Performance Study of Diamond Powder-Filled Sodium Silicate-Based Thermal Conductive Adhesives

At a Glance

Metadata	Details
Publication Date	2023-05-24
Journal	Materials
Authors	Ming Chen, Z. C. Zhou, Xu Wang, Yangchun Zhao, Yongmin Zhou
Institutions	Nanjing Tech University
Citations	2
Analysis	Full AI Review Included

Performance Study of Diamond Powder-Filled Sodium Silicate-Based Thermal Conductive Adhesives: 6CCVD Technical Analysis

This document analyzes the research findings regarding diamond powder-filled inorganic thermal conductive adhesives and outlines how 6CCVD’s advanced MPCVD diamond materials and customization capabilities can support and extend this research for high-performance thermal management applications.

Executive Summary

Application Focus: Addresses the critical heat dissipation bottleneck in miniaturized, highly integrated electronic devices (e.g., computers, mobile phones, LED lighting, automotive modules).
Novel Material System: Developed an innovative inorganic thermal conductive adhesive using a sodium silicate matrix and surface-modified diamond powder filler.
Surface Engineering: Diamond powder (1 µm) was successfully modified using 3-aminopropyltriethoxysilane coupling agent to enhance dispersion and interfacial bonding within the matrix.
Peak Thermal Performance: Achieved a maximum thermal conductivity of 10.32 W/(m·K) at a 50% diamond mass fraction.
Optimal Mechanical Strength: Demonstrated superior adhesion, reaching a maximum tensile shear strength of 1.83 MPa at a 60% diamond mass fraction.
Balanced Performance: The optimal filler range of 50-60% diamond mass fraction provides a robust balance between high thermal conductivity and strong adhesive performance, overcoming limitations associated with traditional organic thermal interface materials (TIMs).

Technical Specifications

The following hard data points were extracted from the experimental results, highlighting the performance metrics of the optimized thermal conductive adhesive system.

Parameter	Value	Unit	Context
Peak Thermal Conductivity (TC)	10.32	W/(m·K)	Achieved at 50% diamond mass fraction (dry weight).
Optimal TC Filler Content	50	%	Diamond powder mass fraction for maximum TC.
Peak Tensile Shear Strength	1.83	MPa	Achieved at 60% diamond mass fraction (dry weight).
Optimal Adhesion Filler Content	60	%	Diamond powder mass fraction for maximum adhesion.
Diamond Powder Particle Size	1	µm	Filler material specification.
Sodium Silicate Modulus	3.3	N/A	Matrix material specification.
Sodium Silicate Mass Fraction	34	%	Solute mass fraction in the solution.
Silane Coupling Agent	3-aminopropyltriethoxysilane	N/A	Used for diamond surface modification.
Modification Reaction Temp.	70	°C	Condensation reflux reaction temperature.
Adhesive Curing Temp.	50	°C	Low-temperature curing process for the final adhesive.

Key Methodologies

The preparation of the high-performance thermal conductive adhesive involved precise surface modification and controlled mixing processes:

Diamond Surface Modification:
- 1 g of 1 µm diamond powder was dispersed in 30 mL of anhydrous ethanol.
- The silane coupling agent (3-aminopropyltriethoxysilane) was mixed with water at a 1:2 ratio (solid-liquid ratio of 5:1 mL/g relative to diamond powder).
- The mixture underwent a condensation reflux reaction in a magnetic stirrer at 70 °C for 3 hours.
- The modified powder was washed, filtered, and dried in a vacuum oven at 70 °C.
Adhesive Colloid Preparation:
- Sodium silicate solution (34% mass fraction, modulus 3.3) was used as the matrix.
- Modified diamond powder was added at varying mass fractions (10% to 80% of overall dry weight).
- The colloid was magnetically stirred for 1 hour.
Specimen Curing and Preparation:
- The colloid was poured into a liquid paraffin-coated disc-shaped graphite mold (diameter Ø 20 mm, height 7 mm).
- Curing was performed in a drying oven at 50 °C for 1 hour.
- Cured samples were polished smoothly to a final thickness of 5 mm for thermal conductivity testing.
Characterization:
- SEM, EDS, and XRD were used to confirm surface modification, element distribution (C, B, O, Si, N), and phase purity.
- Tensile shear strength was measured using a universal testing machine (WY-10TB) at 20 mm/min stretching speed.
- Thermal conductivity was measured using a DM3615 thermal conductivity tester.

6CCVD Solutions & Capabilities

This research validates the use of high-purity diamond as a superior thermal filler for next-generation inorganic thermal interface materials (TIMs). 6CCVD is uniquely positioned to supply the foundational diamond materials and custom engineering required to scale and optimize this technology.

Applicable Materials

To replicate or extend this research into commercial applications, high-quality diamond material is essential.

