Graphene-coated ZnO tetrapod whiskers for thermally and electrically conductive epoxy composites

Published Date
Composites Part A: Applied Science and Manufacturing
March 2017, Vol.94:104–112, doi:10.1016/j.compositesa.2016.12.009

Author 

• Yue Jiang ^a
• Renhui Sun ^a
• Hao-Bin Zhang ^a,,
• Peng Min ^a
• Dongzhi Yang ^a
• Zhong-Zhen Yu^a,b,,

• aState Key Laboratory of Organic-Inorganic Composites, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
• bBeijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China

Received 10 October 2016. Revised 1 December 2016. Accepted 8 December 2016. Available online 9 December 2016. 

Abstract

Graphene-coated tetrapod ZnO whisker (T-ZnO) hybrids are fabricated by chemical modification of T-ZnO with an aminosilane, covalent coating with graphene oxide (GO) sheets, and reduction of the GO component by UV irradiation or thermal annealing. Compared to the moderately reduced hybrid by UV irradiation, the thermally annealed hybrid at 1000 °C (TGO1000@T-ZnO) is highly efficient in improving both thermal and electrical conductivities of epoxy. A high thermal conductivity of 5.06 W/(m K) is achieved for the epoxy composite with 65 vol.% TGO1000@T-ZnO hybrid. The epoxy composite with 65 vol.% TGO1000@T-ZnO also exhibits a high electrical conductivity of 27.2 S/m due to the efficiently formed electrically conducting network with only ∼4 wt.% well-distributed TGO sheets that are coated on T-ZnO substrates. The excellent thermal and electrical conductivities are attributed to the efficient conductance pathways formed by the skeleton of ZnO whiskers and the enhanced phonon and electron transfers by TGO sheets.

Keywords

Graphene

ZnO tetrapod whiskers

Thermal conductivity

Electrical conductivity

Epoxy composites

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• DOC (418K)

Supplementary Data S1

• ⁎ 
  Corresponding authors at: State Key Laboratory of Organic-Inorganic Composites, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.

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Mesoporous guar galactomannan based biocomposite aerogels through enzymatic crosslinking

Published Date
Composites Part A: Applied Science and Manufacturing
March 2017, Vol.94:93–103, doi:10.1016/j.compositesa.2016.12.013

• Author 

• Abdul Ghafar ^a,,
• Pavel Gurikov ^b
• Raman Subrahmanyam ^b
• Kirsti Parikka ^a
• Maija Tenkanen^a
• Irina Smirnova ^b
• Kirsi S. Mikkonen ^a

• aDepartment of Food and Environmental Sciences, P.O. Box 27 (Latokartanonkaari 11), FI-00014 University of Helsinki, Finland
• bInstitute for Thermal Separation Process, Eiβendorfer Str. 38, 21073, Hamburg University of Technology (TUHH), Germany

Received 4 October 2016. Revised 9 December 2016. Accepted 10 December 2016. Available online 15 December 2016. 

Abstract

Guar galactomannan (GM) was crosslinked using a sustainable enzymatic oxidation approach to form hydrogels. Nanofibrillated cellulose was used as reinforcement prior to crosslinking. Thirteen solvents were tested for replacing water in the gels, and the volumetric yields of hydrogels are discussed in relation to the solvents’ Hansen solubility parameters. Ethanol and dimethyl sulfoxide (DMSO) were selected for further stepwise solvent exchange, to characterize the hydrogels’ shrinkage in response to solvents at each step. DMSO displayed a good compatibility with GM-based hydrogels as compared to ethanol during stepwise solvent exchange, and the overall shrinkage value was similar with those two solvents after supercritical CO₂drying. The obtained aerogel exhibited highly porous composite structures with a large surface area (up to 333 m²/g) and good mechanical stiffness. Negligible ethanol residue was detected, which makes the aerogels safe materials for food and other life science applications.

Keywords

A. Biocomposite

A. Cellulose

B. Microstructures

D. Mechanical testing

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 Table 1

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Table 2.

 Table 3

Table 3.

• ⁎ 
  Corresponding author.

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Effect of matrix damage on compressive strength in the fiber direction for laminated composites

Published Date
Composites Part A: Applied Science and Manufacturing
March 2017, Vol.94:86–92, doi:10.1016/j.compositesa.2016.12.012

• Author 

• G. Eyer ^a
• O. Montagnier ^a,b,,
• C. Hochard ^a
• J.-P. Charles ^a

• aAix Marseille Univ, CNRS, Centrale Marseille, LMA, Marseille, France
• bCentre de Recherche de l’Armée de l’Air, École de l’air, B.A. 701, 13661 Salon-Air, France

Received 1 May 2016. Revised 2 December 2016. Accepted 10 December 2016. Available online 19 December 2016. 

Abstract 

An original experimental method is proposed to characterize the influence of matrix damage on the compressive strength of laminated composites in the fiber direction using tubes. These composite tubes have a dumbbell-shaped geometry so that rupture occurs in the specimen center without stress concentration. They can be constituted of unidirectional or woven plies aligned with the axial direction. First, a torsional cyclic load is applied in order to damage the matrix. This damage is measured at the tube scale via the reduction in shear modulus. Second, a compressive load is applied up to failure for various damage levels.

The method is applied to a woven carbon/epoxy material. Results show that the matrix damage affects significantly the compressive strength in the fiber direction. It is yet observed that longitudinal stiffness is not modified by damage. Finally, a simple model is proposed to describe this decrease of strength vs. matrix damage.

Keywords

A. Polymer-matrix composites (PMCs)

B. Strength

C. Damage mechanics

D. Mechanical testing

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Nomenclature

matrix damage (–)

longitudinal modulus of the ply (MPa)

shear modulus of the ply (MPa)

shear modulus of the matrix (MPa)

non linear parameter (–)

longitudinal strain (%)

longitudinal stress (MPa)

fiber volume fraction (–)

Subscript

compression

tension

Superscript

undamaged material

damaged material

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• ⁎ 
  Corresponding author at: Centre de Recherche de l’Armée de l’Air, École de l’air, B.A. 701, 13661 Salon-Air, France.

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