09 Teknik Biomaterials

7/31/2019 09 Teknik Biomaterials

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PEMBUATAN

BIOCERAMICS MATERIAL

(part 1)

JURUSAN TEKNIK MESIN DAN INDUSTRIUNIVERSITAS GADJAH MADA

2011

Muhammad K. Herliansyah, ST. MT. Ph. D



Pembuatan HA Powder The advantages of the wet process are:

– That the by-product is mainly water and the probability ofcontamination during processing is very low (Raynaud et al., 2002;Afshar et al., 2003).

– The wet method is economically feasible

– The wet method can be easily carried out at low temperatures rangingfrom 40 to 100oC (Kumar et al., 2004).

The disadvantages are:

– The composition of the resulting product is greatly affected even by aslight difference in the reaction conditions.

– The powder properties such as surface area and morphology couldvary when the powder is calcined at different temperatures (Patel et al.,2001).

The advantages of the the solid-state reactions give a

stoichiometric and well-crystallized product. The disadvantages of the the solid-state reactions are: – Require a relatively high temperature, – Risk of contamination during milling and long heat treatment times.

– Sinterability of such powders has been reported to be low (Chaikina,1997; Suchanek et al., 2002).



Pembuatan HA Powder: Precipitation The most common method used to prepare HA is aqueous precipitation,

not only because it is closer to in vivo situations, but because it is a

relatively simple procedure that can give a wide variety of apatite particlesizes and morphologies. In general, wet chemical procedure involved HA precipitation via mixing

aqueous solutions of compounds containing Ca2+ and PO43- ion at pH>7,

followed by capturing the precipitate under appropriate conditions.

The most commonly used as Ca2+ sources are CaCl2, Ca(NO3)2, Ca(OH)2,CaSO4.2H2O and (CH3COO)2Ca.

Whereas typical PO43- sources are H3PO4, NH4H2PO4, (NH4)2HPO4, Na3PO4 and K3PO4.

Ammonia gas, NH4OH or NaOH are used to adjust pH of the solution. The rate of the process depends on many factors, such as:

– the concentration of the starting salts, – mixing sequence and rate,

–solution pH,

– reaction temperature and holding time (Tampiere et al., 2000). In view of thiscondition, control over all parameters is critical to ensure reproducible results.

If the pH is not well controlled, HA powders produced by precipitationmethods often result in powders with deviations from stoichiometry (i.e.,Ca/P ≠1.67) producing in additional secondary phases such as TCP or calcium oxide (CaO). Once aged, the precipitate is thoroughly washed,

filtered, and dried.



Pembuatan HA Powder: Precipitation

The two most common methods quotedin the literature are that of Akao, et al.(1981) as shown in equation (2.1), andHayek and Newesely (1963) as shown in

equation (2.2).



Pembuatan HA Powder: Hydrolysis In the process of a chemical mechanism, hydrolysis is a chemical

reaction when molecules of water (H2O) are apart into hydrogen

(H) and hydroxide anions (OH-) Hydrolysis methods incorporatethe hydrolysis of acid calcium phosphates (e.g., dicalciumphosphate dihydrate) in ammonium, carbonate, chloride, fluoride,sodium, or potassium hydroxide solutions subject to the desiredcomposition of apatite (Porter, et al., 2008; Monma, et al., 1981;Rootare and Craig, 1978; Fang, et al., 1981).

Hydrolysis of tricalcium phosphate, monetite, brushite, oroctacalcium phosphate requires low temperatures (usually below100oC) and results in HA needles or blades having the size ofmicrons.

However, in most cases, the hydrolysis product is highlynonstoichiometric (Ca/P ratio in the range of 1.50 –1.71).

Another problem of wet methods is the presence of carbonate ionsand/or other impurities in the lattice of the crystallized HA(Suchanek and Yoshimura, 1998).



Pembuatan HA Powder: Hydrothermal Hydrothermal methods, as the name implies, deal with the

application of elevated temperatures, pressures, and controlled

atmospheres to convert one substance into another via anexchange reaction.

This process also facilitates the precipitation of crystals withdimensions larger than those attainable using ordinary wetmethods.

The primary advantage of such method is to enhance the

crystallinity and purity of the product at elevated temperature andpressure (Yoshimura et al., 2004; Guo and Xiao, 2006).

The reactions in equations (2.2) and (2.3) could be carried outhydrothermally by heating at approximately 250 –300oC understeam pressure of 80 –100 MPa. Although this route is relativelytime consuming, it has the added benefit of the option to preserve

the original architecture, as illustrated by the production of porousHA from calcium carbonate corals (Porter, et al., 2008).



