Main Degradation Process Research Articles

Study of Landslide Hazard Zonation in Mandakini Valley, Rudraprayag District, Uttarakhand Using Remote Sensing and GIS

The Mandakini Valley of Rudraprayag district, Uttarakhand witnessed unprecedented damage to life, property, infrastructure and landscape on 16 and 17 June 2013 due to torrential rains. Run-off discharge data indicate that antecedent rainfall exceeded the limit and the overflow of rivers led to landslide in the region and flash floods in the downstream areas. Fragile geology of the area, close to Main Central Thrust (MCT), degradation processes and torrential rains are responsible for triggering landslides and flash floods. A landslide inventory was carried out in the affected areas based on pre- and post-flood high resolution satellite data (LISS-IV and Cartosat-2). A total of 290 landslides were identified from pre-flood satellite LISS IV (2011) imagery and 1665 were identified in post-flood satellite imagery along major rivers. Using remote sensing and geographic information system techniques, thematic layers were generated. Using the weightage rating system, a landslide hazard zonation map of the area was prepared. Each class within a thematic layer was assigned an ordinal rating from 1 to 9. Summation of these attribute values was then multiplied by the corresponding weights to yield different zones of landslide hazard. A landslide hazard zonation map having five different zones ranging from very low hazard zone to very high hazard zone was prepared with the objective to create a reliable database for post-disaster management and for planning developmental activities in the district.

Thermogravimetric study of thermal degradation of polyetherimide

ABSTRACTThermal stability in nonoxidizing atmosphere of a polyetherimide (PEI) is investigated by thermogravimetry (TG). It is observed that thermal degradation of this product consists of two overlapping processes, which are conveniently separated by fitting the TG curves to mixtures of generalized logistic functions. Thus, each process is represented by a single function. The analysis of the fitting parameter values obtained for the main degradation process in different isothermal and heating ramp conditions allows to obtain insightful kinetic parameters (critical temperature, energy barrier, and reaction‐order) which allow to make predictions in both isothermal and nonisothermal contexts. There is a minimum temperature for each process to occur and a ramp‐energy barrier related to the process rate. In the ramp context, the values of these two parameters explain that, although one process starts at lower temperature, it proceeds at a very low rate until reaching temperatures at which the other process goes much faster. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42329.

Mapping of Ageing Mechanisms in Cylindrical LiFePO4/Graphite Batteries Cycled Under Deep Discharge Steps

Li-ion batteries are good candidates for electric vehicles and stationary applications due to their high power and energy density. Despite significant improvement over the last decade, lifetime and safety remain major issues for large-scale applications. Thus, a better understanding of factors governing battery lifetime and performance loss is crucial. Various types of Li-ion batteries are commercially available and their characteristics and performance depend strongly on the combination of active materials, cell design and manufacturing process. Therefore, the determination of specific degradation mechanisms and their correlation with cell performances is crucial for working on cell concepts that can meet target lifetimes [1-3]. In this work, cycling performance fade of LiFePO4-based cylindrical batteries is evaluated under deep charge/discharge steps (100% DOD). The cycling conditions were chosen to represent highly demanding condition of operation, which covers the analysis of ageing phenomena under the largest possible operating DOD. Diagnostic evaluation of the ageing mechanisms included in-situ electrochemical measurements, and ex-situ destructive physico-chemical and electrochemical analyses of cell components. A thorough study on the degradation mechanisms in different areas of the battery is realised in order to establish a geometrical mapping of the cell degradation. This allows identifying areas of inhomogeneous degradation along the jelly-roll of the battery. Degradation mechanisms were evaluated by microstructural (SEM) and crystallographic (XRD) analyses. Elemental analysis of the electrode composition was determined by EDS and ICP techniques. The electrochemical performances of selected areas of the harvested electrodes were determined by galvanostatic testing in half-cell configuration. These results were combined with non-destructive cell electrochemical measurements to provide a global view of the main degradation processes. [1] M. Safari and C. Delacourt, Journal of the Electrochemical Society, 2011. 158(12): p. A1436-A1447. [2] M. Dubarry and B.Y. Liaw, Journal of Power Sources, 2009. 194(1): p. 541-549. [3] D.P. Abraham, J. Liu, C.H. Chen, Y.E. Hyung, M. Stoll, N. Elsen, S. MacLaren, R. Twesten, R. Haasch, E. Sammann, I. Petrov, K. Amine, and G. Henriksen, Journal of Power Sources, 2003. 119-121: p. 511-516.

