Yttria-stabilized Zirconia Balls Research Articles

Optimization of Ball Milling Parameters for Efficient Copper Slag Valorization

The ball milling process increasingly employed in a symbiotic materials recovery context is associated with high environmental footprint due to its energy-intensive nature. The current paper addresses this issue by optimizing the milling of copper slag, recognized as a promising alternative resource within the construction sector. The slag was milled in a stirred mill using stainless-steel (SS), carbon-steel, and yttria-stabilized zirconia (YSZ) balls with(out) grinding aid (GA). The milling time and energy, besides milled slag properties, were monitored. Performance variations of different milling balls were explained through the impact theory. Results show that efficient size reduction happens in the first hours regardless of the ball material and diameter. In a specific surface area (SSA) between 3600-3800cm2/g (d50=11µm), substituting SS with YSZ balls decreased milling time and energy by ∼50%, comparable to processes performed with GA. The addition of smaller balls (Ø6.3mm) to bigger balls (Ø9.5mm) caused energy consumption to decrease starting from SSA=3200±100cm2/g and cumulative particle size to slightly reduce. The effect of the ball-to-slag ratio on the milling efficiency was found stronger than the ball diameter change. A strong influence of the parameter optimization on the ball milling efficiency was proposed, potentially benefiting powder production industries.

Shift of tellurium solid-solubility limit and enhanced thermoelectric performance of bismuth antimony telluride milled with yttria-stabilized zirconia balls and vessels

As a thermoelectric material, Bi0.3Sb1.7Te3.0+x (x = 0‒0.05) was fabricated by mechanical alloying using yttria-stabilized zirconia (YSZ) ceramic balls and vessels, followed by hot pressing. The effects of the added tellurium on the thermoelectric properties of Bi0.3Sb1.7Te3.0 fabricated with YSZ milling media were investigated. All sintered samples were isotropic and showed p-type conduction. The tellurium solid-solubility limit for Bi0.3Sb1.7Te3.0 was determined to be x = 0.01 by differential thermal analysis (DTA). The solid-solubility limit of the sample fabricated using YSZ was narrower than that of the congener prepared with Si3N4 balls and stainless-steel metal vessels. Among the evaluated compositions, the Bi0.3Sb1.7Te3.01 sintered disk had the highest dimensionless figure of merit, ZT = 1.30, at room temperature. This value was superior to that of Bi0.3Sb1.7Te3.0+x fabricated using metal vessels. Thus, selection of the milling media affected the optimum doping amount and maximum ZT.

백금-루테늄 합금 촉매 및 도핑된 세리아 중간층이 메탄 변환 성능에 미치는 영향

The necessity of converting toxic gas has arisen from the usage of perfluorinated compounds (PFCs), volatile organic compounds (VOCs), and hydrocarbon gases in the semiconductor process and laboratories. Also, recent strong regulations on the emission gas from vehicles also present the need for the highly efficient chemical conversion of toxic emission gases. In this study, we present the fabrication of platinum and ruthenium alloy metal catalysts on the yttria-stabilized zirconia balls, and the application of the metal catalysts to the catalytic converter for methane oxidation. The platinum and ruthenium alloy metal catalysts showed better performance than the platinum catalyst, i.e., 75% increase in the methane conversion efficiency at 500℃. Such improvement seems to be because of the facile oxygen supply from the ruthenium surface. Also, the platinum and ruthenium alloy catalysts with the doped cerium oxide interlayer showed better thermal stability than the platinum and ruthenium alloy metal catalysts, possibly because of the stronger bonding between the metal and oxide support.

Two-Step Water Splitting Process With Solid Solution of YSZ and Ni-Ferrite for Solar Hydrogen Production (ISEC 2005-76151)

Ni-ferrite (NiFe2O4) is a promising reactive ceramics of the ferrite for the solar hydrogen production by a two-step water splitting process using concentrated solar energy. However, it should be pretreated before H2-generation reaction by grinding the Ni-ferrite sintered after the O2-releasing reaction to make a fine powder. If the Ni-ferrite and yttria stabilized zirconia (YSZ) form a solid solution between these oxides (YSZ∕NiFe2O4 solid solution=YSZ(Ni,Fe)), it is expected that the two-step water splitting process with the Ni-ferrite system can proceed without treatment of the reduced product because of the high thermal stability of the YSZ∕NiFe2O4 solid solution. The YSZ∕NiFe2O4 solid solution was prepared by calcination of the mixture of the YSZ balls and NiFe2O4 powder at T=1823K for 1h, and its reactivity and thermal stability were examined for the two-step water splitting process. During the ten times repetition of the two-step water splitting reaction (T=1773K for O2-releasing, and 1473K for H2-generation) with the YSZ∕NiFe2O4 solid solution using infrared imaging furnace, the reactivity for O2-releasing and H2-generation was kept constant. The molar ratio of the released O2 gas volume (the average O2 gas, 1.9cm3∕g) and the generated H2 gas volume (the average H2 gas, 3.8cm3∕g) was nearly 1:2, indicating that the water decomposition process via two steps proceeds. The X-ray diffractometry (XRD) measurement showed that the YSZ(Ni,Fe) keeps the YSZ phase structure during the ten times repetition of the two-step water splitting process. The successive H2 gas production by the two-step water splitting process was performed (ten times repetition of the two-step water splitting process). From comparative study on the reactivity and the thermal stability for the two-step water splitting reaction among the YSZ∕NiFe2O4 solid solution, NiFe2O4 and ZnFe2O4, it is concluded that the YSZ∕NiFe2O4 solid solution is superior to the others.

Synthesis of Nanocrystalline Y2O3:Eu Phosphor by a Metal-Ionic CrossLinker-Containing Polymeric Precursor Method

We synthesized a high-performance red-emitting nano-sized Eu-doped Y2O3 phosphor (Y2O3:Eu) powder by a metal-ionic crosslinker-containing polymeric method using carboxymethyl cellulose (CMC), with post heat treatment at 1000°C in air. This method yields soft but large aggregates of nanocrystalline Y2O3:Eu particles as synthesized, and therefore, to obtain the phosphor powder consisting of nano-sized single grains pulverization of the aggregates by ball milling or other methods is needed; this pulverizing process generally causes a deterioration of the fluorescence of Y2O3:Eu powders. To solve this problem we established a new method to obtain nano-sized Y2O3:Eu powders without mechanical pulverization by using ∅50-μm yttria-stabilized zirconia balls, which were added in a reaction vessel as an aggregation suppressant. By this method high-performance red-emitting Y2O3:Eu powders with grain sizes of 20–30 nm were successfully produced.

Radiographic Characterization of Thermal Spray Jets Produced by Electrothermal Explosion of Ceramic Powders

Thermal spray jets composed of Zr–B–O molten particles produced by the electrothermal explosion of a mixed powder of Zr and B2O3 were quantitatively characterized of their velocity, volumetric mass density, and mass velocity by flash radiography, to investigate a unique characteristic of a coating formed by using such jets, i.e., the mixing of a substrate material with a coating. Yttria-stabilized zirconia balls were used as tracers of jet flow. Mass velocity, i.e., mass flow rate per unit cross section of the flow, in a cylindrical space in front of the virtual position of a substrate was calculated using the velocity of the tracers and the volumetric mass density of the jet. The maximum mass velocity in the present spraying was two orders of magnitude larger than that in conventional plasma spraying. Thus, the very high mass velocity probably contributes to the appearance of the unique characteristic.