Sintered Research Articles

Development, optimization and In vitro evaluation of sintered floating tablets of Antibacterial drug

Floating tablets prolongs drug residence , enhance bioavailability and facilitate effective eradication of helicobacter pylori includes local delivery of antibiotic in stomach. The goal of the existing research changed into to formulate thermally sintered floating Tablets of Amoxicillin Trihydrate, and to test sintering effect on release of drug and floating. A hydrophobic polymer, Carnauba wax, is determined to delay the release of drug as a sintered polymer. Formulations had been organized via granulation technique and had been evaluated through in vitro research such as hardness, friability, uniformity of weight, percentage drug content, buoyancy time, dissolution and release mechanism. Optimization was based on buoyancy time and in vitro release. Hardness ranged from 4-6 kg/cm2. Friability, drug content and weight variation passed USP requirements. Buoyancy time of all tablets was below 3 min and tablet remained floating throughout the study. Effects showed that temperature to sinter and exposure time significantly motivated buoyancy, in addition to dissolution characteristics. Sintering improved floating properties, general time of floating was extended and retarded release of medicament . Robust sintered components (sintering temperature 50°C and time of exposure 4 h became selected, primarily based on retarding character. The formulations characterised with FTIR studies and no interplay become determined between the drug and the polymer.

Validation of an Experimental Procedure to Quantify the Effects of Powder Spreadability on Selective Laser Sintering Process

Glass beads powders of different particle size were spread with a procedure similar to the one adopted for Selective laser sintering in order to verify the effect of the powder compression produced with a roller spreading tool. The effect is verified in terms of indentation strength and of mechanical strength of the sintered specimens. Results indicate a significant effect of powder compression on the SLS process with fine powders.

Effect of waste rubber binder on sintered properties of 316L SS for metallic implant parts

This paper studies the influence of waste rubber binder on the properties of injection moulded 316L stainless steel. The new feedstock was formulated at volume fraction of 65% of metal powder and 35% of binder system. Powder with mean particle size of 45 μm was mixed with binder system and then successfully injection moulded. The samples were immersed in n-heptane for 5 hours at temperature of 60⁰C. Thermal debinding process was carried out to remove the remaining binders. The specimens were then sintered in vacuum condition at different temperature ranges of 1320⁰C to 1380⁰C. The properties of the sintered samples were evaluated. The sintered density recorded from 7.31 g/cm 3 to 7.62 g/cm 3 at 30 minutes and 60 minutes of soaking time. At temperature of 1360⁰C, the maximum tensile strength of 475.5 MPa attained and the highest hardness was obtained at 265 Hv. Keywords: waste rubber; injection moulded; feedstock; sintered density; tensile strength

OPTIMIZATION OF GRADING ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al13Fe4/Al COM- POSITES IN SITU SYNTHESIZED BY MECHANICAL ALLOYING AND SPARK PLASMA SINTERING

Al-Fe alloys are widely applied in automobile, aerospace, military industry and other fields owing to their high specific strength, high specific stiffness and good stability of the microstructure originating from the low diffusivity of Fe in Al. However, conventional casting method leads to inferior mechanical properties of Al-Fe alloys due to the coarse grain microstructure, which cannot meet application requirements. In this work, fully densed Al13Fe4/Al composites were fabricated by combination of mechanical alloying and spark plasma sintering(MA-SPS) approaches. Effect of gradation of grinding balls on microstructure and properties of composites was investigated by means of XRD, SEM, TEM, hardness and compressive test. The results showed that the size of powders became more uniform by ball gradation in MA treatment, and solid solubility was greatly enhanded as well.Furthermore, the Al-Fe powder after MA using a single grinding ball size showed the microstructure of tiny white Fe particles on the surface of each particle, while no white Fe particles were observed for the one with ball gradation, which confirmed that ball gradation was more beneficial to the mixture and solid solution of Al and Fe, resulting in more homogeneously distributed powders with smaller particle sizes of 10 μm. The composites after SPScontained a-Al phase and intermetallic compound Al13Fe4. Three types of Al13Fe4 were observed: large particles(1~2 μm), ultrafine particles(0.1~1.0 μm) and nano-particles(about 20 nm). The large particles and ultrafine Al13Fe4 formed by the reaction between undissolved Fe particles and the Al melt while nano-particles of Al13Fe4 originated from the precipitation of supersaturated Al(Fe) solid solutions. The sintered sample with ball gradation after SPS showed optimized microstructure with coarser a-Al particles and ultrafine Al13Fe4 particles, resulting in good comprehensive properties with 227 HV in microhardness, 845.8 MPa in compressive strength and 13.6% in plastic deformation. The combination of large quantities of coarse a-Al particles and ultrafine Al13Fe4 particles were considered as the reason for high strength and high toughness of Al-Fe alloy.

