What is the role of “pressure” in the use of capillary and slit flows to determine the shear‐rate dependent viscosity of a viscoelastic fluid?

The purpose of this review article is to clear the confusion created by some investigators, who erroneously thought that the pressure transducers mounted on the wall of a capillary or slit die measured a quantity that could meaningfully be called “pressure,” accurately stated “indeterminate isotropic contribution to the total stress,” and then reported on the effect of “pressure” on the shear‐rate dependent viscosity of a viscoelastic fluid. On the other hand, reference to such a quantity is not needed to calculate the wall shear stress and thus shear viscosity in fully developed flow of incompressible, viscoelastic polymer melts in a capillary or slit die; instead only information on the gradient of the total wall normal stress is needed. Further, it is pointed out that much of the literature discussing “pressure shift factor” to describe the effect of “pressure” on the viscosity of polymer melts in flow through a capillary or slit die is based on an erroneous belief that there exists a physically meaningful isotropic “pressure” that can be measured. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

“On Water” Direct and Site‐Selective Pd‐Catalysed C?H Arylation of (NH)‐Indoles

This communication describes the development of a versatile catalytic system based on palladium(II) acetate/bis(diphenylphosphino)methane [Pd(OAc)₂/dppm] that works “on water” giving site‐selective C H arylation of (NH)‐indoles without protecting or directing groups. Remarkably, the control of regioselectivity was achieved by small changes in the “extra‐catalytic” base/halide partners. These innovative methodologies allow a high‐yielding access to both C2 and C3‐arylindoles, as well as 2,3‐diarylindoles, and display high chemo/regioselectivities and structural versatility with regard to either indole or aryl moieties.     

Analysis of the Parameters of the Mössbauer Spectra and the Spectra of Nuclear Quadrupole Resonance of the Superconducting Ceramic YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7</Subscript>

The parameters of the Mössbauer spectra on ⁶⁷Cu(⁶⁷Zn), ⁶⁷Ga(⁶⁷Zn) isotopes, and the data of nuclear quadrupole resonance on an ¹⁷O isotope are anlayzed, and the lattice gradient of the electric field for the crystal lattice YBa₂Cu₃O₇ is calculated. It is shown that these parameters correspond to the model when the hole is predominantly in the sublattice of the oxygen chain.     

Morphological and electrochemical properties of “polyelectrolyte multilayer films” made from polyaniline and ZnO nanoparticles: Deposition as films or as clusters?

Deposits made by the alternated deposition of polyaniline (PANI) and ZnO nanoparticles may offer interesting applications as nonvolatile memory devices owing to the specific properties of each constituent. The rectifying ratio of such devices may strongly depend on the PANI/ZnO interface and on the morphology of the (PANI/ZnO)_n or (PANI/ZnO)_n‐PANI films. In this article we show that even if the morphology of the PEI/PSS‐(PANI/ZnO)_n or of the PEI/PSS‐(PANI/ZnO)_n‐PANI films seems very heterogeneous on the basis of scanning electron micrographs, the deposits consist of clusters deposited on a continuous film. In addition, the deposits become impermeable to ferrocyanide anions after the deposition of n = 10 alternated deposition cycles, confirming the existence of a continuous and impermeable film below the observed clusters. Such deposits may find interesting properties as a nonvolatile memory device. POLYM. COMPOS. 34:1333–1341, 2013. © 2013 Society of Plastics Engineers     

Influence of the presence of bubbles on the parameters of crystal nucleation in the 26Li<Subscript>2</Subscript>O · 74SiO<Subscript>2</Subscript> glass

The crystal nucleation in the glass of composition (mol %) 26Li₂O · 74SiO₂ has been investigated in the cases of homogeneous and heterogeneous nucleation. Parameters of homogeneous nucleation, such as the stationary nucleation rate I _st, the time of nonstationary nucleation τ, and the crystal growth rate U, have been determined. The temperature dependences of these parameters have been constructed. The surface energy σ at the nucleus-glass melt interface has been determined, and its temperature dependence has been obtained. The surface energy σ has been evaluated using the graphical method for solving the transcendental equation derived by transforming the relationships for the stationary crystal nucleation rate and the time of nonstationary crystal nucleation. The critical nucleus sizes r* and the free energy of formation of the critical nucleus Φ* have been determined. The heterogeneous nucleation on bubbles specially produced in the glass has been studied. It has been demonstrated that the presence of bubbles in the initial glass does not affect the crystal growth rate and substantially changes the nonstationary nucleation rate. The largest contribution to the change in the nucleation rate is made by “active” bubbles (filled by water vapor) formed in the glasses synthesized with the use of hydrated silicon dioxide.     

