Study of Ball Milling and the Determination of Lattice Chloride in Zinc Sulfide

Abstract

Ball milling, followed by displacement washing, permits a distinction to be made between lattice chloride and internal surface chloride as parts of volume chloride. The surface area, which is determined by gas adsorption methods, increases rapidly in the beginning and then in a linear manner as a function of milling time. The extent of linearity between surface area and milling time is considered to be a measure of crystallinity. The data indicate that the maximal amount of lattice chloride becomes incorporated at a processing temperature near 700°C after a processing time of 2 hr. Zinc sulfide gradually loses its ability to luminesce under ultraviolet (u.v.) irradiation during milling; the logarithm of the luminescence emission is about proportional to the newly formed surface. It appears that the luminescence centers consist of lattice regions of about 0.2 µ in diameter, as is indicated by the observed minimal size of luminescent particles. The luminescence emission of milled samples can be restored by reprocessing, although the degree of restoration is highly sensitive to impurities introduced during milling.

Luminescent Supraparticles Based on CaF2–Nanoparticle Building Blocks as Code Objects with Unique IDs

“…However, this "top-down" microparticles would not possess the desired optical features anymore due to the destruction of the crystalline lattice, which cannot be avoided upon mechanical treatment (a more detailed discussion follows later on). 29,34 In contrast, it was found that the formation of micrometersized supraparticles via spray-drying of nanoparticles before calcination impedes the sintering to a certain extent. After calcination, the distinct supraparticles are retained i.e., a freeflowing powder can be harvested from the calcination furnace (Figure 2b).…”

“…Strong mechanical forces would then be necessary to break down these hard, macroscale agglomerates back into micrometer-sized particles. However, this “top-down” microparticles would not possess the desired optical features anymore due to the destruction of the crystalline lattice, which cannot be avoided upon mechanical treatment (a more detailed discussion follows later on). , …”

“…First, these micrometre to millimeter-sized particles cannot be reduced in size without their crystal structure being destroyed by mechanical stress and consequently without losing their optical properties. 29 Second, ratiometric quantification of these mixed powders within a matrix material is not possible as the matrix environment might differ among the volume element, which is analyzed. Apart from that, it is advantageous to have particles at hand directly after synthesis, which are sized a few micrometers only and thus are very flexibly integrable in different materials.…”

“…This is advantageous over ratiometrically mixing various commercially available particulate powders with different luminescence properties, which are obtained from ceramic processes. First, these micrometre to millimeter-sized particles cannot be reduced in size without their crystal structure being destroyed by mechanical stress and consequently without losing their optical properties . Second, ratiometric quantification of these mixed powders within a matrix material is not possible as the matrix environment might differ among the volume element, which is analyzed.…”

Particle Growth during Zinc Sulfide Phosphor Preparation

“…A simplified gas adsorption method, microscopic counting, x-ray analysis, and electron photomicro-graphy were employed in determining the particle size and the crystal structure, as discussed previously (9). The same publication (9) also describes a semi-quantitative method which was employed in the present investigation to obtain a measure of photoluminescence intensity.…”