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Ultra-High Temperature Materials (UHTM & UHTC) critical for Jet Engines, Space planes and Hypersonic Missiles

There is growing interest in developing ultrahigh temperature materials (UHTM). These are materials with a temperature capability greater than 1650 °C and able to withstand extreme erosive/corrosive environments. Interest in high-temperature ceramic phases has been growing in recent years, with significant ongoing research programmes in many countries across the world. This has occurred because the conditions in which materials are required to operate are becoming ever more challenging as operating temperatures and pressures are increasing in all areas of manufacture, energy generation, transport and environmental clean-up. Often extreme temperatures are combined with severe chemical environments and exposure to high energy and, in the nuclear industry, to ionizing radiation.


For example, atmospheric re-entry vehicles, rockets and scramjet-powered air-breathing hypersonic cruise vehicles primarily encounter high pressures and heat flux on the leading edges due to air stagnation and shock waves. Also, the respective propulsion systems experience high-temperature exothermic combustion reactions to produce thrust.


The era of hypersonic flight had arrived with a global race to develop Hypersonic Missiles such as US HTV-2 and X-51, Chinese WU-14, Russian Yu-71, that travel at least five times the speed of sound (Mach 5) or more. These vehicles can fly along the edge of space and can glide and maneuver to the targets. When moving at such velocity the heat generated by air and gas in the atmosphere is extremely hot and can have a serious impact on an aircraft or projectile’s structural integrity. That is because the temperatures hitting the aircraft can reach anywhere from 2,000 to 3,000 °C. The structural problems are primarily caused by processes called oxidation and ablation.


Hypersonic flights, re-entry, and propulsion vehicles, regardless of their design, require maneuverability of materials against high temperature erosion in excess of 2400°C. This is when extremely hot air and gas remove surface layers from the metallic materials of the aircraft or object traveling at such high speeds.


“It’s all about the heat,” said hypersonics expert Brad Leland. At speeds of Mach 5 and higher, aerodynamic friction can heat an aircraft’s exterior enough to melt steel. Advanced materials, recently in development, are necessary.


One of the greatest challenges with designing solid rockets and control systems for missiles and space launch vehicles is protecting the hardware and payloads from the intense heat and high pressures generated by burning solid propellants. Flame temperatures can range from 2000 – 6000 degrees Fahrenheit and motor operating pressures can be thousands of pounds per square inch. In this extreme environment, the material used to insulate key components of rocket propulsion control systems begins to erode, decompose or change states, often within tens of seconds. Without insulation, these components can rapidly overheat and fail structurally, limiting a rocket’s performance and operational range.


The  Airframe of Hypersonic Vehicles like SR-72 ( Lockheed Martin reconnaissance drone with strike capability), must include advanced materials to stay intact while subjected to high dynamic loads, and to withstand the extreme aerodynamic heating of hypersonic flight, as air friction alone would melt conventional materials, rites Dora E. Musielak, Ph.D. University of Texas at Arlington.


Hypersonic platforms are ultimately limited by the capacities of the materials available. A prime example of an aircraft’s failure due to inadequate materials is the test flight of the hypersonic Falcon HTV-2, which, according to DARPA, crashed into the ocean after “unexpected aero-shell degradation” due to excessive thermal and structural loads from the brutal shock waves present at such high Mach numbers.


Ultrahigh temperature material (UHTM) requirements

Materials’ selection is governed strongly by environment and trajectory, as well as the location on the vehicle, so as to minimize weight and fuel consumption and maximize payload.

In order to protect the excessive temperature of the underlying metal of a structure, the thermal protection system design provides a smooth, and aerodynamic surface.
UHTM should possess high strength at high temperatures, oxidation resistance, ablation resistance, thermal shock resistance. These materials will be required for hypersonic air-breathing vehicles, hyper-speed cruise missiles, hypersonic aircraft, re-usable launch vehicles to protect leading edges and nose cones that experience very high temperatures (> 2000 °C).


