This paper presents a unified view on applied nanomaterials that have been developed for a group of organic optoelectronic devices such as Organic Light-Emitting Diodes (OLEDs), Solar Cells (OSCs) and Gas Sensors (OGSs). From recent references, included our unpublished one, it has been demonstrated that nanostructured particles of metals, semiconductors, and oxides in conducting polymers embedded in conducting polymers have significantly contributed to improving both the performance parameters and working time of devices. The presence of inorganic nanoparticles in polymeric matrices has strongly influenced all physical properties of the polymers. However, herein the most interesting properties of OLEDs, OSCs, and OGSs are of electro-luminescence, photo-electrical conversion, and gas sensing, respectively. A publication has been seen regarding the nanostructured materials used for the fabrication of nanocomposite devices which aim at different practical purposes.

Screening of surfaces that spontaneously reconstruct is important when investigating realistic surfaces. Evaluating the surface energy after macroscopic reconstruction to form pairs of facets is a very fast procedure to identify surfaces that spontaneously reconstruct. This paper discusses a method to identify orientations of pairs of facets that can form on an arbitrary crystal orientation, which can then be used to derive the surface energy after facet reconstruction. Another use of the algorithm is to find possible orientations of terrace surfaces when the vicinal surface orientation is known for a surface with step edges. The algorithm is expected to further accelerate high-throughput calculations of surface properties.

First-principles calculations were performed to investigate the effect of Fe substitution on the structural transformation of (Mn,Fe)CoGe and Mn(Co,Fe)Ge. The activation energy (barrier) between orthorhombic and hexagonal structures was estimated from the total energy of each of several virtual structures between them.Fe substitution reduces the activation energy, and movements of both of Co and Mn are closely related to the reduction. Moreover, the calculation result for the Fe substitution at the sites of both Mn and Co indicates that Fe atoms randomly occupy Mn and Co sites.

The low-dimensional III-V semiconductors are interesting candidate materials for the tailoring of two dimensional (2D) layered structures. We have performed the first-principles calculations on the structural, electronic, and mechanical properties of few-layer gallium nitride (GaN) nanosheet, formed from various bulk phases and stacking patterns, to investigate the effects of structural modification and sheet thickness on their structural, electronic, and mechanical properties. We observed that with the thickness increases, few-layer GaN nanosheets have suffered from the size-induced transition from indirect semiconductor to metallic as well as from the graphitic – planar honeycomb to the wurtzite buckled 2D form. Optimized geometries, binding energy, phonon spectra, electronic band structure, and elastic tensor calculation has ensured the dynamical and mechanical stability of the sheet. Our study indicates that there are two competing mechanisms that govern the polarity compensation with the sheet’s net dipole served as an important parameter for determining the sheet’s stable formation.

Based on the Full potential linearized augmented plane wave (FLAPW) method, the electronic properties of incommensurate anti-ferromagnetic Sr₄V₂O₆Fe₂As₂ with wave vector q = (0, 0, 0.306) have been investigated. Comparing total energy between those of non-magnetic and incommensurate anti-ferromagnetic states (i-AF) we suggest that the i-AF is the stable configuration in this superconductor. The density of states data exhibit strong spin-polarized effect on the V site and possible hybridization between V-3d and Fe-3d orbitals. We found as many as six bands crossing the Fermi level, indicating strong inter-band scattering. The analysis of Fermi surfaces reveals a multi-sheet character, which is compiled of several hole-type cylinders around the center and electron-type sheets at the corners of the Brillouin zone.

In this work, we investigated the adsorption mechanism of acetone and toluene on the surface of single-vacancy silicene by Density Functional Theory method with taking into account the van der Waals interaction via the optPBE-vdW functional. The potential energy surface and adsorption energy profile are obtained by using the Computational DFT–based Nanoscope tool. It is found that acetone prefers an inclined configuration while toluene favors the parallel one towards the substrate. The single-vacancy silicene maintains its metallic electronic structure after adsorption. The adsorption energies for acetone and toluene adsorptions are −0.36 eV and −0.57 eV, respectively. The Bader charge analysis shows a charge transfer of 0.17e and 0.30e for adsorption of acetone and toluene on silicene, respectively.

DNA has proven to be a promising material in fabrication and construction of complex structures with precise controlled nanoscale features. Most of the systems involving DNA are functioned in an aqueous solution where DNA molecules are strongly negatively charged. Therefore, understanding electrostatics of DNA system is essential for better understanding and design of DNA as a biomaterial and as a biological structure. In this work, the mean-field Poisson-Boltzmann equation for the distribution of mobile ions in a two-dimensional hexagonal lattice of DNA cylinders is solved numerically using finite element method. The weak formulation of the Poisson-Boltzmann equation is derived. The equation is then solved numerically using FreeFem++ scripting language. Our results show that the excess counterions of DNA dominate over the bulk ion concentration for the physiological salt concentration considered, and they condense on the DNA surface leading to very high charge density. The results also demonstrate the strong influence of the entropic confinement of the ions when the distance between neighboring DNA is smaller than 10 nm. This effect cannot be ignored in this case, and should be taken into account in any electrostatic investigation of DNA system.

