Search results for: thermal runaway

Authors: Houda Jalali, Hassan Abbassi

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In this numerical work, natural convection and entropy generation of Al₂O₃–water nanofluid in square cavity have been studied. A two-dimensional steady laminar natural convection in a differentially heated square cavity of length L, filled with a nanofluid is investigated numerically. The horizontal walls are considered adiabatic. Vertical walls corresponding to x=0 and x=L are respectively maintained at hot temperature, T_h and cold temperature, T_c. The resolution is performed by the CFD code "FLUENT" in combination with GAMBIT as mesh generator. These simulations are performed by maintaining the Rayleigh numbers varied as 10³ ≤ Ra ≤ 10⁶, while the solid volume fraction varied from 1% to 5%, the particle size is fixed at dp=33 nm and a range of the temperature from 20 to 70 °C. We used models of thermophysical nanofluids properties based on experimental measurements for studying the effect of adding solid particle into water in natural convection heat transfer and entropy generation of nanofluid. Such as models of thermal conductivity and dynamic viscosity which are dependent on solid volume fraction, particle size and temperature. The average Nusselt number is calculated at the hot wall of the cavity in a different solid volume fraction. The most important results is that at low temperatures (less than 40 °C), the addition of nanosolids Al₂O₃ into water leads to a decrease in heat transfer and entropy generation instead of the expected increase, whereas at high temperature, heat transfer and entropy generation increase with the addition of nanosolids. This behavior is due to the contradictory effects of viscosity and thermal conductivity of the nanofluid. These effects are discussed in this work.

Keywords: entropy generation, heat transfer, nanofluid, natural convection

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Authors: Hassan Samadi, Mustapha El Jarroudi

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In this work, we consider the homogenization of a non-linear problem in periodic medium with two periodic connected media exchanging a heat flux throughout their common interface. The interfacial exchange coefficient λ is assumed to tend to zero or to infinity following a rate λ=λ(ε) when the size ε of the basic cell tends to zero. Three homogenized problems are determined according to some critical value depending of λ and ε. Our method is based on Γ-Convergence techniques.

Keywords: variational methods, epiconvergence, homogenization, convergence technique

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Authors: Hatem Diaf, Patrice Melinon, Antonio Pereira, Bernard Moine, Nicholas Blanchard, Florent Bourquard, Florence Garrelie, Christophe Donnet

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Glassy carbon exhibits excellent biological compatibility with live tissues meaning it has high potential for applications in life science. Moreover, glassy carbon has interesting properties including 'high temperature resistance', hardness, low density, low electrical resistance, low friction, and low thermal resistance. The structure of glassy carbon has long been a subject of debate. It is now admitted that glassy carbon is 100% sp2. This term is a little bit confusing as long sp2 hybridization defined from quantum chemistry is related to both properties: threefold configuration and pi bonding (parallel pz orbitals). Using plasma laser deposition of carbon clusters combined with pulsed nano/femto laser annealing, we are able to synthesize thin films of glassy carbon of good quality (probed by G band/ D disorder band ratio in Raman spectroscopy) without thermal post annealing. A careful inspecting of Raman signal, plasmon losses and structure performed by HRTEM (High Resolution Transmission Electron Microscopy) reveals that both properties (threefold and pi orbitals) cannot coexist together. The structure of the films is compared to models including schwarzites based from negatively curved surfaces at the opposite of onions or fullerene-like structures with positively curved surfaces. This study shows that a huge collection of porous carbon named vitreous carbon with different structures can coexist.

Keywords: glassy carbon, cluster deposition, coating, electronic structure

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Authors: Alexander J. Severinsky

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Radiative forces of greenhouse gases (GHG) increase the temperature of the Earth's surface, more on land, and less in oceans, due to their thermal capacities. Given this inertia, the temperature increase is delayed over time. Air temperature, however, is not delayed as air thermal capacity is much lower. In this study, through analysis and synthesis of multidisciplinary science and data, an estimate of atmospheric temperature increase is made. Then, this estimate is used to shed light on current observations of ice and snow loss, desertification and forest fires, and increased extreme air disturbances. The reason for this inquiry is due to the author’s skepticism that current changes cannot be explained by a "~1 ^oC" global average surface temperature rise within the last 50-60 years. The only other plausible cause to explore for understanding is that of atmospheric temperature rise. The study utilizes an analysis of air temperature rise from three different scientific disciplines: thermodynamics, climate science experiments, and climactic historical studies. The results coming from these diverse disciplines are nearly the same, within ± 1.6%. The direct radiative force of GHGs with a high level of scientific understanding is near 4.7 W/m² on average over the Earth’s entire surface in 2018, as compared to one in pre-Industrial time in the mid-1700s. The additional radiative force of fast feedbacks coming from various forms of water gives approximately an additional ~15 W/m². In 2018, these radiative forces heated the atmosphere by approximately 5.1 ^oC, which will create a thermal equilibrium average ground surface temperature increase of 4.6 ^oC to 4.8 ^oC by the end of this century. After 2018, the temperature will continue to rise without any additional increases in the concentration of the GHGs, primarily of carbon dioxide and methane. These findings of the radiative force of GHGs in 2018 were applied to estimates of effects on major Earth ecosystems. This additional force of nearly 20 W/m² causes an increase in ice melting by an additional rate of over 90 cm/year, green leaves temperature increase by nearly 5 ^oC, and a work energy increase of air by approximately 40 Joules/mole. This explains the observed high rates of ice melting at all altitudes and latitudes, the spread of deserts and increases in forest fires, as well as increased energy of tornadoes, typhoons, hurricanes, and extreme weather, much more plausibly than the 1.5 ^oC increase in average global surface temperature in the same time interval. Planned mitigation and adaptation measures might prove to be much more effective when directed toward the reduction of existing GHGs in the atmosphere.

Keywords: greenhouse radiative force, greenhouse air temperature, greenhouse thermodynamics, greenhouse historical, greenhouse radiative force on ice, greenhouse radiative force on plants, greenhouse radiative force in air

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Authors: Li Maksym, Prabhakar M. N., Jung-Il Song

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In this study, a flame retardant and hydrophobic cotton textile were prepared by utilizing a renewable halogen-free bio-based solution based on chitosan, urea, and phytic acid, named bio-flame retardant liquid (BFL), through facile dip-coating technology. Deposition of BFL on the surface of the cotton was confirmed by Fourier-transform infrared spectroscopy and scanning electron microscope coupled with energy-dispersive X-ray spectrometer. Thermal and flame retardant properties of the cottons were studied with thermogravimetric analysis, differential scanning calorimetry, vertical flame test, cone calorimeter test. Only with 8.8% of dry weight gain treaded cotton showed self-extinguish properties during fire test. Cone calorimeter test revealed a reduction of peak heat release rate from 203.2 to 21 kW/m2 and total heat release from 20.1 to 2.8 MJ/m2. Incidentally, BFL remarkably improved the thermal stability of flame retardant cotton from expressed in an enhanced amount of char at 700 °C (6.7 vs. 33.5%). BFL initiates the formation of phosphorous and silica contain char layer whichrestrains the propagation of heat and oxygen to unburned materialstrengthen by the liberation of non-combustible gases, which reduce the concentration of flammable volatiles and oxygen hence reducing the flammability of cotton. In addition, hydrophobicity and specific ignition test for upholstery application were performed. In conjunction, the proposed flame retardant cotton is potentially translatable to be utilized as upholstery materials in public transport.

