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Open access

S. Anbu Chudar Azhagan and V.S. Kathiravan

Abstract

Crystallization of γ-glycine in the presence of selected concentration (9 g/mL) of tailor-made additive magnesium sulfate heptahydrate salt (MgSO4·7H2O) has been studied at ambient temperature by adopting slow solvent evaporation procedure. The morphological modifications of glycine crystals grown from pure aqueous solutions of glycine and from glycine solutions containing magnesium species in the amount of 0.1 g/mL to 16 g/mL have been investigated thoroughly. The crystalline nature and phase identification of the crystalline material were confirmed by X-ray powder diffraction and SXRD studies. NMR studies revealed the information about the molecular conformation in solution, phase changes, functional groups and chemical environment. FT-IR spectra revealed distinct difference between α and γ-glycine polymorphs in the region around 880 cm−1 to 930 cm−1. The grown γ-glycine crystal had a lower cut-off value at 200 nm and the bandgap value evaluated from the Tauc plot was found to be 5.83 eV. The marked differences between α and γ-polymorphs of glycine were also revealed by DSC thermograms. The mechanical strength of the -glycine crystal was studied with the help of Vickers microhardness instrument. Kurtz-powder NLO study proved the generation of second harmonics (i.e. green light emission) in the grown γ-glycine crystal and its efficiency was calculated as 1.44 times better than that of the reference material potassium dihydrogen phosphate.

Open access

A. Gadalla, M. S. Abd El-Sadek and R. Hamood

Abstract

This paper attempts to describe an effective method for producing a composite of quantum dots consisting of CdSe (core) with CdS (shell). This nanoparticles composite was synthesized from modified organometallic precursors. The sizes of the nanoparticles were estimated from X-ray diffraction data using Debye-Scherer formula and compared with high resolution electron microscopy (HRTEM) and optical spectra. The shape of CdSe/CdS NPs is nearly spherical and revels that the CdS shell with the thickness ~0.6 nm almost fully covers the CdSe core (higher contrast). Using UV-Vis spectroscopy, a systematic red shift in the absorption and emission spectra was observed after the deposition of CdS which confirms the shell growth over the CdSe core. In the CdSe/CdS core/shell structure, the holes are confined to the core, while the electrons are delocalized as a result of similar electron affinities of the core and the shell. The increased time of synthesis resulted in shell thickness increase. The observed properties of prepared CdSe/CdS QDs demonstrate the capability of the nanocomposite for using in the optoelectronics and photonics devices.

Open access

P. Sakthi, R. Rajasekaran and A. Arun

Abstract

An inorganic coordination complex of single crystal containing sodium and aluminum (SA) was grown at room temperature by slow evaporation technique. The crystal was characterized using single crystal X-ray diffraction (XRD), FT-IR, UV-Vis, SHG, SEM, EDX and TG/DTA analyses. The size of the grown crystal was around 17 mm × 15 mm × 5 mm. Both optical and SEM photographs confirmed that the crystal is transparent with smooth surface. The XRD data showed that the crystal belongs to the BCC crystal structure. The crystal shows excellent transparency in the entire region of visible light (cut-off value is 339 cm−1). The dielectric constant as well as dielectric loss of the sample was calculated by varying frequencies at different temperatures and the presence of low dielectric loss proved that this crystal can be used for the NLO application.

