M. MEZAHI Fatima zohra

This work is devoted to study the effect of Na2O to obtain quaternary glass 52S4 by sol-gel route. A different amount of Na2O were added (x= 8%, 11%,14 % et 17% ) to 52 % SiO2, (46-x) % CaO and 4 % P2O5 (% mass). A defined quantities of the precursors were used: tetraethyl orthosilicate (Si(OC2H5)4), triethyl phosphate (OP(OC2H5)3), calcium carbonate (CaCO3) and sodium carbonate (Na2CO3). The acetic acid (2N) was chosen as solvent. The obtained dried gels were calcinet at 550°C and 900°C.
Synthesis products were studied using various analytical methods such as TG-DSC, IR and DRX. The obtained results of all products heat treated at 550°C demonstrate that Na2O play an important role to obtain glass. Only the glass 52S4SG_14 was amorphous. The 52S4SG_8 and 52S4SG_11 were partially crystallized. Or, the 52S4SG_17 was totally crystallized. ATG-DTA results showed that the crystallization and decomposition temperatures of the glasses decrease with the increase of the sodium ratio.
XRD for the samples treated at 900°C demonstrated the formation of three phases: combeite (Na2Ca2Si3O9), wollastonite (CaSiO3) and Hydroxyapatite. The main formed phases were combeite and wollastonite with different ratios according to the sodium ratio. Another phase (NaCaPO4) appeared for 52S4SG_Na11.
So, sodium plays a very important role in the glass structure. The addition of sodium oxide causes the break of a Si-O bond and consequently leads to the apparition of non-bonding oxygen which deteriorates the network and, as a result, reduces the crystallization and decomposition temperatures.

The aim of this work is to study the effect of the volume of ethanol on the synthesis of hydroxyapatite by sol-gel route. Hydroxyapatite with the chemical formula (Ca5(PO4)3OH) is one of the important biomaterials because of its chemical structure close to the mineral structure of bone and its important biological properties that enable it to be used in medical application as bone replacement 1,2,3. Hydroxyapatite is very used in clinical field as orthopaedic and dental implants as bioactive (high density) and resorbable (porous HA) materials. The bioactive materials form a direct biochemical bonds with living tissues 4-6.
This work is to study the effect of solvent type for the preparation of hydroxyapatite (ethanol and or distilled water ) by sol-gel, using triethyl phosphate ((PO(OC2H5)3): TEP) and calcium nitrate tetrahydrate (Ca(NO3)2.4H2O) as phosphor and calcium precursors, respectively. A mixture of distilled water and pure ethanol with different volumes were used as solvent with total volume of 40 ml. Each prepared solution was aged in closed Teflon container at a temperature of 90 °C for one day except one sample was aged for two days. The gelling and drying time was 1 day for each process. All dried gels were calcined at 700 °C for one hour. Different analyses were used in order to follow the structural alterations of formed phases with type of solvent, such as: X- ray diffraction (XRD, Infrared spectroscopy, Raman and the dielectric analyses.
X-ray patterns of the prepared samples showed the formation of two phases: HA as a main phase and CaO as second phase for all samples. It was observed that the peak intensity of the CaO increases when the amount of water decreases and the intensity of the HA peaks decreases only for the sample DW5ETH35_1D which was prepared in solvent composed of mixture of 5 ml distilled water and 35 ml ethanol . For this sample, the peak intensity of CaO decreases and the intensity of the HA peaks intensity increases. For the sample aged for 2 days, it was observed the formation of - tricalcium phase as secondary phase.
The FT-IR spectra of HA samples at 700 C confirms the presence of phosphate(PO-34) in all spectra, but there is a difference in the intensity and width of the absorption band, It gets narrower as the amount of water decreases, This is confirmed by the results of the X-ray. Also, the dielectric properties were measured in order to compare between the prepared samples. The obtained results showed that the volume of ethanol affect the ratio of HA in the prepared powders.

