Magnesium Particles Research Articles

Obtaining particles with the structure Mg@C and (Mg@C)@Pd, their properties and stability in the hydrogenation/dehydrogenation processes

In this work, we studied the change in the properties of powders with a core (magnesium) – shell structure (carbon and carbon/palladium) in the process of hydrogenation/dehydrogenation with hydrogen (99.995 wt%). Magnesium powders were obtained by plasma chemical synthesis in an atmosphere of argon containing a small amount of hydrogen (2–3 at.%) and nitrogen (8–9 at.%), when performing a low-frequency arc discharge between a tungsten electrode and a magnesium melt. The shell (carbon and carbon/palladium) was deposited in a plasma generator with vortex and magnetic stabilization. For all samples, a decrease in the sorption capacity of hydrogen was observed as a result of successive cycles of sorption and desorption reactions. It was found that the reason for this fall is associated with the formation of the MgO and Mg(OH)2 phase, which prevents the diffusion of hydrogen. The carbon shell provides a more complete hydrogenation of the magnesium particles, and an additional palladium shell increases the resistance to cyclic hydrogenation/dehydrogenation and reduces the temperature of these processes. According to the data obtained, powders with particles (Mg@C)@Pd can absorb the largest amount of hydrogen (6.9 wt%) for the duration of 5 cycles, after which the protective shell of the particles begins to collapse and a loss of sorption capacity is observed.

Dynamics of cavitation zone development during sonication of suspensions of magnesium particles

The cavitation activity during ultrasonic treatment of magnesium particles has been investigated. The cavitation activity recorded in a continuous mode of ultrasonic treatment altered in a wide range at constant output parameters of the generator. The rate and nature of cavitation activity variation depended on the mass fraction of particles in the suspension. It has been demonstrated that during the ultrasonic treatment of magnesium aqueous suspensions it is possible to determine the following stages: growth of cavitation activity, reaching a maximum followed by a decrease and reaching a plateau (or repeated cycles of increasing or decreasing cavitation activity). The complex nature of the cavitation activity dynamics is associated with the participation of hydrogen released as a result of the chemical interaction of magnesium particles with water in the formation of the cavitation zone. The magnesium particles modified with ultrasound were characterised with the use of scanning electron microscopy, X-ray phase analysis and thermal analysis. It has been found that ultrasonic treatment of magnesium particles resulted in the formation of magnesium hydroxide and magnesium hydride phases.

Experimentation and kinetic modeling of low-temperature oxidation of magnesium particles for the production of energy with low environmental impact

Future lack of fossil fuels and global warming stimulate researches on new renewable sources of energy, especially for transportation. With high energy densities, metals appear to be relevant energy carriers. In this study, magnesium powder was considered as a metal fuel for energy production through slow oxidation. Temperature Program Oxidation experiments of magnesium powder were performed using thermogravimetric analyses under four low heating rates (1, 2, 3 and 5 °C min−1). The influence of the particle size was investigated by testing three size fractions (20–50, 50–71 and 71–100 µm). Initial and fully or partially oxidized particles (stopping the reaction at selected conversion rates) were characterized using optical microscopy analyses, which highlighted the different stages of the oxidation mechanism. A three-step kinetic model involving heat transfers was finally proposed to describe the slow oxidation of magnesium and to extract optimal values of the kinetic parameters.

Blast enhancement from metalized explosives

Experiments are carried out to determine the effects of particle size and mass loading on the free-field blast wave from spherical, constant volume metalized explosive charges. The charges are comprised of gelled nitromethane with uniformly embedded aluminum, magnesium, or glass particles. Particle sizes are varied over an order of magnitude with particle mass fractions up to 50%. Peak blast overpressures are directly measured within the fireball with piezoelectric pressure gauges and outside the fireball are inferred by tracking the velocity of the blast wave and using the Rankine–Hugoniot relation. With the addition of inert particles, the peak blast overpressure is initially mitigated, but then recovers in the far field. For charges with reactive particles, the particles react promptly with oxidizers in the detonation products and release energy as early as within the first few hundred microseconds in all cases. The particle energy release enhances the peak blast overpressures in the far field by up to twice the values for a constant volume charge of the baseline homogenous explosive. By plotting the peak blast overpressure decay as a function of energy-scaled distance, it is inferred that at least half of the particle energy release contributes to the blast overpressure in the far field of higher mass loadings, and nearly all of the particle energy for a particle mass fraction of 10%. For aluminum, the blast augmentation is not a systematic function of particle size. This observation implies that conventional models for particle combustion that depend on particle surface area are not appropriate for describing the rapid aluminum reaction that occurs in the extreme conditions within the detonation products, which influences the blast wave propagation.

