bluuebunny/crossref_metadata_2025 huggingface dataset:
Porous Silk Fibroin Membrane as a Potential Scaffold for Bone Regeneration
Authors: Weska Raquel Farias , Nogueira Grínia M. , Vieira Wellington C. , Beppu Marisa Masumi
Published: March 2009

The requirements for scaffolds for bone tissue engineering include appropriate chemistry, morphology and structure to promote cell adhesion and synthesis of new bone matrix. Silk fibroin (SF) represents an important biomaterial for biomedical application, due to its suitable mechanical properties, biodegradability, biocompatibility, and versatility in processing. Our group has developed a new method to obtain a porous SF membrane, and the study of its potential for use as a scaffold for bone regeneration was the aim of this study. Porous membranes were obtained from SF solution, through the compression of a material generated by phase separation. For in vitro calcification experiments, porous SF membrane samples were immersed in SBF at pH 7.4 placed in polyethylene flasks. The experiments were carried out for seven days, at 36.5±0.5 °C. After 48 and 96h, the solutions were changed for fresh SBF with the ion concentration 1.5-fold higher than that of the standard one, to accelerate the calcification process. The characterization of morphology and composition of samples was performed by using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The SEM micrographs indicated that the porous SF membranes presented calcium phosphate deposits after undergoing in vitro calcification. These results were confirmed by EDS spectra, which showed a stoichiometric molar Ca/P ratio ranging from 1.27 to 1.52. This fact may suggest that calcification deposits consisted of mixtures of HAP (Ca/P ratio = 1.67) and transient HAP precursor phases, such as octacalcium phosphate (Ca/P = 1.33) and dicalcium phosphate dehydrate (Ca/P = 1), indicating early stage mineralization. The porous silk fibroin membrane analysed in the current study is a promising material to be used as scaffolds for bone regeneration.
Hydroxyapatite Nucleation on Modified Silicon Surface for Use in Biosensors
Authors: de Oliveira Vercik Luci Cristina , Rigo E.C.S. , Vercik A.
Published: March 2009

In this work, we explore the deposition of single-phase and uniform HA coatings on a crystalline silicon surface of microelectronic quality. The used methodology includes an NaOH treatment to produce the silanization of Si surface and a modified biomimetic technique, using sodium silicate solution (SS) as nucleant agent, for apatite-based coating formation. The sodium silicate solution (SS) demonstrated to be effective for the calcium phosphate layer formation, but the treatment can reduce the induction to obtain a uniform surface coating of HA. This suggests that, among the factors that determine nucleation of calcium phosphate on silicon, surface electrical charge could play a key role.
Morphological Study of Apatite Formation on NaOH- and Heat-Treated Titanium Metal
Authors: Yamaguchi Seiji , Takadama Hiroaki , Matsushita Tomiharu , Nakamura Takashi , Kokubo Tadashi
Published: March 2009

Surface structural change of titanium metal with NaOH and heat treatments and the subsequent soaking in a simulated body fluid (SBF) was investigated by observing cross section of its surface layer by scanning electron microscope. A layer of lathlike phase of sodium hydrogen titanate was formed on the surface of the titanium metal 1 µm in thickness by the NaOH treatment. This was transformed into a layer of lathlike form a little densified of sodium titanate and rutile by the subsequent heat treatment. In SBF, apatite started to precipitate in the interior of the surface lathlike layer, filled the interspaces of the lathlike phases and grew over the surface. This integration of the apatite with the surface lathlike layer might be responsible for the strong bonding of the titanium metal to the living bone.
Biocompatibility and Osteo-Differentiation Study of Poly(ε-Caprolactone) and β-Tricalcium Phosphate Composite Membranes
Authors: Salgado C.L. , Solomão Zenaide , Silva Priscilla B. , Sanchez Elisabete M.S. , Zavaglia Cecília A.C.
Published: March 2009

The Tissue Engineering appears with a modern proposal for the treatment of damages or diseases. The study of materials and methods for tissues and organs regeneration by the patient cells culture had been developed on the last years but still couldn’t be used for all different tissues. In this multidisciplinary research field, the present work joins the biodegradability of poly(ε-caprolactone) (PCL) with the osteoconductive properties of β-tricalcium phosphate (β-TCP) in order to create a composite which acts as a temporary support for cell culture without a second surgery to remove the biomaterial. This work evaluates three membranes types, obtained by casting in chloroform, on the biocompatibility and differentiation on mesenquimal stem cells (hMSC). These analyses showed cell viability with the rezasurin method and the alkaline phosphatase activity (ALP). DMA analyses, MEV and OPM were performed.
Effect of Storage Conditions on Biaxial Flexure Strengths of MTA
Authors: Sato Hideo , Kubota Naoko , Ban Seiji , Yamasaki Youichi
Published: March 2009

The aim of this study was to determine the biaxial flexure strength of a commercially available dental pulp capping or cavity liner material, mineral trioxide aggregate (MTA). MTA and a conventional pulp capping material, calcium hydroxide, were used in this study. Each material was prepared into a disk-shaped specimen. Those specimens were stored in 100% humidity atmosphere at 23 or 37°C for 3 or 24 h. Six specimens in each condition were used for the biaxial flexure test using a piston-on-three-ball according to ISO-6872. Surface pH values were determined. The biaxial flexure strengths of MTA after setting in 24h were larger than those of Dycal (p <0.01). pH value of MTA was higher than that of Dycal. These results indicated that MTA was clinically usage material.
Resorbable Mesh Based on Calcium Alginate for Bone Reconstruction Surgical Technologies
Authors: Daculsi G. , Aguado Eric , Moreau Françoise , Goyenvalle Eric
Published: March 2009

