Mixture Of MgO Research Articles

Effects of laser shock peening on silicon nitride ceramic with varying sintering additive ratios

Silicon nitride ceramic (Si3N4) for industrial applications is conventionally manufactured with sintering additives, and the properties of Si3N4 change significantly based on the contents of these additives. In this study, we investigate the effects of laser shock peening (LSP) on Si3N4 sintered with varying ratios of sintering additives.The Si3N4 samples were sintered with a mixture of Y2O3, MgO, and SiO2 sintering additives at 5, 7, 9, and 11 wt%. A Nd:YAG laser (wavelength = 532 nm, maximum pulse energy = 1.4 J, repetition rate = 10 Hz, pulse duration = 8 ns, beam diameter = 11 mm, top-hat profile) was used to irradiate the Si3N4 samples. The samples were coated with a protective layer (100 μm thick aluminum foil) and a water layer to confine plasma. LSP of Si3N4 with 5% sintering additives resulted in a slight change in surface hardness but a 77% decrease in surface compressive residual stress. In contrast, LSP of Si3N4 with 11% sintering additives led to a simultaneous increase in surface hardness (7.3%) and surface compressive residual stress (67%), indicating a significant difference in the effectiveness of LSP depending on the ratio of sintering additives. Additionally, the surface of Si3N4 with 11% sintering additives showed evidence of grain refinement after LSP. It was demonstrated that the bending strength of Si3N4 with 11% sintering additives increased by 15.2%, and the depth of the fracture origin was significantly deepened.

(Invited) Photocatalysis of Mg-Doped SrTiO3 for Conversion of CO2 with H2O

Photocatalysis has been highly attracting the world-wide attentions among many approaches to convert CO2 into value-added products such as CO, HCOOH, CH3OH and CH4, because photocatalytic conversion of CO2 can be a solution for global warming in terms of its renewability, harmlessness, relatively low cost, and stability. Large number of photocatalysts reported in the research field of the photocatalytic conversion of CO2 require the photoirradiation with deep UV light < 300 nm. Recently, our research group found that Al-doped SrTiO3 photocatalyst (Al-STO), which has been previously reported as a superior photocatalyst for overall water splitting[1], also showed the photocatalytic activity for the conversion of CO2 into CO[2]. In this study, the effect of metal dopant in SrTiO3 on the photocatalytic conversion of CO2 was investigated, and it was found that Mg-doped SrTiO3 showed excellent photocatalytic activity for the conversion of CO2 into CO in the presence of AgCo dual cocatalyst[3].Mg-doped SrTiO3 (Mg-STO) was synthesized by a flux method; the mixture of SrTiO3, MgO, and SrCl2 flux was calcined at 1418 K for 15 h. Ag and Co dual cocatalyst was loaded by a chemical reduction method. An aqueous solution of NaH2PO2 reductant was added to the suspension containing Mg-STO, AgNO3, and Co(NO3)2, and it was kept at 353 K for 90 min with vigorous stirring. Photocatalytic conversion of CO2 with H2O was carried out using an external-irradiation-type reaction vessel. AgCo/Mg-STO was dispersed in an aqueous solution of 0.1 M NaHCO3, and high purity CO2 gas was bubbled into the suspension at a flow rate of 30 mL min−1. The monochromatic UV LED lamp (365 nm) was used as a light source. The gaseous products were analyzed by TCD-GC (H2, O2) and FID-GC equipped with a methanizer (CO).AgCo/Mg-STO exhibited much higher photocatalytic activity for the conversion of CO2 into CO than AgCo/STO and AgCo/Al-STO, which were previously reported. CO was produced at a formation rate of 20 μmol h−1, which was 2.3 times larger than that for Al-STO, and the selectivity toward CO evolution was almost 100 %. H2 formation was completely suppressed in this case. Moreover, the stoichiometric amount of O2 was evolved, indicating that H2O should contribute to the photocatalytic conversion of CO2 as an electron donor. The isotope-labeling experiments using 13CO2 gas as a substrate revealed that the carbon source of CO evolved in this photocatalytic reaction CO2 gas bubbled into the suspension. Therefore, we concluded that CO2 surely split into CO and O2 by the photocatalysis of AgCo/Mg-STO. According to SEM images of undoped STO and Mg-STO, particle shape was obviously changed by Mg doping from pure cubes to irregular edge-shaved cubes. {110} facets were observed in Mg-STO accompanied with {100} facets. Moreover, Ag and Co species were selectively located on the {100} facets and the {110} edge-shaved facets, respectively, after the photoirradiation. The photogenerated electrons and holes were considered to be transferred to {100} and {110} facets separately, and the anisotropic charge transfer should result in the high photocatalytic activity of Mg-STO for the conversion of CO2 with H2O.[1] T. Takata et al., Nature, 2020, 581, 411-414.[2] S. Wang et al., Chem. Sci., 2021, 12, 4940-4948.[3] T. Nakamoto et al., Catal. Sci. Technol., 2023, 13, 4534-4541.

