Alumina Research Articles

Quantitative analysis of heat and mass transfer in MoS2-Al2O3/EG hybrid flow between parallel surfaces with suction/injection by numerical modeling of HPM method

This description focuses on how the magnetic field affects mass and heat transfer in a hybrid nanofluid (Hnf) between two parallel, rotating plates. By dispersing aluminum oxide (Al2O3) and molybdenum disulfide (MoS2) nanoparticles (NPs) in ethylene glycol (EG), a hybrid nanofluid (Hnf) is created. This research aims to analyze the heat and mass transfer characteristics in the flow of a hybrid nanofluid (MoS2-Al2O3/EG) between two rotating parallel plates under the influence of a magnetic field. Furthermore, the statistical technique of response surface methodology (RSM) has been employed to optimize the parameters of velocity, temperature, and concentration of the nanofluid within the flow region bounded by the rotating plates. Dimensionless differential equations have been calculated and checked using the Homotopy perturbation method. This study introduces a novel approach by utilizing the RSM method to identify optimal points for velocity and temperature parameters of nanofluids between two stretching plates for the first time. Additionally, the article innovatively applies the exact HPM method to validate dimensionless linear and non-linear coupling equations. As the Reynolds number and the suction/injection coefficient of nanofluids flowing between two plates under tension increase, the results indicate a decrease in the velocity field. This decrease in velocity field can be attributed to the reduction in fluid diffusion as viscous forces diminish with varying Reynolds numbers. The ideal temperature distribution for nanofluids flowing between two parallel plates occurs when they are uniformly dispersed at the midpoint between them. As the distance from the initial point of nanofluid entry to the end of the plates increases, along with the vertical distance from the bottom plate, the temperature gradient diminishes, reducing the thickness of the thermal boundary layer. The velocity gradient and the rate of heat flux transfer between the nanofluid and plate rise by 34 % when the volume percentage is raised from 1 % to 5 %.

High strength of SiC–AlN–TiB2–VC multiphase ceramics induced by interface reactions

In this work, SiC–AlN–TiB2–VC multiphase ceramics with high bending strength were prepared via spark plasma sintering (SPS) at 1900 °C-2100 °C. The effects of interface reactions and solid solution reactions on microstructure and mechanical properties of these multiphase ceramics were investigated. Results show that the densification of multiphase ceramics is promoted effectively by the addition of Y2O3. Yttrium aluminum oxide with low melting point is formed due to the reaction between Al2O3 (on the surface of AlN) and Y2O3, which promotes the densification of SiC multiphase ceramics. Solid-solution reaction and interface reaction occur between matrix (SiC) and reinforcing phases (AlN, TiB2, and VC). Furthermore, solid-solution reactions occur between SiC and AlN, between AlN and TiB2, and between TiB2 and VC. Al5C3N phase is generated by interfacial reaction between SiC and AlN. Layered, rod-like BN(C) phase is formed at grain boundaries due to the reaction between AlN and B2O3 on the surface of TiB2 particles. Mechanical strength of multiphase ceramics is improved by the formation of solid solutions and the occurrence of these interfacial reactions. When sintered at 2000 °C, SiC multiphase ceramics with added Y2O3 exhibit excellent properties, including relative density of 99.8 %, Vickers hardness of 27.1 GPa, and bending strength of 666 MPa.

Production of cycloalkane-rich fuel by vacuum pyrolysis of mixed waste plastics using combined titanium and aluminum oxide: a preliminary investigation

The mitigation of plastic pollution constitutes one of the major challenges worldwide. Innovative research approaches have been solicited to improve the properties of fuel derived from plastic pyrolysis. The present study looks at the effect on the chemical composition of pyrolysis oil of the application in situ of a mixed metal oxide of titanium and aluminum in vacuum pyrolysis of mixed waste polyethylene, polypropylene, and polyethylene terephthalate. The experiment was performed at process parameters of 250 °C temperature, 79.9 Kpa vacuum pressure, and 1:10 catalyst-to-feedstock ratio, first without the mixed metal oxide (parent reaction) and then with the mixed metal oxide (modified reaction). The results showed that the presence of combined titanium and aluminum oxides in the reaction medium accounted for the presence of alkyl-substituted cycloalkanes at an area% of 33.97% in the liquid product, and a calorific value of 11,950 cal/gm was reported for the modified reaction. The parent reaction produced higher liquid and gaseous yields of 28.3% and 43.1% respectively while the modified reaction produced a greater percentage of char (23.8%) and residual wax(36.0%). The fuel properties of the liquid products obtained were equally determined.

