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Structural properties of Mn-substituted hercynite

Abstract

In this work spinel series with the general formula Fe1-xMnxAl2O4 (where x = 0, 0.3, 0.5 and 0.7) were synthesized and characterized with respect to their structure and microstructure. X-ray diffractometry (XRD) was used to identify the phase composition that revealed a single phase spinel material. Rietveld refinements of the XRD patterns were carried out in order to determine the lattice and oxygen positional parameters of the spinel compounds. Mössbauer effect measurements were performed at room temperature to determine the local chemical environment of the Fe ions, their valences, and degrees of spinels inversion. It was shown that an increase in the Mn content led to a decrease in the ratio of Fe2+ to Fe3+. The results obtained from Mössbauer spectroscopy (MS) were used to establish the chemical formulas of the synthesized spinels. Finally, the microstructure that was observed using scanning electron microscopy (SEM) showed a compact microstructure with an octahedral crystal habit.

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Thermo-Insulation Properties Of Hemp-Based Products

, T. and K. Kajimo-Shakantu. (2014) Potential of Hemp as an alternative sustainable component in building materials in World Sustainable Building 2014 . Barcelona. 5. Benfratello, S., et al., (2013) Thermal and structural properties of a hemp–lime biocomposite. Construction and Building Materials, 48: p. 745-754. 6. Theis, M. and B. Grohe, (2002) Biodegradable lightweight construction boards based on tannin/hexamine bonded hemp shaves. Holz als Roh- und Werkstoff, 60(4): p. 291-296. 7. Heller, K., et al., (2014) Fibres that can be produced

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Magnetic and structural properties of Sc(Fe1−xSix)2 Laves phases studied by Mössbauer spectroscopy and neutron diffraction

Abstract

The aim of the presented paper is to study an influence of replacement of Fe atoms by Si atoms in quasibinary Sc(Fe1− xSix)2 Laves phases on their structural and magnetic properties. Powder X-ray diffraction (XRD) and neutron diffraction (ND) measurements carried out at different temperatures from 4.3 K up to about 700 K revealed that samples were single phase with cubic C15 structure for Si concentration x from 0.05 to 0.20 and hexagonal C14 structure for higher concentration. The results of 57Fe Mössbauer measurements showed that the Sc(Fe1− xSix)2 compounds with x ≤ 0.30 are ferrimagnetic at 4.3 K. At temperature 80 K in the samples with x = 0.20 and 0.30, a magnetic cluster spin-glass state has been observed, as ferrimagnetic long-range order disappears. Such picture was supported by the results of ND measurements carried out at 8 K, which confirmed the lack of long-range order for x above 0.10 and an occurrence of hyperfine field distributions in the corresponding Mössbauer spectra. At room temperature, samples with x ≥ 0.20 became paramagnetic. A substitution of Si atoms for Fe ones leads to a decreasing of mean values of hyperfine magnetic fields in samples under investigation. From the neutron diffraction pattern analysis of Sc(Fe0.90Si0.10)2Fe magnetic moment was determined as to be equal to 1.5 μB at 8 K. Combining this result with a value of hyperfine magnetic field on 57Fe probes, the hyperfine coupling constant A in Sc(Fe0.90Cu0.10)2 phases is estimated at about 11.6 T/μB at 8 K.

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A Structural Model of Reconstituted Tobacco Substantiated by Ultrasonic Interrogation

Abstract

The theoretical model and experimental results, as tabulated in Table 1, lead to the following conclusions concerning the elastic and structural properties of the examined reconstituted tobaccos:

The vehicle of ultrasonic interrogation of reconstituted materials proved to be efficacious. In total, the authors observed the advantages of this mode of experimentation to be:

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A Nanoscale Simulation Study of Elastic Properties of Gaspeite

Abstract

The study of structural and mechanical properties of carbonate rock is an interesting subject in engineering and its different applications. In this paper, the crystal structure of gaspeite (NiCO3) is investigated by carrying out molecular dynamics simulations based on energy minimization technique using an interatomic interaction potential.

At first, we focus on the structural properties of gaspeite mineral. And then, the elastic properties are calculated, including the elastic constants, bulk modulus, shear modulus, the S- and P-wave velocities. In the next part of this paper, the pressure effect will be studied on the structural and elastic properties of NiCO3 at high pressure.