Influence of various types of clays on velocity dependence of friction composites

The stick–slip phenomena of various types (halloysite, montmorillonite and wollastonite) of clay-based composite friction materials were evaluated in terms of their velocity-dependent friction response. Scanning electron microscopy of the contact patches suggested breakage of contact plateaus in the composites with halloysite, whereas relatively small contact patches were developed in montmorillonite-based friction composites. The presence of relatively harder ingredients such as magnesium oxide and iron particles on the worn surface have contributed to the stick–slip phenomenon. The presence of wollastonite in the composites leads to the ploughing effect during sliding. The intensity of creep groan remained controlled by the shear strength of the interfacial junction involving asperity contact/welding whereas dynamic groan remains predominated by the stiffness of the composites.

Effects of Particle Size and Concentration of Magnesium Oxide on the Lubricating Performance of a Chloride Molten Salt for Concentrating Solar Power

One engineering challenge for the next-generation concentrating solar power (CSP) is to identify appropriate heat transfer and thermal energy storage media. A chloride salt mixture (20 wt % NaCl + 40 wt % MgCl₂ + 40 wt % KCl) in a molten phase is proposed as a potential fluid for carrying the heat as well as lubricating the CSP pump bearings. Due to the hygroscopic nature of MgCl₂, the presence of magnesium oxide (MgO) particles is inevitable. In order to understand the impact of MgO particles, this study investigated the tribological behavior of the molten chloride salt mixture containing MgO of various particle sizes and concentrations. Tests were conducted at 750 °C in a dry Ar environment using a zirconia ball sliding against a Haynes 244 alloy disc lubricated by the molten salt. There was a clear trend of the increased friction coefficient and wear loss for a larger particle size and/or a higher concentration of MgO. Distinct wear mechanisms were identified for the ceramic ball and alloy disc. Results provide fundamental insights for this new research avenue of molten salt lubrication for CSP.

Experimental and numerical investigation in the series arrangement square cyclone separator

The square cyclone separators are widely utilized in CFB boilers to isolate tiny specks from gas flow. In present investigation, three square cyclones are fabricated, after that which is linked in series manner. The average mean particle size of 2.2 μm (magnesium particles) is utilized in experimental analysis. The estimated collection efficacy of this series arrangement cyclone is 61% at the particle size of 2.2 μm. It is 10.2% higher than the collection efficiency of single square cyclone. The pressure drop is reduced to 14.3% by this series arrangement configuration. The numerical simulation is executed for predicting the pressure drop for different inlet velocities (10 m/s to 28 m/s). The assortment efficacy is appraised for the various size of particles through the CFD analysis. The flow pattern effects are arrived for the particle size of 2.2 μm and 10 μm. The flow pattern result provides better conformity with experimental results.

Simulation of particle fouling characteristics with improved modeling on two different tubes

The fouling characteristics of micron-scale magnesium oxide particles on the inside wall of the circular tube and converging-diverging tube are studied in this paper. An improved method for modeling particles in tubes was developed based on the Eulerian method. The particle deposition mechanism of the model includes: diffusion deposition, turbulent deposition, thermophoretic deposition, and gravity deposition. The model was verified by comparison with experimental results from the literature. The effects of particle concentration and flow velocity were studied for two different tubes. The simulation results show that the change rules of the fouling resistance of the two tubes were similar both the asymptotic value of fouling resistance increases with the increase of the concentration, and decreases with the increase of the inlet velocity. By comparing the fouling resistance of the two tubes, it was found that the values of asymptotic fouling resistance of the converging-diverging tube were smaller than that of the circular tube at different concentrations and velocities.

