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Ab initio study of waterDelle Site, Luigi January 1999 (has links)
No description available.
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Métodos geoestatísticos na caracterização espacial de óxidos de ferro em diferentes pedoformasSilva Junior, João Fernandes da [UNESP] 27 February 2012 (has links) (PDF)
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silvajunior_jf_me_jabo.pdf: 787738 bytes, checksum: 7b3e41cb53972e8468ad03ecb64cfbe1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os óxidos de ferro são importantes indicadores ambientais e possuem grande influência nos atributos físicos e químicos do solo. Entretanto, para o melhor entendimento de sua formação e ocorrência são necessários estudos de variabilidade espacial. A geoestatística é a melhor ferramenta para este estudo, sendo que a Krigagem ordinária (KO) é um interpolador de mínimos quadrados, mais utilizado em ciência do solo. Porém, ela suaviza os detalhes locais da variação espacial, superestimando pequenos valores e subestimando altos valores. Por isso, ela revela-se inadequada na avaliação da verdadeira variabilidade espacial dos óxidos de ferro. Embora a krigagem mostre a melhor estimativa de um atributo Z, ele não representa bem a variação. Deste modo, a alternativa é simulação geoestatística que avalia e quantifica a incerteza de um atributo, de maneira mais realista. A técnica de simulação estocástica mais utilizada é a simulação sequencial gaussiana (SSG), por ser, rápida e direta na construção da função de densidade de probabilidade acumulada condicional (f.d.p.a.c), sendo, portanto preferível à estimação pela KO. Desta forma, é importante testar outros métodos para caracterizar espacial dos óxidos de ferro. Objetivando avaliar o desempenho da (KO), krigagem ordinária dos dados padronizados (KOP) e da simulação seqüencial gaussiana (SSG) da variabilidade espacial dos óxidos de ferro em uma área com pedoformas: côncava e convexa foram coletados 121 amostras de duas malhas nos dois relevos classificados como: côncavo e convexo com espaçamento de 10 metros. O erro médio, o erro quadrático médio e o erro quadrático médio padronizado foram os critérios de avaliação da acurácia da predição. Os valores altos dos coeficientes de variação dos óxidos de ferro afetaram o desempenho dos métodos... / Iron oxides are important environmental indicators and have great influence on the physical and chemical properties of soil. However, for a better understanding of their formation and occurrence studies are necessary spatial variability. Geostatistics is a tool for this study, ordinary kriging (OK) is a least squares interpolator, is the most widely used in soil science. However smooths out local details of spatial, small values overestimating and underestimating high values. Therefore, is inadequate in the evaluation of iron oxides. Although the kriging show the best estimate of an attribute Z, it does not represent well the variation. Thus, the alternative is geroestatisctical simulation that evaluates and quantify the uncertainty of an attribute, more realistically. Since the most widely used is the sequential Gaussian simulation (SGS), to be quickly and directly in the construction of the density function of cumulative probability (fdpac), and are preferred to the estimation. Thus, is important to test other methods to characterize spatially of iron oxides. In order to evaluate the performance of (OK), ordinary kriging of standardized data (OKS) and sequential Gaussian simulation (SGS) of the spatial variability of iron oxides in an area with landform: concave and convex 121 samples were collected data in two loops with two reliefs classified as concave and convex with spacing of 10 meters. The average error, the mean square error and root mean square error were standardized criteria for evaluating the accuracy of prediction. High values of coefficient of variation of iron oxides harmed the performance of the methods. The landforms showed variable differentiated by SGS. The maps of OKS and E-type had higher accuracy and greater detail in relation to landforms in the OK. It is recommended that E-type maps instead of maps OK... (Complete abstract click electronic access below)