Melting temperature is only one of the many properties required of the materials. As most engine and hypersonic leading edge applications will involve exposure to oxidizing fuels or aero-heating, all non-oxide materials will undergo oxidation to form some combination of solid, liquid, or gaseous reaction product. It is the oxidation behavior that is one of the primary constraints associated with the selection process of UHTC materials.  Additionally, the adverse environmental effects include detrimental effects of chemical reactions, mechanical stresses and radiation.


The development of structural materials for use in oxidizing and rapid heating environments at temperatures above 1600°C is therefore of great engineering importance. The trajectories for hypersonic space vehicles demand high thermal resistance for the base material to sustain operating temperatures in range 1873-2673 K. These conditions are beyond the capabilities of many engineering ceramics and have motivated researchers to pursue the development of UHTCs.


The production and processing of next-generation materials capable of operating in these conditions is non-trivial, especially at the scale required in many of these applications. In some cases, totally new compositions, processing and joining strategies have to be developed. The need for long-term reliability in many components means that defects introduced during processing will need to be kept to an absolute minimum or defect-tolerant systems developed, e.g. via fiber reinforcement.


Modelling techniques that link different length and time scales to define the materials chemistry, microstructure and processing strategy are key to speeding up the development of these next-generation materials. Further, they will not function in isolation but as part of a system. It is the behaviour of the latter that is crucial, so that interactions between different materials, the joining processes, the behaviour of the different parts under extreme conditions and how they can be made to work together, must be understood.


A wide range of materials and concepts has been used in flight or is being considered for future vehicles and missions. Refractory diboride composites like ZrB2, HfB2 etc and multilayer coatings of HfC, SiC on C-C composites are most promising UHTM candidates.


Ultrahigh temperature materials (UHTM)

Combustion in airplane engines now reaches or exceeds 1500 degrees centigrade, well above the melting temperatures of engine parts typically made of nickel and cobalt alloys.


The most promising lightweight materials are carbon/carbon (C/C) composites; however, there is a critical need to improve their oxidation and ablation resistance. Carbon fibre-based composites have received much attention due to their excellent high-temperature strength in reducing or neutral atmospheres, high thermal conductivity, low coefficient of thermal expansion and excellent thermal shock resistance; however, they suffer badly from oxidation, in air, even at temperatures below 1000 Deg C . The addition of SiC, as a powder or a dense matrix, can provide protection up to 1300–1400°C or, for short periods, at temperatures up to 1600°C via the formation of a SiO2 film.


Researchers from Florida State University’s High-Performance Materials Institute, with funding from the U.S. Air Force, discovered that soaking sheets of carbon nanotubes in phenol-based resin increases their ability to disperse heat by about one-sixth, allowing a thinner sheet to do the job. Carbon fiber reinforced polymers (CFRP) are becoming increasingly used in aerospace applications which require lightweight and stability at high temperatures.


Researchers describe  a systematic design of a carbon nanotube/phenolic thermal protection layer (TPL) with heat shield functionality while maintaining designed mechanical strength compared to traditional CFRP composites. These TPLs were integrated onto the surface of carbon fiber/bismaleimide composites to act as a heat shield for hybrid composites. A bonding layer of ultra-thin unidirectional carbon fiber was introduced between the TPLs and CFRP to improve the constituent interface. Hybrid composites with different TPL volume fractions were produced. The TPLs resulted in a 17% decrease of the through-thickness thermal conductivity for hybrid composites. “Carbon nanotubes have magnitudes higher in-plane thermal conductivity than carbon fiber,” researcher Ayou Hao explained to Defense One in an email. “Once heat reaches the carbon nanotube thermal protection layer surface, it is quickly dispatched.”


Silicon carbide (SiC)

In nano-scale perspective, Silicon carbide (SiC) was astonishingly smart and adaptive in its characteristics. Not only that, it showed a great strength and modulus, dense equal to that of an aluminum; while ensuring a low cost in comparison. In terms of aerospace application, SiC can be used as a particulate filter in a massive ceramic composite which indicates as an Ultra High Temperature Ceramics (UHTCs), or it can act as a matric that is in reinforced composited (CMCs).