Keywords: cotton farbic, flame retardancy, surface coating, intumescent mechanism

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Authors: Rasha Hosny, Ahmed Zahran, Mahmoud Ramzi, Fatma Mahmoud Abdelhafiz, Ammona S. Mohamed, Mahmoud Fathy Mubarak

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Ionic liquids' ability to be tuned and stability under challenging environmental conditions are their significant features in enhanced oil recovery. In this study, two amino acid ionic liquids (AAILs) were prepared from quaternized hyperbranched polyamidoamine PAMAM (G0.5 C12) and amino acids (Cysteine and Lysine). The chemical structures of the prepared AAILs were verified by using FTIR and 1H-NMR spectra. These AAILs were tested for solubility, thermal stability, and surface activity in the presence of Egyptian medium crude oils under different PVT parameters after being diluted in several brine solutions of various salt compositions at 10% (w/w) salinity. The measurements reveal that the produced AAILs have good solubility and thermal stability. The effect of different concentrations of AAILs (0.1-5%) and salinity (20000-70000 ppm) on Interfacial tension (IFT) were studied. To test the efficacy of (AAILs) for a CEOR, numerous flooding experiments were carried out in samples of sandstone rock. Rock wettability is important for sandstone rocks, so conduct wettability alteration by contact angle (CA) of (30-55) and IFT of (7-13). The additional oil recovery was largely influenced by ionic liquid concentration, which may be changed by dilution with the formation and injected brines. This research has demonstrated that EOR techniques led to a recovery wt. (22-45%).

Keywords: amino acid ionic liquids, surface activity, critical micelle concentration, interfacial tension, contact angle, chemical enhanced oil recovery, wettability

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Authors: Justyna Chrzanowska, Jacek Hoffman, Dariusz Garbiec, Łukasz Kurpaska, Piotr Denis, Tomasz Moscicki, Zygmunt Szymanski

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Tungsten and boron compounds belong to the group of superhard materials and its hardness could exceed 40 GPa. In this study, the properties of the tungsten boride (WB) layers deposited in magnetron sputtering process are investigated. The sputtering process occurred from specially prepared targets that were composed of boron and tungsten mixed in molar ratio of 2.5 or 4.5 and sintered in spark plasma sintering process. WB layers were deposited on silicon (100) and stainless steel 304 substrates at room temperature (RT) or in 570 °C. Layers deposited in RT and in elevated temperature varied considerably. Layers deposited in RT are amorphous and have low adhesion. In contrast, the layers deposited in 570 °C are crystalline and have good adhesion. All deposited layers have a hardness about 40 GPa. Moreover, the friction coefficient of crystalline layers is 0.22 and wear rate is about 0.67•10-6 mm3N-1m-1. After material characterization the WB layers were annealed in argon atmosphere in 1000 °C for 1 hour. On the basis of X-Ray Diffraction analysis, it has been noted that the crystalline layers are thermally stable and do not change their phase composition, whereas the amorphous layers change their phase composition. Moreover, after annealing, on the surface of WB layers some cracks were observed. It is probably connected with the differences of the thermal expansion between the layer and the substrate. Despite of the presence of cracks, the wear resistance of annealed layers is still higher than the wear resistance of uncoated substrate. The analysis of the structure and properties of tungsten boride layers lead to the discussion about the application area of this material.

Keywords: hard coatings, hard materials, magnetron sputtering, mechanical properties, tungsten boride

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Authors: Fnu Asina, Ivana Brzonova, Keith Voeller, Yun Ji, Alena Kubatova, Evguenii Kozliak

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Lignin, a heterogeneous three-dimensional biopolymer, is one of the building blocks of lignocellulosic biomass. Due to its limited chemical reactivity, lignin is currently processed as a low-value by-product in pulp and paper mills. Among various industrial lignins, Kraft lignin represents a major source of by-products generated during the widely employed pulping process across the pulp and paper industry. Therefore, valorization of Kraft lignin holds great potential as this would provide a readily available source of aromatic compounds for various industrial applications. Microbial degradation is well known for using both highly specific ligninolytic enzymes secreted by microorganisms and mild operating conditions compared with conventional chemical approaches. In this study, the degradation of Indulin AT lignin was assessed by comparing the effects of Basidiomycetous fungi (Coriolus versicolour and Trametes gallica) and Actinobacteria (Mycobacterium sp. and Streptomyces sp.) to two commercial laccases, T. versicolour ( ≥ 10 U/mg) and C. versicolour ( ≥ 0.3 U/mg). After 54 days of cultivation, the extent of microbial degradation was significantly higher than that of commercial laccases, reaching a maximum of 38 wt% degradation for C. versicolour treated samples. Lignin degradation was further confirmed by thermal carbon analysis with a five-step temperature protocol. Compared with commercial laccases, a significant decrease in char formation at 850ºC was observed among all microbial-degraded lignins with a corresponding carbon percentage increase from 200ºC to 500ºC. To complement the carbon analysis result, chemical characterization of the degraded products at different stages of the delignification by microorganisms and commercial laccases was performed by Pyrolysis-GC-MS.

