Characterization of Hot-Pressed Silicon Nitride Ceramics with Alkoxide-Derived Oxide Mixtures As the Sintering Aid

1992 ◽  
Vol 287 ◽  
Author(s):  
Y. Sato ◽  
C. Sakurai ◽  
M. Ueki ◽  
K. Sugita
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Weight Ratio ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Oxide Powders ◽  
Nitride Ceramics ◽  
Final Weight ◽  
Alkoxide Method

ABSTRACTA homogeneous mixture of Y2O3, CeO2 and MgO with a final weight ratio of 3:1: 2 was prepared by the alkoxide method. The powder mixture was then added into Si3N4 powder in amounts ranging from 4 to 12 wt%, andconsolidated by hot-pressing. Microstructure and mechanical properties of the sintered bodies were determined and compared to those of materials prepared by the conventional route of mixing the oxide powders as sintering aids individually in essentially same composition. The β-fraction (modification ratio) in same composition was higher in thesintered bodies made through the alkoxide method than those made through the conventional one. The room temperature flexural strength was maximized with 6wt% addition of the alkoxide derived oxide, whereas, 12wt% addition of the total oxide was required to maximize the strength by conventional processing.

Crystallization of Zirconium Nitride in Silicon Nitride Ceramics with Nitrogen Pressures and Sintering Additives

2005 ◽  
Vol 287 ◽  
pp. 253-258 ◽  
Author(s):  
S.M. Lee ◽  
K.H. Park ◽  
Jung Whan Yoo ◽  
Hyung Tae Kim
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Surface Region ◽  
Nitrogen Atmosphere ◽  
Zirconium Nitride ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Heat Treated ◽  
Nitride Ceramics ◽  
Sintered Silicon

We investigated grain boundary crystallization of gas-pressure-sintered silicon nitride with zirconia and magnesia as sintering aids. Cation compositions were mostly uniform throughout the specimen however, ZrO2 was crystallized in the surface region, while ZrN in the inside. When the specimen was heat-treated at 1 atm nitrogen atmosphere, ZrO2 in the surface region transformed to ZrN. The transformation, however, was suppressed when alumina was incorporated as an additional sintering aid. Based on these results, we propose a model describing the reaction among Si3N4, SiO2, ZrO2, ZrN and N2. Observed microstructures and measured mechanical properties were consistent with the model.

scholarly journals Fabrication and Characterization of Electrospun Polycaprolactone Blended with Chitosan-Gelatin Complex Nanofibrous Mats

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Yongfang Qian ◽  
Zhen Zhang ◽  
Laijiu Zheng ◽  
Ruoyuan Song ◽  
Yuping Zhao
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Weight Ratio ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Tissue Engineering Scaffolds ◽  
Elongation At Break ◽  
Nanofibrous Scaffolds ◽  
Two Peaks

Design and fabrication of nanofibrous scaffolds should mimic the native extracellular matrix. This study is aimed at investigating electrospinning of polycaprolactone (PCL) blended with chitosan-gelatin complex. The morphologies were observed from scanning electron microscope. As-spun blended mats had thinner fibers than pure PCL. X-ray diffraction was used to analyze the degree of crystallinity. The intensity at two peaks at 2θof 21° and 23.5° gradually decreased with the percentage of chitosan-gelatin complex increasing. Moreover, incorporation of the complex could obviously improve the hydrophilicity of as-spun blended mats. Mechanical properties of as-spun nanofibrous mats were also tested. The elongation at break of fibrous mats increased with the PCL content increasing and the ultimate tensile strength varied with different weight ratios. The as-spun mats had higher tensile strength when the weight ratio of PCL to CS-Gel was 75/25 compared to pure PCL. Both as-spun PCL scaffolds and PCL/CS-Gel scaffolds supported the proliferation of porcine iliac endothelial cells, and PCL/CS-Gel had better cell viability than pure PCL. Therefore, electrospun PCL/Chitosan-gelatin nanofibrous mats with weight ratio of 75/25 have better hydrophilicity mechanical properties, and cell proliferation and thus would be a promising candidate for tissue engineering scaffolds.

