Exfol iati on and Uti l izati on of

Hexagonal Boron Nitride

a t

By : Anton and Diana

Table of Contents

Introduction

Background • Methods• Sonication Factors• Result Measurement Techniques• Thermal Management

Research and Future Work

Summary

Exfoliation and Utilization of h-BN

Multifunctional Materials | Micro-and-Nanostructuring Laboratory Slide 2

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Introduction

Introduction

- As, 3D chip architecture increases in complexity there is increase in heat flux

- Current polymer encapsulation does not have sufficient Keff

Exfoliation and Utilization of h-BN

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Introduction

Hexagonal boron nitride (h-BN) : • Analog to graphene• Large band gap of ~

5.5eV• High theoretical thermal

conductivity• Difficult to exfoliate

Exfoliation and Utilization of h-BN

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IntroductionExfoliation and Utilization of h-BN

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• Exfoliation Specifically Focused On Liquid Phase Sonication

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Background

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Background- Methods -

MethodsExfoliation and Utilization of h-BN

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Mechanical Cleavage

Ball Milling

Chemical Functionalization

Liquid Phase Sonication

MethodsExfoliation and Utilization of h-BN

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Mechanical Cleavage

Ball Milling

Chemical Functionalization

Liquid Phase Sonication

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Background- Sonication Factors -

Factors

Solvents

Sonication settings

Size of Solutes

Exfoliation and Utilization of h-BN

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Factors

Solvents

Sonication settings

Size of Solutes

Exfoliation and Utilization of h-BN

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Factors - SolventsExfoliation and Utilization of h-BN

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Effective Solvent

Low enthalpy of

system

Low energy for

sonication

Matching surface energy

Inexpensive

Eco friendly

No foreign materials produced

Water as solvent- H-BN normally

hydrophobic in water- Boron- nitrogen bonds

near defect sites make exfoliation easier

- Boron edges formed hydroxyl groups under hydrolysis

Exfoliation and Utilization of h-BN

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Solvent Promoting Chemical Functionalization - Polymer—poly (sodium 4-styrenesulfonate) (PSS)

used as a dispersant and functionalization agent- Improved the separation of layers from h-BN

structure

Multifunctional Materials | Micro-and-Nanostructuring Laboratory Slide 16

Exfoliation and Utilization of h-BN

Isopropyl Alcohol(IPA) solution as solvent

- IPA has matching surface energy to h-BN(44- 65 mJ/m^2)

- Ammonia water also has matching surface energy of ~ 57 mJ/m^2

- Create solution of IPA: ammonia solution of ~3:2- Boron atoms temporarily act like lewis acids and are

susceptible to attack from amines

Exfoliation and Utilization of h-BN

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Factors

Solvents

Sonication settings

Size of Solutes

Exfoliation and Utilization of h-BN

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Multifunctional Materials | Micro-and-Nanostructuring Laboratory

Sonication Settings

Exfoliation and Utilization of h-BN

Slide 19

• Uses sound wave with a preset wavelength to agitate particles in a solution

Factors

Solvents

Sonication settings

Size of Solutes

Exfoliation and Utilization of h-BN

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Size of Solutes

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Sonication Sound Wavelength

Sizes of pristine h-BN≈

→ Higher Exfoliation yield can be achieved

Exfoliation and Utilization of h-BN

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Background- Result Measurement -

Result ManagementExfoliation and Utilization of h-BN

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Infrared Thermal Imaging

Optical Absorption

Raman Spectroscopy X-ray diffraction

Infrared Thermal Imaging

- Model developed by Georgia Institute of Technology is commonly used

- Measures the thermal Resistance & Thermal Conductivity of the sample

Exfoliation and Utilization of h-BN

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R=𝑇h𝑜𝑡−𝑇 𝑐𝑜𝑙𝑑

𝑄k=

𝐿𝑅

=𝑄𝐿

𝑇 h𝑜𝑡−𝑇 𝑐𝑜𝑙𝑑

Optical Absorption

• Band Gap: the bulk h-BN < an isolated h-BNNS• Exfoliation ↑ the absorptivity of the dispersion

Multifunctional Materials | Micro-and-Nanostructuring Laboratory Slide 25

Exfoliation and Utilization of h-BN

Raman Spectroscopy

• Helps identify the number of layers of h-BN

• Mono-layers: slightly upward

• Bi-layers: downward in peak position

Multifunctional Materials | Micro-and-Nanostructuring Laboratory Slide 26

Exfoliation and Utilization of h-BN

X-ray Diffraction (XRD)

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Exfoliation and Utilization of h-BN

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Background- Thermal Management -

Thermal Management

- Ceramics only use the vibration of phonons to transfer heat

- Issue with using ceramic fillers is you need high filler loading (>50 wt%)

- H-BN nanosheets provide a way to increase thermal conductivity substantially

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Exfoliation and Utilization of h-BN

Thermal Management

Thermal Enhancement factor(TEF) of a h-BN/ epoxy composite was observed using:

(kcomposite - kepoxy )/ kepoxy * 100% , k refers to the thermal

conductivity

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Exfoliation and Utilization of h-BN

Thermal Management

- With increase in filler loading, viscosity increases making it more difficult to process

- Coefficient of thermal expansion decreases and glass transition temperature slightly decreases

Multifunctional Materials | Micro-and-Nanostructuring Laboratory Slide 31

Exfoliation and Utilization of h-BN

Thermal Management - Theoretical calculations

show thermal conductivity should increase as amount of layers decreases

- But the experimental data showed this was not the case

- Thickness of sheets proved to be more important as when the sheets are thinner they are less thermally conductiveMultifunctional Materials | Micro-and-Nanostructuring Laboratory Slide 32

Exfoliation and Utilization of h-BN

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Research and Future Work

Research and Future Work

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Exfoliation and Utilization of h-BN

Research and Future Work

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Exfoliation and Utilization of h-BN

Research and Future Work

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Exfoliation and Utilization of h-BN

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Summary

Questions/Comments?

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Exfoliation and Utilization of h-BN