Study on the Influence of Regional Transportation on PM2.5 Based on the RAMS-CMAQ Model in Weihai, a Typical Coastal City of Northern China

Weihai, on the east coast of China, is the only city in Shandong Province that the air quality has reached the Chinese National Ambient Air Quality Class II Standard. However, heavy pollution events still occurred in winter and spring. In this study, the Integrated Source Apportionment Method (ISAM), a source analysis tool coupled with the Regional Atmospheric Modeling System and the Community Multiscale Air Quality modeling system (RAMS–CMAQ), was used to quantify the contribution of regional transport to PM2.5 and its main components in Weihai during February to March in 2018. The results showed that regional transport dominated PM2.5 pollution in Weihai, and the contributions of transport outside Weihai in February and March were 55.6–65.5% and 61.3–68.6%, respectively. Different components in PM2.5 showed the proportion of pollutants varies enormously. Secondary particles were mainly transported via long distances. The proportion of long-range transportation of nitrate had the highest value, and the contribution of regional transportation outside Weihai was 87.5–92.5% and 88.2–91.7%, followed by sulfate, which was 67.9–80.6% and 80.8–86.2%, and the proportion of ammonium salt is the lowest, contributed for 38.8–70.8% and 41.1–71.9% in February and March, respectively. Black carbon (BC), organic carbon (OC), and ions (ions here include chloride, sodium, magnesium, potassium, calcium, iron, aluminium, silicon, titanium, manganese, and other major nonspecific fine particles) were mainly influenced by short-range transportation and local emissions. The contributions of BC outside Weihai were 26.0–49.8% and 34.2–55.2%, the values for OC were 33.5–52.9% and 41.0–53.0%, those for ions were 37.8–49.9% and 44.1–54.4%, respectively. The trajectories indicate that PM2.5 pollution in Weihai is significantly affected by transport from Shandong Province, North China, Northeast China and other regions Thus, the improvement in air quality in Weihai requires strengthening interregional joint pollution prevention.

Parallel Synthesis and Optimization of Magnesium Oxide Nanoparticles Using Tridax Procumbens and Myristica Fragrance

The Magnesium oxide nanoparticles were successfully synthesized using Magnesium nitrate as the precursor and extract of Tridax procumbens leaf and Myristica fragrance (Nutmeg) were used as the reducing and stabilizing agent. Two parallel synthesis of Magnesium oxide nanoparticles were carried out. Synthesized Magnesium oxide particles in nano size were characterized by FT-IR, Ultraviolet-visible SEM & XRD techniques. The formed nanoparticles were confirmed as Magnesium oxide nanoparticles by UV- Visible, FT-IR spectroscopic techniques. The structure and size of the Magnesium oxide nanoparticles were obtained from XRD analysis. The size of the Magnesium oxide nanoparticles was 20.10 nm and 9.21 nm. SEM analysis results sphere like and rhombic crystalline shape and morphology of Magnesium oxide nanoparticles.

