A number of technologies is developed that substitute simple metal cores in the high-pressure casting technology. Soluble cores, namely
on the salt basis, represent the highest prospect. The contribution gives the results of the production of salt cores by high-pressure
squeezing and shooting with using a binder. Special attention is paid to the shape of NaCl salt crystals with additives and the influence on
strength properties of cores. A technology of bonding the salt cores is developing. Salinity of circulating water is studied and it is checked
with the aid of electrical conductance.
We have presented dielectric and conductivity studies of two liquid crystal (LC) compounds- p-octyloxybenzoic acid (8OBA) and p-decyloxybenzoic acid (10OBA). Dielectric permittivity study of those compounds gives the evidence of space charge polarization and ionic conductance in the samples. Dielectric permittivity is found to be the highest for 8OBA than 10OBA. Both compounds found to exhibit positive dielectric anisotropy. Splay elastic constant as a function of temperature has also been investigated. Frequency and temperature dependent electrical conductivity of these two LC compounds have been studied in detail. Activation energy has been estimated from both dc and ac conduction process.
The study investigates the effect of heat treatment on the microstructure evolution and properties of an age-hardened Cu-3Ti-2Mg alloy. The precipitated Cu2Mg and β'-Cu4Ti phases consequently yield a depletion of the Cu matrix in regards to Ti and Mg solutes, which enhances the electrical conductivity. The Cu2Mg Laves phase and β'-Cu4Ti phase precipitates increase the hardness of the alloy due to the consistency and coherency of the later phase. However, the decrease of hardness is mainly associated with the coarse microstructures, that can be formed due to the phase transformation from metastable β'-Cu4Ti phase to more stable Cu3Ti phase. In the range of experiments, the optimum process is solution treatment at 700°C for 4 h, with subsequent age-hardening at 450°C for 4 h. The electrical conductivity, hardness, tensile strength, and elongation of the Cu-3Ti-2Mg alloy were 15.34 %IACS, 344 HV, 533 MPa, and 12%, respectively.
This paper presents the results of obtaining and investigations of Pb1–xBax(Zr1–yTiy)1–zSnzO3 (PBZTS) ceramics with constant x = 0.03 and y = 0.02, and variable z = 0, 0.04, 0.06 and 0.08 (abbreviations of the samples were following PBZTS0, PBZTS4, PBZTS6, PBZTS8, respectively). The investigated compositions are close to rhombohedral-orthorhombic morphotropic phase boundary. The ceramic samples have been obtained by conventional ceramic technology from simple oxides PbO, ZrO2, TiO2, SnO2 and barium carbonate BaCO3. The ceramic powders, after calcination, have been pressed into discs and sintered using free sintering (FS) method. For samples obtained in such a way, the dielectric properties at various frequencies and electrical conductivity have been investigated. The increase of Sn content orders the microstructure of ceramics, and as a result the improvement of the dielectric properties of ceramic samples can be obtained.
In this research, Co-30 mass% Cr alloys were fabricated by a vacuum hot-press sintering process. Different amounts of submicron cobalt and chromium (the mean grain size is 800 and 700 nm, respectively) powders were mixed by ball milling. Furthermore, this study imposed various hot-press sintering temperatures (1100, 1150, 1200 and 1250°C) and pressures (20, 35 and 50 MPa), while maintaining the sintering time at 1 h, respectively. The experimental results show that the optimum parameters of hot-press sintered Co-30 mass% Cr alloys are 1150°C at 35 MPa for 1 h. Meanwhile, the sintered density reaches 7.92 g·cm–3, the closed porosity decreases to 0.46%, and the hardness and transverse rupture strength (TRS) values increase to 77.2 HRA and 997.1 MPa, respectively. While the hot-press sintered Co-30 mass% Cr alloys at 1150°C and 20 MPa for 1 h, the electrical conductivity was slightly enhanced to 1.79 × 104 S·cm–1, and the phase transformation (FCC → HCP) of cobalt displayed a slight effect on sintering behaviors of Co-30 mass% Cr alloys. All these results confirm that the mechanical and electrical properties of Co-30 mass% Cr alloys are effectively improved by using the hot-press sintering technique.