Mechanosynthesis, Radiation-Thermal Modification and Characterization of Nanostructured Scandia Stabilized Zirconia Ceramics

2008 ◽  
Vol 1122 ◽  
Author(s):  
Vladimir V. Zyryanov ◽  
Nikolay F. Uvarov ◽  
Artem S. Ulihin ◽  
Vladislav A. Sadykov
Keyword(s):  
Solid Electrolytes ◽  
Room Temperature ◽  
Complex Impedance ◽  
Impedance Method ◽  
Sintering Aids ◽  
Zirconia Ceramics ◽  
Operation Temperature ◽  
Cubic Structure ◽  
Xrd Patterns

AbstractSSZ-based ceramics were obtained by sintering of nanopowders derived at room temperature by mechanochemical synthesis from refined technical grade ZrO2 nano-precursors. RT-treatment by 2.5 MeV electrons up to 1563 K was used for the modification of ceramics. Powders and ceramics were characterized by XRD, Raman, SEM and EDS, TEM, SIMS techniques. The phase composition of Zr0.89Sc0.1Ce0.01O1.95 ceramics was very close to cubic structure but better fitting of XRD patterns was obtained for rhombohedral lattice. Conductivity of solid electrolytes for IT SOFC was studied by complex impedance method. To stabilize cubic structure and increase conductivity at operation temperature of To ∼ 1000 K, the composition of SSZ solid electrolyte was optimized by addition of yttria and sintering aids. The interaction of admixtures with minor dopants leading to intergrain phase was revealed. During fast sintering, ceramics keep a memory about inhomogeneous disordered solid solutions in a form of nanostructuring. Conductivity data indicate nanostructuring of ceramics too: activation energies of bulk and grain boundary conductivities are close (Eb ∼ 0.9 eV, Egb ∼ 1.05 eV). Annealing of ceramics at high temperatures increases conductivity at To and promotes grain growth.

scholarly journals Microstructural and Mechanical Characterization of Al-0.80Mg-0.85Si-0.3Zr Alloy

2017 ◽  
Vol 17 (4) ◽  
pp. 73-78 ◽  
Author(s):  
F. Kahrıman ◽  
M. Zeren
Keyword(s):  
Mechanical Properties ◽  
Automotive Industry ◽  
Room Temperature ◽  
Tensile Tests ◽  
Direct Chill ◽  
Peak Hardness ◽  
Casting Method ◽  
Industry Standard ◽  
Three Stages

Abstract In this study, Al-0.80Mg-0.85Si alloy was modified with the addition of 0.3 wt.-% zirconium and the variation of microstructural features and mechanical properties were investigated. In order to produce the billets, vertical direct chill casting method was used and billets were homogenized at 580 °C for 6 h. Homogenized billets were subjected to aging practice following three stages: (i) solution annealing at 550 °C for 3 h, (ii) quenching in water, (iii) aging at 180 °C between 0 and 20 h. The hardness measurements were performed for the alloys following the aging process. It was observed that peak hardness value of Al-0.80Mg-0.85Si alloy increased with the addition of zirconium. This finding was very useful to obtain aging parameters for the extruded hollow profiles which are commonly used in automotive industry. Standard tensile tests were applied to aged profiles at room temperature and the results showed that modified alloy had higher mechanical properties compared to the non-modified alloy.

Preparation and Mechanical Characterization of Jute-PP and Coir-PP Bio-Composites

2015 ◽  
Vol 766-767 ◽  
pp. 122-132
Author(s):  
Tippusultan ◽  
V.N. Gaitonde
Keyword(s):  
Mechanical Properties ◽  
Research Work ◽  
Natural Fibers ◽  
Weight Ratio ◽  
Synthetic Fiber ◽  
Synthetic Fibers ◽  
Fiber Loading ◽  
High Initial Cost ◽  
Full Factorial

