High-temperature properties of a silicon nitride/boron nitride nanocomposite

2004 ◽  
Vol 19 (5) ◽  
pp. 1432-1438 ◽  
Author(s):  
Takafumi Kusunose ◽  
Rak-Joo Sung ◽  
Tohru Sekino ◽  
Shuji Sakaguchi ◽  
Koichi Niihara
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
High Temperature ◽  
Young’S Modulus ◽  
Elevated Temperatures ◽  
Young's Modulus ◽  
High Temperature Strength ◽  
Second Phase ◽  
Structural Ceramics ◽  
High Temperature Mechanical Properties

Hexagonal graphitic BN (h-BN) is interesting as a second phase for high-temperature structural ceramics because it has the same crystal structure as graphite, for which fracture strength and Young’s modulus increase with increased temperature. In this study, high-temperature mechanical properties of Si3N4/BN nanocomposite were evaluated to clarify the effect of fine h-BN particles at elevated temperatures. As a result, we found that high-temperature strength and hardness of the nanocomposite were maintained up to high temperatures; also, its Young’s modulus increased gradually, concomitant with elevated temperatures up to 1400 °C. Finally, these properties were compared with those of monolithic Si3N4 and Si3N4/BN microcomposite.

High Temperature Mechanical Properties of Ni-YSZ Cermets for SOFC Anode

2010 ◽  
Author(s):  
Fumitada Iguchi ◽  
Hiromichi Kitahara ◽  
Hiroo Yugami
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Flexural Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Strain Diagram ◽  
Thermal Cycles ◽  
High Temperature Mechanical Properties ◽  
Sofc Anode ◽  
The Difference

The mechanical properties of Ni-YSZ cermets at high temperature in reduction atmosphere were evaluated by the four points bending method. We studied the influences of reduction and thermal cycles, i.e. a cycle from R.T. to 800°C, to flexural strength and Young’s modulus. The flexural strength of Ni-YSZ at room temperature was lower than that of NiO-YSZ by about 10 to 20% mainly caused by the increment of porosity. But, the flexural strength of Ni-YSZ at 800°C was drastically decreased by an half of that at R.T. In addition, the stress–strain diagram of Ni-YSZ at 800°C indicated that it showed weak ductility. The maximum observed strain was over 0.5% at 30MPa. On the contrary, NiO-YSZ showed only brittlely at 800°C. The difference was caused by Ni metal in the Ni-YSZ cermets. Therefore, it was expected that Ni-YSZ is easily deformed in operation, though residual stress between an anode and an electrolyte was low. The influence of thermal cycles to flexural strength and Young’s modulus was not observed clearly. At the same time, the differences of microstructure were not observed. Therefore, it was concluded that the cycle does not change mechanical properties significantly.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

scholarly journals The Influence of La and Ce on Microstructure and Mechanical Properties of an Al-Si-Cu-Mg-Fe Alloy at High Temperature

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 384
Author(s):  
Andong Du ◽  
Anders E. W. Jarfors ◽  
Jinchuan Zheng ◽  
Kaikun Wang ◽  
Gegang Yu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
High Temperature ◽  
Intermetallic Phases ◽  
High Temperature Strength ◽  
Thermal Expansion Mismatch ◽  
Strengthening Mechanisms ◽  
High Temperature Mechanical Properties ◽  
Minor Contribution ◽  
A Minor

The effect of lanthanum (La)+cerium (Ce) addition on the high-temperature strength of an aluminum (Al)–silicon (Si)–copper (Cu)–magnesium (Mg)–iron (Fe)–manganese (Mn) alloy was investigated. A great number of plate-like intermetallics, Al11(Ce, La)3- and blocky α-Al15(Fe, Mn)3Si2-precipitates, were observed. The results showed that the high-temperature mechanical properties depended strongly on the amount and morphology of the intermetallic phases formed. The precipitated tiny Al11(Ce, La)3 and α-Al15(Fe, Mn)3Si2 both contributed to the high-temperature mechanical properties, especially at 300 °C and 400 °C. The formation of coarse plate-like Al11(Ce, La)3, at the highest (Ce-La) additions, reduced the mechanical properties at (≤300) ℃ and improved the properties at 400 ℃. Analysis of the strengthening mechanisms revealed that the load-bearing mechanism was the main contributing mechanism with no contribution from thermal-expansion mismatch effects. Strain hardening had a minor contribution to the tensile strength at high-temperature.