TG/DTG/DTA data used for determining the kinetic parameters of the thermal degradation process of an immunosuppressive agent: mycophenolate mofetil

Mycophenolate mofetil is a strong immunosuppressive therapeutic agent that was primely licensed to prevent rejection of transplanted organs. The decomposition reactions of pharmaceuticals, alongside other processes that occur, are important ones from both fundamental and practical point of view. The thermal stability of pharmaceuticals is important from both fundamental and clinical point of view. Kinetic analysis is one of the best method for an objective and less speculative determination of the Life Time Prediction. Following the ICTAC 2000 Protocol, the thermal behavior of mycophenolate was recorded at five different heating rates, in air atmosphere. The activation energy for the main degradation process was obtained by using four isoconversional methods of kinetic analysis: Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and modified nonparametric kinetic methods. The obtained values of the activation energy were in a very close range.

Madendere Havzası Topraklarında Arazi Kullanım/Arazi Örtüsü ile Bazı Erozyon Duyarlılık İndeksleri Arasındaki İlişkinin Belirlenmesi

In many regions of the world, soil erosion is one of the main land degradation processes that reduce the soil productivity by removing fertile topsoil layers, thus decreasing levels of organic matter and the nutrients. Therefore erosion researches constitute an important part of the research on the soils. The aim of this research is the determination of the relationship between land use/land cover and some erodibility indices in Madendere Watershed soils. Land use and land cover classes were generated from Geoeye-2013 image data classification. Forest is the highest land cover in the study area and has about 38.6 % of the total area, while the lowest land cover is settlement which is about 3.6%. Erosion ratio, dispersion ratio, soil erodibility and aggregate stability were determined for 71 each soil samples collected according to grid method from each 200 m distance point and 0-20 cm soil depth in Watershed. According to the results of erodibility analysis for soil samples taken from different land uses and land covers, it was determined that the soils of watershed are high erodible soils. For 1that reason, it was given some suggestions to take some mesurments for this watershed

Methods for Improving the Lifetime Performance of Organic Photovoltaics with Low‐Costing Encapsulation

Recent years have seen considerable advances in organic photovoltaics (OPVs), most notably a significant increase in their efficiency, from around 4 % to over 10 %. The stability of these devices, however, continues to remain an issue that needs to be resolved to enable their commercialization. This review discusses the main degradation processes of OPVs and recent methods that help to increase device stability and lifetime. One of the most effective steps that can be taken to increase the lifetime of OPVs is their encapsulation, which protects them from atmospheric degradation. Efficient encapsulation is essential for long-term device performance, but it is equally important for the commercialization of OPVs to strike a balance between achieving the maximum device protection possible and using low-cost processing for their encapsulation. Various encapsulation techniques are discussed herein, with emphasis on their cost effectiveness and their overall suitability for commercial applications.

Model of nanodegradation processes in electronic equipment of NPP Kozloduy

From the complex studies it was proof that the main degradation processes in the three groups of elements for the extended period of time are slow; do not lead to a hopping change in basic parameters and to catastrophic failures. This gives grounds to suggest a common diffusion model, which is limited to the following: -in electronic components containing a p-n junction, is performed diffusion of residual cooper atoms, that are accumulated in the area of a spatial charge under the influence of the electric field and the local temperature, creating micro-shunt regions; -in the contactor systems whose contact surfaces are made of metal alloys under the influence of increased temperature starts decomposition of a homogeneous alloy. Conditions are created for diffusion of individual atoms to the surface, micro-phases of homogeneous atoms are formed and modify the contact resistances; -in the course of time in the insulating materials are changed the mechanisms of polarization, double bonds and dipoles are disrupting, leading to the release of carbon atoms. The latter diffuse at elevated temperatures and form conductive cords, which amend the dielectric losses and the specific resistance of the materials.

