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S.K. Kemei, M.S.K. Kirui, F.G. Ndiritu, R.G. Ngumbu, P.M. Odhiambo, D.M.G. Leite, A.L.J. Pereira and J.H. Dias Da Silva

Abstract

Dynamical mechanical analysis yields information about the mechanical properties of a material as a function of deforming factors, such as temperature, oscillating stress and strain amplitudes. GaAs and Mn-doped GaAs at varied levels, used in making electronic devices, suffer from damage due to changes in environmental temperatures. This is a defective factor experienced during winter and summer seasons. Hence, there was a need to establish the best amount of manganese to be doped in GaAs so as to obtain a mechanically stable spin injector material to make electronic devices. Mechanical properties of Ga1-xMnxAs spin injector were studied in relation to temperatures above room temperature (25 °C). Here, creep compliance, Young’s moduli and creep recovery for all studied samples with different manganese doping levels (MDLs) were determined using DMA 2980 Instrument from TA instruments Inc. The study was conducted using displace-recover programme on DMA creep mode with a single cantilever clamp. The samples were prepared using RF sputtering techniques. From the creep compliance study it was found that MDL of 10 % was appropriate at 30 °C and 40 °C. The data obtained can be useful to the spintronic and electronic device engineers in designing the appropriate devices to use at 30 °C and above or equal to 40 °C.

Open access

E. Talik, L. Lipińska, A. Guzik, P. Zajdel, M. Michalska, M. Szubka, M. Kądziołka-Gaweł and R.L. Paul

1 Introduction Lithium manganese oxide (LiMn 2 O 4 ) spinel has been extensively studied as a cathode material for Li-ion batteries, as an alternative to LiCoO 2 , LiNiO 2 or LiFePO 4 used today. Initially, LiMn 2 O 4 spinel has been synthesized mainly using conventional solid state methods [ 1 , 2 ]. Nowadays, other synthetic routes are applied too. One of them is a modified sol-gel (Pechini) technique, which seems to be appropriate for preparation of nanocrystalline cathode materials. Being a solution-based route, it offers a possibility of

Open access

A. Guzik, E. Talik, A. Pajączkowska, S. Turczyński and J. Kusz

Abstract

Monocrystalline fibres of undoped PrAlO3 and PrAlO3:0.1 Mn, have been grown by the pulling-down method under nitrogen atmosphere. The as-grown crystal doped with Mn had a visible brown core surrounded by a green ring, whereas this effect was weaker for the undoped PrAlO3. A coloration of the brown core was caused by a presence of Pr4+ ions. The presence of the Pr4+ ions was confirmed by XPS and magnetic studies. The XPS chemical analysis showed the increased concentration of oxygen in the crystals with the brown core. The most probable valency of manganese is Mn4+. It is located in Al3+ sites.

Open access

K.O. Oyedotun, E. Ajenifuja, B. Olofinjana, B.A. Taleatu, E. Omotoso, M.A. Eleruja and E.O.B. Ajayi

Abstract

Lithium manganese oxide thin films were deposited on sodalime glass substrates by metal organic chemical vapour deposition (MOCVD) technique. The films were prepared by pyrolysis of lithium manganese acetylacetonate precursor at a temperature of 420 °C with a flow rate of 2.5 dm3/min for two-hour deposition period. Rutherford backscattering spectroscopy (RBS), UV-Vis spectrophotometry, X-ray diffraction (XRD) spectroscopy, atomic force microscopy (AFM) and van der Pauw four point probe method were used for characterizations of the film samples. RBS studies of the films revealed fair thickness of 1112.311 (1015 atoms/cm2) and effective stoichiometric relationship of Li0.47Mn0.27O0.26. The films exhibited relatively high transmission (50 % T) in the visible and NIR range, with the bandgap energy of 2.55 eV. Broad and diffused X-ray diffraction patterns obtained showed that the film was amorphous in nature, while microstructural studies indicated dense and uniformly distributed layer across the substrate. Resistivity value of 4.9 Ω·cm was obtained for the thin film. Compared with Mn0.2O0.8 thin film, a significant lattice absorption edge shift was observed in the Li0.47Mn0.27O0.26 film.

Open access

K. Selvarani, R. Mahalakshmi and B. Thanuja

Abstract

Co-crystals of L-phenylalanine hydrochloride (LPAHCl) were grown by slow evaporation technique in the presence of manganese sulphate and cadmium chloride. Crystallinity of the grown crystals was confirmed by single crystal X-ray diffraction. Optical transmission spectra showed very high transmittance in the entire visible region. The cut-off wavelength was observed at 250 nm for both the crystals. The optical band gap energy was found to be 4.37 eV and 4.31 eV for the grown co-crystals of LPAHCl with MnSO4 and CdCl2, respectively. The second harmonic generation of the grown crystals was confirmed by Kurtz and Perry powder SHG method and compared with KDP. The frequency dependent dielectric properties of the co-crystals were studied at different temperatures.

