Статті в журналах: "Diffusion mechanism of degradation"

1

He, Canzhong, Yueqiang Wang, Yongyue Luo, Lingxue Kong, and Zheng Peng. "Thermal degradation kinetics and mechanism of epoxidized natural rubber." Journal of Polymer Engineering 33, no. 4 (July 1, 2013): 331–35. http://dx.doi.org/10.1515/polyeng-2013-0040.

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Abstract Thermal resistance is one of the most dominative properties for polymer materials. Thermal degradation mechanisms of epoxidized natural rubber (ENR) and NR are studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The results show that, the introduction of epoxy groups into the NR molecular main chain leads to a remarkable change in the degradation mechanism. The thermal stability of ENR is worse than that of NR. For the first thermooxidative degradation stage, the thermal decomposition mechanism of ENR is similar to that of NR, which corresponds to a mechanism involving one-dimensional diffusion. For the second stage, the thermal decomposition mechanism of ENR is a three-dimensional diffusion, which is more complex than that of NR. Kinetic analysis showed that activation energy (Eα), activation entropy (ΔH) and activation Gibbs energy (ΔG) values are all positive, indicating that the thermooxidative degradation process of ENR is non-spontaneous.

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2

Boukettaya, Sonia, Ahmad Alawar, Fahad Almaskari, Hachmi Ben Daly, Ahmed Abdala, and Sami Chatti. "Modeling of water diffusion mechanism in polypropylene/date palm fiber composite materials." Journal of Composite Materials 52, no. 19 (January 10, 2018): 2651–59. http://dx.doi.org/10.1177/0021998317752228.

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The aim of this work is to model the water absorption mechanism of the polypropylene/date palm fibers composite materials after their exposure at different immersion conditions. For short immersion period, a model combining the Fick’s law and the time temperature stress principle has been proposed to describe the water absorption mechanism. However, it has been noted that, after a saturation time, the water diffusion mechanism leads to a physical degradation and a mass loss into the composite material, especially under high temperatures and long times of water immersion. Microscopic observations have revealed a decrease of the interfacial adhesion between the fibers and the matrix and fiber degradations. A general new model describing the evolution of the water uptake mechanism and the degradation phenomenon has been also proposed in the present work. A good agreement between the theoretical and experimental data has been obtained.

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3

Suh, Min Chul, Ho Kyoon Chung, Sang-Yeol Kim, Jang Hyuk Kwon, and Byung Doo Chin. "Cathode diffusion and degradation mechanism of polymeric light emitting devices." Chemical Physics Letters 413, no. 1-3 (September 2005): 205–9. http://dx.doi.org/10.1016/j.cplett.2005.07.082.

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4

Li, Chun Yan, Cong Cong Hu, Zhi Guo Wen, and Sheng Xiong Dong. "The In Vitro Degradation Kinetics of Polyurethane Prodrug Materials." Advanced Materials Research 399-401 (November 2011): 1067–70. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.1067.

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The method of high performance liquid chromatography (HPLC) is established to determine the content of antibacterial agent — ciprofloxacin (CF) in the degradation solution of ciprofloxacin-polyurethane (CFPU) and investigate the in vitro degradation kinetics by plotting and fitting the cumulative release curves to inspect the effects of different medium and different concentrations on drug release. The results showed that the HPLC method is accurate, reliable and simple. The drug-release of CFPU was bioresponsive and could be accorded with first order kinetics. It was observed that CF was released from CFPU by a combination of diffusion and erosion mechanism, mainly in the manner of diffusion in the absence of infection while erosion mechanism in the presence of infection.

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5

Sun, Li, Xiaohui Gu, and Pu Song. "Accelerated Degradation Process Analysis Based on the Nonlinear Wiener Process with Covariates and Random Effects." Mathematical Problems in Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/5246108.

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It is assumed that the drift parameter is dependent on the acceleration variables and the diffusion coefficient remains the same across the whole accelerated degradation test (ADT) in most of the literature based on Wiener process. However, the diffusion coefficient variation would also become obvious in some applications with the stress increasing. Aiming at the phenomenon, the paper concludes that both the drift parameter and the diffusion parameter depend on stress variables based on the invariance principle of failure mechanism and Nelson assumption. Accordingly, constant stress accelerated degradation process (CSADP) and step stress accelerated degradation process (SSADP) with random effects are modeled. The unknown parameters in the established model are estimated based on the property of degradation and degradation increment, separately for CASDT and SSADT, by the maximum likelihood estimation approach with measurement error. In addition, the simulation steps of accelerated degradation data are provided and simulated step stress accelerated degradation data is designed to validate the proposed model compared to other models. Finally, a case study of CSADT is conducted to demonstrate the benefits of our model in the practical engineering.

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6

Huang, Qiu An, Su Zhen Mei, Ling Fang Xu, and Wei Ming Yang. "Degradation of Metal-Supported SOFC and One Powerful Investigation Method: Multi-Scale Modeling and Simulation." Applied Mechanics and Materials 110-116 (October 2011): 3376–81. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.3376.

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Metal-supported solid oxide fuel cell (SOFC) has a varieties of potential advantages compared to the traditional ceramic supported SOFC. However, degradation issue of metal-supported SOFC is seriously impeding its further development, in particular, the inter-diffusion and interaction of iron, chromium and nickel at substrate/anode interface is known to be a key issue responsible for cell rapid degradation. With respect to the complexity and nonlinearity of degradation mechanism, multi-scale modeling and simulation is regarded as one powerful method to gain a deep insight on degradation mechanism. In present work, multi-scale models were presented to investigate multi-scale physicochemical phenomena happening at interface of anode/substrate, with the attempt to reveal degradation mechanism. The research procedure for the above goal was addressed in detail as well.

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7

Delmelle, Renaud, Jasmin Terreni, Arndt Remhof, Andre Heel, Joris Proost, and Andreas Borgschulte. "Evolution of Water Diffusion in a Sorption-Enhanced Methanation Catalyst." Catalysts 8, no. 9 (August 21, 2018): 341. http://dx.doi.org/10.3390/catal8090341.

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Sorption-enhanced methanation has consequent advantages compared to conventional methanation approaches; namely, the production of pure methane and enhanced kinetics thanks to the application of Le Châtelier’s principle. In this paper, we address the question of the long-term stability of a sorption-enhanced methanation catalyst-support couple: Ni nanoparticles on zeolite 5A. Compared to most conventional methanation processes the operational conditions of sorption-enhanced methanation are relatively mild, which allow for stable catalyst activity on the long term. Indeed, we show here that neither coking nor thermal degradation come into play under such conditions. However, a degradation mechanism specific to the sorption catalysis was observed under cyclic methanation/drying periods. This severely affects water diffusion kinetics in the zeolite support, as shown here by a decrease of the water-diffusion coefficient during multiple cycling. Water diffusion is a central mechanism in the sorption-enhanced methanation process, since it is rate-limiting for both methanation and drying.

