The Experts below are selected from a list of 26325 Experts worldwide ranked by ideXlab platform
Xiaobo Chen - One of the best experts on this subject based on the ideXlab platform.
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Microwave Absorption of aluminum hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Peng Xiang, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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Recent progress of nanomaterials for Microwave Absorption
Journal of Materiomics, 2019Co-Authors: Michael Green, Xiaobo ChenAbstract:Abstract Microwave absorbing materials have received considerable interest over the years for their applications in stealth, communications, and information processing technologies. These materials often require functionalization at the nanoscale so to achieve desirable dielectric and magnetic properties which induce interaction with incident electromagnetic radiation. This article presents a comprehensive review on the recent research progress of nanomaterials for Microwave Absorption, including the basic mechanism of Microwave Absorption (e.g., dielectric loss, magnetic loss, dielectric/magnetic loss coupling), measurement principle (e.g., fundamentals of analysis, performance evaluation, common interaction pathways: Debye relaxation, Eddy current loss, natural resonance, size and shape factors), and the advances and performance review in Microwave Absorption (e.g., Absorption bandwidth, reflection loss values, Absorption peak position) using various nanomaterials, such as carbon nanotubes, carbon fibers, graphenes, oxides, sulfides, phosphides, carbides, polymers and metal organic frameworks. Overall, this article not only provides an introduction on the fundamentals of Microwave Absorption research, but also presents a timely update on the research progress of the Microwave Absorption performance of various nanomaterials.
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Microwave Absorption of magnesium/hydrogen-treated titanium dioxide nanoparticles
Nano Materials Science, 2019Co-Authors: Michael Green, James Murowchick, Anh Thi Van Tran, Russell Smedley, Adam Roach, Xiaobo ChenAbstract:Abstract Interactions between materials and electromagnetic irradiations in the Microwave frequency are critical for many civil and military applications, such as radar detection, communications, information processing and transport et al. Dipole rotations or magnetic domain resonance are the mainly traditional mechanisms for Microwave Absorption. The recent finding of the excellent Microwave Absorption from hydrogenated TiO2 nanoparticles provides us an alternative approach for achieving such Absorption, by manipulating the structural defects inside nanoparticles through hydrogenation. In this study, we demonstrate that the Microwave Absorption can be not only achieved but fine-tuned with TiO2 nanoparticles thermally treated in a Mg/H2 environment. Their position and efficiency can be effectively controlled by the treating temperature. Specifically, the Microwave Absorption position shifts to the lower frequency region as the treating temperature increases, and there seems to exist an optimal treating temperature to obtain the maximum efficiency, as the absorbing efficiency first increases, and then decreases, with the increase in treatment temperature. Therefore, this study enriches our knowledge and understanding Microwave Absorption from TiO2-based nanomaterials which may inspire new ideas on other systems to enhance their performance as well.
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Microwave Absorption of aluminum/hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Zhanqiang Liu, Xiang Peng, Tan Xinyu, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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Doped, conductive SiO 2 nanoparticles for large Microwave Absorption.
Light science & applications, 2018Co-Authors: Michael Green, Fuqiang Huang, Zhanqiang Liu, Xiang Peng, Yan Liu, Minjie Zhou, Tan Xinyu, Lei Liu, Xiaobo ChenAbstract:Although many materials have been studied for the purpose of Microwave Absorption, SiO2 has never been reported as a good candidate. In this study, we present for the first time that doped, Microwave conductive SiO2 nanoparticles can possess an excellent Microwave absorbing performance. A large Microwave reflection loss (RL) of −55.09 dB can be obtained. The large Microwave Absorption originates mainly from electrical relaxation rather than the magnetic relaxation of the incoming Microwave field. The electrical relaxation is attributed to a large electrical conductivity that is enabled by the incorporation of heterogeneous (N, C and Cl) atoms. The removal of the magnetic susceptibility only results in a negligible influence of the Microwave Absorption. In contrast, the removal of the heterogeneous atoms leads to a large decrease in the electrical conductivity and Microwave Absorption performance. Meanwhile, the Microwave Absorption characteristics can be largely adjusted with a change of the thickness, which provides large flexibility for various Microwave Absorption applications. Doped nanoparticles of silica (SiO2) have been found to act as a very strong absorber of Microwave radiation. A US-Chinese collaboration of scientists discovered that, unlike pure SiO2 nanoparticles, those doped with atoms of N, C and Cl induce a reflection loss at large as −55 dB at a frequency of around 7 GHz. The doped nanoparticles, which measured 4–8 nm in diameter, were fabricated by slowly adding the precursor tetraethyl orthosilicate (TEOS) to the solvent N,N’-dimethylformamide (DMF) and then adding hydrazine monohydrochlorid. The resulting solution was then heated, washed and dried. The resulting nanoparticles were then dispersed in paraffin wax rings and the permittivity and permeability measured in the 1.0–18.0 GHz range using a network analyzer. The team attributes the strong Microwave Absorption to the doped nanoparticles’ good electrical conductivity.
