Material Swelling Research Articles

MAINTENANCE OF FILTRATION AND CAPACITIVE RESERVOIR PROPERTIES DURING TEMPORARY ISOLATION

The article provides the analysis of factors affecting the reservoir properties (filtration and capacity) during repair works. It is revealed that the maintenance of filtration and capacitive reservoir properties is ensured by high-quality blocking and unblocking the reservoir, as well as by prevention of clay material swelling. Solution of these problems is possible through proper selection of the bridging agents (nature, type and fractional composition) used in the blocking composition, and various functional additives (salts, polymeric reagents and surfactants). Furthermore, the reasons of clay minerals swelling and various ways to prevent this process are analyzed. It is determined the peculiarities of clay minerals structure are essential for their properties, and in particular, their ability to swell.

Impact of gap size uncertainty on calculated temperature uncertainty for the advanced gas reactor experiments

Research being conducted on tristructural-isotropic fuel development and qualification involves seven advanced gas reactor (AGR) experiments that were planned to provide fuel qualification data to support the licensing and operation of the high-temperature gas-cooled reactor. Each AGR test consists of multiple independent capsules containing fuel compacts placed in one or more graphite cylinders shrouded by a stainless-steel shell. These capsules are instrumented with thermocouples embedded in the graphite holder, enabling temperature control. The desired fuel temperature is maintained by variation of the neon/helium gas mixture in response to feedback from thermocouple readings. In the absence of direct measurements, the commercial finite-element heat transfer code ABAQUS was used to predict fuel temperatures. Recognizing inherent uncertainties in the simulation model due to complex physical mechanisms, capsule geometries, and material properties, comprehensive temperature uncertainty quantification was performed. The uncertainty results reveal that the uncertainties in gap sizes are among the most influential factors contributing to calculated temperature uncertainty. The gap size uncertainties originate from a lack of direct experimental data for accurate assessment of dimensional change rates of fuel compacts and graphite components due to complex irradiation-induced material shrinkage or swelling. The study described here focuses on the impact of the gap size uncertainties based on the post-irradiation examination metrology data on calculated temperature uncertainty.

A volatile tracer-assisted headspace analytical technique for determining the swelling capacity of superabsorbent polymers

This paper reports on a new method for the determination of swelling capacity of superabsorbent polymers by a volatile tracer-assisted headspace gas chromatography (HS-GC). Toluene was used as a tracer and added to the solution for polymers swelling test. Based on the differences of the tracer partitioned between the vapor and hydrogel phase before and after the polymer’s swelling capacity, a transition point (corresponding to the material swelling capacity) can be observed when plotting the GC signal of toluene vs. the ratio of solution added to polymers. The present method has good precision (RSD<2.1%) and good accuracy, in which the relative deference between the data measured by the HS-GC method and the reference method were within 8.0%. The present method is very suitable to be used for testing the swelling capacity of polymers at the elevated temperatures.

Reduction of material swelling and recovery of titanium alloys in diamond cutting by magnetic field assistance

Ultra precision machining (UPM) is extensively used to fabricate high accuracy products. However, the problematic material swelling/recovery effect due to the elastic recovery of materials in UPM remains unresolved. It causes a ragged surface and extra engineering tolerances which are unadoptable in extremely precise components. In particular to high elastic recovery rate with low thermal conductivity materials like titanium alloys, the swelling effect is intensified during machining processes. In this study, a magnetic field was superimposed on titanium alloys during the single point diamond cutting which aimed to minimize the material swelling effect on the machined surface using the magnetic field influence. In the experiments, titanium alloys were located at the center of two permanent magnets with intensity 0.02T and undergone a diamond groove cutting. The experimental results showed the material swelling/recovery on the machined surface was significantly reduced in presence of magnetic field in comparison to that of diamond cutting without a magnetic assistance; the accuracy of depth of cut, width and radius of cutting groove in a magnetic field reached satisfactorily over 98%. The proposed machining technology solves the problem of material swelling/spingback of low thermal conductivity materials by a cost-efficient way which is needless of complicated equipment.

