Bulletin of Materials Science最新文献

Graphene oxide (GO), as a 2D membrane, exhibits outstanding molecular sieving properties for gas separation. The gas permeation mechanism in GO sheets is quite different from that of traditional polymer membranes due to their multilayer nature. It is still a challenge to directly and accurately measure gas diffusion coefficients in ultrathin multilayer membranes. In this work, we applied a well-proven experimental method to determine the diffusivities for H₂, He, CH₄, N₂, O₂, Ar and CO₂. Unlike polymer membranes, the diffusivity for all gases in 2D membranes depends exponentially on the path length and diffusing time. This study is important for both characterizing and standardizing the gas transport properties of thin GO sheets, designing novel membranes based on carbon materials, and for gas mixture separation or toxic gas removal processes. Some applications of the present investigation are discussed.

Graphical abstract

In the present work, solid-state reaction is used to disperse the holmium in cobalt ferrite (Co-ferrite) matrix at the Fe-site (CoFe_2–xHo_xO₄) and reported structural, optical, magnetic and dielectric properties with a 0.005 increase of Ho-content from x = 0 to 0.02. The spinel structure is retained for all compounds with Ho-doping. The composition x = 0.005 showed different behaviour, which is assumed to be structural anisotropy. The optical and dielectric behaviour is supported by structural properties due to similar variation for the 0.005 sample and the correlations are reported. The small change in magnetization is supposed as the Ho-substitution at the octahedral site of the spinel structure and the size effects. The Ho-content in Co-ferrite increases the functionality of the material to be applicable in magnetic, optical and electrical devices.

In order to reduce the energy consumption of residential buildings, a comparison of the energy-saving effect between electrochromic (EC) glass, ordinary glass and low-radiation-coated glass (low-E glass) is carried out. An architectural model is established by a software called ‘Ecotect’ in this study. Taking residential buildings in the Jinan area of Shandong province as an example, the energy-saving effect of the three different windows is compared on indoor light and heat environment and comprehensive energy consumption. We have used EC as the test group. It is noted that the duration of indoor annual high and low temperatures is reduced by 61 and 50 h, the duration of annual thermal comfort is increased by 50 h, the average lighting coefficient is increased by 2.03%, and the annual comprehensive energy consumption is reduced by 593.581 kW h⁻¹ when ordinary glass windows are used. What’s more, the duration of indoor annual high and low temperatures is reduced by 20 and 28 h, the duration of annual thermal comfort is increased by 23 h, the average lighting coefficient is increased by 0.81%, and the annual comprehensive energy consumption is reduced by 182.311 kW h⁻¹ when low-E is used. The energy-saving effect of the EC is the best. It is shown that EC can adjust the indoor temperature, increase the indoor thermal comfort time, improve the indoor lighting situation and reduce the comprehensive energy consumption of the building, providing a reference value for the photothermal analysis and energy consumption analysis of residential buildings in the Shandong region.

Ni₃Fe/ZnFe₂O₄/NiFe₂O₄ nanocomposites were synthesized via high-energy mechanical milling to explore the influence of milling duration on their structural and magnetic properties. A comprehensive characterization was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), and vibrating sample magnetometry. XRD analysis confirmed the formation of Ni₃Fe, ZnFe₂O₄ and NiFe₂O₄ phases with a body-centred cubic (bcc) and spinel crystal structure, evolving with increased milling time. Crystallite size decreased from 42.82 nm (1 h) to 16.98 nm (30 h), while lattice strain increased from 0.279 to 0.784%, indicating structural refinement and defect accumulation. SEM and EDS analyses revealed morphological homogenization and elemental distribution consistent with the formation of nanocomposites. Magnetic measurements revealed a strong dependence on milling time. Saturation magnetization (M_s) reached a maximum of 59.7 emu g^–1 after 1 h of milling and decreased to 30.96 emu g^–1 at 30 h due to particle size reduction, spin disorder and phase evolution. In contrast, coercivity (H_c), remanent magnetization (M_r) and squareness ratio (M_r/M_s) increased with milling time, reflecting enhanced magnetic anisotropy and domain wall pinning. These findings demonstrate the critical role of mechanical processing in tuning the structural and magnetic behaviour of Ni₃Fe-based nanocomposites, making them promising candidates for applications in electromagnetic devices, magnetic sensors and soft magnetic components.

The main aim of this study is to develop a new approach for analysis of second-order pressure derivative of bulk modulus (text B^{primeprime}_{0}) by utilizing the values of first-order pressure derivative of bulk modulus B₀ and zero order pressure derivative of bulk modulus B₀. The study of (text B^{primeprime}_{0}) is useful in analysing second-order pressure derivative of bulk modulus EOS, and it is found after applying Tait EOS and Gupta and Gupta (equation of state) EOS. The novelty of this work lies in the analytical expression presented as equation (5), which enables direct estimation of (text B^{primeprime}_{0}) without requiring high-order fitting or complex datasets. The pressure dependent elastic behaviour of nanomaterials also depends on the variation of (V/V₀). The obtained data are used in the numerical simulation of the high pressure compression behaviour of nanomaterials, and are compared with the available experimental data and other equations of states. Moreover, nanomaterials viz., carbon nanotube (individual), Fe-filled MWCNT, Zr_0.1Ti_0.9O₂ and α-Fe (filled nanotube) are used to verify this model and the method demonstrates strong agreement with experimental data, confirming its applicability.