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8

Wang, H., Z. Y. Bian, and D. Z. Sun. "Degradation mechanism of 4-chlorophenol with electrogenerated hydrogen peroxide on a Pd/C gas-diffusion electrode." Water Science and Technology 63, no. 3 (February 1, 2011): 484–90. http://dx.doi.org/10.2166/wst.2011.247.

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Using a self-made Pd/C gas-diffusion electrode as the cathode and a Ti/IrO2/RuO2 anode, the degradation of 4-chlorophenol has been investigated in an undivided electrolysis device by the electrochemical oxidation processes. The result indicated that the neutral aqueous solutions can accelerate 4-chlorophenol degradation during electrolysis. The removal efficiency of 4-chlorophenol and COD reached about 89.6% and 62.0% after 120 min electrolysis, respectively. It suggested that most of 4-chlorophenol was oxidised to intermediates using the Pd/C gas-diffusion electrode. Furthermore, the biodegradation ability of the solution was increased significantly during the electrolysis. The degradation of 4-chlorophenol was attributed to the cooperative oxidation processes including electrochemical oxidation at the anode and H2O2 and hydroxyl radical (HO·) produced by the reduction of oxygen at the cathode. Finally, main aromatic intermediates (e.g., hydroquinone and benzoquinone) and main aliphatic carboxylic intermediates (e.g., oxalic, malonic, maleic, succinic, fumaric, and dodecanoic acids) were identified by GC-MS. Moreover, a reaction scheme involving all these intermediates was proposed.

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9

Aizer, Adva, Yehuda Brody, Lian Wee Ler, Nahum Sonenberg, Robert H. Singer, and Yaron Shav-Tal. "The Dynamics of Mammalian P Body Transport, Assembly, and Disassembly In Vivo." Molecular Biology of the Cell 19, no. 10 (October 2008): 4154–66. http://dx.doi.org/10.1091/mbc.e08-05-0513.

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Exported mRNAs are targeted for translation or can undergo degradation by several decay mechanisms. The 5′→3′ degradation machinery localizes to cytoplasmic P bodies (PBs). We followed the dynamic properties of PBs in vivo and investigated the mechanism by which PBs scan the cytoplasm. Using proteins of the decapping machinery, we asked whether PBs actively scan the cytoplasm or whether a diffusion-based mechanism is sufficient. Live-cell imaging showed that PBs were anchored mainly to microtubules. Quantitative single-particle tracking demonstrated that most PBs exhibited spatially confined motion dependent on microtubule motion, whereas stationary PB pairs were identified at the centrosome. Some PBs translocated in long-range movements on microtubules. PB mobility was compared with mitochondria, endoplasmic reticulum, peroxisomes, SMN bodies, and stress granules, and diffusion coefficients were calculated. Disruption of the microtubule network caused a significant reduction in PB mobility together with an induction of PB assembly. However, FRAP measurements showed that the dynamic flux of assembled PB components was not affected by such treatments. FRAP analysis showed that the decapping enzyme Dcp2 is a nondynamic PB core protein, whereas Dcp1 proteins continuously exchanged with the cytoplasm. This study reveals the mechanism of PB transport, and it demonstrates how PB assembly and disassembly integrate with the presence of an intact cytoskeleton.

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10

Park, Yongha, Yeonsu Kwak, Saerom Yu, Arash Badakhsh, Yu-Jin Lee, Hyangsoo Jeong, Yongmin Kim, et al. "Degradation mechanism of a Pd/Ta composite membrane: Catalytic surface fouling with inter-diffusion." Journal of Alloys and Compounds 854 (February 2021): 157196. http://dx.doi.org/10.1016/j.jallcom.2020.157196.

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11

Zhao, Rui, Xuan Zhang, Fanli Chen, Xiaobing Man, and Wenqiang Jiang. "Study on Electrochemical Degradation of Nicosulfuron by IrO2-Based DSA Electrodes: Performance, Kinetics, and Degradation Mechanism." International Journal of Environmental Research and Public Health 16, no. 3 (January 26, 2019): 343. http://dx.doi.org/10.3390/ijerph16030343.

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The widely used sulfonylurea herbicides have caused negative effects on the environment and human beings. Electrochemical degradation has attracted much attention in the treatment of refractory organic compounds due to its advantage of producing no secondary pollution. Three kinds of IrO2-based dimensionally stable anodes (DSAs) were used to degrade nicosulfuron by a batch electrochemical process. The results showed that a well-distributed crack network was formed on the Ti/Ta2O5-IrO2 electrode and Ti/Ta2O5-SnO2-IrO2 electrode due to the different coefficients of thermal expansion between the Ti substrate and oxide coatings. The oxygen evolution potential (OEP) increased according to the order of Ti/RuO2-IrO2 < Ti/Ta2O5-SnO2-IrO2 < Ti/Ta2O5-IrO2. Among the three electrodes, the Ti/Ta2O5-IrO2 electrode showed the highest efficiency and was chosen as the experimental electrode. Single factor experiments were carried out to obtain the optimum electrolysis condition, shown as follows: currency intensity 0.8 A; electrode spacing 3 cm, electrolyte pH 3. Under the optimum conditions, the degradation of nicosulfuron followed first-order kinetics and was mainly due to indirect electrochemical oxidation. It was a typical diffusion-controlled electrochemical process. On the basis of the intermediate identified by high performance liquid chromatograph-mass spectrometry (HPLC-MS), two possible degradation routes were proposed.

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12

Hawraneck, Matthias, Jürgen Zimmer, Wolfgang Raberg, Klemens Prügl, Stephan Schmitt, Thomas Bever, Stefan Flege, and Lambert Alff. "Diffusion based degradation mechanisms in giant magnetoresistive spin valves." Applied Physics Letters 93, no. 1 (July 7, 2008): 012504. http://dx.doi.org/10.1063/1.2956394.

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13

Li, Bin, Kai Xiao Zhang, Chao Yu Feng, Xing Bin Zheng, Kun Xie, and Yue Li. "The Simulation of Photocatalysis Degradation of Formaldehyde Using Nano-TiO₂ Based on the Diffusion Model." Applied Mechanics and Materials 327 (June 2013): 8–12. http://dx.doi.org/10.4028/www.scientific.net/amm.327.8.

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In this paper, the one-dimensional diffusion model about nano-TiO2 photocatalytic degradation of formaldehyde process was established ,through analyzing nano-TiO2 photocatalytic mechanism, and verifying the accuracy of the model by the experimental data combined with Fick's law. According to this model, it concluded that the degradation rate of the formaldehyde is related to the height of purification apparatus, and when the height is smaller, the degradation rate is greater. Within the same cleaning time (t = 200min), when the height is 0.15m, the rate of degradation of formaldehyde is 99%; when the height is 0.3m, the rate of degradation of formaldehyde is 88%; while the height is 0.7m , the rate is only 32%.

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14

Zeng, Yu, Yongkang Tang, Gang Li, Ziqiang Cheng, Yong Liu, and Gaorong Han. "Li-Ion-Trapping-Induced Degradation Mechanism of Colored State in Tungsten Oxide Electrochromic Films." Journal of The Electrochemical Society 168, no. 12 (December 1, 2021): 126507. http://dx.doi.org/10.1149/1945-7111/ac3abf.

