Performance Of MgO Research Articles

Performance of MgO and MgO–SiO2 systems containing seeds under different curing conditions

This study investigated the strength and microstructural development of MgO and MgO-microsilica (MS) systems under sealed and carbonated conditions. The influence of hydromagnesite seeds on the performance of each system was also evaluated. The hydration mechanisms were studied via isothermal calorimetry. A correlation between the strength development and formation of different phases was established. XRD, TG/DTG, FTIR and SEM were used for the identification and quantification of different hydrate and carbonate phases. MgO systems relied on the conversion of brucite into carbonate phases for their strength development, whereas M-S-H was the main source of strength in MgO-MS systems. The effect of seeding was evident in MgO-MS systems, where the extra space provided by the seeds increased the rate and degree of hydration. The formation of M-S-H was responsible for strength development and denser microstructures, which could be further improved via the increased utilization of unreacted MgO and MS.

Nanoscopic Zero-Valent Iron Supported on MgO for Lead Removal from Waters

Lead is one of the most toxic heavy metals that can create a severe risk to water ecosystem health. Zero-valent iron is an effective material for Pb2+ removal treatments. In particular, nanoscopic zero-valent iron (nZVI) particles are characterized by high reaction rates; nevertheless, their utilization in water and groundwater remediation techniques requires further investigations. Indeed, it is necessary to define effective methods able to avoid the drawbacks due to the aggregation tendency of nanoparticles and their potential uncontrolled transport in groundwater. In this work, nZVI was supported on magnesium oxide grains (MgO_nZVI) to synthesize an alternative material for lead removal from aqueous solutions. Many experiments were conducted under several operating conditions in order to analyze the effectiveness of the produced material in Pb2+ abatement. The performance of MgO_nZVI was also compared with those detected using commercial microscopic Fe0 (mZVI) as a reactive material. The experimental findings showed a much greater reactivity of the supported nanoscopic iron particles. By means of a kinetic analysis of batch tests results, it was verified that, both for MgO_nZVI and mZVI, the lead abatement follows a pseudo-second-order kinetic law. The reaction rates were affected by the initial pH of the treatment solution and by the ratio between the Fe0 amount and initial lead concentration. The efficiency of MgO_nZVI in a continuous test was steadily around 97.5% for about 1000 exchanged pore volumes (PV) of reactive material, while by using mZVI, the lead removal was approximately 88% for about 600 PV. X-ray diffraction (XRD) and energy-dispersive spectroscopy EDS analyses suggested the formation of typical iron corrosion products and the presence of metallic lead Pb0 and Pb2+ compounds on exhausted materials.

Performance of MgO:PPLN, KTA, and KNbO_3 for mid-wave infrared broadband parametric amplification at high average power

The performance of potassium niobate (KNbO₃), MgO-doped periodically poled lithium niobate (MgO:PPLN), and potassium titanyl arsenate (KTA) were experimentally compared for broadband mid-wave infrared parametric amplification at a high repetition rate. The seed pulses, with an energy of 6.5 μJ, were amplified using 410 μJ pump energy at 1064 nm to a maximum pulse energy of 28.9 μJ at 3 μm wavelength and at a 160 kHz repetition rate in MgO:PPLN while supporting a transform limited duration of 73 fs. The high average powers of the interacting beams used in this study revealed average power-induced processes that limit the scaling of optical parametric amplification in MgO:PPLN; the pump peak intensity was limited to 3.8 GW/cm² due to nonpermanent beam reshaping, whereas in KNbO₃ an absorption-induced temperature gradient in the crystal led to permanent internal distortions in the crystal structure when operated above a pump peak intensity of 14.4 GW/cm².

Sintering and Performance of MgO from Bischofite with ZrO<sub>2</sub> Additive

Effect of ZrO2 on sintering properties of MgO prepared from natural brine from Qarhan Salt Lake, crystalline bischofite and MgCl2·6H2O(AR) was studied. The results showed that ZrO2 of addition exceeded 1 wt% had promotive effect on sintering of magnesia prepared from MgCl2·6H2O(AR). While 1.5 wt% ZrO2 was added, the bulk density of sample was 3.37 g/cm3, and relative density was 94.1%. With 1 wt% ZrO2, the bulk densities of magnesia prepared from crystalline bischofite and brine were 3.10 and 3.27 g/cm3, and the relative densities increased by 10.0% and 19.6%, respectively. The main reasons for promoting MgO sintering with ZrO2 were that monoclinic phase ZrO2 converted to cubic phase Zr2O and excess ZrO2 reacted with MgO to generate Mg0.13Zr0.87O1.87, which activated lattice and promoted the diffusion of ions during sintering process. In addition, liquid phase sintering was also one of the main reasons for promoting the sintering of brine magnesia.