Influence of eutectic phase precipitation on cracking susceptibility during forging of a martensitic stainless steel for turbine shaft applications

The presence of the eutectic phase (delta ferrite + M23C6) in martensitic stainless steels brings significant deterioration of the in-service mechanical properties of the critical components such as turbine shaft made of these alloys. In the present study, thermodynamic and kinetics of eutectic phase formation during solidification and the reheating stages before forging of a large size X38CrMo16 martensitic stainless steel ingot are investigated. Material characterization and microstructural evolution were characterized in three different zones of a large size ingot. It was observed that the forging temperature and the solidification rate were the two most effective parameters influencing the volume fraction of the eutectic phase and its morphology. Optical and electron microscopy observations along with Energy Dispersion Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD) measurements were used in the investigation. The results showed that the eutectic phase precipitated primarily at the grain boundaries. Furthermore, a clear evolution on the morphology and volume fraction of the eutectic phase including thin film-like and skeleton-like carbides was found from the outer surface to the center of the ingot along the radial direction. EDS analysis revealed the substantial presence of chromium, molybdenum, and carbon within the M23C6 along the grain boundaries. Phase transformation and the precipitation phase sequences were analyzed as a function of temperature and composition of eutectic transformation using the Thermo-Calc software and the predictions were validated with experimental findings

Microcontrol optimization using microfilm with memory feature

The purpose of this paper is to examine the design method of a micro-constraint that, with proper performance, can automatically take a micro-part according to the important parameters of the reaction time and force, and after performing various steps on the part. Be. Release the piece and be ready to take the next piece. The use of CMOS technology in the design of retaining walls and the use of SMA technology in the design of the retaining bracket and its replacement instead of other existing designs in optimizing energy consumption power and reaction time, as well as combining the last two technologies play an essential role in this article. Is responsible. In the following, the mentioned design is examined through stimulation modeling based on mass and spring system and using mathematical software, analytical equations of stimulus movement based on time are extracted so that the time of deformation of stimulus can be calculated as a parameter

Carbon and graphene quantum dots: A review on syntheses, characterization, biological and sensing applications for neurotransmitter determination

Neuro-transmitters have been considered to be essential biochemical molecules, which monitor physiological and behavioral function in the peripheral and central nervous systems. Thus, it is of high pharmaceutical and biological significance to analyze neuro-transmitters in the biological samples. So far, researchers have devised a lot of techniques for assaying these samples. It has been found that electro-chemical sensors possess features of robustness, selectivity, and sensitivity as well as real-time measurement. Graphene quantum dots (GQDs) and carbon QDs (CQDs) are considered some of the most promising carbon-based nanomaterials at the forefront of this research area. This is due to their characteristics including lower toxicity, higher solubility in various solvents, great electronic features, strong chemical inertness, high specific surface areas, plenty of edge sites for functionalization, and versatility, in addition to their ability to be modified via absorbent surface chemicals and the addition of modifiers or nano-materials. Hence in the present review, the synthesis methods of GQDs and CQDs has been summarized and their characterization methods also been analyzed. The applications of carbon-based QDs (GQDs and CQDs) in biological and sensing areas, such as biological imaging, drug/gene delivery, antibacterial and antioxidant activity, photoluminescence sensors, electrochemiluminescence sensors and electrochemical sensors, have also been discussed. This study then covers sensing features of key neurotransmitters, including dopamine, tyrosine, epinephrine, norepinephrine, serotonin and acetylcholine. Hence, issues and challenges of the GQDs and CQDs were analyzed for their further development. This journal is © 2020 The Royal Society of Chemistry

Recent advances in the aptamer-based electrochemical biosensors for detecting aflatoxin b1 and its pertinent metabolite aflatoxin m1

The notable toxicological impacts of aflatoxin B1 (AFB1) and its main metabolite, aflatoxin M1 (AFM1), on human being health make the evaluation of food quality highly significant. Due to the toxicity of those metabolites�even very low content in foodstuffs�it is crucial to design a sensitive and reliable procedure for their detection. Electrochemical aptamer-based biosensors are considered the most encouraging option, based on multi-placed analysis, rapid response, high sensitivity and specificity. The present review specifically emphasizes the potential utilization of the electrochemical aptasensors for determining the AFM1 and AFB1 with different electrodes. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Recent advances in the electrochemical sensing of venlafaxine: An antidepressant drug and environmental contaminant

