Mixture Of Magnesium Research Articles

Characterization of partial wetting by CMAS droplets using multiphase many-body dissipative particle dynamics and data-driven discovery based on PINNs

The molten sand that is a mixture of calcia, magnesia, alumina and silicate, known as CMAS, is characterized by its high viscosity, density and surface tension. The unique properties of CMAS make it a challenging material to deal with in high-temperature applications, requiring innovative solutions and materials to prevent its buildup and damage to critical equipment. Here, we use multiphase many-body dissipative particle dynamics simulations to study the wetting dynamics of highly viscous molten CMAS droplets. The simulations are performed in three dimensions, with varying initial droplet sizes and equilibrium contact angles. We propose a parametric ordinary differential equation (ODE) that captures the spreading radius behaviour of the CMAS droplets. The ODE parameters are then identified based on the physics-informed neural network (PINN) framework. Subsequently, the closed-form dependency of parameter values found by the PINN on the initial radii and contact angles are given using symbolic regression. Finally, we employ Bayesian PINNs (B-PINNs) to assess and quantify the uncertainty associated with the discovered parameters. In brief, this study provides insight into spreading dynamics of CMAS droplets by fusing simple parametric ODE modelling and state-of-the-art machine-learning techniques.

Stacking faults of the hydrous carbonate-containing brucite (HCB) phase in hydrated magnesium carbonate cements

Recently, a hydrous carbonate-containing brucite (HCB) with an approximate composition of MgCO3·35 Mg(OH)2·H2O was postulated as hydration product of binders based on mixtures of reactive magnesia and hydromagnesite (Mg5(CO3)4(OH)2·4H2O). X-ray diffraction showed that the 001 reflection of this phase was split into two reflections at 20 °C, whereas at 60 °C only one reflection occurred. Rietveld refinement revealed that the X-ray pattern of the HCB-phase could be fitted well when a random displacement (stacking faults) and a movement of the layers in x, y and z direction were allowed. The presence of water and/or carbonate leads to different distances between the layers, thus causing the splitting of the 001 reflection. At 60 °C, only carbonate is included in the brucite structure, leading to a similar distance between all brucite layers. The assignment of the additional reflection appearing at 20 °C to a separate, unknown hydrated magnesium carbonate, as suggested in earlier studies, can be excluded.

Green Spectrophotometric Determination of Organophosphate in Selected Fruits and Vegetables.

A simple, sensitive, precise, and environmentally safe spectrophotometry method was developed and validated for the determination of organophosphate in various fruits and vegetables using a UV-Visible spectrophotometer using a magnesia mixture. The volume of reagent used for analysis and the stability of the color complex were also optimized. The drug showed a stable white color complex at 420 nm. The greenness of the methods was estimated using an ecoscale (84), the Green Analytical Procedure Index, and AGREE (0.89), which were found to be excellent green method based on spectrophotometric determination. The method was validated using ICH guidelines and has acceptable values for linearity (0.5-2.5 mg/ml), accuracy (98.5-102.5%), precision, robustness, limit of detection (0.16 mg), and limit of quantification (0.486 mg). The concentration of the organophosphate in the analyzed sample was in the range of 0.003 to 2.45 mg. Altogether, the proposed green analytical method was found to be a simple, selective, sensitive, accurate, and ecofriendly method for the analysis of organophosphate in various fruits and vegetables.

Accelerated thermal history analysis of light-burnt magnesium oxide by surface properties

Homogeneity is of utmost importance in some applications of light-burnt magnesia (LBM), such as shrinkage compensation of cement composites, because if it is not detected reliably before application, it causes unpredicted expansion and cracking. This paper presents an accelerated method for homogeneity and thermal history detection in LBM. The proposed method provides an equation for computing the weighted mesopore probability distribution of light-burnt magnesia (LBM). Then, it deconvolutes the distribution's peaks by Lorentz peak functions to analyze homogeneity. The method's performance is evaluated by examining LBM samples produced by calcining magnesite at four temperatures and walking through several scenarios, including the mixtures of these samples. The results confirmed that the method accurately detects inhomogeneity and gives calcination temperatures and percentages of fractions of magnesia mixtures. These findings make it possible to prevent unpredicted expansion in cement composites incorporating expansive magnesia and can be employed to detect inhomogeneities in other porous materials applications.

