High‐dielectric constant and low‐loss ceramics in the (Zn1−xCox)Ta2O6 ceramics have been prepared by the conventional mixed oxide route and their microwave dielectric properties have been ...investigated. A phase change or crossover from ZnTa2O6 to CoTa2O6 occurred at x=0.07 and was completed at x=0.11 and it tends to form a continuous solid solution elsewhere. An over‐sintered specimen would lead to a slight decrease in the density resulting in a decline of the dielectric constant and the Q×f value. The specimen with x=0.05 possessed an excellent combination of microwave dielectric properties: ɛr∼38.47, Q×f∼112 000 GHz, and τf∼11.2 ppm/°C. It is proposed as a candidate material for today's 3G passive components and especially small‐sized GPS patch antennas.
The microstructure and the microwave dielectric properties of nano‐scaled α alumina (α‐Al2O3) ceramics with various added amounts of nano‐scaled TiO2 have been investigated. The sintering temperature ...of nano‐scaled α alumina can be effectively lowered by increasing the TiO2 content. The Q×f values of nano‐scaled α alumina could be tremendously boosted by adding an appropriate amount of TiO2. However, introducing excessive TiO2 into the alumina ceramics would instead lead to a decrease in the Q×f values. The phases of TiO2 and Al2TiO5 co‐existed at 1350°C, and the maximum Q×f value appeared right after the eradication of TiO2 phase at 1400°C. Consequently, increasing the TiO2 content to 0.5 wt% yielded a Q×f value of 680 000 GHz (measured at 14 GHz) for nano‐scaled α alumina prepared at 1400°C for duration of 4 h. In addition, a very low loss tangent (tan δ) of 2 × 10−5 was also obtained at 14 GHz. The τf value is strongly correlated to the compositions and can be controlled through the existing phases. In fact, τf could be adjusted to near zero by adding 8 wt% TiO2 to α alumina ceramics. A dielectric constant (ɛr) of 10.81, a high Q×f value of 338 000 GHz (measured at 14 GHz), and a temperature coefficient of resonant frequency (τf) of 1.3 ppm/°C were obtained for nano‐scaled α alumina with 8 wt% TiO2 sintered at 1350°C for 4 h. Sintered ceramic samples were also characterized by X‐ray diffraction and scanning electron microscopy.
Plasmon-mediated shape conversion of spherical silver nanoparticles (NPs) to nanostructures with other shapes under the irradiation of green LEDs (520 ± 20 nm, 35 mw/cm²) at various temperatures (60, ...40, 20, 10, 5, and 0 °C) was performed in this study. It was found that the bath temperature used in the reaction can influence the reaction rates,
, the times needed for the shape transformation process were 5, 11.5, 25, 45, 72, and 100 h at 60, 40, 20, 10, 5, and 0 °C, respectively. In addition, the bath temperature can also alter the morphologies of the final products. The major products are silver nanoplates at 60, 40 and 20 °C. However, they became decahedral silver NPs at 5 and 0 °C. The percentages of decahedral silver NPs synthesized at 60, 40, 20, 10, 5, and 0 °C are 0%, 1%, 5%, 45%, 73%, and 89%, respectively. Measuring the surface-enhanced Raman spectroscopy (SERS) spectra of the probe molecule R6G in the presence of KBr showed that both silver nanoplate colloids synthesized at 60 °C and decahedral silver NP colloids synthesized at 0 °C in the absence of PVP had good SERS activities.
In this study, ilmenite‐MgTiO3 films were sputtered on p‐type Si(111) substrates and the extrinsic effects, such as grain size, crystallinity, and orientation of photoluminescence (PL) properties of ...the films are discussed. To reduce the effect of oxygen vacancies (act as shallow defects) on PL emissions in the films, oxygen (O2) was introduced as the sputtering gas and the excitation light source (λ = 532 nm) which has a corresponding energy (hν = 2.33 eV) below the shallow defect states was used. In this study, intense near‐infrared (NIR) PL emission centered at 810.1 nm at room temperature can be observed when the MgTiO3 thin films exhibit the preferred (003)‐orientation and accompanied by the presence of hexagon‐shaped grains. In this study, the experiment results reveal that the NIR emission intensity of MgTiO3 films highly depend on crystal orientation and/or grain morphology.
