Sensitivity of a vibroacoustic signal to a change in the state of the surface layer of ceramics during frictio

The high information content of the vibroacoustic signal in the frequency range of 10‒16 kHz to the change in the state of the surface layer of the ceramic sample during frictional interaction with the steel disk was established. The results obtained indicate the possibility of using vibration diagnostics systems for monitoring the state of ceramic parts during operation and fi tests.

Impact of Thermal Treatment on the Surface of Na0.5Bi0.5TiO3-Based Ceramics

Thermal etching is a widely accepted surface treatment method for studying microstructure in Na0.5Bi0.5TiO3-based compositions. Surprisingly, besides the flat pattern of grains (suitable for evaluating ceramics’ microstructure), images illustrating well-expressed relief and even microstructure consisting of partly bonded cubic-shaped grains are also found among the micrographs presented in various publications. The present paper shows that this different surface character in Eu-modified Na0.5Bi0.5TiO3 can be obtained through thermal treatment across a wide range of temperatures. At higher temperatures, remarkable growth of cubic-shaped grains on the surface is observed. This growth affects the grain size distribution on the surface more than it does within the bulk of a sample. Such micrographs cannot be used to characterise the microstructure of dense ceramics. Intensive growth of TiO2 inclusions at high thermal treatment temperatures is also observed, revealing substantial evaporation of Bi and Na from the surface of a ceramic sample, but not from its core part.

Up-Conversion Luminescence Properties of Nd3+/Yb3+ Doped Lutetium-Based Oxyfluoride Glass Ceramic

Nd[Formula: see text]/Yb[Formula: see text] co-doped lutetium-based glass sample and glass ceramic sample were prepared with the molar ratios of 52SiO2-8Na2CO3-16Al2O3-33NaF-3LuF3-0.15Yb2O3-0.03Nd2O3 by the high temperature melting method in 1400∘C. Under the excitation of 980[Formula: see text]nm diode laser, up-conversion luminescence spectrum of glass sample and glass ceramic sample was measured and three stronger up-conversion luminescence peaks at the wavelength of 552[Formula: see text]nm, 656[Formula: see text]nm and 668[Formula: see text]nm were observed, and up-conversion luminescence strengths of glass ceramic sample are higher than those of glass sample. The two-photon absorption of three emission peaks was determined by the fitting curve graph of up-conversion emission power and LD wording current. Absorption spectrum of glass ceramic sample was obtained and spectral strength parameters were computed as [Formula: see text][Formula: see text]cm2, [Formula: see text][Formula: see text]cm2, [Formula: see text][Formula: see text]cm2 by adopting Judd–Ofelt theory, and the root mean square deviation between the theoretical oscillator strength and the experimental oscillator strength were calculated as [Formula: see text]. Transition probability, branching ratio of 4F[Formula: see text] to its lower level and lifetime of 4F[Formula: see text] level of Nd[Formula: see text] ions were calculated, and the results indicate that the prepared Nd[Formula: see text]/Yb[Formula: see text] co-doped glass ceramic sample is a kind of good up-conversion material.

Study of the phase composition and porosity structure of a ceramic material that is more than four hundred years old (Spain)

The object of the study is a ceramic material taken from the church of St. Mary (Spain). The element-by-element chemical composition of the studied material showed an increased carbon content (15,42 %) indicating the introduction of fuel into the raw material. The increased content of fuel in the raw material contributes to uniform sintering and porosity formation inside the ceramic sample. In the studied sample of the composition, three types of pores are most often found: slit-shaped, isometric and oval-shaped pores. Isometric pores are found in the form of «channels». The presence of isometric pores and oval closed porosity in the material under study give it mechanical strength. The increased content of calcium in the test sample (11,92 %) contributes to the formation of anorthite, which increases the strength of the products.