the silicon nitride nanopores were fabricated by focused Ga ion beam (FIB), and the surface was functionalized with 3-aminopropyltriethoxysilane to change its surface charge density. The positively charged nanopore surface attracted negatively charged nanoparticles when they were in the vicinity of the nanopore. And, nanoparticle translocation speed was slowed down to obtain a clear and deterministic signal. Compared with previous studied small nanoparticles, the electrophoretic translocation of negatively charged polystyrene (PS) nanoparticles (diameter ~100 nm) was investigated in solution using the Coulter counter principle in which the time-dependent nanopore current was recorded as the nanoparticles were driven across the nanopore. A linear dependence was found between current drop and biased voltage. An exponentially decaying function ( t d ~ e -v/v0 ) was found between the duration time and biased voltage. The interaction between the amine-functionalized nanopore wall and PS microspheres was discussed while translating PS microspheres. We explored also translocations of PS microspheres through amine-functionalized solid-state nanopores by varying the solution pH (5.4, 7.0, and 10.0) with 0.02 M potassium chloride (KCl). Surface functionalization showed to provide a useful step to fine-tune the surface property, which can selectively transport molecules or particles. This approach is likely to be applied to gene sequencing.

Silicon surface passivation by silicon nitride deposition

NASA Technical Reports Server (NTRS)

Olsen, L. C.

1984-01-01

Silicon nitride deposition was studied as a method of passivation for silicon solar cell surfaces. The following three objectives were the thrust of the research: (1) the use of pecvd silicon nitride for passivation of silicon surfaces; (2) measurement techniques for surface recombination velocity; and (3) the importance of surface passivation to high efficiency solar cells.

Silicon nitride ceramic having high fatigue life and high toughness

DOEpatents

Yeckley, Russell L.

1996-01-01

A sintered silicon nitride ceramic comprising between about 0.6 mol % and about 3.2 mol % rare earth as rare earth oxide, and between about 85 w/o and about 95 w/o beta silicon nitride grains, wherein at least about 20% of the beta silicon nitride grains have a thickness of greater than about 1 micron.

Surface Area, and Oxidation Effects on Nitridation Kinetics of Silicon Powder Compacts

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Palczer, A. R.

1998-01-01

Commercially available silicon powders were wet-attrition-milled from 2 to 48 hr to achieve surface areas (SA's) ranging from 1.3 to 70 sq m/g. The surface area effects on the nitridation kinetics of silicon powder compacts were determined at 1250 or 1350 C for 4 hr. In addition, the influence of nitridation environment, and preoxidation on nitridation kinetics of a silicon powder of high surface area (approximately equals 63 sq m/g) was investigated. As the surface area increased, so did the percentage nitridation after 4 hr in N2 at 1250 or 1350 C. Silicon powders of high surface area (greater than 40 sq m/g) can be nitrided to greater than 70% at 1250 C in 4 hr. The nitridation kinetics of the high-surface-area powder compacts were significantly delayed by preoxidation treatment. Conversely, the nitridation environment had no significant influence on the nitridation kinetics of the same powder. Impurities present in the starting powder, and those accumulated during attrition milling, appeared to react with the silica layer on the surface of silicon particles to form a molten silicate layer, which provided a path for rapid diffusion of nitrogen and enhanced the nitridation kinetics of high surface area silicon powder.

Method for producing silicon nitride/silicon carbide composite

DOEpatents

Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

1996-07-23

Silicon carbide/silicon nitride composites are prepared by carbothermal reduction of crystalline silica powder, carbon powder and optionally crsytalline silicon nitride powder. The crystalline silicon carbide portion of the composite has a mean number diameter less than about 700 nanometers and contains nitrogen.

Zirconium and hafnium fractionation in differentiation of alkali carbonatite magmatic systems

NASA Astrophysics Data System (ADS)

Kogarko, L. N.

2016-05-01

Zirconium and hafnium are valuable strategic metals which are in high demand in industry. The Zr and Hf contents are elevated in the final products of magmatic differentiation of alkali carbonatite rocks in the Polar Siberia region (Guli Complex) and Ukraine (Chernigov Massif). Early pyroxene fractionation led to an increase in the Zr/Hf ratio in the evolution of the ultramafic-alkali magmatic system due to a higher distribution coefficient of Hf in pyroxene with respect to Zr. The Rayleigh equation was used to calculate a quantitative model of variation in the Zr/Hf ratio in the development of the Guli magmatic system. Alkali carbonatite rocks originated from rare element-rich mantle reservoirs, in particular, the metasomatized mantle. Carbonated mantle xenoliths are characterized by a high Zr/Hf ratio due to clinopyroxene development during metasomatic replacement of orthopyroxene by carbonate fluid melt.

Hot carrier dynamics in plasmonic transition metal nitrides

NASA Astrophysics Data System (ADS)

Habib, Adela; Florio, Fred; Sundararaman, Ravishankar

2018-06-01

Extraction of non-equilibrium hot carriers generated by plasmon decay in metallic nano-structures is an increasingly exciting prospect for utilizing plasmonic losses, but the search for optimum plasmonic materials with long-lived carriers is ongoing. Transition metal nitrides are an exciting class of new plasmonic materials with superior thermal and mechanical properties compared to conventional noble metals, but their suitability for plasmonic hot carrier applications remains unknown. Here, we present fully first principles calculations of the plasmonic response, hot carrier generation and subsequent thermalization of all group IV, V and VI transition metal nitrides, fully accounting for direct and phonon-assisted transitions as well as electron–electron and electron–phonon scattering. We find the largest frequency ranges for plasmonic response in ZrN, HfN and WN, between those of gold and silver, while we predict strongest absorption in the visible spectrum for the VN, NbN and TaN. Hot carrier generation is dominated by direct transitions for most of the relevant energy range in all these nitrides, while phonon-assisted processes dominate only below 1 eV plasmon energies primarily for the group IV nitrides. Finally, we predict the maximum hot carrier lifetimes to be around 10 fs for group IV and VI nitrides, a factor of 3–4 smaller than noble metals, due to strong electron–phonon scattering. However, we find longer carrier lifetimes for group V nitrides, comparable to silver for NbN and TaN, while exceeding 100 fs (twice that of silver) for VN, making them promising candidates for efficient hot carrier extraction.

Iron Carbides and Nitrides: Ancient Materials with Novel Prospects.

PubMed

Ye, Zhantong; Zhang, Peng; Lei, Xiang; Wang, Xiaobai; Zhao, Nan; Yang, Hua

2018-02-07

Iron carbides and nitrides have aroused great interest in researchers, due to their excellent magnetic properties, good machinability and the particular catalytic activity. Based on these advantages, iron carbides and nitrides can be applied in various areas such as magnetic materials, biomedical, photo- and electrocatalysis. In contrast to their simple elemental composition, the synthesis of iron carbides and nitrides still has great challenges, particularly at the nanoscale, but it is usually beneficial to improve performance in corresponding applications. In this review, we introduce the investigations about iron carbides and nitrides, concerning their structure, synthesis strategy and various applications from magnetism to the catalysis. Furthermore, the future prospects are also discussed briefly. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Titanium-nitride-oxide-coated coronary stents: insights from the available evidence.

PubMed

Karjalainen, Pasi P; Nammas, Wail

2017-06-01

Coating of stent surface with a biocompatible material is suggested to improve stent safety profile. A proprietary process was developed to coat titanium-nitride-oxide on the stent surface, based on plasma technology that uses the nano-synthesis of gas and metal. Preclinical in vitro and in vivo investigation confirmed blood compatibility of titanium (nitride-) oxide films. Titanium-nitride-oxide-coated stents demonstrated a better angiographic outcome, compared with bare-metal stents at mid-term follow-up; however, they failed to achieve non-inferiority for angiographic outcome versus second-generation drug-eluting stents. Observational studies showed adequate clinical outcome at mid-term follow-up. Non-randomized studies showed an outcome of titanium-nitride-oxide-coated stents comparable to - or better than - first-generation drug-eluting stents at long-term follow-up. Two randomized controlled trials demonstrated comparable efficacy outcome, and a better safety outcome of titanium-nitride-oxide-coated stents versus drug-eluting stents at long-term follow-up. Evaluation by optical coherence tomography at mid-term follow-up revealed better neointimal strut coverage associated with titanium-nitride-oxide-coated stents versus drug-eluting stents; yet, neointimal hyperplasia thickness was greater. Key messages Stents coated with titanium-nitride-oxide demonstrated biocompatibility in preclinical studies: they inhibit platelet and fibrin deposition, and reduce neointimal growth. In observational and non-randomized studies, titanium-nitride-oxide-coated stents were associated with adequate safety and efficacy outcome. In randomized trials of patients with acute coronary syndrome, titanium-nitride-oxide-coated stents were associated with a better safety outcome, compared with drug-eluting stents; efficacy outcome was comparable.

Microstructure and antibacterial properties of microwave plasma nitrided layers on biomedical stainless steels

NASA Astrophysics Data System (ADS)

Lin, Li-Hsiang; Chen, Shih-Chung; Wu, Ching-Zong; Hung, Jing-Ming; Ou, Keng-Liang

2011-06-01

Nitriding of AISI 303 austenitic stainless steel using microwave plasma system at various temperatures was conducted in the present study. The nitrided layers were characterized via scanning electron microscopy, glancing angle X-ray diffraction, transmission electron microscopy and Vickers microhardness tester. The antibacterial properties of this nitrided layer were evaluated. During nitriding treatment between 350 °C and 550 °C, the phase transformation sequence on the nitrided layers of the alloys was found to be γ → (γ + γ N) → (γ + α + CrN). The analytical results revealed that the surface hardness of AISI 303 stainless steel could be enhanced with the formation of γ N phase in nitriding process. Antibacterial test also demonstrated the nitrided layer processed the excellent antibacterial properties. The enhanced surface hardness and antibacterial properties make the nitrided AISI 303 austenitic stainless steel to be one of the essential materials in the biomedical applications.

Electronic structure and mechanical properties of plasma nitrided ferrous alloys

NASA Astrophysics Data System (ADS)

Portolan, E.; Baumvol, I. J. R.; Figueroa, C. A.

2009-04-01

The electronic structures of the near-surface regions of two different nitrided steels (AISI 316 and 4140) were investigated using X-ray photoelectron spectroscopy. Photoelectron groups from all main chemical elements involved were addressed for steel samples with implanted-N concentrations in the range 16-32 at.%. As the implanted-N concentrations were increased, rather contrasting behaviors were observed for the two kinds of steel. The N1s photoelectrons had spectral shifts toward lower (nitrided AISI 316) or higher (nitrided AISI 4140) binding energies, whereas the Fe2p 3/2 photoelectron spectrum remains at a constant binding energy (nitrided AISI 316) or shifts toward higher binding energies (AISI 4140). These trends are discussed in terms of the metallic nitride formation and the overlapping of atomic orbitals. For nitrided AISI 316, a semi-classical approach of charge transfer between Cr and N is used to explain the experimental facts (formation of CrN), while for nitrided AISI 4140 we propose that the interaction between orbitals 4s from Fe and 2p from N promotes electrons to the conduction band increasing the electrical attraction of the N1s and Fe2p electrons in core shells (formation of FeN x). The increase in hardness of the steel upon N implantation is attributed to the localization of electrons in specific bonds, which diminishes the metallic bond character.

Oxidation of boron nitride in an arc heated jet.

NASA Technical Reports Server (NTRS)

Buckley, J. D.

1971-01-01

Two grades of hot pressed boron nitride and a boron nitride composite were subjected to oxidation tests in a 2.5 megawatt atmospheric arc jet. The results showed that fabrication and/or composition influenced thermal shock and oxidation resistance. Changes in surface structure and recession due to oxidation suggest correlation with specimen composition. The boron nitride composite reacted with the oxygen in the hot subsonic airstream to produce a glassy coating on the hot face surface.

Rolling-element fatigue life of silicon nitride balls: Preliminary test results

NASA Technical Reports Server (NTRS)

Parker, R. J.; Zaretsky, E. V.

1972-01-01

Hot pressed silicon nitride was evaluated as a rolling element bearing material. The five-ball fatigue tester was used to test 12.7 mm (0.500 in.) diameter balls at a maximum Hertz stress of 800,000 psi at a race temperature of 130 F. The fatigue spalls in the silicon nitride resembled those in typical bearing steels. The ten-percent fatigue life of the silicon nitride balls was approximately one-eighth to one-fifth that of typical bearing steels (52100 and M-50). The load capacity of the silicon nitride was approximately one-third that of typical bearing steels. The load capacity of the silicon nitride was significantly higher than previously tested ceramic materials for rolling element bearings.

Aluminum nanoparticles burning - still a puzzle?

NASA Astrophysics Data System (ADS)

Gromov, A. A.; Popenko, E. M.

2009-09-01

The experimental data on the aluminum nanopowders (nAl) combustion in oxidizing media (air, propellants AP∗/HTPB†/Al/HMX‡, and energetic compositions) assuming the phenomenon of nitrides formation with the high yield is generalized. In the present work, the nAl produced by electrical explosion of wires was studied. The temperature, burning rate, and radiation were measured at combustion and the actual burning process was recorded by a videocamera. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and chemical analysis were performed on the both initial powders and final condensed products. It was experimentally proved that the combustion process of aluminum nanoparticles was two staged independently of burning conditions in nitrogen-containing media. The formation of nitrides in presence of molecular nitrogen is the determining stage in the particles combustion. A qualitative discussion is given on the kinetic limitation for AlN (AlON) oxidation due to rapid condensation and encapsulation of solid AlN (AlON).

Nitriding of super alloys for enhancing physical properties

DOEpatents

Purohit, Ankur

1986-01-01

The invention teaches the improvement of certain super alloys by exposing the alloy to an atmosphere of elemental nitrogen at elevated temperatures in excess of 750.degree. C. but less than 1150.degree. C. for an extended duration, viz., by nitriding the surface of the alloy, to establish barrier nitrides of the order of 25-100 micrometers thickness. These barrier nitrides appear to shield the available oxidizing metallic species of the alloy for up to a sixfold improved resistance against oxidation and also appear to impede egress of surface dislocations for increased fatigue and creep strengths.

Experimental and first-principles studies on the elastic properties of α-hafnium metal under pressure

DOE PAGES

Qi, Xintong; Wang, Xuebing; Chen, Ting; ...

2016-03-30

Compressional and shear wave velocities of the α phase of hafnium have been measured up to 10.4 GPa at room temperature using ultrasonic interferometry in a multi-anvil apparatus. A finite strain equation of state analysis yielded K s0 = 110.4 (5) GPa, G 0 = 54.7(5) GPa,K s0' = 3.7 and G 0' = 0.6 for the elastic bulk and shear moduli and their pressure derivatives at ambient conditions. Complementary to the experimental data, the single crystal elastic constants, elastic anisotropy and the unit cell axial ratio c/a of α-hafnium at high pressures were investigated by Density Functional Theory (DFT)more » based first principles calculations. A c/a value of 1.605 is predicted for α-Hf at 40 GPa, which is in excellent agreement with previous experimental results. The low-pressure derivative of the shear modulus observed in our experimental data up to 10 GPa was found to originate from the elastic constant C44 which exhibits negligible pressure dependence within the current experimental pressure range. At higher pressures (>10 GPa), C 44 was predicted to soften and the shear wave velocity ν S trended to decrease with pressure, which can be interpreted as a precursor to the α-ω transition similar to that observed in other group IV elements (titanium and zirconium). Here, the acoustic velocities, bulk and shear moduli, and the acoustic Debye temperature (θ D = 240.1 K) determined from the current experiments were all compared well with those predicted by our theoretical DFT calculations.« less

The role of pore geometry in single nanoparticle detection

DOE PAGES

Davenport, Matthew; Healy, Ken; Pevarnik, Matthew; ...

2012-08-22

In this study, we observe single nanoparticle translocation events via resistive pulse sensing using silicon nitride pores described by a range of lengths and diameters. Pores are prepared by focused ion beam milling in 50 nm-, 100 nm-, and 500 nm-thick silicon nitride membranes with diameters fabricated to accommodate spherical silica nanoparticles with sizes chosen to mimic that of virus particles. In this manner, we are able to characterize the role of pore geometry in three key components of the detection scheme, namely, event magnitude, event duration, and event frequency. We find that the electric field created by the appliedmore » voltage and the pore’s geometry is a critical factor. We develop approximations to describe this field, which are verified with computer simulations, and interactions between particles and this field. In so doing, we formulate what we believe to be the first approximation for the magnitude of ionic current blockage that explicitly addresses the invariance of access resistance of solid-state pores during particle translocation. These approximations also provide a suitable foundation for estimating the zeta potential of the particles and/or pore surface when studied in conjunction with event durations. We also verify that translocation achieved by electro-osmostic transport is an effective means of slowing translocation velocities of highly charged particles without compromising particle capture rate as compared to more traditional approaches based on electrophoretic transport.« less

Stress-rupture strength and microstructural stability of tungsten-hafnium-carbon-wire reinforced superalloy composites

NASA Technical Reports Server (NTRS)

Petrasek, D. W.; Signorelli, R. A.

1974-01-01

Tungsten-hafnium-carbon - superalloy composites were found to be potentially useful for turbine blade applications on the basis of stress-rupture strength. The 100- and 1000-hr rupture strengths calculated for 70 vol. % fiber composites based on test data at 1090C (2000F) were 420 and 280 MN/m2 (61,000 and 41,000 psi, respectively). The investigation indicated that, with better quality fibers, composites having 100- and 1000-hr rupture strengths of 570 and 370 MN/m2 (82,000 and 54,000 psi, respectively), may be obtained. Metallographic studies indicated sufficient fiber-matrix compatibility for 1000 hr or more at 1090C (2000F).

Structural stability and electronic properties of an octagonal allotrope of two dimensional boron nitride.

PubMed

Takahashi, Lauren; Takahashi, Keisuke

2017-03-27

An octagonal allotrope of two dimensional boron nitride is explored through first principles calculations. Calculations show that two dimensional octagonal boron nitride can be formed with a binding energy comparable to two dimensional hexagonal boron nitride. In addition, two dimensional octagonal boron nitride is found to have a band gap smaller than two dimensional hexagonal boron nitride, suggesting the possibility of semiconductive attributes. Two dimensional octagonal boron nitride also has the ability to layer through physisorption. Defects present within two dimensional octagonal boron nitride also lead toward the introduction of a magnetic moment through the absence of boron atoms. The presence of defects is also found to render both hexagonal and octagonal boron nitrides reactive against hydrogen, where greater reactivity is seen in the presence of nitrogen. Thus, two dimensional octagonal boron nitride is confirmed with potential to tailor properties and reactivity through lattice shape and purposeful introduction of defects.

Synthesis of Boron Nitride Nanotubes for Engineering Applications

NASA Technical Reports Server (NTRS)

Hurst, Janet; Hull, David; Gorican, Dan

2005-01-01

Boron Nitride nanotubes (BNNT) are of interest to the scientific and technical communities for many of the same reasons that carbon nanotubes (CNT) have attracted large amounts of attention. Both materials have potentially unique and significant properties which may have important structural and electronic applications in the future. However of even more interest than their similarities may be the differences between carbon and boron nanotubes. Whilt boron nitride nanotubes possess a very high modulus similaar to CNT, they are also more chemically and thermally inert. Additionally BNNT possess more uniform electronic properties, having a uniform band gap of approximately 5.5 eV while CNT vary from semi-conductin to conductor behavior. Boron Nitride nanotubes have been synthesized by a variety of methods such as chemical vapor deposition, arc discharge and reactive milling. Consistently producing a reliable product has proven difficult. Progress in synthesis of 1-2 gram sized batches of Boron Nitride nanotubes will be discussed as well as potential uses for this unique material.

Alkaline fuel cell with nitride membrane

NASA Astrophysics Data System (ADS)

Sun, Shen-Huei; Pilaski, Moritz; Wartmann, Jens; Letzkus, Florian; Funke, Benedikt; Dura, Georg; Heinzel, Angelika

2017-06-01

The aim of this work is to fabricate patterned nitride membranes with Si-MEMS-technology as a platform to build up new membrane-electrode-assemblies (MEA) for alkaline fuel cell applications. Two 6-inch wafer processes based on chemical vapor deposition (CVD) were developed for the fabrication of separated nitride membranes with a nitride thickness up to 1 μm. The mechanical stability of the perforated nitride membrane has been adjusted in both processes either by embedding of subsequent ion implantation step or by optimizing the deposition process parameters. A nearly 100% yield of separated membranes of each deposition process was achieved with layer thickness from 150 nm to 1 μm and micro-channel pattern width of 1μm at a pitch of 3 μm. The process for membrane coating with electrolyte materials could be verified to build up MEA. Uniform membrane coating with channel filling was achieved after the optimization of speed controlled dip-coating method and the selection of dimethylsulfoxide (DMSO) as electrolyte solvent. Finally, silver as conductive material was defined for printing a conductive layer onto the MEA by Ink-Technology. With the established IR-thermography setup, characterizations of MEAs in terms of catalytic conversion were performed successfully. The results of this work show promise for build up a platform on wafer-level for high throughput experiments.

Interlayer interaction and mechanical properties in multi-layer graphene, Boron-Nitride, Aluminum-Nitride and Gallium-Nitride graphene-like structure: A quantum-mechanical DFT study

NASA Astrophysics Data System (ADS)

Ghorbanzadeh Ahangari, Morteza; Fereidoon, A.; Hamed Mashhadzadeh, Amin

2017-12-01

In present study, we investigated mechanical, electronic and interlayer properties of mono, bi and 3layer of Boron-Nitride (B-N), Aluminum-Nitride (Al-N) and Gallium-Nitride (Ga-N) graphene sheets and compared these results with results obtained from carbonic graphenes (C-graphenes). For reaching this purpose, first we optimized the geometrical parameters of these graphenes by using density functional theory (DFT) method. Then we calculated Young's modulus of graphene sheet by compressing and then elongating these sheets in small increment. Our results indicates that Young's modulus of graphenes didn't changed obviously by increasing the number of layer sheet. We also found that carbonic graphene has greatest Young's modulus among another mentioned sheets because of smallest equilibrium distance between its elements. Next we modeled the van der Waals interfacial interaction exist between two sheets with classical spring model by using general form of Lennard-Jones (L-J) potential for all of mentioned graphenes. For calculating L-J parameters (ε and σ), the potential energy between layers of mentioned graphene as a function of the separation distance was plotted. Moreover, the density of states (DOS) are calculated to understand the electronic properties of these systems better.

Iron-Nitride Alloy Magnets: Transformation Enabled Nitride Magnets Absent Rare Earths (TEN Mare)

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2012-01-01

REACT Project: Case Western is developing a highly magnetic iron-nitride alloy to use in the magnets that power electric motors found in EVs and renewable power generators. This would reduce the overall price of the motor by eliminating the expensive imported rare earth minerals typically found in today’s best commercial magnets. The iron-nitride powder is sourced from abundant and inexpensive materials found in the U.S. The ultimate goal of this project is to demonstrate this new magnet system, which contains no rare earths, in a prototype electric motor. This could significantly reduce the amount of greenhouse gases emitted in themore » U.S. each year by encouraging the use of clean alternatives to oil and coal.« less

Silicon doped hafnium oxide (HSO) and hafnium zirconium oxide (HZO) based FeFET: A material relation to device physics

NASA Astrophysics Data System (ADS)

Ali, T.; Polakowski, P.; Riedel, S.; Büttner, T.; Kämpfe, T.; Rudolph, M.; Pätzold, B.; Seidel, K.; Löhr, D.; Hoffmann, R.; Czernohorsky, M.; Kühnel, K.; Thrun, X.; Hanisch, N.; Steinke, P.; Calvo, J.; Müller, J.