Keywords: lignin, microbial degradation, pyrolysis-GC-MS, thermal carbon analysis

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Authors: W. J. Wang, D. F. Lin, L. Y. Chen, K. Y. Liu

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In this study, the ladle furnace slag was used as a mineral filler in asphalt concrete with electric arc furnace slag (EAF asphalt concrete) to investigate the effect on the engineering and thermal properties of asphalt cement mastics and EAF asphalt concrete, the lime was used as a comparison for mineral filler, and the usage percentage of mineral filler was set at 2%, 4%, 6%, and 8%. First of all, the engineering properties of the ladle furnace slag and lime were compared, and then the mineral filler was mixed with bitumen to form the asphalt cement mastics in order to analyze the influence of the ladle furnace slag on the properties of asphalt cement mastics, and lastly, the mineral filler was used in the EAF asphalt concrete to analyze its feasibility of using ladle furnace slag as a mineral filler. The study result shows that the ladle furnace slag and the lime have no obvious difference in their physical properties, and from the energy dispersive spectrometer (EDS) test results, we know that the lime and the ladle furnace slag have similar elemental composition, but the Ca found in the ladle furnace slag belongs to CaO, and the lime belongs to CaCO3, therefore the ladle furnace slag has the property of expansion. According to the test results, the viscosity of asphalt cement mastics will increase with the increase in the use of mineral filler. Since the ladle furnace slag has more CaO content, the viscosity of the asphalt cement mastics with ladle furnace slag will increase more than using lime as mineral filler in the asphalt cement mastics, and the use of ladle furnace slag only needs to be 2% in order to achieve the effect of anti-peeling which is 6% for lime. From the related test results of EAF asphalt concrete, it is known that the maximum stability value can be obtained when the use of mineral filler is about 5%. When the ladle furnace slag is used as the mineral filler, it can improve the stiffness, indirect tension strength, spalling resistance, and thermal insulation of EAF asphalt concrete, which also indicates that using the ladle furnace slag as the mineral filler of bitumen can help to improve the durability of the asphalt pavement.

Keywords: ladle furnace slag, mineral filler, asphalt cement mastics, EAF asphalt concrete

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Authors: Natalia Alzate-Carvajal, Diego A. Acevedo-Guzman, Victor Meza-Laguna, Mario H. Farias, Luis A. Perez-Rey, Edgar Abarca-Morales, Victor A. Garcia-Ramirez, Vladimir A. Basiuk, Elena V. Basiuk

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Direct covalent functionalization of prefabricated free-standing graphene oxide paper (GOP) is considered as the only approach suitable for systematic tuning of thermal, mechanical and electronic characteristics of this important class of carbon nanomaterials. At the same time, the traditional liquid-phase functionalization protocols can compromise physical integrity of the paper-like material up to its total disintegration. To avoid such undesirable effects, we explored the possibility of employing an alternative, solvent-free strategy for facile and nondestructive functionalization of GOP with two representative aliphatic amines, 1-octadecylamine (ODA) and 1,12-diaminododecane (DAD), as well as with two aromatic amines, 1-aminopyrene (AP) and 1,5-diaminonaphthalene (DAN). The functionalization was performed under moderate heating at 150-180 °C in vacuum. Under such conditions, it proceeds through both amidation and epoxy ring opening reactions. Comparative characterization of pristine and amine-functionalized GOP mats was carried out by using Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopy (XPS), thermogravimetric (TGA) and differential thermal analysis, scanning electron and atomic force microscopy (SEM and AFM, respectively). Besides that, we compared the stability in water, wettability, electrical conductivity and elastic (Young's) modulus of GOP mats before and after amine functionalization. The highest content of organic species was obtained in the case of GOP-ODA, followed by GOP-DAD, GOP-AP and GOP-DAN samples. The covalent functionalization increased mechanical and thermal stability of GOP, as well as its electrical conductivity. The magnitude of each effect depends on the particular chemical structure of amine employed, which allows for tuning a given GOP property. Morphological characterization by using SEM showed that, compared to pristine graphene oxide paper, amine-modified GOP mats become relatively ordered layered assemblies, in which individual GO sheets are organized in a near-parallel pattern. Financial support from the National Autonomous University of Mexico (grants DGAPA-IN101118 and IN200516) and from the National Council of Science and Technology of Mexico (CONACYT, grant 250655) is greatly appreciated. The authors also thank David A. Domínguez (CNyN of UNAM) for XPS measurements and Dr. Edgar Alvarez-Zauco (Faculty of Science of UNAM) for the opportunity to use TGA equipment.

Keywords: amines, covalent functionalization, gas-phase, graphene oxide paper

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Authors: Jonghyuk Yoon, Hyoungwoon Song, Youngbae Kim, Eunju Kim

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Recently, with the rapid growth of semiconductor industry, lots of interests have been focused on after treatment system that remove the polluted gas produced from semiconductor manufacturing process, and a wet scrubber is the one of the widely used system. When it comes to mechanism of removing the gas, the polluted gas is removed firstly by chemical reaction in a reactor part. After that, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid. Effective design of the reactor part inside the wet scrubber is highly important since removal performance of the polluted gas in the reactor plays an important role in overall performance and stability. In the present study, a CFD (Computational Fluid Dynamics) analysis was performed to figure out the thermal and flow characteristics inside unit a reactor of wet scrubber. In order to verify the numerical result, temperature distribution of the numerical result at various monitoring points was compared to the experimental result. The average error rates (12~15%) between them was shown and the numerical result of temperature distribution was in good agreement with the experimental data. By using validated numerical method, the effect of the reactor geometry on heat transfer rate was also taken into consideration. Uniformity of temperature distribution was improved about 15%. Overall, the result of present study could be useful information to identify the fluid behavior and thermal performance for various scrubber systems. This project is supported by the ‘R&D Center for the reduction of Non-CO₂ Greenhouse gases (RE201706054)’ funded by the Korea Ministry of Environment (MOE) as the Global Top Environment R&D Program.

Keywords: semiconductor, polluted gas, CFD (Computational Fluid Dynamics), wet scrubber, reactor

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Authors: Maryam Al Mheiri, Khaled Al Awadi

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Urban population is continuously increasing worldwide and the speed at which cities urbanize creates major challenges, particularly in terms of creating sustainable urban environments. Rapid urbanization often leads to negative environmental impacts and changes in the urban microclimates. Moreover, when rapid urbanization is paired with limited landscape elements, the effects on human health due to the increased pollution, and thermal comfort due to Urban Heat Island effects are increased. Urban Heat Island (UHI) describes the increase of urban temperatures in urban areas in comparison to its rural surroundings, and, as we discuss in this paper, it impacts on pedestrian comfort, reducing the number of walking trips and public space use. It is thus very necessary to investigate the quality of outdoor built environments in order to improve the quality of life incites. The main objective of this paper is to address the morphology of Emirati neighborhoods, setting a quantitative baseline by which to assess and compare spatial characteristics and microclimate performance of existing typologies in Abu Dhabi. This morphological mapping and analysis will help to understand the built landscape of Emirati neighborhoods in this city, whose form has changed and evolved across different periods. This will eventually help to model the use of different design strategies, such as landscaping, to mitigate UHI effects and enhance outdoor urban comfort. Further, the impact of different native plants types and native species in reducing UHI effects and enhancing outdoor urban comfort, allowing for the assessment of the impact of increasing landscaped areas in these neighborhoods. This study uses ENVI-met, an analytical, three-dimensional, high-resolution microclimate modeling software. This micro-scale urban climate model will be used to evaluate existing conditions and generate scenarios in different residential areas, with different vegetation surfaces and landscaping, and examine their impact on surface temperatures during summer and autumn. In parallel to these simulations, field measurement will be included to calibrate the Envi-met model. This research therefore takes an experimental approach, using simulation software, and a case study strategy for the evaluation of a sample of residential neighborhoods. A comparison of the results of these scenarios constitute a first step towards making recommendations about what constitutes sustainable landscapes for Abu Dhabi neighborhoods.

