Synthesis and Magnetostrictive Properties of High-Pr Content  ${\rm Sm}_{1-x}{\rm Pr}_{x}{\rm Fe}_{1.9}$ Cubic Laves Alloys
Polycrystalline Sm<sub>1-</sub><i>x</i>Pr<i>x</i>Fe<sub>1.9</sub> (0.4 ≤ <i>x</i> ≤ 1.0) magnetostrictive alloys were synthesized by arc-melting and subsequent high-pressure annealing. Measurements of x-ray diffraction, magnetization, and magnetostriction were performed on the alloys. Due to the effects of high-pressure, the alloys are stabilized in cubic Laves phase with MgCu<sub>2</sub>-type structure. The Curie temperature of the cubic Laves phase decreases linearly with the increase of <i>x</i>, which can be associated with the decreasing strength of 3<i>d</i>-4<i>f</i> coupling. With increasing <i>x</i> , the anisotropy of the alloys first decreases to a minimum at <i>x</i> = 0.6 and then increases. The magnetostriction of Sm<sub>1-</sub><i>x</i>Pr<i>x</i>Fe<sub>1.9</sub> changes signs from negative into a positive at <i>x</i> = 0.6 . The saturation magnetostriction increases with increasing <i>x</i>, while the sample with <i>x</i> = 0.9 shows a peak at low magnetic fields.
Structure, thermal stability and magnetostrictive properties of PrFex (1.5 ≤ x ≤ 3.0) alloys
Abstract Polycrystalline alloys PrFex (x = 1.5, x = 1.8, x = 1.9, x = 2.0, x = 3.0) have been prepared by arc-melting and subsequent high-pressure synthesis method. Their structure, thermal stability, easy magnetization direction and magnetostriction are investigated. Almost single Laves phase (MgCu2-type) is found in sample with x = 1.9. Samples with x = 2.0, x = 3.0 consist of PrFe1.9 phase with MgCu2-type cubic structure and α-Fe phase. The Curie temperature (238 °C) and the decomposed temperature (408 °C) of PrFe1.9 alloys are derived from M–T curves. The easy magnetization direction of PrFe1.9 Laves phase lies along [1 1 1] axis at room temperature which is verified by Mossbauer spectrum. Furthermore, PrFe1.9 alloy shows a large magnetostriction λ|| – λ⊥ = 1081 × 10−6 at a magnetic field of 13 kOe.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.