Research has turned to ceramics that can withstand these temperatures, but they must contend with chemical reactions from the water vapor and unburnt oxygen in the extreme combustion environment. Silicon carbide is the ceramic of choice. However, engine parts made of silicon carbide would last only a few thousand hours of flight time. At such high temperatures, the carbon element reacts with oxygen to form carbon monoxide (a gas), while the silicon forms silica (a solid), but silica reacts with water vapor to form a gaseous silicon hydroxide. In other words, the engine part progressively turns into gas and disappears out the tail pipe.


To protect the ceramic parts, engine manufacturers apply a two-layer coating, called an environmental barrier coating system, to the silicon carbide. The outer layer is designed to slow the spread of oxygen and water vapor toward the silicon carbide during flight, while an inner bond coat made of silicon protects the silicon carbide’s surface by reacting with the oxygen to form a thin layer of silica. But there are still challenges to this design.


Haydn Wadley, Edgar Starke Professor of Materials Science and Engineering at the University of Virginia School of Engineering and Applied Science, and Jeroen Deijkers, a postdoctoral research associate in Wadley’s group, found a way to greatly extend the life of the materials used in these jet engines. Their paper, “A Duplex Bond Coat Approach to Environmental Barrier Coating Systems,” is published in the September 2021 issue of Acta Materialia.


Their solution uses an outer layer of ytterbium disilicate, a rare earth element that shares silicon’s and silicon carbide’s thermal expansion characteristics and is slow to transport oxygen and water vapor toward the silicon layer. They first deposited the silicon bond coat and then placed a thin layer of hafnium oxide between the silicon and the ytterbium disilicate outer layer. Their experimental studies show that as the silica forms on the silicon, it immediately reacts with the hafnia to form a silicon-hafnium oxide, or hafnon. The hafnon’s thermal expansion and contraction is the same as the rest of the coating and will never cause the coating to pop off or crack. Wadley calls it adding a little “hafnia fairy dust.”


However, at higher temperatures the silica begins to soften dramatically and in a low-oxygen atmosphere it develops a substantial vapour pressure.  The addition of SiC, therefore, is not suitable for applications at temperatures above 1600°C.


SiC is usually mixed with carbon fibers to obtain CMCs with the non-oxide matric materials for greater temperature applications. A study suggested that there was no degradation reported when the carbon fibers were tested with a temperature over 2600 °C in a non-oxidizing atmosphere.


This shows that carbon fibers are protected from oxidation reactions; becoming a useful material in space vehicle applications as temperature rises up to 1600 °C during the re-entry phase in atmosphere. The key role of SiC matrix in CMCs is protection of carbon fibers from oxidation processes; which activates at 500 °C temperature, leading to the formation of a protective silica-based glassy layer. Other than that, SiC can be used to protect carbon fiber reinforces carbon composites (C/C); in the form of coating. Furthermore, the Reinforced Carbon-Carbon (RCC) has been used as TPS for applications such as wing leading edges and the nose cap of the Space Shuttle, due to the temperature ranges of 1500-1600 °C whilst the re-entry phase in atmosphere occurs.


Addition of UHTCs, which inherently have a higher thermal conductivity and form in situ oxidation scales, have been reported to improve the oxidation and ablation resistance of C/C, C/SiC and SiC/SiC composites. UHTCs such as HfB2 and ZrB2 have melting points in excess of 3000°C and their oxides melt at >2500°C, they can be used to protect the Cf preforms from oxidation.


Boron carbide (B4C)

Boron carbide B4C, has been applied in engineering materials for various purposes such as wear parts, and abrasives; due to its strength in hardness and exceptional wear resistance. few researchers reported that boron carbide has a higher temperature thermoelectric material and a first-wall material for a fusion reactor. Another study stated the reason that due to its stability in compounds, with a melting point of 2350 °C, and a low density (2.52 g/cc) .
In addition to that, B4C material promises its reliability with various distinctive applications that
require elevated mechanical properties. Other than that, densified B4C can slowly oxidizes at 600 °C, resulting in the formation of a thin B2O3 film; cracking after it reaches a cool temperature. Other researches stated that the oxidation process at 1200 °C, there is limited by diffusion of reagents through the oxide layer. On the other hand, another study stated that combining particles of ZrB2–B4C showed an effective inhibiting oxidation of C–C composites, during a 1500 °C temperature

Over the last couple of decades, there has been a growing interest for UHTCs in general, and for the transition metal di-borides in particular, due to the increasing demands in hypersonic aerospace vehicles, atmospheric re-entry vehicles and energy applications. However, problems pertaining to sintering, moderate fracture toughness and experimental challenges associated with reliably measuring the elevated temperature properties, as well as the properties that determine the performances at the actual service conditions, have limited their widespread applications.