Comparative study in magnetic properties of FeCo alloy nanowires and a first-order reversal curve analysis

FeCo alloy nanowires have potential applications in data storage, magnetic sensors and spintronic devices. In this paper, FeCo alloy nanowires with varying diameters were fabricated within an anodic aluminum oxide (AAO) template using electrodeposition method at a constant potential. Characterization of the morphology and structure revealed that the polycrystalline body-center-cubic(bcc) FeCo alloy nanowires were obtained. The influence of diameter of FeCo alloy nanowires on magnetic interaction, domain state and magnetic mechanism was investigated through a first-order reversal curve (FORC) analysis. The findings showed that with an increase in the diameter of FeCo alloy nanowires from 20 nm to 60 nm and 100 nm, the interaction force between the FeCo alloy nanowires increased, the domain state of FeCo alloy nanowires changed from Single Domain (SD) to Multi-Domain (MD), the magnetic reversal mode changed from coherent reversal mode to curling reversal mode.

Comparison of Tensile Bond Strength of Soft Denture Liner Material on Denture Base Resins

Aim: This study aims to evaluate the tensile bond strength (TBS) of a silicone-based soft denture liner material on denture bases produced via conventional, subtractive, and additive manufacturing techniques and examine the effect of aluminum oxide particle abrasion (APA) on TBS. Material and Methods: A total of 48 cylindrical denture base resin samples were manufactured using three different techniques: conventional, subtractive, and additive manufacturing. The samples were divided into two groups: control and APA. All samples were separated at the center, and the soft liner was applied to the corresponding surfaces. The specimens then underwent TBS testing. Data were analyzed using Two-way ANOVA and Bonferroni post hoc tests. Results: Two-way ANOVA results indicated a significant difference among the denture base resins, while no significant difference was found between the control and APA groups. The highest TBS was observed in the subtractive-manufactured APA group, while the lowest TBS was in the additive-manufactured APA group. Significant differences were found between the subtractive and additive-manufactured groups (p=0.022). Conclusion: This study demonstrates that TBS varies with the DB's manufacturing technique. While APA increased TBS in subtractive manufacturing, it had no statistically significant effect. Further research should explore different soft lining materials and consider in vivo conditions for more comprehensive insights.

Role of scandium addition to microstructure, corrosion resistance, and mechanical properties of AA7085/ZrB2+Al2O3 composites

The effect of varying amounts of scandium (Sc) on the mechanical performance and corrosion resistance of aluminum alloy (AA7085) composites reinforced with Zirconium diboride (ZrB2) and Aluminum oxide (Al2O3) nanoparticles was investigated. The specimens were made using an in-situ process with varying amounts of Sc up to 0.5 wt%, and their microstructural behavior, corrosion, and mechanical properties were explored in detail. Phase structural analysis revealed the successful incorporation of ZrB2 and Al2O3 into the matrix through in-situ synthesis, ranging from 30 to 61.7 nm. In addition, HRTEM and XRD analysis displays the Al3Zr prominence observed with 0.1 wt% Sc content, transforming to Al3(Sc, Zr) in the 0.3 wt% Sc composite, and finally becoming Al3Sc with 0.5 wt% Sc. Corrosion analysis revealed that the 0.3 wt% Sc composite exhibited fine Al3(Sc, Zr) precipitate phases that enhanced corrosion properties. The Sc addition leads to a significant improvement in the mechanical properties of AA7085/ZrB2+Al2O3 composites. The ultimate tensile strength of 678 ± 5 MPa for 0.5 wt% Sc under the hot rolled and T6 aged condition was achieved. The optimum content of Sc in AA7085/ZrB2+Al2O3 composites has identified both corrosion and mechanical properties enhancement at 0.3 wt% and 0.5 wt%, respectively.

Facile Fabrication of Hierarchical Structured Anodic Aluminum Oxide Molds for Large-Scale Production of Superhydrophobic Polymer Films.

