Cryogenic Temperature Conditions Research Articles

Investigation on the lubricity of self-lubricating ball bearings for cryogenic turbine pump

Abstract The lubricity of newly designed self-lubricating 70-mm-bore angular contact ball bearings was tested using a special bearing tester under thrust load of about 20 kN and speed of about 20000 r/min in liquid nitrogen. The test bearing was characterized with the pure polytetrafluoroethylene (PTFE) retainer coupled with the Ag-based lubricant film initially deposited on bearing raceways. After running for 1200 and 2400 s respectively, the states of the PTFE transfer films on the surfaces of the balls and raceways as well as the wear state of the Ag-based solid lubricant film for each tested bearing were analyzed mainly by scanning electron microscopy and X-ray photoelectron spectroscopy. The results indicated that good lubricating conditions were obtained for all tested bearings. The newly designed self-lubricating ball bearing could run steadily for more than 2400 s under high speed, heavy load and at cryogenic temperature conditions. The formation and the evolution of PTFE transfer films with bearing operation are mainly discussed according to the relevant analysis.

Hydrogen desorption using honeycomb finned heat exchangers integrated in adsorbent storage systems

One of the main technical hurdles associated with adsorbent based hydrogen storage systems is relative to their ability to discharge hydrogen effectively, as dictated by fuel cell requirements. A new honeycomb finned heat exchanger concept was examined to evaluate its potential as a heat transfer system for hydrogen desorption. A bench scale 0.5 L vessel was equipped with the proposed heat exchanger, filled with MOF-5® adsorbent material. The heating power, required to desorb hydrogen, was provided by a 100 W electric heater placed in the center of the honeycomb structure. Two desorption tests, at room temperature and under cryogenic temperatures, were carried out to evaluate the hydrogen desorption performance of the proposed system under different operating conditions. The bench scale vessel performance was verified from both an experimental and a modeling point of view, demonstrating the ability to desorb about 45% of the adsorbed hydrogen in reduced time and applying low heating power. Further modeling analyses were also carried out showing the potential of the proposed system to reach high hydrogen discharging rates at cryogenic temperature conditions and operating pressures between 100 bar and 5 bar. The proposed adsorption system also demonstrated to be able to discharge all the available hydrogen in less than 500 s operating at cryogenic conditions and with a nominal heating power of 100 W.

CO2 activation of olive bagasse for hydrogen storage

Hydrogen is considered as the most promising future fuel, as its combustion generates only water vapor besides energy. However, finding efficient, safe and low‐cost storage methods is the basic impediment for the adoption of hydrogen as fuel. For this purpose, an ultramicroporous activated carbon was successfully synthesized from low‐cost biomass residues; olive bagasse. The carbon material was prepared throw physical activation, using carbon dioxide as activating agent, under controlled thermal conditions. Then, it was tested as hydrogen storage material at cryogenic and room temperature conditions. The textural characterizations showed a highly tailored porous texture adequate for gas adsorption. The totality of the created microporosity is of narrow range (d < 0.7 nm). Interestingly, the measured median pore width was about 0.65 nm, likely the optimum pore size for hydrogen adsorption. This feature accorded the AC with exceptional H2 storage capacity, achieving 3.34 wt % at liquid nitrogen temperature. It has outperformed Zeolites and MOFs. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 315–324, 2017

Impossibility of superconductivity electric flow

The solution of an old and urgent scientific and technical problem of superconductivity of electric current is proposed. Discrepancies to the facts and internal contradictions of a hypothesis of superconductivity of electric current by bodies, in the conditions of cryogenic temperatures are revealed. The new (alternate) comprehension of an essence and the adequate theory of the phenomenon which is inaccurately called by the low-temperature superconductivity of electric current without resistance is formulated. The analysis of an Ohm's law and its restrictions proves impossibility of emergence of superconductivity. It is claimed that when cooling the conductor its resistance increases, but does not decrease. When overcooling the conductor there is an isolation of electric current by it. The two-current model and the beginnings of the corresponding theory of an electrical conductivity are offered. It is shown that according to the actual two-current theory of distribution (current) of electric energy on the conductor, superconductivity cannot be. The same conclusion is proved by the law of Joule-Lenz and the facts of increase in resistance from action on the conductor of an external magnetic field and decrease of temperature of the conductor. It is proved that the physical nature of resistance consists in counteraction of an external electromagnetic field (electricity) to the movement on the conductor from the diamagnetic field self-induced in it. It is claimed that at deep overcooling the diamagnetization of the conductor becomes more magnetic field of electricity and the conductor turns into the superdiamagnetic electroisolation center (dielectric). Replacement of the inaccurate doctrine about superconductivity of electricity on long ago the alternate and most reasonable theory of a cold superdiamagnetization of substances offered by the author of this article allows to solve many problems of practical use of the phenomenon of a superdiamagnetization during creation of new processes and perspective technique of the future.