Highly pure hydrogen production via the thermocatalytic decomposition of methane over Ni/SiO2.MgO catalysts: Impact of the catalyst's chemical composition

The goal of current research is to focus on exploring the effects of various MgO/SiO2 ratios, emphasizing their impact on the structure properties and advancing the catalytic activity and the chemical life span of Ni-catalysts by an exciting mixture of SiO2 and MgO to generate COx-bare hydrogen and nanocarbon simultaneously from methane decomposition reactions. SiO2/MgO mixed oxides with different ratios (0.5, 1, and 2) were ready via a facile co-precipitation method from magnesium nitrate and sodium metasilicate and used as supports for various nickel contents (30, 40, 50, and 60 wt%) followed by an impregnation technique. Different analytical techniques, such as XRD, BET, SEM, EDS, H2-TPR, and TPO, were used to characterize the catalysts before and after the catalytic runs. The prepared catalysts with various SiO2/MgO molar ratios depicted the BET surface area limiting from 37.9 to 143.4 m2 g−1, indicating remarkable surface improvements. The vast CH4 conversion of 64 % earned on the 50 wt% Ni/SiO2·MgO at 575 °C. Moreover, lower deactivation was detected regarding this catalyst at 600 min on stream.

Silane Gas Production Through Hydrolysis of Magnesium Silicide by Hydrochloric Acid

Monosilane (SiH4) is a common precursor for the production of high-purity silicon for solar PV applications. As an alternative to carbothermic reduction of silica to produce metallurgical grade silicon with subsequent conversion to silane, an alternative route over magnesiothermic reduction of silica to Mg2Si has been explored in our earlier work. In the current work, silane gas production through hydrolysis of Mg2Si in HCl acid solution was studied. Two sources of Mg2Si were chosen: a commercial Mg2Si source and a Mg2Si source produced through magnesiothermic reduction of high-purity natural quartz. Effects of various parameters on the hydrolysis of Mg2Si, including different experimental setups, temperature of the acid solution, acid concentration, reaction time, and relative amounts of reactants were studied. The evolution of produced gases was determined by two different methods: firstly, by passing the produced gas through a KOH solution to capture Si with subsequent analysis of the Si content in the KOH solution by inductively coupled plasma mass spectrometry and secondly, on-line gas analysis by GC–MS. The silane distribution between different silane species with reaction time was evaluated and the activation energy of silane formation was calculated. The results indicated comparable silane yields obtained from the on-line GC–MS method and KOH solution analysis method, as well as for commercial Mg2Si and the Mg2Si–MgO mixture produced through magnesiothermic reduction. Furthermore, adding HCl acid to Mg2Si in water led to higher SiH4 formation yield than adding Mg2Si to acid. However, the total silane yield for the two methods was similar at approximately 32%.Graphical

Interfacial characteristics, interfacial oxide evolution and bonding mechanism of 2219 aluminum alloy joints manufactured by hot-compression bonding

The bonding joints of 2219 aluminum alloy with different deformations of 30%, 45% and 55% were fabricated using hot-compression bonding, and subsequent subjected to homogenization treatment. The interfacial microstructure and interfacial oxide evolution of the bonding joints were systematically investigated. The results showed that increasing deformation can effectively reduce the formation of interfacial voids and promote the interfacial grain boundary migration (IGBM). As the deformation increased from 30% to 55%, the flat bonding interface transformed into curved grain boundaries, and ultimately being occupied by dynamically recrystallized (DRXed) grains. The development of IGBM and interfacial DRXed grains is crucial for ensuring high-quality bonding joints. At 55% deformation, the interface bonding strength reached 156.2 MPa, corresponding to 98.1% of the matrix bonding strength. In addition, the residual interfacial oxide film Al2O3 reacted with MgO and transformed into MgAl2O4 spinel. The final evolution products at the bonding interface were the mixture of MgO, Al2Cu, Al2O3, and MgAl2O4. The bonding interface at 55% deformation successfully achieved relatively clean atomic bonding after homogenization. Based on interfacial void closure, interfacial oxide film fragmentation and evolution, and interfacial recrystallization, the bonding mechanism of 2219 aluminum alloy joints was proposed. These findings contribute to our understanding of the interfacial bonding process in metal solid bonding.