Anodized aluminum oxide (AAO) molds were used for the production of large-area and inexpensive superhydrophobic polymer films. A controlled anodization methodology was developed for the fabrication of hierarchical micro-nanoporous (HMN) AAO imprint molds (HMN-AAO), where phosphoric acid was used as both an electrolyte and a widening agent. Heat generated upon repetitive high-voltage (195 V) anodization steps is effectively dissipated by establishing a cooling channel. On the HMN-AAO, within the hemispherical micropores, arrays of hexagonal nanopores are formed. The diameter and depth of the micro- and nanopores are 18/8 and 0.3/1.25 µm, respectively. The gradual removal of micropatterns during etching in both the vertical and horizontal directions is crucial for fabricating HMN-AAO with a high aspect ratio. HMN-AAO rendered polycarbonate (PC) and polymethyl methacrylate (PMMA) films with respective water contact angles (WCAs) of 153° and 151°, respectively. The increase in the WCA is 80% for PC (85°) and 89% for PMMA (80°). On the PC and PMMA films, mechanically robust arrays of nanopillars are observed within the hemispherical micropillars. The micro-nanopillars on these polymer films are mechanically robust and durable. Regular nanoporous AAO molds resulted in only a hydrophobic polymer film (WCA = 113-118°). Collectively, the phosphoric acid-based controlled anodization strategy can be effectively utilized for the manufacturing of HMN-AAO molds and roll-to-roll production of durable superhydrophobic surfaces.

One-step hydrothermal fabrication of Co-MOFs/LDH superhydrophobic composite coating with corrosion resistance and wear resistance on anodic aluminum oxide

In recent years, metal–organic framework materials (MOFs) have garnered significant attention in the field of metal corrosion protection. In this study, novel Co-MOFs were synthesized using cobalt nitrate as the metal source and 4,4′-bipyridine as the organic ligand. A one-step solvothermal method was employed to synthesize a black MOFs/LDH composite coating, integrating corrosion resistance, friction reduction, and hydrophobicity into a single coating. The successful reaction between metal ions and organic ligands was confirmed through FTIR, FE-SEM, EDX, XRD, and XPS characterization tests. Cross-sectional SEM and EDX analyses demonstrated the successful synthesis of the coating. Electrochemical tests indicated that after 14 days of immersion in 3.5 wt% NaCl, the composite coating exhibited the lowest corrosion current of 2.23 × 10−9 A∙cm−2, outperforming the aluminum substrate (5.99 × 10−6 A∙cm−2) and anodized aluminum (7.08 × 10−7 A∙cm−2). Hydrophobicity tests showed that without additional modification with low surface energy substances, the composite coating had a contact angle of 154.7°, demonstrating excellent hydrophobicity. Tribological tests revealed that the composite coating exhibited superior tribological performance, with a friction coefficient of 0.3.

Large area pulsed laser deposition of memristive Pr0.7Ca0.3MnO3 heterostructures for neuromorphic computing

Heterostructures of the perovskite Pr0.7Ca0.3MnO3 (PCMO) and a tunnel oxide such as AlOx are highly interesting memristive devices for emulating synaptic properties in neuromorphic circuits. Future chip generations with these memristive elements requires PLD systems which enables PCMO growth on a full wafer. To address the issue of plume broadening in this study, a slit system was used to localize the deposition region, thereby eliminating the need for excessive scanning. This study investigates the effect of the slit system and process gas pressure on plume broadening. This investigation has been used to parameterize a simulation software to assess the effectiveness of different movement speeds and to develop strategies for homogeneous deposition, adjustable to a chosen film thickness in the order of twenty nanometers. We used these strategies to fabricate area dependent switching memory cells on a standard 4″ Si wafer using the material combination of Pr0.7Ca0.3MnO3 and AlOx. The influence of the aluminum oxide thickness on the switching shows that the IV loop starts to exhibit a hysteresis for AlOx thicknesses ≥ 3 nm. An increase in AlOx thickness leads to an increase in resistance and capacitive charging. An additional thermal treatment reduces the resistance and the switching voltage and increases the ratio between low resistive and high resistive state. Devices without thermal treatment of the PCMO are compatible for back end of line processing of standard CMOS technology.

Development of Novel Surface-Enhanced Raman Spectroscopy-Based Biosensors by Controlling the Roughness of Gold/Alumina Platforms for Highly Sensitive Detection of Pyocyanin Secreted from Pseudomonas aeruginosa.