Forging of hollow sintered powder preforms

The forging of sintered metal powder preforms is currently arousing interest in many parts of the world as an economic method of producing components from metal powders. The present investigation has been undertaken with a view to studying the deformation characteristics of hollow sintered copper powder discs at room temperature. A theoretical analysis based on the energy method is presented for the estimation of deformation load using yield criterion for porous sintered materials and an appropriate interfacial friction law. Experiments have also been conducted which involved the forging of hollow discs of electrolytic copper powder at room temperature under axisymmetric conditions. In order to illustrate the validity of the theoretical approach, the theoretical and experimental results have been compared and presented graphically.

OPTIMIZING OF NEW APPROACH SINTERING METHOD ON CARBONATED HYDROXYAPATITE BIOCERAMIC

Synthetic carbonated apatite ceramics are considered as alternative to autograft and allograft materials for bone substitute. This study was to investigate and compare the effect of carbonation introduced during cooling down of sintering of dense CHA with two kind of wet CO2 atmosphere (direct wet CO2 and dry CO2 flow through water). Pelletized samples were sintered to 800°C and soaked for 120 minutes. Upon cooling down to 150, 200, 250 and 300°C, carbonation with wet CO2 in desiccators were performed. The sintered CHA after carbonation at the various cooled temperatures was found to retain as B-type CHA. Carbonation of sintered CHA by dry CO2 through water showed an overall better results as compared to carbonation by direct wet CO2. Sample D200 with carbonation temperature of 200oC has the highest carbonate content (3.35%) and relative density (94%) while D250 with carbonation temperature of 250oC has the highest DTS value (18MPa). In vitro testing using SBF solution showed that apatite layer formed on the sintered CHA surface after one week of immersion, thus indicating the bone-forming ability. This indicated that the CHA synthesized in this study has sufficient biocompatibility to be applied as bone substitutes.

Genoese intonachino plasters between the 14th and the 18th century: archaeometric analyses

In the last twenty years, the authors have analyzed many samples of plaster and surface finish coming from historic buildings in the territory of Genoa (Italy), dating from the 14 th to the 18 th century, excluding the sintered materials used since the 19 th century onwards. This research, therefore, wants to document the technique and the materials used that, through lab investigations, have ascertained different mineralogical compositions (plaster with quartz, slaked lime, cocciopesto, pozzolan, marmorino, etc.), with overall color not always white, but also colored in paste, with the addition of natural or artificial pigments, accompanied by surface treatments, which enhance the color differences between different parts of the monument. The research was carried out using reflected light microscopy techniques on polished cross sections and polarized transmitted light techniques on thin sections, integrated with FTIR spectroscopy analysis.

The Effect of Sintering Temperature on Mechanical Properties of Al/SiC Composites

This paper presents the investigation of the effect of sintering temperature on mechanical properties of Al/SiC composites. The composites were produced via conventional powder metallurgy processing. The particle size of Al and SiC powders are 63 µm and 37 µm respectively. The sintering temperatures exerted on the samples were 550, 570, 590, 610, 630 and 650oC at a fixed time of 1 h. The compressive, hardness and impact tests were performed on the sintered samples to characterize their mechanical properties. It was found that as the sintering temperature increase, the mechanical properties of the samples were also increased at earlier temperature and show a decrease trend thereafter. Similarly, this trend was also observed in the density test. Furthermore, microscopic observations showed that the porosity level decrease as the sintering temperature increase excluding at the temperature of 650oC.

