Optically transparent polycrystalline magnesium aluminate spinel (MgAl 2 O 4 ) has been fabricated by hot-pressing followed by hot isostatic pressing (HIPing). The effect of microstructure on the light transmittance of the sintered MgAl 2 O 4 is discussed. The sintered MgAl 2 O 4 with a thickness of 2 mm has a maximum light transmittance of ∼60 and ∼70% in the UV–visible and near-IR wavelength regions, respectively, although it contains microcracking along its grain boundaries. Light transmittance losses in the sintered MgAl 2 O 4 are explained in terms of light scattering at these microcracked grain boundaries: the light transmittance was determined to decrease with increase in the microcracked grain boundary surface area due to pronounced scattering. The light transmittance is well correlated with microcracked grain boundary surface area per unit volume.

Effect of grain boundary microcracking on the light transmittance of sintered transparent MgAl2O4

https://tandfonline.com/doi/pdf/10.1080/14686996.2019.1591168

Structure and properties of Sn-Cu lead-free solders in electronics packaging

Oxidative coupling of methane over thoria based catalysts

The I2 adsorption in Ni(pz)[Ni(CN)4] clathrate was investigated by combining spectroscopic and computational tools, including electrical measurements, solid UV–vis, infrared, and Raman spectroscopy, and Monte Carlo simulations. We observed that while ionic I3– species are formed at low I2 concentration, iodine in its molecular form is present at higher concentration. The appearance of polyiodides was suggested to result from the interactions between the guest and the [Ni(CN)4]2– moieties of the host framework.

Understanding the Host/Guest Interactions in Iodine/Hofmann-Type Clathrate Ni(pz)[Ni(CN)4] System

Novel approach for the bulk synthesis of nanocrystalline yttria doped thoria powders via polymeric precursor routes

The tetracyanonickelates Ni(NH3)2Ni(CN)4·1.9 H2O (1), Ni(NH3)1.65(C4H8O2)0.2Ni(CN)4·0.8 C4H8O2·0.35 H2O (2) and Ni(en)3Ni(CN)4·H2O (3) exhibit, after contact with a solution of iodine (I2/KI), appreciable weight gains. According to thermal analysis, IR spectra and chemical analysis the new products contain intercalated iodine and iodides with the highest iodine content found in the product formed from (3). The results of high frequency conductance measurements of this product showed the highest value of electrical conductivity σ (10−6 S cm−1). Other compounds show relatively low values of σ (10−8–10−11 S cm−1).

The preparation of tetracyanonickelates showing electrical conductivity

The investigation of microstructure, some electrical and optical parameters of transparent ThO2-15 mol % yo1.5 ceramics has shown: (a) a very low porosity, close to zero; (b) a higher electrical conductivity than is usual for ThO2 ceramics of the same composition, with the activation energy 1.12 eV; (c) a relative permittivity ɛr ∼ 33 under the given conditions; (d) confirmation of a single-phase fluorite-type cubic structure by means of Raman and infrared spectra.

Microstructure and physical properties of transparent thoria-yttria ceramics

Composite materials made up of silver iodide and synthetic mordenite in sodium Na-MD or potassium form K-MD have been prepared by sintering a mixture of silver iodide and Na-MD or K-MD, by modified way of preparation. The prepared composites Na-MD/AgI and K-MD/AgI were characterised by X-ray powder diffractometry and thermal analysis. By integrating certain X-ray peaks quantitative reaction values were obtained. The composite Na-MD/AgI with 19 wt% of AgI content was also characterised by EDS analysis and ac conductivity measurements.

Composite Materials of Synthetic Mordenite and AgI

The presence of iodine and iodide ions in tetracyanonickelates inclusion compounds with the general formula Ni(B) m Ni(CN) 4 . n H 2 O (B = NH 3 or ethylenediamine) changes the properties of these compounds. High frequency conductance measurements in the range of 10 - 105 Hz show that the products with ethylenediamine ligands have a higher electrical conductivity than those with NH 3 ligands. The differences in the electrical properties between the compounds studied are mainly caused by chemical composition, structure and morphology.

Inclusion Compounds of Tetracyano Complexes and Their Electrical Properties

The total a.c. conductivity of a CaxTh1−xO2−x solid solution with fluorite-type structure was measured at 1360 Hz with 0⩽x⩽0.25 and at temperatures of 100 to 600° C. The complex impedance behaviour was investigated at frequencies of 10 to 105 Hz and temperatures of 300 to 500° C. The complex dielectric permittivity was calculated at this frequency and in that temperature range. The activation energy for the bulk conductivity was calculated. Its value is about 1.48 eV forx<0.03 and about 1.25 forx⩾0.03.

Vladimír Šály

Papers

The preparation of tetracyanonickelates showing electrical conductivity

Microstructure and physical properties of transparent thoria-yttria ceramics

Composite Materials of Synthetic Mordenite and AgI

Inclusion Compounds of Tetracyano Complexes and Their Electrical Properties

Electrical behaviour of CaO-doped ThO2