ESCA Studies Research Articles

HTA160 Development of a Web Application for Self-Assessment and Monitoring of Colorectal Surgery Outcome Indicators in the ESCA Study

HTA160 Development of a Web Application for Self-Assessment and Monitoring of Colorectal Surgery Outcome Indicators in the ESCA Study

Electrochemical studies on aniline-pentamer-based electroactive polyimide coating: Corrosion protection and electrochromic properties

In this study, electrochemical investigations of corrosion protection and the electrochromic properties of an aniline-pentamer-based electroactive polyimide (AP-based EPI) coating prepared by oxidative coupling polymerization are presented. The in situ chemical oxidation of the reduced form of soluble, electroactive poly(amic acid) (EPAA) in N-methyl-2-pyrrolidone (NMP) was monitored by UV–Vis absorption spectra. Moreover, the electroactivity of the AP-based EPI was evaluated by performing electrochemical CV studies. Based on a series of electrochemical measurements in 3.5wt% NaCl electrolyte, the AP-based EPI coating was found to exhibit enhanced corrosion protection effects on cold-rolled steel (CRS) electrodes as compared to the corresponding non-electroactive (NEPI) coating. A possible mechanism for the enhanced corrosion protection of EPI coatings on the CRS electrode has been proposed as follows: (1) EPI coatings may act as a physical barrier and (2) the redox catalytic properties of the aniline pentamer units in EPI may induce the formation of a passive metal oxide layer on the CRS electrode, as evidenced by SEM and ESCA studies. The electrochromic performance of EPI was investigated by measuring electrochromic photographs and UV absorption spectra.

Advanced anticorrosive coatings prepared from electroactive epoxy–SiO 2 hybrid nanocomposite materials

A series of electroactive epoxy/amino-SiO 2 nanocomposite materials containing conjugated segments of electroactive amino-capped aniline trimer (ACAT) unit were successfully prepared. First of all, the amino-modified silica (AMS) particles of ∼50 nm in diameter were synthesized by performing the conventional base-catalyzed sol–gel reactions of tetraethyl orthosilicate (TEOS) in the presence of (3-aminopropyl)-trimethoxysilane (APTES) molecules. Subsequently, the AMS nanoparticles were blended into the epoxy ring-opening polymerization reactions between amino-terminated aniline trimer (ACAT)/T-403 and DGEBA, leading to the formation of electroactive epoxy resin–silica hybrid nanocomposites (EES). Furthermore, the redox behavior of as-prepared EES materials was identified by the electrochemical cyclic voltammetry studies. It should be noted that the as-prepared electroactive hybrid materials in the form of coating on cold-rolled steel (CRS) electrode were found to be much superior in corrosion protection over those of non-electroactive epoxy (NEE) and electroactive epoxy (EE) materials based on a series of electrochemical corrosion measurements in saline. The possible mechanism for the advanced enhancement of corrosion protection of EES coatings on CRS electrode could be interpreted as follows: (1) electroactive epoxy coatings may act as physical barrier coating; (2) redox catalytic capabilities of ACAT units existed in electroactive epoxy may induce the formation of passive metal oxide layers on CRS electrode, as further evidenced by SEM and ESCA studies; (3) well-dispersed AMS nanoparticles in EES matrix could act as effective hinder to enhance the oxygen barrier property of electroactive epoxy matrix, the result could be demonstrated by gas permeability analysis (GPA). Electroactive epoxy/SiO 2 nanocomposites were identified by a series of electrochemical measurements such as corrosion potential ( E corr ), polarization resistance ( R p ), corrosion current ( I corr ) and electrochemical impedance spectroscopy (EIS) studied in 5 wt% NaCl electrolyte.

Advanced anticorrosive materials prepared from amine-capped aniline trimer-based electroactive polyimide-clay nanocomposite materials with synergistic effects of redox catalytic capability and gas barrier properties

In this study, preparation and electrochemical corrosion protection studies of a series of polyimide–Clay nanocomposite (PCN) materials were first presented. Subsequently, the as-prepared PCN materials were characterized by FTIR, XRD and TEM studies. In- situ monitoring for redox behavior of as-prepared PCN materials was identified by UV–visible and CV studies. It should be noted that PCN coating was found to reveal advanced corrosion protection effect on cold-rolled steel (CRS) electrode as compared to that of neat non-electroactive polyimide coating based on series of electrochemical corrosion measurements in 5 wt% NaCl electrolyte. Enhancement of corrosion protection of PCN coatings on CRS electrode may be interpreted by following two possible reasons: (1) redox catalytic capabilities ( i. e., electroactivity) of ACAT units existed in electroactive PCN may induce formation of passive metal oxide layers on CRS electrode, as evidenced by SEM and ESCA studies. (2) well-dispersed layered organophilic clay platelets embedded in electroactive PCN matrix could functioned as hinder with high aspect ratio to effectively enhance the oxygen barrier property of PCN, as evidenced by GPA.

