We report the identification of a new ternary Al-Fe-Si phase synthesized by arc-melting. Energy dispersive X-ray spectroscopy measurements show an homogeneous chemical distribution within the intermetallic grain with an overall stoichiometry equal to Al81.0Fe13.6Si5.4 (at.%). Atomically resolved High-Angle Annular Dark Field images collected along the [001] zone-axis are consistent with a cubic structure with an unit cell parameter close to 8.9 Å. Using microdiffraction analysis, it was possible to explore the zero-order Laue zone (ZOLZ) and first-order Laue zone (FOLZ) . This electron diffraction characterization leads to the conclusion that the Al81.0Fe13.6Si5.4 (at.%) crystallizes in the Pm3̄ space group.

We report the formation of large and highly twinned dendrites of the Al13Fe4 approximant phase embedded in an fcc Al-rich matrix. Using a rapid cooling technique, the approximant appears as a 10-fold dendrite. Within each arm, all grains share a common [010] direction. The grain distributions within the arm are quite complex and a single dendrite arm can contain up to four different orientations. Using several techniques, including Electron Back-Scattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM), it has been possible to identify three types of twins, namely {100}, {001} and {201̄} twins. From these observations and previous reports, we propose a growth mechanism to explain the formation of such specific 10-fold motifs. It corresponds to the heteroepitaxial growth of the Al13Fe4 approximant from a well-facetted decagonal Al–Fe quasicrystalline seed.

Y-oriented LiNbO3 films with single-crystal quality were deposited on M-sapphire substrates using direct liquid injection CVD. Significant effort was dedicated to ensuring films with controlled and uniform Li2O composition (+/- 0.05 mol%) across 4-inch wafers, as well as achieving nearly stoichiometric growth. 33 degrees Y-textured LiNbO3 films on Pt electrode have demonstrated e(31) piezoelectric coefficient of -2.4 C/m(2).

In the industrial context, the fine modeling of radiative heat transfer is of paramount importance. For engine manufacturers, this transfer mode is predominant and determines the overall design of the product (wall thickness, pollutant production, etc.). This crucial information is also used to predict the life span of the system. We propose here a numerical methodology based on Monte Carlo method for solving the radiative transfer equation associated with Bayesian artificial neural networks to efficiently model the radiative flux divergence field in a highly heterogeneous axisymmetric domain. This work follows a first validation of the method on homogeneous cases [?]. A very intense and pitted hot spot was also added to the temperature and radiative species fields. This very punctual perturbation aims to demonstrate that the neural network is able to take into account all the heterogeneities of the study case and a strong irregularity often encountered in an industrial context (e.g. knocking phenomenon). Under the condition of a correctly constructed training database, it is possible to model such phenomena very accurately by a multivariate interpolation thanks to adapted neural networks. The use of these tools also allows to drastically reduce the computational time and the amount of resources mobilized for the resolution of the radiative heat transfer compared to a complete point by point calculation with a Monte Carlo method.

In the last decade, a huge amount of work has been devoted to constructing a composite thin film where magnetic anisotropy becomes tunable by coupling ferromagnetic layer to a functionalized layer. Electrical control of interfacial anisotropy with an insulator and interfacial strain transferred from an electrically controlled piezoelectric or ferroelectric material are still heavily pursued. Here, we propose a novel approach to manipulate magnetic anisotropy by interfacial strain transferred from a thermally controlled material, like a shape memory alloy [1]. This innovative architecture benefits from the shape memory effect, in particular, from the two-way shape memory effect (TWSME). The TWSME consists in a reproducible hysteretic transformation of shape memory alloys from a strained B19’ structure (at low temperature) to a differently strained B2 structure (at high temperature) during the thermal cycle. NiTi-based alloys are among the most used shape memory alloys within a wide range of applications in industry, military technologies, health care, etc. [2]. They are metallic and may be grown by regular microelectronics industry deposition techniques. NiTi-based SMAs can produce as much as 4% of TWSME strain and recover up to 10% of the initial deformation [3]. The transformation temperatures can be easily tuned from 250 K to 1000 K [2].

