conductive polymeric nanocomposites Dr. Mohammad Arjmand Polymer Processing Group (PPG) Dept. of Chemical & Petroleum Engineering University of Calgary, Calgary, Alberta, Canada

calgary location

city of calgary Metropolitan Population: 1.2 Million 80 km East of the Front Range of Rockey Mountains Calgary’s Economy is Tied to Oil Industry (Oilsand)

university of calgary Public Research University Founded in 1966 Composed of 14 Faculties and 85 Research Institute Centers 25000 Undergraduate and 6000 Graduate Students Top-ranked University in Canada, the Second Best Post-Secondary Institution in North America, and the Ninth Best in the World, among Universities Established After 1964

polymer processing group Directed by Prof. Sundararaj Areas of Expertise: Nanomaterial Synthesis (Carbon Nanotube, Metallic Nanowire - Graphene – Graphene Nanoribbon - Nanocaly) Nanofiller/Polymer Nanocomposite Development and Characterization, i.e. Electrical, Dielectric, Electromagnetic Interference Shielding, Mechanical, Thermal, Rheological, optical, etc.

facilities in ppg (cont’d) Chemical Vapor Deposition Setup (Carbon Nanotube Synthesis) Nanowire Synthesis Setup Melt Mixing Equipment at Different Scales: Alberta Polymer Asymteric Miniature Mixer (2 cm3), Haake Mixer Setup (70 cm3), and Coperion Pilot Scale Twin-Screw Extruder Injection Molding and Compression Molding Setups TGA and DSC for Thermal Analysis Electro-spinning Setup

facilities in ppg Electromagnetic Interference Shielding Setup and Broad Range of Resistivity Meters and Impedance Spectrometers State-of-the-Art Rheometer, Confocal Microscope and Optical Microscope Dilatometer (Thermal Expansion) Tensile Tester Raman Spectrometer Spin Coater Cryo-Ultramicrotome Setup

what is a polymer composite?! Composite is a multi-component material comprising different phases, in which one of the phases is continuous. Polymer composite is a type of composite in which one of the phases is polymer. Enhanced Properties: Electrical Mechanical Thermal Optical Tribological Rheological http://pslc.ws/macrog/kidsmac/composit.htm

Microcomposite versus Nanocomposite Microfiller 103 nm Nanofiller 103 nm 〜 1 nm 1 vol.% of Filler in 1 m3 Polymer Matrix Surface Area = 60,000 m2 Surface Area = 20,000,000 m2

conductive filler/polymer composites (CPCs) Light weight Low cost Easy processability Presenting wide range of electrical conductivity

multi-walled carbon nanotube (MWCNT): an outstanding filler for CPCs http://www.turbosquid.com sp2 hybrid High Electrical Conductivity Outstanding Thermal Stability

Semi-Conductive Insulative Conductive Quartz Glass Silicon Copper Conductive Filler/Polymer Composites Semi-Conductive Insulative Conductive S/m 10-18 10-12 10-7 10+2 10+8 Quartz Glass Silicon Copper www.bccresearch.com

ELECTRICAL CONDUCTIVITY OF CPCs The percolation curve of MWCNT/polycarbonate composite.1 1 1 Arjmand M, Mahmoodi M, Gelves GA, Park S, Sundararaj U, Carbon, 49, 3430 (2011).

Electromagnetic Interference (EMI) Shielding Mechanisms Incident Power PI EMI Shielding Mechanisms: 1- Reflection 2- Absorption 3- Multiple-Reflections PI-R Reflected Power PR Transmitted Power PT SE = 10 · log (PI/PT) Expressed in dB

WHAT MAKES A CPC UNIQUE FOR CHARGE STORAGE? Nano-Capacitor: Conductive Filler as Nanoelectrode and Polymer Matrix as Nanodielectric

WHAT MAKES CPC DIFFERENT FOR USE AS CHARGE STORAGE MATERIAL? The electric dipole has a magnitude equals to the strength of each charge times the separation between charges. Interfacial Polarization + + + + - + + + + + Electronic Polarization

Improving conductive network Enhanced EMI Shielding Deteriorating conductive network Improved Dielectric Properties Mahmoodi M, Arjmand M, Sundararaj U, Park S. Carbon 2012; 50(4):1455-64.

