Structural,optical, cytotoxicity,and antimicrobial properties of MgO,ZnO and MgO/ZnO nanocomposite for biomedical applications

In this study, MgO nanoparticles were successfully fabricated and incubated inside ZnO NPs to form MgO/ZnO nanocomposite for biomedical applications. The x-ray diffraction analysis of MgO, ZnO, and MgO/ZnO has shown the single-phase x-ray diffraction patterns through X'pert High score. The crystallite sizes were calculated as 18 nm, 42 nm, and 53 nm, respectively. The average particle size of MgO, ZnO, and MgO/ZnO nanopowders depicted from secondary electron images of field emission electron microscopy were 56 nm, 400 nm, and 450 nm, respectively. The presence of MgO NPs inside ZnO NPs was confirmed by transmission electron microscopy. The elemental dispersive spectroscopy of MgO, given the peaks of oxygen and magnesium, also showed only zinc and oxygen peaks in ZnO, which confirms no other impurities in MgO and ZnO powders. The elemental analysis of MgO/ZnO nanocomposite showed the peaks of Zinc and Oxygen, along with a tiny peak of Mg. The photoluminescence and UV–vis spectroscopy revealed the absorbance fluorescence limit of the nanomaterials. Fourier transform infrared spectroscopy confirmed the several groups present in the nanocomposite. The biocompatibility of MgO, ZnO, and MgO/ZnO was observed with human peripheral blood mononuclear cells. The cytotoxicity studies were also performed against human cancer (liver and breast) cell lines. The MgO, ZnO, and MgO/ZnO exhibited the antimicrobial properties against Escherichia coli and Staphylococcus aureus.     

Catalytic combustion synthesis of CNTs/MgO composite powders and the influences on the thermal shock resistance of low-carbon Al2O3–C refractories

Using MgC₂O₄, Mg powders as raw materials and Ni(NO₃)₂?6H₂O as a catalyst, CNTs/MgO composite powders were prepared by a catalytic combustion synthesis method. The CNTs/MgO composite powders were characterized by XRD, Raman spectroscopy, FESEM/EDS and HRTEM. The effects of catalyst content on the degree of graphitization and aspect ratio of the CNTs in composite powders were investigated. Moreover, the thermal shock resistance of low-carbon Al₂O₃–C refractories after adding the composite powder was investigated. The results indicated that the CNTs prepared with 1 wt% Ni(NO₃)₂?6H₂O addition had a higher degree of graphitization and aspect ratio. In particular, the aspect ratio could reach approximately 200. The growth mechanism of hollow bamboo-like CNTs in the composite powders was proven to be a V-L-S mechanism. The thermal shock resistance of Al₂O₃–C samples could be improved significantly after adding CNTs/MgO composite powders. In particular, compared with CM0, the residual strength ratio of Al₂O₃–C samples with added 2.5 wt% composite powders could be increased 63.9%.     

Impact of preheating on the mechanical performance of different MgO–C bricks - Low temperature range

This work complements an initial study regarding the mechanical behavior of MgO–C bricks at 1000 °C. In this case, two bricks bonded with phenolic resin, one of them containing aluminum, were treated at 600 °C and mechanically tested at RT and 600 °C. The thermal treatments attempt to simulate the in-service steelmaking ladle preheating process. At low temperatures, the binder pyrolysis is one of the main transformations and the Al melting neither its chemical reactions occur on a large scale yet. To evaluate the effects as the pyrolysis progresses, the soaking time at 600 °C was varied from 1 to 3 h. Although without significant chemical activity, the presence of Al affected the mechanical behavior of the tested bricks. The consolidation of the C–C network coming from the binder pyrolysis was identified as the main factor responsible for counterbalancing the material's degradation by microcracking. The heating combined with the low compressive pre-load applied on the tested specimens appears to close the microcracks and pores.     

Application of Cr3C2/C composite powders synthesized via molten-salt method in low-carbon MgO–C refractories

High-performance and low-carbon MgO–C refractories are important refractories for smelting ultra-low carbon steel and clean steel. Based on this, Cr₃C₂/C composite powders were synthesized by the molten-salt method, and used as an additive to prepare low-carbon MgO–C refractories under nitrogen atmosphere. The phase, morphology and oxidation kinetics of Cr₃C₂/C composite powders were studied. In addition, the effect of Cr₃C₂/C composite powders on the morphology, mechanical properties, thermal shock resistance, and corrosion resistance of MgO–C refractories was investigated. The results indicated that the Cr₃C₂/C composite powders exhibited superior oxidation resistance than flake graphite. Moreover, the Cr₃C₂/C composite powders were introduced into the MgO–C refractories. Compared with the sample without Cr₃C₂/C composite powders, the introduction of 1 wt% Cr₃C₂/C composite powders significantly improved the thermomechanical properties and corrosion resistance of the material, its CMOR, CCS before and CCS after thermal shock were 9.06 MPa, 50.40 MPa and 32.60 MPa, respectively, and the corrosion index was significantly reduced from 44.6% to 26.5%.     

