MgO Doping Research Articles

Insight into insulation degradation mechanism of Al2O3 involved with positive and negative defects

Al2O3 with the desired electrical insulating properties and thermal shock resistivity has been extensively applied in the field of solid oxide fuel cells and oxygen sensors. However, degradation of the insulating Al2O3 layer is an intractable issue in practical applications. In this study, different point defect structures of Al2O3 were realized with the substitutional doping effect of ZrO2 and MgO. The MgO dopant provides positively charged oxygen vacancies, whereas the ZrO2 dopant tends to trigger negatively charged vacancy formation at Al3+ sites. The oxygen vacancy concentration of Al2O3 exhibits the following trend: MgO-doped Al2O3 > Al2O3 > ZrO2-doped Al2O3. Furthermore, the densification morphology, insulating properties, and oxygen vacancy migration of Al2O3 have been confirmed to be largely affected by the extrinsic factors. This study indicates that oxygen vacancy migration depends on the applied electric field at high temperatures. As the voltage and temperature increase, oxygen vacancy migration shows obvious electric-field-dependent characteristics, and its aggregation macroscopically shows hole defects. The defect position of Al2O3 is nonstoichiometric Al2O3-x with poor crystallinity. Therefore, it is believed that the oxygen vacancy migration triggered by the second phase directly determines the insulation performance and causes the degradation of Al2O3 materials.

An experimental study on jute/banana fiber reinforced poly(vinyl alcohol) composites with nanofiller

AbstractThe incorporation of nanoparticles into natural fiber composites has the potential to alter the characteristics of natural fiber composites. In this study, various properties of jute and banana fiber reinforced poly(vinyl alcohol) (PVA) composites with different nanofillers incorporation were investigated. Samples were prepared using the vacuum bagging technique. Inorganic nanoparticles (Al2O3, ZnO, MgO, CuO, and TiO2) were synthesized using a ball milling machine and in each sample, 3 wt.% of nanofillers were incorporated. The maximum ultimate tensile strength and elongation percentage is found for TiO2, which is 90.433% higher than pure PVA whereas MgO incorporated samples provides maximum flexural strength, which is 162.59% higher than PVA. The sample with Al2O3 provides strongest impact resistance, 17.3 J/cm2. It was found that the decomposition temperatures were slightly higher for MgO and CuO doping than the undoped PVA composite. The FT‐IR spectra exhibited notable hydroxyl groups and minor shifts indicating a reduction in hydrophilicity upon the introduction of nanoparticles. The water absorption exhibited a reduction of up to 36% in conjunction with an increase in density across all samples. The highest crystallinity is found for CuO nanofiller composite, validated by x‐ray diffraction analysis. Additionally, morphological changes in the composites were seen through scanning electron microscopy and EDX shows a strong peak at 2.1 keV indicate some impurities present in the samples.Highlights Jute/banana/PVA composites were prepared with 3 wt% nanoparticles incorporation. Metal oxides such as Al2O3, ZnO, MgO, CuO, and TiO2 were used as nanoparticle. The use of nanoparticle improved the tensile, flexural, and impact properties. Decomposition temperatures were found higher for MgO and CuO incorporated composites. Upon nanoparticle incorporation, water absorption exhibited a reduction of upto 36%.

Ocimum sanctum-mediated co/cu/zn-doped magnesium oxide nanoparticles: Photocatalytic, antibacterial, and antioxidant properties for environmental remediation

