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Lotus rhizome is an important aquatic vegetable, but the blackening of lotus rhizome epidermis (LRE) seriously affects its appearance and quality, which makes lotus rhizome products unmarketable. In this study, the effects of polyphenols and iron on the LRE color were studied to explore the possible mechanism of LRE blackening. Results indicated that the measurable total phenols contents in the mud treatment (MT) group were significantly reduced, and the total iron contents were significantly increased compared with the bruised treatment group (p < 0.05). The high‐performance liquid chromatography results showed that the main polyphenols in LRE were dopa, gallocatechin, and catechin, as well as a small amount of catechol, epicatechin, proanthocyanidin B2, and proanthocyanidin C1. Moreover, the results of color difference and ultraviolet adsorption spectroscopy showed that there were obviously black or brown‐gray of dopa (525 nm), gallocatechin (504.5 nm), and catechin (550 and 504.5 nm) with FeCl2. The simulated system treatment of LRE further confirmed that the chromaticity effect of dopa and iron in bruised LRE was similar to that of the MT group, whereas 1% (w/w) ascorbic acid, 2% (w/w) EDTA‐2Na, or 3% (w/w) citric acid could solely prohibit the blackening. This suggested that the dopa in LRE and FeCl2 in mud may mainly combine into [2(DOPA‐2H+)+Fe3+]− through non‐covalent interaction, which leads to the blackening of bruised LRE under neutral conditions. These results can guide the storage of lotus rhizomes and improve the development of the lotus rhizome industry. [ABSTRACT FROM AUTHOR]

The MgO‐MoO3 system shows significant potential for applications in microwave dielectric ceramics. However, the formation mechanism, crystal structures, and microwave dielectric properties of this system have not been systematically investigated. This work aims to comprehensively study the crystal structures, phase transitions, and microwave dielectric properties of compounds in the MgO‐MoO3 system. In particular, the research delves into the unexplored transformation mechanism from β‐MgMo2O7 to α‐MgMo2O7 and MgMoO4. As a result, the three compounds exhibiting favorable microwave dielectric properties have been successfully fabricated. These compounds can be effectively sintered at temperatures ranging from 685 to 900°C and exhibited dielectric constants (εr) ranging from 5.41 to 6.89, as well as Qf values ranging from 100 000 to 130 000 GHz. Additionally, prototype microstrip antennas are designed and fabricated using β‐MgMo2O7 and MgMoO4 ceramics as substrates. The obtained antenna's performance is excellent, with S11 values below −30 dB and a gain exceeding 6 dB at 5.8 GHz, highlighting the potential of the developed ceramics for practical applications in microwave devices. [ABSTRACT FROM AUTHOR]

With the development of 5G/6G communication, the requirements of portable devices for miniaturization and multifunction make low‐temperature co‐fired ceramic (LTCC) more and more important. In the area of high‐frequency high‐density passive integration, microwave dielectric ceramics with a low dielectric loss and high thermal conductivity are urgently needed to ensure the effective signals transmission and system reliability. However, most microwave dielectric ceramics with a low dielectric loss were not applicable for the LTCC technology due to the high sintering temperature. In this work, a series of MgO‐based ceramics [(100 − x) wt.% MgO–x wt.% (0.2SrF2–0.8LiF) (x = 5,7,10)] were prepared by solid‐state reaction method. The addition of sintering aid 0.2SrF2–0.8LiF (S2L8) decreased the sintering temperature below 880°C without degrading the microwave dielectric properties of ceramics. Microwave dielectric properties of ceramics, including quality factor Q × f, relative permittivity εr, and temperature coefficient of resonant frequency τf, were investigated to find the optimum composition and sintering temperature. In general, MgO–7 wt.% S2L8 ceramic sintered at 860°C exhibits outstanding properties of Q × f = 180 233 GHz, εr = 9.11, τf = −40.33 ppm/°C, and a high thermal conductivity of 24.02 W/(m K). This series of ceramics are suitable to be co‐fired with Ag electrodes. With all those great properties, this series of MgO‐based ceramics are expected to be the candidates for LTCC applications in 5G/6G technology. [ABSTRACT FROM AUTHOR]