@MastersThesis{Assis:2007:EsCoCo,
author = "Assis, Jo{\~a}o Marcos Kruszynski de",
title = "Estudo comparativo de comp{\'o}sitos alumina-zirc{\^o}nia
tetragonal e de cer{\^a}micas de alumina aditivada com
ni{\'o}bia para aplica{\c{c}}{\~o}es estruturais",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2007",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2007-02-26",
keywords = "{\'o}xidos de alum{\'{\i}}nio, zirc{\^o}nia estabilizada com
{\'{\i}}tria, {\'o}xidos de zirc{\^o}nio, {\'o}xidos de
ni{\'o}bio, propriedades mec{\^a}nicas, space engineering and
technology, alumina, yttria-stabilized zirconia, zirconium oxides,
niobium oxides, mechanical properties.",
abstract = "O objetivo deste trabalho {\'e} estudar os efeitos da
adi{\c{c}}{\~a}o de part{\'{\i}}culas de Zirc{\^o}nia na
estrutura de uma composi{\c{c}}{\~a}o de Alumina Ni{\'o}bia em
estudo pelo Projeto Marimba, assim como analisar a respectiva
influ{\^e}ncia nas propriedades mec{\^a}nicas do material para
que possa ser utilizado em aplica{\c{c}}{\~o}es estruturais.
Foram utilizados quatro tipos de Zirc{\^o}nia: Zirc{\^o}nia
Tetragonal Policristalina (TZP) nanom{\'e}trica e estabilizada
com {\'{\I}}tria; Zirc{\^o}nia monocl{\'{\i}}nica
nanom{\'e}trica; Zirc{\^o}nia monocl{\'{\i}}nica
submicrom{\'e}trica (SC15); e Zirc{\^o}nia monocl{\'{\i}}nica
microm{\'e}trica (SC30). Nas composi{\c{c}}{\~o}es onde foram
utilizadas estruturas monocl{\'{\i}}nicas nanom{\'e}tricas, as
Zirc{\^o}nias foram calcinadas por 3 h na temperatura de 1300 ºC
com 15 % ou 20 % em massa de Ni{\'o}bia para fins de
estabiliza{\c{c}}{\~a}o na fase tetragonal. Estas Zirc{\^o}nias
foram adicionadas em porcentagens diferentes nas cer{\^a}micas de
Alumina e sinterizadas via fase v{\'{\i}}trea, em duas
temperaturas escolhidas: - 1250 ºC: quatro composi{\c{c}}{\~o}es
com adi{\c{c}}{\~a}o de 18 % em massa de Zirc{\^o}nia, sendo
uma com Zirc{\^o}nia TZP e tr{\^e}s com Zirc{\^o}nia
monocl{\'{\i}}nica nanom{\'e}trica; - 1450 ºC: seis
composi{\c{c}}{\~o}es com adi{\c{c}}{\~o}es de 7 e 14 % em
massa de Zirc{\^o}nia, sendo duas com Zirc{\^o}nia TZP, duas com
Zirc{\^o}nia monocl{\'{\i}}nica SC15 e duas com Zirc{\^o}nia
monocl{\'{\i}}nica SC30. Foram feitas an{\'a}lises de
distribui{\c{c}}{\~a}o e tamanho de part{\'{\i}}culas e
microscopia eletr{\^o}nica de varredura das misturas dos
p{\'o}s. As cer{\^a}micas sinterizadas foram caracterizadas
quanto {\`a} massa espec{\'{\i}}fica, retra{\c{c}}{\~a}o
t{\'e}rmica linear, difra{\c{c}}{\~a}o de raios X para
determina{\c{c}}{\~a}o das fases cristalinas presentes,
microscopia eletr{\^o}nica de varredura para estudo da morfologia
das superf{\'{\i}}cies, microdureza superficial, tenacidade
{\`a} fratura, ensaios de flex{\~a}o em quatro pontos e
an{\'a}lise estat{\'{\i}}stica de Weibull. Apesar da
an{\'a}lise das curvas de dilata{\c{c}}{\~a}o t{\'e}rmica
linear apontar para uma sinteriza{\c{c}}{\~a}o em 1250 ºC, os
resultados indicam que esta temperatura n{\~a}o foi adequada,
devido {\`a} alta porosidade das cer{\^a}micas sinterizadas. As
cer{\^a}micas sinterizadas em 1450oC,com adi{\c{c}}{\~a}o de
zirc{\^o}nia monocl{\'{\i}}nica (SC15 e SC30) mostraram uma