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Aiming to investigate the degradation mechanism of their colored states, tungsten oxide films with different oxygen/tungsten ratio were prepared by direct current reactive magnetron sputtering through adjusting the oxygen partial pressure. After a long-term cycling test, the sample prepared under low oxygen partial pressure (LO#) showed an excellent cycle stability which its optical modulation amplitude remains stable at 23.6%, while the one prepared under high oxygen partial pressure (HO#) exhibited an obvious degradation process of the colored state, leading to the optical modulation amplitude decreased from 34.0% to 18.6% accompanied with a decay of ionic diffusion coefficient and electrode potential, but having an improved coloration efficiency. Combined with various structural characterizations, including SEM, LA-ICP-MS, Raman and XPS, we demonstrate such colored state degradation is attributed to the so-called shallow trap, which corresponds to the irreversible and non-coloring reaction with interstitial oxygen during the insertion of Li+ cations forming superoxides (e.g. LiO2). All these findings not only offer a new insight into the improvement of cyclic stability based on ion-exchange, but also provide a valued information to understanding the physicochemical mechanisms of degradation in electrochromic materials.

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15

Oyama, Takashi, Nobuyuki Wada, and Hiroshi Takagi. "Analysis of Oxygen Vacancy Trapping at [001] Symmetric Tilt Grain Boundaries in Barium Titanate by Atomistic Simulations." Key Engineering Materials 445 (July 2010): 39–42. http://dx.doi.org/10.4028/www.scientific.net/kem.445.39.

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The role of grain boundaries (GBs) in the diffusion of oxygen vacancies (VO••s) in barium titanate (BaTiO3) and its mechanism were investigated using atomistic simulation techniques. It was found that GBs trapped VO••s at specific sites in the course of the diffusion, and the excess energy reflecting structural distortion of the GB was closely related to the availability of the trapping. GBs therefore act as a resistance of the diffusion of VO••s, suggesting that electrical degradation of multilayer ceramic capacitors (MLCCs), which is derived from vacancy diffusion, enables to be additionally improved by controlling GB structures in BaTiO3-based dielectrics.

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16

Ginting, Riski Titian, Mi-Kyoung Jeon, Kwang-Jae Lee, Won-Yong Jin, Tae-Wook Kim, and Jae-Wook Kang. "Degradation mechanism of planar-perovskite solar cells: correlating evolution of iodine distribution and photocurrent hysteresis." Journal of Materials Chemistry A 5, no. 9 (2017): 4527–34. http://dx.doi.org/10.1039/c6ta09202k.

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The penetration of moisture/O₂ into the perovskite solar cells (PSCs) causes shifts of iodine distribution within the perovskite layer and facilitates diffusion of iodine towards the hole transporting layer. Interestingly, these negative effects can be prevented by a simple encapsulation process and further prolong the stability of PSCs.

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17

Manaila, Elena, Gabriela Craciun, Daniel Ighigeanu, and Maria Daniela Stelescu. "Water Absorption Kinetics in Composites Degraded by the Radiation Technique." Materials 14, no. 16 (August 18, 2021): 4659. http://dx.doi.org/10.3390/ma14164659.

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Rubber-based wastes represent challenges facing the global community. Human health protection and preservation of environmental quality are strong reasons to find more efficient methods to induce degradation of latex/rubber products in order to replace devulcanization, incineration, or simply storage, and electron beam irradiation is a promising method that can be can be taken into account. Polymeric composites based on natural rubber and plasticized starch in amounts of 10 to 50 phr, obtained by benzoyl peroxide cross-linking, were subjected to 5.5 MeV electron beam irradiation in order to induce degradation, in the dose range of 150 to 450 kGy. A qualitative study was conducted on the kinetics of water absorption in these composites in order to appreciate their degradation degree. The percentages of equilibrium sorption and mass loss after equilibrium sorption were found to be dependent on irradiation dose and amount of plasticized starch. The mechanism of water transport in composites was studied not only through the specific absorption and diffusion parameters but also by the evaluation of the diffusion, intrinsic diffusion, permeation, and absorption coefficients.

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18

Kandlikar, S. G., M. L. Garofalo, and Z. Lu. "Water Management in A PEMFC: Water Transport Mechanism and Material Degradation in Gas Diffusion Layers." Fuel Cells 11, no. 6 (December 2011): 814–23. http://dx.doi.org/10.1002/fuce.201000172.

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19

Bugg, Trevor, Julia M. Foght, Michael A. Pickard, and Murray R. Gray. "Uptake and Active Efflux of Polycyclic Aromatic Hydrocarbons by Pseudomonas fluorescens LP6a." Applied and Environmental Microbiology 66, no. 12 (December 1, 2000): 5387–92. http://dx.doi.org/10.1128/aem.66.12.5387-5392.2000.

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ABSTRACT The mechanism of transport of polycyclic aromatic hydrocarbons (PAHs) by Pseudomonas fluorescens LP6a, a PAH-degrading bacterium, was studied by inhibiting membrane transport and measuring the resulting change in cellular uptake. Three cultures were used: wild-type LP6a which carried a plasmid for PAH degradation, a transposon mutant lacking the first enzyme in the pathway for PAH degradation, and a cured strain without the plasmid. Washed cells were mixed with aqueous solutions of radiolabelled PAH; then the cells were removed by centrifugation, and the concentrations of PAH in the supernatant and the cell pellet were measured. The change in the pellet and supernatant concentrations after inhibitors of membrane transport (azide, cyanide, or carbonyl cyanide m-chlorophenyl hydrazone) were added indicated the role of active transport. The data were consistent with the presence of two conflicting transport mechanisms: uptake by passive diffusion and an energy-driven efflux system to transport PAHs out of the cell. The efflux mechanism was chromosomally encoded. Under the test conditions used, neither uptake nor efflux of phenanthrene by P. fluorescens LP6a was saturated. The efflux mechanism showed selectivity since phenanthrene, anthracene, and fluoranthene were transported out of the cell but naphthalene was not.

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20

Shin, Hyun Gyu, Yong Nam Kim, Jun Kwang Song, and Hee Soo Lee. "Accelerated Degradation Test of Indium Tin Oxide (ITO) Thin Films Deposited by RF Magnetron Sputter." Key Engineering Materials 317-318 (August 2006): 577–80. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.577.

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Thermal degradation of indium tin oxide (ITO) thin film has been investigated. ITO thin film was fabricated on glass substrate using RF magnetron sputtering and was characterized. The resistivity of the film which was thermally degraded at high temperatures in air atmosphere was increased highly. Thermally-degraded specimen was analyzed using XPS and Hall measurement to reveal failure mechanism. Result showed that failure mechanism was the decrease in charge carrier concentration and mobility due to oxygen diffusion and chemisorption. Accelerated degradation test (ADT) was performed to predict the lifetime of ITO thin film. The lifetime under normal operating condition could be predicted via statistical analysis and modeling of data acquired from ADT of a short period.

