Room Temperature Research Articles

Effect of Al or Cu Content on Microstructure and Mechanical Properties of Zn Alloys Fabricated Using Continuous Casting and Extrusion

The effect of Al or Cu content on the microstructure and mechanical properties of continuous casting and extrusion Zn alloys has been studied by a room temperature tensile test, X-ray diffraction, and scanning electron microscope. With the increase in Al content, the microstructure of continuous casting and extrusion Zn alloys slightly coarsens, and the lamellar eutectic structure increases. The changes in the above structural factors result in a slight decrease in strength and a significant increase in the elongation of Zn-Al alloys. The strength of Zn alloys increases as the Cu content increases due to the increased content and size of the second phase in the Zn alloys. This means that the mechanical properties of Zn alloys can be adjusted by a continuous casting and extrusion process, and the improvement of equipment capacity can improve the structure and morphology of the alloys.

Enhanced Room-Temperature NO2 Sensing through Deep Functional Group Hybridization in Nitrogen-Doped Monolayer Ti3C2Tx.

Nitrogen dioxide (NO2) is a significant environmental and human health hazard. Current NO2 sensors often lack sensitivity and selectivity under ambient conditions. This study investigates ammonia pyrolysis modification of monolayer Ti3C2Tx MXene to enhance NO2 detection at room temperature. Nitrogen-doped Ti3C2Tx demonstrates a substantial improvement in sensitivity, with a response of 8.87% to 50 ppm of NO2 compared to 0.65% for the original sensor, representing a 13.8-fold increase. The nitrogen-doped sensor also exhibits superior selectivity and linearity for NO2 under ambient conditions. Theoretical analysis shows that nitrogen incorporation promotes enhanced interaction between Ti3C2Tx and its surface oxygen-containing functional groups through electronic hybridization, resulting in improved adsorption energy (1.80 |eV|) and electron transfer efficiency (0.67 |e|) for NO2, thereby enhancing its gas-sensing performance. This study highlights the potential of ammonia pyrolysis-treated Ti3C2Tx MXene for advancing NO2 sensor technologies with heightened performance at room temperature.

The effect of vanadium on the magnetic and mechanical properties of B2 FeCo alloy: a DFT approach

FeCo alloys play an important role in soft magnetic materials with a wide range of technological applications due to their high saturation magnetization and Curie temperature. However, these alloys have low ductility at room temperature. The ductility can be improved by the ternary addition of elements such as V. A density functional theory supercell approach was used to generate B2 Fe50Co50-xVx (0 < x < 50) structures and the properties were evaluated at different atomic percentage compositions to determine the ductility at room temperature. The structures were fully optimized to obtain better equilibrium ground-state properties such as lattice parameters and thermodynamic properties for both binary and ternary systems. The stability of Fe50Co50-xVx was evaluated from the heats of formation, elastic properties, and phonon dispersion curves. Furthermore, magnetic strength was evaluated from magnetic moments. It was found that all structures are thermodynamically stable due to the negative heats of formation. The calculated Pugh's ratio and Poisson's ratio confirm that alloying with V effectively improved the ductility. It was also found that Fe50Co50-xVx showed a positive shear modulus for the entire concentration range investigated, in agreement with phonon dispersion curves. The ternary addition of V to the FeCo system resulted in reduced magnetic strength due to a decrease in magnetic moments. These findings reveal that B2 FeCo-V alloys can be used as components and actuators for the automotive industry.

