The effect of 2-aminoquinoline-6-carboxylic acid on the corrosion behavior of mild steel in hydrochloric acid

The inhibitive effect of 2-aminoquinoline-6-carboxylic acid (AQC) against mild steel corrosion in 1?M HCl solutions was investigated using conventional weight loss, potentiodynamic polarization, linear polarization and electrochemical impedance spectroscopy methods. The weight loss results showed that AQC is an excellent corrosion inhibitor since its efficiency increased with the concentration to attain 91.8?% at 500?mg?l^?1. Electrochemical polarization measurements revealed that AQC acted as a mixed-type inhibitor and the results of electrochemical impedance spectroscopy have shown that the change in the impedance parameters, charge transfer resistance and double layer capacitance, with the change in concentration of the inhibitor is due to the adsorption of the molecule leading to the formation of a protective layer on the surface of mild steel. The adsorption was assumed to occur on the steel surface through the active centers of the molecule. The inhibition action of AQC was discussed in view of Langmuir adsorption isotherm. Density functional theory calculations of quantum parameters were used to explain efficiency in relation with molecular structure.     

菱钾沸石(OFF)的离子交换及对SO2气体吸附性能研究

采用水热合成法制备了菱钾沸石(OFF),通过离子交换得到了H-OFF,Li-OFF,Na-OFF,K-OFF和Cs-OFF.用XRD,SEM,TG,DTA,固体1HNMR,FTIR和低温氮吸附等手段研究了离子交换性质,发现其晶体结构和晶貌在离子交换过程中基本不变,热力学性质随阳离子类型的改变而发生很大变化.样品的比表面积和孔体积随阳离子的增大而减小,B酸随阳离子半径的增大而减小,L酸反之.测定沸石样品对酸性气体SO2的吸附结果表明,Li-OFF在低分压下对SO2有很好的吸附性能.     

Corrosion inhibition and mechanism of mild steel in hydrochloric acid by ceftriaxone and amoxicillin

Corrosion inhibition of mild steel in 1 mol/L HCl by amoxicillin and ceftriaxone in the concentration range of 1.00×10-5-1.00×10-2 mol/L has been studied using weight loss,electrochemical potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),scanning electron microscopy(SEM) and quantum chemistry tests at 298 K.The weight loss experiment showed that the inhibition efficiency increased with amoxicillin and ceftriaxone concentrations to attain the maximums of 80.3% and 94.1%,respectively at...     

Adsorption behavior and corrosion inhibitive potential of xanthene on mild steel/sulphuric acid interface

The inhibition of xanthene (XEN) on the corrosion of mild steel in 0.5 M H₂SO₄ was studied by gravimetric and UV–visible spectrophotometric methods at 303–333 K. Results obtained show that XEN act as inhibitor for mild steel in H₂SO₄ solution. The inhibition efficiency was found to increase with increase in XEN concentration but decreased with temperature. Activation parameters and Gibbs free energy for the adsorption process using Statistical Physics were calculated and discussed. The corrosion process in 0.5 M H₂SO₄ in the absence and presence of XEN follows zero-order kinetics. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a XEN–Fe complex. Quantum chemical calculations using DFT were used to calculate some electronic properties of the molecule in order to ascertain any correlation between the inhibitive effect and molecular structure of xanthene.     

Improvement of hardness and anti-corrosion behavior of mild steel by plasma sprayed coating of Al2O3/GO composite

A robust and fast non-transferred plasma torch method was employed for developing coating of alumina (A₂O₃) and alumina/graphene oxide (A₂O₃/GO) on mild steel. Micro Raman analysis of GO confirms its spectroscopic behavior. The energy band gap of GO was determined as 3.44 eV. The successful coating formation of A₂O₃ and A₂O₃/GO (0.5 wt%) on mild steel was confirmed by X-ray diffraction analysis. Microhardness of mild steel was found to increase about 43.75% after coating with A₂O₃/GO (0.5 wt%) composite. The microstructure of A₂O₃/GO (0.5 wt%) coated mild steel represents better quality of coating and improved structural behavior. Mild steel becomes more corrosive resistance by reduction of corrosion potential (less negative than −0.05 V) after A₂O₃/GO (0.5 wt%) coating on it.     

