INTRODUCTION TO BIOMATERIALS
LABORATORY REPORT
45S5 BIOGLASS AND Al2O3- ZrO2 CERAMIC PRODUCTION AND
CHARACTERIZATION
Submitted to:
Prof. Dr. Gültekin Göller
Prof. Dr. İpek Akın Karadayı
Prepared by:
Ertuğrul Sakallı 060140327
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1. ABSTRACT
In this paper producing 45S5 Bioglass and Al2O3-ZrO2 ceramic and their properties are
investigated. Bioactive bioglasses is a composition of calcium and phosphate. Weighing,
mixing, calcining, meltin and quenching are the processes to produce it. XRD , DTA , Vickers
Hardness Test , Density and toughnes measurements are done to analyse the properties. Al2O3-
ZrO2 is produced with powder, mixing, drying and sintering. Densification behaviour, phases
and microstructure analyses are done after a sample is taken.
INTRODUCTION
1.1 Glasses and Bioglasses
1.1.1 Glasses
Glasses are materials which are amorphous and don’t show periodic atomic arrangment.
Glasses are produced with melting and quenching processes. These processes prevent the
diffusion to exist a crystalline phase. Their fracture toughness and mechanical properties isn’t
similar with crystalline materials.
1.1.2 Bioglasses and Reaction Kinetics in Human Body
Bioglass which is a biomaterial mostly used in human body as a replacement tissue or organ.
Biomaterals can be defined as natura lor synthetically prepared materials that can heal or take
place of a part of human body. SiO2,Na2O,CaO and P2O5 are the composes of bioglasses.
The first bioglass is used in ossicles in middle are as a treatment of hearing problem.Reaction
stages when 45S5 Bioglass is subjected to human body to repair are below:
1) Leaching and formation of silanols(SiOH)
2) Loss of soluble silica and formation of silanols
3) Polycondensation of silanols to form a hydrated silica gel
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4) Formation of an amorphous calcium phosphate layer
5) Crystallization of a hydroxycarbonate apatite(HCA) layer
6) Adsorption of biological moieties in the SiO2 – HCA layer
7) Action of macrophages
8) Attachment of stem cells
9) Generation of matrix
10) Mineralization of matrix
The first five are seen in outside and inside of living organism.
1.2 Ceramics and Bioceramics
Al2O3-ZrO2 is a biomaterial. Alumina is a bionert material and It is also bioceramic which is
used for repair and replace the diseased and damaged parts of the system. Ceramics are
generally inorganic, inert , hard refractory polycrystalline compounds. They are insulators on
electrically and thermally. The bioceramics which maintain their properties while they’re in
the host is called bioinert bioceramics.They have resistance on wear, have toughness and
generally used as bone plates and screws.
1.2.1 Production of Ceramics and Bioceramics
In order to produce ceramics a powder is heated at high temperatures and high pressure. It is
aimed to provide a diffusion between powders to gather a hard structure. Shaping is not easy
so sintering is used to produce ceramics by fabrication. It allows to particles adhere each other
to create a dense structure. Spark Plasma Sintering, Microwave Sintering and Conventional
Sintering. Sintering Plasma Sintering is used for processing biomaterials generally. Al2O3-
ZrO2 ceramic is produced by this method also knowns as SPS. It uses current to create a high
energy in order to heat powders. This energy causes the diffusuion between
atoms.Temperature is also controlled with this current. Grain size can be arranged by
controlling the temperature. Powders are pressed in graphites with a paper on it. SPS allows
us the produce ceramics in a short time.
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2. MATERIALS AND METHODS
2.1 Production of 45S5 Bioglass
2.1.1 Powder Preparation
The appropriate composes wanted in a 45S5 Bioglass is %45SiO2, %24.5Na2O,
%24.5CaO and %6P2O5. Na2CO3 is used to gather Na2O.
Figure 2.1.1.1) Composition of 45S5 Bioglass
2.1.2 Calcination
Powders are mixed then calcination step is applied in order to gather Na2O. Calcination is done
at 950 C Degree for 2 hours.
Na2CO3 ↔ Na2O + CO2
CO2 is removed after the calcination process.
2.1.3 Melting
The powders that we mixed are taken into a pot which we will heat at 1350 C Degrees for 20
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minutes. Platinum pot is used as the pot in order to reduce the reactivity.
Figure 2.1.3.1) Graphite Crucibles
Figure 2.1.3.2) The furnace that we heat the mixture
2.1.4 Quenching
When the melting process is done we wait for 20 minutes then the melted mixture is poured
into water in a graphite pot in order to quench. Quenching is done in order to gather
amorphous glassy structure. Heat is removed easily and solidification is faster when graphite
pot is used. The pot and the glass is being waited to room temperature then 45S5 is formed.