Dissolution enhancement of griseofulvin from griseofulvin-sodium dodecyl sulfate discs investigated by UV imaging

The purpose of study was to investigate the dissolution rate enhancement obtained when sodium dodecyl sulfate (SDS) is co-compressed with griseofulvin into discs using a UV imaging-based flow-through dissolution testing setup. Griseofulvin dissolution rates obtained from discs containing 5.92 and 10.6% (w/w) SDS in phosphate buffer (pH 6.5) were similar to dissolution rates from pure griseofulvin discs when applying 20 and 100 mM SDS as dissolution medium, respectively. Dynamic light scattering of effluent samples revealed nanosized particles (approximately 135 nm in diameter) escaping the discs during dissolution. Scanning electron microscopy of co-compressed griseofulvin-SDS discs prior to dissolution testing showed surfaces apparently consisting of granules (100 and 200 nm in diameter) as well as particles present on the disc surfaces possibly related to the high initial dissolution rates. Material swelling or precipitation was observed for discs containing 10.6 or 15.8% (w/w) SDS. UV imaging revealed increased griseofulvin concentrations near the solid-liquid interface of griseofulvin-SDS discs, e.g., a 45-fold increase in concentration was observed for discs containing 10.6% (w/w) SDS as compared to discs without SDS, which is the likely cause of the enhanced dissolution rates found for the co-compressed griseofulvin-SDS discs.

Thermal Stability and Coefficient of Friction of the Diamond Composites with the Titanium Compound Bonding Phase

In this paper, processes occurring during heat treatment of the diamond-Ti compound composites without Co addition were investigated and compared with commercial PCD. Three types of materials were prepared. The first material was sintered using the mixture containing diamond and 10 mass% of TiC, the second material was prepared using diamond powder and 10 mass% of Ti-Si-C, and the third composite was sintered using the addition of 10 mass% of TiB2. During the research, it was proved that TiO2 formation contributes to material swelling and WO3 (W is present from the milling process) causes a significant increase in coefficient of friction. TiC and Ti-Si-C bonded materials are very susceptible to this process of oxidation; their hardness drops absolutely after wear test at 600 °C. The diamond composite with TiB2 is the most resistant to oxidation from investigated materials.

Competitive growth and rising of bubbles in a yield stress fluid. Consequences on the macroscopic swelling of bitumen drums

The evolution kinetics of a bubble population driven by a uniform production of gas in a yield-stress fluid matrix is investigated in this paper. The context concerns the long time swelling of bitumen drums in which radioactive salts have been dispersed (salts suspensions in a bitumen matrix). Radioactivity generates uniform volume production of hydrogen by radiolysis of bitumen chains. Since the production rate of gas occurs on very long time scales (more than a hundred years), one needs to develop theoretical models to predict the material swelling. It has been shown previously that bitumen is a yield stress fluid and that, in the case of a motionless population (no migration due to buoyancy), the yield stress disturbs the classical scenario of nucleation, bubble growth and Ostwald ripening observed in a Newtonian fluid. In the present work, we consider bubbles nucleation and migration due to buoyancy and we show that the yield stress causes delays in the evolution of a bubble population and that it consequently modifies the macroscopic swelling of the material into the drums.

A new approach to preparation of granulated materials based on chitosan and its imidazole derivative

A new approach to preparation of granulated materials based on chitosan and N-(5-methyl-4-imidazolyl)- methyl chitosan was developed. The procedure is simple and efficient and involves the use of glutaraldehyde as cross-linking agent without using precipitants. The composition and structural features of the materials obtained were determined by elemental analysis and Fourier IR spectroscopy. The dependence of the degree of material swelling on the degree of functionalization with glutaraldehyde was determined. The polymer granules were used as support for Pd0-containing catalysts for reduction of organic compounds.

Ostwald ripening in a yield-stress fluid under uniform gas production

The evolution kinetics of a bubble population driven by a uniform production of gas in a yield-stress fluid matrix is investigated in the context of the long time swelling of bitumen drums in which radioactive salts have been dispersed (salts suspensions in a bitumen matrix). Radioactivity generates uniform volume production of hydrogen by radiolysis of bitumen chains. Since the production rate of gas occurs on very long time scales (more than a hundred years), one needs to set up theoretical models to predict the material swelling. It has been shown in previous studies that bitumen is a yield stress fluid. Therefore, the present work proposes to study the influence of a yield stress and of the production rate of gas on the evolution kinetics of a bubbles population. Usually, in a non-yield stress fluid and without gas creation, a supersaturation of gas leads to a scenario of germination, bubble growth and Ostwald ripening (growth of large bubbles at the expense of smaller ones). Over long times, a self-similar distribution of large bubbles is selected, independent of the initial distribution of nuclei. In this work, it is shown that there exist conditions for which the yield stress competes with the kinetics of ripening and induces hysteresis phenomena on the kinetics of bubbles distribution. The coupled effect of gas production rate and yield stress on the final population is discussed.

