Magnesium Particles Research Articles

Thermal treatment of magnesium particles in polylactic acid polymer films elicits the expression of osteogenic differentiation markers and lipidome profile remodeling in human adipose stem cells

The efficacy of polylactic acid (PLA)/Magnesium (Mg)-based materials for driving stem cells toward bone tissue engineering applications requires specific Mg surface properties to modulate the interface of stem cells with the film. Here, we have developed novel PLA/Mg-based composites and explored their osteogenic differentiation potential on human adipose stem cells (hASCs). Mg-particles/polymer interface was improved by two treatments: heating in oxidative atmosphere (TT) and surface modification with a compatibilizer (PEI). Different contents of Mg particles were dispersed in PLA and composite surface and bulk properties, protein adsorption, stem cell-PLA/Mg interactions, osteogenic markers expressions, and lipids composition profile were evaluated. Mg particles were uniformly distributed on the surface and in the bulk PLA polymer. Improved and modulated particle-polymer adhesion was observed in Mg particle-treated composites.After 21 days in canonical growth culture conditions, hASCs on PLA/MgTT displayed the highest expression of the general osteogenic markers, RUNX2, SSP1, and BGLAP genes, Alkaline Phosphatase, type I Collagen, Osteopontin, and Calcium deposits. Moreover, by LC/MS QTOF mass-spectrophotometry lipidomic analysis, we found in PLA/MgTT-cells, for the first time, a remodeling of the lipid classes composition associated with the osteogenic differentiation. We ascribed these results to MgTT characteristics, which improve Mg availability and composite osteoinductive performance.

Mg-Ni-Nb2O5 Composite Produced by High-Pressure Torsion

A Mg-based composite material has been produced by the consolidation at room temperature of a Mg-5wt.% Ni-2wt.% Nb2O5 powder mixture subjected to high-pressure torsion (HPT), one of the processing methods to induce severe plastic deformations. The microstructure, density, and microhardness of the consolidated disks were characterized after the application of up to 30 revolutions in torsion under compression stresses of 3 and 5 GPa. According to the density measurements, the composite was consolidated in full after the application of five revolutions, although disks subjected to only one revolution exhibited densities close to the maximum measured value. On the other hand, grain size and microhardness measurements showed that differences existed at locations near the center and the periphery of the HPT-processed disks. Under the stress of 5 GPa, the grain size in the central regions stabilized at about 0.35 μm after five revolutions, while at the peripherical regions it gradually decreased with an increasing number of revolutions down to about 0.15 μm after 30 revolutions. In turn, the microhardness measured along a diametral cross section steadily increased with the number of revolutions between 1 and 10 revolutions, maintaining a gradient from the center to the periphery in all cases. With the application of 20 and 30 revolutions, only the peripheral regions increased considerably in hardness. It was discovered that the magnesium particles in the initial powder mixture had formed an oxide—hydroxide surface layer, which changed the expected final density of the consolidated material by about 2 to 4.5%. This superficial contamination of the Mg powders did not prevent the material from achieving full consolidation.

Influence of PANI and Magnesium Particles coating on Aluminium Alloy (5083) Corrosion in 3.5 % Sodium Chloride Solution

Influence of PANI and Magnesium Particles coating on Aluminium Alloy (5083) Corrosion in 3.5 % Sodium Chloride Solution

Mechanical Properties of Carbon Fiber/Epoxy Composites Modified with Micro- and Nano-Sized Magnesium Oxide Particles

A systematic study on evaluating the effect of micro- and nano-sized magnesium oxide (MgO) particles on the mechanical properties of carbon fiber/epoxy composites was conducted by adding various contents of MgO particles into an epoxy resin matrix. The impact and flexural strengths were determined by the Charpy impact tests and three-point bending experiments, respectively. We found that the carbon fiber/epoxy composites filled with nano-MgO particles had higher mechanical strength than that of the carbon fiber/epoxy composites filled with micro-MgO particles. Both impact and flexural strength were enhanced by adding the proper content of nano-MgO particles. Although the impact strength was increased by adding micro-MgO particles, the flexural strength was decreased by adding micro-MgO particles. In addition, the influence of the nano- and micro-particles on the failure modes of the fiber/epoxy composites was also studied and is described.