An Experimental Study of Carbon Nanotube Reinforcements

2011 ◽  
Author(s):  
Lauren Patrin ◽  
Frank Chow ◽  
Gabriela Philippart ◽  
Feridun Delale ◽  
Benjamin Liaw ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Young's Modulus ◽  
Testing Machine ◽  
Type I ◽  
Electrical Measurements ◽  
Standard Type ◽  
Reinforcement Percentage

Due to their high strength and stiffness carbon nanotubes (CNTs) have been considered as candidates for reinforcement of polymeric resins. It is also known that the addition of CNTs to polymeric matrix results in highly conductive nanocomposites, making the material multifunctional. Most of the CNT reinforced polymeric nanocomposite systems reported in the literature have been studied at room temperature. However, in many applications, materials may be subjected from low to elevated temperatures. Thus, the aim of this research is to study CNT reinforced polypropylene (PP) specimens at room, elevated and low temperatures. ASTM standard Type I specimens manufactured via injection molding and reinforced with 0.2%, 1%, 3%, and 6% CNTs were first subjected to tensile loads in a universal testing machine at room temperature. Neat PP resin specimens were also tested to provide baseline data. The tests were repeated at −54°C (−65°F), −20°C (−4°F), 49°C (120°F) and 71°C (160°F). The results were plotted as stress-strain curves and analyzed to delineate the effect of CNT reinforcement percentage and temperature on the mechanical properties. It was noted that as the percentage of CNT reinforcement increases, the resulting nanocomposite becomes stiffer (higher Young’s modulus), has higher strength and becomes more brittle. Temperature has a drastic effect on the behavior of the nanocomposite. As the temperature increases, at a given reinforcement percentage the material becomes more ductile with significantly lower Young’s modulus and strength compared to room temperature. At lower temperatures, the nanocomposite becomes more brittle with higher stiffness and strength, but significantly reduced failure strain. Also electrical measurements were conducted on the specimens to measure their resistance. For specimens reinforced with up to 3% of CNTs no electrical conductivity was detected. As expected at 6% CNT reinforcement (which is above the approximately 4% percolation limit reported in the literature), the specimens became electrically conductive. To predict the mechanical properties obtained experimentally, a micromechanics based model is presented and compared with the experimental results.

Mechanical Properties and Microstructure of the Newly Developed Steel (Low C 18Cr-11Ni-3Cu-Mo-Nb-B-N) After Aging Treatment

2020 ◽  
Author(s):  
Nao Otaki ◽  
Tomoaki Hamaguchi ◽  
Takahiro Osuki ◽  
Yuhei Suzuki ◽  
Masaki Ueyama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Vickers Hardness ◽  
Elevated Temperatures ◽  
Rupture Strength ◽  
Aging Treatment ◽  
High Strength ◽  
High Temperature Strength ◽  
Short Term ◽  
Rich Phase

