Artificial Aging Experiments Research Articles

Investigation of the hygrothermal effects on in-plane failure mechanisms of fine Z-pinned laminates

Hygrothermal effect on the in-plane behavior of fine Z-pinned laminates were studied and the failure mechanisms were explained. Artificial seawater aging experiments were carried out on Z-pinned laminates prepared by ultrasonic vibration equipment. A compression progressive damage numerical model of fine Z-pinned laminates based on moisture-induced interface degradation was proposed to analyze the damage initialization and development of composites. The mechanical results show that the unpinned and Φ0.11 mm Z-pinned laminates have similar in-plane strength retention after 6 months of aging, and the tensile and compressive strengths decrease by 20% and 29%, respectively. EDS analysis confirms that Z-pin provides an additional moisture channel, leading to more elements with high relative atomic mass inside the laminates. It is found through the simulation studies that moisture leads to matrix compression and interlaminar interfacial damage regions to localized areas, weakening the interlayer effect of Z-pins and leading to the decrease of the ultimate bearing capacity of laminates. It denotes that Φ0.11 mm fine Z-pin has the potential to be used in composite marine structures.

A Deep Learning Approach for Digital Color Reconstruction of Van Gogh’s Paintings Using Unpaired Areas Under the Frame

Factors such as dirt accumulation, aging of paint materials and chemical reactions with the surrounding atmosphere lead to alteration and degradation of paintings. As a result, colors in the paintings can change. Van Gogh’s paintings are no exception to this process, and virtual reconstruction of the original colors is a very challenging problem. In this work we propose a novel approach for color reconstruction that does not require any pre-existing digital reconstructions, physical reproductions or artificial aging experiments, and relies purely on the data within the painting. We exploit the fact that areas of the painting located under the frame are typically well-preserved (mainly due to the protection from light exposure and dirt accumulation offered by the frame) and contain colors which are relatively close to their original look. Inspired by the recent advances in machine learning techniques for unpaired image-to-image translation, a practical weakly supervised approach for digital color reconstruction is formulated. Moreover, its performance is demonstrated for paintings by Vincent van Gogh. To our knowledge, this is the first time that a method for color reconstruction that relies purely on the data available within one painting is described in literature.

Bio-based hybrid nanocomposites as multifunctional sustainable materials for stone conservation

This study was aimed at developing a sustainable versatile bio-based epoxy-silica material to be potentially employed as hydrophobic and biocidal consolidating product in the field of stone conservation. For this purpose, two hybrid formulations containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol diglycidylether (CBDO-DGE), a cycloaliphatic epoxy precursor derived from the arnica root, together with (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and octyltriethoxysilane (OcTES) as silica-forming additives, were chosen as the basis of the multifunctional material to be finely adjusted and gain biocidal properties. With this goal in mind, different synthetic strategies based on ionic liquids (ILs), essential oils (EOs) and nanoparticles (NPs) doping have been employed. Specifically, dimethyloctadecyl[3(trimethoxysilyl)propyl]ammonium chloride (QAS), tetradecyl phosphonium chloride (QPS) and thymol, as well as cerium-TiO2 NPs and thymol-loaded SiO2 NPs were incorporated into the starting hybrid formulations, during the sol-gel process, to investigate their influence on the network formation. First, distribution studies by scanning electron microscopy/energy-dispersive X-ray (SEM-EDS) analysis were performed, whereas the suitability of each formulation to match the main requirements for a stone conservation material was evaluated in terms of thermostability, hydrophobicity and inhibition of the microbiological growth by a combination of TG-DTA, DSC, dynamic mechanical analysis (DMA), with contact angle and disk-diffusion measurements, respectively. Based on the data analysis, it was observed that the direct incorporation of ILs and EOs had an adverse effect on the ability of GPTMS to act as a coupling agent. This resulted in decreased thermal stability and a 50 % reduction in glass transition temperatures, along with the retention of hydrophilic behavior. In contrast, the inclusion of NPs did not significantly interfere with the hybrid network formation, and effectively maintained the thermo-mechanical and hydrophobic properties of the hybrids within satisfactory parameters. Consequently, both nanocomposite materials were further tested on stone samples by artificial ageing experiments under acidic atmosphere. In view of the results, the hybrid enriched with thymol-loaded SiO2 NPs demonstrate the most suitable thermo-mechanical and hydrophobic properties (Tonset, Tα and CA values of 276 °C, 54 °C and 100°, respectively), as well as a proper biocidal capability against bacteria. Furthermore, the developed material provided effective stone protection, resulting in a 92 % reduction in material loss, while preserving the substrate chromatic characteristics (ΔE 2.23). These findings suggest that the proposed treatment meets the first main requirements for stone conservation.

