scholarly journals Structural changes in clays subjected to heat treatment: an analysis by structural refinement using the Rietveld method

2021 ◽  
Vol 67 (6 Nov-Dec) ◽  
Author(s):  
Mauro Quiroga Agurto ◽  
Elvira Leticia Zeballos Velásquez ◽  
Felipe Americo Reyes Navarro
Keyword(s):  
Heat Treatment ◽  
Structural Changes ◽  
Rietveld Method ◽  
Mineralogical Composition ◽  
Structural Factors ◽  
Expansive Clay ◽  
Structural Refinement ◽  
Weight Percentage ◽  
Before And After ◽  
Cerro De Pasco

Structural factors in clays influence their physical properties. Therefore, it is particularly important to understand the effects of heat treatment on the structure of the material during the ceramic process. In this work, we have analyzed clays from quarries in the Cerro de Pasco region, Peru, to evaluate their characteristics and the structural changes produced by heating, particularly in the interlaminar region. The samples were thermally treated between 150 oC and 800 oC with intervals of 50 oC. To evaluate the structural changes produced by temperature, X-ray diffraction were carried out before and after each heat treatment. The qualitative analysis of the measurements allowed to identify the mineralogical composition of the samples, finding phases of calcium montmorillonite, kaolinite, illite and quartz. The quantitative analysis by the Rietveld method found structural changes, particularly in the Ca-montmorillonite expansive clay. It was also possible to determine the decrease in the weight percentage of the kaolinite until the collapse of its structure between 450 °C and 500 °C. The illite presented greater thermal stability, with slight variations in its weight percentage during heat treatment, without compromising its structure. Although the quartz phase did not show relevant structure changes, it slightly increased its weight percentage with increasing temperature.

The Precipitation of Si in AlCuSi Thin Films

1973 ◽  
Vol 31 ◽  
pp. 34-35 ◽  
Author(s):  
R. M. Anderson
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Heat Treatment ◽  
Solid Solution ◽  
Integrated Circuit ◽  
Copper Film ◽  
Solution Concentration ◽  
X Ray ◽  
Silicon Thin Films ◽  
Before And After

Aluminum-copper-silicon thin films have been considered as an interconnection metallurgy for integrated circuit applications. Various schemes have been proposed to incorporate small percent-ages of silicon into films that typically contain two to five percent copper. We undertook a study of the total effect of silicon on the aluminum copper film as revealed by transmission electron microscopy, scanning electron microscopy, x-ray diffraction and ion microprobe techniques as a function of the various deposition methods.X-ray investigations noted a change in solid solution concentration as a function of Si content before and after heat-treatment. The amount of solid solution in the Al increased with heat-treatment for films with ≥2% silicon and decreased for films <2% silicon.

Study of fine structure of cold-deformed steel 20 before and after prerecrystallization heat treatment

2015 ◽  
Vol 0 (1) ◽  
Author(s):  
Oleksandr M. Dubovyi ◽  
Oleksandr V. Chechel ◽  
Oleksandr O. Zhdanov
Keyword(s):  
Heat Treatment ◽  
Fine Structure ◽  
Before And After ◽  
Steel 20

Influence of the Zinc Sublayer Method Production and Heat Treatment on the Microhardness of the Composite Ni-Al2O3 Coating Deposited on the 5754 Aluminium Alloy

2014 ◽  
Vol 59 (1) ◽  
pp. 355-358
Author(s):  
M. Karaś ◽  
M. Nowak ◽  
M. Opyrchał ◽  
M. Bigaj ◽  
A. Najder
Keyword(s):  
Heat Treatment ◽  
Aluminium Alloy ◽  
Thermal Shock ◽  
Nickel Coating ◽  
Nickel Sulphate ◽  
Al2o3 Coating ◽  
Nickel Coatings ◽  
Watts Bath ◽  
Before And After ◽  
Zinc Interlayer

