Papers by Keyword: Mn

Abstract: Recycling of aluminium alloys is gaining significant attention due to its economic and environmental benefits. However, close loop recycled aluminium alloys can be adversely affected by impurities and alloying elements present in the recycled feedstock. In this study, the influence of three composites, namely alumina (Al₂O₃), ferric oxide (Fe₂O₃), and manganese (Mn), on the properties of recycled aluminium taldon scraps was investigated to enhance the tensile behaviour of the alloys. The effects of these composites on the mechanical properties, microstructure, and corrosion behaviour of the recycled aluminium alloys were evaluated through experimental characterization techniques. The results showed that the addition of these composites had a significant influence on the properties of recycled aluminium alloys, providing insights into the potential for improving the performance of recycled aluminium alloys through composite additions. The addition of Al₂O₃ enhanced the tensile strength by 44.18 % and the variation can be attributed to the strengthening of the dendritic zones by the formation of α-Al.

Abstract: Physical and optical properties of mixed Mn-Co ions in soda lime silicate glasses were measured and calculated. The results show that, the densities increased with the increasing of CoO content. This indicates that increasing the molecular weight of oxide ions used in the glass was due to the replacing SiO₂ by CoO. The refractive indices were increased with increasing of CoO concentration. The absorption peaks of CoO doped glasses occurred at the wavelength around 511, 584 and 649 nm which are assigned to ⁴A₂(F) ® ²A₁(G), ⁴A₂(F) ® ⁴T₁(P) and ⁴A₂(F) ® ²E(G) transition, respectively.

Abstract: New Al-Mg alloys have been developed for super-plastic forming (SPF) based on commercial AA5083/AA5086 alloys, but with an increased Mn content from 0.5 to 1.5 wt.% and a decreased impurity Fe level from 0.25 to 0.05 wt.%.The effects of Mn and Fe levels on super-plasticity have been investigated by high temperature tensile testing of cold rolled H18 sheets at 425 to 525°C with a strain rate of 2×10^-3 s^-1. The microstructure evolution during different processing stages, grain size and grain size stability were investigated by optical microscopy and scanning electron microscopy. Both Mn and Fe showed a similar and significant contribution to grain size control in recrystallization, but their effect on high temperature sheet formability was different. An increase in Mn level led to an improvement in high temperature tensile elongation, while an increase in Fe content reduced the sheet formability. A new alloy with 1.5 wt.% Mn and 0.05 wt.% Fe, when processed to H18 temper, was able to reach more than 400% tensile elongation at 450 - 500°C with a strain rate of 2×10^-3 s^-1.

Abstract: By adding Mn into SAE8620 gear steel, the effect of Mn on the microstructure and hardness of steel treated by quenching and partitioning process is investigated in this research. Microstructure is observed. Hardness is measured, after that it is converted into tensile strength. And the content of austenite is determined by X-ray diffraction analysis. It is found that higher content of Mn increases the content of martensite and reduces that of blocky ferrite and also leads to higher hardness of steel. In addition, XRD pattern shows obvious existence and enhancement of retained austenite.

Abstract: Precipitates in biomedical Co-Cr-Mo cast alloys are closely related to their wear and mechanical properties. It is important to elucidate the effects of addition of alloying elements listed in ASTM F75 on precipitation and dissolution in order to control microstructural changes in fabricating biomedical Co-Cr-Mo alloy implants. In this study, Si and Mn were selected as the alloying elements. The chemical compositions of two cast alloys were Co-28Cr-6Mo-0.25C with containing 1mass% Si dan Mn. The alloys were solution treated at temperatures at 1448 to 1548 K for holding time of 1.8-43.2 ks, followed by water quenching. The precipitates in the as-cast alloy with Si addition were M₂₃C₆ carbide, h-phase (M₆C-M₁₂C type carbide) and p-phase (M₂T₃X type carbide with a b-Mn structure), while M₂₃C₆ carbide and h-phase were detected in the as-cast alloy with Mn addition. The alloy with Si addition required longer solution treatment time for complete precipitate dissolution as compared with the alloy with Mn addition. The phase and morphology of precipitates observed during solution treatment depended on the heat treatment temperature and holding time and alloy composition.

