bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluations of a Novel Bioactive and Degradable Poly(Ɛ-Caprolactone) Hybrid Material Containing Silanol Group and Calcium Salt as a Bone Substitute
Authors: Rhee Sang Hoon , Lee Yong Keun , Lim Bum Soon , Lee Jae Il , Yoo Jeong Joon , Kim Hee Joong
Published: March 2009

Bioactive poly(e-caprolactone)-siloxane hybrid material was newly developed and its in vitro and in vivo evaluations were made for the potential application as a bone substitute. The polymer precursor, triethoxysilane end capped poly(e-caprolactone) was prepared by the reaction with a,w-hydroxyl poly(e-caprolactone) and 3-isocyanatopropyl triethoxysilane with 1,4-diazabicyclo
[2,2,2] octane as a catalyst and toluene as a solvent. The triethoxysilane end capped poly(e-caprolactone) was hydrolyzed and condensed to yield a hybrid sol-gel material. The gelation was carried out for 1 week at ambient condition in a covered Teflon mold with a few pinholes and then dried under vacuum at room temperature for 48 h. Its bioactivity was evaluated by examining the apatite formation on its surface in the SBF and its osteoconductivity was assessed in the tibia of white rabbit. The hybrid material showed apatite-forming ability in the SBF within 1 week soaking. Besides, new bone was formed on the surface of a cylindrical shaped specimen with no histologically demonstrable intervening non-osseous tissue after 6 weeks implantation. There was no evidence of inflammation or foreign body reaction. From the results, it can be concluded that this newly
developed hybrid material has osteoconductivity and is likely to be used for the application as a bone graft substitute.
Apatite Formation on Organic-Inorganic Hybrid Containing Sulfonic Group
Authors: Miyazaki Toshiki , Imamura Moriyoshi , Ishida Eiichi , Ashizuka Masahiro , Ohtsuki Chikara , Tanihara Masao
Published: March 2009

Apatite formation in living body is essential condition for artificial materials to exhibit
bone-bonding ability, i.e. bioactivity. It has been recently revealed that sulfonic group triggers apatite nucleation in body environment. Organic-inorganic hybrids consisting of organic polymer and the sulfonic group are therefore expected to be useful for novel bone-repairing materials exhibiting flexibility as well as bioactivity. In the present study, organic-inorganic hybrids were prepared from vinylsulfonic acid sodium salt and hydroxyethylmethacrylate (HEMA), a kind of acrylic polymer. Bioactivity of the hybrids was assessed in vitro by examining their acceptance of
apatite formation in simulated body fluid (SBF, Kokubo solution). The obtained hybrids showed the apatite deposition after soaking in SBF within 7 d.
Control of Crystal Orientation of Hydroxyapatite by Imposing a High Magnetic Field
Authors: Wu Cun You , Murakami Yuichiro , Sassa Kensuke , Iwai Kazuhiko , Asai Shigeo
Published: March 2009

The controlled development of texture microstructure in ceramics is one effective way to improve their properties, such as electrical, mechanical properties and biocompatibility. A bioceramics with oriented crystal structure has attracted great interest. In bone reparations, Hydroxyapatite (HAp)-based biomaterials were frequently used. And HAp is the main mineral constituent of the hard tissue of human bodies, which occurs with a hexagonal crystal. A HAp crystal turns out to have different surface properties in a- (or b-) plane and c-plane. In this regard, to
get highly oriented HAp is very important before using HAp as a biomaterial. And the crystal orientated HAp is useful not only as biomaterials but also as protein absorbents. In this research, two different kinds of HAp-based biomaterial with oriented structure (HAp bioceramics and HAp-coated titanium composite) were studied.
Mechanical Behavior of Bioactive Glass-Polyvinyl Alcohol Hybrid Foams Obtained by the Sol-Gel Process
Authors: Pereira Marivalda , Nazhat Showan N. , Jones Julian R. , Hench Larry L.
Published: March 2009

The possibility of enhancing mechanical properties by incorporation of polymeric
components to sol-gel derived materials is extremely attractive to prepare macroporous scaffolds, leading to materials with potential applications in both hard and soft tissue regeneration. In this work bioactive glass-polyvinyl alcohol hybrids were developed and their mechanical behavior was evaluated. Hybrids were synthesized by adding polyvinyl alcohol to a sol-gel precursor solution, which was then foamed with the addition of a surfactant and vigorous agitation. The foams were
cast, aged and dried at 40°C. A cleaning step to decrease the acidic character of the obtained hybrids was undertaken by immersion in a NH4OH solution. The mechanical behavior of the hybrids was evaluated in compression using both stress and strain control tests. Hybrid foams had a high porosity varying from 60-90% and the macropore diameter ranged from 10 to 600 µm. The modal macropore diameter varied with the inorganic phase composition and with the polymer content in the hybrid. The strain at fracture of the as prepared hybrid foams was substantially
greater than pure gel-glass foams. The cleaned hybrids presented a slightly higher strength and lower deformation than the as prepared foams.
Evaluation of a Chitosan Nano-Hybrid Material Containing Silanol Group and Calcium Salt as a Bioactive Bone Graft
Authors: Rhee Sang Hoon , Lee Yong Keun , Lim Bum Soon
Published: March 2009