Columbia’s hypersonic vehicle used black, grey and white tiles on the nozzle. White tiles (1 inch-thick) were used to protect regions such as upper wings and fuselages; black tiles (1-5 inch-thick) were used to protect lower side and nose area and super absorbent gray tiles were used to protect nose tip and leading edges of the Columbia’s wings. These UHTCs are selected for application on the basis of distribution of temperature in various parts of the vehicle. The root cause for the Columbia disaster was the crack initiation due to foam impact in the wing that allowed destructive superhot gases to penetrate the wing, and consequently melted and disintegrated during the reentry of the shuttle into earth’s atmosphere.


Ultra-High-Temperature Ceramic materials are assuming an increasing importance in aerospace research because their high temperature resistance makes them interesting to develop components for extreme applications, such as thermal protection systems for hypersonic or atmospheric reusable re-entry vehicles, specific components for propulsion, combustion chambers, engines intakes or rocket nozzles. Lightweight carbon composites used in hypersonic vehicles such as rockets, re-entry spacecraft and defense projectiles can withstand temperatures of up to 2900 degrees Fahrenheit.


For the past two decades researchers have built on a resurgence in the exploration of UHTCs and have expanded the scope of engineering and design using these novel materials. Topics such as incorporating UHTCs in fiber reinforced composites; investigating unique high entropy carbides and borides, and expanding the field of MAX phases have all led to new developments.


Different methods are being investigated to prepare C/C-UHTC composites, including slurry infiltration , precursor infiltration and pyrolysis (PIP) , reactive melt infiltration (RMI) , chemical vapour decomposition (CVD), chemical vapour infiltration (CVI) , and, in the future, combinations of them. The ceramic matrix used in the design of the composite is going to depend on the working temperature, exposure time and mechanical stresses that the material needs to bear for the application.


Zirconium and hafnium diborides (ZrB2, HfB2)

Recent research is also focused on the development of Hafnium and Zirconium based boride ceramics using advanced ceramic processing techniques for leading edge sections of hypersonic vehicles which experience extreme thermo-mechanical loading. Novel additives are being added to the ceramics to enhance oxidation resistance and thermo-mechanical properties. Carbon nanotubes (CNTs) have shown to improve the fracture toughness of the composites through a range of toughening mechanisms, like CNT pull-outs, crack bridging, and crack deflection.


It is known that the UHTC materials have become known worldwide. As the ZrB2 and HfB2-based UHTCs are the mostly used and researched upon; their characteristics of good oxidation resistance from room temperature to 2000 °C. In comparison, HfC and ZrC have higher melting points than HfBand ZrB2; the diborides are known to have a greater thermal conductivity than the carbides.
Another study discussed the combination of high-temperature capabilities along with their thermal conductivity, which makes HfB2 and ZrB2 particularly attractive to use in sharp wing leading edges and nose tips.
The advantage of diboride-based UHTC materials in performance is obtained from their high-
temperature capability and high thermal conductivity. Convective energy that enters the surface near the stagnation region is conducted away to cooler regions of the leading edge, where it can be radiated back to the environment. The higher the thermal conductivity of the leading-edge material, the more efficient this process becomes. The UHTC leading edge then behaves much like a passive heat pipe, to move energy through, and eventually out of, the system.
Practically, high-temperature oxidation resistance of a pure diboride materials is not sufficient for
aerothermal flight environment. The best oxidation performance is found for monolithic materials hot-pressed from mixtures of ceramic powders containing a silica former as a minor component. SiC matrix reinforced metal borides, such as ZrB2, and HfB2 have been commonly referred to as Ultra High Temperature Ceramics. UHTCs represent a class of promising materials that can be used in extreme applications due to their high melting point and relatively good oxidation resistance in re-entry conditions. ZrB2, and HfB2 are characterized by high melting temperatures (3250 and 3400 °Crespectively), solid state stability, good thermo-chemical, and thermo-mechanical properties

UHTC Materials

Ceramic materials having melting points higher than 3000 °C and suitable for structural applications at above 2000 °C are commonly known as Ultra-High Temperature Ceramics (UHTCs). Several transition metal di-borides, possessing the desired combinations of thermo-mechanical, physical and chemical properties, form an important sub-class of the UHTCs.