Michael Green - One of the best experts on this subject based on the ideXlab platform.
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Microwave Absorption of aluminum hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Peng Xiang, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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Recent progress of nanomaterials for Microwave Absorption
Journal of Materiomics, 2019Co-Authors: Michael Green, Xiaobo ChenAbstract:Abstract Microwave absorbing materials have received considerable interest over the years for their applications in stealth, communications, and information processing technologies. These materials often require functionalization at the nanoscale so to achieve desirable dielectric and magnetic properties which induce interaction with incident electromagnetic radiation. This article presents a comprehensive review on the recent research progress of nanomaterials for Microwave Absorption, including the basic mechanism of Microwave Absorption (e.g., dielectric loss, magnetic loss, dielectric/magnetic loss coupling), measurement principle (e.g., fundamentals of analysis, performance evaluation, common interaction pathways: Debye relaxation, Eddy current loss, natural resonance, size and shape factors), and the advances and performance review in Microwave Absorption (e.g., Absorption bandwidth, reflection loss values, Absorption peak position) using various nanomaterials, such as carbon nanotubes, carbon fibers, graphenes, oxides, sulfides, phosphides, carbides, polymers and metal organic frameworks. Overall, this article not only provides an introduction on the fundamentals of Microwave Absorption research, but also presents a timely update on the research progress of the Microwave Absorption performance of various nanomaterials.
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Microwave Absorption of magnesium/hydrogen-treated titanium dioxide nanoparticles
Nano Materials Science, 2019Co-Authors: Michael Green, James Murowchick, Anh Thi Van Tran, Russell Smedley, Adam Roach, Xiaobo ChenAbstract:Abstract Interactions between materials and electromagnetic irradiations in the Microwave frequency are critical for many civil and military applications, such as radar detection, communications, information processing and transport et al. Dipole rotations or magnetic domain resonance are the mainly traditional mechanisms for Microwave Absorption. The recent finding of the excellent Microwave Absorption from hydrogenated TiO2 nanoparticles provides us an alternative approach for achieving such Absorption, by manipulating the structural defects inside nanoparticles through hydrogenation. In this study, we demonstrate that the Microwave Absorption can be not only achieved but fine-tuned with TiO2 nanoparticles thermally treated in a Mg/H2 environment. Their position and efficiency can be effectively controlled by the treating temperature. Specifically, the Microwave Absorption position shifts to the lower frequency region as the treating temperature increases, and there seems to exist an optimal treating temperature to obtain the maximum efficiency, as the absorbing efficiency first increases, and then decreases, with the increase in treatment temperature. Therefore, this study enriches our knowledge and understanding Microwave Absorption from TiO2-based nanomaterials which may inspire new ideas on other systems to enhance their performance as well.
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Microwave Absorption of aluminum/hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Zhanqiang Liu, Xiang Peng, Tan Xinyu, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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Doped, conductive SiO 2 nanoparticles for large Microwave Absorption.
