Materials Literature
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Abstract A variety of dendrimers up to generation 7 possessing terminal P(S)Cl 2 , (3‐[G 1 ]‐3‐[G 7 ]) or P(O)Cl 2 , (7‐[G 1 ]‐7‐[G 3 ], 7‐[G 3 , 7‐[G 7 ) have been tri‐ and tetrafunctionalized. Selective monosubstitution of P(X)Cl 2 (X = S, 0) termini with allylamine or propargylamine gave the trifunctionalized dendr…
Aromatic, fully conjugated polymers are a class of polymers attracting significant interest in academics as well as industry. In particular, poly-(p-phenylene) (PPP) and poly(p-phenyienevinylene) (PPV) are important materials due to their thermal stability and electrical conductivity after doping. Very recently their…
Abstract The reaction of ferric chloride and β‐diketones (HL) in alkaline methanol solution represents a good synthetic route to hexairon(III) clusters [MFe 6 ‐(OCH 3 ) 12 (L) 6 ] + (M = Na, Li), which exhibit an unusual sixfold molecular symmetry. Single‐crystal X‐ray diffraction showed that the six octahedrally coor…
New experimental techniques have been applied to the study of single-photon double ionization of atoms and molecules. A coincidence technique is described in which the spectra of nearly zero energy photoelectrons are recorded in two identical photoelectron energy analysers. The results are discussed in terms of the av…
Abstract Linear polyurethanes (PUR‐D k ) were prepared by reacting 4,4′‐methylenediphenyl diisocyanate (MDI) with low‐molecular‐weight diols HO(CH 2 ) k OH ( k = 2, 3, 4, and 6) and fractionated by precipitation or extraction with mixtures of N , N ‐dimethylformamide (DMF) and dibutyl ether (DBE). The fractions were…
Binary magnesium alloys containing chromium, manganese, or titanium were made using a physical vapour deposition technique. The corrosion resistance of the alloys was assessed in aqueous chloride solutions using total immersion tests in quiescent 600 mmol L−1 NaCI solutions. Alloying with manganese or titanium was fou…
By using a new impact test apparatus, the particle impact behaviour of ceramic materials at room temperature and elevated temperatures up to 1400°C and under tensile loads were carried out. Samarium cobalt spheres of 1mm diameter and 4mg mass were used as impact particles. The particle velocities ranged from 200 to 10…
Abstract Temperature dependencies of the conductivity and thermopower of bulk amorphous semiconducting alloys Zn 41 Sb 59 and Ga 100−x Sb x with 47.5 < x < 55 were measured at 80 to 370 K and 120 to 370 K, respectively. The samples were prepared by solid state amorphization of the quenched high pressure phases o…
Some of the features of the superspace description of quasiperiodic structures, of the so-called superspace embedding, can be arbitrarily chosen. The superspace approach is reviewed in such a way that these particular features, which are not intrinsic to the theory, are explicitly indicated and separated from the fund…
A theory of thermoelasticity for nonsimple materials is derived within the framework of extended thermodynamics. The theory is linearized, and a uniqueness result is presented. A Galerkin type solution of the field equations and fundamental solutions for steady vibrations are also studied.
The short-range order within amorphous polyaniline ($a$-PANI) has been studied through use of a pair-distribution-function analysis of x-ray scattering data in combination with quantitative refinements of model structure functions. Both the emeraldine base and salt (ES) forms of $a$-PANI are less planar than their cry…
Alumina reacts with 1 atm of SiF 4 below 660°± 7°C to form A1F 3 and SiO 2 . At higher temperatures the product is a mixture of fluorotopaz and AIF 3 . Mixtures of fluorotopaz and AIF3 decompose in 1 atm of SiF 4 at 973°± 8°C and form tabular α‐alumina. The equilibrium vapor pressure of SiF 4 above mixtures of fluorot…
Malate dehydrogenase from the syntrophic propionate-oxidizing bacterium strain MPOB was purified 42-fold. The native enzyme had an apparent molecular mass of 68 kDa and consisted of two subunits of 35 kDa. The enzyme exhibited maximum activity with oxaloacetate at pH 8.5 and 60 degrees C. The Ka for oxaloacetate was 5…
Abstract Four heptamethine cyanine dyes 10, 19–21 containing an ortho ‐hydroxy‐carboxy functionality for metal ion complexation and absorbing at λ max (methanol) 761±1 nm have been synthesized.
The successive phase transitions of KTa1−xNbxO3 (x = 0.3 and 0.4) (KTN) ceramics have been investigated by various techniques including DTA, dielectric, piezoelectric and pyroelectric measurements from 100 to 450 K. In this temperature range, all the phase transactions have been detected by pyroelectric measurements.…
Abstract Eight samples of poly(ethylene‐co‐propylene‐co‐diene) (EPDM, containing 55 wt.‐% ethylene) were vulcanized with 0.5–8.0 phr dicumyl peroxide. The influence of molar volumes V 1 of cyclohexane, hexane, heptane, iso‐octane, tetrachloromethane, carbon disulfide, xylene, benzene, toluene, tetrahydrofuran, trichlo…
A series of novel dis- and trisazo dyes containing a perfluoroalkyl, perfluoroalkylthio and perfluoroalkylsulphonyl groups have been synthesized. The absorption bands of these dyes were more bathochromic than the corresponding alkyl derivatives. The solubility of disazo dyes containing perfluoroalkyl and perfluoroalky…
We have carried out extensive molecular-dynamics simulations of randomly cross-linked polymers and studied the onset of rigidity as the number of cross-links is increased. We find that for our systems, consisting of chains of length N=10, 20, 30, and 50, the shear modulus E vanishes at a concentration of cross-links t…
Abstract Apparatus has been constructed to abrade the flat surface of a rubber disk by rotating it against a stationary knife-blade scraper at constant frictional torque. The ratio of worn surface area to sample volume is relatively large, giving high sensitivity of measurement. Rates of abrasion were measured for sev…
Thermal shock damage in a two‐dimensional woven‐Nicalon (tm) ‐fiber‐reinforced‐CVI SiC‐matrix composite was induced by water quenching and characterized by optical microscopy as a function of quench temperature difference (Δ T ) and number of quench cycles. Mechanical damage generated in flexure on quenched and unquen…