SYNTHESIS OF MULTICOMPONENT ZRO&lt;SUB&gt;2&lt;/SUB&gt;:WO&lt;SUB&gt;3&lt;/SUB&gt;:AL&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;:MGO

In this work, the phase composition and microstructure of multicomponent ZrO2:WO3:Al2O3:MgO ceramics were studied depending on the concentration of the components. The dependences between the concentration of elements in the initial charge and the phase composition, volume shrinkage, density and microstructure of synthesized samples are determined. It was found by Raman spectroscopy that the addition of an Al2O3:MgO mixture to the initial ZrO2:WO3 matrix does not lead to the formation of a ZrO2:WO3:Al2O3:MgO solid solution. With an increase in the content of Al2O3:MgO, there is an increase in volumetric shrinkage and density, which may be associated with the formation of the liquid phase of the WO3:Al2O3 system at a temperature of 1450 °C and, as a result, more efficient migration of pores and defects to the surface. The analysis of the SEM images of the cross sections of the obtained samples showed that all samples have a developed morphology with different grain shapes.

Investigation of the mechanical properties of magnesium chloride on magnesium oxide improved kaolin clay

In our study, samples were prepared by mixing 2%, 4%, and 6% MgO doses with the dry weight of kaolin-type low-plastic clay. In each MgO dose, 1% and 2% of the soil weight, respectively, MgCl2 chemicals were added, and all samples were mixed at the optimum water content ratio (16.2%). All components were mixed with a planetary mixer for 10 minutes until homogeneous, and then the mixture was poured to have 25 blows for 5 layers. All samples were cured under room conditions for 3–10 days to be tested on the Unconfined Compression Test. From the results, it was observed that the undrained shear strength of the sample increased as the percentages of MgCl2 and MgO rose. It can be said that the interaction between MgO and MgCl2 contributes to the cementation of the clay, and sorel cement plays a role in the mechanical strengthening of kaolin clay based on its effect on strength development. Extending the curing time also developed the mechanical properties of kaolin clay and improved the hardness of the samples by increasing the elastic modulus. In this way, early failures were attained at early strains, and the ductility of the samples increased. We finally saw that the mixture of MgO and MgCl2 worked well as a building material for kaolin clay. The study also tried to get rid of some of the problems that come up with filling materials used in geotechnical engineering and shoring projects, like swelling, shrinkage, and low mechanical properties.

Efficient removal of carcinogenic Rosaniline Hydrochloride (Fuchsine) dye with Mg doped FeTiO nanocomposites: Experimental and statistical evaluation

This study focuses on the synthesis of new nanostructured absorbent materials and removal of hazardous Rosaniline Hydrochloride (fuchsine) dye from polluted water. For this, Mg doped FeTiO nanocomposite (FTMO-NCs) was synthesized by co-precipitation method and thoroughly characterized to study its surface properties. The TEM image shows the FTMO-NCs are consists of crystalline particles sized in few nanometers of scale. The SAED pattern suggests the nanoscale polycrystalline nature of the FTMO-NCs. The homogeneously distributed MgO on the FeTiO-NCs further validates the spectra. Furthermore, the successful mixture of MgO with the FeTiO surface and the formation of FTMO-NCs are indicated by the well-defined elemental mapping of Fe, Ti, O, and Mg. Dye adsorption capacity, stability, and regeneration capability of the synthesized FTMO-NCs was evaluated by a series of experiments and varying parameters, such as, agitation time, nanocomposite mass, solution pH, dye concentration, etc. The pseudo-second-order kinetic model was found to be applicable based on the kinetic parameters calculated with a high correlation coefficient of 0.999. The findings indicate that the Langmuir isotherm is a better fit for the experimental data for the fuchsine adsorption on the FTMO-NPs in comparison to the other four models and shows the maximum adsorption capacity (Qmax) of 555.5 mg/g. Moreover, a double layer model was applied to study the statistical prediction of the favorability of the adsorption process of the dye on the nanocomposite. The Nm value for fuchsine adsorption was 550 mg/g, 255 mg/g, and 218 mg/g, respectively at 298 K, 308 K, and 318 K. The use of Mg-doped FeTiO nanocomposites (FTMO-NCs) for removing Rosaniline Hydrochloride (fuchsine) dye is a novel approach that brings together the unique properties of both materials. The incorporation of magnesium (Mg) into the FeTiO nanocomposite introduces new synergies and enhances the adsorption capabilities of the material. This innovation is particularly significant because Mg doping can influence the surface chemistry and electronic structure of the nanocomposite, leading to improved dye removal efficiency.