Pyocyanin is considered a maker of Pseudomonas aeruginosa (P. aeruginosa) infection. Pyocyanin is among the toxins released by the P. aeruginosa bacteria. Therefore, the development of a direct detection of PYO is crucial due to its importance. Among the different optical techniques, the Raman technique showed unique advantages because of its fingerprint data, no sample preparation, and high sensitivity besides its ease of use. Noble metal nanostructures were used to improve the Raman response based on the surface-enhanced Raman scattering (SERS) technique. Anodic metal oxide attracts much interest due to its unique morphology and applications. The porous metal structure provides a large surface area that could be used as a hard template for periodic nanostructure array fabrication. Porous shapes and sizes could be controlled by controlling the anodization parameters, including the anodization voltage, current, temperature, and time, besides the metal purity and the electrolyte type/concentration. The anodization of aluminum foil results in anodic aluminum oxide (AAO) formation with different roughness. Here, we will use the roughness as hotspot centers to enhance the Raman signals. Firstly, a thin film of gold was deposited to develop gold/alumina (Au/AAO) platforms and then applied as SERS-active surfaces. The morphology and roughness of the developed substrates were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The Au/AAO substrates were used for monitoring pyocyanin secreted from Pseudomonas aeruginosa microorganisms based on the SERS technique. The results showed that the roughness degree affects the enhancement efficiency of this sensor. The high enhancement was obtained in the case of depositing a 30 nm layer of gold onto the second anodized substrates. The developed sensor showed high sensitivity toward pyocyanin with a limit of detection of 96 nM with a linear response over a dynamic range from 1 µM to 9 µM.

Tube cross-section flatness optimization to enhance the cooling performance of nanofluid-based photovoltaic thermal systems combined with nano-enhanced phase change material

Photovoltaic (PV) systems have emerged as a crucial technology in transitioning to sustainable energy. Despite their growing prominence, PV panels face challenges related to temperature-induced that can lead to reduced energy output. By considering this, the utilization of cooling systems is useful. In the quest to design the active cooling system for PV panels, a key challenge remains in optimizing tube cross-section configurations. In this study, a validated CFD simulation investigates the impact of the tube cross-section flatness (tube flattening) on the cooling performance of the nanofluid-based photovoltaic thermal system combined with nano-enhanced Phase Change Material (PCM). Evaluation parameters for cooling performance are PV surface temperature (T_s), PCM liquid Fraction (LF), tube pressure drop (ΔP), and the PV temperature uniformity (ΔT). Aluminum Oxide (Al2O3) and Silver (Ag) nanoparticles are used in different concentrations (0 %, 1 %, 5 %, 10 %). Also, using the Response Surface Method (RSM), a multi-objective optimization determines the optimal tube flattening percentage for achieving the best cooling performance. The ideal state entails minimizing T_s, maximizing LF, minimizing ΔP, and minimizing ΔT. The findings indicate that increasing tube flattening leads to a decrease in T_s, a decrease in LF, an increase in ΔP, and a reduction in ΔT. Reducing the T_s and ΔT is a favorable effect but increasing the ΔP and reducing the LF is unfavorable to the system's cooling performance. After evaluating different parameters in the optimized scenarios, the most optimal mode is determined when the system uses Ag nanofluid in 10 % concentration, PCM without nanoparticles, and tube with 44 % flattening. In this scenario T_s, LF, ΔP, and ΔT are respectively 54.04 °C, 37.7 %, 117.67 Pa, and 34.74 °C.

Electrode reactions on the aluminum electrode in 1-butyl-3-methylimidazolium chloride chloroaluminate ionic liquid: A comprehensive study

