To explore the mechanisms and influence factors on the production of 2,4,6-trichloroanisole (2,4,6-TCA) in surface waters, the 2,4,6-TCA formation potential (FP) test was conducted by incubating the ...real lake water with the addition of 2,4,6-trichlorophenol (2,4,6-TCP) precursor. Besides bacteria and fungi, two common cyanobacteria and algae species, i.e., Chlorella vulgaris and Anabaena flos-aquae, have been proved to have strong capabilities to produce 2,4,6-TCA, which may contribute the high 2,4,6-TCA FP (152.2 ng/L) of lake water. The microbial O-methylation of 2,4,6-TCP precursor is catalyzed by chlorophenol O-methyltransferases (CPOMTs), and their characteristics were identified by adding inductive methyl donors or excluding microorganisms via ultrafiltration. The results indicated both S-adenosyl methionine (SAM) dependent and non-SAM dependent CPOMTs played important roles; extracellular CPOMTs also participated in the biosynthesis of 2,4,6-TCA. Moreover, investigating the effects of various environmental factors revealed initial 2,4,6-TCP processor concentration, temperature, pH and some divalent metal cations (i.e., Mn2+, Mg2+ and Zn2+) had obvious effects on the production of 2,4,6-TCA.
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•The production of 2,4,6-TCA by cyanobacteria/algae was revealed for the first time.•Both SAM dependent and non-SAM dependent CPOMTs played important roles.•Extracellular CPOMTs has been proved to participate in biosynthesis of 2,4,6-TCA.•Temperature, pH, and metal ions have obvious effects on biosynthesis of 2,4,6-TCA.•Several strategies have been proposed for the control of 2,4,6-TCA.
The biosynthesis of 2,4,6-TCA was first reported in cyanobacteria and algae species in the lake water, in which various chlorophenol O-methyltransferases were involved.
In this study, Mg
x
Y
3-
x
Al
5-
x
Si
x
O
12
(
x
= 0–0.6) ceramics were prepared via a high-temperature solid state method. Mg
2+
and Si
4+
replacing Y
3+
ions at A-site and Al
3+
at C-site in ...garnet-type Y
3
Al
5
O
12
(YAG) ceramics were designed to discuss the effects of crystal structure, microstructure on microwave dielectric properties for the first time. Liquid phase sintering induced by doping of Mg
2+
-Si
4+
, significantly decreased the sintering temperature and time for the densification of YAG ceramics. X-ray diffraction of the samples showed single phase for
x
≤ 0.5, while a secondary phase of MgAl
2
O
4
formed for
x
= 0.6. From the Rietveld analysis, a decrease in lattice dimensions, bond length and valence and rattling effect were observed, while Raman results showed a change in FWHM of the Eg mode. Based on these parameters, a structure–property relation was developed for Mg
x
Y
3-
x
Al
5-
x
Si
x
O
12
ceramics. Specially, Mg
0.1
Y
2.9
Al
4.9
Si
0.1
O
12
showed a good set of microwave dielectric properties sintered at 1575 °C for 4 h with
ε
r
= 10.67,
Q
×
f
= 58,799 GHz,
τ
f
= -29.5 ppm/°C.
Epoxy resin (EP), as a kind of dielectric polymer, exhibits the advantages of low-curing shrinkage, high-insulating properties, and good thermal/chemical stability, which is widely used in electronic ...and electrical industry. However, the complicated preparation process of EP has limited their practical applications for energy storage. In this manuscript, bisphenol F epoxy resin (EPF) was successfully fabricated into polymer films with a thickness of 10~15 μm by a facile hot-pressing method. It was found that the curing degree of EPF was significantly affected by changing the ratio of EP monomer/curing agent, which led to the improvement in breakdown strength and energy storage performance. In particular, a high discharged energy density (
) of 6.5 J·cm
and efficiency (
) of 86% under an electric field of 600 MV·m
were obtained for the EPF film with an EP monomer/curing agent ratio of 1:1.5 by hot pressing at 130 °C, which indicates that the hot-pressing method could be facilely employed to produce high-quality EP films with excellent energy storage performance for pulse power capacitors.
The combination of low dielectric constant (
ε
r
) and a high-quality factor (
Q
×
f
) in MgO ceramics makes them attractive for 5G applications. However, the large negative temperature coefficient ...of resonance frequency (
τ
f
) impedes these applications. In this paper, the composite ceramics of MgO–
x
MTiO
3
(M = Ca, Sr;
x
= 0, 2.5, 5, 7.5, 10 wt%) with the addition of 4 mol% LiF as a sintering aid were fabricated by the traditional solid-state reaction method. The coexistence both MgO and MT phases can be observed in XRD and SEM in the 4 mol% LiF–MgO–wt%MTiO
3
systems under the high-temperature sintering process. With the addition of MT, the grain size of MgO decreased, the
ε
r
value improved with
τ
f
value gradually increasing from negative to positive value. Optimized microwave dielectric properties were achieved for 4 mol%LiF–MgO–10wt%SrTiO
3
ceramics sintered at 1300 °C for 6 h, yielding
ε
r
= 11.2,
Q
×
f
= 46, 815 GHz, and
τ
f
= + 3.51 ppm/°C. Based on it, a prototype of microstrip patch antenna was designed and fabricated with a center frequency at 5.64 GHz for 5G–Sub6GHz communication applications.
