Wyniki wyszukiwania - BazTech

1

Thermal gravimetric analysis of glass fiber reinforced composite for understanding the impact of copper oxide in relation to titanium oxide filler particles

Alam Shahinoor, Chowdhury Mohammad Asaduzzaman

Composites Theory and Practice

|

2021

|

R. 21, nr 1-2

12--21

EN

In this work, the composite samples required to investigate their thermal properties were fabricated employing the conventional hand lay-up technique, followed by a light compression molding process. A fixed weight of plain woven glass fiber and epoxy with four different types of fillers as calcium carbonate (CaCO3), aluminum oxide (Al2O3), magnesium oxide (MgO) and titanium oxide (TiO2) or copper oxide (CuO) of different weights (5, 10 and 15 g) were studied. According to thermal gravimetric analysis (TGA), it was observed that the melting point (Tm) and glass-transition temperature (Tg) are affected by the presence of CuO and TiO2, which indicate the degree of composite crystallinity established by the stronger interfacial interaction by the CuO than that of the TiO2 particles and the amorphous region of the chain. These studies were supported by examination of the surface morphology of the composites by means of scanning electron microscopy (SEM).

2

Effectiveness of the low-level MgO addition in the two-stage sintering of ultrafine alumina

Moskała Norbert, Pyda Waldemar

Materiały Ceramiczne

|

2020

|

T. 72, nr 3

171--180

EN

Submictrometric (~0.1 µm) alumina powders, pure and doped with 0.05% or 0.5% by weight of magnesia, were cold isostatically pressed and two-stage sintered. The preliminary experiment involved selecting the T1 temperature of the two-stage sintering (TSS). This was done by analysing the grain size as a function of relative density during sintering at a constant heating rate. Thereafter, the lower TSS temperature (T2) was set to 25-50 °C below T1, and the dwell time at T2 was assumed to be in the range of 3-12 hours. A final comparison of the density and grain size between the doped and undoped two-stage sintered samples proved that the sintering effect is better for the magnesium oxide doped materials, but also showed that the effect is non-linear, and less magnesia is more beneficial. Finally, an almost fully densified MgO-doped alumina ceramics with an average grain size close to 0.5 microns was obtained. The reference, conventional sintering process (T1/3 h) also resulted in very well densified materials, but with a coarser microstructure.

PL

Submiktrometryczne (~0,1 µm) proszki tlenku glinu, czysty i domieszkowane 0,05% lub 0,5% mas. tlenku magnezu, prasowano izostatycznie na zimno i spiekano dwuetapowo. Eksperyment wstępny obejmował dobór temperatury T1 dwuetapowego spiekania (TSS). Dokonano tego przez analizę wielkości ziarna w funkcji gęstości względnej podczas spiekania ze stałą szybkością ogrzewania. Następnie ustawiono niższą temperaturę TSS (T2) na 25-50° C poniżej T1, a czas przetrzymania w T2 przyjęto w zakresie 3-12 godzin. Końcowe porównanie gęstości i wielkości ziarna pomiędzy domieszkowanymi i niedomieszkowanymi dwuetapowymi próbkami spiekanymi dwuetapowo wykazało, że efekt spiekania jest lepszy dla materiałów domieszkowanych tlenkiem magnezu, ale także pokazało, że efekt jest nieliniowy, a mniejsza ilość tlenku magnezu jest korzystniejsza. Ostatecznie otrzymano prawie całkowicie zagęszczoną ceramikę z tlenku glinu domieszkowanego MgO o średnim uziarnieniu bliskim 0,5 mikrona. Referencyjny, klasyczny proces spiekania (T1/3 godz.) również skutkował bardzo dobrze zagęszczonymi materiałami, ale o bardziej gruboziarnistej mikrostrukturze.

3

ZnO-based terahertz quantum cascade lasers

Sirkeli Vadim

Opto-Electronics Review

|

2019

|

Vol. 27, No. 2

119--122

EN

High-power terahertz sources operating at room-temperature are promising for many applications such as explosive materials detection, non-invasive medical imaging, and high speed telecommunication. Here we report the results of a simulation study, which shows the significantly improved performance of room-temperature terahertz quantum cascade lasers (THz QCLs) based on a ZnMgO/ZnO material system employing a 2-well design scheme with variable barrier heights and a delta-doped injector well. We found that by varying and optimizing constituent layer widths and doping level of the injector well, high power performance of THz QCLs can be achieved at room temperature: optical gain and radiation frequency is varied from 108 cm−1 @ 2.18 THz to 300 cm−1 @ 4.96 THz. These results show that among II–VI compounds the ZnMgO/ZnO material system is optimally suited for high-performance room-temperature THz QCLs.

