Apontamentos de cristalografia | Resumos Materiais e Sistemas de Construção

Atividade de pesquisa

Aluno: Pedro Liotto

A pesquisa que pretendo desenvolver será a durabilidade do concreto convencional com

substituição parcial de areia por vidro. Assim sendo, trata-se de materiais amorfos.

Artigo 01

Endereço de consulta

https://www.sciencedirect.com/science/article/pii/S0272884222036963?

ref=cra_js_challenge&fr=RR-1

Título

EPR, NMR, DFT and XPS study on LaAlO3 phase transition in glass and influence on glass

structure and Properties

Resumo

Thermal treatment induced phase transition of LaAlO3 in glass and its influence on glass structure

and dielectric, magnetic, and Faraday rotation properties were characterized through various

techniques such as nuclear magnetic resonance, X-ray neutron diffraction, transmission electron

microscopy, X-ray photoelectron microscopy, vibrating-sample magnetometer, and electron

paramagnetic resonance. Cubic LaAlO3 nanocrystals were synthesized and incorporated into

lead-tellurite glasses, after crystallization treatment at 380 ◦C for 2 h, 14-17 nm-cubic LaAlO3

nanocrystals were changed to 14-27 nm-rhombohedral LaAlO3 perovskite due to the

temperature-induced viscosity and strain in the melt. The phase transition of LaAlO3 nanocrystals

in glass matrix was verified through versatile techniques in terms of the octahedral AlO6

distortion, SAED patterns, changes of lattice parameters calculated by Rietveld refinement, and

coordination number changes of AlO6 by NMR and XPS techniques. The modification to the

glass structure was yielded by phase transition through converting TeO4→TeO3, AlO6→AlO4,

BO4→BO3, and producing non-bridging oxygen. In addition, the energy band gap and density of

states of glass after phase transition was calculated through Density functional theory (DFT)

simulation. Glass doped with 10% LaAlO3 exhibited a promising dielectric constant and good

thermal stability due to the phase transition induced polarizability, and improved optical and

magnetic performance which is promising for photonics device applications.

Qual/quais estruturas cristalinas estão presentes?

Inicialmente o LaAIO3 apresenta-se em estrutura cúbica e após tratamento térmico passa a

estrutura romboédrico.

Quais valores para parâmetros de rede?

A constante de rede no plano é fixada na constante de rede relaxada do volume LaAlOJ3J(a =

5,364), Grupo Espacial: Pm3 m3 R c, Número SG: 62, Sistema Cristalino: cúbico/ortorrômbico,

Célula Unitária LaAlO3: α = b = c = 5,364 Å, α = β = γ = 90°, (ou a = 5,369, b = 5,3737, c = 13,029,

α = γ = 90°,β≠90°). Sítio do átomo: La3+=(0,0164, 0,250, 0,6745) + (0,3406, 0,250, 0,4661), Al3+-

=(0,0494, 0,250, 0,1311) + (0,3773, 0,250, 0,0604) + (0,2165, 0,250, 0,8069).

Utilizou-se algum software para refinamento estrutural?

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Baixe Apontamentos de cristalografia e outras Resumos em PDF para Materiais e Sistemas de Construção, somente na Docsity!

Atividade de pesquisa

Aluno: Pedro Liotto A pesquisa que pretendo desenvolver será a durabilidade do concreto convencional com substituição parcial de areia por vidro. Assim sendo, trata-se de materiais amorfos.