This research intends to formulate Ocimum sanctum mediated pure and transition metal (Co2+/Cu2+/Zn2+) doped magnesium oxide nanoparticles (MgO NPs). The cubic structure of so synthesized MgO NPs was confirmed by XRD analysis. As per UV–visible spectral analysis, band gap (Eg) is tuned upon doping; doping with Co, Cu and Zn, their respective Eg are 1.65 eV, 1.96 eV and 3.66 eV in relation to MgO, Eg = 3.50 eV. The average particle size decreased from 17 nm for MgO NPs to 8–13 nm for doped MgO NPs, based on TEM analysis. EDX and XPS analysis verified the presence of Mg, O and dopants, Co, Cu and Zn in synthesized NPs. SEM investigations showed that NPs are agglomerated and spherical. Zn–MgO NPs outperform Co/Cu doped MgO NPs in their photocatalytic efficacy and comparative degradation of methyl orange (MO) and malachite green (MG) dyes confirmed that they are more efficient in degrading MG. Antibacterial investigation revealed that Cu and Zn doped MgO NPs are efficient antibacterial agents against B. subtilis and E. coli than MgO NPs. In this study, Co–MgO NPs were ineffective as antibacterial agents. S. aureus was found resistant to all NPs. Using the DPPH radical scavenging technique, these biosynthesized nanoparticles displayed 62–69 % antioxidant activity.

Absorption Band at 1600 cm-1 in the IR Spectra of Irradiated MgO Crystals

In the IR spectra of nominally pure and doped MgO crystals after irradiation, an intense absorption band appears at 1600 cm-1. This message discusses the model of the corresponding absorption center.

Vitamin D3 Release from MgO Doped 3D Printed TCP Scaffolds for Bone Regeneration.

Regenerating bone tissue in critical-sized craniofacial bone defects remains challenging and requires the implementation of innovative bone implants with early stage osteogenesis and blood vessel formation. Vitamin D3 is incorporated into MgO-doped 3D-printed scaffolds for defect-specific and patient-specific implants in low load-bearing areas. This novel bone implant also promotes early stage osteogenesis and blood vessel development. Our results show that vitamin D3-loaded MgO-doped 3D-printed scaffolds enhance osteoblast cell proliferation 1.3-fold after being cultured for 7 days. Coculture studies on osteoblasts derived from human mesenchymal stem cells (hMSCs) and osteoclasts derived from monocytes show the upregulation of genes related to osteoblastogenesis and the downregulation of RANK-L, which is essential for osteoclastogenesis. Release of vitamin D3 also inhibits osteoclast differentiation by 1.9-fold after a 21-day culture. After 6 weeks, vitamin D3 release from MgO-doped 3D-printed scaffolds enhances the new bone formation, mineralization, and angiogenic potential. The multifunctional 3D-printed scaffolds can improve early stage osteogenesis and blood vessel formation in craniofacial bone defects.

Preparation and investigation of ZrO2-based thermal control coatings doped with MgO

In this study, MgO doped ZrO2 thermal control coatings were prepared using atmospheric plasma spraying technology. The phase composition, microstructure, optical properties of the coatings were characterized. The results showed that all the coatings possessed a significantly layered structure. With the increase of MgO doping content, the phase composition of the coatings showed a transition from monoclinic to cubic phase. Moreover, the solar absorptance (αs) effectively decreased, while the hemispherical emissivity (εH) increased. When the doping content reached 20 mol%, the αs/εH obtained a minimum value of 0.475, where the αs and εH was 0.399and 0.8395 correspondingly. The decrease in solar absorptance is mainly due to the doping of MgO, which reduces the free carrier concentration and attenuates the free carrier absorption. The increase in hemispherical emissivity is attributed to the lattice distortion, which enhances the lattice vibrational intensity.

Effects of MgO doping in Pd/γ-Al2O3 catalysts forthe hydrogenation of perfluoro olefin

Gamma alumina is widely utilized for preparing the supported noble metal catalysts for the hydrogenation reaction. It is an effective strategy to improve the catalytic performance of catalysts via modifying gamma alumina with alkaline earth metal to regulate its surface acidity and electronic properties. Herein, Pd catalysts supported by Al2O3 and Mg-modified Al2O3 are synthesized via the wet impregnation method, and the effects of MgO doping on the structure, composition, and surface acidity of Pd/γ-Al2O3 catalysts are investigated via X-ray diffraction patterns (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Temperature programmed desorption (TPD). The results show that Pd/MgO-Al2O3–2 (γ-Al2O3 modified with 2 wt% Mg) has more metallic state palladium and weak acid sites and exhibits the best catalytic performance for the hydrogenation of perfluoro-4-methyl-2-pentene (D1). Density functional theory (DFT) calculations on Pd/Al2O3 and Pd/MgO-Al2O3–2 catalysts are also performed to further explore the mechanism of D1 hydrogenation. The studies for Gibbs free energy of the potential reaction steps and intermediates reveal a complex process to generate the target product C6F12H2, and the rate-determining-step is the addition of the first hydrogen on the second carbon of perfluoro-4-methyl-2-pentene molecule.