CONCEPTUALIZATION OF EFFECTS OF ALIGNMENT ON EMI SE + + - + + + + - + +

Desired morphologies to improve emi shielding or dielectric properties of mwcnt/polymer composites (ii) (iii) (iv) (i) Alignment (ii) Improving Dispersion (iii) Incorporation of Secondary (Insulative) Filler (iv) Using Copper Nanowire Instead of MWCNTs

Hierarchy of developing conductive filler/polymer composites

Chemical Vapor Deposition (CVD) Setup

marjmand@ucalgary.ca arjmand64@yahoo.com

DIELECTRIC RESPONSE TO APPLIED ELECTRIC FIELD Interfacial Log (ε′) X-Band (8.2-12.4 GHz) 3 8 12 15 Log (Frequency (Hz))

Doping of Carbon Nanotubes: Why Nitrogen and Boron?

Different Types of Nitrogen Bonding in Graphitic Structures Wei DC, Liu YQ, Wang Y, Zhang HL, Huang LP, Yu G. Nano Lett 2009;9(5):1752-8.

Chemical Vapor Deposition (CVD) Setup

Nitrogen-doped (N-CNT) Synthesis Procedure Incipient wetness impregnation of catalyst precursors (Metal Nitrate and Sulfate Components) onto Alumina Support Drying (25ºC) - Calcination with air at 350ºC – Reduction with Hydrogen at 400ºC Synthesis at 750ºC for 2h – Precursor Gases (Ethane and Ammonia) - Carrier Gas (Hydrogen)

Transmission Electron Microscopy Open Channel Bamboo-Shaped Bamboo-Shaped

N-CNT Growth Mechanism Reyes-Reyes M, Grobert N, Kamalakaran R, Seeger T, Golberg D, Ruhle M, et al.. Chem Phys Lett 2004;396(1-3):167-73.

Parameters Affecting Electrical Properties of N-CNT/Polymer Nanocomposite Synthesis Yield (TGA) Length and Diameter (TEM) Crystallinity (Raman Spectroscopy) Metallicity (Raman Spectroscopy and STS) Nitrogen Content and Bonding Type (XPS) CNT Dispersion in Nanocomposite (OM+SEM/TEM)

Thermogravimetric Analysis

Length and Diameter

Nitrogen Content and Nitrogen Bonding Type

Percolation Curve

Electromagnetic Interference Shielding

Co > Fe > Ni Conclusions N-CNTs grown over different catalysts showed the following order of electrical properties from high to low: Co > Fe > Ni Higher electrical properties of (N-CNT)Co was attributed to a combination of high synthesis yield, high aspect ratio, high crystallinity, high metallicity, low nitrogen content and better microdispersion.

Conceptualization of Ohmic Loss and Polarization Loss + + - + +

Shieldings by Reflection and Absorption

BACK-UP SLIDES

Dielectric Properties

Polarization Mechanisms Over the X-Band (8.2-12.4 GHz) Interfacial × Dipolar (PVDF Matrix) × CNT Polarization Yes Electronic Polarization Yes

EXPERIMENTAL (CONT’D) Injection Molding BOY 12A Polystyrene Masterbatch 20 wt% (MB2020-00) Blending with Twin-Screw Extruder “Coperion ZSK” Pure Polystyrene (Styron® 610) Compression Molding

Experimental Injection Molding Our previous study showed that the melt temperature had the greatest impact on MWCNT alignment followed by the injection velocity, while the impacts of mold temperature and injection/holding pressure were insignificant.1 Levels (set points) of the processing parameters used in the injection molding experiments (EXPs). The processing parameters are mold temperature (C1), melt temperature (C2), injection/holding pressure (C3) and injection velocity (C4). EXP # C1 (°C) C2 (°C) C3 (bar) C4 (mm.s-1) 1 60 215 100 240 2 3 24 Parameter Value (mm) a 22.86 b 10.16 c, d 1 e 2 f 10 1Mahmoodi M, Arjmand M, Sundararaj U, Park S. Carbon 2012; 50(4):1455-64.

