Abstract

Needle-like α-Fe₂O₃ particles with the length of 2 µm and the width of 250 nm were prepared by thermal decomposition of β-FeOOH and the electrochemical performances in the all-solid-state cells were examined. The cell using needle-like particles with acetylene black as a conductive additive showed the first discharge capacity of about 700 mAh g⁻¹ at the current density of 0.064 mA cm⁻². The lithium ion and electron conduction path of the electrode was improved by using vapor grown carbon fiber as a conductive additive. The needle-like α-Fe₂O₃ particles were compared with α-Fe₂O₃ spherical particles; the suitability for the active material of all-solid-state batteries was investigated.

Abstract

When a shock wave propagates over a dust layer composed of many small solid particles, lifted and dispersed particles form a dust cloud in the shock-induced flow. The dust cloud has a possibility of causing a propagating dust explosion in galleries of the coal mine and factories which treat flammable powder, so that the analysis and prediction of this phenomenon are very important to forestall the dangerous explosion. In this paper, two results of numerical simulations about the initial process of this phenomenon are introduced. The first result shows that a particle on a wall is lifted by the shock-induced flow, and a lift force on the particle changes with the clearance between the particle and the wall. The second result shows that many particles are lifted and dispersed in the shock-induced flow, and the upward velocities of lifted particles were given by particle-particle interactions rather than by fluid lift forces such as Saffman force and Magnus force. Furthermore, the computed dust cloud was almost same as observed in experiments.

Dispersing chemicals are often used to improve the properties of concrete. In the cement field these chemicals are known as superplasticizers. Basically, the superplasticizers can be divided in to two classes: mainly negatively charged ionic and mainly non-ionic. The backbones of both types of superplasticizers are hydrophobic aliphatic and/or aromatic chains. To function as superplasticizers, these chemicals have to attach themselves to the solid particles of cement pastes. Ionic superplasticizers are generally assumed to attach themselves to positively charged solid particles by electrostatic bonds. The mode of attachment of non-ionic superplasticizers is not well specified.

In this paper, the modes of attachments of both the types of superplasticizers have been reexamined. It is known that silica powder is positively charged below pH 3 and negatively charged above pH 9. Advantage has been taken of this charge reversal of silica powder to study the modes of attachment of both types of superplasticizers. It is observed that negatively charged ß-SNFC functions equally well both with pastes of positively and negatively charged silica particles.This means that ß-SNFC can attach itself to silica particles irrespective of sign of charge on the particles.

Function of a non-ionic superplasticizer is found to be very sensitive to the number density of the solid particles. At high number density this type of dispersant can act as flocculants irrespective of the sign of charge on silica particles. At low number density of solid, this type performs in alkaline medium.

From the above results it has been postulated that all types of superplasticizers attach themselves by depositing their hydrophobic part on to the solid particles. The effects of this type of attachment have been discussed.

The particle image velocimetry (PIV) technique was successfully applied for measuring the velocity of a He II thermal counterflow jet. Neutrally buoyant hydrogen-deuterium solid particles were used as tracer particles for PIV measurement. In the application, the normal component velocity was measured. The jet velocity profile and spatial decay of the jet velocity were compared with those of round jets of ordinary viscous fluids. The velocity that was measured near the jet nozzle was compared with the theoretical prediction.

We report an experimental approach for applying the PIV technique to measurements in He II forced flow. The forced flow of He II is created in a 3.5 m long experimental channel within the Liquid Helium Flow Visualization Facility (LHFVF). We demonstrate that micron size solid hydrogen isotope particles are the best choice for tracing He II forced flow. A novel particle seeding device has been developed to form and seed such solid hydrogen isotope particles directly within He II flow. Velocity field measurements of forced flow He II subjected to a constant locally applied heat flux are presented. Results are compared to analysis based on the two-fluid model.