The bulk structure of the eta-Al5Fe2 intermetallic compound consists in an ordered framework of pentagonal antiprims with composition Al2Fe inside which nearly continuous chains of fractionally occupied Al sites exist. At low temperature, ordering of these Al channel atoms can occur, leading to various superstructures. Although the Al5Fe2 intermetallic phase is of technological importance being present in protective coating for steel parts, a detailed surface investigation of this compound has not been reported yet. Here we describe the growth of a single crystal of the Al5Fe2 compound by the Czochralski method. Its bulk structure is identified as the low temperature polymorph eta ''. Density Functional Theory calculations were performed to determine its formation enthalpy and its electronic structure. A deep pseudogap is noticeable at the Fermi energy, and this compound is found to be magnetic. Two samples have been extracted, presenting a surface oriented either perpendicular to the channel's direction ((0 0 1) surface) or parallel to them ((1 0 0) surface). The two surfaces have been investigated by X-ray photoemission spectroscopy, low-energy electron diffraction and scanning tunneling microscopy. Both surfaces exhibit some superstructures of various complexities, whose origin can be explained in the light of density functional theory calculations performed on model surfaces.

We present an experimental and theoretical study of Pauli paramagnetism and martensite stabilization in a near equiatomic NiTi shape memory alloy. We demonstrate a direct correlation between strain-induced shear of the B19′ NiTi lattice and its electronic and thermodynamical features. An increase in the monoclinic angle β from 97.4 to 98° induces a 7% decrease in the magnetic susceptibility because of a shift and deepening of a dip in B19′ density of states at the Fermi level. It also produces a decrease in the B19′ enthalpy, which translates into an increase in the martensite-to-austenite transition temperature by 60 K.

Heusler magnetic alloys offer a wide variety of electronic properties very promising for spintronics and magnonics. Some alloys exhibit a spin gap in their band structure at the Fermi energy, the so-called half-metal magnetic (HMM) behavior. This particular property leads to two very interesting properties for spintronics, i.e., fully polarized current together with ultra-low magnetic damping, two key points for spin-transfer-torque based devices. This Tutorial gives experimental details to grow and characterize Heusler Co2MnZ compounds in thin films (Z = Al, Si, Ga, Ge, Sn, Sb) by using molecular beam epitaxy in order to get the proper predicted electronic properties. A first part of this Tutorial is dedicated to control the stoichiometry as best as possible with some methods to test it. The chemical ordering within the lattice was examined by using electron diffraction during growth, regular x-ray diffraction, and scanning transmission electron microscopy. In particular, standard x-ray diffraction is carefully analyzed depending on the chemical ordering in the cubic cell and shown to be inefficient to distinguish several possible phases, on the contrary to electron microscopy. The electronic properties, i.e., magnetic moment, spin polarization, and magnetic damping were reviewed and discussed according to the stoichiometry of the films and also theoretical predictions. Polycrystalline films were also analyzed, and we show that the peculiar HMM properties are not destroyed, a good news for applications. A clear correlation between the spin polarization and the magnetic damping is experimentally demonstrated. At least, our study highlights the major role of stoichiometry on the expected properties.

A single crystal of the Al 45 Cr 7 crystalline approximant has been grown using the Czochralski method. The structure of this phase has been resolved in the C2/m space group. Chromium atoms are systematically surrounded by Al atoms forming a distorted icosahedron. The icosahedra are linked either by a vertex or a triangular face or overlap along a five-fold axis. The (010) surface of this single crystal has been investigated under ultrahigh vacuum and shows a (1x1) termination at specific bulk planes. The terraces have a nanostructured appearance which is ascribed to the preservation of the CrAl 12 clusters at the surface. Ab initio calculations shows the presence of a deep pseudogap at the Fermi level, due to both a Hume-Rothery effect combined with strong spd hybridization. The isoelectronic charge densities highlight the fact that the charges are mainly confined within the CrAl 12 icosahedron providing support to a certain stability of the clusters which could explain the nanostructured surface morphology encountered. First results on Al thin film deposition on the (010) surface are also reported.

A magnetic field driven quantum critical point (QCP) is studied experimentally in the Ce 3 Al magnetically anisotropic intermetallic compound, which shows both antiferromagnetic (AFM) ordering and heavy–fermion behavior. Measurements of the magnetic susceptibility, the magnetoresistance and the specific heat on a Ce 3 Al monocrystalline sample performed down to 0.35 K in magnetic fields up to 9 T demonstrate that the QCP is anisotropic regarding the orientation of the magnetic field relative to the magnetically easy direction. External magnetic field drives the AFM transition continuously toward zero temperature when applied in the ( a , b ) easy plane, reaching the QCP at the critical field B c a , b = 4.6 ± 0.4 T, where a quantum phase transition from the AFM to the paramagnetic state takes place. The magnetoresistance experiments below 1 K indicate that intermediate magnetic states may have formed near the QCP. For the field applied along the c hard direction, the QCP has not been observed within our experimental range of the magnetic field. The anisotropic, magnetic field driven QCP in the Ce 3 Al results from competition of the exchange interaction with the Zeeman interaction in the presence of a large magnetocrystalline anisotropy. The anisotropy of the QCP is a consequence of the fact that the magnetic anisotropy locks the magnetization into the easy plane and cannot be pulled out of the plane by the available laboratory field. Consequently, only the component of the magnetic field vector that lies in the easy plane participates in the QCP formation. In AFM systems with a large magnetic anisotropy, the magnetic field driven QCP is a continuous variable of the magnetic field vector orientation relative to the easy direction.