Illustration of the effect of nanotube alignment on the appearance of micrograph of mwcnt-aligned samples Flow Direction Perpendicular to the flow direction Parallel to the flow direction Adapted from Pötschke et al. Eur. Polym. J. 2004;40(1):137-148.

Raman spectroscopy ratios parallel/perpendicular Two significant characteristics in the Raman spectra of the MWCNT/polymer composites are the D band (disorder band), and the G band (graphite band). The Dװ/D ┴and Gװ/G ┴ parallel/perpendicular to the flow direction were used to determine the degree of MWCNT alignment. Raman spectroscopy ratios parallel/perpendicular ┴/DװD ┴/GװG Compression Molding 1.01 EXP #1 1.66 1.51 EXP #2 1.53 1.44 EXP #3 1.35 1.27 The order of the Raman intensity ratios, and consequently MWCNT alignment, from the highest to the lowest is EXP #1 > EXP #2 > EXP #3 > compression molded samples.

Effects of mwcnt alignment on dc conductivity and emi se The order of electrical conductivity and EMI SE from the highest to the lowest is compression molded samples > EXP #3 > EXP #2 > EXP #1. EMI shielding does not require filler connectivity; however, it increases with filler connectivity.

Effects of MWCNT alignment on real permittivity and imaginary permittivity The order of real permittivity and imaginary permittivity from the highest to the lowest is compression molded samples > EXP #3 > EXP #2 > EXP #1.

HIERARCHY OF RANDOM DISTRIBUTION OF MWCNTS AND HIGHER EMI SE Greater Probability of MWCNT Contacts Greater Electrons’ Mean Free Path Higher Imaginary Permittivity and Ohmic loss Higher EMI SE Higher Applied Electric Field Between MWCNTs Higher Real Permittivity and Polarization loss

Conclusions The EMI shielding properties of the compression molded samples of MWCNT/PS composites were superior to those of the injection molded samples. Higher EMI SE in the compression molded samples was related to higher electrical conductivity, real permittivity and imaginary permittivity. Achieving random distribution of MWCNTs is critical in designing the molds to produce highly conductive injection molded composites.

EMBEDDED CAPACITOR In a typical microelectronic product, around 80% of the electronic components are passive components, such as capacitors, which take up more than 40% of the printed circuit board (PCB) surface area.1 2 1J. X. Lu, K. S. Moon, J. W. Xu, and C. P. Wong, J. Mater. Chem. 16 (16), 1543 (2006). 2www.murata.com

CHRONOLOGICAL DEVELOPMENT OF CAPACITORS Conventional Capacitors like Ceramic Capacitors High-k Ceramic Powder / Polymer Capacitors Conductive Filler / Polymer Capacitors (CPCs)

STRATEGIES TO AVOID SHARP INSULATOR – CONDUCTOR TRANSITION Covering the Surface of Conductive Filler with an Insulative Layer Introducing Secondary Particle as Insulating Barrier

The following slides present the results for different processing conditions of injection molding machine.

EXPERIMENTAL (CONT’D) Materials Masterbatch of multi-walled carbon nanotube (MWCNT) in Polystyrene, Hyperion (MB2020-00) Neat Polystyrene (PS), Americas Styrenics LLC (Styron® 610) Composite Preparation Diluting the masterbatch with the neat PS using a Coperion ZSK co-rotating intermeshing twin-screw extruder with a residence time, melt temperature and extruder speed of 2 min, 200 °C and 150 rpm, respectively Composite Molding Compression Molding: Carver Plate Press: 210 oC, 38 MPa, 10 min

EFFECTS OF MWCNT ALIGNMENT ON SHIELDINGS BY REFLECTION AND ABSORPTION

MWCNT ALIGNMENT & DIELECTRIC PROPERTIES

BASIC PREREQUISITES FOR CAPACITORS High Dielectric Constant (Real Permittivity) Low Leakage Current (Imaginary Permittivity) Process Compatibility with printed circuit board