Constructive Characteristics and Degradation Condition of Liceu Secondary Schools in Portugal

Within a full-scope modernization program of Portuguese secondary schools, technical inspections were conducted in order to: 1) identify the main degradation processes that affect different types of school buildings, and 2) provide recommendations for the rehabilitation projects. This article presents the constructive characteristics and a statistical analysis of the degradation condition of a particular type of Portuguese secondary schools, the Liceu, comprising a set of buildings with an invaluable historical and cultural importance and that is very iconic in terms of the historical period in which they were built—the Estado Novo. To that end, a database was designed in order to organize information gathered in the inspection of 15 secondary schools of Liceu typology. The aim of the database was to analyze the most frequent anomalies in this type of school buildings, taking into account the constructive solutions used and establishing statistical relationships between anomalies, probable causes and recommended rehabilitation works. Results obtained allowed concluding that the overall condition of these buildings which, in average, were 60 years old, was severe. The most frequent anomalies in both the buildings envelope and interior are mainly due to design and execution errors, water infiltration, and lack of maintenance. Although the school buildings analyzed are to some extent unique, most lessons learned from this study can be extrapolated to other countries, mostly Mediterranean, where during most of the 20th century, buildings were designed and constructed according to the same architectural and constructive principles, and were subjected to the same type of maintenance.

Recalcitrance and degradation of petroleum biomarkers upon abiotic and biotic natural weathering of Deepwater Horizon oil.

Petroleum biomarkers such as hopanoids, steranes, and triaromatic steroids (TAS) are commonly used to investigate the source and fate of petroleum hydrocarbons in the environment based on the premise that these compounds are resistant to biotic and abiotic degradation. To test the validity of this premise in the context of the Deepwater Horizon disaster, we investigated changes to these biomarkers as induced by natural weathering of crude oil discharged from the Macondo Well (MW). For surface slicks collected from May to June in 2010, and other oiled samples collected on beaches in the northern Gulf of Mexico from July 2010 until August 2012, hopanoids with up to 31 carbons as well as steranes and diasteranes were not systematically affected by weathering processes. In contrast, TAS and C32- to C35-homohopanes were depleted in all samples relative to 17α(H),21β(H)-hopane (C30-hopane). Compared to MW oil, C35-homohopanes and TAS were depleted by 18 ± 10% and 36 ± 20%, respectively, in surface slicks collected from May to June 2010, and by 37 ± 9% and 67 ± 10%, respectively, in samples collected along beaches from April 2011 through August 2012. Based on patterns of relative losses of individual compounds, we hypothesize biodegradation and photooxidation as main degradation processes for homohopanes and TAS, respectively. This study highlights that (i) TAS and homohopanes can be degraded within several years following an oil spill, (ii) the use of homohopanes and TAS for oil spill forensics must account for degradation, and (iii) these compounds provide a window to parse biodegradation and photooxidation during advanced stages of oil weathering.

Effects of acetic acid vapour on the ageing of alkyd paint layers: Multi-analytical approach for the evaluation of the degradation processes

Interactions with volatile organic compounds (VOCs) are one of the main issues within the field of the preventive conservation of artworks. VOCs deriving from wooden frames and museum furniture consist in several aldehydes, formic acid and a high abundance of acetic acid. The aim of this study was to evaluate the interactions between alkyd paints and acetic acid that take place during the curing process of the paint layers. A set of reference Winsor & Newton alkyd paint layers was exposed to acetic acid vapour for six months to model these interactions. In order to evaluate the main degradation pathways occurring during the artificial ageing, a multi-analytical approach based on chromatographic and spectroscopic techniques was used. The results describe the main degradation processes of the organic and inorganic components used in the production of the alkyd resin paint.

