The Hardness and Strength Properties of WC-Co Composites

The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents. A connection is made here between the composite material properties, especially including the material fracture toughness, and the several materials-type considerations of: (1) related hardness stress-strain behaviors; (2) dislocation (viscoplastic) thermal activation characterizations; (3) Hall-Petch type reciprocal square root of particle or grain size dependencies; and (4) indentation and conventional fracture mechanics results. Related behaviors of MgO and Al₂O₃ crystal and polycrystal materials are also described for the purpose of making comparisons.     

热重法研究脱羧反应中MgO／浮石催化剂的积炭行为

利用热重技术考察了反应温度和MgO含量对癸酸与醋酸合成甲基壬基酮MgO/浮石催化剂积炭的影响。确证镁盐流失不是积炭的直接原因,而反应温度对积炭有明显影响,适当调整反应温度可减少积炭的生成。     

铁钛复合添加剂对提高合成镁钙砂抗水化性的研究

就一种新型铁钛复合添加剂对提高合成镁钙砂抗水化性的影响进行了研究,结果表明：铁钛优先固溶到氧化钙中,通过离子扩散和液相作用。促进烧结,提高抗水化性。最佳添加量为ｗ＝０．０１～０．０１５,铁钛最佳质量比为７０／３０。     

电感耦合等离子体原子发射光谱法测定复方田七胃痛胶囊中两组分的含量

摘 要 目的：建立电感耦合等离子体原子发射光谱法测定复方田七胃痛胶囊中氧化镁、碳酸氢钠两组分的含量。方法: 样品经酸溶解,电感耦合等离子体原子发射光谱法测定其镁、钠元素的含量。结果: 镁、钠元素在0～30 μg·ml^-1浓度范围内线性关系良好,相关系数分别为0.999 9,0.999 7;平均加样回收率分别为100.60%（RSD=4.1%,n=9）、99.65%（RSD=4.4%,n=9）。结论:本法专属性强、操作简便、结果准确,可用于复方田七胃痛胶囊中氧化镁、碳酸氢钠的含量测定。     

Assessment of the dose-dependent biochemical and cytotoxicity of zein-coated MgO nanowires in male and female albino rats

Introduction: Recently, zein-coated MgO nanowires were synthesized, which could be promising as an effective antimicrobial compounds that can be combined in the preparation of a diversity of new dental formulations. However, there is a deficiency of information concerning their toxicological profile regarding the human health.Objective: This in vivo study aimed to explore the hepato- and nephrotoxicity of low versus high doses of zein-coated MgO nanowires in rats.Materials and Methods: A 21-day recurrent dose toxicity research was carried out. Wistar rats were divided into 2 main groups, males and females (n = 18). Each group was further subdivided into 3 subgroups: control, MgO-zein nanowires low dose, MgO-zein nanowires high dose. The low dose used was 100 mg/kg while the high dose used was 200 mg/kg.Results: The results showed that MgO-zein nanowires at both doses did not affect the electrolytes levels compared to the control levels. Also, they did not produce any significant alteration in liver function markers in both rats'' genders. MgO-zein nanowires at both doses did not produce any effective alteration in serum creatinine in treated rats of both genders. Moreover, very minimal histological alterations were observed in both doses of MgO-zein nanowires in liver and kidney of both genders.Conclusion: Based on the observed safety of zein-coated MgO nanowires, it can be utilized as an effective antimicrobial compound that can be combined in the preparation of a diversity of new dental formulations.

KEY MESSAGES

• MgO NPs are globally used in multiple fields including the therapeutic field.
• Zein has wide pharmaceutical applications especially coating the tablet over sugar.
• There are no cytotoxic studies that investigate MgO-zein nanowires safety until now.

     

High-Energy Heavy Ion Irradiation of Al2O3, MgO and CaF2

High-energy heavy ion irradiation can produce permanent damage in the target material if the density of deposited energy surpasses a material-dependent threshold value. It is known that this threshold can be lowered in the vicinity of the surface or in the presence of defects. In the present study, we established threshold values for Al₂O₃, MgO and CaF₂ under the above-mentioned conditions, and found those values to be much lower than expected. By means of atomic force microscopy and Rutherford backscattering spectrometry in channelling mode, we present evidence that ion beams with values of 3 MeV O and 5 MeV Si, despite the low density of deposited energy along the ion trajectory, can modify the structure of investigated materials. The obtained results should be relevant for radiation hardness studies because, during high-energy ion irradiation, unexpected damage build-up can occur under similar conditions.     