Superhard nanocrystalline Ti–Cu–N coatings deposited by vacuum arc evaporation of a sintered cathode

Superhard nanocrystalline Ti–Cu–N coatings deposited by vacuum arc evaporation of a sintered cathode

Study of Sintered Aluminum Foil-powder Alumnite Catalyst

Study of Sintered Aluminum Foil-powder Alumnite Catalyst

New Development of Sintered Material for Car

New Development of Sintered Material for Car

Repair of rabbit's radius segmental bone defect with sintered bovine cancellous bone complexed with a BMP2-derived peptide and collagen I

Objective To observe the repair of bone defect with sintered bovine cancellous bone complexed with synthetized BMP2-derived peptide and collagen Ⅰ.Methods Rabbits were divided into 3 groups.Sintered bovine bone was implanted in group A.Sintered bovine bone complexed with collagen 1 was,implanted in group B.Sintered bovine bone complexed with BMP2-derived peptide/eollagen 1 was implanted in group C.Before implantation,the materials were observed under the environmental scanning electron microscopy(ESEM).Thirty-six rabbits were gained to establish models of 10-mm middle radius bone defects and divided into 3 groups with 12 in each group.Postoperatively.the formed new bone was compared among the three implants at the 4th,8th,12th week by X ray score,and at the 8th,12th week by histological score.The bend intensity of implanted materials at the 12th week were tested.respectively.Resuits Thirty-six rabbits were all involved in the resuh analysis.(1)ESEM revealed that the porosity of compound materials was high with close compound.(2)At different postoperative time points,the X ray scores on the group C were significantly greater than in groups A and B(P＜0.05).(3)The histological scores at the 4th and 8th week on the group C were 6.83±0.41 abnd 8.67±0.52 respectively.significanfly higher than in both group A(4.67±0.52,6.17±0.41)and group B(5.33±0.52,7.33±0.52)respectively(P＜0.05).(4)The bend intensity of implanted materials in group C at the 12th week after operation was higher significantly than that in groups A and B.Conclusion Sintered bovine cancellous bone and its compound materials can repair the bone defect,but the sintered bovine bone complexed with BMP2-derived peptide/collagen I is the most ideal. Key words: Sintered bone; Bone defect; BMP2; Type Ⅰ collagen

Preparation and characterization of oligopeptide modified hydroxyapatite crystal scaffolds

Objective To prepare a new osteoinduction hydroxyapatite crystal material using sintered bovine bone combined with bone morphogenetic protein(BMP2)-derived peptide and type Ⅰ collagen,and to study their biological characteristics for developing biomaterials for orthopaedic tissue engineered bone.Methods Sintered bovine bone combined with BMP2-derived peptide and type Ⅰ collagen was as experimental group.and Sintered bovine bone combined with Type Ⅰ collagen Wag as control group.Formation of hydmxyapatite crystals was inveati gated under environmental scanning electron microscopy(ESEM),energy-dispersive spectroscopy(EDS)and X-ray diffraction(XRD).The ceil-material complex Wag observed and cell adhesion rate on each materials WaS calculated using the method of indirect cell count to evaluate the interaction between cells and materials.Results By ESEM,formation of hydroxyapatite crystals in collagen surface was observed in experimental group but none was observed in control group.By EDS and XRD,the contents of calcium and phosphorus elements from mineralized bone surface were 16.23% and 7.76%respectively.The atom percentages of calcium and phosphorus elements were 6.34%and 3.88%respectively.The cell adhesion rate of experimental group after 24 hours co-culture was significantly higher than that of control group (α＜0.05).Conclusion BMP2-derived peptide can induce the formation of hydroxyapatite crystals at the surface of sintered bovine bone combined with type Ⅰcollagen.It can also elevate the osteoinduction and cell adhesion rate and is an ideal scaffold material by combining with sintered bovine bone for the bone tissue engineering. Key words: bone morphogenetic protein-derived peptide; Type Ⅰ collagen; Sintered bone; Hydroxyapetite crystals

Avaliação das propriedades físico-mecânicas de uma massa cerâmica para revestimento poroso (BIII)

O presente trabalho teve por objetivo estudar as propriedades físico-mecânicas de uma massa para revestimento cerâmico poroso base vermelha a partir de matérias-primas da região Norte Fluminense. A massa cerâmica preparada pelo processo via seca foi caracterizada quanto a composição química, análise de tamanho de partícula, difração de raios X e comportamento térmico. Os corpos cerâmicos foram prensados sob 35 MPa e sinterizados entre 1080 e 1200 ºC usando um ciclo de queima rápido. A microestrutura sinterizada foi avaliada por microscopia eletrônica de varredura. Os corpos cerâmicos sinterizados exibiram baixos valores de retração linear, resultando em boa estabilidade dimensional. A microestrutura é caracterizada por alta porosidade. Além disso, foram atingidas as especificações para revestimento poroso (NBR 13818) em termos da tensão de ruptura à flexão e da absorção de água dos corpos cerâmicos sinterizados, indicando o potencial das matérias-primas cerâmicas do Norte Fluminense para este tipo de aplicação.

