Influence of Sb modification on microstructures and mechanical properties of Mg2 Si/AM60 composites

The refining effect and mechanism of Sb on Mg2Si and the microstructure of the matrix were investigated.The results indicate that there are Mg3Sb2 particles in the composites with the addition of Sb,and Mg3Sb2 can promote the formation of fine polygonal type Mg2Si by providing nucleation site.Meanwhile,the grain size of Sb modified alloy is finer than that of the matrix. The improved microstructure results in the improvement of mechanical properties.The ultimate tensile strength is increased by 12.2%with the addition of 0.8%Sb.

Al掺杂Mg2 Ge光电性质的第一性原理计算

应用密度泛函理论框架下的第一性原理超软赝势平面波方法系统地计算了不同Al掺杂浓度下Mg 2 Ge的电子结构及光学性质.建立了四种Mg 2-x Al x Ge(x=0,0.125,0.25,0.5)的掺杂模型,计算结果表示Al掺杂后的Mg 2 Ge,费米能级进入导带,呈现出n型导电特性,掺杂后本征Mg 2 Ge费米能级附近的导带架构发生了改变,变为主要由Al的3p态电子、Ge的4s态电子和Mg的3s、3p态电子组成;静介电常数ε1(0)和折射率n 0均增大;吸收光谱发生红移,吸收系数最大值略微减小;光电导率峰值在x=0.125时取得极大值;能量损失函数发生蓝移且x=0.125时蓝移现象最为明显.

Mg2+、Zn2+掺杂CaWO4∶Eu3+荧光粉的发光性质

采用微波加热固相法合成了Mg2+、Zn2+掺杂CaWO4∶Eu3+荧光粉。利用XRD对样品的晶体结构进行表征,通过荧光分光光度仪对样品的激发光谱、发射光谱和能级寿命进行检测和分析。结果表明,Mg2+、Zn2+、Eu3+掺杂CaWO4不影响CaWO4基质的四方晶相。395nm激发下,与CaWO4∶2%Eu3+样品比较,分别掺杂0.5%的Mg2+或Zn2+的样品发光强度提高了1.3倍和2.1倍;与3%Mg2+或3%Zn2+掺杂CaWO4∶2%Eu3粉体发光比较,当Eu3+浓度增加为3%时,粉体的发光强度分别提高了7.3倍和14.8倍;与CaWO4∶3%Eu3+样品比较,3%的Mg2+或Zn2+掺杂后的样品光强分别提高了1.2倍和1.3倍。262nm比395nm激发同一样品的Eu3+的5D0能级寿命有所增加。与单掺2%Eu3+样品比较,随着Mg2+或Zn2+掺杂浓度增加,样品荧光寿命先增加后减小。同样激发波长下,与Mg2+或Zn2+掺杂CaWO4∶2%Eu3+样品荧光寿命相比,Eu3+浓度增加为3%时,样品的荧光寿命明显变短。

ATRANSMISSION ELECTRONIC MICROSCOPY STUDY ONFORMATION AND MICROSTRUCTURE CHANGE OF Mg2Ni DURING MECHANICAL ALLOYING

The microstructuralchangeof mechanicalalloyingof pureelemental Mg Nipowders wasin vestigated by transmission electronic microscopy ( TEM). The experimental results showed thatafter5 h milling, Mg2 Ni phase precipitated mainly from Mg grain , and no Mg2 Ni wasfound in Ni matrix. Thiscan be attributed tothe asym metricalinterdiffusion between Mg and Ni atom , which causesthecontent of Mg in Ni grain far below thestoichiometric composition of Mg2 Ni. After the growth of Mg2 Ni grain, the severe mechanical deforma tion resulting from mechanicalalloying led tothetransformation of Mg2 Ni from hexagonal tofccstructure partially, which makes Mg2 Ni grain in a composite microstructure fcc + hcp.

