Changes In Micromechanical Properties Research Articles

CO2-induced micro-mechanical alterations of mudstone Caprock: Examples from the Mercia Mudstone Group, East Irish Sea Basin

Mechanical properties of caprock are important for subsurface energy sequestration as they determine the rock stability under the influence of external forces. Despite some advantages, there is a lack of knowledge regarding the interplay between rock texture and mechanical properties and their impact on the caprock stability within a short-term fluid-rock reaction period. Typical caprock samples from the Mercia Mudstone Group in the East Irish Sea Basin are studied in this work. X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) were used to identify minerology and local heterogeneity characteristics. Nanoindentation tests were conducted before and after CO2-brine-rock reaction to investigate the changes of micro-mechanical properties. After CO2-brine treatment, significant dolomite dissolution was observed in all samples (although dolomite content was only minor in some samples). In contrast, the micro-texture of other minerals showed no significant changes indicating minimal to no dissolution at the current resolution. The changes of mechanical properties are lower than expected, which are probably related to the impaired cementation induced by the retained water in pore throats and relatively rough surface after reaction. For long-term carbon sequestration, the layered depositional characteristics of different phases may not only form a barrier to prevent fluids leaking upward, but also complement each other in mechanical properties to maintain stability. This study improves the understanding of the effect of microscale structural and micro-mechanical changes on caprock stability in carbon sequestration related applications.

Variation of Young's modulus suggested the main active sites for four different aging plastics at an early age time

Precisely determining which bonds are more sensitive when plastic aging occurs is critical to better understand the mechanisms of toxic release and microplastics formation. However, the relationship between chemical bonds with the active aging sites changes and the aging behavior of plastics at an early age is still unclear. Herein, the mechanical behavior of four polymers with different substituents was characterized by the high-resolution AFM. Young's modulus (YM) changes suggested that the cleavage of C-Cl bonds in PVC, C-H bonds in PE and PP, and C-F bonds in PTFE are the main active aging sites for plastic aging. The aging degree of the plastics followed the order of PVC > PP > PE > PTFE. Two aging periods exhibited different YM change behavior, the free radical and cross-linking resulted in a minor increase in YM during the initiation period. Numerous free radicals formed and cross-linking reaction happened, causing a significant increase in YM during the propagation period. Raman spectroscopy verified the formation of microplastics. This research develops promising strategies to quantitatively evaluate the aging degrees using AFM and establish the relationship between chemical bonds and mechanical behavior, which would provide new method to predict plastic pollution in actual environments.

Detection of HOCl-driven degradation of the pericardium scaffolds by label-free multiphoton fluorescence lifetime imaging

Artificial biomaterials can significantly increase the rate of tissue regeneration. However, implantation of scaffolds leads not only to accelerated tissue healing but also to an immune response of the organism, which results in the degradation of the biomaterial. The synergy of the immune response and scaffold degradation processes largely determines the efficiency of tissue regeneration. Still, methods suitable for fast, accurate and non-invasive characterization of the degradation degree of biomaterial are highly demandable. Here we show the possibility of monitoring the degradation of decellularized bovine pericardium scaffolds under conditions mimicking the immune response and oxidation processes using multiphoton tomography combined with fluorescence lifetime imaging (MPT-FLIM). We found that the fluorescence lifetimes of genipin-induced cross-links in collagen and oxidation products of collagen are prominent markers of oxidative degradation of scaffolds. This was verified in model experiments, where the oxidation was induced with hypochlorous acid or by exposure to activated neutrophils. The fluorescence decay parameters also correlated with the changes of micromechanical properties of the scaffolds as assessed using atomic force microscopy (AFM). Our results suggest that FLIM can be used for quantitative assessments of the properties and degradation of the scaffolds essential for the wound healing processes in vivo.