Open access

P. Bragiel, P. Ficek, W. Prochwicz, I. Radkowska and N. Veeraiah

Abstract

A series of glasses of the composition 20Na2-O-15CaO-5B2O3-5SiO2-(55 - x) P2O5:xMnO2, was prepared and characterized by XRD, DSC, SEM, and Raman techniques. The samples were later immersed in simulated body fluid (SBF) for checking the potential growth of hydroxyapatite layer (HA). Experiments confirmed that addition of manganese oxide leads to structural changes of the glasses. With increasing content of MnO2, the surface of the samples became more congenial for improving the growth of HA. The formation of HA layer on the surface of the samples was confirmed just after seven days of immersion. The growth rate of HA has gradually increased with the increase of MnO2 content.

Open access

M. Margabandhu, S. Sendhilnathan, S. Senthilkumar and K. Hirthna

present work was carried out on synthesis and investigation of manganese substituted CoFe2O4 nanoparticles dispersed in carrier fluid transformer oil, subjected to external magnetic fields. 2 Experimental 2.1 Materials The chemicals used for the preparation of magnetic nanoparticles and ferrofluids were transformer oil, sodium hydroxide pellets (NaOH), cobalt chloride (CoCl 2 · 6H 2 O), manganese chloride (MnCl 2 · 4H 2 O) and ferric chloride (FeCl 3 · 6H 2 O). They were of very high purity (99 %) and were obtained from Merck and Nice chemicals. Hence

Open access

N. Manjula, M. Pugalenthi, V.S. Nagarethinam, K. Usharani and A.R. Balu

Abstract

Thin films of manganese-doped cadmium oxide (CdO:Mn) with different Mn-doping levels (0, 1, 2, 3 and 4 at.%) were deposited on glass substrates by employing an inexpensive, simplified spray technique using a perfume atomizer at 375 °C. The influence of Mn incorporation on the structural, morphological, optical and electrical properties of CdO films has been studied. All the films exhibit cubic crystal structure with a (1 1 1) preferential orientation. Mn-doping causes a slight shift of the (1 1 1) diffraction peak towards higher angle. The crystallite size of the films is found to decrease from 34.63 nm to 17.68 nm with an increase in Mn doping concentration. The CdO:Mn film coated with 1 at.% Mn exhibit a high transparency of nearly 90 % which decreases for higher doping concentration. The optical band gap decreases with an increase in Mn doping concentration. All the films have electrical resistivity of the order of 10−4 Ω·cm.

Open access

N. Murali, K. Vijaya babu, K. Ephraim babu and V. Veeraiah

Abstract

Layered oxide LiMO2 (Ni, Co, Mn) have been proposed as cathode materials for lithium-ion batteries. Mainly LiNiO2 is accepted as an attractive cathode material because of its various advantages such as low cost, high discharge capacity, good reversibility. The LiNi0.5Mn0.5O2 powders are synthesized by a sol-gel method using citric acid as a chelating agent. The structure of the synthesized material is analyzed by using XRD, FT-IR and the microstructures of the samples are observed by using FESEM. The intensities and positions of the peaks are in a good agreement with the previous results. The morphological changes are clearly observed as a result of manganese substitution. The Fourier transform infrared (FT-IR) spectra obtained with KBr pellet data reveal the structure of the oxide lattice constituted by LiO6 and NiO6 octahedra. The conductivity studies are characterized by (EIS) in the frequency range of 42 Hz to 1 MHz at room temperature to 120 °C. The dielectric properties are analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. It indicates that the conductivity increases with increasing temperature. The fitting data of EIS plots replicate the non-Debye relaxation process with negative temperature coefficient of resistance (NTCR) behavior.

Open access

Fouad El-Metwaly, Morsi Abou-Sekkina, Fawaz Saad and Abdalla Khedr

Abstract

LiMn2O4 is an attractive candidate cathode material for Li-ion rechargeable batteries, but it suffers from severe capacity fading, especially at higher temperature (55 °C) during charging/discharging processes. Recently, many attempts have been made to synthesize modified LiMn2O4. In this work, a new study on the synthesis of pure and U4+-doped nano lithium manganese oxide [LiMn2−x UxO4, (x = 0:00, 0.01, 0.03)] via solid-state method was introduced. The synthesized LiMn1:97U0:03O4 was irradiated by γ-radiation (10 and 30 kGy). The green samples and the resulting spinel products were characterized using thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared (IR), and scanning electron microscopy (SEM) measurements. XRD and SEM studies revealed nano-sized particles in all prepared samples. Direct-current (DC) electrical conductivity measurements indicated that these samples are semiconductors and the activation energies decrease with increasing rare-earth U4+ content and γ-irradiation. ΔEa equals to 0.304 eV for LiMn1:99U0:01O4, ΔEa is 0.282 eV for LiMn1:97U0:03O4 and decreases to ΔEa = 0:262 eV for γ-irradiated LiMn1:97U0:03O4 nano spinel. The data obtained for the investigated samples increase their attractiveness in modern electronic technology.