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21

Delchier, Nicolas, Christiane Ringling, Jean-François Maingonnat, Michael Rychlik, and Catherine M. G. C. Renard. "Mechanisms of folate losses during processing: Diffusion vs. heat degradation." Food Chemistry 157 (August 2014): 439–47. http://dx.doi.org/10.1016/j.foodchem.2014.02.054.

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22

Buono, Rafael Andrade, André Leier, Julio Paez-Valencia, Janice Pennington, Kaija Goodman, Nathan Miller, Paul Ahlquist, Tatiana T. Marquez-Lago, and Marisa S. Otegui. "ESCRT-mediated vesicle concatenation in plant endosomes." Journal of Cell Biology 216, no. 7 (June 7, 2017): 2167–77. http://dx.doi.org/10.1083/jcb.201612040.

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Ubiquitinated plasma membrane proteins (cargo) are delivered to endosomes and sorted by endosomal sorting complex required for transport (ESCRT) machinery into endosome intralumenal vesicles (ILVs) for degradation. In contrast to the current model that postulates that ILVs form individually from inward budding of the endosomal limiting membrane, plant ILVs form as networks of concatenated vesicle buds by a novel vesiculation mechanism. We ran computational simulations based on experimentally derived diffusion coefficients of an ESCRT cargo protein and electron tomograms of Arabidopsis thaliana endosomes to measure cargo escape from budding ILVs. We found that 50% of the ESCRT cargo would escape from a single budding profile in 5–20 ms and from three concatenated ILVs in 80–200 ms. These short cargo escape times predict the need for strong diffusion barriers in ILVs. Consistent with a potential role as a diffusion barrier, we find that the ESCRT-III protein SNF7 remains associated with ILVs and is delivered to the vacuole for degradation.

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23

Yamaji, Katsuhiko. "Effect of Gaseous Impurities on Degradation of SOFC Materials." Materials Science Forum 783-786 (May 2014): 1714–18. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1714.

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Fundamental studies on durability and reliability of SOFC modules/stacks had started as one of the new NEDO project from FY2005 and the organization had been partly modified at FY2008 and FY2013[1]. The main target is to make sure the long term durability within 10 % of degradation rate in the range of 40,000 h (5 years), and reliability during 250 times of starting up and ending operations. In this project, the effect of impurities on degradation of SOFCs was examined for 5 different stacks/modules (Kyocera, Tokyo gas, TOTO, MMC-KEPCO and MHI) at AIST. During the operation of SOFC stacks and modules, several kinds of impurities are carried continuously with air and fuels and react with cell components. The concentration of impurity in cell components was carefully investigated before and after long term operation by using a secondary ion mass spectrometer (SIMS) as a main analytical tool with conventional analytical techniques such as a scanning electron microscopy (SEM) and an electron probe micro analyzer (EPMA). Many approaches were carried out to investigate the effect of gaseous impurities as listed below. (1)The concentration of impurity in cell components was carefully investigated before and after long term operation. (2)Chemical reactivity between impurities and cell components are examined from the view point of thermodynamics. (3)In order to understand the mechanism of the degradation due to impurities, the effect of impurities on degradation of laboratory scale button cell were examined. (4)Cation diffusion were carefully investigated in some diffusion couples to clear the mechanism on formation of secondary phases between the cathode and electrolyte. (5)Acceleration tests on degradation by impurities were also carried out by using a button cell to predict the degradation rate depending on the contamination of impurities in the cathode. The results of the project is partly introduced in this report.

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24

Munj, Hrishikesh R., John J. Lannutti, and David L. Tomasko. "Understanding drug release from PCL/gelatin electrospun blends." Journal of Biomaterials Applications 31, no. 6 (October 10, 2016): 933–49. http://dx.doi.org/10.1177/0885328216673555.

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Electrospinning is one of the efficient processes to fabricate polymeric fibrous scaffolds for several biomedical applications. Several studies have published to demonstrate drug release from electrospun scaffolds. Blends of natural and synthetic electrospun fibers provide excellent platform to combine mechanical and bioactive properties. Drug release from polymer blends is a complex process. Drug release from polymer can be dominated by one or more of following mechanisms: polymer erosion, relaxation, and degradation. In this study, electrospun polycaprolactone (PCL)–gelatin blends are investigated to understand release mechanism of Rhodamine B dye. Also, this article summarizes the effect of high-pressure carbon dioxide on drug loading and release from PCL–gelatin fibers. Results indicate that release media diffusion is a dominant mechanism for PCL–gelatin electrospun fibers. Thickness of electrospun mat becomes critical for blends with gelatin. As gelatin is highly soluble in water and has tendency of gelation, it affects diffusion of release media in and out of scaffold. This article is a key step forward in understanding release from electrospun blends.

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25

Ito, Hiroyuki, Ken Suzuki, and Hideo Miura. "2425 Analytical study of degradation mechanism of Ni-based superalloy caused by stress dependent anisotropic diffusion." Proceedings of the JSME annual meeting 2007.1 (2007): 423–24. http://dx.doi.org/10.1299/jsmemecjo.2007.1.0_423.

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26

Wang, Hui, De-Zhi Sun, and Zhao-Yong Bian. "Degradation mechanism of diethyl phthalate with electrogenerated hydroxyl radical on a Pd/C gas-diffusion electrode." Journal of Hazardous Materials 180, no. 1-3 (August 15, 2010): 710–15. http://dx.doi.org/10.1016/j.jhazmat.2010.04.095.

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27

Sun, Fu Xue, and Yun Hui Zhu. "Experimental Research on Chloride-Induced Service Life of Sturctures under Loading Capacity Criterion." Advanced Materials Research 601 (December 2012): 227–31. http://dx.doi.org/10.4028/www.scientific.net/amr.601.227.

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The whole service life of reinforcement concrete structure under chloride environment was devided into two stages according to mechanism of degradation. Using diffusion test, content of chloride ion was tested to decide diffusion coefficient for different age and damped exponential of diffusion coefficient. Then, through using effective diffusion coeffient into solution of the Fick’s Second Law, service life of the first stage was predicted. For corrosion propogation phase, loading test was carried out to construct relationship between loading capacity of corroded test model and accelerated corrosion time. When using this relationship to actual structure, we calculated the service life of the second stage. These methods and results can be considered as reference to eveluate service life of structure under the samilar environment.

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28

Chen, Hsiang, Kun Min Hsieh, Yun Yang He, Li Chen Chu, Ming Ling Lee, and Kow Ming Chang. "Degradation of InGaN/GaN LEDs under Forward-bias Operations in Salty Water Vapor." Journal of New Materials for Electrochemical Systems 19, no. 1 (February 15, 2016): 007–10. http://dx.doi.org/10.14447/jnmes.v19i1.340.

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Forward-bias stress in salty water vapor can quickly degrade the InGaN/GaN LEDs. To examine the weakness of the device, electrical, optical, and material analyses and characterizations were performed to investigate the failure mechanism. Corrosion of the electrode and Au atom diffusion might result in damages of the device. Results indicate that forward-bias stress in salty water vapor can quickly influence the material properties, optical behaviors, and electrical characteristics of the LED device.

