Majid Haghgoo

Polydispersity is an essential factor in characterizing suspensions, specifically in industrial processes. In the present work, we report the viscosity of non-colloidal polydisperse glass suspensions for the first time and study the predictability of log-transformed quadratic viscosity equations over a wide range of blending ratios at a constant total volume fraction of solid particles. The viscosity and viscoelasticity measurement of multimodal suspensions was carried out by mixing three monomodally distributed solid particle suspensions with a relatively narrow size distribution to prepare bidisperse and tridisperse suspensions. The results showed a good agreement between experimental and predicted viscosity data for multimodal suspensions, making the generalized model a good alternative to describe the viscosity of polydisperse mixtures. The diameter ratio of large-to-small particles and the volume fraction of small particles in bidisperse systems strongly affected the viscoelastic behavior of multimodal suspensions. In addition, the dynamic rheology measurement showed that the storage modulus was independent of frequency, while a linear frequency dependence of loss modulus was observed for multimodal suspensions. In the case of polydisperse suspensions, this yield stress and dimensionless elastic modulus increased by declining the particle size ratio and increasing the volume fraction of small particles in bidisperse subsystems.

Thermal and mechanical properties of polyacrylonitrile (PAN) aerogel nanocomposites containing multi-walled carbon nanotube (MWCNT) prepared by using thermally induced phase separation (TIPS) method were evaluated and presented in this report. Subsequent drying and pyrolysis resulted in free-standing monolithic carbon aerogel nanocomposites with uniform dispersions of carbon nanotubes (CNTs). Significant improvements were achieved in the mechanical and thermal properties of the PAN aerogels by incorporating carboxylated CNTs. For example, the compressive modulus of the PAN aerogels extends by a factor of 16 with the introduction of 25 wt.% of the CNTs. In addition, the CNTs improve the thermal conductivity of the aerogels, e.g., five orders of magnitude enhancement in thermal conductivity with 25 wt.% nanotubes loading were observed.

Here, we present the synthesis and characterization of low-density multi-walled carbon nanotube (MWCNT)/carbon (CA) aerogel by creating a three-dimensional assembly of carbon nanotubes (CNTs) in polyacrylonitrile (PAN)/dimethyl formamide (DMF) solution to create a stable gel, followed by a CO₂ supercritical drying. Aerogels with varying nanotube loading (0–25 wt%) and density (50–500 mg cm⁻³) were fabricated and characterized by optical microscopy, electron microscopy, nitrogen sorption and electrical conductivity analysis. Physical properties of the MWCNT/CA composites were highly dependent upon nanotube loading. The data indicate that the shrinkage value decreases gradually during drying and pyrolysis process when MWCNT content increases in formulations. Surface area as high as 735 m² g⁻¹ was achieved for MWCNT/PAN aerogel with carbon nanotube loading higher than 20 wt%.