Preparation and Corrosion Protection Effect of Electroactive Polyurethane Containing Amino-Capped Aniline Trimer

Electroactive polyurethane (EPU) containing conjugated segments of electroactive amino-capped aniline trimer (ACAT) has been successfully synthesized and characterized through Fourier-Transformation infrared and UV–visible absorption spectroscopy. Subsequently, electroactivity (i.e., redox capability) of as-prepared EPU was investigated by electrochemical cyclic voltammetry (CV) studies. It was noticed that the as-prepared EPU exhibited reversible redox capability was found to reveal better corrosion protection effect on cold-rolled steel (CRS) electrodes than that of non-electroactive polyurethane based on a series of electrochemical measurements such as corrosion potential, polarization resistance, corrosion current and electrochemical impedance spectroscopy (EIS) studies in 5 wt-% NaCl electrolyte. This significant enhancement of corrosion protection on CRS electrodes as compared to non-electroactive polyurethane might be probably ascribed to the redox catalytic property of as-prepared EPU coatings inducing the formation of passive layer of metal oxide, as evidenced by the SEM and ESCA studies.

Effect of amino-capped aniline trimer on corrosion protection and physical properties for electroactive epoxy thermosets

A series of electroactive epoxy thermosets (EETs) containing conjugated segments of electroactive amino-capped aniline trimer (ACAT) unit were successfully prepared and characterized. Furthermore, the redox behavior of as-prepared EET materials was identified by the electrochemical cyclic voltammetry studies. Higher concentration of ACAT component in as-prepare corresponding EETs was found to lead to an remarkably enhanced corrosion protection effect on cold-rolled steel (CRS) electrode based on sequential electrochemical corrosion measurements in 5 wt% NaCl supporting electrolyte. Mechanism for the enhancement of corrosion protection of EET coatings on CRS electrode might be attributed to the redox catalytic capabilities of ACAT units existed in EETs, leading to the formation of passive metal oxide layers, as further evidenced by SEM and ESCA studies. Effect of material composition on thermal stability and mechanical strength of EETs were also investigated by TGA, DSC and DMA, respectively.

Preparation and characterization of carbonaceous materials containing nitrogen as electrochemical capacitor

Carbonaceous materials containing nitrogen (C/N materials) were prepared by a pyrolysis of 2,3,6,7-tetracyano-1,4,5,8-tetraazanaphthalene (CAN). A C/N material prepared by the pyrolysis of CAN at 1070 K (CAN-1070 K) had a C/N atomic ratio of 3.0 and a non-crystalline carbonaceous structure with a BET surface area of 880 m 2 g −1. The material CAN-1070 K showed large capacitances of 160–180 F g −1 and 110–120 F cm −3 in case of current density of 10 mA cm −2 (2 A g −1) by using three-electrode cell in 1 M H 2SO 4 aqueous solution, in comparison with that of activated carbon (160 F g −1 and 55 F cm −3) having BET surface area of 2300 m 2 g −1. ESCA study indicated that pyridinic and quarternary nitrogen atoms existed in the C/N materials, which could result in producing a pseudo-capacitance in addition to the electric double layer capacitance. Also introduction of nitrogen into the carbonaceous material could enhance the wettability of material, which might also improve the capacitance.

Structural changes in chlorine implanted poly(vinyl alcohol) films

Poly(vinyl alcohol) (PVA) films were implanted with chlorine ions in the fluence range of 10 13–10 16 ions/cm 2 on to PVA films of thickness 40 μm. FTIR spectroscopic study was carried out to see the structural changes. It was found that oxidation and carbonization progressively occurs in the film as a function of total fluence. The structural change occurs in the form of scission of C–C, C–OH and C–H bonds. SEM studies were carried out which revealed the surface defects in the form of cracks and etching. ESCA studies established that Cl + ions get deposited on the surface. Changes in the crystallinity were observed from the X-ray diffraction studies. The implanted chlorine ions enhanced the electrical conductivity by the order of 10 +2 S/cm.

