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In this paper, the possible development of a drone for mobile crane inspection is investigated. Since the flying time of the drones currently in commerce is too short for the designed application, proton exchange membrane fuel cells and lithium-ion batteries are considered as alternative power systems to extend the flying time. Both systems are analyzed from an economical point of view and a life cycle assessment is performed to identify the main contributors to the environmental impact. From a commercial point of view, the lightweight fuel cell, being a niche product, results more expensive with respect to the Li-ion battery. On the other hand, the life cycle assessment results show a lower burdens of both technologies with respect to other components of the two systems, as carbon fiber. The source of the hydrogen and the electricity mix play a critical role as well.

A Au 20 Cu 48 Ag 7 Pd 5 Si 20 metallic glass precursor has been used to synthesize nanoporous gold by chemical de-alloying in a mixture of HNO 3 and HF. Gold ligaments of size ranging from 45 to 100 nm were obtained as a function of HNO 3 concentration, electrolyte temperature and de-alloying time. The as-prepared nanoporous gold exhibited strong surface enhanced Raman scattering (SERS) effect using 4,4′-bi-pyridine as probe molecule. For application in melamine sensing, the detection limit of 10 −6 M was achieved, which indicated that this biocompatible material has great potential as SERS active substrate.

In this work, the chemical de-alloying behavior of Au30Cu38Ag7Pd5Si20(at.%) amorphous alloy which was rapidly solidified from the melt in the form of ribbons were investigated. First a comparison between samples de-alloyed in nitric acid with and without HF was conducted to achieve homogeneous de-alloying process. Then the morphology and structure of nanoporous gold (NPG) were adjusted by tuning the de-alloying parameters, such as HNO3 concentration, electrolyte temperature and de-alloying time. Finally the surface enhanced Raman scattering(SERS) capability of the as-prepared NPG was evaluated using 4,4′-bi-pyridine as probe molecule.

Three dimensional nanoporous gold, with an average ligament size of 50 nm, was fabricated by chemical de-alloying from a new Au based metallic glass precursor. The resultant nanoporous gold gives rise to superior surface enhanced Raman scattering (SERS) capability using 4,4′-bi-pyridine as probe molecules. The SERS intensity mapping images confirm the presence of hot spots. A low detection limit down to 10 − 14 M for bipyridine was achieved, which is attributed to the localized enhanced electromagnetic fields around nano-sized ligaments, the electromagnetic coupling between ligaments, and the trapped SERS sensitive atoms.

De-alloying, i.e. selective dissolution of alloys, is currently studied to produce nanoporous gold items suited for use in catalysis, electrochemical applications, sensors and actuators. Both crystalline and amorphous alloys can be selectively etched. In the former, less noble atoms are removed from surface terraces of grains layer by layer, while noble ones form mounds. These evolve by undercutting and electrolyte percolation to form a ligament network. The mechanism of ligament development by de-alloying amorphous alloys is unknown. Here we show that for de-alloying a Au-based glass, in this case Au40Cu28Ag7Pd5Si20, percolation of the electrolyte through cracks of the native surface oxide initiates the formation of protuberances which are soon undercut. An interlayer develops, where Au crystals germinate, grow to nanometer size by diffusion and impinge. This is how ligaments start to coarsen. The interlayer is found at all stages between coarsened ligaments and amorphous phase. The ligaments are defective polycrystals, as opposed to single crystals obtained from crystalline alloys.

An integrated power system of a PEM fuel cell and hydride tanks designed for stationary applications is described. The work was focused on different aspects related to the development of the metal hydride tank and to its integration with the fuel cell, using water as thermal fluid. A commercially available LaNi 4.8 Al 0.2 intermetallic compound was chosen as hydrogen storage material, having sorption characteristics adequate to the working conditions of the system (i.e. 60 °C and 1 atm). Tanks were constituted by stainless steel, together with copper fins for improving heat exchanges between the thermal fluid and the tank. The performances of the integrated system were tested in different working conditions, in order to evaluate its reliability and efficiency. The system can operate for about 6 h, at an average power of 0.76 kW and delivering a total energy of 4.8 kW h, consuming about 3120 Nl of H 2 .

