Influence of filler morphology on percolation threshold of isotropical conductive adhesives (ICA)

Different aspect ratio silver nano-structured materials including nanocubes,nanorods and nanowires were prepared by micro-waved assisted glycol reduction method.Different characterization methods including SEM and XRD were processed on these nanomaterials.Isotropical conductive adhesives(ICA) were developed by using these Ag nanomaterials as conductive fillers.It was found that the conductivity and thermal conductivity percolation threshold of the ICA depended on the morphologies of the fillers,lower percolation threshold could be obtained by using higher aspect ratio filler.A modified percolation threshold theory was put forward to explain and simulate the experiment results,the simulated results could match the experiment results very well.

Shift in the percolation threshold of compressed composites—A 3D Monte Carlo simulation

The shift in the percolation threshold of compressed composites was studied by a 3D continuum percolation model. A Monte Carlo (MC) method was employed in the simulations. The percolation threshold was found to rise with the compression strain, which captures the basic trend in compression-induced conductivity variation from the experiments. Both fiber bending and texture formation contribute to the percolation threshold. The results suggest that fillers with a high aspect ratio are more desirable for sensor and electrical switch applications.

Extended law of corresponding states for percolation threshold of short-range attractive spheres

The percolation threshold(PT)for colloidal system refers to the point at which particles aggregate to form an infinite cluster that spans the suspension[1].It is widely assumed that the percolation transition should follow the concept of scaling,and recent numerical studies[2-5]have shown that the wrapping probability of percolation can be described by the universal scaling functions,which enables the estimation of PTs for different types of system.

The Threshold Percolation Volume Fraction of Vitreous Silica on the Thermal Expansion Behavior of Quartz

In this work, it is shown how the additions of vitreous silica of particle size ?C.

Effective thermal and electrical conductivity of graphite nanoplatelet composites

The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.

Novel capacitance-type humidity sensor based on multi-wall carbon nanotube/SiO_2 composite films

A novel capacitance-type relative humidity(RH) sensor based on multi-wall carbon nanotube/SiO(MWCNTs/SiO) composite film is reported.Details of the fabrication process,possible sensing mechanism and sensing characteristics,such as linearity and sensitivity,are described.The capacitance of the MWCNTs/SiOcomposite film shows typical concentration percolation behavior with increasing MWCNT loading.At loadings below the percolation threshold(1.842wt%),the sensor capacitance increases obviously with increasing MWCNTs. The water condensed in the MWCNTs/SiOlayer can lower the percolation threshold and increase the sensor capacitance.The sensor with MWCNT concentration of 1wt%has the best properties.The sensor has a humidity sensitivity of about 673 pF/%RH and a linearity correlation of 0.98428.The response time of the sensor to RH is about 40 s and the recovery time is about 2 s.

Fabrication of Flexible Transparent Conductive Films with Silver Nanowire by Vacuum Filtration and PET Mold Transfer

The flexible transparent conductive films （FrCFs） of silver nanowire-polyethylene terephthalate （AgNW- PET） were prepared by a facile method including vacuum filtration and mold transferring. The effect of silver nanowire weight density on the optical and electrical properties of films, as well as the electrical percolation was investigated. The obtained typical AgNW-PET film exhibited high figure of merit of 31.3 × 10^-3 Ω^-1 with low sheet resistance of 4.95 D sq^-1 and high transparency at 550 nm of 83.0% （excluding PET substrate）. The resulting FTCFs based on PET substrate with high transmittance and low sheet resistance have a great potential in the application of high-performance flexible electronics and photovoltaic devices.

Critical points in the formulation of pharmaceutical swellable controlled release dosage forms——Influence of particle size

Swellable matrix represents one of the most employed controlled release systems. These dosage forms provide slow release of drugs to reduce the fluctuation of drug concentration in plasma in order to improve the efficiency of treatment and/or to reduce adverse effects. The application of the concepts of statistical physics has allowed discovering the existence of critical points in the formulation of swellable matrices. These points, representing the volume fractions of the tablet components where the properties of the matrix diverge or change suddenly, provide important knowledge of how to rationalize the design of swellable matrices. The critical points are generally related to the percolation threshold of one of the components of the formulation, which corresponds to a geometrical phase transition of this component, passing from isolation to spanning the whole system. The last section of the paper is devoted to more recent findings concerning the influence of particle size of the components on the percolation threshold of the matrix forming polymer, and therefore on the release behaviour of the matrix. Knowledge of the excipient percolation threshold allows a more rational design of swellable matrices, according to the guidelines of the regulatory authorities concerning science-based formulation and quality by design.