Cryogenic Temperature Conditions Research Articles

A 2DEG‐Based GaN‐on‐Si Terahertz Modulator with Multi‐Mode Switchable Control

AbstractAs terahertz (THz) technology has been widely considered as a key candidate for future sixth‐generation wireless communication networks, THz modulators show profound significance in wireless communication, data storage, and imaging. In special, dynamic tuning of THz waves through 2D electron gas (2DEG) incorporated with a hybrid design of metasurface has attracted keen interest due to the combined merits of deliberate structural design, rapid switching speed and the process compatibility. Current meta‐modulator enables very high modulation depth but encounter limited bandwidth. In this paper, by taking into account the co‐functional effects of temperature and voltage‐dependent dynamic control on transmission amplitude, a 2DEG‐based GaN‐on‐Si modulator with two switchable operational states (or four modes) of active wave control is proposed. Under cryogenic temperature conditions, the proposed device exhibits prominent 2D plasmons characteristics with switchable transitions between the gated mode and ungated mode for active control. Under room temperature conditions, the proposed device exhibits non‐resonance broadband spectra characteristics with tunable transitions between the linearity mode and depletion mode for transmission control. The scheme provides an option for the development of the actively tunable THz meta‐modulator and paves a way for the robust multifunctionality of electrically controllable THz switching, and biosensors.

Thermal properties and grey correlation degree analysis of tar-rich coal under cryogenic and pyrolysis condition

The thermal properties of coal are important factors that influence the heat and mass transfer during the pyrolysis process. Therefore, thermal properties were investigated for two tar-rich coal under cryogenic temperature and pyrolysis condition using laser flash analyzer. Gray correlation analysis and chemical composition analysis are combined to analyze the impact of chemical properties on thermal properties. With decreasing temperature, the thermal diffusivity of coal experiences a significant increase by 108.9–121.4 %, while the specific heat capacity decreases by 57.9–65.9 %. The volatile matter and fixed carbon content in tar-rich coal have the highest correlation with thermal properties (∼0.9), followed by moisture content (∼0.62), while the ash content has the lowest correlation with thermal properties (∼0.5). The thermal diffusivity of tar-rich coal increases with increasing volatile matter content. Furthermore, within the range of −100 °C to 300 °C, the thermal diffusivity of tar-rich coal decreases with increasing carbon content, while the specific heat capacity increases with increasing carbon content. The results indicate that under low-temperature cryogenic conditions, the internal heat transfer capability of tar-rich coal is significantly improved.

Fracture-free cut surface characteristics of aluminum alloy sheet (AA5083-H112) using cryogenic press-shaving process

Of late, aluminum alloy sheets are being increasingly used in the fabrication of automotive, marine, and aircraft parts. Typically, a metal-forming process is used to produce these parts. However, the fracture-free cut surface characteristics of these parts are still limited by the die cutting process, and a secondary operation, such as machining, is needed to overcome this limitation. In this study, the use of cryogenic temperatures in press shaving was investigated. In the shearing operation, the cryogenic temperature influenced the ratios of the die-roll, smooth-surface, and fracture-to-material thickness, particularly for the fracture texture. Applying cryogenics in the shearing process increased the smoothness of the surface by approximately 50%, and the concave feature formed on the sheared workpiece was approximately 45% deep. Additionally, the hardness under cryogenic-temperature condition was approximately 15% higher than that at room temperature. However, the shearing force increased by approximately 30%. With the shaving operation, the volume of the shaving allowance was reduced owing to the deeper concave features. This resulted in a downward movement of the shaving allowance during the shaving operation, allowing easier sliding along the punch face and easier bending underneath the punch face. Consequently, tearing could be prevented, and the shearing phase of the shaving operation could be delayed. The results revealed that compared with the conventional press-shaving process, in which tearing and fracture of approximately 0.393 mm were generated, the application of cryogenic temperature to the press-shaving process delayed the tearing and prevented fracture, thereby achieving a fracture-free cut surface characteristic.