A bioactive chitosan-siloxane nano-hybrid material was newly developed and evaluated for the potential application as a bone graft material. The chitosan which can be dissolved in organic solvent was synthesized by the reaction with phtalic anhydride (Ph-Chitosan) and it was then reacted with 3-isocyanatopropyl triethoxysilane (Si-Chitosan) in dimethylformamide. Following this, the
Si-Chitosan was hydrolyzed and condensed to yield a hybrid sol-gel material (Si-O-Chitosan). The gelation was carried out for 1 week at ambient condition in a covered Teflon mold with a few pinholes and then dried under vacuum at room temperature for 48 h. The bioactivity of the chitosan nano-hybrid material was evaluated by examining the apatite forming ability in the simulated body fluid (SBF). The surface microstructure and functional groups of the specimen was analyzed by field emission scanning electron microscopy and Fourier transformed infrared spectroscopy, respectively. The crystal phases of the specimen before and after the bioactivity testing were analyzed by thin film X-ray diffractometry. Newly developed chitosan nano-hybrid material showed apatite-forming ability
in the SBF within 1 week soaking and this ability was believed to come from the silanol group formed on the surface of Si-O-Chitosan and calcium salt which increased the ionic activity product of apatite in the SBF.
In Vivo Evaluation of Porous Hydroxyapatite/Poly D/L-Lactide Composite for Bone Substitute and Scaffold
Authors: Hasegawa Shin , Tamura Jiro , Neo Masashi , Goto Koji , Shikinami Yasuo , Saito Makoto , Nakamura Takashi
Published: March 2009

We investigated the biocompatibility, osteoconductivity, and biodegradability of porous composite of Hydroxyapatite (HA) and Poly D/L-lactide (PDLLA). At 6weeks afterimplantation to rabbit femoral condyle, HA/PDLLA was covered with bone and contacted with bone directly. The amounts of newly formed bone in the pores had increased during the examined period. By 26weeks, bone remodeling of formed bone in the pores was seen and bone marrow tissue formation was seen in
the pores of HA/PDLLA. Porous HA/PDLLA was resorbed much faster than porous HA as a control. Porous HA/PDLLA was resorbed constantly through the bone formation and bone remodeling but porous HA was hardly resorbed during the period. It might be one of the desirable materials for bone substitute. To evaluate for a scaffold, disc shaped blocks loaded with rat bone marrow cell were implanted in the subcutaneous pouch of the back of syngeneic rat. At 3weeks afterimplantation, newly bone formation in the pores was observed at ectopic site. It also suggested the availability of this material as cell scaffolds.
Effect of Calcium Phosphate Glass Scaffold with Chitosan Membrane on the Healing of Alveolar Bone in 1 Wall Intrabony Defect in the Beagle Dogs
Authors: Min D.H. , Kim M.J. , Yun J.H. , Kim C.S. , Lee Yong Keun , Choi Seong Ho , Kim Kyoung Nam , Kim Chong Kwan
Published: March 2009

This study evaluated periodontal repair and biomaterial reaction following implantation of a newly fabricated calcium phosphate block bone with chitosan membrane on the regeneration of 1-wall intrabony defects in the beagle dogs. The surgical control group received a flap operation only, while the experimental group I was treated with a chitosan nonwoven membrane only and the experimental group II was treated with a chitosan nonwoven membrane and a calcium phosphate
block bone. The subjects were sacrificed 12 weeks after surgery and a comparative histometric analysis was done. No root resorption or ankylosis were observed in the experimental group. Mann-Whitney U test showed that the experimental group II produced statistically significant higher gain in connective tissue adhesion, new cementum regeneration and new bone formation. Based on
histological results, the calcium phosphate block bone successfully functioned as a osteoconductive scaffold for invading cells of host.
Comparison of a New Kind of Calcium Phosphate Formula Versus Conventional Calciumphosphate Matrices in Treating Bone Defects – A Long-Term Investigation in Pigs
Authors: Henkel Kai-Olaf , Bienengräber Volker , Lenz S. , Gerber Th.
Published: March 2009

In clinical practice arises an increasing need for bone substitute materials. The main
inorganic part of bone is the hydroxyapatite (HA). A new hydroxyapatite formula was created by a sol-gel-process at low temperature level [4]. The aim of this investigation was to test the biodegradation and the induction of bone formation by this new material and to compare these versus conventional fabricated HA and ß-TCP. 30 one-year-old Goettingen minipigs were divided into five groups. Critical size defect (>5 m3) in the mandible was treated differently in all 5 groups:-group I- filling with pure HA, which was fabricated by sol-gel-technique, group II- control, only gelatinous material was given, group III- conventional ß-TCP [Cerasorb®], in group IV- conventional HA [Endobone®] and in group V [Targobone®], a non denatureted bovine collagen matrix was used. Macroscopical and microscopical
investigations of the former defects were made eight months postoperatively. The bone formation was superior in the sol-gel-HA-group (group I) in comparison with the control groups (group II) and the conventional fabricated ceramics groups (III and IV). In the sol-gel-HA group, the biodegradation of this new biomaterial was considered to very good with a resorption rate of more than 98%; eight months postoperatively. In this group complete bone formation was seen in former defects. In the control group, only an incomplete bone formation with 48.4% of the defect area was noted. This difference was significant (p<0,001). A less bone formation was also observed in group III and IV with 57.6% and 56.9%. The bovine non-denaturated collagen matrix (group V) leads to only 20% of new formed bone.
The new calcium phosphate formula made by a sol-gel method seems to be superior and suitable for filling bone defects.
Synthetic Biomimetic Nanostructured Hydroxyapatite
Authors: Landi Elena , Tampieri Anna , Celotti Gian Carlo , Mattioli-Belmonte Monica , Logroscino Giandomenico
Published: March 2009