Regulating magnesium combustion using surface chemistry and heating rate

The magnesium (Mg) particle surface can be used to regulate fluorination or oxidation reactions depending on the applied heating rate and Mg particle size. Magnesium particles are surrounded by a complex hydroxide shell composed of an inner layer of magnesium oxide (MgO) and outer layer of magnesium hydroxide (Mg(OH)2). As particles approach the nanoscale, the thick oxide shell (e.g., 22 nm) becomes an appreciable portion of the overall powder and can be exploited to regulate reactivity. In this study, the reactivity of 800 nm Mg particles (nMg) was compared to 44 µm Mg particles (µMg) when combined with Perfluoropolyethyer (PFPE), providing both fluorine and oxygen for Mg reactions. Experiments were performed at slow heating rates (10 °C/min) and separate experiments were performed at fast heating rates (6.0 × 105 °C/min). The slow heating rate studies used a differential scanning calorimeter (DSC) and thermogravimetric (TG) analyzer to examine reaction kinetics. The faster heating rate experiments used a hot wire to ignite a thermal run-away reaction. Powder X-ray diffraction (XRD) analysis of recovered residue at various temperatures corresponding to exothermic events in the DSC revealed reaction pathways for nMg + PFPE favoring oxidation reactions. For nMg powders, the outer Mg(OH)2 surface layer dehydrates at low temperatures (313 °C) creating highly reactive sites for surface oxidation reactions in the condensed phase leading to a higher conversion of Mg(OH)2 to MgO and greater consumption of Mg through oxidation reactions. For µMg, higher Mg(OH)2 dehydration temperatures (498 °C) stabilize µMg particles and the bulk of reactions occur at elevated temperatures and in the gas phase producing higher MgF2 concentrations. Under high heating rate conditions, MgF2 formation is favored over MgO formation for both particle sizes owing to the high reaction temperatures that promote gas phase reactions favoring MgF2 formation. Theoretical analysis using density functional theory (DFT) through cluster models for Mg(OH)2 and MgO surfaces further show that the Mg(OH)2 surface is more reactive with fluorine species than MgO, especially at elevated temperatures. The DFT results help explain the high heating rate reaction pathway that favors fluorination reactions independent of Mg particle size.

Analytical investigation of magnesium aerosol combustion based on the asymptotic model of flame structure

Due to shortage and environmental pollution of fossil fuels and environment-dependent production of renewable energies, the metal fuels are promising candidates for alternative energy sources. In this study, the micron-sized magnesium particles are considered as energy carrier and the flame propagation of lean premixed magnesium-air combustion is investigated under zero gravity condition. To analyze dust cloud combustion, an asymptotic model of flame structure is proposed. According to the combustion behavior of single particle, the flame structure consists of four different zones including preheat, liquid magnesium, vaporized magnesium and post-flame zones in which the melting, vaporization and flame occur instantaneously. Afterwards, the non-dimensional forms of governing equations including mass, energy and gaseous fuel mass fraction conservations and the appropriate boundary conditions are derived and analytically solved. Subsequently, as the important achievements of the present study, the explicit formulas are obtained for flame velocity, location and temperature. Eventually, the effects of involved parameters on combustion characteristics are examined. The results indicate that as the particle diameter enhances from 15 to 60 µm, the flame front moves to a place 2.5 times farther away. The flame temperature increases linearly with concentration, while it decreases with the inverse of square of the diameter.

Burning Magnesium Powder with Iron Oxide Additives in the Atmosphere of Air

The specific features of burning in air the cylindrical samples obtained from the bulk density of magnesium powder are studied. We record a significant content of magnesium nitride in the reaction’s products as opposed to burning individual magnesium particles in air, which mainly results in the formation of magnesium oxide. The sample’s increased diameter leads to a significant decrease of the degree of magnesium’s transformation. It is shown that introduction of 1–15% of finely dispersed iron oxide powder leads to an increase in the degree of the chemical transformation of magnesium. The transformation is a two-stage process at the characteristic temperatures of 650 and 1050°С. The mechanism of the action of the iron oxide additive based on the multiple repetition of the reactions of substituting iron by magnesium in the oxide with the formation of free iron and its oxidation with the formation of a new portion of iron oxide is proposed.

Design and preparation of new polypropylene/magnesium oxide micro particles composites reinforced with hydroxyapatite nanoparticles: A study of thermal stability, flame retardancy and mechanical properties