Keywords: landscape, microclimate, native plants, sustainable neighborhoods, thermal comfort, urban heat island

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Authors: Vladimir Vinnikov

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The paper proposes a model of an inhomogeneous rock mass with initially random distribution of microcracks on mineral grain boundaries. It describes the behavior of cracks in a medium under the effect of thermal field, the medium heated instantaneously to a predetermined temperature. Crack growth occurs according to the concept of fracture mechanics provided that the stress intensity factor K exceeds the critical value of Kc. The modeling of thermally induced acoustic emission memory effects is based on the assumption that every event of crack nucleation or crack growth caused by heating is accompanied with a single acoustic emission event. Parameters of the thermally induced acoustic emission memory effect produced by cyclic heating and cooling (with the temperature amplitude increasing from cycle to cycle) were calculated for several rock texture types (massive, banded, and disseminated). The study substantiates the adaptation of the proposed model to humidity interference with the thermally induced acoustic emission memory effect. The influence of humidity on the thermally induced acoustic emission memory effect in quasi-homogeneous and banded rocks is estimated. It is shown that such modeling allows the structure and texture of rocks to be taken into account and the influence of interference factors on the distinctness of the thermally induced acoustic emission memory effect to be estimated. The numerical modeling can be used to obtain information about the thermal impacts on rocks in the past and determine the degree of rock disturbance by means of non-destructive testing.

Keywords: crack growth, cyclic heating and cooling, rock texture, thermo acoustic emission memory effect

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Authors: Jun Yang, Ching-Liang Hsieh, Yi-Wen Lin

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Chronic inflammatory pain results from peripheral tissue injury or local inflammation to increase the release of protons, histamines, adenosine triphosphate, and several proinflammatory cytokines. Transient receptor potential vanilloid 1 (TRPV1) is involved in fibromyalgia, neuropathic, and inflammatory pain; however, its exact mechanisms in chronic inflammatory pain are still unclear. We investigate the analgesic effect of EA by injecting complete Freund’s adjuvant (CFA) in the hind paw of mice to induce chronic inflammatory pain ( > 14 d). Our results showed that EA significantly reduced chronic mechanical and thermal hyperalgesia in the chronic inflammatory pain model. Chronic mechanical and thermal hyperalgesia was also abolished in TRPV1−/− mice. TRPV1 increased in the dorsal root ganglion (DRG) and spinal cord (SC) at 2 weeks after CFA injection. The expression levels of downstream molecules such as pPKA, pPI3K, and pPKC increased, as did those of pERK, pp38, and pJNK. Transcription factors (pCREB and pNFκB) and nociceptive ion channels (Nav1.7 and Nav1.8) were involved in this process. Inflammatory mediators such as GFAP (Glial fibrillary acidic protein), S100B, and RAGE (Receptor for advanced glycation endproducts) were also involved. The expression levels of these molecules were reduced in EA (electroacupuncture) and TRPV1−/−mice but not in the sham EA group. The present study demonstrated that EA or TRPV1 gene deletion reduced chronic inflammatory pain through TRPV1 and related molecules. In addition, our data provided evidence to support the clinical use of EA for treating chronic inflammatory pain.

Keywords: auricular electric-stimulation, epileptic seizures, anti-inflammation, electroacupuncture

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Authors: Mrinal Kanti Bhowmik, Kakali Das Jr., Barin Kumar De, Debotosh Bhattacharjee

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Breast cancer is the most common cancer and a leading cause of death for women in the 35 to 55 age group. Early detection of breast cancer can decrease the mortality rate of breast cancer. Mammography is considered as a ‘Gold Standard’ for breast cancer detection and a very popular modality, presently used for breast cancer screening and detection. The screening of digital mammograms often leads to over diagnosis and a consequence to unnecessary traumatic & painful biopsies. For that reason recent studies involving the use of thermal imaging as a screening technique have generated a growing interest especially in cases where the mammography is limited, as in young patients who have dense breast tissue. Tumor is a significant sign of breast cancer in both mammography and thermography. The tumors are complex in structure and they also exhibit a different statistical and textural features compared to the breast background tissue. Fractal geometry is a geometry which is used to describe this type of complex structure as per their main characteristic, where traditional Euclidean geometry fails. Over the last few years, fractal geometrics have been applied mostly in many medical image (1D, 2D, or 3D) analysis applications. In breast cancer detection using digital mammogram images, also it plays a significant role. Fractal is also used in thermography for early detection of the masses using the thermal texture. This paper presents an overview of the recent aspects and initiatives of fractals in breast cancer detection in both mammography and thermography. The scope of fractal geometry in automatic breast cancer detection using digital mammogram and thermogram images are analysed, which forms a foundation for further study on application of fractal geometry in medical imaging for improving the efficiency of automatic detection.

Keywords: fractal, tumor, thermography, mammography

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Authors: Monalisa Halder, Amit K. Das, Ajit K. Meikap

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Polymer nanocomposites are very significant materials both in academia and industry for diverse potential applicability in electronics. Polymer plays the role of matrix element which has low density, flexibility, good mechanical strength and electrical properties. Use of nanosized multiferroic filler in the polymer matrix is suitable to achieve nanocomposites with enhanced magneto-dielectric effect and good mechanical properties both at the same time. Multiferroic terbium manganate (TbMnO₃) nanoparticles have been synthesized by sol-gel method using chloride precursors. Terbium manganate-polyvinyl alcohol (TbMnO₃-PVA) nanocomposite film has been prepared by solution casting method. Crystallite size of TbMnO₃ nanoparticle has been calculated to be ~ 40 nm from XRD analysis. Morphological study of the samples has been done by scanning electron microscopy and a well dispersion of the nanoparticles in the PVA matrix has been found. Thermogravimetric analysis (TGA) exhibits enhancement of thermal stability of the nanocomposite film with the inclusion of TbMnO₃ nanofiller in PVA matrix. The electrical transport properties of the nanocomposite film sample have been studied in the frequency range 20Hz - 2MHz at and above room temperature. The frequency dependent variation of ac conductivity follows universal dielectric response (UDR) obeying Jhonscher’s sublinear power law. Correlated barrier hopping (CBH) mechanism is the dominant charge transport mechanism with maximum barrier height 19 meV above room temperature. The variation of dielectric constant of the sample with frequency has been studied at different temperatures. Real part of dielectric constant at 1 KHz frequency at room temperature of the sample is found to be ~ 8 which is higher than that of the pure PVA film sample (~ 6). Dielectric constant decreases with the increase in frequency. Relaxation peaks have been observed in the variation of imaginary part of electric modulus with frequency. The relaxation peaks shift towards higher frequency as temperature increases probably due to the existence of interfacial polarization in the sample in presence of applied electric field. The current-voltage (I-V) characteristics of the nanocomposite film have been studied under ±40 V applied at different temperatures. I-V characteristic exhibits temperature dependent rectifying nature indicating the formation of Schottky barrier diode (SBD) with barrier height 23 meV. In conclusion, using multiferroic TbMnO₃ nanofiller in PVA matrix, enhanced thermal stability and electrical properties can be achieved.

