Magnesia induced coagulation of aqueous PZT powder suspensions for direct coagulation casting

Coagulation characteristics of poly(acrylate) dispersed PZT powder suspensions by MgO coagulating agent have been studied. The PZT powder suspensions undergoes coagulation at MgO concentrations much lower than the equivalent amount to react with the dispersant indicating a major shift in the coagulation mechanism from the corresponding alumina powder suspensions. Unlike in alumina powder suspensions, the Mg²⁺ ions generated from the MgO reacts with the ammonium poly(acrylate) adsorbed on particle surface that result in cross-linking of PZT particles by Mg²⁺ through the ammonium poly(acrylate) molecules. The particle bridging induces faster coagulation of the slurry cast in a mould as required for an ideal DCC process. The compressive strength and stability against oscillatory stresses of the wet-coagulated bodies increased with increase in number of cross-links between the particles. The PZT green bodies prepared by the DCC process sintered to near theoretical density and the MgO added as coagulating agent (～0.1 wt%) had only minor influence on its piezoelectric characteristics.     

Delamination of Pearlitic Steel Wires: The Defining Role of Prior-Drawing Microstructure

This article reports the occasional (< 10 pct of the actual production) delamination of pearlitic wires subjected to a drawing strain of ~ 2.5. The original wire rods which exhibited post-drawing delamination had noticeably lower axial alignment of the pearlite: 22 ± 5 pct vs 34 ± 4 pct in the nondelaminated wires. Although all wires had similar through-thickness texture and stress gradients, delaminated wires had stronger gradients in composition and higher hardness across the ferrite–cementite interface. Carbide dissolution and formation of supersaturated ferrite were clearly correlated with delamination, which could be effectively mitigated by controlled laboratory annealing at 673 K. Direct observations on samples subjected to simple shear revealed significant differences in shear localizations. These were controlled by pearlite morphology and interlamellar spacing. Prior-drawing microstructure of coarse misaligned pearlite thus emerged as a critical factor in the wire drawing-induced delamination of the pearlitic wires.     

Defining the Post-Machined Sub-surface in Austenitic Stainless Steels

Metallurgical and Materials Transactions A - Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling....     

Preparation of PZT Microtubes by Slip Casting on Vermicelli,Followed by In Situ Polymerization

Slip casting of lead zirconate titanate (PZT) slurries of higher solids loading (48.8–51.6 vol%) prepared in a urea–formaldehyde (UF) monomer solution on vermicelli of ∼1000 μm diameter has been studied to prepare PZT microtubes with a higher wall thickness (200–960 μm) in a lower dipping time (0.5–4.0 min) to facilitate faster production and lower failure during drying and vermicelli burnout. Polymerization of the UF monomer by exposing the PZT slurry-coated vermicelli to HCl gas provides good strength and stability to the coating. The dielectric and piezoelectric properties of the microtubes compare well with the properties of PZT-5H ceramic compositions.     

Robust dynamic state estimation of power systems based onM-Estimation and realistic modeling of system dynamics

This paper presents a new scheme of dynamic state estimation, utilizing a statistical approach called the M-Estimation to resolve the filtering problem robustly. In the prediction step, realistic treatment of system dynamics based on nodal analysis produces an efficient state prediction method. The proposed Robust Realistic Dynamic State Estimation (RRDSE) has been tested on 5-bus, 14-bus, and 30-bus test systems and the results are presented. The error analysis presented reveals the superiority of the proposed RRDSE particularly when the system measurements are under bad-data condition     

Synthesis of pyrochlore free PMN-PT powder by partial oxalate process route

Pyrochlore phase free PMN-PT powder of morphotrophic phase boundary (MPB) composition has been prepared using the partial oxalate method. The synthesis process has been optimized by thorough characterization of the intermediate compounds such as columbite and (Mg_1/3Nb_2/3)_0.675 Ti_0.325)O₂ by XRD analysis, particle size analysis, surface area measurement and morphological studies. Lead oxalate produced by in situ precipitation in a suspension of (Mg_1/3Nb_2/3)_0.675Ti_0.325)O₂ powder expected to coat on the particle surface, which improved the homogeneity of the precursors and resulted in the formation of pure PMN-PT phase during calcination at 750 °C. The PMN-PT powder contains more than 95% submicron particle with D₅₀ 0.4 μm. The process eliminates the formation of detrimental pyrochlore phase from the PMN-PT powder.     