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Métodos geoestatísticos na caracterização espacial de óxidos de ferro em diferentes pedoformas /Silva Júnior, João Fernandes da. January 2012 (has links)
Orientador: Gener Tadeu Pereira / Coorientador: José Marques Júnior / Banca: Ednaldo Carvalho Guimarães / Banca: Marcílio Vieira Martins Filho / Resumo: Os óxidos de ferro são importantes indicadores ambientais e possuem grande influência nos atributos físicos e químicos do solo. Entretanto, para o melhor entendimento de sua formação e ocorrência são necessários estudos de variabilidade espacial. A geoestatística é a melhor ferramenta para este estudo, sendo que a Krigagem ordinária (KO) é um interpolador de mínimos quadrados, mais utilizado em ciência do solo. Porém, ela suaviza os detalhes locais da variação espacial, superestimando pequenos valores e subestimando altos valores. Por isso, ela revela-se inadequada na avaliação da verdadeira variabilidade espacial dos óxidos de ferro. Embora a krigagem mostre a melhor estimativa de um atributo Z, ele não representa bem a variação. Deste modo, a alternativa é simulação geoestatística que avalia e quantifica a incerteza de um atributo, de maneira mais realista. A técnica de simulação estocástica mais utilizada é a simulação sequencial gaussiana (SSG), por ser, rápida e direta na construção da função de densidade de probabilidade acumulada condicional (f.d.p.a.c), sendo, portanto preferível à estimação pela KO. Desta forma, é importante testar outros métodos para caracterizar espacial dos óxidos de ferro. Objetivando avaliar o desempenho da (KO), krigagem ordinária dos dados padronizados (KOP) e da simulação seqüencial gaussiana (SSG) da variabilidade espacial dos óxidos de ferro em uma área com pedoformas: côncava e convexa foram coletados 121 amostras de duas malhas nos dois relevos classificados como: côncavo e convexo com espaçamento de 10 metros. O erro médio, o erro quadrático médio e o erro quadrático médio padronizado foram os critérios de avaliação da acurácia da predição. Os valores altos dos coeficientes de variação dos óxidos de ferro afetaram o desempenho dos métodos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Iron oxides are important environmental indicators and have great influence on the physical and chemical properties of soil. However, for a better understanding of their formation and occurrence studies are necessary spatial variability. Geostatistics is a tool for this study, ordinary kriging (OK) is a least squares interpolator, is the most widely used in soil science. However smooths out local details of spatial, small values overestimating and underestimating high values. Therefore, is inadequate in the evaluation of iron oxides. Although the kriging show the best estimate of an attribute Z, it does not represent well the variation. Thus, the alternative is geroestatisctical simulation that evaluates and quantify the uncertainty of an attribute, more realistically. Since the most widely used is the sequential Gaussian simulation (SGS), to be quickly and directly in the construction of the density function of cumulative probability (fdpac), and are preferred to the estimation. Thus, is important to test other methods to characterize spatially of iron oxides. In order to evaluate the performance of (OK), ordinary kriging of standardized data (OKS) and sequential Gaussian simulation (SGS) of the spatial variability of iron oxides in an area with landform: concave and convex 121 samples were collected data in two loops with two reliefs classified as concave and convex with spacing of 10 meters. The average error, the mean square error and root mean square error were standardized criteria for evaluating the accuracy of prediction. High values of coefficient of variation of iron oxides harmed the performance of the methods. The landforms showed variable differentiated by SGS. The maps of OKS and E-type had higher accuracy and greater detail in relation to landforms in the OK. It is recommended that E-type maps instead of maps OK... (Complete abstract click electronic access below) / Mestre
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Forest fires and their effect on chemical and physical properties of soils in North-eastern-Libya : assessment of the changes in soil chemical and physical properties of soils in North-eastern-LibyaEldiabani, Gibrel Salah January 2011 (has links)
