High Temperature Capability Research Articles

Low-Density, High-Temperature Co Base Superalloys

Co base superalloys strengthened by coherent L12 ordered γ′ precipitate in a disordered face-centered cubic γ matrix represent a new opportunity for high-temperature alloy development. The emergence of alloys with low density and high specific yield strength at elevated temperatures has further energized the research and development efforts in the last 5 years. Initially stabilized by the addition of small amounts of Nb and Ta, these new generations of alloys with multiple alloying additions to form basic quaternary and ternary alloys have steadily expanded the property envelopes to raise hope for a modern class of superalloys with higher-temperature capabilities. This article reviews the work of a vibrant set of researchers across the globe whose findings are constantly unlocking the potential of these alloys. These developments have achieved high-temperature strength (at 870°C) >0.6 GPa, γ′ solvus temperature exceeding 1,100°C, and densities between 7.8 and 8.6 g/cm3.

Instantaneous nanowelding of ultra‐high temperature ceramics for hypersonics

AbstractUltra‐high temperature ceramics (UHTCs) are a group of advanced ceramic materials that possess excellent high temperature capabilities, which make them especially suitable for extreme environment engineering applications. As an effective assembling method, joining is frequently required for fabricating sophisticated structures for such applications due to the excessive challenges and costs in producing near‐net shapes. Here, we introduce a promising new joining technique to effectively join UHTCs called Instantaneous Nanowelding, which uses direct electric current assisted rapid Joule heating to instantaneously bond hafnium diboride (HfB2) to zirconium diboride (ZrB2) in 1 s down to atomic scale. Our approach is analogous to high temperature spot welding, and the entire process is complete in 10 min, and the instant diffusion occurs in 1 s. Seamless HfB2/ZrB2 interfaces are formed at 1750 for a duration of 1 s. A series of characterizations are done at the interfaces using techniques including SEM, WDS, EBSD, and S/TEM to observe ZrxHf1−xB2 solid solution formation. Highly coherent transition with perfect lattice alignment at atomic scale from ZrB2 to HfB2 is observed using S/TEM, meaning that the two materials are brought to atomic contact.

Critical Assessment 40: A search for the eutectic system of high-temperature cast aluminium alloys

A quest for the eutectic system of novel cast aluminium alloys, having high-temperature capabilities, is critically assessed with two potential candidates of Al–Al3Ni and Al–Al11Ce3 examined and compared to the presently used Al–Si base. The conventionally cast Al–Al3Ni and Al–Al11Ce3 eutectics do not exhibit the anticipated advantage over Al–Si in strengthening retention at temperatures up to 500°C. The promising differences between diffusivities of silicon, nickel, and especially cerium in aluminium, and eutectic melting temperatures, accompanied by high coarsening resistance of Al3Ni, Al11Ce3 phases and the eutectic hardness retention are inconsistent with observed similarities in the temperature-related strengthening-reduction of all three eutectics. These findings will help defining the criteria for development of the eutectic system, suitable for future heat-resistant aluminium alloys.

Investigation on GaN HEMTs Based Three-Phase STATCOM with Hybrid Control Scheme.

The modern trend of decarbonization has encouraged intensive research on renewable energy (RE)-based distributed power generation (DG) and smart grid, where advanced electronic power interfaces are necessary for connecting the generator with power grids and various electrical systems. On the other hand, modern technologies such as Industry 4.0 and electrical vehicles (EV) have higher requirements for power converters than that of conventional applications. Consequently, the enhancement of power interfaces will play an important role in the future power generation and distribution systems as well as various industrial applications. It has been discovered that wide-bandgap (WBG) switching devices such as gallium nitride (GaN) high electron mobility transistors (HEMTs) and silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) offer considerable potential for outperforming conventional silicon (Si) switching devices in terms of breakdown voltage, high temperature capability, switching speed, and conduction losses. This paper investigates the performance of a 2kVA three-phase static synchronous compensator (STATCOM) based on a GaN HEMTs-based voltage-source inverter (VSI) and a neural network-based hybrid control scheme. The proportional-integral (PI) controllers along with a radial basis function neural network (RBFNN) controller for fast reactive power control are designed in synchronous reference frame (SRF). Both simulation and hardware implementation are conducted. Results confirm that the proposed RBFNN assisted hybrid control scheme yields excellent dynamic performance in terms of various reactive power tracking control of the GaN HEMTs-based three-phase STATCOM system.