Effects of magnesium particle size on combustion characteristic of martian ramjet engine

Experiments were conducted to determine the typical magnesium particle size effects on the Mg–CO2 Martian ramjet combustion characteristic. It was carried out at a mainstream mass flow rate of 110 g/s and a temperature of 800 K. In this study, two typical particle sizes (25.2 and 64.6 μm) of magnesium particles that are more easily obtainable in the industry were selected. The morphology, composition, and combustion efficiency corresponding to different particle sizes and equivalence ratios (ER) were analyzed. Results indicate that the 25.2-μm magnesium powder has a wider equivalence ratio adaptation range (ER = 0.13–0.27) and yielded less condensed phase deposition compared to 64.6-μm Mg powder. Combustion efficiency of 85.6% was achieved under the aforementioned conditions. Experimental data shows that 15% of the fine magnesium powder participated in the heterogeneous reaction and caused the pulsating combustion, demonstrating a low frequency (roughly 1 Hz) pressure oscillation. The amplitude even reached 14.6% of the chamber pressure. Remarkably, the condensed phase product produced by the small particle size is mainly magnesium oxide, resulting in an obvious agglomeration phenomenon. In contrast, unburned magnesium particles were detected in the combustion products of large magnesium powder due to the longer combustion time of coarse particles.

Study on explosion characteristic parameters and induction mechanism of magnesium powder/hydrogen hybrids

The explosion of magnesium powder/hydrogen hybrid is a complex reaction process, which will cause more serious harm than the explosion of a single combustible medium. The research on the mechanism of the hybrid explosion can provide corresponding reference for the prevention of such accidents. A 20L explosion device was used to study its explosion mechanism, and the results show that the magnesium particles in the hybrid explosion underwent homogeneous shrinking core reaction. It is found that the explosion pressure curve of the hybrid will appear bimodal structure under certain conditions, so this paper will explore it separately. When the hybrid system is in the “oxygen-poor” state, the explosion characteristic parameters of the first stage will decrease with the increase of combustible materials. And the hydrogen content and oxygen consumption in the gaseous products are also increase gradually, and unreacted magnesium particles are also found. In the “oxygen-rich” state, the opposite is true, and the number of cubic particles and the oxidation degree in the solid explosion products increasing with the increasing combustible materials. In addition, even under “oxygen-rich” conditions, hydrogen remains in the gaseous product of the hybrid.Interestingly, even under the condition of 30%vol-50%vol hydrogen/magnesium powder hybrid in the “oxygen-poor” state. As the combustible materials increase, the explosion characteristic parameters and maximum explosion temperature in the second stage show a change trend of increase first and then decrease.

A Thermal Conductive Epoxy Composite based on Spherical MgO Particles and Boron Nitride Sheets

The performance and life of high-power electronic devices are closely related to heat dissipation. Preparing high thermal conductivity, electrically insulating, polymer-based packaging materials for electronic devices is critical to achieving high heat dissipation. In the research described here spherical magnesium oxide (MgO) particles of various sizes and boron nitride (BN) sheets were used to prepare epoxy composites and their enhancement of heat transfer was investigated. In addition, the BN sheets were surface modified by γ-aminopropyltriethoxy silane (APTES) to increase interfacial compatibility between epoxy resin and BN, which enhanced the composite thermal conductivity. The composites with the highest thermal conductivity were made with 5 µm spherical MgO particles and BN sheets at a filler wt% ratio of 3:1 (MgO: BN). Using functionalized BN sheets enhanced the dispersion and compatibility of the 3:1 mixed filler. The thermal conductivity of the composite containing 45 wt% of the 3:1 mixed filler consisting of 5 µm spherical MgO particles and APTES functionalized BN sheets was 0.92 W/(m·K) as compared to 0.2 W/(m·K) for the epoxy resin alone.

Micro-structured and self-assembled patterns in PLA-cast films as a function of CTAB content, magnesium and substratum hydrophobicity

The fabrication of biomaterials with structured surfaces for medical purposes is a topic of great interest. Producing topographies with certain characteristics can benefit tissue formation and/or reduce the probability of developing an infection due to the hindrance shown by certain micro-structures to microbial adhesion.This work presents a new, economically attractive way to fabricate micro-structured patterns on the surface of one of the currently most interesting bioabsorbable polymeric materials, polylactic acid (PLA). Formation of homogeneously distributed holes is presented as a function of three factors: the concentration of cetyltrimethylammonium bromide (CTAB), the presence or not of the dispersant magnesium, and the hydrophobicity of the support used in the PLA-film fabrication, silicone or glass. The size of the holes increases with the CTAB concentration: from 1 to 5 µm on silicone and 2 to 20 µm on glass. Magnesium particles make CTAB to disperse better inside the PLA matrix, provoking the irregular holes observed on glass become regular with sizes between 0.5 and 2 µm. The topographies obtained on silicone are highly stable over time, while on glass they degrade after 28 days. Consequently, it is possible to design a wide spectrum of micro-structured topographies, covering both antimicrobial and tissue integration targets.