Optimization of thermoelectric generator power density for cryogen cold exergy recovery

The article presents the optimization of the power density of a thermoelectric generator (TEG) operating in cryogenic temperature conditions. Optimization of TEG power density was performed as a function of TEG leg length and its effect on TEG performance. The figure of merit (ZT) of the TEG was experimentally verified for the temperature range of a cold sink from 160 to 250 K, which corresponds to the temperature of the wall subjected to the boiling film of LNG. The numerical model proposed in the article was verified by comparison with experimental data, and then used to simulate the operation of the TEG at a cold sink temperature of 80 K corresponding to the wall temperature in the process of LH2 regasification. The obtained results showed that the optimal length of TEG legs is less than 10 mm and depends on the boiling and heat transfer regime. The results of the presented research can be used to improve the effectivity of cold exergy recovery from cryogenic systems.

Unravelling the atomistic-scale insights into tensile response of equiatomic cupronickel alloy with pre-existing faceted grain boundary interface

The aim of this research work is to investigate the effect of strain rates and temperatures on the mechanical properties of an equiatomic copper-nickel (Cu–Ni) alloy with a pre-existing faceted Σ3 [111] 60° {11 8 5} grain boundary. Molecular dynamics simulations conducted in this scrutiny focuses on understanding the tensile behaviour of bicrystalline equiatomic Cu–Ni alloys (denoted by Cu50Ni50) under various thermodynamic conditions. The uniaxial tensile deformation simulation was carried out at various strain rates (108, 109 and 1010 1/s) in conjunction with different conditions of cryogenic temperature (100 K), room temperature (300 K) and high temperature (500 K). The authors found that the yield stress and Young's modulus of the bicrystalline Cu50Ni50 alloy were highest at the cryogenic temperature, and decreased as the temperature increased. To add on, the yield stress of the bicrystalline Cu50Ni50 alloy increased with an increase in the strain rate value. From the microstructural and dislocation analysis point of view, it was observed that the formation of dislocations was lowest at the cryogenic temperature. Interestingly, at the yield point, the coherent twin boundary tip act as the nucleation site for the dislocations for cryogenic temperature condition. These findings shed light on the relationship between the temperatures, strain rates, and the mechanical properties of Cu–Ni alloys, which will aid in reporting the optimized conditions for their desired engineering applications. It is also proposed that tailoring of the tensile properties is achievable by exposing Cu–Ni alloys to various environmental conditions (cryogenic, ambient, and elevated temperatures with different applied strain rates).

Enhanced extreme temperature bending and delamination resistance of GFRP composites through z-directional aligned nano-reinforcement: Emphasizing the effects of CNT functionalization

Laminated FRP composites' weak out-of-plane mechanical performance prevents their usage in structural applications where homogeneous load bearing qualities are required. In this regard, a z-directional nano-reinforcement approach was implemented to mitigate the poor in-plane shear and out-of-plane response of laminated glass fiber epoxy (GE) composites under extreme in-service temperature conditions. CNT and functionalized CNT (FCNT) were dispersed separately in the GE composites' epoxy matrix and subjected to a z-direction electric field alignment treatment. Flexural and short beam shear tests of GE composites with random and aligned CNT/FCNT were performed at room temperature, in-situ cryogenic and elevated temperature conditions (RT, CT and ET, respectively). GE composite with aligned FCNT (A-FCNT-GE) consistently outperformed other composites at all considered temperatures with remarkable improvements, specifically ∼39%, ∼41% and ∼47% in flexural strength, and ∼30%, ∼30%, and ∼24% in interlaminar shear strength (ILSS) over the control GE composite at RT, CT and ET, respectively. Dynamic mechanical thermal analysis suggested that the synergetic impact of functionalization and alignment of FCNT improved the viscoelastic properties of the A-FCNT-GE composite across a range of temperature conditions. Fractography analysis provided insight into the interfacial and interlayer mechanisms that improved the extreme temperature condition mechanical performance. The reliability of electric field aligned FCNT as a z-directional nano-reinforcement in laminated composites at extreme temperature conditions was established in this study.

