A Low-Cost High-Temperature Sensor Based on Long-Period Fiber/Microfiber Gratings by Local Fictive Temperature Modification

A high temperature-sensitive long-period fiber grating (LPFG) sensor fabricated by the local fictive temperature modification is proposed and demonstrated. High-frequency CO2 laser pulses scan standard single-mode fiber (SMF), and the modification zones extended to the core of SMF. Experimental results demonstrate that the LPFG temperature sensors with 600 μm grating period and 32 period numbers offer the average sensitivity of 0.084 nm/C in the temperature range of room temperature (RM) to 875°C. The LPFGs fabricated here show exponential change in terms of the spectral wavelength shift versus changes in temperature. In addition, the maximum temperature sensitivity of 0.37 nm/C is achieved by employing long-period microfiber grating (LPMFG), fabricated by the microheater brushing technique and the local fictive temperature modification. LPMFG sensor exhibits better temperature characteristics due to a thinner diameter.

ANTI-CORROSION COATINGS FOR OIL PIPELINES

The anti-corrosion coatings obtained on the basis of local raw materials, in particular, cotton soap stock, mineral and vegetable fillers, were studied. The compositions were prepared by mixing in a laboratory multifunctional extruder. The adhesion of the obtained anticorrosion coating was investigated; it was found that the anticorrosive properties of the obtained composition increase with increasing concentrations of sevilen (up to 15%), plant filler (up to 30–35%), carbon black (up to 8–10%) and soapstock (up to 20%). The morphology of the obtained composite with the addition of fillers was investigated. After temperature modification, the structure of the initial composition undergoes changes, the diameter of the fibers of the vegetable filler decreases.

The polymorphs of the Na+ ion conductor Na3PS4 viewed from the perspective of a group-subgroup scheme

The Na+ solid state electrolyte Na3PS4 is currently being investigated due to its high ionic conductivity and its synthesis-dependent crystal structure. Na3PS4 adopts a tetragonal low-temperature modification with space group P 4̅21c that transforms to a cubic high-temperature modification with space group I 4̅3m (Tl3VS4 type). These two modifications are related by a group-subgroup scheme. The symmetry reduction proceeds via a translationengleiche transition from I 4̅3m to I 4̅2m and subsequently via a klassengleiche transition to P 4̅21c. The tetragonal phase with space group I 4̅2m corresponds to the K2HgSnSe4 type. The group-subgroup scheme of this tetragonal branch of the Bärnighausen tree is discussed along with the crystal chemical consequences and results of diffraction experiments. The structure of K3SbSe4 (space group R 3c) belongs to the rhombohedral branch of the aristotype Tl3VS4.

Synthesis and Raman spectra of K-Ca double carbonates: K2Ca(CO3)2 bütschliite, fairchildite, and K2Ca2(CO3)3 at 1 ATM

Here we present results on synthesis of double K-Ca carbonates at atmospheric pressure in closed graphite capsules. The mixtures of K2CO3 and CaCO3 corresponding to stoichiometry of K2Ca(CO3)2 and K2Ca2(CO3)3 were used as starting materials. The low-temperature modification of K2Ca(CO3)2 was synthesized by a solid-state reaction at 500°C during 96 h. The high-temperature modification of K2Ca(CO3)2 as well as the K2Ca2(CO3)3 compound were synthesized both by a solid-state reaction at 600°C during 72 h and during cooling of the melt from 830 to 650°C for 30 min. The obtained carbonates were studied by Raman spectroscopy. The Raman spectrum of bütschliite is characterized by the presence of an intense band at 1093 cm-1 and several bands at 1402, 883, 826, 640, 694, 225, 167 and 68 сm-1. The Raman spectrum of fairchildite has characteristic intense bands at 1077 and 1063 cm-1, and several bands at 1760, 1739, 719, 704, 167, 100 сm-1. In the Raman spectrum of K2Ca2(СO3)3 intense bands at 1078 and 1076 cm-1 and several bands at 1765, 1763, 1487, 1470, 1455, 1435, 1402, 711, 705, 234, 221, 167, 125 and 101 сm-1 were found. The collected Raman spectra can be used to identify carbonate phases entrapped as microinclusions in phenocrysts and xenoliths from kimberlites and other alkaline rocks.