Forest areas are particularly susceptible to fires, which are often manmade. Too-frequent fires are likely to adversely affect the soil properties as well as vegetation composition, and possibly lead to soil erosion and desertification. One of the most fire affected forest regions in the world is the Mediterranean. Libya, in the Mediterranean region, has soils that are considered to be arid except in a small area called Aljabal Alakhdar (Green mountain), which is the geographic area covered by this study. It is the wettest part of Libya, and has an extensive forest and many agricultural crops. Like other forests in the Mediterranean it has suffered extreme degradation. This is mainly due to people removing fire wood, or sometimes converting forested areas to agricultural use, as well as fires which may alter several soil chemical and physical properties. The purpose of this research was to evaluate the effects of fires on the physical and chemical properties of soil of Aljabal Alakhdar forest in the north-east of Libya. The physical and chemical properties of soil following fire in two geographic areas have been determined, with those subjected to the fire compared to those in adjacent unburned areas in one coastal and one mountain site. Physical properties studied were: soil particle size, soil water content, soil porosity and soil particle density; and chemical properties studied were: soil electrical conductivity (EC), soil pH, soluble and exchangeable Na, K, Ca and Mg, cation exchange capacity (CEC), soluble Cl, CO3 and HCO3, SO4, organic matter, total N and total P. For the first time in Libyan soils, the effect of burning on the magnetic susceptibility properties of soils was also tested. The results showed that except for the soil water content and magnetic susceptibility, fire has not had a clear effect on the soils' physical properties, while there has been a strong impact of fire on most of the studied chemical properties. These results have been used to create an index of burning for such soils in each of the geographic areas, as a step towards creating a model which will enable a subset of soil parameters to be used to estimate how recently a site was burned, as well as defining fire severity at a site.
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Análise de cimentos à base de silicato de cálcio associado a diferentes radiopacificadores /Costa, Bernardo Cesar. January 2016 (has links)
Orientador: Mario Tanomaru-Filho / Resumo: O MTA e cimento Portland (PC) são cimentos de silicato de cálcio. O óxido de bismuto presente na MTA pode afetar as propriedades físico-químicas e biológicas do material. Novos radiopacificadores como óxido de itérbio (Yb2O3) e o tungstato de cálcio (CaWO4) podem melhorar propriedades do material. No capítulo 1, foram realizadas avalições de propriedades físico-químicas, citotoxicidade e potencial bioativo do MTA Angelus (MTA), cimento de silicato de cálcio (CSC) e CSC com 30% de óxido de Itérbio (CSC/Yb2O3). O tempo de presa inicial e final foi avaliado com agulhas Gilmore. A resistência à compressão foi analisada em máquina de ensaios mecânicos. A radiopacidade foi verificada com radiografias dos materiais e escala de alumínio. O teste de solubilidade e escoamento foram realizados de acordo com ISO 6876/2002. Os dados foram submetidos ao teste ANOVA e Tukey (5% de significância). A viabilidade celular foi avaliada por meio do ensaio MTT e corante Vermelho Neutro, enquanto o potencial de mineralização por meio da atividade de fosfatase alcalina e vermelho de Alizarina. Os dados foram submetidos aos testes Anova e Tukey e Bonferroni (5% de significância). O potencial bioativo foi avaliado em microcopia eletrônica de varredura. No capítulo 2, materiais à base de silicato tricálcico (TSC) associado ao tungstato de cálcio (CaWO4) e Yb2O3 foram avaliados em comparação ao MTA (Angelus, Londrina, Brasil) e ao TSC. O tempo de presa inicial e final foi avaliado com agulhas Gilmore. A... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor
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Role Of Physico-Chemical Factors In The Heave And Collapse Behaviour Of Laboratory Desiccated SoilsRami Reddy, P Mohan 11 1900 (has links) (PDF)
No description available.