2018-05-01

The recent discovery of ferroelectricity in thin film HfO2 materials renewed the interest in ferroelectric FET (FeFET) as an emerging nonvolatile memory providing a potential high speed and low power Flash alternative. Here, we report more insight into FeFET performance by integrating two types of ferroelectric (FE) materials and varying their properties. By varying the material type [HfO2 (HSO) versus hafnium zirconium oxide (HZO)], optimum content (Si doping/mixture ratio), and film thickness, a material relation to FeFET device physics is concluded. As for the material type, an improved FeFET performance is observed for HZO integration with memory window (MW) comparable to theoretical values. For different Si contents, the HSO based FeFET exhibited a MW trend with different stabilized phases. Similarly, the HZO FeFET shows MW dependence on the Hf:Zr mixture ratio. A maximized MW is obtained with cycle ratios of 16:1 (HfO2:Si) and 1:1 (Hf:Zr) as measured on HSO and HZO based FeFETs, respectively. The thickness variation shows a trend of increasing MW with the increased FE layer thickness confirming early theoretical predictions. The FeFET material aspects and stack physics are discussed with insight into the interplay factors, while optimum FE material parameters are outlined in relation to performance.

Gallium nitride based logpile photonic crystals.

PubMed

Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J; Wang, George T; Fischer, Arthur J

2011-11-09

We demonstrate a nine-layer logpile three-dimensional photonic crystal (3DPC) composed of single crystalline gallium nitride (GaN) nanorods, ∼100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a "line-defect" cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25-30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride based optoelectronic devices.

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

Tracy, C. Edwin; Benson, David K.

1988-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

Tracy, C.E.; Benson, D.K.

1984-07-20

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate prior to metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Isolation and characterization of a uranium(VI)-nitride triple bond

NASA Astrophysics Data System (ADS)

King, David M.; Tuna, Floriana; McInnes, Eric J. L.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.

2013-06-01

The nature and extent of covalency in uranium bonding is still unclear compared with that of transition metals, and there is great interest in studying uranium-ligand multiple bonds. Although U=O and U=NR double bonds (where R is an alkyl group) are well-known analogues to transition-metal oxo and imido complexes, the uranium(VI)-nitride triple bond has long remained a synthetic target in actinide chemistry. Here, we report the preparation of a uranium(VI)-nitride triple bond. We highlight the importance of (1) ancillary ligand design, (2) employing mild redox reactions instead of harsh photochemical methods that decompose transiently formed uranium(VI) nitrides, (3) an electrostatically stabilizing sodium ion during nitride installation, (4) selecting the right sodium sequestering reagent, (5) inner versus outer sphere oxidation and (6) stability with respect to the uranium oxidation state. Computational analyses suggest covalent contributions to U≡N triple bonds that are surprisingly comparable to those of their group 6 transition-metal nitride counterparts.

Functional carbon nitride materials — design strategies for electrochemical devices

NASA Astrophysics Data System (ADS)

Kessler, Fabian K.; Zheng, Yun; Schwarz, Dana; Merschjann, Christoph; Schnick, Wolfgang; Wang, Xinchen; Bojdys, Michael J.

2017-06-01

In the past decade, research in the field of artificial photosynthesis has shifted from simple, inorganic semiconductors to more abundant, polymeric materials. For example, polymeric carbon nitrides have emerged as promising materials for metal-free semiconductors and metal-free photocatalysts. Polymeric carbon nitride (melon) and related carbon nitride materials are desirable alternatives to industrially used catalysts because they are easily synthesized from abundant and inexpensive starting materials. Furthermore, these materials are chemically benign because they do not contain heavy metal ions, thereby facilitating handling and disposal. In this Review, we discuss the building blocks of carbon nitride materials and examine how strategies in synthesis, templating and post-processing translate from the molecular level to macroscopic properties, such as optical and electronic bandgap. Applications of carbon nitride materials in bulk heterojunctions, laser-patterned memory devices and energy storage devices indicate that photocatalytic overall water splitting on an industrial scale may be realized in the near future and reveal a new avenue of 'post-silicon electronics'.

The Effect of Polymer Char on Nitridation Kinetics of Silicon

NASA Technical Reports Server (NTRS)

Chan, Rickmond C.; Bhatt, Ramakrishna T.

1994-01-01

Effects of polymer char on nitridation kinetics of attrition milled silicon powder have been investigated from 1200 to 1350 C. Results indicate that at and above 1250 C, the silicon compacts containing 3.5 wt percent polymer char were fully converted to Si3N4 after 24 hr exposure in nitrogen. In contrast, the silicon compacts without polymer char could not be fully converted to Si3N4 at 1350 C under similar exposure conditions. At 1250 and 1350 C, the silicon compacts with polymer char showed faster nitridation kinetics than those without the polymer char. As the polymer char content is increased, the amount of SiC in the nitrided material is also increased. By adding small amounts (approx. 2.5 wt percent) of NiO, the silicon compacts containing polymer char can be completely nitrided at 1200 C. The probable mechanism for the accelerated nitridation of silicon containing polymer char is discussed.

Nitridation of a Super-Ferritic Stainless Steel for PEMFC Bipolar Plate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, H.; Turner, J. A.; Brady, M. P.

2007-01-01

AL29-4C alloy nitrided in pure nitrogen resulted in a nitrogen-modified oxide surface, which is the same as AISI446 nitrided under identical conditions. When the alloy was nitrided 24h at 900 C in N2-4H2, XRD and XPS analysis indicated that the surface layer consisted of a nitride outer layer ({approx}0.20 {micro}m) and an oxide inner layer ({approx} 0.82 {micro}m). According to XPS, the nitride outer layer is composed of CrN and [Cr(N),Fe]2N1-x, with much more Cr2N than Fe2N. Mn is migrated and enriched in the oxide inner layer and combined with chromium oxide.AL29-4C alloy nitrided in N2-4H2 resulted in low ICRmore » and excellent corrosion resistance in simulated PEMFC environments. Current was at ca. -3.0 {micro}A/cm2 in the PEMFC anode environment, and at ca. 0.3 {approx} 0.5 {micro}A/cm2 in the cathode environment. This is considered to be rather stable. After being polarized in a PEMFC environment, the ICR increased slightly compared with the as-nitrided sample, but was still rather low.« less

Electronic Biosensors Based on III-Nitride Semiconductors.

PubMed

Kirste, Ronny; Rohrbaugh, Nathaniel; Bryan, Isaac; Bryan, Zachary; Collazo, Ramon; Ivanisevic, Albena

2015-01-01

We review recent advances of AlGaN/GaN high-electron-mobility transistor (HEMT)-based electronic biosensors. We discuss properties and fabrication of III-nitride-based biosensors. Because of their superior biocompatibility and aqueous stability, GaN-based devices are ready to be implemented as next-generation biosensors. We review surface properties, cleaning, and passivation as well as different pathways toward functionalization, and critically analyze III-nitride-based biosensors demonstrated in the literature, including those detecting DNA, bacteria, cancer antibodies, and toxins. We also discuss the high potential of these biosensors for monitoring living cardiac, fibroblast, and nerve cells. Finally, we report on current developments of covalent chemical functionalization of III-nitride devices. Our review concludes with a short outlook on future challenges and projected implementation directions of GaN-based HEMT biosensors.

Fabrication of cermet bearings for the control system of a high temperature lithium cooled nuclear reactor

NASA Technical Reports Server (NTRS)

Yacobucci, H. G.; Heestand, R. L.; Kizer, D. E.

1973-01-01

The techniques used to fabricate cermet bearings for the fueled control drums of a liquid metal cooled reference-design reactor concept are presented. The bearings were designed for operation in lithium for as long as 5 years at temperatures to 1205 C. Two sets of bearings were fabricated from a hafnium carbide - 8-wt. % molybdenum - 2-wt. % niobium carbide cermet, and two sets were fabricated from a hafnium nitride - 10-wt. % tungsten cermet. Procedures were developed for synthesizing the material in high purity inert-atmosphere glove boxes to minimize oxygen content in order to enhance corrosion resistance. Techniques were developed for pressing cylindrical billets to conserve materials and to reduce machining requirements. Finishing was accomplished by a combination of diamond grinding, electrodischarge machining, and diamond lapping. Samples were characterized in respect to composition, impurity level, lattice parameter, microstructure and density.

Manufacture of sintered silicon nitrides

NASA Technical Reports Server (NTRS)

Iwai, T.

1985-01-01

Sintered silicon nitrides are manufactured by sintering Si3N powder containing 2 to 15% in wt of a powder mixture composed of nitride powder of lanthanide or Y 100 parts and AIN powder less than 100 parts at 1500 to 1900 deg. temperature under a pressure of less than 200 Kg/sq. cm. The sintered Si3N has high mechanical strength in high temperature. Thus, Si3N4 93.0, Y 5.0 and AlN 2.0% in weight were wet mixed in acetone in N atom, molded and sintered at 1750 deg. and 1000 Kg/sq. cm. to give a sintered body having high hardness.

Silicon-nitride and metal composite

DOEpatents

Landingham, Richard L.; Huffsmith, Sarah A.

1981-01-01

A composite and a method for bonding the composite. The composite includes a ceramic portion of silicon nitride, a refractory metal portion and a layer of MoSi.sub.2 indirectly bonding the composite together. The method includes contacting the layer of MoSi.sub.2 with a surface of the silicon nitride and with a surface of the metal; heating the layer to a temperature below 1400.degree. C.; and, simultaneously with the heating, compressing the layer such that the contacting is with a pressure of at least 30 MPa. This composite overcomes useful life problems in the fabrication of parts for a helical expander for use in power generation.

Silicon-nitride and metal composite

DOEpatents

Landingham, R.L.; Huffsmith, S.A.

A composite and a method for bonding the composite are described. The composite includes a ceramic portion of silicon nitride, a refractory metal portion and a layer of MoSi/sub 2/ indirectly bonding the composite together. The method includes contacting the layer of MoSi/sub 2/ with a surface of the silicon nitride and with a surface of the metal; heating the layer to a temperature below 1400/sup 0/C; and, simultaneously, compressing the layer such that the contacting is with a pressure of at least 30 MPa. This composite overcomes useful life problems in the fabrication of parts for a helical expander for use in power generation.

Atomic layer deposition of hafnium oxide: A detailed reaction mechanism from first principles

NASA Astrophysics Data System (ADS)

Widjaja, Yuniarto; Musgrave, Charles B.

2002-08-01

Atomic layer deposition (ALD) of hafnium oxide (HfO2) using HfCl4 and H2O as precursors is studied using density functional theory. The mechanism consists of two deposition half-reactions: (1) HfCl4 with Hf-OH sites, and (2) H2O with Hf-Cl sites. Both half-reactions exhibit stable intermediates with energies lower than those of the final products. We show that increasing the temperature reduces the stability of the complex. However, increasing temperature also increases the dissociation free-energy barrier, which in turn results in increased desorption of adsorbed precursors. Both half-reactions are qualitatively similar to the corresponding reactions of ZrO2 ALD using ZrCl4 and H2O.

Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen

NASA Astrophysics Data System (ADS)

Hamann, S.; Börner, K.; Burlacov, I.; Spies, H.-J.; Strämke, M.; Strämke, S.; Röpcke, J.

2015-12-01

A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steel samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH4, C2H2, HCN, and NH3). With the help of OES, the rotational temperature of the screen plasma could be determined.

Intrinsic Defect Ferromagnetism: The case of Hafnium Oxide

NASA Astrophysics Data System (ADS)

Das Pemmaraju, Chaitanya

2005-03-01

In view of the recent experimental reports of intrinsic ferromagnetism in Hafnium Oxide (HfO2) thin film systems ootnotetextM. Venkatesan, C. B. Fitzgerald, J. M. D. Coey Nature 430, 630 (2004) Brief Communications, we carried out first principles investigations to look for magnetic structure in HfO2 possibly brought about by the presence of small concentrations of intrinsic point defects. Ab initio electronic structure calculations using Density Functional Theory (DFT) show that isolated cation vacancy sites in HfO2 lead to the formation of high spin defect states which couple ferromagnetically to each other. Interestingly, these high spin states are observed in the low symmetry monoclinic and tetragonal phases while the highly symmetric cubic flourite phase exhibits a non-magnetic ground state. Detailed studies of the electronic structure of cation vacancies in the three crystalline phases of Hafnia show that symmetry leading to orbitally degenerate defect levels is not a pre-requsite for ferromagnetism and that the interplay between Kinetic, Coulomb and Exchange energy together with favourable coupling to the Crystalline environment can lead to high spin ferromagnetic ground states even in extreme low symmetry systems like monoclinic HfO2. These findings open up a much wider class of systems to the possibility of intrinsic defect ferromagnetism.

Nitride coating enhances endothelialization on biomedical NiTi shape memory alloy.

PubMed

Ion, Raluca; Luculescu, Catalin; Cimpean, Anisoara; Marx, Philippe; Gordin, Doina-Margareta; Gloriant, Thierry

2016-05-01

Surface nitriding was demonstrated to be an effective process for improving the biocompatibility of implantable devices. In this study, we investigated the benefits of nitriding the NiTi shape memory alloy for vascular stent applications. Results from cell experiments indicated that, compared to untreated NiTi, a superficial gas nitriding treatment enhanced the adhesion of human umbilical vein endothelial cells (HUVECs), cell spreading and proliferation. This investigation provides data to demonstrate the possibility of improving the rate of endothelialization on NiTi by means of nitride coating. Copyright © 2016 Elsevier B.V. All rights reserved.

Sintering silicon nitride

NASA Technical Reports Server (NTRS)

Bansal, Narottam P. (Inventor); Levine, Stanley R. (Inventor); Sanders, William A. (Inventor)

1993-01-01

Oxides having a composition of (Ba(1-x)Sr(x))O-Al2O3-2SiO2 are used as sintering aids for producing an improved silicon nitride ceramic material. The x must be greater than 0 to insure the formation of the stable monoclinic celsian glass phase.

Modification of Low-Alloy Steel Surface by High-Temperature Gas Nitriding Plus Tempering

NASA Astrophysics Data System (ADS)

Jiao, Dongling; Li, Minsong; Ding, Hongzhen; Qiu, Wanqi; Luo, Chengping

2018-02-01

The low-alloy steel was nitrided in a pure NH3 gas atmosphere at 640 660 °C for 2 h, i.e., high-temperature gas nitriding (HTGN), followed by tempering at 225 °C, which can produce a high property surface coating without brittle compound (white) layer. The steel was also plasma nitriding for comparison. The composition, microstructure and microhardness of the nitrided and tempered specimens were examined, and their tribological behavior investigated. The results showed that the as-gas-nitrided layer consisted of a white layer composed of FeN0.095 phase (nitrided austenite) and a diffusional zone underneath the white layer. After tempering, the white layer was decomposed to a nano-sized (α-Fe + γ'-Fe4N + retained austenite) bainitic microstructure with a high hardness of 1150HV/25 g. Wear test results showed that the wear resistance and wear coefficient yielded by the complex HTGN plus tempering were considerably higher and lower, respectively, than those produced by the conventional plasma nitriding.

Discontinuous Inter-Granular Separations (DIGS) in the Gas Nitride Layer of ISS Race Rings

NASA Technical Reports Server (NTRS)

Figert, John; Dasgupta, Rajib; Martinez, James

2010-01-01

The starboard solar alpha rotary joint (SARJ) race ring on the International space station (ISS) failed due to severe spalling of the outer diameter, 45 degree (outer canted) nitrided surface. Subsequent analysis at NASA-KSC revealed that almost all of the debris generated due to the failure was nitrided 15-5 stainless steel. Subsequent analysis of the nitride control coupons (NCC) at NASA-JSC revealed the presence of discontinuous inter-granular separations (DIGS) in the gas nitride layer. These DIGS were present in the inter-granular networking located in the top 2 mils of the nitride layer. The manufacturer's specification requires the maximum white structure to be 0.0003 inches and intergranular networking below the allowable white structure depth to be cause for rejection; a requirement that the NCCs did not meet. Subsequent testing and analysis revealed that lower DIGS content significantly lowered the probability of nitride spalling in simulated, dry condition runs. One batch of nitride samples with DIGS content similar to the port SARJ (did not fail on orbit) which exhibited almost no nitride spalling after being run on one test rig. Another batch of nitride samples with DIGS content levels similar to the starboard SARJ exhibited significant nitride spalling on the same test rig with the same load under dry conditions. Although DIGS were not the root cause of starboard race ring failure, testing indicates that increased DIGS reduced the robustness of the gas nitride layer under dry operating conditions.

Imaging TiO2 nanoparticles on GaN nanowires with electrostatic force microscopy

NASA Astrophysics Data System (ADS)

Xie, Ting; Wen, Baomei; Liu, Guannan; Guo, Shiqi; Motayed, Abhishek; Murphy, Thomas; Gomez, R. D.

Gallium nitride (GaN) nanowires that are functionalized with metal-oxides nanoparticles have been explored extensively for gas sensing applications in the past few years. These sensors have several advantages over conventional schemes, including miniature size, low-power consumption and fast response and recovery times. The morphology of the oxide functionalization layer is critical to achieve faster response and recovery times, with the optimal size distribution of nanoparticles being in the range of 10 to 30 nm. However, it is challenging to characterize these nanoparticles on GaN nanowires using common techniques such as scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. Here, we demonstrate electrostatic force microscopy in combination with atomic force microscopy as a non-destructive technique for morphological characterization of the dispersed TiO2 nanoparticles on GaN nanowires. We also discuss the applicability of this method to other material systems with a proposed tip-surface capacitor model. This project was sponsored through N5 Sensors and the Maryland Industrial Partnerships (MIPS, #5418).

Silicon nitride/silicon carbide composite densified materials prepared using composite powders

DOEpatents

Dunmead, S.D.; Weimer, A.W.; Carroll, D.F.; Eisman, G.A.; Cochran, G.A.; Susnitzky, D.W.; Beaman, D.R.; Nilsen, K.J.

1997-07-01

Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Direct observation of resonance scattering patterns in single silicon nanoparticles

NASA Astrophysics Data System (ADS)

Valuckas, Vytautas; Paniagua-Domínguez, Ramón; Fu, Yuan Hsing; Luk'yanchuk, Boris; Kuznetsov, Arseniy I.

2017-02-01

We present the first direct observation of the scattering patterns of electric and magnetic dipole resonances excited in a single silicon nanosphere. Almost perfectly spherical silicon nanoparticles were fabricated and deposited on a 30 nm-thick silicon nitride membrane in an attempt to minimize particle—substrate interaction. Measurements were carried out at visible wavelengths by means of the Fourier microscopy in a dark-field illumination setup. The obtained back-focal plane images clearly reveal the characteristic scattering patterns associated with each resonance and are found to be in a good agreement with the simulated results.

Failure Mechanisms for III-Nitride HEMT Devices

DTIC Science & Technology

2013-11-19

rf plasma-assisted molecular beam epitaxy on freestanding GaN substrates, J. Cryst. Growth 380, 14-17 (2013). ii) Conference presentations (Invited...1 eFinal Report – AOARD Grant FA-2386-11-1-4107 Failure Mechanisms for III-nitride HEMT devices 19 November 2013 Principal Investigators: Martha...aspects of III-nitride HEMT materials and devices. Energy-filtered imaging of unstressed and stressed Ni/Au-gated AlGaN/GaN HEMTs indicated that

Investigation of nitrogen transport in active screen plasma nitriding processes - Uphill diffusion effect

NASA Astrophysics Data System (ADS)

Jasinski, J. J.; Fraczek, T.; Kurpaska, L.; Lubas, M.; Sitarz, M.

2018-07-01

The paper presents a structure of a nitrided layer formed with active screen plasma nitriding (ASPN) technique, which is a modification of plasma nitriding. The model investigated material was Fe Armco. The nitriding processes were carried out at 773 K for 6 h and 150 Pa. The main objective of this study was to confirm nitrogen migration effect and its influence on the nitride layer formation in different area of the layer interfaces (ε/ε+γ‧/γ‧). The results of the tests were evaluated using scanning electron microscopy (SEM, SEM/EBSD), transmission electron microscopy - electron energy loss spectroscopy (TEM-EFTEM), secondary ion mass spectroscopy (SIMS) and Wavelength Dispersive X-Ray Spectrometry (WDS). The analysis of the results suggests that the structures of the nitrided layers and nitrides morphology differ for various parameters and are dependent on the surface layer saturation mechanism for each of the temperatures and process parameters. New approaches in diffusion of nitrogen and carbon atoms and optimizing process were also analyzed. Nitrogen and also carbon transport in the sublayer was observed by several effects i.e. uphill diffusion effect which confirmed migration of the atoms in diffusive layer towards top surface (ε/ε+γ‧ interface) and stress change effect in the nitrogen saturation area of the (Fe(C,N)+γ‧) layer. Results showed in the paper might be used both for optimization of ASPN processes, modeling of nitrided layers formation mechanism and for controlling the nitrided layers morphology when nitriding different Fe based materials.

Nitridation of silicon. M.S. Thesis Case Western Reserve Univ.

NASA Technical Reports Server (NTRS)

Shaw, N. J.

1981-01-01

Silicon powders with three levels of impurities, principally Fe, were sintered in He or H2. Non-densifying mechanisms of material transport were dominant in all cases. High purity Si showed coarsening in He while particle growth was suppressed in H2. Lower purity powder coarsened in both He and H2. The same three Si powders and Si /111/ single crystal wafers were nitrided in both N2 and N2/H2 atmospheres. Hydrogen increased the degree of nitridation of all three powders and the alpha/beta ratio of the lower purity powder. Some Si3N4 whiskers and open channels through the surface nitride layer were observed in the presence of Fe, correlating with the nitridation-enhancing effects of Fe. Thermodynamic calculations showed that when SiO2 is present on the Si, addition of H2 to the nitriding atmosphere decreases the amount of SiO2 and increases the partial pressure of Si-containing vapor species, that is, Si and SiO. Large amounts of NH3 and SiH4 were also predicted to form.

Stability and rheology of dispersions of silicon nitride and silicon carbide

NASA Technical Reports Server (NTRS)

Feke, Donald L.

1987-01-01

The relationship between the surface and colloid chemistry of commercial ultra-fine silicon carbide and silicon nitride powders was examined by a variety of standard characterization techniques and by methodologies especially developed for ceramic dispersions. These include electrokinetic measurement, surface titration, and surface spectroscopies. The effects of powder pretreatment and modification strategies, which can be utilized to augment control of processing characteristics, were monitored with these technologies. Both silicon carbide and nitride were found to exhibit silica-like surface chemistries, but silicon nitride powders possess an additional amine surface functionality. Colloidal characteristics of the various nitride powders in aqueous suspension is believed to be highly dependent on the relative amounts of the two types of surface groups, which in turn is determined by the powder synthesis route. The differences in the apparent colloidal characteristics for silicon nitride powders cannot be attributed to the specific absorption of ammonium ions. Development of a model for the prediction of double-layer characteristics of materials with a hybrid site interface facilitated understanding and prediction of the behavior of both surface charge and surface potential for these materials. The utility of the model in application to silicon nitride powders was demonstrated.

Nitride surface passivation of GaAs nanowires: impact on surface state density.

PubMed

Alekseev, Prokhor A; Dunaevskiy, Mikhail S; Ulin, Vladimir P; Lvova, Tatiana V; Filatov, Dmitriy O; Nezhdanov, Alexey V; Mashin, Aleksander I; Berkovits, Vladimir L

2015-01-14

Surface nitridation by hydrazine-sulfide solution, which is known to produce surface passivation of GaAs crystals, was applied to GaAs nanowires (NWs). We studied the effect of nitridation on conductivity and microphotoluminescence (μ-PL) of individual GaAs NWs using conductive atomic force microscopy (CAFM) and confocal luminescent microscopy (CLM), respectively. Nitridation is found to produce an essential increase in the NW conductivity and the μ-PL intensity as well evidence of surface passivation. Estimations show that the nitride passivation reduces the surface state density by a factor of 6, which is of the same order as that found for GaAs/AlGaAs nanowires. The effects of the nitride passivation are also stable under atmospheric ambient conditions for six months.