Microstructure and corrosion resistance of a Mg2Sn-dispersed Mg alloy subjected to pulsed electron beam treatment

We report that the corrosion resistance of a Mg-Sn-based alloy with MgzSn precipitates can be considerably improved by surface modification using pulsed electron beam treatment.The alloy subjected to a pulse electron beam treatment showed a modified surface layer with a thickness of〜12 μm,appearing more resistant to corrosion attack than the bare surface of the alloy.In 0.6 M NaCl solution,the alloys with and without the surface modification exhibited average corrosion rates of 4.3 and 8.1 mm y^-1,respectively.The improved corrosion resistance was attributed to reduced cathodic activation,resulting from the surficial reduction of relatively noble Mg2Sn precipitates.

Synthesis and Photocatalytic Activity of One-dimensional ZnO-Zn2SnO4 Mixed Oxide Nanowires

Mixed oxide photocatalysts, ZnO-Zn2SnO4 （ZnO-ZTO） nanowires with different sizes were prepared by a simple thermal evaporation method. The ZnO-ZTO nanowires were characterized with a scanning electron microscope, X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectrom- eter, and X-ray photoelectron spectra. The photocatalytic activity of the ZnO-ZTO mixed nanowires were studied by observing the photodegradation behaviors of methyl orange aqueous solution. The results suggest that the ZnO-ZTO mixed oxide nanowires have a higher photocatalytic activity than pure ZnO and Zn2SnO4 nanowires. The photocatalyst concentration in the solution distinctly affects the degradation rate, and our results show that higher photodegradation efficiency can be achieved with a smaller amount of ZnO-ZTO nanowire catalyst, as compared to the pure ZnO and ZTO nanowires. Moreover, the photocatalytic activity can also be enhanced by reducing the average diameter of the nanowires. The activity of pure ZnO and ZTO nanowires are also enhanced by physically mixing them. These results can be explained by the synergism between the two semiconductors.

Microstructure and mechanical properties of friction stir processed Al−Mg2Si alloys

The microstructure and mechanical properties of friction stir processed Al−Mg2Si alloys were studied by TEM and EBSD.The results showed that an increase in the tool rotation speed(300−700 r/min)led to a decrease in the defect area(from 10.5 mm2 to zero),whereas the defect area demonstrated the opposite trend(increased to 1.5 mm2 from zero)upon further increasing the rotation speed(700−1200 r/min).The types of defects were transformed from tunnel defects to fusion defects as the rotational speed increased.The coarse Mg2Si dendrites were broken and fine particles(smaller than 10mm)formed in the weld nugget(WN).The amount of low-angle grain boundaries increased significantly from 57.7%to 83.6%,which was caused by an increase in the content of the deformed structure(from 1.7%to 13.6%).The hardness,ultimate tensile strength(UTS)and elongation were all greatly improved for the weld nugget.The hardness values of the WNs had the following order:R300<R1200<R500<R900<R700.The UTS and elongation had the following order:BM(base material)<R300<R1200<R500<R900<R700.The UTS and the elongation for the WN were increased by one and three times,respectively.

聚乙烯亚胺和Mg2+荧光增敏快速检测四环素类抗生素

四环素类抗生素(TCs)是一类广谱抗菌药物,被广泛应用于治疗人畜疾病且效果显著,但过度使用TCs造成其在动物性食品中的残留问题会对自然环境和人体健康造成严重的危害。因此,对食品环境中TCs的残留进行快速检测是十分必要的。迄今为止,对TCs在酸性溶液中荧光检测相关的研究报道较少。在弱酸性条件下,TCs属于弱荧光物质,但与富有氨基的阳离子表面活性剂聚乙烯亚胺(PEI)结合时,在370 nm的激发下,在525 nm处产生较强的绿色荧光;当TCs与PEI和二价金属镁离子(Mg^(2+))共存时,TCs的荧光强度被进一步增强。本研究利用PEI和Mg^(2+)在弱酸性条件下对TCs的协同荧光增敏效应,构建了一种快速、简单、高灵敏检测残留TCs的荧光检测法。实验结果表明:在最优检测条件下,该体系对TCs的定量线性检测范围为5 nmol/L~2μmol/L,其中,美他环素(MTC)、四环素(TC)、土霉素(OTC)的相关系数R^(2)分别为0.939,0.997和0.999,检出限(LOD)分别为3.6,2.7和4.8 nmol/L,均远低于中国和欧盟的限量标准。本方法对MTC、TC、OTC表现出很高的特异性,与常见的其他抗生素均不产生干扰。在实际的牛奶检测中,该体系对TCs的加标回收率为91.64%~104.05%,相对标准偏差为1.20%~10.62%。本方法可适用于酸性体系中残留TCs的分析,为水体和食品中残留TCs检测提供了一种新的依据和思路。