The article examines numerically and theoretically the effects of room aspect ratio on the fire smoke filling process. It aims to evaluate the two-zone models used in fire safety engineering to predict the smoke filling times. Using Fire Dynamics Simulator, numerical simulations are performed and compared to a simplified zone model. The results show that the two-zone model overestimates the smoke filling time in the case of a compartment with a large surface area. To improve the predictions of two-zone models, simple correlations are established for the duration of the phenomena occurring before the formation of a two-layer stratification in a fire compartment. These new correlations allow the zone model to be significantly improved.

A numerical evaluation of visibility through a scattering medium was performed with the underlying idea of application to media involving water mist and/or smoke. The model uses the principles of incoherent imaging which is based on the Point Spread Function (PSF) concept. This PSF corresponds to the image of a single object point produced by an optical system. Here the light propagates through a scattering and possibly absorbing medium between the object and the imaging system, that leads to a supplementary spreading of the PSF. In this work the PSF was calculated by a Monte-Carlo Method (MCM) and it was applied to the image reconstruction of a USAF1951 resolution pattern. The results of the model were validated through comparison with an experiment in which the USAF1951 pattern was imaged through a cell containing a mixture of silica spheres in suspension in water, the optical properties of this medium being fully characterized. The experiment was made in two limit cases: a luminous object in a dark room and a reflecting object in a luminous room. A good agreement was observed in these two cases and the distance of visibility was found close to the prediction given by the T. Jin's correlation.

Strain modulation during a two-way shape memory effect (TWSME) in a sputtered nitinol NiTi is used to reliably induce and switch by 90° a uniaxial magnetic anisotropy of a 20 nm thick Ni film during the thermal cycle from 300 K to 400 K. NiTi strain and its distribution are carefully measured by digital image correlation during tensile prestrain and subsequent temperature cycles in order to compare with Ni strain extracted from the magnetometry measurement and from transmission electron microscopy. In a NiTi/Ni bilayer, a variation of 2.7% strain in NiTi during the TWSME generates 1.3% strain in Ni, which results in a transition from −2 × 104 J/m3 in-plane magnetic anisotropy to +1 × 105 J/m3. Such a composite system offers a way to timely ease writability while maintaining high thermal stability at rest in magnetic media.

The ability of a water curtain to stop smoke and radiation from a fire is investigated in the particular configuration of a tunnel during construction work. Experiments are conducted in reduced scale (1=22nd) in a blind tunnel and simulations are performed in small and real scale configurations. The small-scale experimental model consists of a 6.20 m long polycarbonate circular tunnel with a diameter of 40 cm. It is connected to a 1.20 m cubic space, which represents the wellbore of the tunnel boring machine. The scenario considers a fire occurring in the tunnel and the activation of a water mist downstream from the fire, close to the wellbore, in order to stop smoke and radiation emitted by the fire. The spraying system consists of 5 injection nozzles, regularly distributed on the ceiling of the tunnel. The numerical simulations are carried out using Fire Dynamics Simulator. The results from both small and large scale studies show that the water curtain induces a strong mixing of air and smoke due to drag effect, but it does not stop the smoke flow. Similarly, despite the down drag effect due to the curtain, fresh air continuously feeds the fire, crossing the mist area and flowing in the lowest part of the tunnel as a counter-current flow. Upstream from the water curtain the smoke is filling all the tunnel due to a strong de-stratification, partially diluted with air in the lower counter-current flow. There may be a remaining thermal stratification, but contour plots of soot mass fraction show that soot particles are found even in the lowest part of the tunnel in a layer of smoke cooled by the spray and diluted with air. Radiation from the fire is attenuated as expected due to radiation and droplet interactions, with a radiation attenuation up to 90 % for the large scale water flow-rate investigated in the present case (15 m(3)/h).

