Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Engineering
Type of Medium
Language
Year
  • 1
    Language: English
    In: International Journal of Hydrogen Energy, 2010, Vol.35(11), pp.5764-5764
    Keywords: Engineering
    ISSN: 0360-3199
    E-ISSN: 1879-3487
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Journal of The Electrochemical Society, 2015, Vol.162(9), pp.H681-H685
    Description: A remarkable new supported metal catalyst structure on Mo2C substrates, ‘rafts’ of platinum consisting of less than 6 atoms, was synthesized and found to be catalytically active electrocatalyst for oxygen reduction. A novel catalytic synthesis method: Reduction-Expansion-Synthesis of Catalysts (RES-C), from rapid heating of dry mixture of solid precursors of molybdenum, platinum and urea in an inert gas environment, led to the creation of unique platinum Nanorafts on Mo2C. The Pt Nanorafts offer a complete utilization of the Pt atoms for electrocatalysis with no “hidden” atoms. This structure is strongly affected by its interaction with the substrate as was observed by XPS. In this work, we show for the first time, evidence of electrocatalytic activity with such small clusters of non-crystalline Pt atoms as catalysts for oxygen reduction. Electrochemical half-cell characterization shows that this structure permit more efficient utilization of platinum, with mass activity conservatively measured to be 50% that of platinum particles generated using traditional approaches. These novel material may dramatically enhance stability relative to the commercial Pt/carbon catalysts.
    Keywords: Engineering ; Chemistry;
    ISSN: 0013-4651
    E-ISSN: 1945-7111
    Source: Electrochemical Society (ECS) (via CrossRef)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    In: Materials, 2016, Vol.9(11)
    Description: The dielectric constants of nylon fabrics saturated with aqueous NaCl solutions, Fabric-Superdielectric Materials (F-SDM), were measured to be 〉10 5 even at the shortest discharge times (〉0.001 s) for which reliable data could be obtained using the constant current method, thus demonstrating the existence of a third class of SDM. Hence, the present results support the general theoretical SDM hypothesis, which is also supported by earlier experimental work with powder and anodized foil matrices: Any material composed of liquid containing dissolved, mobile ions, confined in an electrically insulating matrix, will have a very high dielectric constant. Five capacitors, each composed of a different number of layers of salt solution saturated nylon fabric, were studied, using a galvanostat operated in constant current mode. Capacitance, dielectric constant, energy density and power density as a function of discharge time, for discharge times from ~100 s to nearly 0.001 s were recorded. The roll-off rate of the first three parameters was found to be nearly identical for all five capacitors tested. The power density increased in all cases with decreasing discharge time, but again the observed frequency response was nearly identical for all five capacitors. Operational limitations found for F-SDM are the same as those for other aqueous solution SDM, particularly a low maximum operating voltage (~2.3 V), and dielectric “constants” that are a function of voltage, decreasing for voltages higher than ~0.8 V. Extrapolations of the present data set suggest F-SDM could be the key to inexpensive, high energy density (〉75 J/cm 3 ) capacitors.
    Keywords: Article ; Dielectric ; Capacitance ; Energy Storage
    E-ISSN: 1996-1944
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Materials, 01 August 2018, Vol.11(9), p.1519
    Description: A new fundamental principle of the theory of dielectrics in capacitors is demonstrated. That is, dielectric material in any geometry that reduces the field generated by charges on capacitor electrodes is effective in increasing capacitance. Specifically, it is shown that super dielectric material...