Physicochemical and Nutritional Characterization of Green Banana Flour from Discarded Cavendish Bananas

Fifteen percent of harvested bananas are discarded daily in the Canary Islands at packing houses because of marketing standards, mainly based on their appearance, or are retired to avoid falls in the market price of bananas. This discarded fruit is an environmental issue, and green banana flour (GBF) is an interesting management alternative for it. In this paper, the artisanal process for obtaining GBF was optimized. The study of physicochemical and nutritional characteristics of this gluten-free flour indicated a high contribution of starch, fiber, phenolics, K, and Mg to dietary intake. Storage of GBF at room temperature (20 ± 5 °C) for ten months slightly increased its moisture and acidity and decreased its starch content, phenolic content, and pH. Some color changes were observed after 5 months, but sensory characteristics were still acceptable after ten months. Green bananas storage prior to GBF elaboration showed they were suitable for obtaining good quality GBF even after 7 weeks at 6 °C, but only 4 weeks at 12 °C. Discriminant analysis classified the GBF correctly according to the cooperative origin, time, and storage temperature of the bananas used in its preparation. These results provide information that could be used in other banana-producing regions for reducing the environmental impact of fruit waste and obtaining GBF using a simple and inexpensive technological process.

Modulating electrical response and impedance in Co–Cr substituted M-phase barium hexaferrites: Examining microstructure, grain boundaries, charge transport, and computational modeling

This study explores the influence of Co2+ and Cr3+ doping on the microstructure and electrical properties of Ba-hexagonal ferrite synthesized using the sol-gel method. X-ray diffraction (XRD) confirmed the formation of the anticipated hexagonal M-type crystal structure. Field emission scanning electron microscopy (FESEM) revealed the evolution of grain morphology with increasing doping levels, showcasing the formation of needle-like grains. Electrical characterization using an impedance analyzer investigated dielectric, impedance, electric modulus, and conductivity properties at room temperature. The analysis of the dielectric spectra indicated a decrease in dielectric constant and an increase in loss tangent with increasing dopant concentration. The electric modulus spectra provided evidence for non-Debye relaxation behavior, further supported by observations of relaxation processes at varying frequencies in the conductivity spectra. Additionally, an increase in doping led to a decrease in both relaxation time and AC conductivity. Electrochemical impedance spectroscopy (EIS) measurements yielded complex impedance curves. These curves exhibited good agreement with the values obtained through software-based simulations of grain and grain boundary characteristics. Furthermore, the distribution of grains and grain boundaries observed in FESEM micrographs aligned with the patterns predicted by the EIS software.

Multicomponent intermetallic compound CoCrFeNiSi: Crystal structure and magnetic properties

A novel intermetallic compound with a cubic crystal structure was successfully synthesized within the quinary system of CoCrFeNiSi, boasting an almost equiatomic chemical composition. The crystal structures of the intermetallics and the minor impurity phase has been meticulously investigated using X-ray diffraction (XRD), time-of-flight neutron diffraction and transmission electron microscopy. Magnetic measurements of this high-entropy intermetallic compound revealed that CoCrFeNiSi exhibits ferrimagnetic properties at room temperature. The structural disorder was investigated through theoretical calculations and magnetic moment measurements.

Wearable, eco-mimetic, and bicontinuous Ag-doped poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)/MnO2/carbon fabric for multifunctionality

Wearable and bicontinuous Ag-doped poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate)/MnO2/carbon fabric was manufactured in a facile, eco-friendly, and scalable approach. The high temperature-resistant textile performed a maximum specific capacitance of 2.97 F cm−2, and delivered 113 % retention at 80 °C compared with that at room temperature. At a cooling-heating-cooling cycle, the capacitance could recover to its initial value after 10000 charge-discharge tests at 20 mA cm−2. Density function theory proves that Ag dopants and the S-containing functional group improve the adsorption ability with Na+. The maximum energy and power density achieved 19.36 mWh cm−3 and 530.50 mW cm−3 over a wide potential window of 2 V, respectively. Moreover, the fabric could be operated at low-temperature climates by multi-offset Joule heating performance and a deicing/dewatering ability. The antimicrobial capacity against typical bacteria and fungi renders robust safety to the wearable electronics. The fabric performed shielding effectiveness of 45.95 dB at 377 μm and reliable durability after 1000 times bending cycles. The reflection-dominant shielding mechanism was further revealed by COMSOL Multiphysics software. The all-in-one fabric complies with Internet of Things design and can endure extreme environments over a wide temperature range, implying great potential for energy storage, thermal management, bacteriostasis, and electromagnetic protection.