The incorporation of magnesium ions into the hydroxyapatite structure, which is of great interest for the developing of artificial bone, was performed starting from a wet chemical synthesis using magnesium chloride as Mg source. Different doping extents were attempted, four powders were produced and characterized in term of morphology, composition, solubility, thermal resistance,etc. in comparison with stoichiometric HA. In vitro tests with mesenchimal stem cells (MSCs) and human osteoblast like cells MG-63 cells were performed with the powder characterized
with a biological-like doping of 5%Mg. The same powder was used, in form of granules, to carry out in vivo test by filling a defect in the femur on New Zealand White rabbits. All the tests showed better performance of the Mg doped apatite compared to stoichiometric HA, in agreement with the chemico-physical features of the material.
Bone-Bonding Ability of Ce-TZP/Al2O3 Nanocomposite with a Microporous Surface and Calcium Phosphate Coating
Authors: Takemoto Mitsuru , Fujibayashi Shunsuke , Suzuki J. , Kokubo Tadashi , Nakamura Takashi
Published: March 2009

The nano-composite of a ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP) and alumina (Al2O3) polycrystals (Ce-TZP/Al2O3) is attractive as a load-bearing bone substitute because of its mechanical properties and phase stability. We have developed a new method of hydrofluoric acid and heat treatment (HFT) to give a microporous structure to the surface of this Ce-TZP/Al2O3
nanocomposite ceramic. Bone-bonding ability of a microporous surface and calcium phosphate coating on Ce-TZP/Al2O3 composite has been investigated through in vivo detaching model. Thin calcium phosphate coating layer was added by alternate soaking process, and thick CaP layer was produced by soaking in simulated body fluid for 5 days. HFT treated Ce-TZP/Al2O3 composite showed high bone-bonding ability compared with the control group. Thick and thin CaP coating accelerated bone-bonding ability in early post-implantation period. The submicron microporous
surface was beneficial for achieving mechanical interlocking between the ceramic and surrounding bone. These results suggest the possibility of using a Ce-TZP/Al2O3 nanocomposite ceramic with microporous surface and calcium phosphate coating as the bearing material for uncemented total joint
replacements.
Colloidal Processing of SiC with Rare-Earth Ion
Authors: Tabata Shuhei , Hirata Yoshihiro , Sameshima Soichiro , Uemura Yoshimitsu
Published: March 2009

The SiC powder of median size 0.8 µm was mixed with polyacrylic acid (PAA, dispersant) in a 0.3 M-R(NO3)3 solution (R=Yb, Y, Gd, Sm, Nd and La) at pH 5 to adsorb uniformly the sintering additive (R3+ ion) on the SiC surface. The addition of PAA to the SiC suspension with R3+ ion increased the amount of R3+ ion fixed to SiC particles. The aqueous 30 vol% SiC suspension with 0.52 mass% PAA and 1.50 mass% R2O3 (as R3+ ion) against the mass of SiC, was consolidated by filtration through a gypsum mold to form green compacts of 50-52 % of theoretical density. The consolidated green compacts were hot–pressed under a pressure of 39 MPa at 1950°C for 2 h in an Ar flow. The green compacts were densified with grain growth to 76 - 99 % relative density. The addition of smaller R3+ ion was effective to enhance the sinterability of SiC and also to achieve smaller grain size of SiC. The sintering mechanisms were discussed based on the analysis of the shrinkage curves of SiC/R2O3 compacts during the hot-pressing.
Effect of Carbon Black Addition on Reaction-Bonded Silicon Carbide Ceramics
Authors: Kim Joo Sun , Jun H.W. , Song Huesup , Lee Jong Ho , Lee Hai Won
Published: March 2009

High strength reaction-bonded silicon carbide ceramics was successfully produced by reducing the amount of residual silicon and the silicon pocket size with carbon black as an additional carbon source. A prototype of wafer carrier was also produced in near-net dimension by planar contact infiltration of molten silicon into a preform joined with six pieces of simple shape by eliminating process shrinkages. Forming shrinkages were decreased to a negligible level by compression molding, while sintering shrinkage was eliminated by reactive infiltration of molten
silicon.
Effect of Inert Gas Flow Nature on SiC Microtube Synthesis
Authors: Kim Jae Won , Lee Seoung Soo , Park Dong Ho , Jung Yeon Gil , Lee Je Hyun , Jo Chang Yong
Published: March 2009

Silicon carbide (SiC) microtubes with villus-like morphology have been successfully fabricated through a reaction between carbon fiber and SiO gas via the pack cementation process. The effect of gas flow nature (argon and/or hydrogen) on silicon carbide microtube synthesis has been studied. The morphology of the microtubes and the production yield are greatly influenced by the nature of gas flow. Mixed ratio of argon to hydrogen gas has a strong influence on the thickness of the microtubes.
Rare Earth Containing SiAlONS: Microstructure, Mechanical and Tribological Properties
Authors: Holzer Stefan , Häntsche Jan Patrick , Spicher Ulrich , Huchler Bernd , Nagel Alwin , Oberacker Rainer , Badenheim Dirk , Hoffmann Michael J.
Published: March 2009

