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Heat pipes are passive devices crucial for thermal management in various applications. However, conventional water-based fluids can limit their heat transfer capacity, especially in cold environments where freeze protection is necessary. This study investigates the potential of MgO-Al2O3 hybrid nanofluids to enhance heat transfer performance in cylindrical mesh heat pipes while addressing these limitations. The research demonstrates significant improvements in thermal performance compared to a water-ethylene glycol mixture. The MgO-Al2O3 hybrid nanofluid reduces thermal resistance by enhancing surface wettability in the evaporator section. Additionally, the formation of a nanofluid coating on the evaporator surface leads to a higher heat transfer coefficient. Furthermore, RSM successfully models the relationship between nanoparticle concentration, power input, and key thermal responses (thermal resistance and heat transfer coefficient). These findings highlight the effectiveness of MgO-Al2O3 hybrid nanofluids for augmenting heat transfer in heat pipes and provide valuable RSM models for predicting thermal behavior within the investigated range.

In this work, the 0.5BaCuSi4O10–0.5BaCuSi2O6‐based ceramics were synthesized using a standard solid‐phase reaction process, and the inherent relationship between crystal structure and microwave dielectric properties was thoroughly explored. The crystal structure of the 0.5BaCuSi4O10–0.5BaCuSi2O6 ceramic was determined by X‐ray diffractometer, which confirmed the existence of two phases. Microstructure observation of the ceramics was obtained by scanning electron microscope (SEM). Excellent microwave dielectric properties with a low ԑr ∼6.52, a high Q × f ∼46 010 GHz, and the temperature coefficient of resonant frequency (TCF) ∼−14 ppm°C−1 were obtained in the 0.5BaCuSi4O10–0.5BaCuSi2O6 ceramic sintered at 1060°C. By adding sintering additives LiF and Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass, the sintering temperature was decreased from 1060°C to 870°C. Good microwave dielectric properties with a ԑr ∼6.59, a Q × f ∼18 820 GHz, and TCF ∼−14 ppm°C−1 were achieved in the 0.5BaCuSi4O10–0.5BaCuSi2O6 ‐2 wt.% LiF, 1 wt.% LBSCA (2F1LBSCA) ceramic sintered at 870°C. The low‐temperature firing ceramics could also be well co‐fired with Ag with good chemical compatibility. These results indicated that the 0.5BaCuSi4O10–0.5BaCuSi2O6 ceramic with 2F1LBSCA additions can be utilized in low‐temperature co‐fired ceramics technology to produce high‐frequency communication components. [ABSTRACT FROM AUTHOR]

To develop new luminescent materials for optical thermometers, a series of Er3+/Eu3+doped double perovskite La2MgSnO6 phosphors are synthesized by a high-temperature solid-phase method. The structure, luminescence performance, energy transfer, and thermal sensitivity are systematically studied by X-ray diffraction (XRD), scanning electron microscopy fluorescence spectroscopy, lifetime decay curve, and temperature-dependent emission spectra. The prepared samples possess good coincidence with pure perovskite phase, and the refined high-quality XRD data reveal that Eu3+ and Er3+jointly occupy La3+ sites. which is attributed to the effective energy transfer from Er3+ to Eu3+ ions. By adjusting the doping concentration of Eu3+, the emission of Er3+ is attenuated and the luminous color is modulated from green to orange-red. These demonstrate the existence of energy transfer between Er3+ and Eu3+. In addition, the optimized La2MgSnO6: 0.075Er3+, 0.04Eu3+ phosphor exhibits excellent thermal stability and good temperature cycling. The emission intensity showed good cycling in the process of repeated heating and cooling, and maintained to 76% of the initial temperature (303K) at 403K. Studied the optical temperature sensing performance of LMS: 0.075Er3+, 0.04Eu3+ fluorescent powder. The results of fitting the fluorescence intensity ratio with the non-thermal coupling characteristic peaks of 555 and 706nm showed excellent optical sensitivity, and the Sa and Sr were calculated as 0.0029K−1 and 1.21%K−1, respectively. All results indicate that LMS: 0.075Er3+, 0.04Eu3+ phosphors could have potential applications for non-contact optical temperature measurement materials. [ABSTRACT FROM AUTHOR]