Artificial Aging Experiments of Neat and Contaminated Engine Oil Samples

This study highlights how the results from an artificial engine oil aging method compare to used engine oil samples collected from a vehicle fleet. Additionally, this paper presents the effect of contaminating the oil during aging with synthetic fuel alternatives on the physical and chemical properties of artificially aged engine oil samples. A laboratory-scale artificial thermo-oxidative aging experiment was conducted on multiple samples of commercially available formulated fully-synthetic SAE 0W-30 engine oil. The goal of the experiment was to establish the validity of the artificially aged samples as well as the validity of the underlying process in reproducibly fabricating small batches of aged engine oil with comparable chemical and physical properties to real-life used oils. Eight samples were subjected to distinct load cases (temperature, air flow rate, sample volume and aging time). Six additional samples were subjected to an intermediate load case, with five of them contaminated with selected conventional fuels and novel automotive fuel candidates. Conventional oil analysis was conducted on each sample to determine oxidation, residual additive content, kinematic viscosity and total base number. Additionally, analysis results were compared to in-use engine oil samples through PCA. The resulting oil condition after aging is in accordance with independently published results in terms of zinc dialkyldithiophosphate content and kinematic viscosity. Contaminated aging with OME 3-5 resulted in a drop in antioxidant content and elevated kinematic viscosity. Based on the comparison with in-use samples, artificial aging of 200 mL engine oil at 180 °C with 1 L/min air flow for 96 h can produce similar oil conditions as mixed vehicle use for 7000 km.

Parchment browning and the Dead Sea Scrolls – Part I: Artificial aging

The Dead Sea Scrolls, a two-thousand-year-old parchment corpus of manuscripts, thought to be the most important discovery of the 20th century including the first known copies of the Hebrew Bible, have darkened in parts to the point that the text is illegible. This motivated our research to try to understand the browning of parchment mechanisms. The scrolls cannot be analyzed by any destructive methods, so alternatives had to be sought. Here we describe a series of artificial aging experiments using modern parchment, prepared especially for our project, according to traditional methods, demonstrating how the different types of browning observed on the scrolls relate to environmental conditions as well as post finding treatments. Even the most extreme browning could be caused by prolonged exposure to water. This was in complete variance from controlled relative humidity exposure, where even elevated temperatures over a full five months caused only mild browning. We also confirm browning occurs at room temperature and within short periods when parchment is wet. We noted greater darkening of the flesh side in short term experiments, while browning was similar on both sides in conditions where water or humidity levels were maintained over a longer period. Artificial aging also confirmed the damage to the lower ends of many scrolls was likely caused by capillary actions when parchment was standing in water. That experiment also showed a dark tide-line phenomenon at the wet-dry interface, similar to that observed in paper substrates. Using analytical methods including FTIR, SEM, Light microscopy, UV–Vis and Fluorimetry we found the browning was always associated with denaturation, or loss of structure, mostly due to water and heat. This results in a flattening of the parchment structure which could be altering how light is reflected. However, in one artificial aging experiment the color was clearly seen to migrate and disperse over the parchment, after its initial formation. We believe this means the color is due to dark pigments; therefore, the main mechanism we suggest is melanoidin pigment formation due to a Maillard type reaction between amino acids and sugars or oxidized lipids, which are perhaps freed to react due to denaturation and hydrolysis. The results collected here can serve as an important step towards a full mechanistic understanding of parchment browning.