We propose a new algorithm for numerical evaluation of x-ray absorption spectra based on the Green's function formalism in this paper. The method stands on the reduced-shifted conjugate-gradient (RSCG) method, which enables us to obtain the Green's functions with different energy-shifts simultaneously. The seed switching technique is combined into the RSCG method to improve the numerical accuracy and robustness of the algorithm, which we refer to the RSCG-SS method. The RSCG-SS method is applied for calculations of x-ray absorption spectra at the L_2,3-edges of transition metals in simple oxides as a benchmark. The theoretical spectra obtained by the new algorithms are identical to those obtained by the full-diagonalization method following the Fermi's golden rule. The RSCG-SS method can also be applied for the calculation of spectra with a sizable Hamiltonian matrix (∼300,000) with reasonable computational costs.

The Hall effect in an one-dimensional cylindrical quantum wire (CQW) with an infinite potential is studied by using the quantum kinetic equation under the influence a strong electromagnetic wave within the mechanising of scattering on confined acoustic phonons. We consider a case where an one-dimensional CQW is placed in a magnetic field , a constant–electric field and a strong electromagnetic wave (where E₀ and Ω are the amplitude and the frequency of the strong electromagnetic wave, respectively). Analytical expressions for the Hall conductivity tensors and the Hall coefficient (HC) are obtained. It is found that the Hall conductivity tensors and the Hall coefficient depend on the frequency Ω and the amplitude E₀ of the strong electromagnetic wave, the magnetic field B, the temperature T the system, the radius of CQW, and the quantum indies m₁ and m₂ characterizing the phonon confinement. These are different from the case of normal bulk semiconductor and from the case of cylindrical quantum wire with electron–unconfined acoustic phonons scattering mechanism. Numerical calculations are performed using parameters of a GaAs/GaAsAl one-dimensional cylindrical quantum wire. The phonon confinement increase of Hall coefficient by 2.3 times in comparition with the case of unconfined acoustic phonons. When the quantum numbers m₁ and m₂ go to zero, the result is the same as in the case of unconfined phonons. The Hall conductivity tensors (The Shubnikov–de Haas magnetoresistance oscillations) in the case of confined acoustic phonon scattering mechanism and in the presence of a strong electromagnetic wave have more resonance peaks.

The magnetization measurements were carried out for polycrystalline Au₄V in magnetic fields up to 130 kOe. The spontaneous magnetic moment p_s was determined to be 0.255 μ_B/V at 4 K by high field magnetization. The magnetization process was analyzed on the basis of Takahashi’s spin fluctuation theory for weak itinerant electron ferromagnets. The characteristic parameters of the spin fluctuation were estimated to be T_A = 1.3 × 10³ K and T₀ = 2.3 × 10³ K using the data for 110–130 kOe.

Pressure effects on magnetic susceptibility χ and energy gap E_g⁰ of narrow-gap semiconductor FeSb₂ were investigated for the temperature range of 50–300 K and pressures up to 13 kbar. The estimated E_g⁰ for ambient pressure, E_g0(0), was 29 meV. By application of pressure, χ was suppressed, and E_g0(P) was estimated to be 52 meV for 13 kbar. The fourth-order expansion coefficient γ of the free energy in magnetization was positive and enhanced by applying pressures.

This study presents results on crystal structure and phase transition in La_1−yCe_yFe_11.44Si_1.56 (y = 0.1 and 0.3) compounds. All the samples were prepared by using arc-melting method in argon atmosphere. The effect of temperature was studied by X-ray diffraction method. As shown, the compounds possess clear NaZn₁₃-type cubic phase with ferromagnetic spin arrangement of Fe atoms. There reveals a sudden change of lattice constants at 195 K (y = 0.1) and 175 K (y = 0.3) which corresponds to type 1 phase transition.

We have studied the magnetoresistance of an enhanced-biased spin valve device under high pressure. The magnetoresistance decreases by 0.0014 up to 2 GPa with increasing pressure, which is inferred to be due to slight deviation from an antiparallel-spin configuration of the free and pinned layers. In the pressure range between 2 and 2.75 GPa, the exchange bias field generated in the pinned layer decreases and the coercivity of the free layers clearly increases by ∼5 Oe, which is likely to be related to less hydrostatic pressure.

Nitrogenation of Sm₂Fe₁₇ powder was performed under a zero field and a magnetic field of 5 T at 623, 673 and 743 K to clarify the magnetic field effect on nitrogenation. Applying a magnetic field of 5 T induced nitrogenation compared with zero-field nitrogenation, and almost fully nitride Sm₂Fe₁₇N_2.9 was obtained at 743 K. Mössbauer spectroscopy results suggested that a 5-T magnetic field promoted the phase transformation to the fully-nitride Sm₂Fe₁₇N₃ phase. The magnetic field effect was discussed based on the magnetic energy gain and magnetic properties of host Sm₂Fe₁₇ and fully nitride Sm₂Fe₁₇N₃.

The spin reorientation and Curie temperature of Mn_2−xFe_xSb_1−ySn_y (0 ≤ x, y ≤ 0.15) compound were investigated by magnetization measurements. Spin reorientation temperature increased from 255 K at x = 0 to 383 K at x = 0.15, whereas it almost unchanged by Sn substitution. Curie temperature decreased down to 518 K with both Fe and Sn substitution. Substitution of Fe stabilized the ferrimagnetic state with magnetic moment lying in c-plane. Substitution of Sn induced the antiferromagnetic phase at low temperature. It was found that the magnetic hysteresis derived from quasi first-order magnetic phase transition exhibited at x ≥ 0.10 or T ≥ 300 K.