Abstract In this study, the effect of zinc interlayer on the adhesion of nickel coatings reinforced with micrometric Al2O3 particles was examined. Nickel coating was applied by electroplating on EN AW - 5754 aluminium alloy using Watts bath at a concentration of 150 g/l of nickel sulphate with the addition of 50 g/l of Al2O3. The influence of zinc intermediate coating deposited in single, double and triple layers on the adhesion of nickel coating to aluminium substrate was also studied. The adhesion was measured by the thermal shock technique in accordance with PN-EN ISO 2819. The microhardness of nickel coating before and after heat treatment was additionally tested. It was observed that the number of zinc interlayers applied does not significantly affect the adhesion of nickel which is determined by thermal shock. No defect that occurs after the test, such as delamination, blistering or peeling of the coating was registered. Microhardness of the nickel coatings depends on the heat treatment and the amount of zinc in the interlayer. For both single and double zinc interlayer, the microhardness of the nickel coating containing Al2O3 particles increased after heat treatment, but decreased when a triple zinc interlayer was applied.

Physical methods of research and monitoring

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 35-44
Author(s):  
S. G. Sandomirski
Keyword(s):  
Heat Treatment ◽  
Coercive Force ◽  
Remanent Magnetization ◽  
Structural Changes ◽  
Mechanical Load ◽  
Magnetic Hysteresis ◽  
Steel Structures ◽  
Magnetic Characteristics ◽  
Magnetic Parameters ◽  
Saturation Intensity

The main magnetic parameters sensitive to the structure of steels are the parameters of their saturation loop of magnetic hysteresis: the coercive force Hcs and remanent magnetization Mrs. The saturation magnetization or saturation intensity Mr is most sensitive to the phase composition of steels. The variety of steel grades and modes of technological treatment (e.g., heat treatment, mechanical load) determined the use of magnetic structurescopy and magnetic characteristics — the coercive force Hc, remanent magnetization Mr , and specific hysteresis losses Wh on the subloops of the magnetic hysteresis of steels — as control parameters in diagnostics of the stressed and structural states of steel structures and pipelines. It has been shown that changes in Hc, Mr , and Wh are more sensitive to structural stresses and structures of steels than the parameters of the saturation hysteresis loop of magnetic hysteresis (Hcs, Mrs, and Mrs). The formulas for calculating Hc, Mr and Wh are presented to be used for estimation of changes in the parameters upon heat treatment of steels. Features of the structural sensitivity of the subloop characteristics and expediency of their use for magnetic structural and phase analyzes are determined. Thus, the range of changes in Ìr attributed to the structural changes in steels upon gradual Hm decrease is many times wider compared to the range of possible changes in Mrs under the same conditions. Conditions (relations between the magnetic parameters) and recommendations regarding the choice of the field strength Hm are given which provide the justified use of Hc, Mr and Wh parameters in magnetic structurescopy

Heat Treatment Influence on the Corrosion Resistance of a Cu-Al-Fe-Mn Bronze

2018 ◽  
Vol 69 (5) ◽  
pp. 1055-1059 ◽  
Author(s):  
Mariana Ciurdas ◽  
Ioana Arina Gherghescu ◽  
Sorin Ciuca ◽  
Alina Daniela Necsulescu ◽  
Cosmin Cotrut ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Structural Changes ◽  
Heating Temperature ◽  
Galvanic Corrosion ◽  
Cooling Water ◽  
Open Circuit ◽  
Water Quenching ◽  
Heat Treated ◽  
Different Temperatures

Aluminium bronzes are exhibiting good corrosion resistance in saline environments combined with high mechanical properties. Their corrosion resistance is obviously confered by the alloy chemical composition, but it can also be improved by heat treatment structural changes. In the present paper, five Cu-Al-Fe-Mn bronze samples were subjected to annealing heat treatments with furnace cooling, water quenching and water quenching followed by tempering at three different temperatures: 200, 400 and 550�C. The heating temperature on annealing and quenching was 900�C. The structure of the heat treated samples was studied by optical and scanning electron microscopy. Subsequently, the five samples were submitted to corrosion tests. The best resistance to galvanic corrosion was showed by the quenched sample, but it can be said that all samples are characterized by close values of open-circuit potentials and corrosion potentials. Concerning the susceptibility to other types of corrosion (selective leaching, pitting, crevice corrosion), the best corrosion resistant structure consists of a solid solution, g2 and k compounds, corresponding to the quenched and 550�C tempered sample.

