Mechanical, thermal and electrical properties of monolayer and bilayer graded Al/SiC/rice husk ash (RHA) composite
Abstract The mechanical, electrical and thermal properties as well as thermal expansion of Al/SiC/RHA (rice husk ash) monolayer and bilayer composite have been studied using the Taguchi method and analysis of variance (ANOVA). The parameter that most significantly affects the modulus of elasticity of Al/SiC/RHA bilayer composites is processing time, with contribution percentages of 68 and 27% calculated from stress-strain graphs and ultrasonic method, respectively. However, the factor which mostly affects bending strength, CTE value and electrical resistivity of composites is process temperature with contribution percentages of 32, 28, and 22%, respectively. The projected values for modulus…
Thermal oxidation of the intermetallic phases Al 8 Mo 3 and AlMo 3
Abstract The thermal oxidation reactions of the intermetallic phases Al8Mo3 and AlMo3 were investigated and analyzed by ex-situ powder-x-ray diffraction (XRD), difference thermal analysis (DTA), thermogravimetry (TGA), and infrared spectroscopy (IR). The initial oxidation reactions in air were found to yield Al2O3 and AlMo3 in the case of Al8Mo3 (Tonset =725 °C), and MoO3 as well as Al8−xMo3 (Tonset =435 °C) for the pure intermetallic phase AlMo3, respectively. Thus, both intermetallic phases are coexisting in an equilibrium within a temperature range of 300 °C under oxidizing conditions. The formation of β-Al2(MoO4)3 followed the second oxidizing process of the respective minority componen…
Enhanced thermoelectric performance of chalcopyrite nanocomposite via co-milling of synthetic and natural minerals
Chalcopyrite CuFeS2 was shown to be a promising thermoelectric material. Considering thermoelectric efficiency, its relatively high and temperature weakly dependent power factor, economic affordability and ecological benignity is counterbalanced by a high lattice thermal conductivity. Thus it is highly desirable to lower the thermal conductivity of chalcopyrite thermoelectric material without deterioration of other thermoelectric characteristics. In our study, we demonstrate that mechanosynthesis followed by appropriate sintering enables to prepare such nanostructured ceramics with a favourable thermoelectric response. Our study shows that mechanosynthesis is a low-cost technological route …
Bilayer graded Al/B4C/rice husk ash composite: Wettability behavior, thermo-mechanical, and electrical properties
In this study, wettability behavior of B4C substrate as well as B4C/crystalline rice husk ash and B4C/amorphous rice husk ash substrates with two aluminum alloys were studied. The electrical resistivity, thermal expansion coefficients, and thermal diffusivity of bilayer Al/B4C/rice husk ash composite fabricated by one-step pressureless infiltration were measured and the obtained data were systemically analyzed using the Taguchi method and analysis of variance. Boron carbide substrates after addition of amorphous or crystalline rice husk ash display good wettability with molten aluminum alloys. The results show that, electrical resistivity of Al/B4C/rice husk ash composites is mainly influe…
Phase Trapping in Multistep Spin Crossover Compound
The dimeric motif is the smallest unit for two interacting spin centers allowing for systematic investigations of cooperative interactions. As spin transition compounds, dinuclear complexes are of particular interest, since they potentially reveal a two-step spin crossover (SCO), switching between the high spin-high spin [HS-HS], the high spin-low spin [HS-LS], and the low spin-low spin [LS-LS] states. Herein, we report the synthesis and characterization of six dinuclear iron(II) complexes [FeII2(μ2-L1)2](BF4)4 (C1), [FeII2(μ2-L1)2](ClO4)4 (C2), [FeII2(μ2-L1)2](F3CSO3)4 (C3), [FeII2(μ2-L2)2](BF4)4 (C4), [FeII2(μ2-L2)2](BF4)4 (C5), and [FeII2(μ2-L2)2](BF4)4 (C6), based on the 1,3,4-thiadiazo…
Hydrothermal Synthesis, Crystal Structure, and Magnetism of Na 2 [Ir(OH) 6 ] and its Dehydration to Na 2 IrO 3
Electrical and thermomechanical properties of CVI- Si3N4 porous rice husk ash infiltrated by Al-Mg-Si alloys
Abstract The effect of following processing parameters on the electrical and thermomechanical properties of Al/Si3N4 deposited silica composites was investigated using the Taguchi method and analysis of variance (ANOVA): infiltration temperature and time, atmosphere, effect of Si3N4 coating, porosity content in the preforms, and magnesium content in the alloy. The contributions of each of the parameters to modulus of elasticity, electrical resistivity, coefficient of thermal expansion (CTE), and thermal diffusivity of the resulting composites were determined. The maximum modulus of elasticity and electrical resistivity of obtained composites were 265 GPa, and 1.37 × 10−3 Ω m, respectively. …
Iron Oxide Superparticles with Enhanced MRI Performance by Solution Phase Epitaxial Growth
Organized three-dimensional (3D) nanomaterial architectures are promising candidates for applications in optoelectronics, catalysis, or theranostics owing to their anisotropy and advanced structural features that allow tailoring their physical and chemical properties. The synthesis of such complex but well-organized nanomaterials is difficult because the interplay of interfacial strain and facet-specific reactivity must be considered. Especially the magnetic anisotropy with controlled size and morphology plays a decisive role for applications like magnetic resonance imaging (MRI) and advanced data storage. We present a solution phase seed mediated synthesis of colloidal, well dispersible ir…
Second-order Raman scattering in CuO
Polarized second-order Raman scattering spectra of CuO single crystals are reported. It is shown that for some scattering geometries the second-order processes dominate the inelastic light scattering spectra. Group-theoretical symmetry analysis of the selection rules for the first- and second-order scattering processes is performed and phonon dispersion relations are calculated within density functional theory. The main spectral features of the two-phonon spectra are assigned to overtones of the vibrational branches at various special points across the Brillouin zone.
