Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_...Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.展开更多
A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this stud...A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this study.The good low-firing effects are presented due to the high matching relevance between Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass and MgTa_(2)O_(6)ceramics.The pure tri-rutile MgTa_(2)O_(6)structure remains unchanged,and high sintering compactness can also be achieved at 1150℃.We found that the Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass not only greatly improves the low-temperature sintering characteristics of MgTa_(2)O_(6)ceramics but also maintains a high(quality factor(Q)×resonance frequency(f))value while still improving the temperature stability.Typically,great microwave dielectric characteristics when added with 2wt%Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass can be achieved at 1150℃:dielectric constant,ε_(r)=26.1;Q×f=34267 GHz;temperature coefficient of resonance frequency,τ_(f)=-8.7×10^(-6)/℃.展开更多
A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,micros...A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,microstructures,and microwave dielectric properties were investigated.The results of x-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that a single phase of MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with a spinel structure was obtained at x≤0.12,whereas the second phase of MgTi_(2)O_(5)appeared when x>0.12.The cell parameters were obtained by XRD refinement.As the x values increased,the unit cell volume kept expanding.This phenomenon could be attributed to the partial substitution of(Li_(1/3)Ti_(2/3))^(3+)for Al^(3+).Results showed that(Li_(1/3)Ti_(2/3))^(3+)doping into MgAl_(2)O_(4)spinel ceramics effectively reduced the sintering temperature and improved the quality factor(Q_f)values.Good microwave dielectric properties were achieved for a sample at x=0.20 sintering at 1500℃in air for 4 h:dielectric constantε_(r)=8.78,temperature coefficient of resonant frequencyτ_(f)=-85 ppm/℃,and Q_(f)=62300 GHz.The Q_(f)value of the x=0.20 sample was about 2 times higher than that of pure MgAl_(2)O_(4)ceramics(31600 GHz).Thus,MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with excellent microwave dielectric properties can be applied to 5G communications.展开更多
Wastewater electrolysis cells(WECs)for decentralized wastewater treatment/reuse coupled with H_(2) production can reduce the carbon footprint associated with transportation of water,waste,and energy carrier.This study...Wastewater electrolysis cells(WECs)for decentralized wastewater treatment/reuse coupled with H_(2) production can reduce the carbon footprint associated with transportation of water,waste,and energy carrier.This study reports Ir-doped NiFe_(2)O_(4)(NFI,~5 at%Ir)spinel layer with TiO_(2) overlayer(NFI/TiO_(2)),as a scalable heterojunction anode for direct electrolysis of wastewater with circumneutral pH in a single-compartment cell.In dilute(0.1 M)NaCl solutions,the NFI/TiO_(2) marks superior activity and selectivity for chlorine evolution reaction,outperforming the benchmark IrO_(2).Robust operation in near-neutral pH was confirmed.Electroanalyses including operando X-ray absorption spectroscopy unveiled crucial roles of TiO_(2) which serves both as the primary site for Cl−chemisorption and a protective layer for NFI as an ohmic contact.Galvanostatic electrolysis of NH4+-laden synthetic wastewater demonstrated that NFI/TiO_(2)not only achieves quasi-stoichiometric NH_(4)^(+)-to-N_(2)conversion,but also enhances H_(2)generation efficiency with minimal competing reactions such as reduction of dissolved oxygen and reactive chlorine.The scaled-up WEC with NFI/TiO_(2)was demonstrated for electrolysis of toilet wastewater.展开更多
The high-quality gate dielectric on silicon carbide(SiC)surface is critical to fabricate high-performance SiC metal-oxide-semiconductor field-effect transistors(MOSFETs).This research employs microwave plasma annealin...The high-quality gate dielectric on silicon carbide(SiC)surface is critical to fabricate high-performance SiC metal-oxide-semiconductor field-effect transistors(MOSFETs).This research employs microwave plasma annealing(MPA)to obtain high-quality Al_(2)O_(3)/SiC gate stacks.By designing MPA atmosphere and optimizing the plasma power,the SiC MOS capacitor with a Al_(2)O_(3)dielectric film shows the enhanced performance.The interface state density is reduced by 1 order of magnitude to 6×10^(11)cm^(-2)·eV^(-1),the breakdown electric field is increased,and the voltage shift is effectively suppressed Besides,the mechanism of MPA process is discussed in terms of the thermal effect and reactant species.X-ray photoelectron spectroscopy(XPS)results unveil oxygen plasma plays the main role.Optimal plasma power during the MPA process results in defect repairs of the firstneighbor Al-O bonding and partial removal of Al-O-H bond from the interface region.This study demonstrates that MPA process is an effective option to realize highquality dielectric and interface on SiC.展开更多
Microwave irradiation can accelerate the rate of the synthetic reaction of α,β-unsaturated ketones by using KF-Al2O3 as catalyst. The rate enhancement of the reaction is 360-860 fold.
