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1.
Brian Lawn David Marshall Rishi Raj Greg Hirth Trevor Page Julie Yeomans 《Journal of the American Ceramic Society》2021,104(1):23-26
Crystalline quartz has long been identified as among the weakest of abundant crustal minerals. This weakness is particularly evident around the α–β phase inversion at 573°C, in which Si–O bonds undergo a displacive structural transformation from trigonal to hexagonal symmetry. Here we present data using indentation testing methodologies that highlight the precipitous extent of the transformational weakening. Although the indentations are localized over relatively small specimen contact areas, the data quantify the essential deformation and fracture properties of quartz in a predominantly (but not exclusively) compressive stress field, at temperatures and pressures pertinent to conditions in the earth's crust. 相似文献
2.
John D. Rodney S. Deepapriya M. Cyril Robinson C. Justin Raj Suresh Perumal Byung Chul Kim S. Krishnan S. Jerome Das 《International Journal of Hydrogen Energy》2021,46(54):27585-27596
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting. 相似文献
3.
The stretchable electrodes with excellent flexibility, electrical conductivity, and mechanical durability are the most fundamental components in the emerging and exciting field of flexible electronics. This article proposes a method for fabrication of such a stretchable electrode by embedding silver nanorods (AgNRs) into a polydimethylsiloxane (PDMS) matrix that is grown by a unique glancing angle deposition technique. The surface, mechanical, and electrical properties of PDMS are significantly changed after embedding the AgNRs in it. The results show that surface roughness and polarity increase after AgNRs are embedded in the PDMS matrix. Elastic modulus (E) and hardness (H) decrease with an increase in the indentation load as a result of the indentation depth effect. Due to strong interfacial adhesion of AgNRs embedded in the PDMS matrix, the E and H of nanocomposite are increased by 167.6 and 93.3% compared with PDMS film, respectively. Furthermore, the AgNRs-PDMS film has an electrical resistivity value in the order of 10−7 Ωm. It remains conductive during various mechanical strains such as bending, twisting, and stretching, which is demonstrated using a light-emitting diode circuit. Simultaneously, the antimicrobial activity of silver could make it a promising candidate for wearable electronics. 相似文献
4.
The increase in the production of acid gas consisting of H2S, CO2, and associated impurities such as ammonia and hydrocarbons from oil and gas plants and gasification facilities has stimulated the interest in the development of alternative means of acid gas utilization to produce hydrogen and sulfur, simultaneously. The present literature lacks a detailed reaction mechanism that can reliably predict the thermal destruction of NH3 and its blend with H2S and CO2 to facilitate process optimization and commercialization. In this paper, a detailed mechanism of NH3 pyrolysis is developed and is merged with the reactions of NH3 oxidation and H2S/CO2 thermal decomposition from our previous works. The mechanism is validated successfully using different sets of experimental data on the pyrolysis and oxidation of NH3, H2S, and CO2. The proposed mechanism predicts the experimental data on NH3 pyrolysis remarkably better than the existing mechanisms in the literature. The mechanism is used to investigate the effects of NH3 concentration (0–20%) and reactor temperature (1000–1800 K) on the thermal decomposition of H2S and CO2. A synergistic effect is observed in the simultaneous decomposition of NH3 and CO2, i.e., NH3 conversion is improved in the presence of CO2 and the decomposition CO2 to CO is enhanced in the presence of NH3. The presence of H2S suppressed NH3 conversion, while the conversion of H2S remained unchanged with increasing NH3 concentration at temperature below 1400 K due to the low conversion of NH3 (up to 18%). At temperature above 1400 K, NH3 conversion increased rapidly and it triggered a decrease in H2S conversion as well as the yields of H2 and S2. The major reactions involved in the decomposition of H2S, CO2, and NH3 and the production of major products such as H2, S2, and CO are identified. The detailed reaction mechanism can facilitate the design and optimization of acid gas thermal decomposition to produce hydrogen and sulfur, simultaneously. 相似文献
5.
S. Sarkar P. Mohan Raj S. Chakraborty G. Phanikumar K. Chattopadhyay P. Dutta 《Journal of Materials Science》2003,38(1):155-164
A three dimensional, transient model is developed for studying heat transfer, fluid flow and mass transfer for the case of a single-pass laser surface alloying process. The numerical study is performed in a co-ordinate system fixed to the laser which moves with a constant scanning speed. The coupled momentum, energy and species conservation equations are solved using a finite volume technique. Phase change processes are modelled using a fixed-grid enthalpy-porosity technique, which is capable of predicting the continuously evolving solid-liquid interface. The three-dimensional model is able to predict the species concentration distribution inside the molten pool during alloying, as well as in the entire cross section of the solidified alloy. Corresponding experimental results show a good qualitative agreement with the numerical predictions with regard to pool shape and final composition distribution. 相似文献
6.
