Presence Of Hydrochloric Acid Research Articles

Enantioselective Synthesis of Chiral 1,5-Benzodiazepin-2-ones by Pd-Catalyzed Asymmetric Hydrogenation and Reductive Amination.

The enantioselective synthesis of chiral 4-substituted 4,5-dihydro-1H-[1,5]benzodiazepin-2(3H)-ones via asymmetric hydrogenation catalyzed by the Pd/f-spiroPhos complex in the presence of hydrochloric acid as an additive has been developed, achieving excellent enantioselectivities and high turnover numbers, up to 99% ee and TON = 4600. More significantly, the asymmetric reductive amination of β-keto esters with 1,2-phenylenediamine has also been successfully realized to afford chiral 4-substituted 4,5-dihydro-1H-[1,5]benzodiazepin-2(3H)-ones with comparable enantioselectivities of up to 99% ee.

Removal of Heavy Metal Ions from Water Using Chelating Copolymer Resin-IV Derived from 2-Hydroxy, 4-Methoxybenzophenone, 1, 5-Diaminonaphthalene and Formaldehyde

The resin 2-H, 4-MBP-1,5-DANF-IV was synthesized by the condensation of 2-hydroxy, 4-methoxybenzophenone and1, 5-diaminonaphthalene with formaldehyde in the presence of hydrochloric acid as a catalyst. The resin was characterized by elemental analysis, infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and UV-Visible spectral studies. The chelation ion-exchange properties was studied for Ni2+, Cu2+, Co2+, Zn2+ and Pb2+ ions employing a batch equilibrium method. It was used to study of the selectivity of metal-ion uptake involving the measurements of the distribution of a given metal ion between the copolymer sample and a solution containing the metal ion. The study was carried out over a wide pH range and in media of various ionic strength.The resin depicted a higher selectivity for Cu2+ and Ni2+ ion than for Co2+, Zn2+ and Pb2+ ions.

A dual-mode fluorometric/colorimetric sensor for sulfadimethoxine detection based on Prussian blue nanoparticles and carbon dots.

A dual-mode (colorimetric/fluorescence) nanoenzyme-linked immunosorbent assay (NLISA) was developed based on Au-Cu nanocubes generating Prussian blue nanoparticles (PBNPs). It is expected that this method can be used to detect the residues of sulfonamides in the field, and solve the problem of long analysis time and high cost of the traditional method. Sulfadimethoxine (SDM) was selected as the proof-of-concept target analyte. The Au-Cu nanocubes were linked to the aptamer by amide interaction, and the Au-Cu nanocubes, SDM and antibody were immobilized on a 96-well plate using the sandwich method. The assay generates PBNPs by oxidising the Cu shells on the Au-Cu nanocubes in the presence of hydrochloric acid, Fe3+ and K3[Fe (CN)6]. In this process, the copper shell undergoes oxidation to Cu2+ and subsequently Cu2 + further quenches the fluorescence of the carbon point. PBNPs exhibit peroxidase-like activity, oxidising 3,3',5,5'-tetramethylbenzidine (TMB) to OX-TMB in the presence of H2O2, which alters the colorimetric signal. The dual-mode signals are directly proportional to the sulfadimethoxine concentration within the range 10- 3~10- 7 mg/mL. The limit of detection (LOD) of the assay is 0.023 ng/mL and 0.071 ng/mL for the fluorescent signal and the colorimetric signal, respectively. Moreover, the assay was successfully applied to determine sulfadimethoxine in silver carp, shrimp, and lamb samples with satisfactory results.