Low field magneto-caloric response is important for application. We present here the results of a study on crystal structure and magnetic properties of rare-earth doped compounds La_0.8R_0.2(Fe_0.88Si_0.12)₁₃ (R = Y, Ho and Yb). All samples were prepared by using arc-melting method in argon atmosphere. The lattices revealed by X-ray diffraction method show a well-defined NaZn₁₃-type structure with small amounts of α-Fe phase. The dependence of magnetization on temperature M(T) and on field M(H) curves were recorded. The magnetic entropy change −ΔS_m and cooling powers (RCP) of compounds were estimated. The results show considerable better magneto-caloric responses of doped compounds in comparison with that of the undoped compound.

Crystal structures of double perovskite cobalt oxide PrBaCo₂O_6−δ with a wide range of oxygen deficiency content δ (0 ≤ δ ≤ 0.85) have been analyzed by using Rietveld refinement of synchrotron X-ray powder diffraction data. The bond valence sum calculation indicates a monotonic reduction in Co valence with increasing δ. The atomic position of Co ion shifts toward the apical oxygen with whole occupation with increasing δ, together with the gradual decrease in the occupancy for the opposite apical oxygen with partial deficiency. This finding indicates that the local structure around Co ions as catalytically active sites is significantly varied by oxygen deficiency.

We studied magnetotransport property for the layered cobalt oxide BaCo₆O₁₁, which was recently reported as a novel compound with isostructure of magnetoplumbite-derived oxide of SrCo₆O₁₁. A polycrystalline sample of BaCo₆O₁₁ exhibits metallic behavior in the electrical resistivity below the ferromagnetic transition temperature of 11.5 K. A tunneling-type magnetoresistance up to −20% was observed at 11.5 K and 90 kOe. These observations propose a half-metallic electronic state for BaCo₆O₁₁.

Electrochemical water splitting is a useful way for sustainable hydrogen production, whereas sluggish kinetics of oxygen/hydrogen evolution reactions (OER/HER) limits the efficiency; thus, active electrocatalysts to reduce overpotentials are desired. Mixing of multiple transition-metal elements is a promising way to enhance electrochemical catalysis. In the present study, we investigated the OER and HER catalytic activities of tetravalent Fe–Co mixed perovskite oxide CaFe_0.5Co_0.5O₃. CaFe_0.5Co_0.5O₃ demonstrated a higher OER activity than those of the parent compounds CaFeO₃ and CaCoO₃. In contrast, the HER activity of CaFe_0.5Co_0.5O₃ was not significantly enhanced. These observations suggest that the mixing of Fe⁴⁺ and Co⁴⁺ ions is an efficient way to activate OER.

Thermal barrier coatings (TBCs) are necessary to protect nickel-based alloy blades of gas turbine against oxidation and thermal fatigue in high-temperature operating conditions. Ceramic materials, which are very good natural thermal insulator, attract the most interests from engineers and scientists. However, the brittleness of ceramics is a major obstacle for utilizing them as the TBCs, which are also required very good damage tolerance against physical impacts. The cracks appear on the blade surfaces during its operation can lead to the severe failure. In this research, a composite of Y₂Ti₂O₇ and Ni was developed as a self-crack healing material to overcome this problem. The crack-healing behavior is investigated by using Vickers indenter to create cracks on the composite surface intentionally, followed by annealing in an oxidizing environment. It is found that the main crack-healing mechanism is the filling of NiO, which was formed from the oxidation of the Ni fillers, into the cracks. Complete heal of cracks is achieved with 10 vol% Ni filler, which is confirmed by X-ray diffraction and scanning electron microscopy. Thermal conductivity and Weibull distribution for the strength of the composite were also investigated to find the appropriate volume fraction of Ni nanoparticles in this self-healing material.

(La_0.7Sr_0.3Mn_0.98Co_0.02O₃)_1−x(BaTiO₃)_x (x = 0.1; 0.2; 0.3) mixed perovskite were prepared by the solid state reaction method. It is shown that this compound exposes the multiferroic (magnetic and ferroelectric) behavior comparing with magnetic pristine La_0.7Sr_0.3Mn_0.98Co_0.02O₃. The increase of BaTiO₃ fraction from x = 0.1 to 0.3 leads to weakening (enhancing) of the ferromagnetic (ferroelectric) order. The metal-insulator transition (MIT) in the ferromagnetic La_0.7Sr_0.3Mn_0.98Co_0.02O₃ (x = 0) and the multiferroic x = 0.1, 0.2 samples were registered with reduction of the MIT temperature T_MI from 380 K of the x = 0 to 117 K of the x = 0.2 samples. Temperature dependence of resistivity and MIT of these samples are well described by the mixed conducting carrier model, which has crossover between the low temperature spin-scattering electron and the hopping small polarons conductions at T_MI.

The catalytic activity on the oxygen evolution reaction (OER) was investigated for Fe³⁺-containing oxides with various crystal structures: spinel ZnFe₂O₄, post-spinel CaFe₂O₄, and stuffed-tridymite BaFe₂O₄. The latter two oxides exhibited higher catalytic activity than ZnFe₂O₄, indicating that the differences in the coordination polyhedra and their connections are important factors to affect OER activity.

