Composites of epoxy/graphene-modified-diamond filler show enhanced thermal conductivity and high electrical insulation

At a Glance

Metadata	Details
Publication Date	2017-01-01
Journal	RSC Advances
Authors	Jin Jiang, Feixiang Liu, Kunyi Zhuang, Danqing Chen, Guohua Chen
Institutions	Xiamen University of Technology, Huaqiao University
Citations	20
Analysis	Full AI Review Included

Technical Documentation and Analysis: Diamond Composites for Advanced Thermal Management

Executive Summary

This paper successfully demonstrates the fabrication of epoxy composites utilizing high-purity diamond microparticles modified with few-layer graphene (G-D filler). This material innovation significantly enhances passive thermal management capabilities while preserving essential electrical insulation required for modern electronics packaging.

Metric	Result	Comparative Performance	6CCVD Value Proposition
Thermal Conductivity (k)	2.85 W m&supmin;¹ K&supmin;¹	1190% improvement over neat epoxy.	High intrinsic purity of 6CCVD diamond maximizes initial thermal performance before modification.
Electrical Insulation	2.2 x 10&sup10; Ω m	Excellent resistivity maintained.	Confirms suitability of SCD/PCD precursors for dielectric TIM applications.
Methodology	Vacuum-based heating (1273 K) using Ni catalyst.	Achieved controlled 1-3 layer graphene growth.	6CCVD specializes in high-temperature, high-purity CVD processes, validating the base manufacturing approach.
Core Application	High thermal conductivity electronic packaging materials and heat sinks.	Solves the critical requirement for rapid heat dissipation in miniaturized devices.	6CCVD offers custom SCD/PCD materials as foundational components for next-generation composite fillers and substrates.

Technical Specifications

The following table summarizes the key performance metrics and experimental parameters extracted from the research paper, focusing on material requirements and achievable results.

Parameter	Value	Unit	Context
Achieved Thermal Conductivity (k)	2.85	W m&supmin;¹ K&supmin;¹	Composite (70 wt% G-D filler)
Thermal Conductivity of Pure Diamond (Intrinsic)	~2000	W m&supmin;¹ K&supmin;¹	Literature value, target baseline for diamond precursors
Electrical Resistivity (ρ_v)	2.2 x 10&sup10;	Ω m	Confirms excellent electrical insulation
TC Enhancement (vs. Neat Epoxy)	1190	%	Demonstrates significant utility in thermal interface materials (TIMs)
TC Enhancement (vs. Pure Diamond Composite)	101	%	Benefit derived from graphene modification (interfacial resistance reduction)
Diamond Filler Particle Diameter	10-30	µm	Powder dimensions used
Nickel Catalyst Particle Size	1-5	µm	Used for graphene synthesis
Graphene Synthesis Temperature	1273	K	High-temperature, vacuum-based modification
Graphene Layer Count (Optimal Ratio D:Ni=49:1)	1-2	layers	Determined via Raman and HRTEM analysis
Filler Weight Loading (in Epoxy)	70	wt%	High loading fraction used for maximum thermal density

Key Methodologies

The synthesis relies on adapting high-temperature CVD principles for surface modification of microparticles. This process enhances filler dispersion and reduces interfacial thermal resistance (ITR) in the polymer matrix.

Graphene Synthesis on Diamond:
- Precursors: Diamond particles (10-30 µm) and Nickel (Ni) powder (1-5 µm) catalyst.
- Optimal Ratio (D:Ni): Varied from 100:0 down to 1:1, with 49:1 and 9:1 showing optimized results.
- Process: Mixtures placed in a tube furnace and pumped to a base pressure below 5 Pa.
- Heating Cycle: Heated to 1273 K (1000 °C) and held for 2 hours.
- Post-Treatment: Cooled, then acid-etched in dilute hydrochloric acid (HCl) to remove residual Ni catalyst elements (forming NiCl₂).
Composite Preparation:
- Materials: Bisphenol A epoxy resin (E 6002), modified diamond filler (3.5 g), and diethyl methyl benzene diamine (DETDA) curing agent (0.36 g).
- Mixing: Vigorously stirred epoxy and filler for 10 minutes, followed by curing agent addition and another 10 minutes of stirring.
- Curing Profile (Three Stages):
  - Stage 1: 117 °C / 1 hour
  - Stage 2: 135 °C / 0.5 hours
  - Stage 3: 170 °C / 2.5 hours
Characterization Techniques:
- Structural: SEM, HRTEM, XRD, Raman Spectroscopy (confirmed 1-3 layer graphene).
- Thermal: Laser flash method (LFA447) to measure thermal diffusivity (α). Thermal conductivity (k) calculated using k = α * ρ * C_p.
- Electrical: Volume resistivity (ρ_v) measured using AVO meter (UT70A).

