Alumina dissolution process to fabricate bimodal pore architecture alumina with superior green and sintered properties

Herein, a straightforward, adaptable, and cost-effective approach has been proposed to realize the concept of dissolution of alumina in acidic aqueous media to fabricate porous alumina showing exceptional green machining properties and exhibiting good thermomechanical properties through in situ generated blowing agents and thermo-foaming process. The process involves dissolving alumina in concentrated sulfuric acid to generate aluminum hydroxide and aluminum sulfate, which act as blowing agents to produce pores in the final structure through a decomposition process at elevated temperatures. By varying the concentration of deionized water and acidification using sulfuric acid, different alumina slurries are prepared. Sintering shrinkage is well countered through simultaneous consolidation and decomposition process during the heat treatment, and a minimum shrinkage of 0.88% is achieved. In addition to its pore-forming properties, aluminum sulfate also provides strong binding effects to green bodies, contributing to their exceptional green machining properties. The resulting porous alumina exhibits a green flexural strength of up to 17 MPa, making it capable of bearing loads and forces during green machining. The sintered porous alumina fabricated in the study has a porosity range of 34.43%–59.24% and a flexural strength of 27.84–53.21 MPa. The prepared porous alumina also exhibits satisfactory thermal resistivity, with a minimum thermal conductivity of 1.23 W/m K, and has intra/intergranular space in the nano range. The coexistence of a combination of bimodal pores in a single monolithic matrix makes it exceptionally porous and suitable for an extensive spectrum of applications.     

Metabolomic Profiling of Plasma from Melioidosis Patients Using UHPLC-QTOF MS Reveals Novel Biomarkers for Diagnosis

To identify potential biomarkers for improving diagnosis of melioidosis, we compared plasma metabolome profiles of melioidosis patients compared to patients with other bacteremia and controls without active infection, using ultra-high-performance liquid chromatography-electrospray ionization-quadruple time-of-flight mass spectrometry. Principal component analysis (PCA) showed that the metabolomic profiles of melioidosis patients are distinguishable from bacteremia patients and controls. Using multivariate and univariate analysis, 12 significant metabolites from four lipid classes, acylcarnitine (n = 6), lysophosphatidylethanolamine (LysoPE) (n = 3), sphingomyelins (SM) (n = 2) and phosphatidylcholine (PC) (n = 1), with significantly higher levels in melioidosis patients than bacteremia patients and controls, were identified. Ten of the 12 metabolites showed area-under-receiver operating characteristic curve (AUC) >0.80 when compared both between melioidosis and bacteremia patients, and between melioidosis patients and controls. SM(d18:2/16:0) possessed the largest AUC when compared, both between melioidosis and bacteremia patients (AUC 0.998, sensitivity 100% and specificity 91.7%), and between melioidosis patients and controls (AUC 1.000, sensitivity 96.7% and specificity 100%). Our results indicate that metabolome profiling might serve as a promising approach for diagnosis of melioidosis using patient plasma, with SM(d18:2/16:0) representing a potential biomarker. Since the 12 metabolites were related to various pathways for energy and lipid metabolism, further studies may reveal their possible role in the pathogenesis and host response in melioidosis.     

Processing of Piezocomposites by Fused Deposition Technique

Piezoelectric ceramic/polymer composites were made by a fused deposition (FD) technique, which is a solid-freeform fabrication (or layered manufacturing) technique where three-dimensional (3-D) objects are built layer by layer from a computer-aided design (CAD) file on a computer-controlled fixtureless platform. Indirect and direct FD methods were used to fabricate lead zirconate titanate (PZT)/polymer composites. For the indirect method, a CAD file for the negative image of the final part was created. A polymer mold was made via FD using a thermoplastic filament, and composite formation was completed via a lost mold technique. In the direct FD method, a thermoplastic polymeric filament that was filled with 50–55 vol% of PZT powder was used to form a positive image of the desired structure. Three-dimensional honeycomb ("3-D honeycomb") composites and "ladder" composites with 3-3 connectivity, which were formed via the FD technique, showed excellent electromechanical properties for transducer applications. In addition, the FD technique showed the ability to form composites with controlled phase periodicity, various volume fractions, and a variety of microstructures and macrostructures that are not possible with traditional composite-forming techniques.     