New insights into refractive indices and birefringence of undoped and MgO-doped lithium niobate crystals at high temperatures

The lithium niobate single crystal is a well-known optical material that has been employed in a wide range of photonic applications. To realize further applications of the crystal, the birefringence properties need to be determined over a large range of temperatures. We report refractive indices and birefringence properties of undoped and MgO-doped lithium niobate crystals with high accuracy using spectroscopic ellipsometry in the spectral range from 450 to 1700 nm and a temperature range from ambient temperature to 1000 °C. The birefringence results indicate a transition temperature, where the crystal transforms from an anisotropic to isotropic property, and the advance of MgO doping in the crystal, which is related to the optical damage threshold of the materials. In addition, the lattice dynamics of the crystals have been analyzed by revisiting the Raman spectroscopy. The results establish the foundation of optical properties of lithium niobate crystals, providing pathways for their photonic applications.

Evaluation of Structural Stability, Mechanical Properties, and Corrosion Resistance of Magnesia Partially Stabilized Zirconia (Mg-PSZ).

Nano Zirconia (ZrO2) has been used in dental implants due to having excellent mechanical properties and biocompatibility that match the requirements for the purpose. Zirconia undergoes phase transformation during heating: monoclinic (room temperature to 1170 °C), tetragonal (1170 °C to 2370 °C), and cubic (>2370 °C). Most useful mechanical properties can be obtained when zirconia is in a multiphase form or in partially stabilized zirconia (PSZ), which is achieved by adding small amounts of a metal oxide dopant, such as MgO (magnesia). This study aimed to synthesize nano Mg-PSZ from a local resource found in West Kalimantan, Indonesia, and examine its structural stability, biochemical stability, and mechanical properties. Nano Mg-PSZ was prepared from a zircon local to Indonesia, from West Kalimantan Province, MgSO4∙7H2O, and polyethylene glycol (PEG)-6000 was used as a template. The obtained t-ZrO2 after calcination at 800 °C was shown to be stable at room temperature. The highest percentage of the t-ZrO2 phase was obtained at Zr0.95Mg0.05O2 with a variation of 99.5%. The hardness of Mg-PSZ increased from 554 MPa for ZrO2 without MgO doping to 5266 MPa for ZrO2 with a doping of 10% MgO. An in vitro biodegradation test showed that the greater the concentration of MgO in doping the ZrO2, the greater the degradation resistance of Mg-PSZ in simulated body fluid (SBF) solution.

Enhanced dielectric properties and chemical bond characteristics of MgNb2O6 ceramics due to magnesium oxide doping

Herein, the effects of MgO doping on the crystal structure, microstructure, chemical bond properties, vibrational properties and microwave dielectric performances of MgNb2O6 + x mol% MgO (x = 0–3) ceramics fabricated by solid-state reaction were examined. The results show that the doping of MgO does not produce a second phase and Mg2+ ions enter the lattice to form a continuous solid solution. The Q×f value of the system increases from 112,630 GHz (x = 0) to 121,580 GHz (x = 1), which is due to the microstructure and FWHM. In addition, the dielectric constant of ceramics is mainly influenced by the bond ionicity of Nb–O bond, relative density, and porosity. Meanwhile, the τf value shifts in the negative direction due to the variations of bond energy for Nb–O bond, bond valence of Nb–O bond, thermal expansion coefficient of Nb–O bond, and NbO6 octahedral distortion. The MgNb2O6 + 1 mol% MgO ceramics sintered at 1460 °C exhibit amazing microwave dielectric properties (εr = 20.82, Q ×f = 121,580 GHz, and τf = −48.89 ppm/°C), providing a potential candidate for modern microwave communications.

