| viXra.org > Condensed Matter > 2304 |
 |
 |
| viXra.org > Condensed Matter > 2304 |
|
|
[8] viXra:2304.0196 [pdf] submitted on 2023-04-25 13:32:03
Authors: Marcello Colozzo
Comments: 10 Pages.
We propose a theoretical model of non-normal thermodynamic system (i.e. atnegative absolute temperature), through the application (and consequentinstantaneous inversion) of a magnetic field to a crystal.
Category: Condensed Matter
[7] viXra:2304.0146 [pdf] replaced on 2023-05-21 13:51:38
Authors: Victor L. Mironov, Sergey V. Mironov
Comments: 11 Pages.
We present the theoretical description of plane Couette flow based on the previously proposed equations of vortex fluid, which take into account both the longitudinal flow and the vortex tubes rotation. It is shown that considered equations have several stationary solutions describing different types of laminar flow. We also discuss the simple model of turbulent flow consisting of vortex tubes, which are moving chaotically and simultaneously rotating with different phases. Using the Boussinesq approximation we obtain analytical expression for the stationary profile of mean velocity in turbulent Couette flow, which is in good agreement with experimental data and results of direct numerical simulations. Our model demonstrates that near-wall turbulence can be described by a coordinates-independent coefficient of eddy viscosity. In contrast to the viscosity of the fluid itself this parameter characterizes the turbulent flow and depends on Reynolds number and roughness of the channel walls. Potentially, the proposed model can be considered as a theoretical basis for the experimental measurement of eddy viscosity coefficient.
Category: Condensed Matter
[6] viXra:2304.0025 [pdf] submitted on 2023-04-03 19:00:02
Authors: Mainak Saha
Comments: 21 Pages.
The structure-property(S-P) correlation, especially in the context of high-temperature oxidation, in ZrB2-MoSi2 based Ultra High-Temperature Ceramic Matrix Composites (UHTCMCs) have been extensively investigated for quite some time since the last 25 years and a countless amount of published data is presently available in this field. On the other hand, emergence of correlative microscopy [1-10] has completely revolutionised the world of materials research, in a number of ways. However, owing to the challenges of sample preparation, there has hardly been a literature aimed at understanding the aforesaid phenomenon of understanding S-P correlation, based on oxidation in ZrB2-MoSi2 UHTCMCs, which, in future, may open up new frontiers of research in UHTCMCs. The present review intends to discuss some of the most interesting data published existing in this field and intends to provide a brief overview of the challenges associated along with some of the currently unexplored avenues in this field, especially in terms of fundamental research. However, in view of the enormous amount of research already done in understanding oxidation-based S-P correlation in these materials, the author does not claim to address all the issues which may be associated with understanding thesame.
Category: Condensed Matter
[5] viXra:2304.0024 [pdf] submitted on 2023-04-03 19:01:47
Authors: Mainak Saha
Comments: 10 Pages.
Recently, there have been a number of reports on the fabrication of Alumina-Zirconia (Al2O3- ZrO2 (AZ))-based eutectic ceramics using laser additive manufacturing (AM) techniques owing to the exceptional creep and oxidation resistance coupled with excellent microstructural stability in these materials. Moreover, a number of interesting microstructural features (in these materials) have been reported to be formed by the variation of process parameters (especially, laser scanning speed) associated with the aforementioned AM techniques. The present review provides an overview of the present state of research in the area of laser AM AZ-based eutectic ceramics and highlights the challenges and future outlooks in this avenue of research. In addition, the requirement of employing correlative microstructural characterisation in these materials has been highlighted in the outlooks section.
Category: Condensed Matter
[4] viXra:2304.0023 [pdf] submitted on 2023-04-03 19:03:38
Authors: Mainak Saha
Comments: 4 Pages.
In recent times, ultra-high temperature ceramic matrix composites (UHTCMCs) comprising of ultra-high temperature ceramics (UHTCs) such as ZrB2, HfB2 etc. reinforced with additives such as SiC, MoSi2 etc. have been reported to offer tremendous potentials in applications such as Hypersonic Re-entry vehicles, solar thermal absorbers, nuclear fuel claddings etc. Porous ceramics are advantageous in the aforementioned applications areas owing to their high melting points combined with high corrosion and wear resistance. Although ZrB2-SiC UHTCMCs (synthesized using pressureless sintering technique) have been widely investigated for their densification and mechanical properties at both room and elevated temperatures (till 3000°C), there is a very limited information on the densification behaviour and mechanical properties of ZrB2-MoSi2 UHTCMCs prepared using the aforementioned sintering technique. To this end, the present study is aimed at investigating the microstructure and correlating the same with the densification behaviour and mechanical properties of porous sintered ZrB2-20 vol.% MoSi2 (ZM20) UHTCMC. To this end, the composite was ball milled for 2h followed by compaction at different pressures. The compacted samples were sintered at 1700u2070C. X-Ray Diffraction (XRD) analysis was performed for the purpose of understanding phase evolution. Subsequent, microstructural investigation was performed under different magnifications in Scanning Electron Microscope (SEM). Moreover, density measurement; hardness and indentation fracture toughness calculations were performed to investigate the room temperature mechanical properties.
Category: Condensed Matter
[3] viXra:2304.0021 [pdf] submitted on 2023-04-03 23:21:10
Authors: Tiege Zhou
Comments: 6 Pages.
We propose that the change of the electron clouds of the transition metal ions (or/and other ions) is the electron pairing medium in high temperature superconductors. It is just like the vibration of the crystal lattice is the electron pairing medium in conventional superconductors.
Category: Condensed Matter
[2] viXra:2304.0016 [pdf] submitted on 2023-04-02 18:45:09
Authors: Mainak Saha
Comments: 27 Pages.
In materials research involving additive manufacturing (AM)-based techniques for fabrication of a wide variety of materials, the latest trend at present is to focus largely on 3D printing (3DP) of nanoceramics, which at present is highly challenging, from both fundamental and industrial viewpoints inspite of the tremendous versatility offered by these techniques in terms of addressing design complexities. The two main reasons for the same are: low density and poor mechanical properties of nanoceramic parts fabricated using 3DP techniques. The present review is aimed to review some of the most commonly used 3DP techniques for the fabrication of nanoceramics and provide an overview of the future perspectives, associated with the necessity towards developing a systematic structure-property correlation through ‘correlative’ characterisation methodology in these materials.
Category: Condensed Matter
[1] viXra:2304.0014 [pdf] submitted on 2023-04-02 19:51:35
Authors: Thiago M. Nóbrega
Comments: 7 Pages.
The development of energy-efficient, high-density three-dimensional (3D) magnonic devices has garnered significant interest due to their potential for revolutionizing information processing and storage technologies. Building upon recent findings on spin-wave modes in magnetochiral nanotubes with axial and circumferential magnetization, this study investigates the effects of tailored geometries and magnetic configurations on the spin-wave properties of these nanostructures.By employing advanced simulation techniques, experimental methods, and theoretical analysis, we explore the interplay between geometry, magnetization, and spin-wave dynamics in magnetochiral nanotubes. Our results reveal that specific combinations of geometrical parameters and magnetic configurations lead to enhanced spin-wave properties, paving the way for the design of novel 3D magnonic devices with improved performance and energy efficiency.Furthermore, we demonstrate the potential of these optimized magnetochiral nanotubes for various applications, including logic nanoelements and vertical through-chip vias in 3D magnonic device architectures. This study not only advances our understanding of spin-wave dynamics in magnetochiral nanotubes but also provides a foundation for the development of next-generation magnonic devices.
Category: Condensed Matter
| Third-Party Links: |
|