Keywords: correlated barrier hopping, nanocomposite, schottky diode, TbMnO₃, TGA

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Authors: M. Khlifa, A. Youssef, A. F. Zaed, A. Kraft, V. Arrighi

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A series of PS-nanoparticles were prepared by grafting PS from both aggregated silica and colloidally silica using atom-transfer radical polymerisation (ATRP). The mechanical behaviour of the nanocomposites have been examined by differential scanning calorimetry (DSC)and dynamic mechanical thermal analysis (DMTA).

Keywords: ATRP, nanocomposites, polystyrene, reinforcement

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Authors: Shah Fahad

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Managing the Urban Heat Island (UHI) effects is a pressing concern for achieving sustainable urban development and ensuring thermal comfort in major cities of developing nations, such as Lahore, Pakistan. The current UHI effect is mostly triggered by climate change and rapid urbanization. This study explored UHI over the Lahore district and its adjoining urban and rural-urban fringe areas. Landsat satellite data was utilized to investigate spatiotemporal patterns of Land Use and Land Cover changes (LULC), Land Surface Temperature (LST), UHI, Normalized Difference Built-up Index (NDBI), Normalized Difference Vegetation Index (NDVI), and Urban Thermal Field Variance Index (UTFVI). The built-up area increased very fast, with a coverage of 22.99% in 2000, 36.06% in 2010, and 47.17% in 2020, while vegetation covered 53.21 % in 2000 and 46.16 % in 2020. It also revealed a significant increase in the mean LST, from 33°C in 2000 to 34.8°C in 2020. The results indicated a significantly positive correlation between LST and NDBI, a weak correlation was also observed between LST and NDVI. The study used scatterplots to show the correlation between NDBI and NDVI with LST, results revealed that the NDBI and LST had an R² value of 0.6831 in 2000 and 0.06541 in 2022, while NDVI and LST had an R² value of 0.0235 in 1998 and 0.0295 in 2022. Proper environmental planning is vital in specific locations to enhance quality of life, protect the ecosystem, and mitigate climate change impacts.

Keywords: land use land cover, spatio-temporal analysis, remote sensing, land surface temperature, urban heat island, lahore pakistan

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Authors: Lorena Polovina, Maddy Kennedy-Parrott, Mohammad Fakoor

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The construction industry accounts for approximately 40% of total GHG emissions worldwide. In order to limit global warming to 1.5 degrees Celsius, ambitious reductions in the carbon intensity of our buildings are crucial. Passive House presents an opportunity to reduce operational carbon by as much as 90% compared to a traditional building through improving thermal insulation, limiting thermal bridging, increasing airtightness and heat recovery. Up until recently, Passive House design was mainly concerned with meeting the energy demands without considering embodied carbon. As buildings become more energy-efficient, embodied carbon becomes more significant. The main objective of this research is to calculate the embodied carbon impact of a Passive House and compare it with the BC Energy Step Code (ESC). British Columbia is committed to increasing the energy efficiency of buildings through the ESC, which is targeting net-zero energy-ready buildings by 2032. However, there is a knowledge gap in the embodied carbon impacts of more energy-efficient buildings, in particular Part 3 construction. In this case study, life cycle assessments (LCA) are performed on Part 3, a multi-unit residential building in Victoria, BC. The actual building is not constructed to the Passive House standard; however, the building envelope and mechanical systems are designed to comply with the Passive house criteria, as well as Steps 1 and 4 of the BC Energy Step Code (ESC) for comparison. OneClick LCA is used to perform the LCA of the case studies. Several strategies are also proposed to minimize the total carbon emissions of the building. The assumption is that there will not be significant differences in embodied carbon between a Passive House and a Step 4 building due to the building envelope.

Keywords: embodied carbon, energy modeling, energy step code, life cycle assessment

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Authors: Razieh Shamsi, Mehdi Faezipour, Ali Abdolkhani

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In this research, the characteristics of composites prepared from waste silk fibers and recycled polycarbonate polymer (used compacted boards) at four levels of 0, 10, 20, and 30% (silk fibers) and using 2% N- 2-Aminoethyl-3-Aminopropyltrimethoxysilane was investigated as a coupling agent and melt process method. Silk fibers (carpet weaving waste) with dimensions of 8-18 mm were prepared, and recycled polymer with 9 mesh grading was ground. Production boards in 3 thicknesses, 3 mm (tensile test samples), 5 mm (bending test samples, water absorption, and thickness shrinkage), 7 mm (impact resistance test samples) ) with a specific weight of 1 gram per cubic centimeter, hot pressing time and temperature of 12 minutes and 190 degrees Celsius with a pressure of 130 bar, cold pressing time of 6 minutes with a pressure of 50 bar and using the coupling agent N- (2- Aminoethyl)-3-aminopropyltrimethoxysilane was prepared in a constant amount of 2% of the dry weight of the filler. The results showed that, in general, by adding silk fibers to the base polymer, compared to the control samples (pure recycled polycarbonate polymer) and also by increasing the amount of silk fibers, almost all the resistances increased. The amount of water absorption of the constructed composite increased with the increase in the amount of silk fibers, and the thickness absorption was equal to 0% even after 72 hours of immersion in water. The thermal resistance of the pure recycled polymer was higher than the prepared composites, and by adding silk fibers to the base polymer and also by increasing the amount of silk fibers from 10 to 30%, the thermal resistance of the composites decreased.