Highly efficient removal of diclofenac sodium from medical wastewater by Mg/Al layered double hydroxide-poly(m-phenylenediamine) composite

The emerging pollutant non-steroidal diclofenac sodium (DCF) has aroused increasing concerns, and the efficient removal of DCF from wastewater is becoming an urgent problem. In this study, the Mg/Al layered double hydroxide-Poly(m-Phenylenediamine) (LDH-PmPD) composite was synthesized, characterized and used for DCF adsorptive removal. The adsorption kinetics, isotherms as well as various influence factors, e.g., pH, humic acid, ions species and strength on the DCF removal were systematically investigated. The results showed that the presence of LDH weakened the accumulating density of PmPD and increased the specific surface area, which favored DCF adsorption on LDH-PmPD surface. LDH-PmPD exhibited a maximum adsorption capacity of 588 mg/g, which was superior to those of the conventional adsorbents. The artificial aging (100 d) experiment indicates a good stability of LDH-PmPD. Furthermore, due to the presence of electrostatic attraction, π-π electron-donor-acceptor interaction and N···HO hydrogen bonding between DCF and LDH-PmPD, the adsorption process was very effective in medical wastewater. The DCF removal efficiency reached nearly 100% within only 2 min in real medical wastewater using 0.125 g/L adsorbent. All these suggested that the prepared LDH-PmPD has great potential for DCF-contaminated water treatment.

Dynamic interplay between dislocations and precipitates in creep aging of an Al-Zn-Mg-Cu alloy

Creep age forming (CAF) is an advanced forming technology used for manufacturing large complex integrated panel components. However, in creep aging (CA), unlike in sole creep or aging procedure, the dislocation movement and the precipitation process occur simultaneously, leading to difficulty in understanding of the dynamic interplay between these two phenomena. In this work, taking 7050 Al alloy, a typical Al-Zn-Mg-Cu alloy, as the test material, an experimental scheme combining pre-deformation, artificial aging (AA), and tensile/compressive CA is designed to decouple and reveal the dynamic interaction mechanism of both phenomena. From AA experiments, the static interaction between dislocations and precipitates is studied, and then their dynamic interactions in CA and each evolution are comparatively investigated. The research shows that both total strain and strain rate increase with the increase in pre-deformation in tensile and compressive CA. However, the total creep strain in compressive CA is larger than that in tensile CA. In additional, the more the dislocations are induced, the sparser and more heterogeneous the overall distribution of precipitates becomes. For dynamic interplay, in the first stage of CA (I), under thermal-mechanical loading, the GP zones and η′ phases gradually nucleate and grow, while the effect of dislocation multiplication is dominant compared with dislocation annihilation, leading to an increase in total dislocation density. Soon, the dislocation movement is gradually hindered by tangling, pile-up, and the precipitates that have grown on the dislocation lines, this decreases the mobile dislocation density and results in a significant decrease in creep rate. In the second stage (II), the precipitates grow further, especially those lying on the dislocation lines; the effects of pinning and hindrance are enhanced until the dislocation multiplication and annihilation reach a dynamic equilibrium, and the total and mobile dislocation densities tend to be roughly unchanged, thus, the creep rate remains relatively constant in this stage.

In-situ aging monitoring of transformer oil via the relative permittivity and DC conductivity using novel interdigitated dielectrometry sensors (IDS)

Oil filled electrical transformers are present worldwide. Their lifetime is depended on many factors such as load, age and their environment, making the theoretical health prediction a challenge. A smarter approach is to monitor the health of these transformers online using in-situ sensors. Various attempts have been made, but to date a robust, reliable and cost efficient sensor (for industry attractive) that can sense transformer health according to established standards could not be found. We present a novel interdigitated dielectrometry sensor structure for the monitoring of transformer oil degradation. Our capacitive-type sensor uses three electrodes to provide an accurate and precise in-situ measurement of the complex permittivity, εr*, including the DC conductivity, σDC. Measurements were done with these sensors in an artificial oil aging experiment, degrading standard transformer oil and insulating paper at 140 °C over 800 h, mimicking an entire transformer life span of ∼ 60 years. It was found that εr* is proportional to the experiment time, yielding a transformer lifetime, LT. The conductivity increases exponentially with experiment time and is related to the oil acidity number, AN. Importantly, εr* is shown to also reflect the moisture in oil, the degree of polymerisation, DP, and tensile strength, ST, of the insulating paper. This demonstrates the suitability of the presented sensor as an oil health-monitoring instrument. Together with its robust and cost efficient design, it now paves the way for a real-world in-situ, real-time and online health monitoring of electrical transformers.