6CCVD Solutions & Capabilities

This research validates high-purity CVD diamond as the premier solid-state filler for achieving high thermal performance composites. 6CCVD provides the high-quality single crystal and polycrystalline diamond precursors necessary to replicate and scale this technology.

Applicable Materials

The foundation of this high-performance composite is the ultra-high intrinsic thermal conductivity of the diamond filler (up to 2000 W m&supmin;¹ K&supmin;¹). 6CCVD ensures this baseline performance with:

Polycrystalline Diamond (PCD) Precursors: Ideal for cost-effective, large-volume filler production. We offer custom PCD substrates up to 125mm diameter, which can be further processed into microparticles suitable for composite mixing or used as large-area heat spreaders in similar applications.
High-Purity Single Crystal Diamond (SCD): Offers the highest intrinsic thermal properties. While the paper used microparticles, 6CCVD supplies SCD plates (up to 500 µm thick) for researchers developing structured thermal interface layers or thin film architectures requiring maximum lattice purity.
Boron-Doped Diamond (BDD): For applications that require high thermal conductivity combined with tailored electrical conduction (e.g., active heating/cooling elements or integrated electrodes), BDD provides semiconductor or metallic conductivity while maintaining excellent thermal transport.

Customization Potential & Engineering Services

Replication and scaling of this G-D composite technology necessitate precise material preparation and processing expertise—core strengths of 6CCVD.

Required Capability (Paper)	6CCVD Custom Capability	Application Extension
High-purity diamond material baseline.	Supply of Single Crystal Diamond (SCD) or Polycrystalline Diamond (PCD) wafers/plates with tailored thickness (0.1 µm to 500 µm).	Developing macro-scale structured TIM sheets or hybrid diamond/polymer layers.
Surface modification via high-temperature processing (1273 K, vacuum).	Our extensive MPCVD expertise supports custom high-temperature processing and surface treatments necessary for controlled graphene deposition or tailored surface functionalization.	Assisting clients in optimizing the Ni-catalyst CVD process for industrial scale-up of diamond powder fillers.
Potential for electrical contact/integration (Graphene modification alters surface charge).	Custom Metalization: We offer in-house deposition of Au, Pt, Pd, Ti, W, and Cu layers, crucial for creating robust electrical contacts or bonding layers in hybrid thermal/electrical devices.	Integration of high-TC diamond into PCB vias or multi-layer thermal stacks using advanced bonding techniques.
Precise dimensional control for high-density fillers.	Custom Laser Cutting and Polishing: We can prepare and polish SCD plates (Ra < 1 nm) and inch-size PCD (Ra < 5 nm) for subsequent precise crushing or dicing into uniformly sized particles for high-performance fillers.	Ensuring tight tolerance control on particle size distribution for optimal packing density (70 wt%) and thermal percolation in polymer matrices.

Engineering Support

6CCVD’s in-house team of PhD material scientists provides consultative support for projects focused on thermal management, high-power electronics, and next-generation composite fabrication. We assist engineers in selecting the optimal diamond morphology (SCD vs. PCD) and purity grade to maximize intrinsic thermal conductivity for demanding [Thermal Interface Material (TIM)] projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

In this work, we developed a single-step process to cast epoxy composites having a high thermal conductivity but a low electric conductivity.

Tech Support

Original Source

DOI: https://doi.org/10.1039/c7ra07272d