Ultra-High Temperature Ceramics are a family of compounds that display a unique set of properties, including extremely high melting temperatures (>3000°C), high hardness and good chemical stability and strength at high temperatures.


Ultra-high temperature ceramics (UHTCs) are promising materials for potential application in thermal protection systems (TPS) under these extreme thermal and chemical environments. The past few decades have seen phenomenal research on Ultra High Temperature Ceramics (UHTCs), which are commonly defined as materials with very high melting temperatures (~3273 K) and ability to perform under extreme thermal environments.


UHTC materials are typically considered to be the carbides, nitrides, and borides of the transition metals, but the Group IV compounds (Ti, Zr, Hf) plus TaC are generally considered to be the main focus of research due to the superior melting temperatures and stable high-melting temperature oxide that forms in situ. The combination of properties make these materials potential candidates for a variety of high-temperature structural applications, including engines, high-speed vehicles, plasma arc electrodes, advanced nuclear fuels, fusion first walls and divertors, cutting tools, furnace elements and high temperature shielding.


Northrop Grumma’s Engineer develops JT-700 used  to fabricate complete nozzles for rocket propulsion control systems

Tim Dominick, senior principal engineer for propulsion, Northrop Grumman Innovation Systems has been leading the company’s efforts to develop a new type of thermal insulator that remains stable and effective in high-temperature, high-pressure environments.


Known as JT-700, the new insulator is a carbon-fiber-reinforced silicon carbide material. It is part of a class of materials known as ceramic matrix composites (CMC). JT-700 promises to improve the performance and extend the mission duration of solid propulsion control systems by an order of magnitude. “With JT-700, we can meet our customers’ desire for increasingly compact, high-performance rockets that can fly for extended periods of time,” said Dominick.


JT-700, Dominick explains, is an aerospace technology called a structural insulator; it performs well as a thermal insulator (i.e., low in heat conductivity), yet is strong enough to serve as a load-bearing part of a structure. “Carbon-fiber reinforced silicon carbide CMCs have been around for about 25 years, but they’ve exhibited both high strength and high heat conductivity,” said Dominick. “We’ve figured out a way to make JT-700 in a way that retains its strength while driving down its conductivity.”


Northrop Grumman is using JT-700 to fabricate complete nozzles for rocket propulsion control systems, he adds. Each nozzle is machined from a single block of JT-700 CMC material, which simplifies the nozzle assembly process. In the past, these parts were produced from refractory (high-temperature) metals to which phenolic insulation had been bonded.


During rocket flight, explain NASA scientists, combustion of a rocket’s solid propellant produces large amounts of gas at high temperature and high pressure. This exhaust gas flows through the rocket motor’s nozzles, creating thrust. A propulsion control system “steers” the rocket by diverting exhaust gas selectively through each nozzle for discrete periods of time. To date, reports Dominick, Northrop Grumman has validated the JT-700 technology in both laboratory and prototype tests as a zero-erosion, low conductivity nozzle material suitable for use in solid propulsion control systems.


Dominick believes that JT-700’s insulating and structural properties also lend themselves potentially to another high-temperature, high-pressure defense application called hypersonic weapons. Hypersonic air and space vehicles experience extremely high temperatures and high rates of heating during flight,” he said. “This extreme environment demands that we select materials that can best meet the critical temperature, structural and weight requirements of these evolving air and space missions.”


The commercial aircraft industry could also benefit potentially from JT-700, Dominick believes. “In a jet aircraft, a lot of incoming air is diverted and used for cooling metal parts in the engine,” he explains. “Those metal parts can’t survive at higher operating temperatures, which artificially limits the engines to a combustion temperature less than the service temperature of those parts.”


