MODIFIED CARBON-BASED MATERIALS

Abstract

The invention concerns a composite material comprising a carbon-based material and a non-continuous film comprising a plurality of regions of a metal-based wetting material associated with the carbon-based material, the non-continuous film of the wetting material being configured to tune the carbon-based material to adhesively receive thereon a film of at least one polymeric material.

Claims

1.-87. (canceled)

88. A composite in a form of a 3D object of a carbon-based material, the object being associated with a continuous film of at least one polymeric material on at least a region of its surface, the film being associated with the 3D object via a plurality of regions of a metal-based wetting material selected to tune wettability of the carbon-based material, thereby permitting association of the polymeric material with both the carbon-based material forming the object and the metal-based wetting material.

89. The composite according to claim 88, wherein the thickness of the wetting film is between 1 and 100 nm.

90. The composite according to claim 88, wherein the thickness of the regions of the non-continuous wetting film and the polymeric film, combined, ranging from 10 nm to 5 mm.

91. The composite according to claim 88, wherein the carbon-based material is a carbon allotrope.

92. The composite according to claim 88, wherein the carbon-based material is selected from graphite, carbon fibers, carbon black powder, amorphous carbon powder, carbon nanofoam, glassy carbon, graphene and graphene flakes, graphene oxide, reduced graphene oxide, carbon nanofibers, carbon nanotubes (CNTs), fullerenes (buckyballs), diamond powder, diamond nanoparticles and diamond coating.

93. The composite according to claim 92, wherein the carbon-based material is graphene or a graphene-based structure, optionally selected from graphene flakes, graphene nanosheets, graphene nanoribbons, and graphene nanoparticles.

94. The composite according to claim 92, wherein the carbon-based material is CNT.

95. The composite according to claim 94, wherein the CNT is in a form of a collection of CNTs or as a CNT assembly.

96. The composite according to claim 95, wherein the CNT assembly is selected from a CNT bundle or a CNT web.

97. The composite according to claim 88, wherein the non-continuous metal-based wetting film is free of surfactants.

98. The composite according to claim 88, wherein the metal-based wetting material is an inorganic material, organic material or a hybrid material comprising.

99. The composite material according to claim 98, wherein the metal-based wetting material comprises a plurality of metal atoms in-layer associated to each other, directly or via bridging atoms or organic ligands, wherein the metal atoms are further associated with one or more surface exposed functionalities which are selected to endow hydrophilicity to the wetting film.

100. The composite according to claim 99, wherein the surface exposed functionalities are hydroxide functionalities, oxide functionalities, alkoxide functionalities, amine functionalities, or benzyl functionalities.

101. The composite according to claim 88, wherein the carbon-based material is or comprises CNT and the non-continuous wetting film is or comprises a metalcone.

102. The composite according to claim 88, the composite comprising a carbon-based material being or comprising CNT coated with a non-continuous wetting film of a metal-based wetting material, the non-continuous wetting film being associated with a film of an epoxy material (polyepoxide).

103. A composite material comprising a CNT mat having a non-continuous wetting film associating a film of epoxy (polyepoxide).

104. A CNT mat having an epoxy film on at least a region of its surface, the film being associated with the CNT mat via a non-continuous wetting film comprising a plurality of spaced-apart regions of a metal-based wetting material that are non-covalently associated with CNTs in said CNT mat.

105. A process for manufacturing a composite material of at least one carbon-based material and a polymer, the process comprising: vapor deposition of a non-continuous metal-based wetting film; and wet or melt deposition of a polymer film, optionally via deposition of a polymer melt or deposition of a polymerizable polymer precursor.

106. The process according to claim 105, wherein the non-continuous metal-based wetting film is provided directly on the carbon-based material by vapor phase deposition being one or a combination of atomic layer deposition (ALD), molecular layer deposition (MLD), combined ALD/MLD, spatial ALD, and tandem catalyst ALD/MLD.

107. A process for forming a composite according to claim 88, the process comprising: vapor deposition of a metal-based wetting material on a surface of a carbon-based material, wherein the deposition is by ALD, MLD or a deposition method comprising same, to form a non-continuous wetting film on said surface; wet deposition of a composition comprising a polymer or a polymer resin or a prepolymer or deposition of a polymer melt and optionally a hardener on the non-continuous wetting film to form a film of said composition or polymer; and curing the deposited film to thereby permit association of the polymer with the non-continuous wetting film and with exposed regions of the carbon-based material, to thereby obtain the composite.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0175] To better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0176] FIG. 1 shows a CNT mat (31 gm.sup.2) used in accordance with aspects and embodiments of the invention.

[0177] FIG. 2 illustrates an exemplary preparation method of CNT-epoxy composite according to certain embodiments of the invention. (a) Preparation of resin/hardener mixtureresin:hardener weight ratio is 38:100 (w:w). (b) Placing CNT mat on aluminum plate holder covered with non-stick paper and brushing with the resin-hardener mixture (repeated twice). Excess is removed with a silicone wiper. (c) RT curing in a vacuum bag and pump it for 24 h. (d) Post curing 80 C. for 5 h.

[0178] FIG. 3 presents a typical stress-strain curve. The slope of the linear region (part A) represents the stiffness of the material. Yield point is the stress beyond which a material becomes plastic (area B). Ultimate strength is the maximum stress that the material can withstand under external force (part C). Fracture point is the point of strain where the material physically separates.