Early hydration properties and microstructure evolutions of MgO-activated slag materials at different curing temperatures

This study reports on the early hydration properties and microstructure evolutions of MgO-activated slag at five curing temperatures (20 °C, 40 °C, 50 °C, 60 °C, and 80 °C) and three MgO types (S-MgO, M ? MgO, and R-MgO). The results indicated that high-temperature curing substantially increased the compressive strength of the specimens. Particularly, the highest strength was obtained at 40 °C and 60 °C for the S-MgO and M-MgO-activated slag specimens, respectively, and the high curing temperature for the R-MgO-activated slag specimen was 40 °C. We focused on the relationship between the mechanical properties, pore structure characteristics, and hydration products. The combination of calcium-silicate-hydrate (C-S-H) gel and Al increased under high-temperature curing conditions. XRD, FT-IR, TG-DTG, and ²⁷Al MAS-NMR results showed a high Al content in the formation of calcium silicate hydrate with Al in its structure (C-A-S-H gel) for the R-MgO-activated slag pastes under high-temperature curing; however, the microstructure was loose owing to the formation of excessive brucite. For the S-MgO-activated slag specimen, the Ca/Si ratio was high, with more Mg²⁺ penetrating the C-S-H gel interlayer, forming more hydrotalcite-like phases and increasing the chain length of the C-S-H gel. The microstructure showed good compatibility of the hydration products interweaving to form dense microstructures.     

Effects of sintering temperature and Bi2O3, Y2O3 and MgO co-doping on the dielectric properties of X8R BaTiO3-based ceramics

Bi₂O₃, Y₂O₃ and MgO co-doped BaTiO₃ (BT)-based X8R ceramics were synthesized successfully for the first time. The effects of the sintering temperature and Bi₂O₃, Y₂O₃ and MgO dopants on the dielectric properties were investigated systematically. Bi₂O₃ doping can increase the Curie temperature (T_c), but reduces the overall dielectric permittivity. On the other hand, Y₂O₃ doping is beneficial to the formation of core-shell microstructure and the increase of T_c, whereas MgO can prevent excessive Y₂O₃ from diffusing into grain core, and thereby further contributes to the generation of the core–shell microstructure. The generation of the typical core-shell microstructure was confirmed and investigated in detail by using transmission electron microscopy (TEM). It is argued that the synergistic effects of Bi₂O₃, Y₂O₃ and MgO co-doping in terms of the formation of the core-shell structure and the increase of T_c, can help improve the temperature stability of the dielectric permittivity effectively. Increasing the sintering temperature leads to an increase in the grain size, which in turn leads to an increase in the overall dielectric permittivity due to the grain size effect.     

Solar driven MgO/Mg based methane reforming and water splitting process: A thermodynamic inspection

The thermodynamic efficiency analysis of the MgO/Mg based CH₄ reforming and H₂O splitting process is performed in this paper. The study is conducted by considering two process configurations, namely, a) MgO/Mg based open process where Mg and syngas is produced (MS process), and b) MgO/Mg based semi-open process where syngas and H₂ is generated (MSH process). The thermodynamic equilibrium analysis indicate that the best possible thermal reduction temperature for both processes is 2100 K and, in case of the MSH process, the water splitting step is feasible in the range of 500–900 K. As per the findings, for the MS process, the solar energy required to drive the process increases by 958.2 kW as the CH₄/MgO ratio upsurges from 0.1 to 1. For the MSH process, the minimum amount of solar energy needed to run the process i.e., 1203.1 kW can be accomplished at water splitting temperature of 900 K and CH₄/MgO molar ratio = 1. Based on the solar-to-fuel energy conversion efficiency, the MSH process appears to be more advantageous (54.5%) than the MS process (41.3%). The solar-to-fuel energy conversion efficiency of the MSH process can be further enhanced up to 65.6% by reclaiming 50% of the heat dissipated by the coolers and WS reactor.     

Fabrication of ball-milled MgO–Mg(OH)2-hydromagnesite composites and evaluation as an air-stable hydrogen storage material

A phase stability map of metallic magnesium powder, exposed to environmental conditions for 12 months (Mg-12M) and subjected to different high-energy ball-milling speeds and milling times, was constructed. Mg-12M−160 [½MgO-⅓Mg(OH)₂-⅙hydromagnesite] and Mg-12M−640 [¼MgO-⅝Mg(OH)₂-⅛hydromagnesite] composites were obtained changing the milling conditions. The correlation among the accumulated energy (ΔE_accum), the impact energy (ΔE_hit), and the phase stability under different high-energy ball-milling conditions were generated. The Mg-12M−160 composite had a hydrogen storage capacity of 0.63 wt% at −196 °C and 8.3 bar, although further hydrogen adsorption at higher pressures is expected. Structural defects play a significant role in the adsorption capacity. A representation of the possible absorption mechanism is proposed.     

BRISOL钠同位素放射性核束的产生

北京放射性核束装置在线同位素分离器（BRISOL）采用100 MeV、200 μA回旋加速器提供的质子束打靶产生中、短寿命放射性核束，在线分析后供物理用户使用，其质量分辨率好于20 000。为开展²⁰Na核的奇异衰变特性研究，研制了氧化镁靶，并采用100 MeV质子束轰击氧化镁靶在线产生了^20～26Na⁺的钠同位素放射性核束。当质子束流强为8 μA时，²⁰Na⁺离子束的最大产额为2×10⁵ s^-1，²¹Na⁺离子束的最大产额为4×10⁸ s^-1。完成了北京放射性核束装置首个放射性核束物理实验，累计供束近200 h。