Analysis of tissue response around injectable hydrogels in the subcutaneous tissue of Wistar rats

Event Abstract Back to Event Analysis of tissue response around injectable hydrogels in the subcutaneous tissue of Wistar rats Khatharine S. Aoki1*, Yuri Gurfinkel1*, Eliana A. Duek2*, Daniel V. Mistura3* and Newton Oliveira4* 1 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Medical student, Brazil 2 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Physiology Department, Brazil 3 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Laboratory of Biomaterials, Brazil 4 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Morphology and Pathology Department, Brazil Tissue engineering represents an alternative for the recovery of organs and tissues[1]. In this way, the use of polymers as biomaterials has increased, being the hydrogels an option. These polymers have a hydrophilic characteristic, so they swell when in contact with water[2]. Furthermore, they can be presented in solid or liquid form and, in the liquid presentation, the hydrogel can be injected[3]. This pathway is very useful for the release of drugs or viable cells, since the low viscosity material assumes a gel form after application[4]. The ability to be injected allows the material to be presented as a minimally invasive alternative for minor procedures, which may lead to numerous benefits[5]. The aim of the present study was to analyze the application of the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC) in live animals, following the tissue reactions triggered around. The polymer was implanted through injections in the subcutaneous tissue of the posterior dorsum of 21 Wistar rats. After a period of 5, 7, 10, 15, 21 and 30 days the animals were sacrificed by overdose of halothane for subsequent histological analysis. As a result, the absence of inflammatory reaction was verified at the implant sites, in addition to the presence of gaps in the tissue, due to the processing of the implanted hydrogel. Still, histological analysis showed a reduction in the amount of hydrogel, according to the different times of sacrifice. Due to the thermosensitive characteristic of the PNIPAAm component of the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC), it was expected that the polymer could solidify at the site of application and be identified by the swelling caused in this process, or by the remnant of material present on site. However, there was no evidence that the implanted hydrogel had swollen. In addition, there were no macroscopic or microscopic evidences of the polymer in the material collected from implant sites. An association of hydrogel with dye ink was necessary to discover the location of the injected material and carry out further analysis of the sample. The dissipation of the hydrogel and the absence of material swelling may have occurred due to the addition of other substances to the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC) composition, which could modify its thermosensitive characteristic. Otherwise, the implant site may not have been suitable for its solidification. The results presented in this study suggest that the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC) has biocompatibility and potential as a filling material. However, further studies of this hydrogel are needed to get a better definition of its sol-gel transition, in order to understand its thermosensitivity and identify the presence of the polymer without addition of a dye ink.

Measure of the hydride breathing while cyclically absorbing and desorbing hydrogen

When a hydride material absorbs hydrogen, the phase change occurring is accompanied by a volume change of the material. Very often, the material is of granular nature, and the problem boils down to the study of a powder material swelling and shrinking – which is referred to as the hydride breathing – in a close container.Due to this breathing, and depending on the material apparent density and granulometry, severe mechanical stresses can appear and threaten the mechanical integrity of the container.In the present work, an original method for measuring the stresses is presented. It combines the measure of a force transducer and a deformation field by image correlation.Some experiments have been conducted on a metallic hydride type. They show that some configuration can lead to quite strong stresses. Particularly, the influence of the first absorption, namely the activation, is shown to be playing an important role concerning the maximum level of stress created. The initial filling ratio of the container by the hydride powder is also of first importance.

Protein composition alters in vivo resorption of PEG-based hydrogels as monitored by contrast-enhanced MRI