Light science & applications, 2018Co-Authors: Michael Green, Fuqiang Huang, Zhanqiang Liu, Xiang Peng, Yan Liu, Minjie Zhou, Tan Xinyu, Lei Liu, Xiaobo ChenAbstract:Although many materials have been studied for the purpose of Microwave Absorption, SiO2 has never been reported as a good candidate. In this study, we present for the first time that doped, Microwave conductive SiO2 nanoparticles can possess an excellent Microwave absorbing performance. A large Microwave reflection loss (RL) of −55.09 dB can be obtained. The large Microwave Absorption originates mainly from electrical relaxation rather than the magnetic relaxation of the incoming Microwave field. The electrical relaxation is attributed to a large electrical conductivity that is enabled by the incorporation of heterogeneous (N, C and Cl) atoms. The removal of the magnetic susceptibility only results in a negligible influence of the Microwave Absorption. In contrast, the removal of the heterogeneous atoms leads to a large decrease in the electrical conductivity and Microwave Absorption performance. Meanwhile, the Microwave Absorption characteristics can be largely adjusted with a change of the thickness, which provides large flexibility for various Microwave Absorption applications. Doped nanoparticles of silica (SiO2) have been found to act as a very strong absorber of Microwave radiation. A US-Chinese collaboration of scientists discovered that, unlike pure SiO2 nanoparticles, those doped with atoms of N, C and Cl induce a reflection loss at large as −55 dB at a frequency of around 7 GHz. The doped nanoparticles, which measured 4–8 nm in diameter, were fabricated by slowly adding the precursor tetraethyl orthosilicate (TEOS) to the solvent N,N’-dimethylformamide (DMF) and then adding hydrazine monohydrochlorid. The resulting solution was then heated, washed and dried. The resulting nanoparticles were then dispersed in paraffin wax rings and the permittivity and permeability measured in the 1.0–18.0 GHz range using a network analyzer. The team attributes the strong Microwave Absorption to the doped nanoparticles’ good electrical conductivity.
James Murowchick - One of the best experts on this subject based on the ideXlab platform.
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Microwave Absorption of aluminum hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Peng Xiang, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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Microwave Absorption of magnesium/hydrogen-treated titanium dioxide nanoparticles
Nano Materials Science, 2019Co-Authors: Michael Green, James Murowchick, Anh Thi Van Tran, Russell Smedley, Adam Roach, Xiaobo ChenAbstract:Abstract Interactions between materials and electromagnetic irradiations in the Microwave frequency are critical for many civil and military applications, such as radar detection, communications, information processing and transport et al. Dipole rotations or magnetic domain resonance are the mainly traditional mechanisms for Microwave Absorption. The recent finding of the excellent Microwave Absorption from hydrogenated TiO2 nanoparticles provides us an alternative approach for achieving such Absorption, by manipulating the structural defects inside nanoparticles through hydrogenation. In this study, we demonstrate that the Microwave Absorption can be not only achieved but fine-tuned with TiO2 nanoparticles thermally treated in a Mg/H2 environment. Their position and efficiency can be effectively controlled by the treating temperature. Specifically, the Microwave Absorption position shifts to the lower frequency region as the treating temperature increases, and there seems to exist an optimal treating temperature to obtain the maximum efficiency, as the absorbing efficiency first increases, and then decreases, with the increase in treatment temperature. Therefore, this study enriches our knowledge and understanding Microwave Absorption from TiO2-based nanomaterials which may inspire new ideas on other systems to enhance their performance as well.
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Microwave Absorption of aluminum/hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Zhanqiang Liu, Xiang Peng, Tan Xinyu, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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FeP nanoparticles: a new material for Microwave Absorption
Materials Chemistry Frontiers, 2018Co-Authors: Michael Green, James Murowchick, Xiang Peng, Tan Xinyu, Lihong Tian, Xiaobo ChenAbstract:Microwave absorbing materials play a critical role within the realms of information and homeland security in times of both peace and international conflicts; as such, discovering new materials for Microwave Absorption is of critical importance due to their applications in civil and military technologies. In this study, we report for the first time FeP nanoparticles as a promising material for Microwave Absorption. The FeP nanoparticles, fabricated through a facile thermal phosphorization process, display impressive Microwave Absorption performance with a reflection loss of −37.68 dB at 13.6 GHz, indicating a large Absorption efficiency over 99.9%. As the thickness of the Microwave absorber increases from 1.0 to 6.0 mm, the Microwave absorbing peak frequency (fmax) shifts to lower frequencies monotonically, and the critical absorbing peak width (Δf10: peak width at RL = −10 dB) increases monotonically, while the reflection loss stays below −33.0 dB. This indicates a robust performance across a tunable frequency range from 8.86 to 15.1 GHz for Microwave Absorption. These characteristics demonstrate that FeP nanoparticles may act as a new and promising Microwave absorbing material.