Polymers reinforced with synthetic fibers such as glass and carbon offer advantages of high stiffness and strength to weight ratio compared to conventional materials. Despite these advantages, the prevalent use of synthetic fiber-reinforced polymer composite has a tendency to demur because of high initial cost and most importantly their adverse environmental impact. On the contrary, the increased interest in using natural fibers as reinforcement in plastics to substitute conventional synthetic fibers in automobile applications has become one of the main concerns to study the potential of using natural fibers as reinforcement for polymers. In this regard, an investigative study has been carried out to make potential utilization of natural fibers such as Jute and Coir as reinforcements, which are cheap and abundantly available in India. The objective of the present research work is to study the effects of fiber loading and particle size; fiber loading and fiber length on the mechanical properties of Jute-PP and Coir-PP bio-composites respectively. The experiments were planned as per full factorial design (FFD) and response surface methodology (RSM) based second order mathematical models of mechanical properties have been developed. Analysis of variance (ANOVA) has been employed to check the adequacy of the developed models. From the parametric analysis, it is revealed that Jute-PP bio-composites exhibit better mechanical properties when compared to Coir-PP bio-composites.

Attainment and Characterization of the Thermosetting Polymer Loaded with Barite to be Used in the Manufacture of Isolating Plates to Bar the X-Ray Radiation

2006 ◽  
Vol 45 ◽  
pp. 1429-1434
Author(s):  
Leila Figueiredo de Miranda ◽  
Antônio Hortêncio Munhoz Jr. ◽  
Terezinha Jocelen Masson ◽  
Virgínia Carolina Naime ◽  
Gustavo Camargo Costa
Keyword(s):  
Mechanical Properties ◽  
Experimental Design ◽  
Apparent Density ◽  
Weight Ratio ◽  
Average Density ◽  
Radiological Protection ◽  
X Ray ◽  
Protection Area ◽  
Properties Of Composites

The properties of composites based on thermosetting polyester and barite for use in the radiological protection area have been investigated with the objective to study the effect of different variables in the attainment of composites. To verify the efficiency of the composites produced in relation to radiological protection, lead was adopted as reference. A factorial experimental design was carried out and the studied variables were: type of polyester resin (orthophthalic or isophthalic), coupling agent (titanate or organosilane) and the ratio of resin to accelerator, catalyst and barite. The variables analyzed were: efficiency for barring the X-radiation, apparent density and mechanical properties. The effect, obtained from the experimental design, due to ratio of resin to barite in the apparent density was 0.036. The average apparent density of the samples produced with barite/resin value equal 2.0 (weight ratio) was 2.16g/cm3, while the average density of the samples produced with the weight ratio of barite/resin equal 3.0 was 2.2g/cm3. It was observed same trend for the density to mechanical properties. It was observed that the samples attenuated X-ray radiation adequately up to 116 kV.

Microstructure and properties of pressureless sintered ZrC-based materials

2008 ◽  
Vol 23 (7) ◽  
pp. 1882-1889 ◽  
Author(s):  
Laura Silvestroni ◽  
Diletta Sciti
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Flexural Strength ◽  
Room Temperature ◽  
Pressureless Sintering ◽  
Secondary Phases ◽  
Sintering Aid ◽  
Mean Particle Size ◽  
Dense Bodies ◽  
Similar Materials

ZrC-based composites were produced by pressureless sintering thanks to the addition of MoSi2 as sintering aid. After preliminary tests, a baseline ZrC material and two mixed ZrC–HfC and ZrC–ZrB2 composites with 20 vol% MoSi2 were densified at 1900 to 1950 °C reaching final relative densities of 96%–98%. Mean particle size of the dense bodies ranged from 5 to 9 μm. Secondary phases were found to form during sintering, such as SiC and Zr–Mo–Si-based compounds. Room-temperature mechanical properties were in the range of the values reported in the literature for similar materials densified by pressure-assisted techniques. The flexural strength was tested at room temperature, 1200 and 1500 °C.