In this study, differently shaped silver nanoparticles used for the synthesis of gold nanoclusters with small capping ligands were demonstrated. Silver nanoparticles provide a reaction platform that ...plays dual roles in the formation of Au NCs. One is to reduce gold ions and the other is to attract capping ligands to the surface of nanoparticles. The binding of capping ligands to the AgNP surface creates a restricted space on the surface while gold ions are being reduced by the particles. Four different shapes of AgNPs were prepared and used to examine whether or not this approach is dependent on the morphology of AgNPs. Quasi-spherical AgNPs and silver nanoplates showed excellent results when they were used to synthesize Au NCs. Spherical AgNPs and triangular nanoplates exhibited limited synthesis of Au NCs. TEM images demonstrated that Au NCs were transiently assembled on the surface of silver nanoparticles in the method. The formation of Au NCs was observed on the whole surface of the QS-AgNPs if the synthesis of Au NCs was mediated by QS-AgNPs. In contrast, formation of Au NCs was only observed on the edges and corners of AgNPts if the synthesis of Au NCs was mediated by AgNPts. All of the synthesized Au NCs emitted bright red fluorescence under UV-box irradiation. The synthesized Au NCs displayed similar fluorescent properties, including quantum yields and excitation and emission wavelengths.
Lithium-ion batteries (LIBs) are widely used in applications ranging from electric vehicles to wearable devices. Before the invention of secondary LIBs, the primary lithium-thionyl chloride ...(Li-SOCl2) battery was developed in the 1970s using SOCl2 as the catholyte, lithium metal as the anode and amorphous carbon as the cathode1-7. This battery discharges by lithium oxidation and catholyte reduction to sulfur, sulfur dioxide and lithium chloride, is well known for its high energy density and is widely used in real-world applications; however, it has not been made rechargeable since its invention8-13. Here we show that with a highly microporous carbon positive electrode, a starting electrolyte composed of aluminium chloride in SOCl2 with fluoride-based additives, and either sodium or lithium as the negative electrode, we can produce a rechargeable Na/Cl2 or Li/Cl2 battery operating via redox between mainly Cl2/Cl- in the micropores of carbon and Na/Na+ or Li/Li+ redox on the sodium or lithium metal. The reversible Cl^NaCl or Cl2/LiCl redox in the microporous carbon affords recharge-ability at the positive electrode side and the thin alkali-fluoride-doped alkali-chloride solid electrolyte interface stabilizes the negative electrode, both are critical to secondary alkali-metal/Cl2 batteries.
Plasmon-mediated shape transformation from quasi-spherical silver nanoparticles (AgNPs) to silver nanoprisms (AgNPrs) and decahedral silver nanoparticles (D-AgNPs) under irradiation of blue LEDs (λ = ...456 ± 12 nm, 80 mW/cm
) was studied at temperatures ranging between 60, 40, 30, 20, 10, and 0 °C. It was found that reaction temperature affected transformation rates and influenced the morphology distribution of final products. The major products synthesized at temperatures between 60 °C and 0 °C were AgNPrs and D-AgNPs, respectively. The D-AgNPs synthesized at such low temperatures are unstable and become blunt when light irradiation is removed after the photochemical synthesis. These blunt nanoparticles with pentagonal multiple-twinned structures can be further used as the seeds to reconstruct complete D-AgNPs after irradiating blue LEDs at various bath temperatures. Our results showed that these rebuilt D-AgNPs are much more stable when at higher bath temperatures. Furthermore, the rebuilt D-AgNPs (edge lengths ~41 nm) can grow into larger D-AgNPs (edge lengths ~53 nm) after the irradiation of green LEDs. Surface-enhanced Raman spectra of CV in AgNP colloids showed that D-AgNP colloids have better SERS enhancements factors than AgNPrs.