ULTRASTRUCTURAL CHARACTERISTICS OF ERYTHROCYTES AND THEIR RELATIONSHIP WITH OXYGEN TRANSPORT IN PATIENTS WITH CORONARY HEART DISEASE AFTER CORONARY ARTERY BYPASS GRAFTING

TYPE: Abstract TOPIC: Cardiothoracic Surgery PURPOSE: Evaluation of nanostructural and micromechanical red blood cells (RBC) characteristics and their relationship with oxygen transport function after isolated on-pump coronary artery bypass grafting (CABG). METHODS: 30 IHD patients underwent standart CABG procedure with cardiopulmonary bypass(CPB). RBC scanning was performed on a «Bioscope Catalyst» atomic force microscope (AFM) (Bruker, USA). The micromechanical properties were investigated with the «PFQNM-LC-A-CAL» conveyors. The following were recorded: the RBC diameter, the height of their side, area, volume, membrane rigidity, adhesion strength, Young's modulus, elastic deformation. For oxygen transport evaluation oxygen delivery index (DO2I), consumption index (VO2I), and extraction ratio (O2ER) were calculated. RESULTS: On the next day after CABG, a decrease in DO2I, VO2I, and O2ER by 14%, 33% and 16% was recorded respectively, indicating a limitation of gas transport blood function. RBC showed an increase in area by 35%, diameter by 6%, volume by 19%, and the height of the side by 5 times. At the same time, multidirectional changes of micromechanical properties of RBC membranes were noted: Young's modulus and stiffness decreased by 3.2 and 2 times, respectively; the adhesion force increased 2.7 times, and the whippy-elastic deformation – up to 2.2 times. Correlation analysis showed the presence of reliable correlations between oxygen transport indicators and biomechanical RBC membranes parameters CONCLUSIONS: Analysis of nanostructural RBC parameters and oxygen transport indicators expands the pathophysiological mechanisms understanding of postperfusion disorders. CLINICAL IMPLICATIONS: improvement and personification of approaches to cardiopulmonary bypass DISCLOSURE: Nothing to declare. KEYWORD: atomic force microscopy

Impact of solar radiation on chemical structure and micromechanical properties of cellulose-based humidity-sensing material Cottonid

Renewable and environmentally responsive materials are an energy- and resource-efficient approach in terms of civil engineering applications, e.g. as so-called smart building skins. To evaluate the influence of different environmental stimuli, like humidity or solar radiation, on the long-term actuation behavior and mechanical robustness of these materials, it is necessary to precisely characterize the magnitude and range of stimuli that trigger reactions and the resulting kinetics of a material, respectively, with suitable testing equipment and techniques. The overall aim is to correlate actuation potential and mechanical properties with process- or application-oriented parameters in terms of demand-oriented stimuli-responsive element production. In this study, the impact of solar radiation as environmental trigger on the cellulose-based humidity-sensing material Cottonid, which is a promising candidate for adaptive and autonomously moving elements, was investigated. For simulating solar radiation in the lab, specimens were exposed to short-wavelength blue light as well as a standardized artificial solar irradiation (CIE Solar ID65) in long-term aging experiments. Photodegradation behavior was analyzed by Fourier-transform infrared as well as electron paramagnetic resonance spectroscopy measurements to assess changes in Cottonid’s chemical composition. Subsequently, changes in micromechanical properties on the respective specimens’ surface were investigated with roughness measurements and ultra-micro-hardness tests to characterize variations in stiffness distribution in comparison to the initial condition. Also, thermal effects during long-term aging were considered and contrasted to pure radiative effects. In addition, to investigate the influence of process-related parameters on Cottonid’s humidity-driven deformation behavior, actuation tests were performed in an alternating climate chamber using a customized specimen holder, instrumented with digital image correlation (DIC). DIC was used for precise actuation strain measurements to comparatively evaluate different influences on the material’s sorption behavior. The infrared absorbance spectra of different aging states of irradiated Cottonid indicate oxidative stress on the surface compared to unaged samples. These findings differ under pure thermal loads. EPR spectra could corroborate these findings as radicals were detected, which were attributed to oxidation processes. Instrumented actuation experiments revealed the influence of processing-related parameters on the sorption behavior of the tested and structurally optimized Cottonid variant. Experimental data supports the definition of an optimal process window for stimuli-responsive element production. Based on these results, tailor-made functional materials shall be generated in the future where stimuli-responsiveness can be adjusted through the manufacturing process.