Determination of diffusible and total hydrogen concentration in coated and uncoated steel using melt and solid extraction techniques: Part I

It is essentially to know the bulk hydrogen concentration in various types of steel because it indicates the amount of hydrogen that can be trapped by the different alloys of steel. This information leads to more knowledge about the interactions of steel alloys with hydrogen containing environment and stability of the steel material during usage. To get this information precise analytical methods are necessary.Although the analytical methods for the determination of hydrogen in steel samples are often discussed, there are no sufficient systematic studies as far as the influence of the sample preparation on the analytical value is concerned.The influence of different sample preparation methods on the hydrogen determination in steel at parts per million levels by melting extracting methods has been investigated in this work. The hydrogen was measured by thermal conductivity and infrared detection. The flat sheet samples were zinc coated and uncoated ferritic types of steel. The zinc coating was removed by chemical (acid etching) and physical (paper scraping) methods. Dichloromethane acetone/ethanol, tetrachloromethane and alkaline steel cleaner (Ridoline C72) have been used for cleaning the surface of uncoated samples. The results of the total hydrogen content obtained by applying the different methods were evaluated.     

Study on the variation of morphology and separation behavior of the stainless steel supported membranes at high temperature

Palladium composite membranes were prepared on stainless steel (SUS) supports modified by nickel submicron powder and colloidal silica sols. Permeation tests of the palladium composite membranes were carried out at high temperature in order to observe the thermal stability of the membrane. The palladium composite membrane failed with formation of plenty of pinholes in the presence of hydrogen at high temperature. The failure of the composite membrane was verified by comparing the nitrogen permeance before hydrogen permeation test with that after hydrogen permeation test and comparing the H₂/N₂ selectivity for single gas permeation test with that for mixture gas permeation test. The variation of the membrane surface due to the failure of the membrane was characterized in scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) analyses. As a result, it can be concluded that reducible metal oxides can be attributed to the failure of the composite membranes resulting from reduction of the metal oxides by hydrogen whichever position in the membrane the metal oxides are layered.     

Quality testing of human albumin by capillary electrophoresis using thermally cross‐linked poly(vinyl pyrrolidone)‐coated fused‐silica capillary

To detect the quality of medicinal human albumin by capillary electrophoresis, we produced a fused‐silica capillary coated with thermally cross‐linked poly(vinyl pyrrolidone) to prohibit protein adsorption. This type of capillary was easily obtained by injecting an aqueous poly(vinyl pyrrolidone) solution into a fused‐silica capillary and thermally annealing it at 200°C. Notably, stable and low electro‐osmotic flow was obtained in the poly(vinyl pyrrolidone)‐coated capillary at pH 2.20–9.00, and the separation of a mixture of four basic proteins indicated that the poly(vinyl pyrrolidone)‐coated capillary exhibits excellent repeatability and separation efficiency; moreover, the separation of these four basic proteins could even be achieved at pH 7.00. The protein recovery percentage of human serum albumin in a single‐protein solution and a mixed blood proteins solution was determined to be 97.03 and 95.40% in the poly(vinyl pyrrolidone)_50–3 (representing the concentration of the capillary‐injected poly(vinyl pyrrolidone) aqueous solution, 50 mg/mL, and thermal annealing time, 3 h) capillary, respectively. Based on these results, we used the poly(vinyl pyrrolidone)_50–3‐coated capillary to quantify the protein content of human albumin, and the results obtained from run to run, day to day and capillary to capillary demonstrated that the coated capillary could be used for quality testing commercially available human albumin.     