Adsorptive removal of Oxytetracycline hydrochloride using bagasse-based biochar powder and beads

Oxytetracycline Hydrochloride (OTC), a common antibiotic used to treat specific illnesses in humans and animals, is characterized by poor absorption into cells, low volatility, and high hydrophilicity. It is a potent contaminant that poses a serious threat to the ecosystem, particularly the aquatic sources. Adsorption onto natural adsorbents is one of the most successful, economical, and ecologically friendly ways to remove antibiotics from waste water. The present work focuses on the adsorption of OTC utilizing alginate biochar beads (AlBCB) and biochar powder (BC) derived from bagasse. The influence of several factors were studies and optimized through batch studies employing BC and AlBCB. After 50 minutes BC displayed a removal of 97%, at an initial concentration of 10 ppm. The experimental data was discovered to follow PFO kinetics and fit with the Freundlich isotherm adsorption model. AlBCB, after a contact time of 40 minutes, indicated a maximum percentage removal of 86% for initial concentration of 10 ppm OTC. Al-biochar beads showed the maximum percentage removal at pH 10. 0.5 g of adsorbent was used to carry out all batch experiments at room temperature. The adsorption fitted Freundlich adsorption isotherm and intraparticle diffusion kinetics.

Ag2Se as a tougher alternative to n-type Bi2Te3 thermoelectrics

For half a century, only Bi2Te3-based thermoelectrics have been commercialized for near room temperature applications including both power generation and refrigeration. Because of the strong layered structure, Bi2Te3 in particular for n-type conduction has to be texturized to utilize its high in-plane thermoelectric performance, leaving a substantial challenge in toughness. This work presents the fabrication and performance evaluation of thermoelectric modules based on n-type Ag2Se paring with commercial p-Bi2Te3. Ag2Se mechanically allows an order of magnitude larger fracture strain and thermoelectrically secures the module efficiency quite competitive to that of commercial one for both refrigeration and power generation within ± 50 K of room temperature, enabling a demonstration of a significantly tougher alternative to n-type Bi2Te3 for practical applications.

Block Copoly (Ester-Carbonate) Electrolytes for LiFePO4|Li Batteries with Stable Cycling Performance

To address the challenges posed by the narrow oxidation decomposition potential window and the characteristic of low ionic conductivity at room temperature of solid polymer electrolytes (SPEs), carbon dioxide (CO2), epichlorohydrin (PO), caprolactone (CL), and phthalic anhydride (PA) were employed in synthesizing di-block copolymer PCL-b-PPC and PCL-b-PPCP. The carbonate and ester bonds in PPC and PCL provide high electrochemical stability, while the polyether segments in PPC contribute to the high ion conductivity. To further improve the ion conductivity, we added succinonitrile as a plasticizer to the copolymer and used the copolymer to assemble lithium metal batteries (LMBs) with LiFePO4 as the cathode. The LiFePO4/SPE/Li battery assembled with PCL-b-PPC electrolyte exhibited an initial discharge-specific capacity of 155.5 mAh·g−1 at 0.5 C and 60 °C. After 270 cycles, the discharge-specific capacity was 140.8 mAh·g−1, with a capacity retention of 90.5% and an average coulombic efficiency of 99%, exhibiting excellent electrochemical performance. The study establishes the design strategies of di-block polymer electrolytes and provides a new strategy for the application of LMBs.

Novel mixed self-assembled monolayers of L-cysteine and methanol on gold surfaces under ambient conditions.