Construction of a PTFE-based lubricant film on the surface of Nomex/PTFE fabric to enhance the tribological performance at cryogenic temperatures

Hybrid fabric composites with self-lubricating properties have been applied to various joint bearing liners, especially under cryogenic temperature conditions where liquid lubricant fails. Herein, we report a novel Nomex/polytetrafluoroethylene (PTFE) fabric composite with a hierarchical distribution of PTFE by sintering a layer of PTFE/MoS2 coating. The tribological properties of the PMS composite were investigated over a temperature range from − 150–25 ℃ on a pin-on-disk tribometer. The results show that the friction coefficient of the PMS composite has a nonmonotonic relationship with temperature, which is related to the molecular conformation and mobility of PTFE at different temperatures. The wear of the PMS composite decreased with decreasing temperature, exhibiting an unmeasurable ‘zero wear’ at − 150 °C.

Dissipative Quantum Feedback in Measurements Using a Parametrically Coupled Microcavity

Micro- and nanoscale optical or microwave cavities are used in a wide range of classical applications and quantum science experiments, ranging from precision measurements, laser technologies to quantum control of mechanical motion. The dissipative photon loss via absorption, present to some extent in any optical cavity, is known to introduce thermo-optical effects and thereby impose fundamental limits on precision measurements. Here, we theoretically and experimentally reveal that such dissipative photon absorption can result in quantum feedback via in-loop field detection of the absorbed optical field, leading to the intracavity field fluctuations to be squashed or antisquashed. Strikingly, this modifies the optical cavity susceptibility in coherent response measurements and causes excess noise and correlations in incoherent interferometric optomechanical measurements using a cavity. We experimentally observe such unanticipated dissipative dynamics in optomechanical spectroscopy of sideband-cooled optomechanical crystal cavitiess at both cryogenic temperature (approximately 8 K) and ambient conditions. The dissipative feedback introduces effective modifications to the optical cavity linewidth and the optomechanical scattering rate and gives rise to excess imprecision noise in the interferometric quantum measurement of mechanical motion. Such dissipative feedback differs fundamentally from a quantum nondemolition feedback, e.g., optical Kerr squeezing. The dissipative feedback itself always results in an antisqueezed out-of-loop optical field, while it can enhance the coexisting Kerr squeezing under certain conditions. Our result has wide-ranging implications for future dissipation engineering, such as dissipation enhanced sideband cooling and Kerr squeezing, quantum frequency conversion, and nonreciprocity in photonic systems.

Artificial neural network based prediction of ultimate buckling strength of liquid natural gas cargo containment system under sloshing loads considering onboard boundary conditions

In this study, the ultimate buckling strength of a GTT NO96 liquid natural gas (LNG) cargo containment system under a sloshing impact load was investigated while considering the design environmental conditions thereof, such as the cryogenic temperature and flexible boundary conditions owing to the inner hull structures. As the dynamic buckling capacities of LNG cargo containment boxes show a large nonlinearity against several design parameters, we applied an artificial neural network to generalize the numerical analysis results and develop design ultimate capacities of the system for early design purposes. Through one-hot encoding, a character variable was converted into a variable form suitable for the artificial neural network, and a prediction model optimized for the current system was constructed through a model optimization process. A comparison of the design values with finite element (FE) simulation results shows a very good agreement. Finally, we provide a prediction model: a GitHub repository, BUNO96, which is suitable for the calculation of ultimate buckling strength of NO96 box.

