A method of electroless plating was utilized to deposit Cu, Ni, Co, Ag on the surface of carbon nanotubes （CNTs） respectively, in order to prepare millimeter-wave absorbing materials. Field emission scanning electro...A method of electroless plating was utilized to deposit Cu, Ni, Co, Ag on the surface of carbon nanotubes （CNTs） respectively, in order to prepare millimeter-wave absorbing materials. Field emission scanning electron microscope （FE-SEM） and energy dispersive spectrometer （EDS） were used to observe morphologies and chemical compositions of the samples respectively. Millime- ter-wave radiometer imaging detection was employed to measure the absorbing properties of the sam- ples. FE-SEM and EDS results demonstrate the effectiveness of successful metal deposition. The re- suits of millimeter-wave radiometer imaging detection reveal that the millimeter-wave absorbing properties of electroless-silver plating are better than other kinds of samples.展开更多
MnO_2/activated carbon composite（Mn-ACC） wave absorber was prepared by the reaction between Mn（CH_3COO）_2 and KMnO_4 on activated carbon. Then, a novel cement based composite absorbing coating（CB-CAC） was prepar...MnO_2/activated carbon composite（Mn-ACC） wave absorber was prepared by the reaction between Mn（CH_3COO）_2 and KMnO_4 on activated carbon. Then, a novel cement based composite absorbing coating（CB-CAC） was prepared by adding the Mn-ACC, manganese zinc ferrite and rubber particles into cement. XRD method was used to analyze the reaction products of the Mn-ACC. The tensile bond strength and the wave absorbing properties of the CB-CACs were also tested. The results showed that the crystallinity of MnO_2 formed in the Mn-ACC was poor. Adding Mn-ACC into the CB-CAC led to first increase and then decrease of the tensile bond strength. The tensile bond strength reached 1.89 MPa with 8.51% of the Mn-ACC. The CB-CACs obtained the optimal absorbing properties with the cement, manganese zinc ferrite, Mn-ACC, rubber particles and H_2O mass ratio of 7.5？7.5？1？1？5.5, respectively. The band width of the reflection below-10 dB was up to 8.8 GHz, which accounted for 57.14% of the test band.展开更多
Short carbon fibers were treated at high temperatures around 1100℃ through chemical vapor infiltration technology. A thinner layer ofpyrocarbon was deposited on the fiber surface. The dispersion of carbon fibers in a...Short carbon fibers were treated at high temperatures around 1100℃ through chemical vapor infiltration technology. A thinner layer ofpyrocarbon was deposited on the fiber surface. The dispersion of carbon fibers in a cement matrix and the mechanical properties of carbon fiber/cement composites were investigated by scanning electron microscopy （SEM） and other tests. The reflec- tivity of electromagnetic waves by the composites was measured in the frequency range of 8.0-18 GHz for different carbon fiber contents of 0.2wt%, 0.4wt%, 0.6wt%, and 1.0wt%. The results show that the reflectivity tends to increase with the increase of fiber content above 0.4wt%. The minimum reflectivity is -19.3 dB and the composites exhibit wave-absorbing performances. After pyrocarbon is deposited on the fiber, all the refiectivity data are far greater. They are all above -10 dB and display mainly wave-reflecting performances.展开更多
Porous carbon(PC)is a promising electromagnetic(EM)wave absorbing material thanks to its light weight,large specific surface area as well as good dissipating capacity.To further improve its microwave absorbing perform...Porous carbon(PC)is a promising electromagnetic(EM)wave absorbing material thanks to its light weight,large specific surface area as well as good dissipating capacity.To further improve its microwave absorbing performance,silver coated porous carbon(Ag@PC)is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork.Phase compositions,morphological structure,and microwave absorption capability of the Ag@PC has been explored.Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork,which accelerates graphitization process of the amorphous carbon.The Ag@PC composite without adding polyvinyl pyrrolidone(PVP)exhibits higher dielectric constant and better EM wave dissipating capability.This is because the larger particles of Ag give rise to higher electric conductivity.After combing with frequency selective surface(FSS),the EM wave absorbing performance is further improved and the frequency region below-10 d B is located in8.20-11.75 GHz,and the minimal reflection loss value is-22.5 dB.This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.展开更多