Development of New Composites Using Industrial by Products

In this paper thesis describes an experimental investigation of magnesium based cement mortar which consists of fly ash, magnesium oxide (MgO), magnesium Phosphate (MgPO4) and Phosphate tailings. This magnesia based cements are emerged as a viable alternative to Portland cement, with both technical and sustainability advantages. This study aims to use the mixture of cement, fly ash and magnesia. The major drawback of delayed setting time can be eliminated with the use of magnesia based cement. Hence, in this study different admixtures such as magnesium oxide, magnesium phosphate, phosphate tailings are attempted. Initial and final setting time of plain cement, fly ash cement and magnesia based cement are determined and found that the small dosage of magnesium compound reduced the setting time. Further, magnesia based cements are reported to be used along with sea water without much negative effect. In view of all these, this study proposed a magnesia based cement as an alternative for conventional Portland cement. Industrial wastes such as fly ash, and phosphate tailings are used in this study.

Magnesia compositions with technogenic fillers

The paper presents the results of researching magnesia compositions, which contain caustic magnesite and porous technogenic fillers. The research is aimed at creating resource-saving magnesia materials with the density less than 1000 kg/m3. The dependence of the magnesia composition’s density and strength on the size of arboreal particles is exposed. The increase of the particles’ size lowers the density of materials, but worsens the moulding characteristics. The influence of ash microsphere on the structural and mechanical properties of magnesia materials is found out. The content of hollow particles in the magnesia mixture is restricted due to the decrease of the raw materials’ mass plasticity. The mathematical models, presenting the dependences of moulding mass’ properties and composition density on the filler’s composition, are obtained. The compositions of raw materials’ mixtures for getting materials with a reduced density are determined. Moulding masses, which contain the integral filler (20-50% of arboreal particles with the size 0.63-2.5 mm and 50-80% of the ash microsphere), are preferable. The combination of fibrous and spherical hollow particles provides mouldability of the raw materials’ mixture as well as a reduced density of magnesia compositions. The electronic microscopy is used to research the materials’ structure.

Preparation of γ-Al2O3/α-Al2O3 ceramic foams as catalyst carriers via the replica technique

This work describes an effective method for the preparation of open-cell ceramic foams for their further use as catalyst supports. The polyurethane sponge replica technique was applied using a ceramic suspension based on a mixture of α-alumina, magnesia and titania and polyvinyl alcohol solution as a liquid component. The polyurethane sponge was etched with NaOH and covered with colloidal silica to obtain better adhesion of the slurry to the walls of the polymeric material onto it. The surface area of the ceramic carrier was increased by adding a layer of γ-alumina. Deposition of an active catalytic phase (Pt) was done by impregnation. Properties of the carriers and the final catalyst were investigated by a number of physico-chemical methods such as TEM, SEM, XRD and computer tomography. Hydrogenation of ethyl benzoylformate was performed to elucidate the catalytic properties of foam catalysts illustrating their applicability.

НАУКОВЕ ОБҐРУНТУВАННЯ РЕГУЛЮВАННЯ ПРОЦЕСІВ ЕВТРОФІКАЦІЇ ВОДНИХ ОБ’ЄКТІВ (НА ПРИКЛАДІ РІЧКИ ВОРСКЛИ)