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Identification of Pedestrian Bridge Dynamic Response trough Field Measurements and Numerical Modelling: Case Studies

Abstract

In this work, we develop a technique for performing system identification in typical pedestrian bridges, using routine equipment at a minimal configuration, and for cases where actual structural data are either sparse or absent. To this end, two pedestrian bridges were examined, modelled and finally instrumented so as to record their dynamic response under operational conditions. More specifically, the bridges were numerically modelled using the finite element method (FEM) according to what was deduced to be their current operating status, while rational assumptions were made with respect to uncertain structural properties. Next, results from field testing using a portable accelerometer unit were processed to produce response spectra that were used as input to a structural identification software program, which in turn yielded the excited natural frequencies and mode shapes of the bridges. The low level of discrepancy is given between analytical and experimental results, the latter are used for a final calibration of the numerical models.

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Structural and Textural Characteristics of Selected Copper-Bearing Rocks as One of the Elements Aiding in the Assessment of Gasogeodynamic Hazard

Abstract

The characteristics of copper-bearing rocks that include the structural and textural parameters are an important factor determining a possible gas accumulation in those rocks. In September 2009, in the Rudna copper mine in Poland, an outburst of gases and dolomite occurred. The analysis of the outburst mass showed that one of the main causes of the outburst was the different structural properties such as high porosity and presence of gas in the pores. This paper presents data from the structural analysis of dolomite from the Polkowice-Sieroszowice copper mine and the Rudna copper mine. Seven rock samples from various areas of the mines were tested by the following methods: mercury porosimetry (MIP), low pressure gas adsorption (LPNA), scanning electron microscopy (SEM), computed microtomography (micro-CT). The SEM analyses of the rock samples allowed pores of various sizes and shapes to the observed. The porosity (MIP) of the dolomite changed in the range of 3-15%. The total micro and mesopore volume (LPNA) was from 0.002 cm3/g to 0.005 cm3/g. The macropore volume (MIP) was from 0.01 cm3/g to 0.06 cm3/g and the mean macropore diameter was from 0.09 μm to 0.18 μm. The dolomite samples varied in the surface area (LPNA) (0.7-1.5 m2/g) and the pore distribution. The structure of dolomite determines the possibility of the occurrence of gasogeodynamic phenomena and hence it is urgent that research be conducted into its changeability. To better understand the gasogeodynamic processes in copper-bearing rocks, it is necessary to constantly monitor and analyse in detail those areas that have different structural properties.

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Atomic short-range order in mechanically synthesized iron based Fe-Zn alloys studied by 57Fe Mössbauer spectroscopy

Abstract

Mechanical alloying method was applied to prepare nanocrystalline iron-based Fe1− xZnx solid solutions with x in the range 0.01 ≤ x ≤ 0.05. The structural properties of the materials were investigated with the Mössbauer spectroscopy by measuring the room temperature spectra of 57Fe for as-obtained and annealed samples. The spectra were analyzed in terms of parameters of their components related to unlike surroundings of the iron probes, determined by different numbers of zinc atoms existing in the neighborhood of iron atoms. The obtained results gave clear evidence that after annealing process, the distribution of impurity atoms in the first coordination spheres of 57Fe nuclei is not random and it cannot be described by binomial distribution. The estimated, positive values of the short-range order parameters suggest clustering tendencies of Zn atoms in the Fe-Zn alloys with low zinc concentration. The results were compared with corresponding data derived from Calphad calculation and resulting from the cellular atomic model of alloys by Miedema.

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Broadband spectroscopy for characterization of tissue-like phantom optical properties

;3(6):1399-1403. [4] Flock ST, Jacques LS, Wilson CB, et al. Optical properties of Intralipid: a phantom medium for light propagation studies. Lasers Surg Med. 1992;12(5):510-519. [5] Moffitt T, Chen CY, Prahl AS. Preparation and characterization of polyurethane optical phantoms. J Biomed Opt. 2006;11(4): 041103-10. [6] Lamouche G, Kennedy FB, Kennedy MK, et al. Review of tissue simulating phantoms with controllable optical, mechanical and structural properties for use in optical coherence tomography. Biomed Opt Express. 2012;3(6):1381-1398. [7] Chang RC, Johnson

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Mössbauer spectroscopy study of 60P2O5-40Fe2O3 glass crystallization

glass. Nukleonika , 58 (1), 63–66. 9. Stoch, P., Szczerba, W., Bodnar, W., Ciecińska, M., Stoch, A., & Burkel, E. (2014). Structural properties of iron-phosphate glasses: spectroscopic studies and ab initio simulations. Phys. Chem. Chem. Phys ., 16 , 19917–19927. DOI: 10.1039/C4CP03113J. 10. Millet, J. M., Verley, C., Forissier, M., Bussiere, P., & Verdine, J. C. (1989). Mössbauer spectroscopic study of iron phosphate catalysts used in selective oxidation. Hyperfine Interact ., 46 (1), 619–628. DOI: 10.1007/BF02398251. 11. Khan, F. B., Bharuth-Ram, K

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