diminui{\c{c}}{\~a}o das propriedades mec{\^a}nicas. J{\'a} as
cer{\^a}micas compostas de alumina zirc{\^o}nia TZP apresentaram
uma resist{\^e}ncia mec{\^a}nica compar{\'a}vel {\`a} de
alumina ni{\'o}bia, e embora com valores baixos de tenacidade
{\`a} fratura, apresentou valores altos para o modulo de Weibull
e para a dureza, mostrando um bom potencial para
aplica{\c{c}}{\~a}o como material estrutural em especial
blindagem bal{\'{\i}}stica. ABSTRACT: The main goal of this work
is to study the effects of the Zirconia particles addition on the
structure of a composition of Alumina Niobia that has been studied
at the Marimbas Project in CTA. This study also investigated the
respective influence on the mechanical properties of such material
looking for applications as structural material. Four types of
Zirconia were used: 1-nanometric Tetragonal Zirconia Policristals
(TZP) and stabilized with Yttria; 2- nanometric monoclinic
Zirconia; 3- submicrometric monoclinic Zirconia (SC15); and 4-
micrometric monoclinic Zirconia (SC30). Niobia with 15 % and 20 %
in weight, were used to stabilize this monoclinic Zirconia as a
tetragonal phase. After, they were added in different percentages
to Alumina and sintering with vitreous phase, in two chosen
temperatures: 1250 º C: four compositions with addiction of 18 %
in weight of nanometric Monoclinic Zirconia or TZP Zirconia. 1450
ºC: six compositions with addiction of 7 and 14 % in weight of
Zirconia. Particles size and distribution analysis were performed
on powders and a Scanning Electron Microscopy were applied to
study of the surface and powders morphology. X-rays diffraction
were used to investigate the present phases. To structural
characterization micro hardness, fracture toughness and four point
bend strength were measured. During this investigation
Dilatometric analysis were made on compositions produced with
Nanometric monoclinic zirconia showing that at 1250 ºC the
sintering rate was higher. Even with this high rate sintering the
results indicated that this route and temperature were not enough
to promote a good densification mainly due to the grain growth and
a probable formation of different phases to be studied. The
compositions with monoclinic Zirconia addition (SC15 and SC30)
showed lower mechanical properties. Only Alumina Zirconia TZP
composites sintering at 1450 ºC, has the same flexural strength
when compared to Alumina Ni{\'o}bia and despite its low fracture
toughness, its high Weibull modulus and hardness shows a great
potential to be used as structural material, in special in
ballistic applications.",
committee = "Souza, Jos{\'e} Vitor C{\^a}ndido de (presidente) and Piorino
Neto, Francisco (orientador) and Nono, Maria do Carmo de Andrade
(orientador) and Melo, Francisco Cristov{\~a}o Louren{\c{c}}o de
and Silva, Oliv{\'e}rio Moreira de Macedo",
copyholder = "SID/SCD",
englishtitle = "A comparative study between alumina-tetragonal zirconia composites
and alumina - niobia ceramics for structural applications",
language = "pt",
pages = "113",
ibi = "6qtX3pFwXQZGivnK2Y/Qr67M",
url = "http://urlib.net/ibi/6qtX3pFwXQZGivnK2Y/Qr67M",
targetfile = "publicacao.pdf",
urlaccessdate = "04 maio 2024"
}