Low-Temperature Sintering of La(Ca)CrO3 Powder Prepared through the Combustion Process

Ultrafine La(Ca)CrO₃ (LCC) powder was prepared through the glycine–nitrate gel combustion process. It was shown for the first time that the use of relatively inexpensive CrO₃ as a starting material for chromium has potential for the bulk preparation of sinter-active LCC powder. As-prepared powder, when calcined at 700°C, resulted in LCC along with a small amount of CaCrO₄. The calcined powder was found to be composed of soft agglomerates with a particle size of ≈70–290 nm. The cold pressing and sintering of the calcined powder at 1200°C resulted in the mono-phasic La_0.7Ca_0.3CrO₃ with density ≈98% of its theoretical value. This is the lowest sintering temperature ever reported for La_0.7Ca_0.3CrO₃. The conductivity of the sintered La_0.7Ca_0.3CrO₃ at 1000°C was found to be ≈57 S/cm in air. The sintering and electrical behavior achieved for La_0.7Ca_0.3CrO₃ may find application as an interconnect material for high-temperature solid oxide fuel cells if problems with chemical expansion and poor conductivity in fuel can be overcome.     

Investigations of ruthenium pyrochlores as bifunctional oxygen electrodes

The lead–ruthenates oxides were synthesized and characterized by X-ray diffraction and thermogravimetric analysis. Compounds in which part of the ruthenium is substituted with iridium were also prepared. The performance of these oxides for oxygen reduction and generation reactions was investigated in porous, gas-fed electrodes. The performance of pyrochlore oxide electrodes was shown to be excellent for oxygen reduction and generation reactions. It was observed that iridium substituted pyrochlores exhibit somewhat better performance for oxygen reduction than the unsubstituted compounds. The anodic corrosion resistance of pyrochlore-based porous electrodes was improved by using two different anionically conducting polymer overlayers, which slow down the diffusion of ruthenates and plumbate out of the electrode. The use of the conducting polymer overlayers resulted in improved performance of these electrodes.     

Corrosion inhibition behaviour of thiourea derivatives in acid media against mild steel deterioration: An overview

This paper summarizes the inhibitor activity of various reported thiourea derivatives in acid media used against the deterioration of mild steel. Acid solutions have been extensively employed in manufacturing and many industrial processes for pickling and removal of undesirable scale. Mild steel is highly susceptible to corrosion in such aggressive acid media. The additives such as inhibitors are widely employed in those cases to reduce the extent of corrosion as much as possible. The survey of literature on organic inhibitors clearly indicates the potential usage of thiourea derivatives as inhibitors of mild steel corrosion. The influence of physical-chemical properties on the inhibition activity of thiourea derivatives has been discussed. This information is highly useful for different industrial applications where good performing inhibitors are being required for protecting mild steel from aggressive acid media.     

Investigation of Pt and Pd Modified WO<Subscript>3</Subscript> and ZnO Based Thin Film Sensors for Ethanol Sensing

Ethanol sensors based on different WO₃ and ZnO structures are studied in the present work. The XRD and SEM processes are used to characterize the sensing layer’s surface morphology which reveals the presence of nanoparticle in sensing layer. Further reducing the nanoparticle diameter by the addition of palladium (Pd) and platinum (Pt) for both the sensors (ZnO and WO₃) gives good results on sensitivity, operating temperature, response time and recovery time. Nanoparticle diameter for undoped WO₃, Pd-modified WO₃ and Pt-modified WO₃ based sensors is 11.8, 6 and 5.4 nm, whereas nanoparticle diameter for undoped, Pd-modified and Pt-modified ZnO based sensors is 20, 14 and 11 nm, respectively. Analysis of dynamic response of the sensors when exposed to different concentrations of ethanol vapour (from 500 to 10,000 ppm) and various temperatures indicate the improvement in sensitivity up to 77.2% for WO₃ and 74.6% for ZnO based sensors.     

Improvement in shape memory in magnesium niobate modified PZST

A modified lead zirconate stannate titanate system (PZST) has been studied for shape memory effect. Addition of magnesium niobate (MN) slows down the dipole relaxation process, leading to increased (∼3-fold improvement) remnant strain in the PZST system (0.99PZST–0.01PMN). Room temperature X-ray diffraction patterns before poling (antiferroelectric (AFE) tetragonal) and after poling (ferroelectric (FE) rhombohedral), clearly demonstrate that the transition to the ferroelectric phase is stable even in the absence of any electric field. A small applied electric field (∼1.7 kV/cm) in the opposite direction was required to bring the sample back to its original shape. Field-induced strain butterfly loops taken at 50 Hz show that the material response time is quite small.     