Gypsum growth induced by pyrite oxidation jeopardises the conservation of fossil specimens: an example from the Xiaheyan entomofauna (Late Carboniferous, China)

The destruction and damage of fossils in palaeontological collections through pyrite (FeS2) oxidation is a major and well-known issue. In this paper, we investigate the impact of this reaction on the conservation of Xiaheyan fossil entomofauna (Tupo Formation; Late Carboniferous; Ningxia, China) through three steps. First, we examined and characterised the elemental and mineralogical composition of newly excavated specimens, of museum specimens, and of weathering products at the outcrop (using SEM-EDX, Raman microspectroscopy and XRD). Second, in order to determine the potential reactivity of newly excavated fossils, we performed artificial ageing experiments, a technique recently applied in palaeontology that can offer valuable insights into long-term conservation of fossils. Finally, we designed and applied a protocol aiming at forcing the formation of gypsum outside the fossils so as to preserve the fossil integrity, namely ‘crystallisation pits’. Our data demonstrate that the depositional environment at Xiaheyan was rich in sulphur and devoid of oxygen, with perhaps oxygen-rich microenvironments, which led, respectively, to the precipitation of framboidal pyrite and of primary iron oxyhydroxides. The further chemical palaeo-weathering led to an extensive oxidation of pyrite in the outcrop, resulting in the precipitation of secondary iron oxyhydroxides, and of jarosite and gypsum, both sulphates. The low abundance of iron oxyhydroxides and the poor diversity of sulphates, compared to analogous localities, indicate a distinct weathering scenario, with a persistence of acidic water and an extensive leaching leading to the maintenance of only insoluble sulphates. Despite the extensive in situ pyrite oxidation, artificial ageing experiments demonstrated a remaining weak degradation potential. Gypsum (a calcium sulphate) is the near-exclusive efflorescence to develop within artificially aged fossils, contrary to the most commonly encountered efflorescence on pyritised fossils, namely iron sulphate. This instance can be attributed to the complete mobilisation of iron through iron oxyhydroxide precipitation and the availability of calcium ions induced by the dissolution of calcium carbonates present on Xiaheyan outcrops during palaeo-weathering. Unfortunately, the recourse to crystallisation pits failed to prompt gypsum crystallisation. We further suggest preventive storage conditions and prospects for investigation on the gypsum precipitation process at work, notably the role of organic compounds.

Climatic control of seed longevity of Silene during the post-zygotic phase: do seeds from warm, dry climates possess higher maturity and desiccation tolerance than seeds from cold, wet climates?

Seed longevity derived from artificial ageing experiments has been shown to be related to the macroclimate at the sampling site and with individual seed traits. Nevertheless, the ecological interpretation of artificial seed longevity remains to be clarified. In this article, the ecological significance of seed longevity expressed by the p50 index was explored using 16 closely related populations of the genus Silene L. Seeds were subjected to an artificial ageing treatment at 45 °C, 60% relative humidity and regularly tested for germination. The decline of viability to 50% (p50 index) was calculated using probit analysis. Its relationship with known ecological predictors of seed longevity was assessed by multiple regression analysis. Values of p50 ranged from 3.7 to 68.3 days. Seed lots which normally experience drought during the post-zygotic phase in a dry, warm environment, were long-lived. Consistently, precipitation during the driest months of the reproductive period was the strongest predictor of p50 variability (partial regression, R 2 = 0.424). We could not find any relationship between ex situ seed longevity and soil seed bank formation or seed size. Our results indicate that ex situ seed longevity has an ecological significance related to long-term climatic differences at population site. Increased longevity presumably reflects resistance to desiccation stress attained by seeds through local adaptation to warm, dry climates. We cannot exclude that seed tolerance to ageing could also represent phenotypic plasticity mediated by a drier maturation environment. The vulnerability of seeds from wet, cool climates and the adaptive response of seed longevity to different environments may have implications for ex situ conservation in the face of climate warming.

