Thermal and radiative characteristics of oxyfluoride glass singly doped with lanthanide ions

Rare earths-doped oxyfluoride glasses based on germanium oxide and lead fluoride were prepared from commercial raw materials. The glasses with general composition of 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 (Ln=Pr3+-Yb3+), contained different concentrations of optically active dopants (x=0.2 mol.% and 2 mol.%) and PbF2 (y≤15 mol.%). The differential thermal analysis (DTA) was used to determine both thermal characteristic and thermal stability properties of the glasses in the function of the kind of dopant, its concentration, and a glass composition. Characteristic glass temperatures such as glass transition temperature (Tg), glass crystallization temperature (Tc) and temperature corresponding to the maximum of the crystallization rate (Tpc) were evaluated. On the basis of obtained results, the thermal stabilities of glasses under study were evaluated using various thermal stability criteria (Dietzel factor ?T, Saad-Poulain factors H' and S). It was found that the increase in rare earth fluoride contents influenced thermal characteristics when the characteristic temperatures of the individual glass was shifted towards higher values. The effect of the PbF2 content and the kind of rare earth impurity on the glass stability was observed. Absorption spectra of lanthanide-doped glasses were measured at room temperature and used to determine the phenomenological intensity parameters Ωt and next, to estimate radiative properties of lanthanide ions in this matrix. Radiative transition probabilities of luminescent states of Ln3+, branching ratios and radiative lifetimes were determined. The variation of the Ωt along the lanthanide series was presented and discussed.     

Process optimization of electroless copper plating and its influence on electrochemical properties of AB5-type hydrogen storage alloy

The amount of Cu coating by chemical plating was investigated based on quadratic regression orthogonal experimental design being adapted to the variation law of temperature,pH value and Ni2+concentration,and the relevant regression equation was expressed as y=2.1609+0.5295×10-3T2-0.0342P2-0.0265N2+0.0023TP+0.0020TH+0.0199PN-0.0959T+0.3814P-0.2073N.The results showed that the deposition rate augmented with the increasing in temperature,pH value and Ni2+concentration.The experimental parameters of the optimal coating were temperature 75 ℃,pH value 8.5 and Ni2+concentration 1.2 g/L.The electrochemical tests indicated that the cycle stability increased from 60.66% to 75.58%,indicating that the treated alloy exhibited better corrosion resistance.     

天铁热力风机升级改造方案设计

通过对天铁集团高炉现状、风机现状的分析,提出了对热力厂风机升级改造的规划,确定了实施方案.该方案实施后将彻底改变风机渐进式改造的现象,使新高炉的备用机组发挥更大的作用,可增加现有高炉的风压、风量,使现有高炉的产量、冶炼强度进一步提高.     

Recent progress report on DNA B-Z transition modulated by rare earth-amino acid complex and Alzheimer's disease amyloid beta

Rare earth dements have unique physical, magnetic, luminescent and catalytic properties. They have been successfully used as medicine and probes in luminescent resonance energy transfer (LRET) for bioassays, as well as reagents for diagnosis in magnetic resonance imaging (MRI). In this progress report, we will focus on recent progress on how rare earth amino complexes bind to DNA and change DNA structure, especially on DNA B-Z transition induced by rare earth amino acid complex and its potential impact on Alzheimer's disease (AD).     

Numerical Simulation on Inclusion and Bubble Entrapment in Solidified Shell in Model Experiment and in Mold of Continuous Caster With DC Magnetic Field

A model experiment investigating entrapment of inclusions and bubbles on the solidified shell was performed using molten steel,and the conditions for inclusion and bubble entrapment and mechanism of entrapment were studied.The results were applied to the flow behavior in the casting mold of a continuous caster.At the solid-liquid interface,entrapment of inclusions is greatly reduced by the existence of a low velocity flow,e.g.,0.05m/s.The above-mentioned interfacial flow velocity dependency of inclusion entrapment is considered to be largely influenced by changes in the thickness of the concentration boundary layer,which depend on the interfacial flow velocity.Specifically,bubbles and inclusions which enter the concentration boundary layer are drawn to the solid-liquid interface by a suction force which is several orders larger than the Saffman’s force.In addition to the above-mentioned suction force,the so-called cleaning effect is determined by fluid-dynamic forces such as drag force,etc.which act on particles,and furthermore,by resident time of particles at the solid-liquid interface,which depends on the solidification rate.In a FC mold with a 2-stage electromagnetic brake,flotation of bubbles entrained in the jet flow from the nozzle is accelerated with the large DC magnetic field.This is attributed to the braking effect of the DC field on the nozzle jet and the upward flow by the buoyancy of the bubbles.As a result,the interfacial flow velocity can be normalized by increasing the strength of the magnetic field,and entrapment of large bubbles and inclusions can be reduced.     

