采用锌粉喷吹技术从熔融铅中除银(英文)

采用锌粉喷吹技术从Pb-Ag合金中除银。所用锌粉粒径分别为3.55,44.4和734.8μm,以氮气为输送气体,通过从顶部插入的一根喷管喷入熔体中。实验结果表明,采用粒径为44.4μm的锌粉时,银的去除率最高,而采用较小粒径的锌粉时去除率最低。X射线衍射分析表明,采用粒径为44.4和734.8μm的锌粉时,生成的渣中存在AgZn相,这与SEM-EDS分析结果相吻合。根据喷吹进入熔体中锌粉的熔化时间和沉降时间,对实验现象进行了解释。

Precipitation analysis of as-cast HK40 steel after isothermal aging

As-cast HK40 steel was aged at 700, 800, or 900℃ for times as long as 2000 h. Microstructural characterization showed that the primary M_7C_3 carbide network contained a substantial content of manganese, in agreement with the microsegregation of manganese calculated by Thermo-Calc using the Scheil–Gulliver module. The dissolution of primary carbides caused the solute supersaturation of austenite and subsequent precipitation of fine M_(23)C_6 carbides in the austenite matrix for aged specimens. During prolonged aging, the carbide size increased with increasing time because of the coarsening process. A time–temperature–precipitation diagram for M_(23)C_6 carbides was calculated using the Thermo-CalcPRISMA software; this diagram showed good agreement with the experimental growth kinetics of precipitation. The fine carbide precipitation caused an increase in hardness; however, the coarsening process of carbides promoted a decrease in hardness. Nanoindentation tests of the austenite matrix indicated an increase in ductility with increasing aging time.

Synthesis of Tenoltrifluoroacetone Composite Doped with Terbium, Dysprosium and Europium Encapsulated in Silica Oxide Matrix

The synthesis of the thenoyltrifluoroacetone compound doped with terbium, dysprosium and europium encapsulated in a silica matrix (TTA:Tb:Dy:Eu@SiO2) were performed by the sol-gel method. The precursors to obtain the vitreous phase (SiO2) were: Tetraethylorthosilicate (TEOS, C8H2O4Si, 98%, Aldrich), and ethyl alcohol (CH3CH2OH, 99.5%, Meyer), distilled water and 0.05 ml of hydrochloric acid (HCl, Meyer). The sample with molar ratio 20:80 TTA:Tb:Dy:Eu@SiO2 has the best emission intensity. Thermogravimetric analysis (TGA) shown that silica encapsulated samples decompose at lower temperatures than pure TTA:Tb:Dy:Eu luminescent material. Fourier Transform Infrared (IR-TF) shown the characteristic Si-O-Si bands that are presented at a wavelength of 1049, 853 and 440 cm-1 confirming that the luminescent material is encapsulated in a silica matrix, finally X-ray diffraction (XRD) shown that TTA:Tb:Dy:Eu@SiO2 composite is amorphous.

Copper Oxide Inked with Dye Obtained from the Lactarius Indigo Fungus for Energy Production

The results obtained from the characterization of a copper deposit on indium doped tin oxide (ITO), inked with natural dye extracted from the Lactarius indigo fungus, for use in Gratzel type solar cells are reported. An electrolyte composed of 0.1 M HNO3 and 0.5 M CuSO4 was used, this solution was prepared for copper deposits on the ITO. Cyclic voltammetry was performed at different scan rates to obtain the reduction zone for deposition between potentials of ?100 to ?500 mV. The dye was obtained from the indigo Lactarius fungus from maceration, once the inked deposits were obtained, characterizations were performed, the initial test was to obtain the Ultraviolet-Visible (UV-visible) of the pure dye, and later the same test was performed on the inked oxide. Electrochemical Impedance Spectroscopy (EIS) was performed on the samples, as well as Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), to characterize the material properties for its application.

Red, White and Blue Light Emission from Europium Doped Al2O3 Confined into a Silica Matrix

The main drawbacks of fluorescent activated lanthanide luminescent materials in practical optoelectronic applications are the high cost of raw material and the limitation of a specific color depending on the lanthanide ion. In this work, the synthesis of red, white and blue light emitting composite powders of Al2O3:Eu3+@SiO2 were successfully synthesized by the hydrolysis and condensation reactions of TEOS as the raw precursor of silica matrix on the Al2O3:Eu3+ surface. With the aim to change the CIE coordinates different weight ratios of Al2O3:Eu3+/SiO2 powders from 13Al/87Si to 5Al/95Si were prepared. Besides, various excitation wavelength from 280 to 340 nm was used in order to change the ratio intensity;Ired/Iblue, between the red emission coming from the 5D0→7F2 transition of Eu3+ ions and the blue band of silica matrix. Chemical evolution of the hydrolysis and condensation reaction of TEOS were conducted by FTIR spectroscopy. The results indicate that from 500°C a complete TEOS to SiO2 transformation is carried out.