Enhancement of thermal properties of Kevlar 29 coated by SiC and TiO2 nanoparticles and their binding energy analysis

In the fields of military research, aerospace, and vehicle technology, the thermal stability of Kevlar fiber is critical for improving its flame resistance. In this work, the pad mangle machine was used to improve the thermal properties of Kevlar 29 in order to expand the range of applications for thermal aspects. Silicon carbide and titanium oxide nanoparticles provide thermal stability on the fiber surface through intermolecular adhesion. Here, 5 wt% and 10 wt% of nanoparticles with various mass ratios (1:1) have been chosen. Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) analysis, and X-ray Photoelectron Spectroscopy (XPS) analysis have all been used to measure different thermal properties. The surface morphology of samples is represented by FESEM analysis, while the active organic groups are represented by FTIR analysis. The greater crystallization of epoxy and nanoparticles is linked to post-heat treatment of the material. The glass transition temperature of the coated samples shifted maximum from 559.13 °C to 580.51 °C, the end set temperature increased by 30.67 °C compared to the uncoated sample, and the residual weight changed from 29.77 percent to 4.06 percent, according to the findings (i.e., lightweight). When compared to the uncoated sample, the coated sample's enthalpy increased significantly (i.e., the samples can absorb more heat). The smaller the positive binding energy, the higher the activation energy, and hence the slower the chemical reaction, which is especially important in high-temperature applications. Finally, this research reveals a 4.5–5.2 percent increase in thermal characteristics.     

Thermal decomposition of Cu(NO3)2·3H2O at reduced pressures

Thermolysis of Cu(NO₃)₂·3H₂O is studied by means of XRD analysis in situ and mass spectral analysis of the gas phase at P=1/10 Pa at low heating rate. It is shown that stage I of the dehydration (40-80 °C) results in the consecutive appearance of crystalline Cu(NO₃)₂·2.5H₂O and Cu(NO₃)·H₂O. Anhydrous Cu(NO₃)₂ formed during further dehydration at 80-110 °C is moderately sublimed at 120-150 °C. Dehydration is accompanied by thermohydrolysis, leading to the appearance of Cu₂(OH)₃NO₃ and gaseous H₂O, HNO₃, NO₂, and H₂O. The higher pressure in the system, the larger amount of thermohydrolysis products is observed. The formation of the crystalline intermediate CuO_x(NO₃)_y was observed by diffraction methods. Final product of thermolysis (CuO) is formed at 200-250 °C.     

Experimental and DFT analysis of onion peels for its inhibition behavior against mild steel corrosion in chloride solutions

Natural materials are good options for being used as inhibitors due to their high biodegradability, reasonable cost, easiness in use and high efficiency. In this regard, waste natural materials are very useful because they have all the properties of natural materials and easily available at very low cost (almost free). This work reports a similar kind of waste natural materials namely onion peels. The water extract of onion peels (WEOP) is characterized by UV–vis spectroscopy (UVS) and FTIR spectroscopy (FTIS). WEOP is tested for corrosion inhibition of mild steel (MS) in 1 M NaCl by various techniques like typical weight loss measurements (WLM), open circuit potential (OCP) curves, Tafel polarization (TP) curves, electrochemical impedance spectroscopy (EIS) and surface scanning microscopy (SEM). The maximum inhibition of mild steel corrosion is 90% (WLM). The reason of inhibition based on experimental analysis is proposed as adsorption of extract molecules on MS, which is found true in SEM images and Langmuir isotherm study. The WEOP is also examined by density functional theory principles, which recommends that the extract molecules can be easily adsorbed on MS and can stop corrosion of MS in NaCl solutions. Based on investigation, a schematic is introduced for compact explanation.     

A mild and efficient method for preparation of azides from alcohols using acidic ionic liquid [H-NMP]HSO4

We report here an efficient method for the synthesis and characterization of [H-NMP]HSO₄ and its application as an efficient catalyst and solvent for preparation of azides from corresponding alcohols under mild conditions. This processor showed high chemoselectivity for conversion of various alcohols to their corresponding azides.     

