In the course of the last years hexacyanoferrates have been widely studied; even though, the adsorption properties of Zn (II) hexacyanoferrate(II) (labelled here Zn-HII) have not been thoroughly considered. In addition, soft porous crystals, i.e., adsorbents that display structural flexibility have been, as well, extensively studied, however this property has not been reported for Zn (II) hexacyanoferrate(II). In this regard, the key questions addressed here were the synthesis and structural characterization of Zn-HII together with the investigation of their low (up to 1 bar) and high pressure (up to 30 bar) adsorption properties, to found if these materials show structural flexibility. Then, to attain the anticipated goals, structural characterizations were made with: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) and thermo-gravimetric analysis (TGA), simultaneously, with the investigation of the adsorption of carbon dioxide. As a result of the research process we concluded that the Zn-HII displayed Fm3m space group framework. Besides, the carbon dioxide adsorption investigation demonstrated the presence of the framework expansion effect together with an extremely high adsorption heat, properties that could be useful for the use of Zn(II) hexacyanoferrate(II) as an excellent adsorbent. (C) 2016 Elsevier B.V. All rights reserved.

The key questions addressed here were: the structure elucidation and the investigation of the adsorption space and framework expansion effect of a Cu(II) hexacyanoferrate (III) polymorph (labeled Cu-PBA-I). The structural analysis was performed with a broad set of characterization methods. Additionally, a low and high pressure carbon dioxide adsorption investigation was performed, assuming, to comprehend the adsorption experiments, that the adsorbent plus the adsorbed phase were a solid solution. We concluded: that the Cu-PBA-I presented the following composition, K1/4Cu(II)[Fe(III)(CN)6]3/4⋄1/4nH2O, exhibited an antiferromagnetic behavior and displayed a thermally stable I4¯m2 space group lattice in the degassed state. Moreover, the low pressure adsorption study allowed the calculation of the micropore volume, W=0.09cm3/g and the isosteric heat of adsorption, qiso=19kJ/mol; further, the high pressure adsorption data revealed an extremely high adsorption capacity owing to a framework expansion effect. Finally, the DRIFTS spectrum of adsorbed CO2 displayed peaks corresponding to carbon dioxide physically adsorbed and interacting with electron accepting Lewis acid sites. Hence, was produced an excellent adsorbent which combine porosity and anti-ferromagnetism, antagonist properties rarely found together.

The phase transitions and proton transport in BaCe0.95Yb0.05O3-delta perovskite were studied by Raman spectroscopy, X-ray diffraction and synchrotron radiation X-ray diffraction. Proton mobility in this material appears to be intimately associated to the crystal phases of the framework host. Therefore, in the present paper the phase transformations of the BaCe0.95Yb0.05O3-delta perovskite were studied during heating and under hydrogen diffusion. One of the objectives of the present research was to establish the expanse across the phase fields. But, more significantly, the effect of hydrogen diffusion on structure applying a careful structural refining analysis was studied with the help of the Pawley and Rietveld methods. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Mixing 60-70% lead zirconate titanate with 40-30% lead iron tantalate produces a single-phase, low-loss, room-temperature multiferroic with magnetoelectric coupling: (PbZr0.53Ti0.47O3) (1-x)- (PbFe0.5Ta0.5O3)x. The present study combines x-ray scattering, magnetic and polarization hysteresis in both phases, plus a second-order dielectric divergence (to epsilon = 6000 at 475 K for 0.4 PFT; to 4000 at 520 K for 0.3 PFT) for an unambiguous assignment as a C2v-C4v (Pmm2-P4mm) transition. The material exhibits square saturated magnetic hysteresis loops with 0.1 emu/g at 295 K and saturation polarization Pr = 25 μC/cm2, which actually increases (to 40 μC/cm2) in the high-T tetragonal phase, representing an exciting new room temperature oxide multiferroic to compete with BiFeO3. Additional transitions at high temperatures (cubic at T>1300 K) and low temperatures (rhombohedral or monoclinic at T<250 K) are found. These are the lowest-loss room-temperature multiferroics known, which is a great advantage for magnetoelectric devices.

