SYNTHESIS OF CALCIUM-PHOSPHATE MICROSPHERE WITH ...

4 downloads 0 Views 1MB Size Report
Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku,. Kawasaki, 214-8571, Japan, e-mail: [email protected]. Abstract: We performed ...
SYNTHESIS OF CALCIUM-PHOSPHATE MICROSPHERE WITH WELL-CONTROLLED PARTICLE SIZE BY ULTRASONIC SPRAY-PYROLYSIS TECHNIQUE AND THEIR SINTERABILITY MAMORU AIZAWA 1,ATSUSHI ONO 1,TOSHIKI OHNO1, and PAK-KON CHOI2 1) Department of Industrial Chemistry, 2) Department of Physics ,School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, 214-8571, Japan, e-mail: [email protected] Abstract: We performed to synthesize the calcium-phosphate well-controlled particle size by changing the frequency transducer. The crystalline phases of the resulting powders β-tricalcium

phosphate

were

1.50.

about

The

were

composed

of

sizes

increased

with

quite

narrow.

The

controlled

by

(ƒÀ-TCP) SEM

and

observation

microspheres

with

decreasing above

changing

hydroxyapatite indicated a diameter

ultrasonic results the

(HAp);

show frequency

that

of •`1

frequency that of

the the

to •`2.5 , and

the

microsphere with of the ultrasonic were composed of

particle

ultrasonic

the

Ca/P

mola r ratios powders

resulting gm

.

The

particle

distributions size

can

transducer

were be

easily during

spray-pyrolysis.

INTRODUCTION Hydroxyapatite (Ca10(PO4)6(OH)2; HAp) and tricalcium phosphate (Ca3(PO4)2; TCP) are widely used as biomaterials for substituting with human-hard tissues1. We have synthesized the above-mentioned HAp and the apatite-family compounds by ultrasonic spray-pyrolysis technique and examined the properties the resulting powders2-5). An ultrasonic spray-pyrolysis technique is one of the powder preparation techniques via the liquid phases. This technique has advantagesthat one canprepare the stoichiometric and homogeneous compounds instantaneously by spraying the solutions with the desired amounts of cations into the hot zone of electronic furnace. In the case of the powder preparation based on ultrasonic spray-pyrolysis , the particle size is dependent on the size of droplet generated by ultrasonic transducer . The droplet size, dp, is defined by the following equation 5).

1

where, f the

is a frequency, ƒÏ

particle

of

sizes

droplet

by In

the

resulting

changing the

bioceramics, using

of

present

of

solution

solution, ƒÐ

have

calcium-phosphate

the

Ca/P

ratio

transducer,

if one

on

of

to

one

powders 1.50.

Our

well-controlled

and

tension. can

Thus,

control

the

size

transducer. focused

the

with

a surface

well-controlled

ultrasonic

we

with

ultrasonic

be

in the

microspheres

the

spraying

may

frequency

prepared

calcium-phosphate

frequency

the

investigation,

and

starting

of

powder

the

TCP,

the

density

of

the

biodegradable

via

the

above

were

to

aims

particle

examine

the

size

by

sinterability

process synthesize

changing

of

the

the

resulting

powders.

EXPERIMENTAL

Calcium-phosphate

powders

solution.

The

starting

Ca(NO3)2,

0.40

mol•Edm-3

formed

by

2.5

3 MHz.

and

As

of

set

at

two

resulting

diffractometry

(XRF),

measurement

of

0.2

sintered g•Ecm-3).

phase

was

RESULTS of

frequency fraction

as-prepared

the

by

solution

mixing

zone

present

0.60 The

at the

hot

the

the

of

present

investigation,

higher

one

at

the

850•Ž

molidm-3

droplets

frequency

of

for

starting

were

0.5,

1, 1.5,

apparatus

was

lower

furnace

pyrolysis

of

the

The

relative by

The

at

the

the

AND

DISCUSSION

ultrasonic

from that

0.5 the

examined based of ƒÀ-TCP

to

3.0

as-prepared sample on

typical phase

microscopy

(SEM),

1050,

1150 was

theoretical

was

techniques:

X-ray

(FT-IR), and

of

uniaxially

10

and

mm

BET

X-ray

method

densities

pressed

and

1200•Ž

calculated

was

above

the

following

spectrophotometry

diameter

for

for

by

using

100

thickness

5

h

dividing

of ƒÀ-TCP

observed

a

at

heating bulk

SEM

rate:

density

(3.07g•Ecm-3) a

to

of•`2mm.