117 多重解像度分子動力学法による金属ナノクラスター焼結体の評価

117 多重解像度分子動力学法による金属ナノクラスター焼結体の評価

Production of sintered steel from fibre

Production of sintered steel from fibre

Dynamic magnetization observations and reversal mechanisms of sintered and die-upset Nd–Fe–B magnets

In situ TEM magnetizing experiments combined with Lorentz microscopy in Fresnel and Foucault mode were used to study local features of magnetization reversal in polycrystalline sintered and die-upset Nd–Fe–B magnets. The die-upset (DU) magnets featured well-aligned grain texture along the c-axis, while the sintered (SI) magnets have a much wider distribution of grain orientations. Despite the similarity of the hysteresis curves, we found their nanoscale behavior of the magnetization reversal was quite different. The predominant mechanism controlling reversal in DU-magnets was nucleation of reversed domains, preferentially at misaligned grain interfaces, followed by domain wall pinning at grain boundaries. In contrast, magnetization reversal in SI-magnet progressed first by nucleation and expansion of reversed domain dipoles predominantly in misaligned grains at a high magnetic field, and then by the major irreversible process via nucleation and splitting of magnetic domains near the grain boundaries of well-aligned grains at more negative fields. This process is completed with lateral expansion of newly created domain walls. A simple model for the strong pinning–trapping centers observed in DU-magnets is discussed.

Synthesis, structure and dielectric properties of Ba 1-x Sr x M y Ti 1-y O 3 (M = Zr, Sn)

A series of Ba 1-x Sr x M y Ti 1-y O 3 (M = Zr, Sn, 0 x 0.4, 0 y 0.3) solid solutions were synthesized with the soft chemical method below 100 °C. XRD pattern and cell parameters- composition figures of the prepared powder demonstrate that they are completely miscible solid solutions based on BaTiO 3 . Furthermore, TEM shows that they have a shape of uniform, substantially spherical particles with an average particle size of 70 nm in diameter. The sintered ceramics of the powder doped with Sr 2+ and Zr 4+ or Sn 4+ have dielectric constant eight times higher and dielectric loss thirty per cent lower than those of pure BaTiO 3 phase at room temperature.

On the Thermal Boundary Conditions at the Interface Between the Porous Medium and the Impermeable Wall

The present work investigates a heat transfer phenomenon at the interface between a porous medium and an impermeable wall. In an effort to appropriately describe the heat transfer phenomenon at the interface, the heat transfer at the interface between the microchannel heat sink, which is an ideally organized porous medium, and the finite-thickness substrate is examined. From the examination, it is clarified that the he heat flux distribution at the interface is not uniform for the impermeable wall with finite thickness. On the other hand, the first approach, based on the energy balance for the representative elementary volume in the porous medium, is physically reason able. When the first approach is applied to the thermal boundary condition, and additional boundary condition based on the local thermal equilibrium assumption at the interface is used. This additional boundary condition is applicable except for the very th in impermeable wall. Hence, for practical situations, the first approach in combination with the local thermal equilibrium assumption at the interface is suggested as an appropriate thermal boundary condition. In order to confirm our suggestion, convective flows both in a microchannel heat sink and in a sintered porous channel subject to a constant heat flux condition are analyzed. The analytically obtained thermal resistance of the microchannel heat sink and the numerically obtained overall Nusselt number for the sintered porous channel are shown to be in close agreement with available experimental results when our suggestion for the thermal boundary conditions is applied.

THE EFFECTS OF ECLOGITIC HETEROGENEITIES ON UPPER MANTLE MELTING

THE EFFECTS OF ECLOGITIC HETEROGENEITIES ON UPPER MANTLE MELTING