Acidic properties of vanadium oxide on magnesium fluoride

Vanadium oxides supported on magnesium fluoride obtained by the impregnation and the precipitation-deposition method have been studied by IR spectroscopy. The adsorption of pyridine indicated the presence of Lewis acid centers on the impregnated samples, whereas on the samples prepared by precipitation both Lewis and Brønsted centers have been observed. From the adsorption coefficients of the 1540 cm^–1 (Brønsted site) and 1445 cm^–1 (Lewis site) bands the numbers of both sites have been estimated. The hydroxyl groups bound in the chains of the (VO₃)_n tetrahedra or those in the trigonal pyramids VO₅ are believed to be responsible for the protonic centers, whereas the aprotonic centers occur at the ionic vanadium with coordinatively unsaturated spheres.     

Influence of size and volume share of WC particles on the properties of sintered metal matrix composites

Steel matrix composites are being increasingly investigated because of their wear and corrosion properties, allowing their wide application in various industrial sectors. The interaction of tungsten carbide (WC) with the steel matrix, including an analysis of its volume share and particle size, is crucial in determining the resistance to wear and corrosion of the metal matrix composite (MMC). However, there is little information in the literature about sintered MMCs based on low-alloy steels. This paper presents the results of an analysis of the influence of the volume share of WC (5?vol.% and 20?vol.%) and carbide particle size (0.7?µm and 5.0?µm) on the resistance to abrasion of a friction pair: sintered composite and bearing steel, analysed using two rotational speeds (0.02?m/s and 0.2?m/s). Moreover, the resistance to corrosion in 3.5% NaCl solution is also characterized. It is shown that both the volume share and the size of the WC particles used as reinforcement of the steel matrix have a significant impact on the densification behaviour as well as the resistance to abrasive wear and corrosion of sintered MMCs based on low-alloy steel.     

Preparation and characterization of membranes obtained from blends of acrylonitrile copolymers with poly(vinyl alcohol)

New microfiltration and ultrafiltration membranes were obtained using acrylonitrile‐vinyl acetate copolymers in mixture with poly(vinyl alcohol) (PVA). Thus, a blend polymer solution was prepared in dimethylsulfoxide (DMSO) and used to obtain bicomponent polymer membranes by phase inversion. The rheological behavior of the DMSO polymer solutions was, mostly, dilatant at low shear gradients and pseudo plastic with quasi Newtonian tendency at higher gradients. Membranes were characterized by Fourier transform infrared spectrometry (FTIR), optical microscopy, atomic force microscopy, thermal gravimetric analysis‐differential thermal gravimetry, and pure water flux (PWF). FTIR spectra displayed the characteristic bands for acrylonitrile, vinyl acetate, and PVA. The morphology and the porosity can be tailored by the preparation conditions. PVA allows controlling the size of the pores and enables, in principle, to use the resulted membranes as supports for enzyme immobilization. PVA content influences the thermal stability. PWF values depend on the copolymer, on the content in PVA, but also on the coagulation bath composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41013.     

Porous epoxies by reaction induced phase separation of removable alcohols: Control of spheroidal pore size by mass fraction,cure temperature,and reaction rate

The mechanical behavior of acrylonitrile butadiene rubber (NBR) – organo modified layered silicate was modeled using Design of Experiments (DoE). Response surface methodology (RSM), a DoE tool was used to optimize the formulations for optimal performance of the nanocomposites. A Box‐Behnken design with three factors and three levels was used to model the relationship between mechanical properties and levels of ingredients. The factors studied for the design are silica content, nanoclay loading and vulcanization system. The nanocomposites were evaluated for tensile strength, modulus, elongation at break and hardness. The effect of heat aging on mechanical properties was also studied. The predicted properties of the nanocomposites are in good agreement with the experimental results, which confirmed the prognostic ability of response surface methodology. The model equations were used to generate response surfaces and contour plots to study the interaction between the variables. The contour plots were overlaid within the applied constraints to identify the required combination of variables that gives the optimum performance for the nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Tensile and fracture behaviour of PP/wood flour composites

Polypropylene/wood flour composites with different fibre content were prepared. The effect of composition and the incorporation of maleinated polypropylene on the materials tensile and fracture and failure behaviour was investigated. Reliable fracture toughness data that will be useful for structural applications were obtained. In unmodified composites an increase in Young´s modulus was found with the addition of wood flour to PP, whereas tensile strength, strain at break and fracture toughness were observed to decrease as fibre content increased. The presence of MAPP was beneficial to tensile strength and ductility and had no significant effect on fracture toughness, as a result of enhanced fibre dispersion within the matrix and improved interfacial adhesion. Although reduced ductility and toughness were observed for the composites respect to the matrix, in the case of modified composites, environmentally friendly stiffer materials were obtained with cost saving without sacrificing strength.     

Catalytic reduction of no over the modified MFI metallosilicalites

The metallosilicalites (MFI) containing copper ([Cu,Si]), zinc ([Zn,Si]) or both elements ([Cu,Zn,Si]) were prepared and modified as potential catalysts for the NO reduction with propene. The H-[Cu,Si] samples showed the highest activity, which was initially comparable to that of Cu-ZSM-5, but contrary to the latter, it increased with time. The framework Cu or Cu released from the framework probably act as active sites.     

MgF2 as a non‐conventional catalytic support. Surface and structure characterization

The paper presents results of studies on the structure of MgF₂ support, performed using various experimental methods such as XRD, IR, temperature‐programmed techniques and low‐temperature nitrogen adsorption. MgF₂ is characterized by an XRD spectrum with over 40 patterns, which enabled us to follow the changes in crystallite size and internal tension caused by the thermal treatment. TPE‐H₂O and TG allowed an estimation of the surface OH groups concentration as ∼3–4 nm^-2. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selection of formal verification heuristics for parallel execution

Functional verification is “the” major design-phase bottleneck for silicon productivity. Since functional verification is an NP-complete problem, it relies on a large number of heuristics with associated parameters (engines). With the advent of parallel processing, formal verification can be optimized by selecting the best n engines to run in parallel, increasing the chance of reaching successful termination of the verification task. In this paper, we will present a methodology to build engine estimators based on structural metrics and to select n engines to run in parallel. The methodology considers both engines’ estimated performance and engines’ correlation. Results confirmed that the methodology can be a very quick selection mechanism for parallelization of engines in order to increase the chance of running the best engines to solve the problem.     

Sesquiterpene lactones. Part XV. New cytostatic active sesquiterpene lactone from herb of Anthemis nobilis L

From fresh and dried herb (without inflorescences) of Anthemis nobilis L. a new sesquiterpene lactone C20H26O6 was isolated. This compound showed a cytotoxic activity at a level of ED50 HeLa -- 0-56 microgram/ml (1-5 x 10(-6) M), and ED50 KB -- 1.23 microgram/ml (3-5 x 10(-6) M), what qualifies it for further in vivo studies.