Nanoporous gold has been produced by the electrochemical dealloying of a Au 40 Cu 28 Ag 7 Pd 5 Si 20 metallic glass. Suitable conditions of potential and temperature of dealloying have been established from polarization curves and dealloying has been conducted at the critical potential of 1.05 V in three different electrolytes: 1 M HNO 3 , 1 M HClO 4 and 1 M H 2 SO 4 . The resulting material after 6 h of dealloying was constituted by ligaments made of pure Au and pores. The morphology was determined by SEM: ligaments of about 100 nm was observed and their size appears slightly larger (130 nm) when HNO 3 is used. In the first stages of dealloying (30–300 s), nanopores and nanocrystals, randomly oriented, were found by HRTEM. From these observations a diffusivity value for crystal growth was estimated. A change in growth mechanism was suggested when impingement occurs for long dealloying times. It is suggested that the ligament and pore morphology can be tailored in order to obtain materials with different chemical and physical properties.

Cold rolling of Al87Ni7La6 amorphous ribbons was performed on ribbons embedded in pure Al foils and ribbons alone, in order to study their deformation under constraint. A change in behaviour was observed for the two series of samples due to a different load distribution, so that ribbons alone was deformed up to ɛ = 0.029 without formation of cracks while, for composite samples, small fragments were always formed. In ribbons rolled alone, along with a macroscopic strain, a plastic deformation was observed at a finer scale, in the cavities present on the ribbon surface. The locally induced strain was quantified by taking into account the size change of cavities in samples rolled to different extents. The formation of shear bands and fracture occurring during cold rolling was studied for composite samples: the shear offset, interband spacing and distribution of fracture angles were determined. A Zr55Al20Ni12Cu8Ti5 amorphous ribbon was rolled with Al foils and the toughness value was estimated from the shear band offsets finding good agreement with literature data. Therefore, the toughness was estimated also for the Al-based samples obtaining the value of Kc = 28 MPa m1/2.

The process of de-alloying, i.e. removal of a less noble metal from an alloy, is applied here by electrochemical means to a Au-based metallic glass, Au 40 Cu 28 Ag 7 Pd 5 Si 20 , as a function of potential, temperature, and time. Very fine crystals nucleate with random orientation at the solid–electrolyte interface forming ligaments. The resulting material is constituted by ligaments made of pure Au and pores of smaller size whose dimensions coarsen up as a function of time to slightly above two hundred and below one hundred nanometers, respectively. The microstructure is uniform on both surfaces and across the ribbon. The extent of de-alloying is measured by monitoring the heat of crystallisation of the remaining amorphous phase giving linear trend vs time suggesting the reactions occur on continuously renewed surfaces.

Metallic glasses exhibit particularly attractive mechanical properties, like high stresses to fracture and large elastic strain (up to 2%), but they show generally low plasticity. Aim of this work is to investigate the glass forming range in the Cu–Y system, in order to form the ductile CuY phase (CsCl structure) upon crystallization. Cu58Y42, Cu50Y50 and Cu33Y67 alloys have been prepared by rapid solidification and copper mould casting, obtaining ribbons and cylindrical shaped ingots, with diameter of 2 mm. Fully amorphous, partially amorphous and fully crystalline samples have been obtained for different compositions and quenching conditions. In some cases, the X-ray diffraction results, analysed using the Rietveld method, showed CuY nanocrystals embedded in an amorphous matrix. The microstructure was studied by transmission electron microscopy (TEM) and the presence of nanocrystals of the ductile phase CuY has been confirmed. Microhardness results showed a softening of the amorphous phase due to the presence of CuY nanocrystals and a hardening due to the Cu2Y phase.

