Energy Dispersive X-ray Spectroscopy Examinations Research Articles

Effects of glass fiber usage on fracture energy and mechanical behavior of concrete: An experimental approach

In this study, the fracture and mechanical behavior of glass fiber reinforced concrete (GFRC) are investigated comparatively. For this purpose, three-point bending tests were carried out on notched beams produced using GFRC with 1, 2, and 3 kg/m3 fiber contents and the dimension of 6, 12, and 24 mm to determine the fracture energy. Fracture energy values of the GFRC specimens were calculated by analyzing load versus crack mouth opening displacement (CMOD) curves. Compressive strength was determined using cube samples with the dimension of 150x150mm. Tensile strength and Modulus of elasticity were determined using notched beams with the dimensions of 48010050 mm. Also, notched beams were produced and tested in accordance with RILEM recommendations. In addition, microstructural analyses were performed based on Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations. The results showed that the effects of fiber contents on fracture energy were very significant. However, the effect of fiber addition on the compressive strength and modulus of elasticity values was not significant.

An Inhibitive Effect of Aeration on the Pitting Corrosion of Steels in Ethanolic Environments

This work aims to illuminate localized carbon steel corrosion in ethanolic solutions. The effect of chloride, ethanol dehydration, and oxygen level are investigated, which all play a role in the carbon steel pitting behavior in ethanolic environments in the presence of a supporting electrolyte. Open-circuit potential measurement, cyclic potentiodynamic polarization, and potentiostatic testing are conducted on specimens exposed to ethanolic environments prepared from pure dehydrated ethanol to study the pitting behavior of carbon steel. Corrosion and passivation potentials are found to be significantly reduced due to the change in the cathodic reaction and the decrease in passivation kinetics under deaerated conditions. Energy-dispersive x-ray spectroscopy examination and scanning electron microscopy imaging indicate that no pitting corrosion is observed without chlorides, and chloride significantly destabilizes the surface film, resulting in the reduction of both pitting potential and passivation potential. Increasing the amount of dissolved oxygen in the solution reduces pitting susceptibility and, in low chloride concentrations, can eliminate the pitting nucleation. Iron oxide is identified as the significant corrosion product at different water and oxygen concentrations. Therefore, ethanol aeration can be an effective method to increase resistance to pitting corrosion in ethanolic solutions. Aeration can be used with caution due to the effect of oxygen on steel stress corrosion cracking in ethanol.

Real Appearance of Dendritic Cell on Failed Implant Fixture.

Dendritic cells (DCs) are considered a multifunctional cell population that links the innate and adaptive immune systems. Dendritic cells have a capacity for antigen capture and presentation to T cells, which initiates a cascade of inflammatory reactions. On contrary to its importance in immunology, DCs have not been known well in peri-implantitis.A scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy examination was used to examine a fixture that failed due to peri-implantitis, and a transmission electron microscopy was used to examine the peri-implant inflamed soft tissue. The presence of a DC was suggested in both scanning electron microscopy and transmission electron microscopy images. Titanium elements were also detected in the fixture-attached bone with energy-dispersive X-ray spectroscopy analysis. These findings suggested a link between Ti particles and DCs activation. The correlation between the presence of Ti particles and DCs will help to elucidate the detailed mechanism of peri-implantitis.

Improvement of Metallurgical and Mechanical Properties of Gas Tungsten arc Weldments of Alloy 686 by Current Pulsing

