Aromatic polyesters containing pendent 4-(phenylsulfonyl)phenyl groups: synthesis and characterization

A new bisphenol, 1,1-bis-[(4-hydroxyphenyl)-1-(4-phenylsulfonyl)phenyl)]ethane (DPSBP) was synthesized starting from diphenylsulfide and was characterized by spectroscopic methods. DPSBP was polycondensed with isophthalic acid chloride (IPC), terephthalic acid chloride (TPC) and a mixture of IPC and TPC (50:50 mol%) by phase-transfer catalysed interfacial polymerization method to obtain aromatic polyesters containing pendent 4-(phenylsulfonyl)phenyl groups. A series of copolyesters was also obtained by polycondensation of varying molar proportions of DPSBP and bisphenol-A (BPA) with TPC. (Co)polyesters exhibited inherent viscosities in the range 0.56–1.57 dLg^?1 and number average molecular weights (Mn) were in the range 28,650–80,230 g/mol. Polyesters dissolved readily in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran and aprotic polar solvents such as N-methylpyrrolidone, and N,N-dimethylacetamide. Tough, transparent and flexible films of polyesters could be cast from their chloroform solutions. X-Ray diffraction studies indicated amorphous nature of aromatic polyesters. Polyesters showed T_g values in the range 223–257 °C while T₁₀ values were in the range of 469–484 °C indicating their excellent thermal stability.     

Destruction of chlorinated organics by hydrotreatment using Ru/TiO2 catalyst

Catalytic hydrodechlorination reactions of p‐chloro‐m‐cresol (PCMC) and p‐chloroaniline (PCA) were investigated in a slurry reactor using a Ru/TiO₂ catalyst. The organic reaction intermediates, m‐cresol and aniline, were further converted into methylcyclohexanol and cyclohexylamine respectively. Kinetics of PCMC hydrogenation was studied over the ranges in temperature, 323–373 K, H₂ partial pressure, 0.34–1.38 MPa, PCMC concentration, 3.5–14 mM and catalyst loading, 0.1–2 kg/m³. The reaction orders with respect to PCMC and H₂ were evaluated as 0.5 and 0.8 respectively. It was found that aniline hydrogenation is the rate‐determining step in the hydrotreatment of PCA. Kinetics of aniline hydrogenation was studied at 343 and 363 K over the ranges in H₂ partial pressure, 0.34–1.38 MPa, aniline concentration, 5.4–21.5 mM and catalyst loading, 0.1–0.6 kg/m³. The reaction orders with respect to aniline and H₂ were found to be 1.3 and 1.0 respectively. © 2012 Canadian Society for Chemical Engineering     

Exceptionally High Dielectric Constant in Ceramic Pr2CuO4

The pristine layered cuprate Pr₂CuO₄ samples of >95% density were fabricated as thin disks. The samples, analyzed by X‐ray diffraction and Scanning electron microscopy, showed clean T′‐type phase with Rietveld refined lattice parameters a = b = 3.95805(±5) Å and c = 12.2262(±5) Å. The measured dielectric properties of the Pr₂CuO₄ ceramics, in the temperature range ?100°C–150°C and frequencies (ν) 0.1 Hz–1 MHz, showed extremely high ε_r′ > 10⁴ (above ?30°C), and dissipation (tan δ = ε_r′′/ε_r′) between 0.1 and 5 (for 500 Hz ≤ ν ≤ 1 MHz, and ?100 ≤ T ≤ 150°C). The ac conductivity of Pr₂CuO₄ ceramics ranged between 10^?6 and 10^?3 Scm^?1 for the measured frequencies and temperatures, and showed frequency‐dependent double power law behavior akin to a modified Jonscher's power law.     

Bubble columns for condensation at high concentrations of noncondensable gas: Heat‐transfer model and experiments

Carrier gas based thermodynamic cycles are common in water desalination applications. These cycles often require condensation of water vapor out of the carrier gas stream. As the carrier gas is most likely a noncondensable gas present in very high concentrations (60–95%), a large additional resistance to heat transfer is present. It is proposed to reduce the aforementioned thermal resistance by condensing the vapor–gas mixture in a column of cold liquid rather than on a cold surface using a bubble column heat exchanger. A theoretical predictive model for estimating the heat‐transfer rates and new experimental data to validate this model are described. The model is purely physics based without the need for any adjustable parameters, and it is shown to predict heat rates within 0 to ?20% of the experimental values. The experiments demonstrate that heat‐transfer rates in the proposed device are up to an order magnitude higher than those achieved in existing state‐of‐the‐art dehumidifiers. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1780–1790, 2013     

Resistive switching memory characteristics of Ge/GeOx nanowires and evidence of oxygen ion migration