The aim of this work is to study the effect of magnesium on the physic-chemical properties of hydroxyapatite prepared by sol-gel route. Magnesium Nitrate Hexahydrate, Calcium Nitrate tetrahydrate, and triethyl phosphate (TEP) were used as precursors for Mg, Ca, and P, respectively. Noted that the molar ratio (Ca +Mg)/P was kept constant at 1.67 when the magnesium was added (0 to 10 % (mol)) to the prepared solutions. Based on the our previous results, all solutions were aged at 70°C for 24 h, the distilled water was used as medium solvent. The same conditions were used for gelling and drying of the aged solutions. All dried gels were calcined at 700°C for 1 h and heat treated at 1100, 1200 and 1300°C for 4 h in order to study the effect of magnesium on the crystallization of doped hydroxyapatite (Ca10-xMgx (PO4)6(OH)2, crystal lattice parameters, thermal stability and morphological of hydroxyapatite. The XRD and FTIR results showed that the hydroxyapatite is the major formed phase at all temperatures without any decomposition to the tricalcium phosphate. The CaO was present as secondary phase at 700°C. But the intensity of this phase decreased with temperature. Also, a minor ratio of MgO was present in samples doped by 5% and 10% MgO. The lattice parameters of doped hydroxyapatite decreased in comparison to pure hydroxyapatite because the ion radius of magnesium is lower than that of calcium. The results of analysis of distribution size confirmed the formation of agglomerates as results of the assemblage of small grains as confirmed by SEM images. The obtained results confirmed the incorporation of the magnesium in the lattice structure of HA.

for 2 h. Moreover, the in vitro bioactivity of β-Ca2SiO4 was investigated by soaking the powders in a simulated body fluid
(SBF) for various time periods to analyse the growth of hydroxyapatite (HA) on the surface of these powders. The synthesised
powders were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared
(FTIR), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis. The simulated body fluid
results showed that the β-Ca2SiO4 powders had good bioactivity to induce hydroxyapatite formation on their surface.
The results obtained showed that (HCA) can be formed on the surface of β-Ca2SiO4 soaked in the SBF solution for 1 day,
and a continuous layer of dense HCA deposits covered the surface of β-Ca2SiO4 powders after 3 days of soaking in the SBF
solution. Finally, the results obtained suggest that β-Ca2SiO4 ceramics are promising candidates for bone regeneration.

Hydroxyapatite (HA) is a biocompatible and bioactive material used as bone-substitute materials in both orthopedics and dentistry. This work is devoted to study the synthesis of hydroxyapatite (HA) by sol-gel route using triethyl phosphate (TEP) and calcium nitrate tetrahydrate as calcium and phosphor precursors. In order to optimize the hydrolysis of TEP, each prepared solution was aged in closed Teflon® container. Several factors were tested in order to improve the synthesis conditions of well crystallized HA. The effect of aging time (4 h, 16 h and 24 h) was tested. All dried gels were calcined at 700°C for 1 h. The obtained results showed that the crystallinity degree of hydroxyapatite increases with aging time. It was remarked that HA peaks are dominant peaks and their intensities increase in contrast to that of CaO peaks with aging time. In addition, the width of the peaks becomes narrower. So, these results are a sign of an increase in the crystallinity degree and the crystallite size with aging time.

Cordierite (Mg2Al4Si5O18) formation via sol-gel route using Tetraethyl orthosilicate TEOS, Aluminum nitrate nonahydrate Al(NO3)3.9H2O, and Magnesium nitrate hexahydrate Mg(NO3)2.6H2O as starting materials was studied by means of high-temperature by heating from room temperature up to 1350 °C. Differential thermal analysis (DTA) technique, under non-isothermal conditions is the appropriate for studying high-temperature reaction kinetics. The activation energies and kinetics parameters of cordierite formation measured by both isothermal (Johnson–Mehl–Avrami (JMA) theory using Ligero method) and non-isothermal (Ozawa, Boswell and Kissinger methods) treatments. The growth morphology parameters n (Avrami parameter which indicates the crystallization mode) and m (a numerical factor which depends on the dimensionality of crystal growth) were also determined. Powders obtained were characterized using high temperature x-ray powder diffraction (XRD), and Scanning electron microscopy (SEM). Finally, the thermodynamic parameters (ΔG#, ΔH# and ΔS#) for cordierite crystals were determined.