Synthesis and characterization of solid-phase super acid catalysts and their application for isomerization of n-alkanes

In the present work, first, the reference catalyst super acidic nanostructured sulfated zirconia (SZ) and super acidic nanostructured aluminum chloride impregnated sulfated zirconium oxides in mole ratios of Zr⁴⁺:Al³⁺ as 2:1 (ACSZ-1), 1:1 (ACSZ-2), and 1:2 (ACSZ-3) were synthesized by a simple precipitation method. The catalytic performance of these four catalysts were evaluated during the isomerization of n-hexane, n-heptane, and n-octane to their corresponding branched chain isomers at low temperature and pressure conditions. ACSZ-2 shows high activity toward isomerization of n-hexane, n-heptane, and n-octane into their corresponding branched chain isomers. The reference catalyst SZ was proved to be less effective compare to the other three synthesized ACSZ catalysts. Ammonia-temperature-programmed desorption of these two materials ensures that the super acidity of ACSZ-2 is higher than that of SZ. Atomic force microscopic and scanning electron microscopic pictures predict the nature of the surface of the catalysts. Transmission electron micrographic analysis indicates the presence of particle-bulks having average size 12–20?nm, presenting an amorphous nature and having no definite surface morphology of ACSZ-2. Fourier transform infrared provides an outline regarding different linkages and bond connectivities between atoms and groups in ACSZ-2 and SZ. After catalyst evaluation and characterization a probable reaction mechanism has been proposed theoretically. The reactivity and selectivity of ACSZ-2 and SZ as well as the order and activation energy of the isomerization reactions in presence of ACSZ-2 have been calculated. The use of ACSZ-2 is beneficial from the point of cost efficiency as well as its use is energy saving.     

Effect of Sol-Gel-Derived Nano-silica on the Properties of Natural Rubber-Poly Butadiene Rubber-Reclaim Rubber Ternary Blends/Silica Nanocomposites

Silica incorporation into natural rubber (NR)-polybutadiene rubber (PBR)-reclaim rubber (RR) ternary blend system was carried out by sol-gel technique at different temperatures. The effect of RR on silica reinforcement was studied for NR-PBR-RR blend systems. The physicochemical properties of sol-gel vulcanizates indicates that the reinforcing efficiency of the nanocomposites increases with increasing RR content. Sol-gel vulcanizates prepared at 50°C shows superior mechanical properties than others. The amount of silica incorporated by sol-gel technique was determined through thermogravimetry analysis, which indicates the increasing trend of thermal stability with silica content. SEM studies indicate the coherency and homogeneity in the NR-PBR-RR/SiO ₂ nanocomposites.     

ARTIFICIAL NEURAL NETWORKS: PRINCIPLE AND APPLICATION TO MODEL BASED CONTROL OF DRYING SYSTEMS - A REVIEW

Abstract

This paper reviews the developments in the model based control of drying systems using Artificial Neural Networks (ANNs). Survey of current research works reveals the growing interest in the application of ANN in modeling and control of non-linear, dynamic and time-variant systems. Over 115 articles published in this area are reviewed. All landmark papers are systematically classified in chronological order, in three distinct categories; namely, conventional feedback controllers, model based controllers using conventional methods and model based controllers using ANN for drying process. The principles of ANN are presented in detail. The problems and issues of the drying system and the features of various ANN models are dealt with upto-date. ANN based controllers lead to smoother controller outputs, which would increase actuator life. The paper concludes with suggestions for improving the existing modeling techniques as applied to predicting the performance characteristics of dryers. The hybridization techniques, namely, neural with fuzzy logic and genetic algorithms, presented, provide, directions for pursuing further research for the implementation of appropriate control strategies. The authors opine that the information presented here would be highly beneficial for pursuing research in modeling and control of drying process using ANN     

A Systematic Study of Mixed Surfactant Solutions of a Cationic Ester-Bonded Dimeric Surfactant with Cationic, Anionic and Nonionic Monomeric Surfactants in Aqueous Media

