TECHNOLOGY OF MANUFACTURE OF RADIO ABSORPTION CERAMICS

The object of the work is the technology of manufacturing radio-absorbing ceramics on the basis of facing tiles with the addition of silicon carbide. The method of hydrostatic weighing in water was used to determine the physical properties. X-ray phase analysis and spectral characteristics - transmission and reflection coefficients, in the frequency range 25.8 – 37.5 GHz were also determined. Tiles consist of two layers. First, separately obtain a press powder for the I and II layer of raw materials in a given amount, which were weighed, moistened, ground in a ball mill; the slip was dried in an oven, then ground and passed through a suitable sieve. The moistened press powder for the first layer was weighed and poured into a mold for pressing, after which the moistened press powder for the second layer was weighed and poured into the mold for pressing. The resulting raw material was dried. The semi-finished product was covered with watering and placed in an oven. The finished semi-finished product was fired in a silite furnace. The two-layer tile with an irrigated covering made on the developed technology was characterized by the following characteristics: water absorption – 9,8 %, imaginary density – 1,90 g/cm3. The developed ceramics, according to the classification, can be referred to the class of radio-absorbing ceramics.

The applying of layer-by-layer laser remelting in the technology of laser metal deposition

Layer-by-layer laser remelting (LRM) was used in the technology of laser metal deposition in order to reduce the porosity of the layer in the case of single-layer and multi-layercoatings. The layer porosity is shown to decreases with LRM at a rate 5 times higher than the rate of metal deposition. The dependence of the porosity estimated using the method of the hydrostatic weighing on the rate of laser remelting is obtained.

Application of acoustic microscopy for evaluation of numismatic material

A new non-destructive express method for assessing the authenticity of numismatic material is considered in the paper. Non-destructive methods of pulsed acoustic microscopy in the frequency range of 50-100 MHz were applied. Samples of silver coins dated 1924 and 1979 were examined. The characteristic values of the longitudinal and transverse sonic velocity of the samples were obtained. The method of hydrostatic weighing was used to measure the density of the metal. It was shown that assessment of the authenticity and the safety degree of coins can also be carried out by revealing the internal defects such as corrosion. Acoustic visualization in the reflection mode allows imaging the offset of the obverse relative to the reverse and to determine the centre of the coin deviation, which also confirms the quality of the minting.

Mid-IR Optical Property of Dy:CaF2-SrF2 Crystal Fabricated by Multicrucible Temperature Gradient Technology

Dy3+-doped CaF2-SrF2 crystals with various Dy3+ dopant concentrations were synthesized by multicrucible temperature gradient technology (MC-TGT). Dy:CaF2-SrF2 crystals were fluorite structured and crystallized in cubic Fm3¯m space group, as characterized by X-ray diffraction. The crystallographic site concentration was calculated from the measured density by Archimedes’ hydrostatic weighing principle. The optical transmission reached over 90% with a sample thickness of 1.0 mm. The Sellmeier dispersion formula was obtained following the measured refractive index in a mid-IR range of 1.7–11 μm. Absorption coefficients of 6.06 cm−1 and 12.71 cm−1 were obtained at 804 nm and 1094 nm in 15% Dy:CaF2-SrF2 crystal. The fluorescence spectra of 15 at.% Dy:CaF2-SrF2 showed the strongest wavelength peak at 2919 nm with a full width at half maximum (FWHM) of 267 nm under an excitation wavelength of 808 nm. The fluorescence lifetimes were illustrated for different Dy3+ dopant levels of 5%, 10% and 15%. The results indicate that the Dy:CaF2-SrF2 crystal is a promising candidate for compact mid-IR lasers.

Hydrostatic Determination of Test Weight Density and Uncertainty Evaluation by Monte Carlo Method

This paper presents the characterization of the hydrostatic weighing facility of the National Metrology Laboratory (NML) of the Philippines. The study aimed to evaluate its suitability for determination of solid density. It was used to hydrostatically measure the density of a stainless steel (OIML Class F1) test weight weighing 200 g. The measurement result obtained was 7.5827 g cm-3 ± 0.0041 g cm-3 at an approximately 95 % level of confidence. The uncertainty evaluated by the Law of Propagation of Uncertainty (LPU) according to JCGM 100:2008 (GUM) was verified by the Monte Carlo method (MCM), which gave a result of 0.0040 g cm-3. The value determined for the solid density of the sample with its associated expanded uncertainty was found to be within the tolerance interval between 7.39 g cm-3 and 8.73 g cm-3 as required in OIML R111-1 for Class F1 test weights.

First density comparison on viscoelastic samples by oscillation-type densimetry

To provide a deeper insight about the damping effects produced by the viscoelasticity of non- Newtonian fluids during density measurements with oscillation-type density meters, and about how reference laboratories overcome these effects, an international comparison was performed, within the scope of the EMPIR Project 17RPT02 rhoLiq. The results of the comparison evidenced the possibility to measure density of viscoelastic samples by means of oscillation-type density meters with an uncertainty between 0.10 kg·m^-3 and 0.25 kg·m^-3. However, these instruments may be able to reach lower uncertainties if compared with higher precision density measurement methods such as hydrostatic weighing.

Enhancing the handling of standard substitution weights on a hydrostatic weighing apparatus

The hydrostatic weighing apparatus is a first-level method used to measure the density of solids and liquids. At the Portuguese Institute for Quality the hydrostatic tests for the determination of the liquids’ density implies the multiple manual placement of a set of standard substitution weights on apparatus’ balance pan, leading to undesirable perturbations in the weighing environment. Also, by this the eccentricity effects on the balance, contribute for an unwanted increase of the measurement uncertainty. To overcome these phenomena, an automated mechanism was designed and implemented, which allows the placing and recollection of the set of standard weights on the balance. To validate the new mechanism, tests to ultrapure water at 20 °C were executed before and after its implementation and the obtained results were compared.<br />Despite a 3-fold increase in density measurement uncertainty, mainly due to the exposure of the standard substitution weights to air convection currents, the execution of hydrostatic tests was improved, not only for the fact that the measurements are now carried out quicker, but also for the fact that the operator only needs to intervene once during the whole test. Moreover, the smaller absolute deviation from the reference density value for ultrapure water at 20 °C results also in a normalised error <em>E</em>_n lower than 1 (0.3), thus validating the designed automated mechanism for the handling of standard substitution weights.