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Safe choice of structural steels in a region of ultra-high number of load cycles

Abstract

In this paper the authors introduce their own selected experimental results in the field of the investigation of fatigue resistance of structural steels. The experiments were carried out on the nine structural steels including high strength steels, DOMEX 700MC, HARDOX 400, HARDOX 450, 100Cr6 (UTS from 446 MPa to 2462 MPa) at high-frequency cyclic loading (f = 20 kHz, T = 20 ± 5 °C, R = -1) in the region of number cycles ranged from N ≈ 2×106 to N ≈ 2×109 cycles of loading. The continuous decrease of fatigue strength in dependence on the number of loading cycles was observed with the average value of ratio σa2×109/σa2×106 = 0.69.

Open access
Single Step Solid-State Synthesis of Lanthanum Molybdate

Abstract

In this study, LaxMoyOz powders were synthesized by a cost-effective solid-state synthesis method. Four different heating cycles were designed to investigate the effects of synthesis temperature and holding time on lanthanum molybdate (LMO) formation, phase assemblies, particle size and morphology. X-Ray Diffraction (XRD) and scanning electron microscopy (SEM) studies were performed to observe crystal structure and particle morphology of synthesized powders. The results showed that nearly ninety percent β - La2Mo2O9 (43,3 nm crystal size) phase was obtained at 1000 °C for 6 h holding time. Longer holding times at 1000 °C favor more oxygen-rich compounds which cause recrystallization of various new crystalline phases. The grain size of the synthesized powder was increased from 0,2 µm to 1,5 µm with increasing holding time. In summary, it is possible to manufacture LMO powders rich in β - La2Mo2O9 by one - step solid - state synthesis method. The phase assembles and particle size of LMO powders could also be tailored by optimization of heat treatment cycle.

Open access
Synthesis, Characterization and Some Biological Properties of PVA/PVP/PN Hydrogel Nanocomposites: Antibacterial and Biocompatibility

Abstract

In this study, it was aimed to synthesize hydrogel based antibacterial, biocompatible and non-toxic wound dressing materials by solvent removal method usingpoly(vinylalcohol) (PVA), poly(vinylpyrolidone) (PVP) and nano pomegranate seed (PN).The morphology, swelling capacity, contact angle, antibacterial activity, biocompatibility and cytotoxicity of the synthesized films were determined. From the experimental findings, it was found that the PN particles were nano-sized, showed homogeneous and spherical distribution and improved the hydrophobic properties of the materials obtained by the addition of PN. And also, their swelling capacities were decreased with increased PN amount and all of the materials showed similar antibacterial activity, hemocompatibility and cytotoxicity.

Open access
The use of quality management techniques to analyse the cluster of porosities on the turbine outlet nozzle

Abstract

As part of continuous quality improvement in well-managed enterprises, identifying unconformity should initiate actions to find their causes. Therefore, it was proposed to the enterprise located in Podkarpacie to use in the sequential way the Ishikawa diagram and 5Why method. The aim was to analyse of unconformity (porosity cluster) on the turbine outlet nozzle and identify the root of its creation. In the enterprise, the quality analysis of the products with a fluorescent method was carried out, but after identifying the unconformity, non-analysis of their reason for their occurrence was not practiced. Therefore, it was intentional to propose the use of sequence i.e. Ishikawa diagram and 5Why method to identify the root of unconformity. The subject of study was the turbine outlet nozzle, on which the fluorescent method the porosity cluster was identified. With the use of the Ishikawa diagram, the main cause of the problem was pointed (unconformity during production), and by the 5Why method the root cause of the problem, i.e. unconformity material from the supplier, was identified. The proposed method sequence is a simple and effective way to make analyses of unconformities and it can be used in different products and service enterprises.

Open access
Structural and surface analysis of chemical vapor deposited boron doped aluminum nitride thin film on aluminum substrates

Abstract

Chemical vapor deposition (CVD) process was conducted for synthesis of boron (B) doped aluminum nitride (B-AlN) thin films on aluminum (Al) substrates. To prevent melting of the Al substrates, film deposition was carried out at 500 °C using tert-buthylamine (tBuNH2) solution delivered through a bubbler as a nitrogen source instead of ammonia gas (NH3). B-AlN thin films were prepared from three precursors at changing process parameters (gas mixture ratio). X-ray diffraction (XRD) technique and atomic force microscope (AFM) were used to investigate the structural and surface properties of B-AlN thin films on Al substrates. The prepared thin films were polycrystalline and composed of mixed phases {cubic (1 1 1) and hexagonal (1 0 0)} of AlN and BN with different orientations. Intensive AlN peak of high intensity was observed for the film deposited at a flow rate of the total gas mixture of 25 sccm. As the total gas mixture flow decreased from 60 sccm to 25 sccm, the crystallite size of AlN phase increased and the dislocation density decreased. Reduced surface roughness (10.4 nm) was detected by AFM for B-AlN thin film deposited on Al substrate using the lowest flow rate (25 sccm) of the total gas mixture.

