Mullite Whisker Reinforced Zirconia Toughened Alumina for High Temperature Applications

2014 ◽  
Author(s):  
Taylor Robertson ◽  
Xiao Huang ◽  
Richard Kearsey
Keyword(s):  
High Temperature ◽  
Cost Effective ◽  
Mechanical Tests ◽  
Processing Route ◽  
Molten Salt Method ◽  
The Matrix ◽  
Mullite Whiskers ◽  
Monolithic Ceramics ◽  
Zirconia Toughened Alumina ◽  
Temperature Applications

Particulate enhanced oxide ceramics are an attractive class of materials for high temperature applications because they possess many of the high temperature capabilities of monolithic ceramics but also have enhanced mechanical properties due to their multi-phase structure. High temperature structural ceramics have the potential to operate above at higher temperatures than current super alloys; however, processing costs and lack of reliability has prevented their commercialization. In this work a particulate reinforced ceramic composed entirely of oxides is proposed as a more oxidation resistant and cost effective structural ceramic which will have potentially improved resistance to environmental degradation. Zirconia Toughened Alumina (ZTA), as the matrix, has enhanced toughness, strength, and creep resistance over single phase alumina or zirconia. ZTA can further be strengthened by the incorporation of SiC type whiskers; however, these whiskers are prone to deterioration at temperatures above 1000°C through oxidation. In this work Mullite, in whisker form, is proposed as the reinforcement to ZTA due to its stability in oxidizing atmospheres at high temperatures. Mullite whiskers are grown through the molten salt method and incorporated into the ZTA matrix using a colloidal processing route in this study. The composition of the ZTA matrix is 15wt% Yttria stabilized Zirconia (YSZ), 85 wt% α-Alumina. The Mullite whiskers make up 20 vol% of the composite, yielding a final composition of 71.6 wt% Alumina, 12.7 wt% YSZ, and 15.6 wt% Mullite. The green compacts are fired in a two stage sintering process incorporating atmospheric pressure sintering to 92% density (seal the pore channels) and then hot isostatic pressure pressing (HIP) to increase the density. Samples have been tested for room temperature flexural strength using a three point bend test and fracture toughness through Gong’s Vickers indentation method. The results of microstructure study and mechanical tests are reported in this paper.

scholarly journals Surface Science of Graphene-Based Monoliths and Their Electrical, Mechanical, and Energy Applications

2020 ◽  
Author(s):  
Mujtaba Ikram ◽  
Sana Arbab ◽  
Bilal Tariq ◽  
Rayha Khan ◽  
Husnain Ahmad ◽  
...  
Keyword(s):  
High Temperature ◽  
Smart Materials ◽  
Porous Carbon ◽  
Dielectric Materials ◽  
Point Of View ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Energy Applications ◽  
Monolithic Ceramics ◽  
Temperature Applications

Ceramic monoliths are applied in many insulating and high resistive engineering applications, but the energy application of ceramics monoliths is still vacant due to less conductivity of monolithic ceramics (for example, in silica- and alumina-based hybrids). This book chapter is a significant contribution in the graphene industry as it explains some novel and modified fabrication techniques for ceramics-graphene hybrids. The improved physical properties may be used to set ceramics-graphene hybrids as a standard for electrical, mechanical, thermal, and energy applications. Further, silica-rGO hybrids may be used as dielectric materials for high-temperature applications due to improved dielectric properties. The fabricated nano-assembly is important for a technological point of view, which may be further applied as electrolytes, catalysts, and conductive, electrochemically active, and dielectric materials for the high-temperature applications. In the end, this chapter discussed porous carbon as a massive source of electrochemical energy for supercapacitors and lithium-ion batteries. Carbon materials which are future of energy storage devices because of their ability to store energy in great capacity, so sustainability through smart materials got a huge potential, so hereby keeping in view all the technological aspects, this chapters sums up important contribution of graphene and porous carbon for applied applications.