Polarized stimulated-emission depletion and dark-state lifetime at vacuum and cryogenic temperature conditions

With the growing popularity of cryogenic correlative light and electron microscopy, it is becoming increasingly important to bridge the resolution gap between these two modalities. At cryogenic temperatures, the photon yield of fluorophores is a few orders of magnitude higher than at room temperature, enabling localization precisions on the \AA{}ngstr\"om scale. The current challenge is to induce sparsity at cryogenic temperatures such that individual fluorescent molecules can be localized. In this paper, we demonstrate the progress of using polarized stimulated-emission depletion (STED) to induce sparsity at cryogenic temperatures and in vacuum. We generate linear polarization of arbitrary in-plane orientations to achieve polarized STED with a sparsity of 3.3:1. Furthermore, we have probed the dark-state lifetime of ATTO 647N at cryogenic temperatures and in vacuum at room temperature. This dark state in vacuum is long-lived ($\ensuremath{\tau}=38$ ms) and could be the cause for reduced photostability of fluorophores under STED illumination in vacuum. The experiments were done on an in-house designed and built liquid nitrogen cryostat, enabling 30 hours of stable cryogenic fluorescence microscopy.

The Effects of In-Process Cooling during Friction Stir Welding of 7475 Aluminium Alloy

Certain age hardenable alloys such as AA7475 cannot be joined with perfection using fusion welding techniques. This requires non-conventional welding technique such as friction stir welding process to join these ‘difficult to weld’ alloys. In this study, three different cooling conditions i.e. cryogenic, sub-zero, and zero-degree Celsius temperature conditions have been analyzed to understand its impact on the welding process. In-process cooling was found to behave effectively and also enhanced the mechanical properties of the welded joints. A stable microstructure was clearly seen in the images observed under the metallurgical microscope. The weld efficiencies were found to be good in each of the samples which are indicative of a strong metallic joint. The effective cooling conditions employed had an overall positive impact on the joint.

Theoretical and experimental investigation on temperature coefficient of optical fiber delay at cryogenic ranges

The temperature coefficient of optical fiber delay is theoretically and experimentally investigated under the condition of cryogenic temperature. The effects of temperature variation on the refractive index of the fiber core and the strain of the fiber coating are studied in the theoretical analysis. Based on the analysis, an equation that linearly relates the optical fiber delay and the temperature, which induces the changes of the fiber-core refractive index and physical length, is derived. It is found that the temperature coefficient of optical fiber delay is constant at the cryogenic temperature condition. In the experiment, the temperature coefficient of optical fiber delay is measured to be a constant of 50.9ps•km−‍1•K−1 at the temperature range from 110K to 220K. Good agreement is found between the theoretical analysis and the experimental verification.

Ab initio Molecular Dynamics Simulations of Field-Coupled Nanocomputing Molecules

Molecular Field-Coupled Nanocomputing (FCN) represents one of the most promising solutions to overcome the issues introduced by CMOS scaling. It encodes the information in the molecule charge distribution and propagates it through electrostatic intermolecular interaction. The need for charge transport is overcome, hugely reducing power dissipation.At the current state-of-the-art, the analysis of molecular FCN is mostly based on quantum mechanics techniques, or ab initio evaluated transcharacteristics. In all the cases, studies mainly consider the position of charges/atoms to be fixed. In a realistic situation, the position of atoms, thus the geometry, is subjected to molecular vibrations. In this work, we analyse the impact of molecular vibrations on the charge distribution of the 1,4-diallyl butane. We employ Ab Initio Molecular Dynamics to provide qualitative and quantitative results which describe the effects of temperature and electric fields on molecule charge distribution, taking into account the effects of molecular vibrations. The molecules are studied at near-absolute zero, cryogenic and ambient temperature conditions, showing promising results which proceed towards the assessment of the molecular FCN technology as a possible candidate for future low-power digital electronics. From a modelling perspective, the diallyl butane demonstrates good robustness against molecular vibrations, further confirming the possibility to use static transcharacteristics to analyse molecular circuits.

Simultaneous blockade of a photon, phonon, and magnon induced by a two-level atom

The hybrid microwave optomechanical-magnetic system has recently emerged as a promising candidate for coherent information processing because of the ultrastrong microwave photon-magnon coupling and the long life of the magnon and phonon. As a quantum information processing device, the realization of single excitation holds special meaning for the hybrid system. In this paper, we introduce a single two-level atom into the optomechanical-magnetic system and show that an unconventional blockade due to destructive interference cannot offer a blockade of both the photon and magnon. Meanwhile under the condition of single excitation resonance, the blockade of the photon, phonon, and magnon can be achieved simultaneously even in a weak optomechanical region, but the phonon blockade still requires the cryogenic temperature condition.