Influence of Controlled Rolling and Cooling Process on the Mechanical Properties of Low Carbon Cold Forging Steel

In the present paper,controlled rolling and cooling processing was conducted by using a laboratory hot rolling mill.The influence of different processing parameters on the mechanical properties of low carbon cold forging steel was investigated.The results show that the faster cooling after the deformation (especially in low temperature rolling conditions) leads to the refinement of the ferrite grain.The specimen exhibits very good mechanical properties owing to the finer ferrite grains.The pearlite morphologies can also affect the mechanical properties of low carbon cold forging steel.The mechanical properties increase with decreasing final cooling temperature within the range from 650℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony.The mechanical properties of the specimens with fast cooling after the conventional rolling are not only better than those of the specimens with slow cooling after low temperature rolling,but also almost similar to those of the specimens with fast cooling after low temperature rolling.It is suggested that fast cooling after high temperature rolling (the conventional rolling) process would be of important industrial value.     

The LIMMCAST Program at HZDR:Modelling of Fluid Flow and Transport Phenomena in the Continuous Casting Process

Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications.We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of200-400℃.The parameters of the facility and the dimensions of the test sections will be given,and the possibilities for flow investigations in tundish,submerged entry nozzle and mould will be discussed.In addition,the smaller set-up Mini-LIMMCAST will be presented,which works with the room-temperature liquid alloy GaInSn.The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution.New ultrasonic and electromagnetic techniques for measuring the velocity in liquid metal flows came up during the last decade allowing for a satisfying characterisation of flow quantities in the considered temperature range up to 400℃.First results from LIMMCAST and Mini-LIMMCAST will be presented covering the following phenomena:fully contacfless electromagnetic tomography of the flow in the mould,flow monitoring by a multitude of ultrasonic sensors,and analysis of the flow in the mould under the influence of an electromagnetic brake:intensification of the flow turbulence contrary to the expected flow damping,injection of argon bubbles through the stopper rod:occurrence of pressure oscillations.     

汽车零件强度、寿命与可靠性分析与模型

The elasto-plastic stress/strain behavior of an automobile rear axle was analyzed by three-dimension finite element method.Based on the stress in critical area where fatigue crack appears,the fatigue life of the welded structure was predicted using the critical shear stress plane criterion.To improve the fatigue property of the rear-axle,the welding-seam was strengthened by both pellet spraying and plasma melting,and evident improvement was experimentally illustrated.Based on the viewpoint that a complex component is also a system in the respect of reliability assessment and statistical dependence among component failures(i.e.the so call"common cause failure")is inherent for system under stochastic load environment,a system-level load-strength interference model was presented and the reliability of the rear axle was estimated as a system,instead of a component.     

铝土矿、氧化铝和电解铝产业链市场及利润流向

本文主要介绍近几年铝土矿、氧化铝和电解铝产业链的市场和利润流向演变以及未来发展形势.     

提高轧制重轨BS75A成材率的措施

介绍了武钢大型厂生产重轨BS75A时,利用现有设备,通过不断研究,找到了一条提高重轨(BS75A)生产成材率的方法,并取得了较好的经济效益.     

Thermodynamic properties of oxygen in yttrium-oxygen solid solutions

The oxygen potential in yttrium-oxygen (Y-O) solid solutions was measured by equilibration with titanium-oxygen (Ti-O) solid solutions. Yttrium and titanium samples were immersed in calcium-saturated CaCl₂ melts at temperatures between 1108 and 1438 K, and oxygen levels in the two metals were measured. With the Ti-O system acting as a reference, oxygen potentials in Y-O solid solutions were determined. By this technique, it was possible to make reliable measurements of extremely low oxygen potentials (as low as 10^?44 atm at 1273 K), far beyond the range of solid oxide electrolyte sensors.     

Effect of doping elements on catalytic performance of CeO2-ZrO2 solid solutions

CeZr, CeYZr, LaCeZr, LaCePrZr, LaCePrYZr, and LaCePr solid solutions were prepared via the coprecipitation method, and characterized by means of X-Ray Diffraction (XRD) and Brunauer-Emmett-Teller (BET) techniques. The oxygen storage capacity (OSC) of the solid solutions was evaluated by the pulse technique and the catalytic activity was assessed using a 4-channel catalysis device. It was seen that the solid solutions presented cubic structure. The specific surface area and thermal stability could be enhanced by doping Y into the solid solutions. Doping a small amount of La had a positive effect on the thermal durability while doping a large amount of La decreased the specific surface area and the thermal stability. LaCePrZr and LaCePrYZr solid solutions synthesized using Baotou rare earth mineral residue enriched with LaCePr after Nd extraction presented a certain higher value in specific surface area and thermal stability, thereby enabling to be used as economic catalysts for automobile exhaust purification. Coating Al2O3 or SiO2 layer on the surface of ceria-zirconia solid solutions increased the specific surface area and thermal resistance.     