Surface Patterning of Metal Zinc Electrode with an In‑Region Zincophilic Interface for High‑Rate and Long‑Cycle‑Life Zinc Metal Anode

The undesirable dendrite growth induced by non-planar zinc(Zn)deposition and low Coulombic efficiency resulting from severe side reactions have been long-standing challenges for metallic Zn anodes and substantially impede the practical application of rechargeable aqueous Zn metal batteries(ZMBs).Herein,we present a strategy for achieving a high-rate and long-cycle-life Zn metal anode by patterning Zn foil surfaces and endowing a Zn-Indium(Zn-In)interface in the microchannels.The accumulation of electrons in the microchannel and the zincophilicity of the Zn-In interface promote preferential heteroepitaxial Zn deposition in the microchannel region and enhance the tolerance of the electrode at high current densities.Meanwhile,electron aggregation accelerates the dissolution of non-(002)plane Zn atoms on the array surface,thereby directing the subsequent homoepitaxial Zn deposition on the array surface.Consequently,the planar dendrite-free Zn deposition and long-term cycling stability are achieved(5,050 h at 10.0 mA cm^(−2) and 27,000 cycles at 20.0 mA cm^(−2)).Furthermore,a Zn/I_(2) full cell assembled by pairing with such an anode can maintain good stability for 3,500 cycles at 5.0 C,demonstrating the application potential of the as-prepared ZnIn anode for high-performance aqueous ZMBs.

Adsorption equilibrium, kinetics, and dynamic separation of Ca2+ and Mg2+ ions from phosphoric acid–nitric acid aqueous solution by strong acid cation resin

The separation of Ca2+and Mg2+ions from phosphoric acid-nitric acid aqueous solution is very significant for the neutralization process of nitrophosphate fertilizer.This paper studied the adsorption equilibrium,kinetics,and dynamic separation of Ca2+and Mg2+ions by strong acid cation resin,and the effects of phosphoric acid and nitric acid on the adsorption process were investigated.The results reveal that the adsorption process of Ca2+and Mg2+ions in pure water on resin is in good agreement with the Langmuir isotherm model and their maximal adsorption capacities are 1.86 mmol·g-1 and 1.83 mmol·g-1,respectively.The adsorption kinetics of Ca2+and Mg2+ions on resin fits better with the pseudo-first-order model,and the adsorption equilibrium in pure water is reached within 10 min contact time,while at the present of phosphoric acid,the adsorption rate of Ca2+and Mg2+ions on resin will go down.The dynamic separation experiments demonstrate that the designed column adsorption is able to undertake the separation of metal ions from the mix acids aqueous solution,but the dynamic operation should control the flow rate of mix acid solution.Besides nitric acid solution was proved to be effective to completely regenerate the spent resin and achieve the recyclable operation of separation process.

Plasma-assisted aerogel interface engineering enables uniform Zn^(2+)flux and fast desolvation kinetics toward zinc metal batteries