Leaching of catalyst platinum from cured silicone elastomers: A preliminary study for comparing reagents

Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly CC, but also CO or CN double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples was 12.6 ± 0.2 mg/kg for a commercial silicone impression material and 6.3 ± 0.5 mg/kg for a silicone baking mold, measured by graphite furnace atomic absorption spectrometry (GF-AAS). Samples were first frozen with liquid nitrogen to improve brittleness and then crushed with a simple food processor to obtain a silicone granule. Various acid mixtures, mainly based on sulfuric acid, were investigated as digestion methods in order to extract platinum from the silicone network. These had different effects on the dissolution behavior of silicone samples and the amount of platinum extracted in each case. The amount of platinum leached from the filtrate of the digested samples in each case was measured by ICP-OES to evaluate the efficiency of different leaching mixtures. In addition, the dissolved platinum species present in the solutions was identified by UV/VIS as tetrachloridoplatinate(II) complex. The best platinum leaching results so far were obtained with two methods, both of which used a leaching mixture based on sulfuric acid and hexamethyldisiloxane (M2). In the presence of hydrochloric acid, 9.6 ± 1.6 mg platinum/kg was leached from the silicone impression material and 4.2 ± 0.8 mg platinum/kg from the silicone baking mold. With the additional use of aqua regia instead of hydrochloric acid, 10.4 ± 2.8 mg platinum/kg was extracted from the silicone impression material and 4.8 ± 1.0 mg platinum/kg was extracted from the silicone baking mold. These methods were replicated with n = 3. Using statistical evaluation methods (F-test, t-test, and confidence interval), no significant difference was found between these two best methods. Recovery of platinum(0) from leach mixtures has not yet been achieved due to high dilution and very low platinum concentration in samples and will be part of another study.

Stimuli‐Responsive Emission from Hybrid Metal Halides

AbstractStimuli‐responsive photoluminescent (PL) materials have attracted considerable attention in recent years owing to their potential applications in anti‐counterfeiting, information encryption, and sensing. Further investigations of the transformation mechanism and potential applications of stimulus‐responsive PL materials are considerably important. In the current study, an organic–inorganic metal halide, C9H15N3SbCl5 ([C9H13N3]2+ is a 1‐(2‐pyridyl) piperazine cation) is obtained, which exhibits a 0D structure with P‐1 space group. At room temperature, when excited by UV light, the C9H15N3SbCl5 single crystals exhibit unimodal blue light emission at 405 nm, and grinding or hydrostatic pressure induces double‐peak emissions at 405 and 650 nm. Interestingly, double‐emission samples can be restored to single‐emission samples by short annealing or storage in air for 2 weeks, and this process is reversible. Luminescence response to mechanical stimuli can also be achieved in the presence of hydrochloric acid and water. Spectral analysis and the analysis of the microstructural changes revealed that the structural modifications of the inorganic group play a pivotal role in the response to the stimulus. Finally, a composite film device based on C9H15N3SbCl5 is prepared to demonstrate the potential of these smart materials in anti‐counterfeiting and sensing applications.

Development of a fluorometric Cuboni test for the semi-quantitative measurement of urinary estrogen levels and pregnancy detection in mares.

The aim of the present study was to develop a semi-quantitative urine pregnancy test for mares based on the Cuboni reaction and to verify the reliability of this test. The urine specimens were hydrolyzed by heating in the presence of hydrochloric acid. The resulting free estrogens were extracted from the urine matrix using toluene. Sulfuric acid was added to the toluene extract and the mixture was heated again. The lower layer in the test tube containing sulfuric acid was used for fluorescence measurements with excitation at 355 nm and measurement at 535 nm. The fluorometric Cuboni test revealed that the fluorescence counts in urine samples collected after the second trimester of gestation were significantly higher than those obtained from barren mares. The levels of estrogens, including equilin, estrone and estardiol-17β exhibited a dose-dependent increase in fluorescence counts, whereas other steroids, such as progesterone, testosterone, and cortisol, did not affect fluorescence. Heat treatment of urine samples with hydrochloric acid significantly increased the fluorescence counts in those collected after the second trimester of gestation compared to non-pregnant samples, implying the presence of large amounts of conjugated estrogens in pregnant mare urine. Fluorescence counts in urine samples obtained during pregnancy showed a positive relationship with estrone concentrations as measured by enzyme immunoassay. The results of the present study showed that the fluorometric Cuboni test facilitates urine fluorescence counts depending on the urinary estrogen content and is capable of discriminating between pregnancy and non-pregnancy states beyond the second trimester of gestation in mares.