Formation of the bubble structure in the 26Li<Subscript>2</Subscript>O · 74SiO<Subscript>2</Subscript> glass

The formation of a bubble structure in the glass of composition 26Li₂O · 74SiO₂ is investigated. The stable reproducible characteristics of the bubble structure are obtained, namely, dependences of the number of bubbles on the conditions of glass synthesis, i.e., the synthesis temperature, the synthesis time, and the type of initial reagents. It is shown that the number of bubbles decreases with an increase in the height of the sample (glass melt in the crucible), as well as with an increase in the synthesis temperature at a fixed synthesis time or with an increase in the synthesis time for each specific temperature. The bubble size distribution curves are obtained for all synthesis conditions. The reproducible bubble structure is determined for each layer of the glass sample, which is subsequently used in studying the kinetics of heterogeneous nucleation.     

LGE-201交联剂

<正> 要化学成分低分子量聚醚多元醇性状无色或淡黄色透明粘稠状液体。本品无毒、无臭、无腐蚀,非易燃、非易爆。相当于国外牌号 GE-250及 Voranol2025。规格外观透明无机械杂质羟值 mgKOH/g 670±25酸值 mgKOH/g <0.2水份％ <0.4粘度 25℃ P 3～4     

Reductive amination of monoethanolamine in the presence of the NiCo/BPO<Subscript>4</Subscript> · γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst: Process optimization based on a mathematical model and calculation of the basic design parameters of the reactor

Based on experimental kinetic data for the reductive amination of monoethanolamine in the presence of the NiCo/BPO₄ · γ-Al₂O₃ catalyst, a mechanism of this process is suggested and the corresponding kinetic model is constructed. A mathematical model of the reactor process is developed, and this model is used to solve three process optimization problems. Optimal values of operating parameters are found, and these values are used in the calculation of basic dimensions of a commercial-scale reactor. The flexible process design suggested allows all of the three process variants corresponding to the three optimization problems to be carried out.     

Synthesis of the study of solid solutions based on the ZrO<Subscript>2</Subscript>–HfO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript>(CeO<Subscript>2</Subscript>) system

The results of the studies of the conditions of the liquid-phase synthesis of highly dispersed xerogels with a low degree of agglomeration and precursor nanopowders (~10–12 nm) based on zirconium dioxide in the ZrO₂–HfO₂–Y₂O₃(CeO₂) system are presented. The thermal decomposition of xerogels and formation of crystalline solid solutions with the structure of fluorite are investigated. The optimal conditions for the solidification of nanodispersed powders for fabricating compact ceramics based on solid solutions of ZrO₂ and the physical–chemical properties of these ceramics are studied.     

Asymmetric Aza‐Morita?Baylis?Hillman Reaction of N‐Sulfonated Imines with Methyl Vinyl Ketone Catalyzed by Chiral Phosphine Lewis Bases Bearing Perfluoroalkanes as “Pony Tails”

In the aza‐Morita–Baylis Hillman reaction of N‐sulfonated imines (N‐arylmethylidene‐4‐methylbenzenesulfonamides and others) with methyl vinyl ketone (MVK), we found that in the presence of a catalytic amount of the chiral phosphine Lewis bases (R)‐(−)‐6,6′‐bis[tris(3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl)silyl]‐2′‐(diphenylphosphanyl)‐[1,1′]binaphthalenyl‐2‐ol LB2 and (R)‐(−)‐6,6′‐(3,3,4,4,5, 5,6,6,7,7,8,8,8‐tridecafluorooctyl) ‐2′‐(diphenylphosphanyl)‐[1,1′]binaphthalenyl‐2‐ol LB3 bearing two perfluoroalkane chains at 6,6′‐positions of the naphthalene framework, the corresponding adducts could be obtained in good yields with good to high ee (52–95% ee) at room temperature (15 °C) or low temperature (−20 °C) in THF, respectively. LB3 is more effective in this reaction than the previously reported original chiral phosphine Lewis base (R)‐(−)‐2′‐diphenylphosphanyl‐[1,1′]binaphthalenyl‐2‐ol LB1 .     

S201电动工具电刷

该电刷是哈尔滨电研究所最近研制成功的新产品。它的耐磨性能已经超过了法国克科伍德公司生产的2880F电刷及英国摩根公司生产的PM803电刷。 由于它具有噪音低、换向性能良好、对换向器磨损小和使用寿命长等特点,所以被广泛的应用在换向恶劣、振动大、体积小、重量轻、速度高、比输出大等轻便电器的单相交流整流子电动机上。如手电钻、抛光机、混合机、吸尘器、电动搬手和缝纫机等。     

WD-201高效能防锈油

金属表面或内腔的防锈一直是防腐领域的难题 ,不是防锈处理成本高 ,就是防腐效果不理想。由武汉现代工业技术研究院研制的ＷＤ - 2 0 1高效能防锈油不仅克服了以上问题 ,而且是无公害、无污染产品 ,并适用于黑色金属和有色金属的防锈。该防锈油特点是 :粘度小 ,涂、喷、刷等施     

Change of the thermal behavior of 55Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> ⋅ 45B<Subscript>2</Subscript>O<Subscript>3</Subscript> glass at annealing close to the vitrification temperature

The characteristic properties of relaxation processes for 55Bi₂O₃ ? 45B₂O₃ glass were described. The pattern of changes of the vitrification temperature (T _g ) is found to be quasi-periodic; the value of the endothermic effect near T _g (ΔC’ _p ) and the difference between the softening point and the vitrification temperature (T _m –T _g ) were determined. The temperature-time parameters of the transition from quasi-periodic to the continuous change of the properties were determined and an explanation of such behavior of the system was offered.     

