Tuskegee-Cornell PREM A Research and Educational Partnership in Nanomaterials between Tuskegee University and Cornell University

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1 Tuskegee-Cornell PREM A Research and Educational Partnership in Nanomaterials between Tuskegee University and Cornell University Synthesis and Characterization of Polymeric Nanocomposites: Some Highlights Mahesh Hosur, Tamara Floyd Smith, Vijaya Rangari, Shaik Jeelani Tuskegee University, Tuskegee, AL Anil Netravali, Lynden Archer, Melissa Hines Cornell University, Ithaca, NY PREM-MRSEC PI s Joint Meeting 2011 Humaco, Puerto Rico March 9-11, 2011

2 TU-Cornell-PREM-Research Task1: Synthesis and Characterization of Cubic Cobalt Oxide Nanocomposite Fluids Understand the effect of particle volume fraction on nanocomposite fluid rheological properties A nanocomposite fluid is a suspension of nanoparticles Compare literature data on spheres to our cubes to gain insight into shape effects Tamara Floyd Smith (TU) and Lynden Archer (Cornell) Student/Postdoctoral Participants: Dwayne Vickers, Wanda Jones, Sabrina Lee and David Baah

3 Co 3 O 4 Nanocube Characterization Particle posses narrow size distribution Images taken at 165k magnification Cubic shape particles evident from micrograph Average particle size of 56nm ± 9 nm 100nm TEM Micrograph of purified Co 3 O 4 Nanocubes Feng et.al. proposed simple, general scheme for synthesizing Co 3 O 4 cubes with narrow size distribution Feng, J.; Zeng, H.; Chem. Mater. 2003, 15,

4 Low Volume Fraction Rheology

5 High Volume Fraction Rheology

6 Nanocomposite Fluid Theory Einstein Equation Modified Krieger- Dougherty Equation Krieger-Dougherty (KD) Equation Where η = suspension viscosity η r = relative viscosity η s =suspending medium viscosity [η] = intrinsic viscosity φ = particle volume fraction φ m = maximum particle volume fraction α = swelling factor

7 Experiment vs. Theory Einstein equation is followed at low volume fraction Modified KD is followed at moderate volume fraction KD is followed at high volume fraction Transition between modified KD and KD occurs for αφ~1.0. Einstein KD Modified KD

8 TU-Cornell-PREM-Research Task 2: Polyhedral Oligomeric Silsesquioxane (POSS) coated SiC nanoparticles and their polymer nanocomposites Objective: To investigate the structural, mechanical, thermal properties of nanofiller, SiC NPs modified or coated by three types of POSS: OctaIsobutyl (OI), EpoxyCychohexyl (EC) & GlycidylEthyl (GE) POSS by sonochemical synthesis method Vijaya K.Rangari, (TU), Hines and Archer (Cornell), Students: Rabby, James and Brittani Batts

9 XRD (X-ray Diffraction) Pattern: a c d b (a) designates that the nanomaterials was Moissanite-3C SiC (Matched with JCPDS ). (b) demonstrates that POSS OI is high crystalline material as it has sharp peaks at approximately 2θ=9 and following two figures (c) (c) & (d)) are the coated SiC by OI POSS which indicates the presence of both SiC and POSS OI nanomaterials. X-ray Diffractogram for (a). Neat SiC, (b). Neat OI POSS, (c). SiC: OI=1:1 and d. SiC: OI=1:2

10 TEM Analysis a b TEM image of SiC coated by OI POSS (1:1 ratio) c

11 Epoxy Nanocomposite Characterization: Differential Scanning Calorimetry (DSC) (a) (b) Figure: DSC graphs of: (a) room temperature cured & (b) Microwave cured SC-780 epoxy resin with different loading of SiC and POSS OI coated SiC Sample Name Glass Transition Temperature, o C Thermal cured Microwave cured Neat SC SC % SiC SC % SiC SC % SiC SC % OI coated SiC SC % OI coated SiC SC % OI coated SiC