Oxidative leaching of rhenium from grinding waste of rhenium-containing superalloys

The study investigated the feasibility of oxidative leaching rhenium in the presence of hydrochloric acid from machining waste (grinding waste) derived from products made of ZhS-32VI, a nickel-based heat-resistant alloy containing rhenium. This was achieved through agitation leaching process. The grinding waste fraction size of –0.071 mm, which accounted for the highest yield (49.2 wt.%), was utilized in the experiments. The rhenium leaching process was conducted in two variations: in the first option, grinding waste was mixed with a hydrochloric acid solution at ~100 °C, followed by the addition of hydrogen peroxide to the leaching solution after it had cooled; in the second option, leaching was performed using a hydrochloric acid solution with the gradual addition of hydrogen peroxide solution. The highest degree of rhenium leaching (91.0 %) was achieved in the first option. In this case, the initial concentration of hydrochloric acid was 8 M, and the molar ratio of the added reagents was ν(HCl): ν(H2O2) = 2.7 : 1.0. The kinetics of nickel leaching using a 6 M hydrochloric acid solution at 70 °C, with a solid-to-liquid phase ratio of 1 g : 50 ml, was also examined. The analysis of the kinetic data, processed using the “contracting sphere,” Ginstling–Brounshtein, and Kazeev–Erofeev models, indicates that the nickel leaching process occurs within the kinetic region. Additionally, the kinetics of rhenium leaching from the solid residue obtained after the hydrochloric acid leaching of nickel from grinding waste was investigated. Employing the same kinetic models to analyze the data, it was determined that the limiting stage of this process involves the diffusion of hydrogen peroxide within the rhenium-containing solid residue.

Synthesis and DFT calculations of mono‐ and di‐methylated cucurbit[7]uril based on imidazole derivatives

AbstractNowadays, functionalized cucurbit[n]urils are considered one of the most important examples of macromolecules and have attracted a lot of attention due to their potential applications in several sectors. In the present work monomethyl‐cucurbit[7]uril (3) was synthesized for the first time through facile synthetic route with high purity form by the reaction of monomethylglycoluril (3a‐methyltetrahydroimidazo[4,5‐d]imidazole‐2,5(1H,3H)‐dione) with glycoluril (tetrahydroimidazo[4,5‐d]imidazole‐2,5(1H,3H)‐dione) in the ratio of 1:6, respectively, and formaldehyde in the presence of hydrochloric acid as a catalyst for 24 h at 95°C through Mannich reaction. Moreover, dimethyl‐cucurbit[7]uril (5) was successfully synthesized through the reaction of dimethylglycoluril (3a,6a‐dimethyltetrahydroimidazo[4,5‐d]imidazole‐2,5(1H,3H)‐dione) with glycoluril (tetrahydroimidazo[4,5‐d]imidazole‐2,5(1H,3H)‐dione), following the same procedure as for the monomethyl‐cucurbit[7]uril. The chemical structures of the obtained compounds were established by mass spectrometry, NMR spectroscopy, and quantum‐chemical calculations.