Hydroxyapatite (HA: Ca10(PO4)6(OH)2) is one of the most attractive materials for human hard tissue implants because of its close physical and chemical properties to mineral part of bone and teeth1. Several works have been carried out on structural modifications and mechanical properties of HA in the presence of oxides or metallic dispersions used as reinforcing agents2–4.

So, this work is devoted study the thermal stability of pure hydroxyapatite and doped hydroxyapatite (HA + 5% wt. diopside, HA + 5% wt. doloma and HA + 5% wt. silica) when they heated at 1300°C.
The results show that the trace elements have a great influence on the density and the thermal stability of hydroxyapatite.

The density of pure treated hydroxyapatite was near to theoretical density. A weak change was occurred in density value when the doloma was added. Or, the addition of silica and diopside has a remarkable effect on the density of hydroxyapatite. The densities of treated samples were decreased.

After heat treatment at 1300°C, the XRD results show that the composition of pure hydroxyapatite has not changed. However, the addition of the doloma led to the partial decomposition of HA into -tricalcium phosphate (-TCP) as minor phase. While the addition of the diopside and silica leads to the formation of silicate hydroxyapatite "the silicocarnotite" as major phase. The FTIR results confirmed the XRD results. The IR characteristic bands of (-TCP) and the silicocarnotite were well distingued.

This work is devoted to study the reactivity of a quaternary glass: 52% SiO2, 30% CaO, 14% Na2O and 4% P2O5 (wt %) (named 52S4F), synthesized by the melting route. The physicochemical properties of 52S4F glasses were determined before and after immersion in simulated body fluid (SBF). The obtained results by various analysis methods, such as ICP, IR, SEM-EDS and solid state NMR, have shown that different structural modifications at the glass surface as a function of immersion time were occurred. The silica gel (SiO2) and the calcium phosphate layer (HA) were formed at the glass surfaces after the immersion in SBF. The crystallite size of HA layer is in the order of nano (as shown by SEM). NMR analysis highlights the different structural’s alterations during immersion in SBF. It shows that, after 1 day immersion time, the silica gel is formed and it has grown until 15 days. In addition, it demonstrates that after 5 days the precipitation process becomes more dominant than the dissolution process of the glass, which confirms the results of the other used methods. Finally, according to the obtained results, the quaternary glass 52S4F is a bioactive glass.

Hydroxyapatite (HA) Ca10 (PO4)6 (OH)2 is a very important inorganic material; first mineral constituent of bones, tooth enamel and dentin. It is very flexible in terms of composition and morphology.
HA is known as a non-resorbable and surface-active bioceramic and is mainly used for many medical applications thanks to its biocompatibility and bioactivity.
The aim of this work is devoted to study of the effect of the sodium addition (Na) with different molar ratio (0, 1, 5, 10, 15 and 20%) on the synthesis of hydroxyapatite by the sol-gel route.
From the obtained results, it was possible to obtain well crystallized hydroxyapatite at 700 ° C; synthesized from the precursors: the calcium nitrate and tri-ethyl phosphate. Sodium nitrates were used as a source of Na. The synthesis was carried out for 3 days; one day for aging the prepared solutions; one day to obtain a gel, one day to dry the gel.
The obtained results showed that the addition of sodium stabilize the hydroxyapatite synthesized by the sol-gel route. As ratio of Na increases, the intensity of the XR peaks of HA increases and that of CaO decreases. Thus, DRX has shown the apparition of a new phase (-CaNaPO4) at 1000 ° C and 1300 ° C for the large concentrations of Na (15 % and 20 %).

This work is devoted to study the reactivity of the quaternary glass 52S4 (52% SiO2–30% CaO–14% Na2O–4% P2O5 (wt%)),
synthesized by sol-gel process versus the treatment temperature. The dried gel was heat treated at 600 and 650 °C and soaked in
simulated body fluid (SBF). XRD results confirm the amorphous character of glass treated at 600 °C even though the heat
treatment at 650 °C induces Na2Ca2Si3O9 formation. After soaking in SBF, SEM and EDS results show the formation of
carbonated hydroxyapatite (CHA) at the glass surface for both temperatures. For the glasses treated at 600 and 650 °C, two
phenomena were observed: the glass dissolution in SBF and the CHA precipitation, but the reactivity kinetics of glass was
different when temperature changes. For SGDG600, the CHA began to crystallize after 16 h. For SGDG650, a glass ceramic
made of a glassy matrix and of Na2Ca2Si3O9, the crystallized carbonated HA was observed after 2 h. In addition, a new
crystallization at the glass surface of Na2Ca2Si3O9 was observed after 15 days.