Tungsten-based bcc-superalloys

Applications from nuclear energy to rockets and jet engines are underpinned by advanced high temperature materials. Whilst state of the art, the performance of current nickel-based superalloys is fundamentally limited to Ni’s melting point, Tm=1455∘C. Here, we develop an analogous superalloy concept but with superior high temperature capability by transitioning to a bcc tungsten base, Tm=3422∘C. This strategy involves reinforcing bcc β-W by β′ TiFe intermetallic compound, which results in impressive high temperature compressive strengths of 500 MPa at 1000∘C. This bcc-superalloy design approach has wider applicability to other bcc alloy bases, including Mo, Ta, and Nb, as well as to refractory-metal high entropy alloys (RHEAs). By investigation of the underlying phase equilibria, thermodynamic modelling, characterisation and mechanical properties, we demonstrate the capability of ternary W-Ti-Fe tungsten-based bcc-superalloys as a new class of high temperature materials.

Packaging and high-temperature characterization of a 650 V, 150 A eGaN HEMT

Among the salient features of gallium nitride (GaN) power semiconductor devices is their high-temperature capability. However, commercial GaN devices, such as the high-electron-mobility transistors (HEMTs), are limited to 125 °C junction-temperature operation because of their packaging. To explore the high-temperature capability of GaN power devices, a commercial 650 V, 150 A enhancement-mode GaN HEMT chip was packaged by silver-sintering die-bonding on direct-bond-copper substrate and encapsulation in a high-temperature polymer enclosure filled with nitrogen. Static characteristics of the packaged GaN device were measured at temperatures up to 250 °C. The threshold voltage of the transistor at 250 °C decreased to around 0.9 V, about 30% lower than that at room temperature. At temperatures beyond 150 °C, the saturation current fell sharply below the rated current, resulting in a rapid rise in the on-resistance versus current. At 250 °C, the saturation current decreased rapidly to around 67 A, <45% of the rated current. The reverse leakage also increased sharply at temperatures beyond 150 °C. Although the packaged device was operational at 250 °C, one would need to significantly lower the expectations for its performance and address the challenges of packaging and thermal management if it were to be used in a high-temperature power converter.

Investigation on the Temperature Distribution of Asphalt Overlay on the Existing Cement Concrete Pavement in Hot-Humid Climate in Southern China

Temperature is known to be one of the most important factors affecting the design and performance of asphalt concrete pavement. The distresses of asphalt overlay are closely related to its temperature, particularly in Guangxi, a hot-humid-climate region in China. This research is to analyze the impact of meteorological factors on temperature at 2 cm depth in asphalt overlay by ReliefF algorithm and also obtain the temperature prediction model using MATLAB. Two test sites were installed to monitor the temperatures at different pavement depths from 2014 to 2016; meanwhile, the meteorological data (including air temperature, solar radiation, wind speed, and relative humidity) were collected from the two meteorological stations. It has been found that the temperature at 2 cm depth experiences greater temperature variation, and the maximum and minimum temperatures of asphalt overlay, respectively, occur at 2 cm depth and on the surface. Besides, the results of ReliefF algorithm have also shown that the temperature at 2 cm depth is affected significantly by solar radiation, air temperature, wind speed, and the relative humidity. Based on these analyses, the prediction model of maximum temperature at 2 cm depth is developed using statistical regression. Moreover, the data collected in 2017 are used to validate the accuracy of the model. Compared with the existing models, the developed model was confirmed to be more effective for temperature prediction in hot-humid region. In addition, the analysis of rutting depth and overlay deformation for the two test sections with different materials is done, and the results have shown that reasonable structure and materials of asphalt overlay are vital to promote the high-temperature antideforming capability of pavement.

Overview of Joining and Repairing Techniques of Ni-Based Superalloy for Industrial Gas Turbine Applications

In industrial gas turbine (IGT) engine manufacturing, nickel-based superalloys are used mainly to meet the needs of components of the hot gas pathway. Although these alloys have high-temperature capabilities, the parts are prone to damage during service. The high working temperatures of these engines lead to component degradation due to creep, fatigue, and oxidation reactions; therefore, due to the high cost of newly produced superalloy components, it is usually more cost-effective to repair the damaged parts rather than completely replacing them. Joining and repairing techniques are necessary when manufacturing and repairing these alloys. This article will present an overview of the Ni-based superalloy for industrial gas turbine application by studying the microstructure of Ni-based superalloy, weldability issues, and cracking phenomena. Joining/repairing techniques of Ni-base superalloy with advantages and limitations to each technique are discussed to know a suitable technique for use in the high-temperature application.