The Effectiveness of Ni-Based Bimetallic Catalysts Supported by MgO-Modified Alumina in Dry Methane Reforming

Syngas is produced through the carbon dioxide reforming of methane. The traditional nickel-based catalysts are substantially destroyed by carbon deposition. The reforming reaction was conducted in a tubular microreactor at 700 °C using bimetallic Ni catalysts supported over 37% Al2O3 and 63% MgO mixtures. The impregnation process formed the catalysts, which were subsequently examined by N2-physisorption, XRD, H2-TPR, TGA, and Raman spectroscopy. The 2.5Ni+2.5Co/37%Al2O3+63%MgO bimetallic catalyst, which displayed 72% and 76% conversions of CH4 and CO2 over the course of a seven-hour procedure, was discovered to be the most active in DRM. The bimetallic catalyst with the largest weight loss in TGA, 2.5Ni+2.5Fe-MG63, had a loss of 61.3%, a difference of 26% and 21% in the activity performance of CH4 and CO2, respectively, of the tested bimetallic Ni catalysts was recorded. The long-time of 30 h on-stream CH4 and CO2 conversion reactions for 2.5Ni+2.5Co-MG63 and 2.5Ni+2.5Ce-MG63 catalysts showed the catalysts’ high stability. The TPO analysis for the 2.5Ni+2.5Cs-MG63 catalyst showed a peak at 650 °C, attributed to the oxidation of the filamentous carbon, whereas the TPO analysis for the 2.5Ni+2.5Co-MG63 catalyst depicted a peak at 540 °C, ascribed to the presence of amorphous/graphite carbon.

Influence of nano additive blended watermelon seed biodiesel on the performance and exhaust emissions of a VCR compression ignition engine

An innovative idea have been proposed in this work, to increase fuel efficiency and minimize emission from Diesel engine. This research mainly focuses on the systhesis of two nano materials namely MgO, TiO2. The synthesized nano additives was blended in equal proportion with Biodiesel prepared from Watermelon seed oil through the process of trans-esterification. Then 20% Biodiesel was mixed with 80% diesel and now the fuel is called as B20. Equal proportion of MgO and TiO2 mixture was prepared which is called as Nano Additive Mix(NAM) and added with B20 blend. A 5HP mono Barrel Diesel engine was powered with B20 and with various proportion of NAM in the range of 50ppm, 100ppm, 150ppm and 200ppm. The results obtained revealed that B20 blended with NAM150 minimized CO, HC and Smoke emission considerably when equated to other mixtures. The BTE at peak load for Diesel was 28.4% and for the same load it was 28.2% for B20 @ NAM150 blend. The B20 with 150NAM blend become the best alternative fuel combination to operate the engine with less emission and best fuel consumption and power output.

Photocatalytic Conversion of CO2 By H2o As an Electron Donor over Mg-Doped SrTiO3