4

Mechanical properties and cell viability of MgO-reinforced biografts fabricated for biomedical applications

Demirel M.

Acta of Bioengineering and Biomechanics

|

2018

|

Vol. 20, no. 4

83--90

EN

In the present study, biografts were produced by sol gel method by adding different rates of MgO which has bone-like crystal structure and high endurance into different proportions of Ca(NO3)24H2O, KOH, NaNO3, and P2O5 compounds. The biografts were investigated in terms of mechanical and biocompatibility properties. FTIR, SEM and XRD analyses were carried out to examine the chemical characteristics and changes in structural morphology. Mechanical properties were also investigated by conducting hardness and compression tests. In addition, cytotoxicity tests were conducted by using osteoblast cells. While results of FTIR and XRD analyses revealed that all biografts had HA (hydroxyapatite) and β-TCP contents, MgO peaks were also observed in biografts. In SEM images, grains of NonMgO and MgO-10 biografts had sharper edges, pores formed between grains and grain size increase with increasing MgO amount (MgO-20 and MgO-30). It was found that compression stress and hardness values increased as MgO content elevated. From the cytotoxicity tests, no any toxic effect was observed in the syntesized biografts.

5

Dobór i kształtowanie właściwości materiałów ogniotrwałych na bazie MgO

Śnieżek E., Prorok R., Szczerba J.

Materiały Ceramiczne

|

2017

|

T. 69, nr 4

335--342

PL

W artykule omówiono główne aspekty odgrywające kluczową rolę w procesie doboru materiałów ogniotrwałych, które bierze się pod uwagę w trakcie projektowania obmurzy ogniotrwałych. Analizę przeprowadzono na przykładzie modyfikowanych magnezjowych materiałów ogniotrwałych mogących stanowić wykładzinę strefy wysokotemperaturowej pieca obrotowego do produkcji klinkieru portlandzkiego. Przedmiotem pracy były materiały magnezjowe, których głównymi składnikami fazowymi był MgO, CaZrO3 oraz kilku procentowy dodatek MgAl2O4. Omówiono proces powstawania klinkieru portlandzkiego, warunki pracy materiałów ogniotrwałych, główne czynniki korozyjne, równowagi fazowe i właściwości komponentów – MgO, CaZrO3 i MgAl2O4. Otrzymane materiały scharakteryzowano pod kątem ich właściwości fizycznych i odporności korozyjnej. Wskazano rolę CaZrO3 i MgAl2O4 w kształtowaniu właściwości materiałów magnezjowych. Stwierdzono, że MgAl2O4 wpływa korzystnie na kształtowanie właściwości magnezjowych materiałów ogniotrwałych zawierających CaZrO3, podnosząc ich odporność na nagłe zmiany temperatury oraz ułatwiając tworzenie się na ich powierzchni stabilnego napieku ochronnego.

EN

The article discusses the main aspects that play a key role in the refractory selection process and are considered in the design of refractory linings. The analysis was carried out on the example of modified magnesia refractories which could be the high-temperature zone lining of the cement rotary kiln. Magnesia refractories are a subject of the work, in that MgO, CaZrO3 and a few percentage of MgAl2O4 were the main phase components. The process of Portland clinker formation, working conditions of refractory materials, main corrosive factors, phase equilibria, and component properties are discussed. The obtained materials were characterized for their physical properties and corrosion resistance. The role of CaZrO3 and MgAl2O4 in shaping the properties of magnesium materials was indicated. It has been found that MgAl2O4 positively influences the properties of magnesium refractory materials composed of CaZrO3, increasing their resistance to thermal shocks, and facilitating the formation of a stable protective coating on them.

6

Position of Fe ions in MgO crystalline structure

Szczerba J., Prorok R., Stoch P., Śnieżek E., Jastrzębska I.