Synthesis and characterization of Ce0.5Bi0.5VO4/rGO nanocomposite by sonochemical method for photocatalytic desulfurization of petroleum derivatives

In order to improve the desulfurization efficiency of petroleum derivatives, Ce0.5Bi0.5VO4/rGO nanocomposite was synthesized by sonochemical method. The prepared nanocomposites were characterized by XRD, FESEM, EDS, FT-IR, BET, and DRS analyses. XRD analysis shows that the synthesized nanocomposite is amorphous. FESEM images showed that nanostructures with a smaller particle size distribution were synthesized under optimal conditions, i.e. controlling the synthesis temperature between 0 and 5 °C. The results of desulfurization showed that nanocomposites containing reduced graphene oxide (rGO) have higher photocatalytic efficiency than pure samples, the main reason of which can be better charge separation in the samples through the π electron in the rGO structure. The highest amount of desulfurization of CeVO4/rGO, BiVO4/rGO, and Ce0.5Bi0.5VO4/rGO nanocomposites was 95.62, 91.25, and 96.38%, respectively, after exposure to UV light for 40 min. The enhancement of photocatalytic activity of Ce0.5Bi0.5VO4/rGO composite could be attributed to the efficient separation of electron–hole pairs and the inhibition of recombination. Desulfurization in the presence of hydrochloric acid and hydrogen peroxide increased the efficiency by 12%, which is a significant amount.

Opening band gap of multi-color graphene quantum dots using D-fructose as a green precursor

Graphene was successfully isolated by Professors Andre Geim and Kostya Novoselov in 2004. Graphene has attracted considerable research importance for its distinctive properties and potential applications. In this study, low-cost and high blue, yellow, and green photoluminescent (PL) graphene quantum dots (GQDs) were synthesized with deionized water (DI) and D-fructose as precursors by the dehydration method in the presence of hydrochloric acid. Transmission electron microscopy imaging proved the changing size of the GQDs and, by nuclear magnetic resonance spectroscopy, we observed the hydrogen-functionalized GQDs. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the synthesized GQDs were determined, and an energy bandgap was obtained from optical investigations.

Multifunctional polysaccharide structure as green adsorbent for efficient removal and preconcentration of chlorophenols from the aqueous medium: experimental and modeling approaches.

The growing concerns about water pollution have prompted researchers to explore new materials for remediating and purifying it. In recent years, there has been a focus on polysaccharides as eco-friendly polymers that exhibit high efficiency in removing chlorophenols from waste water. This study aims to develop a trifunctional polysaccharide structure using a biodegradable matrix. The chitosan/alginate-polyethyleneimine-phenyl-phosphonamidic acid (CHIT/ALG-PEIPPAA) matrix was employed for removing chlorophenols from water. The study carefully examined the impact of various physicochemical parameters such as pH, reaction time, chlorophenols concentration, temperature, and ionic strength to determine the optimal conditions for the adsorption process. Several techniques were used to confirm the morphology, physicochemical properties, structure, and functionalization of the polymer. Scanning electron microscopy (SEM) images revealed a heterogeneous morphology with agglomerates of different particle sizes, ranging from a few micrometers with irregular shapes. The FTIR spectrum and zeta potential characterization indicated the presence of hydrophilic groups and a highly positive charge (around 31.4 mV) on the surface of the CHIT/ALG-PEIPPAA adsorbent. The optimal pH for chlorophenols removal was found to be approximately 4.4. The kinetic data supported the pseudo-second-order kinetic model, which accurately described the adsorption behavior of both chlorophenol molecules. The fitting of the isotherm analysis revealed that the Langmuir model provided a better representation of the adsorption process. The maximum adsorption capacities for 4-chlorophenol and 2,4-chlorophenol were approximately 118 mg.g-1 and 249 mg.g-1, respectively. The calculated thermodynamic functions confirmed an exothermic and spontaneous adsorption process for chlorophenols, with ∆H values of -6.98 kJ.mol-1 and -2.74 kJ.mol-1 for 4-chlorophenol and 2,4-chlorophenol, respectively. The regeneration process of the CHIT/ALG-PEIPPAA adsorbent showed higher efficacy in the presence of hydrochloric acid (2.0 mol.L-1), resulting in up to 91% desorption of chlorophenols. The CHIT/ALG-PEIPPAA adsorbent demonstrated good reusability after regeneration, with only a slight decrease in extraction efficiency: 34.63% for 4-chlorophenol and 79.03% for 2,4-chlorophenol, under the same optimal conditions as the initial adsorption cycle.