To improve the flame retardant efficiency of PP, a new ternary polypropylene (PP) hybride containing, micro-size magnesium oxide (MgO) and nano size hydroxyapatite (HA) particles was prepared via melt blending technique. To better distribute particles in the PP matrix and enhance the effect of flame retardancy, SABO-STAB UV94 (SABO) was mixed in MgO (SABO@MgO) and used for the preparation of the PP composite and nanocomposites. X-ray diffraction (XRD) and elemental mapping results indicated that the HA nanoparticles were uniformly dispersed in the PP matrix. According to the results of thermogravimetric analysis (TGA), the maximum mass loss temperature (Tmax) and char residue of the PP systems were increased, as compared to the neat PP. The cone calorimeter results also indicated that the total heat release (THR) of the PP nanocomposite with 20 mass% SABO@MgO and 5 mass% HA nanoparticles was decreased from 124 kJ/m2 to 102 kJ/m2, as compared to the neat PP, passing the V-0 rating at the UL-94 test. The peak heat release rate (pHRR) of the PP nanocomposite with 20 mass% MgO and 5 mass% HA nanoparticles was also decreased from 834 kW/m2 to 545 kW/m2. Further, according to the results of the tensile test, the tensile strength of the PP nanocomposite with 20 mass% MgO and 5 mass% HA nanoparticles was increased from 44.4 MPa (for the neat PP) to 54.1 MPa.

Effects of inert silica powder on the properties of magnesium oxysulfate cement

The effects of silica powder (SP) with different fineness values on the properties of magnesium oxysulfate cement (MOSC) were compared with the effects of fly ash (FA). X-ray diffraction, mercury porosimetry and scanning electron microscopy were used to analyse the effects of the particle morphology and fineness of FA and SP on the mechanical properties, hydration products and microstructure of MOSC. The results showed that when the α-MgO/MgSO4.7H2O/H2O molar ratio was constant, the concentration of magnesium sulfate and the uniformity of magnesium oxide particles in the slurry were the main factors determining the composition of the hydration products and the microstructure of MOSC. Spherical FA was found to improve the uniformity of magnesium oxide particles in the slurry and exert a nucleation effect, thereby increasing the formation of the 5.1.7 phase of the hydration products. Polyhedral SP with a certain fineness increased the concentration of magnesium sulfate in the slurry and had a filling effect, thus promoting formation of the 5.1.7 phase and optimising the microstructure. Therefore, with a certain magnesium sulfate concentration and a homogeneous slurry, both active FA and inert SP can improve the water resistance of MOSC by optimising the composition of the hydration products and microstructure.

Ultrasound-assisted synthesis of mixed calcium magnesium oxide (CaMgO2) nanoflakes for photocatalytic degradation of methylene blue

In the present study, mixed calcium magnesium oxide (CaMgO2) nanoflakes were synthesized using an ultrasound-assisted co-precipitation method. The physicochemical, structural and functional properties and elemental composition of the nanoflakes had been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), High-resolution transmission electron microscopy (HR-TEM), Fourier Transform Infrared spectroscopy (FTIR), UV–VIS spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Moreover, the photocatalytic actions of the nanoflakes were evaluated by the removal rates of methylene blue (MB) and p-nitrophenol (4-NP) under UV irradiation at room temperature. SEM-EDS studies revealed that the nanoflakes consisted of mixed oxide such as magnesium oxide (MgO) and calcium oxide (CaO) particles. The size of the nanoflakes was found to be in the range of 10–30 nm and the average size was 25 nm as confirmed by HR-TEM analysis. XRD revealed that the standard crystal size was calculated to be 25 nm. The synthesized nanoflakes had a strong photocatalytic activity for methylene blue (MB) and p-nitrophenol (4-NP) degradation in the presence of H2O2 under UV light irradiation within 60 min and 30 min, respectively. Hence, the present study proposes that the CaMgO2 nanoflakes can be employed for the removal of dyes from wastewater.

Optimization of Process Parameters in Drilling of Al6063 Reinforced with Magnesium Oxide Nano Particles

Aluminum Nano Metal Matrix Composites are extensively utilized for high-performance operations such as branches of engineering and medicine due to their enhanced physical and mechanical properties compared to traditional metals and metal alloys. In this research, Al6063 alloy was reinforced with 15 nm sized Magnesium Oxide particles in different weight percentages. The development of Nano Metal Matrix Composites (NMMC) was completed through stir casting method at 750 °C temperature. The fabricated Nanocomposites were examined for the mechanical properties and impact of drilling parameters on chips and burr formation. The input parameters adopted for analysis were speed, feed, and material of the drill tool. The drill tools made of HSS & TiN coated HSS were utilized in the drilling of NMMC. The influence of process parameters on chips and burr formation were analyzed and optimized the process parameters for better output intended for this experimental environment through the Artificial Immune Algorithm technique.

