International Journal of Physics | Vol. 3, No. 6, June 2012 | pp. 43–50
DOI: 10.46882/2012/IJP/000026
Research Article
Title: Synthesis and Thermoelectric Properties of Nanostructured Bismuth Telluride Thin Films via Electrochemical Deposition
Names of Authors: K. Y. Tanaka¹, R. M. Santos², A. L. Chevalier³
Authors’ Affiliations: ¹Department of Materials Science, Tokyo Institute of Technology, Tokyo 152-8550, Japan; ²Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil; ³Institut Néel, CNRS, Université Grenoble Alpes, F-38042 Grenoble, France
Abstract: Nanostructured thermoelectric materials provide a viable pathway for converting ambient waste heat directly into usable electrical energy. This study evaluates the structural morphology and thermoelectric performance metrics of nanostructured bismuth telluride (Bi²Te³) thin films. These films were successfully synthesized on silicon substrates using a controlled electrochemical deposition methodology. X-ray diffraction patterns confirm the presence of a single-phase rhombohedral crystal geometry with preferred orientation along the (015) lattice plane. Field emission scanning electron microscopy images demonstrate uniform grain size distributions centered tightly around 34 nm. The transport coefficients were meticulously measured across an operating temperature range spanning 300 K to 450 K. The optimal film configuration exhibited a high Seebeck coefficient value of -185 μV/K at 350 K. This combined with an electrical conductivity reading of 820 S/cm. The resulting maximum thermoelectric power factor reached 2.81 mW/(m*K²). This performance value represents a significant enhancement over bulk un-nanostructured equivalents. The enhancement is primarily attributed to increased quantum confinement effects and strong energy filtering mechanisms occurring at the grain boundaries. These outcomes highlight the practical viability of using scalable electrochemical routines to manufacture high-efficiency micro-thermoelectric generators.
Keywords: Thermoelectric materials; bismuth telluride; electrochemical deposition; thin films; Seebeck coefficient; power factor
Manuscript Timeline: Received: April 5, 2012; Revised: May 3, 2012; Accepted: May 19, 2012; Published: June 18, 2012
Citation: Tanaka, K. Y., Santos, R. M., & Chevalier, A. L. (2012). Synthesis and Thermoelectric Properties of Nanostructured Bismuth Telluride Thin Films via Electrochemical Deposition. International Journal of Physics, 3(6), 43–50.
International Journal of Physics | Vol. 3, No. 2, February 2012 | pp. 10–18
DOI: 10.46882/2012/IJP/000026
Article Type: Original Research Paper
Title: Synthesis and Upconversion Luminescence Enhancement of Erbium-Ytterbium Co-Doped Sodium Yttrium Fluoride Core-Shell Nanoparticles
Names of Authors: P. C. Nwosu¹, L. E. Martinez²
Authors’ Affiliations: ¹Department of Physics, University of Port Harcourt, Port Harcourt, Nigeria; ²Department of Chemistry and Materials Science, Autonomous University of Madrid, Madrid, Spain
Abstract: Lanthanide-doped upconversion nanoparticles are highly attractive for deep-tissue biological imaging and solar cell efficiency enhancement because they convert near-infrared excitation into visible light emissions. This study describes a hydrothermal synthesis route for creating highly crystalline core-shell sodium yttrium fluoride (NaYF₄) nanoparticles co-doped with trivalent erbium (Er³⁺) and ytterbium (Yb³⁺) ions. To suppress surface quenching channels, an undoped passive NaYF₄ shell layer was grew epitaxially over the active core structures. The core size and shell thickness were verified using transmission electron microscopy (TEM), which revealed uniform spherical particles with an average core diameter of 22 nm and a shell thickness of 4.5 nm. Under continuous-wave laser excitation at 980 nm, the core-shell architecture demonstrated a 35-fold enhancement in upconversion luminescence intensity compared to bare core structures. The emission spectrum exhibited strong green peaks at 525 nm and 542 nm, alongside a red peak at 660 nm, corresponding to the radiative transitions of the Er³⁺ ion. Power-dependent luminescence measurements confirmed a two-photon upconversion mechanism driving both emissions. These findings outline a method for producing bright fluorescent probes suitable for targeted bio-imaging applications.
Keywords: Upconversion nanoparticles; Hydrothermal synthesis; Core-shell structures; Luminescence enhancement; Lanthanide ions; Surface quenching; Two-photon mechanism; Biological imaging.
Manuscript Timeline: Received: November 12, 2011; Revised: December 22, 2011; Accepted: January 14, 2012; Published: February 07, 2012.