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Study of commercial and experimental MTA-based sealers for root canal filling = Estudo de cimentos comerciais e experimentais à base de MTA para obturação de canais radiculares / Estudo de cimentos comerciais e experimentais à base de MTA para obturação de canais radicularesVitti, Rafael Pino, 1984- 22 August 2018 (has links)
Orientador: Mário Alexandre Coelho Sinhoreti / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-22T06:42:26Z (GMT). No. of bitstreams: 1
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Previous issue date: 2013 / Resumo: Os objetivos neste trabalho foram (1) avaliar e comparar propriedades físico-químicas de cimentos endodônticos, sendo um recentemente desenvolvido à base de mineral trióxido agregado (MTA Fillapex, Angelus, Londrina, Brasil) e outro à base de resina epóxica (AH Plus, Dentsply, Konstanz, Alemanha); e (2) desenvolver e avaliar propriedades físico-químicas de três cimentos endodônticos experimentais à base de MTA e uma resina de salicilato com diferentes fosfatos de cálcio (CaP). Os materiais foram manipulados de acordo com as instruções dos fabricantes. Os cimentos experimentais foram compostos de pastas bases e catalisadoras misturadas em 1:1. A pasta base foi composta de 60% de óxido de bismuto e 40% de butilenoglicol dissalicilato. Três diferentes pastas catalisadoras foram formuladas contendo: (1) 60% de MTA, 39% de Resimpol 8 e 1% de dióxido de titânio; (2) 40% de MTA, 39% de Resimpol 8, 20% de hidroxiapatita e 1% de dióxido de titânio e; (3) 40% de MTA, 39% de Resimpol 8, 20% de fosfato dibásico de cálcio diidratado e 1% de dióxido de titânio. MTA Fillapex foi usado como controle. O tempo de trabalho e escoamento foi testado de acordo com a ISO 6876:2001 e o tempo de presa de acordo com a ASTM C266 (n=3 para cada material e teste). Os materiais foram colocados em moldes de PVC (8 mm x 1,6 mm) e armazenados em recipientes contendo 20 ml (testes de solubilidade e absorção de água) ou 10 ml (ensaios de pH e liberação de cálcio) de água deionizada a 37ºC (n=10 para cada material e teste). Em 1, 7, 14 e 28 dias as amostras foram removidas dos recipientes e secas para aferiação da solubilidade e absorção de água. Após 3 e 24 horas e 4, 7, 14 e 28 dias, a água dos recipientes foi coletada para análises do pH e liberação de cálcio. Os dados foram analizados usando ANOVA um fator e teste de Tukey (5%). MTA Fillapex mostrou menores valores de escoamento e tempos de trabalho e presa em relação ao AH Plus (p<0,05). MTA Fillapex obteve os maiores valores de escoamento e tempos de trabalho e presa em comparação aos materiais experimentais (p<0,05). MTA Fillapex apresentou os menores valores de solubilidade e absorção de água (p<0,05). Todos os cimentos experimentais e o MTA Fillapex apresentaram pH básico e liberação de íons cálcio. MTA Fillapex e AH Plus mostraram valores de acordo com a ISO 6876:2001. Os materiais experimentais apresentaram propriedades físico-químicas satisfatórias / Abstract: The aims of this study were (1) to evaluate and to compare physicochemical properties of endodontic sealers, a recent calcium-silicate based sealer (MTA Fillapex, Angelus, Londrina, Brazil) and other an epoxy resin based sealer (AH Plus, Dentsply, Konstanz, Germany); and (2) to develop and to evaluate physicochemical properties of three experimental root canal sealers made by mineral trioxide aggregate (MTA) and a salicylate resin with different calcium phosphates (CaP). The materials were handled following the manufacturer's instructions. The experimental materials were composed of a base and a catalyst pastes mixed in a 1:1. The base paste was made by 60% bismuth oxide and 40% butyl ethylene glycol disalicylate. Three different catalyst pastes were formulated with: (1) 60% MTA, 39% Resimpol 8 and 1% titanium dioxide; (2) 40% MTA, 39% Resimpol 8, 20% hydroxyapatite and 1% titanium dioxide and; (3) 40% MTA, 39% Resimpol 8, 20% dibasic calcium phosphate dihydrate and 1% titanium dioxide. MTA Fillapex was used as control. The working time and flow were tested according to ISO 6876:2001 and the setting time according to ASTM C266 (n=3 for each material and