Synthesis and characterization of metallic Pd embedded TiO_2 nanoparticles by reverse micelle and sol-gel processing

Metallic Pd clusters were embedded into TiO2 nanoparticles that were synthesized within reverse micelle via a solution reduction of Pd(NO3)2 by hydrazine hydrate. The size of the particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of titanium tetra-isopropoxide within the micro-emulsion. The spherical equivalent size for the Pd clusters formed in TiO2 matrix was estimated to be around (3±1) nm. The presence of Pd in the matrix was demonstrated by EDS spectroscopy. The effects of synthesis parameters, such as the concentration of Pd solution, the molar ratio of water to TIP, and the molar ratio of water to surfactant, were discussed.

Asymmetric Special Theory of Relativity

Einstein’s Special Theory of Relativity (SR) relates time dilation to the velocity between the observer and the observed object as if they are identical. Our new theory breaks this symmetry by relating the velocity of the object not directly to the observer, but instead to the center of gravity of object and observer. The reason why such a mass influence has not been reported might be that the mass of the observer in most experiments is much greater than that of the object, for example when earth is observing, satellites or detectors are studying nuclear masses.

Validation and Comparison of Calibration Techniques for Measurements of Carbon Dioxide in Atmospheric Air Standards

The increase in the concentration of carbon dioxide (CO2) in the atmosphere has led the scientific community to investigate the adverse effects on humanity and nature, including the greenhouse effect, which contributes to global warming and can lead to climate change, besides the risks associated with human health. Due to the importance of metrological issues in the current scenario, the Laboratory of Gas Analysis (Lanag) of the National Institute of Metrology, Quality and Technology (Inmetro) is developing the methodology of preparation of such primary standard gas mixtures through gravimetry. For the preparation of these standards, an analysis verification step is necessary, carried out by means of an analytical technique of comparison, at low levels of concentration, by cavity ringdown (CRDS) and by gas chromatography using a flame ionization detector coupled to a methaniser catalyst (GC-FIDmeth). This work presents the method validation of both methodologies developed to analyze a range of concentration of atmospheric standards of CO2 at a matrix of synthetic clean dry air (SCDA) by CRDS and GC-FIDmeth, of which the analysis results can compromise the measurements on atmospheric air quality. The objective is to compare results of method validation of both analytical methods for low CO2 concentration through the use of primary reference mixtures developed and also by certified reference material. The validation measurement results were analyzed according to the requirements of ISO 5725: 1994 parts 1 and 2, and the calculation of measurement uncertainty followed the methodology described in ISO 6143:2001, with results showing satisfactory consistent between both selected techniques. According to the work presented here, the obtained validation results for CRDS are better than the GC results, such as the relative uncertainty of samples evaluated for CRDS was 0.4% and 2.7% for GC_FID meth.

Sulfate reduction behavior in pressure-bearing leachate saturated zone

Attention should be paid to the sulfate reduction behavior in a pressure-bearing leachate saturated zone.In this study,within the relative pressure range of 0–0.6 MPa,the ambient temperature with the highest sulfate reduction rate of 50℃ was selected to explore the difference in sulfate reduction behavior in a pressure-bearing leachate saturated zone.The results showed that the sulfate reduction rate might further increase with an increase in pressure;however,owing to the effect of pressure increase,the generated hydrogen sulfide (H_(2)S) could not be released on time,thereby decreasing its highest concentration by approximately 85%,and the duration extended to about two times that of the atmospheric pressure.Microbial community structure and functional gene abundance analyses showed that the community distribution of sulfate-reducing bacteria was significantly affected by pressure conditions,and there was a negative correlation between disulfide reductase B(dsrB) gene abundance and H_(2)S release rate.Other sulfate reduction processes that do not require disulfide reductase A (dsrA) and dsrB genes may be the key pathways affecting the sulfate reduction rate in the pressure-bearing leachate saturated zone.This study improves the understanding of sulfate reduction in landfills as well as provides a theoretical basis for the operation and management of landfills.

Enabling rapid X-ray CT characterisation for additive manufacturing using CAD models and deep learning-based reconstruction

Metal additive manufacturing(AM)offers flexibility and cost-effectiveness for printing complex parts but is limited to few alloys.Qualifying new alloys requires process parameter optimisation to produce consistent,high-quality components.High-resolution X-ray computed tomography(XCT)has not been effective for this task due to artifacts,slow scan speed,and costs.We propose a deep learning-based approach for rapid XCT acquisition and reconstruction of metal AM parts,leveraging computer-aided design models and physics-based simulations of nonlinear interactions between X-ray radiation and metals.This significantly reduces beam hardening and common XCT artifacts.We demonstrate high-throughput characterisation of over a hundred AlCe alloy components,quantifying improvements in characterisation time and quality compared to high-resolution microscopy and pycnometry.Our approach facilitates investigating the impact of process parameters and their geometry dependence in metal AM.

Comparative study of tensile and high-cycle fatigue properties of extruded AZ91 and AZ91-0.3Ca-0.2Y alloys

Mg-Al-Zn-Ca-Y alloys with excellent ignition and corrosion resistances—termed SEN alloys(where the letters"S,""E,"and"N"stand for stainless,environmentally friendly,and non-flammable,respectively)—have been developed recently.In this study,the microstructure,tensile properties,and high-cycle fatigue properties of an extruded Mg-9.0Al-0.8Zn-0.1Mn-0.3Ca-0.2Y(SEN9)alloy are investigated and compared with those of a commercial Mg-9.0Al-0.8Zn-0.1Mn(AZ91)alloy extruded under the same conditions.Both the extruded SEN9 alloy and the extruded AZ91 alloy have a fully recrystallized structure comprising equiaxed grains,but the former has a smaller average grain size owing to the promoted dynamic recrystallization during extrusion.The extruded AZ91 alloy contains coarse Mg_(17)Al_(12) discontinuous precipitate(DP)bands parallel to the extrusion direction,which are formed during its cool down after extrusion.In contrast,the extruded SEN9 alloy contains relatively fine undissolved Al_(2)Ca,Al_(8)Mn_(4)Y,and Al_(2)Y second-phase particles,which are formed during the solidification stage of the casting process.The tensile strength of the extruded SEN9 alloy,which has finer grains and more abundant particles,is slightly higher than that of the extruded AZ91 alloy.However,the difference in their strengths is relatively small because the stronger solid-solution hardening and precipitation hardening effects in the extruded AZ91alloy offset the stronger grain-boundary hardening and dispersion hardening effects in the extruded SEN9alloy to some extent.The tensile elongation of the extruded AZ91 alloy is significantly lower than that of the extruded SEN9 alloy because the large cracks formed in the DP bands in the former cause its premature fracture.Although the extruded SEN9 alloy has higher tensile properties than the extruded AZ91alloy,the high-cycle fatigue life and fatigue strength of the former are shorter and lower,respectively,than those of the latter.The DP bands in the extruded AZ91 alloy do not act as fatigue crack initiation sites,and therefore,fatigue cracks initiate on the specimen surface at all stress amplitude levels.In contrast,in most of the fatigue-fractured specimens of the extruded SEN9 alloy,fatigue cracks initiate on the undissolved Al_(2)Ca and Al_(2)Y particles present on the surface or subsurface of the specimens because of the high local stress concentration on the particles during cyclic loading.This particle-initiated fatigue fracture eventually decreases the high-cycle fatigue resistance of the extruded SEN9 alloy.