Gas Cross-over and Durability of Membrane Electrode Assemblies

Durability of the membrane electrolyte is a key factor for the longevity of polymer electrolyte fuel cells. A loss of gas separation is the most detrimental failure mode of perfluorosulfonic acid membranes. Mechanical formation of micron sized membrane defects is the main degradation process during fuel cell operation. This process is accelerated by variations in the operating conditions, such as humidity and temperature, and by imperfections and local defects of the gas diffusion electrodes.The impact of these local defects, termed pinholes is studied by implementing artificial micron sized defects in the membrane by focused ion beam (FIB) milling. Such membranes were then operated in different accelerated stress tests to study the development of chemical, mechanical and thermal degradation processes. Degradation at membrane defects was investigated post mortem using synchrotron based X-ray tomographic microscopy (XTM) and FTIR spectro-microscopy (see Figure 1) [1]. Gas cross-over, a key function for degradation, is controlled by operating conditions and material characteristics and was measured in-situ by mass spectrometry using a tracer gas concept [2, 3].From the results an overall degradation mechanism at membrane defects can be thus formulated [4].[1] S. Kreitmeier, M. Michiardi, A. Wokaun, F. N. Büchi, Factors determining the gas crossover through pinholes in polymer electrolyte fuel cell membranes, Electrochim. Acta, 80, 240-247 (2012)[2] G. A. Schuler, A. Wokaun, F. N. Büchi, Local online gas analysis in PEFC using tracer gas concepts, J. Power Sources, 195, 1647–1656 (2010)[3] S. Kreitmeier, G. A. Schuler, A. Wokaun, F. N. Büchi, Investigation of membrane degradation in polymer electrolyte fuel cells using local gas permeation analysis, J. Power Sources, 212, 139-147(2012)[4] S. Kreitmeier, P. Lerch, A. Wokaun, F.N. Büchi, Local degradation at membrane defects in polymer electrolyte fuel cells, J. Electrochem. Soc. 160, F456-F463 (2013)

Theoretical investigation of the atmospheric chemistry of methyl difluoroacetate: reaction with Cl atoms and fate of alkoxy radical at 298 K

A theoretical study on the mechanism of the reactions of methyl difluoroacetate (MDFA) CF2 HC(O)OCH3 with Cl atoms is presented. Two conformers relatively close in energy have been identified for MDFA. Geometry optimization and frequency calculations have been performed at the MPWB1K/6-31?G(d,p) level of theory, and energetic information is further refined by calculating the energy of the species using G2(MP2) the- ory. Transition states (TSs) are searched on the potential energy surface involved during the reaction channels, and each of the TSs is characterized by the presence of only one imaginary frequency. The existence of TSs on the corre- sponding potential energy surface is ascertained by per- forming intrinsic reaction coordinate calculation. Our calculations reveal that hydrogen abstraction from the -CH3 group is thermodynamically and kinetically more facile than that from the -CF2H group. Theoretically cal- culated rate constants at 298 K using the canonical tran- sition state theory are found to be in good agreement with the experimentally measured ones. The atmospheric life- time of CF2HC(O)OCH3 was estimated to be 16 years. The atmospheric fate and the main degradation process of alkoxy radical CF2HC(O)OCH2O are also discussed for the first time. Our calculation indicates that the fluorine atoms substitution has deactivating effect for the a-ester rearrangement.

Kinetics, mechanism and thermochemistry of the gas phase reactions of CF3CH2OCH2CF3 with OH radicals: A theoretical study

Theoretical investigations have been carried out on the mechanism, kinetics and thermochemistry of the gas-phase reactions between CF3CH2OCH2CF3 and OH radical using a newly developed DFT based M06-2X functional method. Two important H abstraction channels have been identified according to different orientations of the two H atoms bonded to same carbon atom in CH2 group, and one transition state has been located for each reaction channel. At the entry of each reaction channel, formation of pre-reactive complex indicates an indirect hydrogen-abstraction reaction. The rate coefficients were calculated for the first time over a wide range of temperature (250–1000K) and can be expressed as a model equation: kOH=2.55×10−11exp(−(2883.7−387626/T)/T)cm3molecule−1s−1. At 298K, our calculated rate coefficient for CF3CH2OCH2CF3 with OH radical 1.32×10−13cm3molecule−1s−1 is in very good agreement with the experimental result of kOH=1.30×10−13cm3molecule−1s−1. Using a group-balanced isodesmic reaction, the standard heats of formation for CF3CH2OCH2CF3 and CF3CHOCH2CF3 radical are estimated to be −365.64 and −316.84kcalmol−1, respectively. The calculated bond dissociation energy for the CH bond in CF3CH(H)OCH2CF3 is found to be 95.82kcalmol−1 at 298K. The atmospheric lifetime of CF3CH2OCH2CF3 was estimated to be around 0.272 years. The global warming potential and the main degradation process of alkoxy radical CF3CH(O)OCH2CF3 are also discussed.