Mechanisms of Al electrochemical deposition/dissolution in acidic AlCl3–1-butyl-3-methylimidazolium chloride (BMImCl) ionic liquids are studied. Stationary polarization curves (SPCs) are obtained in the anodic range of potentials. The anodic SPCs are characteristic of electrode processes, which are complicated by passivation phenomena. The peaks intensity of AlCl4−, Al2Cl7− ions were obtained by in-situ Raman spectroscopy during the aluminum electrode polarization and correlated with the behavior of the SPCs. Based on the results obtained, a mechanism of electrochemical oxidation of aluminum in AlCl3–BMImCl IL is proposed. According to the mechanism in question, the anodic process is complicated by the presence of a following chemical reaction involving AlCl3. Chronopotentiometric studies were carried out to determine diffusion coefficients of Al2Cl7− anion, which are unaffected by the change in the molar ratio of AlCl3 to BMImCl (N). The activation energy (Ea) for the Al2Cl7− diffusion coefficient is independent of N and equals 14.5 ± 0.4 kJ mol−1. Exchange current density (i0) at the Al | AlCl3–BMImCl interface was determined using impedance spectroscopy for the compositions with 1.1 ≤ N ≤ 2.0 at temperatures from 303 to 386 K. The i0 increases from 0.54 ± 0.13 to 2.73 ± 0.22 mA cm−2 with the concentration of the electrochemically active Al2Cl7− anion in the concentration range indicated above at 303 K. The data on i0 is used to calculate the transfer coefficient of cathodic reaction (α = 0.18 ± 0.02), the electrochemical reaction rate constant (ks= (1.1 ± 0.3)∙10−6 cm s−1 (at T = 303 K)) and the Ea for the ks (Eaks = 36.5 ± 0.9 kJ mol−1), which do not depend on the IL composition.

Effect of phosphoric acid etching and blasting with aluminum oxide on the enamel topography and adhesion of resin composite to intact or abraded enamel

ObjectivesTo evaluate the effects of the phosphoric acid (PA) etching, self-etching technique (SE) and blasting with Al2O3 particles (BL) on the bonding of a dental adhesive to intact (INT) or abraded (ABR) enamel. MethodsEnamel surfaces were treated as follows: 1- ABR-PA: INT was abraded with SiC paper and etched with PA (20 s) before Clearfil Universal Bond Quick adhesive application; 2- ABR-SE: ABR was SiC and adhesive applied in SE mode; 3- INT-PA: INT was etched with PA and adhesive applied; 4- INT-SE: the adhesive (SE mode) was applied to INT; 5- INT-BL: INT was BL and the adhesive was applied (SE mode), and 6- INT-BA: INT was BL, etched with PA and adhesive applied (SE mode). The enamel surface treated was examined with scanning electron microscopy (SEM) (n = 3) and Al2O3 particles were characterized using SEM and EDX. The enamel bond strength was measured by microtensile test (24 h and 1 year) (n = 8) and the morphology of enamel-adhesive interfaces were analyzed by SEM (n = 3). Bond strength data were analyzed by two-way ANOVA and Tukey’s test (α = 0.05). ResultsAl2O3 particles had an irregular shape, their length varied (50–20 µm) and the perimeter mean was 38.8 µm. The enamel morphology significantly influenced the enamel bond strength. ABR-PA, INT-BL, and INT-BA provided greater and stable enamel-dentin interaction and bond strength. SignificanceThe enamel morphology significantly influenced the enamel bond strength. Using the adhesive in etch-and-rinse mode, enamel must be abraded before etching and must be Al2O3-blasted when used in SE mode.

Cobalt-free cathodes and silicon thin-film anodes towards high-capacity solid-state batteries

This study provides a comprehensive analysis of a novel battery system, which integrates a high-loading (∼5 mAh/cm2) cobalt-free cathode composed of lithium nickel manganese aluminum oxide (LiNi0.9Mn0.05Al0.05O2, NMA) into an all-solid-state cell for the first time. The argyrodite (Li6PS5Cl) solid electrolyte is used in conjunction with a 99 wt% silicon thin-film anode. Room temperature discharge capacities of >210 mAh/gNMA and > 170 mAh/gNMA were achieved at cycling rates of 0.05C and 0.25C, respectively. Electrochemical impedance spectroscopy measurements, taken during the first cycle detail onset of electrolyte degradation, lithiation of the silicon anode, and the change in charge transfer kinetics as a function of cell voltage. Raman, Fourier Transform Infrared, and X-ray photoelectron spectroscopy are used to identify the argyrodite degradation products that form in the catholyte on cycling, unveiling lithium carbonate as a potential source of oxygen-related degradation commonly alluded to in literature. Furthermore, high cell stack pressure, 350 MPa during fabrication, led to fracturing and pulverization of some cathode particles.

