Materials Literature
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More environmentally acceptable blowing agents, such as hydrochlorofluoro-carbons (HCFCs), hydrofluorocarbons (HFCs), hydrocarbons, and carbon dioxide have now replaced chlorofluorocarbon (CFC) blowing agents in many rigid polyurethane (PUR) and polyisocyanurate-modified polyurethane (PIR) foam applications. However,…
Crack growth behaviors in continuous fiber-reinforced ceramic matrix composites have been analyzed in termes of stress intensity factors using the finite-element method. Namely, the effects of Young's modulus ratio, Em/Ef, and fiber volume fraction, Vf, on the stress intensity factors have been investigated. As a resu…
To obtain an improved understanding of the production, development, and transport of crystal fragments during directional solidification of binary alloys, experiments have been performed for an aqueous ammonium chloride solution. For vertical directional solidification (VDS) induced by cooling from below, fragmentatio…
Lead magnesium niobate, Pb(Mg1/3Nb2/3)O3 (PMN), has been prepared from aqueous nitrate solutions by freeze-drying and stepwise precipitation using an ammonia solution as the precipitant. Perovskite PMN powders with less than 5% pyrochlore phase were obtained when the resulting precursors were calcined at temperatures…
The chemical structure of two homogeneously doped polyenes, namely poly(propargylalcohol) (PPOH) and poly(N,N-dimethylpropargylamine) (Pd-PDMPA), has been investigated by means of x-ray photoelectron spectroscopy (XPS). The study of FeCl3 and I2 doped PPOH films gave evidence of different chemical states for the dopan…
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Substituted pyridine derivatives (X-py: X=H, 2,4-Me2 , 2-Me, 3-Cl, 3-Br and 4-CN) and bipyridine compounds (2,2′- and 4,4′-pyYpy: –Y–=none, –C2H2 –, –SS– and –C2H4 –) reacted with powdered gel-V2O5 1.6H2O or VOPO4 2H2O suspended in ethanol to afford intercalation compounds. They contained 0.1–0.4 mol of guest molecule…
The smelting of iron ore into metallic iron was first accomplished by primitive blast furnaces approximately three thousand years ago. Improvements in the process over many centuries eventually led to the mass production of iron and to the industrial revolution. The reactions of the blast furnace involve 1) combustion…
With the advances made in clean steel technology in recent times, most current techniques to quantify inclusion contents fail to provide relevant feed-back to process engineering. This is a particular dilemma in that the larger a defect, the more dangerous it is, and the harder it is to find as inclusion size distribu…
Two families of liquid crystalline compounds: 4-hexyl-4-alkoxyazobenzenes and 4-heptyl-4'-alkoxyawbenzenes have been synthesised for alkyl chain from methoxy up to octadecyloxy. On the base of the DSC calorimetry and polarizing microscopy rich polymorphism was detected. Maximum four mesophases were found: nematic, sme…
Five-membered rings are of interest as building blocks for nonlinear optical (NLO) materials. We found easy access to the title compounds: thiazolo[5,4-d]thiazole 1 has been obtained in three simple steps starting with the chlorination of ethyl isothiocyanatoacetate 8, followed by dehydrohalogenation to the diethyl 2,…
This paper outlines the mechanism of Stress Corrosion Cracking (SCC) and how it can cause premature failure of rock bolts. SCC occurs due to the progressive development and growth of cracks in the surface of a metal, and it is caused by the combined effects of stress and a corrosive environment affecting susceptible m…
The silica gels derived from triethoxysilane and tetraethoxysilane were studied by Raman spectroscopy. The vibrational band at 492cm-1, ordinally labeled D1, was shifted to 506cm-1 with the introduction of Si-H groups into the silica network. This suggests that this band is ascribable to the symmetric stretch oxygen v…
Complexation of triosmium clusters to pyridyl functionalised metalloporphyrins gives heterometallic derivatives that possess the overall recognition and spectroscopic properties of the porphyrin fragment, while incorporating the electronic and structural characteristics of the cluster.
The different reaction routes of n-pentoxy radicals in O2/N2 mixtures were investigated in the temperature range 423–523 K under atmospheric pressure. Flow experiments were performed in several reactors, with wall efficiencies increasing from passivated quartz to Pyrex, and with a great variety of mol fractions of O2…
Abstract The surface reactions involved in the palladium‐catalyzed formation of benzene from acetylene are discussed as an example of the way in which such strategies can be used to understand catalytic reaction pathways in detail. This provides an ideal system for surface science/catalysis studies since benzene is fo…
By creating and developing materials whose properties could be fully characterized, Professor George W. Gray has played a pivotal role in advancing our knowledge of liquid crystal states of matter. To honour him on his birthday, I briefly sketch some of my experimental results where the purity and stability of his cya…
Frost growth on cooling surfaces held at subfreezing temperatures has been shown to cause degradation of the heat transfer performance of the cooler. Despite the initial increase in the heat transfer rate due to the temporary increase in the heat transfer area, periodic frost removal is necessary. This paper presents…
The choice of the empirical pseudopotential method for studying the electronic band structure of SbSI-type crystals is discussed. The method is applied to study the SbSI crystal in the paraelectric and ferroelectric phases. Differently from previous studies, a covalent crystal structure is assumed. The total density o…
The UV–VIS–NIR absorption of the rhombohedral NdOF was measured at selected temperatures between 9 and 300 K. The emission spectra of NdOF, LaOF:Nd3+ and GdOF:Nd3+ were obtained at 4.2, 9, 77 and 300 K. The energy level scheme of the Nd3+ ion (the 4 configuration) derived from the optical spectra was simulated with a…