Kinetic Model of the Process of Polycondensation of Concentrated Phenols of Coal Tar with Formaldehyde

Phenolformaldehyde resins were obtained by polycondensation of concentrated phenols with formaldehyde in the presence of hydrochloric acid. Concentration of phenols is carried out by treating the phenolic fraction of coal tar with an aqueous solution of sodium hydroxide followed by neutralization of water-soluble phenolates with hydrochloric acid. The kinetic dependences of resin yield and softening temperature on the duration of the process at 333, 353, and 373 K were obtained. The order of the reaction was determined and the effective activation energy of this process was determined by a graphical method. In the interval 333-373 K for polycondensation reactions, the equation of the dependence of the resin yield on the temperature and duration of the process was obtained.

Pair of (Hg2II)3L2 Chiral Cages and Successive Transformation into (HgII)3L2 Chiral Cages: Chiral DOPA Recognition via Chiral Cages.

Self-assembly of Hg(ClO4)2 with a pair of C3-symmetric chiral ligands, (1S,1'S,1″S,2R,2'R,2″R)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (s,r-L) and (1R,1'R,1″R,2S,2'S,2″S)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (r,s-L), produces a pair of chiral cages C4H8O2@[(Hg2II)3(ClO4)6(s,r-L)2(H2O)7](C4H8O2)7 and C4H8O2@[(Hg2II)3(ClO4)6(r,s-L)2(H2O)7](C4H8O2)7, respectively, via straightforward formation of the reduced Hg2II species with an inner cavity in which a single dioxane molecule is nestled. The pair of chiral cages are transformed into their downsized pair of cages, [Hg3II(ClO4)6(s,r-L)2] and [Hg3II(ClO4)6(r,s-L)2], respectively, in the presence of hydrochloric acid. The original chiral cages are more effective than the corresponding downsized cages for enantiorecognition of chiral 3,4-dihydroxyphenylalanine (DOPA) via the shifts of electrochemical oxidation potentials observed by linear sweep voltammetry (LSV) technique. Furthermore, the photoluminescence (PL) spectral shifts show that the downsized chiral cages significantly recognize chiral DOPA.

Controllable exothermic effect at the contact interface between liquid metal gallium and silver chloride

Liquid metal gallium (LM-Ga) has aroused wide interest due to fluidity and deformability in contrast with solid metal. Especially, an intriguing phenomenon was found that a large amount of heat was released after LM-Ga was mixed with silver chloride (AgCl) for a period of time, accompanied by the presence of hydrochloric acid (HCl). Through a series of characterization, it was discussed that the process was divided into three stages: slow heating, violent reaction and slow cooling, which involved four different reactions where a threshold temperature of 35 °C was required for this vigorous reaction to occur. Moreover, by adjusting the temperature and humidity, the occurrence time of the violent reaction could be extended or shortened, and the maximum temperature could be tunable in the range of 50–280 °C by changing the ratio of reactant. These mechanism of the reaction of LM-Ga with AgCl are expected to be applied to a series of fields such as tumor thermal ablation, antibacterial dressing and Ga2O3 optoelectronic devices.

Polypyrrole-Ag/AgCl Nanocomposite-Enabled Exhaled Breath-Acetone Monitoring Non-Invasive Biosensor for Diabetes Diagnostics