Silicon nitride based ceramics have been investigated since more than forty years. Nevertheless, a good understanding of the microstructure-properties relationships on the level of small samples is not enough to bring ceramic parts into the industrial market. More convincing is a demonstration of the excellent potential in specific applications where the requirements of a more complex system are considered. In this work, sialons are investigated for a use in lubricated wear applications. The target system is a fuel injection pump for pressures up to 30 MPa. It requires very small friction coefficients and wear rates. Isooctane was used as lubricating liquid. A friction coefficient of 0.3 has been achieved with a piston-on-plate configuration for two sialon ceramics with different a/b-ratios. The sample surfaces were in a ground condition. For comparison, tribological testing was also performed with commercial alumina and silicon nitride materials which exhibited higher friction coefficients. In order to be closer to the real conditions a test rig has been designed and constructed with a piston running in a cylinder that actually pumps isooctane at the desired pressures of up to 30 MPa. With it, the high potential of sialon ceramics for lubricated sliding applications was proven. In the fields of microstructural design neodymia and ytterbia containing sialons with varying a/b-sialon ratios and different amounts of additives have been investigated. These parameters have a strong effect on the achieved aspect ratios of the sialon grains which can be correlated to the amount of liquid phase during sintering, kinetic considerations and the additives' cationic radii. Finally, the effect of these varying grain shapes on the mechanical properties hardness and fracture toughness has been determined.
Biomimetic Application of Hierarchically Ordered Nanoporous Silica Ceramics
Authors: Chang Jeong Ho , Liu Jun
Published: March 2009

This work describes chemically functionalized nanoporous silica as a novel catalyst for the rapid hydrolysis of a phenyl ester. Work demonstrates a very simple and flexible approach to control surface reactivity on the nanometer scale using a self-assembled organic monolayer consisting of polar, (dihydroxyl, carboxyl, ethylene-diamine, and dihydroimidazole), and non-polar (isobutyl) groups. All five functional groups are an essential requirement in preparing an enzymelike catalyst because of the synergistic effect and hydrophobic partitioning, which has been verified by a 13C CP- MAS solid-state NMR technique. Catalytic activities were obtained from the catalytic efficiency constant and specificity constant using Michaelis-Menten kinetics. Catalytic activities were close to those of a natural enzyme when 12% of the surface was covered by hydrophobic isobutyl silane. The rate of enzyme catalyzed activity was dependent on the energy of the transition
state as defined in terms of an energy barrier derived from the relationship between transfer free energy and specificity constant.
Development of EBC for Silicon Nitride
Authors: Ueno Shunkichi , Jayaseelan Daniel Doni , Kondo Naoki , Ohji Tatsuki , Kanzaki Shuzo , Lin Hua Tay
Published: March 2009

Various coating methods of EBC layer for silicon nitride were discussed. High density EBC layer was successfully coated by different techniques such as sputtering, sol-gel and reaction sintering methods. Water vapor corrosion and recession mechanisms of Lu2Si2O7 which is a potential material for EBC were discussed. The problems in the development of EBC revealed by corrosion tests were summarized. The most important problem addressed here was the corrosion of silica at grain boundary. Due to corrosion of silica at the boundary, formation of porous surface is inevitable, then the silicon nitride substrate gets easily oxidized and/or corroded by water vapor. To resolve this issue, we propose a new EBC material without boundary silica and the corrosion mechanism of this improved EBC material is discussed.
Performance of CVD Mullite Coatings on Silicon Nitride under High Temperature High Load Conditions
Authors: Zemskova S.M. , Lin Hua Tay , Ferber Mattison K. , Haynes A.J.
Published: March 2009

Previous studies have demonstrated that dense coatings of CVD mullite (3Al2O3×2SiO2) provide excellent oxidation protection for Si3N4 and SiC in a high pressure, steam environment. In this study the mechanical properties of CVD mullite coated silicon nitride materials from different vendors (AS800, NGKSN88, Kyocera SN281) were evaluated following ASTM test procedures. The dynamic fatigue tests werep erformed in ambient air at temperatures of 850 and 1200°C under fast (30 MPa/s) and slow (0.003 MPa/s) load rates. The static fatigue tests were carried out at a constant load of 350 MPa for 1000h at 1200°C. The cyclic fatiguetests at 850°C consisted of a loading ramp from 20 to 400 MPa in 30 seconds followed by unloading ramp from 400 to 20 MPa. A total of 10,000 cycles were applied to the fatigue test specimens before fast fracture tests were conducted at room temperature. The strength test results indicated that CVD mullite coatings showed excellent adhesion during dynamic fatigue tests and exhibited no creep behavior. Minor flexure strength reduction observed at low stressing rate and at high temperatures appeared to be related to Si3N4 properties such as SCG (slow crack growth) susceptibility. During cyclic and static fatigue tests, a glassy silica/aluminosilicate phase was formed due to oxidation. This resulted in localized coating separation and buckling. However, accumulation of this corrosion layer was not critical since the coated specimens showed a flexure strength increase of ~7-9.5%.
An Implantable Immunosuppressive Cyclosporine Drug Delivery System
Authors: Wang Shen Guo , Cai Qing , Bei Jian Zhong , Shi Wei Yun , Xie Li Xin
Published: March 2009

In the article a kind biodegradable drug carrier (glycolide-co-lactide-co-caprolactone) tricomponent copolymer (PGLC) was synthesized by ring opening copolymerization of glycolide (GA), lactide (LA) and ε-caprolactone (CL), and was used to manufacture an implantable drug preparation---Cyclosporine-PGLC drug delivery system (Cs-PGLC DDS).The Cs could slowly
release from the Cs-PGLC DDS near linearly and last for a long time in vitro. A clinically significant Cs concentration in the cornea and anterior chamber could be achieved by implanting the Cs-PGLC DDS in anterior chamber. It was demonstrated that the Cs-PGLC DDS is a long-effective intraocular immunosuppressive agent for remaining corneal allograft clear and significantly prolong its survival time.
Preparation of Hydroxyapatite-Fibroin Nanocomposites
Authors: Kong X.D. , Wang Xue Min , Yu X. , Cui Fu Zhai
Published: March 2009

