Influence of high-temperature thermal cycles on the pore structure of red sandstone

A new cermet sinter with sweat-gland micro-pore structure has been developed by powder metallurgy technology in vacuum. The effects of the pore-forming materials on micro-pore structure and Y2O3 additions as well mechanical properties of TiC/FeCrWMoV cermets were investigated. Some typical sweat-gland micro-pores were formed while compound additives TiH2 and CaCO3 adding into the sinter matrix. The porosity of the cermet sinters changes from 20% to 28% with the compound additives from 6% to 8%, and the micro-pores of sinters exist a regularized and interpenetrated network structure just like human’s sweat-gland one and obeying to Rayleigh Distribution. As such the sinters could be easily infiltrated with high-temperature solid lubricant. For improving the property of the ceramet sinter, the elements Y2O3 of 0.6～0.8% (vol. fraction ) was also added into the sinter matrix and its effect on the sinter has been also discussed .

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Pore structure and crack characteristics in high-temperature granite under water-cooling

Case Studies in Thermal Engineering ◽

10.1016/j.csite.2021.101646 ◽

2021 ◽

pp. 101646

Author(s):

Xinghui Wu ◽

Qifeng Guo ◽

Yu Zhu ◽

Fenhua Ren ◽

Jie Zhang ◽

...

Keyword(s):

High Temperature ◽

Pore Structure ◽

Water Cooling

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Creep damage behavior of red sandstone after high temperature

10.22541/au.162108952.29835546/v1 ◽

2021 ◽

Author(s):

Xiaokang Pan ◽

Filippo Berto ◽

Xiaoping Zhou

Keyword(s):

High Temperature ◽

Uniaxial Compression ◽

Deformation Modulus ◽

Creep Damage ◽

Viscosity Coefficient ◽

Creep Tests ◽

Red Sandstone ◽

Instantaneous Strain ◽

Treated Sample ◽

Instantaneous Deformation

This work discusses the results from tests conducted to investigate the uniaxial compression and creep behavior of red sandstone. The original untreated sample and the 800 ℃ treated sample have been selected to carry out the experiments. It has been found that high temperature has obvious influence on the mechanical properties of red sandstone. The relationship between creep strain and instantaneous strain, as well as instantaneous deformation modulus and creep viscosity coefficient have been analyzed. It has been found that high temperature reduces the ability of red sandstone to resist instantaneous deformation and creep deformation. Acoustic emission (AE) technology has been also used in the loading process of uniaxial compression and creep tests, providing a powerful means for damage evolution analysis of red sandstone.

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Advanced wire bonding for high reliability and high temperature applications

International Symposium on Microelectronics ◽

10.4071/isom-2016-wa51 ◽

2016 ◽

Vol 2016 (1) ◽

pp. 000214-000218

Author(s):

M. Guyenot ◽

M. Reinold ◽

Y. Maniar ◽

M. Rittner

Keyword(s):

High Temperature ◽

Band Gap ◽

Mechanical Performance ◽

High Reliability ◽

Calculation Model ◽

Basic Knowledge ◽

Thermal Cycles ◽

White Band ◽

The Impact ◽

Mission Profile

Abstract The next generation of switches for power electronic will be based on white band gap (WBG) semiconductor GaN or SiC. This materials supports higher switching current and high frequency. White band gap semiconductors enables higher application temperature. Certainly, high temperature capability is also to discuss in combination with high number of thermal cycles. For a frame module concept shows these paper a comparison of different joining techniques with the focus on the reliability issue on wire and ribbon bonding. Beside to the 1000 passive thermal cycles from −40°C to +125°C there are active thermals cycles for technology qualification required [3]. Depending on the application and mission profile a high thermal cycling capability is necessary. For this reason, new high temperature joining techniques for die attach, e.g. Silver sintering or diffusion soldering, were developed in the recent past [4]. All of this new joining techniques focusing on higher electrical, thermal and thermo-mechanical performance of power modules. By using an optimized metallization system for the WBG the numbers of thermal cycles can be increased and the maximum operating temperature advanced up to 300°C. In these new temperature regions silicon semiconductors will be substituted by WBG semiconductors. The present work shows an active power cycling capability of different wire and ribbon bonds and the failure mechanism will be discussed. A calculation model explained the reliability for the different wire diameter and the impact of bonding materials. This reliability calculation explain the thermo-mechanical effects and based on materials and geometry data and is not optimized for evidence. Through these physical background understanding more than 1.000.000 thermal cycles with a 150 K temperature swing from +30°C to +180°C are now possible. These is a the basic knowledge for a design for reliability based on current, mission profile and reliability optimization for future high end applications with wire or ribbon bonding technique.