Windlass H. Raj P.M. Balaraman D. Bhattacharya S.K. Tummala R.R. 《Electronics Packaging Manufacturing, IEEE Transactions on》2003,26(2):100-105
Polymer ceramic composites form a suitable material system for low temperature fabrication of embedded capacitors appropriate for the MCM-L technology. Improved electrical properties such as permittivity can be achieved by efficient filling of polymers with high dielectric constant ceramic powders such as lead magnesium niobate-lead titanate (PMN-PT) and barium titanate (BT). Photodefinable epoxies as the matrix polymer allow fine feature definition of the capacitor elements by conventional lithography techniques. The optimum weight percent of dispersant is tuned by monitoring the viscosity of the suspension. The dispersion mechanism (steric and electrostatic contribution) in a slightly polar solvent such as propylene glycol methyl ether acetate (PGMEA) is investigated from electrophoretic measurements. A high positive zeta potential is observed in the suspension, which suggests a strong contribution of electrostatic stabilization. By optimizing the particle packing using a bimodal distribution and modified processing methodology, a dielectric constant greater than 135 was achieved in PMN-PT/epoxy system. Suspensions are made with the lowest PGMEA content to ensure the efficiency of the dispersion and efficient particle packing in the dried film. Improved colloidal processing of nanoparticle-filled epoxy is a promising method to obtain ultra-thin capacitor films (<2/spl mu/m) with high capacitance density and improved yield. Capacitance of 35 nF/cm/sup 2/ was achieved with the thinnest films (2.5-3.0 /spl mu/m). 相似文献
7.
The expression of the NMDA subtype of glutamate receptors was investigated by Western blot analysis and RT-PCR in cultured chick Bergmann and Müller glial cells. Using subunit-specific antibodies directed to the carboxy terminus of the rat NMDAR2A/B we detected the expression of the NMDAR2 subunit in both kinds of culture. The functional subunit of the NMDA receptor, NMDAR1, was detected by means of RT-PCR. These results, together with our previous functional characterization of NMDA receptors in radial glia, provide conclusive evidence for the expression of functional NMDA receptor/channels in Bergmann and Muller glia cells. Our findings strengthen the notion of a modulatory role of glial cells in synaptic transmission. 相似文献
8.
A dynamic model for computer simulation and control of steelmaking has been developed. It is essentially based on multicomponent mixed transport control theory with the incorporation of energy balance calculations. The model is applicable to both steelmaking in electric furnaces as well as in oxygen steelmaking converters. The adjustable parameters of the model for simulation of oxygen steelmaking are gas evolution rate (Gco). oxygen flux factor (Fo) and emulsification factor (EM). These simulation parameters, when combined with on-line measurement of off-gas composition and temperature, enable complete dynamic control of the process. The model developed is applied, as an example, to an industrially produced heat in a top blown oxygen steelmaking converter and the results of simulation are discussed. 相似文献
9.
Volatilization resulting from the thermal decomposition of Si3 N4 causes the large weight loss and desintering phenomenon observed during pressureless sintering of Si3 N4 -5% MgO and sialon (z =2)-5% MgO. The addition of a few weight percent of Si to the powder suppresses this volatilazation and helps to achieve fully dense Si3 N4 components. 相似文献
10.
Seema Hiranandani Joel Saltz Piyush Mehrotra Harry Berryman 《Journal of Parallel and Distributed Computing》1991,12(4)
Many researchers approach the problem of programming distributed memory machines by assuming a global shared name space. Thus the user views the distributed memory of the machine as though it were shared. A major issue that arises at this point is how to manage the memory. When a processor accesses data stored on another processor's memory, data must be moved between the two processors. Once these data are retrieved from another processor's memory, several interesting issues are raised. Where should these data be stored locally? What transformations must be performed to the code to guarantee that the nonlocal accesses reference the correct memory location? What optimizations can be performed to reduce the time spent in accessing the nonlocal data? In this paper we examine various data migration mechanisms that allow an explicit and controlled mapping of data to memory. We describe, experimentally evaluate, and model a set of schemes for storing and retrieving off-processor array elements. The schemes are all based on using hash tables for efficient access of nonlocal data. The three different techniques evaluated are the basic hashed cache, partial enumeration, and full enumeration, the details of which are described in the paper. In all three schemes, nonlocal data are stored in hash tables—the difference is in the amount of memory used by the schemes and the retrieval mechanisms for nonlocal data. 相似文献