Experimental and theoretical investigation of an innovative composite nanofluid for solar energy photothermal conversion and storage

Molten salts play a key role in the heat transfer and thermal energy storage processes of concentrated solar power plants. A novel composite material was prepared in this work by adding micron-sized magnesium particles into Li2CO3-Na2CO3-K2CO3 molten salt, the heat transfer and thermal energy storage properties of the composites were studied experimentally. A stable composite nanofluid can be obtained, and a thermal conductivity of 0.728 W/(m·K) at 973 K with an enhancement of 31% is achieved for the Mg/molten carbonate nanofluid. And the strengthening mechanism of thermal conductivity was revealed by using ab-initio molecular dynamics method. It is found that the main bonding interactions exist between Mg and O atoms at the surface of Mg particles. A compressed ion layer with a more compact and ordered ionic structure is formed around Mg particles, and the Brownian motions of Mg particles lead to the micro-convections of carbonate ions around them. These factors are helpful to the enhancement of thermal conduction with the improved probability and frequency of ion collisions. This work can provide a guidance for further studies and applications on metal/molten salt composites with enhanced heat transfer and thermal energy storage capacity.

Static and Total Pressure Analysis of Three Way Catalytic Convertor Using CFD

Air pollution from automobiles both commercial and passenger vehicles push the research to make changes in catalytic convertor. Most of the commercial vehicles like coal transport and mineral transport trucks relay on diesel fuel in this regard, we consider the effects carbon monoxide, hydrocarbons that have not been burned, and nitrogen oxides. As a result of incomplete combustion, alcohols, aldehydes, and other partial oxidation products are released into the air. The whole process of this project is done with the help of CFD approach because it will reduce the material waste and we can optimize according to our desired results. In this study, a numerical analysis has been carried out on the catalytic converter by varying the coating materials. Magnesium Oxide (MgO) and Platinum with Palladium was selected as coating materials. For comparison purpose, normal catalytic converter without coating was analysed using CFD software. Different output characteristics of the exhaust gases’ static pressure and total pressure in the catalytic convertor are compared with each other. Outcomes of the numerical analysis shows that the catalytic converter which is coated with Platinum and Palladium particles yields the better static and total pressure than that of normal and magnesium oxide (MgO) particles coated catalytic converter.

Synthesis of Magnesium Hydroxide Using Post‐Reaction Filtrate as Ammonia Carrier and Morphology Analysis

AbstractThis study proposes an advanced technology using post‐reaction filtrate as an ammonia carrier to synthesize magnesium hydroxide (MH) with small particles, which can benefit subsequent hydrothermal modification. In this work, the limitation of ammonia gas and ammonia water methods is avoided. The impact of operating parameters including MgCl2 concentration, temperature, ammonia‐to‐magnesium molar ratio, feed rate, volume of ammonia mother liquor and aging time on the magnesium yield, particle size, and morphology of MH is studied. The temperature and ammonia‐to‐magnesium molar ratio are identified as key factors affecting magnesium yield. MH with a half‐content diameter of 1.70 µm and a morphology resembling small irregular flakes is successfully synthesized at a magnesium yield of 90.06%. The predictions of idea crystal habits are also performed using Morphology and CASTEP modules with Materials Studio Software. The (0 0 1) face can be preserved with the largest facet area because of the slowest crystal growth rate and the smallest attachment energy, which exhibits that MH crystals tend to be flakes.

Highly stable nano magnesium oxide organic coatings for nondestructive protection of acidic paper documents

Paper documents possess significant cultural, history and art values. However, acidification as the main factor causes rapid degradation of paper documents. For the nondestructive protection of acidic paper documents, the highly stable nano magnesium oxide (MgO) organic coatings based on the synergistic dispersion of trimethylsilylcellulose (TMSC) and isopropanol (IPA) were prepared. It was clarified in detail by experimental and computational studies. IPA played a significant role in aggregation inhibition of nano MgO through the reduction of interparticle attraction potential to reduce the particle size. Meanwhile, the dispersion stability was further improved with the greater steric hindrance of TMSC (more than 1 month). The highly stable nano MgO organic coatings were applied for deacidification of the acidic paper documents via impregnation. Evaluation showed that nano MgO particles were evenly deposited on the paper, which has little influence on the clarity of writing by increasing the optical density of ink. Moreover, acidic paper after treatment, with a good alkaline reserve and anti-mold performance, is expected to have excellent stability during aging.