Good quality ceramics costs a lot that has limited their use in developing countries. This work was devoted to prepare low-cost and good quality anorthite based ceramics. The proposed composition was 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide (CaO). The choice of these raw materials was dictated by their natural abundance coupled with a modified milling system, as another interesting advantage. Previous studies have shown that a simple vibratory multidirectional milling system using bimodal distribution of highly resistant ceramic milling elements has been successfully applied for obtaining fine powders. The influence of the relatively lower sintering temperature, ranging from 800 to 1100 °C, on the porosity and the average pore size (APS) have been investigated. The APS and the porosity values of samples sintered at 950 °C were about 1 μm and 4%, respectively. The best Vickers microhardness and 3-point bending strength values for these sintered samples, using this proposed milling system, were 7.1 GPa and 203 MPa, respectively. Finally, the crystalline phase evolution during heat treatment was investigated by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques.

In the current study, the effect of P2O5 on the mechanical properties of porous natural
hydroxyapatite (NHA) derived from cortical bovine bones sintered at 1,050°C is assessed.
Hydroxyapatite (HA: Ca10(PO4)6(OH)2) was synthesized using several methods and manufactured
from natural materials such as coral or bone after removal of the organic matter by
heating (noted NHA). The in vitro and in vivo studies showed that the natural apatite was
well tolerated and has better osteoconductive properties than synthetic HA. Consequently,
the NHA was manufactured from cortical bovine bone in all our studies. Nevertheless, its
poor mechanical properties are one of the most serious obstacles for wider applications. So,
P2O5 was added into NHA in order to enhance its initially poor mechanical strength. A
careful combination between the main parameters controlling NHA elaboration such as
milling techniques, compacting pressure, sintering temperature, and holding time may lead
to an interesting NHA-based bioceramics. In this way, a vibratory multidirectional milling
system using bimodal distribution of highly resistant ceramics has been used for obtaining
submicron-sized NHA powders. To enhance the densification and lower the sintering temperature
of porous NHA, different percentages of P2O5 (0.5–5.0 wt%) were added into NHA
powders. The porosity ratio ranged between 36 and 41%. Using this modified milling
system, the best Vickers micro-hardness and the three-point bending strength values of
powders sintered at 1,050°C were 1 GPa and about 46 MPa, respectively. The latter value is
significantly higher than that reported by other researchers (35 MPa) using the sol–gel
method.

Hydroxyapatite (HA: Ca10(PO4)6(OH)2) can be synthesized using several methods or manufactured from
natural materials such as coral or bone after removal of the organic matter by heating (denoted as NHA). The
in vitro and in vivo studies showed that the natural apatite was well tolerated and has better osteoconductive
properties than synthetic HA. In addition, the exploitation of natural source represents an economical way of
synthesizing NHA by means of sintering, rather than by sol-gel techniques. For these reasons, the NHA was
manufactured from cortical bovine bones in all our studies. Moreover, there has been much eort to improve the
mechanical properties of HA by introducing foreign oxides or nding out other alternative processes such as grain
growth control. Indeed, encouraging lower AGS instead of exaggerated grain growth may be jugged useful for many
applications. Since the works carried out on the correlation between AGS and physico-chemical properties of NHA
were very limited, the present study was mainly focused on its grain growth. A carful combination between the main
parameters controlling NHA production such as milling techniques, compacting pressure, sintering temperature
and holding time may lead to an interesting NHA based bio-ceramics. In this way, a simple and energetically
vibratory multidirectional milling system using bimodal distribution of highly resistant ceramics has been used for
obtaining sub-micron sized NHA powders. For example, the AGS was ranged between 0.75 and 1.40 m (using
intercept method) when NHA samples were sintered at 1250 C for 15 and 480 min, respectively.