Keywords: wood composite, recycled polycarbonate, silk fibers, polymer

Procedia PDF Downloads 92

Authors: Haseen Siddiqui, Sanjay M. Mahajani

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Various important reactions in chemical and metallurgical industries fall in the category of gas-solid reactions. These reactions can be categorized as catalytic and non-catalytic gas-solid reactions. In gas-solid reaction systems, heat and mass transfer limitations put an appreciable influence on the rate of the reaction. The consequences can be unavoidable for overlooking such effects while collecting the reaction rate data for the design of the reactor. Pyrolysis reaction comes in this category that involves the production of gases due to the interaction of heat and solid substance. Pyrolysis is also an important step in the gasification process and therefore, the gasification reactivity majorly influenced by the pyrolysis process that produces the char, as a feed for the gasification process. Therefore, in the present study, a non-isothermal transient 1-D model is developed for a single biomass pellet to investigate the effect of heat and mass transfer limitations on the rate of pyrolysis reaction. The obtained set of partial differential equations are firstly discretized using the concept of ‘method of lines’ to obtain a set of ordinary differential equation with respect to time. These equations are solved, then, using MATLAB ode solver ode15s. The model is capable of incorporating structural changes, porosity variation, variation in various thermal properties and various pellet shapes. The model is used to analyze the effectiveness factor for different values of Lewis number and heat of reaction (G factor). Lewis number includes the effect of thermal conductivity of the solid pellet. Higher the Lewis number, the higher will be the thermal conductivity of the solid. The effectiveness factor was found to be decreasing with decreasing Lewis number due to the fact that smaller Lewis numbers retard the rate of heat transfer inside the pellet owing to a lower rate of pyrolysis reaction. G factor includes the effect of the heat of reaction. Since the pyrolysis reaction is endothermic in nature, the G factor takes negative values. The more the negative value higher will be endothermic nature of the pyrolysis reaction. The effectiveness factor was found to be decreasing with more negative values of the G factor. This behavior can be attributed to the fact that more negative value of G factor would result in more energy consumption by the reaction owing to a larger temperature gradient inside the pellet. Further, the analytical expressions are also derived for gas and solid concentrations and effectiveness factor for two limiting cases of the general model developed. The two limiting cases of the model are categorized as the homogeneous model and unreacted shrinking core model.

Keywords: effectiveness factor, G-factor, homogeneous model, lewis number, non-catalytic, shrinking core model

Procedia PDF Downloads 138

Authors: P. Mirahmadpour, M. H. Banitaba, D. Nematollahi

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The chemistry of coordination polymers in recent years has grown exponentially not only because of their interesting architectures but also due to their various technical applications in many fields including ion exchange, chemical catalysis, small molecule separations, and drug release. The use of bridging ligands for the controlled self-assembly of one, two or three dimensional metallo-supramolecular species is the subject of serious study in last decade. Numerous different synthetic methods have been offered for the preparation of coordination polymers such as (a) diffusion from the gas phase, (b) slow diffusion of the reactants into a polymeric matrix, (c) evaporation of the solvent at ambient or reduced temperatures, (d) temperature controlled cooling, (e) precipitation or recrystallisation from a mixture of solvents and (f) hydrothermal synthesis. The electrosynthetic process suggested several advantages over conventional approaches. A general advantage of electrochemical synthesis is that it allows synthesis under milder conditions than typical solvothermal or microwave synthesis. In this work we have introduced a simple electrochemical method for growing metal coordination polymers based on copper with a flexible 2,2’-thiodiacetic acid (TDA) and rigid 1,2,4,5-benzenetetracarboxylate (BTC) ligands. The structure of coordination polymers were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), elemental analysis, thermal gravimetric (TG) and differential thermal analyses (DTA). The single-crystal X-ray diffraction analysis revealed that different conformations of the ligands and different coordination modes of the carboxylate group as well as different coordination geometries of the copper atoms. Electrochemical synthesis of coordination polymers has different advantages such as faster synthesis at lower temperature in compare with conventional chemical methods and crystallization of desired materials in a single synthetic step.

Keywords: 1, 2, 4, 5-benzenetetracarboxylate, coordination polymer, copper, 2, 2’-thiodiacetic acid

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Authors: Belen Montero, Carmen Ramirez, Maite Rico, Rebeca Bouza, Irene Derungs

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Starch is a promising polymer for producing biocomposite materials because it is renewable, completely biodegradable and easily available at a low cost. Thermoplastic starches (TPS) can be obtained after the disruption and plasticization of native starch with a plasticizer. In this work, the solvent casting method was used to obtain TPS films from wheat starch plasticized with glycerol and reinforced with nanocellulose (CNC). X-ray diffraction analysis was used to follow the evolution of the crystallinity. The native wheat starch granules have shown a profile corresponding to A-type crystal structures typical for cereal starches. When TPS films are analyzed a high amorphous halo centered on 19º is obtained, indicating the plasticization process is completed. SEM imaging was made in order to analyse the morphology. The image from the raw wheat starch granules shows a bimodal granule size distribution with some granules in large round disk-shape forms (A-type) and the others as smaller spherical particles (B-type). The image from the neat TPS surface shows a continuous surface. No starch aggregates or swollen granules can be seen so, the plasticization process is complete. In the surfaces of reinforced TPS films aggregates are seen as the CNC concentration in the matrix increases. The CNC influence on the mechanical properties of TPS films has been studied by dynamic mechanical analysis. A direct relation exists between the storage modulus values, E’, and the CNC content in reinforced TPS films: higher is the content of nanocellulose in the composite, higher is the value of E’. This reinforcement effect can be explained by the appearance of a strong and crystalline nanoparticle-TPS interphase. Thermal stability of films was analysed by TGA. It has not observed any influence on the behaviour related to the thermal degradation of films with the incorporation of the CNC. Finally, the resistance to the water absorption films was analysed following the standard UNE-EN ISO 1998:483. The percentage of water absorbed by the samples at each time was calculated. The addition of 5 wt % of CNC to the TPS matrix leads to a significant improvement in the moisture resistance of the starch based material decreasing their diffusivity. It has been associated to the formation of a nanocrystal network that prevents swelling of the starch and therefore water absorption and to the high crystallinity of cellulose compared to starch. As a conclusion, the wheat film reinforced with 5 wt % of cellulose nanocrystals seems to be a good alternative for short-life applications into the packaging industry, because of its greatest rigidity, thermal stability and moisture sorption resistance.