By replacing key metal turbine parts with a structural insulator such as JT-700, Dominick proposes, the need to cool those metal parts with “bleed air” could be eliminated. These “new” turbines would be able to operate at much higher temperatures, which would allow them to operate more efficiently and burn less fuel, an important economic consideration for any airline fleet.


Chinese Researchers reported in 2019 to  have developed a ceramic-metal composite that can withstand temperatures up to 3,000 degrees Celsius

Researchers in central China have developed a non-carbon-based heat-resistant material with potential for use in hypersonic vehicles, according to Chinese media reports. The team, led by Professor Fan Jinglian from Central South University in Hunan province, developed a ceramic-metal material that can endure temperatures as high as 3,000 degrees Celsius (5,430 Fahrenheit), according to Hunan Television.


Fan, a top researcher in high-temperature-resistant materials, said the composite could be used in various devices, from engines to space rockets and nuclear reactors. The new material’s heat resistance also means that it might be suitable for use in hypersonic aircraft, which can heat up to as high as 3,000 degrees Celsius through atmospheric friction.


Hong Kong-based military analyst Song Zhongping said it would be simpler if the material was only used in rockets, which were generally “disposable”. “[The technology] would be much more difficult if the material was for use in hypersonic aircraft because it needs to be reusable,” Song said. “A new military technology should satisfy three criteria: be innovative, of a high standard and of quality materials. “It can be created if it has all three elements and integrates them successfully and seamlessly.” In August 2019, China successfully tested the Starry Sky-2, a missile-capable hypersonic aircraft, in northwest China, according to the China Academy of Aerospace Aerodynamics.


Raytheon Technologies’ Collins Aerospace has created a new business unit that will allow the company to build critical parts for next-generation military aircraft and hypersonic weapons.

The unit, called Advanced Structures will work towards developing new types of composite materials that could be used to make futuristic planes and missiles lighter and make them able to resist extreme forces and temperatures.


Advanced Structures combines two of Collins’s business units, Mechanical Systems and Aerostructures. The Mechanical Systems group produces parts for aircraft which include landing gear, wheels, brakes, and propellers, while the Aerostructures group is known for building nacelles, the casing wrapped around a plane’s engine.


According to Mehta, some of the existing technologies that the company possesses can be game-changers if they are applied to aerostructure-type projects, such as ‘carbon-carbon’, a material that the company uses in making brakes that can also be used to make an aircraft structure withstand high-speed flight.


Carbon-carbon (C-C) composites consist of carbon fibers that are arranged in the form of a matrix. The C-C composites can conduct heat without expanding and has low density. One of the most important features of this material is its resistance to temperatures as high as 1000 degrees Celsius.


“One of the challenges in hypersonics is you have to protect the payload in the most extreme environment,” Mehta said. “You think about friction, you think about some of the heat characteristics and requirements, that a hypersonic, whether it’s a projectile or whether it’s an aircraft. This is the type of material that helps solve that particular problem.”


This new venture by Collins can mean a major boost to the US effort to catch up to weapons advances by China and Russia who are also engaged in developing similar technologies.


XMat – materials systems for extreme environments

The overall objective of this programme was to establish the UK’s capability to discover and understand new materials that can operate under increasingly extreme conditions, thus enabling a wide range of new technologies. The vision was to develop the required understanding of how the processing, microstructures and properties of materials systems operating in extreme environments interact to the point where materials with the required performance could be designed and then manufactured.


Immediately before this project, DSTL funded research (at Loughborough University in the UK where the team was based at the time) where carbon fibre reinforced UHTC materials were developed and tested at temperatures exceeding 2500°C and HfB2 particulate filled Cf/C composites were deemed to have the best oxidation resistance


The work funded by DSTL focused on the design and optimisation of a manufacturing route to produce large plates of Cf-HfB2 composite measuring 300 × 300 × 18 mm and 150 × 250 × 18 mm for TPS applications; these were satisfactorily achieved. At the end of the research programmes, it could be concluded that the Cf reinforced UHTC composite material demonstrated excellent thermal resistance, thermal insulation and good structural properties and could be made as both large panels and complex-shaped components. Through the design, manufacture and testing, a TRL of 3 to 4 was achieved for the Cf-UHTC composite technology.