A novel cationic biodegradable dimeric (gemini) surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride (16-E2-16), containing an ester-linked spacer was synthesized. Its pure and mixed micellization properties with monomeric surfactants cetyl trimethyl ammonium chloride, cetyl pyridinium chloride, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, cetyl alcohol ethoxylate (20EO) and tert-octylphenol ethoxylate (9.5EO) were investigated by surface tension measurements at 30 °C. The critical micelle concentration (CMC) of 16-E2-16 is well below that of cetyl trimethyl ammonium chloride containing the same number of carbon atoms in the hydrophobic tail per polar head. At different mole fractions of the gemini surfactant, the CMCs of the gemini-conventional binary mixtures were determined and were found to be less than the ideal CMC values in all the cases indicating synergistic interactions. Aggregation number and Stern–Volmer constant, obtained by the fluorescence quenching technique, also support the synergistic behavior of the surfactant systems.     

Platinum on nitrogen doped graphene and tungsten carbide supports for ammonia electro-oxidation reaction

Ammonia electrooxidation reaction involving multistep electron-proton transfer is a significant reaction for fuel cells, hydrogen production and understanding nitrogen cycle. Platinum has been established as the best electrocatalyst for ammonia oxidation in aqueous alkaline media. In this study, Pt/nitrogen-doped graphene (NDG) and Pt/tungsten monocarbide (WC)/NDG are synthesized by a wet chemistry method and their ammonia oxidation activities are compared to commercial Pt/C. Pt/NDG exhibits a specific activity of 0.472 mA∙cm^–2, which is 44% higher than commercial Pt/C, thus establishing NDG as a more effective support than carbon black. Moreover, it is demonstrated that WC as a support also impacts the activity with further 30% increase in comparison to NDG. Surface modification with Ir resulted in the best electrocatalytic activity with Pt-Ir/WC/NDG having almost thrice the current density of commercial Pt/C. This work adds insights regarding the role of NDG and WC as efficient supports along with significant impact of Ir surface modification.     

Tensile ductility and necking in consolidated amorphous alumina

Oxide glass, one of the most transformative materials in the modern world, breaks easily under load due to its brittleness. Using classical molecular dynamics simulations, we prepared amorphous alumina by consolidating glass nanoparticles at room temperature. We showed that consolidated amorphous alumina exhibits work hardening ability, hence deforms homogeneously and fractures via necking under tension, while amorphous alumina obtained from the traditional melt-quench process fractures catastrophically due to severe shear banding. This finding suggests that if processed properly, amorphous oxides could deform and fracture like ductile metals, which will significantly expand the applications of oxide glasses into new areas where load bearing or mechanical reliability is necessary.     

Investigation of Nd3+ incorporation in Ce-rhabdophane: Insight from structural flexibility and occupation mechanism

LnPO₄ · 0.667H₂O rhabdophane has been considered as a potential material for the precipitation of actinides from radioactive waste liquid, owing to its outstanding characteristics of high actinide bearing and easy synthesis in acid solutions. However, a comprehensive understanding of the actinide occupation and the precipitation response of rhabdophane to remove actinides has yet to be established. In this study, the effect of ions concentration and pH values on the detailed precipitation reaction of Ce_xNd_1-xPO₄ · 0.667H₂O rhabdophane in acid solutions are systematically investigated. Some specific issues such as structural distortion and flexibility, and occupation mechanism are discussed by combining with experiments and density functional theory (DFT) calculation. The results reveal that ions concentration and pH values have a significant impact on the crystallization nucleation step before 12 h. The obtained removal rate of Nd³⁺ is more than 99% in pH 1–5 solutions with the ions concentration of 0.05–0.1 mol/L. Moreover, incorporating Nd in CePO₄ · 0.667H₂O rhabdophane will easily result in the lattice distortion in b-axis. DFT calculation and X-ray photoelectron spectroscopy (XPS) results reveal that Nd is preferentially incorporated in nonhydrated site to form a weaker binding energy of NdO₈ polyhedron.