Nanocomposites of hydroxyapatite-fibroin (HA-FB) were prepared using the biomimetic process. The Nanocomposites were detected with X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The FTIR results showed that chemical bond forms between HA nanocrystals and fibroin protein. The secondary structure of fibroin can be affected by the mineralization process. TGA results indicated the content of mineralized fibroin in the nanocomposites can be freely adjusted by changing the initial concentration of fibroin solution. TEM image showed that the diameter of the single mineralized nanofibrils is about 2-3 nm and the nanofibrils can aggregate into bundles with the size of 6-8 nm in width and 30-60 nm in length.
A Simple but Effective Demineralizing Method for Osteogenic Allograft Preparation
Authors: Shin Hong In , Ryoo H.M. , Kim Suk Young
Published: March 2009

Bone regeneration with demineralized bone preparations has demonstrated its potential in grafting procedures in surgical disciplines of both medicine and dentistry. To improve the effectiveness in preparation and osteogenic regeneration, we developed a simple and rapid demineralizing method for osteogenic allograft preparation and evaluated its osteogenic effect using an ectopic bone formation assay. The rat diaphyseal cortical bones were demineralized in heated 0.6N HCl at 60° C for 10 to 30 mins using a controlled-heat ultrasonic cleaner, washed with sterilized distill water, and dehydrated with graded alcohol after 30% H2O2 treatment. The prepared grafts were implanted in rat dorsal subcutaneous pouches for 1-3 weeks and then the harvested tissue samples were prepared for routine light microscopic observation. The allografts demineralized with 60°C HCl for more than 20 mins in an ultrasonic condition were completely demineralized and effectively induced ectopic formation without specific pathologic findings. These findings suggest that demineralization with 60°C HCl for around 20 mins using a controlled-heat ultrasonic cleaner and dehydration with graded alcohol after short treatment with 30% H2O2 is a very simple but effective osteogenic allograft preparation method with minimal antigenicity and sterilizing effects.
Fibrin-Reinforced Collagen Matrix Enhances Tissue Regeneration and Angiogenesis
Authors: Seol Dong Lim , Jang Won Hee , Lee Sung Jae , Yang Young Il
Published: March 2009

The goal of this study was to investigate effects of fibrin reinforcement of collagen
sponges on fibroblasts-mediated contraction and in vivo tissue regeneration, especially angiogenesis. Human dermal fibroblasts (HDFs)-populated collagen sponges reinforced with or without fibrin were cultivated via the free-floating method in vitro. They were then evaluated using xenogeneic implantation into nude mice. The HDFs-populated collagen sponges reinforced with fibrin exhibited significantly decreased HDFs-mediated contraction in vitro (p<0.05). Microvascular and cellular densities of the collagen sponges were significantly higher with fibrin than without (p<0.01). Cell ingrowths, neovascularization, and deposition of ECM matrix were more evenly distributed in the fibrin-reinforced collagen matrices. The results demonstrated that fibrin reinforcement of porous collagen sponges can reduce cell-mediated contraction in vitro while enhancing functional integration with surrounding tissue in vivo.
Effect of Rare Earth Y2O3 Content on Microstructure of Gradient Bioceramic Composite Coating Produced by Wide-Band Laser Cladding
Authors: Liu Qi Bin , Zou Long Jiang , Zheng Min , Dong Chuang
Published: March 2009

In the present paper, bioceramic coating with gradient compositional design was prepared on surface of Ti alloy by using wide-band laser cladding. Effect of rare earth Y2O3 content on gradient bioceramic composite coating was studied. The experimental results indicated that adding rare earth can refine grain. Different contents of rare earth affect formation of HA andβ-TCP in bioceramic coating. With increase of rare earth content, HA andβ-TCP were synthesized. When content of rare earth ranged from 0.4% to 0.6%, the active extent of rare earth in synthesizing HA andβ-TCP got best, which indicated that “monosodium glutamate” effect of rare earth played a dominant role. However, when rare earth content was up to 0.8%, the active extent of rare earth in synthesizing HA and β-TCP conversely went down, which demonstrated that rare earth gradually lost its catalysis in manufacturing HA andβ-TCP.
Preparation of Porous Poly (L-Lactic Acid) (PLLA) Scaffold by Porogen Leaching and Freeze Drying
Authors: Dong Y.S. , Guo C. , Lin Ping Hua , Yin L.H. , Pu Yong Ping
Published: March 2009

The poly (L-lactic acid) (PLLA) porous scaffolds were prepared by porogen leaching combined freeze drying with the porogen particulates of ice in this paper. The ice particulates are made of distilled water sprayed into liquid nitrogen through a nozzle under a certain pressure. The pore morphology, porosity and residual porogen of the scaffolds was studied. There is no residual porogen when the ice particulate is used and the leaching mechanism of porogen is discussed. The scaffolds are composed of macro and micro pores and with a porosity of 80-90%. The macro pores are formed by ice particulate and the micro pores by thermal induced phase separation of solvent. The pore size can be changed easily by altering the size of ice particulate. The MTT assay was used to estimate cellular activity by L-929 cells culture in vitro. The results demonstrate that the scaffolds have no cytotoxicity. It could confidently be stated that the combined process seems to be a promising technique for the fabrication of porous polymer scaffold.
A Potent Osteogenic Composite of Stem Cells – Tricalcium Phosphate Ceramic Enhanced the Posterior Spinal Fusion
Authors: Yeung H.Y. , Liu J.Z. , Qin Ling , Hu Yun Yu , Lu Chang Wei , Lee K.M. , Chiu Y.M. , Cheng Jack C.Y.
Published: March 2009

