National Defense Aspects of Energy Imports

The United States is now importing 46.6 percent of its petroleum. This 46.6 percent amounts to over 7,000,000 barrels per day. This paper discusses the adverse effects of these oil imports primarily from an Antisubmarine Warfare (ASW) point of view. in the event of an oil embargo and/or an attack by enemy submarines, there are serious questions as to the U.S. ability to support NATO, or even to sustain an efficient economy

Kinetic control of catalytic CVD for high-quality graphene at low temperatures.

Low-temperature (∼600 °C), scalable chemical vapor deposition of high-quality, uniform monolayer graphene is demonstrated with a mapped Raman 2D/G ratio of >3.2, D/G ratio ≤0.08, and carrier mobilities of ≥3000 cm(2) V(-1) s(-1) on SiO(2) support. A kinetic growth model for graphene CVD based on flux balances is established, which is well supported by a systematic study of Ni-based polycrystalline catalysts. A finite carbon solubility of the catalyst is thereby a key advantage, as it allows the catalyst bulk to act as a mediating carbon sink while optimized graphene growth occurs by only locally saturating the catalyst surface with carbon. This also enables a route to the controlled formation of Bernal stacked bi- and few-layered graphene. The model is relevant to all catalyst materials and can readily serve as a general process rationale for optimized graphene CVD.Acknowledgment. R.S.W. acknowledges funding from EPSRC (Doctoral Training Award). S.H. acknowledges funding from ERC grant InsituNANO (no. 279342). This research was partially supported by the EU FP7 Work Programme under grant GRAFOL (project reference 285275).This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/nn303674g

New low pressure gas switches

This thesis describes an investigation the aim of which was the development of low pressure gas switches with the advantages of zero standby power consumption and instant readiness. Hydrogen thyratrons use a hollow anode to give the switch a convenient reverse conduction capability. The hollow anode structure has been shown to pass a 4 kA pulse current at 500 Hz for 1010 shots. The use of the hollow anode structure as a cold cathode for a low pressure switch is proposed and triggering of the structure by ions is demonstrated. Under conditions of low gas pressure and high discharge voltage, electrons make few collisions in the cathode dark space of a glow discharge and form extensive beams which travel many centimetres in the gas. Current/voltage characteristics of this 'electron beam' type of discharge are presented for deuterium at pressures between 0.2 and 1.0 torr. The electron beam discharge was found to be space-charge limited with I V3/2 at pressures below about 0.25 torr and I V3/2 at pressures above about 0.25 torr. It is proposed that the current in the electron beam discharge is limited by the flow of positive ions in the cathode dark space. Control of the emission area of a discharge in a hollow metal cylinder is demonstrated and is used as a triggering method for a new type of low pressure gas switch. Tests in a pulse modulator at repetition rates up to 1 kHz show that the switch operates satisfactorily. The triggering mechanism is shown to depend on the properties of the cold cathode glow discharge which, in certain circumstances, leads to the unusual phenomenon of post trigger-pulse firing of the switch. The phenomenon is shown to result from the interaction of the trigger discharge cathode dark space and the geometry of the switch. The glow discharge electron beam is successfully applied as a triggering method in several new low pressure gas switches. In one arrangement, the electron beam is used to pre-ionise the switch and subsidiary grids are used to trigger main conduction. In another arrangement, the electron beam is directed into the high voltage region to trigger conduction directly. The designs of these switches are discussed and their operation is demonstrated

Shale gas extraction – the case for a multi-disciplinary study

Shale gas extraction (SGE) and, more precisely, hydraulic fracturing, also known as fracking, has a propensity to court controversy wherever it is proposed. Many processes within SGE are essentially civil engineering processes and while numerous studies into the efficacy of SGE exist, answers to ethical and societal questions relating to safety, health and environmental sustainability remain unanswered. Recently, the UK Department of Energy and Climate Change announced its intention to support studies that encourage the development of innovative technologies for safe and responsible exploitation of the UK's shale gas resources. This paper explores the current state of knowledge regarding safety, health and wellbeing in the SGE industry, and presents the case for a detailed multi-disciplinary value-engineering study to develop pre-drill assessments and to provide ongoing monitoring tools that will assure public authorities, market operators and citizens that best-practice environmental, safety and sustainability approaches are available and feasible. </jats:p

Long-Term Passivation of Strongly Interacting Metals with Single-Layer Graphene.

The long-term (>18 months) protection of Ni surfaces against oxidation under atmospheric conditions is demonstrated by coverage with single-layer graphene, formed by chemical vapor deposition. In situ, depth-resolved X-ray photoelectron spectroscopy of various graphene-coated transition metals reveals that a strong graphene-metal interaction is of key importance in achieving this long-term protection. This strong interaction prevents the rapid intercalation of oxidizing species at the graphene-metal interface and thus suppresses oxidation of the substrate surface. Furthermore, the ability of the substrate to locally form a passivating oxide close to defects or damaged regions in the graphene overlayer is critical in plugging these defects and preventing oxidation from proceeding through the bulk of the substrate. We thus provide a clear rationale for understanding the extent to which two-dimensional materials can protect different substrates and highlight the key implications for applications of these materials as barrier layers to prevent oxidation.RSW acknowledges a Research Fellowship from St. John’s College, Cambridge and a Marie Skłodowska-Curie Individual Fellowship (Global) under grant ARTIST (no. 656870) from the European Union’s Horizon 2020 research and innovation programme. LD and SC acknowledge EPSRC Doctoral Training Awards and AC-V acknowledges a Conacyt Cambridge Scholarship and the Roberto Rocca Fellowship. S.H. acknowledges funding from ERC grant InsituNANO (no. 279342). This research was partially supported by the EUFP7 Work Programme under grant GRAFOL (project reference 285275), and EPSRC under grant GRAPHTED (project reference EP/K016636/1).This is the final version of the article. It was first available from ACS via http://dx.doi.org/10.1021/jacs.5b0872

Towards a general growth model for graphene CVD on transition metal catalysts.

The chemical vapour deposition (CVD) of graphene on three polycrystalline transition metal catalysts, Co, Ni and Cu, is systematically compared and a first-order growth model is proposed which can serve as a reference to optimize graphene growth on any elemental or alloy catalyst system. Simple thermodynamic considerations of carbon solubility are insufficient to capture even basic growth behaviour on these most commonly used catalyst materials, and it is shown that kinetic aspects such as carbon permeation have to be taken into account. Key CVD process parameters are discussed in this context and the results are anticipated to be highly useful for the design of future strategies for integrated graphene manufacture.We wish to thank Dr. M.-B. Martin for careful reading of the manuscript. A.C.V. acknowledges the Conacyt Cambridge Scholarship and Roberto Rocca Fellowship. R.S.W. acknowledges a Research Fellowship from St. John’s College, Cambridge and a Marie Skłodowska-Curie Individual Fellowship (Global) under grant ARTIST (no. 656870) from the European Union’s Horizon 2020 research and innovation programme. S.C. acknowledges funding from EPSRC (Doctoral training award). S.H. acknowledges funding from ERC grant InsituNANO (No. 279342) and EPSRC under grant GRAPHTED (Ref. EP/K016636/1).This is the final version of the article. It first appeared from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C5NR06873