Combined effects of Brownian motion and thermophoresis parameters on three-dimensional (3D) Casson nanofluid flow across the porous layers slendering sheet in a suspension of graphene nanoparticles

Neural Computing and Applications - The present study emphases on the three-dimensional (3D) Casson nanofluid flow across a slendering sheet in porous layers by considering the thermophoresis and...     

Microstructural Engineering in Eutectoid Steel: A Technological Possibility?

Eutectoid wire rods were subjected to controlled thermo-mechanical processing (TMP). Both increased cooling rate and applied stress during the austenite-to-pearlite decomposition produced significant changes in the microstructure: major increases in the pearlite’s axial alignment and minor decreases in the interlamellar spacing. The pearlite alignment was correlated with changes in the ferrite crystallographic texture and the state of residual stress. Microstructural engineering, improved axial alignment of pearlite, through controlled TMP gave a fourfold increase in torsional ductility. TMP of eutectoid steel thus appears to have interesting technological possibilities.     

A nitrogen rich Ni(II)–dithiolate system exhibiting acid–base behavior: Synthesis,supramolecular structure and spectroscopy of [Bu4N]2[NiII(ppdt)2] (ppdt = pyrido[2,3-b]pyrazine-2,3-dithiolate)

The compound [Bu₄N]₂[Ni(ppdt)₂] (1) (ppdt = pyrido[2,3-b]pyrazine-2,3-dithiolate) has been synthesized, starting from pyrido[2,3-b]pyrazine-2,3-dithiol, nickel chloride and tetrabutylammonium bromide in methanol. Compound 1 crystallizes in P2₁/c space group (monoclinic system). Its crystal structure is characterized by interesting C–H?S and C–H?N supramolecular weak interactions. Its solution state has been described with acid–base (protonation–deprotonation) behavior, that has rarely been investigated for a metal–dithiolene system. Compound 1 is first instance of a metal–dithiolene compound that has three ring nitrogen on each dithiolate ligand. The pH dependent changes in the charge-transfer absorption band are attributed to the protonation on an imine nitrogen of the ppdt ligand. The complex is electrochemically quasi-reversible with an oxidation potential of E_1/2 = +0.46 V vs. Ag/AgCl in methanol.     

A semi-supervised probabilistic model for clustering large databases of complex images

Image content clustering is an effective way to organize large databases thereby making the content based image retrieval process much easier. However, clustering of images with varied background and foreground is quite challenging. In this paper, we propose a novel image content clustering paradigm suitable for clustering large and diverse image databases. In our approach images are represented in a continuous domain based on a probabilistic Gaussian Mixture Model (GMM) with the images modeled as mixture of Gaussian distributions in the selected feature space. The distance metric between the Gaussian distributions is defined in the sense of Kullback–Leibler (KL) divergence. The clustering is done using a semi-supervised learning framework where labeled data in the form of cluster templates is used to classify the unlabelled data. The clusters are formed around initially chosen seeds and are updated in the due course based on user inputs. In our clustering approach the user interaction is done in a structured way as to get maximum inputs from the user in a limited time. We propose two methods to carry out the structured user interaction using which the cluster templates are updated to improve the quality of the clusters formed. The proposed method is experimentally evaluated on benchmark datasets that are specifically chosen to include a wide variation of images around a common theme that is typically encountered in applications like photo-summarization and poses a major semantic gap challenge to conventional clustering approaches. The experimental results presented demonstrate the effectiveness of the proposed approach.