Vol. 2, No. 4,
Outubro-Dezembro de 2012
ORIGINAL ARTICLE
MECHANICS CHARACTERIZATION OF INTELLIGENT GLASS
CERAMIC OF ANORTITA WITH APPROACH OF THE RESULTS
FOR BIOENGINEERING APPLICATION
Etney
Neves1,2, C. A. Fortulan 3, B. de M. Purquerio3
1
Professor Visitante do Departamento de Engenharia de Alimentos, UNEMAT.- Universidade do Estado
de Mato Grosso, Campus Barra do Bugres - MT.
2
Pesquisador Associado a Associação Nacional Instituto Hestia de Ciência e Tecnologia, HESTIA.Brasil.
3
LTC - Laboratório de Tribologia e Compósitos/Depto de Eng. Mecânica – EESC-USP
[email protected]
Abstract
The general properties of an anorthite glass ceramic are being studied. Initially the
anorthite is being suggested for application as biomaterial. The samples for tests are
conformed from glass processing. The anorthite crystals are subsequently obtained of a
controlled crystallization of the glass. Initial results describe the anorthite as an
intelligent material. This glass ceramic was tested in vitro and in vivo (implanted in
rabbits). The results of these researches describe a biocompatible material. Mechanical
tests were suggested and are being conducted in an attempt to enlarge the field of
knowledge and consequently, the application of glass ceramic. Preliminary results were
positive. The arithmetic average of mechanical bending resistance testing (three points)
was of 124 N/mm2. The discussion of the results will be drive to the field of
bioengineering, considering the experimental data of resistance to compression,
hardness and wear.
Keywords: Intelligent glass ceramic; anorthite; bioengineering.
1. Introduction
Biomateriais are used in medicine in order to interact with biological systems.
Recently, research showed that anorthite is a good example of these materials. 1,2,3,4
Samples of anorthite obtained by controlled crystallization of glass were studied
(sample "A"). Initial results showed biocompatibility. 2,5 Biocompatibility represents the
absence of rejection with interaction between the implant and the adjacent tissue. 6
The study aims to evaluate the mechanical performance of glass ceramics. The
composition is a non-stoichiometric point of anortita region. The first mechanical tests

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Vol. 2, No. 4, Outubro - Dezembro 2012, Página 18
were performed in a study with main focus on developing the anorthite structure from
glass.7 In this new work unprecedented mechanical tests were conducted. A discussion
on the results of mechanical compression, abrasive wear and microhardness were
carried out with focus to applications in bioengineering.
2. Materials and Methods
Bodies test of anorthite were obtained following the same footsteps of previous
studies.4,7 Three types of samples of the material were prepared: A1, A2 and A3, Figure
1. The material characterized in previous studies received the designation of A0 sample.
The sample A1 was developed with raw materials of high purity. The A2 sample was
obtained from commercial raw materials. In the sample A3 an alternative raw material
(coal ash) was used. The lot of ash has been well characterized. The quantity bulk of the
oxides in the mixture were strictly controlled.
Figure 1. Part of the ternary diagram SiO2-Al2O3-CaO, anorthite region
detach the theoretical point of the chemical composition of samples "A".
The mechanical strength was evaluated by bending tests on 3 points, using a
machine testing Emic DL 10000. By definition, the break module is the maximum force
that can be applied in a body to the fracture. For a rectangular body, can be calculated
using equation I:
(I)
Module of Rupture = MOR = 3Fl_
2bh2
Where F is the force applied (kp); b is the width of the test body; h is the height of the
test body (cm) and l the distance between the two points of support (cm).
Tests of wear used the method of pin-on-disk .9 The disc was produced in Al2O3
(96%). The roughness of the disc was measured (Ra = 0.3 m). The heads of the pins
were produced in the format of half sphere with a diameter of 5 mm. Flat samples were
prepared for the microhardness test. The finishing of the areas followed a pattern
mirrored.
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3. Results and Discussions
The brittle fracture has some characteristics formations near the origin of
fracture .8 The main are: the mirror of the fracture, the region mist and hackle. These
formations can, sometimes, not being visible or not even exist. In the specific case of
bodies test "A3", the fracture showed exactly the described in literature, Figure 2. When
a crack starts in an internal defect, is spread radially on the same plane, while
accelerates. The surface is flat and smooth, being called the region speculate or mirror
of fracture. This crack, reaching the critical speed to their spread, up to the interception
of one inclusion, or finding a change in direction of the main area of the tension, begins
to gently deviate the original plan, forming small ridges on the surface of the radial
fracture. The first ridges are very weak, almost indistinguishable, being called mist
region. The mist region is commonly seen in areas of fractures of glass, however, may
not be visible in crystalline ceramics and polycrystalline metals. The transition to
crystals is called hackle. The regions of transition between hackle and ramifications of
macroscopic cracks, as the remainder of the surface of the fracture, are usually in a plan
perceptibly different of the fracture mirror and hackle. The speculate region is
approximately circular and the origin of fracture is at its center. Note also that lines
drawn alongside the hackle, would be cut at the origin of the fracture or very close to
this.