Experimental analysis on the thermoelectric effect of various solid-state devices used for direct conversion of thermal energy into electrical energy

In this present investigation, the performance of thermoelectric generators (TEGs) was determined for the TEGs made of lead telluride (PbTe3), bismuth telluride (Bi2Te3), silicon germanium (SiGe), and aluminum oxide (Al2O3). In response to variations in the heat input rate and water flow rate, the electric power generated by the TEG was recorded and studied for the aforementioned TEG materials. During the investigation, the water flow rate to the TEG's cold side was chosen to be 0.5 lpm to 2 lpm in the step of 0.5 lpm, and the thermal energy input rate to the hot side was set at 30 W–120 W in the step of 30 W. Among all the TEGs Bi2Te3 was superior in terms of power generation potential in comparison to other TEGs in all the test conditions. The investigation also reveals that all TEGs appear to have a high-power generation when the cooling water flow rate was 2 lpm and the heat input rate was 120 W. At a water flow rate of 2 lpm for the case of Bi2Te3, the power generation potential was elevated by about 20.3 %, 14.4 %, and 6.5 % in comparison to Al2O3, PbTe3, and SiGe respectively.

Self-Assembled Plasmonic Structural Color Colorimetric Sensor for Smartphone-Based Point-Of-Care Ammonia Detection in Water.

Monitoring chemical levels is crucial for safeguarding both the environment and public health. Elevated levels of ammonia, for instance, can harm both humans and aquatic ecosystems, often indicating contamination from agriculture, industry, or sewage. Developing portable, high-resolution, and affordable methods for in situ monitoring of ammonia is thus imperative. Plasmonic sensors offer a promising solution, detecting ammonia by correlating changes in their optical response to the target analyte's concentration. While they are highly sensitive and can be fabricated in a variety of portable and user-friendly formats, some still require reagents or expensive optical equipment, which hinder their widespread adoption. Here, we present a self-assembled nanoplasmonic colorimetric sensor capable of directly detecting ammonia concentrations in aqueous matrices. The proposed sensor exploits the plasmonic resonance of the nanostructures to transduce changes in the chemical environment into alterations in color, offering a label-free method for real-time analysis. The sensor is fabricated using a self-assembling technique compatible with low-cost mass production based on aluminum and aluminum oxide, ensuring affordability and avoiding the use of other toxic chemicals. We developed a model to predict ammonia concentrations based on visible color change of the sensor, achieving a detection limit of 8.5 ppm. Furthermore, to address the need for on-site detection, we integrated smartphone technology for real-time color change analysis, eliminating the need for expensive, bulky optical instruments. Indeed, our approach offers a cost-effective, portable, and user-friendly solution for ammonia detection in water without the need for chemical reagents or spectrometers, making it ideal for field applications. Interestingly, this platform extends its applicability beyond ammonia detection, enabling the monitoring of various chemicals using a smartphone, without the need for any additional costly equipment.

Streamlines and neural intelligent scheme for thermal transport to infinite shear rate for ternary hybrid nanofluid subject to homogeneous-heterogeneous reactions

SignificanceThe CuO, Al2O3, and TiO2 nanoparticles find extensive applications in advanced chemical reaction-based thermal transport and quadratic convective nanofluids due to their exceptional thermal properties and chemical stability. Increased thermal conductivity of these nanoparticles used to enhance heat transfer in various chemical reactors, resistance to chemical degradation and photocatalytic reactors and solar energy applications. MotiveThis study brings the investigation about quadratic convection-based thermal transport to infinite shear rate for magnetized ternary radiative cross nanofluid with homogeneous-heterogeneous chemical reactions. Water is taken as base fluid and three nanoparticles are Copper oxide (CuO), aluminium oxide (Al2O3), and titanium dioxide (TiO2). Heat transport analysis is made through quadratic convection, magnetic field and thermal radiation. Concentration of nanofluid is scrutinized though homogeneous-heterogeneous chemical reactions. Methodology: Physical problem with assumptions generates the system of partial differential equations (PDEs) and these PDEs are transformed into ordinary differential equations (ODEs) through similarity variables. Furthermore, a unique combination of Bvp4c and Levenberg Marquardt neural network (LM-NN) schemes is utilized to fetch the numerical solutions. Bvp4c is utilized to solve the governing equations, while LM-NN serves to enhance predictive capabilities and capture intricate nonlinear relationships. FindingsMagnetic environment, chemical process, radiations effects and volumetric fraction of nanoparticles make better heat transfer efficiency and control.