Microstructural Characterization of Large Area C₆₀Films Obtained by Conventional Microwave Oven Irradiation

In the present work the synthesis of C60 produced in a conventional microwave oven from the decomposition of camphor resin is reported. The polycrystalline structure of the sample was determined by X-Ray Diffraction (XRD), the sample showed several phases, the main phase corresponds to fullerene C60 ordered in a Face-Centered Cubic structure (FCC), with two more structures: one orthorhombic system and the other the monoclinic system coexisting also with graphite 2H phase. It was observed in a Scanning Electron Microscopy (SEM), that the sample formed thin films of stacked carbon. Whereas in a High Resolution Transmission Electron Microscopy (HRTEM), measurements in Bright Field mode revealed that the main phase of the material is C60 ordered in FCC structure and the elemental composition and atomic bonding state can be determined by analyzing the energy with the electron microscope by Elesctron Energy- Loss Spectroscopy (EELS), technique allowed confirm all the phase C60 established with XRD observations.

Rare-Earth Doped GdVO4 by Sol-Gel Method: Structural and Luminescence Properties

Rare earths have been extensively developed in recent years, however, new hosts allow high excitation and emission efficiency, in this sense, gadolinium vanadate has been extensively studied and in previous works it has been widely used in down conversion systems. Because of the strong absorption of the VO4 groups and efficient energy transfer from GdVO4 to lanthanide ions, in this work its up-conversion properties were studied when is co-doped with Yb3+, X3+ where X = Tm, Er and Ho. The powders synthesized presented a high crystallinity and a rounded morphology and exhibit a high luminescence when are excited with IR radiation.

Precipitation kinetics of carbides during cyclical and isothermal aging of 2.25Cr–1Mo steel and its effect on mechanical properties

The carbide precipitation was analyzed during aging of 2.25Cr–1Mo steel at 550℃.The as-received steel was aged in two different manners:the first treatment was an isothermal aging at 550℃ for time up to 1000 h,and the second one was carried out by a cyclical aging,which consisted of aging at 550℃ for 1 h,water quenching at room temperature and then newly heating at 550℃.This procedure was repeated up to 300 times.The M_(23)C_(6) and M6C carbide precipitation took place intragranularly and intergranularly for both aging treatments.The carbide coarsening was detected to occur with the increasing aging time.Nevertheless,the growth kinetics of precipitation occurred more rapidly in the case of cyclical aging.The specimen hardness decreased with the aging time in both cases;however,it occurred in shorter aging time for the cyclical aging.Nanoindentation testing indicated the increase in ductility with the aging time,and the cyclically aged specimens showed larger ductility than the isothermally aged specimens.

Phase separation and coarsening of NiAl(β′)intermetallic in quench-aged Fe-Ni-Al alloys

The coarsening behavior of four quench-aged Fe-Ni-AI alloys with different Ni and Al con tents is studied.The alloys were solubilized at 1100℃for 24 h,water-quenched and aged at 850℃for periods ranging from 1 to 100 h to promote phase separation and coarsening.The two alloys with the highest combined Ni and Al contents(>35 at.%)showed signs of spinodal decomposition,while the alloys with lower Ni and Al contents followed a classical nucleation process.Higher Ni and Al contents promoted an increase in NiAl(β′)phase fraction in concordance with phase equilibrium diagrams.The alloy with the highest[3'fraction presented a completely interconnected structure.The coarsening ofβ′particles in the other three alloys followed the predictions of the Lifshitz-Slyozov-Wagner(LSW)theory.The general trend was an increase in the coarsening kinetics with higher Ni and Al contents.The highest hardness was found in the alloys with higher fraction albeit these compositions are less resistant to coarsening and have been reported to present a low room-temperature ductility.

Influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on friction coefficients of a wet clutch in the running-in stage

In this paper,the influence of oxidation of automatic transmission fluids(ATFs)and sliding distance on the friction coefficients of a wet clutch in approached running-in conditions was investigated.The ATFs were oxidized by a laboratory process approaching oxidation occurred in actual ATFs.Oxidation was evaluated by means of increase in carbonyl compounds and depletion of zinc dialkyldithiophosphates(ZDDPs)additives.Also,the changes in kinematic viscosity and viscosity index were evaluated.Pin-ondisk tests were conducted to replicate the actual sliding contact in a wet clutch.The pin specimens were cut from friction material composite plates and the disks were actual steel separators both from an automotive wet clutch.Friction coefficient, μ,was measured at progressive sliding velocity,ν,to obtain μ–νcurves at 26 and 100°C.Three μ–νtests were consecutively run using the same pair of specimens and oil.The cumulative sliding distance for each μ–νtest generated surface flattening using the oils.The friction coefficients of the wet clutch increased due to the ATFs oxidation meanwhile the dm/dv values decreased in most cases.It suggests that ATF oxidation can enhance torque capacity of the wet clutch,but it could reduce anti-shudder property.Progressive sliding distance improved the slopes in the μ–νresults using fresh ATFs meanwhile it generated a slope decrease by using aged ATFs.