Current resorbable membranes are generally from animal origin, like collagen, and are largely used in dentistry or orthopaedic for TGR (Tissue Guided Regeneration), in neurosurgery for Dura matter healing and others. Calcium alginates are generally used for wound dressing (external uses). The purpose of this study was to evaluate the osteogenic property of meshes realized with calcium alginate fibers. Membrane meshes were implanted in critical size defect of rabbit femoral epiphysis during 3 and 6 weeks. Micro CT and histological analysis demonstrated biocompatibility of calcium alginate meshes in bony area. Calcium alginate meshes have no osteogenic and osteoconductive properties, however calcium alginate meshes could be a good candidate for replacement of dacron balloon used in vertebroplasty.
The Effects of Hydroxyapatite on Demineralization Resistance and Bonding Strength in Light-Curing Glass Ionomer Dental Cement
Authors: Kim J.H. , Lee Yong Keun , Choi B.J. , Son H.K. , Lee Jae Hoon , Kim S.O. , Song J.S. , Choi H.J.
Published: March 2009

he aim of this study was to evaluate the effect of HA on the demineralization resistance and bonding strength of light-curing glass ionomer dental cement. Tests were conducted using (1) pure Fuji II LC GIC, (2) 15% micro HA-Fuji II LC GIC. Physical properties, demineralization resistance and bonding strength to dentin of teeth were determined. The curing depth in all groups were satisfied the requirement of curing depth of ISO 9917-2:2004(minimum curing depth = 1mm). The depth of cure was reduced with addition of HA, presumably due to the light scattering effect of HA particles. Regarding sensitivity to ambient light, there were no detectable changes of the homogeneity in any groups. Also all groups were satisfied the requirement of the flexural strength of ISO 9917-2:2004(minimum flexural strength = 20MPa). 15% HA-Fuji II LC GIC group was found to present a greater flexural strength than pure Fuji II LC GIC, as the addition of HA promotes a chemical reaction between the HA, the glass powder, and the polyacid. Observing under the CLSM after 4 days of demineralization, there were significant differences in the CLSM and SEM images. Pure Fuji II LC GIC group showed greater enamel demineralization layer than in 15% HA-Fuji II LC GIC group. In SEM analysis, there was greater enamel demineralization in the pure Fuji II LC GIC group, and less demineralized under the influence of HA particles, 15% HA-Fuji II LC GIC group had more even surface particles. 15% HA-Fuji II LC GIC group was found to present a greater bonding strength than pure Fuji II LC GIC group. Observing the fractured surfaces under SEM after the bonding strength test, the cohesive failure rate was found to be in increasing order of pure Fuji II LC GIC, 15% HA-Fuji II LC GIC group. There were bone-like apatite particles observed to be formed in 15% HA-Fuji II LC GIC group.
Whisker-Like Hydroxyapatite Synthesized by Molten Salt Synthesis (MSS) of Nano-Hydroxyapatite in a KCl/NaCl Flux
Authors: Ramos S.L.F. , Motisuke M. , Rodrigues L.R. , Zavaglia Cecília A.C.
Published: March 2009

A lot of attention has been given to bone cements due to their lack of mechanical properties. The improvement of this property is essential, once it makes possible the usage of these biomaterials in sites that require a significant mechanical strength resistance. To do so, reinforcement agents, such as fibers, in particular biocompatible fibers, have been synthesized [1]. This study reports the synthesis of stequiometric Hydroxyapatite whisker-like fibers utilizing the Molten Salt Synthesis process of nanometric Hydroxyapatite with a salt flux mixture of KCl/NaCl. According to SEM images, EDS analysis and X-ray diffraction, the fibers obtained presented well defined and elongated (main length of about 70µm) hexagonal morphology with Ca/P ratio of 1.66.
Comparison of Calcium CPP, HAp and TeCP Phosphates, Obtained by Direct Reaction
Authors: de Oliveira Sara Verusca , Fook Marcus Vinícius Lia , Araújo Elaine Patrícia , Fook A.C.B.M. , Lima R.S.C. , Barbosa W.P.F.
Published: March 2009

In bioscience, there are several apatites constituteds by differents compositions. In the biological environment, apatites are found in bones and teeth of vertebrates with Ca/P ration from 2.0 to 0.5. It is not easy to determine the exact proportion of Ca2 + and PO43- in solution in the preparation of the process. In this study, apatites with Ca/P ration 1.0, 1.67 and 2.0 were prepared by direct reaction in an solution of H3PO4 in a suspension of Ca(OH)2, of same molarity, evalueting the crystallinity of CPP, Hap e TeCP with 1 mol/l, 3 mol/l and 5 mol/l. The samples characterized by X-ray diffraction (XRD) were compared with the standard of reference of the data base JCPDS. The composition of calcium phosphate for the differents molarity studied, resulted in a combination of phases with the exception of hydroxyapatite Ca/P ration 1.67 at concentrations 1 mol/l and 3 mol/l. But the diffractograms revealed that the increased molarity provided a decrease of some peaks of reflection of calcium phosphates with Ca/P ration 1.67. However, for the Ca/P ration 1.0 increasing the concentration, showed an increase of crystallinity of calcium phosphates. The FTIR confirmed the presence of phosphates in the spectrums around 1045 cm-1. The calcium phosphates obtained through direct reaction showed Ca/P ration is related with the technique employed, consolidating it in the preparation of these bioceramics.
Calcium Phosphate Porous Materials with Unique Microstructures
Authors: Ioku Koji , Kamitakahara Masanobu , Watanabe Noriaki , Kawaguchi Osamu , Murakami Setsuaki , Ikeda Tohru
Published: March 2009

