X-ray photoelectron spectroscopic analysis of barium-labelled carbon fibre surfaces

A technique for labelling acidic functional groups on carbon fibre surfaces with barium has been developed for X-ray photoelectron spectroscopy analysis of the surface acidity of commercial Type II fibres, with differing degrees of oxidation. As the dibasic barium is believed to label adjacent monobasic groups, the results show that up to 58% of the surface oxygen, on the commercially treated fibres, is present in the acidic form.     

TEM and high-temperature X-ray diffractometric studies on the structural transformations in Ni3Al

High-temperature X-ray diffraction and TEM studies were conducted on nickel-rich boron-doped Ni₃Al in order to confirm our earlier observations on the existence of a structural transformation in these alloys. The results obtained are discussed through a model proposed. The L1₂ structure appears to transform to another L1₂ or to a DO₂₂ structure during heating. Such a transformation starts at around 700 °C and seems to complete around 1100 °C and appears to be of a continuous type. In the temperature range 700–1100 °C both phases coexist, which causes a tetragonal distortion of the L1₂ lattice giving rise to a tweed morphology in TEM observations. The transformation mechanism involves a periodic modulation of lattice constant. The calculated values for this periodicity (expressed as a number of unit cells in the [100] direction) obtained from X-ray diffraction (L = 62, 70, 74) matched well with that (L = 65) obtained using TEM.     

Microhardness studies of renal calculi

The development of acoustic and other methods of kidney stone fragmentation has given importance to the study of the mechanical properties of such stones. Renal calculi based upon calcium oxalate, calcium phosphate, uric acid, cystine, and magnesium ammonium phosphate have been studied using Knoop microhardness indentation methods. The microhardness of dry stones was found to vary with the calculi chemical composition, yet remained consistent within composition groups. The hardest calculi were found to be calcium oxalates with a Knoop microhardness of 68–88 kg/mm². Other compositions have hardness of up to a factor of two lower than this.     

X-ray photoelectron spectroscopic studies of sprayed CdS films

The chemical composition of sprayed CdS films has been evaluated using X-ray photoelectron spectroscopy. The general impurity content in the film is discussed, throwing light on the pyrolysis reaction involved in CdS deposition. Further, the stoichiometry of these films is studied as a function of process parameters such as pyrolysis temperature, Cd/S ratio in the solution, deposition rate and film thickness. A definite correlation is observed between composition and process parameters. The compositional variation appears to be related to the structure of CdS films as well as the growth mechanism. The effects induced by annealing in nitrogen, hydrogen and ambient air are also discussed. Hydrogen and nitrogen annealing is responsible for oxygen desorption from CdS. On the other hand air annealing induces stoichiometric variations along with oxygen intake in the films.     

X-ray photoelectron spectroscopic studies of carbon fibre surfaces

Carbon fibres were anodically surface treated by passing them continuously through an electrochemical bath, thus simulating a possible industrial surface-treatment process. Composites were made from these fibres with an epoxy resin and their interlaminar shear strength (ILSS) tested. The surfaces of the fibres were examined by X-ray photoelectron spectroscopy after treatment. Both golvanostatic and potentiostatic cell control led to treated fibres that produced composites with high interlaminar shear strengths (80 to 90 MPa). The effect of potential, reaction time, electrolyte and subsequent heating of the fibres in a vacuum on the ILSS of the composites is reported. The rise in ILSS with surface treatment is not dependent upon the O-1 s: C-1 s ratios or the amount of carboxyl functionality present on the surface. This suppors the view that mechanical keying of the resin to the fibre surface plays an important role in forming the fibre-resin bond.     

Crystal morphology and texture in calcium oxalate monohydrate renal calculi

The morphology of calcium oxalate monohydrate crystals in renal calculi has been studied. Morphology modifications with respect to equilibrium morphology have been explained from the structure of (1 0 0) crystal faces and the effect of polyelectrolytes present in urine. The texture of the stones has been considered as the result of both primary aggregation and crystal aggregation produced by anionic macromolecules. The arrangement in concentric layers of crystals with a radial disposition has been related to a process of intense nucleation induced by anionic macromolecules and typical polycrystalline growth on films.     

In vitro comminution of model renal calculi using histotripsy

Shock wave lithotripsy (SWL) suffers from the fact that it can produce residual stone fragments of significant size (>2 mm). Mechanistically, cavitation has been shown to play an important role in the reduction of such fragments to smaller debris. In this study, we assessed the feasibility of using cavitationally-based pulsed ultrasound therapy (histotripsy) to erode kidney stones. Previous work has shown that histotripsy is capable of mechanically fractionating soft tissue into fine, acellular debris. Here, we investigated the potential for translating this technology to renal calculi through the use of a commonly accepted stone model. Stone models were sonicated using a 1-MHz focused transducer, with 5-cycle pulses delivered at a rate of 1 kHz. Pulses having peak negative pressures ranging from 3 to 21 MPa were tested. Results indicate that histotripsy is capable of effectively eroding the stone model, achieving an average stone erosion rate of 26 mg/min at maximum treatment pressure; substantial stone erosion was only observed in the presence of a dense cavitational bubble cloud. Sequential sieving of residual stone fragments indicated that debris produced by histotripsy was smaller than 100 μm in size, and treatment monitoring showed that both the cavitational bubble cloud and model stone appear as hyperechoic regions on B-mode imaging. These preliminary results indicate that histotripsy shows promise in its use for stone comminution, and an optimized erosion process may provide a potential adjunct to conventional SWL procedures.     

X-ray photoelectron and x-ray absorption spectroscopic study of rare-earth molybdenum oxides

The chemical state of atoms in rare-earth molybdenum oxides has been studied by x-ray photoelectron and x-ray absorption (XANES) spectroscopies. The photoelectron spectra has been analyzed in the Mo 3d, Mo 3p, O 1s, Ce 3d, Y 3d, Er 4d, and Yb 4d regions. The results indicate that the oxidation state of the molybdenum in the compounds studied is 6+. The measured Mo K-edge spectra and XANES calculations are used to develop a model of a molybdenum-oxygen cluster in the rare-earth molybdenum oxides.     

X-ray photoelectron spectroscopic studies of partially coked HZSM-5 catalysts

XPS studies of partially coked HZSM-5 catalysts have been carried out. As a result of the coke deposition Si(2s) and O(1s) binding energies were decreased by 1.0 eV due to the electron charge transfer from the coke to the framework atoms. The electron energy loss peaks were observed for Si(2s) of coked HZSM-5 catalyst. The results suggest that the coke was deposited on SiO₄ tetrahedra.