Model study of modern oil-based paint media by triacylglycerol profiling in positive and negative ionization modes

Lipid binders have traditionally been determined in paintings by using gas chromatography/mass spectrometry (GC/MS) to identify the characteristic profiles and ratios of fatty acids . However, the presence of mixtures in contemporary and modern oil paints makes the GC/MS determination of fatty acids insufficient to fully characterize the lipid binding media. In this study we prove that triacylglycerol (TAG) profiling by high-performance liquid chromatography with high-resolution tandem mass spectrometry, using ESI in positive and negative ionization modes is highly effective. We exploited this analytical approach to study the curing and degradation processes undergone by six plant oils used in the formulation of media in modern paints, using both natural and artificial ageing experiments. We believe that is the first time that a negative ionization mode has been applied for this purpose and that a survey with HPLC-ESI-Q-ToF has been carried out to study the ageing kinetics of plant oils. TAG profiling enabled us to study the evolution over time of the constituents of modern oils, with respect to curing and ageing. The data analyzed in this study demonstrate that our approach is efficient to study the oxidation of TAGs during ageing. The data also improve current knowledge on the properties of vegetable oils, which could lead to the development of new paint materials and conservation treatments for modern and contemporary works of art.

Alterations of fossil-bearing shale (Autun, France; Permian), part III: Framboidal pyrite and sulfur as the main cause of efflorescence

Fossil-bearing shale specimens that include sulfides are chemically reactive and sometimes also mechanically fragile. This decay is provoked by iron sulfate efflorescence resulting from the oxidation of sulfide compounds. The processes underlying these degradations are poorly known, thus impeding the elaboration of curative or preventive treatments. The present contribution aims to identify the origin of museum specimen alterations. It focuses on the Flouest collection housed at the Muséum national d’Histoire naturelle (MNHN, Paris, France) and originating from the Autun Basin (Saône-et-Loire, France; Permian). To evaluate the alteration of MNHN specimens, it appeared necessary to compare their composition with that of unaltered shale so as to identify chemical changes occurring during ageing. Therefore new material was collected in the Autun Basin, among others on the locality of Muse that corresponds to the same lithostratigraphic unit than that of the MNHN specimens. This work is divided in three parts. The two first, presented elsewhere, deal with the composition of the shale matrices and led to the conclusion that these matrices could not account for the large iron(II) sulfate efflorescence provoking damage on the MNHN specimens. The last part of this work, presented here, focus on artificial ageing experiments performed on new shale material. Most of the alterations observed on artificially aged samples correspond to dispersed crystals of calcium sulfate (gypsum). Similar crystals may be found on MNHN specimens, but they are relatively few and sporadically distributed. They are thus considered as damage of secondary importance with respect to iron sulfate efflorescence. These latter could be reproduced on three samples only (upon the 142 aged samples). They were also found on a coprolite and on a wood remain that had got severely damaged in ambient conditions within a few months after their excavation. On all these samples iron sulfate had grown on brownish layers consisting in crystals of framboidal pyrite (1 to 3μm) and eventually sulfur (20 to 50μm). These brownish layers are associated to thin maceral layers probably because of bacterial activity: during fossil diagenesis, bacteria need organic matter for their metabolism to produce hydrogen sulfide, a precursor of sedimentary pyrite formation. Most of the damaged specimens of the Flouest collection show as well a thin maceral layer nearby iron(II) sulfate efflorescence. On one of them, this layer is particularly thick. It corresponds to vitrinite and shows in some areas a brownish aspect. The topology of this surface (observed with scanning electron microscopy) shows numerous small holes (<2μm) and large holes (10–20μm). This morphology is compatible with a former occurrence of isolated grains and aggregates of framboidal pyrite. These observations suggest that iron sulfate efflorescence was provoked by the oxidation of framboidal pyrite forming deposits on maceral layers. Because of their brownish aspect, they can easily go unnoticed by naked eye. This work will also help to improve visual assessment of currently collected fossils so as to identify the most reactive ones.