Three types of calcium phosphate porous materials were prepared by the applied hydrothermal method. One of them was non-stoichiometric hydroxyapatite (HA) with calcium deficient composition and the others were β-tricalcium phosphate (β-TCP) and HA/β-TCP bi-phase material. Granules with several millimeter in size of calcium deficient HA, β-TCP and HA/β-TCP could be prepared. These granules with porosity over 70 % were composed of rod-shaped particles with aspect ratio about 10. Rod-shaped particles were locked together to make sub-micro-sized pores of about 0.1 to 0.5 µm in size. These materials must be suitable for the bone graft materials and as the scaffolds of cultured bone.
Evaluation and Biocompatibility of a New Type of Scaffold for Tissue Growth Based on Calcium Phosphate Cement
Authors: de Moraes Machado Jéferson Luis , Santos Luis Alberto
Published: March 2009

Growth of cells in three-dimensional porous scaffolds has gaining importance in the field of tissue engineering. The scaffolds guide cellular growth, synthesize extra-cellular matrix and other biological molecules, and make the formation of tissues and functional organs easier. The aim of this work was to use α-TCP (α-tricalcium phosphate) cement in order to obtain such scaffolds, with the aid of paraffin spheres as pores generators. These spheres were produced by suspension in an aqueous solution of polyvinylalcohol (PVA) and sodium sulphate (Na2SO4). The porosity of the scaffolds produced with paraffin spheres was analyzed and compared to the literature, and the study of scaffolds permeability using Forchenheimer equation allowed the analysis of pores interconnectivity. In vitro tests showed the behavior of scaffolds in solutions of SBF (Simulated Body Fluid), and viability and cell proliferation were also evaluated. Use of paraffin spheres showed to be appropriate to the formation of pores suitable size to allow cellular growth.
Performance Evaluation of Hydroxyapatite Coatings Thermally Sprayed on Surgical Fixation Pins
Authors: Rocha Alves Heleno , Wagner N.S. , Branco Jose R.T.
Published: March 2009

Today, in the period of one year, in Brazil and throughout world, hundreds of thousands of surgical implants, both permanent and temporary, are carried out with a high cost for the patients, especially those of SUS – Sistema Único de Saúde. In addition, the SUS costs for treatment of infections that appear as a result of introduction of an implant into the human body create expenses about three times greater than the use of implants coated with biomaterials. Hydroxyapatite (HA) constitutes the base of one important group of biomaterials with excellent implant characteristics. Hydroxyapatite has been extensively studied, but the adherence relationship at the coating/substrate interface is not yet well understood. The coatings in this study were produced using substrates of AISI 316L stainless steel shaped as external fixation pins, with HA applied by a high energy plasma spray gun (HEP). The coating thicknesses were between 15µm and 98µm. The mechanical evaluation of coating adhesion was conducted by scratch testing with progressive loads. Results show an increase of failure load with an increase in thickness. The clinical evaluation was carried out in the Trauma and Orthopedics Sector of the Baleia Hospital, and shows a significant decrease in inflammatory response in the human body.
Preparation and Characterization of Porous Scaffolds Consisted of Hydroxyapatite, Polysaccharides and Collagen for Cartilage Tissue Engineering
Authors: Adegawa Takuro , Ohyabu Yoshimi , Uemura Toshimasa , Yoshioka Tomohiko , Shinozaki Kazuo , Tanaka M.
Published: March 2009

Porous scaffolds, consisted of hydroxyapatite (HAp), chondroitinsulfate (ChS) and collagen, were prepared by freeze-drying technique. HAp/ChS composite particles were incorporated into a collagen matrix. Scanning electron microscope (SEM) observations showed that the porous scaffolds involved interconnected pores whose size was 80~200 µm in diameter. The HAp/ChS particles were homogeneously distributed in the collagen matrix. Surface area of the scaffolds was increased by the incorporation of the particles. Compression tests in phosphate buffer saline indicated that the porous scaffolds had elastic property and had larger compressive modulus than the pure collagen scaffold. The porous scaffolds obtained in this study could be useful for a cartilage tissue engineering.
Zinc Substituted Hydroxyapatite – A Comparison of Modelling and Experimental Data
Authors: Chappell Helen , Shepherd David , Best Serena
Published: March 2009

The effect of substitution of zinc into the hydroxyapatite lattice(ZnHA) was evaluated using experimental precipitation studies and with ab initio modelling data. When attempting to introduce zinc into the hydroxyapatite (HA) lattice not all of the zinc is substituted and ICP confirms its presence in the supernatant. Modelling suggests that this is likely to be because of the high formation energy introducing zinc into the pure hydroxyapatite lattice, 4.6 - 4.9eV. In the experimental study it was found that a maximum of 0.61wt% zinc could be substituted into the HA lattice at 10oC with less being substituted at room temperature »22oC. Experimental measurements revealed that the presence of zinc in the lattice decreased the a-lattice parameter and increased the c-lattice parameter. Modelling showed that this was likely to be caused by the movement of the hydroxyl ions away from the c-axis, towards the zinc atoms which were substituted in calcium type II positions. The type II position was shown to be the most stable substitution site.
Protein Adsorption on Nanohydroxyapatites: Spectroscopic Investigations at Molecular Level
Authors: Bertinetti Luca , Ceschino Raffaella , Bollati Daniele , Landi Elena , Tampieri Anna , Martra Gianmario
Published: March 2009