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Sealing Performance and Mechanism of a High-Temperature Near-Neutral Sealing Adhesive in the Ternary System of ZrO2-Al2O3-SiO2

Materials Science Forum ◽

10.4028/www.scientific.net/msf.977.65 ◽

2020 ◽

Vol 977 ◽

pp. 65-71

Author(s):

Li Biao Xiao ◽

Dian Zhang ◽

Yi Jun Liu ◽

Li Min Pan ◽

Qun Hu Xue

Keyword(s):

High Temperature ◽

Volume Expansion ◽

Gas Permeability ◽

Raw Materials ◽

Magnesium Aluminate Spinel ◽

Stabilized Zirconia ◽

Thermal Cycles ◽

Sealing Performance ◽

Critical Particle Size ◽

Sintering Shrinkage

A high-temperature sealing adhesive was prepared using kyanite, andalusite, and magnesia fully stabilized zirconia (Mg-FSZ) as raw materials and nanozirconia (ZrO2) sol as binder. The adhesive is chemically near-neutral and suitable for bonding acid, neutral, or alkaline materials at 1560 °C. The mineral composition, volume expansion, and air permeability of multiple thermal cycles were analyzed. Results showed that the volume expansion caused by the mullitization of kyanite and andalusite can compensate for the sintering shrinkage high temperature. MgO could gradually desolvatize from the Mg-FSZ particles and react with SiO2 and Al2O3 to produce a stable forsterite and magnesium aluminate spinel. Hence, Mg-FSZ became unstable, and cubic ZrO2 transformed into monoclinic ZrO2 when cooled, leading to a volume expansion of the adhesive, which ensured the sealing effect. A larger critical particle size of Mg-FSZ can provide the adhesive with a more persistent volume expansion during thermal cycles due to the more durable desolvatization of MgO. The nanoZrO2 sol binder can improve the sintering of the adhesive and bonding of the joint, resulting in a low gas permeability.

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Fractal analysis of pore structure of granite after variable thermal cycles

Environmental Earth Sciences ◽

10.1007/s12665-019-8703-4 ◽

2019 ◽

Vol 78 (24) ◽

Cited By ~ 3

Author(s):

Fei Zhao ◽

Qiang Sun ◽

Weiqiang Zhang

Keyword(s):

Pore Structure ◽

Fractal Analysis ◽

Thermal Cycles

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Research on the Pore Evolution of Sandstone in Cold Regions under Freeze-Thaw Weathering Cycles Based on NMR

Geofluids ◽

10.1155/2020/8849444 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Zheng Pan ◽

Keping Zhou ◽

Rugao Gao ◽

Zhen Jiang ◽

Chun Yang ◽

...

Keyword(s):

Magnetic Resonance ◽

Pore Structure ◽

Western China ◽

Cold Regions ◽

Abrupt Decrease ◽

Evolution Law ◽

Red Sandstone ◽

Freeze Thaw ◽

Evolution Characteristics ◽

Pore Evolution

The evolution of the rock pore structure is an important factor influencing rock mechanical properties in cold regions. To study the mesoscopic evolution law of the rock pore structure under freeze-thaw weathering cycles, a freeze-thaw weathering cycle experiment was performed on red sandstone from the cold region of western China with temperatures ranging from -20°C to +20°C. The porosity, T2 spectral distribution, and magnetic resonance imaging (MRI) characteristics of the red sandstone after 0, 20, 40, 60, 80, 100, and 120 freeze-thaw weathering cycles were measured by the nondestructive detection technique nuclear magnetic resonance (NMR). The results show that the porosity of sandstone decreases first and then increases with the increase of the freeze-thaw weathering cycles and reaches the minimum at 60 of freeze-thaw weathering cycles. The evolution characteristics of porosity can be divided into three stages, namely, the abrupt decrease in porosity, the slow decrease in porosity, and the steady increase in porosity. The evolution characteristics of the T2 spectrum distribution, movable fluid porosity (MFP), and MRI images in response to the freeze-thaw weathering process are positively correlated with the porosity. Analysis of the experimental data reveals that the decrease in the porosity of the red sandstone is mainly governed by mesopores, which is related to the water swelling phenomenon of montmorillonite. Hence, the pore connectivity decreases. As the number of freeze-thaw cycles increases, the effect of the hydrophysical reaction on the porosity gradually disappears, and the frost heaving effect caused by the water-ice phase transition gradually dominates the pore evolution law of red sandstone.

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