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29

Kohout, J. "Modelling of changes in physical and mechanical properties of structural materials during long-term exposures at elevated temperatures." Journal de Physique IV 120 (December 2004): 191–99. http://dx.doi.org/10.1051/jp4:2004120022.

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Long-term exposures of various industrial structural materials at sufficiently elevated temperatures cause substantial changes in materials structures and, consequently, substantial changes in their physical and materials properties. The paper is focused to the influence of thermodegradation of glass-fibre-reinforced polyamide 66 in dry air and gear oil on its mechanical properties. As the thermodegradation of polymer materials is diffusion controlled process, the paper starts with the description of water diffusion in tested material. Then a very simple degradation mechanism is proposed for modelling the main features of real degradation processes. Regression functions describing the changes in mechanical properties of polyamide details during exposure are verified by the fit of experimental results. In the end of the paper some general considerations about the changes in other structural materials during exposures are done and supported by some experimental results.

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Cheng, Huanbo, Jie Zhang, Haihong Huang, and Zhifeng Liu. "Mass transfer model of supercritical fluid degradation for carbon fiber composites." Journal of Composite Materials 51, no. 8 (July 17, 2016): 1073–85. http://dx.doi.org/10.1177/0021998316658944.

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It is critical to study the mass transfer of supercritical fluid degradation for carbon fiber composites to investigate their degradation mechanism, design the reactor, and develop recycling processes. The mass transfer process of supercritical fluid degradation was described from two aspects: mass diffusion from outside to inside, and from inside to outside. Mass transfer model of supercritical fluid degradation was established based on a proposed concentric cylindrical representative volume element. The reaction kinetic parameters were incorporated into the mass transfer equation, and the concentration distribution of supercritical fluid, mass transfer rate, reaction order, and reaction rate constant during the carbon fiber composites degradation process were calculated. Relaxation time was incorporated into the mass transfer process, and the supercritical fluid concentration calculation method considering non-Fick effect was proposed. Finally, two pretreatment methods were adopted to speed up the mass transfer process.

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Tan, Hao, Delong Kong, Qingyun Ma, Qingqing Li, Yiqing Zhou, Xu Jiang, Zhiye Wang, Rebecca E. Parales, and Zhiyong Ruan. "Biodegradation of Tetracycline Antibiotics by the Yeast Strain Cutaneotrichosporon dermatis M503." Microorganisms 10, no. 3 (March 5, 2022): 565. http://dx.doi.org/10.3390/microorganisms10030565.

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In this study, the Cutaneotrichosporon dermatis strain M503 was isolated and could efficiently degrade tetracycline, doxycycline, and chlorotetracyline. The characteristics of tetracycline degradation were investigated under a broad range of cultural conditions. Response surface methodology (RSM) predicted that the highest degradation rate of tetracycline could be obtained under the following conditions: 39.69 °C, pH of 8.79, and inoculum dose of 4.0% (v/v, ~3.5 × 106 cells/mL in the medium). In accordance with the five identified degradation products of tetracycline, two putative degradation pathways, which included the shedding of methyl and amino groups, were proposed. Moreover, the well diffusion method showed that the strain of M503 decreases the antibacterial potency of tetracycline, doxycycline, and chlorotetracycline. These findings proposed a putative mechanism of tetracycline degradation by a fungus strain and contributed to the estimation of the fate of tetracycline in the aquatic environment.

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32

Wang, Tao, Xianlin Xu, Yanlin Ren, Songtao Qin, Xiaoyang Sui, and Lina Wang. "Kinetics of Thermal Degradation of Viscose Fiber and Fire Retardant Viscose Fiber." Journal of Engineered Fibers and Fabrics 9, no. 2 (June 2014): 155892501400900. http://dx.doi.org/10.1177/155892501400900205.

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The thermal decomposition behavior of fire retardant viscose fiber and viscose fiber were studied by thermogravimetric analysis (TGA) under air atmosphere at heating rates of 10, 20, 30 and 40oC/min. The activation energy and pre-exponential factor were calculated by using the Kissinger method, Flynn-Wall-Ozawa (FWO) method and Satava-Sestak method. The results show that the activation energy for the fire retardant viscose fiber calculated by Kissinger and FWO method was 102.51kJ/mol and 103.73kJ/mol, respectively. The activation energy for viscose fiber calculated by Kissinger and FWO method was 103.58 kJ/mol and 104.83kJ/mol, respectively. The kinetic mechanism function of fire retardant viscose fiber was G(α) = [(1+ α)13-1]2 following a kinetic model of three-dimensional diffusion and the kinetic mechanism function of viscose fiber was G(α) = α3/2 following the power function rule.

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33

Ganas, Petra, and Roderich Brandsch. "Uptake of l-nicotine and of 6-hydroxy-l-nicotine by Arthrobacter nicotinovorans and by Escherichia coli is mediated by facilitated diffusion and not by passive diffusion or active transport." Microbiology 155, no. 6 (June 1, 2009): 1866–77. http://dx.doi.org/10.1099/mic.0.028688-0.

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The mechanism by which l-nicotine is taken up by bacteria that are able to grow on it is unknown. Nicotine degradation by Arthrobacter nicotinovorans, a Gram-positive soil bacterium, is linked to the presence of the catabolic megaplasmid pAO1. l-[14C]Nicotine uptake assays with A. nicotinovorans showed transport of nicotine across the cell membrane to be energy-independent and saturable with a K m of 6.2±0.1 μM and a V max of 0.70±0.08 μmol min−1 (mg protein)−1. This is in accord with a mechanism of facilitated diffusion, driven by the nicotine concentration gradient. Nicotine uptake was coupled to its intracellular degradation, and an A. nicotinovorans strain unable to degrade nicotine (pAO1−) showed no nicotine import. However, when the nicotine dehydrogenase genes were expressed in this strain, import of l-[14C]nicotine took place. A. nicotinovorans pAO1− and Escherichia coli were also unable to import 6-hydroxy-l-nicotine, but expression of the 6-hydroxy-l-nicotine oxidase gene allowed both bacteria to take up this compound. l-Nicotine uptake was inhibited by d-nicotine, 6-hydroxy-l-nicotine and 2-amino-l-nicotine, which may indicate transport of these nicotine derivatives by a common permease. Attempts to correlate nicotine uptake with pAO1 genes possessing similarity to amino acid transporters failed. In contrast to the situation at the blood–brain barrier, nicotine transport across the cell membrane by these bacteria was not by passive diffusion or active transport but by facilitated diffusion.

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Engelmann, Hans-Jürgen, René Hübner, Michael Hecker, Norbert Mattern, Christian Wenzel, Ehrenfried Zschech, and Klaus Wetzig. "Microstructure and degradation mechanisms of TaSiN diffusion barriers for Cu interconnects." Microscopy and Microanalysis 9, S03 (September 2003): 248–49. http://dx.doi.org/10.1017/s1431927603023067.

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Ossowska, Agnieszka, and Andrzej Zieliński. "The Mechanisms of Degradation of Titanium Dental Implants." Coatings 10, no. 9 (August 28, 2020): 836. http://dx.doi.org/10.3390/coatings10090836.

