Synergetic effect of multiple phases on hydrogen desorption kinetics and cycle durability in ball milled MgH2–PrF3–Al–Ni composite

A new MgH₂–PrF₃–Al–Ni composite was prepared by ball milling under hydrogen atmosphere. After initial dehydrogenation and rehydrogenation, Pr₃Al₁₁, MgF₂, PrH₃ and Mg₂NiH₄ nanoparticles formed accompanying the main phase MgH₂. The hydrogen absorption-desorption properties were measured by using a Sieverts-type apparatus. The results showed that the MgH₂–PrF₃–Al–Ni composite improved cycle stability and enhanced hydrogen desorption kinetics. The improvement of hydrogen absorption-desorption properties is ascribed to the synergetic effect of the in situ formed Pr₃Al₁₁, MgF₂, PrH₃ and Mg₂NiH₄ nanoparticles. This work provides an important inspiration for the improvement of hydrogen storage properties in Mg-based materials.     

Effect of Al on microstructure and mechanical properties of as-extruded Mg–1Mn alloy sheet

The effect of Al addition on microstructure and mechanical properties of hot extruded Mg–1 Mn alloy sheet was investigated. The results revealed that the dynamic recrystallization was promoted by increasing Al content. The ultimate tensile strength and yield strength of the alloy increased with the increase of Al content. The Mg–9 Al–1 Mn alloy exhibited the highest strength, with tensile strength of 308 MPa, 307 MPa, 319 MPa, yield strength of 199 MPa, 207 MPa, 220 MPa and the elongation of 20.9%, 20.1%, 19.2% in 0°, 45°, 90°, respectively.The high strength was mainly attributed to the formation of fine dynamically recrystallized grains and large amounts of the second phase. The strengthening mechanism of the alloys was explained.     

Mineralization of flue gas CO2 with coproduction of valuable magnesium carbonate by means of magnesium chloride

CO2 mineralization and utilization is a new area for reducing the CO2 emissions. By reacting with natural mineral or industrial waste, CO2 can be transformed into valuable solid carbonate （such as calcium carbonate or magnesium carbonate） with recovery of some products simultaneously. In this paper, a novel method was proposed to mineralize CO2 by means of magnesium chloride with small energy consumption. In this method, magnesium chloride was firstly transformed into magnesium hydroxide by electrolysis. The formed magnesium hydroxide showed high reactivity to mineralize CO2. In our study, even at low concentration, CO2 can be effectively mineralized by this method, which makes it possible to directly mineralize flue gas CO2, avoiding the expensive process of CO2 capture and purification. Moreover, valuable products such as hydromagnesite and nesquehonite can be recovered by this method. Because of the wide distribution of magnesium chloride in nature, largescale CO2 mineralization is potential by means of magnesium chloride.     

Effect of pickling processes on the microstructure and properties of electroless Ni–P coating on Mg–7.5Li–2Zn–1Y alloy

The electroless plating Ni–P is prepared on the surface of Mg–7.5Li–2Zn–1Y alloys with different pickling processes.The microstructure and properties of Ni–P coating are investigated.The results show that the Ni–P coatings deposited using the different pickling processes have a different high phosphorus content amorphous Ni–P solid solution structure,and the Ni–P coatings exhibit higher hardness.There is higher phosphorus content of Ni–P amorphous coating using 125 g/L Cr O3and 110 ml/L HNO3(w68%)than using 180 g/L Cr O3and 1 g/L KF during pre-treatment,and the coating structure is more compact,and the Ni–P coatings exhibit more excellent adhesion with substrate(Fcup to22 N).The corrosion potential of Ni–P coating is improved and exhibits good corrosion resistance.As a result,Mg-7.5Li-2Zn-1Y alloy is remarkably protected by the Ni–P coating.     

In vitro and in vivo studies on biodegradable magnesium alloy

The microstructure, mechanical property, electrochemical behavior and biocompatibility of magnesium alloy(Bio De MSM^TM) were studied in the present work. The experimental results demonstrated that grain refining induced by extrusion improves the alloy strength significantly from162 MPa for the as-cast alloy to 241 MPa for the as-extruded one. The anticorrosion properties of the as-extruded alloy also increased.Furthermore, the hemolysis ratio was decreased from 4.7% for the as-cast alloy to 2.9% for the as-extruded one, both below 5%. Bio De MSM^TMalloy shows good biocompatibility after being implanted into the dorsal muscle and the femoral shaft of the New Zealand rabbit, respectively, and there are no abnormalities after short-term implantation. In vivo observation indicated that the corrosion rate of this alloy varies with different implantation positions, with higher degradation rate in the femur than in the muscle.     

In fl uence of HEPES buffer on the local pH and formation of surface layer during in vitro degradation tests of magnesium in DMEM

The human body is a buffered environment where p H is effectively maintained. HEPES is a biological buffer often used to mimic the buffering activity of the body in in vitro studies on the degradation behavior of magnesium. However, the influence of HEPES on the degradation behavior of magnesium in the DMEM pseudo-physiological solution has not yet been determined. The research aimed at elucidating the degradation mechanisms of magnesium in DMEM with and without HEPES. The morphologies and compositions of surface layers formed during in vitro degradation tests for 15–3600 s were characterized. The effect of HEPES on the electrochemical behavior and corrosion tendency was determined by performing electrochemical tests. HEPES indeed retained the local p H, leading to intense intergranular/interparticle corrosion of magnesium made from powder and an increased degradation rate. This was attributed to an interconnected network of cracks formed at the original powder particle boundaries and grain boundaries in the surface layer, which provided pathways for the corrosive medium to interact continuously with the internal surfaces and promoted further dissolution. Surface analysis revealed significantly reduced amounts of precipitated calcium phosphates due to the buffering activity of HEPES so that magnesium became less well protected in the buffered environment.     

分析化学实验拾零

本文介绍了用ＥＤＴＡ间接滴定法测定ＳＯ４＾２－含量时产生的一种异常现象的处理方法，使用ＨＮＯ３－ＨＣｌＯ４混酸消化某些有机物时出现异常现象的处理方法，以及定性鉴定Ｍｇ＾２＋的一种新方法。     

Current Research Progress in Magnesium Borohydride for Hydrogen Storage (A review)

Hydrogen storage in solid-state materials is believed to be a most promising hydrogen-storage technology for high efficiency, low risk and low cost. Mg(BH₄)₂ is regarded as one of most potential materials in hydrogen storage areas in view of its high hydrogen capacities (14.9 ​wt% and 145–147 ​kg ​cm⁻³). However, the drawbacks of Mg(BH₄)₂ including high desorption temperatures (about 250 ​°C–580 ​°C), sluggish kinetics, and poor reversibility make it difficult to be used for onboard hydrogen storage of fuel cell vehicles. A lot of researches on improving the dehydrogenation reaction thermodynamics and kinetics have been done, mainly including: additives or catalysts doping, nanoconfining Mg(BH₄)₂ in nanoporous hosts, forming reactive hydrides systems, multi-cation/anion composites or other derivatives of Mg(BH₄)₂. Some favorable results have been obtained. This review provides an overview of current research progress in magnesium borohydride, including: synthesis methods, crystal structures, decomposition behaviors, as well as emphasized performance improvements for hydrogen storage.     

多波长数据线性回归光度法同时测定钙和镁

本文研究了酸性铬蓝K体系用于同时测定钙和慎的显色条件，借助多波长线性回归法处理数据，提出光度测定钙和镁的简便方法，免去了分离手续。应用于三个水样中钙、镁含量的测定，结果满意。