Atmospheric CO2 is considered as the main cause of climate change, which is known as one of the serious problems for the earth, and several approaches are employed to convert CO2 into value-added products, such as CO, HCOOH, CH3OH and CH4. Among those approaches, photocatalysis has been highly attracting the world-wide attention, because photocatalytic conversion of CO2, which is called as “artificial photosynthesis”, can be a solution for climate change in terms of its renewability, harmlessness and low cost. Ga-based mixed oxide photocatalysts such as ZnGa2O4 were reported as superior photocatalysts for the photocatalytic conversion of CO2 by using H2O3. Recently, our group reported that Ag and Co dual cocatalysts-loaded Al-doped SrTiO3 photocatalyst showed relatively high formation rate of CO for the photocatalytic conversion of CO2 by H2O under photoirradiation with a monochromatic light (365 nm)1, although Ga-based photocatalysts exhibited the activity under the photoirradiation with less than 300 nm. In this study, the effect of metal dopant in SrTiO3 on the photocatalytic conversion of CO2 was investigated. It was found that Mg-doped SrTiO3 showed higher formation rate of CO for the photocatalytic conversion of CO2 into CO under photoirradiation at 365 nm than Al-doped SrTiO3.Mg-doped SrTiO3 was synthesized by a flux method. After grinding mixture of SrTiO3, MgO, and SrCl2 flux, the obtained powder was calcined at 1418 K for 15 h. Ag and Co dual cocatalysts were loaded by chemical reduction method. An aqueous solution of NaH2PO2 reductant was added to the suspension containing Mg-doped SrTiO3, AgNO3, and Co(NO3)2, and it was kept at 353 K for 1.5 h with stirring. The photocatalytic conversion of CO2 by H2O was carried out using an external-irradiation-type reaction vessel. Ag and Co-loaded Mg-doped SrTiO3 was dispersed in 0.1 M NaHCO3 aqueous solution, and high purity CO2 gas was bubbled into the suspension at a flow rate of 30 mL min−1. Monochromatic UV LED lamp (365 nm) was used as a light source. The gaseous products were analyzed by TCD–GC (H2, O2) and FID–GC equipped with methanizer (CO).XRD patterns of pristine and Mg-doped SrTiO3 showed that diffraction peaks are shifted to the lower angle by Mg2+ doping, which might be corresponded to Mg2+ doping into Ti4+ site in the bulk of SrTiO3. SEM images displayed that a shape of Mg-doped SrTiO3 is an edge-shaved cube, while that of pristine SrTiO3 is irregular. In other words, {110} facets were observed in Mg-doped SrTiO3 in addition to {100} facets. According to the previous report2, the photoexcited carriers, electrons and holes, were transported to different crystal facets of the perovskite oxide, especially {100} and {110} facets, respectively. This anisotropic charge distribution would decrease the charge recombination rate in Mg-doped SrTiO3, resulting in the high photocatalytic activity for CO2 conversion.The attached figure shows formation rates of H2 (gray), O2 (white) and CO (black) and selectivity toward CO evolution (black diamond) for the photocatalytic conversion of CO2 by H2O over Ag and Co-loaded pristine SrTiO3, Al-doped SrTiO3, and Mg-doped SrTiO3. Mg-doped SrTiO3 exhibited much higher photocatalytic activity than pristine SrTiO3 and Al-doped SrTiO3. The formation rate of CO over Mg-doped SrTiO3 was 20 μmol h−1, which was 2.3 times larger than that over Al-doped SrTiO3. Surprisingly, the selectivity toward CO evolution was almost 100 % over both Al-doped and Mg-doped SrTiO3. Moreover, the stoichiometric amount of O2 evolution was observed during this reaction, indicating that H2O worked as an electron donor for the photocatalytic conversion of CO2.The control experiments revealed that the reduction of CO2 did not proceed in the absence of photocatalyst, photoirradiation, or additive (0.1 M NaHCO3). These results clearly indicated that the significant photocatalytic performance was observed by using the Ag and Co-loaded Mg-doped SrTiO3 photocatalyst under photoirradiation with a NaHCO3 additive in the suspension. To confirm that the generated CO is not derived from any organic contamination, the isotope-labeling experiments using 13CO2 gas was carried out. GC-MS analysis of the outlet gas in the photocatalytic conversion of 13CO2 over Mg-doped SrTiO3 clarified that 13C-labeled CO (m/z = 29) was evolved in priority to 12CO (m/z = 28). Accordingly, we concluded that CO gas evolved in our system is originated from CO2 gas bubbled into the suspension. Wang, et al., Chem. Sci., 2021, 12, 4940–4948Takata, et al., Nature, 2020, 581, 411–414Wang, et al., J. Mater. Chem. A 2015, 3, 11313–11319 Figure 1

An exploration of the physical, optical, mechanical, and radiation shielding properties of PbO–MgO–ZnO–B2O3 glasses