This work devoted to study the reactivity of the quaternary glass (52S4) versus the treatment temperature. The glass composition is: 52 % SiO2 -30 % CaO - Na2O - 14% 4 % P2O5 (wt%), it was synthesized by the sol-gel process. The dried gel was treated at 550 °C and 600 °C and soaked in Simulated Body Fluid (SBF) during different times (from 2 h to 30 days). XRD results confirm the amorphous aspect of treated glass. After soaking in SBF, SEM images show the formation of the carbonated hydroxyapatite (CHA) at the surface of soaked glass for both temperatures. While, the ICP results show that reactivity kinetic of glass in SBF are different when the treatment temperature changes from 550 °C to 600 °C. For glass treated at 550 °C, it only observed the migration of Ca and P from the SBF to the glass surface to form CHA after 2 h soaking in SBF. The XRD and IR results show that the new amorphous CHA phase is formed even after 30 days. As for the glass treated at 600 °C, two phenomena are observed: the glass dissolution in SBF and precipitation of CHA. This phase is amorphous at beginning and crystallizes only at 3 days. This means that the process of dissolution glass is more accelerated than the precipitation process. As the temperature increases, the surface area decreases and consequently the precipitation process slows which allows us to observe the dissolution phenomenon for glasses treated at 600 °C.

A new composition of bioactive glass, in the quaternary system SiO2–CaO–Na2O–P2O5, was synthesized using
melting and sol–gel routes. The prepared glass, 52S4: (wt.%) 52% SiO2–30% CaO–14% Na2O–4% P2O5, was
soaked in Simulated Body Fluid (SBF) in order to evaluate the kinetic reactivity of this glass versus the
synthesis mode. The obtained results have shown that 52S4 is a bioactive glass if it is prepared either by melting
or sol–gel methods. The bone-like apatite was formed at the glass surface prepared by sol–gel route after
2 h. However, the formation of this apatite was delayed to 1 day when the glass was prepared by melting
method. In addition, this apatite was crystallized, after 30 days soaking in SBF, only if the glass is prepared
by melting route. The glass prepared by sol–gel method was more resorbable and leads to silica gel formation
up on amorphous apatite layers at any time. So, this silica gel inhibited the crystallization of amorphous
apatite.

In this study, the ability to form bone‐like apatite on surface of both pure natural hydroxapatite (N‐HA) and natural hydroxyapatite containing 5 wt% of ZrO2 or TiO2 or Al2O3, sintered at 1300°C for 2 h and soaked in the simulated body fluid for different times, was studied. It has been found that the presence of β‐tricalcium phosphate in N‐HA + 5 wt% ZrO2 or TiO2 has promoted the precipitation of bone‐like apatite in the Zr or Ti poorest regions. By contrast, the presence of 5 wt% of Al2O3 did not induce any apatite precipitation on N‐HA sample surfaces.

The behaviour of the natural Hydroxyapatite (N-HA) prepared from bovine bones and synthetic hydroxyapatite (S-HA) was studied. The sintering effects on the structure and on the kinetic of bioactivity of natural and synthetic hydroxyapatite were highlighted. Obtained results show some differences between these biomaterials. XRD patterns showed that the crystallographic structure of pure N-HA was not affected by the sitering at different temperatures when several modifications in S-HA were registered. To evaluate their kinetic of bioactivity, ICP-OES method was employed. The experimental results show that the kinetic of bioactivity of N-HA increases with the sintering temperature. Consequently, the new phosphate phase was formed with higher thick on the surface of granules sintered at high temperatures. However, in S-HA, the formation of bone like apatite is very sensitive to phase’s existent at any sintering temperature. The formation of TCP has favourites and activates the formation of new phase

New sol–gel experimental conditions were tested to prepare a new SiO2-based bioactive glass with high Na2O content. The aim of this work is to investigate the real influence of the synthesis route (sol–gel versus melting) on the glass intrinsic properties and then, later, on the glass behavior and particularly on bioactivity. The obtained glass and its melt derived counterpart were characterized from structural and morphological (porosity, specific surface area) point of view. It could be noticed that the synthesis mode has no significant influence on glass structure. Conversely, the synthesis mode greatly influences the glass texture. The sol–gel derived glass exhibits a greatly higher specific surface area and pore volume than melt derived glass. This parameter may be a key factor of glass bioactivity.