In this research, short bamboo fiber (BF) has been used as filler in the fabrication of the composite based on polyamide 11 (PA11) by melt-mixing method. In order to improve the compatibility between BF and PA11, maleic anhydride grafted ethylene vinyl acetate copolymer (EVAgMA) was introduced into the composite preparation process. The effect of EVAgMA contents on mechanical, thermal or weathering resistant properties of the composites was investigated. In the presence of the EVAgMA, the tensile strength, impact strength and flexural modulus of composites showed the improvement in comparison to without compatibilizer. Differential scanning calorimetry (DSC) analysis indicated that the melting temperature of composites did not depend on the EVAgMA contents, while its fusion heat (ΔHm) decreased with increasing EVAgMA contents. Dynamic mechanical thermal analysis (DMTA) evaluated the role of EVAgMA on the enhancement of composites’s storage modulus (G′) in the glassy plateau and the interaction between BF and PA11 matrix. After 840 hours of accelerated weathering test, the composites using EVAgMA were decomposed faster than that of neat PA11 and PA11/BF composite. This result was also agreed with the observation of scanning electronic microscopy (SEM) images and the change of carbonyl index (CI). However, the retention of tensile properties of PA11/EVAgMA/BF composites is higher than that of PA11/BF composite.

In our work, MoS₂/graphene/MOF hybrid materials were synthesized via a two-step process consisting of the plasma-assisted electrochemical preparation of MoS₂/graphene and the wet formation of Cu-based metal-organic framework (MOF). The hybrid materials were characterized with Field Emission Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, X-ray Diffraction and Raman Spectroscopy. Furthermore, some initial results on their electrochemical properties for hydrogen evolution and oxygen evolution reactions were also presented, showing the potential to be a bi-functional catalyst.

Multiwalled carbon nanotubes (CNTs) were modified with the Hummers method and coated onto Pt electrodes patterned on SiO₂/Si(001) surface to fabricate chemical sensors. The modified CNTs showed a different structure and increased number of defects compared with pristine CNTs, these properties facilitated the adsorption of NH₃ gas molecules on the CNT surfaces. NH₃ gas sensing results indicate that the sensor exhibited an enhanced response to gas at room temperature. The response of the modified CNT-based sensor was 10 times higher than that of pristine CNT-based sensors.

In this study, natural rubber-based electromagnetic shielding materials for coating application were made. Expanded graphite was prepared using our method and dispersed in the polyaniline/natural rubber matrix. The effect of PAni and expanded graphite on the properties of resulting materials was evaluated. The characterization of properties that are important for an electromagnetic shielding coating (i.e., mechanical properties, electromagnetic shielding, wettability resistance, thermal properties, and the morphology of the material) was investigated. The result shows that the properties of natural rubber/polyaniline blends are enhanced owing to the presence of expanded graphite. The superior properties are achieved when the amount of added expanded graphite in natural rubber/polyaniline is 5 parts per 100 g of natural rubber. The enhancement of properties is attributed to the good dispersion of expanded graphite in the natural rubber/polyaniline matrix, which improves the compatibility of the natural rubber and polyaniline phase.

Every year, trillions of cigarette butts (CB) are discarded all over the world without being recycled, thus causing negative impacts on the ecological environment as well as the health of living species. Cellulose acetate (CA), the main component of cigarette butts, is a valuable polymer for numerous applications. For the first time, by using a cost-effective freeze-drying method in the presence of polyvinyl alcohol (PVA) as a cross-linker, high-value engineering cellulose acetate aerogels were successfully fabricated from CB. The effects of component concentrations on the morphology of the CA aerogels were investigated by changing concentration of CA fibers (1–3.0 wt.%) and PVA (0.1–1.0 wt.%). The CA aerogels exhibited an extremely low density (25.4–45.6 mg/cm³), a high porosity (96.46–98.01%), and a low thermal conductivity (0.034–0.039 W/(m^*K)). The modified CA aerogels also expressed a great capacity of oil absorption (11.82–25.22 g/g). Hence, the CA aerogel is a promising material for future uses in thermal insulation and oil spill treatment.

Carbon nanotubes (CNTs) for field emission applications were grown directly on 304 stainless steel (SS304) by using hot-filament chemical vapour deposition (hot-filament CVD). Vertically-aligned CNTs (VACNTs) with 1.5-millimetre-diameter in shape were successfully grown on the SS304 substrate. We obtained efficient electron emission with turn-on fields as low as 0.66 V/µm, emitting currents of 1.5 mA at an applied field of about 1.5 V/µm. The VACNTs-SS304 emitter also demonstrated high stability in emission current of 860 µA (± 12.5 µA) which even better than that of the VACNTs grown on conventional silicon. This VACNTs-stainless steel is a promising candidate for X-ray tubes that require small, bright, and cold emitters.

MgO nanocrystals with cube, wire and flower shapes were fabricated by thermal evaporation technique in air at atmospheric pressure. Mg powder mixed with graphite powder was used as the source material and no catalyst was used in the synthesis process. The morphology of the MgO nanocrystals was significantly changed from cube shape to wire and then flower-like shape with increasing the mass ratio of graphite to Mg in the source material. This indicates that the mass ratio of Mg/graphite in the source material played a crucial role in the morphological change of MgO nanocrystals. All the MgO crystals had a cubic crystal structure. The cube-shaped MgO crystals exhibited a blue emission centered at 420 nm, whereas the wire and flower-shaped MgO crystals showed an ultraviolet emission at 380 nm.