WD-201高效能防锈油

金属表面或内腔的防锈一直是防腐领域的难题 ,不是防锈处理成本高 ,就是防腐效果不理想。由武汉现代工业技术研究院研制的 WD- 2 0 1高效能防锈油不仅克服了以上问题 ,而且是无公害、无污染产品 ,并适用于黑色金属和有色金属的防锈。该防锈油特点是 :粘度小 ,涂、喷、刷等施工方法都能涂布均匀 ,涂量少、效果好 ,只需沾上一薄层即有长期的防腐效果 ,对一些需防锈金属的内腔、表面、沟槽甚至缝隙部位均可得到保护。该技术广泛应用于机械、电子、仪表、汽车、军工、冶金等领域 ,是防止大气腐蚀的最主要的手段 ,是一般防锈油不具备的优良防锈…     

Effect of the thermal treatment on the phase composition of the surface of coatings based on Si–B–ZrB<Subscript>2</Subscript> and modified with ZrO<Subscript>2</Subscript> fibers

Coatings on graphite that are stable to oxidation and based on the silicon–boron–zirconium boride composite containing from 5 to 50% of fibrous zirconium dioxide as a modifying dopant have been produced by the suspension–annealing method. A nonporous layer is formed at the zirconium dioxide content ranging from 5 to 15%, while a porous layer is formed at its 50% content. A glass-forming melt, as well as zirconium dioxide and silicate, is formed during thermal treatment as a result of the chemical reactions with the oxygen in air. The zirconium silicate content increases, along with the modifier’s concentration and temperature.     

The Effect of Coating TiO<Subscript>2</Subscript> on the CO Oxidation of the Pt/γ-Alumina Catalysts

Abstract  

The effect of coating TiO₂ on the CO oxidation of the Pt/γ-alumina catalysts was observed through activity tests and surface characterization spectroscopy by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) experiments. XPS results evidenced the occurrence of different Pt²⁺ species and metallic Pt⁰ at the surface which suggest electron transfer of titanium (cation) to the platinum atom and the reduction of titanium (Ti⁴⁺ → Ti³⁺). FTIR analyses suggested oxygen spillover mechanism at the interface between titanium dioxide and platinum that may explain the catalytic activity of the platinum titania-supported catalysts. The apparent activation energy for the CO oxidation was 52.5 kJ/mol and similar for all catalysts. However, the frequency factor changed significantly, indicating interfacial phenomena caused by CO and oxygen adsorptions over TiO _x species and Al₂O₃ support with similar dispersions.     

Effects of the geometry and operating temperature on the stability of Ti/IrO<Subscript>2</Subscript>–SnO<Subscript>2</Subscript>–Sb<Subscript>2</Subscript>O<Subscript>5</Subscript> electrodes for O<Subscript>2</Subscript> evolution

Ternary IrO₂–Sb₂O₅–SnO₂ anode has shown its superiorities over IrO₂ and many other electrocatalysts for O₂ evolution, in terms of electrochemical stability, activity and cost. The performance of IrO₂–Sb₂O₅–SnO₂ anodes is affected by its electrochemical properties and operating conditions. In this paper, the electrochemical stability and activity of the Ti/IrO₂–Sb₂O₅–SnO₂ anodes prepared with three different geometries were investigated under different operating conditions. It was found that anodes with large mean curvature have high electrochemical stability. Although increasing temperature results in a decrease in the stability of Ti/IrO₂–Sb₂O₅–SnO₂, the anode with a mean curvature of 200 m⁻¹ still shows acceptable service life even at 70 °C. This tolerance of high temperature was attributed to the thermal expansion difference between the substrate and the coating layer, the redox window for Ir(V)/Ir(IV) conversion, and the redox reversibility of Sb and Sn species in the coating layer.     

Phase relationships in the Na<Subscript>2</Subscript>ZnP<Subscript>2</Subscript>O<Subscript>7</Subscript>–LiKZnP<Subscript>2</Subscript>O<Subscript>7</Subscript> system

The phase relationships in the Na₂ZnP₂O₇–LiKZnP₂O₇ system are studied. They are represented by a mixture of the starting components in the subsolidus region. The eutectic was found at a temperature of 640°C and composition of 0.5LiKZnP₂O₇. The phase formation of this system is compared with the previously studied NaKZnP₂O₇–LiKZnP₂O₇ system. It is shown that a structural factor affects the geometry of the state diagrams.