Land-use change and land degradation in Turkmenistan in the post-Soviet era

The Central Asian Newly Independent States have experienced dramatic political and economic changes over the last three decades. Despite these changes, significant areas of the drylands in this region have not been studied since the 1980s. Landsat images acquired before and after the collapse of the Soviet Union, were analyzed to evaluate land-use/land-cover changes and desertification processes in northern Turkmenistan. Vegetation and crust indices, albedo, and spectral mixture analysis, supplemented by field work, were applied to estimate the long-term degradation/re-growing of vegetation cover.The major land-use change identified was an 86% increase in irrigated agricultural areas, equivalent to a loss of about 4500 km2 previously available for natural pastures. Pastures adjacent to the irrigated (and populated) areas were not affected, and in many places, increased vegetation cover was observed. The main degradation processes in these pastures are flooding and technogenic desertification; both occur around man-made structures. Remote pastures have experienced a higher degree of vegetation degradation, mainly due to the development of soil biogenic crust. These observations emphasize the controversy and variability of land degradation processes in this region: distant pastures show a degradation trend, while closer to populated areas, there are signs of rehabilitation.

Characterization of Ubuçu (Manicaria Saccifera) Natural Fiber Mat

Ubuçu (Manicaria saccifera) is a natural palm found in the Brazilian Amazon estuary. This palm has its fruits protected by a fibrous sac, called tururi, from where a natural mat like material can be extracted. Although the ubuçu palm has local economic importance, the physical, mechanical and chemical characteristics of its fibers have not yet been reported. In this work, in natura tururi fibers were analyzed by thermal analysis (TGA), X-rays diffraction, FT-IR and DSC. The morphology of the fibers was characterized through SEM/EDS, and the tensile breaking load of the fibers' natural mat was also determined. The results show that the fibers have a crystalline index of 60.6%, and are thermally stable up to approximately 264°C. The activati°n energy of the main thermal degradation process was found to be 180.2 kJ/mol. Silica rich protrusions were identified at the fibers surface and the fibrous mat has and apparent density of 0.97 g/cm3, and a tensile breaking load of 432 N.

The ability of biologically based wastewater treatment systems to remove emerging organic contaminants—a review

Biologically based wastewater treatment systems are considered a sustainable, cost-effective alternative to conventional wastewater treatment systems. These systems have been used and studied for the treatment of urban sewage from small communities, and recently, it has been reported that they can also effectively remove emerging organic contaminants (EOCs). EOCs are a new group of unregulated contaminants which include pharmaceutical and personal care products, some pesticides, veterinary products, and industrial compounds among others that are thought to have long-term adverse effects on human health and ecosystems. This review is focused on reporting the ability of biologically based wastewater treatment systems to remove EOCs and the main elimination mechanisms and degradation processes (i.e., biodegradation, photodegradation, phytoremediation, and sorption) taking place in constructed wetlands, ponds, and Daphnia and fungal reactors.

Bi-phase flame-retardant effect of hexa-phenoxy-cyclotriphosphazene on rigid polyurethane foams containing expandable graphite

The flame-retardant rigid polyurethane (PU) foams with hexa-phenoxy-cyclotriphosphazene/expandable graphite (HPCP/EG) were prepared through box-foaming in our laboratory. The flame retardancy of PU foams was characterized using the limiting oxygen index and cone calorimeter. The results show that the incorporation of HPCP into the PU foams containing EG enhanced flame retardancy. The main degradation process of HPCP in PU foams was investigated by pyrolysis gas chromatography/mass spectroscopy. HPCP during combustion generated phenoxyl and PO2 free radicals, which could quench the flammable free radicals produced by the matrix and hamper the free radical chain reaction of combustion. This observation shows that HPCP produced a gas-phase flame-retardant effect in this specimen. Additionally, micro-morphology, elemental composition and content of residual char of the flame-retardant PU foams after the cone calorimeter test were also characterized using scanning electron microscope and energy dispersive X-ray microanalyser. The results exhibit that the partial phosphorus from HPCP remained in the residual char, and HPCP significantly enhanced the strength and compatibility of the char layer formed by the PU foams containing EG. These results indicate the important function of HPCP in condensed phase. Thus, HPCP exhibited gas-phase and condensed-phase flame-retardant effects on the PU/EG foams.