The impregnation of 2.5D woven carbon fibre preform with UHTC powder before infiltration with carbon has allowed the temperature capabilities of the carbon–carbon composites to be extended beyond 2500°C. Using ZrB2 powder, the composites are capable of withstanding ∼2500°C, while with HfB2 powder this is extended up to ∼3000°C.


UK Researchers found World’s most heat resistant material

Now Researchers have discovered that tantalum carbide and hafnium carbide materials can withstand scorching temperatures of nearly 4000 degrees Celsius. In particular, the team from Imperial College London discovered that the melting point of hafnium carbide is the highest ever recorded for a material. Being able to withstand temperatures of nearly 4000°C could pave the way for both materials to be used in ever more extreme environments, such as in heat resistant shielding for the next generation of hypersonic space vehicles.


Researchers from Imperial College London in the UK discovered that the melting point of hafnium carbide is the highest ever recorded for a material. Tantalum carbide (TaC) and hafnium carbide (HfC) are refractory ceramics, meaning they are extraordinarily resistant to heat. Their ability to withstand extremely harsh environments means that refractory ceramics could be used in thermal protection systems on high-speed vehicles and as fuel cladding in the super-heated environments of nuclear reactors. However, there has not been the technology available to test the melting point of TaC and HfC in the lab to determine how truly extreme an environment they could function in. The researchers developed a new extreme heating technique using lasers to test the heat tolerance of TaC and HfC.


They used the laser-heating techniques to find the point at which TaC and HfC melted, both separately and as mixed compositions of both. They found that the mixed compound (Ta0.8Hf0.20C) was consistent with previous research, melting at 3,905 degrees Celsius, but the two compounds on their own exceeded previous recorded melting points. The compound TaC melted at 3,768 degrees Celsius, and HfC melted at 3,958 degrees Celsius. The findings may pave the way for the next generation of hypersonic vehicles, meaning spacecraft could become faster than ever.


Dr Cedillos-Barraza said: “The friction involved when travelling above Mach 5 – hypersonic speeds – creates very high temperatures. So far, TaC and HfC have not been potential candidates for hypersonic aircraft, but our new findings show that they can withstand even more heat than we previously thought – more than any other compound known to man. This means that they could be useful materials for new types of spacecraft that can fly through the atmosphere like a plane, before reaching hypersonic speeds to shoot out into space. These materials may enable spacecraft to withstand the extreme heat generated from leaving and re-entering the atmosphere.”


Examples of potential uses for TaC and HfC could be in nose caps for spacecraft, and as the edges of external instruments that have to withstand the most friction during flight.


New Ceramic Plane Coating Could Be Used in Hypersonic Flight

 Collaborating with Central South University in China, researchers at the University and the Henry Royce Institute – the national organisation based in Manchester that is leading on advanced materials research and applications – have designed and fabricated a new carbide coating that’s vastly superior in resisting these temperatures.


The new carbide coatings are formed when carbon combines with other elements that have a lower rate of surface erosion at high temperatures. The study was led in Manchester by Professor Ping Xiao from the School of Materials. It’s his belief that these compounds could revolutionise hypersonic travel for air and space.


Researchers at the University of Manchester and the Royce Institute, in collaboration with the Central South University of China (CSU), started working with zirconium carbide (ZrC) to figure out a cost-effective solution to overheating. ZrC is used commercially for drill bits on power tools, so it’s well known for being strong and heat resistant. The researchers used a process called reactive melt infiltration while making the material, increasing the speed of fabrication, and then reinforced it with a carbon–carbon composite. Often used in Formula One car brake systems, carbon-carbon composites can handle the extreme forces of high speed.


Simulation, Modelling and testing

Modelling techniques that link different length and time scales to define the materials chemistry, microstructure and processing strategy are key to speeding up the development of these next-generation materials. Further, they will not function in isolation but as part of a system. It is the behaviour of the latter that is crucial, so that interactions between different materials, the joining processes, the behaviour of the different parts under extreme conditions and how they can be made to work together, must be understood.


