ON LIMITING THE VOLUME FRACTION OF PARTICLES IN THE DISPERSE SAMPLE (FOR THE TASkS ON CONTROLLING THEIR MAGNETIC PROPERTIES)

Abstract

It was found that it is sufficient to have the values of magnetic susceptibility X of a disperse sample containing ferroparticles to obtain the values of magnetic susceptibility Xч of its particles (particularly, in solving many scientific applied tasks of magnetic control and/or magnetophoresis of such particles). It is important that the values of volume fraction (concentration) γ of the ferroparticles be low (feasible), when simple dependence is acceptable for determining Xч values: Xч = X/γ. The question of the criterion value of γ is considered (it is still a discussion question). This value is up to γ=0.02-0.05 (this is evaluated data existing for a long time) for magnetite samples and even up to γ=0.2-0.25 (circumstantial evidence - by determining the demagnetization factor of disperse ferromagnetic samples). Direct experiments based on the ponderomotive Faraday method are realized with the use of a powder sample within the range of volume fraction γ ≤ 0.3 (for disperse phase - magnetite). The results of the experiments show that the linear part of X(γ) relation ends at γ 0.2. This is confirmed by many other consolidate data obtained by using disperse samples of magnetite (powder, colloid). However, at lower values of γ (γ ≤ 0.02-0.05) “individual” linear relation between X and γ is found as the consolidate data show. Taking into account the proportionality coefficient this relation differs from the previous relation by about 18%. This means that it is appropriate to use X values obtained at γ ≤ 0.02-0.05 for obtaining more accurate values of Xч.

Keywords

• disperse phase of medium
• ferroparticles
• magnetite
• volume fraction
• criterion value
• field intensity
• magnetic susceptibility