Polycrystalline Diamond (PCD) Stock: 6CCVD provides high-purity PCD material suitable for processing into micron-sized powder fillers (like the 1 µm powder used in the study). Our PCD material ensures maximum intrinsic thermal conductivity, chemical inertness, and stability required for high-performance TIMs.
Single Crystal Diamond (SCD) Substrates: For applications requiring extreme heat spreading beneath the adhesive layer, 6CCVD offers high-quality SCD plates (up to 500 µm thick) with superior thermal conductivity (up to 2000 W/(m·K)).
Boron-Doped Diamond (BDD): If the application requires a conductive adhesive system (not insulation), 6CCVD can supply BDD material for conductive filler development.

Customization Potential

The study utilized specific sample dimensions and required precise surface preparation. 6CCVD’s in-house capabilities directly address these needs:

Research Requirement	6CCVD Customization Capability
Custom Filler Precursors	We supply SCD and PCD plates/wafers up to 125mm in diameter, ready for laser cutting or grinding into custom filler sizes or heat spreaders.
Precision Polishing	Our polishing services achieve surface roughness of Ra < 1nm (SCD) and Ra < 5nm (Inch-size PCD), critical for minimizing thermal boundary resistance (TBR) when bonding diamond components.
Advanced Interfacial Layers	While the paper used silane coupling, 6CCVD offers internal metalization services (Au, Pt, Pd, Ti, W, Cu) to create robust, low-resistance interfaces on diamond components for direct bonding or integration into complex thermal stacks.
Custom Substrate Thickness	We provide SCD and PCD materials in thicknesses ranging from 0.1 µm to 500 µm (wafers) and substrates up to 10mm thick, allowing engineers to design optimal heat paths.

Engineering Support

The development of high-performance inorganic TIMs for high-power density applications requires specialized knowledge in diamond material science.

Expert Consultation: 6CCVD’s in-house PhD engineering team can assist researchers and manufacturers in selecting the optimal diamond grade (SCD vs. PCD), particle size distribution, and surface preparation methods necessary to maximize thermal conductivity and adhesion for similar Thermal Interface Material (TIM) projects.
Global Supply Chain: We offer global shipping (DDU default, DDP available) to ensure rapid delivery of custom diamond materials worldwide, accelerating your R&D and production timelines.

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

View Original Abstract

With the development of miniaturized, highly integrated, and multifunctional electronic devices, the heat flow per unit area has increased dramatically, making heat dissipation a bottleneck in the development of the electronics industry. The purpose of this study is to develop a new inorganic thermal conductive adhesive to overcome the contradiction between the thermal conductivity and mechanical properties of organic thermal conductive adhesives. In this study, an inorganic matrix material, sodium silicate, was used, and diamond powder was modified to become a thermal conductive filler. The influence of the content of diamond powder on the thermal conductive adhesive properties was studied through systematic characterization and testing. In the experiment, diamond powder modified by 3-aminopropyltriethoxysilane coupling agent was selected as the thermal conductive filler and filled into a sodium silicate matrix with a mass fraction of 34% to prepare a series of inorganic thermal conductive adhesives. The thermal conductivity of the diamond powder and its content on the thermal conductivity of the adhesive were studied by testing the thermal conductivity and taking SEM photos. In addition, X-ray diffraction, infrared spectroscopy, and EDS testing were used to analyze the composition of the modified diamond powder surface. Through the study of diamond content, it was found that as the diamond content gradually increases, the adhesive performance of the thermal conductive adhesive first increases and then decreases. The best adhesive performance was achieved when the diamond mass fraction was 60%, with a tensile shear strength of 1.83 MPa. As the diamond content increased, the thermal conductivity of the thermal conductive adhesive first increased and then decreased. The best thermal conductivity was achieved when the diamond mass fraction was 50%, with a thermal conductivity coefficient of 10.32 W/(m·K). The best adhesive performance and thermal conductivity were achieved when the diamond mass fraction was between 50% and 60%. The inorganic thermal conductive adhesive system based on sodium silicate and diamond proposed in this study has outstanding comprehensive performance and is a promising new thermal conductive material that can replace organic thermal conductive adhesives. The results of this study provide new ideas and methods for the development of inorganic thermal conductive adhesives and are expected to promote the application and development of inorganic thermal conductive materials.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma16113937

References

2019 - Mechanically robust, electrically and thermally conductive graphene-based epoxy adhesives [Crossref]
2019 - Synergistic effect of polypyrrole and reduced graphene oxide on mechanical, electrical and thermal properties of epoxy adhesives [Crossref]
2020 - Thermal conductive epoxy adhesive composites filled with carbon-based particulate fillers: A comparative study [Crossref]
2006 - Evaluation and identification of electrical and thermal conduction mechanisms in carbon nanotube/epoxy composites [Crossref]
2012 - The rheological behavior and thermal conductivity of melt-compounded polycarbonate/vapor-grown carbon fibercomposites [Crossref]
2016 - Thermal Properties of Epoxy Composites with Silicon Carbide and/or Graphite [Crossref]