Evaluation of Dexmedetomidine Dosing in Obese Critically Ill Patients

2021 ◽  
pp. 089719002110215
Author(s):  
Sara A. Atyia ◽  
Keaton S. Smetana ◽  
Minh C. Tong ◽  
Molly J. Thompson ◽  
Kari M. Cape ◽  
...  
Keyword(s):  
Body Weight ◽  
Critically Ill ◽  
Critically Ill Patients ◽  
Statistical Difference ◽  
Ideal Body Weight ◽  
Weight Percentage ◽  
Before And After ◽  
Light Sedation ◽  
Icu Sedation ◽  
Dose Dependent

Background: Dexmedetomidine is a highly selective α2-adrenoreceptor agonist that produces dose-dependent sedation, anxiolysis, and analgesia without respiratory depression. Due to these ideal sedative properties, there has been increased interest in utilizing dexmedetomidine as a first-line sedative for critically ill patients requiring light sedation. Objective: To evaluate the ability to achieve goal intensive care unit (ICU) sedation before and after an institutional change of dosing from actual (ABW) to adjusted (AdjBW) body weight in obese patients on dexmedetomidine. Methods: This study included patients ≥ 18 years old, admitted to a surgical or medical ICU, required dexmedetomidine for at least 8 hours as a single continuous infusion sedative, and weighed ≥ 120% of ideal body weight. Percentage of RASS measurements within goal range (−1 to +1) during the first 48 hours after initiation of dexmedetomidine as the sole sedative agent or until discontinuation dosed on ABW compared to AdjBW was evaluated. Results: 100 patients were included in the ABW cohort and 100 in the AdjBW cohort. The median dosing weight was significantly higher in the ABW group (95.9 [78.9-119.5] vs 82.2 [72.1-89.8] kg; p = 0.001). There was no statistical difference in percent of RASS measurements in goal range (61.5% vs 69.6%, p = 0.267) in patients that received dexmedetomidine dosed based on ABW versus AdjBW. Conclusion: Dosing dexmedetomidine using AdjBW in obese critically ill patients for ongoing ICU sedation resulted in no statistical difference in the percent of RASS measurements within goal when compared to ABW dosing. Further studies are warranted.

scholarly journals Investigation of Hydrothermally Stressed Silicone Rubber/Silica Micro and Nanocomposite for the Coating High Voltage Insulation Applications

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3567
Author(s):  
Faiza Faiza ◽  
Abraiz Khattak ◽  
Safi Ullah Butt ◽  
Kashif Imran ◽  
Abasin Ulasyar ◽  
...  
Keyword(s):  
Silicone Rubber ◽  
Structural Changes ◽  
Polymer Chains ◽  
Hydrothermal Conditions ◽  
Silica Filler ◽  
Before And After ◽  
Aging Conditions ◽  
The Stability ◽  
Micro Silica ◽  
Applied Stresses

Silicone rubber is a promising insulating material that has been performing well for different insulating and dielectric applications. However, in outdoor applications, environmental stresses cause structural and surface degradations that diminish its insulating properties. This effect of degradation can be reduced with the addition of a suitable filler to the polymer chains. For the investigation of structural changes and hydrophobicity four different systems were fabricated, including neat silicone rubber, a micro composite (with 15% micro-silica filler), and nanocomposites (with 2.5% and 5% nanosilica filler) by subjecting them to various hydrothermal conditions. In general, remarkable results were obtained by the addition of fillers. However, nanocomposites showed the best resistance against the applied stresses. In comparison to neat silicone rubber, the stability of the structure and hydrophobic behavior was better for micro-silica, which was further enhanced in the case of nanocomposites. The inclusion of 5% nanosilica showed the best results before and after applying aging conditions.

