Growth of Sub-5 nm Metal Nanoclusters in Polymer Melt Aerosol Droplets

Transcription

1 Supporting Information Growth of Sub-5 nm Metal Nanoclusters in Polymer Melt Aerosol Droplets Yong Yang, Michelangelo Romano, Guangjie Feng, Xizheng Wang, Tao Wu, Scott Holdren and Michael R. Zachariah * University of Maryland, College Park, Maryland 20742, United States *Corresponding author. mrz@umd.edu

2 1. Stability of of PVP molecules against heat treatment Figure S1 TGA of PVP polymer (MW. 8000g/mol) with a heating rate of 10C/min in Ar gas

3 Figure S2 FTIR spectra of PVP polymers with different molecular weights before and after spray pyrolysis at 600 C with 5% H 2 and 95%N 2 as carrier gas Figure S3 SEM images of PVP polymers with different molecular weights after spray pyrolysis: (a) 8000g/mol; (b)58000g/mol;(c) g/mol

4 2. Component analysis of metal polymer nanocomposites Figure S4 XRD Patterns of metal (Ni, Co, Cu) polymer nanocomposites Table S1: Volume fraction of metal, areal concentration and average diameter of metal in polymer. Nanocomposites Mass fraction between metal and PVP matrix Volume fraction of metal in PVP matrix Areal concentration (#/nm 2 ) Number average diameter (nm) Ni PVP8k 16.8% 2.7% Co PVP58k 16.8% 2.7% Cu PVP8k 7.9% 1.0% Scanning TEM, EDS mapping and line scanning characterization for Ni-PVP-8k nanocomposite. STEM images shown in Figure S5 (a-c) indicates that ultrasmall Ni nanoparticles are uniformly distributed in the polymer matrix. The line scanning profile shown in Figure S5 (d) reveals these Ni nanoclusters has a diameter of ~5nm. EDS mappings in Figure S (e-f) provide elemental distribuitons of Ni, C, O, and N elements, respectively. C, O and N belong to the PVP matrix. The weaker signal intensities of O and N elements compared to C elements is due to the lower molar ratio between O/N and C (1:6) in PVP molecules.

5 Figure S5. (a-c) STEM images of Ni PVP8k nanocomposite prepared at 600 C from a precursor with a 1 to 1 metal salt to polymer ratio; (d) Line scanning profile of two nickel nanoparticles labeled with two red arrows in image (c); (e-f) EDS mapping of Ni, C, O and N elements, respectively. 4. Property data used for the characteristic time analysis Viscosity of polymer melt Masuko and Magill model is llllll ηη = AA exp BB TT gg TT 1 ηη gg TT They have shown that A and B are constants which are independent of materials. The average values for A and B in this model are AA = ± 1.04 BB = 6.47 ± 1.13

6 Figure S6. Viscosity of PVP polymer (MW. 8000g/mol) as a function of temperature. (Values of empirical constant A and B are 6.7 and 7.6 respectively in order to achieve a good fit.) Figure S7. Diffusion coefficient of Ni nanoclusters as a function of diameter in polymer melt at 600 ºC Melting point of Ni nanoparticle, TT mmmm dd pp The melting point of Ni nanoparticles is size-dependent, which was approximated using the following empirical equation 1 : 2 ρρ ll TT mmmm dd pp = TT mm 1 4 LLρρ pp dd pp (σσ ss σσ ll ρρ pp 3 ) (S.1) Here, T m is the bulk melting point (1728 K), L is the latent heat of melting ( J/kg), σ s and σ l are the surface tension (J/m 2 ), σ s = 2.47 N/m, σ l =1.8 N/m (surface tension of molten metals at their melting points 2 ), ρ p and ρ l are the respective solid and liquid phase densities (kg/m 3 ), ρ p = 8900 kg/mm 3 (assume it is temperature independent), ρ l = 7800 kg/mm 3 (data obtained from 3, assume it is temperature independent.) Figure S8 shows how the melting point of Ni nanoparticle

7 changes with its diameter. Our calculation in Figure S8 shows that the nanoparticle with a diameter of less than 1.5 nm is in liquid phase at the temperature of 600 ºC. Figure S8. Variation of melting point as a function of Ni nanoparticle diameter. Viscosity of Ni nanoparticle, μμ μμ is the viscosity of Ni nanoparticle, which is given as 4 : μμ = MM TT 1/2 LL mmmm(dd pp ) exp ( RRTTpp ) LL vv mm eeeeee RRTTmmmm(ddpp) (S.2) Where LL is the latent heat of melting (J/mol), J/mol (which is equal to J/kg), σσ ll are the surface tension (J/m 2 ), M is the molar weight, kkkk/mmmmmm, R is the gas constant, J/mol/K, vv mm is the molar volume, mm 3 /mmmmmm. Effective atomic diffusion coefficient, DD eeeeee Assuming volume diffusion is dominant, DD eeeeee is predicted by the bulk self-diffusion coefficient of Ni, DD vv, which is given by 5 : DD vv = exp ( 278kkkk/mmmmmm )mm 2 ss 1 RRRR DD vv is equal to DD vv = mm 2 ss 1 at a temperature of 600 ºC. (S.3) References (1) Buffat, P.; Borel, J. P. Size effect on the melting temperature of gold particles. Physical review A 1976, 13, (2) Keene, B. Review of data for the surface tension of pure metals. International Materials Reviews 1993, 38,

8 (3) Schmon, A.; Aziz, K.; Pottlacher, G. Density Determination of Liquid Copper and Liquid Nickel by Means of Fast Resistive Pulse Heating and Electromagnetic Levitation. Metallurgical and Materials Transactions A 2015, 46, (4) Mukherjee, D.; Sonwane, C.; Zachariah, M. Kinetic Monte Carlo simulation of the effect of coalescence energy release on the size and shape evolution of nanoparticles grown as an aerosol. The Journal of chemical physics 2003, 119, (5) Prokoshkina, D.; Esin, V.; Wilde, G.; Divinski, S. Grain boundary width, energy and selfdiffusion in nickel: effect of material purity. Acta Materialia 2013, 61,