Nanoparticle Addition to Enhance the Mechanical Response of Magnesium Alloys Including Nanoscale Deformation Mechanisms

NASA Astrophysics Data System (ADS)

Paramsothy, Muralidharan; Gupta, Manoj

In this study, various magnesium alloy nanocomposites derived from AZ (Aluminium-Zinc) or ZK (Zinc-Zirconium) series matrices and containing Al2O3, Si3N4, TiC or carbon nanotube (CNT) nanoparticle reinforcement (representative oxide, nitride, carbide or carbon nanoparticle reinforcement, respectively) were fabricated using solidification processing followed by hot extrusion. The main aim here was to simultaneously enhance tensile strength and ductility of each alloy using nanoparticles. The magnesium-oxygen strong affinity and magnesium-carbon weak affinity (comparison of extremes in affinity) are both well known in the context of magnesium composite processing. However, an approach to possibly quantify this affinity in magnesium nanocomposite processing is not clear. In this study accordingly, Nanoscale Electro Negative Interface Density or NENID quantifies the nanoparticle-alloy matrix interfacial area per unit volume in the magnesium alloy nanocomposite taking into consideration the electronegativity of the nanoparticle reinforcement. The beneficial (as well as comparative) effect of the nanoparticles on each alloy is discussed in this article. Regarding the mechanical performance of the nanocomposites, it is important to understand the experimentally observed nanoparticle-matrix interactions during plastic deformation (nanoscale deformation mechanisms). Little is known in this area based on direct observations for metal matrix nanocomposites. Here, relevant multiple nanoscale phenomena includes the emanation of high strain zones (HSZs) from nanoparticle surfaces.

Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vargas, Mirella; Murphy, N. R.; Ramana, C. V., E-mail: rvchintalapalle@utep.edu

2014-03-10

Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s} = 25–700 °C). HfO{sub 2} films grown at T{sub s} < 200 °C were amorphous, while those grown at T{sub s} ≥ 200 °C were monoclinic, nanocrystalline with (1{sup ¯}11) texturing. X-ray reflectivity (XRR) analyses indicate that the film-density (ρ) increases with increasing T{sub s}. The index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (λ)} = 550 nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-ρ-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and themore » microstructure of HfO{sub 2} films.« less

Nitriding of super alloys for enhancing physical properties

DOEpatents

Purohit, A.

1984-06-25

The invention teaches the improvement of certain super alloys by exposing the alloy to an atmosphere of elemental nitrogen at elevated temperatures in excess of 750/sup 0/C but less than 1150/sup 0/C for an extended duration, viz., by nitriding the surface of the alloy, to establish barrier nitrides of the order of 25 to 100 micrometers thickness. These barrier

Lattice matched crystalline substrates for cubic nitride semiconductor growth

DOEpatents

Norman, Andrew G; Ptak, Aaron J; McMahon, William E

2015-02-24

Disclosed embodiments include methods of fabricating a semiconductor layer or device and devices fabricated thereby. The methods include, but are not limited to, providing a substrate having a cubic crystalline surface with a known lattice parameter and growing a cubic crystalline group III-nitride alloy layer on the cubic crystalline substrate by coincident site lattice matched epitaxy. The cubic crystalline group III-nitride alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter of the substrate (a). The group III-nitride alloy may be a cubic crystalline In.sub.xGa.sub.yAl.sub.1-x-yN alloy. The lattice parameter of the In.sub.xGa.sub.yAl.sub.1-x-yN or other group III-nitride alloy may be related to the substrate lattice parameter by (a')= 2(a) or (a')=(a)/ 2. The semiconductor alloy may be prepared to have a selected band gap.

Ammonium-tungstate-promoted growth of boron nitride nanotubes

NASA Astrophysics Data System (ADS)

E, Songfeng; Li, Chaowei; Li, Taotao; Geng, Renjie; Li, Qiulong; Lu, Weibang; Yao, Yagang

2018-05-01

Ammonium tungstate ((NH4)10W12O41 · xH2O) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (B2O2) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability. The experimental results demonstrate that the mole ratio of B and (NH4)10W12O41 · xH2O is a key parameter in determining the formation, quality and quantity of BNNTs when stainless steel is employed as a catalyst. We also found that Mg(NO3)2 and MgO nanoparticles (NPs) can be used as catalysts to grow BNNTs with the same precursor. The BNNTs obtained from the Mg(NO3)2 catalyst were straighter than those obtained from the MgO NP catalyst. This could have been due to the different physical forms of the catalysts that were used.

Ammonium-tungstate-promoted growth of boron nitride nanotubes.

PubMed

E, Songfeng; Li, Chaowei; Li, Taotao; Geng, Renjie; Li, Qiulong; Lu, Weibang; Yao, Yagang

2018-05-11

Ammonium tungstate ((NH 4 ) 10 W 12 O 41  · xH 2 O) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (B 2 O 2 ) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability. The experimental results demonstrate that the mole ratio of B and (NH 4 ) 10 W 12 O 41  · xH 2 O is a key parameter in determining the formation, quality and quantity of BNNTs when stainless steel is employed as a catalyst. We also found that Mg(NO 3 ) 2 and MgO nanoparticles (NPs) can be used as catalysts to grow BNNTs with the same precursor. The BNNTs obtained from the Mg(NO 3 ) 2 catalyst were straighter than those obtained from the MgO NP catalyst. This could have been due to the different physical forms of the catalysts that were used.

Nitridation of silicon by nitrogen neutral beam

NASA Astrophysics Data System (ADS)

Hara, Yasuhiro; Shimizu, Tomohiro; Shingubara, Shoso

2016-02-01

Silicon nitridation was investigated at room temperature using a nitrogen neutral beam (NB) extracted at acceleration voltages of less than 100 V. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of a Si3N4 layer on a Si (1 0 0) substrate when the acceleration voltage was higher than 20 V. The XPS depth profile indicated that nitrogen diffused to a depth of 36 nm for acceleration voltages of 60 V and higher. The thickness of the silicon nitrided layer increased with the acceleration voltages from 20 V to 60 V. Cross-sectional transmission electron microscopy (TEM) analysis indicated a Si3N4 layer thickness of 3.1 nm was obtained at an acceleration voltage of 100 V. Moreover, it was proved that the nitrided silicon layer formed by the nitrogen NB at room temperature was effective as the passivation film in the wet etching process.

Vertical integration of high-Q silicon nitride microresonators into silicon-on-insulator platform.

PubMed

Li, Qing; Eftekhar, Ali A; Sodagar, Majid; Xia, Zhixuan; Atabaki, Amir H; Adibi, Ali

2013-07-29

We demonstrate a vertical integration of high-Q silicon nitride microresonators into the silicon-on-insulator platform for applications at the telecommunication wavelengths. Low-loss silicon nitride films with a thickness of 400 nm are successfully grown, enabling compact silicon nitride microresonators with ultra-high intrinsic Qs (~ 6 × 10(6) for 60 μm radius and ~ 2 × 10(7) for 240 μm radius). The coupling between the silicon nitride microresonator and the underneath silicon waveguide is based on evanescent coupling with silicon dioxide as buffer. Selective coupling to a desired radial mode of the silicon nitride microresonator is also achievable using a pulley coupling scheme. In this work, a 60-μm-radius silicon nitride microresonator has been successfully integrated into the silicon-on-insulator platform, showing a single-mode operation with an intrinsic Q of 2 × 10(6).

Plasma nitriding monitoring reactor: A model reactor for studying plasma nitriding processes using an active screen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamann, S., E-mail: hamann@inp-greifswald.de; Röpcke, J.; Börner, K.

2015-12-15

A laboratory scale plasma nitriding monitoring reactor (PLANIMOR) has been designed to study the basics of active screen plasma nitriding (ASPN) processes. PLANIMOR consists of a tube reactor vessel, made of borosilicate glass, enabling optical emission spectroscopy (OES) and infrared absorption spectroscopy. The linear setup of the electrode system of the reactor has the advantages to apply the diagnostic approaches on each part of the plasma process, separately. Furthermore, possible changes of the electrical field and of the heat generation, as they could appear in down-scaled cylindrical ASPN reactors, are avoided. PLANIMOR has been used for the nitriding of steelmore » samples, achieving similar results as in an industrial scale ASPN reactor. A compact spectrometer using an external cavity quantum cascade laser combined with an optical multi-pass cell has been applied for the detection of molecular reaction products. This allowed the determination of the concentrations of four stable molecular species (CH{sub 4}, C{sub 2}H{sub 2}, HCN, and NH{sub 3}). With the help of OES, the rotational temperature of the screen plasma could be determined.« less

Fatigue life of high-speed ball bearings with silicon nitride balls

NASA Technical Reports Server (NTRS)

Parker, R. J.; Zaretsky, E. V.

1974-01-01

Hot-pressed silicon nitride was evaluated as a rolling-element bearing material. The five-ball fatigue tester was used to test 12.7-mm- diameter silicon nitride balls at maximum Hertz stresses ranging from 4.27 x 10 to the 9th power n/sq m to 6.21 x 10 to the 9th power n/sq m at a race temperature of 328K. The fatigue life of NC-132 hot-pressed silicon nitride was found to be equal to typical bearing steels and much greater than other ceramic or cermet materials at the same stress levels. A digital computer program was used to predict the fatigue life of 120-mm- bore angular-contact ball bearings containing either steel or silicon nitride balls. The analysis indicates that there is no improvement in the lives of bearings of the same geometry operating at DN values from 2 to 4 million where silicon nitride balls are used in place of steel balls.

Facile CO Cleavage by a Multimetallic CsU2 Nitride Complex.

PubMed

Falcone, Marta; Kefalidis, Christos E; Scopelliti, Rosario; Maron, Laurent; Mazzanti, Marinella

2016-09-26

Uranium nitrides are important materials with potential for application as fuels for nuclear power generation, and as highly active catalysts. Molecular nitride compounds could provide important insight into the nature of the uranium-nitride bond, but currently little is known about their reactivity. In this study, we found that a complex containing a nitride bridging two uranium centers and a cesium cation readily cleaved the C≡O bond (one of the strongest bonds in nature) under ambient conditions. The product formed has a [CsU2 (μ-CN)(μ-O)] core, thus indicating that the three cations cooperate to cleave CO. Moreover, the addition of MeOTf to the nitride complex led to an exceptional valence disproportionation of the CsU(IV) -N-U(IV) core to yield CsU(III) (OTf) and [MeN=U(V) ] fragments. The important role of multimetallic cooperativity in both reactions is illustrated by the computed reaction mechanisms. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitride-Based Materials for Flexible MEMS Tactile and Flow Sensors in Robotics

PubMed Central

Abels, Claudio; Mastronardi, Vincenzo Mariano; Guido, Francesco; Dattoma, Tommaso; Qualtieri, Antonio; Megill, William M.; De Vittorio, Massimo; Rizzi, Francesco

2017-01-01

The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, SixNy/Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described. PMID:28489040

Preparation of boron nitride fiber by organic precursor method

NASA Astrophysics Data System (ADS)

Zhou, Yingying; Sun, Runjun; Zhang, Zhaohuan; Fan, Wei; Zhou, Dan; Sheng, Cuihong

In this paper, boron nitride polymer precursor was made by boric acid, melamine, twelve sodium alkyl sulfate as raw materials and pure water as medium which is heated to 70 °C. Boron nitride precursor polymer was soluble in formic acid solution. The boron nitride precursor can be electrostatically spun at the voltage in 23 kV and the distance between the positive and negative poles is 15 cm. The formed fiber is very uniform. The properties of the precursors were analyzed through electron microscope, infrared spectrum, X-ray and ultraviolet spectrum. The aim of the job is to got the precursor of BN and spun it.

Apparatus for the production of boron nitride nanotubes

DOEpatents

Smith, Michael W; Jordan, Kevin

2014-06-17

An apparatus for the large scale production of boron nitride nanotubes comprising; a pressure chamber containing; a continuously fed boron containing target; a source of thermal energy preferably a focused laser beam; a cooled condenser; a source of pressurized nitrogen gas; and a mechanism for extracting boron nitride nanotubes that are condensed on or in the area of the cooled condenser from the pressure chamber.

Infrared Dielectric Properties of Low-stress Silicon Nitride

NASA Technical Reports Server (NTRS)

Cataldo, Giuseppe; Beall, James A.; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D.; Wollack, Edward J.

2012-01-01

Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented.

Evaluation of boron nitride nanotubes and hexagonal boron nitrides as nanocarriers for cancer drugs.

PubMed

Emanet, Melis; Şen, Özlem; Çulha, Mustafa

2017-04-01

Boron nitride nanotubes (BNNTs) and hexagonal boron nitrides (hBNs) are novel nanostructures with high mechanical strengths, large surface areas and excellent biocompatibilities. Here, the potential use of BNNTs and hBNs as nanocarriers was comparatively investigated for use with cancer drugs. Doxorubicin (Dox) and folate are used as model drugs and targeting agents, respectively. The obtained results indicate that BNNTs have about a threefold higher Dox loading capacity than hBNs. It was also found that cellular uptake of folate-Dox-BNNTs was much higher when compared with Dox-BNNTs for HeLa cells, due to the presence of folate receptors on the cell surface, leading to increased cancer cell death. In summary, folate and Dox conjugated BNNTs are promising agents in nanomedicine and may have potential drug delivery applications.

Synthesis of crumpled nanosheets of polymeric carbon nitride from melamine cyanurate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dante, Roberto C., E-mail: rcdante@yahoo.com; Martín-Ramos, Pablo; Sánchez-Arévalo, F.M.

2013-05-01

Polymeric carbon nitride was synthesized by pyrolysis in nitrogen flux at different temperatures between 450 and 700 °C using melamine cyanurate as a reagent and sulfuric acid as a catalyst. The obtained carbon nitride consisted of curled nanosheets (650 °C), and globular particles (700 °C) with formula C₆N₇NHNH₂. The reaction yield of the catalyzed reaction was around the 15% for the sample treated at 700 °C, in a tapped crucible. The optical band gap of the polymer obtained at 700 °C is around 2.9 eV. The gap to the Fermi level is around 2 eV, considerably above the half ofmore » the band gap (due to electrons trapped in the gap), indicating that the polymer is probably a n-type semiconductor. - Graphical abstract: Transition from amorphous to crystalline carbon nitride, which is composed of globular particles and is a n-type wide band semiconductor. Highlights: • We synthetized carbon nitride using melamine cyanurate. • The reaction of carbon nitride formation is catalyzed by sulfuric acid. • The carbon nitride obtained at 700 °C is composed of globular particles. • The material obtained at 700 °C is a n-type semiconductor.« less

Rolling Contact Fatigue Failure Mechanisms of Plasma-Nitrided Ductile Cast Iron

NASA Astrophysics Data System (ADS)

Wollmann, D.; Soares, G. P. P. P.; Grabarski, M. I.; Weigert, N. B.; Escobar, J. A.; Pintaude, G.; Neves, J. C. K.

2017-05-01

Rolling contact fatigue (RCF) of a nitrided ductile cast iron was investigated. Flat washers machined from a pearlitic ductile cast iron bar were quenched and tempered to maximum hardness, ground, polished and divided into four groups: (1) specimens tested as quenched and tempered; (2) specimens plasma-nitrided for 8 h at 400 °C; (3) specimens plasma-nitrided and submitted to a diffusion process for 16 h at 400 °C; and (4) specimens submitted to a second tempering for 24 h at 400 °C. Hardness profiles, phase analyses and residual stress measurements by x-ray diffraction, surface roughness and scanning electron microscopy were applied to characterize the surfaces at each step of this work. Ball-on-flat washer tests were conducted with a maximum contact pressure of 3.6 GPa, under flood lubrication with a SAE 90 API GL-5 oil at 50 °C. Test ending criterion was the occurrence of a spalling. Weibull analysis was used to characterize RCF's lifetime data. Plasma-nitrided specimens exhibited a shorter RCF lifetime than those just quenched and tempered. The effects of nitriding on the mechanical properties and microstructure of the ductile cast iron are discussed in order to explain the shorter endurance of nitrided samples.

Osteoblastlike cell adhesion on titanium surfaces modified by plasma nitriding.

PubMed

da Silva, Jose Sandro Pereira; Amico, Sandro Campos; Rodrigues, Almir Olegario Neves; Barboza, Carlos Augusto Galvao; Alves, Clodomiro; Croci, Alberto Tesconi

2011-01-01

The aim of this study was to evaluate the characteristics of various titanium surfaces modified by cold plasma nitriding in terms of adhesion and proliferation of rat osteoblastlike cells. Samples of grade 2 titanium were subjected to three different surface modification processes: polishing, nitriding by plasma direct current, and nitriding by cathodic cage discharge. To evaluate the effect of the surface treatment on the cellular response, the adhesion and proliferation of osteoblastlike cells (MC3T3) were quantified and the results were analyzed by Kruskal-Wallis and Friedman statistical tests. Cellular morphology was observed by scanning electron microscopy. There was more MC3T3 cell attachment on the rougher surfaces produced by cathodic cage discharge compared with polished samples (P < .05). Plasma nitriding improves titanium surface roughness and wettability, leading to osteoblastlike cell adhesion.

Effects of Temperature on Microstructure and Wear of Salt Bath Nitrided 17-4PH Stainless Steel

NASA Astrophysics Data System (ADS)

Wang, Jun; Lin, Yuanhua; Fan, Hongyuan; Zeng, Dezhi; Peng, Qian; Shen, Baoluo

2012-08-01

Salt bath nitriding of 17-4 PH martensitic precipitation hardening stainless steels was conducted at 610, 630, and 650 °C for 2 h using a complex salt bath heat-treatment, and the properties of the nitrided surface were systematically evaluated. Experimental results revealed that the microstructure and phase constituents of the nitrided surface alloy are highly process condition dependent. When 17-4PH stainless steel was subjected to complex salt bathing nitriding, the main phase of the nitrided layer was expanded martensite (α'), expanded austenite (γN), CrN, Fe4N, and (Fe,Cr) x O y . In the sample nitrided above 610 °C, the expanded martensite transformed into expanded austenite. But in the sample nitrided at 650 °C, the expanded austenite decomposed into αN and CrN. The decomposed αN then disassembled into CrN and alpha again. The nitrided layer depth thickened intensively with the increasing nitriding temperature. The activation energy of nitriding in this salt bath was 125 ± 5 kJ/mol.

Colloidal characterization of ultrafine silicon carbide and silicon nitride powders

NASA Technical Reports Server (NTRS)

Whitman, Pamela K.; Feke, Donald L.

1986-01-01

The effects of various powder treatment strategies on the colloid chemistry of aqueous dispersions of silicon carbide and silicon nitride are examined using a surface titration methodology. Pretreatments are used to differentiate between the true surface chemistry of the powders and artifacts resulting from exposure history. Silicon nitride powders require more extensive pretreatment to reveal consistent surface chemistry than do silicon carbide powders. As measured by titration, the degree of proton adsorption from the suspending fluid by pretreated silicon nitride and silicon carbide powders can both be made similar to that of silica.

Conductive and robust nitride buffer layers on biaxially textured substrates

DOEpatents

Sankar, Sambasivan; Goyal, Amit; Barnett, Scott A.; Kim, Ilwon; Kroeger, Donald M.

2004-08-31

The present invention relates to epitaxial, electrically conducting and mechanically robust, cubic nitride buffer layers deposited epitaxially on biaxially textured substrates such as metal and alloys. The invention comprises of a biaxially textured substrate with epitaxial layers of nitrides. The invention also discloses a method to form such epitaxial layers using a high rate deposition method as well as without the use of forming gases. The invention further comprises epitaxial layers of oxides on the biaxially textured nitride layers. In some embodiments the article further comprises electromagnetic devices which may be super conducting properties.

Conductive and robust nitride buffer layers on biaxially textured substrates

DOEpatents

Sankar, Sambasivan [Chicago, IL; Goyal, Amit [Knoxville, TN; Barnett, Scott A [Evanston, IL; Kim, Ilwon [Skokie, IL; Kroeger, Donald M [Knoxville, TN

2009-03-31

The present invention relates to epitaxial, electrically conducting and mechanically robust, cubic nitride buffer layers deposited epitaxially on biaxially textured substrates such as metals and alloys. The invention comprises of a biaxially textured substrate with epitaxial layers of nitrides. The invention also discloses a method to form such epitaxial layers using a high rate deposition method as well as without the use of forming gases. The invention further comprises epitaxial layers of oxides on the biaxially textured nitride layer. In some embodiments the article further comprises electromagnetic devices which may have superconducting properties.

Tribological and microstructural characteristics of ion-nitrided steels

NASA Technical Reports Server (NTRS)

Spalvins, T.

1983-01-01

Three steels AISI 4140, AISI 4340 and AISI 304 stainless steel were ion nitrided in a plasma consisting of a 75:25 mixture of H2:N2, sometimes with a trace of CH4. Their surface topography was characterized by SEM and two distinct compound phases were identified: the gamma and the epsilon. The core-case hardness profiles were also established. The low Cr alloy steels have an extended diffusion zone in contrast to the 304 stainless steels which have a sharp interface. The depth of ion-nitriding is increased as the Cr content is decreased. Friction tests reveal that the gamma surface phase has a lower coefficient of friction than the epsilon phase. The lowest coefficient of friction is achieved when both the rider and the specimen surface are ion nitrided.

Single-Photon Emitters in Boron Nitride Nanococoons.

PubMed

Ziegler, Joshua; Blaikie, Andrew; Fathalizadeh, Aidin; Miller, David; Yasin, Fehmi S; Williams, Kerisha; Mohrhardt, Jordan; McMorran, Benjamin J; Zettl, Alex; Alemán, Benjamín

2018-04-11

Quantum emitters in two-dimensional hexagonal boron nitride (hBN) are attractive for a variety of quantum and photonic technologies because they combine ultra-bright, room-temperature single-photon emission with an atomically thin crystal. However, the emitter's prominence is hindered by large, strain-induced wavelength shifts. We report the discovery of a visible-wavelength, single-photon emitter (SPE) in a zero-dimensional boron nitride allotrope (the boron nitride nanococoon, BNNC) that retains the excellent optical characteristics of few-layer hBN while possessing an emission line variation that is lower by a factor of 5 than the hBN emitter. We determined the emission source to be the nanometer-size BNNC through the cross-correlation of optical confocal microscopy with high-resolution scanning and transmission electron microscopy. Altogether, this discovery enlivens color centers in BN materials and, because of the BN nanococoon's size, opens new and exciting opportunities in nanophotonics, quantum information, biological imaging, and nanoscale sensing.

Friction and transfer behavior of pyrolytic boron nitride in contact with various metals

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1976-01-01

Sliding friction experiments were conducted with pyrolytic boron nitride in sliding contact with itself and various metals. Auger emission spectroscopy was used to monitor transfer of pyrolytic boron nitride to metals and metals to pyrolytic boron nitride. Results indicate that the friction coefficient for pyrolytic boron nitride in contact with metals can be related to the chemical activity of the metals and more particularly to the d valence bond character of the metal. Transfer was found to occur to all metals except silver and gold and the amount of transfer was less in the presence than in the absence of metal oxide. Friction was less for pyrolytic boron nitride in contact with a metal in air than in vacuum.

Iron-based alloy and nitridation treatment for PEM fuel cell bipolar plates

DOEpatents

Brady, Michael P [Oak Ridge, TN; Yang, Bing [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN

2010-11-09

A corrosion resistant electrically conductive component that can be used as a bipolar plate in a PEM fuel cell application is composed of an alloy substrate which has 10-30 wt. % Cr, 0.5 to 7 wt. % V, and base metal being Fe, and a continuous surface layer of chromium nitride and vanadium nitride essentially free of base metal. A oxide layer of chromium vanadium oxide can be disposed between the alloy substrate and the continuous surface nitride layer. A method to prepare the corrosion resistant electrically conductive component involves a two-step nitridization sequence by exposing the alloy to a oxygen containing gas at an elevated temperature, and subsequently exposing the alloy to an oxygen free nitrogen containing gas at an elevated temperature to yield a component where a continuous chromium nitride layer free of iron has formed at the surface.

Thin films of aluminum nitride and aluminum gallium nitride for cold cathode applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sowers, A.T.; Christman, J.A.; Bremser, M.D.