Accumulation of radiation defects and modification of micromechanical properties under MgO crystal irradiation with swift 132Xe ions

Accumulation of F-type defects under irradiation of MgO crystals by 0.23-GeV 132Xe ions with fluence varying by three orders of magnitude has been investigated via the spectra of optical absorption and low-temperature cathodoluminescence. The number of single centers continuously increases with fluence without any marks of saturation. At the highest fluence, a mean volume concentration of 3.1 × 1019 and 3.35 × 1019 cm−3 is reached for F and F+ centers, respectively. The F+ emission strongly dominates in the cathodoluminescence of irradiated MgO and its enhancement with fluence is detected. However, the creation efficiency of the F2 aggregate centers is very low and fluence dependence has a complicated shape. Radiation-induced changes of micro-mechanical properties of the same samples have been analysed; the depth profiles of hardening correlate with the ion energy loss. A joint contribution of ionization and impact mechanisms in the formation of structural defects under MgO irradiation with Xe ions is considered.

Shale-brine-CO2 interactions and the long-term stability of carbonate-rich shale caprock

The success of geological carbon storage (GCS) depends on the sealing properties of caprocks, typically mudrocks, and their laminated variety – shales. In this study, we examined mineralogical changes in carbonate-rich Mancos Shale and corresponding changes in micro-mechanical properties following the reaction with carbon dioxide (CO2). Mineralogical changes of Mancos Shale depended on the pressure of CO2 during its exposure to the CO2-brine mixtures for up to 8 weeks. Dedolomitization was observed in the reactors pressurized with 100 psi of CO2, combined with the precipitation of gypsum. In the reactor pressurized with 2500 psi of CO2, the complete dissolution of calcite, partial dissolution of dolomite, and precipitation of magnesite and anhydrite were observed. Localized mechanical weakening was observed only for dolomite-muscovite-illite-rich laminae following whole shale puck alteration at 2500 psi of CO2, and a decrease of up to 50 ± 20% in scratch toughness was observed. The quartz-calcite-rich laminae did not exhibit a measurable difference in scratch toughness before and after reaction in CO2-rich brine. The predicted changes in mineralogy, porosity, density, and hardness of Mancos Shale are limited, according to the geochemical models describing alteration of shale by CO2-rich brine lasting for 5000 years. This study illustrates a coupled and localized chemical-mechanical response of caprock to the injection of CO2.

Changes in micromechanical properties of Na-montmorillonite caused by CO2/H2O sorption

CO2/H2O intercalation causes changes in the elastic mechanical properties of clay. This phenomenon is critical to geologic carbon sequestration (GCS) and enhancing oil rate (EOR) via CO2 adsorption. In this work, the elastic stiffness and hydrostatic mechanical behavior of Na-montmorillonite (MMT) exposure to variable component of CO2/H2O mixture are investigated using combinations of Monte Carlo and Molecular Dynamic methods. In the hydrostatic test simulation of 1W and 2W hydrated state, volume and basal spacing d001 linearly decrease with the increasing hydrostatic pressure. Moreover, gradients of 1W hydrated state are smaller than that of the gradients of 2W hydrated state. The linear gradient is related to the elastic modulus. Therefore higher hydrated state results in softer structure. Additionally, the yielding bulk modulus linearly decreases with the pressure. The decreasing gradient almost keeps at a constant of 1.0GPa/GPa with variable component of CO2/H2O. At the super critical condition of CO2 (P=0.01GPa, T=304.5K), the elastic stiffness fluctuates with the variable component of H2O/CO2. CO2 intercalation strongly affects the out-of-plane elastic stiffness while has little influence on the in-plane stiffness.