Pembuatan HA Powder: Hydrothermal The synthesis of HA powders can also be carried out hydrothermally at

various temperatures and under varying stem pressure (LeGeros and

Legeros, 1993). The hydrothermal method was first used for HA formation directly from

corals, a natural calcium carbonate material with aragonite structure (i.e.,a polymorphic phase of CaCO3) by Della Roy and Linnehan (1974).

Since then onwards, various research have been done on corals(Sivakumar et al., 1996; Xu et al., 2001), nacre (Zaremba et al., 1998;Lemos et al., 2006), seashell (Vecchio et al., 2007) and cuttlefish shell

(Rocha et al., 2005; Zhang & Vecchio, 2007), through the hydrothermalmethod.

Although HA could be obtained, it involves a complicated processes inthe hydrothermal conversion of these natural aquatic species to HAmaterial.

Several researches also try to obtain HA from other natural mineral byusing hydrothermal method such as synthesizing HA from egg shell

(Rivera et al., 1999; Sasikumar & Vijayaraghavan, 2006, Herliansyah, et al,2011), natural gypsum (Herliansyah et al., 2006) and natural calcite(Herliansyah et al., 2007).



Pembuatan HA Powder: Hydrothermal Although the hydrothermal process is able to produce

single phase HA, this process is very time consumingand requires equipment that must be corrosionresistant, able to with stand high pressures and hightemperatures.

A similar observation was also reported by Jingbing et

al. (2003) who discovered that the pH value andhydrothermal temperature are critical controllingparameters for obtaining desirable HA morphology.

They found that well elongated HA particles with highaspect ratio > 20 (having typical diameter of 40 nm andlength of 600 nm) could only be obtained on conditionthat the pH and temperature of the starting reactionsolution was 9 and 120oC, respectively.



Pembuatan HA Powder: Mechanochemical & Solid

State Reactions The fact that an intimate heterogeneous mixture of appropriate solid

ingredients when heated to an optimum temperature could lead to the

formation of a desired lattice through solid state diffusion of theconstituent ions has spurred research in this area in recent years. This process, categorized as dry chemical method (also known as

mechanochemical method) make use of the solid-state diffusion duringcalcinations between calcium and phosphorus compound in thetemperature range of 1000oC to 1300oC, and have the advantages ofproviding a stoichiometric (Ca/P = 1.67) and well-crystallized HA product

(Orlovskii et al., 2002). The calcium and phosphorus compounds used as the starting materials

in this process are dicalcium phosphate anhydrous (CaHPO4), dicalciumphosphate dehydrate (CaHPO4.2H2O), monocalcium phosphatemonohydrate (Ca(H2PO4)2.H2O), calcium pyrophosphate (Ca2P2O7),calcium carbonate (CaCO3), calcium oxide (CaO) and calcium hydroxide(Ca(OH)2), etc. (Otsuka et al., 1994; Chaikina, 1997).

In solid-state reactions HA is produced via the stoichiometric mixing ofreactants at specific temperatures. Examples of this method are given inequations (2.3) and (2.4).

The calcium compounds are mixed, formed, and then sintered above950oC (Trombe and Montel, 1978)




State Reactions

Mechanochemical powder synthesis takes advantage of theperturbation of surface-bonded species by pressure to enhancethermodynamic and kinetic reactions between solids at theexpense of high consumption of power (high temperature) andlong heat-treatments time (Senna, 2001; Mochales et al., 2004;Suchanek et al., 2002).

Since synthesis by this method is normally carried out at hightemperatures, H2O vapour must be supplied continuously duringthermal treatment as a source of OH- in HA (Chen et al., 2004).

Solid state reactions usually give a stoichiometric and well-crystallized product, but they require relatively high temperatures

and long heat-treatment times and according to Suchanek andYoshimura (1998) the powder from mechanochemical products ofsuch processes lack homogeneity and exhibit low sinterability.




State Reactions Since the mechanochemical synthesis involves only solid-state

reaction, it should be clearly distinguished from mechanochemical-hydrothermal synthesis (i.e. “wet” mechanichemical), whichincorporates an aqueous phase in the system.

An aqueous phase can actively participate in the mechanochemicalreaction by accelerating kinetic processes such as dissolution,diffusion, adsorption and crystallization (nucleation and growth)(Yoshimura and Suchanek, 1997).

According to Yeong et al. (2001), the mechanochemical activation ofslurries can generate local zones of high temperature (up to 450-700oC) and high pressure due to frictional effect and adiabaticheating of gas bubbles (if present in the slurry), while the overalltemperature is close to the room temperature.

Thus, the mechanochemical-hydrothermal technique is considered

a hybrid of hydrothermal and mechanochemical processing. Themechanochemical-hydrothermal processing has been reported tobe more effective and has been employed by many researchers tomanufacture single phase HA powders (Suchanek and Yoshimura,1998).