The state-of-the-art diabetes diagnosis is concerned with developing non-invasive nano-enabled exhaled breath-acetone detection strategies. This communication details the potential of polypyrrole(PPy)– Silver/silver chloride (Ag/AgCl) ternary nanocomposites (NCs) for monitoring low-trace of acetone in human breath for diabetes diagnosis. The PPy–Ag/AgCl NCs were synthesized through in situ chemical oxidative polymerization of aniline by silver nitrate in the presence of hydrochloric acid. The morphological analysis revealed the existence of spherical Ag/AgCl nanoparticles (diameter ∼50 nm) embedded in PPy matrix of nano fibrillar morphology (diameter ∼20 nm). The structural investigations confirm the co-existence of PPy, Ag and AgCl nanoparticles in the ternary nanocomposite. The NC exhibited manifold superior sensing performance towards low trace (as low as ∼1 ppm) of breath-acetone with excellent sensitivity (∼20%), prompt response (∼20 s), fast recovery (∼100s), linear detecting range, and high repeatability at room temperature compared to pristine PPy. It is attributed to synergistic effects in ternary NC due to physicochemical merits of all precursors. Moreover, it showed high stability and selectivity towards acetone in the presence of prominent interfering VOCs and varying humidity. It opens a new window for non-invasive, economic, energy-efficient and point-of-care sensors for diagnosing diabetes in humans and, revolutionizing clinical diagnostics and personal healthcare.

Effect of Titanium Dioxide Nanoparticles on the Properties of Poly(Vinyl Alcohol)/Silica Hybrid Films Prepared by the Sol-Gel Method

This work is focused on the preparation and characterization of poly (vinyl alcohol)/silica gel/Nano-TiO2, and the study of titanium dioxide (TiO2) nanoparticles (from 1 to 5%) on the properties of poly (vinyl alcohol) (PVA)/silica films. This new material was prepared by the sol-gel method using poly (vinyl alcohol) powder with Tetraethyl Orthosilicate (TEOS) as a precursor source of silica. TEOS was hydrolyzed and condensed in water and ethanol in the presence of hydrochloric acid (HCl) used as a catalyst. Fourier transform infrared (FT-IR), water absorption, water contact angle, ultraviolet-visible spectrometry (UV-VIS), and thermogravimetric analysis (TGA) were used to characterize the hybrid films obtained. The PVA/SiO2/Nano-TiO2 films were successfully synthesized. Owing to the FT-IR Analysis, the chemical bonds have clearly shown that the PVA backbone is linked to the (SiO2-TiO2) network. UV-VIS tests indicated that the hybrid films' UV shielding properties were drastically enhanced as a result of the addition of TiO2. According to the TGA tests, the hybrid films are more heat tolerant than neat PVA films. The water contact angle results revealed that TiO2 nanoparticles used as a doping compound possess an important influence on the hydrophilicity of PVA/SiO2 as thin films. The film's water resistance has also been enhanced.

Design and synthesis of TiO2/Ti3C2 composites for highly efficient photocatalytic removal of acetaminophen: The relationships between synthesis parameters, physicochemical properties, and photocatalytic activity

In this study, we report the potential of TiO2/Ti3C2 composite fabricated by oxidation of MXene for degradation of persistent organic pollutants. The effect of the synthesis conditions (time, temperature, and reaction environment) on the morphology, physicochemical properties, and photocatalytic activity was investigated. It was found that acetaminophen degradation was positively correlated with TiO2 content in the composite structure. Furthermore, the findings confirmed that the synthesis reaction environment strongly influenced the obtained materials photocatalytic activity. The TiO2/Ti3C2 composite obtained by solvothermal route in the presence of hydrochloric acid and ammonium fluoride exhibited the highest efficiency towards acetaminophen degradation than other composite materials, for which ACT removal reached 92 % within 60 min of irradiation under simulated solar light. The improved photocatalytic performance can be attributed to the presence of anatase-rutile polymorphs exposing highly active { 0 0 1} and { 1 0 1} facets coupled with MXene. Superoxide anion radicals and hydroxyl radicals played a major role in ACT degradation. Moreover, 3-hydroxyacetaminophen was detected as the first intermediate of ACT degradation, leading quickly to aromatic ring opening and production of aliphatic acids. Overall, this work provides an effective strategy for designing novel and efficient MXene-based photocatalysts for the degradation of emerging contaminants in water systems.

