A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbo...A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.展开更多
挠曲电效应广泛应用于柔性传感、医疗复健、振动能量收集等领域,然而尚未有研究探讨挠曲形变量对挠曲电响应性能的影响。基于此,以MoS_(2)/PAN复合挠曲电传感薄膜为例,制备MoS_(2)/PAN弯曲传感器,采用X射线衍射仪和扫描电子显微镜对复...挠曲电效应广泛应用于柔性传感、医疗复健、振动能量收集等领域,然而尚未有研究探讨挠曲形变量对挠曲电响应性能的影响。基于此,以MoS_(2)/PAN复合挠曲电传感薄膜为例,制备MoS_(2)/PAN弯曲传感器,采用X射线衍射仪和扫描电子显微镜对复合挠曲电传感薄膜的晶体结构、微观形貌进行表征。在弯曲角度为0.1°、0.5°、1.5°、4°、7°、15°、30°和45°情况下,通过数字源表收集不同弯曲角度下MoS_(2)/PAN弯曲传感器的挠曲响应电压、电流和响应时间,分析挠曲形变量对挠曲电响应性能的影响规律,基于悬臂梁方法测试计算挠曲电系数。结果表明:MoS_(2)/PAN弯曲传感器挠曲电效应显著,挠曲电系数高达1.95 n C/m,当弯曲角度为7°时,MoS_(2)/PAN弯曲传感器获得最优的挠曲电响应,当弯曲角度小于7°时,挠曲电响应随弯曲角度的增大而增大,但是当弯曲角度大于7°时,挠曲电效应减弱。展开更多
针对现有分级多PAN太赫兹无线网络MAC(Medium Access Control)协议中存在的子网形成方案不合理以及私有CTA(Channel Time Allocation)与子网内实际负载不匹配等问题,提出了一种高效低时延的MAC层优化协议.该协议采用基于泛听的按需形成...针对现有分级多PAN太赫兹无线网络MAC(Medium Access Control)协议中存在的子网形成方案不合理以及私有CTA(Channel Time Allocation)与子网内实际负载不匹配等问题,提出了一种高效低时延的MAC层优化协议.该协议采用基于泛听的按需形成子网机制避免了子网分布不均匀以及因子网形成后没有节点加入而造成的私有CTA资源浪费的问题.在子网形成后,子微微网协调器(Piconet Coordinator,PNC)根据子网内实际负载情况自适应选择私有CTA时隙资源优化机制,让有数据传输需求的节点及时将数据发出.仿真结果表明,所提出的方案能有效地降低数据帧平均接入时延,提高吞吐量以及数据帧的传输成功率.展开更多
Dynamic viscoelastic properties of polyacrylonitrile(PAN)/DMSO/H2O solutions with different H2O contents were studied as a function of temperature.These PAN solutions gradually became gel with decreasing temperature.T...Dynamic viscoelastic properties of polyacrylonitrile(PAN)/DMSO/H2O solutions with different H2O contents were studied as a function of temperature.These PAN solutions gradually became gel with decreasing temperature.The sol-gel transition took place at a critical gel temperature,at which the scaling law of G'(ω)～G″(ω)∝ωn held,allowing an accurate determination of the critical gel temperature by means of the frequency independence of the loss tangent.The gel point of PAN solutions increases with increasing H2O content.The scaling exponent n(=0.86) at the gel point is confirmed to be universal for PAN gels,which is independent of temperature,suggesting the similarity of the fractal structure in the critical PAN gels.展开更多
基金Project(2006CB600903) supported by the National Basic Research Program of China
文摘A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.
文摘挠曲电效应广泛应用于柔性传感、医疗复健、振动能量收集等领域,然而尚未有研究探讨挠曲形变量对挠曲电响应性能的影响。基于此,以MoS_(2)/PAN复合挠曲电传感薄膜为例,制备MoS_(2)/PAN弯曲传感器,采用X射线衍射仪和扫描电子显微镜对复合挠曲电传感薄膜的晶体结构、微观形貌进行表征。在弯曲角度为0.1°、0.5°、1.5°、4°、7°、15°、30°和45°情况下,通过数字源表收集不同弯曲角度下MoS_(2)/PAN弯曲传感器的挠曲响应电压、电流和响应时间,分析挠曲形变量对挠曲电响应性能的影响规律,基于悬臂梁方法测试计算挠曲电系数。结果表明:MoS_(2)/PAN弯曲传感器挠曲电效应显著,挠曲电系数高达1.95 n C/m,当弯曲角度为7°时,MoS_(2)/PAN弯曲传感器获得最优的挠曲电响应,当弯曲角度小于7°时,挠曲电响应随弯曲角度的增大而增大,但是当弯曲角度大于7°时,挠曲电效应减弱。
基金Project(2006CB606505) supported by the National Basic Research Development Program of ChinaProject(50333050) supported by the National Natural Science Foundation of China+1 种基金Project(07DJ14002) supported by the Shanghai Fundamental Theory ProgramProject(20020255010) supported by the Specialized Research Fund for the Doctoral Program of Higher Education
文摘Dynamic viscoelastic properties of polyacrylonitrile(PAN)/DMSO/H2O solutions with different H2O contents were studied as a function of temperature.These PAN solutions gradually became gel with decreasing temperature.The sol-gel transition took place at a critical gel temperature,at which the scaling law of G'(ω)～G″(ω)∝ωn held,allowing an accurate determination of the critical gel temperature by means of the frequency independence of the loss tangent.The gel point of PAN solutions increases with increasing H2O content.The scaling exponent n(=0.86) at the gel point is confirmed to be universal for PAN gels,which is independent of temperature,suggesting the similarity of the fractal structure in the critical PAN gels.