In this work, we carried out an experimental and theoretical study on the formation of self-assembled monolayers of L-cysteine molecules on gold surfaces in the presence of methanol as a solvent. We report for the first time L-cysteine and methanol ordered structures forming a mixed self-assembled mono-layer on Au(100) surfaces under ambient conditions. Finger-like ordered structures with a relative height of 0.10-0.20 nm, average width of 2.0 nm and variable lengths were observed using scanning tunneling microscopy under room temperature and ambient pressure conditions. Using X-ray photoemission spectroscopy, it was determined that L-cysteine molecules bind to the gold surface through the sulfur atom of their thiol group in two molecular configurations: neutral and zwitterionic. We found that the finger-like structures are the result of complex interactions of L-cysteine molecules with gold surfaces and L-cysteine molecules with methanol molecules and among all three components of the system (L-cysteine + methanol + gold surfaces). These interactions were detected through attenuated total reflectance-Fourier transform infrared spectroscopy. Furthermore, adsorbate/substrate interactions were studied by employing ab initio calculations using density functional theory, resulting in molecular arrangements formed by chains of L-cysteine pairs surrounded by physisorbed methanol molecules.

Thermally Induced Moisture Flow in a Silty Sand under a 1-D Thermal Gradient

Thermally induced moisture flow in unsaturated soils involves complex coupled thermal–hydro processes with the moisture flow in both the vapor and liquid phases. The accurate measurement of the moisture flow in unsaturated sands remains a challenging task due to low moisture migration, the temperature effect on moisture sensors, and the gravity effect on moisture flow. This study aims to accurately measure transient moisture flow, heat transfer, and thermal conductivity in a silty sand with 35% non-plastic fines in a closed heat cell with a controlled 1-D temperature gradient. The heat cell consists of two temperature-controlled heat exchanger plates, heat flux sensors, moisture sensors, thermocouples, and thermal conductivity sensors. The soil moisture sensors were calibrated in the test soil at room temperature and then at elevated incremental temperatures. Soil samples compacted at various initial moisture contents were tested under a constant 1-D temperature gradient of 4 °C/cm. Soil moisture redistribution, temperature, and thermal conductivity profiles were determined from the test results. Transient temperature responses indicated that a lower initial moisture content led to a higher temperature drop after reaching the peak, or a more concaved temperature profile in a steady state due to enhanced moisture migration driven by the temperature gradients. Dry soils exhibited uniform thermal properties, while moist soils showed varying thermal conductivity profiles. A critical moisture content was identified when the maximum moisture migration occurred. Thermal conductivity in soils increased with the distance from the heat source due to thermally induced moisture migration. These findings provide valuable insights into coupled moisture–heat flow dynamics in unsaturated sands.

Optical cooling of a Yb-doped alumino-phosphosilicate fiber in air by −250 mK

Recent progress in the fabrication of Yb-doped silicate fibers with low concentration quenching and low background absorption loss has led to the demonstration of anti-Stokes-fluorescence cooling in several aluminosilicate compositions. This breakthrough is critical to combat deleterious thermal effects due to the quantum defect in fiber lasers and amplifiers. Since cooling efficiencies remain low (1–2.7%), it is paramount to engineer compositions that improve this metric. We report a silica fiber with a core glass heavily doped with aluminum and phosphorus that sets, to our knowledge, a few new records. This few-mode fiber (16-µm core) was cooled in air by −0.25 K from room temperature with ∼0.5 W of 1040-nm power. The measured cooling efficiency is 3.3% at low pump power and 2.8% at the power that produced maximum cooling. The critical quenching concentration inferred from the measured dependence of cooling on pump power and careful calibration of the pump absorption and saturation is 79 wt.%. The inferred background absorption loss is 15 dB/km. Together with the fiber’s average Yb concentration of 4.2 wt.%, these metrics rank among the best reported in a silica glass.