In this study, hydoxyapatite (HA) prepared
from calcined bovine bone was studied. Two methods were
used for HA sintering: conventional sintering (CS) and
microwave sintering (MS). HA was obtained by calcination
of bovine bone at 800 C for 4 h followed by wet ball
milling. Afterwards, the powder was compacted under 75
MPa and sintered for 2 h at different temperatures, from
1050 to 1200 C. It has been found that the bulk density of
HA increases by increasing sintering temperature when
both CS and MS were used. Nevertheless, at the same
temperature and for a shorter time (15 min), the HA sintered
by microwave were characterised by a density relatively
higher than that of sintered by conventional furnace.
For example, at 1100 C the bulk densities of samples
using CS and MS were about 2.49 (for 120 min) and 2.93
(for 15 min) g/cm3, respectively. Furthermore, a near theoretical
density (98.6%) was obtained when HA samples
were sintered at 1200 C for 15 min only but using the
proposed MS, which was much higher than that (89.7%) of
HA samples sintered at the same temperature for longer
holding time (120 min). Besides this, the X-ray analyses
have shown that heat-treatment, using these two processes,
has lead to HA decomposition into tricalcium phosphate
and/or tetracalcium phosphate.

he dissolution kinetic and structural behaviour of natural hydroxyapatite (N-HA) and synthetic Hydroxyapatite (S-HA) was studied versus sintering temperature and using “in vitro” experiments. Obtained results highlight the chemical stability of N-HA. Any structural modification was observed until 1200°C. In the fact S-HA undergo some modifications. XRD diagrams show the tricalcium phosphate (TCP) phase formation between 800 and 1100°C and tetracalcium phosphate (TetCP) phase formation at 1200°C. The “in vitro” assay show that the dissolution was occurred more in N-HA than in S-HA. The formed TCP activated the dissolution kinetic and then the precipitation phenomena. However, the dissolution of TetCP leaded to delay the kinetic precipitation.

Bioactive ceramics such as bioactive glasses, calcium carbonate and sintered hydroxyapatite are widely used in biomaterials field because of their high biocompatibility. In this study, natural hydroxyapatite (N-HA) and synthetic Hydroxyapatite (S-HA) were heat treated at 800 C and studied using “in vitro” experiments. Several physicochemical methods like: SRD, FTIR, SEM and ICP-OES were employed to evaluate the effects of the thermal treatment and to compare their behaviour after soaking in the Simulated Body Fluid SBF at different times. The formation of TCP has favours the formation of new phase. Obtained results show that the dissolution occurred more in N-HA than in S-HA and consequently the precipitation of new phosphate phase is more important in N-HA. This is due to the presence of Mg, Sr and Zn in N-HA with concentration higher to that in S-HA.

The dissolution kinetic and structural behaviour of natural hydroxyapatite (N-HA) and synthetic hydroxyapatite (S-HA) was studied vs. sintering temperature and using ‘in vitro’ experiments. Obtained results highlight the chemical stability of N-HA. Any structural modification was observed until 1200°C. In the fact S-HA undergoes some modifications. XRD diagrams show the tricalcium phosphate (TCP) phase formation between 800 and 1100°C and tetracalcium phosphate (TetCP) phase formation at 1200°C. The ‘in vitro’ assay shows that the dissolution was occurred more in N-HA than in S-HA. The formed TCP activated the dissolution kinetic and then the precipitation phenomena when a continuous dissolution of TetCP leaded to slow down the kinetic precipitation.

A new glass formulation, with themolar composition 60% SiO2–35% CaO–5% P2O5,was synthesized using
the sol–gel process, for applications as biomaterial in orthopaedic or maxillo facial surgery. Pellets, made
of glass powder, were uniaxially compacted and soaked in simulated body fluid (SBF) for up to 7 days at
37 8C to evaluate glass bioactivity. Ionic exchanges at the interface glass-SBF were evaluated by studying
evolutions of calcium, phosphorus and silicon concentrations in SBF using ICP-OES. Changes in glass
surface, and the formation of crystalline phases were analyzed using XRD, SEM, EDS and FTIR methods.
Results form ICP-OES showed a high reactivity of the glass surface with a very high and continuous
release of calcium, a limited glass dissolution and an uptake of phosphorous from SBF. Results from both
FTIR and XRD analysis indicated that the glass surface was progressively covered by two different phases:
CaCO3 as calcite and a carbonated apatite layer. The formation of these phases, following two different
schemas, was observed after 2 h of immersion and confirmed after 7 days. SEM micrographs and EDS
analysis demonstrated that the main phase, a carbonated apatite, was present as micro-spheroids and the
secondary phase, calcite, was materialized by agglomerates which have diameters up to 10–15 mm.
These results are in accordance with a bioactive feature of the glass studied.