Nukleonika

|

2015

|

Vol. 60, No. 1

143--145

EN

Magnesium oxide (MgO) is one of the most important raw materials in many branches of industry. Magnesium oxide is a popular refractory raw material because of its high refractoriness and high resistance to basic slags and environment. In many cases, use of MgO is limited by its properties, especially the presence of secondary phases like iron oxides. The amount and distribution of iron oxides can strongly infl uence the technological properties of MgO and depend on the manufacturing method, particularly the heat-treatment process. The aim of the study was to evaluate the infl uence of the heat-treatment process on amount and distribution of iron ions in a magnesium oxide lattice. The 57Fe Mössbauer effect measurements of fused and sintered magnesium oxide samples doped by the iron oxide were conducted. Investigation reveals in both cases the presence of Fe2+ as well as Fe3+ ions. Fe2+ ions occupy Mg2+ octahedral sites in the MgO lattice, whereas the Fe3+ ions are located in highly distorted octahedral coordination. The amount of Fe2+ varies from around 66% for fused samples to 30% for sintered samples.

7

Effect of calcinated magnesite on rheology of bentonite suspensions. Magnesia-bentonite interaction

Cinku K., Karakas F., Boylu F.

Physicochemical Problems of Mineral Processing

|

2014

|

Vol. 50, iss. 2

453--466

EN

In this study, the effect of calcination temperature and time on the structure of calcinated magnesite was investigated. In addition, the effect of calcinated magnesite on rheology when added into bentonite suspension was also examined. Electrokinetic, rheological and stabilization studies including coagulation and gelation tests were performed to explain the mechanism of viscosity increase in bentonite suspension upon addition of the calcinated products. FTIR, SEM, BET analyses and rheological data were used to determine the transition degree of MgCO3 to MgO, and evaluate the structure of MgO and bentonite suspensions. The results from this study showed that specific surface area (SSA) and mean pore radius (MPR) values for the calcinated products were directly affected by the calcination temperature and time. According to the ignition loss and transition ratio from MgCO3 to MgO of the calcinated samples, it was found that the calcination was completed above 800 oC. In order to obtain a bentonite suspension with higher viscosity, interaction of the sufficient amount of MgO particles with bentonite particles were necessary. Based on these results, the formation of gelation and heterocoagulation between MgO and bentonite particles were found to be responsible for these effects.

8

Hydrotermalna hydratacja wybranych kruszyw ogniotrwałych zawierających cyrkonian wapnia

Jastrzębska I., Szczerba J., Prorok R., Śnieżek E.

Materiały Ceramiczne

|

2014

|

T. 66, nr 3

310--315

PL

W niniejszej pracy przedstawiono badanie podatności na hydratację spiekanych i topionych kruszyw ogniotrwałych na bazie związku CaZrO3 oraz układu CaZrO3-MgO, stosowanych do produkcji zasadowych materiałów ogniotrwałych. Skład fazowy badanych kruszyw wyznaczono metodą XRD. Badanie hydratacji przeprowadzono w autoklawie, zgodnie z normą ASTM C 544-92 w warunkach hydrotermalnych w temperaturze 162 °C i przy odpowiadającym jej ciśnieniu autogenicznym pary wodnej. Po autoklawizacji próbki poddano analizie fazowej XRD, termicznej DTA/TG oraz przeprowadzono obserwacje mikroskopowe SEM/EDS. Badania wykazały, że skład fazowy i mikrostruktura kruszyw, ukształtowane podczas jego wytwarzania, mają zasadniczy wpływ na podatność na hydratację. Kruszywa topione, a także zasobniejsze w cyrkonian wapnia oraz uboższe w tlenek magnezu wykazują większą odporność na działanie wody w porównaniu do kruszyw spiekanych.

EN

This work presents a hydration test of sintered and fused refractory aggregates based on CaZrO3 and the CaZrO3-MgO system. The phase composition of starting materials was identified by X-ray powder diffractometry. The hydration test was carried out in an autoclave, according to ASTM 544-92 at a temperature of 162 °C under an autogenous saturated water vapour pressure. After-hydration, the samples were analyzed by the XRD, and DTA/TG methods. The microstructure was observed using a scanning electron microscope combined with an energy-dispersive X-ray spectrometer (SEM/EDS). The results showed that the phase composition and microstructure of aggregates, that were produced during heat treatment, play a key role in controlling their susceptibility to hydration. The fused aggregates and those enriched with calcium zirconate, and impoverished with MgO were found to be less prone to hydration in comparison to the sintered ones.

9

Influence of Hydration on Transport and Storage of Spinel-Based Refractory Raw Materials

Jastrzębska I., Szczerba J., Prorok R., Śnieżek E.