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Titanium dental implants show very good properties, unfortunately there are still issues regarding material wear due to corrosion, implant loosening, as well as biological factors—allergic reactions and inflammation leading to rejection of the implanted material. In order to avoid performing reimplantation operations, changes in the chemical composition and/or modifications of the surface layer of the materials are used. This research is aimed at explaining the possible mechanisms of titanium dissolution and the role of oxide coating, and its damage, in the enhancement of the corrosion process. The studies of new and used implants were made by scanning electron microscopy and computer tomography. The long-term chemical dissolution of rutile was studied in Ringer’s solution and artificial saliva at various pH levels and room temperature. Inductively coupled plasma mass spectrometry (ICP-MS) conjugated plasma ion spectrometry was used to determine the number of dissolved titanium ions in the solutions. The obtained results demonstrated the extremely low dissolution rate of rutile, slightly increasing along with pH. The diffusion calculations showed that the diffusion of titanium through the oxide layer at human body temperature is negligible. The obtained results indicate that the surface damage followed by titanium dissolution is initiated at the defects caused by either the manufacturing process or implantation surgery. At a low thickness of titanium oxide coating, there is a stepwise appearance and development of cracks that forms corrosion tunnels within the oxide coating.

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Kolnes, Mart, Jakob Kübarsepp, Fjodor Sergejev, Märt Kolnes, Marek Tarraste, and Mart Viljus. "Performance of Ceramic-Metal Composites as Potential Tool Materials for Friction Stir Welding of Aluminium, Copper and Stainless Steel." Materials 13, no. 8 (April 24, 2020): 1994. http://dx.doi.org/10.3390/ma13081994.

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The aim of the research was to disclose the performance of ceramic-metal composites, in particular TiC-based cermets and WC-Co hardmetals, as tool materials for friction stir welding (FSW) of aluminium alloys, stainless steels and copper. The model tests were used to study the wear of tools during cutting of metallic workpiece materials. The primary focus was on the performance and degradation mechanism of tool materials during testing under conditions simulating the FSW process, in particular the welding process temperature. Carbide composites were produced using a common press-and-sinter powder metallurgy technique. The model tests were performed on a universal lathe at the cutting speeds enabling cutting temperatures comparable the temperatures of the FSW of aluminium alloys, stainless steels and pure copper. The wear rate of tools was evaluated as the shortening of the length of the cutting tool nose tip and reaction diffusion tests were performed for better understanding of the diffusion-controlled processes during tool degradation (wear). It was concluded that cermets, in particular TiC-NiMo with 75–80 wt.% TiC, show the highest performance in tests with counterparts from aluminium alloy and austenitic stainless steel. On the other hand, in the model tests with copper workpiece, WC-Co hardmetals, in particular composites with 90–94 wt.% WC, outperform most of TiC-based cermet, including TiC-NiMo. Tools from ceramic-metal composites wear most commonly by mechanisms based on adhesion and diffusion.

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37

González, M. A., D. I. Martínez, C. T. Saucedo, I. Guzmán, and J. C. Díaz. "Characterization of the Microstructural Degradation of Platinum Modified Aluminide Coating." Materials Science Forum 755 (April 2013): 29–38. http://dx.doi.org/10.4028/www.scientific.net/msf.755.29.

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This work presents the degradation mechanism of the platinum modified aluminide diffusion coating of the GTD 111 SC Ni-base superalloy turbine blades after 16000 h of exposition at different thermal cycles (critical heating temperatures reported ~1000°C and 1120°C). The initial coating condition and the evolution of degradation were characterized applying conventional microscopy and backscatter scanning electron microscopy. The initial microstructure condition consisted of a two phase coating (intermetallics PtAl2 dispersed in a matrix β-(Ni,Pt)Al). The major microstructure degradation was associated with: intermediate and interdiffusion zones growing, partial transformation of β-(Ni,Pt)Al to γ´-Ni3Al, and the dissolution of the intermetallic PtAl2 resulting in a more brittle single phase β-(Ni,Pt)Al coating. The degradation facilitates spallation and crack initiation, resulting in the loss of the coating and by consequence the blade failure.

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38

Huang, Jack Jia-Sheng, and Yu-Heng Jan. "A New Kinetics Defect Diffusion Model and the Critical Current Density of Semiconductor Laser Degradation." Applied Physics Research 8, no. 4 (July 6, 2016): 11. http://dx.doi.org/10.5539/apr.v8n4p11.

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Critical current density on the electromigration failure is a commonly observed phenomenon in the integrated circuit (IC) interconnect. The critical current density is important for the lognormal distribution and failure time extrapolation of IC metal conductors. In this paper, we report the critical current density (jc) of semiconductor laser degradation for the first time. Despite of the different physical origin, the jc of the laser degradation exhibits similar effect on the failure time distribution. We develop a new kinetic defect diffusion model that can account for the existence of jc. We discuss the physical mechanism and its implication in the reliability extrapolation of diode lasers.

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39

Irkha, V. I., P. Yu Markolenko, and T. D. Markolenko. "THE INFLUENCE OF THE MOVEMENT OF IMPURITY IONS ON THE STABILITY OF LEDS." Proceedings of the O.S. Popov ОNAT 1, no. 1 (August 27, 2020): 101–7. http://dx.doi.org/10.33243/2518-7139-2020-1-1-101-107.

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The influence of the motion of impurity centers on the stability of GaInAsP-based light- emitting diodes and their efficiency are studied. The stability and efficiency of the electroluminescence of LEDs is mainly determined by the ratio between the intensities of the radiative and non-radiative recombination of charge carriers. We studied the electroluminescent and electrical characteristics of LEDs. To clarify the degradation mechanism of LEDs, we studied the effect of their current training for 3000 hours at various current densities for stability and efficiency and for their electrical characteristics. It was shown that the degradation of LEDs at low injection levels is associated with the drift of impurity centers near the inhomogeneities of р-л-junctions. It is shown that during the degradation of LEDs, the magnitude of the radiative current component at a fixed voltage varies little. At the same time, nonradiative current components increase significantly. It was established that the growth of nonradiative current components is associated with the drift of mobile impurities to inhomogeneities of the р-л-junction. The kinetics of LED degradation was calculated using certain assumptions. The diffusion coefficient of the ions responsible for the degradation of the diodes is estimated. It is shown that “sudden” LED failures are of the same nature as their gradual degradation. They can occur at a sufficiently high concentration of mobile impurities. The obtained dependences of the radiation intensity on the duration of degradation can be used to estimate the diffusion coefficient of a mobile impurity.

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Sadiq, S. Kashif. "Reaction–diffusion basis of retroviral infectivity." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2080 (November 13, 2016): 20160148. http://dx.doi.org/10.1098/rsta.2016.0148.