Open access
Structural, morphological, optical and diode properties of chemical bath deposited nano-structured CdS thin films using EDTA as a complexing agent

Abstract

CdS thin films with (1 1 1) orientation were prepared by chemical bath deposition technique at 80±5 °C using the reaction between NH4OH, CdCl2 and CS(NH2)2. The influence of annealing temperature varying from 150 °C to 250 °C was studied. X-ray diffraction studies revealed that the films are polycrystalline in nature with cubic structure. Various parameters, such as dislocation density, stress and strain, were also evaluated. SEM analysis indicated uniformly distributed nano-structured spherically shaped grains and net like morphology. Optical transmittance study showed the wide transmittance band and absence of absorption in the entire visible region. I-V characterization of p-Si/n-CdS diode and photoluminescence studies were also carried out for the CdS films.

Open access
Synthesis, growth and characterization of semiorganic nonlinear optical single crystal bis(thiourea) barium nitrate (BTBN) for frequency conversion

Abstract

A novel semiorganic nonlinear optical (NLO) crystal, bis(thiourea) barium nitrate (BTBN) was synthesized and grown by slow evaporation method. Structure of the new crystalline compound was confirmed by single crystal X-ray diffraction analysis and it showed that BTBN belongs to orthorhombic crystal system. The crystalline nature of the BTBN was confirmed by powder X-ray diffraction study. Important functional groups of BTBN were identified by FT-IR spectroscopic analysis. UV-Vis-NIR spectral study showed that the grown crystal is transparent in the entire visible region with low cut off wavelength of 304 nm. BTBN exhibits a SHG efficiency which is nearly 2.38 times higher than that of KDP. The BTBN crystal has high mechanical strength and belongs to soft category, which was confirmed by micorhardness study. The thermal stability of BTBN was determined from TGA and DTA thermal study which revealed that the BTBN crystal has thermal stability up to 243.1 °C. The surface properties and presence of elements was analyzed by SEM and EDAX study, respectively.

Open access
A New Method for the Estimation of Hydraulic Permeability, Coefficient of Consolidation, and Soil Fraction Based on the Dilatometer Tests (DMT)

Abstract

The main issue of the paper is the estimation of soil hydraulic permeability based on the DMT test. DMTA, DMTC and SASK methods performed in the Nielisz dam, Stegny and the SGGW Campus of the Warsaw University of Life Sciences sites are described. The article presents the implementation of the dilatometer Marchetti test (DMT) in the determination of soil fraction and effects of its occurrence in the subsoil, tested in the Nielisz dam located in the Wieprz river valley in the Lublin province, and in various sites in Warsaw (Stegny site and SGGW Campus of the Warsaw University of Life Sciences). In order to acquire the needed data, the flat dilatometer test (DMT) method was used. A direct and indirect pressure methodology of interpreting soil swelling was characterized in the article. The paper shows the possibilities of determining sand, silt and clay soil fractions based on po and p 1 pressures from dilatometer tests (DMT) and the effective (σvo) and total (σvo) vertical in situ overburden stress. Additionally, the main advantage of this paper is the proposal of use of a new chart to determine hydraulic permeability and soil fraction, based on DMT tests.

Open access
Shear Strength Enhancement of Cemented Reinforced Sand: Role of Cement Content on the Macro-Mechanical Behavior

Abstract

Sands reinforced by hydraulic binders (cement) have constituted in recent decades a major asset for the expansion of several areas of engineering. The mechanical behavior of sand-cement mixtures has undergone some controversies studied on the Chlef sand. In this paper, we present an experimental study to investigate the mechanical behavior of a sandy soil reinforced by a hydraulic binder (cement), using the direct shear apparatus emphasizing on the shear strength characteristics and the vertical deformation variation of cemented reinforced sand. The parameters used in this study are mainly: relative density (Dr = 80%), normal stress (σn = 100, 200, 400 kPa), water content (3, 7 and 10%), cement content (2.5, 5, 7.5 and 10 %) and cure time (7, 14 and 28 days). The experimental results show that the mechanical characteristics in terms of internal cohesion (C) and internal frication angle (φ) give a better mechanical performance with the binder inclusion, and the cure conditions play an effective role on the improvement of the shear strength. This result also showed that 10% of the cement content gave us a maximum value of shear strength and an optimal influence on the mechanical characteristics. The addition of cement not only improves the shear strength of soil, but also provides diversity in the resistance against the deformations imposed load, which can be established by a dilatant character.

Open access
DFT study of optoelectronic spectra of barium cadmium chalcogenides (Ba2CdX3,X = S, Se and Te)

Abstract

DFT analyses of electronic and optical spectra of barium cadmium chalcogenides (Ba2CdX3, X =S, Se, Te) have been carried out. The study of electronic spectra has been made in terms of band structure and density of states using full potential linear augmented plane wave plus local orbital method. Band structure calculations have been carried out under the approximations PBE-GGA, PBE-Sol, LDA and TB-mBJ. Band structures of these materials show that Ba2CdS3, Ba2CdSe3 and Ba2CdTe3 crystals possess a band gap less than 1 eV, underestimated relative to the experimental/theoretical literature values. Optical spectra of these chalcogenides have been analyzed in terms of real and imaginary parts of dielectric function, reflectivity, refractive index, extinction coefficient, absorption coefficient, optical conductivity and electron energy loss. Optical results show large anisotropy along different directions. These results provide a physical basis of barium cadmium chalcogenides for potential application in optoelectronic devices.

Open access