Bone marrow mesenchymal stem cells (BMSCs) possess a high replicative capacity and have the capacity to differentiate into various connective tissue cell types. With the advance in cell culture technique, the BMSCs have been induced to differentiate to osteoblastics linage. To improve the situation of non-union in posterior spinal fusion (PSF), tissue engineering approach to combine BMSCs supported by the calcium phosphate ceramics was applied in PSF and its effect
was investigated in the present study. Autologous BMSCs from 16-week-old rabbit tibiae were expanded and induced to differentiate into osteoblastic cells with defined medium and osteogenic supplement. Calcium phosphate ceramic (CPC) was used as the scaffold to deliver the cells to the standardized rabbit posterior spinal fusion model. The assessment of bone mineral and fusion mass volume was conducted at week 7 post-operation with quantitative computed tomography and
micro-computed tomography. When compared with control, the composite of BMSCs with CPC enhanced the fusion mass volume by 40% (p<0.05) and bone mineral content in the CPC was 7% (p=0.05) higher. Our study showed that additional BMSCs at the fusion site of PSF did provide extra resource for new bone formation and enhanced the fusion rate.
A New Cellular Model for In Vitro Biocompatibility Evaluation of Microcapsule Materials
Authors: Zhang Hua'an , Sun Lin , Wang Wei , Ma Xiao Jun
Published: March 2009

Fibrosis caused by the host response to long-term transplanted microcapsules and the limitation of traditional L929 cell model for biocompatibility testing inspire the development of an assay of biocompatibility based on macrophage behavior. In this paper, the human monocytic cell line THP-1 was utilized for biocompatibility evaluation of microcapsule materials. The cell viability and secretion of nitric oxide (NO) and cytokines served as index of biocompatibility were assayed. It was found that the evaluated microcapsule materials had no effect on the stimulation of NO and cytokines secretion, which meant that these materials were biocompatible. Furthermore, it suggests the THP-1 cell a convenient in vitro experimental model that might be useful for long-term predictions of material biocompatibility.
A Novel Method for Evaluating Compatibility of Hepatocytes with some Kinds of Biomaterials
Authors: Xu Yingxin , Wang Wen Jie , Zhang Yong , Song Xu Hua , Li Li , Wang Jian Jiang , Cui Fu Zhai , Feng Qing Ling
Published: March 2009

To evaluate the biocompatibility of biomedical materials for hepatic tissue engineering, another new method was introduced to observe hepatocytes functions. In this experiment, hepatocytes were seeded onto four kinds of membranes of PLLA, PLGA (90:10), PLGA (75:25), and Chitosan cross-linked with collagen. The culture mediums were collected at 21 day after seeding, and then albumin (Alb), Urea (UN), glucose (Glu), total protein (TP), and triglyceride (TG) in the supernatant were detected by automatic biochemical analyzer. Results showed that hepatocytes on film of Chitosan cross-linked with collagen exhibited the highest level of TP and TG. These results were highly corresponding with the results of morphological observation. This data indicated that analyzing TP and TG in culture medium by automatic biochemical analyzer might be applied to evaluate hepatocytes biocompatibility on materials as a convenient and feasible method.
In Vitro Degradation Studies of Calcium Polyphosphate Ceramics Prepared by Controlled Degree of Polymerization and Crystallization
Authors: Qiu Kai , Wang Chang Xiu , Zhang Qi , Chen Xin , Su Hongfa
Published: March 2009

Porous calcium polyphosphate(CPP) have been shown to promise for tissue engineered implant application. The process from Ca(H2PO4)2 to CPP, as a polycondensation reaction, has been researched to evaluate the number average degree of polymerization. CPP with different degree of polymerization were prepared by controlling the calcining time. Amorphous and different crystalline CPP were prepared by the quenching from the melt and crystallization of amorphous CPP. Two specimens were soaked into citric acid and tris-buffer solution for 1 to 30 days. The weight loss of CPP with different degree of polymerizations and crystal types are different. With the increasing of degree of polymerization, the weight loss during the degradation is decreasing, contrarily the strength of CPP is increasing. The degradation velocity of amorphous CPP, α-CPP,β-CPP and γ-CPP with the same degree of polymerization decreased in turn at the same period. The full weight loss period of CPP can be changed between 17 days and more than 1 year. The degradation and deposition was faster in the citric acid than the tris-buffer solution.
Fretting Damage of Human Cortical Bone in Transverse Orientation against Titanium
Authors: Yu H.Y. , Cai Zhen Bing , Zhou Zhong Rong , Zhu Min Hao
Published: March 2009

Under simulated human physiological solution, the fretting behaviors of flat
cortical bone specimen from fresh human femur in the transverse orientation were
investigated by sliding against pure titanium ball counterpart (tangential fretting technique). The friction coefficients and logs were calculated automatically. The worn surfaces of the cortical bone were analyzed by means of laser confocal scanning microscopy. The results show that the fricion coefficient of cortical bone directly relate with the magnitudes of displacement. The friction logs for cortical bone change with the magnitudes of displacement (Fn=90N) from elastic partial slip (D≤5 µm), plastoelastic partial slip (D=10 µm) to slip (D ≥20 µm) respectively. The fretting damages of cortical bone in the elastic partial slip were slight. But ploughs and delaminations were observed in the plastoelastic partial slip and gross
sliding with loss of contact stiffness of cortical bone. The wear depth increased with cycles and well related to the friction coefficient of cortical bone in each fretting regime. Controlling the displacement amplitude and friction coefficients of bone-implant interface, it might be helpful to increase the anti-fretting capacities of human cortical bone.
Failure Mechanisms in Directionally Solidified Alumina-Titania Composites
Authors: Baudín Carmen , Sayir Ali , Berger Marie Helene
Published: March 2009