This study investigates the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) series ceramics synthesised by solid-state reaction.According to the X-ray diffraction and micros...This study investigates the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) series ceramics synthesised by solid-state reaction.According to the X-ray diffraction and microstructural analyses,the as-prepared MgO-2B_(2)O_(3) ceramics possess a single-phase structure with a rod-like morphology.The effects of different quantities of H_(3)BO_(3) and BaCu(B_(2)O5)(BCB)on the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) ceramics were investigated.Accordingly,the optimal sintering temperature was obtained by adding 30 wt%H_(3)BO_(3) and 8 wt%BCB.We also reduced the sintering temperature to 825°C.Furthermore,the addition of 40 wt%H_(3)BO_(3) and 4 wt%BCB increased the quality factor,permittivity,and temperature coefficient of resonance frequency of MgO-2B_(2)O_(3) to 44,306 GHz(at 15 GHz),5.1,and-32 ppm/℃,respectively.These properties make MgO-2B_(2)O_(3) a viable low-temperature co-fired ceramic with broad applications in microwave dielectrics.展开更多
s Ba_4Zn_zCo_(2-z)Fe_(36)O_(60) hexaferrites with Z = 2.0, 1.5, 1.0, 0.5, and0.0 were prepared by a citrate Sol-gel process. The complex dielectric constant and complexpermeability of hexaferrite-paraffin wax composit...s Ba_4Zn_zCo_(2-z)Fe_(36)O_(60) hexaferrites with Z = 2.0, 1.5, 1.0, 0.5, and0.0 were prepared by a citrate Sol-gel process. The complex dielectric constant and complexpermeability of hexaferrite-paraffin wax composites were measured in the range from 0.1 to 6.0 GHz.Measured results showed that both the complex dielectric constant and the dielectric loss exhibitedno significant change as the measuring frequency increasing except for the sample with Z = 0.0. Thereal part of permeability decreased with increasing frequency for all samples in the whole measuringfrequency range, and the natural resonance phenomena were observed in all μ″ spectrum but Co_2U.The results also indicate that the content of zinc closely affects the microwave properties ofBa_4Zn_zCo_(2-z)Fe_(36)O_(60) ferrites, and the greater the zinc content, the lower the naturalresonance frequency is.展开更多
基金financially supported by the Key Project of Natural Science Research in Colleges and Universities of Anhui Province,China(No.2022AH050816)the Open Research Grant of Joint National-Local Engineering Research Centre for Safe and Precise Coal Mining(Nos.EC2023013 and EC2022018)+1 种基金the National Natural Science Foundation of China(No.52200139)the Introduction of Talent in Anhui University of Science and Technology,China(Nos.2021yjrc18 and 2023yjrc79)。
文摘Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.