Fabrication and Characterization of Alumina/Zirconia Ceramic Compound

2012 ◽  
Vol 724 ◽  
pp. 249-254 ◽  
Author(s):  
Bum Rae Cho ◽  
Ji Hoon Chae ◽  
Bo Lang Kim ◽  
Jong Bong Kang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Low Temperature ◽  
Mechanical Strength ◽  
Sem Analysis ◽  
Zirconia Ceramic ◽  
Sintering Process ◽  
Sintering Aids ◽  
X Ray Diffraction

Sintered ZTA(zirconia toughened alumina) which has good mechanical properties at a low temperature was produced by milling and mixing with Al2O3 and ZrO2(3Y-TZP). In order to examine the effect of sintering aids on the mechanical properties of ZTA, fracture toughness and hardness of the produced ZTA were observed in accordance with change of the added quantity of ZrO2 Scanning electron microscopy and X-ray diffraction technique were applied to observe microstructural change and phase transformation during the process. Experimental results showed that the addition of sintering aids in ZTA at a low temperature induced densification and adding SiO2 and talc lowered sintering temperature and promoted crystallization process of the compound. The mechanical strength of ZTA added ZrO2 showed higher mechanical strength and SEM analysis revealed that Al2O3 and ZrO2 during the sintering process restrained the grain growth each other. Especially, the 92% Al2O3 added sintering aids showed more than 98% of the theoretical density and more than 1500 Hv of hardness value at a low temperature of 1400. It was also showed that the fracture toughness is gradually increasing first and decreasing later in accordance with the quantity of ZrO2.

Preparation and Characterization of SiC/MoSi2 Composites from Powder Resulting from a Mechanical-Assistant Combustion Synthesis Method

2010 ◽  
Vol 105-106 ◽  
pp. 70-74
Author(s):  
Jian Guang Xu ◽  
Hui Qiang Li ◽  
Hou An Zhang
Keyword(s):  
Mechanical Properties ◽  
Cyclic Oxidation ◽  
Room Temperature ◽  
Synthesis Method ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Oxidation Properties ◽  
Mosi2 Composite

SiC reinforced MoSi2 composites have been successfully prepared by pressureless sintering from mechanical-assistant combustion synthesized powders. The sintering temperatures and holding time were 1500°C~1650°C at a heating rate of 10K/min and 1 hour, respectively. The microstructure and mechanical properties of the as-sintered composites were investigated. SEM micrographs of SiC/MoSi2 composites showed that SiC particles were homogeneously distributed in MoSi2 matrix. The Vickers hardness, flexural strength and fracture toughness of the SiC/MoSi2 composites were up to 15.50GPa, 468.7MPa and 9.35MPa•m1/2, respectively. The morphologies of fractured surface of the composites revealed the mechanism to improve mechanical properties of MoSi2 matrix. At last, the cyclic oxidation behavior of the composites was discussed. The results of this work showed that in situ SiC/MoSi2 composite powder prepared by MASHS technique could be successfully sintered via pressureless sintering process and significant improvement of room temperature mechanical and anti-oxidation properties could be achieved.

Microstructure and Properties Characterization of Polycrystalline Ni-Fe-Cr-Based Superalloy EP-718E after Electric Upsetting

2016 ◽  
Vol 721 ◽  
pp. 467-472 ◽  
Author(s):  
Lembit Kommel
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Energy Dispersive Spectrometry ◽  
Fatigue Testing ◽  
Tension Stress ◽  
Tension Testing ◽  
Electric Upsetting ◽  
Number Of Cycles ◽  
Cycles To Failure

The purpose of this study is to analyze the effect of electric upsetting on the microstructure defects eliminating and mechanical properties evolution of the Ni-Fe-Cr-based polycrystalline superalloy EP718E. The microstructure was examined by scanning electron microscope and energy dispersive spectrometry techniques. The material mechanical properties were characterized by nanoindentation, by tension testing of micro samples and high cycle fatigue testing at room temperature. The results show, that the microstructure defects on confluence of grain boundaries (depending on the processing stages) were step-by-step eliminated. The tension stress was lowered but elongation was increase. As a result of such changes in microstructure and mechanical properties of alloy the fatigue strength (δ-1) was increased from δ-1 = 300 MPa to δ-1 = 540 MPa and the number of cycles to failure was increased from N1 = 2·107 up to N4 = 4 x (2·107), respectively.

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