The rapid development of high-frequency electronic devices and fifth-generation wireless communication systems has increased the demand for polymer-based materials with both electromagnetic interference shielding and ...The rapid development of high-frequency electronic devices and fifth-generation wireless communication systems has increased the demand for polymer-based materials with both electromagnetic interference shielding and microwave absorption capabilities.In this work,carbon-fiber-reinforced polycarbonate/acrylonitrile-butadiene-styrene composites were prepared by twin-screw melt compounding,and the effects of carbon fiber content,fiber type,and feeding strategy on the mechanical and electromagnetic properties were investigated.Two feeding modes,namely main feeding and side feeding,were compared to regulate the fiber length distribution and conductive-network structure in the PC/ABS matrix.Compared with main feeding,side feeding effectively reduced fiber breakage during extrusion.For example,the number-average fiber length of MC10%-SF reached 165.7μm,whereas that of MC10%prepared by main feeding was only 111.7μm.The retained long fibers promoted the formation of continuous conductive pathways,leading to enhanced dielectric loss and improved electromagnetic attenuation.Among the investigated formulations,MC20%-SF exhibited a maximum reflection loss of-51 dBat 15.5 GHzwith a thickness of 1.7 mmand an effective absorption bandwidth of 4.56 GHz.Meanwhile,it maintained favorable mechanical properties,including a tensile strength of 115 MPaand a flexural modulus of 13,249 MPa.For EMI shielding,HC30%-SF achieved a total shielding effectivenessclose to 55 dBin the X-band.These results indicate that controlling fiber length through side feeding is an effective strategy for balancing mechanical reinforcement,microwave absorption,and EMI shielding performance in PC/ABS-based conductive composites.展开更多
The atom-bond sum-connectivity(ABS)index of a graph G=(V,E)is defined as■,where d(ζ)represents the degree of vertexζ∈V.By using ABS index,the heat of formation of octane and heptane can be accurately predicted.The...The atom-bond sum-connectivity(ABS)index of a graph G=(V,E)is defined as■,where d(ζ)represents the degree of vertexζ∈V.By using ABS index,the heat of formation of octane and heptane can be accurately predicted.The extremal trees with fixed degree sequences that maximize or minimize the ABS index are characterized in this paper.Meanwhile,we offer construction algorithms for these kinds of trees.展开更多
The atom-bond sum-connectivity(ABS)index,put forward by[J.Math.Chem.,2022,60(10):20812093],exhibits a strong link with the acentric factor of octane isomers.The experimental physico-chemical properties of octane isome...The atom-bond sum-connectivity(ABS)index,put forward by[J.Math.Chem.,2022,60(10):20812093],exhibits a strong link with the acentric factor of octane isomers.The experimental physico-chemical properties of octane isomers,such as boiling point,of formation are found to be better measured by the ABS index than by the Randi,atom-bond connectivity(ABC),and sum-connectivity(SC)indices.One important source of information for researching the molecular structure is the bounds for its topological indices.The extrema of the ABS index of the line,total,and Mycielski graphs are calculated in this work.Moreover,the pertinent extremal graphs were illustrated.展开更多
摘要The rapid development of high-frequency electronic devices and fifth-generation wireless communication systems has increased the demand for polymer-based materials with both electromagnetic interference shielding and microwave absorption capabilities.In this work,carbon-fiber-reinforced polycarbonate/acrylonitrile-butadiene-styrene composites were prepared by twin-screw melt compounding,and the effects of carbon fiber content,fiber type,and feeding strategy on the mechanical and electromagnetic properties were investigated.Two feeding modes,namely main feeding and side feeding,were compared to regulate the fiber length distribution and conductive-network structure in the PC/ABS matrix.Compared with main feeding,side feeding effectively reduced fiber breakage during extrusion.For example,the number-average fiber length of MC10%-SF reached 165.7μm,whereas that of MC10%prepared by main feeding was only 111.7μm.The retained long fibers promoted the formation of continuous conductive pathways,leading to enhanced dielectric loss and improved electromagnetic attenuation.Among the investigated formulations,MC20%-SF exhibited a maximum reflection loss of-51 dBat 15.5 GHzwith a thickness of 1.7 mmand an effective absorption bandwidth of 4.56 GHz.Meanwhile,it maintained favorable mechanical properties,including a tensile strength of 115 MPaand a flexural modulus of 13,249 MPa.For EMI shielding,HC30%-SF achieved a total shielding effectivenessclose to 55 dBin the X-band.These results indicate that controlling fiber length through side feeding is an effective strategy for balancing mechanical reinforcement,microwave absorption,and EMI shielding performance in PC/ABS-based conductive composites.
基金Supported by Ningbo NSF(No.2021J234)Zhejiang Provincial Philosophy and Social Sciences Planning Project(No.24NDJC057YB)。
摘要The atom-bond sum-connectivity(ABS)index of a graph G=(V,E)is defined as■,where d(ζ)represents the degree of vertexζ∈V.By using ABS index,the heat of formation of octane and heptane can be accurately predicted.The extremal trees with fixed degree sequences that maximize or minimize the ABS index are characterized in this paper.Meanwhile,we offer construction algorithms for these kinds of trees.
基金Supported by Ningbo NSF(No.2021J234)Zhejiang Provincial Philosophy and Social Sciences Planning Project(No.24NDJC057YB)。
摘要The atom-bond sum-connectivity(ABS)index,put forward by[J.Math.Chem.,2022,60(10):20812093],exhibits a strong link with the acentric factor of octane isomers.The experimental physico-chemical properties of octane isomers,such as boiling point,of formation are found to be better measured by the ABS index than by the Randi,atom-bond connectivity(ABC),and sum-connectivity(SC)indices.One important source of information for researching the molecular structure is the bounds for its topological indices.The extrema of the ABS index of the line,total,and Mycielski graphs are calculated in this work.Moreover,the pertinent extremal graphs were illustrated.