ISOLATION OF DIHYDROQUERCETIN AND ARABINOGALACTAN FROM LARCH WOOD WITH WATER-ETHANOL SOLUTIONS

Siberian larch wood (Larix sibirica Lebed.) contains such valuable biologically active substances as dihydroquercetin (DHQ) and arabinogalactan (AG), promising for the use in the pharmaceutical and food industries. An urgent task is to improve the methods of extraction isolation of these compounds from wood. In this work, we studied the possibility of simultaneous isolation of dihydroquercetin and arabinogalactan by extraction of larch wood with 5–25% aqueous ethanol solutions. It has been shown that by extracting wood with aqueous solutions with a low concentration of ethanol, it is possible to exclude the stage of separation of resinous substances from the target products of DHQ and AG. By experimentally optimizing of water-ethanol extraction process, it was shown that the highest yields of DHQ (1.8% mas.) and AG (18.0% mas.) were achieved by extraction of larch wood, crushed to particles of 1–3 mm in size, with a 15% ethanol solution for 2 hours. That the preliminarily mechanical treatment of larch wood allows to reduce the time of water-alcohol extraction to 30 minutes and to obtain DHQ and AG with high yields. The structure of DHQ and AG was confirmed by FTIR and NMR spectroscopy. Identification and purity of DHQ isolated from larch wood were confirmed by a photometric method using the reaction of cyanidin chloride formation when DHQ in heated in ethanol in the presence of hydrochloric acid.

Uniform oxidation in steam and nodular corrosion in gas phase of Zr-2.5Nb pressure tube material - effect of nature of initial oxide

Oxide layers of similar starting thicknesses were grown on Zr-2.5Nb pressure tube material in air at 400 °C and in steam at 400 °C and 10 MPa. Both types of oxides were subjected to (a) further long term exposure up to 85 days in steam at 400 °C and 10 MPa and (b) nodular corrosion in a gas mixture of CO2 and O2 in presence of a contaminant, HCl at 350 °C. The air oxidized material gave an advantage of no hydrogen pick-up to start with as against steam oxidized material. Both types of oxides exhibited similar uniform oxidation and hydrogen pick up behaviour during long term exposure in steam at 400 °C and 10 MPa. On the other hand, the air-formed oxide was found to be more resistant to nodular corrosion in a gas mixture of CO2 and O2 at high temperature in presence of hydrochloric acid. The superior nodular corrosion resistance was attributed to a thicker impervious layer in the oxide rendering better protection from local oxide damage. This has been explained through the global mechanism for nodular corrosion in gas phase. The usefulness of air oxidation in the final steps of pressure tube fabrication has been discussed as well.

Acid polymerized V2O5-PANI aerogels with outstanding specific shielding effectiveness in X, Ku and K bands

Only very few aerogels could show exceptional electromagnetic interference (EMI) shielding above 60 dB with broad bandwidth, without employing conductive metallic fillers. Herein, a meticulously designed 3-dimensional array of V2O5 nanofibers reinforced by polyaniline (PANI) in presence of hydrochloric acid is created, which is demonstrated as a green and economic strategy for developing novel ultra-lightweight electromagnetic (EM) wave absorbers. The composite aerogel showed exceptional shielding effectiveness of 68.1 dB in X-band, with a steady bandwidth. Even in the K band also, a stunning shielding performance with a maximum of 86.1 dB is displayed, which is translated to a record-breaking specific shielding efficiency of 2777.4 dB cm3/g. Our research findings demonstrate that hierarchically porous three-dimensional (3D) architecture realized through a meticulous control of acid polymerization can lead to impressively high shielding performance, even without employing costly metallic, carbonaceous or MAX phase fillers. These ultra-low dense, sturdy aerogels could be used as efficient electromagnetic interference shields in portable devices and avionic applications.