2.2 Characterization
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2.2.1 XRD Analysis
After quenching the melt of glass into water, tained glassy structure is characterized in terms
of crystallinity and crystallography by applying X-ray diffraction. XRD technique is used in
laboratory research. In XRD technique, we use monochromatic X-ray beams and send them
through material. When the beams interact with the sample, beams are scattered with some
angles and gives peaks in analysis if there is a strong crystal structure. In some orders there
will be sharp peaks separately. In XRD technique we use Bragg’s law to decide if there is any
crstallinity inside the material. [1]
Figure 2.2.1.1) XRD Schematic
Figure 2.2.1.2) XRD Machine
Glass particles was milled to powder and soaked with ethanol to avoid dispersing. Sample
was put into XRD machine with an angle 2*theta(theta=0) = 0 degrees. Machine make the
analysis with a change in angle 2*theta=10 degrees per minute. The whole process end up
within 8 to 10 minutes. After the machine stopped our sample was standing with an angle
theta 40 degrees. The sample is removed and we looked at the XRD data and saw the results
in Figure6.
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Figure 2.2.1.3) Glass powder XRD results
There aren’t any sharp peaks in the graph. That shows the amorphous structure because there
is no arrangment between atoms. Crystallization temperature and glass transition temperature
of the sample should have known in order to get stable structure. This allows us to obtain a
crystalline structure inside a material with heat treatment. DTA should’ve examined in order
to understand this.
2.2.2 DTA Analysis
DTA is used for learning the crystallization temperature and glass transition temperature.
Endothermic or exothermic reaction can be understood by DTA analysis. Sample and
reference put in platinium pots and heated. The information we learned is below at the
graphic.
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Figure 2.2.2.1) DTA results of the powder sample
Heat treatment is applied in order to get crystals inside the sample. XRD Analysis
2.2.3 XRD Analysis of Heat Treated Sample
Results of the second analysis are shown in the Figure8.
Figure 2.2.3.1)Heat treated sample’s XRD results treatment
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Sharp peak is seen which means glass-ceramic structure is obtained. Heat treatment let us
gather crystallized structure.
2.2.4 Density Measurement
We used Archimedes principle in order to measure density. In Archimedes principle, the
density of an object is proportional to the product of its weight in air and inverse of the
difference between the weight in air and the weight in liquid. We used water as liquid in this
measurement because its density is 1g/cm^3 and gives us ease of calculation. Formula of this
calculation is ;
DENSITY = (WEIGHT IN AIR)/(WEIGHT IN AIR – WEIGHT IN LIQUID)
Figure 2.2.4.1) Density measurement machine
2.2.5 Vickers Hardness Test
After the density measurement hardness test is needed. Vickers hardness machine is preferred
for our test. A diamond indenter which is in the form pyramid and have an angel of 136
degrees between faces applies a load between 1 to 100 kgf. This force is applied for 10-15
seconds. After this time is done the calculations are done by investigating the specimen. The
area is calculated and the result is obtained by dividing the kgf load by the square mm area of
indentation. [2]
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Figure 2.2.5.1) Vickers hardness test schematic
Figure 2.2.5.2) Vickers hardness test machine
Figure 2.2.5.3) Formula of Vickers Hardness
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Figure 2.2.5.4) Hardness Image that is taken from the sample
2.2.6 Fracture Toughness Test
Indication of the amount of stress required to propagate a preexisting flaw is fracture
toughness. The flaw occurence is not avoidable so fracture toughness is important. They may
appear as cracks, inclusions, defects. [3] We applied 1000 g and saw some cracks the results
are below.
Figure 2.2.6.1) Fracture mechanism
Figure 2.2.6.2) The crack propagation we see from the sample
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Figure 2.2.6.3) Fracture Toughness formula
Elasticity modulus of the sample is 305 GPa, k constant is 0.016, applied load is 9.8N,
Vickers Hardness is 383 Hv which is 3.756 GPa, and c is 25.7 micrometer . From this values,
the fracture toughness is calculataed as 0.06109 GPa*m^(1/2).