Abstract This study presents the results of an investigation into the physical, optical, and mechanical characteristics of glasses prepared from a mixture of ZnO, MgO, B2O3, and PbO. It was found that increasing the concentration of PbO in the glasses led to an increase in both the density (ρ) and molar mass (M). The addition of PbO also affected the packing arrangement of oxygen atoms in the glass network, resulting in changes to the oxygen molar volume (V o) and oxygen packing density. Furthermore, the investigation found that the optical basicity (Ʌ th) of the glass elevated with increasing PbO concentration. Finally, the behavior of the average electronegativity (χav) and electronic polarizability ( α o − 2 {\alpha }_{{\rm{o}}}^{-2} ) with respect to the concentration of PbO in the glasses is discussed, whereby the addition of PbO affected the glasses’ mechanical characteristics as follows: (i) the addition of PbO increased the complexity of the glass network by enhancing the average cross-link density ( n c ̅ \bar{{n}_{{\rm{c}}}} ) and the number of bonds per unit volume of the glasses (n b); (ii) the glasses’ Young’s modulus (E), bulk modulus (B), and shear modulus (G) declined as the mol percent of the PbO increased; (iii) the longitudinal modulus (L) reduced but remained greater than G; (iv) the glass network cross-linking reduced the Poisson ratio (σ); (v) the glasses’ fractal bond connectivity (d) values indicated a three-dimensional network; and (vi) lead oxide hardened the glass, suggesting that a stronger structure manifests. These findings collectively demonstrate that PbO improves the rigidity and interconnectivity of glass. The gamma radiation-shielding characteristics of the glasses were evaluated using the Phy-X software in the 0.015–15 MeV energy range. The radiation-shielding properties of the studied glasses can be compared with other materials by introducing a new parameter known as the radiation coefficient ratio (R). It is observed that Q4 glass sample had superior shielding performance.

Research on effects of the cement and magnesium oxide contents on some characteristics of stabilized dredging soil in Ca Mau province

Using a mixture of cement combined with additives including (fly ash, blast furnace slag and magnesium oxide) to harden dredged silt as a substitute for sand is necessary in construction areas where sand resources are scarce nature. In the study, the mixtures (cement + fly ash + ground blast furnance slag + magnesium oxide) were used to harden mud in brackish and salt water areas in Ca Mau province of the Mekong Delta. The experimental results show that when hardening dredged sludge with content of 6% Cement combined with a mixture of ground blast furnace slag, fly ash and MgO, the viscosity, internal friction angle, adhesive force and compressive strength of the mixture sludge solidification will improve. The higher the ratio of MgO content, the lower the viscosity; the greater the internal friction angle, adhesive force and compressive strength of the hardened sludge. However, in order to balance the design requirements of the sludge after hardening, it was found that: With the rate of 4% fly ash, 2% ground blast furnace slag and 0.5% MgO, the design requirements were met, the quality of the dredging soil after hardening meets the requirements according to TCVN 8217:2009, equivalent to the hard plastic state (0.25 &lt; IL &lt; 0.5, Ctc = 32÷57 kPa and  = 11 ÷ 18°). With such hardening mud quality, it will meet the requirement of replacing sand for embankment, embankment and other works in Ca Mau in particular, and the whole Mekong Delta in general.

Enhancing compressive properties and sound absorption characteristic of open-cell Mg foams through plasma electrolytic oxidation treatment

Plasma electrolytic oxidation (PEO) technology was used to deposit a ceramic coating on the strut of open-cell Mg foams. In this experiment, the microstructure, the phase composition, and the elemental distribution of the PEO-coated Mg foams were investigated. Effect of the PEO treatment on the compressive properties and the sound absorption characteristic of open-cell Mg foams were studied. The experimental results indicate that PEO coating is mainly composed of a mixture of MgO and MgAl2O4 ceramics with high hardness and high brittleness. The compressive strength and the energy absorption capacity of Mg foams improved after being subjected to PEO treatment; however, the brittleness of the PEO-coated foams was more noticeable than that of the uncoated foams. The sound absorption coefficient of the PEO-coated Mg foams is slightly greater than that of the uncoated foams, which is mainly attributed to increased viscous friction induced by the micro-pores in the PEO coatings.

Application of MgO-Titanomagnetite mixture in high-temperature catalytic pyrolysis of radiata pine