Effect of UV Radiation on HTV-Silicon Rubber under Different Humidity

Along with our country " west-east electricity transmission " project and UHV projects,HTV-silicon rubber has been more and more widely used in the western regions of China,such as xining, Lhasa, hami and other regions, has strong solar radiation, long sunshine time, but the region environment humidity conditions are different. Therefore, it is necessary to study the Effect of UV Radiation on HTV-Silicon Rubber under different humidity. In this paper, the extraction of relative humidity variable, under different humidity conditions,HTV silicone rubber material taken for artificial ultraviolet aging experiment, to explore under different humidity conditions,HTV silicone rubber material’s ultraviolet aging properties. Experimental samples of artificial ultraviolet aging experiment taken in static contact angle test, hardness test, fourier transform infrared spectroscopy (FTIR) analysis, then integrate the test data and make theoretical analysis.The experimental results show that both samples hardness are larger, the flexibility are reduced; their both surface static contact angle are decreased, the hydrophobic are part of the loss; their both surface roughness are bigger,and a part of filler is leaked; FTIR of peak area of Si-CH3 and Si-O-Si keys absorption peak are reduced, shows a portion of the Si-CH3 and Si-O-Si keys is interrupted into free radicals; UV radiation has a certain influnce on HTV silicone rubber.Humidity variable has two contray sides influence on ultraviolet aging characteristics of HTV silicone rubber material,its process is complicated.

Anfis model for vibration signals based on aging process in electric motors

In this study, the aging process of an electric motor is accomplished by adaptive neuro-fuzzy inference system (ANFIS) using vibration signals. Different ANFIS models are compared for representing the aging process in the best possible way. An artificial aging experiment is performed and vibration data taken from the initial (healthy) and final (faulty) cases are used to identify the aging process. Four different ANFIS models are presented. Moving average (MA) filters are applied to the input and output pairs for different lagging factors to change the smoothness degree of the data and thus the performance of system identification. The success of the models is evaluated on three conditions; the performance of the ANFIS and the linear correlation between expected output (faulty case data) and aging model output, in time and frequency domains.The study also evaluates the influence of preprocessing using MA filtering on the ANFIS performance for vibration data which have stochastic characteristics.

Correlation of Natural and Artificial UV Aging of B.mori Silk Fabric

Ultraviolet aging of B.mori silk fabric was carried out under natural and artificial weathering conditions. A series of properties evaluations such as whiteness, mechanical property, ultraviolet protection factor (UPF) and Fourier Transform Infrared (FTIR) Spectroscopy were applied to test on the structure and properties of B.mori silk fabric. The correlation between natural and artificial aging experiments was also investigated. The results showed that the whiteness index of B.mori silk surface declined with increasing aging time. The breaking strength decreased rapidly with the extension of aging time, and adopting the curve regression analysis method to analysis the correlation between two types of aging experiments. The accelerated factor obtained is about 12.33 between natural and artificial aging experiments. In addition, ultraviolet protection factor depicted the anti-ultraviolet performance enhanced. And FTIR spectra confirmed the intensity of characteristic peaks such as amide I and II, etc. decreasing in the aging process.

Properties and performance of silane: blended cement systems

The paper presents the results of a study dealing with the performance of water repellents on hardened blended cement pastes. Since on the European market Portland cement does not play the dominant role anymore and due to the new national and European policies concerning Greenhouse Gases and sustainability, cement manufacturers produce more and more blended cements (CEM II–CEM V). Nevertheless, the majority of experience concerning the efficacy of water repellents is gained from Portland cement; therefore knowledge in regard to the interactions of blended cement with water repellent agent is minimal. Two silane-based products were applied on ‘fresh’ and carbonated cement substrates containing limestone, fly ash, slag and trass, and were investigated in terms of their functionality. The evaluation of the treatments’ performance and effectiveness were assessed using various laboratory measurements. Hydrophobicity, water absorption, colour changes and the penetration depth of silanes into the substrate were evaluated before and after artificial aging experiments. Moreover, the outdoor weathering test was performed to shed light on treated surface appearance in a ‘real’ outdoor environment. The results showed that surface wettability was independent on water ingress or colour variations, especially for cement specimens artificially aged by accelerated carbonation. Cement pastes containing slag and trass seemed to more distinctly affect the water repellents’ surface performance.

