HighP–TNano-Mechanics of Polycrystalline Nickel

We have conducted highP–Tsynchrotron X-ray and time-of-flight neutron diffraction experiments as well as indentation measurements to study equation of state, constitutive properties, and hardness of nanocrystalline and bulk nickel. Our lattice volume–pressure data present a clear evidence of elastic softening in nanocrystalline Ni as compared with the bulk nickel. We show that the enhanced overall compressibility of nanocrystalline Ni is a consequence of the higher compressibility of the surface shell of Ni nanocrystals, which supports the results of molecular dynamics simulation and a generalized model of a nanocrystal with expanded surface layer. The analytical methods we developed based on the peak-profile of diffraction data allow us to identify “micro/local” yield due to high stress concentration at the grain-to-grain contacts and “macro/bulk” yield due to deviatoric stress over the entire sample. The graphic approach of our strain/stress analyses can also reveal the corresponding yield strength, grain crushing/growth, work hardening/softening, and thermal relaxation under highP–Tconditions, as well as the intrinsic residual/surface strains in the polycrystalline bulks. From micro-indentation measurements, we found that a low-temperature annealing (T < 0.4 Tm) hardens nanocrystalline Ni, leading to an inverse Hall–Petch relationship. We explain this abnormal Hall–Petch effect in terms of impurity segregation to the grain boundaries of the nanocrystalline Ni

La storia di Fusignano

Il volume \ue8 il frutto di un lungo lavoro collettivo, basato sull'esplorazione sistematica della documentazione archivistica e a stampa relativa alla storia di Fusignano e della Bassa Romagna. La struttura del volume risponde all'esigenza di privilegiare alcuni aspetti fondamentali: la dimensione politico-istituzionale; i nodi storici che hanno scandito la vicenda del territorio nel corso dei secoli; i processi di formazione dell'identit\ue0 locale; le tracce documentarie presenti nel territorio e nelle istituzioni bibliotecarie e archivistich

La storia di Fusignano

Il volume è il frutto di un lungo lavoro collettivo, basato sull'esplorazione sistematica della documentazione archivistica e a stampa relativa alla storia di Fusignano e della Bassa Romagna. La struttura del volume risponde all'esigenza di privilegiare tre aspetti: la dimensione politico-istituzionale; i nodi storici che hanno scandito la vicenda del territorio nel corsos dei secoli; i processi di formazione dell'identità locale; le tracce documentarie presenti nel territorio e nelle istituzioni bibiotecarie e archivistich

Pressure and temperature variation of the depolarized light scattering spectra of the fragile glass-former liquid salol

The pressure and temperature dependences of the depolarized light scattering spectra of salol have been measured at isobaric condition P = 1 bar for T between 328 and 393 K, and at isothermal condition T = 343 K for P between 1 and 625 bar, i.e. outside the metastable liquid region. The experimental results for both the α- and β-relaxations can be well described by the Mode Coupling Theory. The independence of the power-law parameters a, and consequently $\it b$ and γ, from the thermodynamic variables T and P is demonstrated.The critical temperature Tc at 1 bar and the critical pressure Pc at T = 343 K have been determined from the normal liquid state

Corrosion behaviour of titanium diboride in neutral chloride solutions

The corrosion of a dense TiB2 material (hot pressed with 1.5 wt.% Ni as sintering aid) in 3.5% NaCl aqueous solution was studied at T=25°C, T=45°C, T=65°C for exposure times up to 30 days. Results revealed by polarization curves, polarization resistance measurements and potentiostatic tests, coupled with microstructure analyses of the sample surface and chemical analyses of the solutions after the corrosion tests, allowed us to asses that TiB2 behaves like a passive metal at 25°C and 45°C as a rather protective hydrated titanium oxide film forms, the film protectivity is markedly reduced at 65°C, the corrosion attack is preferentially localized on a Ni-rich grain boundary phase, besides electrochemical corrosion, chemical corrosion also occurs, which plays an important role in the whole corrosion process as long as passive conditions are maintained

PRORA USV - TECH sharp hot structures: Advanced ceramic materials and related technology for slender-shaped hot structures

In the framework of the Italian National Space Research Program (PRO.RA), supported by the Italian Ministry of Education and Research (M.I.U.R), a dedicated technology project, managed by the Italian Aerospace Research Centre (C.I.R.A. S.c.p.A.) and aimed to assess the use of ultra high temperature ceramics in the manufacturing of future RLV hot structures, is now running. A multi-material structure, which couple diborides (addressed as the sole materials that can be conveniently employed at temperatures above 2200K) to a C/SiC frame, is under investigation with the aim to demonstrate an innovative concept of nose cap. The current state of the research work is presented and the to-date results are described. Experimental data related to plasma sprayed coatings and self-standing components as well as to hot isostatically pressed samples are reported and discussed