This research article examines the metallurgical and mechanical behavior of twenty-first-century nickel-based superalloy 686. The weld joints were produced with ERNiCrMo-4 and ERNiCrMo-14 filler wires by continuous current gas tungsten arc welding (GTAW) and pulsed current gas tungsten arc welding (PCGTAW) mode. Optical and scanning electron microscope (SEM) analyses were performed to evaluate the microstructure of welded joints. PCGTAW weldments showed refined microstructure, narrower weld bead and minimum heat-affected zone compared to GTAW. SEM analysis revealed the presence of secondary phases in the interdendritic regions of GTA and PCGTA weldments made of ERNiCrMo-4 and GTA ERNiCrMo-14 fillers. Energy-dispersive X-ray spectroscopy examination was also performed to assess the microsegregation of alloying elements in the weldments. The results proved nonexistence of microsegregation in the case of PCGTA weldments made by ERNiCrMo-14 filler. However, segregation of alloying element Mo was noticed in other weldments. Strength and toughness of the weld joints were evaluated by conducting tensile and Charpy impact tests. The refined microstructure with the absence of microsegregation obtained in the PCGTA welding made with ERNiCrMo-14 filler wire resulted in the higher strength and toughness than other weldments.

Effect of calcium lactate on compressive strength and self-healing of cracks in microbial concrete

This paper presents the effect on compressive strength and self-healing capability of bacterial concrete with the addition of calcium lactate. Compared to normal concrete, bacterial concrete possesses higher durability and engineering concrete properties. The production of calcium carbonate in bacterial concrete is limited to the calcium content in cement. Hence calcium lactate is externally added to be an additional source of calcium in the concrete. The influence of this addition on compressive strength, self-healing capability of cracks is highlighted in this study. The bacterium used in the study is bacillus subtilis and was added to both spore powder form and culture form to the concrete. Bacillus subtilis spore powder of 2 million cfu/g concentration with 0.5% cement was mixed to concrete. Calcium lactates with concentrations of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of cement, was added to the concrete mixes to test the effect on properties of concrete. In other samples, cultured bacillus subtilis with a concentration of 1×105 cells/mL was mixed with concrete, to study the effect of bacteria in the cultured form on the properties of concrete. Cubes of 100 mm×100 mm×100 mm were used for the study. These cubes were tested after a curing period of 7, 14 and 28 d. A maximum of 12% increase in compressive strength was observed with the addition of 0.5% of calcium lactate in concrete. Scanning electron microscope and energy dispersive X-ray spectroscopy examination showed the formation of ettringite in pores; calcium silicate hydrates and calcite which made the concrete denser. A statistical technique was applied to analyze the experimental data of the compressive strengths of cementations materials. Response surface methodology was adopted for optimizing the experimental data. The regression equation was yielded by the application of response surface methodology relating response variables to input parameters. This method aids in predicting the experimental results accurately with an acceptable range of error. Findings of this investigation indicated the influence of added calcium lactate in bio-concrete which is quite impressive for improving the compressive strength and self-healing properties of concrete.

Effect of basalt fibers on fracture energy and mechanical properties of HSC

Fracture energy is one of the key parameters reveal cracking resistance and fracture toughness of concrete. The main purpose of this study is to determine fracture behavior, mechanical properties and microstructural analysis of high strength basalt fiber reinforced concrete (HSFRC). For this purpose, three-point bending tests were performed on notched beams produced using HSFRCs with 12 mm and 24mm fiber length and 1, 2 and <TEX>$3kg/m^3$</TEX> fiber content in order to determine the value of fracture energy. Fracture energies of the notched beam specimens were calculated by analyzing load versus crack mouth opining displacement curves by the help of RILEM proposal. The results show that the effects of basalt fiber content and fiber length on fracture energy are very significant. The splitting tensile and flexural strength of HSFRC increased with increasing fiber content whereas a slight drop in flexural strength was observed for the mixture with 24mm fiber length and <TEX>$3kg/m^3$</TEX> fiber content. On the other hand, there was no significant effect of fiber addition on the compressive strength and modulus of elasticity of the mixtures. In addition, microstructural analysis of the three components; cement paste, aggregate and basalt fiber were performed based on the Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations.