Proper thermal treatments allowed to modify the number of surface Ca2+ able to coordinate water molecules on the surface of hydroxyapatite (HA) nanoparticles surrounded by an amorphous layer. Despite the consequent significant difference in the first hydration level between untreated and treated HA, the amount of adsorbed BSA, used as a model protein, remained essentially unchanged and the native structure of adsorbed protein was retained (as indicated by mid-IR ATR). Near-IR spectroscopy evidenced that adsorbed proteins should be in direct contact with surface Ca2+ through a displacement of H2O molecules by charged acidic residues. In agreement with a previous study that evidenced the heterogeneity of surface Ca2+ ions in terms of Lewis acidity, it was then proposed that the adsorption of BSA on such nano-HA should be ruled by some feature of the local structure of surface Ca2+ sites, prevailing on the total number of cationic sites exposed and the related features of the first hydration layer.
Evaluation of Interlaminar Damage and Crack Propagation through Digital Image Correlation Method
Authors: Constantinescu Dan Mihai , Sandu Marin , Marsavina Liviu , Negru Radu , Miron Matei Constantin , Apostol Dragos Alexandru
Published: March 2009

Interface damage characterization and interlaminar failure of sandwich specimens with two initial interlaminar defects (inserts) is done by using the digital image correlation method. Mode I tests reveal interesting particularities on damage localization and unstable crack propagation. After analyzing the experimentally obtained results, we propose as a failure parameter the local strain at the crack tip or, alternatively, the crack tip opening displacement which quantifies the non-linear phenomena.
Experimental and Numerical Analysis of Buckling Behaviour of the Ship Plates Made of Composite Materials
Authors: Beznea Elena Felicia , Chirica Ionel , Chirica Raluca
Published: March 2009

In this paper, results obtained on buckling behavior of ship deck plates made of composite materials are presented. The fabrication technologies used in ship structures made of composite materials are mostly based on the hand made. So, the probability to occur material imperfections is too high. The influence of the imperfections on the buckling characteristics of the panels is analyzed. The results obtained so by numerical and by experimental analysis of the composite plates with initial transversal imperfections are compared with the results obtained for the plates made of steel, having the same type of imperfections.
Mathematical Modelling of the Crack Propagation in Wood Materials
Authors: Craciun Eduard Marius , Sadowski Tomasz
Published: March 2009

In this paper we study the behaviour of a Mode I crack in a pre-stressed wood composite material. A mathematical model is associated to the mechanical problem. Starting from the boundary, constitutive and far field conditions we obtain the representation of the incremental displacement, stress and strain fields using two complex potentials. Using numerical analysis we determine the critical value, which causes crack propagation and the direction of crack propagation in a particular case of a Pine wood composite.
Experimental Assessment by Finite Elements Method of the Residual Stress State and of the Heat Flow from the Laser Weldings of the Alloys of CoCrMo Used in RPD (Removable Partial Dentures) Technology
Authors: Bortun Cristina , Faur Nicolae , Cernescu Anghel , Sandu Liliana
Published: March 2009

The welded joints are used in the technology of the removable partial dentures for the rehabilitation of their metal component. The welding procedure and the adequate equipment are established according to the components dimension, the quality of the alloys used and the dentures section. The modifications within the welded structures can be investigated by means of non-destructive tests such as the radiography or the analysis with finite elements. The work was based on the experimental checking of the optimal procedures of welded joint of the alloys of CoCrMo in order to increase their durability. The welded joints were performed in a butt joint configuration with addition of material on the alloys of CoCrMo used in the technology of the framed dentures. The finite elements method was used (software Solid works 2007) in order to simulate the welding process (thermal analysis) and to assess the residual stress areas appeared after the various welding procedures.
Fatigue Crack Growth under Variable Amplitude Loadings: A Theoretical Study
Authors: Dumitru Ion , Cernescu Anghel
Published: March 2009

The purpose of this study was making evident the overload effect in a spectre with constant amplitude cycles. The crack growth simulation was made on cracked specimen and was studied for four loading cases. Fatigue crack growth rate was calculated applying NASGRO equation and the crack growth retardation analyzed.
Bulk Amorphous Soft Magnetic Iron Based Alloy with Mechanical Strength and Corrosion Resistance
Authors: Şerban Viorel Aurel , Codrean Cosmin , Uţu Ion Dragoş
Published: March 2009

The paper makes a review about the opportunity, forming conditions and obtaining methods of bulk amorphous alloys and their properties. There are also presented the experiments regarding the obtaining and characterization from mechanical and chemical point of view of some alloys from Fe70 (Cr5-x Nix)5 Ga4 P13 Si5 C3 ( x = 0,1,2,4) family, pointing out the negative effect of the nickel on their resistance characteristics.
Analytical Model for Corrosion Penetration Depth at Cover Cracking in RC Structures
Authors: Song Hua , Niu Di Tao , Liu Si Yuan
Published: March 2009