Artigo 01

Endereço de consulta https://www.sciencedirect.com/science/article/pii/S0272884222036963? ref=cra_js_challenge&fr=RR- Título EPR, NMR, DFT and XPS study on LaAlO3 phase transition in glass and influence on glass structure and Properties Resumo Thermal treatment induced phase transition of LaAlO3 in glass and its influence on glass structure and dielectric, magnetic, and Faraday rotation properties were characterized through various techniques such as nuclear magnetic resonance, X-ray neutron diffraction, transmission electron microscopy, X-ray photoelectron microscopy, vibrating-sample magnetometer, and electron paramagnetic resonance. Cubic LaAlO3 nanocrystals were synthesized and incorporated into lead-tellurite glasses, after crystallization treatment at 380 ◦C for 2 h, 14-17 nm-cubic LaAlO nanocrystals were changed to 14-27 nm-rhombohedral LaAlO3 perovskite due to the temperature-induced viscosity and strain in the melt. The phase transition of LaAlO3 nanocrystals in glass matrix was verified through versatile techniques in terms of the octahedral AlO distortion, SAED patterns, changes of lattice parameters calculated by Rietveld refinement, and coordination number changes of AlO6 by NMR and XPS techniques. The modification to the glass structure was yielded by phase transition through converting TeO4→TeO3, AlO6→AlO4, BO4→BO3, and producing non-bridging oxygen. In addition, the energy band gap and density of states of glass after phase transition was calculated through Density functional theory (DFT) simulation. Glass doped with 10% LaAlO3 exhibited a promising dielectric constant and good thermal stability due to the phase transition induced polarizability, and improved optical and magnetic performance which is promising for photonics device applications. Qual/quais estruturas cristalinas estão presentes? Inicialmente o LaAIO3 apresenta-se em estrutura cúbica e após tratamento térmico passa a estrutura romboédrico. Quais valores para parâmetros de rede? A constante de rede no plano é fixada na constante de rede relaxada do volume LaAlO 3 (a = 5,364), Grupo Espacial: Pm3 m3 R c, Número SG: 62, Sistema Cristalino: cúbico/ortorrômbico, Célula Unitária LaAlO 3 : α = b = c = 5,364 Å, α = β = γ = 90°, (ou a = 5,369, b = 5,3737, c = 13,029, α = γ = 90°,β≠90°). Sítio do átomo: La3+=(0,0164, 0,250, 0,6745) + (0,3406, 0,250, 0,4661), Al3+- =(0,0494, 0,250, 0,1311) + (0,3773, 0,250, 0,0604) + (0,2165, 0,250, 0,8069). Utilizou-se algum software para refinamento estrutural?

Utilizou-se o software de computador CSTEP que emprega o método de pseudopotencial de onda plana da teoria do funcional da densidade, que pode ser realizada nos cálculos da mecânica quântica de primeiros princípios, incluindo estrutura de banda e densidade de estados (DOS). OBS.: Apesar do trabalho não estar ligado diretamente com a engenharia civil, é interessante verificar como são modelados e apresentados os resultados.

Apontamentos de cristalografia, Resumos de Materiais e Sistemas de Construção

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Artigo 01

Artigo 02

Endereço de consulta

https://www.sciencedirect.com/science/article/pii/S

Título do artigo: Effect of waste glass powder as partial replacement of cement & sand

in concrete - Case Studies in Construction Materials. Volume 19, December 2023,

e02512.

Resumo

The use of waste materials in concrete is now a global trend for effective waste

management in order to create a sustainable, eco-friendly concrete. This has the added

benefits of protecting natural resources by means of producing more sustainable concrete

that has better mechanical properties. This study investigates the characteristics of

concrete that contains waste glass powder (WGP) as partial replacement of cement and

sand. Laboratory tests were performed to determine the compressive strength and split

tensile strength of concrete with 0%, 5%, 10%, 15% and 20% partial replacement of

cement and sand separately by WGP after 7, 28, 60 and 90 days of moist curing.

Microstructural investigations of X-ray diffractometry (XRD) and scanning electron

microscopy (SEM) were performed to determine the effect of WGP on the microstructure

of concrete. Results has shown that compressive strength of concrete can be improved to a

considerable value at 7, 28, 60 and 90 days when WGP is used as partial replacement of

cement by 5%, 10% and 15%, which can be considered as a reasonable amount in

producing sustainable concrete. Further replacement percentages resulted in a decrease in

compressive strength. WGP enhances the microstructure of concrete in the term of

pozzolanic activity and decreasing the microcracks.

Qual/quais estruturas cristalinas estão presentes?

O Vidro trata-se de um material amorfo.

Quais grupos espaciais destas estruturas?

O artigo não apresenta os grupos.

Quais valores para parâmetros de rede?

O artigo não apresenta os valores para parâmetros de rede.

Utilizou-se algum software para refinamento estrutural?

NÃO.