Direct e-beam writing of high aspect ratio nanostructures in PMMA: A tool for diffractive X-ray optics fabrication

We present a fast and reliable fabrication method of dense, periodic and high aspect ratio PMMA and metallic nanostructures. Biased lines are directly exposed by a 100 keV electron beam in thick layers of polymethyl-methacrylate (PMMA) resist to produce polymer mold which is later used to grow Au high aspect ratio structures by electroplating. Dense PMMA and Au nanostructures with aspect ratios >11 were manufactured in 520 nm and with aspect ratios >12 in ～1 μm thick layers of PMMA. This method was successfully applied to produce various X-ray optics devices, such as beam shaping condensers, Fresnel zone plates and diffraction gratings. The performance of a beam shaper was tested at 10 keV photon energy showing a good diffraction efficiency of 10%.     

The effect of crystal polymorphism of ferroelectric copolymer vinylidene fluoride-hexafluoropropylene on its high-voltage polarization

Dielectric response of vinylidene fluoride-hexafluoropropylene copolymer, crystallized in different polymorph modifications, to a high-voltage electric field was studied. Polarization switching at high electric fields below coercive was detected. It was found that crystallization of the copolymer predominantly in nonpolar α-phase is accompanied by more intensive growth of electric displacement at polarization. For the sample with higher content of polar γ-phase, the value of high-voltage conductivity “anomalously” decreased with increasing field at fields above coercive. The data on the field dependences of the remnant polarization showed that this should be attributed to an increase of the effective capture cross section of deep traps of γ-phase polar planes for impurity and injected carriers. X-ray diffraction has revealed the field-induced transition of a part of the chains of the amorphous phase to the crystal.     

Effects of calcite and dolomite on conversion of heavy oil under subcritical condition

This paper discusses the physical simulation of aquathermolysis for heavy oil in the presence of minerals – dolomite and calcite. According to the SARA-analysis and IR-spectroscopy, the presence of calcite provides significant effects on the reduction of resins and asphaltenes, their condensability and aromaticity by destructing the least stable C-S-C bonds. Based on the results of gas chromatography, the thermal conversion of heavy oil increased the hydrocarbon content with homologous series of С19-С30. The analysis of geochemical coefficients revealed the high maturity of organic matters in thermally conversed heavy oil from model system with dolomite.     

A simultaneous inversion for deformation rates and topographic errors of DInSAR data utilizing linear least square inversion technique

We demonstrate here a computer code for calculation of time series and also mean and linear deformation rates from a set of coregistered unwrapped differential interferograms using a linear least-squares inversion technique based on the small baseline subset (SBAS) algorithm. The computer code is written in C and uses a singular value decomposition (SVD) routine from the LAPACK library and the fast Fourier transform for spatial filtering from the FFTW library. Various offset estimation and topographic correction algorithms are implemented, including simultaneous inversion for deformation rates and residual topographic error. This approach is particularly useful when applied to ALOS PALSAR interferograms that are coherent even at large perpendicular baselines and acquired with orbital parameters correlated with the time of acquisition. This methodology is applied to produce time series of ground deformation at Tauhara and Wairakei geothermal fields (Taupo Volcanic Zone, North Island, New Zealand) from 12 ALOS PALSAR images acquired between July 2007 and December 2009. We also present here a high-resolution deformation map of the ground subsidence caused by the extraction of geothermal groundwater for power generation, with maximum rates of subsidence of about 7 cm/y.     

Elastoplastic deformation of nonhomogeneous plates

Efficient projective-iterative schemes for the numerical implementation of the finite-element method are developed to calculate the stress and strain fields in elements of plate-and-shell systems, in particular in nonhomogeneous plates, under elastic and elastoplastic deformation. Rectangular plates with variously shaped (rectangular, circular, elliptic) holes in a plane stress state are considered. The effect of the elastoplastic deformation of the material on the stress and strain fields due to a slowly increasing load is studied. Schemes of successive approximations to account for plastic deformations in combination with projective-iterative schemes of numerical implementation of the finite-element method are constructed. The interaction of variously shaped holes is studied. The efficiency of projective-iterative variants of the finite-element method offering a several-fold reduction in running time is demonstrated. The proposed schemes are particularly attractive for the use of the finite-element method in numerical simulation of the nonlinear deformation of nonhomogeneous plate-and-shell systems. The numerical models considered can be used to good advantage in the study of the effect of other nonhomogeneities (geometrical shape irregularities, various inclusions, reinforcements). They can be used in fracture mechanics: failure starts with the development of discontinuities in variously shaped holes. The hole shape and dimensions can change during loading.     

Atomic-scale mechanisms of oxygen electrode delamination in solid oxide electrolyzer cells

Materials used for different components (electrodes, electrolyte, steel interconnects, etc.) of solid oxide electrolyzer cell (SOEC) devices for hydrogen production have to function in aggressive, corrosive environments and in the presence of electric fields. This results in a number of degradation processes at interfaces between components. In this study, we used a combination of first-principles, density-functional-theory (DFT) calculations and thermodynamic modeling to elucidate the main processes that contribute into the oxygen delamination in typical SOEC device consisting of yttria-stabilized zirconia (YSZ) electrolyte and Sr-doped LaMnO₃ (LSM) oxygen electrode. We found that high temperature inter-diffusion of different atoms across the LSM/YSZ interface significantly affects structural stability of the materials and their interface. In particular, we found that La and Sr substitutional defects positioned in ZrO₂ oxide and near LSM/YSZ interface significantly change oxygen transport which may develop pressure buildup in the interfacial region and eventually develop delamination process. Simple models for estimating these effects are proposed, and different possibilities for inhibiting and/or mitigating undesirable delamination processes are discussed.     

In-plane spectroscopy of microfluidic systems made in photosensitive glass

This work manifests the use of microstructures made in Apex? photosensitive glass for in-plane investigation of microfluidic systems by demonstrating the ability to detect chemical fluids through etched glass sidewalls. Absorption spectra of liquid ethanol in the near infrared (NIR) region and Raman spectroscopy of dimethyl sulfoxide in microcuvettes made in Apex? photosensitive glass demonstrate the high potential of photosensitive glass processing in microfluidic applications in which stacks of microfluidic systems are analyzed from the sidewalls. This eliminates the need for non-planar observation of microfluidic systems.