1997-10-01

Cold cathode structures have been fabricated using AlN and graded AlGaN structures (deposited on n-type 6H-SiC) as the thin film emitting layer. The cathodes consist of an aluminum grid layer separated from the nitride layer by a SiO{sub 2} layer and etched to form arrays of either 1, 3, or 5 {mu}m holes through which the emitting nitride surface is exposed. After fabrication, a hydrogen plasma exposure was employed to activate the cathodes. Cathode devices with 5 {mu}m holes displayed emission for up to 30 min before failing. Maximum emission currents ranged from 10{endash}100 nA and required grid voltages rangingmore » from 20{endash}110 V. The grid currents were typically 1 to 10{sup 4} times the collector currents. {copyright} {ital 1997 American Institute of Physics.}« less

Synthesis of Continuous Boron Nitride Nanofibers by Electrospinning

NASA Astrophysics Data System (ADS)

Li, Xia; Wen, G.; Zhang, Tao; Xia, Long; Zhong, Bo; Fan, Shaoyu

Continuous boron nitride nanofibers (BNNFs) have been gotten by electrospinning. The appropriate precursor of BNNFs was electrospinned to green born nitride nanofibers (GBNNFs) with temperatures from 80°C to 100°C in the protection of N2. By successive heat treatments in N2, the organics in GBNNFs disappeared and BN ceramics nanofibers came into being. The average diameters of BNNFs by electrospinning are less than 10 μm

Method of nitriding, carburizing, or oxidizing refractory metal articles using microwaves

DOEpatents

Holcombe, Cressie E.; Dykes, Norman L.; Tiegs, Terry N.

1992-01-01

A method of nitriding an article of refractory-nitride-forming metal or metalloids. A consolidated metal or metalloid article is placed inside a microwave oven and nitrogen containing gas is introduced into the microwave oven. The metal or metalloid article is heated to a temperature sufficient to react the metal or metalloid with the nitrogen by applying a microwave energy within the microwave oven. The metal or metalloid article is maintained at that temperature for a period of time sufficient to convert the article of metal or metalloid to an article of refractory nitride. in addition, a method of applying a coating, such as a coating of an oxide, a carbide, or a carbo-nitride, to an article of metal or metalloid by microwave heating.

Method of nitriding, carburizing, or oxidizing refractory metal articles using microwaves

DOEpatents

Holcombe, C.E.; Dykes, N.L.; Tiegs, T.N.

1992-10-13

A method of nitriding an article of refractory-nitride-forming metal or metalloids. A consolidated metal or metalloid article is placed inside a microwave oven and nitrogen containing gas is introduced into the microwave oven. The metal or metalloid article is heated to a temperature sufficient to react the metal or metalloid with the nitrogen by applying a microwave energy within the microwave oven. The metal or metalloid article is maintained at that temperature for a period of time sufficient to convert the article of metal or metalloid to an article of refractory nitride. in addition, a method of applying a coating, such as a coating of an oxide, a carbide, or a carbo-nitride, to an article of metal or metalloid by microwave heating.

Silicon Nitride Equation of State

NASA Astrophysics Data System (ADS)

Swaminathan, Pazhayannur; Brown, Robert

2015-06-01

This report presents the development a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4) . Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonalβ-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products and then combined with the single component solid models to study the global phase diagram. Sponsored by the NASA Goddard Space Flight Center Living With a Star program office.

Microscopic modeling of nitride intersubband absorbance

NASA Astrophysics Data System (ADS)

Montano, Ines; Allerman, A. A.; Wierer, J. J.; Moseley, M.; Skogen, E. J.; Tauke-Pedretti, A.; Vawter, G. A.

III-nitride intersubband structures have recently attracted much interest because of their potential for a wide variety of applications ranging from electro-optical modulators to terahertz quantum cascade lasers. To overcome present simulation limitations we have developed a microscopic absorbance simulator for nitride intersubband devices. Our simulator calculates the band structure of nitride intersubband systems using a fully coupled 8x8 k.p Hamiltonian and determines the material response of a single period in a density-matrix-formalism by solving the Heisenberg equation including many-body and dephasing contributions. After calculating the polarization due to intersubband transitions in a single period, the resulting absorbance of a superlattice structure including radiative coupling between the different periods is determined using a non-local Green's-function formalism. As a result our simulator allows us to predict intersubband absorbance of superlattice structures with microscopically determined lineshapes and linewidths accounting for both many-body and correlation contributions. This work is funded by Sandia National Laboratories Laboratory Directed Research and Development program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin.

Transferrable monolithic III-nitride photonic circuit for multifunctional optoelectronics

NASA Astrophysics Data System (ADS)

Shi, Zheng; Gao, Xumin; Yuan, Jialei; Zhang, Shuai; Jiang, Yan; Zhang, Fenghua; Jiang, Yuan; Zhu, Hongbo; Wang, Yongjin

2017-12-01

A monolithic III-nitride photonic circuit with integrated functionalities was implemented by integrating multiple components with different functions into a single chip. In particular, the III-nitride-on-silicon platform is used as it integrates a transmitter, a waveguide, and a receiver into a suspended III-nitride membrane via a wafer-level procedure. Here, a 0.8-mm-diameter suspended device architecture is directly transferred from silicon to a foreign substrate by mechanically breaking the support beams. The transferred InGaN/GaN multiple-quantum-well diode (MQW-diode) exhibits a turn-on voltage of 2.8 V with a dominant electroluminescence peak at 453 nm. The transmitter and receiver share an identical InGaN/GaN MQW structure, and the integrated photonic circuit inherently works for on-chip power monitoring and in-plane visible light communication. The wire-bonded monolithic photonic circuit on glass experimentally demonstrates in-plane data transmission at 120 Mb/s, paving the way for diverse applications in intelligent displays, in-plane light communication, flexible optical sensors, and wearable III-nitride optoelectronics.

Ordering of lipid membranes altered by boron nitride nanosheets.

PubMed

Zhang, Yonghui; Li, Zhen; Chan, Chun; Ma, Jiale; Zhi, Chunyi; Cheng, Xiaolin; Fan, Jun

2018-02-07

Boron nitride nanosheets are novel promising nanomaterials with a lower cytotoxicity than graphene making them a better candidate for biomedical applications. However, there is no systematic study on how they interact with cell membranes. Here we employed large scale all-atom molecular dynamics simulations to provide molecular details of the structure and properties of membranes after the insertion of boron nitride nanosheets. Our results reveal that the boron nitride nanosheet can extract phospholipids from the lipid bilayers and is enveloped by the membrane. Afterwards, the acyl chains of lipid molecules re-orient and become more ordered. As a result, a fluid to gel phase transition occurs in the 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer. Consequently, the bending moduli of the bilayers increase, and the diffusivity of the individual lipid molecule decreases. These changes will affect relevant cellular activities, such as endocytosis and signal transduction. Our study provides novel insights into the biocompatibility and cytotoxicity of boron nitride nanosheets, which may facilitate the design of safer nanocarriers, antibiotics and other bio-nanotechnology applications.

Nitride micro-LEDs and beyond--a decade progress review.

PubMed

Jiang, H X; Lin, J Y

2013-05-06

Since their inception, micro-size light emitting diode (µLED) arrays based on III-nitride semiconductors have emerged as a promising technology for a range of applications. This paper provides an overview on a decade progresses on realizing III-nitride µLED based high voltage single-chip AC/DC-LEDs without power converters to address the key compatibility issue between LEDs and AC power grid infrastructure; and high-resolution solid-state self-emissive microdisplays operating in an active driving scheme to address the need of high brightness, efficiency and robustness of microdisplays. These devices utilize the photonic integration approach by integrating µLED arrays on-chip. Other applications of nitride µLED arrays are also discussed.

Semipolar III-nitride laser diodes with zinc oxide cladding.

PubMed

Myzaferi, Anisa; Reading, Arthur H; Farrell, Robert M; Cohen, Daniel A; Nakamura, Shuji; DenBaars, Steven P

2017-07-24

Incorporating transparent conducting oxide (TCO) top cladding layers into III-nitride laser diodes (LDs) improves device design by reducing the growth time and temperature of the p-type layers. We investigate using ZnO instead of ITO as the top cladding TCO of a semipolar (202¯1) III-nitride LD. Numerical modeling indicates that replacing ITO with ZnO reduces the internal loss in a TCO clad LD due to the lower optical absorption in ZnO. Lasing was achieved at 453 nm with a threshold current density of 8.6 kA/cm 2 and a threshold voltage of 10.3 V in a semipolar (202¯1) III-nitride LD with ZnO top cladding.

Surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding

NASA Astrophysics Data System (ADS)

Abd El-Rahman, A. M.; Maitz, M. F.; Kassem, M. A.; El-Hossary, F. M.; Prokert, F.; Reuther, H.; Pham, M. T.; Richter, E.

2007-09-01

The present work describes the surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400 W.

FOREWORD: The physics of III-V nitrides The physics of III-V nitrides

NASA Astrophysics Data System (ADS)

Ridley, B. K.

2009-04-01

The evolution of semiconductor physics is driven by the increasing sophistication of the art of crystal growing and fabrication techniques. From Ge at the birth of the transistor, possibly the purest material ever grown, through Si, the work-horse of the crystal revolution, to the III-Vs, whose optical properties opened up a second front, namely, optoelectronics. Crystal growth with monolayer control gave us quantum wells, superlattices, quantum wires and quantum dots, along with the quantum Hall effect and quantized resistance. The potential for high-power devices triggered interest in the III-V nitrides with their large bandgaps. The nitrides mostly crystallize in the hexagonal form, and this has introduced the phenomenon of spontaneous polarization into mainstream semiconductor physics. Its effect manifests itself in huge electric fields in heterostructures like AlGaN/GaN which, in turn, causes the induction of substantial electron populations in the channel of a HFET without the need for doping. High-power microwave transistors have been successfully fabricated, even though there are features associated with spontaneous polarization that still needs clarifying. Another strange effect is the large electron population on the surface of InN. The lack of a suitable substrate for growing GaN has meant that the dislocation density is higher than we would wish, but that situation is expected to steadily improve. Given the current interest in the physics of nitrides, it is natural to come across a special issue devoted to this topic. The difficulty presented by the surface layer in InN in the attempt to measure transport properties is discussed in the paper by King et al. A property that can affect transport is the lifetime of optical phonons and its dependence on electron density. Measurements of phonon lifetime in InN are reported by Tsen and Ferry, and in GaN channels, via the measure of hot-electron fluctuations, by Matulionis. The dependence on electron density is

Friction and Wear of Unlubricated NiTiHf with Nitriding Surface Treatments

NASA Technical Reports Server (NTRS)

Stanford, Malcolm K.

2018-01-01

The unlubricated friction and wear properties of the superelastic materials NiTi and NiTiHf, treated by either gas nitriding or plasma nitriding, have been investigated. Pin on disk testing of the studied materials was performed at sliding speeds from 0.01 to 1m/s at normal loads of 1, 5 or 10N. For all of the studied friction pairs (NiTiHf pins vs. NiTi and NiTiHf disks) over the given parameters, the steady-state coefficients of friction varied from 0.22 to 1.6. Pin wear factors ranged from approximately 1E-6 against the NiTiHf and plasma nitrided disks to approximately 1E-4 for the gas nitrided disks. The plasma nitrided disks provided wear protection in several cases and tended to wear by adhesion. The gas nitrided treatment generated the most pin wear but had essentially no disk wear except at the most severe of the studied conditions (1N load and 1m/s sliding speed). The results of this study are expected to provide guidance for design of components such as gears and fasteners.

A physical model for evaluating uranium nitride specific heat

NASA Astrophysics Data System (ADS)

Baranov, V. G.; Devyatko, Yu. N.; Tenishev, A. V.; Khlunov, A. V.; Khomyakov, O. V.

2013-03-01

Nitride fuel is one of perspective materials for the nuclear industry. But unlike the oxide and carbide uranium and mixed uranium-plutonium fuel, the nitride fuel is less studied. The present article is devoted to the development of a model for calculating UN specific heat on the basis of phonon spectrum data within the solid state theory.

Coating and dispersion of ceramic nanoparticles by UV-ozone etching assisted surface-initiated living radical polymerization.

PubMed

Arita, Toshihiko

2010-10-01

Commercially available unmodified ceramic nanoparticles (NPs) in dry powder state were surface-modified and dispersed in almost single-crystal size. The surface-initiated living radical polymerization after just UV-ozone soft etching enables one to graft polymers onto the surface of ceramic NPs and disperse them in solvents. Furthermore, a number of NPs were dispersed with single-crystal sizes. The technique developed here could be applied to almost all ceramic NPs including metal nitrides.

Second-harmonic generation in substoichiometric silicon nitride layers

NASA Astrophysics Data System (ADS)

Pecora, Emanuele; Capretti, Antonio; Miano, Giovanni; Dal Negro, Luca

2013-03-01

Harmonic generation in optical circuits offers the possibility to integrate wavelength converters, light amplifiers, lasers, and multiple optical signal processing devices with electronic components. Bulk silicon has a negligible second-order nonlinear optical susceptibility owing to its crystal centrosymmetry. Silicon nitride has its place in the microelectronic industry as an insulator and chemical barrier. In this work, we propose to take advantage of silicon excess in silicon nitride to increase the Second Harmonic Generation (SHG) efficiency. Thin films have been grown by reactive magnetron sputtering and their nonlinear optical properties have been studied by femtosecond pumping over a wide range of excitation wavelengths, silicon nitride stoichiometry and thermal processes. We demonstrate SHG in the visible range (375 - 450 nm) using a tunable 150 fs Ti:sapphire laser, and we optimize the SH emission at a silicon excess of 46 at.% demonstrating a maximum SHG efficiency of 4x10-6 in optimized films. Polarization properties, generation efficiency, and the second order nonlinear optical susceptibility are measured for all the investigated samples and discussed in terms of an effective theoretical model. Our findings show that the large nonlinear optical response demonstrated in optimized Si-rich silicon nitride materials can be utilized for the engineering of nonlinear optical functions and devices on a Si chip.

Enhanced cell adhesion on severe peened-plasma nitrided 316L stainless steel

NASA Astrophysics Data System (ADS)

Jayalakshmi, M.; Bhat, Badekai Ramachandra; Bhat, K. Udaya

2018-04-01

Plasma nitriding is an effective technique to enhance the wear resistance of austenitic stainless steels. Recently, severe surface deformation techniques are extensively used prior to nitriding to enhance diffusion kinetics. In the present study, AISI 316L austenitic stainless steel is subjected to peening-nitriding duplex treatment and biocompatibility of treated surfaces is assessed through adhesion of the fibroblast cells. Three-fold increase in the surface microhardness is observed from the un-peened sample to the peened-nitrided sample; with severe peened sample showing intermediate hardness. Similar trend is observed in the number of the fibroblast cells attached to the sample surface. Spreading of some of the fibroblast cells is observed on the sample subjected to duplex treatment; while the other two samples showed only the spindle shaped fibroblasts. Combined influence of surface nanocrystallization and presence of nitride layer is responsible for the improved biocompatibility.

Process dependency of radiation hardness of rapid thermal reoxidized nitrided gate oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weishin Lu; Kuanchin Lin; Jenngwo Hwu

The radiation hardness of MOS capacitors with various reoxidized nitrided oxide (RNO) structures is studied by changing the durations of rapid thermal processes during sample preparation and by applying irradiation-then-anneal (ITA) treatments on samples after preparation. It is found that the initial flatband voltage and midgap interface trap density of MOS capacitors exhibit turnaround'' dependency on the total time of nitridation and reoxidation processes. For samples with nitrided oxide (NO) structures, the radiation-induced variations of above parameters are also turnaround''-dependent on nitridation time. However, when the reoxidation process is performed, the radiation hardness for all samples will be gradually improvedmore » with increasing reoxidation time no matter what the nitridation time is. The most radiation-hard process for RNO structures is suggested. Finally, it is found that when ITA treatments are applied on samples after preparation, their radiation hardness is much improved.« less

Tribological and microstructural characteristics of ion-nitrided steels

NASA Technical Reports Server (NTRS)

Spalvins, T.

1983-01-01

Three steels AISI 4140, AISI 4340 and AISI 304 stainless steel were ion nitrided in a plasma consisting of a 75:25 mixture of H2:N2, sometimes with a trace of CH4. Their surface topography was characterized by SEM and two distinct compound phases were identified: the gamma and the epsilon. The core-case hardness profiles were also established. The low Cr alloy steels have an extended diffusion zone in contrast to the 3034 stainless steels which have a sharp interface. The depth of ion-nitriding is increased as the Cr content is decreased. Friction tests reveal that the gamma surface phase has a lower coefficient of friction than the epsilon phase. The lowest coefficient of friction is achieved when both the rider and the specimen surface are ion nitrided. Previously announced in STAR as N83-24635

Modelling of the modulation properties of arsenide and nitride VCSELs

NASA Astrophysics Data System (ADS)

Wasiak, Michał; Śpiewak, Patrycja; Moser, Philip; Gebski, Marcin; Schmeckebier, Holger; Sarzała, Robert P.; Lott, James A.

2017-02-01

In this paper, using our model of capacitance in vertical-cavity surface-emitting lasers (VCSELs), we analyze certain differences between an oxide-confined arsenide VCSEL emitting in the NIR region, and a nitride VCSEL emitting violet radiation. In the nitride laser its high differential resistance, caused partially by the low conductivity of p-type GaN material and the bottom contact configuration, is one of the main reasons why the nitride VCSEL has much worse modulation properties than the arsenide VCSEL. Using the complicated arsenide structure, we also analyze different possible ways of constructing the laser's equivalent circuit.

Low-Temperature Nitriding of Pure Titanium by using Hollow Cathode RF-DC Plasma

NASA Astrophysics Data System (ADS)

Windajanti, J. M.; S, D. J. Djoko H.; Abdurrouf

2017-05-01

Pure titanium is widely used for the structures and mechanical parts due to its high strength, low density, and high corrosion resistance. Unfortunately, titanium products suffer from low hardness and low wear resistance. Titanium’s surface can be modified by nitriding process to overcome such problems, which is commonly conducted at high temperature. Here, we report the low-temperature plasma nitriding process, where pure titanium was utilized by high-density RF-DC plasma combined with hollow cathode device. To this end, a pure titanium plate was set inside a hollow tube placed on the cathode plate. After heating to 450 °C, a pre-sputtering process was conducted for 1 hour to remove the oxide layer and activate the surface for nitriding. Plasma nitriding using N2/H2 gasses was performed in 4 and 8 hours with the RF voltage of 250 V, DC bias of -500 to -600 V, and gas pressure of 75 to 30 Pa. To study the nitriding mechanism as well as the role of hollow cathode, the nitrided specimen was characterized by SEM, EDX, XRD, and micro-hardness equipment. The TiN compound was obtained with the diffusion zone of nitrogen until 5 μm thickness for 4 hours nitriding process, and 8 μm for 8 hours process. The average hardness also increased from 300 HV in the untreated specimen to 624 HV and 792 HV for 4 and 8 hours nitriding, respectively.

Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

PubMed

Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

2014-01-01

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm(2) using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

PubMed Central

2014-01-01

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si. PMID:25593562

Metal surface nitriding by laser induced plasma

NASA Astrophysics Data System (ADS)

Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

1996-10-01

We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

Chemical precursors to non-oxide ceramics: Macro to nanoscale materials

NASA Astrophysics Data System (ADS)

Forsthoefel, Kersten M.

Non-oxide ceramics exhibit a number of important properties that make them ideal for technologically important applications (thermal and chemical stability, high strength and hardness, wear-resistance, light weight, and a range of electronic and optical properties). Unfortunately, traditional methodologies to these types of materials are limited to fairly simple shapes and complex processed forms cannot be attained through these methods. The establishment of the polymeric precursor approach has allowed for the generation of advanced materials, such as refractory non-oxide ceramics, with controlled compositions, under moderate conditions, and in processed forms. The goal of the work described in this dissertation was both to develop new processible precursors to technologically important ceramics and to achieve the formation of advanced materials in processed forms. One aspect of this research exploited previously developed preceramic precursors to boron carbide, boron nitride and silicon carbide for the generation of a wide variety of advanced materials: (1) ultra-high temperature ceramic (UHTC) structural materials composed of hafnium boride and related composite materials, (2) the quaternary borocarbide superconductors, and (3) on the nanoscale, non-oxide ceramic nanotubules. The generation of the UHTC and the quaternary borocarbide materials was achieved through a method that employs a processible polymer/metal(s) dispersion followed by subsequent pyrolyses. In the case of the UHTC, hafnium oxide, hafnium, or hafnium boride powders were dispersed in a suitable precursor to afford hafnium borides or related composite materials (HfB2/HfC, HfB2/HfN, HfB2/SiC) in high yields and purities. The quaternary borocarbide superconducting materials were produced from pyrolyses of dispersions containing appropriate stoichiometric amounts of transition metal, lanthanide metal, and the polyhexenyldecaborane polymer. Both chemical vapor deposition (CVD) based routes employing a

Methods for improved growth of group III nitride buffer layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphologymore » of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).« less

Group III-nitride thin films grown using MBE and bismuth

DOEpatents

Kisielowski, Christian K.; Rubin, Michael

2002-01-01

The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

Group III-nitride thin films grown using MBE and bismuth

DOEpatents

Kisielowski, Christian K.; Rubin, Michael

2000-01-01

The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

Effect of Silica Nanoparticles on the Photoluminescence Properties of BCNO Phosphor

NASA Astrophysics Data System (ADS)

Nuryadin, Bebeh W.; Faryuni, Irfana Diah; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal, Khairurrijal

2011-12-01

Effect of additional silica nanoparticles on the photoluminescence (PL) performance of boron carbon oxy-nitride (BCNO) phosphor was investigated. As a precursor, boric acid and urea were used as boron and nitrogen sources, respectively. The carbon sources was polyethylene glycol (PEG) with average molecule weight 20000 g/mol.. Precursor solutions were prepared by mixing these raw materials in pure water, followed by stirring to achieve homogeneous solutions. In this precursor, silica nanoparticles were added at various mass ratio from 0 to 7 %wt in the solution. The precursors were then heated at 750 °C for 60 min in a ceramic crucible under atmospheric pressure. The photoluminescence (PL) spectrum that characterized by spectrophotometer showed a single, distinct, and broad emission band varied from blue to near red color, depend on the PEG, boric acid and urea ratio in the precursor. The addition of silica nanoparticles caused the increasing of PL intensity as well as the shifting of peak wavelength of PL spectrum. The peak shifting of PL was affected by the concentration of silica nanoparticles that added into the precursor. We believe that the BCNO-silica composite phosphor becomes a promising material for the phosphor conversion-based white light-emitting diodes.

Impurity-induced disorder in III-nitride materials and devices

DOEpatents

Wierer, Jr., Jonathan J; Allerman, Andrew A

2014-11-25

A method for impurity-induced disordering in III-nitride materials comprises growing a III-nitride heterostructure at a growth temperature and doping the heterostructure layers with a dopant during or after the growth of the heterostructure and post-growth annealing of the heterostructure. The post-growth annealing temperature can be sufficiently high to induce disorder of the heterostructure layer interfaces.

Development of III-Nitride Based THz Inter-Subband Lasers

DTIC Science & Technology

2009-09-30

tested both resonant tunneling diodes and quantum well infrared photodetectors in order to investigate quantum transport in III-Nitrides. Based on the...and tested both resonant tunneling diodes and quantum well infrared photodetectors in order to investigate quantum transport in III- Nitrides. Based...strain on bandstructure and piezo-as well as spontaneous- electric fields. Interband photoluminescence and intersubband absorption measurements were

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, Richard A.

1994-01-01

A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

Physical fundamentals of criterial estimation of nitriding technology for parts of friction units

NASA Astrophysics Data System (ADS)

Kuksenova, L. I.; Gerasimov, S. A.; Lapteva, V. G.; Alekseeva, M. S.