A critical analysis of transport models for refueling of MOF-5 based hydrogen adsorption system

This work presents a critical analysis of 2D model of refueling a hydrogen storage tank containing MOF-5 adsorbent under cryogenic and room temperature conditions. Three isotherm models, viz. Unilan, modified Dubinin–Astakhov DA and Tóth, were fitted with experimental data of hydrogen adsorption from the literature, and their effect on refueling of adsorbent bed is analyzed. The choice of isotherm has the greatest impact on predicting refueling behavior, for both flow-through and end-flow (i.e., batch) systems. A comparison between the ideal gas assumption and virial equation of state indicates that the former reasonably captures the overall behavior at lower computational cost. Analysis of the role of momentum balance, solved as full Navier–Stokes model and with Darcy’s approximation, indicates same hydrogen uptake in the adsorbent bed and only a minor difference in the predicted velocity profiles. Finally, effect of temperature-dependent physical properties of gas, adsorbent and walls is analyzed.

FATIGUE PROCESS OF AUTOMOBILE MATERIALS

During operation, the structural elements of cars are exposed to temperatures and vibrations. Overwhelming majority of the destruction of metal structures is caused by their fatigue. It causes economic losses and often human casualties from accidents. Therefore, the task of ensuring the operability of parts and components of automobiles is one of the most relevant in the modern automotive industry. So it is necessary to know the patterns of behavior of metallic materials, obtained by different technologies, when they are exposed to vibration. Destruction of the metal structure directly affects the behavior of the samples deflection, reflecting the competition of two mutually oppositephenomena – hardening and softening. It directly influences structural damageability of the metal. The article is devoted to the study of kinetics of fatigue failure of automotive materials using the calibration of structural damage to their surface with behavior of the curves of changes in current deflection under alternating loading. The paper considers automotive materials (steel grades 20KhI3, 14Kh17N2, 35KhGSА) and model metals and alloys (Copper M1, Brass L63T, aluminum alloy V95pchT2) in different structural state under cyclic loading for low, room and high temperatures with fixation of the sample deflection and structural damage corresponding to it. It is possible to study kinetics of fatigue destruction of the sample material by the deflection curves, which is an integral characteristic of destructive processes occurring under alternating loading. Using these processes, one can track the stages of damage during fatigue of metallic materials – damage to the structure at the initial stage, moment of the macroscopic crack appearance, its subsequent advancement up to complete separation of the structural material. It is probable to identify ratio of the period duration before the appearance of a fatigue crack and its subsequent growth, as well as to determine the average rate at which the fatigue crack moves through the body of the metal sample. It is important that it is also possible to estimate the kinetics of materials destruction under the conditions when direct study of the structural state of the sample surface is impossible, for example, in conditions of cryogenic and high temperatures, and also, for example, in the presence of corrosive media. In combination with fractographic and metallographic analysis of the fatigue process, the deflection curves allow, based on the evaluation of the stages of materials destruction, to carry out selection of the latter for the structural elements of a car taking into account its operating conditions and optimizing the technology of parts manufacturing to increase serviceability and maintainability.

Experimental characterization of temperature dependent dynamic properties of glass fiber reinforced polyurethane foams

The static and dynamic compressive behaviors of glass fiber-reinforced polyurethane foams were characterized under cryogenic temperature conditions to help identify the essential design and parameters required to model the response of the foam accurately under the various loading conditions encountered in liquefied natural gas cargo containment systems. The material properties of polyurethane foams with varying concentrations and orientations of the glass fiber continuous strand mat were characterized by quasi-static, dynamic mechanical analysis (DMA), and low velocity impact testing. The testing results showed increased strength with increasing density and strain rate, as well as similar failure modes independent of the strain rate. In addition, the glass fibers dominated the DMA behavior and a glass transition temperature at or above 130 °C was observed for all foam varieties. Overall, the glass fiber reinforced polyurethane foam showed the typical static and dynamic compressive behaviors of foams at both room and cryogenic temperatures.