WITHDRAWN: Stress transfer properties of carbon nanotube reinforced polymer composites at low temperature environment

Abstract Multi-scale modeling method was used to study tensile properties of single-walled carbon nanotube (SWCNT) and double-walled carbon nanotube (DWCNT) reinforced polymer-based composites at room temperature (RT) and cryogenic temperature (like liquid nitrogen temperature 77 K) conditions. At RT, Young's Modulus of a SWCNT reinforced polymer composite is 1.88 times of a DWCNT reinforced polymer composite due to a weak interfacial bonding between layers of DWCNT, which is bound by the weak Van der Waal interaction. The Young's Modulus of DWCNT reinforced polymer composite is significantly improved with the decrease of temperature and the difference in Young's Modulus between SWCNT and DWCNT reinforced polymer composites has been largely reduced. The radial stress imposed on an outer surface of nanotubes due to the contraction of polymer at liquid nitrogen environment is examined to explain the stress transfer mechanism in a composite system. The extra stresses imposed on the surface of DWCNT increase bonding forces between outer and inner layers of DWCNT. This tendency agreed well with experimental results found in other literature.

Microstructure Evolution In Metal Nanostructures Under Extreme Conditions Of Temperature And Strain Rate

This paper explores a fundamental connection between ductility and domain size in metallic solids under extreme conditions of cryogenic temperatures and strain rates (10 8 s –1 ). A series of novel experiments, backed by multiscale modelling and transmission electron microscopy (TEM) analysis, are presented that involve loading of TEM-ready single crystal nanopillar samples of Cu of varying lengths (50 nm to 1 mm) and aspect ratios (50 nm to 100 nm in diameter) by laser-generated stress waves of sub-nanosecond rise times, under extreme conditions of strain rate (>10 8 s –1 ) and temperature (100K). The nucleation stress for Shockley partials, which can be taken as a proxy for the onset of ductile deformation, was measured to be only 1 GPa. This is an order of magnitude lower than the previously measured values of 35 GPain bulk geometries. TEM observations show remarkable ability of the material to re-arrange itself through motion of dislocations to form subgrain boundaries within a very short duration of only few nanoseconds.

Beyond directed ortho metalation: Ru-catalyzed CAr-O activation/cross-coupling reaction by amide chelation.

Disclosed is a new, catalytic, and general methodology for the chemical synthesis of biaryl, heterobiaryl, and polyaryl molecules by the cross-coupling of o-methoxybenzamides with aryl boroneopentylates. The reaction is based on the activation of the unreactive C-OMe bond by the proximate amide directing group using catalytic RuH2(CO)(PPh3)3 conditions. A one-step, base-free coupling process is thereby established that has the potential to supersede the useful two-step directed ortho metalation/cross-coupling reaction involving cryogenic temperature and strong base conditions. High regioselectivity, orthogonality with the Suzuki-Miyaura reaction, operational simplicity, minimum waste, and convenient scale-up make these reactions suitable for industrial applications.

Influence of Annealing Conditions on Structural Development of Cryo Rolled FeSi Steel

of Cryo Rolled FeSi Steel T. Kvackaj∗, J. Bidulska, R. Bidulsky, A. Kovacova, R. Kocisko, P. Bella, M. Luptak, J. Bacso Faculty of Metallurgy, Technical University of Ko2ice, Vysoko2kolska 4, 042 00 Ko2ice, Slovakia Non grain oriented isotropic electrical steels, commercially called NGOES, were investigated in cryogenic temperature conditions. At cryogenic temperatures plastic deformations form strong structural heterogeneities in the sample thickness. Samples processed by cryo rolling show a bigger storage energy. To achieve abnormal grain growth through the process of static recrystallization, the annealing conditions were applied to the deformed samples. Moreover, minimal magnetic losses were reached when mean grain size diameter was approximately 150 μm.