    Keywords: Capacitor ; Super Dielectric Material ; Dielectric Theory ; Engineering
    E-ISSN: 1996-1944
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    In: Earth Surface Processes and Landforms, January 2016, Vol.41(1), pp.16-26
    Description: Biotic influences on geomorphology (and vice‐versa) are ubiquitous. This paper explores whether landforms may be extended (composite) phenotypes of biota, based on four criteria: process–form relationships between biota and landforms; evolutionary synchrony; selective pressure via ecosystem engineering and niche construction; and positive feedback benefitting the engineer organism(s). Coral reefs, peat bogs, biomantles, insect mounds, grassland soils, salt marshes, mangrove swamps, and some vegetation‐dependent sand dune types clearly meet these criteria. Karst landforms, meandering rivers, and tree uprooting pit‐mound systems meet the first three criteria, but positive feedback to engineer organisms has not been established. Research in biogeomorphology will surely identify other extended phenotypes. Implications are that biological evolution will continue to drive landscape metamorphosis, the appearance of new landform types, and presumably the disappearance of extended phenotypes associated with extinct species. Independently of extended phenotypes, tightly‐coupled geomorphological–ecological interactions such as coevolution, and biogeomorphic forms of ecosystem engineering and niche construction are common. The toposphere, encompassing Earth's landforms, is partly a biotic construct. Some elements would be present in an abiotic world, but the toposphere would not exist in anything resembling its contemporary state without a biosphere. This raises important questions with respect to Earth system evolution. The bio, litho‐, atmo‐, hydro‐, topo‐, and pedospheres coevolve at the global scale. Major biotic events have driven revolutions in the other spheres, but the atmosphere and the global hydrological system seem to have been relatively steady‐state at the global scale. The toposphere and pedosphere have not. This suggests that perhaps landforms and soils provide the major mechanisms or degrees of freedom by which Earth responds to biological evolution. Landforms and soils may thus be the ‘voice’ of the biosphere as it authors planetary change, even if clear biotic signatures are lacking. Copyright © 2015 John Wiley & Sons, Ltd.
    Keywords: Biogeomorphology ; Niche Construction ; Extended Phenotype ; Biogenic Landforms ; Toposphere
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: International Journal of Hydrogen Energy, 2009, Vol.34(24), pp.9816-9823
    Description: A new model of quantum mechanics, Classical Quantum Mechanics, is based on the (nearly heretical) postulate that electrons are physical objects that obey classical physical laws. Indeed, ionization energies, excitation energies, etc. are computed based on picturing electrons as ‘bubbles’ of charge that symmetrically surround a nucleus. Hence, for example, simple algebraic expressions based on Newtonian force balances are used to predict ionization energies and stable excitation states with remarkable precision. One of the most startling predictions of the model is that there are stable ‘sizes’ of the hydrogen atom electron (bubble diameter) that are smaller (‘hydrinos') than that calculated for the ‘ground state’. Experimental evidence in support of this novel physical/classical version of quantum is alleged to be found in the existence of super-heated hydrogen atoms reported by many teams in a variety of plasmas. It is postulated that the energy required for creating super-heated H atoms comes from the shrinkage of ground state H atoms to form hydrinos. This claim is discussed with reference to a brief review of the published studies of selective Balmer series line broadening in pure H and mixed gas plasmas, and astrophysical data.
    Keywords: Hydrogen ; Plasma ; Balmer Lines ; Line Broadening ; Quantum Theory ; Classical Quantum Mechanics ; Engineering
    ISSN: 0360-3199
    E-ISSN: 1879-3487
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    In: Materials, 2014, Vol.7(12), p.8197-8212
    Description: Evidence is provided here that a class of materials with dielectric constants greater than 10 5 at low frequency (〈10 −2 Hz), herein called super dielectric materials (SDM), can be generated readily from common, inexpensive materials. Specifically it is demonstrated that high surface area alumina powders, loaded to the incipient wetness point with a solution of boric acid dissolved in water, have dielectric constants, near 0 Hz, greater than 4 × 10 8 in all cases, a remarkable increase over the best dielectric constants previously measured for energy storage capabilities, ca. 1 × 10 4 . It is postulated that any porous, electrically insulating material (e.g., high surface area powders of silica, titania, etc. ), filled with a liquid containing a high concentration of ionic species will potentially be an SDM. Capacitors created with the first generated SDM dielectrics (alumina with boric acid solution), herein called New Paradigm Super (NPS) capacitors display typical electrostatic capacitive behavior, such as increasing capacitance with decreasing thickness, and can be cycled, but are limited to a maximum effective operating voltage of about 0.8 V. A simple theory is presented: Water containing relatively high concentrations of dissolved ions saturates all, or virtually all, the pores (average diameter 500 Å) of the alumina. In an applied field the positive ionic species migrate to the cathode end, and the negative ions to the anode end of each drop. This creates giant dipoles with high charge, hence leading to high dielectric constant behavior. At about 0.8 V, water begins to break down, creating enough ionic species to “short” the individual water droplets. Potentially NPS capacitor stacks can surpass “supercapacitors” in volumetric energy density.