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•The electrospun fiber membrane has the highest CO2 adsorption capacity of 3.42 mmolCO2/gadsorbent at 30 °C.•The CO2 adsorption membrane effectively filtered carbon dioxide (400 ppm ...in air) for up to 16 h.•Zinc-air battery with the CO2 adsorption membrane exhibited a higher discharge capacity.
Zinc-air batteries (ZABs) are an important option for energy storage applications because of their high specific capacity. However, when ZABs are operated in ambient air, the CO2 (400 ppm) in the air can react with the alkaline electrolyte, forming carbonates, which shorten the battery lifetime. In this work, we fabricated an electrospun polystyrene (PS)/polyethylenimine (PEI) fiber membrane to capture CO2 from ambient air before the air is admitted into a ZAB to enhance battery performance. The result show that the PS/PEI fibers have a CO2 adsorption capacity of 3.42 mmolCO2/gadsorbent or 7.58 mmolCO2/gPEI at room temperature. The fibers retain 91% of their initial CO2 adsorption capacity after 15 cycles of the adsorption–desorption process. A ZAB cell equipped with PS/PEI fibers exhibited a better discharge capacity (802 mA h/g) compared to that of a ZAB without the fibers (762 mA h/g).
Coral reefs worldwide are declining due to increasing concentrations of greenhouse gases, which, combined with local anthropogenic pressure, are exacerbating unprecedented mass coral bleaching. For ...corals to survive, restoring coral reefs through cryopreservation is crucial. The aim of this study was to vitrify and laser-warm
Stylophora pistillata
planulae to allow for feasible settlement, post-settlement survival, and the production of adult corals. The no-observed-effect concentrations were used to determine the best cryoprotective agents for
S. pistillata
. The larvae were then subjected to cooling and nanolaser warming (300 V, 10 ms pulse width, 2 mm beam diameter) by using two vitrification solutions (VSs; VS1: 2 M dimethyl sulfoxide and 1 M ethylene glycol and VS2: 2M EG and 1M DMSO and gold nanoparticles. The results revealed that VS1-treated larvae had a higher vitrification rate (65%), swimming rate (23.1%), settlement rate (11.54%), and post settlement survival rate (11.54%) than those treated with VS2. Seasonal variations also affected the cryopreservation of the planulae; VS1 was more favorable for the planulae in spring than in fall. Although laser-warmed larvae developed slower morphologically than their controlled counterparts, the production of adult
S. pistillata
corals from cryopreserved larvae was achieved. The proposed technique can improve the cryopreservation of corals and advance efforts to protect endangered coral species.
Low‐loss ceramics having the chemical formula Mg2(Ti1−xSnx)O4 for x ranging from 0.01 to 0.09 have been prepared by the conventional mixed oxide route and their microwave dielectric properties have ...been investigated. X‐ray powder diffraction patterns indicate the corundum‐structured solid solutions for the prepared compounds. In addition, lattice parameters, which linearly increase from 8.4414 to 8.4441 Å with the rise of x from 0.01 to 0.09, also confirm the forming of solid solutions. By increasing x from 0.01 to 0.05, the Q×f of the specimen can be tremendously boosted from 173 000 GHz to a maximum 318 000 GHz. A fine combination of microwave dielectric properties (ɛr∼15.57, Q×f∼318 000 GHz at 10.8 GHz, τf∼−45.1 ppm/°C) was achieved for Mg2(Ti0.95Sn0.05)O4 ceramics sintered at 1390°C for 4 h. Ilmenite‐structured Mg(Ti0.95Sn0.05)O3 (ɛr∼16.67, Q×f∼275 000 GHz at 10.3 GHz, τf∼−53.2 ppm/°C) was detected as a second phase. The presence of the second phase, however, would cause no significant variation in the dielectric properties of the specimen, because the second phase properties are very similar to the primary phase. These unique properties, in particular, low ɛr and high Q×f, can be utilized as a very promising dielectric material for ultra‐high‐frequency applications.
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