2013-03-01

Characteristics of the structure and properties of surface layers of nitrided structural steels and alloys, which affect the level of surface fracture under friction, are studied. A generalized structural parameter for optimizing the nitriding process and a rapid method for estimating the quality of the surface layer of nitrided parts of friction units are developed.

Use of additives to improve microstructures and fracture resistance of silicon nitride ceramics

DOEpatents

Becher, Paul F [Oak Ridge, TN; Lin, Hua-Tay [Oak Ridge, TN

2011-06-28

A high-strength, fracture-resistant silicon nitride ceramic material that includes about 5 to about 75 wt-% of elongated reinforcing grains of beta-silicon nitride, about 20 to about 95 wt-% of fine grains of beta-silicon nitride, wherein the fine grains have a major axis of less than about 1 micron; and about 1 to about 15 wt-% of an amorphous intergranular phase comprising Si, N, O, a rare earth element and a secondary densification element. The elongated reinforcing grains have an aspect ratio of 2:1 or greater and a major axis measuring about 1 micron or greater. The elongated reinforcing grains are essentially isotropically oriented within the ceramic microstructure. The silicon nitride ceramic exhibits a room temperature flexure strength of 1,000 MPa or greater and a fracture toughness of 9 MPa-m.sup.(1/2) or greater. The silicon nitride ceramic exhibits a peak strength of 800 MPa or greater at 1200 degrees C. Also included are methods of making silicon nitride ceramic materials which exhibit the described high flexure strength and fracture-resistant values.

Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices

DOE PAGES

Xiao, Zhigang; Kisslinger, Kim

2015-06-17

Thin films of hafnium dioxide (HfO 2) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this paper, the authors report the growth of thin films of HfO 2 using e-beam evaporation, and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using this HfO 2 thin film as the gate oxide. The authors analyzed the thin films using high-resolution transmission electron microscopy and electron diffraction, thereby demonstrating that the e-beam-evaporation-grown HfO 2 film has a polycrystalline structure and forms an excellent interface with silicon. Accordingly, we fabricated 31-stage CMOS ringmore » oscillator to test the quality of the HfO 2 thin film as the gate oxide, and obtained excellent rail-to-rail oscillation waveforms from it, denoting that the HfO 2 thin film functioned very well as the gate oxide.« less

Process for producing ceramic nitrides anc carbonitrides and their precursors

DOEpatents

Brown, G.M.; Maya, L.

1987-02-25

A process for preparing ceramic nitrides and carbon nitrides in the form of very pure, fine particulate powder. Appropriate precursors is prepared by reaching a transition metal alkylamide with ammonia to produce a mixture of metal amide and metal imide in the form of an easily pyrolyzable precipitate.

Low-temperature nitridation of manganese and iron oxides using NaNH2 molten salt.

PubMed

Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

2013-10-21

Manganese and iron nitrides are important functional materials, but their synthesis processes from oxides often require high temperatures. Herein, we show a novel meta-synthesis method for manganese and iron nitrides by low-temperature nitridation of their oxides using NaNH2 molten salt as the nitrogen source in an autoclave at 240 °C. With this method, nitridation of micrometer-sized oxide particles kept their initial morphologies, but the size of the primary particles decreased. The thermodynamic driving force is considered to be the conversion of oxides to sodium hydroxide, and the kinetic of nitridation is improved by the decrease of particle size and the low melting point of NaNH2. This technique as developed here has the advantages of low reaction temperature, reduced consumption of ammonia, employing nonspecialized equipment, and providing facile control of the reactions for producing nitrides from oxides.

Catalytic CVD synthesis of boron nitride and carbon nanomaterials - synergies between experiment and theory.

PubMed

McLean, Ben; Eveleens, Clothilde A; Mitchell, Izaac; Webber, Grant B; Page, Alister J

2017-10-11

Low-dimensional carbon and boron nitride nanomaterials - hexagonal boron nitride, graphene, boron nitride nanotubes and carbon nanotubes - remain at the forefront of advanced materials research. Catalytic chemical vapour deposition has become an invaluable technique for reliably and cost-effectively synthesising these materials. In this review, we will emphasise how a synergy between experimental and theoretical methods has enhanced the understanding and optimisation of this synthetic technique. This review examines recent advances in the application of CVD to synthesising boron nitride and carbon nanomaterials and highlights where, in many cases, molecular simulations and quantum chemistry have provided key insights complementary to experimental investigation. This synergy is particularly prominent in the field of carbon nanotube and graphene CVD synthesis, and we propose here it will be the key to future advances in optimisation of CVD synthesis of boron nitride nanomaterials, boron nitride - carbon composite materials, and other nanomaterials generally.

Clusterization Effects in III-V Nitrides: Nitrogen Vacancies, and Si and Mg Impurities in Aluminum Nitride and Gallium Nitride

NASA Astrophysics Data System (ADS)

Gubanov, V. A.; Pentaleri, E. A.; Boekema, C.; Fong, C. Y.; Klein, B. M.

1997-03-01

We have investigated clusterization of nitrogen vacancies and Si and Mg doping impurities in zinc-blende aluminum nitride (c-AlN) and gallium nitride (c-GaN) by the tight-binding LMTO technique. The calculations used 128-site supercells. Si and Mg atoms replacing ions in both the cation and anion sublattices of the host lattices of the host crystals have been considered. The Mg impurity at cation sites is found to form partially occupied states at the valence-band edge, and may result in p-type conductivity. When Si substitutes for Ga, the impurity band is formed at the conduction-band edge, resulting in n-type conductivity. Si impurities at cation sites, and Mg impurity at anion sites are able to form resonance states in the gap. The influence of impurity clusterization in the host lattice and interstitial sites on electronic properties of c-AlN and c-GaN crystals are modeled. The changes in vacancy- and impurity-state energies, bonding type, localization, density of states at the Fermi level in different host lattices, their dependence on impurity/vacancy concentration are analyzed and compared with the experimental data.

Defect reduction in seeded aluminum nitride crystal growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.

2017-04-18

Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Defect reduction in seeded aluminum nitride crystal growth

DOEpatents

Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.; Slack, Glen A.

2017-06-06

Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density .ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Defect reduction in seeded aluminum nitride crystal growth

DOEpatents

Bondokov, Robert T.; Schowalter, Leo J.; Morgan, Kenneth; Slack, Glen A; Rao, Shailaja P.; Gibb, Shawn Robert

2017-09-26

Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Grafting titanium nitride surfaces with sodium styrene sulfonate thin films

PubMed Central

Zorn, Gilad; Migonney, Véronique; Castner, David G.

2014-01-01

The importance of titanium nitride lies in its high hardness and its remarkable resistance to wear and corrosion, which has led to its use as a coating for the heads of hip prostheses, dental implants and dental surgery tools. However, the usefulness of titanium nitride coatings for biomedical applications could be significantly enhanced by modifying their surface with a bioactive polymer film. The main focus of the present work was to graft a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film from titanium nitride surfaces via a two-step procedure: first modifying the surface with 3-methacryloxypropyltrimethoxysilane (MPS) and then grafting the pNaSS film from the MPS modified titanium through free radical polymerization. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used after each step to characterize success and completeness of each reaction. The surface region of the titanium nitride prior to MPS functionalization and NaSS grafting contained a mixture of titanium nitride, oxy-nitride, oxide species as well as adventitious surface contaminants. After MPS functionalization, Si was detected by XPS, and characteristic MPS fragments were detected by ToF-SIMS. After NaSS grafting, Na and S were detected by XPS and characteristic NaSS fragments were detected by ToF-SIMS. The XPS determined thicknesses of the MPS and NaSS overlayers were ∼1.5 and ∼1.7 nm, respectively. The pNaSS film density was estimated by the toluidine blue colorimetric assay to be 260 ± 70 ng/cm2. PMID:25280842

Erosion-corrosion resistance properties of 316L austenitic stainless steels after low-temperature liquid nitriding

NASA Astrophysics Data System (ADS)

Zhang, Xiangfeng; Wang, Jun; Fan, Hongyuan; Pan, Dong

2018-05-01

The low-temperature liquid nitriding of stainless steels can result in the formation of a surface zone of so-called expanded austenite (S-phase) by the dissolution of large amounts of nitrogen in the solid solution and formation of a precipitate-free layer supersaturated with high hardness. Erosion-corrosion measurements were performed on low-temperature nitrided and non-nitrided 316L stainless steels. The total erosion-corrosion, erosion-only, and corrosion-only wastages were measured directly. As expected, it was shown that low-temperature nitriding dramatically reduces the degree of erosion-corrosion in stainless steels, caused by the impingement of particles in a corrosive medium. The nitrided 316L stainless steels exhibited an improvement of almost 84% in the erosion-corrosion resistance compared to their non-nitrided counterparts. The erosion-only rates and synergistic levels showed a general decline after low-temperature nitriding. Low-temperature liquid nitriding can not only reduce the weight loss due to erosion but also significantly reduce the weight loss rate of interactions, so that the total loss of material decreased evidently. Therefore, 316L stainless steels displayed excellent erosion-corrosion behaviors as a consequence of their highly favorable corrosion resistances and superior wear properties.

Rational design of metal nitride redox materials for solar-driven ammonia synthesis.

PubMed

Michalsky, Ronald; Pfromm, Peter H; Steinfeld, Aldo

2015-06-06

Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700-1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia.

Rational design of metal nitride redox materials for solar-driven ammonia synthesis

PubMed Central

Michalsky, Ronald; Pfromm, Peter H.; Steinfeld, Aldo

2015-01-01

Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700–1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia. PMID:26052421

Silicon nitride equation of state

NASA Astrophysics Data System (ADS)

Brown, Robert C.; Swaminathan, Pazhayannur K.

2017-01-01

This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences.

Synthesis of rhenium nitride crystals with MoS2 structure

NASA Astrophysics Data System (ADS)

Kawamura, Fumio; Yusa, Hitoshi; Taniguchi, Takashi

2012-06-01

Rhenium nitride (ReN2) crystals were synthesized from a metathesis reaction between ReCl5 and Li3N under high pressure. The reaction was well controlled by the addition of a large amount of NaCl as reaction inhibitor to prevent a violent exothermic reaction. The largest rhenium nitride crystals obtained had a millimeter-order size with a platelet shape. X-ray diffraction analysis revealed that rhenium nitride has MoS2 structure similar to hexagonal rhenium diboride (ReB2) which has recently been investigated as an ultra-hard material. The structure was different from any structures previously predicted for ReN2 by theoretical calculations.

Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride

NASA Astrophysics Data System (ADS)

Rinaldo, Steven G.

This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 -- 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the

On the buckling of hexagonal boron nitride nanoribbons via structural mechanics

NASA Astrophysics Data System (ADS)

Giannopoulos, Georgios I.

2018-03-01

Monolayer hexagonal boron nitride nanoribbons have similar crystal structure as graphene nanoribbons, have excellent mechanical, thermal insulating and dielectric properties and additionally present chemical stability. These allotropes of boron nitride can be used in novel applications, in which graphene is not compatible, to achieve remarkable performance. The purpose of the present work is to provide theoretical estimations regarding the buckling response of hexagonal boron nitride monolayer under compressive axial loadings. For this reason, a structural mechanics method is formulated which employs the exact equilibrium atomistic structure of the specific two-dimensional nanomaterial. In order to represent the interatomic interactions appearing between boron and nitrogen atoms, the Dreiding potential model is adopted which is realized by the use of three-dimensional, two-noded, spring-like finite elements of appropriate stiffness matrices. The critical compressive loads that cause the buckling of hexagonal boron nitride nanoribbons are computed with respect to their size and chirality while some indicative buckled shapes of them are illustrated. Important conclusions arise regarding the effect of the size and chirality on the structural stability of the hexagonal boron nitride monolayers. An analytical buckling formula, which provides good fitting of the numerical outcome, is proposed.

Development of silicon nitride of improved toughness

NASA Technical Reports Server (NTRS)

Brennan, J. J.

1979-01-01

The application of reaction sintered Si2N4 energy absorbing surface layers to hot-pressed Si3N4 was investigated. The surface layer was formed by in-place nitridation of silicon powder. It was found that reaction sintered Si3N4 layers of 1 mm thickness, fabricated from either -100, +200, -200, or -325 mesh Si powder and nitrided in 96% N2/4% H2 so that approximately 20-25 vol % unnitrided Si remained in the layer, resulted in a sevenfold increase in ballistic impact resistance of a 0.64 cm thick hot-pressed SI3N4 substrate from RT 1370 C. Both NC-132 SI3N4, with MgO additive, and NCX-34 Si3N4, with Y2O3 additive, were evaluated as substrate material. The finer grain size -200 and -325 mesh nitrided Si layers were for their smoothness and relatively high density. It was found that nitriding in N2/H2 mixtures, rather than pure N2, resulted in a microstructure that did not substantially degrade the strength of the hot-pressed Si3N4 substrate. Thermal cycling tests on the RSSN/HPSN combinations from 200 C to 1370 C for 75 cycles in air did not degrade the impact resistance nor the interfacial bonding, although a large amount of internal silica formation occurred within the RSSN layer. Mach 0.8, 5 hr, hot gas erosion tests showed no surface recession of RSSN layers at 1200 C and slight surface recession at 1370 C.

Surface Texturing-Plasma Nitriding Duplex Treatment for Improving Tribological Performance of AISI 316 Stainless Steel

PubMed Central

Lin, Naiming; Liu, Qiang; Zou, Jiaojuan; Guo, Junwen; Li, Dali; Yuan, Shuo; Ma, Yong; Wang, Zhenxia; Wang, Zhihua; Tang, Bin

2016-01-01

Surface texturing-plasma nitriding duplex treatment was conducted on AISI 316 stainless steel to improve its tribological performance. Tribological behaviors of ground 316 substrates, plasma-nitrided 316 (PN-316), surface-textured 316 (ST-316), and duplex-treated 316 (DT-316) in air and under grease lubrication were investigated using a pin-on-disc rotary tribometer against counterparts of high carbon chromium bearing steel GCr15 and silicon nitride Si3N4 balls. The variations in friction coefficient, mass loss, and worn trace morphology of the tested samples were systemically investigated and analyzed. The results showed that a textured surface was formed on 316 after electrochemical processing in a 15 wt % NaCl solution. Grooves and dimples were found on the textured surface. As plasma nitriding was conducted on a 316 substrate and ST-316, continuous and uniform nitriding layers were successfully fabricated on the surfaces of the 316 substrate and ST-316. Both of the obtained nitriding layers presented thickness values of more than 30 μm. The nitriding layers were composed of iron nitrides and chromium nitride. The 316 substrate and ST-316 received improved surface hardness after plasma nitriding. When the tribological tests were carried out under dry sliding and grease lubrication conditions, the tested samples showed different tribological behaviors. As expected, the DT-316 samples revealed the most promising tribological properties, reflected by the lowest mass loss and worn morphologies. The DT-316 received the slightest damage, and its excellent tribological performance was attributed to the following aspects: firstly, the nitriding layer had high surface hardness; secondly, the surface texture was able to capture wear debris, store up grease, and then provide continuous lubrication. PMID:28773996

PHYSICAL PROPERTIES OF ZIRCONIUM NITRIDE IN THE HOMOGENEITY REGION (in Ukrainian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samsonov, G.V.; Verkhoglyadova, T.S.

1962-01-01

The x-ray method was used to determine the homogeneity region of zirconium nitride as 40 to 50 at.% (9.5 to 13.3% by weight) of nitrogen. It is also shown that part of the ionic bond in the zirconium nitride lattice increases with a decrease in the nitrogen content in this region, this increase being higher than in the homogeneity region of titunium nitride due to the smaller degree of unfilling of the electron d-shell of the zirconium atom in comparison with that of the titanium atom. (auth)

Crystallization of the glassy grain boundary phase in silicon nitride ceramics

NASA Technical Reports Server (NTRS)

Drummond, Charles H., III

1991-01-01

The role was studied of the intergranular glassy phase in silicon nitride as-processed with yttria as a sintering aid. The microstructure, crystallization, and viscosity of the glassy phase were areas studied. Crystallization of the intergranular glassy phase to more refractory crystalline phases should improve the high temperature mechanical properties of the silicon nitride. The addition of a nucleating agent will increase the rate of crystallization. The measurement of the viscosity of the glassy phase will permit the estimation of the high temperature deformation of the silicon nitride.

Viscoelastic Behavior of PDMS Filled with Boron Nitrides

NASA Astrophysics Data System (ADS)

Bian, J. F.; Weinkauf, D. H.; Jeon, H. S.

2004-03-01

The addition of high thermal conductive filler particles such as boron nitride, aluminum nitride, or carbon fiber is an effective way to increase the thermal conductivity of polymeric materials for the industrial applications such as electronic packaging materials, encapsulants, and thermal fluids among others. The effects of particle dispersions, concentrations, and the interactions between BN and polymer matrix on the viscoelastic properties of the boron nitride (BN)/polydimethylsiloxane (PDMS) composites prepared by mechanical mixing are investigated using oscillatory shear rheology. Both untreated and plasma treated boron nitride (BNP) particles with hexafluoropropylene oxide monomers have been used in this study. The addition of the plasma treated BN particles to the PDMS matrix decrease significantly the complex viscosity as well as storage and loss modulus of the composites due to the reduced interfacial energy between the surface of BNP and PDMS chains. For the PDMS/BN and PDMS/BNP composites, the maximum volume packing fraction ( ˜0.4) of the particles has been determined from the complex viscosity as a function of the frequency. Additionally, the shear-induced alignment of the BN particles dispersed in the PDMS matrix decreases the viscoelastic properties of the composites with the irregular oscillations which is related to the network formation of dispersed BN particles at the higher volume fractions (> ˜0.2).

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, R.A.

1994-04-05

A process for chemical vapor deposition of crystalline silicon nitride is described which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide. 5 figures.

Hydrolytic Unzipping of Boron Nitride Nanotubes in Nitric Acid.

PubMed

Kim, Dukeun; Muramatsu, Hiroyuki; Kim, Yoong Ahm

2017-12-01

Boron nitride nanoribbons (BNNRs) have very attractive electrical and optical properties due to their unique edge states and width-related properties. Herein, for the first time, BNNRs were produced by a simple reflux of boron nitride nanotubes (BNNTs) in nitric acid containing water, which had led to unzipped sidewalls through hydrolysis. Their high reactivity that originated from edges was verified via a strong interaction with methylene blue.

Validity of "sputtering and re-condensation" model in active screen cage plasma nitriding process

NASA Astrophysics Data System (ADS)

Saeed, A.; Khan, A. W.; Jan, F.; Abrar, M.; Khalid, M.; Zakaullah, M.

2013-05-01

The validity of "sputtering and re-condensation" model in active screen plasma nitriding for nitrogen mass transfer mechanism is investigated. The dominant species including NH, Fe-I, N2+, N-I and N2 along with Hα and Hβ lines are observed in the optical emission spectroscopy (OES) analysis. Active screen cage and dc plasma nitriding of AISI 316 stainless steel as function of treatment time is also investigated. The structure and phases composition of the nitrided layer is studied by X-ray diffraction (XRD). Surface morphology is studied by scanning electron microscopy (SEM) and hardness profile is obtained by Vicker's microhardness tester. Increasing trend in microhardness is observed in both cases but the increase in active screen plasma nitriding is about 3 times greater than that achieved by dc plasma nitriding. On the basis of metallurgical and OES observations the use of "sputtering and re-condensation" model in active screen plasma nitriding is tested.

Laser Beam Welding of Nitride Steel Components

NASA Astrophysics Data System (ADS)

Gu, Hongping; Yin, Guobin; Shulkin, Boris

Laser beam welding is a joining technique that has many advantages over conventional GMAW welding, such as low heat input, short cycle time as well as good cosmetic welds. Laser beam welding has been widely used for welding powertrain components in automotive industry. When welding nitride steel components, however, laser beam welding faces a great challenge. The difficulty lies in the fact that the nitride layer in the joint releases the nitrogen into the weld pool, resulting in a porous weld. This research presents an industrial ready solution to prevent the nitrogen from forming gas bubbles in the weld.

Polymeric carbon nitride for solar hydrogen production.

PubMed

Li, Xiaobo; Masters, Anthony F; Maschmeyer, Thomas

2017-07-04

If solar hydrogen production from water is to be a realistic candidate for industrial hydrogen production, the development of photocatalysts, which avoid the use of expensive and/or toxic elements is highly desirable from a scalability, cost and environmental perspective. Metal-free polymeric carbon nitride is an attractive material that can absorb visible light and produce hydrogen from water. This article reviews recent developments in polymeric carbon nitride as used in photocatalysis and then develops the discussion focusing on the three primary processes of a photocatalytic reaction: light-harvesting, carrier generation/separation/transportation and surface reactions.

Boron nitride nanotube-mediated stimulation modulates F/G-actin ratio and mechanical properties of human dermal fibroblasts

NASA Astrophysics Data System (ADS)

Ricotti, Leonardo; das Neves, Ricardo Pires; Ciofani, Gianni; Canale, Claudio; Nitti, Simone; Mattoli, Virgilio; Mazzolai, Barbara; Ferreira, Lino; Menciassi, Arianna

2014-02-01

F/G-actin ratio modulation is known to have an important role in many cell functions and in the regulation of specific cell behaviors. Several attempts have been made in the latest decades to finely control actin production and polymerization, in order to promote certain cell responses. In this paper we demonstrate the possibility of modulating F/G-actin ratio and mechanical properties of normal human dermal fibroblasts by using boron nitride nanotubes dispersed in the culture medium and by stimulating them with ultrasound transducers. Increasing concentrations of nanotubes were tested with the cells, without any evidence of cytotoxicity up to 10 μg/ml concentration of nanoparticles. Cells treated with nanoparticles and ultrasound stimulation showed a significantly higher F/G-actin ratio in comparison with the controls, as well as a higher Young's modulus. Assessment of Cdc42 activity revealed that actin nucleation/polymerization pathways, involving Rho GTPases, are probably influenced by nanotube-mediated stimulation, but they do not play a primary role in the significant increase of F/G-actin ratio of treated cells, such effect being mainly due to actin overexpression.

Purchase of a Raman and Photoluminescence Imaging System for Characterization of Advanced Electrochemical and Electronic Materials

DTIC Science & Technology

2016-01-05

regularly used the Raman imaging system to characterize the doping chemistry of colloidal indium nitride nanoparticles . This material shows an interesting...regularly used the Raman imaging system to characterize the doping chemistry of colloidal indium nitride nanoparticles . This material shows an...analysis of thin film coatings, bulk materials, powders and nanoparticles . The instrument is extensively used to characterize advanced electrochemical and

Infrared absorption spectra of metal carbides, nitrides and sulfides

NASA Technical Reports Server (NTRS)

Kammori, O.; Sato, K.; Kurosawa, F.

1981-01-01

The infrared absorption spectra of 12 kinds of metal carbides, 11 kinds of nitrides, and 7 kinds of sulfides, a total of 30 materials, were measured and the application of the infrared spectra of these materials to analytical chemistry was discussed. The measurements were done in the frequency (wave length) range of (1400 to 400/cm (7 to 25 mu). The carbides Al4C3, B4C, the nitrides AlN, BN, Si3N4, WB, and the sulfides Al2S3, FeS2, MnS, NiS and PbS were noted to have specific absorptions in the measured region. The sensitivity of Boron nitride was especially good and could be detected at 2 to 3 micrograms in 300 mg of potassium bromide.