Keywords: biocomposites, nanocellulose, starch, wheat

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Authors: Nguyen Van Toan, Suguru Sangu, Tetsuro Saito, Naoki Inomata, Takahito Ono

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This paper presents the design and fabrication of an optical window for an optical modulator toward image sensing applications. An optical window consists of micrometer-order SiO2 capillaries (porous solid) that can modulate transmission light intensity by moving the liquid in and out of porous solid. A high optical transmittance of the optical window can be achieved due to refractive index matching when the liquid is penetrated into the porous solid. Otherwise, its light transmittance is lower because of light reflection and scattering by air holes and capillary walls. Silicon capillaries fabricated by deep reactive ion etching (DRIE) process are completely oxidized to form the SiO2 capillaries. Therefore, high aspect ratio SiO2 capillaries can be achieved based on silicon capillaries formed by DRIE technique. Large compressive stress of the oxide causes bending of the capillary structure, which is reduced by optimizing the design of device structure. The large stress of the optical window can be released via thin supporting beams. A 7.2 mm x 9.6 mm optical window area toward a fully integrated with the image sensor format is successfully fabricated and its optical transmittance is evaluated with and without inserting liquids (ethanol and matching oil). The achieved modulation range is approximately 20% to 35% with and without liquid penetration in visible region (wavelength range from 450 nm to 650 nm).

Keywords: thermal oxidation process, SiO2 capillaries, optical window, light transmittance, image sensor, liquid penetration

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Authors: Nazanin Sheibanian, Raffaella Sesana, Sedat Ozbilen

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In recent years, high-entropy alloys (HEAs) have attracted considerable attention due to their unique properties and potential applications. In this study, novel HEA coatings were prepared on Mg substrates using mechanically alloyed HEA powder feedstocks based on Al_(0.1-0.5)CoCrCuFeNi and MnCoCrCuFeNi multi-material systems. The coatings were deposited by the Cold Spray (CS) process using three different temperatures of the process gas (N2) (650°C, 750°C, and 850°C) to examine the effect of gas temperature on coating properties. In this study, Infrared Thermography (non-destructive) was examined as a possible quality control technique for HEA coatings applied to magnesium substrates. Active Thermography was employed to characterize coating properties using the thermal response of the coating. Various HEA chemical compositions and deposition temperatures have been investigated. As a part of this study, a comprehensive macro and microstructural analysis of Cold Spray (CS) HEA coatings has been conducted using macrophotography, optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM+EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), microhardness tests, roughness measurements, and porosity assessments. These analyses provided insight into phase identification, microstructure characterization, deposition, particle deformation behavior, bonding mechanisms, and identifying a possible relationship between physical properties and thermal responses. Based on the figures and tables, it is evident that the Maximum Relative Radiance (∆RMax) of each sample differs depending on both the chemical composition of HEA and the temperature at which Cold Spray is applied.

Keywords: active thermography, coating, cold spray, high- entropy alloy, material characterization

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Authors: David Robert Irvine

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In the dental restoration sector, there has been a shift to using zirconia. With the ever increasing need to decrease lead times to deliver restorations faster the zirconia is machined in its pre-sintered state instead of grinding the very hard sintered state. As with all machining, there is tool wear and while investigating the tooling used to machine pre-sintered zirconia it became apparent that the wear rate is based more on material build up and abrasion than it is on plastic deformation like conventional metal machining. It also came to light that the tool material can currently not be selected based on wear resistance, as there is no data. Different works have analysed the effect of the individual wear mechanism separately using similar if not the same material. In this work, the testing method used to analyse the wear was a modified from ISO 8688:1989 to use the pre-sintered zirconia and the cutting conditions used in dental to machine it. This understanding was developed through a series of tests based in machining operations, to give the best representation of the multiple wear factors that can occur in machining of pre-sintered zirconia such as 3 body abrasion, material build up, surface welding, plastic deformation, tool vibration and thermal cracking. From the testing, it found that carbide grades with low trans-granular rupture toughness would fail due to abrasion while those with high trans-granular rupture toughness failed due to edge chipping from build up or thermal properties. The results gained can assist the development of these tools and the restorative dental process. This work was completed with the aim of assisting in the selection of tool material for future tools along with a deeper understanding of the properties that assist in abrasive wear resistance and material build up.

Keywords: abrasive wear, cemented carbide, pre-sintered zirconia, tool wear

Procedia PDF Downloads 159

Authors: Yogi Sirodz Gaos, Irvan Wiradinata

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In the 500 kW Organic Rankine Cycle (ORC) power plant in Indonesia, an AFT (according to the Tubular Exchanger Manufacturers Association – TEMA) type shell and tube heat exchanger device is used as a pre-heating system for the ORC’s hot water circulation system. The pre-heating source is a waste heat recovery of the brine water, which is tapped from a geothermal power plant. The brine water itself has 5 MWₜₕ capacities, with average temperature of 170ᵒC, and 7 barg working pressure. The aim of this research is to examine the performance of the heat exchanger in the ORC system in a 500 kW ORC power plant. The data for this research were collected during the commissioning on the middle of December 2016. During the commissioning, the inlet temperature and working pressure of the brine water to the shell and tube type heat exchanger was 149ᵒC, and 4.4 barg respectively. Furthermore, the ΔT for the hot water circulation of the ORC system to the heat exchanger was 27ᵒC, with the inlet temperature of 140ᵒC. The pressure in the hot circulation system was dropped slightly from 7.4ᵒC to 7.1ᵒC. The flow rate of the hot water circulation was 80.5 m³/h. The presentation and discussion of a case study on the performance of the heat exchanger on the 500 kW ORC system is presented as follows: (1) the heat exchange duty is 2,572 kW; (2) log mean temperature of the heat exchanger is 13.2ᵒC; (3) the actual overall thermal conductivity is 1,020.6 W/m².K (4) the required overall thermal conductivity is 316.76 W/m².K; and (5) the over design for this heat exchange performance is 222.2%. An analysis of the heat exchanger detailed engineering design (DED) is briefly discussed. To sum up, this research concludes that the shell and tube heat exchangers technology demonstrated a good performance as pre-heating system for the ORC’s hot water circulation system. Further research need to be conducted to examine the performance of heat exchanger system on the ORC’s hot water circulation system.