Experimental determinations of the glass transition and related properties in alloys are reviewed. Several recent measurements of viscosity, specific volume and heat capacity in the undercooling regime have become possible after the discovery of bulk glass forming alloys. The data allow verification of models on the kinetics and thermodynamics of such melts. The notion of melt fragility, borrowed from the description of inorganic and molecular glasses, has become popular also for metallic alloys: the kinetic fragility is described by the viscous behavior of the liquid and the thermodynamic fragility by the entropy loss on undercooling. The experimental viscosity data for metallic glass formers presently available can be reasonably framed within the strong–fragile classification. On the other hand, there are major discrepancies for the thermodynamic fragility of metallic glass formers with respect to conventional ones. The reason for such disagreement is twofold: on the experimental ground there are difficulties in obtaining fully reliable thermodynamic data in sufficiently wide temperature ranges; on the conceptual side the definition of the configurational entropy of the liquid with a suitable reference state is controversial. Among fragility indexes, the reduced width of the transition range proves most useful. The trend of the glass transition as a function of composition is also discussed in relation to the progressive ordering of the liquid on undercooling.

Mechanical properties of Al87Ni7RE6 amorphous and devitrified alloys (RE = Ce, Nd, La) are reported in this work. The microhardness of samples annealed at different devitrification stages is determined and an improvement is observed for all compositions when Al nanocrystals are present in the amorphous matrix. A further increase is found after a second transformation due to precipitation of an unknown phase in Al87Ni7Nd6. The fracture surfaces resulting from tensile tests of amorphous samples are examined both with scanning electron microscopy and transmission electron microscopy, where shear bands, vein patterns and protrusion are seen. There is no sign of crystallisation in shear bands and in vein patterns although their shape suggests a rise in temperature during deformation. Also in cold rolled samples the crystallization is avoided during deformation.

Supersaturated Au80Fe20 and Au70Fe30 solid solutions have been obtained by melt spinning. Heat treatments of as-quenched ribbons in the temperature range between 320 and 550 °C induced the precipitation of a fcc Fe-rich phase. From structural and microstructural analysis of precipitates and residual matrix, a discontinuous (cellular) transformation mechanism has been observed. Calculated driving forces for nucleation of bcc and fcc phases suggest a critical role of defect concentration on observed phase transformations.

This paper describes the crystallisation of Al 87 Ni 7 La 6 and Al 87 Ni 7 Sm 6 metallic glasses. The substitution of Sm for La in the alloy causes a variation in the transformation mode evidenced by the number of differential scanning calorimeter (DSC) peaks: two for the La containing alloy at low heating rates, than three at high heating rates, and three for the one with Sm. The glass transition becomes manifest for each alloys at a typical heating rate below which it is overlapped by the first crystallisation event due to precipitation of fine Al crystals in both materials. The Kissinger plot for Al 87 Ni 7 La 6 is not strictly linear as a possible consequence of overlapping processes. The second and third transformations of both alloys produce a metastable intermediate and the equilibrium phases, respectively. The second crystallisation steps of Al 87 Ni 7 Sm 6 and Al 87 Ni 7 La 6 involve linear Kissinger plots. The crystallisation behaviour of the two alloys is compared with that of Al 87 Ni 7 Ce 6 and Al 87 Ni 7 Nd 6 which were earlier shown to present two and three transformations, respectively.

Cu80−xNixFe20 (x=0, 5 and 20) alloys have been rapidly solidified by planar flow casting. X-ray diffraction (XRD) analysis of as-quenched ribbons shows bcc-Fe precipitates embedded in an fcc phase (x=0), two co-existing fcc solid solutions (x=5) and a complete solid solution of the parent elements (x=20). Thermal treatments in the temperature range between 400 and 600 °C give precipitation and spinodal decomposition reactions. These phase transformations have been evidenced from a variation of lattice constants, from a broadening of diffraction peaks and from TEM observations. The role of Ni content on competition between precipitation and decomposition reactions during rapid solidification and annealing is discussed in terms of thermodynamic arguments. Recent CALPHAD assessment of thermodynamic properties for Cu–Fe–Ni system has been used for an estimation of composition and volume fraction of equilibrium phases.

