Ceramic Emission Research Articles

Luminescence of the tungsten-activated MgF2 ceramics synthesized under the electron beam

Abstract For the first time the possibility of synthesizing of an optical ceramics MgF2 using a powerful electron beam as a heater is shown. In the process of synthesis, the charges consisting of magnesium fluoride powder with different ratio between the dopants WO3 and LiOH were exposed to an electron beam with 1.4 MeV electron energy and power of 18 kW on an area of 1 cm2. Investigations of the elemental composition and structure of the synthesized ceramics showed the presence of crystalline phases MgF2, W, WO3, and Mg in the samples. The size of the crystalline grains and efficiency of their formation depend on the composition of the charge. It was found that the synthesized ceramics samples luminesce in the 470 nm region at 300 K. Excitation spectrum of this emission in ceramics consists of two bands with maxima at 250 nm and about 200 nm. The spectral properties of MgF2 ceramics in general are similar to those in ZnWO4 single crystals and LiF crystals doped with tungsten oxide.

Monitoring of PM10 and PM2.5 around primary particulate anthropogenic emission sources

Investigations on the monitoring of ambient air levels of atmospheric particulates were developed around a large source of primary anthropogenic particulate emissions: the industrial ceramic area in the province of Castelló (Eastern Spain). Although these primary particulate emissions have a coarse grain-size distribution, the atmospheric transport dominated by the breeze circulation accounts for a grain-size segregation, which results in ambient air particles occurring mainly in the 2.5–10μm range. The chemical composition of the ceramic particulate emissions is very similar to the crustal end-member but the use of high Al, Ti and Fe as tracer elements as well as a peculiar grain-size distribution in the insoluble major phases allow us to identify the ceramic input in the bulk particulate matter. PM2.5 instead of PM10 monitoring may avoid the interference of crustal particles without a major reduction in the secondary anthropogenic load, with the exception of nitrate. However, a methodology based in PM2.5 measurement alone is not adequate for monitoring the impact of primary particulate emissions (such as ceramic emissions) on air quality, since the major ambient air particles derived from these emissions are mainly in the range of 2.5–10μm. Consequently, in areas characterised by major secondary particulate emissions, PM2.5 monitoring should detect anthropogenic particulate pollutants without crustal particulate interference, whereas PM10 measurements should be used in areas with major primary anthropogenic particulate emissions.

Crack Growth and Acoustic Emission in Ceramics During Thermal Shock

It is recognized that microcracks may contribute to failure of ceramics undergoing thermal shock, although there is little direct experimental evidence. The combination of acoustic emission (AE) and SEM observations provides such evidence. In this work AE data were analyzed after rapid quenching of samples in silicone oil. A thermal shock resistant material, alumina, and a material resistant to thermal damage, advanced zirconia refractory, have been examined. Cracks were detected by analysis of AE amplitudes and durations and their growth was monitored by systematic SEM observations as thermal shocks of increasing severity were applied. Three‐point bending strengths were determined in air after quenching. For the first time SEM images are presented showing early stages of crack initiation for temperature differences less than ΔTcrit, i.e., where the fracture was not believed to occur. Further development of the cracks leads to abrupt strength reduction in alumina and controlled strength loss in zirconia, although AE data did not indicate any particular pattern of catastrophic crack propagation when substantial loss of strength occurred.