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Effect of hydrogenation on the Microwave Absorption properties of BaTiO3 nanoparticles
Journal of Materials Chemistry A, 2015Co-Authors: Lihong Tian, James Murowchick, Lei Liu, Xiaodong Yan, Petra Wallenmeyer, Xiaobo ChenAbstract:Microwave absorbing materials (MAMs) have numerous important applications in electronic communications, signal protection, radar dodging, etc. Although it has been proposed as a promising MAM, BaTiO3 has a high reflection coefficient at the interface with air, causing a large reflection. Thus, its efficiency of Microwave Absorption is not satisfactory. Here, we report that hydrogenation has largely improved the Microwave Absorption of BaTiO3 nanoparticles. Hydrogenation is performed on BaTiO3 nanoparticles by treating pristine BaTiO3 nanoparticles at 700 °C for 4 hours in a pure H2 environment. The enhanced Microwave Absorption efficiency with a reflection loss value (−36.9 dB) is attributed to the increased resonance of polar rotations with the incident electromagnetic field which is amplified by the increased interfacial polarization caused by the built-in electrical field along the boundaries between different grains created within these nanoparticles.
Xuefeng Zhang - One of the best experts on this subject based on the ideXlab platform.
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Tuning Microwave Absorption properties of multi-walled carbon nanotubes by surface functional groups
Journal of Materials Science, 2018Co-Authors: Haopeng Liu, Yanhui Zhang, Mu Zhang, Xianguo Liu, Xuefeng ZhangAbstract:Multi-walled carbon nanotubes (MWCNTs) have been proven effective for Microwave Absorption due to the high dielectric loss capacity; however, the influence of surface functional groups on the Absorption efficiency still remains unknown. Herein, we investigated the Microwave Absorption properties of pristine MWCNTs, hydroxyl-containing MWCNTs and carboxyl-containing MWCNTs, evidencing the Absorption efficiencies of > 33%, > 50% and > 45% at 8–18 GHz, respectively. Experimental characterizations reveal that the tunability of Microwave Absorption capacity is originated from the atomic symmetry breaking of surface structure for carbon nanotubes, leading to the differences of electric conductivity and dielectric loss capacity. The present study provides an insight into the structural origin of Microwave Absorption and has important significance to design Microwave Absorption materials by chemical surface engineering.
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Improved Microwave Absorption properties by atomic-scale substitutions
Carbon, 2018Co-Authors: Xiaofang Liu, Rongge Liu, Xueyong Pang, Yanhui Zhang, Gaowu Qin, Xuefeng ZhangAbstract:Abstract To solve the electromagnetic impedance matching issue, Microwave Absorption materials are usually composed of magnetic and dielectric components with heterogeneous interfaces at micro/nanoscales. Herein we demonstrate an arc-discharging approach to optimize Microwave Absorption properties of magnetic@dielectric Fe@C nanocapsules by in-situ substituting nitrogen heteroatoms in graphitic layers. By increasing the nitrogen content, we find that the electromagnetic properties can be effectively tuned, presenting the decreased transmission, the increased absorbance and the slight change for the reflection efficiencies. Experimental and theoretical results reveal that nitrogen dopants result in the atomic-scale symmetry breaking, inducing the separation of space charge at nitrogen-substituted sites, which play a role of electric dipole for the electromagnetic polarization. The present study has important significance in understanding the structural origin of Microwave Absorption, and meanwhile provides an effective way for designing Microwave absorbents at atomic-scale.
Fuqiang Huang - One of the best experts on this subject based on the ideXlab platform.
