The 13th Global Conference on
Materials Science and Engineering (CMSE 2024)

Abstract: Semiconducting metal-based nanoparticle (MBNP) research is an area of intense scientific activity due to variety of potential applications. The size, shape and crystallinity of these MBNPs strongly modulate their physical properties. Their outstanding properties led to the fabrication of various nanostructures by engaging a variety of synthesis methods of MBNPs which can alter the shape, size and crystallinity and hence, control their properties. However, these methods have some demerits, e.g., usually require longer time of reaction, involve expensive and eco-toxic chemicals. Therefore, the green synthesis technique has drawn much interest in the contemporary research and is becoming increasingly crucial. Extracts of certain plant-parts act as substrates for the green synthesis of nanomaterials. As plants possess a rich variety of phytochemicals, these phytochemicals present in the plant extract act as reducing agent to react with metal ions of the precursor compound to reduce their size into nano range, and also act as capping and stabilizing agents to determine the final shape and size of the MBNPs. Green synthesis is a simple, safe, eco-friendly, and cost-effective technique where the production of hazardous substances that harm the ecosystem is eliminated. In the age of environmentally friendly development, the green synthesis of MBNPs from plant extracts has become a focus of research attention. Herein, discussions will be made on the physical aspects of some green synthesized MBNPs and their application potentials.

Abstract: We propose the materials design of smart oxide films with thicknesses ranging from 2 to 2000 nm for wide applications. We have succeeded in the 100-nm-thick high Hall mobility (µH) Ce-doped hydrogenated In₂O₃ films for use as electrodes in photovoltaic solar cells, that have been commercial. In order to develop new type of 2D materials, we very recently reported high µH W-doped In₂O₃ polycrystalline films with thicknesses ranging from 5 to 10 nm. For Ga-doped ZnO (GZO) films, we have found that a decrease in thicknesses of 50 nm or less causes a reduction of Young modulus, i.e., such thin films show the flexibility. This research produces polymer substrates with GZO films. On the other hand, thick some micron meter-thick GZO films show magnetic shielding characteristics. We have been developing the unique deposition apparatus; reactive plasma deposition with dc arc discharge (RPD) through the academic-industrial collaboration that has been already commercial. The typically film-deposition rates is 200 nm/min. The RPD provides smart oxide films deposited on the substrates with a large size of 1m×1m. In this presentation, we show smart materials design together with the above business.

Keywords: Highly transparent conductive oxides, 2D, flexibility, carrier transport, reactive plasma deposition.

References:
Eiji Kobayashi, Yoshimi Watabe, Tetsuya Yamamoto, Yoichi Yamada,Sol. Energy Mater. Sol. Cells 149 (2016) 85–90;
Yutaka Furubayashi, Makoto Maehara, Tetsuya Yamamoto, Nanoscale Res. Lett. 14 (2019) 20;
Tetsuya Yamamoto, Rajasekaran Palani, Hisashi Kitami, Hisao Makino, JSAP Rev. (2024) 240404-1-240404-5.

Acknowledgements: We have been continuing a joint research and development with Sumitomo Heavy Industries, Ltd. We would like to express our deepest gratitude to all involved.

Abstract: Nb-Si based ultrahigh temperature alloys possess low densities, high melting point and good high temperature mechanical properties, which are expected to be employed as the promising high-temperature structural materials to replace nickel-based superalloy at 1200-1400 ℃ for aviation turbine engine blades. In the present presentations, the Nb-Si based alloys adding element carbon were prepared by vacuum non-consumable arc melting. The microstructure, nanoindentation microhardness, room temperature fracture toughness, compressive strength at 1250℃ and oxidation resistance of the alloy were evaluated. The results show that adding carbon in multi-elemental Nb-Si based alloys can make the eutectic point of the alloy move to the direction of lower silicon content, and increase the degree of hypereutectic alloy. Alloying with carbon inhibit the formation of (Nb,X)₃Si phase and promote the formation of γ(Nb,X)₅Si₃ phase, and precipitate (Ti,X)C in the alloys. The dissolved carbon (mainly in γ(Nb,X)₅Si₃) has the effect of solid solution strengthening and improve the nanoindentation hardness of phases. Alloying with carbon increase the compressive strength at 1250 ℃ of the alloys. The high temperature compressive strength of 4C alloy is 31.8% higher than that of 0C alloy due to the solid solution strengthening, the increase of primary silicide contents and (Ti,X)C precipitation. The addition of carbon can improve the fracture toughness at room temperature, the KQ value of 3C alloy was 13.5 MPa·m^1/2, which is the highest value among the six alloys. Alloying with carbon reduces the oxidation resistance of the alloy at 1250 ℃, and the oxide film thickness and porosity of the alloy increase.

