Key Engineering Materials
Vols. 342-343
Vols. 342-343
Key Engineering Materials
Vols. 340-341
Vols. 340-341
Key Engineering Materials
Vol. 339
Vol. 339
Key Engineering Materials
Vols. 336-338
Vols. 336-338
Key Engineering Materials
Vols. 334-335
Vols. 334-335
Key Engineering Materials
Vol. 333
Vol. 333
Key Engineering Materials
Vols. 330-332
Vols. 330-332
Key Engineering Materials
Vol. 329
Vol. 329
Key Engineering Materials
Vols. 326-328
Vols. 326-328
Key Engineering Materials
Vols. 324-325
Vols. 324-325
Key Engineering Materials
Vols. 321-323
Vols. 321-323
Key Engineering Materials
Vol. 320
Vol. 320
Key Engineering Materials
Vol. 319
Vol. 319
Key Engineering Materials Vols. 330-332
Paper Title Page
Abstract: Resist pattern was developed on a cathode for EPD and a polytetrafluoroethylene (PTFE)
film was set on the cathode. Then EPD was performed with a suspension of hydroxyapatite (HA)
nuclei in ethanol. In this process, HA nuclei were deposited on a porous PTFE film so as to
transcribe the resist pattern. The substrate was soaked in simulated body fluid (SBF) and HA was
selectively induced on HA nuclei. As a result, HA pattern whose resolution was as high as the resist
pattern was fabficated.
3
Abstract: Biphasic calcium phosphate powders (BCP) of hydroxyapatite (HA) and tricalcium
phosphate (β-TCP) with the various ratio of HA to β-TCP were prepared by utilizing mechanochemical
synthesis. Calcium hydrogen-phosphate dihydrate (brushite, CaHPO4⋅2H2O) and calcium
carbonate (calcite, CaCO3) powders have been chosen as the starting materials. The original Ca/P
ratio of CaHPO4⋅2H2O - CaCO3 batch was set to be 1.67. A mixture of starting materials was milled
using a planetary mill (ZrO2 jar and balls) with water for 3, 4, 5, 6 and 7 hrs. The XRD study of
calcined powders was conducted for phase identification and for HA/β-TCP ratio as well. The
phases of the calcined powders were HA and β-TCP, and the HA/β-TCP ratio varied with the
milling time. The mass fraction of HA and β-TCP phases was calculated from the XRD intensities
of HA and β-TCP. The ratio of the mixture milled for 4 hrs and calcined at 900°C was
85(HA):15(β-TCP) (BCP 85/15) and the content of β-TCP increased with the milling time. It is
believed defective HA powder formed at relatively short period of milling time (less than 3 hrs The
research revealed that nanocrystalline BCP powders could be synthesized by an employment of a
medium-high energy mechanical activation at room temperatures (~25°C) without any preliminary
chemical processing.
7
Abstract: Structure parameters of minerals in human bone, bioapatite, are very important for
biomaterials. In situ micro-XRD and Rietveld structure refinement were used to extract subtle
structure information of human ribs. Rietveld refinement testified that lattice parameters, crystallite
size and microstrain for cortical and cancellous bones were significant difference. Anisotropic
crystallite sizes of human rib showed preferential growth of apatite along c-axis and the graded
variation at radial direction of bone axis. The variations of the subtle structures of bioapatite, such as,
P occupancy and P-O2 bond length, as well as distortion index of P-O tetrahedron, demonstrated the
tendency of mineralization and the content of CO3
2- in human ribs.
11
Abstract: To increase the mechanical properties of PLA used for fracture inner fixation, β-calcium
metaphosphate whiskers were prepared by controlled crystallization in the glass. The factors
influencing the morphology of the samples, such as component, time and temperature of
crystallization were discussed. Results showed that the high quality of β-calcium metaphosphate
whiskers can be obtained by crystallization treating for 36 hours and washing for 48 hours at 80°C
distilled water. β-calcium metaphosphate whiskers having high aspect ratios of 20-100 with
diameters of 1-5μm were achieved at the optimized conditions.
15
Abstract: Carbonate hydroxyapatite (CHA) bioceramics can be synthesised to contain sodium ions
as a co-substituted ion, or as sodium-free compositions. It is unclear, however, which composition
would produce the optimum biological response. The aim of this study was to find a reliable
method to produce sodium co-substituted and sodium-free CHA compositions that would have the
same level of carbonate substitution, and to characterise the effects of the two different substitutions
on the structure of the CHA samples. After sintering at 900oC in a CO2 atmosphere, all samples
contained approximately equal amounts of carbonate groups on the A- and B-sites, as observed by
FTIR. The sample produced with NaHCO3 and the sodium-free sample (CHA1) have comparable
carbonate contents, whereas the sample produced with Na2CO3 contains significantly more
carbonate, probably due to the excess sodium ions allowing more carbonate co-substitution. The
sodium-free CHA sample, however, has significantly smaller unit cell parameters compared to both
sodium co-substituted CHA samples, and also to HA. This characterisation of the samples shows
that the sodium-free CHA sample (CHA1) and the sample produced with NaHCO3 would provide
CHA compositions for biological testing with similar carbonate contents and distributions, but with
structural differences due to the sodium substitution.