However, the HA phase stability is governed by the milling medium

and milling duration.



Pembuatan HA Powder: Sol Gel Routes A number of publications have addressed the details of synthesis of HA

based on sol-gel processing (Liu et al., 2002; Bezzi et al., 2003; Bigi et al.,

2004; Feng et al., 2005; Hsieh et al., 2001; Fathi and Hanifi, 2007) andrevealed that HA synthesis by this method exhibit several advantagesover other methods, such as: – good homogeneity composition of HA powder (Bezzi, et al., 2003; Gibson, et

al., 2001), – highly pure HA product due to the possibility of a strict control of the process

parameters,

–

nanosized dimensions of the HA product that is imperative in improvingcontact reaction and the stability at the artificial/natural bone interface – high reactivity (Bezzi, et al., 2003) compared to conventional methods such as

solid-state reaction, hydrothermal, and wet chemical precipitation (Suchanekand Yoshimura, 1998). The high reactivity of the sol –gel powder allows areduction of the processing temperature and of degradation phenomenonoccurring during the sintering process.

All these advantages give evidence to the possibility of using the sol-gel

method in HA surface coating process. In the sol-gel synthesis of HA, alkoxides or metal salts are frequently used

are either calcium or phosphorus precursor (Bezzi, et al., 2003). In mostcases, phosporus alkoxides were frequently employed as on of the majorconstituents, together with stoichiometric amount of calcium alkoxides orcalcium salts, to form HA (Bigi et al., 2004).



Pembuatan HA Powder: Sol Gel Routes



Pembuatan HA Powder: Sol Gel Routes The sol-gel processing of HA, however is not without shortcomings. This

includes: –

the use of either expensive alkoxide based precursor – or the need for several complicated steps to ensure complete dissolution of

the precursor to generate pure HA phase after post heat treatment (Kim andKumta, 2004).

– sol preparation time, e.g. 24 h or longer, is commonly reported in literature toform desirable HA morphology (Layrolle, et al., 1998). This is due to the slowreaction between Ca and P precursor in the sol phase (the reactivity alsodepends on the chemical nature of the most often-used, highly active

phosphorus alkoxide, i.e. triethyl phosphate), to interact with calcium alkoxidein order to obtain HA. In the case of less-active triethyl phosphate,

– longer time and higher temperature treatment were necessary to activate theinteraction with calcium acetate to form crystalline HA (Jillavenkatesa andCondrate, 1998)

– Furthermore, Jillavenkatesa and Condrate (1998) also reported that sol-gelderived HA is frequently accompanied by secondary phase of calcium oxide(CaO) mainly due to the chemistry of the sol-gel routes. Similar results wereobtained by Varma et al., (1998). In another research performed by Weng et al.,(2002), the authors reported that -TCP could be observed upon calcinationsthe HA powder at 800oC. Nevertheless, this can be overcome by washing thederived powders using a dilute solution of hydrogen chloride (HCl) or otheracids, or by exercising proper aging steps prior to the drying process followedsubsequently by water washing instead of vigorous acid washing method assuggested by Hsieh et al. (2001)



Pembuatan HA Powder: Others There are also alternative techniques for HA powder

preparation, such as: – electrocrystallization technique (Shirkhanzadeh, 1994),

– Spray-pyrolysis (Vallet-Regi et al., 1994), – emulsion route (Lim et al., 1996 and 1997),

– freeze-drying (Lu et al., 1998; Itatani et al., 2000),

– microwave irradiation (Kumar et al., 2000; Manjubala and

Sivakumar, 2001; Yang et al., 2004) – microwave hydrothermal (Fang, et al., 1981; Han et al., 2006;

Herliansyah, et al, 2011).

All these techniques are unique in their own ways andproduces HA powders of varying degree of

homogeneity and purity. However the complexity of each method, the

requirements for expensive precursors/chemicals, theneed for special reaction conditions and equipmentsused makes them economically unfeasible from thepoint of view of reproducibility and mass production.



Pembuatan HA Powder: Others It is well established that the processing of ceramics is

complicated by the number of steps typically requiredfor the manufacturing and the need to optimize theprocessing steps.

The processing of ceramics is extremely importantbecause ceramics are basically flawed intolerant

materials, meaning that, minor chemical and physicaldefects can severely degrade its mechanical andphysical properties.

Proper selection of raw materials and processingconditions is especially important in ceramics becausemistakes generally cannot be rectified during the firingand post-firing processes.



TERIMA KASIH ATAS PERHATIAN DAN KERJASAMANYA

Muhammad K. Herliansyah, ST. MT. Ph.D

[email protected]@ugm.ac.id

http://herliansyah.staff.ugm.ac.id

09 Teknik Biomaterials

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