Abstract In petroleum refinery plants, materials with high sensitization resistance are required. 347AP has particularly been developed for such applications and shows good sensitization resistance owing to its low C content. However, further improvement in high temperature strength is required for high temperature operations in complex refineries, such as delayed cokers. Recently, a new austenitic stainless steel (low C 18Cr-11Ni-3Cu-Mo-Nb-B-N, UNS No. S34752) with high sensitization resistance and high strength at elevated temperatures has been developed. In this study, the mechanical properties and microstructures of several aged specimens will be reported. By conducting several aging heat treatments in the range of 550–750 °C for 300–10,000 h on the developed steel, it was revealed that there were only few coarse precipitates that assumed sigma phase even after aging at 750 °C for 10,000 h. This indicates that the newly developed steel has superior phase stability. The developed steel drastically increased its Vickers hardness by short-term aging treatments. Through transmission electron microscopy observations, the fine precipitates of Cu-rich phase were observed dispersedly in the ruptured specimen. Therefore, the increase in Vickers hardness in short-term aging is possibly owing to the dispersed precipitation of Cu-rich phase. There was further increase in Vickers hardness owing to Z phase precipitation; however, the increment was smaller than that caused by Cu-rich phase. The newly developed alloy demonstrated excellent creep rupture strength even in the long-term tests of approximately 30,000 h, which is attributed to these precipitates.

Performance of ilmenite concrete at sustained elevated temperatures

1988 ◽  
Vol 15 (5) ◽  
pp. 776-783
Author(s):  
H. S. Wilson
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Temperature ◽  
Flexural Strength ◽  
Key Words ◽  
Elevated Temperatures ◽  
Cement Ratio ◽  
Nondestructive Tests ◽  
High Temperature Mechanical Properties ◽  
Curing Period

Two similar mixes were made with cement contents of about 350 kg/m3 and a water–cement ratio of 0.50. The concrete specimens, moist cured for 7 days, were cured in air for 28 and 120 days, respectively, prior to heating. The exposure temperatures were 75, 150, 300, and 450 °C. The periods of exposure at each temperature were 2, 30, and 120 days.The compressive strengths, before heating, of the specimens cured for 35 and 120 days were 41.0 and 46.2 MPa, respectively, and the flexural strengths were 4.9 and 5.8 MPa. Compared with those strengths, the strengths of the specimens heated for 30 days or more increased at 75 °C but decreased at higher temperatures. The losses increased with increase in temperature, reaching about 30% at 450 °C.The flexural strength of the concrete cured in air for 28 days was more adversely affected than was the compressive strength. The flexural and compressive strengths of the concrete cured in air for 120 days were affected to about the same degree. The longer curing period had little effect on the relative losses in compressive strength, but the longer curing period reduced the loss in flexural strength. In most applications, the loss in strength could be compensated by proportioning the mix to overdesign for strength. Key words: high-density concrete, ilmenite, aggregates, high temperature, mechanical properties, nondestructive tests.

Microstructure and high-temperature mechanical properties of second-phase enhanced Mo-La2O3-ZrC alloys post-treated by cross rolling

2019 ◽  
Vol 796 ◽  
pp. 167-175 ◽  
Author(s):  
Jianning Gan ◽  
Qianming Gong ◽  
Yanqi Jiang ◽  
Hao Chen ◽  
Yilun Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Second Phase ◽  
Cross Rolling ◽  
High Temperature Mechanical Properties

Effect of Zr Addition on High Temperature Mechanical Properties of Near Alpha Ti-Al-Zr-Sn Based Alloy

2014 ◽  
Vol 783-786 ◽  
pp. 580-583 ◽  
Author(s):  
Murugesan Jayaprakash ◽  
De Hai Ping ◽  
Y. Yamabe-Mitarai
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Room Temperature ◽  
High Temperature Strength ◽  
Test Results ◽  
High Temperature Mechanical Properties ◽  
Ti Alloys ◽  
Zr Addition ◽  
And Performance ◽  
Compressive Tests

Titanium (Ti) alloys are widely used in aerospace industries successfully up to 600°C. Increasing the operating temperature and performance of these alloys would be very useful for fuel economy. Numerous numbers of research works has been focused on the improvement of the high temperature performances of Ti alloys. It has been well known that Zirconium (Zr) is one of the important solid-solution strengthener in Ti-alloys. In the present study, the effect of Zr addition on the microstructure and mechanical properties of the near–α Ti-Al-Zr-Sn based alloys has been investigated.The compression test results showed that Zr addition significantly improves both room temperature and high temperature strength. The results obtained were explained based on the microstructural observation, room temperature and high temperature compressive tests.