Smoke propagation into a corridor configuration is an important issue in fire safety engineering. One important characteristic is the smoke behaviour in the steady state, namely, the smoke layer thickness, its mean temperature and its mean velocity. The question that is investigated here is how these quantities vary as a function of the corridor geometrical characteristics and of the fire heat release rate. To achieve this goal, new experimental data are provided in a small scale configuration. The results show that the smoke layer thickness is independent of the heat release rate of the pool fire. By rescaling the velocity and temperature profiles with respect to the fire heat release rate, these profiles fall onto unique curves. Finally, based on energy and mass conservation equations, a scaling relation is proposed for the smoke enthalpy.

This paper reports a cathodoluminescence (CL) spectroscopic study of nanogranular A1N0Er, samples with erbium content, x, in the range 0.5-3.6 at%. A wide range of erbium concentration was studied with the aim of understanding the concentration quenching of CL. The composition of thin films, deposited by radiofrequency reactive magnetron sputtering, was accurately determined by Energy Dispersive X-ray Spectroscopy (EDS). CL emission was investigated in the extended visible spectral range from 350 nm to 850 nm. The critical concentration of luminescent activator Er3+ above which CL quenching occurs is 1%; the corresponding critical distance between Er3+ ions in A1N0Er(x) is about 1.0 nm. The quenching mechanism is discussed. We discount an exchange-mediated interaction in favour of a multipole-multipole phonon-assisted interaction.

NiO thin films with random, fiber and in-plane textures have been successfully deposited at near room temperature by reactive magnetron sputtering on glass, silicon and Al2O3 (0001) substrates. Self-texture related with the deposition conditions and crystallographic characters competes with the driving force from the matched substrate. Such a competition can be used to control the texture of thin films on matched substrates, especially when the promoting orientations from self-texture and substrate are different. Enhancing this competition tends to suppress the self-texture of NiO thin films on Al2O3 (0001) substrates, whereas restricting the competition is beneficial to produce the in-plane textured NiO thin films. In addition, it is found that the optical transmittance of NiO thin films on Al2O3 (0001) substrates can also be tuned by such competition. Interfacial microstructure analyses of NiO thin films on amorphous substrates clearly evidence the existence a nanocomposite layer at the initial growth, which is composed of NiO nanocrystals surrounded by amorphous matrix. In contrast, in-plane textured NiO thin films on Al2O3 (0001) substrates exhibit sharp interface without nanocrystals or amorphous matrix. We believe these results provide a general framework of tuning the textures and properties of thin films on matched substrates.

The paper examines experimentally and theoretically the virtual origin position of a fire plume in the so-called simultaneous filling and emptying box problem. Small-scale experiments are carried out with a pool fire placed into a rectangular box with an opening vent located at the ceiling. At steady state, a balance is achieved between the smoke mass flow rate supplied by the fire plume and the mass flow rate of smoke that escapes through the ceiling vent. A theoretical model for the simultaneous filling and emptying of a box is proposed, to predict the thickness and the temperature of the smoke layer. The model involves the conservation of mass and energy for the smoke layer as well as the calculation of the heat transfer through the walls. The characteristics of the fire plume at the layer interface are evaluated using the self-similar solutions including a correction of the virtual origin position. A new correction is suggested for the virtual origin position. The comparison of the model including the new virtual origin correction with the experimental data shows a good agreement.

Zinc tin nitride (ZnSnN2) thin films have been deposited on glass and silicon substrates using a reactive co-sputtering process. Although the deposition temperature was limited to the room temperature, the films show a highly crystallization level and a strong preferred orientation in the [001] direction. The film composition, measured using energy dispersive X-ray spectroscopy and electron probe microanalysis, indicates a possible tin understoichiometry (or a zinc and a nitrogen overstoichiometry). As confirmed by transmission electron microscopy, the main oxygen contamination of the films results from oxidation of the grains boundaries after air exposure of the samples. X-ray photoelectron spectroscopy and Mossbauer spectrometry have been used to determine the chemical environment of atoms in the ZnSnN2 crystals. Both methods confirm that Sn4+ ions are bonded to nitrogen atoms and that the oxygen contamination results in the formation of Sn2+ ions. Zinc tin nitride exhibit an electron mobility at room temperature close to 3.8 cm(2) V-1 s(-1) and an optical band gap of 1.8 eV as measured independently from UV-visible spectrometry and ellipsometry. The results obtained in the present study confirm the suitability of ZnSnN2 thin films as an Earth abundant material for absorber layer in photovoltaic devices.