Copper(Cu)-containing single-source precursors(SSPs)for the preparation of SiCuCN-based ceramic nanocomposites were successfully synthesized for the first time using polysilazane(PSZ),copper(II)acetate monohydrate(CuA...Copper(Cu)-containing single-source precursors(SSPs)for the preparation of SiCuCN-based ceramic nanocomposites were successfully synthesized for the first time using polysilazane(PSZ),copper(II)acetate monohydrate(CuAc),and 2-aminoethanol via nucleophilic substitution reactions at silicon(Si)centers of PSZ.The synthesis process,polymer-to-ceramic transformation,and high-temperature microstructural evolution of the prepared ceramics were characterized.Dielectric properties and electromagnetic wave(EMW)absorbing performance of the ceramics were investigated as well.The results show that the polymer-to-ceramic transformation finishes at ca.900 ℃,and Cu nanoparticles are homogeneously distributed in a SiCN matrix,forming a SiCN/Cu nanocomposite.After annealing at 1200 ℃,the Cu nanoparticles completely transform into copper silicide(CusSi).Interestingly,the thermal stability of the Cu nanoparticles can be strongly improved by increasing the free carbon content,so that a part of metallic Cu nanoparticles can be detected in the ceramics annealed even at 1300 ℃,forming a SiCN/Cu/Cu_(3)Si/C nanocomposite.Compared with SiCN,the SiCuCN-based nanocomposites exhibit strongly enhanced dielectric properties,which results in outstanding EMW absorbing performance.The minimum reflection coefficient(RC_(min))of the SiCN/Cu/Cu_(3)Si/C nanocomposites annealed at 1300 ℃ achieves-59.85 dB with a sample thickness of 1.55 mm,and the effective absorption bandwidth(EAB)broadens to 5.55 GHz at 1.45 mm.The enhanced EMW absorbing performance can be attributed to an in situ formed unique network,which was constructed with Cu and Cu_(3)Si nanoparticles connected by ring-like carbon ribbons within the SiCN matrix.展开更多
为了研究铁氧体的电磁性能以及铁氧体引入量的质量分数和样块厚度对材料性能的影响,以玻璃和陶瓷造粒料为基料,炭黑为发泡剂,引入铁氧体,经过球磨、烧结、发泡、退火工艺后制备出泡沫吸波材料.结果表明:900℃处理对铁氧体的电磁性能无...为了研究铁氧体的电磁性能以及铁氧体引入量的质量分数和样块厚度对材料性能的影响,以玻璃和陶瓷造粒料为基料,炭黑为发泡剂,引入铁氧体,经过球磨、烧结、发泡、退火工艺后制备出泡沫吸波材料.结果表明:900℃处理对铁氧体的电磁性能无明显影响.铁氧体引入量的质量分数为5%和10%的吸波性能优于铁氧体为15%和20%引入量的吸波性能;研究初步显示,该结果是由于铁氧体的引入影响多孔材料的泡孔结构.铁氧体引入量的质量分数为10%时,材料的吸波性能随着样块厚度的增加而增大;样块厚度为50 mm时,材料的有效吸收带宽(反射率小于-10 d B)达18 GHz,反射率低至-23.4 d B.展开更多
文摘A method of electroless plating was utilized to deposit Cu, Ni, Co, Ag on the surface of carbon nanotubes （CNTs） respectively, in order to prepare millimeter-wave absorbing materials. Field emission scanning electron microscope （FE-SEM） and energy dispersive spectrometer （EDS） were used to observe morphologies and chemical compositions of the samples respectively. Millime- ter-wave radiometer imaging detection was employed to measure the absorbing properties of the sam- ples. FE-SEM and EDS results demonstrate the effectiveness of successful metal deposition. The re- suits of millimeter-wave radiometer imaging detection reveal that the millimeter-wave absorbing properties of electroless-silver plating are better than other kinds of samples.
基金Funded by the International Cooperation Office of the Ministry of Science and Technology of China(2013DFR50360)the Postdoctoral Research Foundation of Shenyang Ligong University,the Open Fund from Advanced Processing Technology of Metal Materials of Liaoning Key Laboratory,Shenyang Ligong Universitythe Guide Project from Liaoning Natural Science Foundation of China(No.201602646)
文摘MnO_2/activated carbon composite（Mn-ACC） wave absorber was prepared by the reaction between Mn（CH_3COO）_2 and KMnO_4 on activated carbon. Then, a novel cement based composite absorbing coating（CB-CAC） was prepared by adding the Mn-ACC, manganese zinc ferrite and rubber particles into cement. XRD method was used to analyze the reaction products of the Mn-ACC. The tensile bond strength and the wave absorbing properties of the CB-CACs were also tested. The results showed that the crystallinity of MnO_2 formed in the Mn-ACC was poor. Adding Mn-ACC into the CB-CAC led to first increase and then decrease of the tensile bond strength. The tensile bond strength reached 1.89 MPa with 8.51% of the Mn-ACC. The CB-CACs obtained the optimal absorbing properties with the cement, manganese zinc ferrite, Mn-ACC, rubber particles and H_2O mass ratio of 7.5？7.5？1？1？5.5, respectively. The band width of the reflection below-10 dB was up to 8.8 GHz, which accounted for 57.14% of the test band.