Venlafaxine (VEN), as one of the popular anti-depressants, is widely utilized for the treatment of major depressive disorder, panic disorder, as well as anxiety. This drug influences the chemicals in the brain, which may result in imbalance in depressed individuals. However, venlafaxine and its metabolites are contaminants in water. They have exerted an adverse influence on living organisms through their migration and transformation in various forms of adsorption, photolysis, hydrolysis, and biodegradation followed by the formation of various active compounds in the environment. Hence, it is crucial to determine VEN with low concentrations in high sensitivity, specificity, and reproducibility. Some analytical techniques have been practically designed to quantify VEN. However, electroanalytical procedures have been of interest due to the superior advantages in comparison to conventional techniques, because such methods feature rapidity, simplicity, sensitivity, and affordability. Therefore, this mini-review aims to present the electrochemical determination of VEN with diverse electrodes, such as carbon paste electrodes, glassy carbon electrodes, mercury-based electrodes, screen-printed electrodes, pencil graphite electrodes, and ion-selective electrodes. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Recent developments in voltammetric and amperometric sensors for cysteine detection

This review article aims to provide an overview of the recent advances in the voltammetric and amperometric sensing of cysteine (Cys). The introduction summarizes the important role of Cys as an essential amino acid, techniques for its sensing, and the utilization of electrochemical methods and chemically modified electrodes for its determination. The main section covers voltammetric and amperometric sensing of Cys based on glassy carbon electrodes, screen printed electrodes, and carbon paste electrodes, modified with various electrocatalytic materials. The conclusion section discusses the current challenges of Cys determination and the future perspectives. © The Royal Society of Chemistry 2021

Electrocatalytic oxidation and selective voltammetric detection of methyldopa in the presence of hydrochlorothiazide in real samples

The combination of methyldopa and hydrocholorothiazide are used to treat high blood pressure. The present research dealt with the synthesis and utilization of the hexagonal-shaped of ZnO nanoparticles (NPs) to develop a new, sensitive, and exclusive electrochemical sensor for detection of methyldopa. Thus, we did our examination on the methyldopa detection via cyclic voltammetry (CV) method, differential pulse voltammetry (DPV) technique, and chronoamperometry (CH) at molybdenum (VI) complex-ionic liquid�ZnO NP modified carbon paste electrode (MCILZNMCPE) in 0.1 M PBS (pH of 7.0) solution. The use of DPV showed linear dependence of methyldopa peak current at pH of 7.0 solution on their concentration ranging between 0.05 and 300.0 µM. Then, limit of detection (LOD) has been determined to be 20.0 nM for methyldopa. Ultimately, the modified electrode has been utilized for detecting methyldopa in the presence of hydrochlorothiazide by DPV. © 2020 Elsevier B.V

Recent developments in polymer nanocomposite-based electrochemical sensors for detecting environmental pollutants

The human population is generally subjected to diverse pollutants and contaminants in the environment like those in the air, soil, foodstuffs, and drinking water. Therefore, the development of novel purification techniques and efficient detection devices for pollutants is an important challenge. To date, experts in the field have designed distinctive analytical procedures for the detection of pollutants including gas chromatography/mass spectrometry and atomic absorption spectroscopy. While the mentioned procedures enjoy high sensitivity, they suffer from being laborious, expensive, require advanced skills for operation, and are inconvenient to deploy as a result of their massive size. Therefore, in response to the above-mentioned limitations, electrochemical sensors are being developed that enjoy robustness, selectivity, sensitivity, and real-time measurements. Considerable advancements in nanomaterials-based electrochemical sensor platforms have helped to generate new technologies to ensure environmental and human safety. Recently, investigators have expanded considerable effort to utilize polymer nanocomposites for building the electrochemical sensors in view of their promising features such as very good electrocatalytic activities, higher electrical conductivity, and effective surface area in comparison to the traditional polymers. Herein, the first section of this review briefly discusses the most important methods for polymer nanocomposites synthesis, such as in situ polymerization, direct mixing of polymer and nanofillers (melt-mixing and solution-mixing), sol-gel, and electrochemical methods. It then summarizes the current utilization of polymer nanocomposites for the preparation of electrochemical sensors as a novel approach for monitoring and detecting environmental pollutants which include heavy metal ions, pesticides, phenolic compounds, nitroaromatic compounds, nitrite, and hydrazine in different mediums. Finally, the current challenges and future directions for the polymer nanocomposites-based electrochemical sensing of environmental pollutants are outlined. © 2021 American Chemical Societ