Eu³⁺ doped La₃PO₇ nanoparticles were successfully synthesized under facial combustion method. The nano-phosphors then were characterized by some techniques including X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), photoluminescence spectrum (PL), and lifetime decay. SEM and TEM micrographs reveal exhibit of the La₃PO₇: Eu³⁺ nanopowders in spherical morphology with an average size of about 20 nm, matching with Scherrer’s formula calculation. Otherwise, the influence of annealing temperature and concentration of Eu³⁺ ions on optical characteristics of Eu³⁺ was doped La₃PO₇, and optical properties were investigated too. The photoluminescence shows the strong red emission originating from the ⁵D₀ → ⁷F_J (J = 1, 2, 3, and 4) transitions of Eu3+ and the 614 nm emission from the ⁵D₀ → ⁷F₂ electronic dipole transition is dominant.

The upconversion luminescence (UCL) of Gd₂O₃: Er³⁺ monodisperse nanospheres, synthesized by multistep chemical method, and nanoparticles, produced by combustion synthesis, are presented for comparison. The UCL of nanospheres Gd₂O₃: Er³⁺ and Gd₂O₃: Er³⁺@Silica have shown strong red or green emission under excitation at 976 nm or 980 nm by a diode laser with a remarkable increase of the bright red color in the nanospheres. In the core/shell structured nanospheres Gd₂O₃: Er³⁺@Silica, we find a higher intensity of upcoversion emission, increased stability and better dispersion capability in solvents and water. The UCL intensities of green and red color while 976 nm or 980 nm excitation were dependent on the diode laser power. The slope values of Er³⁺ ion’s transitions ²H_11/2–⁴I_15/2, ⁴S_3/2–⁴I_15/2 and ⁴F_9/2–⁴I_15/2 in the silica-coated nanospheres are 1.99, 1.62 and 1.66 respectively, which properly indicate the two-photon mechanism of upconversion emission. The synthesized Gd₂O₃ nanospheres codoped with Yb and Er show strong UCL intensity than those of Gd₂O₃: Er³⁺. The obtained Gd₂O₃: Er³⁺ nanospheres and nanoparticles, as well as Gd₂O₃: Yb³⁺, Er³⁺ and its silica-coated versions, are promising materials to develop with potential application in high technology and biomedicine.

In this paper, the Gd₂O₃:Eu³⁺ nanospheres with the ratio Eu³⁺/Gd³⁺ of 6% mol were successfully synthesized by a multi-step chemical method with the mean nanoparticles size of about 200 to 220 nm and a low standard deviation. The morphology, structure and optical behavior of as-synthesized and annealed Gd₂O₃:6%Eu³⁺ samples were investigated by field-emission scanning electron microscopy (FESEM), X-ray diffractions (XRD), and photoluminescence spectroscope (PL) The luminescence lifetime of samples was also investigated and discussed. The biomedical nanocomplexes of Gd₂O₃:6%Eu³⁺ with IgG were fabricated by glutaraldehyde linking after covering nanospheres with amino Silica. The luminescent nanocomplexes Gd₂O₃:6%Eu³⁺@Silica-NH₂-IgG with different concentrations have been incubated with CEA tumor cells to investigate and evaluate the detection capacity by using a fluorescence optical microscopy for the early detection and treatment of cancer.

In this study, a ferroelectric nanocomposite was prepared from triglycine sulfate (TGS) with cellulose nanoparticles (CNP) pretreated at different carbonization temperatures. The results showed that along with the increase in electrical conductivity, the phase transition temperature of TGS decreased significantly with increasing carbonization temperatures due to the partial destruction of interaction between CNP and TGS during cellulose carbonization. The dielectric measurements were performed under a weak electric field (2 V/cm) in the frequency range of 10⁻³–10⁶ Hz. The work provides deeper insights on the influence of dielectric components on the properties of ferroelectrics.

In this paper, a model is developed to identify the microstructure of low-carbon steel by deep learning. In classifying steel microstructures using a machine learning model, predictions are interpreted using local interpretable model-agnostic explanations (LIME) for the first time. The constructed model can accurately distinguish between eight microstructure types, including upper bainite, lower bainite, martensite, and their mixed structures. The model accuracy is 94.1% when individually predicted and 97.9% when predicted by majority vote. In addition, as a result of interpreting the predictions of the model by LIME, it is evident that the recognition criterion of the constructed model is partially consistent with the classic recognition criterion.

In order to investigate the effectiveness of ultrasonic shot peening treatment (USP) as repairing method for SCS6 material with surficial fatigue crack for hydraulic turbine runner, plane bending fatigue tests were carried out for USP treated SCS6 containing a surface fatigue crack with 1 mm in length and the fatigue crack propagation after USP was observed by a plastic replica method. As a result, the fatigue crack propagation life of SCS6 containing a surface fatigue crack was dramatically improved by USP treatment. Furthermore, the initial effective stress intensity factor ranges were calculated in the USP treated and untreated SCS6 containing a surface fatigue crack, respectively. According to the calculation, it was clear that the surficial fatigue crack could be harmless under the condition that the calculated initial effective stress intensity factor range considering the stress opening a fatigue crack, which was acquired by the unloading elastic compliance method, was less than the threshold of effective stress intensity factor range. Therefore, USP treatment is effective for repairing method of SCS6 containing surficial fatigue crack for hydraulic turbine runner. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 68 (2019) 897–903.