A low-cost and efficient method should be developed to synthesize the stable nickel ferrites NiFe₂O₄ with the inverse spinel crystal structure, which is beneficial for improving product performance and broadening product application prospects. In the primary oxidation roasting process, nickel ferrite NiFe₂O₄ with a magnetization saturation (M_s) of 31.96 emu g^–1 and a coercive force (H_c) of 91.96 Oe was synthesized in an air atmosphere. In the secondary oxidation roasting technology, the synthesized NiFe₂O₄ with a M_s of 40.93 emu g^–1 and a H_c of 149.4 Oe had a BET surface area of 10.58 m² g^–1. The formation mechanism of nickel ferrites could be categorized in the synthesis process of NiFe₂O₄. The nickel ferrite NiFe₂O₄ was classified as an inverse spinel crustal structure. The secondary oxidation roasting process could facilitate the transformation from disordered to ordered structure and normal spinel to inverse spinel in the crystal structure of nickel ferrite NiFe₂O₄.

In this paper, we design a gradient metamaterial with a double resonance mode and measure the near-field radiative heat transfer (NFRHT) properties in 5–40 THz. The metamaterial sample achieves two NFRHT peaks based on the surface plasmon polarization (SPP) and the local surface plasmons (LSP) modes. The amplitudes and resonance positions of these NFRHT peaks are modulated by changing the gradient nanoparticles. We propose a sensing scheme based on this gradient metamaterial samples to reveal the thermal characteristics in the fabric field. The measured results verify the feasibility for expanding the applications of the metamaterials and developing new photoelectric devices.

Surface frictional drag developed by marine vessels utilizes a considerable percentage of fuel for propulsion. Superhydrophobic (SH) surface normally traps a layer of air at the interface and significantly reduces the surface frictional drag. Herein, the efficacy of the SH coating towards the surface drag reduction of the sailing boat is recognized by conducting a facile experiment where the bottom of the model boat is coated with SH additives. AlNiCo nanoparticles and nickel stearate prepared by ball-milling and co-precipitation methods, respectively, are drop-casted layer by layer over the surface of the model boat to impart SH. The fuel efficiency of the SH boat is improved by 51.49% substantiating the reduction in surface drag of the vessel. Further, the trapped air provides extra buoyancy force, enhancing the load-bearing capability of the SH boat by 5.77%.

The multiferroic RMnO₃ (R= Rare earth) are extensively investigated because of their critically important physical properties, as well as their potential applications in spintronics. Due to their magnetocaloric properties, they are also adequate for magnetic refrigeration in the low temperature regime. Most importantly, as refrigerants, they provide an electrical insulation combined with high chemical and mechanical stability. Such critical properties at the basis of the applications mainly depend on the local structure and chemistry. Therefore, the mechanical properties of manganite perovskites RMnO₃ (R=Tb, Dy, Ho and Er) have been studied by atomic simulation using the density-functional theory (DFT) as interatomic potential implemented in the Quantum Espresso code. For each perovskite RMnO₃, the hexagonal (h-RMO) and orthorhombic (o-RMO) crystal structures have been considered, and the bulk modulus (B), the elastic constants (C_ij), the shear’s modulus (G), Young’s modulus (E), the Poisson’s ratio (ν), the Pugh’s ratio (B/G), the universal anisotropy index (A^U), and the Debye temperature (θ_D), have been calculated. As a result, a relation between the plastic behaviour and the crystal structures has been established. The perovskites RMnO₃ tend to be brittle in the hexagonal phase (1.35 ≤ B/G ≤ 1.39) and ductile in the orthorhombic phase (1.85 ≤ B/G ≤ 2.00). The high values of the Young’s modulus, 281 GPa ≤ E ≤ 300 GPa for h-RMO and 237 GPa ≤ E ≤ 251 GPa for o-RMO, indicate that the investigated systems are solid materials. The values of the Poisson’s ratio found between 0.21 and 0.28 reflect their ionic character. The values of the universal anisotropy index, 0.47 ≤ A^U ≤ 0.74 for h-RMO and 0.09 ≤ A^U ≤ 0.15 for o-RMO, indicate that their mechanical anisotropy is higher for h-RMO than o-RMO, and the elastic anisotropy is better for o-RMO than h-RMO.

H atoms in strong O–H...O hydrogen bonds having double-well potential energy contours exhibit interesting dynamic behaviour that depends primarily on the shape of the double-well potential. Effective barrier height and asymmetry between the two wells of the potential are two important criteria determining the shape of double-well potential. The Diabatic state model for hydrogen bonds is utilized here to generate the double-well hydrogen bond potential for the O–H...O hydrogen bonds of some of the well-studied hydrogen-bonded crystalline solids, namely potassium dihydrogen phosphate (KDP), tris-potassium hydrogen bisulphate (TKHS) and urea phosphoric acid (UPA). Change in crystal temperature affects the H atom dynamics uniquely in each of these chosen examples, KDP undergoes a structural phase transition at 122 K with freezing of H atom disorder in its O–H...O bonds, whereas TKHS having O–H...O bonds very similar to that in KDP exhibits no structural phase transition, and H atom disorder in TKHS continues even at very low temperatures up to 5 K, while H atom in O–H...O bonds of UPA exhibits temperature-induced mobile proton behaviour. We attempt here to understand the unique H atom dynamics in each of these crystals on the basis of temperature-induced changes in the shapes of their double-well O–H...O hydrogen bond potentials.