Investigation on abrasive wear of hard layers

Vytauto Didžiojo universitetasŽemės ūkio akademij

Agricultural Corps Nutrition with Potassium in Sandy and Silty Loamy Cambisolsn of Lithuania

Vytauto Didžiojo universitetasŽemės ūkio akademij

Properties of supercapacitors fabricated by plasma technologies

Fizikos katedraKauno technologijos universitetasLietuvos energetikos institutasVytauto Didžiojo universiteta

Removal of ammonium ion from aqueous solutions by using unmodified and H2O2-modified zeolitic waste

Article number: 352In the petroleum industry during a catalytic cracking process, the used zeolitic catalyst becomes waste. This article investigated the sorption capacities of ammonium ions from aqueous solutions onto the previously mentioned zeolitic waste by batch experiments. Three types of zeolitic waste were used: unmodifed zeolitic waste with two diferent particle size distributions and H2O2-modifed zeolitic waste. Several techniques, including X-ray difraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) multilayer adsorption theory measurements, and X-ray fuorescence analysis (XRF) were used to demonstrate experimentally that the zeolitic waste could be used as a sorbent for the water decontamination of NH4 + ions. The morphology of zeolitic waste investigated by scanning electron microscopy (SEM) revealed particles with a spherical shape. The nitrogen adsorption–desorption isotherms showed an isotherm mixture of types I (pure microporous) and IV (mesoporous). This suggested that the investigated zeolitic materials were mesoporous (4.84nm) and microporous (0.852nm), as well as containing slit/cylindric pores, according to a quench solid density functional theory (QSDFT) adsorption branch model. Zeolitic waste from the oil industry showed good NH4 + sorption properties (removal efciency of 72%), thus becoming a potential adsorbent to be used in the treatment of contaminated aqueous efuents polluted with ammonium ions. Simultaneous waste and water decontamination can be achieved, providing a new tool and enhanced capabilities for environmental remediationKauno technologijos universitetasLietuvos energetikos institutasVytauto Didžiojo universitetasŽemės ūkio akademij

Influence of fluor-oligomeric coat to the surface of steel

Vytauto Didžiojo universitetasŽemės ūkio akademij

Crystal Structure Refinement of Synthetic Pure Gyrolite

Pure calcium silicate hydrate – gyrolite was prepared under the saturated steam pressure at 473 K temperature in rotating autoclave. The crystal structure of synthetic gyrolite was investigated by X-ray diffraction and refined using Le Bail, Rietveld and crystal structure modelling methods. Background, peak shape parameters and verification of the space group were performed by the Le Bail full pattern decomposition. Peculiarities of interlayer sheet X of gyrolite unit cell were highlighted by Rietveld refinement. Possible atomic arrangement in interlayer sheet X was solved by global optimization method. Most likelihood crystal structure model of gyrolite was calculated by final Rietveld refinement. It was crystallographically showed, that cell parameters are: a = 0.9713(2) nm, b = 0.9715(2) nm, c = 2.2442(3) nm and alfa = 95.48(2) º, beta = 91.45(2) °, gamma = l20.05(3) °.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5460</p

Effect of copper content on the properties of graphite-copper composites formed using the plasma spray process

Graphite-copper composite coatings are often used for the production of electrical machines because they are characterized by stable electrical and mechanical properties. The plasma spraying method was used to form such coatings in this work, as we aimed to evaluate the influence of copper content in the initial powders on the properties of graphite‑copper composite coatings. The graphite-copper coatings were deposited on stainless steel and quartz glass substrates, as the copper content of the initial powder ranged from 2 to 60%. As shown by SEM studies, at small amounts of copper (up to 10%) in the initial powder the micro-derivatives of the spherical form are formed on the coatings. Meanwhile, XRD analysis have shown that mechanical stresses due to different thermal expansion coefficients between the coating and the substrate are characteristic for graphite-copper coatings. The measurements of electrical conductivity shown that the maximum electrical conductivity (of 10 S) is obtained when the copper content in the initial powder reaches 20%. Despite the increase of the copper content in the initial powder above 20% the electrical conductivity of the coatings remain constant. The microhardness studies have shown that with the increase of copper content in initial powder from 2 to 60%, the microhardness of graphite-copper composite coatings is reduced by about 2 times, while the plasticity increase from 11 to 19% is observedKauno technologijos universitetasLietuvos energetikos institutasVytauto Didžiojo universitetasŽemės ūkio akademij