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Retrovirus particle (virion) infectivity requires diffusion and clustering of multiple transmembrane envelope proteins (Env 3 ) on the virion exterior, yet is triggered by protease-dependent degradation of a partially occluding, membrane-bound Gag polyprotein lattice on the virion interior. The physical mechanism underlying such coupling is unclear and only indirectly accessible via experiment. Modelling stands to provide insight but the required spatio-temporal range far exceeds current accessibility by all-atom or even coarse-grained molecular dynamics simulations. Nor do such approaches account for chemical reactions, while conversely, reaction kinetics approaches handle neither diffusion nor clustering. Here, a recently developed multiscale approach is considered that applies an ultra-coarse-graining scheme to treat entire proteins at near-single particle resolution, but which also couples chemical reactions with diffusion and interactions. A model is developed of Env 3 molecules embedded in a truncated Gag lattice composed of membrane-bound matrix proteins linked to capsid subunits, with freely diffusing protease molecules. Simulations suggest that in the presence of Gag but in the absence of lateral lattice-forming interactions, Env 3 diffuses comparably to Gag-absent Env 3 . Initial immobility of Env 3 is conferred through lateral caging by matrix trimers vertically coupled to the underlying hexameric capsid layer. Gag cleavage by protease vertically decouples the matrix and capsid layers, induces both matrix and Env 3 diffusion, and permits Env 3 clustering. Spreading across the entire membrane surface reduces crowding, in turn, enhancing the effect and promoting infectivity. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface’.

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Setargew, Nega, та Daniel J. Parker. "Zinc diffusion induced precipitation of σ-phase in austenitic stainless steel". Metallurgical Research & Technology 116, № 6 (2019): 618. http://dx.doi.org/10.1051/metal/2019040.

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Zinc diffusion-induced degradation of AISI 316LN austenitic stainless steel pot equipment used in 55%Al-Zn and Zn-Al-Mg coating metal baths is described. SEM/EDS analyses results showed that the diffused zinc reacts with nickel from the austenite matrix and results in the formation of Ni-Zn intermetallic compounds. The Ni-Zn intermetallic phase and the nickel depleted zones form a periodic and alternating layered structure and a mechanism for its formation is proposed. The role of cavities and interconnected porosity in zinc vapour diffusion-induced degradation and formation of Ni-Zn intermediate phases is also discussed. The formation of Ni-Zn intermediate phases and the depletion of nickel in the austenite matrix results in the precipitation of σ-phase and α-ferrite in the nickel depleted regions of the matrix. This reaction will lead to increased susceptibility to intergranular cracking and accelerated corrosion of immersed pot equipment in the coating bath. Zinc diffusion induced precipitation of σ-phase in austenitic stainless steels that we are reporting in this work is a new insight with important implications for the performance of austenitic stainless steels in zinc containing metal coating baths and other process industries. This new insight will further lead to improved understanding of the role of substitutional diffusion and the redistribution of alloying elements in the precipitation of σ-phase in austenitic stainless steels.

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Shine, Connor J., Peter E. McHugh, and William Ronan. "Impact of Degradation and Material Crystallinity on the Mechanical Performance of a Bioresorbable Polymeric Stent." Journal of Elasticity 145, no. 1-2 (May 20, 2021): 243–64. http://dx.doi.org/10.1007/s10659-021-09835-7.

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AbstractBioresorbable polymeric stents (BPS) offer possibilities to help address the long-term complications associated with permanent vascular implants, however in-vivo degradation behaviour is not yet fully understood. Here, finite element analysis (FEA) techniques based on physio-chemical reaction diffusion equations are used to predict and analyse BPS degradation behaviour. Physio-chemical degradation models for polymers, both amorphous and semi-crystalline, are incorporated into the FEA software package Abaqus/Standard allowing for BPS degradation rate predictions to be made, with a focus on poly-L-lactide (PLLA). The outputs of the degradation models are linked to mechanical behaviour via three different damage models which couple the changes in molecular weight and crystallinity with a hyperelastic constitutive model for PLLA mechanical behaviour. A simplified representation of a PLLA BPS in an artery is used as a demonstration case. The effects of applied degradation product diffusion boundary conditions on the molecular weight and crystallinity of PLLA BPS under simulated degradation are examined, and the impact of material heterogeneities and mechanical load boundary condition on the scaffolding performance and elastic properties of the degrading stent are investigated. The results suggest that the BPS performance are strongly dependent on the assumed boundary conditions, both in terms of degradation product diffusion and mechanical loading.

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Orha, Corina, Cornelia Bandas, Carmen Lazau, Mina Ionela Popescu, Anamaria Baciu, and Florica Manea. "Advanced Electrodegradation of Doxorubicin in Water Using a 3-D Ti/SnO2 Anode." Water 14, no. 5 (March 6, 2022): 821. http://dx.doi.org/10.3390/w14050821.

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This study investigated the application of an advanced electrooxidation process with three-dimensional tin oxide deposited onto a titanium plate anode, named 3-D Ti/SnO2, for the degradation and mineralization of one of the most important emerging contaminants with cytostatic properties, doxorubicin (DOX). The anode was synthesized using a commercial Ti plate, with corrosion control in acidic medium, used as a substrate for SnO2 deposition by the spin-coating method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that porous SnO2 was obtained, and the rutile phase of TiO2 was identified as an intermediary substrate onto the Ti plate. The results of CV analysis allowed us to determine the optimal operating conditions for the electrooxidation process conducted under a constant potential regime, controlled by the electron transfer or the diffusion mechanisms, involving hydroxyl radicals. The determination of UV–VIS spectra, total organic carbon (TOC), and chemical oxygen demand (COD) allowed us to identify the degradation mechanism and pathway of DOX onto the 3-D Ti/SnO2 anode. The effective degradation and mineralization of DOX contained in water by the electrooxidation process with this new 3-D dimensionally stable anode (DSA) was demonstrated in this study.

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Meng, Xiang Li, Ling Jiang, and Yu Dong Huang. "Characterization and Thermal Degradation of Polyimide Derived from 5-amino-2(p-aminophenyl) Benzoxazole Monomer with Pyromellitic Dianhydride." Advanced Materials Research 455-456 (January 2012): 806–14. http://dx.doi.org/10.4028/www.scientific.net/amr.455-456.806.

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- 5-amino-2(p-aminophenyl) benzoxazole (AAPB) and its derived polyimide prepared with pyromellitic dianhydride (PMDA) were synthesized successfully. Their structures were characterized by FT-IR, 1H NMR, Element analysis, 13C NMR, Solid-state 13CNMR, DSC, TG and XRD. The polyimide was synthesized via a conventional two-stage method. The intermediate poly (amic acid) had inherent viscosity of 1.06dL/g and could be thermally converted into light yellow polyimide film. The polyimide showed excellent solvent resistance and good thermal stability. The glass transition temperature (Tg) was found to be 314°C, the decomposition started at a temperature above 500°C in air and above 550°C in argon atmosphere. The thermal degradation of the polyimide was studied by thermogravimetric analysis (TGA) in order to determine the actual reaction mechanisms of the decomposition process. The apparent activation energy (Ea) was obtained following Flynn-Wall-Ozawa method. The activation energies of different mechanism models and pre-exponential factor (A) were determined by Coats-Redfern method. Compared with the value obtained from the Ozawa method, the actual reaction mechanism obeyed three-dimensional diffusion model, Jander equation (D3) with integral form g(α)=[1-(1-α)1/3]2.