Effect of Calcium Compounds in Lubrication Oil on the Frictional Properties of Fe2O3-Al2O3 Ceramics under Boundary Lubricating Conditions

Calcium sulfonate, a detergent/dispersant component in lubricating oils, greatly increase the friction coefficient of TiO2 added Fe2O3-Al2O3 ceramics under boundary lubricating conditions. ESCA studies showed that the average thickness of an organic thin film sticking to the surface of wear tracks was thicker than that away from wear tracks, and the concentrations of Ca, S and P were much higher in the wear track than those off the wear track, suggesting that most of the -SO3-Ca-OH groups in sulfonate remained unchanged. It is concluded that oil containing rich calcium compounds possibly formed a layer, blocking other oily additives with which the surface would have been wettable. This is assumed to increase the friction coefficient of the TiO2 added Fe2O3-Al2O3 ceramics.

Corrosion of 2205 duplex stainless steel in chloride medium containing sulfate-reducing bacteria

Sulfate-reducing bacteria (SRB) play significant role in the corrosion of stainless steels exposed to marine and soil environment. Sulfate reduction by bacterial species results in the production of H 2S, which can significantly influence the anodic and cathodic processes and ultimately enhances the corrosion of materials. In the present study, 2205 type duplex stainless steel (DSS) coupons in solution-annealed condition were exposed to chloride medium containing SRB species, Desulfovibrio desulfuricans, for 40 days and examined by microscopy. Etching of the duplex structure, pitting as well as crevice attack were noticed. Similar results were obtained by microscopic studies with coupons exposed for 14 days in medium containing SRB followed by anodic polarization. SEM studies, of crevices observed after anodic polarization, indicated that the attack was initiated at the grain boundaries and slowly encroached into austenite grains. The initiation of attack was also evident from AFM studies of coupon exposed under freely corroding conditions for 7 days. ESCA studies reveal that under anaerobic conditions of SRB growth sulfidation of passive film occurs. The modified passive film found to depolarize the cathodic reactions. The nature and mechanism of SRB attack on DSS and possibility of detection at early stages were discussed.

Passivation of vanadium in an equilibrium FCC catalyst at short contact-times

An equilibrium FCC (ECAT) sample containing 2800 ppm vanadium and 2500 ppm nickel was characterized by ESR and ESCA, and tested in a microactivity test (MAT) to study the effect of reductive pretreatments at elevated temperatures. From ESR and ESCA studies, it is found that the vanadium of the ECAT sample consists of V 4+ converting to a considerable part of V 3+ after a treatment with 5% H 2 in N 2 between 650 and 750 °C. Approximately, 40% of the vanadium exists as V 3+ after such a treatment at 700–750 °C. The reductive procedure led to an increase in the gasoline yield and a reduction in the coke yield in MAT when processing an atmospheric residue from the North Sea at 524 °C. It is shown that it is sufficient with a reduction/passivation time as short as 3 min in hydrogen at 689 °C to obtain a significant effect on the gasoline and coke yields. The results indicate that the main part of the observed reduction occurs in the outer layer of the particle at such short reduction times.

Hydroisomerization of ethylbenzene over bimetallic bifunctional zeolite catalysts: Maximization of xylene production

Zeolite-β and mordenite were impregnated with 0.1 wt.% Pt and varying (0, 0.1, 0.3, 0.5 wt.%) amount of Ni and reduced at 475 °C. The line broadening in the XRD patterns reveals that the increasing Ni addition decreases the crystallinity of zeolites. The catalysts were also characterized by TEM, ESCA and TPD of ammonia and pyridine. The TEM results show that the average metal particle size increases with increasing Ni addition. ESCA studies clearly points to the maximum percentage of Ni reduction in the Pt loaded zeolite-β and mordenite catalysts. The acidity measurements by both TPD of ammonia and pyridine adsorbed FT-IR spectroscopy show that the number of the acid sites of the catalysts decreases upon the addition of the Ni species. Hydroisomerization of ethylbenzene over the Pt–Ni loaded zeolite and mordenite was carried out in the temperature range 250–400 °C. It has been found that the addition of Ni up to 0.3 wt.% over 0.1 wt.% Pt loaded zeolite-β and 0.1 wt.% over 0.1 wt.% Pt loaded mordenite greatly enhances the ethylbenzene conversion, isomerization selectivity and sustainability of the catalysts. Further addition of Ni above the threshold value leads to a drastic reduction in the activity and isomerization selectivity. Zeolite-β-based Ni–Pt catalysts show higher activity and selectivity than mordenite-based catalysts under the optimized reaction conditions.