Erosion Properties of Ceramic Composite Material Based on Nano-Mullite Whisker and Zirconia-Toughened Alumina

2017 ◽  
Author(s):  
Fabian Erazo ◽  
Taylor Robertson ◽  
Xiao Huang ◽  
Rick Kearsey ◽  
Qi Yang
Keyword(s):  
Gas Turbines ◽  
Ceramic Coatings ◽  
Mechanical Mixture ◽  
Zirconia Ceramic ◽  
Molten Salt Method ◽  
Erosion Properties ◽  
Mullite Whiskers ◽  
Material Removal Mode ◽  
Positive Effect ◽  
Zirconia Toughened Alumina

The improvement of bulk ceramic properties through the addition of a secondary or even tertiary phase is a field of research that has been actively pursued since the mid twentieth century. This pursuit has become more relavent with the adoption of ceramic phases to protect structural components within the hotpath of gas turbines. Improving the properties of these ceramic coatings and tiles has the potential of reducing catastrophic damage events leading to an overall reduction in unplanned maintence and downtime. To date, Several approaches have been undertaken to improve the physical properties of these ceramics including preferential microstructural grain growth and doping to develop metastable crystal phases. This paper examines the effect of whisker additions to a mechanical mixture of oxide ceramics on the erosion properties. The baseline structure is a mechanical mixture of zirconia and alumina particles in the ratio of 89.8vol% alumina to 10.2vol% partially stabalized zirconia. A ratio of 20.0vol% mullite whiskers is incorporated into the structure as a toughening agent. The mullite whiskers are grown using a molten salt method. The overall structural composition is 20.0vol% mullite whiskers, 8.2vol% partially stabilized zirconia, and 71.8vol% alumina. This whisker toughened material is compared to a baseline 89.8vol% alumina 10.2vol% zirconia ceramic. Erosion tests were conducted using a 50 μm diameter alumina erodant with a velocity of 104 m/s. Impingement angles of 30°, 60° and 90° were examined to determine the effect of whisker additions at steeper attack angles. Despite the increased hardness, tensile strength and fracture toughness, whisker-enhanced zirconia-toughened alumina has shown similar erosion rate as non-reinforced ZTA at 30° ad 90° and much higher erostion at 60°. It can be surmised that whisker-enhanced toughening of ceramics has little positive effect on the erosion resistance of ceramics at room temperature and is potentially harmful. Microstructure analysis results are also presented within to illustrate the erosion material removal mode under different conditions.

An improved approach to evacuation of subungual hematoma

1989 ◽  
Vol 79 (11) ◽  
pp. 566-568 ◽  
Author(s):  
HJ Palamarchuk ◽  
M Kerzner
Keyword(s):  
High Temperature ◽  
Nail Plate ◽  
Cost Effective ◽  
Small Hole ◽  
Precise Method ◽  
Hematoma Evacuation ◽  
The Matrix ◽  
Subungual Hematoma

An improved approach to subungual hematoma evacuation has been presented. Hand-held cautery is a cost-effective, precise method of treatment of subungual hematoma. Its use decreases the likelihood of unnecessary delay in the regrowth of the nail plate and secondary dystrophy that might result from pressure on the matrix caused by accumulated blood under the nail. The high temperature and fine tip make the cautery an excellent instrument to precisely and painlessly burn a small hole in the nail plate, allowing for evacuation of subungual hematoma.

Mechanical Behavior of Electron Beam Powder Bed Fusion Additively Manufactured Ti6Al4V Parts at Elevated Temperatures

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Md Jamal Mian ◽  
Jafar Razmi ◽  
Leila Ladani
Keyword(s):  
Mechanical Properties ◽  
Electron Beam ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Weight Ratio ◽  
Cost Effective ◽  
Powder Bed Fusion ◽  
Boundary Slip ◽  
Powder Bed ◽  
Temperature Applications

Abstract Ti6Al4V is one of the vital metal alloys used in various industries including aerospace, especially at high-temperature applications, because of having high strength-to-weight ratio, and high melting temperature. Manufacturing these metal parts by the conventional subtractive methods have been challenging due to the difficulty involved with the cutting and machining it. However, additive manufacturing (AM) offers a convenient way for shaping this metal into the desired complex parts. Although different powder bed fusion (PBF) AM processes are time and cost effective, degradation of mechanical properties during high-temperature applications could be a concern for parts produced by them. Therefore, this study focuses on the anisotropic and high-temperature elastic and plastic behaviors of Ti6Al4V parts made using electron beam powder bed fusion (EB-PBF) process. Mechanical properties, like modulus of elasticity, 0.2% yield strength, ultimate tensile strength (UTS), and percent elongation, have been determined at 200 °C, 400 °C, and 600 °C temperatures from the samples produced in different build orientations. Considerable anisotropic behavior and temperature dependency were observed for all the analyzed properties. At 600 °C, various softening mechanisms such dislocation glide, grain boundary slip, and grain growth were anticipated to be activated reducing the flow stress and increasing the elasticity. Fractography analysis on fractured surfaces of the samples reveals various defects, including partially melted or unmelted powder particles near the surface and subsurface areas. Those internal and external defects are analyzed further using X-ray computed tomography (CT) and surface profilometer to show their effect on the anisotropic behaviors.