19
Abstract: The aim of this paper was the HA and β-TCP powers were synthesized by a new wetchemical
method using eggshell and phosphoric acid. The biocompatibility of synthesized natural
HA, HA/β-TCP(50:50) and β-TCP derived from eggshell was compared with those of as
commercial chemical powder with mesenchymal stem cells derived from human bone marrow.
Development of crystalline phases of the mixtures was studied as functions of mixing ratio and
temperature using X-ray diffractometer. The morphological characteristics of the calcined
eggshell and synthesized powders were examined by scaning electron microscopy. The in-vitro
cytotoxicity and cell attachment of sintered disks were examined using human bone marrowderived
multipotent stem cells(hBMSCs). Cell response was characterized by MTT assay ,
Alkaline phosphatase stain and RT-PCR analysis. Pure HA was synthesized in the mixing ratio of
1:1.1 wt% at 900°C for 1h. the crystallization of HA was started at 800°C in the 1:1.1 mixing
ratio, ant the HA phase was continued up to the high temperatures. In the ratio of 1:1.3 and
1:1.5 wt%, β-TCP was effectively synthesized at 900°C. In the 1:1.5 ratio, β-TCP phase was
detected at 700°C, and complete crystallized β-TCP was observed above 900°C. At the higher
temperature than 1000°C, the β-TCP was gradually decreased and α-TCP was observed. The HA
and β-TCP disk does not exert cytotoxic effect on the hBMSCs undergoing osteoblastic
differentiation. In addition, the hBMSCs are adhered on the surface of synthesized natural HA
and β-TCP disk as successfully as on the culture plate or as commercial chemical HA and β-TCP
disk. The hBMSCs adhered on either synthesized natural HA, β-TCP or as commercial chemical
HA, β-TCP disk displays undistinguishable actin arrangement and cellular phenotypes, indicating
that synthesized natural HA, β-TCP does not disrupt normal cellular responses. Analysis of
differentiation of the hBMSCs cultured on culture plate, synthesized natural HA, β-TCP and as
commercial chemichal HA, β-TCP disk shows that three matrices are able to support osteoblastic
differentiation of the hBMSCs as accessed by alkaline phosphatase staining.
23
Abstract: Porous alpha- tricalcium phosphate (α-TCP) was implanted in rabbit and dog models to
investigate its induction of calcium phosphate (Ca-P) formation. The morphology and structure of
the formed Ca-Ps were examined using scanning electron microscopy (SEM) and transmission
electron microscopy (TEM), respectively. The results showed an animal-dependent behavior of in
vivo Ca-P formation. There were flake-like octacalcium phosphate (OCP) precipitates in the rabbit
but rod-like hydroxyapatite (HA) precipitates in the dog model. In addition, high-resolution TEM
(HRTEM) image revealed that there was OCP structure in certain portions of the rod-like HA
precipitates in the dog model. And the orientation relation of OCP/HA was deduced as OCP
(010)//HA (0 10) and OCP (001)//HA (00 1) . This implied that the in vivo HA was formed via
OCP precursor phase.
27
Abstract: Several sintering additives for hydroxyapatite have been tested in order to enhance its
sinterability without decomposing the hydroxyapatite(Ca10(PO4)6(OH)2) and without decreasing the
bioactivity and/or biocompatibility. In case of sintered pure hydroxyapatites significant dissolution
was occurred after immersion in distilled water or in simulated body fluid. At first the dissolution
was iniciated at grain boundary creating the nano-size defects such as small pores and grew up to
micro scale by increasing the immersion time. This dissolution resulted in grain separation at the
surfaces and finally in fracture. And the dissolution was concentrated on those grains adjacent to
pores rather than those in the dense region. So glass-reinforced hydroxyapatite(GR-HA) ceramics
were prepared to strengthening the grain boundary to prevent dissolution. Several glasses were
added at 0 to 10wt.% and sintered at 1200 °C for 2h in air with moisture protection. Glass phase
was incorporated into hydroxyapatite to act as the sintering aids followed by crystallization in order
to improve the mechanical properties without reducing the biocompatibility. From dissolution test,
significant damage was reduced even more than 7days. X-ray diffraction and SEM showed no
decomposition of hydroxyapatite to secondary phases and fracture toughness was increased more
than pure hydroxyapatite.
31
Abstract: Porosity and macroporosity in porous calcium phosphate bioceramics play an important
role in conducting cells and vessels penetrating into pores and forming bone ingrowth inside
bioceramics. Histological results indicated new bone volume (NBV) was higher in β-tricalcium
phosphate (β-TCP) implants than that in hydroxyapatite (HA) implants for identical porosity of
75% at both 1 month and 3 months, and the degradation of β-TCP was too quick to keep its
original shape at 3 month. According to the XRD analysis, chemical dissolution seemed to be one
part of degradable mechanism forβ-TCP
35
Abstract: The aim of this study is to explore the effects of quenching and milling processing on
setting property of calcium phosphate cement (CPC). For this purpose, non-quenched α-tricalcium
phosphate (α-TCP) and quenched α-TCP were synthesized and their corresponding cement systems
were prepared. The particle size of α-TCP powder was introduced as a variable. Then, setting
properties of these CPC systems were estimated. By a comparison between non-quenched CPC and
the quenched one, it is found that milling processing mainly influences the initial setting stage by
decreasing reactant particle size whereas the quenching treatment affects the final setting stage by
changing α-TCP content, which supports that CPC setting initially depends on the surface area of
reactants and subsequently on the diffusion through the hydrated layer formed around the reactants.
39