Citation: Nwosu, P. C., & Martinez, L. E. (2012). Synthesis and Upconversion Luminescence Enhancement of Erbium-Ytterbium Co-Doped Sodium Yttrium Fluoride Core-Shell Nanoparticles. International Journal of Physics, 3(2), 10–18.
International Journal of Physics | Vol. 3, No. 6, June 2012 | pp. 43–51
DOI: 10.46882/2012/IJP/000030
Article Type: Review Paper
Title: A Review of Spontaneous Symmetry Breaking Mechanisms in Extended Electroweak Gauge Theory Models
Names of Authors: R. H. Davies¹, A. O. Okafor²
Authors’ Affiliations: ¹Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK; ²Department of Physics, University of Benin, Benin City, Nigeria
Abstract: The discovery of a Higgs-like scalar particle marks a milestone in validation testing of the Standard Model's electroweak symmetry breaking sector. This review evaluates the theoretical foundations of spontaneous symmetry breaking (SSB) mechanisms, contrasting the minimal single-doublet Brout-Englert-Higgs model with extended gauge frameworks. We analyze the mathematical architectures of Two-Higgs-Doublet Models (2HDM), Minimal Supersymmetric Standard Model (MSSM) extensions, and Left-Right Symmetric theories that address neutrino mass generation. The review tracks how these multi-scalar extensions generate mass profiles for vector bosons and fermions while avoiding flavor-changing neutral currents. We evaluate current constraints imposed by global collider datasets on vacuum stability conditions, oblique parameters (S, T, U), and scalar coupling profiles. While the single-doublet model matches current data, several parameter windows within 2HDM alignment limits remain viable options. We discuss the role of CP-violating phases in extended scalar potentials, which are critical for generating the baryon asymmetry observed in the universe. The paper concludes by outlining search strategies for heavy neutral and charged Higgs scalars at current and upgraded particle accelerator facilities.
Keywords: Spontaneous symmetry breaking; Electroweak theory; Higgs mechanism; Two-Higgs-Doublet model; Vacuum stability; CP violation; Flavor-changing neutral currents; Collider constraints.
Manuscript Timeline: Received: March 01, 2012; Revised: April 15, 2012; Accepted: May 12, 2012; Published: June 09, 2012.
Citation: Davies, R. H., & Okafor, A. O. (2012). A Review of Spontaneous Symmetry Breaking Mechanisms in Extended Electroweak Gauge Theory Models. International Journal of Physics, 3(6), 43–51.
International Journal of Physics | Vol. 3, No. 1, January 2012 | pp. 1–9
DOI: 10.46882/2012/IJP/000025
Article Type: Original Research Paper
Title: Phonon Dispersion Relation and Thermal Conductivity Anomalies in Graphene Nanoribbons with Specular Boundary Edge Roughness
Names of Authors: O. T. Sanusi¹, Y. M. Takahashi²
Authors’ Affiliations: ¹Department of Physics, Federal University of Technology, Minna, Nigeria; ²Institute of Industrial Science, University of Tokyo, Tokyo, Japan
Abstract: Managing thermal transport at the nanoscale is essential for avoiding thermal throttling in next-generation ballistic transistors and high-density microprocessor units. This paper models phonon dispersion relations and lattice thermal conductivity variations in armchair and zigzag graphene nanoribbons (GNRs) featuring structural edge roughness. The lattice vibrations were calculated via a modified valence force-field model, while the thermal conductivity profiles were extracted using the phonon Boltzmann transport equation under the relaxation time approximation. The nanoribbon widths were systematically adjusted between 5 nm and 30 nm at operational temperatures up to 500 K. Our simulations reveal that boundary edge roughness induces severe confinement, which reduces lattice thermal conductivity by up to 72% compared to pristine graphene sheets. This dramatic drop stems from enhanced diffuse backscattering of high-frequency acoustic phonons at the rough boundaries. Zigzag configurations displayed a 15% higher thermal tolerance than armchair variants due to localized edge phonon modes that resist phase space scattering. The calculations show that at 300 K, a 10 nm wide nanoribbon exhibits an effective thermal conductivity of 420 W/(m*K). These results provide layout metrics for managing heat dissipation in graphene nano-circuitry.
Keywords: Graphene nanoribbons; Phonon dispersion; Thermal conductivity; Boltzmann transport equation; Edge roughness; Valence force field; Nanoscale heat transfer; Ballistic transistors.
Manuscript Timeline: Received: October 20, 2011; Revised: November 29, 2011; Accepted: December 19, 2011; Published: January 04, 2012.
Citation: Sanusi, O. T., & Takahashi, Y. M. (2012). Phonon Dispersion Relation and Thermal Conductivity Anomalies in Graphene Nanoribbons with Specular Boundary Edge Roughness. International Journal of Physics, 3(1), 1–9.