test). The materials were placed into PVC molds (8 mm x 1.6 mm) and stored in containers with 20 mL (solubility and water absorption tests) or 10 mL (calcium release and hydroxyl ions tests) of deionized water at 37°C (n=10 for each material and test). At 1, 7, 14 and 28 days the samples were removed from the solutions and dry for solubility and water absorption tests. After 3 and 24 h and 4, 7, 14, 28 days the soaking water was collected for Ca and pH analysis. The data were analyzed using one-way ANOVA with Tukey's test (5%). MTA Fillapex showed lower values of flow and working and setting times when compared to AH Plus (p<.05). MTA Fillapex had the higher values of flow and working and setting times when compared to experimental materials (p<.05). MTA Fillapex presented the lowest values of solubility and water absorption (p<.05). All experimental cements and MTA Fillapex showed basifying activity and released calcium ions. MTA Fillapex and AH Plus showed values in according to the ISO 6876:2001. The experimental materials showed satisfactory physicochemical properties / Doutorado / Materiais Dentarios / Doutor em Materiais Dentários
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Influência do pré-aquecimento e do envelhecimento em propriedades físico-químicas e mecânicas de um infiltrante / Influence of pre-heating and aging in physical chemical and mechanical properties of infiltrantSantos-Caldeira, Milena Maria Pierre, 1980- 24 February 2015 (has links)
Orientador: Luís Roberto Marcondes Martins / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-27T03:21:27Z (GMT). No. of bitstreams: 1
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Previous issue date: 2015 / Resumo: Dentro da abordagem minimamente invasiva da doença cárie, um material resinoso a base de metacrilatos, denominado infiltrante Icon® (DMG), foi apresentado com objetivo de paralisar lesões cariosas incipientes em esmalte pela penetração e polimerização dentro das mesmas. Para análise deste material, os objetivos do presente estudo foram: 1) avaliar a influência do pré-aquecimento (AQ) nas propriedades grau de conversão (GC), resistência à flexão (RF), módulo de elasticidade (ME), dureza Knoop (KN) e redução percentual de dureza (RD) de Icon®; e, 2) avaliar a influência do envelhecimento (EN) nas propriedades rugosidade superficial (RS), KN, RF e ME de Icon®. Para avaliação do efeito de AQ (n=10), corpos de prova foram confeccionados (7x2x1mm) de acordo com os grupos divididos em: G1, Icon sem aquecimento; G2, Icon pré aquecido em estufa a 37oC por 1h; G3, Icon com aplicação de ar frio (23oC) por 20 s; G4, Icon com aplicação de ar quente (40oC) por 20 s. GC foi avaliado através da Espectroscopia por Infravermelho Transformada de Fourier (FTIR). RF e ME foram obtidos pelo teste de resistência à flexão de 3 pontos, em máquina de ensaio universal a 0,5mm/min. KN foi avaliada pela média de 3 indentações sob carga de 50g por 15s, e, RD foi avaliada por KN após imersão dos corpos de prova em etanol por 24h. Os dados para avaliação de AQ foram submetidos a ANOVA um critério (5%). Para avaliação de EN (n=20), amostras do infiltrante foram confeccionadas (7x2x1mm) e armazenadas em saliva artificial, a 37oC, até o momento das análises. O fator tempo foi avaliado, nos mesmos espécimes, em 3 níveis (24h, 6 meses e 12 meses) para RS e KN; porém, para RF e ME, tempo foi avaliado em 2 fases (24h e 12 meses) em espécimes distintos devido ao teste destrutivo utilizado. RS foi avaliada, em 24h, 6 e 12 meses, pela média de 3 leituras Ra em rugosímetro. KN foi avaliada em 24h, 6 e 12 meses como previamente descritos para AQ. Enquanto, RF e ME foram avaliados em 24h e 12 meses como também descrito para AQ. Os dados de RS e KN foram submetidos à análise de medidas repetidas e teste de Tukey, enquanto que os dados de RF e ME foram submetidos a ANOVA um critério (5%). O aumento da temperatura do material Icon, não mostrou nenhuma melhora em relação a GC, RF, ME, KN e RD pelos diferentes métodos de preparo testados. Após envelhecimento, RS aumentou significativamente da análise comparado a 6 e 12 meses, enquanto KN sofreu redução nos mesmos 3 tempos testados, havendo correlação inversamente