Nitrogen Doped Graphene Generated by Microwave Plasma and Reduction Expansion Synthesis

The article of record as published may be found at http://dx.doi.org/10.1166/nnl.2016.2055This work aimed to produce nitrogen doped graphene from Graphite Oxide (GO) by combining the Expansion Reduction Synthesis (RES) approach, which utilizes urea as doping/reducing agent, with the use of an Atmospheric Plasma torch (Plasma), which provides the high temperature reactor environment known to thermally exfoliate it. The use of this combined strategy (Plasma-RES) was tried in an attempt to increase the surface area of the products. The amount of nitrogen doping was controlled by varying the urea/GO mass ratios in the precursor powders. X-ray diffraction analysis, SEM, TEM, BET surface areas and conductivity measurements of the diverse products are presented. Nitrogen inclusion in the graphene samples was corroborated by the mass spectral signal of the evolved gases generated during thermal programmed oxidation experiments of the products and by EDX analysis. We found that the Plasma-RES method can successfully generate doped graphene in situ as the urea and GO precursors simultaneously decompose and reduce in the discharge zone. When using the same amount of urea in the precursor mixture, samples obtained by Plasma-RES have higher surface area than those generated by RES, however, they contain a smaller nitrogen content

Surface Modification of Synthetic Diamond for Producing Adherent Thick and Thin Film Etallizations for Electronic Packaging

PatentAn article and a method of making surface modified synthetic diamond substrates at temperatures below 5000 C. for electronic packaging applications are described. The article consists of a synthetic diamond substrate, the surface of which has been modified by providing an adherent thin coating of a ceramic (alumina) material so as to enable metallization of synthetic diamond by current industrial methods. The method of surface modification comprises deposition of a thin transition metal layer on the synthetic diamond substrate prior to low temperature reactive vapor deposition of aluminum followed by annealing in an oxygen atmosphere

Evolution of stir zone microstructure during FSP of cast NiAI bronze

Yutaka Sato, Yuri Hovanski, and Ravi Verma TMS (The Minerals, Metals & Materials Society), 2011The article of record as published may be located at http://dx.doi.org/10.1002/9781118062302.ch12The evolution of the stir zone microstructure during single-pass and multi-pass 'FSP of an as-cast NiAl bronze material was evaluated by optical and high-resolution scanning electron microscopy (SEM) methods, including orientation imaging microscopy (OIM). Deformation commences ahead of the tool as the local temperature exceeds the eutectoid temperature ("800'C) while subsequent recrystallization in the primary a is accompanied by dissolution of Kiv particles dispersed in this constituent. The recrystallized a grains remain equiaxed and appear annealed despite large displacements onward into the resulting stir zone (SZ). Characteristic shear texture components are retained in the thermomechanically affected zone (TMAZ) but the texture of the primary a becomes random after recrystallization and remains so into both single-pass and multipass SZs. Mechanisms to account for recrystallization and subsequent deformation are proposed.Office of Naval ResearchNOOO I 409WR2020

The effect of concurrent straining on phase transformation in NiAl bronze during the friction stir processing thermomechanical cycle

The article of record as published may be found at http://dx.doi.org/10.1007/s11661-011-0638-7Equivalent strains up to a value of ⊨2.7 were determined by evaluation of the shape changes of the phases in a duplex a(fcc)/b(bcc) microstructure formed ahead of the pin tool extraction site during the friction stir processing (FSP) thermomechanical cycle in a cast NiAl bronze alloy. Correlation of the local strains with volume fractions of the various microstructure constituents in this alloy shows that the concurrent straining of FSP results in acceleration of the a + b fi b reaction in the thermomechanically affected zone (TMAZ) ahead of the pin extraction site. The resulting volume fraction of b (as determined by the volume fraction of its transformation products formed during post-FSP cooling) corresponds closely to the volume fraction expected for the peak stir zone temperature measured separately by means of thermocouples embedded within the tool pin profile along the tool path. The stir zone (SZ) in this material exhibits near-equilibrium microstructures despite brief dwells near the peak temperature (Tpeak ⊨ 0.95 Tmelt), reflecting large local strains and strain rates associated with this process.Defense Advanced Projects Agency (DARPA)Offoce of Naval ResearchContract no. N00014-06-WR-2-0196 (ONR)Contract no. N00014-09-WR20201 (ONR