Dual-driving parametric locking of GHz phonon sources to sub-hertz linewidth in optomechanical systems

In the exploration of collective dynamics and advanced information processing, synchronization and frequency locking of mechanical oscillations are cornerstone phenomena. Traditional synchronization techniques, which typically involve a single mechanical mode, are limited by their inability to distinguish between intrinsic mechanical oscillations and external signals after locking. Addressing this challenge, we introduce a parametric approach that enables simultaneous frequency locking of two gigahertz mechanical modes within an optomechanical crystal cavity. By modulating the pump light to match the sum and difference frequencies of the mechanical modes, we significantly narrow their linewidths from tens of kilohertz to below 1 Hz at room temperature and ambient pressure. This dual-locking scheme also drastically reduces the phase noise of the mechanical modes by 76.6 dBc/Hz at a 100 Hz offset, while allowing flexible tuning of the locked modes’ frequencies via input signal adjustments. Our method not only facilitates direct observation of mechanical oscillations under the locking regime but also enriches the understanding of coherent phonons in multimode regimes, opening new avenues for optomechanical applications in signal processing.

Facile assembly of flexible, stretchable and attachable symmetric microsupercapacitors with wide working voltage windows and favorable durability

With the increasing development of intelligent robots and wearable electronics, the demand for high-performance flexible energy storage devices is drastically increasing. In this study, flexible symmetric microsupercapacitors (MSCs) that could operate in a wide working voltage window were developed by combining laser-direct-writing graphene (LG) electrodes with a phosphoric acid-nonionic surfactant liquid crystal (PA-NI LC) gel electrolyte. To increase the flexibility and enhance the conformal ability of the MSC devices to anisotropic surfaces, after the interdigitated LG formed on the polyimide (PI) film surface, the devices were further transferred onto a flexible, stretchable and transparent polydimethylsiloxane (PDMS) substrate; this substrate displayed favorable flexibility and mechanical characteristics in the bending test. Furthermore, the electrochemical performances of the symmetric MSCs with various electrode widths (300, 400, 500 and 600 μm) were evaluated. The findings revealed that symmetric MSC devices could operate in a large voltage range (0–1.5 V); additionally, the device with a 300 μm electrode width (MSC-300) exhibited the largest areal capacitance of 2.3 mF cm−2 at 0.07 mA cm−2 and an areal (volumetric) energy density of 0.72 μWh cm−2 (0.36 mWh cm−3) at 55.07 μW cm−2 (27.54 mW cm−3), along with favorable mechanical and cycling stability. After charging for ~20 s, two MSC-300 devices connected in series could supply energy to a calculator to operate for ~130 s, showing its practical application potential as an energy storage device. Moreover, the device displayed favorable reversibility, stability and durability. After 12 months of aging in air at room temperature, its electrochemical performance was not altered, and after charging-discharging measurements for 5000 cycles at 0.07 mA cm−2, ~93.6% of the areal capacitance was still retained; these results demonstrated its practical long-term application potential as an energy storage device.

Synthesis and characterization of cubic δ–phase stabilized Bi2O3 electrolytes by triple rare earth cation doping for intermediate temperatures SOFCs

Face–centered cubic–Bi2O3 (δ–phase), a high–ion conductor, is an essential solid electrolyte option, particularly for low–low–temperature SOFC applications. It is widely accepted that δ–Bi2O3 exhibits higher conductivity than the YSZ electrolytes typically utilized in HT–SOFC units. The present study investigates the structural, thermal, surface, and conductivity characteristics of the Bi2O3 electrolytes co–doped with Tb–Sm–Gd rare earth. The XRD data indicate that, except composition 20Tb20Sm20Gd, all compositions are stabilized with the cubic δ–phase at room temperature. The estimated lattice constants additionally suggest lattice contraction, confirming that the partial cation substitutes between host Bi3+ and rare earth cations are successful. The DTA curves do not have any endothermic or exothermic peaks, indicating a possible phase transition. Arrhenius plots prove that DC conductivity decreases as the dopant ratio increases, implying a drop in polarization power. The highest conductivity is found to be 0.131 S/cm for the composition 10Tb10Sm10Gd.

