Effect of Mechanical Alloying on Structural and Electrical Properties of (P2O5)(x)-(Y2O3)(0.03)-(ZrO2)(0.97) Electrolyte

Pentavalent phosphorous oxide doped yttria-stabilized zirconia (P2O5)X-(Y2O3)0.03-(ZrO2)0.97 with x=0.06 mol.% was achieved via an economical technique using mechanical alloying (MA) technique. Three types of nanocomposite powders of electrolyte were produced by high-energy ball milling with different milling times. The phases of synthesized electrolyte powders and sintered electrolytes were illustrated by X-ray diffraction (XRD). The average particle sizes of powders indicated around (360, 245, and 48) nm at milling duration (1, 10, and 45) hrs, respectively. The XRD analysis results of 1 h MA electrolyte powder obtained tetragonal ZrO2, while the 45 h MA electrolyte manifested a minority phase of monoclinic ZrO2. Then, the XRD of the sintered electrolyte with the optimum electrical properties appeared two phases. The major phase of the tetragonal zirconium yttrium oxide and a minor phase was a monoclinic zirconium oxide. The average grain sizes of the three types of the sintered manufacturing electrolytes were (7.638, 2.642, and 1.245 µm) after the mechanical alloying duration of (1, 10, and 45) hrs, respectively and sintered at 1873 °K. The DC conductivity (σ) studied corresponded to the influence of milling times on the microstructure for each sintered electrolyte. From the results, the synthesized sintered electrolyte with a long MA duration gave a maximum DC (σ) 1.03E-1S.m. And, the DC conductivity (σ) was 1.11E-02 of electrolyte produced with 10 hr mechanical alloying. Otherwise, the lower DC conductivity got with the electrolyte prepared in the lowest milling duration was 8.9 E-2 S.m.

Milling Duration Influence on Strontium Hexaferrite Technological Characteristics

Fine powders of strontium hexaferrite are widely used in powder metallurgy for the production of permanent magnets resistant to atmospheric oxygen and high working temperatures. Obtaining powders with predefined technological characteristics in minimal time and with minimal energy consumption is an actual problem of powder metallurgy. The paper provides the results of experimental studies of technological characteristics of strontium hexaferrite powder (SrFe12O19) during milling in a beater mill. Mechanical milling of coarse strontium hexaferrite was carried out in the mill with the system of rotating beaters for 120 minutes without and with the creation of a pseudo fluidized bed. The fluidization was formed by a perpendicular constant and alternating magnetic field with induction gradients of 150 and 210 mT/m. Average particle size and powder bulk density dependencies from milling time were studied. Experimental data show that milling with the formation of a magneto fluidized bed allows intensifying the process. Beginning from 70 minutes, the dependencies of average particle size and bulk density come to almost asymptotic behavior making further milling rather ineffective. Carried out research allows choosing optimal milling duration for obtaining the required average particle size.

Mechanically activated mine tailings for use as supplementary cementitious materials

Two mine tailings are evaluated for their potential as supplementary cementitious materials. The mine tailings were milled using two different methods – ball milling for 30 minutes and disc milling for durations ranging from 1 to 15 minutes. The modified R3 test was carried out on the mine tailings to quantify their reactivity. The reactivity of the disc milled tailings is greater than those of the ball milled tailings. Strong correlations are obtained between milling duration, median particle size, amorphous content, dissolved aluminum and silicon, and reactivity of the mine tailings. The milling energy results in an increase in the fineness and the amorphous content, which do not appreciably increase beyond a disc milling duration of 8 minutes. The reactivity increases significantly beyond a certain threshold fineness and amorphous content. Cementitious pastes were prepared at 30% supplementary cementitious materials replacement level at a water-to-cementitious materials ratio of 0.40. No negative effects of the mine tailings were observed at early ages in cement pastes based on isothermal calorimetry and thermogravimetric analysis, demonstrating the potential for these materials to be used as supplementary cementitious materials.

Solvent-Free Mechanochemical Synthesis of ZnO Nanoparticles by High-Energy Ball Milling of ε-Zn(OH)2 Crystals

A detailed investigation is presented for the solvent-free mechanochemical synthesis of zinc oxide nanoparticles from ε-Zn(OH)2 crystals by high-energy ball milling. Only a few works have ever explored the dry synthetic route from ε-Zn(OH)2 to ZnO. The milling process of ε-Zn(OH)2 was done in ambient conditions with a 1:100 powder/ball mass ratio, and it produced uniform ZnO nanoparticles with sizes of 10–30 nm, based on the milling duration. The process was carefully monitored and the effect of the milling duration on the powder composition, nanoparticle size and strain, optical properties, aggregate size, and material activity was examined using XRD, TEM, DLS, UV-Vis, and FTIR. The mechanism for the transformation of ε-Zn(OH)2 to ZnO was studied by TGA and XPS analysis. The study gave proof for a reaction mechanism starting with a phase transition of crystalline ε-Zn(OH)2 to amorphous Zn(OH)2, followed by decomposition to ZnO and water. To the best of our knowledge, this mechanochemical approach for synthesizing ZnO from ε-Zn(OH)2 is completely novel. ε-Zn(OH)2 crystals are very easy to obtain, and the milling process is done in ambient conditions; therefore, this work provides a simple, cheap, and solvent-free way to produce ZnO nanoparticles in dry conditions. We believe that this study could help to shed some light on the solvent-free transition from ε-Zn(OH)2 to ZnO and that it could offer a new synthetic route for synthesizing ZnO nanoparticles.

Exploring the Effects of Synthetic and Postsynthetic Grinding on the Properties of the Spin Crossover Material [Fe(atrz)3](BF4)2 (atrz = 4-Amino-4H-1,2,4-Triazole)

The effects of mechanochemical synthesis and postsynthetic grinding on the spin crossover material [Fe(atrz)3](BF4)2 was examined in detail using a combination of X-ray diffraction, magnetometry, EXAFS and TEM. Mechanochemical synthesis yielded a different polymorph (β-phase) to the solution synthesised sample (α-phase), with a lower temperature spin crossover. Milling duration did not significantly affect this temperature but did result in the production of smaller nanoparticles with a narrower size distribution. It is also possible to convert from α- to the β-phase via postsynthetic grinding.