The effect of high amounts of sodium on intergranular fracture of Al–5% Mg alloys without and with additional bismuth or indium was studied under different heat treatment conditions. A set of experiments made it evident that the intergranular fracture occurred even at room temperature when the amount of sodium in the Al–5%Mg alloy exceeded 23 ppm under homogenization treatment. On the contrary, Al–5%Mg alloy with large amounts of sodium (23 and 200 ppm) did not show intergranular fracture at 300°C under homogenization treatment. In addition, the Al–5%Mg alloy containing 4 ppm of sodium showed obvious intergranular fracture when the alloy was pre-deformed and subjected to the solution heat treatment. This suggests that the effect of sodium on the intergranular fracture of the Al–Mg alloys varies according to the sodium concentration, heat treatment, and testing temperature. We have also clarified that the room-temperature intergranular fracture caused by 200 ppm of sodium in the Al–5%Mg alloys was suppressed by 0.1%-ordered additional elements such as bismuth or indium. It is presumed that the suppression of the intergranular fracture by the addition of bismuth or indium was caused by the formation of sodium-bearing compounds in the Al–5%Mg alloys, leading to scavenging of sodium from GBs at room temperature.

In this study, a Ti-based bulk metallic glass (BMG) was used to investigate the influence of the addition of Al on mechanical properties and glass forming ability (GFA). The experimental results show that the plastic flow stress value of the alloy will change with the change of strain and strain rate. As the strain rate increases, the plastic flow stress value increases. The fracture surface of the specimens can be observed through a scanning electron microscope. It can be seen that the fracture surface has the characteristics of a dimple-like structure. The appearance, distribution density, and grain density of the vein-like structure depend on the strain rate and the addition of the Al element.

Friction stir processing (FSP) is a solid state method for surface modifications through severe plastic deformation and frictional heat using a rotational tool. Reducing the heat input of FSP should improve the mechanical properties of the stir zone. This study investigated a low-heat-input FSP on beads of low carbon steel plates using tungsten inert gas welding. The FSP was controlled by decreasing the rotational speed and increasing the travel speed of the tool. Low-heat-input FSP produced significant grain refinement in the weld microstructure and the associated hardness increased at the stir zone surface. The estimated improvement ratio of fatigue strength was twice as large as that produced by the conventional FSP. The fatigue strength in the stir zone at the retreating and advancing sides produced by low-heat-input FSP were independent of the residual stress because the hard stir zone helped prevent fatigue crack initiating at the surface. To improve fatigue strength, increasing the hardness in the stir zone is preferable to decreasing the tensile residual stress associated with the incomplete recovery and recrystallization. Consequently, further grain refinement upon decreasing the FSP heat input can be an effective way to significantly improve the mechanical properties of steel welds.

Three-dimensional printing (3DP) was widely applied in sand mold fabrication. One of the major concerns about sand mold is the mechanical strength which determines such defects as sand cut, sand blister, sand explosion, and expansion of the castings. In this study, the linear regression and the BP neural network were applied to predict the bending strength of 3DP samples. Orthogonal experiments were designed to obtain data for training the prediction models. Three-point bending test was used to characterize the actual bending strength. The results showed that the sample weight, resolution X and layer thickness are significant factors while the activator content, recoater speed and sample location are not significant. The maximum error of linear regression is 11.2%, which is very big. A three-layer BP neural network with 6 input nods, 14 hidden nods and 1 output nod was proposed to predict the bending strength of 3DP samples, and the maximum error is 4.3%, which is lower than that of linear regression. So it is more valuable in practical applications.

Copper electrowinning is important not only for the solvent extraction – electrowinning process (SX-EW), which produces primary copper metal from copper oxide minerals, but also for the copper recycling process, which comprises smelting, leaching, and electrowinning. The electrolyte used in the copper recycling process contains various impurities that are usually negligible in the electrolyte used in the SX-EW process. In this study, the effect of aqueous antimony species on the corrosion of a Pb–Sn–Ca alloy in copper electrowinning was investigated using galvanostatic electrolysis, followed by X-ray diffractometry, scanning electron microscopy – energy dispersive X-ray spectroscopy, and inductively coupled plasma – optical emission spectrometry analyses. The electrolysis was conducted at various current densities in a synthetic copper electrolyte containing H₂SO₄, Cu(II), Ni(II), Co(II), and 0–4.1 mmol·dm⁻³ of Sb(III) at 65°C. When the electrolyte did not contain any antimony species, the anode surface was covered with scale comprised of αPbO₂ and βPbO₂. The PbO₂ scale grew along the grain boundaries, and its growth rate was considerably slow. In contrast, when the electrolysis was conducted in an electrolyte containing Sb(III), scale consisting of Sb₂O₅ and αPbO₂ formed on the anode surface. A laminated Sb₂O₅–αPbO₂ mixture scale was observed on the anode surface, and its growth rate was significantly faster than that of the PbO₂ scale. The flakes of the Sb₂O₅–αPbO₂ mixture scale periodically fell from the anode surface, and consequently, the corrosion of the Pb–Sn–Ca alloy anode was accelerated. The oxidation of Sb(III) to Sb₂O₅ was likely caused by an anode reaction rather than by direct reaction with the oxygen formed on the anode surface. The formation of Sb₂O₅ on the Pb–Sn–Ca alloy resulted in a considerable decrease in aqueous antimony in the copper electrolyte, indicating its effectiveness in enhancing the electrowinning process targeting pure copper cathode production, copper liberation, and antimony removal from the tailing electrolyte in copper electrorefining.