Ultra nano-hardness of surface layer of irradiated high–density polyethylene (HDPE)

Using high doses of beta radiation for high-density polyethylene (HDPE) and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The specimens of high-density polyethylene (HDPE) were made by injection moulding technology and irradiated by high doses of beta radiation (0, 33, 66 and 99 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented ultra nano-hardness test. The results of the measurements showed considerable decrease in micromechanical properties (indentation hardness, indentation elastic modulus) when low doses of beta radiation are used.

Mechanical properties of surface layer of unfilled polypropylene

Using high doses of beta radiation for unfilled polypropylene (PP) and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The testing sapmles polypropylene (PP) were made by injection moulding technology and irradiated by high doses of beta radiation (0, 15 and 33 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented ultra nano-hardness test. The results of the measurements showed considerable increase in micromechanical properties (indentation hardness, indentation elastic modulus) when low doses of beta radiation are used.

Changes in bamboo fiber subjected to different chemical treatments and freeze-drying as measured by nanoindentation

The effects of chemical treatments (H2O2 + CH3COOH, acidified NaClO2, and NaOH) and freeze-drying on bamboo fibers were studied at a submicron level, to characterize chemical and mechanical changes to the secondary cell wall. Specifically, a field emission environmental scanning electron microscope (FE-ESEM) and imaging fourier transform infrared spectroscopy (FTIR) were used to demonstrate degradation in morphology and molecular structure, and nanoindentation was used to track changes in micromechanical properties. The results showed that cellular structures after chemical treatments clearly displayed wrinkles, pores, and microfibrils. The decreased bands at 1508 cm-1 and 1426 cm−1 showed that lignin was degraded on treatment of H2O2 + CH3COOH and acidified NaClO2, which directly resulted in a decrease in hardness (H) in the secondary cell wall for treated fibers. In addition, a diminishing peak at 1733 cm−1 caused by NaOH solution indicated that hemicellulose was seriously degraded. It resulted in a decreased modulus (E r) by 13.71 % in bamboo fibers, while no obvious reduction was observed in the first two steps.

The Behaviour of Cross-Linking Filled PA66 by Micro-Indentation Test

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micro-mechanical changes in the surface layer of glass-fiber filled PA 66 modified by beta radiation were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. The specimens were prepared by injection technology and subjected to radiation doses of 0, 33, 66 nad 99 kGy. The change of micro-mechanical properties is greatly manifested mainly in the surface layer of the modified polypropylene where a significant growth of micro-hardness values can be observed. Indentation modulus increased from 1.8 to 3.0 GPa (increasing about 66%) and indentation hardness increased from 87 to 157 MPa (increasing about 80%). This research paper studies the influence of the dose of irradiation on the micro-mechanical properties of semi-crystalline polyamide 66 filled by 30% glass fiber at room temperature. The study is carried out due to the ever-growing employment of this type of polymer.

Micro-Hardness of Irradiated Polyamide

The influence of beta radiation on the changes in the structure and selected properties (mechanical and thermal) was proved. Using high doses of beta radiation for glass fiber filled polyamide (PA) and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The specimens of glass fiber filled PA were made by injection moulding technology and irradiated by low doses of beta radiation (0, 132, 165 and 198 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented microhardness test. The results of the measurements showed change some in micromechanical properties (indentation hardness) when high doses of beta radiation are used.

Thermal history dependence of indentation induced densification in an aluminosilicate glass

The mechanical properties of glasses are not only determined by their chemical composition, but also by their thermal history, i.e., fictive temperature. In this paper, we consider an alkaline earth aluminosilicate glass composition which has been annealed to exhibit a wide range of fictive temperatures (~130K). Hardness and brittleness index have previously been shown to increase with decreasing fictive temperature, whereas the crack resistance decreases. Through quantification of the indentation depth before and after heat treatments, we show that these changes in micromechanical properties arise from an increased resistance to densification under the indenter when the glasses are annealed. We discuss these results in relation to the indentation size effect and the overall network compaction.