International Journal of Physics | Vol. 3, No. 4, April 2012 | pp. 27–34
DOI: 10.46882/2012/IJP/000028
Article Type: Original Research Paper
Title: Fluid Flow Characteristics and Heat Transfer Optimization of Al2O3-Water Nanofluids in Corrugated Heat Exchangers
Names of Authors: A. O. Bello¹, M. A. Al-Mansoori²
Authors’ Affiliations: ¹Department of Physics, University of Ilorin, Ilorin, Nigeria; ²Department of Mechanical Engineering, United Arab Emirates University, Al Ain, UAE
Abstract: Traditional thermal fluids, such as water and ethylene glycol, are limited by poor thermal conductivities that hinder the development of high-efficiency, compact cooling networks. This study analyzes the forced convection heat transfer coefficient and pressure drop configurations of alumina-water (Al₂O₃-H₂O) nanofluids flowing through a sinusoidal corrugated channel. The multi-phase fluid domain was simulated numerically using a finite-volume framework under steady laminar and turbulent flow conditions. The nanoparticle volume fractions were varied from 1.0% to 4.0%, while the Reynolds number (Re) was adjusted from 500 to 5000. Our numerical findings show that the Nusselt number scales directly with both the nanoparticle concentration and the Reynolds number. A maximum heat transfer enhancement of 32% was achieved using a 4.0% nanoparticle volume fraction at Re = 4500. This enhancement comes from corrugation-induced vortex shedding and brownian motion particles accelerating heat transfer across layers. However, adding nanoparticles increased the fluid viscosity, leading to a 18% increase in pumping power requirements. We evaluate the system's thermal-hydraulic performance index, confirming that corrugated channels optimize net energy gains when using dilute nanofluid mixtures.
Keywords: Nanofluids; Heat transfer enhancement; Alumina nanoparticles; Corrugated channel; Finite volume method; Nusselt number; Reynolds number; Pumping power.
Manuscript Timeline: Received: January 14, 2012; Revised: February 25, 2012; Accepted: March 18, 2012; Published: April 06, 2012.
Citation: Bello, A. O., & Al-Mansoori, M. A. (2012). Fluid Flow Characteristics and Heat Transfer Optimization of Al2O3-Water Nanofluids in Corrugated Heat Exchangers. International Journal of Physics, 3(4), 27–34.
International Journal of Physics | Vol. 3, No. 5, May 2012 | pp. 35–42
DOI: 10.46882/2012/IJP/000029
Article Type: Original Research Paper
Title: Quantitative Characterization of Mechanical Degradation in Composite Polymer Solid Electrolytes for Lithium-Ion Batteries
Names of Authors: I. G. Usman¹, H. S. Peterson²
Authors’ Affiliations: ¹Department of Physics, Ahmadu Bello University, Zaria, Nigeria; ²Department of Materials Science, Royal Institute of Technology, Stockholm, Sweden
Abstract: Solid-state lithium batteries offer enhanced safety profiles and higher energy densities compared to conventional liquid-electrolyte cells, though they remain limited by localized mechanical degradation during cycling. This paper explores the microstructural evolution, ionic conductivity, and mechanical failure mechanisms of polyethylene oxide (PEO) solid polymer electrolytes blended with lithium perchlorate (LiClO₄) and titania (TiO₂) nanoparticles. The composite films were evaluated using electrochemical impedance spectroscopy (EIS) and nanoindentation testing across a temperature range of 298 K to 350 K. The experimental measurements show that adding 10% wt TiO₂ nanoparticles increases the room-temperature ionic conductivity from 2.4 x 10⁻⁶ S/cm to 4.8 x 10⁻⁵ S/cm, driven by a reduction in polymer crystallinity. Nanoindentation profiles showed a 45% increase in Young's modulus, which helps suppress dendritic lithium growth at the anode interface. However, tracking structural profiles over 200 charge-discharge cycles revealed micro-crack formation at the electrode-electrolyte boundary caused by localized strain gradients during lithium plating. These results highlight the importance of controlling nanoparticle distributions to balance mechanical durability and ionic transport in solid-state energy storage networks.
Keywords: Solid polymer electrolyte; Lithium-ion batteries; Ionic conductivity; Nanoindentation; Lithium dendrites; Polyethylene oxide; Microstructural degradation; Nanoparticle additives.
Manuscript Timeline: Received: February 10, 2012; Revised: March 22, 2012; Accepted: April 14, 2012; Published: May 04, 2012.
Citation: Usman, I. G., & Peterson, H. S. (2012). Quantitative Characterization of Mechanical Degradation in Composite Polymer Solid Electrolytes for Lithium-Ion Batteries. International Journal of Physics, 3(5), 35–42.