Corrosion products which occupy much greater volume accumulate, and generate expansive pressures on the surrounding concrete. The pressure builds up and eventually leads to the cover cracking of the structures. The cracking accelerates further corrosion and leads to the loss of the bond strength and the load carrying capacity. Corrosion cracking would reveal the reducing of the residual service life of the corrosion-affected structures. In this paper, an analytical model is proposed to predict the critical corrosion penetration at cover cracking in RC structures based on the crack process. An attempt has been made to develop the model by considering material properties of the surrounding concrete and expansive corrosion products. The problem is established as a boundary-value problem and the governing equations are expressed in terms of the radial displacement. The analytical predictions of the proposed model have also been in agreement with the available experimental data.
Study on Stressed Performance of the Transfer Truss after Deviation of Diagonal Web Member
Authors: Li Feng Wu , Fan Yun Lei , Chen Da Chuan , Zou Yin Sheng
Published: March 2009

Based on the analysis of internal force and stress of the truss after diagonal web member deviated in vierendeel truss type transfer story in a tall building, influence on the truss after diagonal web member deviated and suggestion of reinforcement are introduced. After reinforcement, this building has been put into use. Based on the observation of the transfer story in this building after use, it is found that the transformation satisfies applying requirements and no crack occurs.
Sensitivity Study of RC Columns’ Reliability to Random Parameters
Authors: Ma De Yun , Zuo Yong Zhi , Huo Da , Teng Hai Wen
Published: March 2009

The value of sensitive factors in structural reliability analysis greatly affects reliability calculation results. These factors must be accurately determined and studied to improve the accuracy of calculated results. Based on the analysis of existing sensitivity calculation methods, a new practical sensitive factor analysis method was put forward to analyzing sensitive factors in structural strength reliability calculations. The dimensionless sensitive indexes of structural reliability were defined in the new method to compare the influence degree of random parameters to reliability. And the method was applied to analyze sensitivity under the two conditions of the structural resistance decreasing and not changing with time. Random variables, defined by their probability distribution and corresponding distribution parameters, were used to describe uncertainties in the reliability calculation. Different forced state RC columns were taken as examples to analyze the structural sensitivity, and sensitive factors affecting the columns’ structural reliability were obtained. The results show that the reliability of time-varying structure has descended to some extent compared with that without time-varying structure, and the effect from the random parameters to reliability index. The example and theory demonstrate the feasibility and rationality of the new method. This article has certain reference value to the structural design, construction and detection.
Elasto-Plastic Analysis of Concrete-Filled Circular Steel Tubular Stub Columns after Exposed to High Temperatures
Authors: Ding Fa Xing , Yu Zhi Wu , Ou Jin Ping
Published: March 2009

Based on the research achievements of the mechanical properties of concrete at uniaxial compression and steel at uniaxial tension after exposed to high temperatures, the axisymmetric- triaxial-compressive stress-strain relationships of concrete and multiaxial stress-strain relationships of steel after exposed to high temperatures was suggested. Based on continuum mechanics, the mechanical model of concentric cylinders of circular steel tube with concrete core of entire section loaded after exposed to high temperature was determined. By applying Elasto-Plastic Analysis Method, theoretical calculation formulas for composite elastic modulus and composite stress-strain relationships of concrete-filled circular steel tubular (CFST) stub columns were proposed and a FORTRAN program was developed and the load-axial strain relationships of CFST stub columns after exposed to high temperatures were analyzed. The analysis results were in reasonable agreement with the experiment ones from references.
Experimental Study and FEM Analysis of Seismic Behavior of Joints for Frame Structures Comprised of Precast Prestressed Concrete Components
Authors: Cai Jian Guo , Feng Jian , Zhu Hong Jin , Liu Ya Fei , Huang Li Feng
Published: March 2009

An experimental investigation was undertaken into the seismic performance of a precast prestressed concrete frame system. A total of three beam-to-column connection models were designed, built, and tested to failure to evaluate their strength and ductility properties under cyclic loading. The comparative study showed that the hysteretic loops were full and the joints had better energy dissipation capacity. It was concluded that satisfactory seismic performance could be expected from this frame system if the slip of the U-shaped reinforcing steel bar was controlled well on the zone of joint. Then the finite element method (FEM) was used to analyze the specimen and the calculation results were in good agreement with those of the test.
A New Route of Forming Silicon Carbide Nanostructures with Controlled Morphologies
Authors: Cheng Yi Bing , Wang Kun , Wang Huan Ting
Published: March 2009

Mesoporous silica-carbon nanocomposites (C-SiO2) were synthesized and used as a host carrier in carbothermal reduction to fabricate highly crystalline silicon carbide nanoparticles and nanofibers. SiC nuclei were introduced into the mesopores as seeds by infiltration of preceramic precursor polycarbosilane (PCS) prior to the heat-treatment of carbothermal reduction. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption analysis were used to characterize C-SiO2 nanocomposites and SiC products. Crystalline SiC was not formed in the mesoporous C-SiO2 nanocomposites with a low carbon content (e.g. C/SiO2 ratio = 1.01) at 1450 °C. However, when a given amount of PCS was infiltrated into the mesoporous C-SiO2, SiC nanofibers and nanoparticles were produced at 1450 °C even in the low carbon content sample. The major morphology formed from the mesoporous C-SiO2 nanocomposites without PCS infiltration was nanoparticles, while nanofibers dominated in the products of the PCS infiltrated compositions. The results indicate that the conversion of PCS into SiC nuclei in mesopores prior to carbothermal reduction has facilitated the formation of SiC nanofibers. Therefore infiltration of seeds into mesopores of C-SiO2 precursors appears to be an effective means in accelerating the reaction and controlling of nanostructures of silicon carbide.
Sintering Shrinkage Behavior of Si3N4 Ceramics Prepared by a Post-Reaction Sintering Technique
Authors: Yabuki Hiromasa , Wakihara Toru , Tatami Junichi , Komeya Katsutoshi , Meguro Takeshi , Kita Hideki , Kondo Naoki , Hirao Kiyoshi
Published: March 2009