Study of the Mechanisms of Polymorphic Transformations in Zirconium Dioxide upon Doping with Magnesium Oxide, as Well as Establishing the Relationship between Structural Changes and Strength Properties

The aim of this work is to study the mechanisms of polymorphic transformations in ZrO2 ceramics doped with MgO with different concentrations during thermal isochronous annealing, as well as the effect of the phase composition of ceramics on the change in strength properties and resistance to mechanical stress. Solving the problem of polymorphic transformations in zirconium dioxide by doping them with MgO will increase the resistance of ceramics to external influences, as well as increase the mechanical strength of ceramics. According to the data of X-ray phase analysis, it was found that the addition of the MgO dopant to the composition of ceramics at the chosen thermal annealing temperature leads to the initialization of polymorphic transformation processes, while changing the dopant concentration leads to significant differences in the types of polymorphic transformations. In the case of an undoped ZrO2 ceramic sample, thermal annealing at a temperature of 1500 °C leads to structural ordering due to the partial removal of deformation distortions of the crystal lattice caused by mechanochemical grinding. During the study of the effect of MgO doping and polymorphic transformations in ZrO2 ceramics on the strength properties, it was found that the main hardening effect is due to a change in the dislocation density during the formation of a ZrO2/MgO type structure. At the same time, polymorphic transformations of the m—ZrO2 → t—ZrO2 type have a greater effect on hardening at low dopant concentrations than t—ZrO2 → c—ZrO2 type transformations.

Oxygen Vacancy Promoted Generation of Monatomic Oxygen Anion over Ni2+ -Doped MgO for Efficient Glycolysis of Waste PET.

Developing efficient and eco-friendly catalysts for selective degradation of waste polyethylene terephthalate (PET) is critical to the circular economy of plastics. Herein, we report the first monatomic oxygen anion (O- )-rich MgO-Ni catalyst based on a combined theoretical and experimental approach, which achieves a bis(hydroxyethyl) terephthalate yield of 93.7 % with no heavy metal residues detected. DFT calculations and electron paramagnetic resonance characterization indicate that Ni2+ doping not only reduces the formation energy of oxygen vacancies, but also enhances local electron density to facilitate the conversion of adsorbed oxygen into O- . O- plays a crucial role in the deprotonation of ethylene glycol (EG) to EG- (exothermic by -0.6 eV with an activation barrier of 0.4 eV), which is proved effective to break the PET chain via nucleophilic attack on carbonyl carbon. This work reveals the potential of alkaline earth metal-based catalysts in efficient PET glycolysis.

Effect of MgO doping on energy storage and electrocaloric properties of ferroelectric 0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3 ceramics

This study highlights the effect of MgO doping on microstructure, dielectric, ferroelectric, energy storage and electrocaloric properties of lead-free (1-x)(0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3)–xMgO ceramics with x varying from 0-5%. X-ray diffraction studies revealed that BZCT-MgO ceramics exhibited a morphotropic phase boundary (MPB), i.e. coexistence of both tetragonal and rhombohedral phases at room temperature for x ≤ 1%. Scanning electron microscope (SEM) images revealed that grain size is decreased with the increase of MgO content. The Raman analysis and temperature dependent dielectric studies further confirm the MPB behaviour at low MgO content. Besides, the MgO additive improves the diffused phase transition (DPT) behaviour of BZCT ceramics, lowers transition temperature and enhances their relaxor behaviour. It is observed that 0.99BZCT–0.01MgO showed optimum energy storage properties with a recoverable energy density of 177.6 mJ/cm3 and an efficiency of 79% at an electric field of 45 kV/cm. Moreover, they exhibited a robust energy storage performance even after passing 107 cycles. Further, the electrocaloric temperature change and responsivity are found 1.12 K at 45 kV/cm and 0.024 Kcm/kV, respectively in 0.99BZCT–0.01MgO ceramics.