Experimental Setup for the Determination of Mechanical Solder Materials Properties at Elevated Temperatures

2010 ◽  
Vol 638-642 ◽  
pp. 3793-3798
Author(s):  
Wolfgang H. Müller ◽  
Holger Worrack ◽  
Jens Sterthaus
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Elevated Temperatures ◽  
Young's Modulus ◽  
Linear Optimization ◽  
Strain Curve ◽  
Stress And Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Non Linear

The fabrication of microelectronic and micromechanical devices leads to the use of only very small amounts of matter, which can behave quite differently than the corresponding bulk. Clearly, the materials will age and it is important to gather information on the (changing) material characteristics. In particular, Young’s modulus, yield stress, and hardness are of great interest. Moreover, a complete stress-strain curve is desirable for a detailed material characterization and simulation of a component, e.g., by Finite Elements (FE). However, since the amount of matter is so small and it is the intention to describe its behavior as realistic as possible, miniature tests are used for measuring the mechanical properties. In this paper two miniature tests are presented for this purpose, a mini-uniaxial-tension-test and a nanoindenter experiment. In the tensile test the axial load is prescribed and the corresponding extension of the specimen length is recorded, both of which determines the stress-strain- curve directly. The stress-strain curves are analyzed by assuming a non-linear relationship between stress and strain of the Ramberg-Osgood type and by fitting the corresponding parameters to the experimental data (obtained for various microelectronic solders) by means of a non-linear optimization routine. For a detailed analysis of very local mechanical properties nanoindentation is used, resulting primarily in load vs. indentation-depth data. According to the procedure of Oliver and Pharr this data can be used to obtain hardness and Young’s modulus but not a complete stress-strain curve, at least not directly. In order to obtain such a stress-strain-curve, the nanoindentation experiment is combined with FE and the coefficients involved in the corresponding constitutive equations for stress and strain are obtained by means of the inverse method. The stress-strain curves from nanoindentation and tensile tests are compared for two mate-rials (aluminum and steel). Differences are explained in terms of the locality of the measurement. Finally, material properties at elevated temperature are of particular interest in order to characterize the materials even more completely. We describe the setup for hot stage nanoindentation tests in context with first results for selected materials.

Effects of Alloying Elements on Mechanical Properties of Mg-Al Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 845-848 ◽  
Author(s):  
Yeon Jun Chung ◽  
Jung Lae Park ◽  
Nack J. Kim ◽  
Kwang Seon Shin
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Casting Machine ◽  
Al Alloys ◽  
Alloying Elements ◽  
Tensile Creep ◽  
Thermally Stable ◽  
Creep Tests ◽  
High Temperature Mechanical Properties

The effects of alloying elements on the microstructure and high temperature mechanical properties of Mg-Al alloys were investigated in this study. In order to improve the high temperature mechanical properties, Sr or Mm was added to the Mg-9Al alloy. The effect of Sn on the Mg-9Al alloy was also examined since Sn was expected to improve the high temperature mechanical properties by forming the thermally stable Mg2Sn phase. The specimens used in this study were produced on a 320 ton cold chamber high-pressure die casting machine. The microstructures of the specimens were examined by optical and scanning electron microscopy and tensile and creep tests were performed at elevated temperatures. Tensile tests were carried out at room temperature, 150oC and 200oC using an initial strain rate of 2×10-4/sec. In addition, tensile creep tests were conducted at the stress levels of 50 MPa and 70 MPa. From the microstructure analyses of the specimens after heat treatment at 400oC for 12 hours, it was found that most of the Mg17Al12 precipitate dissolved into the matrix, while the thermally stable phases continued to exist. The high temperature mechanical properties of the Mg-9Al alloys were found to improve significantly with the additions of Sr, Mm and Sn, due to the formation of the thermally stable precipitates.

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