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Synthesis of NiO nanoparticles by sol-gel technique

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
Synthesis, sintering, specific heat and magnetism of Eu3S4 by low-temperature CS2-gas sulfurization of Eu2O3 nanospheres

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
Temperature dependence of the energy band gap of CuSi2P3 semiconductor using PSOPW method

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
Addictive and Substractive Combined Production of Cobalt-Crome-Based Frames in Dentistry

Abstract

The following study analyses the use of modern 3D printing technology in dentistry with its necessary manufacturing and machining processes. Fitting of the manufactured metal structures is examined depending on their use, in terms of conventional adhesion-based denture designs and screw-fixed dentures on implants. Influencing factors and effects of the required post-processing steps are examined. Aspects such as sand-blasting, heat treatment, equipment and tools required for cutting are analyzed. The aim of this study is to create a manufacturing process that enables the required precision fitting of the created frame structure types.

Open access
Analysis of Recrystallization Peak Occuring During DSC Measurement

Abstract

Severe plastic deformation (SPD) is a well-established methodology for the processing of bulk ultrafine grained materials. Among various methods, equal channel angular pressing (ECAP) is the most popular way of creating ultrafine grained materials. The stored energy after ECAP in these substances highly influences the microstructural processes: recovery and recrystallization of the processed materials. We analyzed the recrystallization kinetics of room and elevated temperature ECAP processed copper samples using differential scanning calorimetry (DSC). For the processing of the measurement data we developed a MATLAB processing routine.

Open access
Application of High Energy Absorbing Materials for Blast Protection

Abstract

In the current century, building protection is very important in the face of terrorist attacks. The old buildings in Europe are not sufficiently resilient to the loads produced by blasts. We still do not fully understand the effects of different explosives on buildings and human bodies. [1–3] Computing blast loads are different from that of traditional loads and the material selection rules for this type of impact load are diverse. Historical and old buildings cannot be protected simply by new walls and fences. New ways need to be found to improve a building’s resistance to the effects of a blast. It requires sufficiently thin yet strong retrofitted materials in order to reinforce a building’s walls [4–6].

Open access
Comparative Study of Roman Iron Slags Discovered in the Roman Auxiliary Fort and Settlement of Călugăreni

Abstract

Iron slag samples unearthed at the eastern border of Roman Dacia, in the auxiliary fort and the military settlement of Călugăreni (Mikháza) are investigated by macroscopic inspection, optical microscopy (OM) and FTIR spectroscopy in order to comparatively characterize their macro- and microstructure as well as their mineralogical composition. During the recent archaeological excavations, a large number of iron artefacts were discovered together with a great quantity of iron slag fragments. The present paper focuses on the data obtained from 17 slag samples.

Open access
Corrosion Testing of Additively Manufactured Metals and Biomedical Devices

Abstract

Additive manufacturing (AM) is becoming increasingly important, making it possible to produce a product in a short time, to specific individual requirements, and even in the presence of the customer. This research is related to direct metal laser sintering of additive manufacturing. This new technology is increasingly being used in more sectors, for example in biomedical industry, where a damaged product can potentially endanger human life. Corrosion tests were carried out during our research. Cyclic voltammetry curves and corrosion rates were determined with a potentiostat. Two typical biocompatible implant materials were compared, a cobalt chromium alloy (powder metallurgy) and a titanium alloy (3D printed). The results will help in specifying the corrosion properties of additively manufactured materials.

Open access
The Influence of Heat Treatment on the Mechanical Properties of 3D-Printed Cobalt-Chrome Alloy Used in Dental Laboratory Practice

Abstract

The material used for manufacturing of dental implantation prostheses is cobalt-chromium alloy. The following study presents a new heat treatment technology for dental implantation prostheses. Specimens were created with the innovative technology of 3D printing. The brittleness of specimens subjected to heat treatment with parameters recommended by the manufacturer made it necessary for us to reconsider the heat-treating process. After changing given heat treatment processes, tensile and hardness tests were performed. From these tests, the optimal heat treatment process technology was chosen.

Open access
Investigation of Laser Welding Technology of Diamond Drilling Segments

Abstract

Segments containing diamond particles are fixed to replaceable inserts or to steel tool bodies for cost-effectiveness. The joining technology used should meet both environmental and technical requirements. The joining zone is subjected to high mechanical and significant thermal loads during use. In the event of an improper joint, the segments may detach from the base and fly away causing injury. Nowadays, many methods of welding or brazing are used to fix diamond segments. Among the possible segment fixing technologies, laser beam welding has been investigated. The microstructure of the joints has been examined by optical and scanning electron microscopy and chemical element maps have been recorded. Joints have been subjected to fracture and hardness testing. The mechanical properties and composition changes of the joints with different joining technologies have been evaluated and compared.

Open access