The in-situ orientation of drilled core samples provides valuable information for a broad range of geological and geophysical studies, such as the determination of in-situ principal stress directions or analyses of geological structure. However, the in-situ orientation of core samples is not available in many cases. In this paper, we present a method for restoring the in-situ orientation of drilled whole-round core samples and its application to hemipelagic sedimentary rocks. The method is based on the natural remanent magnetization (NRM) of rocks. As a case study, we apply this method to 15 oceanic sedimentary soft rock samples recovered from the toe of the Nankai Trough off Cape Muroto, SW Japan, during International Ocean Discovery Program Expedition 370.We developed a new sample-preparation procedure that enables more data acquisition and evaluated the NRM measurement results. Some samples could not be reoriented owing to magnetic overprints associated with the drilling operations. To evaluate the magnetic overprints caused by drilling and assess the data quality of the core reorientation by this method, we propose an evaluation system with three ranks defined for different levels by which NRM results are affected by drilling. This evaluation system is also useful for assessing the data quality of core reorientation by the NRM method in other similar applications. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 69 (2020) 256–262.

Flotation of pyrophyllite using the anionic collector (sodium oleate, SO) was examined in this study. The floatability of pyrophyllite was improved by increasing SO concentration (1.0 × 10⁻⁷–1.0 × 10⁻² M). The adsorption of SO on the pyrophyllite surface was confirmed by the zeta potential changes and FT-IR spectrometry. However, due to the high concertation of SO to achieve the higher floatability of pyrophyllite, it was tried to enhance the floatability of pyrophyllite at a low SO concentration. Ammonium ion (ammonium chloride, AC) was introduced to induce the additional interactions in between the pyrophyllite surface and SO. The floatability of pyrophyllite was improved in the presence of AC (0.2–1.0 M) at a low SO concentration (1.0 × 10⁻⁷ M). In the same flotation conditions employing AC and SO, the amounts of the floated quartz which is main gangue mineral in the pyrophyllite ore were smaller than those of pyrophyllite. The adsorption of AC and SO on the pyrophyllite surface was also confirmed by the zeta potential changes and FT-IR spectrometry.

We investigated electroreduction of Ti²⁺ to metallic titanium in the LiCl–KCl–CsCl system, which has a eutectic point at 263 °C. Cyclic voltammetry was carried out in the TiCl₂-saturated LiCl–KCl–CsCl at 300 °C, and the effect of F⁻ addition on the reduction behavior of Ti²⁺ was investigated. It was revealed that addition of F⁻ increases the limiting current density of electrodeposition of titanium at 300–500 °C. This might be mainly attributed to the increase in total concentration of soluble titanium ions in the molten salt. Then, we demonstrated the electrodeposition of metallic titanium in the LiCl–KCl–CsCl with and without F⁻ at 350 °C. After the electrolysis in F⁻-added molten salt and acid leaching, LiF remained on the deposited titanium. This is because the solubility of LiF in aqueous solution is quite low. An efficient method to remove LiF is required when F⁻-added LiCl–KCl–CsCl is used as electrolyte.

In this study, pure Al powder was compression molded on the surface of flame-retardant Mg alloy plate, and integration of pure Al and Mg alloy was attempted by melting and solidification in air. In order to integrate different materials by liquid diffusion of metal elements, the structure, composition phase and hardness of the formed integrated materials were investigated.It was found that heating the specimens for 180 s results in melting and liquid diffusion between Al and Mg. When heated and melted with pure Al down and Mg alloy up (Type B), shrinkage cavity was formed on the former Mg alloy side of the former Al/former Mg alloy interface. When heated at 450 s, the specimen was composed of Al–Mg system stable phases of Al₃Mg₂ and Al₁₂Mg₁₇, and Al–Mg system metastable phases of Al_0.37Mg_0.63 and Al_0.1Mg_0.9. In Type A with pure Al up and Mg alloy down and Type B, stable phases of Al₃Mg₂ and Al₁₂Mg₁₇ were formed on the former Al side. The constituent phase of the former Mg alloy side was composed of metastable phases of Al_0.37Mg_0.63 and Al_0.1Mg_0.9, but the structure morphologies of Type A and B differed near the surface of the former Mg alloy side, and the primary phase was Al_0.37Mg_0.63 and Al_0.1Mg_0.9 respectively. The final solidification phase consisted of eutectic phases of Al_0.37Mg_0.63 and Al_0.1Mg_0.9. The hardness on the former Al side was about 250 HV, and the hardness on the former Mg alloy side had decreased. Type B was evaluated to be lower than Type A. This Paper was Originally Published in Japanese in J. JFS 92 (2020) 69–74.

The ProCAST simulation software is used to simulate the temperature field and the mushy zone of the blade under different blade orientations, and then grain growth was investigated based on them. It is found that the temperature field and the mushy zone of the blade samples in the parallel orientation are stably horizontally distributed at the same height, while the perpendicular orientation has a degree of inclination. In the heat preservation zone, the sample temperature close to the furnace wall is higher than that of the sample temperature near the center (referred to here as the Center-Side), and the temperature field is inclined upwards. However, in the cooling zone, the temperature field is inclined downwards because the temperature near the furnace wall (referred to here as the Wall-Side) is lower than that of the Center-Side. The grain growth of the blades with parallel orientation is superior as single crystal blade castings are formed. The blade samples in a perpendicular orientation have a certain heterocrystal tendency. The grain growth of the mutated cross-section of the blade samples is summarized using variable cross-section samples. Heterocrystals are used to be formed at the edge plate of complex structure, the mutation section and the end of spiral crystal separator.