基金This study is supported by the National Key Research and Development Program of China(No.2022YFB2807405)the Qinchuangyuan Citing High-level Innovation and Entrepreneurship Talent Projects(No.QCYRCXM-2022-40)+2 种基金the National Natural Science Foundation of China(Nos.U2341263 and 62371366)Open project of Yunnan Precious Metals Laboratory Co.,Ltd(No.YPML-2023050246)Innovation Capability Support Program of Shaanxi,China(Nos.2023-CX-PT-30 and 2022TD-28).
文摘A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this study.The good low-firing effects are presented due to the high matching relevance between Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass and MgTa_(2)O_(6)ceramics.The pure tri-rutile MgTa_(2)O_(6)structure remains unchanged,and high sintering compactness can also be achieved at 1150℃.We found that the Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass not only greatly improves the low-temperature sintering characteristics of MgTa_(2)O_(6)ceramics but also maintains a high(quality factor(Q)×resonance frequency(f))value while still improving the temperature stability.Typically,great microwave dielectric characteristics when added with 2wt%Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass can be achieved at 1150℃:dielectric constant,ε_(r)=26.1;Q×f=34267 GHz;temperature coefficient of resonance frequency,τ_(f)=-8.7×10^(-6)/℃.
基金the Chengdu University of Technology(Grant No.KYQD201907728)。
文摘A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,microstructures,and microwave dielectric properties were investigated.The results of x-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that a single phase of MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with a spinel structure was obtained at x≤0.12,whereas the second phase of MgTi_(2)O_(5)appeared when x>0.12.The cell parameters were obtained by XRD refinement.As the x values increased,the unit cell volume kept expanding.This phenomenon could be attributed to the partial substitution of(Li_(1/3)Ti_(2/3))^(3+)for Al^(3+).Results showed that(Li_(1/3)Ti_(2/3))^(3+)doping into MgAl_(2)O_(4)spinel ceramics effectively reduced the sintering temperature and improved the quality factor(Q_f)values.Good microwave dielectric properties were achieved for a sample at x=0.20 sintering at 1500℃in air for 4 h:dielectric constantε_(r)=8.78,temperature coefficient of resonant frequencyτ_(f)=-85 ppm/℃,and Q_(f)=62300 GHz.The Q_(f)value of the x=0.20 sample was about 2 times higher than that of pure MgAl_(2)O_(4)ceramics(31600 GHz).Thus,MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with excellent microwave dielectric properties can be applied to 5G communications.
基金supported by the National Research Foundation of Korea(NRF)grants(2022R1A2C4001228,2022M3H4A4097524,2022M3I3A1082499,and 2021M3I3A1084818)the Technology Innovation Program(20026415)of the Ministry of Trade,Industry&Energy(MOTIE,Korea)the supports from Nanopac for fabrication of scaled-up reactor.
文摘Wastewater electrolysis cells(WECs)for decentralized wastewater treatment/reuse coupled with H_(2) production can reduce the carbon footprint associated with transportation of water,waste,and energy carrier.This study reports Ir-doped NiFe_(2)O_(4)(NFI,~5 at%Ir)spinel layer with TiO_(2) overlayer(NFI/TiO_(2)),as a scalable heterojunction anode for direct electrolysis of wastewater with circumneutral pH in a single-compartment cell.In dilute(0.1 M)NaCl solutions,the NFI/TiO_(2) marks superior activity and selectivity for chlorine evolution reaction,outperforming the benchmark IrO_(2).Robust operation in near-neutral pH was confirmed.Electroanalyses including operando X-ray absorption spectroscopy unveiled crucial roles of TiO_(2) which serves both as the primary site for Cl−chemisorption and a protective layer for NFI as an ohmic contact.Galvanostatic electrolysis of NH4+-laden synthetic wastewater demonstrated that NFI/TiO_(2)not only achieves quasi-stoichiometric NH_(4)^(+)-to-N_(2)conversion,but also enhances H_(2)generation efficiency with minimal competing reactions such as reduction of dissolved oxygen and reactive chlorine.The scaled-up WEC with NFI/TiO_(2)was demonstrated for electrolysis of toilet wastewater.