Ni–Pt/H–Y Zeolite Catalysts for Disproportionation of Toluene and 1,2,4-trimethylbenzene

Ni–Pt/H–Y zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250–400 °C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl2O4. A TEM study shows the formation of bimetallic (Ni–Pt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH3-TPD and pyridine-adsorbed FT–IR spectroscopy show the increasing occupation of acid sites by increasing nickel loading. The catalytic activity of Ni–Pt/H–Y zeolite and Pt/H–Y catalysts was compared and it was found that addition of Ni up to 0.3 wt.% increases conversion of toluene and 1,2,4-trimethylbenzene, disproportionation selectivity and sustainability of the catalysts. Further addition of Ni leads to a decrease in conversion and disproportionation selectivity and increasing dealkylated products, which may be due to the presence of unreduced Ni species and pore blockage by large-sized bimetallic particles formed.

Magnetic nanowires via template electrodeposition

The magnetic NiFex nanowires were prepared via template-guided electrodeposition. Anodized nanoporous aluminum was used as a template. The pore density and dimensions of alumina templates can be controlled by anodization conditions. Magnetic nanorods (or nanowires) with various aspect ratios were prepared by controlling the electrodeposition time. SEM and TEM micrographs revealed the wire and rod shape morphologies with 50 nm in diameter and 1.5 ~ 10 μm in length. Elemental analysis and ESCA studies suggested that NiFe3 magnetic alloy was formed. The X-ray diffraction pattern indicates that all the nanowires are stabilized in a BCC structure with a [1 1 0] texture oriented along the long axis of the nanowires. The magnetic measurement showed no hysteresis loops for the whole aspect ratios of the nanowires. Nevertheless, the magnetization is more temperature sensitive for nanowires with lower aspect ratio. This is caused by the fact that the easy magnetization axis is always parallel to the long axis of the nanowires.

Static TOF-SIMS Surface Analysis of a CCl2F2Activated Chromia Catalyst Used for a Cl/F Exchange Reaction

Static TOF-SIMS results strongly underpin earlier conclusions from ESCA, XANES, and tracer studies that the accumulation of fluorine and chlorine at the surface of chromia by a heterogeneous reacti...

Ni–Pt loaded silicoaluminophosphate molecular sieves for hydroisomerisation of n-heptane

Silicoaluminophosphates SAPO-5 and SAPO-11 were hydrothermally synthesised and loaded with 0.2 wt.% Pt and varying (0, 0.2, 0.4 and 0.6 wt.%) amount of Ni. The line broadening XRD and TEM analyses of Ni–Pt/SAPOs indicate that the average size of Ni–Pt particles increases with increasing Ni addition. The ESCA studies reveals that complete reduction of Ni is observed only up to 0.4 wt.% Ni addition. The acidity of the catalysts analysed by TPD of ammonia revealed that added Ni species occupy the acid sites of SAPOs. Catalysts 0.4 wt.% Ni and 0.2 wt.% Pt loaded SAPOs show enhanced activity in n-heptane conversion, isomerisation selectivity and stability of the catalysts. Further, the selectivity towards the multibranched (MTB) isomers by protonated cyclopropane (PCP) intermediate formation is enhanced over the above catalysts. SAPO-5 based Ni-Pt catalysts show better activity than SAPO-11 based catalytic systems.

Effects of the preparation methods of hydroxypropyl methylcellulose/polyacrylic acid blended films on drug release

Hydroxypropyl methylcellulose (HPMC)/polyacrylic acid (PAA) blended films were prepared under different conditions (i.e. temperature, solvent, and cross-linking agent). The effects of hydrogen-bonding interactions or a chemical reaction between the two-component polymers in the blended films on drug release were studied. Two model drugs were used for comparison: a water-soluble drug, dl-propranolol hydrochloride, and a lipophilic drug, ketoprofen. The H-bonding interaction of HPMC/PAA was found to be stronger in the blended films prepared from H2O than that from H2O/EtOH. However, the H-bonding effect between HPMC and PAA on drug release is indistinct. Chemical esterification of the carboxylic acid groups of PAA with the hydroxyl groups of HPMC was proposed from the solid-state NMR, ESCA, and FTIR studies when the blended films were dried at 110°C. This chemical reaction also resulted in insolubilization of the blended films.

