Nicholas J. Calos

A step towards designing Fe–Cr–B–C cast alloys

Abstract Using mass balance equations and structural analysis results, the chemical compositions of the constituent phases of forty Fe–Cr–B–C alloys were determined. The dependence between chemical compositions and lattice parameters of (Cr, Fe)2B borides was also established. A set of statistical models was developed from these results, which articulate the chemical composition of the matrix as a function of the nominal chemical composition of the alloy. Partition coefficients for Cr and C in these alloys were then established. The developed statistical models, when used in conjunction with existing thermodynamic information, make it possible to estimate the chemical composition of the matrix and the types of, and semi-quantitatively the amounts of, boraides, carbides and boro-carbide precipitates.

STRUCTURE OF CALCIUM ALUMINATE SULFATE CA4AL6O16S

The commensurately modulated structure of polycrystalline calcium aluminate sulfate was determined using spectroscopic and electron microscopic information and calculations with the bond-valence method. The neutron powder diffraction data were refined by the Rietveld profile technique. Calcium aluminate sulfate, Ca4Al6O16S, MW = 2440 Da, orthorhombic, Pcc2, a = 13.028(3) Angstrom, b = 13.037(3) Angstrom, c = 9.161(2) Angstrom, U = 1556(1) Angstrom(3), Z = 4, Dc = 2.60 g cm(3), lambda (neutron) = 1.893 Angstrom (Ge monochromated), mu R(neutron) = 0.42, R(Bragg) = 0.046, R(p) = 0.06, R(wp) = 0.08 is a twofold superstructure of sodalite which is generated by z modulation of the framework along [1 1 0] of the cubic subcell

Characterization of stress-whitening of tensile yielded isotactic polypropylene

The microstructure of tensile tested isotactic polypropylene (iPP) specimens was studied by grey level measurement, scanning electron microscopy (SEM), differential scanning calorimetry (d.s.c.) and X-ray diffraction (XRD). SEM revealed that the necked regions of specimens in which stress-whitening had occurred as determined by the grey level measurement had craze-like structures which were parallel to the drawing direction. D.s.c. analysis showed that the necked regions of tensile specimens which remained transparent after yielding had an additional low-melting temperature peak. However, no additional melting peaks were found in the stress-whitened specimens. Inspection of the XRD patterns indicated that, apart from its original α-crystallites (a monoclinic structure) which were broken and reoriented after drawing, there was no new types of crystals formed in the transparent specimens. It was found by quantitative XRD analysis that the crystallites were broken into finer pieces in the whitened specimens than in the transparent ones.

Crystallinity of poly(β-hydroxybutyrate) using the Rietveld technique

Provided the structure is known, a method has been developed using the Rietveld technique on X-ray powder data collected on a commercial diffractometer to determine the amount of crystallinity in a polymer film such as poly(β-hydroxybutyrate). This film was found to be 46% crystalline for a fresh sample and 60% when degraded.

Radiation chemistry of poly(tetrafluoroethylene-co-perfluoromethyl vinyl ether): Effects of oxygen and crystallinity

The presence of oxygen had a varied effect on the gamma-radiolysis of the amorphous copolymer, poly[tetrafluoroethylene-co-perfluoro(methylvinyl ether)] (TFE/PMVE), depending upon radiolysis conditions. Radiolysis undertaken in stages, up to a dose of 1500 kGy (1 rad = 10(-5) kGy) in the presence of air, resulted predominantly in chain scission and a wax-like substance was produced; whereas, other studies have shown that continuous radiolysis of the polymer produced a crosslinked network. Radiolysis of semicrystalline TFE/PMVE in vacuum up to a dose of 4200 kGy produced little change in the crystalline content. Crosslinking, however, predominated in the amorphous regions, which had the effect of lowering the crystallization temperature upon cooling from above the crystalline melt

Molecular cocrystals of carboxylic acids. XIII: Spectral characterization of the adducts of triphenylphosphine oxide with substituted benzoic acids and the crystal structures of the 1:1 adducts with 2,4,6-trinitrobenzoic acid and 3,5-dinitrobenzoic acid

The 1:1 adducts of triphenylphosphine oxide with the 2-, 3- and 4-nitro-, 3,5-dinitro-, and 2,4,6-trinitro-substituted benzoic acids have been prepared, and characterized by infrared and 31P n.m.r. spectroscopy. The crystal structures of two of these adducts, (triphenylphosphine oxide-3,5-dinitrobenzoic acid) and ( triphenylphosphine oxide-2,4,6-trinitrobenzoic acid), have been determined by X-ray diffraction. In all examples, the presence of single directed hydrogen bonds between the phosphoryl oxygen and the carboxylic acid proton is confirmed. For the X-ray structures, the O…O distances are 2.54(4) and 2.55(1)Ǻ respectively. Solid-state 31P n.m.r. spectroscopy has also proved a convenient technique for the detection of the presence of a single conformational adduct type in cocrystals.

Structural and Raman analyses of the (A1−xPbx) TiO3(A=Ca, Sr, Ba) perovskites

Powder X-ray diffraction and laser Raman spectroscopy were used to study systematically the structural and dynamical changes in three series of plumbous perovskites of composition Ba1−xPbxTiO3Sr1−xPbxTiO3 and Ca1−xPbxTiO3 with 0 <x < 1. For the latter two series prominent phase transitions were found atx ca. 0.5 and 0.55, respectively. As well, Raman spectroscopy provided the means to track the evolution of active vibrational modes characteristic of the end-members across the doping range. The temperature dependence of the Raman spectra showed that the ferroelectric transition temperature of the (Ca, Pb) series can be tailored over a wide temperature range by judicious doping.

On the short C–C bond lengths in macrocyclic ligand systems incorporating ether donors: a comparative neutron and X-ray diffraction study of an O2N3 donor macrocycle: 6,7,8,9,10,11,12,13,19,20-decahydro-5H-dibenzo[e,p][1,4,8,11,14]dioxatriazacycloheptadecine

The neutron diffraction structure of a 17-membered macrocyclic ligand incorporating an O2N3-donor set has been determined in order to investigate whether the C–C bond in the –OCH2CH2O– atom string remains short as found in the corresponding X-ray structure of this compound; the evidence suggests that the short bond found by X-ray diffraction in this as well as in many other polyether compounds is largely an artefact with the ‘real’ component of the shortening being quite minor.

Mineral analysis using X-ray powder data

Quantitative X-ray powder diffractometry was applied to the phase analysis of a mineral specimen containing two sulfur-rich isomorphous mineral phases, beudantite [PbFe3(AsO4)(SO4)(OH)6] and osarizawaite [PbFeAlCu(SO4)2(OH)6], together with goethite (FeOOH) and some hematite (Fe2O3). The application of the Rietveld method was extended to provide elemental as well as phase analysis.