DETAILED DESCRIPTION OF EMBODIMENTS

Materials and Methods

CNT Mat Substrate

[0179] CNT mats were obtained from Tortech nano fibers, A4 sheet size. The CNT mats were synthesized by floating catalyst chemical vapor deposition (FCCVD) reaction. The feedstock contains carbon source, methane, ethanol, ferrocene and thiophene. The ferrocene acts as the catalyst source for this reaction. Pyrolysis under reducing environment results in iron nanoparticles with Sulphur shell. Fullerene caps form on the surface of the nanoparticles which then evolve into individual CNTs. As CNTs become longer and bind into a network of CNT bundles induced by van der walls interactions. This continuous cylindrical network form is spun around the drum and drawn into a non-woven mat (shown in FIG. 1). CNT mats can be obtained with thickness ranging between 10 s-100 s of microns depending on the drum collection time with the corresponding surface densities of 2-50 gm.sup.2. The CNT mats contain about 10% w/w of catalyst residues (Fe and S) originating from the synthesis.

[0180] Ultra-high purity Ar gas is used as a carrier gas in a hot wall reactor and purge between reactant exposures. The control of the precursors dosing is done by computer controlled pneumatic valves at a steady pressure of 1.510.sup.1 mbar maintained during the process. Whole CNT mats samples (6090 mm) are prepared by loading the samples to the reactor allowing the temperature to stabilize for 30 minutes and dosing the reactant precursors into Ar carrier gas. The silane precursors are kept at 80 C. and the sample reactor temperature is set to 171 C. with actual sample tray temperature 153 C.

Wet Lay-Up Technique

[0181] Epoxy system Araldite LY 5052 resin Aradur 5052 hardener is used to form the CNT mat-epoxy composites of the invention. The resin density is 1.17 g/cm.sup.3 and the hardener density is hardener Density 0.95 g/cm.sup.3. This epoxy system is commonly used in aircraft components with relatively low mixture viscosity of 0.500-700 cP (at 25 C.) and molar mass is less than 700 gmol.sup.1. Preparation of CNT mat-epoxy composite is performed as described below (FIG. 2): [0182] (I) A mixture of resin:hardener was prepared in a weight ratio of 100:38 (w:w). [0183] (II) Samples are placed on aluminum plate coated with non-stick teflon film and were loaded with the resin:hardener mixture layer and applied using a brush to ensure full and uniform impregnation of the mixture onto the mat excess mixture is removed using a silicone spatula. This step is repeated twice. [0184] (III) Samples were loaded to a vacuum bag connected to a pump for 24 hours curing at room temperature under external pressure of 2000 psi. [0185] (IV) Samples were cured for 5 hours at 80 C. under external pressure of 2000 psi.

[0186] For all experiments, both M/ALD treated and un-treated composite samples are prepared for comparison. Epoxy type Araldite LY 5052 Aradur 5052 compose of epoxy resin phenol novolac (EPN) and Isophorone diamine (IPDA) as the hardener.

Contact Angle Measurement

[0187] Contact angle (CA) is defined as the angle formed by a liquid at the three-phase boundary where a liquid-vapor interface meets a solid surface. CA is often used to quantify the surface wettability of a solid surface by liquid.

[0188] CA measurements were performed using ultra-pure water (>18M, ELGA purification system) and epoxy Araldite LY5052 Aradur 5052 mixture that is used for the composite formation using Attension goniometer equipped with Theta Lite software. The measurement is performed three times for each sample to achieved repeatability.

Tensile Testing

[0189] Tensile testing is applied to CNT mats and their epoxy composites for mechanical testing. Material properties measured via a tension test include ultimate strength, elongation, young's modulus and toughness. Material properties are expressed by stress, force per unit area () and strain, percent change in length (). To obtain the stress, the force is divided by the sample cross sectional area (=F/A). Strain is obtained by dividing the change in length by the initial length of the sample (=L/L). It is common to plot the stress as a function of the strain, referred to as Stress-Strain Curve (FIG. 3). Each material has a unique curve, but for most materials, the initial curve is a straight line reflecting the linear relationship between the stress and strain. This is called the Elastic range which can describe by Hooke's Law (F=kL), where the ratio of stress to strain is constant:

[00001]$\begin{array}{cc}\frac{F}{A}=E\frac{L}{L}& \left(\mathrm{Eq}.5\right)\end{array}$

[0190] The slope of the stress strain curve at the linear region is equivalent to young's modulus of elasticity (E). Young's modulus is a measure of the stiffness of the material and defines the ability of a material to withstand changes in length when under longitude tension. This linear region represents basic linear elastic stress-strain relationship assuming there is no plastic deformation. Toughness is a mechanical property which defines the ability of a material to absorb energy and plastically deform without fracturing. Toughness is quantified as the area under the stress-strain curve. Young's modulus, toughness, ultimate strength and Ultimate strain.

[0191] Elastic Hysteresis is the difference between the strain energy required to generate a given stress in a material, and the material's elastic energy at that stress. This energy is dissipated as internal friction (heat) in a material during one cycle of testing (loading and unloading). It is clear that modified CNT mat shows different behavior in the plastic region. The untreated CNT mat reveals the maximal strain of 3.2% while for modified CNT mat, the strain values are 7.7% and 4.5% for M/ALD (DMASi) and M/ALD (MMASi) treatments, respectively. This observation demonstrates that the M/ALD treatment allows the CNT mat-epoxy composite to absorb more energy before rupture and to withstand under higher stress values. It also can be seen that the M/ALD (DMASi) treatment show better improvement than M/ALD (MMASi) treatment, as shown in the mechanical property analysis above.