In order to ensure the operational reliability and infor-mation security of sophisticated electronic components and to protect human health,efficient electromagnetic interference(EMI)shielding materials are required t...In order to ensure the operational reliability and infor-mation security of sophisticated electronic components and to protect human health,efficient electromagnetic interference(EMI)shielding materials are required to attenuate electromagnetic wave energy.In this work,the cellulose solution is obtained by dissolving cotton through hydrogen bond driving self-assembly using sodium hydroxide(NaOH)/urea solution,and cellulose aerogels(CA)are prepared by gelation and freeze-drying.Then,the cellulose carbon aerogel@reduced graphene oxide aerogels(CCA@rGO)are prepared by vacuum impregnation,freeze-drying followed by thermal annealing,and finally,the CCA@rGO/polydimethylsiloxane(PDMS)EMI shielding composites are prepared by backfilling with PDMS.Owing to skin-core structure of CCA@rGO,the complete three-dimensional(3D)double-layer con-ductive network can be successfully constructed.When the loading of CCA@rGO is 3.05 wt%,CCA@rGO/PDMS EMI shielding composites have an excellent EMI shielding effectiveness(EMI SE)of 51 dB,which is 3.9 times higher than that of the co-blended CCA/rGO/PDMS EMI shielding composites(13 dB)with the same loading of fillers.At this time,the CCA@rGO/PDMS EMI shielding composites have excellent thermal stability(T_(HRI) of 178.3℃)and good thermal conductivity coefficient(λ of 0.65 W m^(-1) K^(-1)).Excellent comprehensive performance makes CCA@rGO/PDMS EMI shielding composites great prospect for applications in lightweight,flexible EMI shielding composites.展开更多
With the increasing applications of novel materials and structures in new-generation aircraft,conventional joining techniques in aircraft component assembly are greatly challenged.To meet those challenges,the electrom...With the increasing applications of novel materials and structures in new-generation aircraft,conventional joining techniques in aircraft component assembly are greatly challenged.To meet those challenges,the electromagnetic riveting(EMR)technique was developed as an advanced joining tool,which exhibits obvious advantages in the assembly of new-generation aircraft.In this paper,the riveting principle of EMR was analyzed,and its development history and status were presented in detail.Then,equipment features of three typical EMR systems were given.Moreover,three important applications of EMR were covered,i.e.,composite structure riveting,titanium rivet and large-size aluminum rivet riveting,and interference fit bolt installation.Specially,a novel strengthening method for mechanical linking holes based on EMR was also presented,which can significantly improve the fatigue behaviors of mechanical joints.Finally,open questions in the EMR field were discussed,and some recommendations for future work were also made.This paper can be useful for optimizing the joint designs of aircraft components and improving the level of aircraft maintenance.展开更多
With the widespread application of electronic communication technology,the resulting electromagnetic radiation pollution has been significantly increased.Metal matrix electromagnetic interference(EMI)shielding materia...With the widespread application of electronic communication technology,the resulting electromagnetic radiation pollution has been significantly increased.Metal matrix electromagnetic interference(EMI)shielding materials have disadvantages such as high density,easy corrosion,difficult processing and high price,etc.Polymer matrix EMI shielding composites possess light weight,corrosion resistance and easy processing.However,the current polymer matrix composites present relatively low electrical conductivity and poor EMI shielding performance.This review firstly discusses the key concept,loss mechanism and test method of EMI shielding.Then the current development status of EMI shielding materials is summarized,and the research progress of polymer matrix EMI shielding composites with different structures is illustrated,especially for their preparation methods and evaluation.Finally,the corresponding key scientific and technical problems are proposed,and their development trend is also prospected.展开更多
基金the Foundation of National Natural Science Foundation of China(51773169 and 51973173)the Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province of China(2019JC-11)+2 种基金the Natural Science Basic Research Plan in Shaanxi Province of China(2020JQ-164)Y.Q.Guo thanks the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX202055)Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘In order to ensure the operational reliability and infor-mation security of sophisticated electronic components and to protect human health,efficient electromagnetic interference(EMI)shielding materials are required to attenuate electromagnetic wave energy.In this work,the cellulose solution is obtained by dissolving cotton through hydrogen bond driving self-assembly using sodium hydroxide(NaOH)/urea solution,and cellulose aerogels(CA)are prepared by gelation and freeze-drying.Then,the cellulose carbon aerogel@reduced graphene oxide aerogels(CCA@rGO)are prepared by vacuum impregnation,freeze-drying followed by thermal annealing,and finally,the CCA@rGO/polydimethylsiloxane(PDMS)EMI shielding composites are prepared by backfilling with PDMS.Owing to skin-core structure of CCA@rGO,the complete three-dimensional(3D)double-layer con-ductive network can be successfully constructed.When the loading of CCA@rGO is 3.05 wt%,CCA@rGO/PDMS EMI shielding composites have an excellent EMI shielding effectiveness(EMI SE)of 51 dB,which is 3.9 times higher than that of the co-blended CCA/rGO/PDMS EMI shielding composites(13 dB)with the same loading of fillers.At this time,the CCA@rGO/PDMS EMI shielding composites have excellent thermal stability(T_(HRI) of 178.3℃)and good thermal conductivity coefficient(λ of 0.65 W m^(-1) K^(-1)).Excellent comprehensive performance makes CCA@rGO/PDMS EMI shielding composites great prospect for applications in lightweight,flexible EMI shielding composites.
基金funded by the Major National Research Project of Numerical Control Machine and Basic Manufacturing Equipment of China(No.2016ZX04002004-008).
文摘With the increasing applications of novel materials and structures in new-generation aircraft,conventional joining techniques in aircraft component assembly are greatly challenged.To meet those challenges,the electromagnetic riveting(EMR)technique was developed as an advanced joining tool,which exhibits obvious advantages in the assembly of new-generation aircraft.In this paper,the riveting principle of EMR was analyzed,and its development history and status were presented in detail.Then,equipment features of three typical EMR systems were given.Moreover,three important applications of EMR were covered,i.e.,composite structure riveting,titanium rivet and large-size aluminum rivet riveting,and interference fit bolt installation.Specially,a novel strengthening method for mechanical linking holes based on EMR was also presented,which can significantly improve the fatigue behaviors of mechanical joints.Finally,open questions in the EMR field were discussed,and some recommendations for future work were also made.This paper can be useful for optimizing the joint designs of aircraft components and improving the level of aircraft maintenance.
基金The authors are grateful for the support and funding from the Foundation of National Natural Science Foundation of China(51903145 and 51973173)Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province of China(2019JC-11)+1 种基金Fundamental Research Funds for the Central Universities(D5000210627)This work is also financially supported by Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘With the widespread application of electronic communication technology,the resulting electromagnetic radiation pollution has been significantly increased.Metal matrix electromagnetic interference(EMI)shielding materials have disadvantages such as high density,easy corrosion,difficult processing and high price,etc.Polymer matrix EMI shielding composites possess light weight,corrosion resistance and easy processing.However,the current polymer matrix composites present relatively low electrical conductivity and poor EMI shielding performance.This review firstly discusses the key concept,loss mechanism and test method of EMI shielding.Then the current development status of EMI shielding materials is summarized,and the research progress of polymer matrix EMI shielding composites with different structures is illustrated,especially for their preparation methods and evaluation.Finally,the corresponding key scientific and technical problems are proposed,and their development trend is also prospected.