Open access

Anu Dhupar, Suresh Kumar, Vandana Sharma and J.K. Sharma

Abstract

In the present work, mixed structure Zn(S,O) nanoparticles have been synthesized using solution based chemical coprecipitation technique. Two different zinc sources (Zn(CH3COO)2·2H2O and ZnSO4·7H2O) and one sulfur source (CSNH2NH2) have been used as primary chemical precursors for the synthesis of the nanoparticles in the presence and absence of a capping agent (EDTA). The structural, morphological, compositional and optical properties of the nanoparticles have been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transmission infra-red (FT-IR) and UV-Visible (UV-Vis) spectroscopy. XRD revealed the formation of mixed phases of c-ZnS, h-ZnS and h-ZnO in the synthesized nanoparticles. The surface morphology was analyzed from SEM micrographs which showed noticeable changes due to the effect of EDTA. EDX analysis confirmed the presence of zinc, sulfur and oxygen in Zn(S,O) nanoparticles. FT-IR spectra identified the presence of characteristic absorption peaks of ZnS and ZnO along with other functional group elements. The optical band gap values were found to vary from 4.16 eV to 4.40 eV for Zn(S,O) nanoparticles which are higher in comparison to the band gap values of bulk ZnS and ZnO. These higher band gap values may be attributed to the mixed structure of Zn(S,O) nanoparticles.

Open access

W.C. Shen, L.L. Lin, C.Y. Shen, S. Xing and Z.B. Pan

Abstract

TbxHo0.9−xNd0.1(Fe0.8Co0.2)1.93/epoxy (0 ⩽ x ⩽ 0.40) composites are fabricated in the presence of a magnetic field. The structural and dynamic magnetoelastic properties are investigated as a function of both magnetic bias field Hbias and frequency f at room temperature. The composites are formed as textured orientation structure of 1–3 type with 〈1 0 0〉 preferred orientation for x ⩽ 0.10 and 〈1 1 1〉-orientation for x ⩾ 0.25. The composites generally possess insignificant eddy-current losses for frequency up to 50 kHz, and their dynamic magnetoelastic properties depend greatly on Hbias. The elastic modulus (E3H and E3B) shows a maximum negative ΔE effect, along with a maximum d33, at a relatively low Hbias ~ 80 kA/m, contributed by the maximum motion of non-180° domain-wall. The 1–3 type composite for x ⩾ 0.25 shows an enhanced magnetoelastic effect in comparison with 0 to 3 type one, which can be principally ascribed to its easy magnetization direction (EMD) towards 〈1 1 1〉 axis and the formation of 〈1 1 1〉-texture-oriented structure in the composite. These attractive dynamic magnetoelastic properties, e.g., the low magnetic anisotropy and d33,max as high as 2.0 nm/A at a low Hbias ~ 80 kA/m, along with the light rare-earth Nd element existing in insulating polymer matrix, would make it a promising magnetostrictive material system.

Open access

Denis Sokol, Maksim Ivanov, Andrei N. Salak, Robertas Grigalaitis, Juras Banys and Aivaras Kareiva

Abstract

Magnesium-aluminum-bismuth layered double hydroxides (Mg3Al1−xBix; LDHs) were prepared using both coprecipitation and sol-gel methods. For the preparation of Mg/Al/Bi LDH by the co-precipitation method, the appropriate amounts of dissolved starting materials (Al(NO3)3 · 9H2O, Mg(NO3)2 · 6H2O and Bi(NO3)3 · 5H2O) were mixed with a solution of NaHCO3:NaOH. In the sol-gel processing, the precursor Mg–Al–Bi–O gels were synthesized using the same starting materials and ethylene glycol as complexing agent. The mixed-metal oxides obtained by subsequent heating of Mg–Al–Bi–O gels at 650 °C were reconstructed to Mg3Al1−xBix LDHs in water at 80 °C. All the synthesized products were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and dielectric measurements.

Open access

Mohammad Abu Haija, Georgia Basina, Fawzi Banat and Ahmad I. Ayesh

Abstract

Spinel ferrite nanoparticles in the form CuFe2O4 were tested for gas sensing applications. Nanoparticles pressed in a disk form were used to construct conductometric gas sensors. The disk was placed between two electrical electrodes wherein the top electrode had a grid structure. The produced sensors were tested against H2S and H2 gases and they were found to be selective and sensitive to H2S concentration as low as 25 ppm. The composition of the nanoparticles was confirmed by X-ray diffraction and energy dispersive X-ray spectroscopy measurements. The crystal structure was verified by both X-ray diffraction and transmission electron microscope. The observations obtained from the experiments demonstrated the high potential of using CuFe2O4 nanoparticles for H2S sensing applications.

Open access

Božana Čolović, Danilo Kisić, Bojan Jokanović, Zlatko Rakočević, Ilija Nasov, Anka Trajkovska Petkoska and Vukoman Jokanović

Abstract

Thin films of titanium oxides, titanium oxynitrides and titanium nitrides were deposited on glass substrates by the methods of direct current (DC) and pulsed magnetron sputtering and cathodic arc evaporation. Phase analysis of the deposited films by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) showed the presence of phases with various Ti oxidative states, which indicated a high concentration of oxygen vacancies. The films morphology was investigated by scanning electron microscopy (SEM). Investigations of the films wettability, either with water or ethylene glycol, showed that it depends directly on the concentration of oxygen vacancies. The wettability mechanism was particularly discussed.

Open access

Madiha Sarfraz, Nasar Ahmed, Khizar-ul-Haq, Shabnam Shahida and M. A. Khan

Abstract

Transition metals, such as chromium (Cr) and manganese (Mn) doped zinc oxide (ZnO) magnetic nanoparticles, were synthesized via sole gel auto-combustion method. The prepared magnetic (Zn1−(x+y)MnxCryO, where x, y = 0, 0.02, 0.075) nanoparticles were calcined in an oven at 6000 °C for 2 hours. The morphologies of the nanoparticles were investigated using different techniques. X-ray diffraction (XRD) analysis revealed that the hexagonal wurtzite structure of the synthesized nanoparticles was unaffected by doping concentration. The crystallite size measured by Scherrer formula was in the range of 32 nm to 38 nm at different doping concentrations. Nanosized particles with well-defined boundaries were observed using a field emission scanning electron microscopy (FE-SEM). Fourier transform infrared (FT-IR) spectra showed a wide absorption band around 1589 cm−1 in all the samples, corresponding to the stretching vibration of zinc and oxygen Zn–O bond. A blue shift in optical band gaps from 3.20 eV for ZnO to 3.08 eV for Zn0:85Mn0:075Cr0:075O nanoparticles was observed in diffuse reflectance spectra, which was attributed to the sp-d exchange interactions. The field-dependent magnetization M-H loops were measured using vibrating sample magnetometer (VSM). The VSM results revealed diamagnetic behavior of the ZnO nanoparticles which changed into ferromagnetic, depending on the doping concentration and particle size. The compositions of Zn, Cr, Mn and O in the prepared samples were confirmed by using the energy dispersive X-ray spectroscopy (EDX). Our results provided an interesting route to improve magnetic properties of ZnO nanoparticles, which may get significant attention for the fabrication of magnetic semiconductors.

Open access

S.N. Alam, N. Jindal and N. Naithani

Abstract

The present work reports the effect of Cu addition on the melting point, hardness and electrical resistivity of Sn-57 wt.% Bi eutectic solder alloy. Both binary eutectic Sn-57 wt.% Bi and ternary Sn-(57-x)Bi-xCu (x = 0.1, 0.3, 0.5, 0.7 and 1 wt.%) alloys containing various amounts of Cu were developed by melting casting route. The microstructure of the various solder alloys was analyzed using an optical microscope and a SEM. The variation in melting point, hardness and electrical resistivity of the Sn-Bi eutectic solder alloys with the addition of Cu was determined. The melting point of the eutectic Sn-Bi solder alloy was found to decrease up to the addition of 0.7 wt.% Cu. However, further addition of Cu led to an increase in the melting point of the alloy. Addition of Cu led to an increase in the hardness of the eutectic Sn-Bi solder alloy whereas the electrical resistivity of this alloy was found to increase up to the addition of 0.7 wt.% of Cu beyond which a decrease in the electrical resistivity was observed. A change in the microstructure of the solder alloy was observed when it was reheated above the melting temperature.