Table 1 - Average bending in three points of test bodies of intelligent glass ceramic (anorthite).
A0 (Literature)
124 N/mm2
Teste A2
202 N/mm2
Teste A3
180 N/mm2
The results of bending resistance with the test bodies A2 and A3 were compared
with the previous study A0, Table 1. Increased resistance to fracture of A2 and A3,
regarding A0, is attributed to the progress in control of processing the material.
Biocompatible materials with the resistance observed in this study could be used, for
example, to detention of fractures of the upper limbs.
Figure 2. Main fracture region of a body test of glass ceramic
A3 showing the characteristics of the fracture surface of
fragile materials in the environs of the origin of the fracture
started on the surface.
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The abrasive wear of the samples followed the order A1> A2> A3. The best
performance of the samples A3 and A2 can be the basis of the presence of other
elements in the composition. This can be seen by comparing the performance of the
samples in a distance of 500 m, Figure 3. The sample A3 has more than 10% of other
elements in the structure. The other extreme is the sample A1 with the amount of other
elements <1%. One possible consequence of this difference was the bodies test A1 have
been severely worn in the first 500 m, ending the test. Glass ceramic intelligent, with
crystalline structure formed mainly by anorthite, is suggested for special cases involving
the mechanical strength with the controlled dissolution of the material implanted.2 The
first results of this study encourage a search for medical conditions that require
components for temporary implants, requiring the characteristic of resistance to abrasive
wear.
Figure 3. Abrasive wear of glass ceramic samples "A" indicating
a reduction in the height of the body test depending on the
distance traveled.
Tests of microhardness, Figure 4, indirectly indicate that the K IC (toughness
fracture) of the sample A1 is smaller than that of samples A2 and A3. This is based on
linking the applied load test with the observation of the spread of crack from the area of
printing in the sample. Compared the loads of 4.9 N, the materials "A" show HV
hardness of 3 times lower that alumina and 1.9 times lower than hardness HV of a
zirconium.10, 11
Figure 4. Measures of Vickers microhardness of glass ceramic samples
"A" indicating the hardness depending on the loads applied.
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4. Conclusions
The controlled crystallization of glasses represents in this work an important
way of process to obtain the samples of ceramic glass anorthite. According indicated in
the literature, it can also represent the way for construction of a new biocomponent.
The results suggest that changes in raw material can significantly increase the
fracture toughness, resistance to wear and mechanical strength of the material. In the
ash formulating there was an increase of up to 50% in mechanical resistance to bending,
wear soft scheme without the verification of fracture of the body and more forcefully
over the pure raw material that the test of attrition was broken leading to the spread of
severe wear and spread of crack in the trial of micro-hardness. The feeling of the
authors indicates that it is possible to raise the performance of ceramic glass through
new studies of the structure of the material and advances in control of processes.
5. Bibliographic References
[1] NEVES, E., et all. Anorthite Glass Ceramic to Biomaterial, 3rd International
Symposium on non-crystalline solids and the 7th Brazilian Symposium on glass
and related materials, Maringá, PR (Brazil) 2005.
[2] CAVALHEIRO, L. Estudo da Biocompatibilidade e Tempo de Degradação do
Vitrocerâmico Anortita, Mestrado, PUCPR, (Brazil) 2005.
[3] FERNANDES, B. L and NEVES, E. In Vitro Degradation Analysis of Intelligent
Glass Ceramic, III Congresso Latino-Americano de Engenharia Biomédica, João
Pessoa, PB (Brazil) 2004.
[4] NEVES, E. and SPILLER, A. L. Intelligent Glass Ceramic Materials, Glass
Odissey – 6th European Congress on Glass, Montpellier, France, June 2002
[5] REAÇÃO CITOTÓXICA NÃO DETECTADA. Laudo Tecnológico 05008607,
Laboratório de Microbiologia e Toxicologia, Instituto de Tecnologia do Paraná
(Brazil) 2005.
[6] HENCH, L. L; ETHRIDGE, E. C. Biomaterials: an interfacial approach. United
States, Academic Press, 1982.
[7] NEVES, E. Obtenção de Vitrocerâmicos a partir de Cinza Pesada de Carvão
Mineral, UFSC, Tese (Brazil) 2002.
[8] RICHERSON, D. W. Modern Ceramic Engineering: Properties, Processing,
and Use in Design. Marcel Dekker, Second Edition, Revised and Expanded. New
York, 1992.
[9] FORTULAN, C. A. Desempenho das Cerâmicas Estruturais Associado aos
Métodos de Conformação por Injeção, Prensagem Isostática e Projetos de
Equipamentos e Moldes, USP, Tese (Brazil) 1997.
[10] GARCIA, A. et all. Ensaios dos Materiais, Editora LTC, Rio de Janeiro (Brazil)
2000.
[11] AVILLA FILHO, S. G. A. Caracterização Mecânica de Vitrocerâmico
Inteligente para Aplicações Médicas, Monografia, Engenharia Mecânica,
PUCPR (Brazil) 2004.
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