Ni–Pt/H-Y Zeolite Catalysts for Hydroisomerization of n-Hexane and n-Heptane

Ni–Pt/H-Y zeolite catalysts with different Ni contents were prepared and applied to the hydroisomerization of n-hexane and n-heptane in the temperature range 225-375 °C. ESCA studies show the complete reduction of Ni species up to 0.3 wt% Ni addition over 0.1 wt% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl2O4. A TEM study shows the formation of bimetallic (Ni–Pt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH3-TPD and pyridine-adsorbed FTIR spectroscopy show the increasing occupation of acid sites by the added nickel when increasing the nickel loading. The catalytic activity of Ni–Pt/H-Y zeolite and Pt/H-Y catalysts was compared and it was found that addition of Ni up to 0.3 wt% increases the n-hexane and n-heptane conversion, multibranched isomer selectivity and sustainability of the catalysts due to better metal-acid synergism, complete reduction of Ni species and the formation of catalytically active Ni–Pt bimetallic particles. Further Ni addition leads to a decrease in conversion and multibranched isomer selectivity and an increase in the cracked products, which may be due to the presence of unreduced Ni species and pore blockage by larger-sized bimetallic particles formed.

Effect of carbon fiber surface functional groups on the mechanical properties of carbon–carbon composites with HTT

The present investigation describes the quantitative measurement of surface functional groups present on commercially available different PAN based carbon fibers, their effect on the development of interface with resol-type phenol formaldehyde resin matrix and its effect on the physico–mechanical properties of carbon–carbon composites at various stages of heat treatment. An ESCA study of the carbon fibers has revealed that high strength (ST-3) carbon fibers possess almost 10% reactive functional groups as compared to 5.5 and 4.5% in case of intermediate modulus (IM-500) and high modulus (HM-45) carbon fibers, respectively. As a result, ST-3 carbon fibers are in a position to make strong interactions with phenolic resin matrix and HM-45 carbon fibers make weak interactions, while IM-500 carbon fibers make intermediate interactions. This observation is also confirmed from the pyrolysis data (volume shrinkage) of the composites. Bulk density and kerosene density more or less increase in all the composites with heat treatment up to 2600 °C. It is further observed that bulk density is minimum and kerosene density is maximum upon heat treatment at 2600 °C in case of ST-3 based composites compared to HM-45 and IM-500 composites. It has been found for the first time that the deflection temperature (temperature at which the properties of the material start to decrease or increase) of flexural strength as well as interlaminar shear strength is different for the three composites (A, B and C) and is determined by the severity of interactions established at the polymer stage. Above this temperature, flexural strength and interlaminar shear strength increase in all the composites up to 2600 °C. The maximum value of flexural strength at 2600 °C is obtained for HM-45 composites and that of ILSS for ST-3 composites.

An ESCA study of the effectiveness of antiwear and extreme‐pressure additives based on substituted phosphorodithioate derivatives, and a comparison with ZDDP

AbstractAshless substituted dithiophosphoric acid derivatives (ADPs) are a new generation of multifunctional additives with promising antiwear (AW) and extreme‐pressure (EP) characteristics. Three such additives synthesised in the authors' laboratory have been evaluated for their AW and EP properties by standard four‐ball friction and wear tests. The friction‐reducing properties of these additives were compared with those of a commercial zinc dialkyldithiophosphate (ZDDP). It was found that the phosphorodithioate compounds studied here possessed excellent AW/EP properties. Their AW characteristics were found to be comparable to those of ZDDP at low loads. However, at higher loads they show inferior AW characteristics in comparison to ZDDP. Nevertheless, ADP derived from cashew nut shell oil had a higher load‐carrying capacity than ZDDP.The mechanism of the AW and EP behaviour exhibited by the different additives was investigated using X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and scanning electron microscopy (SEM) of the worn surfaces formed during friction. XPS and AES analyses of the worn surfaces reveal that the tribochemical film formed on the ADP‐tested surfaces consisted mainly of metal phosphates and only a small amount of metal sulphides, even though the ADPs contained twice the number of sulphur atoms than phosphorus atoms. The ZDDP‐tested surface showed a mixture of metal sulphides and metal phosphates. Alkylamino substitution appeared to have no significant effect on the AW/EP properties of the additive.XPS and AES analyses also revealed that the tribochemical film formed on an ADP‐tested surface was thicker than that present on the ZDDP‐tested surface at low loads, whereas at higher loads the reverse was true. The higher weld load obtained for the blend containing cashew nut shell oil‐derived ADP is attributed to the thicker adsorbed reaction film formed on the surface due to the long alkyl groups present in the original additive structure. Short‐chain alkyl groups, however, form only a thin adsorbed layer, which may get rubbed off during the friction at high load. The low sulphide formation on ADP‐tested surfaces was attributed to the absence of any metal atom in the additive, which would help in the formation of metal sulphides during tribofragmentation and further tribochemical reactions.