Corrosion inhibition and adsorption behavior of methionine on mild steel in sulfuric acid and synergistic effect of iodide ion

The corrosion inhibition of mild steel in sulfuric acid by methionine (MTI) was investigated using electrochemical techniques. The effect of KI additives on corrosion inhibition efficiency was also studied. The results reveal that MTI inhibited the corrosion reaction by adsorption onto the metal/solution interface. Inhibition efficiency increased with MTI concentration and synergistically increased in the presence of KI, with an optimum [KI]/[MTI] ratio of 5/5, due to stabilization of adsorbed MTI cations as revealed by AFM surface morphological images. Potentiodynamic polarization data suggest that the compound functioned via a mixed-inhibition mechanism. This observation was further corroborated by the fit of the experimental adsorption data to the Temkin and Langmuir isotherms. The inhibition mechanism has been discussed vis-à-vis the presence of both nitrogen and sulfur atoms in the MTI molecule.     

Berberine isolated from Mahonia nepalensis as an eco-friendly and thermally stable corrosion inhibitor for mild steel in acid medium

BackgroundThe environmental and economic benefits have been the driving force in search of efficient corrosion inhibitors for iron/steel used in industrial acidic medium. This study reports on berberine isolated from methanol extract of high-altitude (1347 m) shrub Mahonia nepalensis as a highly efficient and thermally stable corrosion inhibitor for mild steel (MS) in 1.0 M H₂SO₄ simulating acid pickling condition.MethodsThe weight-loss and electrochemical methods revealed the fast adsorption of berberine.Significant Findings: It achieved above 91% inhibition efficiency (IE) in 0.25 h and reached 94% in 6 h for 1000 ppm berberine. The IE increased with concentration and temperature, giving an IE of 97.2% at 328 K, which makes it a promising candidate for industrial application. It behaved as a mixed type of inhibitor as revealed by open circuit potential and polarization curves. The results indicated suppression of the corrosion by effectively forming an adsorbed berberine layer on the MS surface. Adsorption of the berberine followed a Langmuir adsorption isotherm. The thermodynamic parameters such as activation energy (43.19 kJ/mol), free energy (−35.05 kJ/mol), enthalpy (40.55 kJ/mol), and entropy (−97.83 J/molK) of adsorption supported both physical and chemical interactions of berberine with MS surface. The obtained results also revealed that the adsorption process was endothermic and spontaneous in nature.     

Structural study of polymorphism and thermal behavior of CaZr(PO4)2

The crystal structure of CaZr(PO₄)₂ has been revised by ab initio Rietveld analysis of X-ray powder diffraction data. At room temperature, CaZr(PO₄)₂ crystallizes in the orthorhombic space group Pna2₁ (Z = 4). Differential thermal analysis suggests a reversible second order transition at 1000 °C confirmed by high temperature XRD analysis that brings out the existence of a high temperature form, very similar to the room temperature one, but more symmetrical (Pnma, Z = 4). Analysis of the crystal parameters evolution during heating reveals that CaZr(PO₄)₂ exhibits a quite low thermal expansion coefficient of 6.11·10⁻⁶ K⁻¹. This value stems from a combination of several mechanisms, including Coulombic repulsion and bridging oxygen rocking motion.     

Effect of branching on the degradation behaviour and caloric properties of PVC

Nine different PVC samples with defined chlorine content and degree of branching have been investigated. The aim of the work was the influence of these parameters on some caloric properties as well as the degradation behaviour and the degradation products. As expected, the heat of combustion decreases with increasing chlorine content. As determined by simultaneous thermal analysis/mass spectrometry, the volatile degradation products of the pyrolysis in nitrogen atmosphere vary. The higher the chlorine content, the higher the amount of chlorinated degradation products and the lower the amount of polycyclic aromatic hydrocarbons (PAH). A higher number of branching promotes the formation of alcylated aromatic hydrocarbons.     