We report on the use of magnetic resonance imaging (MRI)-based non-invasive monitoring to document the role of protein adjuvants in hydrogel implant integration in vivo. Polyethylene glycol (PEG) hydrogels were formed with different protein constituents, including albumin, fibrinogen and gelatin. The hydrogels were designed to exhibit similar material properties, including modulus, swelling and hydrolytic degradation kinetics. The in vivo resorption properties of these PEG-based hydrogels, which contained a tethered gadolinium contrast agent, were characterized by MRI and histology, and compared to their in vitro characteristics. MRI data revealed that PEG–Albumin implants remained completely intact throughout the experiments, PEG–Fibrinogen implants lost about 10% of their volume and PEG–Gelatin implants underwent prominent swelling and returned to their initial volume by day 25. Fully synthetic PEG–diacrylate (PEG–DA) control hydrogels lost about half of their volume after 25 days in vivo. Transverse MRI cross-sections of the implants revealed distinct mechanisms of the hydrogel's biodegradation: PEG–Fibrinogen and PEG–Albumin underwent surface erosion, whereas PEG–Gelatin and PEG–DA hydrogels mainly underwent bulk degradation. Histological findings substantiated the MRI data and demonstrated significant cellular response towards PEG–DA and PEG–Gelatin scaffolds with relatively low reaction towards PEG–Fibrinogen and PEG–Albumin hydrogels. These findings demonstrate that PEG–protein hydrogels can degrade via a different mechanism than PEG hydrogels, and that this difference can be linked to a reduced foreign body response.

He–vacancy interaction and multiple He trapping in small void of silicon carbide

In fusion environment, large amounts of helium (He) atoms are produced by transmutation along with structural damage in the structural materials, causing material swelling and degrading of physical properties. To understand the microscopic mechanism of He trapping in vacancies and voids, we explored He–vacancy interactions in HenVam (Va for vacancy) clusters (n, m=1–4) and multiple He trapping in a 7-atom void of silicon carbide (SiC) by first-principles calculations. The binding energy between He and the HenVam clusters increases with the number of vacancies, while the vacancy binding energy gradually increases with the number of He atoms. Furthermore, a small cavity of about 0.55nm in diameter can accommodate up to 14 He atoms energetically and the corresponding internal pressure is estimated to be 2.5GPa. The tendency of He trapping in small voids provides an explanation for the experimentally observed He bubble formation at vacancy defects in SiC materials.

Hyperelastic Internal Balance by Multiplicative Decomposition of the Deformation Gradient

The multiplicative decomposition of the deformation gradient \({{\bf F} = {{\hat{\bf F}}}{\bf F}^*}\) is often used in finite deformation continuum mechanics as a basis for treating mechanical effects including plasticity, biological growth, material swelling, and notions of material morphogenesis. Evolution rules for the particular effect from this list are then posed for F*. The tensor \({{{\hat{\bf F}}}}\) is then invoked to describe a subsequent elastic accommodation, and a hyperelastic framework is put in place for its determination using an elastic energy density function, say \({W({\hat{\bf F}})}\), as a constitutive specification. Here we explore the theory that emerges if both F* and \({{\hat{\bf F}}}\) are governed by hyperelastic criteria; thus we consider energy densities \({W({{\hat{\bf F}}}, {\bf F}^*)}\). The decomposition of F is itself determined by energy minimization, and the variation associated with the multiplicative decomposition gives a tensor relation that is interpreted as an internal balance requirement. Our initial development purposefully proceeds with minimal presumptions on the kinematic interpretation of the factors in the deformation gradient decomposition. Connections are then made to treatments that ascribe particular kinematic properties to the decomposition factors—the theory of structured deformations is especially significant in this regard. Such theories have broad utility in describing certain substructural reconfigurations in solids. To demonstrate in the context of the present variational treatment we consider a boundary value problem that involves an imposed twist. If the twist is small then the minimizer is classically smooth. At larger values of twist the energy minimizer exhibits a non-smooth deformation that localizes slip at a singular surface.

The improved resistance of PDMS to pressure-induced deformation and chemical solvent swelling for microfluidic devices

We present a fabrication technique that increases the resistance of PDMS to deformation under pressure driven flow and chemical solvents swelling without the use of any foreign materials. This is achieved by enhancing the material properties of PDMS by coupling two previously isolated processes. First, the weight ratio of the prepolymer to the curing agent was increased from 10:1 to 5:1, with the latter showing 20% less deformation under pressurized conditions. Second, the cured PDMS was thermally aged at 200°C for a few hours, resulting in 140% less deformation for the thermally aged chip under the same pressure conditions. The combined processes benefit from a nonlinear coupling effect on improvement and show 860% less deformation under pressure driven flow in the enhanced PDMS chip compared to that in the standard 10:1 PDMS chip. The deformation of the standard and the enhanced PDMS microchannels under pressure driven flow is quantified using fluorescence microscopy. The compatibility of PDMS with nonpolar solvents was also explored by quantifying material swelling due to toluene absorption using brightfield imaging of the microchannel. The enhanced PDMS showed less than 10% swelling against toluene compared to 55% in the standard PDMS. The enhanced PDMS is also less permeable to the small hydrophobic molecule rhodamine B (RhB), as quantified by epi-fluorescence microscopy of the absorbed dye. The improved surface and material properties of the thermally treated PDMS are certainly beneficial in microfluidic applications that use this common soft lithography material.