Effect of doping elements on catalytic performance of CeO2-ZrO2 solid solutions

CeZr, CeYZr, LaCeZr, LaCePrZr, LaCePrYZr, and LaCePr solid solutions were prepared via the coprecipitation method, and characterized by means of X-Ray Diffraction （XRD） and Brunauer-Emmett-Teller （BET） techniques. The oxygen storage capacity （OSC） of the solid solutions was evaluated by the pulse technique and the catalytic activity was assessed using a 4-channel catalysis device. It was seen that the solid solutions presented cubic structure. The specific surface area and thermal stability could be enhanced by doping Y into the solid solutions. Doping a small amount of La had a positive effect on the thermal durability while doping a large amount of La decreased the specific surface area and the thermal stability. LaCePrZr and LaCePrYZr solid solutions synthesized using Baotou rare earth mineral residue enriched with LaCePr after Nd extraction presented a certain higher value in specific surface area and thermal stability, thereby enabling to be used as economic catalysts for automobile exhaust purification. Coating Al2O3 or SiO2 layer on the surface of ceria-zirconia solid solutions increased the specific surface area and thermal resistance.     

Effects of alkaline-earth metals on the properties of Cr0.5Ti0.5Si2 and Cr0.94Ta0.06Si2

Studies have been made on the effects of alkaline-earth metals on the structure and electrical parameters of Cr_0.5Ti_0.5Si₂ and Cr_0.94Ta_0.06Si₂ solid solutions. Solubility gaps occur for magnesium, calcium, and barium in the solid solutions. The alkaline-earth metals affect the fatigue resistance and thermo-emf coefficient. The alkaline-earth metals, added within their solubility limits, reduce the temperature coefficients of resistance for the solid solutions by an order of magnitude. The effects on the electrical parameters of the initial solid solutions are dependent on the electronic structures of the alkaline-earth metals.Translated from Poroshkovaya Metallurgiya, No. 7(367), pp. 101–105, July, 1993.     

Preparation and Characterization of Cex Th1-xO2 Solid Solutions Prepared by Sol-Gel Method

Ceriumoxidehasbeenwidelystudiedinrecent yearsbecauseofitsusefulnessindifferentareasof chemistry.Incatalyticfield,forexample,CeO2has beenusedasanimportantcomponentofautomotive three waycatalystsforreducingtheexhaust.The mainroleofceriainthree waycatalystsi…     

Features of solid solution formation with a fluorite type structure in the system ZrO2-HfO2-Y2O3 with different synthesis methods

X-ray phase, petrographic, and thermal analysis methods are used to study the properties of solid solutions with a fluorite type structure in the ternary system ZrO₂-HfO₂-Y₂O₃ in relationship to preparation method: mixing of the original powders followed by solid-phase sintering and melting in solar furnaces; hydrothermal synthesis of nanocrystalline powders followed by solid-phase sintering. It is shown that in specimens whose composition lies at the isoconcentrate of 10 mole% Y₂O₃ a single phase forms independent of preparation method, i.e. a solid solution with a fluorite type structure. The azeotrope, situated at the liquidus of the limiting binary system ZrO₂-Y₂O₃ in the region of fluorite-like solid solutions, affects the melting temperature of ternary solid solutions and the lattice parameters of specimens after melting in a solar furnace. __________ Translated from Poroshkovaya Metallurgiya, Nos. 1–2(447), pp. 3–11, January–February, 2006.     

Effect of heat treatment on the dispersity of Sn(IV)—Sb—O powders and the porosity of thick-film gas sensors based on them

A study is made of how the granulometric composition and porosity of powders of solid solutions in the system Sn(IV)−Sb−O is affected by the conditions of precipitation of mixtures of tin hydroxide and antimony hydroxide and the heat-treatment temperature. Powders of tin and antimony hydroxides have a microporous structure and a high (≥200 m ²/g) specific surface. Heat treatment above 870 K forms Sn_1−xSb_xO₂ solid solutions, this being accompanied by an increase in the size of the particles and transformation of the microporous structure to a mesoporous structure. An increase in the antimony content of the solid solutions helps form finer powders. A examination is made of the parameters of the pore structure of bulk specimens of semiconductor gas sensors obtained by heat-treating mixtures of powders of solid solutions and ultrafine clay. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(407), pp. 111–116, May–June, 1999.     

Physicochemical materials research

For alloys in the range Os-OsAl₂-IrAl_2.7-Ir, as-cast and annealed at 1400 °C (Os-OsAl-IrAl-Ir) and 1250°C (OsAl-OsAl₂-IrAl_2.7-IrAl), phase equilibria are studied by powder x-ray diffraction (PXRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). Between isostructural aluminides OsAl and IrAl there exists a continuous solid solution (Os,Ir)Al. Other unary and binary phases form terminal solid solutions: (Os), (Ir), (OsAl₂), and (IrAl_2.7).     

Catalytic Activity of Ceria-Zirconia Nanostructured Materials Prepared via Reversed Microemulsion Method

CeO2-ZrO2mixed oxides have a number of i mpor-tant catalytic applications[1].They are extensively em-ployed in current automotive three-way catalysts(TWCs)as the oxygen storage promoters,i.e.materi-als that regulate the oxygen partial pressure throughtheC…