У статті проведено дослідження процесу евтрофікації водних екосистем. Визначено, що нині усвіті активно здійснюється розробка теоретичних основ і пошук практичних заходів з боротьби змасовим розвитком ціанобактерій у поверхневих водоймах. Водночас питання використання бакте-рій для очищення поверхневих водних об’єктів є на сьогодні недостатьо вивченими, постає потребав дослідженні евтрофікаційних процесів водних об’єктів при використанні різних методів біологіч-ного очищення. Зважаючи на це, метою роботи стало дослідження хімічних та біологічних методіввідновлення водних об’єктів через зменшення в них кількості ціанобактерій, на основі чого наданінаукові рекомендації щодо боротьби із «цвітінням» поверхневих водоймищ. Методика дослідженнявключала проведення аналітичних, натурних та лабораторних досліджень, розрахункову частину.Для дослідження процесу евтрофікації води в річці Ворскла було взято проби на глибині 0,2‒0,5 м відповерхні водойми (в різних районах м. Полтави та на околицях міста). На першому етапі дослі-дження вивчали хімічні методи боротьби із «цвітінням води». Найкращий результат спостерігалипри застосуванні перманганату калію (0,2*106 кл/л), молібденової рідини (0,3*106), магнезіальної су-міші (0,4*106), хлору (0,5*106) та хелату заліза (0,6*106). На другому етапі дослідження проводилививчення пробіотиків для боротьби із «цвітінням води» на наявність токсичної дії до ціанобактерій.З’ясовано, що використання біологічних методів очищення водних об’єктів від ціанобактерій є більшефективним порівняно з хімічними методами, зокрема використання пробіотику Світеко-Агробіотик-01, який ефективно знищує ціанобактерії до 94 %. Такий результат отримано при за-стосуванні перманганату калію (0,2*106), але негативним наслідком цього є те, що використанняхімічних методів загалом створює вторинне забруднення водоймищ. Також визначено ефективністьінших хімічних методів боротьби із «цвітінням води»: молібденової рідини (ефективність – 91 %),магнезіальної суміші (88 %), хлору (85 %) та хелату заліза (82 %). Дещо гірші результати дало за-стосування нітрату срібла (70 %) та хлориду барію (41 %). Найбільша кількість синьо-зелених водо-ростей залишилася при дії на останні сульфату алюмінію спільно з мідним купоросом (26 %). Прове-дені дослідження є основою розробки комплексних систем очистки водних екосистем екологічно без-печними методами від ціанобактерій, що є одним із пріоритетів розвитку урбанізованих територійта сталого розвитку суспільства.

Characterizing properties of magnesium oxychloride cement concrete pavement

The performance of magnesium oxychloride cement concrete (MOCC) in road engineering in the arid region in northwest China was investigated over a two-year period. Two categories of MOCC pavement, light-burnt magnesia concrete road (Road-L) and dolomite concrete road (Road-D), were prepared with light-burnt magnesia and a mixture of light-burnt magnesia and caustic dolomite (1:3 by mass), respectively. Variations in the properties of the MOCC pavement, such as compressive and flexural strength, mineralogical phase, and microstructure, after being exposed to two rainy seasons in the field were monitored. The compressive strength of the cored samples were conducted after being aged for 28 d, and the compressive and flexural strength were tested at ages of 1, 2, 3, 28, 90, 180, 270, 360 and 720 d. The mineralogical phase and microstructure of the pavement were also analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results demonstrate that MOCC pavement obtained desirable compressive and flexural strengths after curing for 3 d for Road-L and 28 d for Road-D. Both of the compressive and flexural strength of Road-L and Road-D decreased slightly after experiencing two rainy seasons, with the major hydration products being 5Mg(OH)2·MgCl2·8H2O (Phase 5) and 3Mg(OH)2·MgCl2·8H2O (Phase 3). The decomposition of Phase 5 is mainly responsible for reducing the mechanical strength of the MOCC pavement.

TOXICITY OF GRAPHENE NANOPARTICLES WITH SODIUM COPPER CHLOROPHYLLIN OR MAGNESIUM CHLOROPHYLLIN AND EFFECT ON LEVELS OF ACID AND ALKALINE PHOSPHATASE ENZYME OF PEACH FLY, Bactrocera zonata (DIPTERA: TEPHRITIDAE)