Corrosion of femtosecond laser surface textured aluminium alloy

The article of record may be found at http://dx.doi.org/10.1080/1478422X.2017.1348090With superhydrophobic properties being extended to a variety of metallic substrates through the process of ablation due to femtosecond laser surface processing (FLSP), it is important to understand corrosion behaviour of such a processed material. The material was tested through the use of an accelerated corrosion fog chamber using both treated and untreated aluminium alloy samples. During the accelerated corrosion testing, the FLSP-treated sample suffered from pitting corrosion at a rate faster than the untreated sample, effectively removing the surface treatment. While there are significant hydrodynamic benefits to this material, the elevated corrosion rates raise concerns about the resiliency of this surface treatment.This research was sponsored by Office of Naval Researc

Corrosion of femtosecond laser surface textured aluminium alloy

The article of record may be found at https://doi.org/10.1080/1478422X.2017.1348090With superhydrophobic properties being extended to a variety of metallic substrates through the process of ablation due to femtosecond laser surface processing (FLSP), it is important to understand corrosion behaviour of such a processed material. The material was tested through the use of an accelerated corrosion fog chamber using both treated and untreated aluminium alloy samples. During the accelerated corrosion testing, the FLSP-treated sample suffered from pitting corrosion at a rate faster than the untreated sample, effectively removing the surface treatment. While there are significant hydrodynamic benefits to this material, the elevated corrosion rates raise concerns about the resiliency of this surface treatment

Long-term corrosion resistance of iron-based amorphous metal coatings

Novel iron-based amorphous metals, including SAM2X5 Fe(49.7)Cr(17.7)Mn(1.9)Mo(7.4)W(1.6)B(15.2)C(3.8)Si(2.4)), SAM1651 (Fe(48.0)Cr(15.0)Mo(14.0)B(6.0)C(15.0)Y(2.0)), and other compositions have been developed for use as corrosion-resistant coatings for spent nuclear fuel containers, as criticality control materials, and as ultra-hard corrosion-resistant material for ship applications. These amorphous alloys appear to have corrosion resistance comparable to (or better than) that of Ni-based Alloy C-22 (UNS # N06022), based on measurements of breakdown potential and corrosion rate in seawater. A variety of characterization tools, including scanning electron microscopy, cyclic polarization, linear polarization and electrochemical impedance spectroscopy, have been used to develop a thorough understanding of the corrosion performance of these alloys over prolonged exposure in seawater and concentrated brines at elevated temperature.U.S. Department of Energy, National Nuclear Security AdministrationContract DE-AC52-07NA2734

Studies of passive films on friction stir processed Ni-Al bronze

The Friction Stir Processing (FSP) and Friction Stir Welding (FSW) welding of nickel aluminum bronze (NAB) is used for a variety of naval applications. This paper investigates the beneficial effects of FSP on NAB passivity, and provides important benchmark data for future studies. Further enhancement of FSP NAB through application of LP will be discussed in subsequent papers, using the data presented here as a basis of comparison. This work shows that FSP has a beneficial effect on both the microstructure of this alloy, as well as on the integrity of the passive film formed in chloride electrolytes, including natural seawater. In addition to using a variety of characterization techniques to determine the effects of friction stir processing on microstructure, including scanning electron microscopy (SEM) with focused ion beam milling, we have used cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS) to develop an understanding of passive film behavior for this material in the as-received state, as well as after friction stir processing. A variety of interfacial impedance models have been explored for fitting the data, including transmission line models. Results on this important alloy, before and after processing will be presented.Department of Energy (DOE)Contract DE-AC52-07NA2734