Thermal ageing of rocket propellant formulations containing ε-HNIW (ε-CL20) investigated by heat generation rate and mass loss

New types of rocket propellant batches have been formulated with the objective of achieving higher burning rates. The main ingredients are (1) the energetic plasticizers glycidyl azide polymer-α,ω-diazide (GAP)-A (short chain GAP with azide end groups), trimethylolethane trinitrate (TMETN) and 1,2,4-butanetriol trinitrate (BTTN), (2) the energetic substances ammonium perchlorate (AP) and ε-CL20 (ε-HNIW, hexanitrohexazaisowurtzitane, crystallised in ε-phase). The binder is GAP (glycidyl azide polymer, diol component) cured with the polyisocyanate Desmodur™ N100. From the point of view of stability and ageing, the interesting fact is that the formulations contain none of the typical stabilisers for the nitric acid ester components TMETN and BTTN, although their contents range up to 21 mass%. One reason for doing so is to increase the content of the high energy ingredients. Seven formulations were examined in more detail. To assess basic stability the autoignition temperature test, Dutch mass loss test and vacuum stability test were used. To investigate ageing, two measurement quantities are applied: heat generation rate (heat flow) as function of time at 70, 80 and 89 °C and mass loss as function of time at the temperatures of 70, 80 and 90 °C. The evaluation of the measurements was done with reaction kinetic models. One batch (#189) containing BTTN shows significantly lower activation energy and pre-exponential factor. From mass loss one gets as activation energy for #189 of 101 kJ mol⁻¹ in comparison to the range of 126-135 kJ mol⁻¹ for the six other batches. But, based on the ageing caused by chemical decomposition reactions, all seven batches showed a good ageing behaviour. A use time period of up to 20 years of use seems realistic.     

Influence of molecular architecture on behavior of thermoresponsive poly-2-ethyl-2-oxazine in saline media

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Mixed ligand complexes of AEE hexafluoroacetylacetonates with diglyme: Synthesis,crystal structure and thermal behavior

The novel mixed ligand complexes [Ca(hfa)₂(diglyme)(H₂O)] (I), [Sr(hfa)₂(diglyme)(H₂O)] (II) and [Ba(hfa)₂(diglyme)₂] (III) (Hhfa = 1,1,1,5,5,5-hexafluoropentane-2,4-dione, diglyme = 2,5,8-trioxanonane) were synthesized by the reactions of the alkaline earth element (AEE) carbonates in n-hexane with a mixture of Hhfa and diglyme, and they were characterized by elemental analysis, ¹H and ¹³C NMR, and FTIR spectroscopy. The crystal structures of I–III, consisting of mononuclear isolated molecules, have been determined. The thermal behavior and composition of the vapor phase have been studied for I–III by thermal analysis at low pressure and mass spectrometry using a Knudsen cell. The stability of the mixed ligand complexes [M(hfa)₂(diglyme)_n] to the removal of diglyme molecules under heating decreases in the row I > II ≈ III, and only I evaporates as the mixed ligand complex after water removal.     

Processing,structure, microstructure,and transport properties of the oxygen-conducting ceramics (La,Sr)(Ga,M)O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> (M=Mg,Fe, Ni)

The structure, microstructure, and dielectric and transport properties of (La,Sr)(Ga,M)O_y (M=Mg, Fe, and Ni) ceramic solid solutions have been studied by X-ray diffraction, thermogravimetry, and dilatometry in various gas atmospheres. Enhancement of conductivity and an increase of the thermal expansion coefficient have been confirmed to correlate with an increasing concentration of oxygen vacancies at high temperatures in the samples studied. Transformation from pure ionic to mixed conductivity has been revealed in the samples with increasing iron or nickel content.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003