Polymer composites for tribological applications

Abstract Many different polymers and polymer composites are used for engineering applications in which friction and wear are critical issues. This article briefs (a) the importance of polymer tribology in general, (b) the special design principles of polymer composites for low friction and wear under sliding against smooth metallic counterparts, and (c) synergistic effects of nano-particles and traditional fillers and fibers for an optimal tribological performance. Based on these fundamental aspects, the article reviews traditional applications of polymeric tribo-components in mechanical and automotive engineering, including slide elements in textile machines, filament wound bushings for harsh environments, cages of high-precision ball bearings in dental turbines, and hybrid bushings in Diesel fuel injection pumps. A following chapter on special developments of tribo-components outlines (a) ways to achieve electrical conductivity of polymer bearings, (b) the enhancement of self-lubrication and self-healing potential by the incorporation of micro-capsules into the polymer matrix, (c) modern additive manufacturing methods for friction and wear loaded polymer parts, (d) the application and properties of high temperature polymer coatings, and (e) the composition and use of polymer composites under friction at cryogenic temperature conditions.

Effect of temperature on the magnetic abrasive finishing process of Mg alloy bars

Experiments were conducted to evaluate the effect of temperature during magnetic abrasive finishing of Mg alloy bars. A magnetic abrasive finishing process is an unconventional finishing technique that has been used to achieve high-quality surfaces with dimensional accuracy. In this study, a Mg alloy bar, which is widely used in automobiles, aircraft, IT, and the defense industry, was chosen as a cylindrical workpiece. The workpiece was then finished with a magnetic abrasive finishing process at three different temperatures, i.e., a cryogenic temperature, room temperature, and high temperature. In the cryogenic temperature condition, liquid nitrogen and argon gas were used as the cryogenic cooling gases in the finishing process; the results from this treatment were compared with those obtained at room temperature and high temperature conditions. At the room temperature condition, the finishing process of the cylindrical workpiece was performed at 24 °C. To carry out the high temperature condition, a hot air dryer was used to maintain a finishing temperature of 112 °C. The experimental results show that the room and cryogenic temperatures could yield excellent performance in terms of the surface roughness. However, in terms of the removal weight and change in diameter, the high temperature condition was found to be superior. In the present research, the improvements of the surface roughness (Ra) at room temperature (24 °C) and cryogenic temperature (-120 °C) conditions were 84.21 % and 55 %, respectively.

On the Accuracy in Determination of the Mechanical Material Characteristics at Low Temperatures

The paper considers the processes related to the specimens and loading device in the tensile testing of metals in strain-controlled mode, including under the conditions of cryogenic temperatures up to 4.2 K. It is demonstrated how the potential elastic energy accumulation and its subsequent relaxation in the development of the specimen strain affect the process of kinetics. The strain rate dependencies on the strain value and stiffness factor (relation between the values of stiffness of the specimen and the machine) are obtained. Noteworthy is that the values of initial and nominal strain rates can differ by an order of magnitude in case of the machine compliance. To obtain the strain rates that are similar for different machines at the initial stage of the process, the formula is proposed allowing one to calculate the required nominal rate. At the temperatures lower than 30 K there is a dramatic increase of the influence of the machine stiffness, dimensions and shape of the specimens on the obtained characteristics, which requires the special measures in the process of testing. Some international and national standards are considered. It is shown that, at present, the process of standardization for tensile testing of metals is inadequate, and the requirements of the current regulatory documents are the minimum, which are not in agreement with the development paces of testing equipment. To significantly enhance the level of accuracy of the obtained mechanical characteristics, it is required to employ the urgent measures as the machine compliance limitation, as well as the decrease of the dimensions range for the specimens together with the standardization of the permissible range of the stiffness factor, and the required selection of the nominal strain rate considering the latter.