Effects of the Process Parameters on the Microstructure and Properties of Nitrided 17-4PH Stainless Steel

NASA Astrophysics Data System (ADS)

Wang, Jun; Lin, Yuanhua; Zeng, Dezhi; Yan, Jing; Fan, Hongyuan

2013-04-01

The effects of process parameters on the microstructure, microhardness, and dry-sliding wear behavior of plasma nitrided 17-4PH stainless steel were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and wear testing. The results show that a wear-resistant nitrided layer was formed on the surface of direct current plasma nitrided 17-4PH martensitic stainless steel. The microstructure and thickness of the nitrided layer is dependent on the treatment temperature rather than process pressure. XRD indicated that a single α N phase was formed during nitriding at 623 K (350 °C). When the temperature increased, the α N phase disappeared and CrN transformed in the nitrided layer. The hardness measurement demonstrated that the hardness of the stainless substrate steel increased from 320 HV0.1 in the untreated condition increasing to about 1275HV0.1 after nitriding 623 K (350 °C)/600 pa/4 hours. The extremely high values of the microhardness achieved by the great misfit-induced stress fields associated with the plenty of dislocation group and stacking fault. Dry-sliding wear resistance was improved by DC plasma nitriding. The best wear-resistance performance of a nitrided sample was obtained after nitriding at 673 K (350 °C), when the single α N-phase was produced and there were no CrN precipitates in the nitrided layer.

Pyroelectric response in crystalline hafnium zirconium oxide (Hf 1- x Zr x O 2 ) thin films

DOE PAGES

Smith, S. W.; Kitahara, A. R.; Rodriguez, M. A.; ...

2017-02-13

Pyroelectric coefficients were measured for 20 nm thick crystalline hafnium zirconium oxide (Hf 1-xZr xO 2) thin films across a composition range of 0 ≤ x ≤ 1. Pyroelectric currents were collected near room temperature under zero applied bias and a sinusoidal oscillating temperature profile to separate the influence of non-pyroelectric currents. The pyroelectric coefficient was observed to correlate with zirconium content, increased orthorhombic/tetragonal phase content, and maximum polarization response. The largest measured absolute value was 48 μCm -2K -1 for a composition with x = 0.64, while no pyroelectric response was measured for compositions which displayed no remanent polarizationmore » (x = 0, 0.91, 1).« less

Colloidal characterization of silicon nitride and silicon carbide

NASA Technical Reports Server (NTRS)

Feke, Donald L.

1986-01-01

The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

Zinc nitride thin films: basic properties and applications

NASA Astrophysics Data System (ADS)

Redondo-Cubero, A.; Gómez-Castaño, M.; García Núñez, C.; Domínguez, M.; Vázquez, L.; Pau, J. L.

2017-02-01

Zinc nitride films can be deposited by radio frequency magnetron sputtering using a Zn target at substrate temperatures lower than 250°C. This low deposition temperature makes the material compatible with flexible substrates. The asgrown layers present a black color, polycrystalline structures, large conductivities, and large visible light absorption. Different studies have reported about the severe oxidation of the layers in ambient conditions. Different compositional, structural and optical characterization techniques have shown that the films turn into ZnO polycrystalline layers, showing visible transparency and semi-insulating properties after total transformation. The oxidation rate is fairly constant as a function of time and depends on environmental parameters such as relative humidity or temperature. Taking advantage of those properties, potential applications of zinc nitride films in environmental sensing have been studied in the recent years. This work reviews the state-of-the-art of the zinc nitride technology and the development of several devices such as humidity indicators, thin film (photo)transistors and sweat monitoring sensors.

Reduction of Defects on Microstructure Aluminium Nitride Using High Temperature Annealing Heat Treatment

NASA Astrophysics Data System (ADS)

Tanasta, Z.; Muhamad, P.; Kuwano, N.; Norfazrina, H. M. Y.; Unuh, M. H.

2018-03-01

Aluminium Nitride (AlN) is a ceramic 111-nitride material that is used widely as components in functional devices. Besides good thermal conductivity, it also has a high band gap in emitting light which is 6 eV. AlN thin film is grown on the sapphire substrate (0001). However, lattice mismatch between both materials has caused defects to exist along the microstructure of AlN thin films. The defects have affected the properties of Aluminium Nitride. Annealing heat treatment has been proved by the previous researcher to be the best method to improve the microstructure of Aluminium Nitride thin films. Hence, this method is applied at four different temperatures for two hour. The changes of Aluminium Nitride microstructures before and after annealing is observed using Transmission Electron Microscope. It is observed that inversion domains start to occur at temperature of 1500 °C. Convergent Beam Electron Diffraction pattern simulation has confirmed the defects as inversion domain. Therefore, this paper is about to extract the matters occurred during the process of producing high quality Aluminium Nitride thin films and the ways to overcome this problem.

Formation of porous surface layers in reaction bonded silicon nitride during processing

NASA Technical Reports Server (NTRS)

Shaw, N. J.; Glasgow, T. K.

1979-01-01

An effort was undertaken to determine if the formation of the generally observed layer of large porosity adjacent to the as-nitride surfaces of reaction bonded silicon nitrides could be prevented during processing. Isostatically pressed test bars were prepared from wet vibratory milled Si powder. Sintering and nitriding were each done under three different conditions:(1) bars directly exposed to the furnance atmosphere; (2) bars packed in Si powder; (3) bars packed in Si3N4 powder. Packing the bars in either Si of Si3N4 powder during sintering retarded formation of the layer of large porosity. Only packing the bars in Si prevented formation of the layer during nitridation. The strongest bars (316 MPa) were those sintered in Si and nitrided in Si3N4 despite their having a layer of large surface porosity; failure initiated at very large pores and inclusions. The alpha/beta ratio was found to be directly proportional to the oxygen content; a possible explanation for this relationship is discussed.

Growth of single-layer boron nitride dome-shaped nanostructures catalysed by iron clusters.

PubMed

Torre, A La; Åhlgren, E H; Fay, M W; Ben Romdhane, F; Skowron, S T; Parmenter, C; Davies, A J; Jouhannaud, J; Pourroy, G; Khlobystov, A N; Brown, P D; Besley, E; Banhart, F

2016-08-11

We report on the growth and formation of single-layer boron nitride dome-shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized in situ at high temperature inside a transmission electron microscope while the e-beam was blanked. The formation process, typically originating at defective step-edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. Computational modelling showed that the domes exhibit a nanotube-like structure with flat circular caps and that their stability was comparable to that of a single boron nitride layer.

Wafer-Scale and Wrinkle-Free Epitaxial Growth of Single-Orientated Multilayer Hexagonal Boron Nitride on Sapphire.

PubMed

Jang, A-Rang; Hong, Seokmo; Hyun, Chohee; Yoon, Seong In; Kim, Gwangwoo; Jeong, Hu Young; Shin, Tae Joo; Park, Sung O; Wong, Kester; Kwak, Sang Kyu; Park, Noejung; Yu, Kwangnam; Choi, Eunjip; Mishchenko, Artem; Withers, Freddie; Novoselov, Kostya S; Lim, Hyunseob; Shin, Hyeon Suk

2016-05-11

Large-scale growth of high-quality hexagonal boron nitride has been a challenge in two-dimensional-material-based electronics. Herein, we present wafer-scale and wrinkle-free epitaxial growth of multilayer hexagonal boron nitride on a sapphire substrate by using high-temperature and low-pressure chemical vapor deposition. Microscopic and spectroscopic investigations and theoretical calculations reveal that synthesized hexagonal boron nitride has a single rotational orientation with AA' stacking order. A facile method for transferring hexagonal boron nitride onto other target substrates was developed, which provides the opportunity for using hexagonal boron nitride as a substrate in practical electronic circuits. A graphene field effect transistor fabricated on our hexagonal boron nitride sheets shows clear quantum oscillation and highly improved carrier mobility because the ultraflatness of the hexagonal boron nitride surface can reduce the substrate-induced degradation of the carrier mobility of two-dimensional materials.

Biologically Self-Assembled Memristive Circuit Elements

DTIC Science & Technology

2010-01-01

hydrothermal approach, TiO2 nanoparticles were synthesized by slowly stirring a 1:3 volumetric ratio mixture of titanium isopropoxide (TTIP) and isopropyl...Synthesis of TiO2 nanoparticles by hydrolysis and peptization of titanium isopropoxide solution. Journal of Materials Processing Technology 2007, 189...important role interfacing with group IV metal oxides such as hafnium, providing a stable linkage to the surface [3]. Titanium dioxide (TiO2), which is

Carbon nitride supported Fe2 cluster catalysts with superior performance for alkene epoxidation.

PubMed

Tian, Shubo; Fu, Qiang; Chen, Wenxing; Feng, Quanchen; Chen, Zheng; Zhang, Jian; Cheong, Weng-Chon; Yu, Rong; Gu, Lin; Dong, Juncai; Luo, Jun; Chen, Chen; Peng, Qing; Draxl, Claudia; Wang, Dingsheng; Li, Yadong

2018-06-15

Sub-nano metal clusters often exhibit unique and unexpected properties, which make them particularly attractive as catalysts. Herein, we report a "precursor-preselected" wet-chemistry strategy to synthesize highly dispersed Fe 2 clusters that are supported on mesoporous carbon nitride (mpg-C 3 N 4 ). The obtained Fe 2 /mpg-C 3 N 4 sample exhibits superior catalytic performance for the epoxidation of trans-stilbene to trans-stilbene oxide, showing outstanding selectivity of 93% at high conversion of 91%. Molecular oxygen is the only oxidant and no aldehyde is used as co-reagent. Under the same condition, by contrast, iron porphyrin, single-atom Fe, and small Fe nanoparticles (ca. 3 nm) are nearly reactively inert. First-principles calculations reveal that the unique reactivity of the Fe 2 clusters originates from the formation of active oxygen species. The general applicability of the synthesis approach is further demonstrated by producing other diatomic clusters like Pd 2 and Ir 2 , which lays the foundation for discovering diatomic cluster catalysts.

Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies

DOE PAGES

Cao, Bingfei; Neuefeind, Joerg C.; Adzic, Radoslav R.; ...

2015-02-09

Monometallic (δ-MoN, Mo 5N 6, and Mo 2N) and bimetallic molybdenum nitrides (Co 0.6Mo 1.4N 2) were investigated as electrocatalysts for the oxygen reduction reaction (ORR), which is a key half-reaction in hydrogen fuel cells. Monometallic hexagonal molybdenum nitrides are found to exhibit improved activities over rock salt type molybdenum nitride (γ-Mo 2N), suggesting that improvements are due to either the higher molybdenum valence or a more favorable coordination environment in the hexagonal structures. Further enhancements in activity were found for hexagonal bimetallic cobalt molybdenum nitride (Co 0.6Mo 1.4N 2), resulting in a modest onset potential of 0.713 V versusmore » reversible hydrogen electrode (RHE). Co 0.6Mo 1.4N 2 exhibits good stability in acidic environments, and in the potential range lower than 0.5 V versus RHE, the ORR appears to proceed via a four-electron mechanism based on the analysis of rotating disc electrode results. A redetermination of the structures of the binary molybdenum nitrides was carried out using neutron diffraction data, which is far more sensitive to nitrogen site positions than X-ray diffraction data. In conclusion, the revised monometallic hexagonal nitride structures all share many common features with the Co 0.6Mo 1.4N 2 structure, which has alternating layers of cations in octahedral and trigonal prismatic coordination, and are thus not limited to only trigonal prismatic Mo environments (as was originally postulated for δ-MoN).« less

Single photon emitters in boron nitride: More than a supplementary material

NASA Astrophysics Data System (ADS)

Koperski, M.; Nogajewski, K.; Potemski, M.

2018-03-01

We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation.

Method and apparatus for use of III-nitride wide bandgap semiconductors in optical communications

DOEpatents

Hui, Rongqing [Lenexa, KS; Jiang, Hong-Xing [Manhattan, KS; Lin, Jing-Yu [Manhattan, KS

2008-03-18

The present disclosure relates to the use of III-nitride wide bandgap semiconductor materials for optical communications. In one embodiment, an optical device includes an optical waveguide device fabricated using a III-nitride semiconductor material. The III-nitride semiconductor material provides for an electrically controllable refractive index. The optical waveguide device provides for high speed optical communications in an infrared wavelength region. In one embodiment, an optical amplifier is provided using optical coatings at the facet ends of a waveguide formed of erbium-doped III-nitride semiconductor materials.

Sulfide Stress Cracking and Electrochemical Corrosion of Precipitation Hardening Steel After Plasma Oxy-Nitriding

NASA Astrophysics Data System (ADS)

Granda-Gutiérrez, E. E.; Díaz-Guillén, J. C.; Díaz-Guillén, J. A.; González, M. A.; García-Vázquez, F.; Muñóz, R.

2014-11-01

In this paper, we present the results of a duplex plasma nitriding followed by an oxidizing stage process (which is also referred as oxy-nitriding) on the corrosion behavior of a 17-4PH precipitation hardening stainless steel. The formation of both, expanded martensite (b.c.t. α'N-phase) and chromium oxide (type Cr2O3) in the subsurface of oxy-nitrided samples at specific controlled conditions, leads in a noticeable increasing in the time-to-rupture during the sulfide stress cracking test, in comparison with an untreated reference sample. Oxy-nitriding improves the corrosion performance of the alloy when it is immersed in solutions saturated by sour gas, which extends the application potential of this type of steel in the oil and gas extraction and processing industry. The presence of the oxy-nitrided layer inhibits the corrosion process that occurs in the near-surface region, where hydrogen is liberated after the formation of iron sulfides, which finally produces a fragile fracture by micro-crack propagation; the obtained results suggest that oxy-nitriding slows this process, thus delaying the rupture of the specimen. Moreover, oxy-nitriding produces a hard, sour gas-resistant surface, but do not significantly affect the original chloride ion solution resistance of the material.

Process for making boron nitride using sodium cyanide and boron

DOEpatents

Bamberger, Carlos E.

1990-02-06

This a very simple process for making boron nitride by mixing sodium cyanide and boron phosphate and heating the mixture in an inert atmosphere until a reaction takes place. The product is a white powder of boron nitride that can be used in applications that require compounds that are stable at high temperatures and that exhibit high electrical resistance.

Process for making boron nitride using sodium cyanide and boron

DOEpatents

Bamberger, Carlos E.

1990-01-01

This a very simple process for making boron nitride by mixing sodium cyanide and boron phosphate and heating the mixture in an inert atmosphere until a reaction takes place. The product is a white powder of boron nitride that can be used in applications that require compounds that are stable at high temperatures and that exhibit high electrical resistance.

The structure and function of supported molybdenum nitride and molybdenum carbide hydrotreating catalysts

NASA Astrophysics Data System (ADS)

Dolce, Gregory Martin

1997-11-01

A series of gamma-Alsb2Osb3 supported molybdenum nitrides and carbides were prepared by the temperature programmed reaction of supported molybdates with ammonia and methane/hydrogen mixtures, respectively. In the first part of this research, the effects of synthesis heating rates and molybdenum loading on the catalytic properties of the materials were examined. A significant amount of excess carbon was deposited on the surface of the carbides during synthesis. The materials consisted of small particles which were very highly dispersed. Oxygen chemisorption indicated that the nitride particles may have been two-dimensional. The dispersion of the carbides, however, appeared to decrease as the loading increased. The catalysts were evaluated for hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodeoxygenation (HDO). The molybdenum loading had the largest effect on the activity of the materials. For the nitrides, the HDN and HDS activities were inverse functions of the loading. This suggested that the most active HDN and HDS sites were located at the perimeter of the two-dimensional particles. The HDN and HDS activities of the carbides followed the same trend as the oxygen uptake. This result suggested that oxygen titrated the active sites on the supported carbides. Selected catalysts were evaluated for methylcarbazole HDN, dibenzothiophene HDS, and dibenzofuran HDO. The activity and selectivity of the nitrides and carbides were competitive with a presulfided commercial catalyst. In the second part of this work, a series of supported nitrides and carbides were prepared using a wider range of loadings (5-30 wt% Mo). Thermogravimetric analysis was used to determine the temperature at which excess carbon was deposited on the carbides. By modifying the synthesis parameters, the deposition of excess carbon was effectively inhibited. The dispersions of the supported nitrides and carbides were constant and suggested that the materials consisted of two

Silicon Nitride for Direct Water-Splitting and Corrosion Mitigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Head, J.; Turner, J.A.

2006-01-01

Todays fossil fuels are becoming harder to obtain, creating pollution problems, and posing hazards to people’s health. One alternative to fossil fuels is hydrogen, capable of serving as a clean and efficient energy carrier. Certain semiconductors are able to harness the energy of photons and direct it into water electrolysis in a process known as photoelectrochemical water splitting. Triple junction devices integrate three semiconductors of different band gaps resulting in a monolithic material that absorbs over a broader spectrum. Amorphous silicon (a-Si) is one such material that, when stacked in tandem, possesses water-splitting capabilities. Even though a-Si is capable ofmore » splitting water, it is an unstable material in solution and therefore requires a coating to protect the surface from corrosion. A stable, transparent material that has the potential for corrosion protection is silicon nitride. In this study, silicon nitride thin films were grown using DC magnetron sputtering with varying amounts of argon and nitrogen added to the system. X-ray diffraction indicated amorphous silicon nitride films. Current as a function of potential was determined from cyclic voltammetry measurements. Mott-Schottky analysis showed n-type behavior with absorption and transmission measurements indicated variation in flatband potentials. Variation in band gap values ranging from 1.90 to 4.0 eV. Corrosion measurements reveal that the silicon nitride samples exhibit both p-type and n-type behavior. Photocurrent over a range of potentials was greater in samples that were submerged in acidic electrolyte. Silicon nitride shows good stability in acidic, neutral, and basic solutions, indicative of a good material for corrosion mitigation.« less

Anomalous thermal conductivity of monolayer boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tabarraei, Alireza, E-mail: atabarra@uncc.edu; Wang, Xiaonan

In this paper, we use nonequilibrium molecular dynamics modeling to investigate the thermal properties of monolayer hexagonal boron nitride nanoribbons under uniaxial strain along their longitudinal axis. Our simulations predict that hexagonal boron nitride shows an anomalous thermal response to the applied uniaxial strain. Contrary to three dimensional materials, under uniaxial stretching, the thermal conductivity of boron nitride nanoribbons first increases rather than decreasing until it reaches its peak value and then starts decreasing. Under compressive strain, the thermal conductivity of monolayer boron nitride ribbons monolithically reduces rather than increasing. We use phonon spectrum and dispersion curves to investigate themore » mechanism responsible for the unexpected behavior. Our molecular dynamics modeling and density functional theory results show that application of longitudinal tensile strain leads to the reduction of the group velocities of longitudinal and transverse acoustic modes. Such a phonon softening mechanism acts to reduce the thermal conductivity of the nanoribbons. On the other hand, a significant increase in the group velocity (stiffening) of the flexural acoustic modes is observed, which counteracts the phonon softening effects of the longitudinal and transverse modes. The total thermal conductivity of the ribbons is a result of competition between these two mechanisms. At low tensile strain, the stiffening mechanism overcomes the softening mechanism which leads to an increase in the thermal conductivity. At higher tensile strain, the softening mechanism supersedes the stiffening and the thermal conductivity slightly reduces. Our simulations show that the decrease in the thermal conductivity under compressive strain is attributed to the formation of buckling defects which reduces the phonon mean free path.« less

Engineering and Localization of Quantum Emitters in Large Hexagonal Boron Nitride Layers.

PubMed

Choi, Sumin; Tran, Toan Trong; Elbadawi, Christopher; Lobo, Charlene; Wang, Xuewen; Juodkazis, Saulius; Seniutinas, Gediminas; Toth, Milos; Aharonovich, Igor

2016-11-02

Hexagonal boron nitride is a wide-band-gap van der Waals material that has recently emerged as a promising platform for quantum photonics experiments. In this work, we study the formation and localization of narrowband quantum emitters in large flakes (up to tens of micrometers wide) of hexagonal boron nitride. The emitters can be activated in as-grown hexagonal boron nitride by electron irradiation or high-temperature annealing, and the emitter formation probability can be increased by ion implantation or focused laser irradiation of the as-grown material. Interestingly, we show that the emitters are always localized at the edges of the flakes, unlike most luminescent point defects in three-dimensional materials. Our results constitute an important step on the roadmap of deploying hexagonal boron nitride in nanophotonics applications.

Structural, electronic, mechanical and magnetic properties of rare earth nitrides REN (RE= Pm, Eu and Yb)

NASA Astrophysics Data System (ADS)

Murugan, A.; Rajeswarapalanichamy, R.; Santhosh, M.; Iyakutti, K.

2015-07-01

The structural, electronic and mechanical properties of rare earth nitrides REN (RE=Pm, Eu and Yb) are investigated in NaCl and CsCl, and zinc blende structures using first principles calculations based on density functional theory. The calculated lattice parameters are in good agreement with the available results. Among the considered structures, these nitrides are most stable in NaCl structure. A pressure induced structural phase transition from NaCl to CsCl phase is observed in all these nitrides. The electronic structure reveals that these rare earth nitrides are half metallic at normal pressure. These nitrides are found to be covalent and ionic in the stable phase. The computed elastic constants indicate that these nitrides are mechanically stable and elastically anisotropic. Our results confirm that these nitrides are ferromagnetic in nature. A ferromagnetic to non-magnetic phase transition is observed at the pressures of 21.5 GPa and 46.1 GPa in PmN and YbN respectively.

The effect of surface nanocrystallization on plasma nitriding behaviour of AISI 4140 steel

NASA Astrophysics Data System (ADS)

Li, Yang; Wang, Liang; Zhang, Dandan; Shen, Lie

2010-11-01

A plastic deformation surface layer with nanocrystalline grains was produced on AISI 4140 steel by means of surface mechanical attrition treatment (SMAT). Plasma nitriding of SMAT and un-SMAT AISI 4140 steel was carried out by a low-frequency pulse excited plasma unit. A series of nitriding experiments has been conducted at temperatures ranging from 380 to 500 °C for 8 h in an NH 3 gas. The samples were characterized using X-ray diffraction, scanning electron microscopy, optical microscopy and Vickers microhardness tester. The results showed that a much thicker compound layer with higher hardness was obtained for the SMAT samples when compared with un-SMAT samples after nitriding at the low temperature. In particular, plasma nitriding SMAT AISI 4140 steel at 380 °C for 8 h can produced a compound layer of 2.5 μm thickness with very high hardness on the surface, which is similar to un-SMAT samples were plasma nitrided at approximately 430 °C within the same time.

Kinetic modelling of chlorination of nitrided ilmenite using MATLAB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramakrishnan, Sivakumar, E-mail: srsivakumar@usm.my; Kwok, Teong Chen, E-mail: ctck@live.com; Hamid, Sheikh Abdul Rezan Sheikh Abdul, E-mail: rezanshk@gmail.com

In the present study, chlorination of nitride ilmenite using 2{sup k} factorial design was investigated. The reduction experiments were carried out in a temperature range of 400°C to 500°C, chlorination duration from 1 hour to 3 hours and using different type of carbon reactant. Phases of raw materials and reduced samples were analyzed by X-ray diffraction (XRD). Ilmenite was reduced to TiO{sub x}C{sub y}N{sub z} through carbothermal and nitridation for further chlorination into titanium tetrachloride. The Design of Experiment analysis suggested that the types of carbon reactant contribute most influence to the extent of chlorination of nitride ilmenite. The extentmore » of chlorination was highest at 500°C with 3 hours chlorination time and carbon nanotube as carbon reactant.« less

Homogeneous and heterogeneous micro-structuring of austenitic stainless steels by the low temperature plasma nitriding

NASA Astrophysics Data System (ADS)

Aizawa, T.; Yoshihara, S.-I.

2018-06-01

The austenitic stainless steels have been widely utilized as a structural component and member as well as a die and mold substrate for stamping. AISI316 dies and molds require for the surface treatment to accommodate the sufficient hardness and wear resistance to them. In addition, the candidate treatment methods must be free from toxicity, energy consumption and inefficiency. The low temperature plasma nitriding process has become one of the most promising methods to make solid-solution hardening by the nitrogen super-saturation. In the present paper, the high density RF/DC plasma nitriding process was applied to form the uniform nitrided layer in the AISI316 matrix and to describe the essential mechanism of inner nitriding in this low temperature nitriding process. In case of the nitrided AISI316 at 673 K for 14.4ks, the nitrided layer thickness became 60 μm with the surface hardness of 1700 HV and the surface nitrogen content of 7 mass %. This inner nitriding process is governed by the synergetic interrelation among the nitrogen super-saturation, the lattice expansion, the phase transformation, the plastic straining, the microstructure refinement and the acceleration of nitrogen diffusion. As far as this interrelation is sustained during the nitriding process, the original austenitic microstructure is homogeneously nitrided to have fine grains with the average size of 0.1 μm and the high crystallographic misorientation angles and to have two phase (γ + α’) structures with the plateau of nitrogen content by 5 mass%. Once this interrelation does not work anymore, the homogeneous microstructure changed itself to the heterogeneous one. The plastic straining took place in the selected coarse grains; they were partially refined into subgrains. This plastic localization accompanied the localized phase transformation.