    Keywords: Article ; Capacitor ; Dielectric ; Energy
    E-ISSN: 1996-1944
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Geomorphology, 15 September 2016, Vol.269, pp.1-7
    Description: In some cases biomechanical effects of individual trees may locally deepen or thicken regolith, especially in relatively shallow soils. This biogeomorphic ecosystem engineering phenomenon is at least partly contingent on the geological setting. The purpose of this research was to gain further insight into the biogeomorphic phenomenon, and to assess the relative importance of biomechanical and geological effects. Earlier studies in the Ouachita Mountains of Arkansas showed that individual trees locally thicken the regolith via mechanisms associated with root penetration of bedrock. However, that work was conducted mainly in areas of strongly dipping and contorted rock, where joints and bedding planes susceptible to root penetration were thought to be common and accessible. This project extended the research to the Cumberland Plateau region of Kentucky, where flat, level-bedded sedimentary rocks are dominant. Soil depth beneath trees was compared to that of non-tree sites by measuring depth to bedrock beneath rotted tree stumps and at adjacent sites with 1.0 m. While soil thickness beneath stumps was greater in the Ouachita Mountains compared to the Kentucky sites, in both regions soils beneath stumps are significantly deeper than adjacent soils. Further, there were no statistically significant differences in the difference between stump and adjacent sites between the two regions. This suggests the local deepening effects of trees occur in flat-bedded as well as steeply dipping lithologies.
    Keywords: Biogeomorphology ; Soil Depth Variability ; Biomechanical Weathering By Trees ; Tree Rooting ; Soil Thickness ; Geography ; Geology
    ISSN: 0169-555X
    E-ISSN: 1872-695X
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Materials, 01 September 2015, Vol.8(9), pp.6208-6227
    Description: The construction and performance of a second generation of super dielectric material based electrostatic capacitors (EC), with energy density greater than 200 J·cm−3, which rival the best reported energy density of electric double layer capacitors (EDLC), also known as supercapacitors, are...
    Keywords: Energy Storage ; Capacitor ; Dielectric Materials ; Titania Nanotube Arrays ; Engineering
    E-ISSN: 1996-1944
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Metallurgical and Materials Transactions B, 2013, Vol.44(1), pp.115-122
    Description: Recently the reductive expansion synthesis (RES) method was introduced as a means to create nano- and sub-micron metal particles and alloys by rapid heating of physical mixtures of urea with a metal nitrate. In the present work the generality of the RES method was demonstrated by creating metal micron and sub-micron particles from oxide and hydroxide precursors, and outlining the impact of temperature, precursor ratio, and gas flow rate on the product. For example, precursor selection impacted the temperature required for complete reduction, the amount of carbon present, and the size of the metal particles. For complete NiO reduction to micron scale particles, high urea content and a high temperature [ ca. 1073 K (800 °C)] were required. In contrast, Ni(OH) 2 was reduced to metal at far lower temperatures. Moreover, the Ni particles formed from NiOH were sub-micron ( ca. 200 nm) in size and carbon encapsulated. Other parameter variations had a similarly significant impact. Indeed, the reciprocal relationship between inert gas flow rate and the extent of reduction supports the supposition that the primary mechanism of reduced metal particle formation is the reduction of metal oxide particles by gases produced by urea decomposition. Collectively these and other findings indicate the RES method can be manipulated to create a range of micron and sub-micron reduced metal particle architectures appropriate for different applications.
    Keywords: Hydroxides ; Alloys ; Architecture ; Urea;
    ISSN: 1073-5615
    E-ISSN: 1543-1916
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages