Browse

You are looking at 21 - 30 of 891 items for :

  • Materials Characterization and Properties x
Clear All
Open access

Damjan Klobčar, Maja Lindič and Matija Bušić

Abstract

This paper presents an overview of additive manu­facturing technologies for production of metal parts. A special attention is set to wire arc additive manufac­turing (WAAM) technologies, which include MIG/MAG welding, TIG welding and plasma welding. Their advan­tages compared to laser or electron beam technologies are lower investment and operational costs. However, these processes have lower dimensional accuracy of produced structures. Owing to special features and higher productivity, the WAAM technologies are more suitable for production of bigger parts. WAAM technology has been used together with welding robot and a cold metal transfer (CMT) power source. Thin walls have been produced using G3Si1 welding wire. The microstructure and hardness of produced structures were analysed and measured. A research was done to deter­mine the optimal welding parameters for production of thin walls with smooth surface. A SprutCAM software was used to make a code for 3D printing of sample part.

Open access

T.G. Abdullah, S.A. Sami and M.S. Omar

Abstract

Theoretical formalism based on the orthogonalized plane wave method supplemented by a potential scaling scheme was used to predict the temperature dependence of energy gap of CuSi2P3 semiconductor. A computer code in Pascal was used to perform the variation of fundamental energy gap with temperature in the range of 150 K to 800 K. The dependence of energy gap on temperature for lattice dilation contribution, lattice vibration contribution and total temperature effect were performed separately. The results revealed that, as temperature increases, the top of the valence band and the bottom of the conduction band increase, while the energy band gap decreases. Generally, at low temperatures, the energy gap varies slowly and exhibits a nonlinear dependence and approaches linearity as temperature increases. The calculated energy gap of CuSi2P3 at T = 300 K is 0.4155 eV. The temperature coefficients in the linear region due to lattice dilation contribution, lattice vibration contribution and total temperature effect were calculated as –1.101 × 10−5 eV/K, –1.637 × 10−4 eV/K and –1.7523 × 10−4 eV/K, respectively. Also, the ratio of temperature coefficient of the energy gap due to LV contribution to its value and LD contribution in the linear region is equal to 14.868. That ratio is compared to those of CuGe2P3 and III-V compounds, where those of the latter show a systematic change with Eg. Moreover, the Eg of all the compounds shows a quadratic dependence on the inverse of mean bond length.

Open access

Yuqi Chen, Liang Li and Shinji Hirai

Abstract

Single-phase Eu3S4 was obtained via CS2 gas sulfurization of Eu2O3 nanospheres at 773 K for longer than 0.5 h. The primary particle size of Eu3S4 became larger than that of Eu2O3 during the sulfurization process. Pure synthetic Eu3S4 powders were unstable and transformed to EuS at 873 K under vacuum. Eu3S4 compacts were sintered in temperature range of 773 K to 1173 K and they transformed to EuS at 1473 K during spark plasma sintering. Specific heat of sintered Eu3S4 did not show an anomalous behavior in the range of 2 K to 50 K. The magnetic susceptibility of polycrystalline Eu3S4 followed a Curie-Weiss law from 2 K to 300 K. Magnetization of polycrystalline Eu3S4 was larger than that of single crystal Eu3S4 when the magnetic field was less than 3.5 kOe.

Open access

Zohra Nazir Kayani, Mahek Zaheen Butt, Saira Riaz and Shahzad Naseem

Abstract

NiO nanoparticles were fabricated by sol-gel route using ammonium hydroxide and nickel nitrate as precursors. The NiO nanoparticles were calcinated at 400 °C and 1000 °C. The nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), thermogravimetry analysis/differential thermal analysis (TGA/DTA). The structural properties were evaluated by X-ray diffraction (XRD). XRD confirmed the formation of well-crystallized and high purity NiO phase. The XRD showed that the peaks were sharpened and the crystallite size increased as the calcination temperature increased. The average crystallite size ranged from 12 nm to 20 nm, when calcined at temperatures 400 °C and 1000 °C, respectively. Fourier transform infrared spectroscopy (FT-IR) revealed the chemical composition and confirmed the formation of NiO nanoparticles. The nanoparticles showed paramagnetic behavior.

Open access

N.V. Lemesh and P.E. Strizhak

Abstract

In this work, multi-walled carbon nanotubes (MWCNTs) with significantly different mean diameters were produced by catalytic CVD over Ni and Co-based supported catalysts. Our results indicate that Ni nanoparticles in the Ni/MgO catalyst are responsible for controlling the inner diameters of the carbon nanotubes. Contrary, Co nanoparticles in the Co/MgO catalyst control the outer diameters of MWCNTs. The “base-growth” mechanism and smaller diameters of the MWCNTs grown on the Ni/MgO catalyst are associated with a strong metal-support interaction (SMSI) resulting from NixMg1−xO mixed oxide formation. The concept of the weak metal-support interaction (WMSI) between Co nanoparticles and MgO for the Co/MgO catalyst confirms the “tip-growth” mechanism of the MWCNTs.

Open access

S. Reena Devi, S. Suresh, S. Kalaiyarasi, M. Nizammohideen and R. Mohan Kumar

Abstract

A novel 4-methylpyridinium 3-nitrophthalate (4MP3NP) was synthesized and the crystals were grown by using slow evaporation method. The structural data of the grown crystal was collected by single crystal X-ray diffraction. It revealed that the 4MP3NP crystal belongs to triclinic crystal system with a space group P1. Structure of the synthesized compound was established using SHELXL 97 program package. The crystalline nature and composition of the grown crystal was established using high resolution X-ray diffraction and FT-IR analyses. UV-Vis transmittance and photoluminescence studies revealed the optical transmission window and electronic transition mechanism of ions, respectively. The laser damage threshold of the grown crystal was estimated by Nd:YAG laser and these results were mutually related to specific heat capacity of the grown crystal. The third-order nonlinear optical susceptibility of the grown crystal was studied by Z-scan technique.

Open access

İsmet Kaya, Feyza Kolcu, Sabriye Satilmiş and Zeynep Yazicioglu

Abstract

A series of polyimines, bearing phenolic groups were successfully synthesized in aqueous alkaline solution via chemical oxidative polycondensation. Polymeric Schiff bases were synthesized by condensation of 2,4-dihydroxybenzaldehyde and 3-hydroxy-4-metoxybenzaldehyde with 2-aminophenol and 3-aminophenol. The molecular structures of the synthesized Schiff bases and their corresponding polymers were studied by FT-IR, UV-Vis, 1H-NMR and 13C-NMR spectroscopic methods. Thermal stability of the imine polymers was evidenced by their initial degradation temperatures found in the range of 170 °C to 271 °C without any sign of melting. The results of UV-Vis and cyclic voltammetry (CV) measurements were coherent with the optical Eg and the electrochemical E′g band gaps of the polyimines which were lower than those of their corresponding Schiff bases. Fluorescence spectral analysis of P4 (Schiff base polymer P4 derived from 3-aminophenol and 3-hydroxy-4-methoxybenzaldehyde) revealed a bicolor emission with blue and green light. Electrical conductivity of the synthesized imine polymers was measured by four-point probe technique. P4 showed the highest electrical conductivity as a result of iodine vapor contact time. Morphology characterization of the synthesized polyimines was carried out using a scanning electron microscope SEM at different magnifications. The study revealed that P4 is a promising candidate for both blue and green light emitters which could be used in the production of photovoltaic materials and solar cells.

Open access

A. Abu El-Fadl, A.M. Abdel-Salam and A.M. Nashaat

Abstract

Single crystal of glycine hydroflruoride (GHF) was grown from aqueous solution by slow evaporation technique. The structure of the grown crystal was tested and analyzed through X-ray powder diffraction. The functional groups have been identified from the FT-IR spectra. Slabs cut normal to the b-axis from the grown crystal were subjected to incident radiation with a wavelength range of 200 nm to 800 nm to investigate the transmittance and reflectance spectra. Linear optical parameters such as extinction coefficient k, refractive index n and both the real and imaginary parts: ∊real and ∊im of the dielectric permittivity were calculated as functions of the incident photon energy. The dispersion of the refractive index was fitted in terms of Cauchy formula and Wemple-DiDomenico single oscillator model. GHF crystals exhibited indirect optical interband transition and the optical energy gap Eg was determined by using Tauc plot. The indirect band gaps at elevated temperatures were determined and their temperature dependence was estimated. Optical band gap Eg values were found to decrease with an increase in crystal temperature; however, the band tail width exhibited opposite behavior. The nonlinear optical potential was examined by the second harmonic generation (SHG) test.

Open access

B. Punithaveni, K. Thilagavathy, N. Muthukumarasamy, D. Nithyaprakash and M. Saravanabhavan

Abstract

New organic single crystals of 2-amino-6-methylpyridinium 2-hydroxybenzoate (2A6M2H) were grown by slow evaporation solution growth technique at room temperature. The grown crystal structure was studied using single crystal XRD. Crystalline nature and phases were confirmed by powder XRD analysis. FT-IR study was used to identify the functional groups present in the compound. UV-Vis study revealed that the lower cut off wavelength of the crystal is at 350 nm. The dielectric studies indicated the low value of dielectric loss at high frequency. Mechanical properties of the crystals were studied using Vickers microhardness test. The Z-Scan studies were conducted for the crystal using He–Ne laser.

Open access

Surendra Singh, Anshuman Sahai, S.C. Katyal and Navendu Goswami

Abstract

We have synthesized zinc-copper ferrite (ZCFO) employing exploding wire technique (EWT). The X-ray diffraction (XRD) data confirm the formation of single phase spinel ZCFO, which is in good agreement with Fourier transform infrared spectroscopy (FT-IR), UV-Vis, and Raman spectroscopic analyses. It is also clearly seen in the SEM micrographs that the grains in ZCFO ferrite are very rough, which allows adsorption of gas like oxygen and therefore, the material can behave as active sensing surface. The size range of the grains in prepared sample is of 200 nm to 500 nm. The FT-IR spectrum of the nanocomposite consists of two broad bands, one at 580.4 cm−1 due to M–O stretching mode at the tetrahedral site and the other at 400.7 cm−1 due to M–O stretching mode at the octahedral site. The nanoparticles show a UV-Vis absorption band in the wavelength region of 400 nm to 700 nm. The energy band gap for the prepared nanomaterial was estimated to be 3.16 eV. Thus, the ferrite nanocomposite prepared by EWT is optically active. According to present literature, Raman spectroscopy study on zinc-copper ferrite system has not been reported till date. By suitable attributing various Raman modes, we have further confirmed the formation of ZCFO nanophase through the present novel approach.