The study of the morphologies of the single walled carbon nanotube (SWCNT), magnetite nanoparticles (MNP), and the composite based on them was carried with combined X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). These techniques together with thermogravimetric analyses (TGA) and diffuse reflectance infrared transform spectroscopy (DRIFTS) confirmed the production of pure single phases, and that the composite material consisted of MNP attached to the outer surface of the SWCNT. The Mössbauer spectroscopy (MS) research showed the presence of a large quantity of Lewis acid sites in the highly dispersed magnetite particles supported on the SWCNT outer surface. The DRIFTS carbon dioxide adsorption study of the composites revealed significant adsorption of carbon dioxide, fundamentally in the Lewis acid sites. Then, the Lewis acid sites were observed to be catalytically active. Further, the electron exchange between the Lewis acid sites and the basic or amphoteric adsorbed molecules could influence the magnetic properties of the magnetite. Consequently, together with this first ever use of MS in the study of Lewis acid sites, this investigation revealed the potential of the composites for catalytic and sensors applications.

A careful structural characterization was carried out to unequivocally determine the structure of the synthesized material. The TGA, DRIFTS and a Pawley fitting of the XRD powder profiles indicate that the hydrated and in situ dehydrated polymorph crystallizes in the orthorhombic space group Pnma. Meanwhile, the CO2 isosteric heat of adsorption appears to be independent of loading with an average value of 30kJ/mol. This translates to a physisorption type interaction, where the adsorption energy corresponding to wall and lateral interactions are mutually compensated to produce, an apparently, homogeneous adsorption energy. The somewhat high adsorption energy is probably due to the confinement of the CO2 molecules in the nitroprusside pores. Statistical Physics and the Dubinin theory for pore volume filling allowed model the CO2 equilibrium adsorption process in Cu-nitroprusside. A DRIFTS test for the adsorbed CO2 displayed a peak at about 2338cm−1 that was assigned to a contribution due to physical adsorption of the molecule. Another peak found at 2362cm−1 evidenced that this molecule interacts with the Cu2+, which appears to act as an electron accepting Lewis acid site. The aim of the present paper is to report a Pnma stable Cu-nitroprusside polymorph obtained by the precipitation method that can adsorb carbon dioxide.

A thorough structural characterization of the synthesized Ni-, Zn-, and Cd-nitroprussides (NPs) with X-ray diffraction (XRD), thermogravimetric analysis, diffuse reflectance infrared Fourier transf...

A functional gradient (FG) layer based on Ni-ZrO2 (3mol% Y2O3) was obtained by spraying diluted organic suspensions with an airbrush. The different layers were sequentially sprayed onto Y-TZP and Ni substrates, in 25 vol.% compositional steps. Afterwards, two ZrO2 bulk pieces as well as ZrO2 and Ni adherents were successfully joined using this type of FG structure as an interlayer. The microstructure and the possible reactions between the ZrO2 and Ni phases were analyzed. The porosity of each layer was evaluated by micro-hardness measurements.

A Ni–ZrO2 (stabilised with 3mol% Y2O3) functionally graded (FG) layer of around 150μm thick was prepared by airbrush spraying of diluted organic suspensions. Five layers including the two pure end compounds were sequentially sprayed onto Y2O3-doped tetragonal zirconia substrates, in 25vol.% compositional steps. Two ZrO2 bulk samples were joined by this FG interlayer when heated in a high-vacuum furnace at temperatures of 1100–1200°C. Neither cracking nor delaminating occurred within the FG interlayer or at the interfaces with the bulk material. For the 1200°C treatment, some reaction at the ZrO2 bulk/Ni interface and also a small amount of nucleation of m-ZrO2 within the interlayer occurred. The porosity in each layer was estimated from microhardness tests.

Joining of hot pressed silicon nitride using three types of stainless steel (AISI 304, 316 and 321) as interlayer was done by diffusion bonding at 1100°C for 120min. An extensive reaction zone of about 7μm was formed in the contact region, where Cr2N, FexSiy and α-Fe were observed, outside that region the austenitic phase with precipitates of chromium nitride was observed. In the Mo-containing stainless steel (AISI 316) formation of Mo3Si was also detected. Moderate strengths were measured by shear testing for these joints.