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45

Langdon, Erin M., and Amy S. Gladfelter. "A New Lens for RNA Localization: Liquid-Liquid Phase Separation." Annual Review of Microbiology 72, no. 1 (September 8, 2018): 255–71. http://dx.doi.org/10.1146/annurev-micro-090817-062814.

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RNA localization mechanisms have been intensively studied and include localized protection of mRNA from degradation, diffusion-coupled local entrapment of mRNA, and directed transport of mRNAs along the cytoskeleton. While it is well understood how cells utilize these three mechanisms to organize mRNAs within the cytoplasm, a newly appreciated mechanism of RNA localization has emerged in recent years in which mRNAs phase-separate and form liquid-like droplets. mRNAs both contribute to condensation of proteins into liquid-like structures and are themselves regulated by being incorporated into membraneless organelles. This ability to condense into droplets is in many instances contributing to previously appreciated mRNA localization phenomena. Here we review how phase separation enables mRNAs to selectively and efficiently colocalize and be coregulated, allowing control of gene expression in time and space.

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46

Pérez-Flores, Juan Carlos, Miguel Castro-García, Vidal Crespo-Muñoz, José Fernando Valera-Jiménez, Flaviano García-Alvarado та Jesús Canales-Vázquez. "Analysis of Performance Losses and Degradation Mechanism in Porous La2−X NiTiO6−δ:YSZ Electrodes". Materials 14, № 11 (25 травня 2021): 2819. http://dx.doi.org/10.3390/ma14112819.

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The electrode performance and degradation of 1:1 La2−xNiTiO6−δ:YSZ composites (x = 0, 0.2) has been investigated to evaluate their potential use as SOFC cathode materials by combining electrochemical impedance spectroscopy in symmetrical cell configuration under ambient air at 1173 K, XRD, electron microscopy and image processing studies. The polarisation resistance values increase notably, i.e., 0.035 and 0.058 Ωcm2 h−1 for x = 0 and 0.2 samples, respectively, after 300 h under these demanding conditions. Comparing the XRD patterns of the initial samples and after long-term exposure to high temperature, the perovskite structure is retained, although La2Zr2O7 and NiO appear as secondary phases accompanied by peak broadening, suggesting amorphization or reduction of the crystalline domains. SEM and TEM studies confirm the ex-solution of NiO with time in both phases and also prove these phases are prone to disorder. From these results, degradation in La2−xNiTiO6−δ:YSZ electrodes is due to the formation of La2Zr2O7 at the electrode–electrolyte interface and the ex-solution of NiO, which in turn results in the progressive structural amorphization of La18NiTiO6−δ phases. Both secondary phases constitute a non-conductive physical barrier that would hinder the ionic diffusion at the La2−xNiTiO6−δ:YSZ interface and oxygen access to surface active area.

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47

Zhao, Munan, and Chongwei Cui. "High adsorption of fulvic acid by amino modified styrene-type macroporous resin and evaluation of its mechanism." Water Science and Technology 81, no. 5 (March 1, 2020): 1000–1010. http://dx.doi.org/10.2166/wst.2020.187.

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Abstract Amino-modified HPD 100 styrene-type macroporous resin (M-HPD 100) was successfully synthesized by the atom transfer radical polymerization process. The modified resin showed excellent performance in the degradation of fulvic acid (FA). FA removal was pH, temperature and flow velocity dependent. The adsorption data could be well interpreted by the Freundlich model. The maximum adsorption efficiency for M-HPD 100 obtained from the Freundlich model was 92.5% at 298 K, which was 37% higher than that of unmodified styrene-type macroporous resin (HPD 100). The adsorption process could be described by the pseudo-second-order kinetic model. The intra-particle diffusion and film diffusion were believed to be the rate-limiting process for both adsorbents. Thermodynamic parameters suggested it was a multi-layer physicochemical process. More importantly, although limited improvements were seen, the results of this study suggested that the surface of resin can be modified with functional groups to enhance the adsorption of FA from aqueous solution and may give other advantages; for example, despite the interference of the pore diffusion coefficient and other substances, M-HPD 100 has excellent regeneration capacity, and the adsorption and desorption efficiency was 74% and 64.28% respectively after six regenerations, which proved it has engineering application value.

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48

Cao, Bin, Ji-Wei Dong, and Ming-He Chi. "Electrical Breakdown Mechanism of Transformer Oil with Water Impurity: Molecular Dynamics Simulations and First-Principles Calculations." Crystals 11, no. 2 (January 27, 2021): 123. http://dx.doi.org/10.3390/cryst11020123.

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Water impurity is the essential factor of reducing the insulation performance of transformer oil, which directly determines the operating safety and life of a transformer. Molecular dynamics simulations and first-principles electronic-structure calculations are employed to study the diffusion behavior of water molecules and the electrical breakdown mechanism of transformer oil containing water impurities. The molecular dynamics of an oil-water micro-system model demonstrates that the increase of aging acid concentration will exponentially expedite thermal diffusion of water molecules. Density of states (DOS) for a local region model of transformer oil containing water molecules indicates that water molecules can introduce unoccupied localized electron-states with energy levels close to the conduction band minimum of transformer oil, which makes water molecules capable of capturing electrons and transforming them into water ions during thermal diffusion. Subsequently, under a high electric field, water ions collide and impact on oil molecules to break the molecular chain of transformer oil, engendering carbonized components that introduce a conduction electronic-band in the band-gap of oil molecules as a manifestation of forming a conductive region in transformer oil. The conduction channel composed of carbonized components will be eventually formed, connecting two electrodes, with the carbonized components developing rapidly under the impact of water ions, based on which a large number of electron carriers will be produced similar to “avalanche” discharge, leading to an electrical breakdown of transformer oil insulation. The water impurity in oil, as the key factor for forming the carbonized conducting channel, initiates the electric breakdown process of transformer oil, which is dominated by thermal diffusion of water molecules. The increase of aging acid concentration will significantly promote the thermal diffusion of water impurities and the formation of an initial conducting channel, accounting for the degradation in dielectric strength of insulating oil containing water impurities after long-term operation of the transformer.

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Hübner, R., M. Hecker, N. Mattern, V. Hoffmann, K. Wetzig, Ch Wenger, H. J. Engelmann, Ch Wenzel, and E. Zschech. "Degradation mechanisms of Ta and Ta–Si diffusion barriers during thermal stressing." Thin Solid Films 458, no. 1-2 (June 2004): 237–45. http://dx.doi.org/10.1016/j.tsf.2003.11.313.

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50

Ziebarth, Benedikt, Matous Mrovec, Christian Elsässer, and Peter Gumbsch. "Potential-induced degradation in solar cells: Electronic structure and diffusion mechanism of sodium in stacking faults of silicon." Journal of Applied Physics 116, no. 9 (September 7, 2014): 093510. http://dx.doi.org/10.1063/1.4894007.

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