Keywords: shell and tube, heat exchanger, organic Rankine cycle, performance, commissioning

Procedia PDF Downloads 143

Authors: Bin Shi, Mouhab Meshreki, Grégoire Bazin, Helmi Attia

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Large monolithic components are widely used in the aerospace industry in order to reduce airplane weight. Milling is an important operation in manufacturing of the monolithic parts. More than 90% of the material could be removed in the milling operation to obtain the final shape. This results in low rigidity and post-machining distortion. The post-machining distortion is the deviation of the final shape from the original design after releasing the clamps. It is a major challenge in machining of the monolithic parts, which costs billions of economic losses every year. Three sources are directly related to the part distortion, including initial residual stresses (RS) generated from previous manufacturing processes, machining-induced RS and thermal load generated during machining. A finite element model was developed to simulate a milling process and predicate the post-machining distortion. In this study, a rolled-aluminum plate AA7175 with a thickness of 60 mm was used for the raw block. The initial residual stress distribution in the block was measured using a layer-removal method. A stress-mapping technique was developed to implement the initial stress distribution into the part. It is demonstrated that this technique significantly accelerates the simulation time. Machining-induced residual stresses on the machined surface were measured using MTS3000 hole-drilling strain-gauge system. The measured RS was applied on the machined surface of a plate to predict the distortion. The predicted distortion was compared with experimental results. It is found that the effect of the machining-induced residual stress on the distortion of a thick plate is very limited. The distortion can be ignored if the wall thickness is larger than a certain value. The RS generated from the thermal load during machining is another important factor causing part distortion. Very limited number of research on this topic was reported in literature. A coupled thermo-mechanical FE model was developed to evaluate the thermal effect on the plastic deformation of a plate. A moving heat source with a feed rate was used to simulate the dynamic cutting heat in a milling process. When the heat source passed the part surface, a small layer was removed to simulate the cutting operation. The results show that for different feed rates and plate thicknesses, the plastic deformation/distortion occurs only if the temperature exceeds a critical level. It was found that the initial residual stress has a major contribution to the part distortion. The machining-induced stress has limited influence on the distortion for thin-wall structure when the wall thickness is larger than a certain value. The thermal load can also generate part distortion when the cutting temperature is above a critical level. The developed numerical model was employed to predict the distortion of a frame part with complex structures. The predictions were compared with the experimental measurements, showing both are in good agreement. Through optimization of the position of the part inside the raw plate using the developed numerical models, the part distortion can be significantly reduced by 50%.

Keywords: modelling, monolithic parts, optimization, post-machining distortion, residual stresses

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Authors: Bina Gupta, Rashmi Singh, Harshit Mahandra

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Molybdenum is a strategic metal and finds applications in petroleum refining, thermocouples, X-ray tubes and in making of steel alloy owing to its high melting temperature and tensile strength. The growing significance and economic value of molybdenum has increased interest in the development of efficient processes aiming its recovery from secondary sources. Main secondary sources of Mo are molybdenum catalysts which are used for hydrodesulphurisation process in petrochemical refineries. The activity of these catalysts gradually decreases with time during the desulphurisation process as the catalysts get contaminated with toxic material and are dumped as waste which leads to environmental issues. In this scenario, recovery of molybdenum from spent catalyst is significant from both economic and environmental point of view. Recently ionic liquids have gained prominence due to their low vapour pressure, high thermal stability, good extraction efficiency and recycling capacity. The present study reports recovery of molybdenum from Mo-Co spent leach liquor using Cyphos IL 102[trihexyl(tetradecyl)phosphonium bromide] as an extractant. Spent catalyst was leached with 3.0 mol/L HCl, and the leach liquor containing Mo-870 ppm, Co-341 ppm, Al-508 ppm and Fe-42 ppm was subjected to extraction step. The effect of extractant concentration on the leach liquor was investigated and almost 85% extraction of Mo was achieved with 0.05 mol/L Cyphos IL 102. Results of stripping studies revealed that 2.0 mol/L HNO3 can effectively strip 94% of the extracted Mo from the loaded organic phase. McCabe- Thiele diagrams were constructed to determine the number of stages required for quantitative extraction and stripping of molybdenum and were confirmed by countercurrent simulation studies. According to McCabe- Thiele extraction and stripping isotherms, two stages are required for quantitative extraction and stripping of molybdenum at A/O= 1:1. Around 95.4% extraction of molybdenum was achieved in two-stage counter current at A/O= 1:1 with the negligible extraction of Co and Al. However, iron was coextracted and removed from the loaded organic phase by scrubbing with 0.01 mol/L HCl. Quantitative stripping (~99.5 %) of molybdenum was achieved with 2.0 mol/L HNO₃ in two stages at O/A=1:1. Overall ~95.0% molybdenum with 99 % purity was recovered from Mo-Co spent catalyst. From the strip solution, MoO₃ was obtained by crystallization followed by thermal decomposition. The product obtained after thermal decomposition was characterized by XRD, FE-SEM and EDX techniques. XRD peaks of MoO₃ correspond to molybdite Syn-MoO₃ structure. FE-SEM depicts the rod-like morphology of synthesized MoO₃. EDX analysis of MoO₃ shows 1:3 atomic percentage of molybdenum and oxygen. The synthesised MoO₃ can find application in gas sensors, electrodes of batteries, display devices, smart windows, lubricants and as a catalyst.

Keywords: cyphos Il 102, extraction, spent mo-co catalyst, recovery

Procedia PDF Downloads 172

Authors: Sebastiano Candamano, Antonio Iorfida, Patrizia Frontera, Anastasia Macario, Fortunato Crea

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Alkali-activated materials are promising binders obtained by an alkaline attack on fly-ashes, metakaolin, blast slag among others. In order to guarantee the highest ecological and cost efficiency, a proper selection of precursors and alkaline activators has to be carried out. These choices deeply affect the microstructure, chemistry and performances of this class of materials. Even if, in the last years, several researches have been focused on mix designs and curing conditions, the lack of exhaustive activation models, standardized mix design and curing conditions and an insufficient investigation on shrinkage behavior, efflorescence, additives and durability prevent them from being perceived as an effective and reliable alternative to Portland. The aim of this study is to develop alkali-activated cements mortars containing high amounts of industrial by-products and waste, such as ground granulated blast furnace slag (GGBFS) and ashes obtained from the combustion process of forest biomass in thermal power plants. In particular, the experimental campaign was performed in two steps. In the first step, research was focused on elucidating how the workability, mechanical properties and shrinkage behavior of produced mortars are affected by the type and fraction of each precursor as well as by the composition of the activator solutions. In order to investigate the microstructures and reaction products, SEM and diffractometric analyses have been carried out. In the second step, their durability in harsh environments has been evaluated. Mortars obtained using only GGBFS as binder showed mechanical properties development and shrinkage behavior strictly dependent on SiO2/Na2O molar ratio of the activator solutions. Compressive strengths were in the range of 40-60 MPa after 28 days of curing at ambient temperature. Mortars obtained by partial replacement of GGBFS with metakaolin and forest biomass ash showed lower compressive strengths (≈35 MPa) and shrinkage values when higher amount of ashes were used. By varying the activator solutions and binder composition, compressive strength up to 70 MPa associated with shrinkage values of about 4200 microstrains were measured. Durability tests were conducted to assess the acid and thermal resistance of the different mortars. They all showed good resistance in a solution of 5%wt of H2SO4 also after 60 days of immersion, while they showed a decrease of mechanical properties in the range of 60-90% when exposed to thermal cycles up to 700°C.

Keywords: alkali activated cement, biomass ash, durability, shrinkage, slag

Procedia PDF Downloads 325