(the the

MPa

of

and ƒ¿-TCP

and

the

crystalline

XRD.

,

frequenc

1 shows

the

infrared

a

microstructure by

by

powder

density

identified

the

characterized

area.

with

fired

Figure

the

g of

compact

(3.07

all

mol•Edm-3NHO3.

and

electron surface

were

10•Ž.min-1).

indicated

0.40

the

transform

specific

compact

compacts

were

scanning

disk-shaped

frequency

In

droplets

Fourier

the

About

Effect

of

powders

(XRD),

fluorometry

the

drying

prepared

2-5), the

furnaces.

spray-pyrolysing

was

starting

reported

by

salts. The

The

and the

previously

for

synthesized

solution

(NH4)2HPO4

electric

300•Ž

precipitated

form

aqueous

ultrasonically-vibrating

composed was

were

on

XRD MHz

the powder properties

patterns on

XRD decreased

the

powders

spray-pyrolysis

powders powders.

of

were As

process.

composed

examining

intensities

the

2

down

by

These

of ƒÀ-TCP

of ƒÀ-TCP

from•`65%

prepared

phase

and changes

(0210) to•`45%

and

changing XRD

HAp with

the patterns

biphase

in

ultrasonic

HAp

(211),

with

increasing

the

Figure ultrasonic

frequency, In

assigned

the

to

absorption

of

absorption

PO4

phase

of

0.03.

group

is,

of

above

the

resulting

The

Ca/P

Ca/P=1.50.

Figure

group

were

group

cm-1

the

the

results

increased

above

assigned

in

that

the

.

powders 600 3570

, the

and cm-1

570 .

cm-1

In

NO3-groupderived , except

NO3-

absorptions , and

the

addition,

the

from

starting

are

assigned

group,

ultrasonic

of

frequency

influences

the

crystalline

powders. the

harmony the

the

absorptions

calcium-phosphate

are

to

at

to•`55%

HAp.

show

ratios

up

1300-900,

detected

These

and

from•`35%

at

slightly was

powders.

calcium-phosphate

detected

HNO3. TCP

of the as-prepared

HAp

was

Thus,

calcium-deficient

of of

molar

values

patterns

spectra

and

The

These

that

1600-1300

Ca(NO3)2

to the

that

PO4 OH

of

materials,

while

FT-IR

the

1 XRD

apatite

resulting

with

the phase

powders

were

stoichiometric present

in

the

composition in

the

resulting

range of

of

1 .50 •}

TCP

powder

phase may

, be

apatite. 2

shows

the

particle

morphologies

of

the

resulting

powders

Figure 2 SEM micrographs of the resulting calcium-phosphate powders: (a) Ultrasonic frequency: 0.5 MHz, (b) 1.5 MHz, (c) 3.0 MHz.

3

((a)

ultrasonic that

frequency:

the

∼2 .5

as-prepared

ƒÊm

the

measuring

to

the

of

the

diameters in

(c)

3 MHz)

composed

increased

than

of

of

the

.

of

with

These

SEM

microspheres

micrographs with

decreasing

of

solvent

from

In

the

mean

particle

frequency

from

above

observations

resulting

indicated

a diameter

ultrasonic

with

.

The .

the

frequencv

results

of be

the

increased

of the

due

from

1

in

of•`1

to

. and

the

size

by

particle

each

droplet

sample)

generated

the

.0 to

spray

2.5 ƒÊm

The

particle

shrinkage

during

. according

spray-pyrolysized to

droplet

mean

-376

diameter

may of

determined (n=253

diameter

surface

3 down

the

This

size

, we

particles

together

droplet

evaporation

The

the

frequencies

that

addition,

SEM

Fig . 3,

ultrasonic

ultrasonic

and

were

sizes

bases

illustrated

various

smaller

particle

1.5,

were quite narrow.

On

is

(b)

powders

The

distributions

result

0.5,

was

based

-pyrolysis

with

on

the

process

a decrease

of

. the

to 0 .5 MHz.

indicate

that

the

particle

size

can

be

easily

controlled

b y

changing

the

frequency

Figure

of

transducer

during

3 Relationship

between

mean

frequency,

together

with

ultrasonic The

ultrasonic

sinterability

of

the

spray

particle

-pyrolysis

.

size and

the size of the droplet

calcium-phosphate

microspheres

.

was

ex

Figure

4

amined ring

the

green

relationship

compacts

between

at

firing

800

,

1050

and

temperature

and

1200 •Ž relative

for

5

density

h. of

shows

the sintered

In

the

case

of

the

firing

temperature

all

the

examined

specimens.

compact.