In the present work, five compositions in the BaO–MgO–SiO2 ternary system were chosen, and ceramics were prepared using the solid‐state reaction method. Single phases were formed easily for the first four compositions, and BaMgSi3O8 ceramics were found to be a mixture of both BaSi2O5 and MgSiO3, according to X‐ray diffraction results. Among all the compositions, Ba2MgSi2O7 ceramic sintered at 1225°C possesses the highest Qf (Q = 1/dielectric loss = 1/tanδ, f = resonant frequency) value ∼55 010 GHz along with relative permittivity ∼8.0 and temperature coefficient of resonant frequency (TCF) ∼−57.5 ppm/°C. With 3 wt.% BCB (BaO–B2O3–CuO) additions, Ba2MgSi2O7 ceramic was well densified at 950°C with a relative permittivity ∼8.1, Qf value ∼28 920 GHz (at 12.37 GHz) and TCF value ∼‒56.6 ppm/°C. These series ceramics with low relative permittivity values might be good candidates for low‐temperature co‐fire ceramic technology substrate applications. [ABSTRACT FROM AUTHOR]

Low‐εr (the low dielectric constant) microwave dielectric ceramics play an important role in sub‐6 GHz band communication by virtue of their small signal delay. In this paper, Ba2CoSi2O7 ceramics were synthesized by the solid‐phase reaction method, and X‐ray diffraction (XRD) confirms that they belong to a new melilite structure, with C2/c (No.15) space group, and the ceramics have good microwave dielectric properties with an εr ∼ 7.37, a Q×f (Q = 1/dielectric loss, f = resonant frequency) ∼ 26,320 GHz and a TCF (the temperature coefficient of resonant frequency) ∼ −55 ppm/°C after being sintered at 1150°C, and the theoretical dielectric constants derived from the Clausius–Mosotti as well as the porosity equation, respectively, are also used to further demonstrate the low‐εr properties. Based on the group theory, the one‐dimensional integrable representations of Γacoustic (the phonon modes) and Γoptical (optical modes) of Ba2CoSi2O7 are obtained, and the internal vibrational modes of Ba2CoSi2O7 are deconstructed and the main modes of influence of the electronic polarization are analyzed in conjunction with the results of the validly fitted peaks of the 17 Raman and 25 IR tests. A microstrip Yagi antenna is also designed based on the ceramic properties, which can achieve a gain of 9.65 dBi at the center tuning frequency of 5.47 GHz, with a S11 (return loss) close to −60 dBi. Based on the above results, the Ba2CoSi2O7 ceramic is a low‐εr microwave dielectric ceramic with significant potential for communication application. [ABSTRACT FROM AUTHOR]

Today, the utilization of small‐scale solar systems for houses has increased significantly around the globe. The rise of electricity prices due to elevated prices of fossil fuels coupled with the global concerns about the increased emission of greenhouse gases has fueled the increased application of renewable energy systems. However, such policies have been ineffective in particular countries where the electricity prices are kept too low to control social atmosphere and enhance the people's well‐being for political purposes—in this case, solar systems have witnessed no growth as they have rendered not economically justifiable. In this respect, the present research considers Iran as a country with very low electricity prices coupled with very large potentials for utilizing solar energy in the presence of imbalanced electricity supply and demand, with the research objective being an investigation of the required incentive policies to promote the utilization of distributed solar photovoltaic (DSPV) systems in the country. According to the results, it was figured out that, under the current conditions, escalating the price of electricity for houses (even to as high as 10 times the current prices) cannot cover the costs of the equivalent DSPV systems, indicating a need for another cluster of policies. As an option, one may consider buying the generated electricity by the customer (from renewable sources) at a higher price than that at which the electricity is offered to households via the grid (by a margin of 15 folds), which is supposed to provide the required incentive to expand the utilization of DSPV systems. [ABSTRACT FROM AUTHOR]