NOx emissions in a swirled-stabilized magnesium flame

Alternative sources of clean energy with reduced greenhouse gas emissions have to be considered. Among them, the combustion of metal fuels such as aluminum or magnesium is promising. Nitrogen oxides (NOx) are the only undesirable gases produced during such metal combustion. The present study analyzes the amounts of NOx (NO and NO2) produced by a swirled stabilized magnesium flame. Two geometric swirl numbers are considered: 0.7 (low swirl number) and 7.3 (high swirl number). Different air–fuel ratios – equivalence ratio ranging from 0.17 to 1 – are considered, being obtained by changing the mass flow rate of the injected fuel which is a pulverized fuel of pure magnesium particles with a size fraction 50–70 µm. Thermocouples and a bichromatic pyrometer are implemented to monitor the gas temperature and the flame temperature, respectively. Oxygen (O2) is measured using an in-line paramagnetic analyzers and NOx are measured using an IR-UV analyzer.Whatever the swirl conditions and the air–fuel ratio tested, a stabilized flame of Mg is obtained. The metal combustion exhibits very stable performances. NOx emissions versus equivalent ratio follow a bell-shape curve. Under the tested experimental conditions, the amount of NOx never exceeds 7 gNOx/kWh, which is lower than the maximal value of NOx emission from a gasoline engine. The NOx mole fraction increases when the air–fuel ratio increases, as the power dissipated by the flame increases. The temperature of MgO particles in the flame reaches 2250 °C and the gas temperature never exceeds 1400 °C. The thermal NOx formation is estimated applying Zeldovich’s model. The model indicates that NOx can be produced in the gas surrounding the hot MgO particles. For the highest equivalence ratio, even if the gas temperature is still increasing, the NOx production is disfavored in the rich mixture. Based on these results, a global scheme for NOx formation is proposed which includes four successive steps.

Graphene Oxide-Based Multi-Component Antimicrobial Hydrogels

Abstract Graphene oxide (GO)-based hydrogel composed of magnesium oxide (MgO) and povidone-iodine (PVP-I) is synthesized. GO in the hydrogel plays two roles; gelator by self-assembling and carrier for MgO and PVP-I. MgO particles act as cross-linking initiators and fillers that increase the cohesion and adhesion strengths of the hydrogels. Besides, MgO promotes antibacterial activities and regulates cellular activities over the lifetime of the hydrogel. In addition, PVP-I slowly releases free iodine from the hydrogel, exhibiting germicidal activity over time. A combination of GO, MgO, and PVP-I in the hydrogel exhibit improved electrical conductivity, fluid uptake ability, water retention capacity, water vapor transmission rate, and integrity value. Furthermore, the hydrogel has shown antimicrobial properties against Staphylococcus aureus. These findings are unique and indicate that GO-based hydrogel could be a promising material for biomedical application, especially for the treatment of pathological and surgical wounds.

Thermal Behaviour and Kinetic Parameters of Ternary Mg+SrO2+DNAN Pyrotechnic Compositions

AbstractThermal analyses of raw components are necessary to understand the behavior of pyrotechnic compositions they are incorporated in. Ternary compositions containing strontium peroxide, magnesium, and 2,4‐dinitroanisole (DNAN) are studied thermally using TGA and DSC. Activation energies are given for the components using three different methods. Thermal behavior of strontium peroxide is focused on as little scientific literature exists about it: heat capacity is measured, and a thermal evolution model is given. Effects of magnesium particles size are also studied. The results obtained show that the presence of DNAN decreases activation energies of all reactions within the ternary compositions. Decreasing magnesium granulometry only decreases the activation energy of magnesium oxidation, but does not play a role in other reactions.

Removal of phosphate by a novel activated sewage sludge biochar: Equilibrium, kinetic and mechanism studies

In this study, a novel biochar adsorbent (Mg-SB) modified by magnesium oxide particles is synthesized via pyrolysis of activated sewage sludge. Its phosphate removal performance is explored in aqueous environment under various conditions. It is found that Mg-SB could effectively remove phosphate with the maximum capacity of 97,450 mg kg−1 PO43−. The values are favorable compared to other adsorbents in the literatures. The pH and ionic strength can obviously affect the adsorption of phosphate onto Mg-SB. The adsorption data are best fitted by the pseudo-first-order model and the Langmuir model. Characterization of adsorbents with SEM-EDS, XRD and FTIR showed magnesium oxide on Mg-SB surface was the main phosphate adsorption site. Furthermore, the high phosphate adsorption efficiency and bioavailability makes the P-load-Mg-SB possible to directly apply to agricultural fields as a slow release fertilizer to improve soil fertility or to restore the contaminate soil.