Post-reaction sintering is one of the fabrication processes of Si3N4 ceramics, which has received considerable attention as a cost-effective process due to the use inexpensive Si powder as a raw material. So far, many researches on the development of this method have been performed in order to improve their properties; however, the sintering shrinkage behavior, which is valuable for the optimization of the firing conditions, has not been well clarified. In this study, we focus on the post-reaction sintering of the Si-Y2O3-Al2O3 system, and investigate its sintering shrinkage behavior by dilatometery. It was found that there is no shrinkage from 1400 to 1600 °C due to grain rearrangements in the green body of the reaction-bonded Si3N4. Furthermore, the shrinkage of the reaction-bonded Si3N4 commenced at approximately 1750 °C, which is higher than the shrinkage temperature of the green body of conventional Si3N4 powder. The restriction of the shrinkage appears to result from the neck growth and strong aggregation among the reacted Si3N4 particles.
Fabrication and Evaluation of AlN–SiC Solid Solutions with p-Type Electrical Conduction
Authors: Kobayashi Ryota , Tatami Junichi , Wakihara Toru , Komeya Katsutoshi , Meguro Takeshi , Tu Rong , Goto Takashi
Published: March 2009

AlN–SiC solid solutions with p-type electrical conduction were fabricated with the addition of small amounts of Al and C. Powder mixtures of AlN and SiC with small amounts of Al and C (below 10 mol%) were consolidated by spark plasma sintering (SPS) at 2000°C for 10 min under 1 atm Ar, and then heat-treated at 2200°C for 3 h in an Ar flow to afford 2H AlN–SiC solid solutions. The relative densities of the 50AlN-50SiC-Al4C3 (A50-1AC) and 50AlN-50SiC-3Al4C3 (A50-3AC) samples were about 95%, whereas that of the 75AlN-25SiC-Al4C3 (A75-1AC) sample was about 86%. X-ray diffractometry (XRD) analysis showed that the samples comprised only the 2H phase, and except in the case of the A50-3AC sample, no diffraction peaks of Al and C were observed. Although the samples without the additives (Al and C) were electrical insulators, addition of Al and C introduced p-type semiconduction. The electrical conductivities at 300°C of the A50-1AC and A50-3AC samples were about 30 and 100 S/m, respectively, whereas that of the A75-1AC sample was about 10–1 S/m. It was found that addition of Al and C brought about electrical conduction in AlN–SiC solid solutions.
Experimental Investigation of Temperatures in Diamond Wire Sawing Granite
Authors: Huang Hui , Guo N. , Xu Xi Peng
Published: March 2009

The background temperatures in the sawing of granite with a diamond wire were measured by foil thermocouple. The influences of the measuring position in the cutting zone, cutting speed, feed rate and coolant on the temperature were investigated. The results indicated that the background temperature would be stable after a short-term rise. It was shown that the background temperature increased with cutting speed, but there was no obvious relationship between the background temperature and feed rate. The maximum background temperature appeared at the front part of the cutting zone at a lower feed rate. With an increase of feed rate, the background temperature at the middle of the cutting zone was the highest. The coolant had an obvious influence on the maximum background temperature.
A Review of Electrolytic In-Process Dressing (ELID) Grinding
Authors: Rahman Mustafizur , Senthil Kumar A. , Biswas I.
Published: March 2009

ELID Grinding, since its introduction over two decades ago, has helped in material removal of hard and difficult-to-cut engineering materials. A gist of the important research milestones on the process has been organized in this report. The hybrid process of ELID Grinding has a simultaneous electrolytic reaction and grinding action. Electrolysis takes place between the conductive anodic wheel and highly conductive cathode in presence of a special electrolyte. The resulting anodic oxide wears off easily to allow efficient grinding. The different parameters involved in electrolysis complicate the mechanism of grinding and makes it significantly different from conventional grinding. Different variants of the process have also been reported, though the basic philosophy of operation is the same as basic ELID. Several authors have also suggested mathematical explanations, among other fundamental studies, that provide further insight. The basic components of the process, machine tool, power supply, grinding wheel, electrode and electrolytes, have also undergone several modifications and developments to deliver better results and suit specific purposes. The process has been successfully applied in stock removal operations for hard and brittle ceramic materials with low grinding forces compared to conventional grinding. Fine finishing of almost all kinds of hard and brittle materials, ranging from hardened steels, BK7 glass, mono-crystalline silicon, silicon carbide, aluminum nitride, silicon nitride etc, has been successfully carried out, to provide high quality surfaces with low sub-surface damage. Finally, discussions on the different stages of evolution of the process have been put forward as a conclusion to the report.
Influence of Superplasticizer and Shrinkage-Reducing Admixtures on Early Age Shrinkage of Concrete
Authors: Qian Xiao Qian , Zhan Shu Lin , Zhu Yao Tai
Published: March 2009