Micro-hardness of surface layer of irradiated Polybutene Terephthalate (PBT)

Using high doses of beta radiation for polybutylene terephthalate (PBT) and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The specimens of PBT were made by injection moulding technology and irradiated by high doses of beta radiation (0, 132, 165 and 198 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented microhardness test. The results of the measurements showed considerable increase in micromechanical properties (indentation hardness, indentation elastic modulus) when high doses of beta radiation are used.

Effect of High Doses Beta Irradiation on the Micromechanical Properties of Surface Layer of Glass-Filled Polypropylene

The presented article deals with the research of micro-mechanical properties in the surface layer of modified Polypropylene filled by 25% of glass fibers. These micro-mechanical properties were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. Radiation doses used were 0, 66 and 99 kGy for filled Polypropylene with the 6% cross-linking agent (triallyl isocyanurate). The change of micromechanical properties is greatly manifested mainly in the surface layer of the modified polypropylene where a significant growth of microhardness values can be observed.

Effect of low doses beta irradiation on micromechanical properties of surface layer of injection molded polypropylene composite

Abstract The influence of beta radiation on the changes in the structure and selected properties (mechanical and thermal) was proved. Using low doses of beta radiation for 25% glass fiber filled polypropylene and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The specimens of 25% glass fiber filled PP were made by injection molding technology and irradiated by low doses of beta radiation (0, 15 and 33 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using FTIR, SEM, WAXS and instrumented microhardness test. The results of the measurements showed considerable increase in micromechanical properties (indentation hardness, indentation elastic modulus) when low doses of beta radiation are used.

Influence of Content of Crosslinking Agent on the Micromechanical Properties of Glass-Filled Polyamide 6

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Some types of polymers do not cross-link during radiation crosslinking but degrade. In order to create 3D net in the polymer structure it is necessary to add a crosslinking agent. The specimens were prepared by injection technology with the TAIC crosslinking agent at 0, 1, 2 and 3 %. The changes of micromechanical properties of the surface layer were measured by instrumented microhardness test. It was found that micromechanical properties of the surface layer of the tested polyamide changed.

Effect of Beta Low Irradiation Doses on the Micromechanical Properties of Surface Layer of LDPE

The experimental study deals with the effect of modification of the surface layer by irradiation cross-linking on the micromechanical properties of the low-density polyethylene (LDPE) tested using the instrumented nanohardness test. The surface layer of LDPE specimen made by injection technology was modified by irradiation cross-linking using beta irradiation, which significantly influences micromechanical properties of the surface layer. Compared to the heat and chemical-heat treatment of metal materials (e.g. hardening, nitridation, case hardening), cross-linking in polymers affects the surfaces in micro layers. These micromechanical changes of the surface layer are observed in the instrumented microhardness test. Our research confirms the comparable properties of surface layer of irradiated LDPE with highly efficient polymers. The subject of this research is the influence of irradiation dosage on the changes of micromechanical properties of surface layer of LDPE.

The effect of beta irradiation on morphology and micro hardness of polypropylene thin layers

This experimental study describes the influence of radiation cross-linking to the structure and properties of polypropylene. The structure of polypropylene was assessed using microhardness measurement. It was verified that the structure influences the resulting material parameters. Polypropylene modified by radiation cross-linking at doses of 30, 45, 60 and 90kGy shows substantial changes of the structure and hence changes to resulting mechanical and micromechanical properties. The change of micromechanical properties is greatly manifested mainly in the surface layer of the modified polypropylene where a significant growth of microhardness values can be observed. The changes were examined and confirmed by X-ray diffraction and measurement on Transmission electron microscopy.