基金financially supported by Beijing Municipal Natural Science Foundation(No.4234091)the National Natural Science Foundation of China(Nos.62304245,61974159,62174176,62174122 and U2241244)+1 种基金the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20200039)the Out-standing Member Project of the Youth Innovation Promotion Association of CAS(No.Y2021046)。
文摘The high-quality gate dielectric on silicon carbide(SiC)surface is critical to fabricate high-performance SiC metal-oxide-semiconductor field-effect transistors(MOSFETs).This research employs microwave plasma annealing(MPA)to obtain high-quality Al_(2)O_(3)/SiC gate stacks.By designing MPA atmosphere and optimizing the plasma power,the SiC MOS capacitor with a Al_(2)O_(3)dielectric film shows the enhanced performance.The interface state density is reduced by 1 order of magnitude to 6×10^(11)cm^(-2)·eV^(-1),the breakdown electric field is increased,and the voltage shift is effectively suppressed Besides,the mechanism of MPA process is discussed in terms of the thermal effect and reactant species.X-ray photoelectron spectroscopy(XPS)results unveil oxygen plasma plays the main role.Optimal plasma power during the MPA process results in defect repairs of the firstneighbor Al-O bonding and partial removal of Al-O-H bond from the interface region.This study demonstrates that MPA process is an effective option to realize highquality dielectric and interface on SiC.
文摘Microwave irradiation can accelerate the rate of the synthetic reaction of α,β-unsaturated ketones by using KF-Al2O3 as catalyst. The rate enhancement of the reaction is 360-860 fold.
基金supported by the National Natural Science Foundation of China(Nos.61761015 and 12064007)the Natural Science Foundation of Guangxi(Nos.2018GXNSFFA050001,2017GXNSFDA198027,and 2017GXNSFFA198011)High Level Innovation Team and Outstanding Scholar Program of Guangxi Institutes.
文摘This study investigates the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) series ceramics synthesised by solid-state reaction.According to the X-ray diffraction and microstructural analyses,the as-prepared MgO-2B_(2)O_(3) ceramics possess a single-phase structure with a rod-like morphology.The effects of different quantities of H_(3)BO_(3) and BaCu(B_(2)O5)(BCB)on the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) ceramics were investigated.Accordingly,the optimal sintering temperature was obtained by adding 30 wt%H_(3)BO_(3) and 8 wt%BCB.We also reduced the sintering temperature to 825°C.Furthermore,the addition of 40 wt%H_(3)BO_(3) and 4 wt%BCB increased the quality factor,permittivity,and temperature coefficient of resonance frequency of MgO-2B_(2)O_(3) to 44,306 GHz(at 15 GHz),5.1,and-32 ppm/℃,respectively.These properties make MgO-2B_(2)O_(3) a viable low-temperature co-fired ceramic with broad applications in microwave dielectrics.
基金This work was financially supported by the National Natural Science Foundation of China (No. 59995320.4).
文摘s Ba_4Zn_zCo_(2-z)Fe_(36)O_(60) hexaferrites with Z = 2.0, 1.5, 1.0, 0.5, and0.0 were prepared by a citrate Sol-gel process. The complex dielectric constant and complexpermeability of hexaferrite-paraffin wax composites were measured in the range from 0.1 to 6.0 GHz.Measured results showed that both the complex dielectric constant and the dielectric loss exhibitedno significant change as the measuring frequency increasing except for the sample with Z = 0.0. Thereal part of permeability decreased with increasing frequency for all samples in the whole measuringfrequency range, and the natural resonance phenomena were observed in all μ″ spectrum but Co_2U.The results also indicate that the content of zinc closely affects the microwave properties ofBa_4Zn_zCo_(2-z)Fe_(36)O_(60) ferrites, and the greater the zinc content, the lower the naturalresonance frequency is.