The poor reversibility of Zn anodes induced by dendrite growth,surface passivation,and corrosion,severely hinders the practical applicability of Zn metal batteries.To address these issues,a plasmaassisted aerogel(PAG)interface engineering was proposed as efficient ion transport modulator that can simultaneously regulate uniform Zn^(2+)flux and desolvation behavior during battery operation.The PAG with ordered mesopores acted as an ion sieve to homogenize Zn deposition and accelerate Zn^(2+)flux,which is favorable for corrosion resistance and dendrite suppression.Importantly,the plasma-assisted aerogel with abundant hydrophilic groups can facilitate the desolvation kinetics of Zn^(2+)due to the multiple hydrogen-bonding interaction with the activated water molecules,thus accelerating the Zn^(2+)migration kinetics.Consequently,the Zn/Zn cell assembled with PAG-modified separator demonstrates stable plating and stripping behavior(over 1400 h at 1 mA cm^(-2))and high Coulombic efficiency(99.8%at1 mA cm^(-2)after 1100 cycles),and the Zn‖MnO_(2)full cell shows excellent long-term cycling stability and maintains a high capacity of 154.9 mA h g^(-1)after 1000 cycles at 1 A g^(-1).This study provides a feasible approach for the large-scale fabrication of aerogel functionalized separators to realize ultra-stable Zn metal batteries.

Effect of Microwave Power on the Zn2SnO4 Synthesis and Its Use for Photodegradation of Phenol

Spinel structure Zn2SnO4 was successfully synthesized by microwave-assisted hydrothermal process. The effects of the microwave power on the formation and physical properties of the Zn2SnO4 particles are discussed. The products were characterized by X-ray diffraction, atomic force microscopy, infrared spectroscopy, and N2 adsorption. The results indicated that the microwave power had important influence on the formation of the spinel phase. The results also revealed that the physical properties of Zn2SnO4 particles did not change with the increase of the microwave power above 600 W, with 20 min of reaction time. Furthermore, the photocatalytic activity of the Zn2SnO4 particles for the phenol degradation under sunlight was also investigated.

Hydriding and dehydriding kinetics of melt spun nanocrystalline Mg20Ni10-xCux (x = 0-4) alloys

The nanocrystalline Mg2Ni-type electrode alloys with nominal compositions of Mg20Ni10-xCux (x = 0, 1, 2, 3, 4) were synthesized by melt-spinning technique. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinet-ics of the alloys were measured using an auto-matically controlled Sieverts apparatus. The re- sults show that all the as-spun alloys hold ty- pical nanocrystalline structure. The substitution of Cu for Ni does not change the major phase Mg2Ni but it leads to the formation of the sec-ondary phase Mg2Cu. The hydrogen absorption capacity of the alloys first increases and then decreases with rising Cu content, but the hy-drogen desorption capacity of the alloys mono- tonously grows with increasing Cu content. The melt spinning significantly improves the hydro- genation and dehydrogenation capacities and kinetics of the alloys.

Thermodynamic equilibrium theory-guided design and synthesis of Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4)/C cathode for lithium-ion batteries

Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.

Hydrogen Absorption and Electrochemical Properties of As-Quenched Nanocrystalline Mg20Ni10 – xCux (x = 0 – 4) Alloys

Nanocrystalline Mg2Ni-type alloys with nominal compositions of Mg20Ni10 – xCux (x = 0, 1, 2, 3, 4) were synthesized by rapid quenching technique. The microstructures of the as-cast and quenched alloys were characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that all the as-quenched alloys hold a typical nanocrystalline structure, and the rapid quenching does not change the major phase Mg2Ni. The hydrogen absorption and desorption capacities of the alloys significantly increase with rising quenching rate. Additionally, the rapid quenching significantly improves the electrochemical hydrogen storage capacity of the alloys, but it slightly impairs the cycle stability of the alloys.

Effect of insulin in combined with Chinese medicine formulae on the serum Mg2+ and visfatin levels, maternal and infant outcome in pregnant women with gestational diabetes mellitus