The effect of Ag2O and MgO dopants on the bioactivity, biocompatibility, and antibacterial properties of 58S bioactive glass synthesized by the sol-gel method

In the current investigation, the bioactive glasses (BGs) in 60SiO2–26CaO-4P2O5–5SrO-xMgO-(5-x)Ag2O systems (x = 0–5 mol.%) were fabricated via the sol-gel method. The effect of Ag and Mg dopants on in vitro apatite-forming ability, antibacterial properties, and cell viability were studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and Fourier transform infrared spectroscopy (FTIR) were carried out for morphological and structural evaluations. Based on the results, the BG-A2M3 (2 mol% Ag2O and 3 mol% MgO) sample had the highest ability to form a hydroxyapatite layer. The antibacterial and 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay data indicated the antibacterial properties due to the presence of Ag and biocompatibility of synthesized BGs, respectively. Accordingly, BG-A2M3 was selected as the optimized sample with great biocompatibility and optimum antibacterial and bioactive properties. This sample is suitable for dental and orthopedic applications.

Dopant and compositional modulation triggered long-wavelength ultra-broadband and tunable NIR emission in MgO: Cr3+ phosphor for NIR spectroscopy applications

Efficient ultra-broadband near-infrared (NIR) phosphors with long-wavelength ( λ max > 850 nm) and wide full width at half-maximum (FWHM, >200 nm) have sparked tremendous interest, demonstrating their immense potential in NIR spectroscopy technology. Nevertheless, the development of NIR spectroscopy technology suffers from the restricted capability to efficiently emit the ultra-broadband NIR light. Herein, the synergetic enhancement strategy of heterogeneous substitution and compositional modulation was applied to create a novel Cr 3+ doped long-wavelength ultra-broadband MgO: Cr 3+ , Ga 3+ phosphor, which exhibited a long-wavelength ultra-broadband NIR emission ( λ max = 850 nm) covering the range of 650–1300 nm on the electromagnetic spectrum with the FWHM of more than 200 nm under the excitation of 468 nm light. Furthermore, the tunable NIR emission from 818 nm to 862 nm with an optimized quantum efficiency of 30% was accomplished by the Ga 3+ ions substitution and Cr 3+ ions modulation. The phosphor exhibited remarkable thermal stability up to 100 °C, remaining 83% of the integrated emission intensity at room temperature. A prototype of the NIR phosphor-converted LED (pc-LED) demonstrated that the novel MgO: Cr 3+ , Ga 3+ phosphor possessed a relatively strong NIR output power (15.05 mW at 100 mA driven current) with a photoelectric conversion efficiency of 5.53%, which is impressive compared with other Cr 3+ -doped long-wavelength ultra-broadband phosphors. This work not only proposes a novel long-wavelength ultra-broadband NIR phosphors with industrialization and great application prospect in night vision but highlights a synergetic enhancement strategy to effectively boost the performance of long-wavelength ultra-broadband NIR pc-LED light sources.

Green Synthesized Mgo Doped Gc3n4 Incorporated on Pan/Peg for Biodegradable Bone Regenerative Scaffolds and its Biological Evaluation

Green Synthesized Mgo Doped Gc3n4 Incorporated on Pan/Peg for Biodegradable Bone Regenerative Scaffolds and its Biological Evaluation

Effect of Doping Content of MgO on Solar Absorptivity to IR Emissivity Ratio of Al2O3 Coatings

High-emissivity coatings are often used on the surfaces of solar probes to block heat from the sun. Therefore, improving the thermal control ability is the standard for determining the quality of the coatings. In this study, MgO was doped into Al2O3 to improve the thermal control ability of the coatings and to analyse the effect of different MgO doping contents. The solar absorptivity to infrared (IR) emissivity ratio (α/ε) was used to evaluate the thermal control ability of the coatings. The results showed that 5 wt.% MgO doping content is the best choice. The main reason for the change in α/ε is related to the doping of MgO, which affects the grain size of Al2O3.