Water-resistant properties improvement of aluminium oxide nanoparticles treated kraft paper by sparking process

This study aims to improve the hydrophobicity of non-sizing Kraft paper (KP) surfaces using nanoparticle coating through the sparking process. The aluminium oxide nanoparticles (Al2O3 NPs) were used for surface modification on KP through the sparking process, optimizing with varying sparking cycles (5–20 times), annealing temperatures (60–120 °C), and annealing times (1–3 h). Then, the Al2O3 NPs treated KP were examined by XRD, FT–IR, SEM, EDX, and AFM, respectively. The water contact angle (CA) was used to examine the water-resistant properties of the treated KP. The treated KP with varying sparking cycles up to 15 times showed higher surface coverage and enhanced fine roughness surface on the treated KP. The fine roughness surface of KP induced hydrophobicity (126° of CA) on the surface of KP at 15 sparking cycles. Similarly, the higher CA for hydrophobicity surface on treated KP from varying temperatures and times of the annealing process was demonstrated at 120° for 3 h. Therefore, the treated KP with 15 times of sparking cycle, annealing temperature at 120 °C for 3 h was defined as the optimized condition in this work. Furthermore, the developments of hydrophobicity and superhydrophobicity on the treated KP with CA at 135 and 155° were observed for the non-sizing and sizing KP, respectively. This indicated that the increased surface roughness and reduced surface energy of the treated KP simultaneously delayed the water absorption times on the KP surface. Consequently, the nano-treating of Al2O3 NPs using the sparking process shows the promising feature of inducing superhydrophobicity on the KP surface, which can produce a water-repellent corrugated box as an alternative packaging material.

Atomically Precise Graphene Nanoribbon Transistors with Long-Term Stability and Reliability.

Atomically precise graphene nanoribbons (GNRs) synthesized from the bottom-up exhibit promising electronic properties for high-performance field-effect transistors (FETs). The feasibility of fabricating FETs with GNRs (GNRFETs) has been demonstrated, with ongoing efforts aimed at further improving their performance. However, their long-term stability and reliability remain unexplored, which is as important as their performance for practical applications. In this work, we fabricated short-channel FETs with nine-atom-wide armchair GNRs (9-AGNRFETs). We revealed that the on-state (ION) current performance of the 9-AGNRFETs deteriorates significantly over consecutive full transistor on and off logic cycles, which has neither been demonstrated nor previously considered. To address this issue, we deposited a thin ∼10 nm thick atomic layer deposition (ALD) layer of aluminum oxide (Al2O3) directly on these devices. The integrity, compatibility, electrical performance, stability, and reliability, of the GNRFETs before and/or after Al2O3 deposition were comprehensively studied. The results indicate that the observed decline in electrical device performance is most likely due to the degradation of contact resistance over multiple measurement cycles. We successfully demonstrated that the devices with the Al2O3 layer operate well up to several thousand continuous full cycles without any degradation. Our study offers valuable insights into the stability and reliability of GNR transistors, which could facilitate their large-scale integration into practical applications.

Nanometer-thick molecular beam epitaxy Al films capped with in situ deposited Al2O3—High-crystallinity, morphology, and superconductivity

Achieving high material perfection in aluminum (Al) films and their associated Al/AlOx heterostructures is essential for enhancing the coherence time in superconducting quantum circuits. We grew Al films with thicknesses ranging from 3 to 30 nanometers (nm) epitaxially on sapphire substrates using molecular beam epitaxy (MBE). An integral aspect of our work involved electron-beam (e-beam) evaporation to directly deposit aluminum oxide (Al2O3) films on the freshly grown ultrathin epitaxial Al films in an ultra-high-vacuum (UHV) environment. This in situ oxide deposition is critical for preventing the oxidation of parts of the Al films, avoiding the formation of undesired native oxides, and thereby preserving the nm-thick Al films in their pristine conditions. The thicknesses of our Al films in the study were accurately determined; for example, coherence lengths of 3.0 and 20.2 nm were measured in the nominal 3.0 and 20 nm thick Al films, respectively. These Al films were epitaxially grown on sapphire substrates, showing an orientational relationship, denoted as Al(111)⟨21¯1¯⟩∥sapphire(0001)[21¯1¯0]. The Al/sapphire interface was atomically ordered without any interfacial layers, as confirmed by in situ reflection high-energy electron diffraction (RHEED) and cross-sectional scanning transmission electron microscopy (STEM). All sample surfaces exhibited smoothness with a roughness in the range of 0.1–0.2 nm. The Al films are superconducting with critical temperatures ranging from 1.23 to around 2 K, depending on the film thickness.