Effects of basalt and glass chopped fibers addition on fracture energy and mechanical properties of ordinary concrete: CMOD measurement

This study investigates fracture behavior of basalt fiber reinforced concrete (BFRC) and glass fiber reinforced concrete (GFRC) comparatively. For this purpose, three-point bending tests were carried out on notched beams produced using BFRC and GFRC with 0.5, 1, 2 and 3kg/m3 fiber contents to determine the value of fracture energy. Fracture energies of the notched beam specimens were calculated by analyzing load versus crack mouth opining displacement (CMOD) curves by the help of RILEM proposal. In addition, microstructural analysis of the three components; cement paste, aggregate, basalt and glass fiber were performed based on the Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations and analysis were discussed. The results showed that the effects of the fiber contents on fracture energy were very significant. The splitting tensile and flexural strength of BFRC and GFRC were improved with increasing fiber content whereas a slight drop in flexural strength was observed for high volume of fiber content. On the other hand, effect of fiber addition on the compressive strength and modulus of elasticity of the mixtures was insignificant.

Investigation of sulfidation and regeneration of a ZnO-adsorbent used in a biomass tar removal process based on catalytic steam reforming

In the field of allothermal biomass gasification with steam in a fluidized bed, the removal of tar is the critical step in the process chain. In the approach presented in this work, in a catalytic steam reforming process the tar species are converted to permanent gas components by means of a Ni-catalyst at 500°C. The issue with catalysts based on nickel is that these are poisoned by sulfur components in the synthesis gas. This leads to an increased catalyst deactivation and consequently to elevated operating costs of the facility. The main sulfur species in the synthesis gas of an allothermal steam gasifier is hydrogen sulfide (H2S). In order to reduce the sulfur-related deactivation of the Ni-catalyst, zinc oxide (ZnO) can be used as an upstream adsorbent to remove the main sulfur compound H2S.The aim of this work is to investigate the loading process and the regenerability of a commercial ZnO-adsorbent under realistic conditions. The sulfidation of the ZnO was done with a real synthesis gas produced from wood pellets with a steam blown laboratory gasifier. In order to examine the sulfidation process in the packed bed, the permanent gas composition and the H2S-concentration of the synthesis gas were measured at five sampling points in the reactor and at the reactor outlet. The adsorbent was operated at a constant temperature of 300°C.As a second focus, the regeneration of the used zinc oxide was examined. Regeneration cycles were carried out with mixtures of air, nitrogen and steam in different compositions at elevated temperatures between 650°C and 800°C.The sulfided and regenerated adsorbents were analyzed with a scanning electron microscope (SEM) in combination with energy-dispersive X-ray spectroscopy (EDXS).The sulfidation tests showed the development of the sulfidation process in the packed bed during the experiment. In contrast to the related literature, the ZnO-adsorbent used here turned out to be unsuitable for regeneration under the tested conditions. The used adsorbent was a commercially available product and mainly consisted of ZnO. The SEM–EDXS examination showed that the sulfur was still bonded on the adsorbent after different regeneration experiments.

An Investigation of Electrical Contacts for Higher Manganese Silicide

Five metals with large work functions including Co, Ni, Cr, Ti, and Mo and two silicides including MnSi and TiSi2 were examined to determine the best contact material for the thermoelectric material higher manganese silicide (HMS). Three-layer structures of HMS/contact/HMS were prepared in a sintering process. The contact resistance was measured versus temperature. The structures were subjected to x-ray diffraction and energy-dispersive x-ray spectroscopy examination. Thermal stability of the structures was determined by heating the samples to 700°C for different time intervals. The pure metals failed to make reliable contacts due to poor mechanical and chemical stability at high temperatures. In contrast, the metal silicides (MnSi and TiSi2) showed superior chemical and mechanical stability after the thermal stability test. The observed contact resistance of MnSi and TiSi2 was within the range of practical interest (10−5 Ω cm2 to 10−4 Ω cm2) over the entire range of investigated temperatures (20°C to 700°C). The best properties were found for the nanograined MnSi, for which the resistance of the contact was as low as 10−6 Ω cm2.