The mechanical properties of directionally solidified two-phase eutectics can be superior to that of either constituent alone due to the strong constraining effects of the interlocking microstructure. The present work focuses on the failure mechanisms that occur in Al2O3-Al2TiO5 composites fabricated by directional solidification. Two compositions rich in alumina have been considered. The constituents were the same in both materials, primary Al2O3 dendrites surrounded
by a TiO2-containing phase, with different morphological and size characteristics. The dendrites in the material containing the smallest amount of Al2O3 were short and highly interpenetrated by the secondary phase whereas those of the material with the highest Al2O3 content were long and much less interpenetrated. The mechanical behaviour in bending was determined by these microstructural differences because the load bearing phase in these directionally solidified materials in the system Al2O3-Al2TiO5 are the Al2O3 dendrites.
Thermal Shock Resistance of the RE-Oxide and Oxynitride Glasses
Authors: Lofaj František , Dorčáková Františka
Published: March 2009

Thermal shock resistance of the RE-Si-Mg-O-N glasses (RE = La, Nd, Yb, Lu) with 0 and 20 eq.% of nitrogen was investigated by the indentation-quench method based on propagation of Vickers cracks. Crack growth was measured on the same sample for a test series of different quenching temperatures. Thermal shock resistance of the studied materials was determined as a temperature difference resulting in 10 % growth of the initial cracks (∆T10) and by the thermal shock parameter R calculated from the material properties. Although the comparison of ∆T10 and R values as a function of glass composition revealed some differences between these two approaches, also a common trend was observed. Thermal shock resistance increased with the fractional glass compactness resulting from RE type and N content increase.
Indentation Testing of an Al2O3/Al2O3 + ZrO2 Layered Composite
Authors: Zimovčák Peter , Köves Tibor , Dusza Ján , Pešek Ladislav , Chalvet Francis , de Portu Goffredo
Published: March 2009

Micro- and macro-hardness of the individual layers of an Al2O3 / Al2O3 + ZrO2 layered composite have been investigated. The indentation load size effect has been studied in a range of indentation load of 25 mN – 100 N using depth sensing indentation technique and conventional Vickers hardness testers. Fracture toughness values of the layers have been measured using indentation fracture method. The effect of residual stresses on the KIC value has been analyzed.
Thermal Stresses in SiC-Si3N4 Cubic-Cell-Divided Multi-Particle-Matrix System
Authors: Ceniga L.
Published: March 2009

The paper deals with crack formation of thermal stresses in an isotropic multi-particle-matrix system of homogeneously distributed spherical particles in an infinite matrix divided to cubic cells containing a central particle. Originating during a cooling process as a consequence of the difference in thermal expansion coefficients between a matrix and a particle, the thermal stresses are thus investigated within the cubic cell and extreme at the critical particle volume fraction. Resulting from the derived crack formation condition related to an ideal-brittle particle, the critical particle radius considering the critical particle volume fraction is presented along with an application to the thermalstress- strengthened SiC-Si3N4 ceramics.
Characterization of ELID-Ground Granite Surfaces
Authors: Shen Jian Yun , Lin Wei Min , Ohmori Hitoshi , Xu Xi Peng
Published: March 2009

In the present study, natural granites were ELID ground with metal-resin bonded diamond wheels on a lap-grinding machine to achieve smooth surface. The surface roughness during the grinding process and final glossiness were examined to describe the formation of finely finished granite surfaces. According to the detailed micro-observation of ground surfaces, it can be concluded that natural granite surface on the main mineral components can be smoothly finished with ELID lap
grinding. However, the appearance of natural defects and residual fracture on the ground surface lead to the scattered surface roughness, and restrict the improvement of surface glossiness.
Dressing Monitoring by Acoustic Emission
Authors: Denkena Berend , Jacobsen J. , Kramer Niklas
Published: March 2009

In modern grinding processes the field of application for vitrified bonded wheels is constantly increasing. Regarding the grinding itself, the advantages of these wheels are obvious. But their ability to be dressed offers further benefits as well. Usually in-machine dressing is favorable. Nevertheless, in-machine dressing causes non-productive-times during which no part production is possible. To reduce this disadvantage, a powerful monitoring is needed in order to minimize the number of needed dressing strokes and to verify the created grinding wheel geometry. The approach applicable for industry is to use an acoustic emission sensor for monitoring, which is usually integrated in modern grinding machines to minimize the air grinding time. This article also provides basic knowledge about Acoustic Emission.
Effects of TiH2 on the Properties of Fe-Based Diamond Composites
Authors: Dai Qiu Lian , Xu Xi Peng
Published: March 2009

Effects of TiH2 on the mechanical properties and microstructures of Fe-based diamond composites as well as the performance of diamond segments in circular sawing of granites are presented in this paper. Experimental results reveal that the addition of 2%TiH2 into the Fe-based matrix leads to decreases in the mechanical properties of both matrix and diamond composites. The wear resistance of the saw-blade segments decreases by 7.3%. Microscope observations reveal that the specimen without TiH2 shows fewer pores and denser structures in the base matrix. The fracture surfaces of the bending test specimens exhibit ductile cup and cone behavior and strong bonding between the matrix and diamond. SEM micrographs indicate that there are much more pull-outs of diamond grits, much more serious wear of diamond particles and erosion of metal matrix on the worn surface of saw-blades segments with 2% TiH2 in the matrix.
Characterization of the Magnetic Abrasive Finishing Method and Its Application to Deburring
Authors: Baron Yuri M. , Ko S.L. , Park Jung Il
Published: March 2009