3.1 Production of Al2O3-ZrO2 Ceramic
Dental and orthopedic implants like total hip and knee replacements are generally prefers high
density sintered alumina based ceramics. They are bionert and they have high hardness. Their
fracture is lower than other materials. In our experiment fracture toughness of alumina is
wanted to be improved by adding zirconia. Zirconia is more ductile than alumina. The
powders of alümina and yttria are mixed. Yttria is used for stabilizing zirconia in order to
prevent volume change.( Zirconia can show volume change in high temperature. ) It stabilizes
the cubic phase of zirconia. Powders are milled in ethanol for 1 day and dried. Powders are
put in to a die and covered with graphite. Vacuum enviroment is needed. High current is
passed between electrodes and pressure is applied continously from the beginning. The
sample is heated by the current. After sintering process is ended the sample is made waited to
be cool. The characterization steps are below.
Figure 3.1.1) Spark Plasma Sintering Schematic
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3.2.1 Characterization of Al2O3-ZrO2 Ceramic
3.2.1.1 Density Measurement
Archimedes principle is talked about in this paper. We had a sample which contains 90%
Al2O3 , ZrO2 and TiO2. We used water as liquid in this measurement because its density is
1g/cm^3 and gives us ease of calculation. Formula of this calculation is ;
DENSITY = (WEIGHT IN AIR)/(WEIGHT IN AIR – WEIGHT IN LIQUID)
Our sample’s weight in air was 12.610 g in air and 9.580 g in water so the density is 1.316
g/cm3.
3.2.1.2 Densification Behavior
After the sample was prepared the density of the sample with respect to initial powder
situation is shown in the graphic.
Figure 3.2.1.2.1) Densification Behavior of Al2O3-ZrO2 Ceramic
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3.2.1.3 Scanning Electron Microscopy(SEM) Analysis
Topography of the surface and the phases can be seen in scanning electron microscopy. It uses
a electron gun in a vacuum which throws electrons to the sample. Electrons scatter depending
on the atomic dimensions and phases present. Electrons crashes to the atoms after they gained
speed from magnetic area. In collision electrons scatter back. In elastic collision electrons
scatter back and they called secondary electrons.Back scattered electrons verifies the
information about the phases. Dark image show the lower atomic mass which have light
atomic number. Secondary electrons give the information about topography.[4]
In our experiment, we applied SEM analysis to the sample and image is shown below. A point
is where atomic mass is higher and dark is where atomic mass is lower.
Figure 3.2.1.3.1) Sem image of the sample
3.2.1.4 Fracture Toughness
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Fracture toughness is defined in bioglass production part.
Adding zirconia to alumina increases the fracture toughness of alumina.
3. RESULTS
At first we have verified that the 45S5 powders that is applied some processes on it has
amorphous structure because It doesn’t have any sharp peaks in XRD result. Glass transition
temperature is approximately 600 C degrees and crystallization temperature was like 750 C
degrees at DTA analysis result. Heat treatment is done to gather crystals inside the specimen.
Second XRD result showed us we have succeed the crystallization because we saw sharp
peaks. Glass-ceramic is obtained. Tests are done to see the mechanic properties of the
material. Vickers hardness test is done. Then fracture toughness is done and the calculated
value is 0.06109 GPa*m^(1/2). Spark Plasma Sintering is used to create Al2O3-ZrO2
because we want our material to be dense. Zirconia addition made us densificate easier
according to densification behavior results. Ceramic material is investigated through the SEM.
Zirconia particles are seen in the sample.Fracture toughness is increased by adding zirconia.
4. DISCUSSION
We learned that the mechanical properties of a glassy structure can be improved by applying
heat treatment. Heat treatment causes the crystals occur. This is made in order to reduce
mechanical weakness of the bioglasses. Durability and biocompatability increases with these
processes.
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Mechanical properties of zirconia added alümina is investigated and our effect is seen in the
results. Yttira is used to stabilize zirconia. SPS lets us control these mechanical behaviours of the
ceramics that we gained from powders. Densification behavior is the controlled physical
property. Density is measured in both studies. Heat treatment , SPS , additions can be used to
change mechanical properties of biomaterials which allows us to use them in many fields.
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REFERENCES
[1] X-Ray Diffraction – XRD. (n.d.). Retrieved from http://particle.dk/methods-analytical-
laboratory/xrd-analysis/
[2] Vickers test procedure. (2018, May 24). Retrieved from https://www.emcotest.com/en/the-
world-of-hardness-testing/hardness-know-how/theory-of-hardness-testing/vickers/vickers-test-
procedure/
[3] Fracture Toughness. (n.d.). Retrieved from https://www.nde-
ed.org/EducationResources/CommunityCollege/Materials/Mechanical/FractureToughness.htm
[4] Scanning Electron Microscopy, Energy Dispersive X-Ray Analysis (SEM EDX EDA).
(n.d.). Retrieved from https://www.lucideon.com/testing-characterization/techniques/sem-edx
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