The development of UHTM requires an in-depth understanding of the structural stability of the ceramic by evaluating micro-structural characteristics, determination of high temperature mechanical properties, study of shock-material interaction under different experimental conditions (shock wave velocity, number of pulses, environment and pulse duration) etc.


“Through simulation and testing, we are able to analyze properties of microstructures, using this knowledge to develop new materials with new properties,” said research scientist Jason Poleski. “This isn’t just about using the latest in heat-resistant materials. In order to manage heat dissipation, we need to consider both materials on a microscale as well as the vehicle topology in order to create a vehicle that won’t melt under the heat caused by wind resistance at Mach speeds.”


High-temperature material properties measurement methods for hypersonic vehicle systems

PSI has been awarded a Phase I SBIR contract from the US Air Force Research Laboratory to determine the high-temperature properties of thermal protection system materials and structural materials utilized in the development, design, fabrication and testing of hypersonic vehicles.


Test vehicle flights aimed at understanding the structural integrity of hypersonic demonstrators have been performed from about Mach 5 to 20, but these vehicles have not been recovered. The post-test forensics is difficult due to the lack of the high temperature properties of the thermal protection layer and the structural material strength. In order to properly design hypersonic test vehicles and the weapon systems that evolve from them, it is necessary to better understand the materials in their proper thermal environment. The goal of this effort is to determine these high-temperature properties by a combination of experimental laser testing and modeling. PSI has achieved prior success in such evaluations using a well-characterized thermal source and matching as many experimental test results as possible as a function of the experiment time duration.


The acquisition of validated high-temperature properties for thermal protection materials and structural materials will lead to rapid improvements in the design, development and testing of new hypersonic weapon systems. The recommended hypersonic material database development will be of keen interest to the Air Force, DoD and DARPA as the development of hypersonic vehicles accelerates. NASA and commercial corporations will also find the database and the innovative material data acquisition process very useful as they develop hypersonic technology for earth and other planetary ventures.


Army Rapid Capabilities and Critical Technologies Office  calls for hypersonic protection systems

In March 2021, The U.S. Army seeked white papers on systems that would protect hypersonic weapons from the harmful effects of heat. White papers are sought to satisfy the U.S. Army RCCTO’s requirements for a prime contractor to drive the development of materials and processes to prototype Thermal Protection Systems (TPSs) in support of the Long Range Hypersonic Weapon (LRHW).


The TPS prototypes are required to protect the Common Hypersonic Glide Body (CHGB) from heat induced during hypersonic flight, working as a thermal insulator, aerodynamic body, and structural component.


The main goal of the TPS Prime Prototype Project is to create TPS prototypes from a Technical Data Package (TDP) for the first time. Throughout the duration of this pOTA, the TPS prototypes will be provided to other programs as Government Furnished Property (GFP) and subjected to testing to include flight test.


The prime contractor will take the TPS TDP under configuration control to coordinate design updates, prioritizing the directed subcontractors’ prototyping efforts to meet test events and develop novel methods to inspect and accept the prototypes to include materials research
and precision measurements. The TPS prototype prime contractor requirements include fabrication or acquisition of subcomponents from an existing supply chain, assembly of the TPS prototypes and mating of the TPS prototypes to the CHGB.


In Mar 2021,  Army’s Rapid Capabilities and Critical Technologies Office seeked white papers for development of a prototype TPS based on a technical data package and support other government programs through the resulting product. A future contractor for the effort would procure or produce needed components, build prototypes and integrate the TPS with CHGB units. The contractor would also coordinate TPS design changes, support subcontractors and develop assessment methods for the TPS prototypes.


Leidos‘ Dynetics subsidiary has won a $478.6 million contract from the U.S. Army  in Nov 2021,  to develop a thermal protection system intended to protect surface-to-surface hypersonic missiles from intense heat during flight.


Dynetics will build the Hypersonic Thermal Protection System prototype and help the military branch conduct materials research, inspection and acceptance efforts under the cost-plus-fixed-fee contract, the Department of Defense said Friday.


According to a solicitation document, the TPS will be developed to function as a thermal insulator, aerodynamic body and structural component of the LRHW’s Common Hypersonic Glide Body. Five bids were submitted to the Army Rapid Capabilities and Critical Technologies Office in pursuit of the prototype project.


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