Parametric study on tensile and flexural properties of ULTEM 1010 specimens fabricated via FDM

Purpose Fused deposition modelling (FDM) is increasingly being explored as a commercial fabrication method due to its ability to produce net or near-net shape parts directly from a computer-aided design model. Other benefits of technology compared to conventional manufacturing include lower cost for short runs, reduced product lead times and rapid product design. High-performance polymers such as polyetherimide, have the potential for FDM fabrication and their high-temperature capabilities provide the potential of expanding the applications of FDM parts in automotive and aerospace industries. However, their relatively high glass transition temperature (215 °C) causes challenges during manufacturing due to the requirement of high-temperature build chambers and controlled cooling rates. The purpose of this study is to investigate the mechanical properties of ULTEM 1010, an unfilled polyetherimide grade. Design/methodology/approach In this research, mechanical properties were evaluated through tensile and flexural tests. Analysis of variance was used to determine the significance of process parameters to the mechanical properties of the specimens, their main effects and interactions. The fractured surfaces were analysed by scanning electron microscopy and optical microscopy and porosity was assessed by X-ray microcomputed tomography. Findings A range of mean tensile and flexural strengths, 60–94 MPa and 62–151 MPa, respectively, were obtained highlighting the dependence of performance on process parameters and their interactions. The specimens were found to fracture in a brittle manner. The porosity of tensile samples was measured between 0.18% and 1.09% and that of flexural samples between 0.14% and 1.24% depending on the process parameters. The percentage porosity was found to not directly correlate with mechanical performance, rather the location of those pores in the sample. Originality/value This analysis quantifies the significance of the effect of each of the examined process parameters has on the mechanical performance of FDM-fabricated specimens. Further, it provides a better understanding of the effect process parameters and their interactions have on the mechanical properties and porosity of FDM-fabricated polyetherimide specimens. Additionally, the fracture surface of the tested specimens is qualitatively assessed.

Microstructural Degradation of the AlMo0.5NbTa0.5TiZr Refractory Metal High-Entropy Superalloy at Elevated Temperatures.

Refractory metal high-entropy superalloys (RSA), which possess a nanoscale microstructure of B2 and bcc phases, have been developed to offer high temperature capabilities beyond conventional Ni-based alloys. Despite showing a number of excellent attributes, to date there has been little consideration of their microstructural stability, which is an essential feature of any material employed in high temperature service. Here, the stability of the exemplar RSA AlMo0.5NbTa0.5TiZr is studied following 1000 h exposures at 1200, 1000 and 800 °C. Crucially, the initial nanoscale cuboidal B2 + bcc microstructure was found to be unstable following the thermal exposures. Extensive intragranular precipitation of a hexagonal Al-Zr-rich intermetallic occurred at all temperatures and, where present, the bcc and B2 phases had coarsened and changed morphology. This microstructural evolution will concomitantly change both the mechanical and environmental properties and is likely to be detrimental to the in-service performance of the alloy.

A multi-input, multi-stage step-up DC-DC converter for PV applications

The paper introduces a step-up multiple-input multi-stage dc-dc converter with a soft-switching for Photovoltaic (PV) applications. The proposed topology is constructed from series connection of switched capacitor circuits to minimize the effects of partial shading and mismatch between PV modules. A soft switching is achieved for the entire switches in the converter with no need for additional components. The applied technique utilizes the stray inductance of PCB traces to create a LC circuit so that the zero current switching is achieved for all switches. Moreover, the converter will take advantage of the superior features of Wideband gap devices in order to operate at high switching frequency. As a result, bulky capacitors in switched-capacitor circuits are significantly reduced, hence, small size multilayers ceramic capacitors with high temperature capability will be employed. Furthermore, with the lower losses and the higher temperature capability of Wideband gap devices, the thermal requirements will be reduced and with fast reverse recovery time, the snubber circuit are not required. Simulation results are presented, laboratory prototype is constructed, and experimental results are given at rated power to validate the feasibility of proposed dc-dc converter under soft switching operation.

High-Temperature Characterizations of a Half-Bridge Wire-Bondless SiC MOSFET Module

SiC MOSFET allows higher temperature capability with higher switching efficiency than that of conventional Si devices, due to its superior electrical and thermal properties. Nevertheless, there are few reports on the systematic characterization of the SiC MOSFET power module operating at high-temperature. In this paper, a SiC MOSFET power module with planar interconnection was designed and fabricated to achieve low parasitic inductance and improved thermal performance. The static and dynamic performance of the SiC power module were characterized at 200°C. The thermal resistance of the double-sided cooling power module is 28.5% lower than that of the one with single-sided cooling.