This study aimed to investigate the effect of MgO and titanomagnetite mixture on the high-temperature pyrolysis of radiata pine wood in a fluidised bed reactor at 850 °C. The catalytic performance of the MgO-titanomagnetite (MgO-TM) mixture was experimentally evaluated based on product distribution, gas composition, gas properties, and tar composition. The results revealed that addition of MgO-titanomagnetite resulted in a decrease in gas yield (67.2 wt.%) compared to addition of titanomagnetite (TM) alone (72.9 wt.%), but an improvement was found compared to addition of MgO alone (63.9 wt.%). The hydrogen concentration in the gas product was significantly enhanced (23.2 vol.%) compared to titanomagnetite alone (12.8 vol.%) or to non-catalytic (NC) pyrolysis (14.1 vol.%) but was similar to that with addition of MgO alone (22.6 vol.%). However, the addition of MgO and titanomagnetite mixture resulted in a reduction in CO concentration to 2.7 vol.% in the gas product whereas increased the CO2 and light olefins formation. It was also found that the addition of the MgO and titanomagnetite mixture significantly increased the total concentration of ethylene and propylene (18.3 vol.%) compared to addition of titanomagnetite (5.8 vol.%), MgO (9.0 vol.%), or non-catalytic pyrolysis (12.0 vol.%). The lower heating value of the gas product and the H2 to CO ratio (17.5 MJ/Nm3 and 8.7) were also improved with addition of the MgO-titanomagnetite mixture. These findings demonstrate that application of physically mixed MgO and titanomagnetite as catalyst is a promising method for converting biomass into a H2-rich gas product via high-temperature pyrolysis. This study offers a useful reference for the development of novel catalytic systems for biomass conversion.Graphical

Formation of nano and micro scale hierarchical structures in MgO and ZnO quantum dots doped LC media: the role of competitive forces

In this paper, we have studied the effect of doping of ZnO and MgO nanoparticles (NPs) in 4-(trans-4-n-hexylcyclo-hexyl) isothiocyanatobenzoate. A thorough comparison of dielectric properties, optoelectronic properties, and calorimetric phase transition properties has been done for MgO and ZnO NP doped LC. We prepare their homogenous mixture of MgO and ZnO NPs in toluene and transfer into cells made of glass and Indium Tin-Oxide (ITO) coated glass. The observed microstructures in the hybrid system can be classified into three main categories: grain like structures formed by aggregation of smaller size MgO nanoparticles while liquid crystal molecules anchor over the surfaces of nanoparticles, the grtu grain-like structures further integrate to form inorganic polymeric type of honeycomb-like mesostructures in presence of glass surface, and flower-like clusters of MgO nanoparticles on ITO surface. The smaller size nanoparticles can maintain the energy balance by allowing the anchoring of liquid crystal molecules over their surfaces whereas the larger size nanoparticles cannot compromise or maintain the energy balance with the liquid crystal molecules and are separated out to nucleate and form bigger size nanoaggregate or clusters. The energy preference of the substrate and nanoparticle’s surface to liquid crystal molecules plays an important role in the formation of different types of hierarchical nano- and microstructures. We account the reasons for the formation of nano and micro scale hierarchical structures on the basis of the competition between the forces: NP-NP, LC-LC, NP-LC, Glass/ITO-NP, and Glass/ITO-LC interactions. We observed a considerable change in the dielectric properties, transition temperature, bandgap, and other parameters of LC molecules when MgO NPs are doped, but a minor change occurs when ZnO NPs are doped in LC. Optical microscopy, FTIR, Raman, IR, HR-XRD and FESEM-EDX characterization data confirm and validate our guiding conceptions.

Thermophysical Properties of Biodiesel with Ethyl Levulinate, Ethyl Acetoacetate, and Ethyl Pyruvate + MgO Mixtures from 288.15 to 338.15 K

Thermophysical properties are important to design the fuel system components and to evaluate new alternative fuels in diesel engine tests. Also, experimental properties allow us to understand the type of interactions present in the studied mixtures. Densities, viscosities, and refractive indices of biodiesel + ethyl levulinate, + ethyl acetoacetate, and + ethyl pyruvate with MgO mixtures have been measured from 288.15 to 338.15 K at 0.1 MPa over the whole composition range and at a constant concentration of 5 × 10–6 in mass fraction for MgO. Our experimental properties for the pure ketoesters agree with data reported in the literature within an average absolute percentage deviation of 0.056, 3.140, and 0.027 % for density, viscosity, and refractive index, respectively. Vibrating tube densimeter, glass capillary viscosimeter, and Abbemat refractometer have been used to measure the properties. Densities and viscosities of the biodiesel mixtures have been compared with the biodiesel fuel standard EN 14214. Flash point, cetane index, and calorific value of the biodiesel mixtures that meet the EN 14214 norm have been measured. Excess molar volume, viscosity deviation, and refractive index deviation are obtained from experimental data and correlated using the Redlich–Kister equation. Equations reported in the literature are used to correlate the thermophysical properties of the investigated mixtures.