scholarly journals The Interface Zone of Explosively Welded Titanium/Steel after Short-Term Heat Treatment

2021 ◽  
Author(s):  
Marcin Szmul ◽  
Katarzyna Stan-Glowinska ◽  
Marta Janusz-Skuza ◽  
Agnieszka Bigos ◽  
Andrzej Chudzio ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Intermetallic Phase ◽  
Welding Process ◽  
Carbon Diffusion ◽  
Sharp Interface ◽  
High Plasticity ◽  
Interface Zone ◽  
Before And After ◽  
Wavy Interface ◽  
The Waves

AbstractThis work presents a detailed description of a bonding zone of explosively welded Ti/steel clads subjected to stress relief annealing, applied in order to improve the plasticity of the final product. The typical joint formed by the welding process possesses a characteristic wavy interface with melted regions observed mainly at the crest regions of waves. The interface of Ti/steel clads before and after annealing was previously investigated mostly in respect to the melted regions. Here, a sharp interface between the waves was analyzed in detail. The obtained results indicate that the microstructure of a transition zone of that area is different along the width. After the heat treatment at 600 °C for 1.5 hours, titanium carbide (TiC) together with α-Fe phase forms at the interface in local areas of relatively wide interlayer (~ 1 µm), while for most of the sharp interface, a much thinner zone up to about 400 nm, formed by four sublayers containing intermetallic phase and carbides, is present. This confirms that carbon diffusion induced by applied heat treatment significantly influences the final microstructure of the Ti/steel interface zone. Side bending tests confirmed high plasticity of welds after applied heat treatment; however, the microhardness measurements indicated that the strengthening of the steel in the vicinity of the interface had not been removed completely.

scholarly journals Redox Mechanism of Azathioprine and Its Interaction with DNA

2021 ◽  
Vol 22 (13) ◽  
pp. 6805
Author(s):  
Mihaela-Cristina Bunea ◽  
Victor-Constantin Diculescu ◽  
Monica Enculescu ◽  
Horia Iovu ◽  
Teodor Adrian Enache
Keyword(s):  
Electron Microscopy ◽  
Mass Spectrometry ◽  
Scanning Electron Microscopy ◽  
Structural Changes ◽  
Differential Pulse ◽  
Immunosuppressive Drug ◽  
Redox Mechanism ◽  
Before And After ◽  
Dna Film ◽  
Scanning Electron

The electrochemical behavior and the interaction of the immunosuppressive drug azathioprine (AZA) with deoxyribonucleic acid (DNA) were investigated using voltammetric techniques, mass spectrometry (MS), and scanning electron microscopy (SEM). The redox mechanism of AZA on glassy carbon (GC) was investigated using cyclic and differential pulse (DP) voltammetry. It was proven that the electroactive center of AZA is the nitro group and its reduction mechanism is a diffusion-controlled process, which occurs in consecutive steps with formation of electroactive products and involves the transfer of electrons and protons. A redox mechanism was proposed and the interaction of AZA with DNA was also investigated. Morphological characterization of the DNA film on the electrode surface before and after interaction with AZA was performed using scanning electron microscopy. An electrochemical DNA biosensor was employed to study the interactions between AZA and DNA with different concentrations, incubation times, and applied potential values. It was shown that the reduction of AZA molecules bound to the DNA layer induces structural changes of the DNA double strands and oxidative damage, which were recognized through the occurrence of the 8-oxo-deoxyguanosine oxidation peak. Mass spectrometry investigation of the DNA film before and after interaction with AZA also demonstrated the formation of AZA adducts with purine bases.

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