2023 Volume 64 Issue 3 Pages 707-714
Microstructure of the materials is essential to design new functional materials, especially from atomic scale to micron order structures. Many attempts have been carried out to give nanostructures and such structures have been analyzed using cutting-edge methods both theoretically and experimentally. In this report, recent trends in research on functional materials related to the micro-structures in nano-meter scale are reviewed by mainly introducing the contents of the special issue published in Materials Transactions, vol. 61, No. 8, in which following 6 categories of the topics are included; computational materials science, magnetic materials, advanced functional oxides, carbon and organic materials, and optical materials.
Joint international symposium of 5th Frontiers in Materials Science (FMS) and 3rd Nano Materials, Technology and Applications (NANOMATA).
The functional materials, which are fabricated to have desired properties such as magnetic, electric and optical properties, have been extensively studied for some specific applications. The micro-structure of the materials in nanometer or sub-nanometer scale including the crystal structures and atomic arrangement in an atomic scale is essential to determine the physical properties of the functional materials. There are many papers for the functional materials already published not only in Materials Transactions but also in various kinds of international journals such as in materials science, physical chemistry and condensed matter physics. Recent studies on the severe plastic deformation (SPD) for nanomaterials with advanced functionality were collected in a special issue,1) and the historical developments and recent advances in nanomaterials by SPD were summarized as an excellent review paper including 965 references.2) In these years, we have compiled a series of the special issues focusing upon the micro-structure of the materials.
The first special issue in Materials Transactions we organized was published in 2015 as Vol. 56, No. 93) named “Nanostructured Functional Materials and Their Applications”, in which 40 excellent papers mainly selected from the 2nd International Symposium on Nano Materials, Technology and Applications (NANOMATA) held in Hanoi, Vietnam, in November, 2014. This symposium covered a wide area of the materials science, and the special issue was divided into 6 research areas, that are magnetic materials,4–10) functional oxide materials,11–19) nano materials,20–26) optical materials,27–30) soft-matter31–34) and analysis and computational materials science.35–43)
In 2015, the 2nd International Symposium on Frontiers in Materials Science (FMS) was held in Tokyo, Japan, in November, which covered wide area of the materials science researches. Selected papers on the cutting-edge studies related to the nanostructured functional materials were published in a special section named “cutting-edge physics in functional materials” in Journal of Applied Physics (JAP),44) which includes 26 excellent works45–70) on the topics such as THz magnetism and spintronics, magnetism in structures and materials, first-principle studies of strongly correlated systems and effects in nanostructured materials. In addition, the proceedings book of the symposium was also published to cover broader topics than the above special topic section in JAP as one of the AIP-Conference Proceedings,71) in which novel results on magnetism and nano-structured magnetic materials,72–82) functional materials,83–86) theoretical and computational materials science87–91) and nano-scale materials characterization92–98) were compiled. The 3rd FMS was held in Hanoi in November, 2016, and the selected papers mainly associated with the condensed-matter physics in the symposium were published in a special issue of Physica B,99) in which 16,100–115) 17116–132) and 9133–141) papers related to structural, mechanical and thermal properties of condensed matters, electronic structure, electrical and magnetic properties of condensed matters and optical properties of condensed matters, respectively, were included.
The second special issue of the series in Materials Transactions was published as Vol. 59, No. 7, in 2018,142) for which the papers were mainly collected from the 4th FMS held in Greifswald, Germany, in September, 2017. A series of FMS focuses upon the cutting-edge nanostructured functional materials and their applications. In this second special issue, 15 cutting-edge researches for nanostructured functional materials are included, which were divided into 5 categories, i.e., nanostructure analysis,143,144) advanced ab initio simulations,145,146) nanomaterials with highly correlated electron systems,147–149) advanced spectroscopy150,151) and advanced processing of nanomaterials.152–157)
The third special issue of the series was published as Vol. 61, No. 8, in 2020158) in Materials Transactions. For this special issue, papers were collected from the joint international symposium of 5th FMS and 3rd NANOMATA held in Danang, Vietnam, in November, 2019. The symposium also covered wide area of the materials science such as advanced optoelectronic and photonic materials, green energy materials and applications, nano-structured magnetic materials, computational materials science, spintronics and multiferroics, and nano-chemical and bio-technologies. There is no doubt in the success of this symposium, in which 197 presentations including 4 plenary, 48 invited and 34 oral talks and 111 poster presentations were given and there were more than 300 participants from many countries such as Estonia, France, Germany, India, Japan, Korea, Netherlands, Poland, Taiwan, Thailand, USA and Vietnam. Since this special issue was open for the submission from outside the above symposium, the related latest excellent works have been also included in this third special issue. In total 31 cutting-edge papers related to the nanostructured materials were included in this special issue, which are divided into 6 categories, i.e., 1 invited review article159) and 8 papers in computational materials science,160–167) 7 papers in magnetic materials,168–174) 6 papers in advanced functional oxides,175–180) 6 papers in carbon and organic materials181–186) and 4 papers in optical materials.187–190)
The invited review article159) is given by prof. Nguyen Nanh Dinh, which reports mainly on the organic optoelectronic devices such as Organic Light-Emitting Diodes (OLEDs), Organic Solar Cells (OSCs) and Organic Gas Sensors (OGSs). It is demonstrated that incorporation of nanostructured particles of metals and semiconductors in conducting polymers show significant improvement of the performance of the devices. Figure 1 shows the results I-V characteristics of OLED based on PFO/MEH-PPV with different amounts of additions of SiO2/TiO2 composites. As shown in this figure, peak intensity is enhanced by addition of SiO2/TiO2, whose maximum was obtained at 1.0 wt% of SiO2/TiO2 addition.