Magnetic Resonance Study of the Spin-1/2 Quantum Magnet BaAg2Cu[VO4]2
Abstract BaAg2Cu[VO4]2 contains Cu(II) S=1/2 ions on a distorted two-dimensional triangular lattice interconnected via non-magnetic [VO4] entities. DFT band structure calculations, quantum Monte-Carlo simulations, and high-field magnetization measurements show that the magnetism of this compound is determined by a superposition of ferromagnetic (FM) and antiferromagnetic (AFM) uniform spin-1/2 chains with nearest neighbor exchange couplings of J FM=−19 K and J AFM=9.5 K (A. Tsirlin, A. Möller, B. Lorenz, Y. Skourski, H. Rosner, Phys. Rev. B 85 (2012) 014401). Here we report the study of BaAg2Cu[VO4]2 by high-field/frequency electron spin resonance (HF-ESR) and nuclear magnetic resonance (NM…
From Single Molecules to Nanostructured Functional Materials: Formation of a Magnetic Foam Catalyzed by Pd@FexO Heterodimers
Multicomponent nanostructures containing purely organic or inorganic as well as hybrid organic–inorganic components connected through a solid interface are, unlike conventional spherical particles, able to combine different or even incompatible properties within a single entity. They are multifunctional and resemble molecular amphiphiles, like surfactants or block copolymers, which makes them attractive for the self-assembly of complex structures, drug delivery, bioimaging, or catalysis. We have synthesized Pd@FexO heterodimer nanoparticles (NPs) to fabricate a macroporous, hydrophobic, magnetically active, three-dimensional (3D), and template-free hybrid foam capable of repeatedly separati…
The surface chemistry of iron oxide nanocrystals: surface reduction of γ-Fe2O3 to Fe3O4 by redox-active catechol surface ligands
The effect of surface functionalization on the structural and magnetic properties of catechol-functionalized iron oxide magnetic (γ-Fe2O3) nanocrystals was investigated. γ-Fe2O3 nanocrystals (NCs) were synthesized from iron acetyl acetonate in phenyl ether with 1,2-tetradecanediol, oleic acid, and oleylamine. X-ray powder diffraction in combination with Mossbauer spectroscopy revealed the presence of γ-Fe2O3 (maghemite) particles only. Replacement of oleic acid (OA) with catechol-type 3,4-dihydroxyhydrocinnamic acid (DHCA) or polydentate polydopamine acrylate (PDAm) surface ligands leads to a pronounced change of the magnetic behavior of the γ-Fe2O3 nanocrystals and separated them into two …
Determining Magnetite/Maghemite Composition and Core–Shell Nanostructure from Magnetization Curve for Iron Oxide Nanoparticles
Iron oxide magnetic nanoparticles produced by chemical synthesis are usually composed of both magnetite and maghemite phases. Information about the phase composition is typically obtained using Mos...
Synthesis, crystal structures, magnetic properties, and lattice dynamics of Ba2XCu(OH)[V2O7] with X=Cl, Br
Abstract We have synthesized Ba2XCu(OH)[V2O7] with X=Cl, Br by hydrothermal methods. The isotypic structures (Pnma, Z=4, a≈15.1 A, b≈6.1 A, c≈9.6 A) contain distorted hexagonal layers of Ba and X in a BN-type arrangement. Each halide is further coordinated by one out-of plane Ba atom in an alternate up-down fashion resulting in an overall Ba 2 X 3 + ∞ 2 structural feature. The planar Ba–X hexagonal rings are centered by divanadate groups in an eclipsed orientation. Edge-sharing chains of CuO 2/2 (OH) 2/2 O 2/1 5 - ∞ 1 complement the structure. The magnetic properties are associated with the magnetic Cu2+ ions and can be described as an antiferromagnetic quasi 1D S=1/2 Heisenberg system. Co…
Pd@Fe2O3 Superparticles with Enhanced Peroxidase Activity by Solution Phase Epitaxial Growth
Compared to conventional deposition techniques for the epitaxial growth of metal oxide structures on a bulk metal substrate, wet-chemical synthesis based on a dispersible template offers advantages such as low cost, high throughput, and the capability to prepare metal/metal oxide nanostructures with controllable size and morphology. However, the synthesis of such organized multicomponent architectures is difficult because the size and morphology of the components are dictated by the interplay of interfacial strain and facet-specific reactivity. Here we show that solution-processable two-dimensional Pd nanotetrahedra and nanoplates can be used to direct the epitaxial growth of γ-Fe2O3 nanoro…
FeMoO4 Revisited: Crosslike 90° Noncollinear Antiferromagnetic Structure Caused by Dzyaloshinskii–Moriya Interaction
The ground state of Fe2+ (S = 2) in α- and β-FeMoO4 is investigated by experiments including X-ray diffraction, Raman scattering, and 57Fe–Mossbauer spectroscopy below 300 K and evaluated by theore...
Reactivity and Structural Defects in Glaserite-Type Iron-Vanadates
CCDC 1949845: Experimental Crystal Structure Determination
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CCDC 1949842: Experimental Crystal Structure Determination
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CCDC 1959867: Experimental Crystal Structure Determination
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CCDC 1949843: Experimental Crystal Structure Determination
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CCDC 1959865: Experimental Crystal Structure Determination
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CCDC 1949841: Experimental Crystal Structure Determination
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CSD 2047359: Experimental Crystal Structure Determination
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CCDC 1959866: Experimental Crystal Structure Determination
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CCDC 1959864: Experimental Crystal Structure Determination
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CCDC 1949844: Experimental Crystal Structure Determination
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