Corrosion Resistance of MgO and Cr2O3-Based Refractory Raw Materials to PbO-Rich Cu Slag Determined by Hot-Stage Microscopy and Pellet Corrosion Test

Chemical resistance of commercial refractory raw materials against Cu slag is critical to consider them as candidates for the production of refractories used in Cu metallurgy. In this study, we show the comparative results for the corrosion resistance of four commercial refractory raw materials—magnesia chromite co-clinkers FMC 45 and FMC 57, PAK, and fused spinel SP AM 70—against aggressive, low-melting PbO-rich Cu slag (Z1) determined by hot-stage microscopy (up to 1450 °C) and pellet test (1100 and 1400 °C). Samples were characterized after the pellet test by XRD, SEM/EDS, and examination of their physicochemical properties to explore the corrosion reactions and then assess comparatively their chemical resistance. Since many works have focused on corrosion resistance of refractory products, the individual refractory raw materials have not been investigated so far. In this work, we show that magnesia chromite co-clinker FMC 45 exhibits the most beneficial properties considering its application in the production of refractories for the Cu industry. Forsterite (Mg₂SiO₄) and güggenite (Cu₂MgO₃) solid solutions constitute corrosion products in FMC 45, and its mixture with slag shows moderate dimensional stability at high temperatures. On the other hand, the fused spinel SP AM 70 is the least resistant to PbO-rich Cu slag (Z1); it starts to sinter at 970 °C, followed by a fast 8%-shrinkage caused by the formation of güggenite solid solution in significant amounts.     

Direct Polypropylene and Polyethylene Liquefaction in CO2 and N2 Atmospheres Using MgO Light and CaO as Catalysts

The polyolefin to lighter molecules reaction reduces the waste-plastic residues to produce fuels and valuable chemicals. Commercial MgO light and CaO were used as catalysts for the direct polyethylene and polypropylene liquefaction in N₂ or CO₂ atmospheres. The products were analyzed (ATR-FTIR, GC-FID/TCD, GC-FID, density, refractive index). The use of MgO light and CaO improved the conversion of propylene and ethylene to liquid products. In addition, low gaseous and solid products yields were obtained. A good production of organic liquids in the gasoline, diesel and kerosene boiling range was obtained. The use of CO₂, in some cases, led to a higher conversion into liquids compared with the reactions performed in the N₂ atmosphere. In addition, the use of the CO₂ atmosphere led to a higher content of products with a boiling range in the diesel and kerosene ranges.     

Ag/MgO Nanoparticles via Gas Aggregation Nanocluster Source for Perovskite Solar Cell Engineering

Nanocluster aggregation sources based on magnetron-sputtering represent precise and versatile means to deposit a controlled quantity of metal nanoparticles at selected interfaces. In this work, we exploit this methodology to produce Ag/MgO nanoparticles (NPs) and deposit them on a glass/FTO/TiO₂ substrate, which constitutes the mesoscopic front electrode of a monolithic perovskite-based solar cell (PSC). Herein, the Ag NP growth through magnetron sputtering and gas aggregation, subsequently covered with MgO ultrathin layers, is fully characterized in terms of structural and morphological properties while thermal stability and endurance against air-induced oxidation are demonstrated in accordance with PSC manufacturing processes. Finally, once the NP coverage is optimized, the Ag/MgO engineered PSCs demonstrate an overall increase of 5% in terms of device power conversion efficiencies (up to 17.8%).     

The Preparation of Dense Materials in the MgO–ZrO2 System by the Application of Nanometric Powders

Crystallization under hydrothermal conditions allowed us to prepare nanometric powders in the MgO–ZrO₂ system of different magnesia concentrations. Sintering runs of these powder compacts studied using dilatometry measurements during heating and cooling revealed essential differences in their behavior. The microstructure of the resulting polycrystal is strongly related to the magnesia content in the starting powder, which strongly influences the phase composition of the resulting material and its mechanical properties. It should be emphasized that the novel processing method of such materials differs from the usual applied technology and leads to magnesia–zirconia materials of a different microstructure than that of “classical” materials of this kind.