Objective:To explore the effect of insulin in combined with Chinese medicine formulae on the serum Mg2+ and visfatin levels, maternal and infant outcome in pregnant women with gestational diabetes mellitus (GDM).Methods:A total of 108 pregnant women with GDM who were admitted in our hospital were included in the study and randomized into the observation group (n=55) and the control group (n=53). The patients in the two groups were given diet control, exercise therapy, and subcutaneous injection of insulin. On this basis, the patients in the observation group were given self-made Chinese medicine formulae, continuously for 2 weeks. The blood sugar level, and serum Mg2+ and visfatin (VF) levels before treatment and before delivery in the two groups were detected. The maternal and infant outcome in the two groups was evaluated.Results:The serum HbA1c, FPG, 1 h PBG, 2 h PBG, and VF levels before delivery in the two groups were significantly reduced when compared with before treatment (P<0.05), while the serum Mg2+ level was significantly elevated when compared with before treatment (P<0.05). The improvement of the above indicators before delivery in the observation group was more significant when compared with the control group (P<0.05). The occurrence rate of cesarean section, premature delivery, gestational hypertension, fetal distress, and macrosomia in the observation group was significantly lower than that in the control group (P<0.05).Conclusions:Insulin in combined with self-made Chinese medicine formulae can effectively control the blood sugar level in pregnant women with GDM, and improve the maternal and infant outcome.

TiO_(2)@C catalyzed hydrogen storage performance of Mg-Ni-Y alloy with LPSO and ternary eutectic structure

A designed Mg_(88.7)Ni_(6.3)Y_(5)hydrogen storage alloy containing 14H type LPSO(long-period stacking ordered)and ternary eutectic structure was prepared by regulating the alloy composition and casting.The hydrogen storage performance of the alloy was improved by adding nano-flower-like TiO_(2)@C catalyst.The decomposition of the LPSO structure during hydrogenation led to the formation of plenty of nanocrystals which provided abundant interphase boundaries and activation sites.The nanoscale TiO_(2)@C catalyst was uniformly dispersed on the surface of alloy particles,and the"hydrogen overflow''effect of TiO_(2)@C accelerated the dissociation and diffusion of hydrogen on the surface of the alloy particles.As a result,the in-situ endogenous nanocrystals of the LPSO structure decomposition and the externally added flower-like TiO_(2)@C catalyst uniformly dispersed on the surface of the nanoparticles played a synergistic catalytic role in improving the hydrogen storage performance of the Mg-based alloy.With the addition of the TiO_(2)@C catalyst,the beginning hydrogen desorption temperature was reduced to 200℃.Furthermore,the saturated hydrogen absorption capacity of the sample was 5.32 wt.%,and it reached 4.25 wt.%H_(2) in 1 min at 200℃and 30 bar.

Constructing interfacial electric field and Zn vacancy modulated ohmic junctions ZnS/NiS for photocatalytic H_(2) evolution

Adjusting the interfacial transport efficiency of photogenerated electrons and the free energy of hydrogen adsorption through interface engineering is an effective means of improving the photocatalytic activity of semiconductor photocatalysts.Herein,hollow ZnS/NiS nanocages with ohmic contacts containing Zn vacancy(V_(Zn)-ZnS/NiS)are synthesized using ZIF-8 as templates.An internal electric field is constructed by Fermi level flattening to form ohmic contacts,which increase donor density and accelerate electron transport at the V_(Zn)-ZnS/NiS interface.The experimental and DFT results show that the tight interface and V_(Zn) can rearrange electrons,resulting in a higher charge density at the interface,and optimizing the Gibbs free energy of hydrogen adsorption.The optimal hydrogen production activity of V_(Zn)-ZnS/NiS is 10,636 mmol h^(-1) g^(-1),which is 31.9 times that of V_(Zn)-ZnS.This study provides an idea for constructing sulfide heterojunctions with ohmic contacts and defects to achieve efficient photocatalytic hydrogen production.

Microstructure evolution,mechanical properties and fracture behavior of Al-xSi/AZ91D bimetallic composites prepared by a compound casting

In this paper,the effect of the Si content on microstructure evolution,mechanical properties,and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically.The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer(MRL),whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites,while the hypereutectic Al-Si/AZ91D composites were opposite.The MRL included eutectic layer(E layer),intermetallic compound layer(IMC layer)and transition region layer(T layer).In the IMC layer,the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg_(2)Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides,increasing Si content,the thickness proportion of the T layer increased,forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content,and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa,which was 73.4% higher than the Al-6Si/AZ91D composite.The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content.The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg_(2)Si particle reinforcement,the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.

Ca and Sr co-doping induced oxygen vacancies in 3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts for boosting low-temperature oxidative coupling of methane

It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.