Graphene nanoparticles are one of the most attractive nanomaterials forcommercialization applications. They have been widely used for antimicrobial, electronic andbiomedical products. In this review, The exposure time to light plays an important role in mortalitypercentage, the percentage mortality increase when the exposure time increase and there an inverserelationship between concentration with the exposure time. Photoactive compound magnesiumchlorophyllin had more significant effect on adult Bactrocera zonata after exposure to sunlight thanmagnesium chlorophyllin with graphene nanoparticles so that there was no benfit to use the mixture ofmagnesium chlorophyllin with graphene nanoparticles, magnesium chlorophyllin was more effeciantthan Copper chlorophyllin with graphene nanoparticles or Copper chlorophyllin. Level of acidphosphatases in the homogenate of Bactrocera zonata, After exposure to sunlight for two hours aftertreated by compound Copper chlorophyllin or Magnesium chlorophyllin, results showed high increase(52.44%, 40.71%). After treated by compound Copper chlorophyllin with graphene nanoparticle orMagnesium chlorophyllin with graphene nanoparticle, the changes in alkaline phosphatases aftertreated by compound Copper chlorophyllin show limited rduction (-16.28%), on the other handMagnesium chlorophyllin showed high incrase (77.14%) relative to control

Effect of temperature and magnesia on phase transformation kinetics in stoichiometric and non-stoichiometric cordierite ceramics prepared from kaolinite precursors

The influence of temperature and magnesia content on the formation of phases and their transformation kinetics in stoichiometric and non-stoichiometric cordierite ceramics prepared from Algerian kaolinite precursors was investigated. High-temperature X-ray diffraction was used to study the formation of phases and their transformations. Non-isothermal differential thermal analysis was used to determine kinetic parameters for the formation of μ and α cordierite. Activation energies were calculated by Kissinger, Boswell, and Ozawa equations. The Augis–Bennett and Matusita equations were used to calculate the mode of crystallization (n) and dimension of growth (m) parameters, respectively. The synthesized materials showed similar phase transformations, which finally led to the formation of cordierite in stoichiometric kaolinite–magnesia mixture, and cordierite along with other phases in kaolinite–magnesia mixture containing excess magnesia. The activation energy for the formation of α cordierite was higher than that of μ cordierite. Energies of formation of μ and α cordierite phases in the non-stoichiometric samples were higher than those in the stoichiometric sample. The activation energy was less sensitive to the calculation method; however, it changed significantly with MgO content. Activation energies between 573 and 964 kJ mol−1 were obtained. Magnesia changed the crystallization mode and crystal growth dimension. The kinetic parameters n and m, for the formation of μ or α cordierite, had values between 2 and 3.

An experimental investigation of hydration mechanism of the binary cementitious pastes containing MgO and Al2O3 micro-powders

The reactivity of the binary mixtures of reactive magnesia and hydratable alumina micro-powders with various compositions was investigated by calorimetric method, X-ray diffraction, simultaneous DSC–TGA with thermal evolved gas analysis–mass spectrometry and scanning electron microscope observations. The effect of the MgO/Al2O3 molar ratio (2:1, 1:1 and 1:2) and temperature on the hydration behavior of pastes has been explored using the TAM Air isothermal calorimetry system at 25 and 50 °C. Some structural aspects of a M–A–H (M≡MgO, A≡Al2O3, H≡H2O) binding phase formed upon the hydration of MgO–Al2O3 micro-powders at different curing time have been explored. The main hydrate considered to be important in this system is hydrotalcite Mg6Al2CO3(OH)16·4H2O formed via the isomorphous substitution of Mg2+ ions by trivalent Al3+ one in the brucite-like sheet. This was expressed as a systematic shift of the peak at 2-theta value corresponding to the (003) reflection. Since both hydrotalcite and brucite are identified in the hydrating samples, the thermal stability of hydroxyls in these hydration products can be placed in the decreasing order as follows: (Mg2Al)–OH-hydrotalcite group > (Mg3)–OH-brucite group > (Mg3)–OH-hydrotalcite group.