Characterization of transient cavitation activity during sonochemical modification of magnesium particles

Investigation of the cavitation activity during ultrasonic treatment of magnesium particles during nanostructuring has been performed. Cavitation activity is recorded in the continuous mode after switching the ultrasound on with the use of ICA-5DM cavitometer. It has been demonstrated that this characteristic of the cavitation zone may be varied in a wide range of constant output parameters of the generator. The speed and nature of the cavitation activity alteration depended on the concentration of Mg particles in the suspension and the properties of the medium in which the sonochemical treatment has been performed. Three stages of the cavitation area evolution can be distinguished: 1 – the initial increase in cavitation activity, 2 – reaching a maximum with a subsequent decrease, and 3 – reaching the plateau (or the repeated cycles with feedback loops of enlargement/reduction of the cavitation activity).The ultrasonically treated magnesium particles have been characterized by scanning electron microscopy, X-ray diffraction analysis and thermal analysis. Depending on the nature of the dispersed medium the particles can be characterized by the presence of magnesium hydroxide (brucite) and magnesium hydride. It is possible to reach the incorporation of magnesium hydride in the magnesium hydroxide/magnesium matrix by varying the conditions of ultrasonic treatment (duration of treatment, amplitude, dispersed medium etc.). The influence of the magnesium reactivity is also confirmed by the measurements of cavitation activity in organic dispersed media (ethanol, ethylene glycol) and their aqueous mixtures.

Comparison of Ti–35Nb–7Zr–5Ta and Ti–6Al–4V hydrofluoric acid/magnesium-doped surfaces obtained by anodizing

ObjectivesDevelopment of a new generation of stable β alloy, free of aluminum or vanadium and with better biological and mechanical compatibility and evaluate the surface properties of Ti–6Al–4V and Ti–35Nb–7Zr–5Ta after anodization in hydrofluoric acid, followed by deposition of different electrolyte concentrations of magnesium particles by micro arc-oxidation treatment. MethodsDisks were anodized in hydrofluoric acid. After this first anodization, the specimens received the deposition of magnesium using different concentration (8.5% and 12.5%) and times (30s and 60s). The surface morphology was assessed using scanning electron microscopy, and the chemical composition was assessed using energy dispersive x ray spectroscopy. The surface free energy was measured from the contact angle, and the mean roughness was measured using a digital profilometer. ResultsAnodization in hydrofluoric acid provided the formation of nanotubes in both alloys, and the best concentration of magnesium considered was 8.5%, as it was the condition where the magnesium was incorporated without covering the morphology of the nanotubes. X-ray dispersive energy spectroscopy showed magnesium incorporation in all conditions. The average roughness was increased in the Ti–35Nb–7Zr–5Ta alloy. ConclusionsIt was concluded that anodizing could be used to deposit magnesium on the surfaces of Ti–6Al–4V and Ti–35Nb–7Zr–5Ta nanotubes, with better results obtained in samples with magnesium concentration in 8.5% and the process favored the roughness in the Ti–35Nb–7Zr–5Ta group.

A low-current atmospheric pressure discharge generating atomic magnesium fluxes

In the present work, we studied the stable operation of an atmospheric pressure discharge with magnesium electrodes in air and argon flows. We employed a plasma generator consisting of a central cathode and a coaxial anode. At a direct discharge current up to 200 mA, spontaneous transitions to a low-voltage (30–40 V) burning regime were observed when the current was slightly raised by several milliamperes. This phenomenon is reflected in the optical spectrum by the appearance of corresponding lines of singly charged and exited magnesium atoms. It has been found that for a discharge fed by a pulsed power supply, at a unipolar pulse repetition rate of 100 kHz, with the working gas of argon, the aerosol emission becomes stabilized. The aerosol consists of magnesium particles suspended in the argon flow that eventually mixes up with the surrounding air. Based on our estimates, we have made an assumption that the physical nature of the discharge maintenance lies in the ion–electron emission due to the interaction of argon ions with the magnesium cathode surface.