Keywords: Nb-Si based ultrahigh temperature alloy, carbon alloying, phase constituents, room-temperature fracture toughness, high-temperature compressive strength, high-temperature oxidation resistance, nanoindentation hardness.

Abstract: [2.2]Paracyclophane is a common cyclophane compound consisting of face-to-face benzene rings fixed by ethylene chains at the para-positions. Two eclipsed benzene rings are closely stacked, causing suppression of their rotatory motion. [2.2]Paracyclophane compounds with one or more substituents are planar chiral compounds depending on the substitution position(s). Enantiopure [2.2]paracyclophane compounds have been employed mainly as chiral ligands and chiral auxiliaries in organometallic and organic chemistry, respectively. However, there are only a few examples of their applications in the fields of polymer and materials chemistry [1]. Recently, we achieved optical resolutions of six kinds of di- and tetrasubstituted [2.2]paracyclophanes by the diastereomer method using appropriate chiral auxiliaries [2]. Subsequently, we synthesized various optically active molecules [3] containing planar chiral [2.2]paracyclophane units; the obtained chiral molecules exhibited excellent circularly polarized luminescence (CPL) properties.

We introduce syntheses of optically active cyclic oligomers [4] and macromolecules [5] based on the planar chiral [2.2]paracyclophanes as chiral building blocks. Their synthetic procedures and chiroptical properties, in particular good CPL profiles, are disclosed.

Keywords: Circularly polarized luminescence (CPL), cyclic oligomer, macrocycle, [2.2]Paracyclophane, planar chirality.

References:
[1] Bull. Chem. Soc. Jpn. 2019, 92, 265-274.
[2] For example: (a) J. Am. Chem. Soc. 2014, 136, 3350-3353. (b) Chem. Commun. 2021, 57, 9256-9259. (c) J. Mater. Chem. C 2023, 11, 986-993.
[3] For recent examples: (a) Chem. Asian J. 2022, 17, e202200418. (b) Bull. Chem. Soc. Jpn. 2022, 95, 1353-1359e. (c) Science 2022, 377, 673-678.
[4] (a) Chem. Asian J. 2022, 17, e202101267. (b) Chem. Eur. J. 2023, 29, e202203533.
[5] (a) Bull. Chem. Soc. Jpn. 2022, 95, 110-115. (b) Adv. Funct. Mater. in press (DOI: 10.1002/adfm.202310566).

Abstract: Tensile, creep, fatigue and impact properties of materials are necessary for design of components, assessment of their structural integrity during service, and extension of life of components. These mechanical properties are usually evaluated by conducting tests using standard specimens and in accordance with testing procedures which are recommended by national or international standards. A relatively large quantity of material is required to generate sufficient data to characterize the mechanical properties of materials, and to generate design curves. While this may not be a serious issue for generating data with existing materials, large quantity of material will not be available for evaluating properties of newly developed materials or components in service without compromising the integrity of component. Innovations in miniaturized testing techniques, also called small scale mechanical testing, have been therefore developed to characterize mechanical properties of materials. Impression Creep, Small Punch Creep and Ball Indentation are three major innovative small scale testing methods which can be used to determine tensile and creep strength of materials.

Ball Indentation test is used for evaluation of tensile properties and fracture toughness of materials at high temperatures as well as at cryogenic temperatures. The test involves strain-controlled multiple indentations followed by partial unloading which are made at a single penetration location on a polished surface of a material using a spherical indenter. A combination of elasticity and plasticity theories, and semi-empirical relationships which govern material behavior under multiaxial indentation loading, are applied to derive the true stress-true strain curve from the load-depth of penetration data, and the tensile properties are evaluated.

Impression creep test is used to determine creep deformation behavior of materials. In impression creep test, a constant compressive load is applied to a flat specimen using a cylindrical indenter having a flat end. The depth of penetration of the indenter in the material is continuously measured as a function of time to understand its creep deformation behavior and generate the creep parameters. Small Punch Creep test is used to evaluate creep deformation and fracture properties of materials using a small thin specimen which is subjected to a constant load at high temperature using a spherical ball indenter made of ceramic material. The bending deflection of the specimen is measured continuously as a function of time till the sample undergoes fracture.

Being material non-intensive, these testing methods have applications in materials development, structural integrity assessment for life extension of components, and characterization of mechanical properties of different narrow microstructural zones in weld joints. This paper reviews the results of detailed studies carried out using these three small scale testing techniques, and discusses their relative advantages and limitations.

Keywords: Creep, ball indentation, impression creep, small punch creep.