Soil degradation processes in the Italian agricultural and forest ecosystems

A number of processes of degradation threaten soil functions. Ten of them are acknowledged by the European Union and fifteen by the Organisation for Economic Co-operation and Development (OECD), but at least another seven have been indicated by different authors in Italy and in other parts of the world. This short review paper summarizes the nature, economic relevance, and territorial impact of soil degradation in Italy, and with reference to Europe as a whole, and highlights the most relevant research needs in soil conservation. The direct annual costs of the main soil degradation processes are estimated to be over 38,000,000,000 euro per year in Europe as a whole, while in Italy, only for landslides, floods, and soil erosion, costs amount to 900,000,000 euro. Loss of the ability to produce food commodities because of soil degradation is particularly important in Italy, since selfsufficiency in food has recently decreased to less than 80% and Italian agricultural soils are hit by several problems, such as limited soil drainage, unfavorable texture and stoniness, shallow rooting depth, and poor chemical properties. On average, soil sealing, reduction in organic matter, and soil compaction in Italy are comparable with those of many other countries, but the occurrence of soil erosion, floods, and landslides is more widespread than in most parts of Europe, and also the presence of salt-affected soils is becoming a major worry. The fight against soil degradation in Italy is certainly more difficult than in other countries because of the high environmental variability. However, according to the current trends, Italy is mostly probably destined not to achieve the European objective to significantly reduce main soil degradation processes by the year 2020. There are several research needs in the field of soil conservation in Italy. These include: i) a better basic knowledge about many soil degradation processes and of pedodiversity; ii) reliable, sensitive, and locally validated models for main degradation processes; iii) assessment of resilience of different soils against degradation processes, as well as of their reaction to the measures foreseen in the current European agricultural policy.

Effect of nanotubes on the thermal stability of polystyrene

It has been shown that introducing carbon nanotubes (CNT) into a polymer matrix has a beneficial effect on thermal stability of composites. While the specific effects noted differ depending on many parameters, the general trend is an increase in the degradation temperature and reduction in the degradation rate, quantified as the mass decline over time. The purpose of this study is to evaluate how CNTs influence the main degradation process of composites made with polystyrene containing 2, 3 and 5 % of CNTs. Thermogravimetric experiments are performed, with nitrogen purge, at multiple linear heating ramps. The effects of the nanotubes on the degradation of polystyrene are evaluated. Insightful kinetic parameters were obtained for the main process making use of a recently developed model, which is adapted to the thermogravimetric context. The model allows the means to separate the main process from other processes, which could interfere with the kinetic analysis, and also subtract the residual mass, which could produce an apparent stabilizing effect. The main degradation process is clearly stabilized by the presence of nanotubes, although the stabilization is more pronounced at the lowest of the filler contents considered. Clear effects of nanotubes on kinetic parameters were observed.

In Situ X‐Ray Diffraction and Stress Analysis of Solid Oxide Fuel Cells

AbstractTo increase the long term stability and performance of solid oxide fuel cell (SOFC) materials, it is important to understand the main degradation processes in their functional layers. In this work, the interface between electrolyte and anode material was investigated by in situ X‐ray diffraction (XRD) stress and phase analysis. It has been found that the determining process for the initial degradation of SOFC is the reduction of the anode material with hydrogen. During this process a tensile strength of 600–700 MPa is measured. These stresses are induced in the electrolyte material and produce crack networks. The reduction from nickel oxide to pure nickel was monitored by in situ phase analysis. This reaction induces tensile stress at the interface between electrolyte and anode. The stress produced in the electrolyte material was also confirmed by the observation of crack networks detected using scanning electron microscopy (SEM). Finally, the reducing process was optimized using different process gases, decreasing the destructive tensile stress level.