I-V characteristics of OLED based on PFO/MEH-PPV in the presence of SiO2/TiO2 nanocomposites. 1 wt%. is the optimal percentage of the MEH-PPV in PFO.59)
In the second category of the research papers in the special issue is focused on the “computational materials science”, in which 8 cutting-edge papers are included. The first paper160) reports the automated identification of facet pair orientations. They discuss a method to identify orientations of pairs of facets, which can form on an arbitrary crystal orientation. In the second paper,161) structural and magnetic properties of Fe-doped MnCoGe were studied by using the first principles calculations within the density functional theory level. They found Fe substitution reduces the barrier energy from orthorhombic to hexagonal structures, which have strong correlation with the movements of both of Co and Mn. The structural, electronic and mechanical properties of few-layer GaN nanosheet were investigated in the third one162) also by the first-principles calculations. It is reported that 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 with the thickness increases. Stability of the structures are also studied by using the calculated phonon dispersion curves as shown in Fig. 2. In the fourth paper,163) the electronic properties of superconducting Sr4V2O6Fe2As2 were investigated by using the full potential linearized augmented plane wave method. In the fifth work,164) the adsorption mechanism of organic molecules such as acetone and toluene on silicene surface is studied by the first principles method taking van der Waals interaction into consideration by the use of optPBE-vdW functional. The optimized structures and their electronic structures of acetone and toluene adsorbed silicene surfaces are investigated in detail. Numerical studies of the mean-field Poisson-Boltzmann equation for the distribution of mobile ions in a two-dimensional hexagonal lattice of DNA cylinders are reported using finite element method in the sixth paper165) for the application of DNA as a biomaterial. In the seventh paper,166) a new algorithm for numerical evaluation of X-ray absorption spectra is proposed based on the Green’s function formalism. To evaluate the validity of the new algorism, results by the new method is compared with the theoretical spectrum obtained by the full diagonalization method, in which it is shown that these two results are fully identical. The eighth paper,167) which is a final one in the second category of the special issue, demonstrates numerically influence of confined phonons and a strong electromagnetic wave on the Hall effect in a one-dimensional cylindrical quantum wire of GaAs/GaAsAl.
Phonon spectra of selected nanosheet of GaN with different numbers of layers, stacking sequence and reconstruction.62)
Six excellent papers are included in the third category of the special issue focusing upon the “magnetic materials”. The first paper168) in this category reports the results on magnetization measurements of polycrystalline Au4V up to 130 kOe at low temperature between 4 and 60 K. Magnetic parameters of Au4V, such as magnetic moment and parameters of Takahashi’s spin fluctuation theory for weak itinerant electron ferromagnets are determined by their measurements. Magnetic measurements of narrow-gap semiconductor FeSb2 under pressure is reported in the second paper,169) in which pressure effects on magnetic susceptibility and energy gap of FeSb2 are investigated at temperatures between 50 and 300 K under pressure up to 13 kbar. The third paper170) investigates effect of temperature on the structure of La1−yCeyFe11.44Si1.56 at the temperatures between 100 and 295 K using the X-ray diffraction technique. Figure 3 shows dependence of lattice constants on the temperature of La1−yCeyFe11.44Si1.56, which suggests that first order phase transitions occur and Ce concentration affects the transition temperature. In the fourth paper,171) the magnetoresistance measurements of exchange-biased spin valve device under high pressure to aim to promote the study of high-pressure studies on spintronic devices with nano structures. The fifth paper172) reports the magnetic field effect on nitrogenation of Sm2Fe17 under a zero field and a magnetic field of 5 T changing the temperature, i.e., at 623, 673 and 743 K, which revealed that application of magnetic field enhances nitrogenation. The sixth paper173) investigates the spin reorientation and Currie temperature of Mn2−xFexSb1−ySny. Results suggest that the spin reorientation temperature increases from 255 to 383 K at x = 0 and 0.15, respectively, while it is independent from Sn concentration, y. The last paper174) in this magnetic materials category, crystal structures of rare-earth doped compounds La0.8R0.2(Fe0.88Si0.12)13 (R = Y, Ho and Yb) are studied by the X-ray diffraction method and their magnetic properties are observed, which suggest that the Currie temperature increases with increasing of filling 4f states.