Carbon-coated SnO2 nanowires (NWs) were fabricated and applied as electrode to study the lithiation process using in situ transmission electron microscopy. A critical coating thickness (∼9nm) was ...found, above which the carbon coating is able to constrain the lithiation-induced expansion of SnO2 core without failure. Theoretical modeling and numerical simulation were performed and revealed that such thickness-dependent fracture can be attributed to the thickness-dependent maximum stress developed in the carbon coating during the lithiation of SnO2 core. Our work provides direct evidence of the mechanical robustness of thick carbon coating and offers a minimum thickness of carbon coating for constraining the deformation of anode materials with large lithiation-induced volume change.
A novel category of polyphenylene oxide/high-impact polystyrene (PPO/HIPS) alloy was used as the polymer matrix (abbreviated as mPPO) and loaded with different volume fractions (0, 10, 20, 30, 40, 50 ...vol.%) of MgTiO3–Ca
0
.
7
La
0
.
2
TiO3 (abbreviated as MTCLT) ceramics to prepare composites by injection molding. Its micromorphology, density, dielectric, thermal and mechanical properties were analyzed in detail. The experimental results show that the composites possess a compact microstructure because HIPS increases the fluidity of PPO. Due to the excellent dielectric properties of both mPPO and MTCLT, the composites have an extremely low dielectric loss. The realization of the high ceramic filler fraction greatly limits the thermal expansion of the polymer chain by introducing the interphase, so that the coefficient of thermal expansion of the composite material could be as low as 21.8 ppm/
∘
C. At the same time, the presence of ceramic particles could reinforce the mechanical property of the composites. When the ceramic filler fraction is higher than 20 vol.%, the bending strength of the composite material is around 110 MPa. When the ceramic filler fraction is 40 vol.%, the composite possesses the best comprehensive performance. The dielectric constant is 6.81, the dielectric loss is 0.00104, the thermal expansion coefficient is as low as 25.3 ppm/
∘
C, and the bending strength is 110.4 MPa. Due to its excellent properties, this material can be a good candidate in the field of microwave communication.
In this work, Y2.95R0.05MgAl3SiO12 (R = Yb, Y, Dy, Eu, Sm) microwave single-phase dielectric ceramics were successfully prepared via a conventional ceramic sintering technology by doping a series of ...rare earth elements (Yb, Y, Dy, Eu, Sm) with different ionic radii for the first time. The effects of A-sites occupied by rare earth elements on the microwave dielectric properties of Y2.95R0.05MgAl3SiO12 were studied using crystal structure refinement, a scanning electron microscope (SEM), bond valence theory, P-V-L theory, and infrared reflection spectroscopy. It was found that the ionicity of the Y-O bond, the lattice energy, the bond energy, and the bond valance of the Al(Tet)-O bond had important effects on the microwave dielectric properties. Particularly, the optimum microwave dielectric properties, εr = 9.68, Q × f = 68,866 GHz, and τf = −35.8 ppm/°C, were obtained for Y2.95Dy0.05MgAl3SiO12 when sintered at 1575 °C for 6 h, displaying its potential for 5G communication.
In this study, dense composites of xNaCl-(1−x)Ni0.5Zn0.5Fe2O4 (referred to as NaCl-NZO) and xH3BO3-(0.8−x)Ni0.5Zn0.5Fe2O4-0.2NaCl (referred to as HB-NZO-NaCl) were prepared using the cold sintering ...process. The objective was to investigate the cold sintering procedure for fabricating ferrite composite ceramics with comparable permeability and dielectric constants suitable for radio-frequency electronic device applications. Optimal cold sintering conditions were determined as 200 °C/30 min/500 MPa with a relative density of 95% for NaCl-NZO and 120 °C/30 min/300 MPa with a relative density of 95.4% for HB-NZO-NaCl. X-ray diffraction and scanning electron microscope analyses confirmed the absence of secondary phases. The resulting composite ceramics showed promising characteristics, with the 0.5NaCl-0.5NZO composition exhibiting a dielectric constant of 6.2 @ 100 MHz, dielectric loss of 0.02 @ 100 MHz, permeability of 2.5 @ 100 MHz, and magnetic loss of 0.001 @ 100 MHz. Similarly, the 0.3HB-0.5NZO-0.2NaCl composition displayed a dielectric constant of 5.9 @ 100 MHz, dielectric loss of 0.02 @ 100 MHz, permeability of 5.1 @ 100 MHz, and magnetic loss of 5 × 10−4 @ 100 MHz. These findings indicate potential applications in wireless communication.
Mg2SiO4 and MgSiO3 ceramics with superior microwave dielectric properties are considered to be promising candidates for 5G applications. However, a slight deviation from the stoichiometric Mg/Si ...ratio will significantly influence their microwave dielectric properties, which will hinder their practical applications. In this work, the xMgO-SiO2 (x = 1~2) ceramics were synthesized by a solid-state reaction method. The influence of the Mg/Si ratio x on the crystalline phase, microstructure, and microwave dielectric properties was investigated through X-ray diffraction (XRD), a scanning electron microscope (SEM), and the resonant cavity method. The XRD patterns revealed the coexistence of Mg2SiO4 and MgSiO3 within the x range of 1~2, which was further demonstrated by the energy-dispersive X-ray spectra. The SEM images show a typical polycrystalline morphology of ceramics with an inhomogeneous grain size distribution. It is found that the microwave dielectric properties fluctuate at both sides of the x range while those remain relatively stable with minor changes at the intermediate components, indicating an obvious low composition dependence helpful for practical applications. Further, a demonstrator of a microstrip patch antenna for 5G applications using the 1.5MgO-SiO2 ceramic was designed and fabricated, and a return loss of −16.2 dB was demonstrated, which demonstrated the potential applications.