Field-Plated NiO/Ga2O3 p-n Heterojunction Power Diodes With High-Temperature Thermal Stability and Near Unity Ideality Factors

In this work, vertical NiO/Ga2O3 heterojunction diodes (HJDs) integrated with SiNx/Al2O3 double-layered insulating field plate (FP) structures have been demonstrated. With the additional post-annealing, the resultant diode exhibits a decreased differential specific on-resistance (Ron,sp) of 5.4 mωcm2 and an enhanced breakdown voltage (BV) of 1036 V. The improved performance is attributed by the combination of the FP-suppressed crowding electric field at the device edge and the reduced trap density at the NiO/Ga2O3 interface. In particular, the near-unity ideality factor has been achieved for this p-n HJD at an elevated temperature of 275∘C, indicating that the diffusion current is dominated. The high-temperature operation capability is owing to the quality improvement of NiO/Ga2O3 interface, where the Shockley-Read-Hall (SRH) recombination mediated by deep-level defects within the depletion region is thus suppressed.

Development of New Ni-based Cast Superalloy with Low Density and High Temperature Capability for Turbine Wheel in Automotive Turbocharger

Development of New Ni-based Cast Superalloy with Low Density and High Temperature Capability for Turbine Wheel in Automotive Turbocharger

Enhancement thermal stability of polyetherimide-based nanocomposites for applications in energy storage

Improving thermal stability of high-performance polymer-based nanocomposite films for electrical energy storage is essential to meet ever-increasing demands for the electrical industry, especially at harsh environment applications. Here, the polyetherimide (PEI)-based composites films are prepared via grafting method in the presence of SrTiO3 (ST) nanofillers to substantially improved capacitive performances at elevated temperature. The composites films with the optimized filler compositions show a high discharged energy density of 6.76 J/cm3 under 600 MV/m at room temperature. Meantime, excellent high-temperature discharged energy density of 6.6 J/cm3 at 100 °C for the composites films is also achieved, which is superior to most of the previously reported. The simulations further demonstrate that the ST nanoparticles embedded into the composites films could effectively improve heat dissipation in comparison with pristine PEI matrix, resulting in enhancement high-temperature energy storage capabilities. This work gives considerable promise for high energy density polymer-based nanocomposite films capacitors under harsh environments.

Na2SO4 + V2O5 Corrosion Behavior of BaNd2Ti3O10 for Thermal Barrier Coating Applications

BaNd2Ti3O10 has been considered as a promising thermal barrier coating (TBC) candidate material, which reveals many advantages over the widely used TBC material of yttria partially stabilized zirconia, such as lower thermal conductivity, better high-temperature capability, and higher resistance to environmental deposits corrosion. In this study, the hot corrosion behavior of BaNd2Ti3O10 in Na2SO4 + V2O5 molten salt at 900 °C and 1000 °C is investigated. Exposed to the salt for 4 h at 900 °C, BaNd2Ti3O10 pellets had an obvious reaction with the salt, forming corrosion products of NdVO4, TiO2, and BaSO4, and the reaction layer was ~30 μm, beneath which no salt trace could be found. Prolonging the corrosion time to 20 h, the type of the corrosion products had no change. At an elevated corrosion temperature of 1000 °C for 4 h, the corrosion products were still NdVO4, TiO2, and BaSO4, but NdVO4 revealed a significant growth, which fully covered the pellet surface. The mechanisms by which the corrosion reaction between BaNd2Ti3O10 and the molten salt occurred were discussed.