The influence of superplasticizer (SP) and shrinkage-reducing admixtures (SRA) on the early age shrinkage of concrete with a controlled slump of 80±10 mm was investigated using a measuring apparatus developed specially. In addition, the influence of early age curing methods on the early age shrinkage of concrete was also studied. The early age shrinkage was increased sharply by the addition of SP when the concrete was exposed to the drying environment after initial setting. While under the same conditions the addition of SRA could reduce the early age shrinkage effectively. However, under sealed curing conditions at the early age, concretes with or without chemical admixtures all exhibited low early age shrinkage, which implies if a good method for curing could available then the addition of SRA will be unnecessary and the adverse effect of SP in enlarging shrinkage could also be eliminated.
Research on Technology and Mechanism of Grouting by Using High-Moisture Quick-Concreting Material
Authors: Bai Jian Biao , Wang Xiang Yu , Wang Hao , Hou Chao Jiong
Published: March 2009

The high-moisture quick-concreting material is a special type of cement which can be quick-concreting and full solidifying under the condition of high water cement ratio (2.5 : 1 ) . Thus , the mechanical performances of high-moisture quick-concreting material are as follows : 1) The grout fluidity is better and the penetrability is strong ; 2)The volume of concretion is tiny expansion in favor of solid filling in steel tube and exiguous gap ; 3) Concreting speed is rapid and the early strength is big , and the concreting speed may be also adjusted ; 4)The water cement ratio and the mixing ratio can be changed to meet requirement of different strengths ; 5)There is a good plasticity . The residual strength of concreting body may account for about 50% of the peak value strength if the uniaxial compressive strain reaches to 15% ; 6) As a result of the big water cement ratio , little dosage of the unit volume and low price , the cost for using high-moisture quick-concreting material to reinforce the foundation pit wall and ground base and to fill the steel tube is lower. In this study , the mechanical property and concreting mechanism of high-moisture quick-concreting material to reinforce the loose coal body are studied and analysed by the field test and laboratory test . The test results indicated that there is a notable effect to consolidate roadway , foundation pit wall and ground base by grouting of high-moisture quick-concreting material . Finally , the engineering example of grouting by using the high-moisture quick-concreting material is presented.
Microstructure, Mechanical and Corrosion Behaviour of Dissimilar Weldments between AISI 304 Stainless Steels and AISI 1020 Carbon Steels Produced by Gas Tungsten Arc Welding Using Different Consumables
Authors: Chuaiphan W. , Chandra-Ambhorn Somrerk , Sornil B. , Bleck Wolfgang
Published: March 2009

Gas tungsten arc welding was applied to join AISI 304 stainless steel and AISI 1020 carbon steel sheets with three types of consumables – AISI 308L, AISI 309L and AISI 316L stainless steel wires. Weld metals produced by all consumables exhibited the identical hardness of ca. 350 HV. This value was higher than those of stainless steel and carbon steel base metals, indicating the relatively high strength of weld metals. The corrosive behaviour of weld metals was investigated by a potentiodynamic method. Specimens were tested in 3.5 wt% NaCl solution saturated by laboratory air at 27°C. A pitting potential of weld metal produced by the AISI 309L consumable was higher than those of weld metals produced by the AISI 308L and AISI 316L consumables respectively. The chemical compositions and microstructure of weld metals were also investigated. The pitting corrosion resistance of weld metals produced by different consumables is discussed in the paper in terms of the pitting resistance equivalent number (PREN) calculated from the chemical compositions and the content of delta ferrite in the austenite matrix of the weld metals.
Tool Geometry in Friction Stir Welding of Magnesium Alloy Sheets
Authors: Bruni Carlo , Buffa Gianluca , d’Apolito L. , Forcellese Archimede , Fratini Livan
Published: March 2009

Friction Stir Welding (FSW) has been arousing a continuously increasing interest among joining processes since its invention in 1991. Although mainly used for aluminum alloys, it can also be applied to other light alloys. In the present work, experimental and numerical campaigns have been performed with the aim to study the effect of the tool geometry on the mechanical properties of FSW-ed AZ31 magnesium alloy sheets. The results, presented in terms of tensile strength, ductility, micro-hardness values and numerical field variables distributions, allow to reach a deeper knowledge on the behaviour of such relatively new material when FSW-ed, and can be used for a full optimization of the joints.
A Simple Analytical Approach to Describe a Beam Conditioning System
Authors: Verman Boris , Seshadri Srivatsan , Kim Bonglea
Published: March 2009

A simple analytical approach is given to calculate the performance of parabolic mirrors for various wavelengths. Expressions are given for the efficiency of the parabolic mirror system and insertion gain. As examples, parameters for some mirrors for CuKα and MoKα radiation are calculated.
Non-Crystallographic Nanopores in Single Crystals: A New Approach in Nanomaterials Chemistry
Authors: Jacobsen Claus J.H. , Schmidt Iver , Brorson Michael , Boisen Astrid , Hansen Thomas W. , Dahl Søren
Published: March 2009

Nanomaterials are the building blocks of nanotechnology. Recently, nanotube materials have attracted considerable attention due to their unique physical and chemical properties. Here we discuss how nanotubes can be used as templates for preparation of a new family of materials, the nanoporous single crystals, and for the preparation of metal sulfide nanotube materials. Today, the characterization of these materials depends heavily on electron microscopy. However, as rational synthesis schemes are becoming available, more well-defined, homogeneous nanotube samples will be produced and the role of diffraction techniques may increase.
On the Development of Copper Textures – Neutron Diffraction Control over a Period of 12 Years –
Authors: Jansen E. , Schäfer Wolfgang , Kirfel A. , Palacios J.
Published: March 2009