Additive manufacturing of highly entangled polymer networks.

Incorporation of polymer chain entanglements within a single network can synergistically improve stiffness and toughness, yet attaining such dense entanglements through vat photopolymerization additive manufacturing [e.g., digital light processing (DLP)] remains elusive. We report a facile strategy that combines light and dark polymerization to allow constituent polymer chains to densely entangle as they form within printed structures. This generalizable approach reaches high monomer conversion at room temperature without the need for additional stimuli, such as light or heat after printing, and enables additive manufacturing of highly entangled hydrogels and elastomers that exhibit fourfold- to sevenfold-higher extension energies in comparison to that of traditional DLP. We used this method to print high-resolution and multimaterial structures with features such as spatially programmed adhesion to wet tissues.

Lattice dynamics and free energies of Fe–V alloys with thermal and chemical disorder

Molecular dynamics simulations of Fe-V binary alloys with body-centered cubic as the underlying lattice were performed using a classical potential for chemically ordered and disordered states at finite temperatures for a common set of volumes. The equation of state was fitted to the computational data to obtain temperature- and chemical-order-dependent state functions via the Moruzzi-Janak-Schwarz approximation. Additionally, vibrational entropies that account for both thermal and chemical disorder were calculated for the equiatomic compositions from phonon density-of-states curves computed using effective force constants obtained from fits to the simulations. The latter predicts that the vibrational entropy at room temperature at equiatomicity is higher for the ordered phase than for the solid solution, a peculiar behavior previously observed experimentally. The internal energy of mixing favors ordering at all compositions, with a maximum at equiatomicity that decreases as the solute concentration decreases. The configurational entropy contribution to the free energy of mixing is almost entirely responsible for the stability of the high-temperature disordered phase.

Novel eutectic refractory high entropy alloys with superior mechanical performance

In this letter, MoNbTaTiCx(MNTTCx) alloys with a good combination of room-temperature fracture strain and high-temperature (1473 K) strength were successfully prepared by vacuum arc melting. The alloy is composed of the BCC matrix phase and the FCC carbide phase. With the increase of C content, the morphology changed from hypoeutectic to eutectic to hypereutectic finally. The eutectic structures ensure the good comprehensive mechanical properties of the fully eutectic MNTTC0.5 alloy by second-phase strengthening and grain refining, which has a fracture strain of 13.4 % at room temperature and a yield strength of 496 MPa at 1473 K, surpassing many of the reported refractory high-entropy alloys.

Study of temperature-dependent copper iodide thin film by thermal evaporation system

The development of heterostructure devices has gained significant attention towards scientific communities in the present time. This article reports on the effective use of the horizontal thermal evaporation (TE) method to successfully fabricate copper iodide (CuI) films on silicon (Si) substrates. By using the TE technique, CuI-based heterojunctions have been fabricated in this research . CuI exhibits semiconductor qualities of the p-type, making it a promising option for optoelectronic devices in the future. The temperature was varied from room temperature (RT) to 230 °C to synthesise the CuI/Si heterojunction. The structural, morphological, optical, and electrical analyses have been carried out with various substrate temperatures. The x-ray diffraction (XRD) data shows that the CuI films have demonstrated a polycrystalline character and have lattice parameters of 6.03 Å. The Raman spectroscopy study shows the microstructural analysis of CuI films. The field emission scanning electron microscopy (FESEM) study reveals the variation of grain size and shape with synthesis temperature. The atomic force microscope (AFM) was used to estimate the surface roughness. The CuI films were found to be p-type by the Hall effect measurement. The sample synthesised at 130 °C shows the highest mobility of 83.12 cm2 V−1 s−1 with a carrier concentration of 1019 cm−3. The UV-visible (UV–vis) spectroscopy measurements show good absorption of UV light by the CuI thin films. The CuI/Si heterojunctions are rectifying, as demonstrated by the I-V measurements, and those respond well to UV light irradiation.