Plazmos proceso parametrų įtaka YSZ dangų mikrostruktūrai

Plonos itriu stabilizuoto cirkonio oksido (YSZ) dangos plačiai taikomos šiuolaikinėje technikoje. Dažnai jos sudaromos plazminio purškimo būdu. Tyrimai atlikti taikant nepusiausvirąją oro plazmos technologiją dviem plazminio purškimo režimais priklausomai nuo ištekėjimo iš anodo profilio: Lavalio tūtos – L režimas ir cilindro profilio – C režimas. Dangoms gauti buvo naudojami itriu stabilizuoto cirkonio oksido (10 mol % Y2O3) milteliai (50 – 100 ?m). Buvo tiriama, kaip keičiasi cirkonio oksido miltelių morfologija plazminio purškimo metu, nagrinėjamos plazminiu būdu gautų YSZ dangų charakteristikos priklausomai nuo plazmos proceso parametrų bei naudotų miltelių smulkumo ir jų terminio apdorojimo. Straipsnyje pateikta gautų dangų struktūros, tankio, porėtumo, storio bei kristalitų dydžio priklausomybė nuo plazmos proceso parametrų. Parodyta, kad dirbant cilindrinio ištekėjimo iš anodo režimu, gaunamos didesnio tankio YSZ dangos. Proceso metu cirkonio oksido milteliai visiškai išsilydo kanale ir įgyja rutulio pavidalą. Dirbant Lavalio tūtos režimu, dangų parametrus pagerina išankstinis miltelių terminis apdorojimas 700 ° C temperatūroje. Gautų dangų fazinė sudėtis išlieka tokia pat kaip ir pradinių žaliavų – kubinio ZrO2Yttria-stabilized zirconia (YSZ) powders (50 - 100 mm in diameter) have been used to prepare plasma-sprayed thin ceramic films on the stainless steel and nickel sheets employing non-equilibrium plasma spray technology at atmospheric pressure. The dependency of microstructure of coatings on initial powder characteristics was investigated. Furthermore, effects of various plasma spray conditions on microstructure, crystallite size, phase content of the coatings have been evaluated. Plasma spray zirconium oxide coatings deposited onto different substrates have been characterized using optical microscope, scanning electron microscope (SEM) and X-ray diffractometer (XRD) for study of microstructure and phase analysis as a part of a process optimisation study. The deposits characteristics were compared with the processing parameters and revealed that the deposit characteristics strongly depended on the in-flight particle parameters. The coating sprayed using finer powder displays better structural characteristics than the counterpart sprayed using coarse-grained powder feed. The density of the film increases with the spray temperature. The crystallite size of the film also exhibits a strong dependency on the spray conditions. It was demonstrated how the spray regime affects the thickness, density and porosity of the obtained filmsLietuvos energetikos institutasLietuvos energetikos institutas, [email protected] energetikos institutas, [email protected] energetikos institutas, [email protected] energetikos institutas, [email protected]

Structural and surface analysis of plasma processed zirconia coatings

Lietuvos energetikos institutasLietuvos energetikos institutas, cesnienė@mail.lei.ltVytauto Didžiojo universitetasŽemės ūkio akademij

Functional and microstructural alterations in hydrated and freeze–thawed cement-oil shale ash composites

The oil shale industry generates a large amount of solid waste, the finer fraction of which can be utilized in civil engineering projects. However, for environmental, economic or technological reasons, oil shale is blended with other fuels, resulting in significant changes in the chemical composition of the residual ash. In this laboratory work, the fly ash from the combustion of oil shale with and without biomass in an industrial power plant was used as a binder substitute in cement-based materials to assess the potential of reuse of this ash. The hydration and pore structure of blended cementitious material subjected to long-term hydration and freeze–thawing has been characterized with a range of techniques, such as XRD, TGA and N2 physisorption. The results revealed that the ash type influences the phase assemblage related to the content of ettringite and monocarboaluminate, significantly affecting the volume of gel (1–6 nm) pores and small (10–30 nm) capillary pores. These microstructural changes impact the mechanical strength and water sorptivity properties in an opposite way after both long-term hydration and freeze–thawing. The results showed that the incorporation of ash obtained after combustion with biomass possesses higher mesoporosity and delays the hydration of cement, increases the total volume of gel (<6 nm) and small capillary pores (20–30 nm) of the composition, and deteriorates the functional properties after freeze–thawing