Combined Surface and Electrochemical Study of the Lithiation/Delithiation Mechanism of the Iron Oxide Thin-Film Anode for Lithium-Ion Batteries

Iron oxide (mostly α-Fe2O3) model thin-film electrodes were prepared by thermal oxidation of pure metal iron substrates at 300 ± 5 °C in air and used for comprehensive investigation of the lithiation/delithiation mechanisms of anode material undergoing an electrochemical conversion reaction with lithium ions. Surface (X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS)) and electrochemical (cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS)) analytical techniques were combined. The results show that intercalation of Li in the Fe2O3 matrix and solid electrolyte interphase (SEI) layer formation both precede conversion to metallic iron and Li2O upon lithiation. Depth profile analysis evidences stratification of the converted thin-film electrode into fully and partially lithiated outer and inner parts, respectively, due to mass transport limitation. The SEI layer has a stable composition (Li2CO3 with minor ROCO2Li) but dynamically increases/decreases in thickness upon lithiation/delithiation. Conversion, proceeding mostly in the outer part of the electrode, causes material swelling accompanied by SEI layer thickening. Upon delithiation, lithium is trapped in the deconverted electrode subjected to shrinking, and the SEI layer mostly decomposes and reduces in thickness after deconversion. The nonreversibility of both conversion and surface passivation mechanisms is demonstrated.

The nano films refractive index values changing in the acidic environment studies

Nano films produced by the sol-gel technology were now widely used in the different science and technology areas for the effective properties modification of the glass substrates. The composite with such a nano film refractive index value changing after its interaction with the hydrochloric acid solution of the different concentration has been studied in this work. It has been obtained that the process of the nano dimensional film produced from the film-forming solution and acid solution interaction was consists of two mutually opposing effects--film material swelling and dissolution. If the nano film has been dissolved without of the swelling its refractive index was decreased. But the film material under the hydrochloric acid solution action passes through the swelling stage its refractive index increases in proportion of the swelling ratio.

Numerical Modeling of Ablation Heat Transfer

A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme uses a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple example of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.

Wet‐Spun Stimuli‐Responsive Composite Fibers with Tunable Electrical Conductivity

AbstractWet‐spun stimuli‐responsive composite fibers made of covalently crosslinked alginate with a high concentration of single‐walled carbon nanotubes (SWCNTs) are electroconductive and sensitive to humidity, pH, and ionic strength, due to pH‐tunable water absorbing properties of the covalently crosslinked alginate. The conductivity depends on the material swelling in humid atmosphere and aqueous solutions: the greater the swelling, the smaller is the electrical conductivity. The covalently crosslinked fibers reversibly deform during the swelling/shrinking. In the swollen state, the fibers are less conductive, while they return to the same level of conductivity after shrinking. This unique reversible change of electroconductivity of the SWCNT‐alginate fibers is due to the elastic deformation of the alginate network in the area of electrical contacts between SWCNT bundles arrested in the alginate matrix. Fibers of this kind can be used as a simple, robust, disposable, and biocompatible platform for electrotextiles, biosensors, and flexible electronics in biomedical and biotechnological applications.

An investigation into material-induced surface roughness in ultra-precision milling

This paper presents a theoretical and experimental investigation into the effect of the workpiece material on surface roughness in the ultra-precision milling process. The influences of material swelling and tool-tip vibration on surface generation in ultra-precision raster milling are studied. A new method is proposed to characterize material-induced surface roughness on the raster-milled surface. A new parameter is defined to characterize the extent of surface roughness profile distortion induced by the materials being cut. An experiment is conducted to compare the proposed method with surface roughness parameters and power spectrum density analysis method by machining three different workpiece materials. The results show that the presence of elastic recovery improves the surface finish in ultra-precision raster milling and that, among the three materials being cut in the experiment, aluminum bronze has the greatest influence on surface finish due to its highest elastic recovery rate and hardness. The results also show that, in the case of faster feed rates, the proposed method more efficiently characterizes material-induced surface roughness.