Comparative natural aging of thermoplastic elastomeric and silicon rubber insulators in Pakistan

Polymeric insulators have gained popularity since the last 30 years throughout the world. The main concern about them is variation in their performance with varying environments. Investigation of their performance by natural and artificial aging experiments is under the way by many researchers all over the world. The natural aging is usually short-term experiment ranging from few days to few years. The artificial aging is usually long-term investigation in lab that simulates the real service environment. However, first of all to develop the artificial aging schemes, natural aging to some extent is necessary. This article presents a part of research on polymeric insulators ongoing at the University of Engineering &amp; Technology, Taxila, in which 2 different kinds of polymeric insulators were naturally aged in a period of 1 year. The materials used were the thermoplastic elastomeric and thermoset silicone rubber (SiR) insulators. They were aged in outdoor environment of Hattar, which is a heavily polluted industrial area of Pakistan. The actual 11 kV full-scale insulators were installed in open environment at a height of about 30 m. The samples were cut from the insulators and analyzed using visual observation, hydrophobicity classification, leakage current and Fourier transform infrared spectroscopy and scanning electron microscopy. The main aims of this aging were estimation of the useful life of these insulators under the environment studied and development of basis for multistress lab aging cycles. The results were also used to compare the performance of these two materials with each other.

EPR of Radicals in Primitive Organic Matter: A Tool for the Search of Biosignatures of the Most Ancient Traces of Life

In this paper we report on electron paramagnetic resonance (EPR) of paramagnetic centers in the carbonaceous matter of primitive siliceous rocks, known to contain the most ancient traces of life. The EPR lines observed are attributed to π-radicals stabilized by the aromatic structure of this matter. It is found that the line widths and the line shapes vary continuously during geological periods and show a progressive pattern evolution from Gaussian–Lorentzian (recent) to purely Lorentzian (ca. 2000 million years [Myr]), and to supra-Lorentzian (ca. 3500 Myr). Artificial ageing experiments allowed us to define four stages of maturation of the organic matter according to the evolution of g-factors, EPR intensity, peak-to-peak line width and line shape. We suggest that the peculiar supra-Lorentzian line shape observed for organic matter older than 2000 Myr should be related to a low-dimensional (two- or one-dimensional) spatial distribution of electron spins. From these results, we derive a relationship between the line shape and the age of the organic matter, valid for ages ranging from about 600 Myr to about 3500 Myr.

Comparative investigation into the corrosion of different bronze alloys suitable for outdoor sculptures

Several bronze alloys, suitable for production of outdoor sculptures, were developed in the frame of the European project “Eurocare–Bronzart”. The elemental composition of the alloys was searched to fulfil specific criteria such as: reduction of lead content, good resistance toward corrosion and aesthetic characteristics conformable to artistic purposes. After metallurgical characterization, the resistance toward corrosion was evaluated in artificial environments. Ageing experiments were performed in a salt spray cabinet and in a climatic chamber in the presence of a controlled concentration of SO 2. The Thin Layer Activation (TLA) method was applied to calculate the thickness loss of activated specimens exposed to artificial corrosive atmospheres. After artificial ageing experiments the surface of the materials was investigated by SEM–EDS techniques. The bronze alloys containing different percentage of nickel showed the best properties of resistance toward corrosion.

Quantification of Volatile Organics in Soil Aging Experiments Using Fourier Transform Infrared Spectroscopy

On-line Fourier transform infrared (FT-IR) spectroscopy was applied to monitor the concentration of halogenated volatile organic compounds in a sample-preparation process that simulates long-term, slow accumulation of contaminants in soils (i.e., aging). Artificial aging is conducted by circulating a supercritical fluid solution containing the contaminant(s) of interest through a packed soil column. Mid-infrared spectra of several volatile halocarbons were measured in supercritical Xe and CO(2) to evaluate possible interferences from the strong absorption of CO(2). Although some of the C-X bands were partially masked in supercritical CO(2), all of the compounds studied had distinct spectral features in the region 1400-700 cm(-1) and could be monitored in either solvent. Quantitative measurements of halogenated volatile organics in supercritical CO(2) were demonstrated with CCl(4). Excellent results were obtained over the range 7-280 mM. Representative artificial aging experiments were conducted on two test soils using CCl(4) as the contaminant. On-line (FT-IR) estimates of the aged soil concentrations were 1.3-4.4 times higher than off-line concentrations obtained by gas chromatography/mass spectrometry. The discrepancies were primarily ascribed to post-aging losses that occurred during depressurization and subsequent sample handling. FT-IR spectroscopy is shown to be a powerful tool for monitoring soil loading behavior and for developing artificial aging protocols.