Logistyka

|

2014

|

nr 4

4372--4379, CD6

EN

This work concerns the hydration resistance of spinel MgAl2O4-based aggregates which comprise the common raw materials for the production of refractories. A sintered product along with the melted one were taken for the investigation. The starting materials were characterized in terms of their chemical and phase composition by XRF and XRD methods, respectively. Subsequently, the samples were subjected to hydration test according to ASTM C 554-92. The after-hydration samples were analyzed by XRD and SEM/EDS methods. It was found that sintered spinel aggregates enriched in Mg2+ ions and containing free MgO are highly susceptible to water exposure.

PL

Praca dotyczy badania i oceny odporności na hydratację spiekanych i topionych kruszyw na bazie spinelu MgAl2O4, które stanowią grupę surowców szeroko stosowanych do produkcji formowanych i nieformowanych materiałów ogniotrwałych. Wyjściowe materiały zbadano pod względem ich składu fazowego (XRD) i chemicznego (XRF). Następnie przeprowadzono badanie hydratacji metodą autoklawizacji według normy ASTM C 554-92. Próbki po hydratacji poddano analizie składu fazowego (XRD) i mikrostruktury (SEM/EDS). Badania wykazały, iż kruszywa spinelowe wzbogacone w spinel o nadmiarze jonów Mg2+ i zawierające wolny MgO wykazują największą zdolność do hydratacji.

10

Wpływ rodzaju surowców magnezjowych na właściwości fizyczne i termomechaniczne betonów zasadowych

Jastrzębska I., Szczerba J., Madej D.

Materiały Ceramiczne

|

2013

|

T. 65, nr 3

327--331

PL

W pracy przedstawiono zależności występujące pomiędzy podatnością na hydratację surowców magnezjowych oraz ich składem chemicznym a właściwościami fizykochemicznymi oraz termomechanicznymi betonów przygotowanych na ich bazie. Do badań użyto czterech rodzajów surowców magnezjowych o zróżnicowanym składzie chemicznym. Surowce poddano badaniu podatności na hydratację w warunkach hydrotermalnych. Następnie przygotowano na ich bazie betony i wykonano badania wytrzymałości na zginanie w podwyższonych temperaturach oraz w temperaturze otoczenia, wytrzymałości na ściskanie, gazoprzepuszczalności, porowatości otwartej oraz gęstości pozornej.

EN

In this work a correlation between hydration susceptibility and chemical composition of magnesia raw materials and physico-chemical, thermo-mechanical properties of castables made of these magnesia raw materials was discussed. The four types of magnesia raw materials of different chemical compositions were selected to examine. First, susceptibility to hydration of magnesia raw materials was determined under hydrothermal conditions. Then castables were prepared with the use of the selected magnesia raw materials. Finally, the castables were tested to determine moduli of rupture at room and elevated temperatures, cold crushing strength, permeability, open porosity and apparent density.

11

Preparation and properties of porous carbon material containing magnesium oxide

Przepiórski J., Czyżewski A., Kapica J., Casa-Lillo M. A. de la

Polish Journal of Chemical Technology

|

2011

|

Vol. 13, nr 4

42-46

EN

Porous carbons loaded with magnesium oxide were prepared through one-step process. Poly(ethylene terephthalate) and natural magnesite were used as carbon source and MgO precursor, respectively. An impact of a temperature and relative amounts of raw components used for preparations on the textural parameters of resulting hybrid materials is presented and discussed. As found, pore structure parameters tend to decrease along with MgO loading and temperature used during preparation process. Micropore area is the parameter being reduced primarily.

12

The effect of modifiers and precipitation conditions on physicochemical properties of MgCO3 and its calcinates

Pilarska A., Paukszta D., Szwarc K., Jesionowski T.

Physicochemical Problems of Mineral Processing

|

2011

|

Vol. 47

79-90

EN

The effects of modifiers and process conditions on synthesis of magnesium oxide by the carbonatization method and properties of the product are studied. Magnesium carbonate obtained from magnesium hydroxide and carbon dioxide was subjected to thermal decomposition at 800 C. The reaction of precipitation was performed checking the influence of temperature, rate and mode of reagents introduction, type and concentration of the modifier. The modifiers were the non-ionic compounds from the group of poly(ethylene glycols). The magnesium oxides produced were characterised by determination of their dispersivemorphological properties, wettability profiles, specific surface area, total volume and mean size of pores. The products were also subjected to identification by the X-ray diffraction method and TG/DTA analysis. The results revealed a significant impact of the concentration and type of modifiers on the physicochemical properties of MgO samples obtained and permitted selection of the best products for particular applications.