Silicon nitride reinforced with molybdenum disilicide

DOEpatents

Petrovic, John J.; Honnell, Richard E.

1991-01-01

Compositions of matter comprised of silicon nitride and molybdenum disilicide and methods of making the compositions, where the molybdenum disilicide is present in amounts ranging from about 5 to about 50 vol. %.

Thermionic field emission in gold nitride Schottky nanodiodes

NASA Astrophysics Data System (ADS)

Spyropoulos-Antonakakis, N.; Sarantopoulou, E.; Kollia, Z.; Samardžija, Z.; Kobe, S.; Cefalas, A. C.

2012-11-01

We report on the thermionic field emission and charge transport properties of gold nitride nanodomains grown by pulsed laser deposition with a molecular fluorine laser at 157 nm. The nanodomains are sandwiched between the metallic tip of a conductive atomic force microscope and a thin gold layer forming thus a metal-semiconductor-metal junction. Although the limited existing data in the literature indicate that gold nitride was synthesized previously with low efficiency, poor stability, and metallic character; in this work, it is shown that gold nitride nanodomains exhibit semiconducting behavior and the metal-semiconductor-metal contact can be modeled with the back-to-back Schottky barrier model. From the experimental I-V curves, the main charge carrier transport process is found to be thermionic field emission via electron tunneling. The rectifying, near symmetric and asymmetric current response of nanocontacts is related to the effective contact area of the gold nitride nanodomains with the metals. A lower limit for the majority charge carriers concentration at the boundaries of nanodomains is also established using the full depletion approximation, as nanodomains with thickness as low as 6 nm were found to be conductive. Current rectification and charge memory effects are also observed in "quite small" conductive nanodomains (6-10 nm) due to stored charges. Indeed, charges near the surface are identified as inversion domains in the phase shift mapping performed with electrostatic force microscopy and are attributed to charge trapping at the boundaries of the nanodomains.

Inter-layer potential for hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Leven, Itai; Azuri, Ido; Kronik, Leeor; Hod, Oded

2014-03-01

A new interlayer force-field for layered hexagonal boron nitride (h-BN) based structures is presented. The force-field contains three terms representing the interlayer attraction due to dispersive interactions, repulsion due to anisotropic overlaps of electron clouds, and monopolar electrostatic interactions. With appropriate parameterization, the potential is able to simultaneously capture well the binding and lateral sliding energies of planar h-BN based dimer systems as well as the interlayer telescoping and rotation of double walled boron-nitride nanotubes of different crystallographic orientations. The new potential thus allows for the accurate and efficient modeling and simulation of large-scale h-BN based layered structures.

Low-temperature direct synthesis of mesoporous vanadium nitrides for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Lee, Hae-Min; Jeong, Gyoung Hwa; Kim, Sang-Wook; Kim, Chang-Koo

2017-04-01

Mesoporous vanadium nitrides are directly synthesized by a one-step chemical precipitation method at a low temperature (70 °C). Structural and morphological analyses reveal that vanadium nitride consist of long and slender nanowhiskers, and mesopores with diameters of 2-5 nm. Compositional analysis confirms the presence of vanadium in the VN structure, along with oxidized vanadium. The cyclic voltammetry and charge-discharge tests indicate that the obtained material stores charges via a combination of electric double-layer capacitance and pseudocapacitance mechanisms. The vanadium nitride electrode exhibits a specific capacitance of 598 F/g at a current density of 4 A/g. After 5000 charge-discharge cycles, the electrode has an equivalent series resistance of 1.42 Ω and retains 83% of its initial specific capacitance. This direct low-temperature synthesis of mesoporous vanadium nitrides is a simple and promising method to achieve high specific capacitance and low equivalent series resistance for electrochemical capacitor applications.

An investigation of nitride precipitates in archaeological iron artefacts from Poland.

PubMed

Kedzierski, Z; Stepiński, J; Zielińska-Lipiec, A

2010-03-01

The paper describes the investigations of nitride precipitates in a spearhead and a sword found in the territory of Poland, in cremation graveyards of the Przeworsk Culture, dated to the Roman Period. Three different techniques of the examination of nitride precipitates were employed: optical microscope, scanning electron microscope (scanning electron microscope with energy dispersive X-ray spectrometer) and transmission electron microscope. Two types of precipitates have been observed, and their plate-like shape was demonstrated. The large precipitate has been confirmed to be gamma'-Fe(4)N, whereas the small one has been identified as alpha''-Fe(16)N(2). The origin of nitride precipitates in archaeological iron artefacts from Poland is probably a result of the manufacturing process or cremation as part of burial rites. An examination of available iron artefacts indicates that nitride precipitates (have only limited effect on mechanical properties) influence the hardness of metal only to a very limited degree.

Investigating Tribological Characteristics of HVOF Sprayed AISI 316 Stainless Steel Coating by Pulsed Plasma Nitriding

NASA Astrophysics Data System (ADS)

Mindivan, H.

2018-01-01

In this study, surface modification of aluminum alloy using High-Velocity Oxygen Fuel (HVOF) thermal spray and pulsed plasma nitriding processes was investigated. AISI 316 stainless steel coating on 1050 aluminum alloy substrate by HVOF process was pulsed plasma nitrided at 793 K under 0.00025 MPa pressure for 43200 s in a gas mixture of 75 % N2 and 25 % H2. The results showed that the pulse plasma nitriding process produced a surface layer with CrN, iron nitrides (Fe3N, Fe4N) and expanded austenite (γN). The pulsed plasma nitrided HVOF-sprayed coating showed higher surface hardness, lower wear rate and coefficient of friction than the untreated HVOF-sprayed one.

Dynamic Multiaxial Response of a Hot-Pressed Aluminum Nitride

DTIC Science & Technology

2012-01-05

Hutchinson, Adv. Appl . Mech. 29 (1992). [34] H. Ming-Yuan, J.W. Hutchinson, Int. J. Solids Struct. 25 (1989) 1053. [35] J. Salem , L. Ghosn, Int. J...Dynamic Multiaxial Response of a Hot- Pressed Aluminum Nitride by Guangli Hu, C. Q. Chen, K. T. Ramesh, and J. W. McCauley ARL-RP-0487...Laboratory Aberdeen Proving Ground, MD 21005-5066 ARL-RP-0487 June 2014 Dynamic Multiaxial Response of a Hot- Pressed Aluminum Nitride

In vitro bio-functionality of gallium nitride sensors for radiation biophysics.

PubMed

Hofstetter, Markus; Howgate, John; Schmid, Martin; Schoell, Sebastian; Sachsenhauser, Matthias; Adigüzel, Denis; Stutzmann, Martin; Sharp, Ian D; Thalhammer, Stefan

2012-07-27

There is an increasing interest in the integration of hybrid bio-semiconductor systems for the non-invasive evaluation of physiological parameters. High quality gallium nitride and its alloys show promising characteristics to monitor cellular parameters. Nevertheless, such applications not only request appropriate sensing capabilities but also the biocompatibility and especially the biofunctionality of materials. Here we show extensive biocompatibility studies of gallium nitride and, for the first time, a biofunctionality assay using ionizing radiation. Analytical sensor devices are used in medical settings, as well as for cell- and tissue engineering. Within these fields, semiconductor devices have increasingly been applied for online biosensing on a cellular and tissue level. Integration of advanced materials such as gallium nitride into these systems has the potential to increase the range of applicability for a multitude of test devices and greatly enhance sensitivity and functionality. However, for such applications it is necessary to optimize cell-surface interactions and to verify the biocompatibility of the semiconductor. In this work, we present studies of mouse fibroblast cell activity grown on gallium nitride surfaces after applying external noxa. Cell-semiconductor hybrids were irradiated with X-rays at air kerma doses up to 250 mGy and the DNA repair dynamics, cell proliferation, and cell growth dynamics of adherent cells were compared to control samples. The impact of ionizing radiation on DNA, along with the associated cellular repair mechanisms, is well characterized and serves as a reference tool for evaluation of substrate effects. The results indicate that gallium nitride does not require specific surface treatments to ensure biocompatibility and suggest that cell signaling is not affected by micro-environmental alterations arising from gallium nitride-cell interactions. The observation that gallium nitride provides no bio-functional influence on

Structural modifications due to interface chemistry at metal-nitride interfaces

PubMed Central

Yadav, S. K.; Shao, S.; Wang, J.; Liu, X.-Y.

2015-01-01

Based on accurate first principles density functional theory (DFT) calculations, an unusual phenomenon of interfacial structural modifications, due to the interface chemistry influence is identified at two metal-nitride interfaces with strong metal-nitrogen affinity, Al/TiN {111} and Al/VN {111} interfaces. It is shown that at such interfaces, a faulted stacking structure is energetically preferred on the Al side of the interface. And both intrinsic and extrinsic stacking fault energies in the vicinity Al layers are negligibly small. However, such phenomenon does not occur in Pt/TiN and Pt/VN interfaces because of the weak Pt-N affinity. Corresponding to structural energies of metal-nitride interfaces, the linear elasticity analysis predicts characteristics of interfacial misfit dislocations at metal-nitride interfaces. PMID:26611639

III-nitrides on oxygen- and zinc-face ZnO substrates

NASA Astrophysics Data System (ADS)

Namkoong, Gon; Burnham, Shawn; Lee, Kyoung-Keun; Trybus, Elaissa; Doolittle, W. Alan; Losurdo, Maria; Capezzuto, Pio; Bruno, Giovanni; Nemeth, Bill; Nause, Jeff

2005-10-01

The characteristics of III-nitrides grown on zinc- and oxygen-face ZnO by plasma-assisted molecular beam epitaxy were investigated. The reflection high-energy electron diffraction pattern indicates formation of a cubic phase at the interface between III-nitride and both Zn- and O-face ZnO. The polarity indicates that Zn-face ZnO leads to a single polarity, while O-face ZnO forms mixed polarity of III-nitrides. Furthermore, by using a vicinal ZnO substrate, the terrace-step growth of GaN was realized with a reduction by two orders of magnitude in the dislocation-related etch pit density to ˜108cm-2, while a dislocation density of ˜1010cm-2 was obtained on the on-axis ZnO substrates.

Study of the kinetics and mechanism of the thermal nitridation of SiO2

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Madhukar, A.; Grunthaner, F. J.; Naiman, M. L.

1985-01-01

X-ray photoelectron spectroscopy (XPS) has been used to study the nitridation time and temperature dependence of the nitrogen distribution in thermally nitrided SiO2 films. The XPS data show that the maximum nitrogen concentration near the (SiO(x)N(y)/Si interface is initially at the interface, but moves 20-25 A away from the interface with increasing nitridation time. Computer modeling of the kinetic processes involved is carried out and reveals a mechanism in which diffusing species, initially consisting primarily of nitrogen, react with the substrate, followed by formation of the oxygen-rich oxynitride due to reaction of the diffusing oxygen displaced by the slower nitridation of the SiO2. The data are consistent with this mechanism provided the influence of the interfacial strain on the nitridation and oxidation kinetics is explicitly accounted for.

77 FR 54897 - Ferrovanadium and Nitrided Vanadium from the Russian Federation: Revocation of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-06

... nitrided vanadium from the Russian Federation (Russia) would not be likely to lead to continuation or... the antidumping duty order on ferrovanadium and nitrided vanadium from Russia. \\1\\ See Ferrovanadium and Nitrided Vanadium From Russia, 77 FR 51825 (August 27, 2012) (ITC Final). DATES: Effective Date...

Gallium nitride-based micro-opto-electro-mechanical systems

NASA Astrophysics Data System (ADS)

Stonas, Andreas Robert

Gallium Nitride and its associated alloys InGaN and AlGaN have many material properties that are highly desirable for micro-electro-mechanical systems (MEMS), and more specifically micro-opto-electro-mechanical systems (MOEMS). The group III-nitrides are tough, stiff, optically transparent, direct bandgap, chemically inert, highly piezoelectric, and capable of functioning at high temperatures. There is currently no other semiconductor system that possesses all of these properties. Taken together, these attributes make the nitrides prime candidates not only for creating new versions of existing device structures, but also for creating entirely unique devices which combine these properties in novel ways. Unfortunately, their chemical resiliency also makes the group III-nitrides extraordinarily difficult to shape into devices. In particular, until this research, no undercut etch technology existed that could controllably separate a selected part of a MEMS device from its sapphire or silicon carbide substrate. This has effectively prevented GaN-based MEMS from being developed. This dissertation describes how this fabrication obstacle was overcome by a novel etching geometry (bandgap-selective backside-illuminated photoelectochemical (BS-BIPEC) etching) and its resulting morphologies. Several gallium-nitride based MEMS devices were created, actuated, and modelled, including cantilevers and membranes. We describe in particular our pursuit of one of the many novel device elements that is possible only in this material system: a transducer that uses an externally applied strain to dynamically change the optical transition energy of a quantum well. While the device objective of a dynamically tunable quantum well was not achieved, we have demonstrated sufficient progress to believe that such a device will be possible soon. We have observed a shift (5.5meV) of quantum well transition energies in released structures, and we have created structures that can apply large biaxial

Silicon Nitride Photonic Integration Platforms for Visible, Near-Infrared and Mid-Infrared Applications

PubMed Central

Micó, Gloria; Pastor, Daniel; Pérez, Daniel; Doménech, José David; Fernández, Juan; Baños, Rocío; Alemany, Rubén; Sánchez, Ana M.; Cirera, Josep M.; Mas, Roser

2017-01-01

Silicon nitride photonics is on the rise owing to the broadband nature of the material, allowing applications of biophotonics, tele/datacom, optical signal processing and sensing, from visible, through near to mid-infrared wavelengths. In this paper, a review of the state of the art of silicon nitride strip waveguide platforms is provided, alongside the experimental results on the development of a versatile 300 nm guiding film height silicon nitride platform. PMID:28895906

Discontinuous precipitation in a nickel-free high nitrogen austenitic stainless steel on solution nitriding

NASA Astrophysics Data System (ADS)

Mohammadzadeh, Roghayeh; Akbari, Alireza; Grumsen, Flemming B.; Somers, Marcel A. J.

2017-10-01

Chromium-rich nitride precipitates in production of nickel-free austenitic stainless steel plates via pressurised solution nitriding of Fe-22.7Cr-2.4Mo ferritic stainless steel at 1473 K (1200 °C) under a nitrogen gas atmosphere was investigated. The microstructure, chemical and phase composition, morphology and crystallographic orientation between the resulted austenite and precipitates were investigated using optical microscopy, X-ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (TEM) and Electron Back Scatter Diffraction (EBSD). On prolonged nitriding, Chromium-rich nitride precipitates were formed firstly close to the surface and later throughout the sample with austenitic structure. Chromium-rich nitride precipitates with a rod or strip-like morphology was developed by a discontinuous cellular precipitation mechanism. STEM-EDS analysis demonstrated partitioning of metallic elements between austenite and nitrides, with chromium contents of about 80 wt.% in the precipitates. XRD analysis indicated that the Chromium-rich nitride precipitates are hexagonal (Cr, Mo)2N. Based on the TEM studies, (Cr, Mo)2N precipitates presented a (1 1 1)γ//(0 0 2)(Cr, Mo)2N, ?γ//?(Cr, Mo)2N orientation relationship with respect to the austenite matrix. EBSD studies revealed that the austenite in the regions that have transformed into austenite and (Cr, Mo)2N have no orientation relation to the untransformed austenite.

Cell behavior on gallium nitride surfaces: peptide affinity attachment versus covalent functionalization.

PubMed

Foster, Corey M; Collazo, Ramon; Sitar, Zlatko; Ivanisevic, Albena

2013-07-02

Gallium nitride is a wide band gap semiconductor that demonstrates a unique set of optical and electrical properties as well as aqueous stability and biocompatibility. This combination of properties makes gallium nitride a strong candidate for use in chemical and biological applications such as sensors and neural interfaces. Molecular modification can be used to enhance the functionality and properties of the gallium nitride surface. Here, gallium nitride surfaces were functionalized with a PC12 cell adhesion promoting peptide using covalent and affinity driven attachment methods. The covalent scheme proceeded by Grignard reaction and olefin metathesis while the affinity driven scheme utilized the recognition peptide isolated through phage display. This study shows that the method of attaching the adhesion peptide influences PC12 cell adhesion and differentiation as measured by cell density and morphological analysis. Covalent attachment promoted monolayer and dispersed cell adhesion while affinity driven attachment promoted multilayer cell agglomeration. Higher cell density was observed on surfaces modified using the recognition peptide. The results suggest that the covalent and affinity driven attachment methods are both suitable for promoting PC12 cell adhesion to the gallium nitride surface, though each method may be preferentially suited for distinct applications.

Synthesis of High Symmetry Phase of Hafnium Dioxide Thin Films and Nickel Ferrite's Effect on Microstructure in Composite Heterostructure

NASA Astrophysics Data System (ADS)

Straka, Weston J.

Hafnium dioxide has attracted a great deal of attention recently due to its potential use in two different electronic applications: CMOS and FeRAM. In CMOS, the usefulness of hafnia comes in due to its high dielectric constant and compatibility with current IC processing parameters. For FeRAM, hafnia's recent discovery to exhibit ferroelectricity in an orthorhombic phase makes this material attractive for replacement of the ferroelectric material in FeRAM. This study shows the feasibility of depositing thin films of hafnium oxide via chemical solution deposition for integration into these devices. The processing parameters necessary to produce this phase show how non-equilibrium processing plays a role in its synthesis. The temperature necessary to achieve the high symmetry phase was at 725 °C for 3 minutes on sapphire, silicon, and coated silicon substrates. The thermal conductivity of each was viewed as the property that allowed the hafnia formation. The dielectric constant of the hafnia films were between 30 and 32 with low dissipation factors and up to 47 with a poor dissipation factor all at 1 kHz. The formation of this phase was shown to be thickness independent with the high symmetry phase existing up to 300 nm film thickness. Interfacing the hafnia film with nickel ferrite was also studied to identify the possibility of using this composite for non-destructive reading of FeRAM. The magnetic properties showed an unchanged nickel ferrite film but the interface between the two was poor leading to the conclusion that more work must be done to successfully integrate these two films.

Inverse magnetostrictive characteristics of Fe-Co composite materials using gas-nitriding process

NASA Astrophysics Data System (ADS)

Nakajima, Kenya; Yang, Zhenjun; Narita, Fumio

2018-03-01

The inverse magnetostrictive response, known as the Villari effect, of magnetostrictive materials is a change in magnetization due to an applied stress. It is commonly used for sensor applications. This work deals with the inverse magnetostrictive characteristics of Fe-Co bimetal plates that were subjected gas-nitriding process. Gas-nitriding was performed on bimetal plates for 30 min at 853 K as a surface heat treatment process. The specimens were cooled to room temperature after completing the nitriding treatment. Three-point bending tests were performed on the plates under a magnetic field. The changes on the magnetic induction of the plates due to the applied load are discussed. The effect of the nitriding treatment on the inverse magnetostrictive characteristics, magnetostrictive susceptibility, and magnetic hysteresis loop was examined. Our work represents an important step forward in the development of magnetostrictive sensor materials.

Hydrogen adsorption capacities of multi-walled boron nitride nanotubes and nanotube arrays: a grand canonical Monte Carlo study.

PubMed

Ahadi, Zohreh; Shadman, Muhammad; Yeganegi, Saeed; Asgari, Farid

2012-07-01

Hydrogen adsorption in multi-walled boron nitride nanotubes and their arrays was studied using grand canonical Monte Carlo simulation. The results show that hydrogen storage increases with tube diameter and the distance between the tubes in multi-walled boron nitride nanotube arrays. Also, triple-walled boron nitride nanotubes present the lowest level of hydrogen physisorption, double-walled boron nitride nanotubes adsorb hydrogen better when the diameter of the inner tube diameter is sufficiently large, and single-walled boron nitride nanotubes adsorb hydrogen well when the tube diameter is small enough. Boron nitride nanotube arrays adsorb hydrogen, but the percentage of adsorbed hydrogen (by weight) in boron nitride nanotube arrays is rather similar to that found in multi-walled boron nitride nanotubes. Also, when the Langmuir and Langmuir-Freundlich equations were fitted to the simulated data, it was found that multi-layer adsorptivity occurs more prominently as the number of walls and the tube diameter increase. However, in single-walled boron nitride nanotubes with a small diameter, the dominant mechanism is monolayer adsorptivity.

Synthesis of Aluminum-Aluminum Nitride Nanocomposites by a Gas-Liquid Reaction II. Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Borgonovo, Cecilia; Makhlouf, Makhlouf M.

2016-04-01

In situ fabrication of the reinforcing particles in the metal matrix is an answer to many of the challenges encountered in manufacturing aluminum matrix nanocomposites. In this method, the nanoparticles are formed directly within the melt by means of a chemical reaction between a specially designed aluminum alloy and a gas. In this publication, we describe a process for synthesizing aluminum-aluminum nitride nanocomposites by reacting a nitrogen-containing gas with a molten aluminum-lithium alloy. We quantify the effect of the process parameters on the average particle size and particle distribution, as well as on the tendency of the particles to cluster in the alloy matrix, is quantified. Also in this publication, we present the measured room temperature and elevated temperature tensile properties of the nanocomposite material as well as its measured room temperature impact toughness.

Boron nitride encapsulated graphene infrared emitters

NASA Astrophysics Data System (ADS)

Barnard, H. R.; Zossimova, E.; Mahlmeister, N. H.; Lawton, L. M.; Luxmoore, I. J.; Nash, G. R.

2016-03-01

The spatial and spectral characteristics of mid-infrared thermal emission from devices containing a large area multilayer graphene layer, encapsulated using hexagonal boron nitride, have been investigated. The devices were run continuously in air for over 1000 h, with the emission spectrum covering the absorption bands of many important gases. An approximate solution to the heat equation was used to simulate the measured emission profile across the devices yielding an estimated value of the characteristic length, which defines the exponential rise/fall of the temperature profile across the device, of 40 μm. This is much larger than values obtained in smaller exfoliated graphene devices and reflects the device geometry, and the increase in lateral heat conduction within the devices due to the multilayer graphene and boron nitride layers.

A new molybdenum nitride catalyst with rhombohedral MoS 2 structure for hydrogenation applications

DOE PAGES

Wang, Shanmin; Ge, Hui; Sun, Shouli; ...

2015-03-23

Here, nitrogen–rich transition–metal nitrides hold great promise to be the next–generation catalysts for clean and renewable energy applications. However, incorporation of nitrogen into the crystalline lattices of transition metals is thermodynamically unfavorable at atmospheric pressure; most of the known transition metal nitrides are nitrogen–deficient with molar ratios of N : metal less than a unity. In this work, we have formulated a high–pressure route for the synthesis of a nitrogen–rich molybdenum nitride through a solid–state ion–exchange reaction. The newly discovered nitride, 3R–MoN 2, adopts a rhombohedral R3m structure, isotypic with MoS 2. This new nitride exhibits catalytic activities that aremore » three times more active than the traditional catalyst MoS 2 for the hydrodesulfurization of dibenzothiophene and more than twice higher in the selectivity to hydrogenation. The nitride is also catalytically active in sour methanation of syngas with >80% CO and H 2 conversion at 723 K. Our formulated route for the synthesis of 3R–MoN 2 is at a moderate pressure of 3.5 GPa and is thus feasible for industrial–scale catalyst production.« less

A new molybdenum nitride catalyst with rhombohedral MoS2 structure for hydrogenation applications.