proporcional entre estas propriedades de Icon®. Adicionalmente, houve redução significante de RF e ME após envelhecimento de Icon®. Desta forma, pode-se concluir que o aquecimento do material não interferiu nas propriedades testadas, e o envelhecimento deteriorou as propriedades do infiltrante / Abstract: Within the minimally invasive approach to caries, a methacrylates based material, Icon® infiltrant (DMG), was presented in order to paralyze incipient enamel carious lesions by penetration and polymerization inside caries lesions. For material analysis, the aims of this study were: 1) to evaluate the effect of pre heating material (HE) in conversion degree (CD), flexural strength (FL), elastic modulus (EM), Knoop hardness (KN) and softening ratio (SR); and, 2) to evaluate the effect of artificial aging (AG) in surface roughness (SU), KN, FL and EM. For HE evaluation (n = 10), 10 specimens were prepared (7x2x1mm) according to the groups that were set up as follows: G1, unheated Icon; G2, preheated Icon in oven at 37°C for 1h; G3, Icon with cold air application (23°C) for 20s; G4 Icon with heated air application (40°C) for 20s. CD was measured by Fourier Transform Infrared spectroscopy (FTIR). FL and EM were evaluated by three-point bending test using an universal testing machine by 0,5mm/min. KN was assessed by three indentations average on load of 50g for 15s. And crosslink density was indirectly assessed by hardness softening ratio after ethanol immersion for 24h. The HE evaluation data were submitted to one-way ANOVA (5%). For AG evaluation (n = 20), samples were prepared (7x2x1mm) and stored in artificial saliva at 37°C until the analysis time. The time factor was evaluated in the same specimens, on 3 levels (24h, 6 months and 12 months) for SU and KN; however, for FL and EM, the time was evaluated in 2 levels (24h and 12 months) at different specimens because of the destructive testing. SU was evaluated at 24h, 6 and 12 months, by 3 readings roughness average (Ra cut-off). KN was assessed at 24h, 6 and 12 months, as previously described for AQ. FL and EM were evaluated at 24h and 12 months as well as described for AQ. Data from SU and KN were submitted to repeated measures analysis and Tukey test, while FL and EM data were submitted to one-way ANOVA (5%). Hight temperature did not improved CD, FL, EM, KN and SR by different prepare methods tested. Aging significantly increased SU from the initial analysis compared to 6 and 12 months, while KN decreased in the same three times tested, with inverse correlation between the properties. There was a significant FL and EM reduction after material aging. Therefore, it can be concluded that heating did not affect material properties tested, however, aging deteriorated infiltrant properties / Doutorado / Dentística / Doutora em Clínica Odontológica
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Density functional tightbinding studies of TiO2 polymorphsGandamipfa, Mulatedzi January 2020 (has links)
Thesis (Ph.D. (Physics)) -- University of Limpopo, 2021 / Titanium dioxide is among the most abundant materials and it has many of interesting physical and chemical properties (i.e., low density, high thermal and mechanical strength, insensitivity to corrosion) that make it a compound of choice for electrodes materials in energy storage. There are, however, limitations on the theoretical side to using the main electronic structure theories such as Hartree-Fock (HF) or densityfunctional (DFT) especially for large periodic and molecular systems. The aim of the theses is to develop a new, widely transferable, self-consistent density functional tight binding SCC-DFTB data base of TiO2, which could be applied in energy storage anodes with a large number of atoms. The TiO2, LiTiO2 and NaTiO2 potentials were derived following the SCC-DFTB parameterization procedure; where the generalized gradient approximation (GGA) and local density approximation (LDA) exchange-correlation functional were employed yielding Slater-Koster DFTB parameters. The results of derived parameters were validated by being compared with those of the bulk rutile and brookite polymorphs. The structural lattice parameters and