Highly Cyclic Stability and Absorbent Activity of Carbide Slag Doped with MgO and ZnO for Thermochemical Energy Storage.

Carbide slag is a solid waste with a high content of reactive CaO, which can be used as an active material for the chemical absorption of CO2 and calcium looping. Calcium looping of CaO-based absorbents is one of the most promising methods of thermochemical energy storage. However, the sintering of pores and a reduction in the CO2 diffusion rates as the carbonization/calcination cyclic reaction progresses have posed challenges to the practical application of CaO-based absorbents. This study proposes a method for alleviating the sintering of the pore structure by improving the activity and cycling stability of such absorbents by doping carbide slag with MgO and ZnO powders. Results showed that the raw material ratio, reaction temperature, and reaction time have a considerable influence on the CO2 absorption rate. Furthermore, the specific surface area and pore volume of the absorbents increased with increasing ZnO and MgO doping levels in the carbide slag. Thus, the problems of sintering and clogging of pores in CaO-based absorbents were effectively alleviated, and the MgO and ZnO-doped absorbents CMZ85 and CMZ90 maintained 41-42% CO2 absorption after 10 cycles. These results confirmed that the cyclic stability and absorbent activity improved significantly with the MgO and ZnO doping of carbide slag for the calcium looping process.

Tough and damage-tolerant monolithic zirconia ceramics with transformation-induced plasticity by grain-boundary segregation

Conventional ceria-stabilized tetragonal zirconia (Ce-TZP) with modest flexural strength has rarely been used as compared to yttria-stabilized zirconia, even though it has excellent hydrothermal stability and high toughness. Ce-TZP-based composites were recently developed, being tough and remarkably in combination with transformation-induced plasticity. However, distinct from the widely applied composite approach to improve the strength of Ce-TZP, in this study, a simpler and easily tailorable method was proposed by doping aliovalent oxides that are able to segregate at the zirconia-grain boundaries. 0.2–1 mol% divalent oxides with different cation size (Mg2+, Ca2+, Ba2+ and Sr2+) were selected to dope 10 mol% ceria-stabilized zirconia. CaO and MgO dopants were able to enter the tetragonal Ce-TZP lattice and showed a grain-boundary segregation effect, thereby tailoring the microstructure and transformation behavior. At a higher dopant concentration of 1 mol% MgO or CaO, the ceramics were strong but brittle with a typical elastic linear fracture behavior, whereas at a low dopant concentration of 0.1–0.2 mol% CaO or 0.2–0.4 mol% MgO doping, the ceramics deformed in-elastically to a certain degree without changing the Young’s modulus. At the transition between both fracture behaviors, the best combination of toughness (>10 MPa m1/2), biaxial strength (≥1200 MPa), reliability (Weibull modulus up to 30) and damage-tolerance was obtained. In-situ fracture testing revealed that transformation in such tough and deformable zirconia ceramics took place well before crack initiation with a large transformation zone of ∼100 µm ahead of the crack tip having been formed before failure.

The role of oxide in hydrogen absorption and desorption kinetics of MgH2-based material

MgH2-based hydrides have a very high affinity to oxygen, leading to the degradation of their hydrogen storage properties. Herein, we use MgO doping and air exposure methods to add oxygen to the MgH2-TiH2 materials, and the hydrogen storage properties of these materials are systematically investigated. The results show that MgO doping accelerates the ambient temperature absorption kinetics, impedes the Mg crystalline growth, and reduces the desorption temperature. In contrast, the air exposure significantly deteriorated the kinetics of MgH2-TiH2 under both ambient and high temperature. The hydrogenation kinetics of the air-exposed sample can be recovered under cycling. Our results indicate that the effect of MgO is highly dependent of the means to introduce MgO and the location of MgO in the matrix structure. Air-exposure is the main factor for the degradation of hydrogen storage properties, but the MgO doping positively affects the performance of the Mg-based hydride.