Mechanism and assessment of the pozzolanic activity of melting-quenching lithium slag modified with MgO

The current energy consumption and waste emission are mainly produced from the process of cement manufacturing. Lithium slag (LS), a solid waste from lithium smelting, has been utilized as concrete additives with a low rate of approximately 10 %, and the remaining nearly 90 % of LS are stored as industrial solid waste, which not only occupies large amounts of land, but also causes serious resource waste and environmental pollution. For the purpose of developing a kind of cleaner binders using LS to reduce cement consumption and environmental pollution, a novel activation method of “chemical modification-melting granulation-mechanical pulverization” was conducted in this present study. Alkali cations, such as Mg2+, Ca2+, etc., are beneficial to improve the pozzolanic activity of LS according to previous results. Thus, a chemical modification was first performed by preparing the melted-quenched mixtures of LS and MgO in different ratios, and coded as MGLS. The characterization results of MGLS demonstrate that MgO modification can enhance the pozzolanic activity of LS by accelerating the dissolution of the amorphous networks. Pastes of PPC and P-MGLS (70 % PPC + 30 % MGLS) were prepared for UCS tests (a maximum allowable rate of 30 % for LS as concrete additives, according to engineering experience), showing clear retardations of strength development for P-MGLS pastes due to the low extent of pozzolanic reaction in the early period of 3 ∼ 7 d. The 7 ∼ 90 d strengths significantly increase with the content of MgO for P-MGLS pastes, and the P-MGLS15 paste cured for 90 d gains the UCS value of 52.49 MPa, even higher than that of PPC paste at 90 d, due mainly to the enhanced pozzolanic reaction with large amounts of CSH/CAH gels formed by MgO modification, and a compact microstructure, as well as higher values of Ca/Si and Al/Si ratios are measured in the CSH/CAH gels of P-MGLS15 paste, indicating that more reactive constituents can be released to enhance the formation of pozzolanic products for the pastes richer in MgO. Results of the present study may provide a potential way for the applications such as construction building, backfill mining, etc., that can be developed using MGLS, which also promotes the sustainability for cement and environmental industries.

Multiwalled carbon nanotubes as an additive to Mg-Mg2Si in situ composite obtained by powder sintering

This paper reports on the possibility of applying carbon nanotubes as an additive to metallic materials, where a new phase forms in situ from the powder mixture. Multi-walled carbon nanotubes (MWCNT) amounts of 1 vol% and 3 vol% were applied to synthesize a composite with interpenetrating phases obtained from magnesium microsized powder and nanosized silicon (n)Si by sintering under vacuum. In the experiments, two ordered Mg-(n)Si-MWCNT powder mixtures with a (n)Si: MWCNT ratio of 2: 1 were prepared by sonication. The effects of Mg2Si silicide in situ synthesis on the behavior of MWCNTs and the Mg2Si and Mgα morphology were studied. Using LM with quantitative metallography, SEM with EDS, XRD, HREM, it was found that the MWCNTs were a component of the skeleton formed by submicron and nanosized Mg2Si, MgO, and Mgα mixture. Non-agglomerated MWCNTs were also found in microsized Mg2Si particles in the composite. A decrease in the silicide crystallite size was also observed compared with material without a carbon nanocomponent. The transformation of MWCNTs into another phase or their morphology change was not observed. Therefore, the effects described in this paper can be adapted to technologies focused on different types of composites and for designing Mg2Si-based thermoelectric materials and intermetallic alloys.

Effect of stray current on corrosion behavior of Mg alloy sacrificial anode in buried pipeline

In this work, a self-designed stray current simulated system was employed in corrosion evaluation test, and the effect of stray current on corrosion behavior of Mg alloy was investigated. The anti-corrosion performance of Mg alloy directly related to its corrosion film. The corrosion film covered on Mg surface was incomplete, which was a mixture of porous MgO + Mg(OH)2, and the corrosion happened on the bare Mg substrate at the rupture of corrosion film. The pitting corrosion randomly occurred on α-Mg, and the anodic hydrogen evolution (AHE) further damaged the corrosion film. With the extension of time, the pits developed into severe localized corrosion and the corrosion rate was accelerated. The stray current was composed of direct current (DC) and low-frequency alternating current (AC), which promoted the rupture of corrosion film, hence the stray current significantly accelerated the corrosion rate of Mg alloy.