electronic properties, such as the bandgaps were well reproduced. Most mechanical properties were close to those in literature, except mainly for C33 which tended to be underestimated due to the choice of exchange-correlation functional. The variation of the bulk lattice parameter and volume with lithiation and sodiation were predicted and compared reasonably with those in literature. The newly derived DFTB parameters were further used to calculate bulk properties of the anatase, which is chemically more stable than other polymorphs. Generally, the accuracy of the lattice structural, electronic and mechanical properties of the bulk anantase were consistent with those of the rutile and brookite polymorphs. Furthermore, nanostructures consisting of a large number of atoms, which extend beyond the normal scope of the conventional DFT calculations, were modelled both structurally and electronically. Structural variations with lithiation was consistent with experimental and sodiation tends to enhance volume expansion than lithiation. Anatase TiO2 and LiTO2 nanotubes of various diameters were generated using NanoWrap builder within MedeA® software. Its outstanding resistance to expansion during lithium insertion and larger surface area make the TiO2 nanotube a promising candidate for rechargeable lithium ion batteries. The outcomes of this study will be beneficial to future development of TiO2 nanotube and other nanostructures. Lastly, our DFTB Slater-Koster potentials were applied to recently discovered trigonal bipyramid (TB), i.e. TiO2 (TB)-I and TiO2 (TB)-II polymorphs, which have enormous 1D channels that provide suitable pathways for mobile ion transport. All structural, electronic properties were consistent with those in literature and all elastic properties agreed excellently with those that were calculated using DFT methods. Finally, the bulk structures of the two polymorphs, were lithiated and sodiated versions and electronic and structural properties were studied, together with the lithiated versions of associated nanostructures consisting of a large number of atoms. Generally, the TiO2 (TB)-I structure was found to be mechanically, energetically more stable and ductile than TiO2 (TB)-II. Hence, it will be beneficial to use TiO2 (TB)-I as an anode material for sodium ion batteries (SIB), due to its unique ductility and larger 1D channels. / National Research Fund (NRF), Department of Science and Innovation (DSI), Material Modelling Centre
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Characterisation and standardisation of different-origin end-of-life building materials toward assessment of circularityOzcelikci, E., Yildirim, Gurkan, Siad, H., Lachemi, M., Sahmaran, M. 10 November 2023 (has links)
Yes / Construction and demolition waste (CDW) management and recycling practices are crucial for transitioning to a circular economy. This study focuses on the detailed characterization of CDWs, including hollow brick (HB), red clay brick (RCB), roof tile (RT), concrete (C), and glass (G), collected from seven different sites. The CDWs were characterized based on particle size distribution, chemical composition, and crystalline nature. Pozzolanic activity was evaluated through compressive strength measurements of cement mortars with 20% cement replacement by CDWs at 7, 28, and 90 days. The results showed that clayey CDWs exhibited similar physical/chemical properties and crystalline structures. Compositions of Cs varied significantly based on their original materials. CDWs satisfied the minimum strength activity index for supplementary cementitious materials, with pozzolanic activity influenced by fineness and SiO2+Al2O3 contents. The average strength activity indexes for HB, RCB, RT, C, and G were 84.5%, 86.3%, 83.4%, 80.7%, and 75.8%, respectively. Clayey CDWs contributed to mechanical strength development, while Cs' contribution was related to hydration of unreacted cementitious particles. G exhibited the weakest pozzolanic activity due to its coarser particle size. Overall, CDWs demonstrated suitable properties for use as supplementary cementitious materials in PC-based systems.
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