Simplistic approach to reduce thermal issues in 3D IC integration technology

Abstract A practical exhibition of the consequences of the 3D IC in heat management by adding the fin and heat spreaders to thermal through silicon via (TTSV) and IC respectively is proposed in this paper. Thermal cooling and its distribution of burnt potentials at various conditions are the different possessions which can be simulated using FEM simulator. This paper illustrate materials like Silicon nitride (Si3N4), Aluminium oxide (Al2O3), Silicon dioxide (SiO2) as they have the high thermal conductivity and high temperature capabilities which leads to the thermal management in the 3D IC design. Currently, semiconductor industries has cognizance of the metrics such as low density, high thermal strength, good facture of toughness, excellent wear resistance of Silicon nitride and it also shows better capabilities of high temperature, oxidation resistance and high retention strength compared to other metals. Besides silicon nitride has good resistance to thermal shock due to low coefficient of thermal expansion. Aluminium oxide is known for an better electrical insulator but has high thermal conductivity and which can be utilized as the substrate for integrated circuits. The high temperature furnace insulations and electrical insulations are designed by using the aluminium oxides as it has high boiling points and melting points. This makes the rapid use of alumina films in manufacture of IC industry. The other uses of alumina films include spark plug insulators, micro-electric substrates and insulating heat sinks. Silicon dioxide has the properties which helps to use them as the insulator material in IC technology as it has high thermal stability and making it useful for device integration and has high dielectric strength and thermal expansion coefficient is very low and in this paper we have taken these three materials and these materials have been implemented in our model and advertence the outcomes that which material is working efficiently and preciously.

Surface-Dependent Performance of Ultrathin TiN Films as an Electrically Conducting Li Diffusion Barrier for Li-Ion-Based Devices.

An in-depth understanding of lithium (Li) diffusion barriers is a crucial factor for enabling Li-ion-based devices such as three-dimensional (3D) thin-film batteries and synaptic redox transistors integrated on silicon substrates. Diffusion of Li ions into silicon can damage the surrounding components, detach the device itself, lead to battery capacity loss, and cause an uncontrolled change of the transistor channel conductance. In this study, we analyze for the first time ultrathin 10 nm titanium nitride (TiN) films as a bifunctional Li-ion diffusion barrier and current collector. Thermal atomic layer deposition (ALD) and pulsed chemical vapor deposition (pCVD) are employed for manufacturing ultrathin films. The 10 nm ALD films demonstrate excellent blocking capability with an insertion of only 0.03 Li per TiN formula unit exceeding 200 galvanostatic cycles at 3 μA/cm2 between 0.05 and 3 V versus Li/Li+. An ultralow electrical resistivity of 115 μΩ cm is obtained. In contrast, a partial barrier breakdown is observed for 10 nm pCVD films. High surface quality with low contamination is identified as a key factor for the excellent performance of ALD TiN. Conformal deposition of 10 nm ALD TiN in 3D structures with high aspect ratios of up to 20:1 is demonstrated. The measured capacities of the surface area-enhanced samples are in good agreement with the expected values. High-temperature blocking capability is proven for a typical electrode crystallization step. Ultrathin ALD TiN is an ideal candidate for an electrically conducting Li-ion diffusion barrier for Si-integrated devices.

Linear Reciprocating Wear of Yttria-Stabilized Zirconia-Based Composite Coatings Developed by Thermal Spray

Ceramic matrix composites are the preferred material for high-temperature application due to their low density, improved strength and toughness, and high-temperature capabilities. In the present study, we report the kinetics and mechanism of linear reciprocating wear of yttria-stabilized zirconia (YSZ)-based composite coatings developed by thermal spray technique. Composite coatings with different volume fractions of CoNiCrAlY and YSZ phases were subjected to linear reciprocating wear under an applied normal load of 10 N against a WC counter-body. The kinetics of wear was investigated by measuring the wear depth over time of coated components against WC surface. Adhesive wear in the 100% CoNiCrAlY coating was responsible for increased friction in the coating which changed to a three-body abrasion in the case of 100% YSZ coating. The composition coatings had a significant effect on the wear mechanism with the ceramic coatings were fractured under reciprocating load. Microcrack propagation and fracturing of ceramic splats were the dominant modes of wear in the ceramic coatings. The 100% YSZ coating showed significant wear than 100% CoNiCrAlY and 50% YSZ + 50% CoNiCrAlY coatings. The mode of wear changed with the presence of a metallic phase in the 50% YSZ + 50% CoNiCrAlY coating. The mode of wear was further studied by the detailed microstructural observation of worn track and correlating it with the wear kinetics and coefficient of friction.

Extreme Environment Integrated Circuits Based on Enhancement Mode SiC JFETs

This paper presents results on developing high temperature capable SiC JFET based IC technology that can operate at temperatures up to 500 °C. All JFET devices are fully planar, formed by ion implantation, and the device design allows the use of semi-insulating or conductive SiC substrates. Basic analog and logic ICs were built in order to demonstrate the technology high temperature capability. All circuits used enhancement mode n-channel JFETs as active transistors, and depletion mode transistors as active loads. The logic circuits built included NOT, NAND, and NOR gates. The analog circuits built included a simple one-stage operational amplifier. JFETs and ICs were packaged in ceramic packages and tested at temperatures up to 500 °C.