CHALLENGES IN MANIPULATING CPCS AS CHARGE STORAGE MATERIALS According to the percolation theory, a high real permittivity with a low leakage current is achievable at filler loadings below and close to percolation threshold region.1 The insulator–conductor transition, which occurs at percolation threshold region, precludes CPCs from being used at filler loadings above percolation threshold. There is a typical narrow insulator-conductor transition window to regulate dielectric properties. This leads to challenges in manipulating CPCs as charge storage materials. 1Dang ZM, Yao SH, Yuan JK, and Bai JB. J Phys Chem C 2010; 114: 13204-9.

EFFECT OF ALIGNMENT ON INSULATOR – CONDUCTOR TRANSITION WINDOW 0.7 – 2.0 wt% 5.0 – 8.5 wt% 1 Arjmand M, Mahmoodi M, Park S, Sundararaj U, Compos Sci Tech, 78, 24 (2013).

Effects of alignment on real permittivity and imaginary permittivity

EFFECTS OF ALIGNMENT ON DISSIPATION FACTOR

MORPHOLOGICAL ANALYSIS Injection Molding Compression Molding

CONDUCTIVE FILLER ALIGNMENT: A NOVEL APPROACH TO IMPROVE DIELECTRIC PROPERTIES The Inverse Relationship Between MWCNT Alignment and Electrical Conductivity1 The Direct Relationship Between Electrical Conductivity and Imaginary Permittivity Compression Molding Injection Molding 1 Arjmand M, Mahmoodi M, Park S, Sundararaj U, Compos Sci Tech, 78, 24 (2013).

CHARGE STORAGE The electric dipole has a magnitude equals to the strength of each charge times the separation between charges. Interfacial Polarization + + + + - + + + + + Electronic Polarization

Design of Experiments (Injection Molding Process) Factors c1 c2 c3 c4 1 - 2 + 3 4 5 6 7 8 9 10 11 12 13 14 15 16 c1: Mold Temperature c2 : Melt Temperature c3 : Injection/Holding Pressure c4 : Injection Velocity Level Factors c1 (°C) c2 (°C) c3 (bar) c4 (mm/sec) + 60 240 100 - 25 215 24 Parameter Value (mm) a 22.86 b 10.16 c, d 1 e 2 f 10

(I) Design of Experiments Balancing the cavities based on same filling time strategy Full factorial design of experiments Exp. # Factors c1 c2 c3 c4 1 - 2 + 3 4 5 6 7 8 9 10 11 12 13 14 15 16 c1: Mold Temperature c2 : Melt Temperature c3 : Injection/holding Pressure c4 : Injection Velocity Cavity 2 Fan Gate Cavity 1 Edge Gate Cavity 3 Level Factors c1 (°C) c2 (°C) c3 (bar) c4 (mm/sec) + 60 240 100 - 25 215 24

Experimental design (5.0wt% MWCNT/PS Composites)

What Does Make CPC Different For Use As Charge Storage Material What Does Make CPC Different For Use As Charge Storage Material? (Cont’d) The electric dipole has a magnitude equals to the strength of each charge times the separation between charges. Interfacial Polarization + + + + - + + + + + Electronic Polarization

Impedance Spectroscopy to recognize Conductive Materials Undoped CNT/PVDF Nanocomposites N-CNT/PVDF Nanocomposites

What Makes Doping Important for Electronic Properties? Isolator-Metal. Available from: http://commons.wikimedia.org/wiki/File:Isolator-metal.svg http://www.physics.udel.edu/~watson/scen103/98w/clas0128b.html

N-CNT Growth Mechanism Bamboo-Shaped Fe Catalyst Open-Channel Co Catalysts van Dommele S, Romero-Izquirdo A, Brydson R, de Jong KP, Bitter JH. Carbon 2008;46(1):138-48. Hofmann S, Sharma R, Ducati C, Du G, Mattevi C, Cepek C, et al. Nano Lett 2007;7(3):602-8.