This paper analyzes the effectiveness of using Magnetic Abrasive Finishing (MAF) to remove burrs on drilled holes located on planes. Basic elements of the equipment in this method are a magnetic inductor; powder with magnetic and abrasive properties, which serves as the cutting tool; and the face electromagnetic inductor and the vibrating table, which were developed for deburring and finishing on flat surfaces. The performance of magnetic abrasive powders produced by industry is also evaluated. A new technique was developed to compare the performance of the magnetic abrasive powders and to find the powder that is appropriate for finishing and deburring drilled holes placed on a plane steel surface.
Time Series Analysis for the Mechanical Lapping of Single Crystal Diamond Cutting Tools
Authors: Zong Wen Jun , Li Dan , Wang H.X. , Sun T. , Cheng K. , Chen Ming Jun
Published: March 2009

In order to avoid the stochastic damage of micro cleavage on cutting edge, a brittle-ductile transition lapping mechanism is proposed for the mechanical lapping of single crystal diamond cutting tools to direct the tools lapping. As expected, the critical depths of cut for brittle-ductile transition in different orientations and on different crystal planes are calculated. According to the theoretical results, the actual dynamic depth of cut is controlled within the critical depth of cut, which ensures that the tool lapping is carried out in ductile regime and the changes of cutting edge radius
characterize with some specific time laws in lapping. Therefore, the time series and nonlinear least square methods are used to analyze the changing laws of cutting edge radius. As a result, a coupled model to build a bridge between the cutting edge radius changes and lapping time is developed. In terms of this developed model, a required cutting edge radius restricts a tool’s lapping time. Above all, the cutting edge radius is known in advance and has no needs measuring. So the production
efficiency of diamond cutting tools is improved and its production cost is reduced accordingly.
Ultra-Precision Finishing of Micro Aspherical Surface by Ultrasonic Vibration Assisted Polishing
Authors: Suzuki H. , Kawamori R. , Miyabara M. , Okino T. , Hijikata Yasuto , Yamamoto Y. , Nakamoto K. , Moriwaki T. , Shibutani H.
Published: March 2009

Micro axis-symmetric aspherical glass lenses are being increasingly used in digital devices and optical devices. The glass lenses are molded by using micro ceramic dies such as tungsten carbide [1].Recently, as the pixel number of digital image sensors increases, the accuracy of micro molding dies are required to be much more precise than ever [2]. In this study, ultrasonic assisted polishing method is proposed and developed in order to finish micro axis-symmetric aspherical dies which were pre-ground with a diamond wheel [3]. In this paper, the proposed polishing method was applied to the micro aspherical molding dies to finish form compensation processing.
Characteristics of High Rotational Speed Polishing with Oscillation Speed Control
Authors: Yoshitomi Kenichiro , Une Atsunobu , Mochida Masaaki
Published: March 2009

The miniaturization of semiconductor devices is advancing rapidly. The requirement for wafer flatness is becoming increasingly stringent as the use of shorter wavelengths in the latest laser lithography results in a smaller focusing depth of field. In our research, a flatness of 0.1 µm has been achieved over an entire 12" wafer surface by planarization with oscillation speed control type polishing. However, in addition it is necessary to increase the removal rate in order to reduce the polishing time. Although high rotational speed polishing is a solution to meet this requirement, the polishing characteristics change with the rotational conditions. Using a simulation program, we calculated that the stock removal saturates as the rotational speeds of the wafer and polishing pad are increased beyond a certain point. Also, experimental results showed that at high rotational speeds actual stock removal is significantly less than that indicated by the simulation, and that too much slurry causes unnecessary etching.
Investigation of Chemical Mechanical Polishing of GaAs Wafer by the Effect of a Photocatalyst
Authors: Hong S.H. , Isii H. , Touge Mutsumi , Watanabe Junji
Published: March 2009

The GaAs wafer is widely applied to semiconductor element related to telecommunication and semiconductor laser. In this research, novel fine polishing technology of GaAs wafer was investigated using TiO2-H2O2-H2O slurry system instead of NaOCl which is conventionally used as polishing slurry. And then the ultraviolet ray was applied in order to investigate the effect of TiO2 photocatalyst. The polishing characteristics were estimated by optical microscope and WYKO optical profiler. It was found that the slurry system was available for GaAs wafer polishing although the polishing rate was lower than NaOCl. Moreover, the effect of the photocatalyst of TiO2 including in slurry was investigated. In this polishing system, the effect of the photocatalyst on GaAs wafer CMP mechanism has not been confirmed yet.
Dynamic Analysis of a Biglide Parallel Grinder
Authors: Zou Ping
Published: March 2009

In this paper, the moving platform of the biglide parallel grinder with six degrees of
freedom will keep moving horizontally at any time using parallelograms. Besides grinding the helical drill point, this grinder also can work as drilling and welding machine tool as well as a CMM. The joint-velocity Jacobian matrix is calculated. Moreover, the dynamic equations are derived by applying the Lagrangian formulation.
Development of Shrinking Tool Holder Utilizing of Shape Memory Alloy
Authors: Kitajima Koichi , Sogabe H. , Hiromi M.
Published: March 2009

This paper investigates how to use shape memory alloy (SMA, Ni-Ti alloy) as a method of chucking parts. It is because tool holder can be simplified and miniaturized. SMA cannot be utilized as chucking tool because it is one-way direction, but it is possible to shrink and release a tool by changing temperature in case SMA is made of combing cylinder with alloy tool steel (SKD61 in JIS). In this report, prototype shrinking tool holder that used combing cylinder with SMA was developed and tried milling processes. As a result, it is clear that combing cylinder with SMA can endure cutting force.