Immiscible alloys have been rapidly solidified for the preparation of granular materials with giant magnetoresistance properties. Au-based (Au–Co and Au–Fe) and Cu-based (Cu–Co and Cu–Fe) systems have been investigated. Single supersaturated solid solution has been obtained for Au–Fe, whereas three FCC solid solutions with different Co content have been found for Au–Co. For Cu–Co and Cu–Fe a limit of solubility in Cu has been observed. Ni additions to Cu–Fe strongly enhance solid solubility. A thermodynamic analysis has been used to describe the competition between partition-less solidification and phase separation in undercooled liquid.

Al–TM–RE (TM: transition metal, RE: rare earth metal) and Al–RE alloys were analysed with the aim of studying phase selection under various processing conditions. The metastable phases formed in binary Al-rich systems (notably Al–Sm) are revised for a unified interpretation of the literature. Two groups of alloys had different behaviour as for phase selection. In Al 88 Fe 9 Nd 3 and Al 87 Ni 10 Ce 3 stable intermetallic compounds form as primary phases during solidification. Nanocrystalline Al is formed at high undercooling. This may occur directly in rapid solidification or when fully amorphous materials are suitably annealed. In Al 90 Sm 8 Ni 2 and Al 90 Sm 8 Fe 2 metastable intermetallics form during rapid solidification together with a fraction of amorphous phase, whereas nanocrystalline Al forms on annealing the amorphous phase.

Various multicomponent alloys containing Ni-Fe-Si-B and refractory metals have been rapidly solidifed in order to check their tendency to produce glassy phases and their devitrification behaviour has been studied. Among these a Ni36Fe32Ta7Si8B17 alloy presents primary crystallization with production of fcc nanocrystals embedded in the glassy matrix. The kinetics of the transformation is determined at 530 °C showing that it consists in two steps: fast nucleation and growth of nanocrystals plus homogenization of the remaining matrix with crystal coarsening. Evidence based on TEM observations, XRD patterns and DSC experiments, are reported in favour of a homogeneous mechanism of nucleation. Faceting of nanocrystals is observed for the first time in such transformations and is attributed to a stress effect on the particles.

Metallic glasses have been obtained in the form of small ingots with the composition Zr40Ti14Cu11Ni10Be25, by means of water quenching. All glasses transform on annealing to a mixed state comprising a nanocrystalline phase embedded in an amorphous matrix. The transformation of the glasses occurs via a phase separation in the amorphous alloy, followed by the formation of the nanocrystalline phase. The process is analyzed by means of isothermal and non-isothermal differential scanning calorimetry (DSC) and X-ray diffraction. The isothermal heat of transformation has two steps as a function of temperature which are due to the transformation sequence. Similarly, non-isothermal traces have multiple signals, the intensities of which depend on the heating rate. A Ni36Fe32Ta7Si8B17 alloy has been shown to display glass forming tendency, as indicated by the reduced crystallization onset temperature of 0.6. Amorphous ribbons of this material reach a thickness of 100 μm. On annealing, an austenitic nanocrystalline phase is obtained through a nucleation and growth mechanism. In practice, the growth is limited and rarely proceeds beyond a particle size of 10 nm, as revealed by transmission electron microscopy. The present results allow a comparison of the DSC behaviour for alloys undergoing devitrification with different mechanisms.

The formation, size and morphology of crystals in Al 100-x Sm x (8

FeSiB tapes have long been commercialised for their excellent soft-magnetic properties but do not manifest a glass transition temperature Tg as crystallisation intervenes. In this work, we present the crystallisation and properties of two Fe-based glasses, which show a glass transition before crystallisation. Using Ni and Co substitution, we can design glasses that form primary FCC or BCC FeNiCo solutions in their first stage of crystallisation followed by the formation of the metastable (FeNiCo)4B (C6Cr23-type cF116) intermetallic phase. Thermal and structural and magnetic properties were compared during heat treatment.