CMC-Jacketed Piping for High-Temperature Applications: Concept, Laboratory Tests and Large-Scale Application Test

2019 ◽  
Vol 809 ◽  
pp. 547-552
Author(s):  
Maximilian Friedrich ◽  
Min Huang ◽  
Anne Jüngert ◽  
Andreas Klenk ◽  
Stefan Weihe ◽  
...  
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Large Scale ◽  
Cost Effective ◽  
Renewable Sources ◽  
Electrical Grid ◽  
Highly Efficient ◽  
Effective Option ◽  
Materials Used ◽  
Temperature Applications

The increasing market share of highly volatile electricity generated from renewable sources like wind or solar energy, leads to enormous challenges in the energy sector. Since large-scale storage systems are neither currently nor in the near future available, the gap between electricity from renewable sources and current electricity demand has to be closed with flexibly operated conventional power plants. In order to be a viable, cost-effective option in tomorrow’s energy market future power plants must be highly efficient while having low CO2 emissions. Furthermore, they have to be highly reactive to counter instabilities in the electrical grid due to fluctuations in renewable sources. Current materials used in power plants are only within limits suited to experience extreme changes in operational loads. However, extreme changes of operational loads will become increasingly severe with a growing share of renewables. Our project team has developed a new concept for CMC-jacketed pipes to alleviate these issues. Recently, this concept was further developed and tested in laboratory as well as a large-scale application test at Grosskraftwerk Mannheim (GKM). All tests are still ongoing. Additionally, to the use in modern highly efficient power plants such CMC-jacketed piping is also suitable for other high-temperature applications, like e.g. solar power plants or industrial chemical applications.

SA-Tyrannohex-Based Composite for High Temperature Applications

2010 ◽  
Vol 71 ◽  
pp. 118-126 ◽  
Author(s):  
Toshihiro Ishikawa
Keyword(s):  
High Temperature ◽  
Internal Structure ◽  
Matrix Material ◽  
Carbon Layer ◽  
Close Packing ◽  
Close Packed Structure ◽  
The Matrix ◽  
Tremendous Amount ◽  
Monolithic Ceramics ◽  
Hexagonal Columnar

To modify the relatively low fracture toughness of monolithic ceramics, the incorporation of long ceramic fibre within a matrix material has been extensively performed. In this case, as cracks form in the matrix material and approach the fibres, they will be deflected at the interface between the fibre and the matrix. We developed another approach toward improving the toughness of ceramics involving the creation of a textured internal structure within the ceramic itself, similar in some respects to the fibrous structure of wood. Actually, we developed a tough ceramic, which consists of a highly ordered, close-packed structure of very fine hexagonal columnar fibres with a thin interfacial carbon layer between fibres. The interior of the fibre element was composed of sintered beta-silicon carbide crystal. This concept is fundamentally different from that described previously, in that it is extremely difficult to distinguish separate “fibre” and “matrix” phases in the traditional composite sense. The toughness of the material in this case derives from the tremendous amount of interface area created within the internal structure through the close packing of the hexagonal columnar fibres. Furthermore, this ceramic also achieved the excellent high temperature properties, high thermal conductivity and low density. These properties will make it very attractive for replacement of heavy metal super alloy components.

Cement Composites for High Temperature Applications

2014 ◽  
Vol 982 ◽  
pp. 154-158 ◽  
Author(s):  
Dana Koňáková ◽  
Eva Vejmelková ◽  
Veronika Spedlova ◽  
Kirill Polozhiy ◽  
Robert Černý
Keyword(s):  
High Temperature ◽  
Thermal Resistance ◽  
Mechanical Performance ◽  
Fire Hazard ◽  
Silica Sand ◽  
Cement Composites ◽  
Reinforced Composites ◽  
The Matrix ◽  
Aluminous Cement ◽  
Temperature Applications

Fiber reinforced composites designed for better thermal resistance, which can be used in constructions with a higher fire hazard, are studied. The matrix of studied composite is based on aluminous cement, because of its proved higher thermal resistance than ordinary Portland cement. Basalt sand is used as alternative aggregate replacing silica sand, and basalt fibers are employed for an improvement of mechanical performance. The presented analysis of basic physical properties, mechanical, hygric and thermal properties shows that basalt is an appropriate material for cement based composites for high temperature applications.

Sign in / Sign up

Export Citation Format

Share Document