13

Synthesis of MgO in magnesium hydroxide carbonatisation process

Pilarska A., Jesionowski T.

Physicochemical Problems of Mineral Processing

|

2011

|

Vol. 46

83-94

EN

A method for synthesis of magnesium oxide by calcination of magnesium carbonate, obtained by carbonisation of magnesium hydroxide with carbon dioxide, is presented and the products obtained are characterised. The influence of the following experimental conditions on the final product properties was established: pH of the reaction medium, mode and rate of reagents supply. The final products were characterised by determination of their dispersion properties, wettability profiles (with water), specific surface area (BET), size and volume of pores. The products were identified by the X-ray diffraction method. The results proved a significant influence of the reaction conditions on the physicochemical parameters of the final magnesium oxide.

PL

Przedstawiono badania nad otrzymywaniem tlenku magnezu z użyciem wodorotlenku magnezu i ditlenku węgla metodą karbonizacji. Otrzymany węglan magnezu poddano termicznemu rozkładowi, prowadzonemu stopniowo w odpowiednich warunkach temperaturowych do uzyskania produktu finalnego - tlenku magnezu. W reakcji strącania uwzględniono następujące warunki eksperymentalne: pH medium reakcyjnego, temperaturę, sposób i szybkość dozowania reagentów. Określono właściwości dyspersyjne oraz profile zwilżalności w układach wodnych tlenku magnezu. W celu sprawdzenia charakteru adsorpcyjnego wytworzonych produktów wyznaczono wielkość powierzchni właściwej BET, wielkość i objętość porów. Ponadto produkt poddano identyfikacji metoda rentgenograficzną. Dowiedziono istotnego wpływu warunków prowadzenia procesu na parametry fizykochemiczne otrzymanego MgO oraz wyłoniono produkty o najbardziej reprezentatywnych właściwościach.

14

Structure studies on nanocrystalline powder of MgO xerogel prepared by the sol-gel method

Dercz G., Prusik K., Pajak L., Pielaszek R., Jmalinowski J. J., Pudlo W.

Materials Science Poland

|

2009

|

Vol. 27, No. 1

201--207

EN

Structure studies were performed on nanocrystalline powder of MgO xerogel prepared by the sol-gel technique, producing high purity, chemically homogeneous materials of relatively high specific surface area. Magnesium methoxide was used as an MgO precursor. The wet gel was dried under conventional conditions, yielding xerogel with periclase phase; the only crystalline form of magnesium oxide. The X-ray diffraction, scanning and transmission electron microcopies were used as the tools of structure analysis. The Toraya PRO-FIT procedure and the Rietveld refinement method were applied for X-ray data analysis. Both techniques apply the Pearson VII function for the description of line profiles. The gamma crystallite size distribution was determined using the FW(1/5)/(4/5)M method proposed by Pielaszek. The obtained values of and ? (measure of polydispersity) of particle size parameters are equal to 7.1 nm and 2.1 nm, respectively, whereas the average crystallite size, estimated by the Williamson- Hall procedure, was equal to 7.5 nm. The Rwp, and S fitting parameters obtained from the Rietveld refinement were equal to 6.4% and 1.8, respectively. This would seem the most satisfactory result, when considering the nanosize of MgO crystallites and a very probable presence of amorphous phase.

15

Hydrogen atoms at the palladium surface, at the MgO surface and at the Pd-MgO metal-support boundary. Towards computer modelling of the spillover effect

Bartczak W.M., Stawowska J.

Materials Science Poland

|

2006

|

Vol. 24, No. 2/1

421--432

EN

The work is devoted to computer modelling of interactions of atomic hydrogen with palladium and MgO surfaces, and with Pd atoms adsorbed on MgO surface. Quantum calculations were performed using the methods of the Density Functional Theory (DFT) with gradient-corrected functionals for electron exchange and correlation. The potential energy surfaces were calculated for a hydrogen atom interacting with Pd and MgO surfaces. The results indicate an easy (0.17 eV activation barrier) diffusion of hydrogen atoms over the metal surface. A possibility of migration of H atoms from the metal surface onto the MgO support surface (the "spillover effect") is discussed. It was found that the transfer of a hydrogen atom from the vicinity of a Pd atom to O sites of the MgO surface results in the energy gain of the order of 0.5 eV. The transfer, however, is an activated process with the activation energy about 0.8 eV.