The longtime stability of copper textures has been periodically monitored over 12 years by neutron diffraction pole figure measurements on a cold rolled and a partially recrystallized copper specimen, always using the same diffractometer and the same procedure of data analysis. The texture component fractions of 'rolled' copper suffered a continuous decrease over about 8 years and seem to reverse since then. The decrease is accompanied by recrystallization from initial 3 to 34 vol. % at present. Texture changes in the partially recrystallized specimen are less pronounced. In this sample, the fraction of random orientations changed from initially 11 % to 31 % over the about first six years and followed by a decrease to 24 % at present.
Standardisation of X-Ray Powder Diffraction Methods
Authors: Berti Giovanni , Delhez Rob , Norval S. , Peplinski B. , Tolle E. , Verollet J.
Published: March 2009

This paper outlines the standardisation process for the XRPD method that is currently being considered by a Working Group (WG10) of Technical Committee 138 "Non-destructive Testing" of the European Committee for Standardisation CEN.
Several Standard Documents are on the verge of being released. These documents concern the general principles of (X-ray) diffraction, its terminology, and the basic procedures applied. Another document concerns the instruments used and it offers procedures to characterise and control the performance of an X-ray diffractometer properly. It is intended to issue Standard Documents on specific methods, e.g. determination of residual stresses. In fact work is in progress on this subject. The Standard Documents can be used by industry, government organisations, and research centres with activities related to safety, health and the environment, as well as for educational purposes.
Structural Studies of the Spinel System GaxCoFe1-xCrO4 (0 ≤ x ≤ 1) by Neutron Powder Diffraction
Authors: Azad A.K. , Eriksson S.-G. , Yunus S.M. , Eriksen J. , Rundlöf Håkan
Published: March 2009

Solid solutions of GaxCoFe1-xCrO4 ( x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were obtained by solid state reactions in air at 1623K. X-ray and neutron powder diffraction measurements have been performed on the materials in order to characterize them. Rietveld refinement of neutron powder diffraction data showed cubic symmetry corresponding to the space group Fd-3m for all of the samples in the series. The results reveal that Ga has been substituted for Fe selectively. Ga exclusively occupies the octahedral site up to x = 0.8, while at x =1.0 a small amount of Ga (5%)enters into the tetrahedral site in the compound. Cr, Fe and Co cations are distributed between the tetrahedral 8 a and octahedral 16 d sites. Their proportion at each site varies with composition. The fractional coordinates of oxygen are almost the same in all the samples while the lattice parameter shows a slight decrease with increasing Ga content. The magnetic structure at room temperature was ferrimagnetic for the composition x = 0.0 and x = 0.2.
Neutron Powder Diffraction Investigation of Pd2.7Ni0.3P0.94
Authors: Vennström M. , Andersson Y.
Published: March 2009

Pd3P, which crystallises in the cementite, Fe3C-type structure, forms a solid solution with nickel. The crystal structure contains two crystallographically different palladium sites (8d and 4c). Refinements of neutron powder diffraction intensities using the Rietveld method show that all nickel atoms occupy the eight-fold position. The unit cell parameters were refined to a=5.7812(4) Å, b=7.4756(6) Å and c=5.1376(4) Å, for Pd2.7Ni0.3P0.94.
Temperature Dependence of Lattice Parameters in Martensite and Effect of the External Magnetic Field on Martensite Structure in Ni2MnGa Studied In-Situ with Neutron Diffraction
Authors: Glavatska Nadiya , Mogylnyy G. , Danilkin S. , Hohlwein D.
Published: March 2009

The crystal structure of Ni1.99Mn1.14Ga0.87 single-crystal that exhibits large magnetic field induced strain in the martensitic phase is studied by neutron diffraction within temperature range 300K-4K. The 5-layered modulated structure is observed within the whole temperature interval and no another martensitic transformations occur. The anisotropic change of the martensite lattice
parameters during cooling from 300K down to 4K is found. The combined change in the a- and c-lattice parameters affects change of the (c/a) ratio in martensite with cooling down by 2.32%. Redistribution of twin martensitic variants in the external magnetic field is studied in-situ at temperatures 98K-296K.
Electrical and Optical Characterization of Indium Tin Oxide (ITO) Films for Low Resistance Transparent Electrode
Authors: Yoo Dong Hyun , Shin Moo Whan
Published: March 2009

One of obstacles hindering a realization of large area size twisted nematic liquid crystal
display (TN-LCD) flat panel (for example, 1100 x 1250 mm) is a slow response time. The slow
response time is due to the inverse proportionality of turn on time with the frame frequency and pixel
number (number of gate lines) in the twisted nematic liquid crystal system. It is known that the slow
response time in the active matrix system of LCD be solved by reducing the sheet resistance of color
filter electrodes. In this paper, we report on the processing details of the deposition of transparent ITO
films using a DC sputtering system. The thickness of ITO layer was set for high transmittance and
good conductivity and the films were characterized with respect to the transmittance and sheet
resistance. The deposited ITO films show a good uniformity across the whole area and the average
thickness of the ITO is about 1350 Å under the DC power of 10.7 kW. The transmittance is increased
from 72.5 to about 93 % as the oxygen content is increased to 2.5 sccm for the samples without
annealing. It was found that the transmittance is significantly improved by the annealing process at
220 oC for 40 min. up to 94 %. The sheet resistance is decreased with the DC power and exhibits
below 22 / after the samples were annealed.