PubMed

Wang, Shanmin; Ge, Hui; Sun, Shouli; Zhang, Jianzhong; Liu, Fangming; Wen, Xiaodong; Yu, Xiaohui; Wang, Liping; Zhang, Yi; Xu, Hongwu; Neuefeind, Joerg C; Qin, Zhangfeng; Chen, Changfeng; Jin, Changqin; Li, Yongwang; He, Duanwei; Zhao, Yusheng

2015-04-15

Nitrogen-rich transition-metal nitrides hold great promise to be the next-generation catalysts for clean and renewable energy applications. However, incorporation of nitrogen into the crystalline lattices of transition metals is thermodynamically unfavorable at atmospheric pressure; most of the known transition metal nitrides are nitrogen-deficient with molar ratios of N:metal less than a unity. In this work, we have formulated a high-pressure route for the synthesis of a nitrogen-rich molybdenum nitride through a solid-state ion-exchange reaction. The newly discovered nitride, 3R-MoN2, adopts a rhombohedral R3m structure, isotypic with MoS2. This new nitride exhibits catalytic activities that are three times more active than the traditional catalyst MoS2 for the hydrodesulfurization of dibenzothiophene and more than twice as high in the selectivity to hydrogenation. The nitride is also catalytically active in sour methanation of syngas with >80% CO and H2 conversion at 723 K. Our formulated route for the synthesis of 3R-MoN2 is at a moderate pressure of 3.5 GPa and, thus, is feasible for industrial-scale catalyst production.

Low-loss and tunable near-zero-epsilon titanium nitride

NASA Astrophysics Data System (ADS)

Popović, M.; Novaković, M.; Schmidt, E.; Schöppe, P.; Bibić, N.; Ronning, C.; Rakočević, Z.

2017-10-01

Titanium nitride (TiN) has emerged as alternative plasmonic material in the visible and near-infrared spectral range due to its metallic properties. We studied the influence of silver ion implantation (fluence range from 0.5 × 1016-6 × 1016 ions/cm2) on the structural and optical properties of reactively sputtered 260 nm thick TiN films. The columnar structure was partially destroyed by the irradiation and up to 5 at.% of Ag was incorporated into the films within the projected ion range. The formation of cubic Ag nanoparticles with size of 1-2 nm was observed by high resolution transmission electron microscopy and subsequent fast Fourier transform analysis. This presence of Ag within the TiN matrix drastically changes both the real and imaginary component of the dielectric function and provides low optical losses. A Drude Lorentz dielectric analysis based on free electron and oscillator model are carried out to describe the silver influence on the optical behavior of TiN. With increasing ion fluence, the unscreened plasma frequency decreased and broadening increased. The energy, strength and broadening of the interband transitions were studied with respect to the silver ion fluence and correlated with the microstructural changes induced in TiN films.

Structural modifications due to interface chemistry at metal-nitride interfaces

DOE PAGES

Yadav, S. K.; Shao, S.; Wang, J.; ...

2015-11-27

Based on accurate first principles density functional theory (DFT) calculations, an unusual phenomenon of interfacial structural modifications, due to the interface chemistry influence is identified at two metal-nitride interfaces with strong metal-nitrogen affinity, Al/TiN {111} and Al/VN {111} interfaces. It is shown that at such interfaces, a faulted stacking structure is energetically preferred on the Al side of the interface. And both intrinsic and extrinsic stacking fault energies in the vicinity Al layers are negligibly small. However, such phenomenon does not occur in Pt/TiN and Pt/VN interfaces because of the weak Pt-N affinity. As a result, corresponding to structural energiesmore » of metal-nitride interfaces, the linear elasticity analysis predicts characteristics of interfacial misfit dislocations at metal-nitride interfaces.« less

Structure and Growth of Hexagonal Boron Nitride on Ir(111).

PubMed

Farwick Zum Hagen, Ferdinand H; Zimmermann, Domenik M; Silva, Caio C; Schlueter, Christoph; Atodiresei, Nicolae; Jolie, Wouter; Martínez-Galera, Antonio J; Dombrowski, Daniela; Schröder, Ulrike A; Will, Moritz; Lazić, Predrag; Caciuc, Vasile; Blügel, Stefan; Lee, Tien-Lin; Michely, Thomas; Busse, Carsten

2016-12-27

Using the X-ray standing wave method, scanning tunneling microscopy, low energy electron diffraction, and density functional theory, we precisely determine the lateral and vertical structure of hexagonal boron nitride on Ir(111). The moiré superstructure leads to a periodic arrangement of strongly chemisorbed valleys in an otherwise rather flat, weakly physisorbed plane. The best commensurate approximation of the moiré unit cell is (12 × 12) boron nitride cells resting on (11 × 11) substrate cells, which is at variance with several earlier studies. We uncover the existence of two fundamentally different mechanisms of layer formation for hexagonal boron nitride, namely, nucleation and growth as opposed to network formation without nucleation. The different pathways are linked to different distributions of rotational domains, and the latter enables selection of a single orientation only.

Effects of gaseous nitriding AISI4140 alloy steel on corrosion and hardness properties

NASA Astrophysics Data System (ADS)

Tamil Moli, L.; Wahab, N.; Gopinathan, M.; Karmegam, K.; Maniyarasi, M.

2016-10-01

Corrosion is one of the major problems in the industry especially on machinery since it weakens the structure of the machinery part and causes the mechanical failure. This will stop the production and increase the maintenance cost. In this study, the corrosion behaviour of gas nitriding on a screw press machine shaft made from AISI 4140 steel was investigated. Pitting corrosion was identified as a major cause of the shaft failure and this study was conducted to improve the corrosion resistance on the AISI 4140 alloy steel shaft by gas nitriding as a surface hardening treatment. Gas nitriding was performed with composition of 15% ammonia and 85% nitrogen at temperatures of 525 °C, 550 °C and 575 °C and with the soaking time of 30, 45 and 60 minutes, respectively. The samples were prepared as rectangular sized of 30mm x 12mm x 3mm for immersion testing. The results showed that corrosion rate of untreated samples was 77% higher compared to the nitrided samples. It was also found that hardness of the nitrided samples was higher than untreated sample. All in all, it can be concluded that gaseous nitriding can significantly improve the surface hardness and the corrosion resistance of the shaft made of AISI 4140 alloy steel, hence reduces the pitting that is the root cause of failure.

Lateral electrochemical etching of III-nitride materials for microfabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Jung

Conductivity-selective lateral etching of III-nitride materials is described. Methods and structures for making vertical cavity surface emitting lasers with distributed Bragg reflectors via electrochemical etching are described. Layer-selective, lateral electrochemical etching of multi-layer stacks is employed to form semiconductor/air DBR structures adjacent active multiple quantum well regions of the lasers. The electrochemical etching techniques are suitable for high-volume production of lasers and other III-nitride devices, such as lasers, HEMT transistors, power transistors, MEMs structures, and LEDs.

Tribology of nitrided-coated steel-a review

NASA Astrophysics Data System (ADS)

Bhaskar, Santosh V.; Kudal, Hari N.

2017-01-01

Surface engineering such as surface treatment, coating, and surface modification are employed to increase surface hardness, minimize adhesion, and hence, to reduce friction and improve resistance to wear. To have optimal tribological performance of Physical Vapor Deposition (PVD) hard coating to the substrate materials, pretreatment of the substrate materials is always advisable to avoid plastic deformation of the substrate, which may result in eventual coating failure. The surface treatment results in hardening of the substrate and increase in load support effect. Many approaches aim to improve the adhesion of the coatings onto the substrate and nitriding is the one of the best suitable options for the same. In addition to tribological properties, nitriding leads to improved corrosion resistance. Often corrosion resistance is better than that obtainable with other surface engineering processes such as hard-chrome and nickel plating. Ability of this layer to withstand thermal stresses gives stability which extends the surface life of tools and other components exposed to heat. Most importantly, the nitrogen picked-up by the diffusion layer increases the rotating-bending fatigue strength in components. The present article reviews mainly the tribological advancement of different nitrided-coated steels based on the types of coatings, structure, and the tribo-testing parameters, in recent years.

Ultra-thin ohmic contacts for p-type nitride light emitting devices

DOEpatents

Raffetto, Mark [Raleigh, NC; Bharathan, Jayesh [Cary, NC; Haberern, Kevin [Cary, NC; Bergmann, Michael [Chapel Hill, NC; Emerson, David [Chapel Hill, NC; Ibbetson, James [Santa Barbara, CA; Li, Ting [Ventura, CA

2012-01-03

A semiconductor based Light Emitting Device (LED) can include a p-type nitride layer and a metal ohmic contact, on the p-type nitride layer. The metal ohmic contact can have an average thickness of less than about 25 .ANG. and a specific contact resistivity less than about 10.sup.-3 ohm-cm.sup.2.

One step process for producing dense aluminum nitride and composites thereof

DOEpatents

Holt, J. Birch; Kingman, Donald D.; Bianchini, Gregory M.

1989-01-01

A one step combustion process for the synthesis of dense aluminum nitride compositions is disclosed. The process comprises igniting pure aluminum powder in a nitrogen atmosphere at a pressure of about 1000 atmospheres or higher. The process enables the production of aluminum nitride bodies to be formed directly in a mold of any desired shape.

Fabrication of sinterable silicon nitride by injection molding

NASA Technical Reports Server (NTRS)

Quackenbush, C. L.; French, K.; Neil, J. T.

1982-01-01

Transformation of structural ceramics from the laboratory to production requires development of near net shape fabrication techniques which minimize finish grinding. One potential technique for producing large quantities of complex-shaped parts at a low cost, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material. Binder selection methodology, compounding of ceramic and binder components, injection molding techniques, and problems in binder removal are discussed. Strength, oxidation resistance, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material.

Synthesis of boron nitride powders

NASA Astrophysics Data System (ADS)

Dreissig, Dirk Horst

2002-09-01

In the materials science community there is much interest in the development of new, efficient approaches for preparing ceramic powders having properties or performance characteristics not found with powders produced by traditional metallurgical synthesis methods. In this regard, aerosol-based syntheses are finding general acceptance for the preparation of non-metal and metal oxide powders. In contrast, much less effort has been given to aerosol-type syntheses for non-oxide powders despite potentially useful benefits. This dissertation describes the application of two chemical systems in aerosol assisted vapor phase synthesis (AAVS) for the preparation of spherical morphology boron oxynitride, BNxOy, powders that are subsequently converted to spherical morphology boron nitride in a second nitridation step. Chapter 1 describes the AAVS synthesis of BNxOy powders using a reaction of an aqueous boric acid containing aerosol with ammonia at 1000°C. The effect of reactor tube material, total gas flow rate, ammonia concentration, boric acid concentration, and urea addition to the boric acid aerosol on the percent oxygen composition is described. The resulting BNxOy powders contain significant amounts of oxygen that require replacement in a second stage nitridation reaction at elevated temperature under ammonia. The influences of the reaction temperature profile, crucible geometry and transformation additive on final oxygen composition and powder crystallinity are described. Chapter 2 outlines the formation of BNxOy powders from an AAVS reaction between the boron precursor (MeO)3B and ammonia. The formation of the powders is studied as a function of total gas flow rate and ammonia concentration. In all cases the resulting powders contain lower levels of oxygen compared to powders produced from aqueous boric acid aerosols. The conversion of the BNxOy powders in the second stage nitridation reaction with ammonia is examined as a function of crucible geometry, temperature

Improved reaction sintered silicon nitride. [protective coatings to improve oxidation resistance

NASA Technical Reports Server (NTRS)

Baumgartner, H. R.

1978-01-01

Processing treatments were applied to as-nitrided reaction sintered silicon nitride (RSSN) with the purposes of improving strength after processing to above 350 MN/m2 and improving strength after oxidation exposure. The experimental approaches are divided into three broad classifications: sintering of surface-applied powders; impregnation of solution followed by further thermal processing; and infiltration of molten silicon and subsequent carburization or nitridation of the silicon. The impregnation of RSSN with solutions of aluminum nitrate and zirconyl chloride, followed by heating at 1400-1500 C in a nitrogen atmosphere containing silicon monoxide, improved RSSN strength and oxidation resistance. The room temperature bend strength of RSSN was increased nearly fifty percent above the untreated strength with mean absolute strengths up to 420 MN/m2. Strengths of treated samples that were measured after a 12 hour oxidation exposure in air were up to 90 percent of the original as-nitrided strength, as compared to retained strengths in the range of 35 to 60 percent for untreated RSSN after the same oxidation exposure.

Superplastic forging nitride ceramics

DOEpatents

Panda, Prakash C.; Seydel, Edgar R.; Raj, Rishi

1988-03-22

The invention relates to producing relatively flaw free silicon nitride ceramic shapes requiring little or no machining by superplastic forging This invention herein was made in part under Department of Energy Grant DE-AC01-84ER80167, creating certain rights in the United States Government. The invention was also made in part under New York State Science and Technology Grant SB1R 1985-10.

Resistance of Silicon Nitride Turbine Components to Erosion and Hot Corrosion/oxidation Attack

NASA Technical Reports Server (NTRS)

Strangmen, Thomas E.; Fox, Dennis S.

1994-01-01

Silicon nitride turbine components are under intensive development by AlliedSignal to enable a new generation of higher power density auxiliary power systems. In order to be viable in the intended applications, silicon nitride turbine airfoils must be designed for survival in aggressive oxidizing combustion gas environments. Erosive and corrosive damage to ceramic airfoils from ingested sand and sea salt must be avoided. Recent engine test experience demonstrated that NT154 silicon nitride turbine vanes have exceptional resistance to sand erosion, relative to superalloys used in production engines. Similarly, NT154 silicon nitride has excellent resistance to oxidation in the temperature range of interest - up to 1400 C. Hot corrosion attack of superalloy gas turbine components is well documented. While hot corrosion from ingested sea salt will attack silicon nitride substantially less than the superalloys being replaced in initial engine applications, this degradation has the potential to limit component lives in advanced engine applications. Hot corrosion adversely affects the strength of silicon nitride in the 850 to 1300 C range. Since unacceptable reductions in strength must be rapidly identified and avoided, AlliedSignal and the NASA Lewis Research Center have pioneered the development of an environmental life prediction model for silicon nitride turbine components. Strength retention in flexure specimens following 1 to 3300 hour exposures to high temperature oxidation and hot corrosion has been measured and used to calibrate the life prediction model. Predicted component life is dependent upon engine design (stress, temperature, pressure, fuel/air ratio, gas velocity, and inlet air filtration), mission usage (fuel sulfur content, location (salt in air), and times at duty cycle power points), and material parameters. Preliminary analyses indicate that the hot corrosion resistance of NT154 silicon nitride is adequate for AlliedSignal's initial engine

Photodetectors using III-V nitrides

DOEpatents

Moustakas, Theodore D.

1998-01-01

A bandpass photodetector using a III-V nitride and having predetermined electrical properties. The bandpass photodetector detects electromagnetic radiation between a lower transition wavelength and an upper transition wavelength. That detector comprises two low pass photodetectors. The response of the two low pass photodetectors is subtracted to yield a response signal.

Plasma induced sp 2 to sp 3 transition in boron nitride

NASA Astrophysics Data System (ADS)

Zhang, J.; Cui, Q.; Li, X.; He, Z.; Li, W.; Ma, Y.; Guan, Q.; Gao, W.; Zou, G.

2004-12-01

The transition from sp 2 to sp 3 hybridization in boron nitride has been induced in plasma. Nano-crystals of cubic boron nitride (cBN) have been synthesized by direct current arc discharge method using hexagonal boron nitride (hBN) as the starting material. The characterization of the as-grown powders is carried out by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. It has been shown that cBN and hBN grains with 20-60 nm in size co-exist in the powders. A reaction route of sublimation - re-hybridization - crystallization had been put forward to explain the mechanism of the hybridization transition and the growth of cBN by this method.

Effect of oxygen plasma on nanomechanical silicon nitride resonators

NASA Astrophysics Data System (ADS)

Luhmann, Niklas; Jachimowicz, Artur; Schalko, Johannes; Sadeghi, Pedram; Sauer, Markus; Foelske-Schmitz, Annette; Schmid, Silvan

2017-08-01

Precise control of tensile stress and intrinsic damping is crucial for the optimal design of nanomechanical systems for sensor applications and quantum optomechanics in particular. In this letter, we study the influence of oxygen plasma on the tensile stress and intrinsic damping of nanomechanical silicon nitride resonators. Oxygen plasma treatments are common steps in micro and nanofabrication. We show that oxygen plasma for only a few minutes oxidizes the silicon nitride surface, creating several nanometer thick silicon dioxide layers with a compressive stress of 1.30(16) GPa. Such oxide layers can cause a reduction in the effective tensile stress of a 50 nm thick stoichiometric silicon nitride membrane by almost 50%. Additionally, intrinsic damping linearly increases with the silicon dioxide film thickness. An oxide layer of 1.5 nm grown in just 10 s in a 50 W oxygen plasma almost doubled the intrinsic damping. The oxide surface layer can be efficiently removed in buffered hydrofluoric acid.

Boron nitride encapsulated graphene infrared emitters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnard, H. R.; Zossimova, E.; Mahlmeister, N. H.

2016-03-28

The spatial and spectral characteristics of mid-infrared thermal emission from devices containing a large area multilayer graphene layer, encapsulated using hexagonal boron nitride, have been investigated. The devices were run continuously in air for over 1000 h, with the emission spectrum covering the absorption bands of many important gases. An approximate solution to the heat equation was used to simulate the measured emission profile across the devices yielding an estimated value of the characteristic length, which defines the exponential rise/fall of the temperature profile across the device, of 40 μm. This is much larger than values obtained in smaller exfoliated graphene devicesmore » and reflects the device geometry, and the increase in lateral heat conduction within the devices due to the multilayer graphene and boron nitride layers.« less

Is hexagonal boron nitride always good as a substrate for carbon nanotube-based devices?

PubMed

Kang, Seoung-Hun; Kim, Gunn; Kwon, Young-Kyun

2015-02-21

Hexagonal boron nitride sheets have been noted especially for their enhanced properties as substrates for sp(2) carbon-based nanodevices. To evaluate whether such enhanced properties would be retained under various realistic conditions, we investigate the structural and electronic properties of semiconducting carbon nanotubes on perfect and defective hexagonal boron nitride sheets under an external electric field as well as with a metal impurity, using density functional theory. We verify that the use of a perfect hexagonal boron nitride sheet as a substrate indeed improves the device performances of carbon nanotubes, compared with the use of conventional substrates such as SiO2. We further show that even the hexagonal boron nitride with some defects can show better performance as a substrate. Our calculations, on the other hand, also suggest that some defective boron nitride layers with a monovacancy and a nickel impurity could bring about poor device behavior since the imperfections impair electrical conductivity due to residual scattering under an applied electric field.

Enhancing the Hardness of Sintered SS 17-4PH Using Nitriding Process for Bracket Orthodontic Application

NASA Astrophysics Data System (ADS)

Suharno, B.; Supriadi, S.; Ayuningtyas, S. T.; Widjaya, T.; Baek, E. R.

2018-01-01

Brackets orthodontic create teeth movement by applying force from wire to bracket then transferred to teeth. However, emergence of friction between brackets and wires reduces load for teeth movement towards desired area. In order to overcome these problem, surface treatment like nitriding chosen as a process which could escalate efficiency of transferred force by improving material hardness since hard materials have low friction levels. This work investigated nitriding treatment to form nitride layer which affecting hardness of sintered SS 17-4PH. The nitride layers produced after nitriding process at various temperature i.e. 470°C, 500°C, 530°C with 8hr holding time under 50% NH3 atmosphere. Optical metallography was conducted to compare microstructure of base and surface metal while the increasing of surface hardness then observed using vickers microhardness tester. Hardened surface layer was obtained after gaseous nitriding process because of nitride layer that contains Fe4N, CrN and Fe-αN formed. Hardness layers can achieved value 1051 HV associated with varies thickness from 53 to 119 μm. The presence of a precipitation process occurring in conjunction with nitriding process can lead to a decrease in hardness due to nitrogen content diminishing in solid solution phase. This problem causes weakening of nitrogen expansion in martensite lattice.

One step process for producing dense aluminum nitride and composites thereof

DOEpatents

Holt, J.B.; Kingman, D.D.; Bianchini, G.M.

1989-10-31

A one step combustion process for the synthesis of dense aluminum nitride compositions is disclosed. The process comprises igniting pure aluminum powder in a nitrogen atmosphere at a pressure of about 1,000 atmospheres or higher. The process enables the production of aluminum nitride bodies to be formed directly in a mold of any desired shape.

Tracing the history of submarine hydrothermal inputs and the significance of hydrothermal hafnium for the seawater budget - A combined Pb-Hf-Nd isotope approach

USGS Publications Warehouse

van de Flierdt, T.; Frank, M.; Halliday, A.N.; Hein, J.R.; Hattendorf, B.; Gunther, D.; Kubik, P.W.

2004-01-01

Secular variations in the Pb isotopic composition of a mixed hydrogenous-hydrothermal ferromanganese crust from the Bauer Basin in the eastern Equatorial Pacific provide clear evidence for changes in hydrothermal contributions during the past 7 Myr. The nearby Galapagos Rise spreading center provided a strong hydrothermal flux prior to 6.5 Ma. After 6.5 Ma, the Pb became stepwise more radiogenic and more similar to Equatorial Pacific seawater, reflecting the westward shift of spreading to the presently active East Pacific Rise (EPR). A second, previously unrecognized enhanced hydrothermal period occurred between 4.4 and 2.9 Ma, which reflects either off-axis hydrothermal activity in the Bauer Basin or a late-stage pulse of hydrothermal Pb from the then active, but waning Galapagos Rise spreading center. Hafnium isotope time-series of the same mixed hydrogenous-hydrothermal crust show invariant values over the past 7 Myr. Hafnium isotope ratios, as well as Nd isotope ratios obtained for this crust, are identical to that of hydrogenous Equatorial Pacific deep water crusts and clearly indicate that hydrothermal Hf, similar to Nd, does not travel far from submarine vents. Therefore, we suggest that hydrothermal Hf fluxes do not contribute significantly to the global marine Hf budget. ?? 2004 Elsevier B.V. All rights reserved.

High Temperature Oxidation of Boron Nitride. Part 1; Monolithic Boron Nitride

NASA Technical Reports Server (NTRS)

Jacobson, Nathan; Farmer, Serene; Moore, Arthur; Sayir, Haluk

1997-01-01

High temperature oxidation of monolithic boron nitride (BN) is examined. Hot pressed BN and both low and high density CVD BN were studied. It is shown that oxidation rates are quite sensitive to microstructural factors such as orientation, porosity, and degree of crystallinity. In addition small amounts of water vapor lead to volatilization of the B2O3 oxide as H(x)B(y)O(z). For these reasons, very different oxidation kinetics were observed for each type of BN.

Early stages of plasma induced nitridation of Si (111) surface and study of interfacial band alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shetty, Satish; Shivaprasad, S. M., E-mail: smsprasad@jncasr.ac.in

2016-02-07

We report here a systematic study of the nitridation of the Si (111) surface by nitrogen plasma exposure. The surface and interface chemical composition and surface morphology are investigated by using RHEED, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM). At the initial stage of nitridation two superstructures—“8 × 8” and “8/3 × 8/3”—form, and further nitridation leads to 1 × 1 stoichiometric silicon nitride. The interface is seen to have the Si{sup 1+} and Si{sup 3+} states of silicon bonding with nitrogen, which suggests an atomically abrupt and defect-free interface. The initial single crystalline silicon nitride layers are seen to become amorphous at higher thicknesses.more » The AFM image shows that the nitride nucleates at interfacial dislocations that are connected by sub-stoichiometric 2D-nitride layers, which agglomerate to form thick overlayers. The electrical properties of the interface yield a valence band offset that saturates at 1.9 eV and conduction band offset at 2.3 eV due to the evolution of the sub-stoichiometric interface and band bending.« less

Predicting the structural and electronic properties of two-dimensional single layer boron nitride sheets