Effect of Composite Modification of Nickel Slag Powder and Polypropylene Fiber on Mechanical Properties of MKPC Mortar

In order to explore the influence of nickel slag powder (Ni) and polypropylene fiber (PP) on the performance of MPKC mortar, different mass fractions of Ni (5%–20%) and different volume fractions (0.6% and 1.0%) of PP were added to MKPC. The composite modified MKPC (CM-MKPC) specimens were tested and analyzed for flexural strength, compressive strength, split tensile strength, and bending performance. With the help of scanning electron microscope, the microstructure and fracture morphology of the modified MKPC specimens for related research. The results show that the addition of PP and Ni improves the mechanical properties of MKPC and improves its flexibility and deformation properties. When the content of Ni and volume of PP are 15% and 1.0%, respectively, the mechanical properties and bending properties of the modified MKPC mortar are the largest in the same group. Ni added to the MKPC gel system can reduce the friction between irregular magnesium oxide particles and between aggregates. In this way, PP fiber can well enter into the aggregate and play a bridging role at the interface, so that MKPC can better play its mechanical properties.

Examining Metal Additives in a Marine Hybrid-Propellant, Water-Breathing Ramjet

This research focuses on theoretically and experimentally evaluating the performance of a metallized hybrid-propellant, water-breathing ramjet. The aluminum and/or magnesium particles added to a polymeric (polyester) fuel grain are hydro-reactive, using the surrounding water as an oxidizer, in addition to a source of gas. Theoretically, the metal additives significantly increase the specific impulse of the motor, and as the percentage of the hydro-reactive ingredient increases, the theoretical performance increases as well. Additionally, aluminum is more energetic than magnesium. However, it was experimentally discovered that the addition of aluminum beyond 20% resulted in a slag formation and did not increase the specific impulse. Adding 30% of magnesium was relatively favorable to aluminum due to its better reactivity, enabling the achievement of an actual specific impulse of up to 485 s at standard conditions, approximately double the performance of common solid rockets.

Enhanced Flame Retardancy in Ethylene–Vinyl Acetate Copolymer/Magnesium Hydroxide/Polycarbosilane Blends

A polymer ceramic precursor material—polycarbosilane (PCS)—was used as a synergistic additive with magnesium hydroxide (MH) in flame-retardant ethylene–vinyl acetate copolymer (EVA) composites via the melt-blending method. The flame-retardant properties of EVA/MH/PCS were evaluated by the limiting oxygen index (LOI) and a cone calorimeter (CONE). The results revealed a dramatic synergistic effect between PCS and MH, showing a 114% increase in the LOI value and a 46% decrease in the peak heat release rate (pHRR) with the addition of 2 wt.% PCS to the EVA/MH composite. Further study of the residual char by scanning electron microscopy (SEM) proved that a cohesive and compact char formed due to the ceramization of PCS and close packing of spherical magnesium oxide particles. Thermogravimetric analysis coupled with Fourier-transform infrared spectrometry (TG–FTIR) and pyrolysis–gas chromatography coupled with mass spectrometry (Py–GC/MS) were applied to investigate the flame-retardant mechanism of EVA/MH/PCS. The synergistic effect between PCS and MH exerted an impact on the thermal degradation products of EVA/MH/PCS, and acetic products were inhibited in the gas phase.

Influence of supplementary materials on the early age hydration reactions and microstructural progress of magnesium phosphate cement matrices

The microstructures of magnesium phosphate cement (MPC) compounds are porous due to rapid speed of hydration reaction and great level heat release at very early ages. Consequently, MPCs lose mass in water region for spongy structure, which limits the application in the water structures. For improving the solidity of microstructures, decrease of high hydration heat discharge and little extension of final setting time (FST) of the magnesium phosphate cement (MPC) composites at early hydration ages, different supplementary cementitious materials (SCMs) such as fly ash (FA), silica fume (SF), bauxite (BX), Phosphogypsum (PG), aluminum silicate (AS) and silica nanoparticles (SNP) were introduced to MPC compositions. It was revealed that pH was not too acidic for adding foreign materials at very early stages (i.e. 4 mins–10 min), where dissolving speed of magnesia (MgO) particles were declined. Thus, FST was delayed and decreased heat release of fresh specimens except for combination with SNP. The research also identified the different intermediate crystals such as mullite, enstatite, berlinite, lizardite, CSH and ettringite in the microstructures of MPC blended with SCMs, which was confirmed by XRD, SEM and FTIR experiments. Furthermore, the structural integrity of samples was significantly improved as compared to control for the existence of secondary rocks, where the specimens having FA, BX and AS presented the mechanical strength properties 30% higher at 28d than the reference matrix. However, the explored results might be a potential solution to design and improve the water resistance properties of MPC compounds for applying in the water structures.