12 Summary Flexural strength and modulus were found to be increased when cured at room temperature for both SiC & POSS OI coated SiC infusion by 9.5%-14.3% with 1% loading. Glass transition temperature (T g ) were enhanced by 7 C due to SiC infusion at 1% loading. Coefficient of thermal expansion (CTE) was decreased with nanoparticle infusion at higher loading. Using microwave irradiation technique, epoxy polymer can be cured in 30 minutes instead of 12 hrs. of room temperature curing with additional 6 hrs post curing. Maximum strain to failure from the flexural response increased by 25-40% for lower loading of SiC by microwave curing. 12

13 TU-Cornell-PREM-Research Task 3: Processing and Characterization of Epoxy Nanocomposites with Multi-Walled Carbon Nanotubes Faculty Participants: Mahesh Hosur, Mohammad Hossain, Yuanxin Zhou (currently in GE), Dr. Shaik Zainuddin Student Participants: Dr. Merlin Theodore (currently at UTC), Tamanna Rahman (currently at Georgia Tech), Okoro Chinedu (MS, ME), Rajib Barua (currently at McGill Univ.), Shifra Burton (BS, CE), Shamira Theodore (BS, CE) Cornell Participants: Dr. Anil Netravali, Dr. Kumar

14 Single Fiber Fracture Tests for determining Interfacial Shear Strength 200 μm 0% clay Interfacial debonding Fiber break Matrix crack Fragmentation and Debonding Under Polarized Microscope (500x resolution)

15 SFC Test Results HNT contents (%) Without Plasma Treatment (control) Number of sample Critical length (µm) Strength (MPa) Diameter (µm) IFSS (MPa) (4.55) (0.26) 6.10 (1.94) 30.3 (5.53) (19.8) (1.12) 5.93 (2.80) 35.6 (20.6) (5.03) (0.28) 5.98 (0.12) 35.1 (5.2) (10.2) (0.60) 5.97(4.65) 34.6 (14.3)

16 Matrix Modification Infusion of nanoparticles through sonication and magnetic stir mixing Nanoparticles used: Nanoclay, single and multi-walled carbon nanotubes (SWCNT, MWCNT), carbon nanofibers (CNF) Functionalization of MWCNT s Through oxidation, fluorination, amine functionalization

17 Dispersion Methods: Isolation/ combination Sonication 3 roll shear mixing Thinky mixer

18 Results- Rheology Sample Viscosity (cps) % change w.r.t. neat 1 N 380± NF 460± NH 2 -C 458± NH 2 -S 455± NF 495± NH 2 -C 495± NH 2 -S 492± NF 540± NH 2 -C 540± NH 2 -S 535± C-conventional, S-solvent, NH 2 -amino functional group, NF- Non functional

19 Dynamic Mechanical Analysis Nanocomposite Plateau Modulus (MPa) % difference Crosslink Density, (mol cm^-3 ) x 10^-3 Neat MWCNT -UNMOD % MWCNT -COOH % MWCNT -F % Increase factor MWCNT-NH %

20 Effect of CNT Contents on K IC The fracture toughness (K1) of materials was calculated from the peak load of each load-displacement curve, and was plotted as a function of the CNT weight fraction It shows that enhancement reaches a maximum for the fracture toughness at 0.3 wt%. At the higher contents, fracture toughness decreased with filler loading

21 Fracture Analysis Fracture surfaces from HSR test Plain surface Vivid ridges Cracking Cracking Neat Nanophased epoxy Schematic of crack propagation path

22 Observations Incorporation of functionalized MWCNTs into epoxy matrix improves the strength and modulus (flexure, tensile, compressive) of the neat composite due to enhancement in interactions DMA analysis show the effect on crosslink density resulting from enhancement in interfacial interactions between the matrix and the functionalized MWCNTs Electrical conductivity threshold is obtained at 0.2% CNT loading Fracture toughness was maximum at 0.3% loading of CNTs However, uniform dispersion still remains an issue Hence, we need to look at alternate methods of uniform dispersion as well as increase the % loading of CNTs