In situ observation of Cu segregation and phase nucleation at a solid–liquid interface in an Al alloy

This paper presents a systematic study comparing experimental in situ transmission electron microscopy observation of microstructural and compositional evolution with complementary thermodynamic calculations, to better understand the redistribution of solute elements and the nucleation behavior of different phases in a commercial Al-alloy powder (AA390). The results show that Cu segregation to the solid Si–liquid Al interface, as well as the significant undercooling achieved in the liquid under non-equilibrium conditions because the Al phase cannot nucleate homogeneously, play a important roles in nucleating Al₂Cu at the interface prior to the Mg₂Si phase in the alloy. Although Cu segregation can occur at various locations along the interface, the Al₂Cu phase appears to preferentially nucleate at a high-index Si–liquid interface as opposed to a low-index one. The Cu concentration during segregation remains essentially constant with time, indicating that the observed segregation behavior is a thermodynamic and not a kinetic phenomenon. These in situ observations and complementary thermodynamic calculations substantially enhance our understanding of potential crystal nucleation and growth processes.     

Performance of cold sprayed Ni‐20Cr and Ni‐50Cr coatings on SA 516 steel in actual industrial environment of a coal fired boiler

Power plants are one of the major industries suffering from severe erosion–corrosion (E‐C) problems resulting in substantial losses. One way of tackling this problem is by the use of thermal spray coatings. In the current investigation a new emerging technique i.e. cold spray coating process was used to deposit Ni‐20Cr and Ni‐50Cr powder on SA 516 (grade 70) boiler steel. The bare as well as the coated steels were subjected to cyclic experimental studies, in the superheater zone of a coal fired boiler. Weight change, thickness loss, XRD, FE‐SEM/EDS and X‐ray mapping techniques were used to analyse the eroded‐corroded specimens. The uncoated steel showed weight gain after exposure in the actual boiler environment, whereas, for the coated steels there was initial weight loss followed by negligible weight change. Based upon thickness loss data the cold‐sprayed Ni‐50Cr coating was found to provide better E‐C resistance than the Ni‐20Cr coating.     

Nano fibrillated cellulose-based foam by Pickering emulsion: Preparation,characterizations, and application as dye adsorbent

An ecofriendly and biodegradable porous structure was prepared from drying aqueous foams based on nano fibrillated cellulose (NFC), extracted from softwood pulp by subcritical water/CO₂ treatment (SC-NFC). The primary aim of this work was to use the modified SC-NFC as stabilizer for a water-based Pickering emulsion which upon drying, yielded porous cellulosic materials, a good dye adsorbent. In order to exploit the carboxymethylated SC-NFC (CMSC-NFC, with a degree of substitution of 0.35 and a charge density of 649 μeqv/g) as a stabilizer for water-based Pickering emulsion in subsequent step, an optimized quantity of octyl amine (30 mg/g of SC-NFC) was added to make them partially hydrophobic. A series of dry foam structures were prepared by varying the concentrations of treated CMSC-NFCs and 4 wt% was found to be the optimum concentration to yield foam with high porosity (99%) and low density (0.038 g/cc) along with high compression strength (0.24 MPa), superior to the conventionally extracted NFC. The foams were applied to capture as high as 98% of methylene blue dyes, making them a potential green candidate for treating industrial effluent. In addition, the dye adsorption kinetics and isotherms were found to be well suited with second order kinetics and Langmuir isotherm models.     

Proton Nuclear Magnetic Resonance-Based Method for the Quantification of Epoxidized Methyl Oleate

Epoxidized methyl esters (EMO) with their high oxirane ring reactivity, acts as a raw material in the synthesis of various industrial chemicals including polymers, stabilizers, plasticizers, glycols, polyols, carbonyl compounds, biolubricants etc. EMO has been generally quantified by the gas chromatography (GC) and high-performance liquid chromatography (HPLC) techniques. Taking into the account of the limitations of these techniques, two qHNMR-based equations have been proposed for the quantification of EMO in the mixture of EMO and methylesters (MO). The validity of the proposed method was determined using standard mixtures of MO and EMO having different molar concentrations. The developed equations have been applied on the samples of EMO prepared from oleic acid in two-step process viz., esterification followed by epoxidation. The qHNMR-based EMO quantification showed acceptable agreement with the results obtained from HPLC analysis.