Dependence of lattice constant a on the temperature for La1−yCeyFe11.44Si1.56 (y = 0.1 and 0.3).70)
The fourth category of the special issue is on “advanced functional oxides”, in which 6 excellent papers are included. A crystal structure analysis of the A-site ordered double perovskite oxide, PrBaCi2O6−δ, is demonstrated in the first paper175) using Rietveld refinement of synchrotron X-ray powder diffraction data. In the second paper,176) magnetotransport property for the layered cobalt oxide BaCo6O11 is studied. Observed magnetic field dependence of magnetization at 5 K and magnetoresistance at 10, 15, 20 and 25 K are shown in Figs. 4(a) and (b), respectively, from which slight negative magnetoresistance was observed at 25 K and that show gradual increase in the magnitude as temperature decrease. Electrocatalytic activity of Fe4+–Co4+ mixed oxides are investigated in the third paper177) for the use of oxygen and hydrogen evolution reactions. In this study the materials were successfully synthesized by the high-pressure synthesis method. In the fourth paper,178) yttrium titanate (Y2Ti2O7)/nickel composites with self clack-healing ability were developed for the use as thermal barrier coating materials. The fifth paper179) reports the results on the metal-insulator transition in (La0.7Sr0.3Mn0.98Co0.02O3)1−x(BaTiO3)x multiferroic materials, in which crystal structures of the synthesized samples are characterized with the X-ray diffraction method and their magnetic and electric properties are examined in detail. The final study in this category180) is focused upon the oxygen evolution catalysis for iron oxides with various structures. The catalytic activity of Fe3+-containing oxides, such as ZnFe2O4 spinel, CaFe2O4 post-spinel and BaFe2O4 stuffed-tridymite, on the oxygen evolution reaction is investigated.
Magnetic field dependence of (a) magnetization at 5 K and (b) magnetoresistance (= μ(H)/μ (0 Oe)) at 10, 15, 20, and 25 K.76)
In the fifth category, 6 cutting-edge results on the “carbon and organic materials” are summarized. The first paper181) in this category reports effect of maleic anhydride grafted ethylene vinyl acetate compatibilizer on the mechanical and thermal properties and weathering resistance of polyamide 11/Bamboo fiber composite. The second paper182) shows the results of plasma-assisted preparation of MoS2/graphene/MOF (metal-organic framework) hybrid materials and their electrochemical properties. In this work, the 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 MOF, which are schematically shown in Fig. 5. In the third paper,183) development of gas sensors for the NH3 using the carbon nanotubes is shown, in which multiwalled carbon nanotubes (CNTs) were coated onto Pt electrodes patterned on SiO2/Si(001) surface. The fourth paper184) reports preparations of natural rubber-based electromagnetic shielding materials for coating application, in which expanded graphite was prepared and dispersed in the polyaniline/natural rubber matrix. The advanced fabrication and applications of cellulose acetate aerogels from cigarette butts are reported in the fifth paper.185) In the final paper186) in this category, field emission properties of vertically aligned carbon nanotubes grown on stainless steel by hot-filament chemical vapor deposition is shown.
Schematic of the synthesis of (a) MoS2/graphene, (b) metal-organic framework (MOF) and (c) G-MOF.82)
In the final category, which is sixth one in this special issue, there are 4 excellent reports on the “optical materials”. The first paper187) reports optical properties of MgO nanocrystals with different morphologies, such as cube, wire and flower shapes, synthesized with facile catalyst-free one-pot method. In the second paper,188) Eu3+ doped La3PO7 nanoparticles are synthesized by combustion method and their optical properties are investigated in detail. The third paper189) shows the results of upconversion luminescence properties of Ge2O3 nanoparticles doped with Er3+ and that combined with silica nanocomposite. In the fourth paper,190) characterization of Gd2O3:Eu3+ nanocomplexes conjugate with IgG for the identification of CEA tumor cells. The observed tumor cells with and without nanocomplex based on the Gd2O3 doped with Eu3+ are shown in Fig. 6, which shows the efficient luminescence by the Gd2O3:Eu3+.
CEA tumor cells without (a) and with nanocomplexes of 3 mg/100 µl (b) and 10 mg/100 µl (c) under the fluorescence microscope.90)
In this report, recent advances in the field of nanostructured functional materials are reviewed mainly taken from the topics summarized in the special issue of Materials Transactions vol. 61, No. 8. This is the third special issue in a series of “Nanostructured functional materials and their applications”, which are combined with a series of two international symposia, i.e., 1) International Symposium on Frontiers in Materials Science (FMS) and 2) International Symposium on Nano Materials, Technology and Applications (NANOMATA). As both of FMS and NANOMATA are planned to be continued, we hope further special issues will be also compiled to collect cutting-edge studies in nanostructured functional materials.
This work was partially supported by the Joint Research Center for Environmentally Conscious Technologies in Materials Science (Grant No. JPMXP0618217637) at ZAIKEN, Waseda University.