Hydroxyapatite (HAp: Ca5(PO4)3OH), has been studied for many years as an implant material because it is similar to the major constituents (mineral parts) of bone and tooth. Generally, there are two main ways of producing HAp, one is inorganic synthesis and the other is from natural bone. In this study, HAp powder was obtained by calcination of bovine bone at 800°C for 4 hours followed by ball milling. Afterwards, the powder was compacted at 75 MPa. The compacts were prepared, using both Conventionally Sintering (CS) and Micro-Wave Sintering (MS). It has been found that the relative density of samples sintered at 1250°C for 2 hours was about 92.5% which is much lower than that of samples (95.9%) sintered at the same temperature for shorter times (15 minutes), using MS.

In this work, the hydroxyapatite was prepared from cortical bone after calcination at
700°C during 1 hour. In order to improve mechanical properties of HA, 5 wt% of the ZrO2
(stabilized with 12.0 wt% CeO2), Al2O3 and TiO2 were added to HA powder as a reinforcing phase.
All the powders were sintered at 1300°C for 2 hours. The XRD was utilized to identify the phases
composition. It was found that the initial calcined powder is hydroxyapatite with the following
chemical composition Ca5(PO4)3OH. In addition, the phenolphthalein test has put into evidence the
existence of free CaO. For powders containing ZrO2, the XRD spectra has showed a little percent of
formed b-tricalcium phosphate (b-TCP); the HA was decomposed to (b-TCP) and CaO which
forms with ZrO2 the calcium zirconate (CaZrO3). Nevertheless, in powders containing TiO2, the
XRD spectra showed that a partial decomposition of HA to b-TCP was occurred with formation of
calcium titanium oxide (CaTiO3). However, for powders containing Al2O3, a nearly full
decomposition of HA to b-TCP was occurred, the free Al2O3 was present. Finally, it has been found
that HA composites containing a large amount of b-tricalcium phosphate are resorbale than HA
composites containing a small amount of b-TCP and they were not well densified. The
microhardness values of HA- ZrO2 composites were greater than those of HA- Al2O3 and HATiO2
composites.

Diopside CaMgSi2O6 is an attractive material because of its multi applications. It was
prepared by sintering the mixture at different temperatures (900°C-1300°C). Starting materials were
pure SiO2 and dolomite raw materials. In order to improve the properties of sintered samples, such
as the density egg white (ovalbemin) has been added into diopside.
Furthermore, the effect of P2O5 addition on the sintering of the prepared diopside in the range of 0.5
to 5.0 wt% was studied as a function of the sintering temperature. A density of 96.5% of theoretical
has been achieved when 5.0 wt% P2O5 was added, at a sintering temperature of 1225°C, whereas
the density of diopside samples, without P2O5 addition was lower than 83.0% of theoretical.

In this study, hydroxyapatite (HA) was prepared from cortical bone after calcination at
700°C for 1 hour. In order to improve mechanical properties of HA, the ZrO2 (stabilised with 12.0
wt% CeO2 ) was added to HA powder as a reinforcing phase in varying proportions (1, 5, 10 and 20
wt%). All the powders were sintered at 1300°C for 2 hours. The XRD was used to identify the
existing crystalline phases. It has been found that the initial calcined powder has the following
chemical composition Ca5(PO4)3OH. In addition, the phenolphthalein test has put into evidence the
existence of free CaO. The prepared specimens without and with ZrO2 additions (1and 5 wt%) were
highly densified. The main phase present in samples containing 1 wt% ZrO2 is HA. Nevertheless,
for powders containing 5, 10 and 20 wt% ZrO2, the HA was decomposed into b-tricalcium
phosphate and CaO which forms with ZrO2 calcium zirconate (CaZrO3).