基金supported by the National Natural Science Foundation of China (No.50172039)
文摘Short carbon fibers were treated at high temperatures around 1100℃ through chemical vapor infiltration technology. A thinner layer ofpyrocarbon was deposited on the fiber surface. The dispersion of carbon fibers in a cement matrix and the mechanical properties of carbon fiber/cement composites were investigated by scanning electron microscopy （SEM） and other tests. The reflec- tivity of electromagnetic waves by the composites was measured in the frequency range of 8.0-18 GHz for different carbon fiber contents of 0.2wt%, 0.4wt%, 0.6wt%, and 1.0wt%. The results show that the reflectivity tends to increase with the increase of fiber content above 0.4wt%. The minimum reflectivity is -19.3 dB and the composites exhibit wave-absorbing performances. After pyrocarbon is deposited on the fiber, all the refiectivity data are far greater. They are all above -10 dB and display mainly wave-reflecting performances.
基金supported by National Natural Science Foundation of China(No.52103361)Shaanxi University Youth Outstanding Talents Support Plan,Scientific and Technological Plan Project of Xi’an Beilin District(No.GX2143)。
文摘Porous carbon(PC)is a promising electromagnetic(EM)wave absorbing material thanks to its light weight,large specific surface area as well as good dissipating capacity.To further improve its microwave absorbing performance,silver coated porous carbon(Ag@PC)is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork.Phase compositions,morphological structure,and microwave absorption capability of the Ag@PC has been explored.Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork,which accelerates graphitization process of the amorphous carbon.The Ag@PC composite without adding polyvinyl pyrrolidone(PVP)exhibits higher dielectric constant and better EM wave dissipating capability.This is because the larger particles of Ag give rise to higher electric conductivity.After combing with frequency selective surface(FSS),the EM wave absorbing performance is further improved and the frequency region below-10 d B is located in8.20-11.75 GHz,and the minimal reflection loss value is-22.5 dB.This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.
基金Qingbo Wen thanks the National Natural Science Foundation of China(No.52102085)the National Science Fund for Excellent Young Scholars(Overseas)+1 种基金State Key Laboratory of Powder Metallurgy,Central South University(No.621022222)for financial supportXiang Xiong thanks the National Natural Science Foundation of China(No.52072410)for financial support.
文摘Copper(Cu)-containing single-source precursors(SSPs)for the preparation of SiCuCN-based ceramic nanocomposites were successfully synthesized for the first time using polysilazane(PSZ),copper(II)acetate monohydrate(CuAc),and 2-aminoethanol via nucleophilic substitution reactions at silicon(Si)centers of PSZ.The synthesis process,polymer-to-ceramic transformation,and high-temperature microstructural evolution of the prepared ceramics were characterized.Dielectric properties and electromagnetic wave(EMW)absorbing performance of the ceramics were investigated as well.The results show that the polymer-to-ceramic transformation finishes at ca.900 ℃,and Cu nanoparticles are homogeneously distributed in a SiCN matrix,forming a SiCN/Cu nanocomposite.After annealing at 1200 ℃,the Cu nanoparticles completely transform into copper silicide(CusSi).Interestingly,the thermal stability of the Cu nanoparticles can be strongly improved by increasing the free carbon content,so that a part of metallic Cu nanoparticles can be detected in the ceramics annealed even at 1300 ℃,forming a SiCN/Cu/Cu_(3)Si/C nanocomposite.Compared with SiCN,the SiCuCN-based nanocomposites exhibit strongly enhanced dielectric properties,which results in outstanding EMW absorbing performance.The minimum reflection coefficient(RC_(min))of the SiCN/Cu/Cu_(3)Si/C nanocomposites annealed at 1300 ℃ achieves-59.85 dB with a sample thickness of 1.55 mm,and the effective absorption bandwidth(EAB)broadens to 5.55 GHz at 1.45 mm.The enhanced EMW absorbing performance can be attributed to an in situ formed unique network,which was constructed with Cu and Cu_(3)Si nanoparticles connected by ring-like carbon ribbons within the SiCN matrix.
文摘为了研究铁氧体的电磁性能以及铁氧体引入量的质量分数和样块厚度对材料性能的影响,以玻璃和陶瓷造粒料为基料,炭黑为发泡剂,引入铁氧体,经过球磨、烧结、发泡、退火工艺后制备出泡沫吸波材料.结果表明:900℃处理对铁氧体的电磁性能无明显影响.铁氧体引入量的质量分数为5%和10%的吸波性能优于铁氧体为15%和20%引入量的吸波性能;研究初步显示,该结果是由于铁氧体的引入影响多孔材料的泡孔结构.铁氧体引入量的质量分数为10%时,材料的吸波性能随着样块厚度的增加而增大;样块厚度为50 mm时,材料的有效吸收带宽(反射率小于-10 d B)达18 GHz,反射率低至-23.4 d B.