Thermal and tribological characterizations of millscale-particles-reinforced ceramic matrix composites

ABSTRACTThis paper evaluates some basic functional properties of iron-millscale-reinforced ceramic matrix composites (CMCs) as potential material for automobiles and aircraft brake pads’ application. The particulate CMCs were produced by the powder metallurgy method. Iron millscale particles’ addition varied from 3 to 18 wt.% in a matrix comprising a mixture of silica, magnesia and bentonite. After sintering, the composites were subjected to coefficient of friction (COF), wear, thermal and microstructural characterizations. Microstructure of the composites showed a uniform distribution of millscale particles in the ceramic matrix with a strong interfacial bonding between the particles. The composites demonstrated a comparatively high resistance to wear, appreciable COF (0.506–0.561) and a modest thermal conductivity (0.39–0.53 W/m K) coupled with high thermal stability. Contributions to these superlative performances were provided by the high level of friction induced on composites’ surfaces and strong interfacial bonding developed during sintering.

Effects of SnO2 Addition on the Synthesis of Magnesium Aluminate Spinel Microplatelets

In order to prepare platelet-like spinel expected as the reinforcing phase, different amounts (5 – 20 at %) of SnO2 were added into the mixture of magnesia and alumina platelets, and then heated at 1300 – 1600 °C for 5 h. Effects of SnO2 addition on the synthesis of magnesium aluminate spinel microplatelets were investigated. The synthesized spinel was characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Spinel platelets like “sesame cookie” formed derived from platelet alumina based on the template process. The highest spinel content in samples with 10 % of SnO2 addition achieved. The amount of Al2O3 and SnO2 in solid solution and degree of orneriness for spinel depended on SnO2 addition.DOI: http://dx.doi.org/10.5755/j01.ms.24.1.17530

Phase formation and crystallization kinetics in cordierite ceramics prepared from kaolinite and magnesia

In this work, Algerian kaolinite, a naturally occurring clay mineral, was used as low-cost precursor for the synthesis of cordierite ceramics. The kaolinite was mixed with synthetic magnesia, and the mixture was ball milled and reaction sintered in the temperature range 900–1350°C for 2h. Thermogravimetry (TG), differential thermal analysis (DTA), dilatometry, high temperature x-ray powder diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) complementary techniques were used to analyze sintering behavior, characterize phase transformations, and investigate crystallization kinetics. Milling the kaolinite and magnesia mixture for 10h yielded a homogenous powder, decreased the average particle size, and improved the roundness of particles. Different crystalline phases were present in the samples sintered in the temperature range 900–1150°C, the cordierite phase started to crystallize at 1200°C, and the formation of highly dense cordierite (99%) was complete at 1250°C. The activation energy values for cordierite formation calculated using Kissinger, Boswell, and Ozawa methods were found to be equal to 577, 589, and 573kJ/mol, respectively. The kinetic parameters n and m had values close to 2. Bulk nucleation with a constant number of nuclei was the dominant mechanism in cordierite crystallization, followed by two-dimensional growth controlled by interface reaction.

Remarkable mechanical enhancement achieved by interfacial strengthening of organic/inorganic/fiber composites

In this study, a series of organic/inorganic composites were fabricated by melt-mixing ultra-high molecular weight polyethylene (UHMWPE) powder with a mixture of magnesia, potassium di-hydrogen phosphate and water. The microstructure and chemical composition of the composites were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Three point bending tests showed that the flexural strength and toughness of the composites were improved with the increase of polymer content. The flexural strength of the composite with 25.0wt% UHMWPE was 7.7MPa, and can be dramatically enhanced to 21.1MPa by incorporating only 0.1vol% of oriented thermotropic liquid crystalline copolyester (TLCP) fibers. The improvement is due to the enhanced interfacial bonding between the polymer and fibers, which was much stronger than that between the inorganic phase and fibers, making the fibers adequately contribute to the mechanical strength of the three-component composite. Our results demonstrated that the interfacial strengthening between fiber and inorganic matrix achieved by interpenetrated organic phase helps to establish a strong composite system.

