13,007 research outputs found
Friction Stir Processing at High Rotation Rates of a Magnesium Alloy: Mechanical Properties at High Temperatures and Microstructure
No full textA high-pressure die-cast magnesium alloy plate was friction stir processed at high rotation rates with different advancing speeds. The stirred zone was very narrow around the tool and this made the friction stir process difficult to occur in the whole thickness of the plate. Intermetallicphase network at grain boundaries was refined due to partial dissolution and fragmentation of Mg17Al12 β-phase during the friction stir process; the likely increment of solute content in solid solution was exploited for aging to improve hardness. The ductility of friction stir processed samples deformed at 300° and 350°C substantially increased compared to the base material and to room temperature strained samples
Variation Resilient Adaptive Controller for Subthreshold Circuits
No full textSubthreshold logic is showing good promise as a viable ultra-low-power circuit design technique for power-limited applications. For this design technique to gain widespread adoption, one of the most pressing concerns is how to improve the robustness of subthreshold logic to process and temperature variations. We propose a variation resilient adaptive controller for subthreshold circuits with the following novel features: new sensor based on time-to-digital converter for capturing the variations accurately as digital signatures, and an all-digital DC-DC converter incorporating the sensor capable of generating an operating operating Vdd from 0V to 1.2V with a resolution of 18.75mV, suitable for subthreshold circuit operation. The benefits of the proposed controller is reflected with energy improvement of up to 55% compared to when no controller is employed. The detailed implementation and validation of the proposed controller is discussed
Approximation of general stochastic hybrid systems by switching diffusions with random hybrid jumps
No full textModeling of the microstructural and yield strength evolution of an age-hardenable Al alloy for high temperature applications.
No full textThe mechanical properties of Al alloys are strongly affected by their microstructure: the
size and shape of precipitates, their homogeneous distribution and their coherency with the matrix
are of primary importance for an effective strengthening of the alloys at room and elevated
temperatures.
Physically-based models are powerful tools to predict the influence of the mentioned parameters
on the mechanical properties of the alloy after age hardening, and also to predict the effect of high
temperature service conditions on microstructure evolution.
Scope of this work is to model the dimensional kinetic evolution of plate shaped precipitates of
an Al-based alloy during aging and after different overaging times at elevated temperature, and use
these results to estimate the alloy yield strength. The alloy strengthening response is due to three
terms, linearly summed: the intrinsic strength of Aluminum, the contribution from solute in solid
solution and the contribution arising from precipitates.
The consistency of the model is verified with experimental data obtained from a 2014 Al alloy
Measurement of the mass difference m(B-0)-m(B+)
No full textUsing 230 x 10(6) B (B) over bar events recorded with the BABAR detector at the e(+)e(-) storage rings PEP-II, we reconstruct approximately 4100 B-0 -> J/psi K+pi(-) and 9930 B+ -> J/psi K+ decays with J/psi -> mu(+)mu(-) and e(+)e(-). From the measured B-momentum distributions in the e(+)e(-) rest frame, we determine the mass difference m(B-0) - m(B+) = (+0.33 +/- 0.05 +/- 0.03) MeV/c(2)
A lattice Boltzmann formulation to the analysis of radiative heat transfer problems in a participating medium
Get PDFMetal Matrix Composites as Environment-Friendly Protective Coatings
No full textProtective coatings able to provide improved tribological behavior and corrosion resistance are demanded in many industrial applications. Although hard chrome is a very effective solution and is widely used, environmental issues related to hexavalent chromium push to develop alternative treatments. Within the framework of the HardAlt European Project, electrodeposited composite coatings have been developed and main results of this investigation are reported in this work. Boron carbide micro-particles were dispersed in a Ni-P matrix under different operating conditions, in order to produce coatings with different composition and particle content. Structural and morphological characterization was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties were evaluated by micro-indentation and the tribological performance was assessed by block-on-ring tests. Electrochemical experiments were carried out to examine the corrosion behavior of the composite coatings. Interesting results were obtained for composite coatings as regards hardness values, tribological behavior and corrosion resistance, even though some improvements can be realized. However, the results presented in this work show that composite coatings may represent a promising alternative to hard chrome for selected applications and also suggestions for further investigation are gained
Innovation in Electrical Power Engineering, Communication, and Computing Technology Proceedings of IEPCCT 2019
No full textDesigning molecular precursors for inorganic nanomaterials
No full textSSCI-VIDE+CDFA+SMRInternational audienceIndustrial development of chemical solution and vapor routes such as Sol-gel, MOD or MOCVD methods to inorganic nanomaterials is strongly dependent on the molecular engineering that involves design of tunable metal-organic precursors. These molecular precursors are usually the starting point of the processes and influence the micro- & nano-structure and, therefore, the nature and the properties of the obtained materials.1 The use of well-defined precursors also allows to establish relationships between the precursors and the final material and, therefore, to get some insight in to their transformation. This presentation will address different concepts of the ‘bottom-up’ approach with a special emphasis on the design of homo or heterometallic (‘single-source’) precursors which have (i) a formulation that matches well with that of the final materials, particularly stoichiometry between metals for multimetallic materials, (ii) appropriate physicochemical properties (solubility, thermal stability, volatility…), (iii) the required chemical functionalities (coordination sphere with an appropriate set of ligands), and (iv) a clean, low temperature conversion into materials with minimized undesired residues in the end.2,3 Catalytic applications of the obtained nanomaterials, especially in the field of photocatalysis, will be described. Keywords: molecular precursor, nanomaterials, Sol-Gel, metal-organic decomposition, metal oxide, metal selenide nanoparticles, metal fluoride composites, photocatalysisREFERENCES [1] S. Mishra, S. Daniele, Metal-organic derivatives with fluorinated ligands as precursors for inorganic nanomaterials, Chem. Rev. 2015, 115, 8379-8448.[2] a) S. Mishra, F. Morfin, V. Mendez, P. N. Swamy, J.-L. Rousset, S. Daniele, Nanometric NaYF4 as an unconventional support for Gold catalysts for oxidation reactions, ACS Omega, 2019, 4, 5852−5861; b) S. Mishra, E. Jeanneau, S. Mangematin, H. Chermette, M. Poor Kalhor, G. Bonnefont, G. Fantozzi, S. Le Floch, S. Pailhese, S. Daniele, A convenient and quantitative route to Sn(IV)–M [M = Ti(IV), Nb(V), Ta(V)] heterobimetallic precursors for dense mixed-metal oxide ceramics, Dalton Trans., 2015, 44, 6848–6862; c) Y. Chen, S. Mishra, G. Ledoux, E. Jeanneau, M. Daniel, J. Zhang, S. Daniele, Direct synthesis of hexagonal NaGdF4 nanocrystals from a single-source precursor: Upconverting NaGdF4:Yb3+,Tm3+ and its composites with TiO2 for near-IR-driven photocatalysis. Chem. Asian J., 2014, 9, 2415‒2421.[3] a) S. Gahlot, E. Jeanneau, F. Dappozze, C. Guillard, S. Mishra, Precursor-mediated synthesis of Cu2-xSe nanoparticles and its composites with TiO2 for improved photocatalysis, Dalton Trans. 2018, 47, 8897–8905; b) S. Mishra, D. Du, E. Jeanneau, F. Dappozze, C. Guillard, J. Zhang, S. Daniele, A facile molecular precursor-based synthesis of Ag2Se nanoparticles and its composites with TiO2 for enhanced photocatalytic activity, Chem. Asian J. 2016, 11, 1658-1663
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