This

This

at

800 •Ž

value

was

almost

the

that

the

firing

, the

relative

density same

as

was the

compact.

about

relative

50%

insufficient

to promote

result the

sintering

suggests of

the

resulting

4

powders

temperature .

of

in

d ensity

green

by fi the

800 •Ž

of is

Figure 4 Relationship the sintered compact On the

case

of

the the

in

slightly

decreased be

all

the

due

hands,

firing

density

may

other

transformation

relative

temperature

examined and

to

the

the

between relative density and ultrasonic frequency.

at

densities

1050•Ž

specimens.

the

values

In

were

in

the

were

and

these

the

case

ranges

in

the

values of

of

range were

1200•Ž

of

84%

of the

highest

, the to

92%

90%

to

96% relative

relative .

This

density decrease

phase

of ƒÀ-TCP

into ƒ¿-TCP. Actually, crystalline

phase

sintered and

compact

1050•Ž

phase that

was

the

the

at

800

a single

was of ƒ¿-TCP.

FT-IR

spectra

sintered

while

compact

phase

a

at single The

of

the

compacts

indicated

also

that

absorptions the

of

of ƒÀ-TCP, of

1200•Ž

to

the

were PO4

group

the assigned of

the Figure

5 Microstructure

5

of

typical ƒÀ-TCP

ceramics.

in

TCP

phase.

The

NO3-

group

present

in

the

as-prepared

powder

disappeared

after

firing. Among relative

density

frequency: Fig.

5.

be

MHz,

It was of

during

obtained

the

grain

by

conclusion,

the we

particle

the

sizes

make can

that

be

The

that

of

2-3

easily

the

.ƒÊm.

with

of

ultrasonic

microstructure

Thus,

96%

powder; is

dense ƒÀ-TCP

at 0.5

the

ceramics

sample

5 h.

frequency

clear

dense

following

observation

ultrasonic

sizes

spray-ovrolysis

the

most

1050 •Ž,

SEM

with

setting

the

from

conditions:

from

uniform

well-controlled

specimens,

firing

seen

obtained In

examined

were

0.5

composed may

the

shown

ceramics

easily-sinterable

in were

powder

MHz

calcium-phosphate

synthesized

by

microspheres changing

with

the

frequency

technique.

CONCLUSION

We

performed

well-controlled The

particle

crystalline

The

Ca/P

the

the

The

maximum of

ultrasonic

by

were

about

with

in

were

show

that

of

the

of

the

SEM

powder

the

with

particle

of•`1 the

can

be

and

that

easily

were

controlled In

the

the

to•`2.5 ƒÊm.

distributions

spray-pyrolysis.

by

biphase.

indicated

and

sinterability prepared

transducer.

of ƒÀ-TCP/HAp

a diameter

size

with

ultrasonic

observation

during

a good

microsphere

composed

frequency,

transducer had

case

The

ultrasonic

ultrasonic

the

frequency

microspheres

the

microsphere 96%

the powders

of

results

calcium-phosphate

1.50.

composed

of

the

changing

resulting

above

frequency

synthesize

the

increased

calcium-phosphate

attained MHz

were

sizes

narrow.

changing

of

ratios

powders

particle

quite

size

phases molar

resulting The

to

relative

spray-pyrolysing

by

addition, density at 0.5

frequency.

ACKNOWLEDGMENT

A part of the present research is supported by the Research Project (A) by Institute of Science and Technology Meiji University. REFERENCES 1) L. L. Hench, J. Am Ceram. Soc., 81, 1705-28 (1998). 2) M. Aizawa, F. S. Howell and K. Itatani, J.Ceram. Soc.Jpn., 107, 1007-1011 (1999). 3) M. Aizawa, T. Hanazawa, K. Itatani, F. S. Howell and A. Kishioka, J. Mater. Sci., 34, 2865-2873 (1999). 4) M. Aizawa, T. Hanazawa, K. Itatani, F. S. Howell and A. Kishioka, Phosphorus Res., Bull., 6, 217-220 (1996). 5) K. Itatani and M. Aizawa, J. Soc. Inorg. Mater. Jpn., 10, 285-292(2003).

6