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Microwave Absorption of aluminum hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Peng Xiang, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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Microwave Absorption of aluminum/hydrogen treated titanium dioxide nanoparticles
Journal of Materiomics, 2019Co-Authors: Michael Green, James Murowchick, Fuqiang Huang, Zhanqiang Liu, Xiang Peng, Tan Xinyu, Xiaobo ChenAbstract:Abstract Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport et al. Traditional mechanisms for such interactions in the Microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study, we present the first report of the Microwave Absorption of Al/H2 treated TiO2 nanoparticles, where the Al/H2 treatment not only induces structural and optical property changes, but also largely improves the Microwave Absorption performance of TiO2 nanoparticles. Moreover, the frequency of the Microwave Absorption can be finely controlled with the treatment temperature, and the Absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of Microwave Absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased Microwave Absorption properties are largely increased visible-light and IR Absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
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Doped, conductive SiO 2 nanoparticles for large Microwave Absorption.
Light science & applications, 2018Co-Authors: Michael Green, Fuqiang Huang, Zhanqiang Liu, Xiang Peng, Yan Liu, Minjie Zhou, Tan Xinyu, Lei Liu, Xiaobo ChenAbstract:Although many materials have been studied for the purpose of Microwave Absorption, SiO2 has never been reported as a good candidate. In this study, we present for the first time that doped, Microwave conductive SiO2 nanoparticles can possess an excellent Microwave absorbing performance. A large Microwave reflection loss (RL) of −55.09 dB can be obtained. The large Microwave Absorption originates mainly from electrical relaxation rather than the magnetic relaxation of the incoming Microwave field. The electrical relaxation is attributed to a large electrical conductivity that is enabled by the incorporation of heterogeneous (N, C and Cl) atoms. The removal of the magnetic susceptibility only results in a negligible influence of the Microwave Absorption. In contrast, the removal of the heterogeneous atoms leads to a large decrease in the electrical conductivity and Microwave Absorption performance. Meanwhile, the Microwave Absorption characteristics can be largely adjusted with a change of the thickness, which provides large flexibility for various Microwave Absorption applications. Doped nanoparticles of silica (SiO2) have been found to act as a very strong absorber of Microwave radiation. A US-Chinese collaboration of scientists discovered that, unlike pure SiO2 nanoparticles, those doped with atoms of N, C and Cl induce a reflection loss at large as −55 dB at a frequency of around 7 GHz. The doped nanoparticles, which measured 4–8 nm in diameter, were fabricated by slowly adding the precursor tetraethyl orthosilicate (TEOS) to the solvent N,N’-dimethylformamide (DMF) and then adding hydrazine monohydrochlorid. The resulting solution was then heated, washed and dried. The resulting nanoparticles were then dispersed in paraffin wax rings and the permittivity and permeability measured in the 1.0–18.0 GHz range using a network analyzer. The team attributes the strong Microwave Absorption to the doped nanoparticles’ good electrical conductivity.
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Graphitic carbon nitride nanosheets for Microwave Absorption
Materials Today Physics, 2018Co-Authors: Michael Green, Fuqiang Huang, Z. Liu, R. Smedley, H. Nawaz, Xiaobo ChenAbstract:Abstract In this study, we have demonstrated for the first time that the graphitic carbon nitride (g-C3N4) nanosheets can possess interesting Microwave Absorption performance. A large reflection loss (RL) value of −36.1 dB has been demonstrated, corresponding to Absorption efficiency over 99.9%. Meanwhile, we have also elucidated the independent contributions of the permittivity and permeability to the Microwave Absorption. Without the contribution of the electrical or magnetic relaxations, the Microwave Absorption efficiency decreases. Specifically, the Microwave Absorption performance decreases much faster without the contribution of the magnetic relaxation than without the contribution of the electrical relaxation. Therefore, the magnetic relaxation in g-C3N4 nanosheets has a large role in their Microwave Absorption. The origins of those relaxations can be traced back to the dipole rotation and magnetic domain resonance inside the materials. In addition, we have also proposed a macroscopic interference model for the Microwave Absorption behavior of the g-C3N4 nanosheets, so that the frequency to reach maximum RL can be precisely predicted given the thickness of the g-C3N4 nanosheet absorber.