Abstract: Three kinds of organic materials were used for culture experiment, namely livestock manures, natural organic materials and half decomposed organic materials. And the modified BCR sequential extraction procedure was used to analyze the morphologic changes of Mn. The study was focus on the effects of different kinds of organic materials on contents and morphologic changes of Mn in black soil. And the results show that different kinds of organic materials all increase the total Mn contents in soil. The amplifications of livestock manures and natural organic materials are higher then half decomposed organic materials. Comparing with fertilizers only, all kinds of organic materials increase the contents of each Mn fraction. For Weak acid soluble (Aci.) fraction of Mn, natural organic materials increase most, for Reducible (Red.) fraction, livestock manures increase most, for Oxidizable (Oxi.) fraction, all kinds of organic materials are nearly the same, and for Residual (Res.) fraction, livestock manures increase most. In addition, different kinds of organic materials also lead to morphologic transformation of Mn, comparing with fertilizers only, livestock manures lead to inert transformation, while natural organic materials lead to active transformation, and half decomposed organic materials lead to inert transformation.

Abstract: A fast and effective method was developed for determination of Mn in leisure foods by incomplete digestion-microemulsion sampling-high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). Microemulsions were prepared with digestive liquor and n-butyl alcohol as an auxiliary emulsifier after incomplete digestion treatment. The factors influencing determination were investigated by single factor experimental design. The optimal determination conditions were found as follows: the tartaric acid (1 mg/mL) was added as a chemical modifier with the volume of 4 μL; pyrolysis temperature 1100°C; atomization temperature 2000°C. The results showed that the correlation coefficient was better than 0.996, the characteristic concentration was 0.09 μg/L, the precision (RSD) for 6 replicate measurements of Mn was 2.8% and the average of recoveries was 97.3%. F-test and t-test (95% confidence level) in between the proposed method and the microwave digestion-HR-CS GFAAS method had no significant difference. Therefore, the proposed method was accurate and stable with a high practical value. It provided scientific basis for determination of metal elements in food.

Abstract: Two bearing steels, with higher Mn and Si content than GCr15, were refined in 50kg vacuum induction furnace followed by multi-pass rolling to 12mm thick flat on two-high mill. Mechanical properties and microstructures were measured and observed. The results show that higher content of Mn and Si decreases the martensite starting temperature (Ms), which is beneficial to the forming of martensite. The microstructure changes from martensite plus troostite to martensite, leading to higher hardness of steel and improvement of wear resistance. However, the band microstructure is easily formed by increase of Mn and Si, which is harmful to transverse property.

Abstract: ZnO belongs to the II-VI semiconductor group with a direct band-gap of 3.2-3.37 eV in 300K and a high exciton binding energy of 60 meV. It has good transparency, high electron mobility, wide, and strong room-temperature luminescence. These properties have many applications in a wide area of emerging applications. Doping ZnO with the transition metals gives it magnetic property at room temperature hence making it multifunctional material, i.e. coexistence of magnetic, semiconducting and optical properties. The samples can be synthesized in the bulk, thin film, and nanoforms which show a wide range of ferromagnetism properties. Ferromagnetic semiconductors are important materials for spintronic and nonvolatile memory storage applications. Doping of transition metal elements into ZnO offers a feasible means of tailoring the band gap to use it as light emitters and UV detector. As there are controversial on the energy gap value due to change of lattice parameters we have synthesized Mn-doped ZnO nanoparticles by co-precipitation method with different concentrations to study the effect of lattice parameters changes on gap energy. The doped samples were studied by XRD, SEM, FT-IR., and UV-Vis. The XRD patterns confirm doping of Mn into ZnO structure. As Mn concentrations increases the peak due to of Mn impurity in FT-IR spectra becomes more pronounces hence confirming concentrations variation. We find from UV-Vis spectra that the gap energy due to doping concentration increases due to the Goldschmidt-Pauling rule this increase depends on dopant concentrations and increases as impurity amount increases.

Abstract: First-principle software bundle based on the density functional theory (DFT) is used to investigate pure CeOB_2B and Mn-doped CeOB_2B with different doping concentration. The structural model of CeOB_2B crystal is constructed and geometrically optimized, the electron density of states and band structure calculated. The results are as follows: the valence band top of CeOB_2B is made up with O2p and Ce5d states, and the existence of 4f unoccupied molecular orbital of CeOB_2B facilitates the electronic storage. The theoretical calculation models of Mn-doped CeOB_2B with different concentration are constructed and calculated, including 2*1*1, 2*2*1 and 2*2*2 supercell models. After CeOB_2B is doped, hybridization happens between 4s orbitals of Mn atoms and 2p orbital of O atoms, resulting in 4s orbitals of Mn atoms lose electrons.Moreover, Mn atom is electron donor and O atoms is the electron acceptor. As the doping concentration decreases, the formation energy also decreases.And a smaller formation energy leads to a more stable structure.