The resistive switching memory of Ge nanowires (NWs) in an IrO_x/Al₂O₃/Ge NWs/SiO₂/p-Si structure is investigated. Ge NWs with an average diameter of approximately 100 nm are grown by the vapor–liquid-solid technique. The core-shell structure of the Ge/GeO_x NWs is confirmed by both scanning electron microscopy and high-resolution transmission electron microscopy. Defects in the Ge/GeO_x NWs are observed by X-ray photoelectron spectroscopy. Broad photoluminescence spectra from 10 to 300 K are observed because of defects in the Ge/GeO_x NWs, which are also useful for nanoscale resistive switching memory. The resistive switching mechanism in an IrO_x/GeO_x/W structure involves migration of oxygen ions under external bias, which is also confirmed by real-time observation of the surface of the device. The porous IrO_x top electrode readily allows the evolved O₂ gas to escape from the device. The annealed device has a low operating voltage (<4 V), low RESET current (approximately 22 μA), large resistance ratio (>10³), long pulse read endurance of >10⁵ cycles, and good data retention of >10⁴ s. Its performance is better than that of the as-deposited device because the GeO_x film in the annealed device contains more oxygen vacancies. Under SET operation, Ge/GeO_x nanofilaments (or NWs) form in the GeO_x film. The diameter of the conducting nanofilament is approximately 40 nm, which is calculated using a new method.     

Impact of electrically formed interfacial layer and improved memory characteristics of IrOx/high-κx/W structures containing AlOx,GdOx, HfOx,and TaOx switching materials

Improved switching characteristics were obtained from high-κ oxides AlO_x, GdO_x, HfO_x, and TaO_x in IrO_x/high-κ_x/W structures because of a layer that formed at the IrO_x/high-κ_x interface under external positive bias. The surface roughness and morphology of the bottom electrode in these devices were observed by atomic force microscopy. Device size was investigated using high-resolution transmission electron microscopy. More than 100 repeatable consecutive switching cycles were observed for positive-formatted memory devices compared with that of the negative-formatted devices (only five unstable cycles) because it contained an electrically formed interfacial layer that controlled ‘SET/RESET’ current overshoot. This phenomenon was independent of the switching material in the device. The electrically formed oxygen-rich interfacial layer at the IrO_x/high-κ_x interface improved switching in both via-hole and cross-point structures. The switching mechanism was attributed to filamentary conduction and oxygen ion migration. Using the positive-formatted design approach, cross-point memory in an IrO_x/AlO_x/W structure was fabricated. This cross-point memory exhibited forming-free, uniform switching for >1,000 consecutive dc cycles with a small voltage/current operation of ±2 V/200 μA and high yield of >95% switchable with a large resistance ratio of >100. These properties make this cross-point memory particularly promising for high-density applications. Furthermore, this memory device also showed multilevel capability with a switching current as low as 10 μA and a RESET current of 137 μA, good pulse read endurance of each level (>10⁵ cycles), and data retention of >10⁴ s at a low current compliance of 50 μA at 85°C. Our improvement of the switching characteristics of this resistive memory device will aid in the design of memory stacks for practical applications.     

Targeting and design of water networks for fixed flowrate and fixed contaminant load operations

Water-using processes are typically modeled as either fixed flowrate operations or fixed contaminant load operations. A new method for targeting the minimum freshwater and pinch in a single-contaminant water network is proposed, which can be applied to both kinds of operations. The method consists of plotting separate source and demand composites with flowrate as the horizontal axis and contaminant load unusually as the vertical axis. It is elegant, non-iterative, and can handle hybrid problems where both kinds of operations coexist.To design minimum freshwater networks for fixed flowrate problems, an algorithm is presented based on a newly developed principle of nearest neighbors. The principle simply states that the source streams to be chosen to satisfy a particular water demand must be the nearest available neighbors in terms of contaminant concentration.To design minimum freshwater networks for fixed contaminant load problems, the nearest neighbors algorithm is applied to process units that lie across the pinch. Units that lie entirely on one side of the pinch are satisfied by the cleanest source available on that side of the pinch. In other words, below-pinch units are satisfied by freshwater and above-pinch units are satisfied by the cleanest available stream above the pinch. Designs based on this methodology, apart from meeting the minimum freshwater target, also minimize the water flowing through the process units resulting in reduced network capital cost.     

Easy Access to 1‐Amino and 1‐Carbon Substituted Isoquinolines via Cobalt‐Catalyzed C?H/N?O Bond Activation

A green atom‐economical method for the synthesis of highly functionalized 1‐amino and 1‐carbon substituted isoquinolines from the reaction of N′‐hydroxybenzimidamides and aryl ketoximes, respectively, with alkynes via pentamethylcyclopentadienylcobalt(III)‐catalyzed C H/N O bond activation is described. The external oxidant‐free annulation reaction uses the =NOH moiety in N′‐hydroxybenzimidamides or N‐aromatic ketone oximes as the directing group and internal oxidant. This first row transition metal‐catalyzed annulation serves as an efficient alternative for the synthesis of isoquinolines, as water is the only by‐product and expensive noble metals such as rhodium(III), iridium(III), palladium(II), and ruthenium(II) are not required. The reaction proceeds via C H activation, alkyne insertion, reductive elimination, and N O activation.

     

A Novel RFET Sensor for Label-Free Biomolecule Detection

Silicon - In the current scenario, COVID-19 has created a havoc negative impact on the lives of the people, which have triggered the research interest on the design and development of sensitive,...