Rapid phase mapping in heat‐treated powder mixture of alumina and magnesia utilizing cathodoluminescence

Scanning electron microscope–cathodoluminescence (SEM‐CL) analysis was carried out for the rapid phase identification of a single particle with the size of approximately 100 µm consisting of alumina (Al2O3) and spinel (MgAl2O4) phases. We selected this particle as the analyte because Al2O3 and MgAl2O4 are typical inclusions in steel, and their identification is important for steel production. Samples were prepared by pressing a mixture of Al2O3 and magnesia (MgO) powders heated at 1300 °C and copper powder into a pellet. The formation of a MgAl2O4 phase in the powder mixture of Al2O3 and MgO heated at 1300 °C was confirmed by X‐ray diffraction analysis. CL images of samples were obtained using a camera attached to a SEM. We confirmed that Al2O3 and MgAl2O4 phases in a CL image produced blue and green luminescence, respectively, by comparing the CL image with elemental mappings of aluminum and magnesium in the sample obtained using an energy‐dispersive X‐ray detector attached to a SEM. We also observed the shift of a phase boundary between Al2O3 and MgAl2O4 with dozen micrometers scale by obtaining CL images of samples containing a mixture of Al2O3 and MgO powders heated at 1300 °C with different heat‐treatment durations. The time required to obtain a CL image was 1 s. Thus, SEM‐CL analysis will contribute to the rapid phase identification of Al2O3 and MgAl2O4 in a single particle. Copyright © 2017 John Wiley & Sons, Ltd.

Fused dolomite-magnesia co-clinker for fired dolomite refractories

In this work a new method of obtaining doloma-magnesia co-clinker, which involves fusing a mixture of dolomite decarbonate and caustic magnesia, has been presented. Fused dolomite clinker and fused doloma-magnesia co-clinker have been prepared from high purity raw materials. The properties of a fired material obtained from such co-clinker were compared with a product obtained from fused dolomite clinker without any addition of MgO and with a product enriched with magnesium oxide in the traditional way – by substituting the finest grain fractions with magnesia clinker. It has been proved that it is possible to obtain a fired doloma-magnesia material based on fused doloma-magnesia co-clinker characterized by high chemical purity as well as high resistance to corrosion, hydration and thermal shocks.

Calorimetry and other methods in the studies of reactive magnesia–hydratable alumina–microsilica hydrating mixtures

The reactivities of the binary and ternary mixtures of reactive magnesia (MgO≡M), hydratable alumina (Al2O3≡A) and microsilica (SiO2≡S) micropowders were investigated by calorimetric method and other analytical techniques (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential thermal/thermogravimetric (DTA-TG) analysis and scanning electron microscope (SEM) observations). Effect of water/solid mass ratio and temperature on the hydration behavior of the M–A, M–A–S, M–S, A–M–S and A–S hydratable binders were established. The methodological considerations on both in situ and ex situ mixing techniques have also been taken. The initial mixing peak was due to wetting of the binder particles and initial dissolution reactions. A second, extensive heat peak was associated with the formation of crystalline and noncrystalline hydration products, i.e., brucite Mg(OH)2, magnesium aluminate hydrate (MAH; H≡H2O)-like phase, magnesium silicate hydrate (MSH)-like phase and magnesium aluminum silicate hydrate gels (MASH). Negligible heat was evolved during the hydration reaction of A–S mixture, and the second reaction peak was not observed. Nevertheless, the presence of Al2O3 and SiO2 in other combinations contributes to the consumption of Mg(OH)2 which was formed during the initial stages of hydration and leads to the formation of cementitious products, like M–A–H, M–S–H and M–A–S–H.

Influence of parameters of high-energy ball milling on the synthesis and densification of magnesium aluminate spinel

This study investigated the effect of planetary ball mill parameters on the particle size of a powder mixture of alumina and magnesia, the composition of synthetic magnesium aluminate spinel (MAS), and the subsequent densification of MAS. The results show that the particle size of the milled powders decreases gradually from 32.39 μm to 11.69 μm with the increase of milling time from 1 h to 7 h at milling speed of 120 rpm. The particle size of the milled powders decreases gradually from 42.92 μm to 9.00 μm as the milling speed was increased from 60 rpm to 240 rpm at a milling time of 3 h. Only a spinel phase can be obtained from these calcined powders when the starting powders of the calcined powders are milled for more than 1 hour or at above 60 rpm. The relative density and flexural strength of the sintered products exceed 86.67% and 105 MPa, respectively.