The effects of Ir addition and coating method on the microstructure and oxidation behavior of Pt–xIr (x = 0–30 at%) diffusion coatings were investigated. A nickel-based single crystal superalloy UCSX-8 was used as a substrate material, while the coatings were developed by either an electroplating or a paste coating method followed by an annealing heat treatment. The phase identification and microstructure analyses by XRD and SEM/EDS revealed that the alloying of Ir in Pt diffusion coating resulted in the formation of L1₀ ordered α-NiPt₂Al structure. Cyclic oxidation tests were carried out at 1423 K in still air in order to investigate the thermal stability and oxidation behavior of the coatings. It was found that Ir can significantly retard the formation of voids in both the coating and substrate. In addition, by replacing electroplating method to the paste coating method, the crack problem due to the brittle feature of electroplated Pt–Ir coatings could be solved. Therefore, the Pt–20Ir diffusion coating prepared by the paste-coating method is promising as the bond-coating material due to formation of less voids, no crack and stable Al₂O₃ on the surface.

The ability of a variety of hydroxyapatite (HAp) sources, including animal bone and calcium phosphate glasses, is demonstrated to immobilize fluorine in slag through calcining processes. The slowly cooled slags were calcined in a furnace along with hydroxyapatite, animal bone, and calcium meta-phosphate glasses. As a result, fluoro-hydroxyapatite was formed, confining the fluorine ions in the formed crystal, leading to the suppression of the dissolution of fluorine ion. Each of the samples demonstrated a low elution of fluorine ions (less than 0.8 ppm), measured by leaching method. The quantity evaluation of formed apatite-like crystal and other subsidiaries were conducted for the treatments by adding recycled animals’ bones as the source of calcium phosphate, as well as reagent HAp and meta calcium phosphate glasses.

C6932 is a lead-free 75.5Cu–3Si–Zn alloy (hereinafter, “C6932”) which is excellent in machinability, strength, corrosion resistance, hot workability, and castability. C6932 is widely used for water-related products and in automobile and electricity fields, and over 40,000 tons of this alloy is distributed world-wide under the brand name of ECOBRASS^®.In the United States, a law to restrict lead in drinking water was put into force across the nation in 2014. Lead is going to be restricted in Europe also in the automobile field as well as electronic and electrical field. Considering this trend, more free-cutting copper alloys are likely to be free of lead. Concurrently, in the automobile field, for instance, there is a higher demand for improved fuel efficiency by reducing component weight and improved reliability by using components of higher strength.Based on these backgrounds, we have developed a lead-free, high-strength free-cutting copper alloy by optimizing the composition of a Cu–Si–Zn alloy and controlling its metallographic structure. The developed alloy shows significantly higher strength compared to C6932 without sacrificing its machinability and ductility. The alloy we have developed is a lead-free, high strength free-cutting copper alloy with tensile strength of 650 MPa and an elongation of 43%, which can be realized by annealing a 76.3Cu–3.2Si–0.2Sn–Zn alloy and controlling the grain size to 8 µm. This Paper was Originally Published in Japanese in J. Japan Inst. Copper 58 (2019) 40–44. Captions of Figures and Tables were slightly modified.

This paper investigates the evolution of microstructure during isothermal aging at 1173 K in the wrought nickel-based superalloy Udimet 520, after being solution-treated at 1393 K for 4 h, followed by various cooling rates. Age-hardening behavior was observed during isothermal aging for water-quenched (WQ) and air-cooled (AC) specimens after the solution treatment, whereas it could not be detected for a furnace-cooled (FC) specimen. No primary γ′ particles were observed in any continuously cooled samples. For the WQ and AC specimens, the size of the secondary γ′ precipitates increased during the isothermal aging along the Ostwald ripening and their morphology evolved from spherical to an intermediate shape between spherical and cuboidal. Conversely, the secondary γ′ particles exhibited an octodendritic shape for the FC specimen, and the octodendritic character of the secondary γ′ particles was emphasized during isothermal aging, resulting in the splitting of the secondary γ′ particles. It was found that the splitting of γ′ particles occurred during the isothermal aging for Alloy 80A with a lower volume fraction of γ′ phase around 20%. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 84 (2020) 11–18.

Effects of size and crystallinity of a quadruple perovskite oxide, CaCu₃Fe₄O₁₂, were investigated for its catalytic activity for the oxygen evolution reaction (OER). Pristine CaCu₃Fe₄O₁₂ powder sample was synthesized under high-pressure and high-temperature conditions of 8 GPa and 1000°C, and a portion was treated by ball milling for 120 min to obtain a powder sample with smaller particle size. The specific surface area significantly increased from 0.38 to 10.30 m²g⁻¹ by ball-milling, leading to increased OER activity. However, it was found that the milling did not improve the OER activity efficiency in proportion to that expected from the increase in specific surface area as determined by Brunauer-Emmett-Teller analysis of adsorption/desorption isotherms measured with nitrogen gas because the crystallinity was lowered by ball milling, which suppressed the catalytic activity. This study provides important information on how to achieve the best OER catalytic performance in terms of both size and crystallinity.