Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial i...Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial intelligence and wearable electronics.In this work,silver nanowires(AgNWs)are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent,and boron nitride(BN)is performed to prepare BN nanosheets(BNNS)with the help of isopropyl alcohol and ultrasonication-assisted peeling method,which are compounded with aramid nanofibers(ANF)prepared by chemical dissociation,respectively,and the(BNNS/ANF)-(AgNWs/ANF)thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the"vacuum-assisted filtration and hot-pressing"method.Janus(BNNS/ANF)-(AgNWs/ANF)composite films exhibit"one side insulating,one side conducting"performance,the surface resistivity of the BNNS/ANF surface is 4.7×10^(13) Ω,while the conductivity of the AgNWs/ANF surface is 5,275 S/cm.And Janus(BNNS/ANF)-(AgNWs/ANF)composite film with thickness of 95 pm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K)and superior electromagnetic interference shielding effectiveness of 70 dB.The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa.It also has good temperature-voltage response characteristics(high Joule heating temperature at low supply voltage(5 V,215.0℃),fast response time(10 s)),excellent electrical stability and reliability(stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).展开更多
为探究热塑性酚酞基聚醚酮(Polyaryletherketone with Cardo,PEK-C)树脂薄膜及膜厚对层间增韧碳纤维/环氧树脂复合材料力学性能的影响,利用浸渍提拉法制备了三种不同厚度(分别约为1μm、10μm、30μm)的PEK-C膜,通过热压成型制备了层间...为探究热塑性酚酞基聚醚酮(Polyaryletherketone with Cardo,PEK-C)树脂薄膜及膜厚对层间增韧碳纤维/环氧树脂复合材料力学性能的影响,利用浸渍提拉法制备了三种不同厚度(分别约为1μm、10μm、30μm)的PEK-C膜,通过热压成型制备了层间增韧碳纤维/环氧树脂复合材料层合板,对其进行了Ⅰ型层间断裂韧性、冲击后压缩强度、层间剪切及弯曲性能测试,并利用SEM观察微观形貌及AFM扫描微观相图。结果表明:不同PEK-C膜厚增韧碳纤维/环氧树脂复合材料的Ⅰ型层间断裂韧性、冲击后压缩强度及层间剪切强度有不同程度提高,Ⅰ型层间断裂韧性及层间剪切强度以膜厚为10μm最佳,分别增大了157.17%和17.57%,冲击后压缩强度以膜厚为30μm最佳,达到了186.67MPa,这是由于PEK-C与环氧树脂在热压固化过程中形成了双相结构,改善了材料韧性;但弯曲性能持续下降,强度及模量由未增韧的1 551 MPa、106 GPa分别降至30μm时的965MPa、79GPa,这是由于PEK-C树脂扩散进入环氧树脂中,降低了纤维体积分数及材料刚度。展开更多
A series of bionic grooves based on bird wing, such as cluster spiral groove, multi-array spiral groove and flow-split spiral groove, are introduced to improve the film stiffness and sealing properties of dry gas seal...A series of bionic grooves based on bird wing, such as cluster spiral groove, multi-array spiral groove and flow-split spiral groove, are introduced to improve the film stiffness and sealing properties of dry gas seal. A theoretical model solved with Finite Difference Method （FMD） is developed to study the static sealing performance, such as film stiffness and leakage rate of these bionic groove dry gas seals. Then, a performance comparative study between the bionic groove dry gas seals and common spiral groove dry gas seal with different groove geometry parameters such as groove depth ratio, spiral angle and micro groove number under different average linear velocity at seal ring face and seal pressure is carried out. The closing force, film thickness and leakage rate of dry gas seals with bionic grooves and common spiral groove are measured experimentally. Results show that cluster spiral groove and multi-array spiral groove dry gas seals have superiority in the film stiffness and stiffness-leakage ratio compared with common spiral groove under the condition of high-speed and low-pressure, while flow-split spiral groove dry gas seal has no obvious advantages of performance. Film stiffness of cluster spiral groove dry gas seal and stiffness-leakage ratio of multi-array spiral groove dry gas are 20% and 50% larger than that of common spiral groove dry gas seal, respectively, which are verified by the experimental results.展开更多
基金The authors are grateful for the support and funding from the Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120093)Foundation of National Natural Science Foundation of China(Nos.U21A2093 and 51973173)Technological Base Scientific Research Projects(Highly Thermal conductivity Nonmetal Materials).
文摘Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry,artificial intelligence and wearable electronics.In this work,silver nanowires(AgNWs)are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent,and boron nitride(BN)is performed to prepare BN nanosheets(BNNS)with the help of isopropyl alcohol and ultrasonication-assisted peeling method,which are compounded with aramid nanofibers(ANF)prepared by chemical dissociation,respectively,and the(BNNS/ANF)-(AgNWs/ANF)thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the"vacuum-assisted filtration and hot-pressing"method.Janus(BNNS/ANF)-(AgNWs/ANF)composite films exhibit"one side insulating,one side conducting"performance,the surface resistivity of the BNNS/ANF surface is 4.7×10^(13) Ω,while the conductivity of the AgNWs/ANF surface is 5,275 S/cm.And Janus(BNNS/ANF)-(AgNWs/ANF)composite film with thickness of 95 pm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K)and superior electromagnetic interference shielding effectiveness of 70 dB.The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa.It also has good temperature-voltage response characteristics(high Joule heating temperature at low supply voltage(5 V,215.0℃),fast response time(10 s)),excellent electrical stability and reliability(stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).
基金Acknowledgment The research is financially support by The National Key Basic Research Development Plan （973 Plan, 2014CB046404）, National Nature Science Foundation of China （51575490） and Key Program of Zhejiang Provincial Natural Science Fund Project （LZ15E050002）.
文摘A series of bionic grooves based on bird wing, such as cluster spiral groove, multi-array spiral groove and flow-split spiral groove, are introduced to improve the film stiffness and sealing properties of dry gas seal. A theoretical model solved with Finite Difference Method （FMD） is developed to study the static sealing performance, such as film stiffness and leakage rate of these bionic groove dry gas seals. Then, a performance comparative study between the bionic groove dry gas seals and common spiral groove dry gas seal with different groove geometry parameters such as groove depth ratio, spiral angle and micro groove number under different average linear velocity at seal ring face and seal pressure is carried out. The closing force, film thickness and leakage rate of dry gas seals with bionic grooves and common spiral groove are measured experimentally. Results show that cluster spiral groove and multi-array spiral groove dry gas seals have superiority in the film stiffness and stiffness-leakage ratio compared with common spiral groove under the condition of high-speed and low-pressure, while flow-split spiral groove dry gas seal has no obvious advantages of performance. Film stiffness of cluster spiral groove dry gas seal and stiffness-leakage ratio of multi-array spiral groove dry gas are 20% and 50% larger than that of common spiral groove dry gas seal, respectively, which are verified by the experimental results.