The Influence of Thermo-Plastic Processes on Materials Recovery

The influence of thermo-plastic processes through methods of severe plastic deformations (SPD) and rolling carried out at ambient and cryogenic temperatures on recovery of two materials was investigated. The aim of this study was to insert strains to materials having middle and high stacking fault energy (SFE) in ambient and cryogenic temperature conditions, respectively and subsequently, through DSC method, to observe an influence of the storage energy on structural recovery of materials. As experimental materials were used oxygen free high conductivity copper (OFHC Cu) and C-Si steel which represent materials with middle and high stacking fault energy (SFE), respectively. The OFHC Cu was subjected to equal channel angular rolling (ECAR) by seven passes. ECAR is a method belonging to a SPD group. It was shown, five ECAR passes have a significant effect on material properties. The rolling performed at cryogenic temperatures using a laboratory duo rolling mill was carried out only once. This study implies that a recovery process (characterized by the mobility of structural defects) starts as follows: for OFHC Cu without ECAR and processed by 5thECAR passes: 0.31·Tmeltand 0.19·Tmelt, respectively, for C-Si steel processed by cryorolling: 0.095·Tmelt.

Mechanical performance degradation of glass fiber insulation material after neutron irradiation

Epoxy based glass fiber reinforced plastic composites G-10 CR grade are suitable material for electrical insulation breaks of the superconducting fusion device. At IPR, under the national fusion program, characterization of G-10 CR material with the neutron irradiation dose is studied. This study will help us towards the indigenous development project of electrical insulation breaks for future superconducting fusion magnets under the radiation environment. The insulation material has been irradiated by 14 MeV neutrons D-T generator in the Fusion Neutronics Laboratory, I.P.R. The mechanical and electrical performance was investigated after irradiation (with a fluence of 8.63×1014 n/m2) at room and cryogenic temperature condition. The results show that the mechanical degradations (by ∼ 9 to 30%) after neutron irradiation in tensile strength and impact strength at 300 K and 77 K. In this paper, we present the experimental details of the neutron irradiation and the data have been compared using MCNP code for flux calculation on glass fiber insulation composite along with Stycast 2850 GT epoxy. Investigation of mechanical, electrical, SEM analysis for internal surface morphology, glass transition temperature measurement of insulation material and its test results at 300 K and 77 K before and after neutron irradiation will be presented.

An Ultrasonic Motor Using a Titanium Transducer for a Cryogenic Environment

We have fabricated an ultrasonic motor using a titanium transducer. This motor is for driving in the cryogenic temperature condition with a highly intense magnetic field. Titanium has low magnetic permeability and a thermal expansion coefficient close to that of lead zirconate titanate (PZT). These features mean that a transducer made of titanium has good properties for use in such an environment. We have fabricated and evaluated the ultrasonic motor in a cryogenic environment and an intense magnetic field. We have simulated the thermal stress applied to PZT in consideration of nonlinear material properties in the cryogenic environment. The thermal stress of the titanium transducer is smaller than that of the SUS304 transducer. Moreover, we have achieved driving of the ultrasonic motor at 4.5 K. Additionally, we have confirmed that there is little effect of the intense magnetic field on the driving of the motor.

Characterisation of operational amplifiers at cryogenic temperatures for space applications

There is considerable interest in using commercial off-the-shelf (COTS) electronic components for space applications. These devices can provide many advantages for the development of space hardware. These advantages include: lower power consumption, better availability, superior performance and higher levels of integration. One significant performance parameter for devices is their lowest operational temperature. Extending the operational range of devices is important to decrease the amount of energy used to maintain their operating environment. Lower energy consumption enables their use in smaller instruments and spacecraft with low energy generation potential and/or low thermal mass. In this paper, we present the results of the testing of a variety of commercial operational amplifiers. CMOS, JFET and bipolar operational amplifiers were tested under cryogenic temperature conditions to determine their suitability for space applications. The performance characteristics studied were: offset voltage, total harmonic distortion (THD), change in open loop gain, and noise voltage.

An ultrasonic motor for cryogenic temperature using bolt-clamped Langevin-type transducer

In this study, a small ultrasonic motor driven under cryogenic temperature conditions has been fabricated and evaluated.Since transducer performance generally decreases at cryogenic temperatures, we designed and fabricated a bolt-clamped Langevin-type transducer for operation at cryogenic temperature. We simulated the influence of thermal stress on the transducer. The results from simulation were used to design the transducer, and it was then used to fabricate an ultrasonic motor for cryogenic temperature. The maximum diameter and the height of the motor are 30mm and 38.7mm.To enable the motor to be driven at cryogenic temperature, we evaluated the relationship between the contact pre-load and the lowest rotatable temperature. The motor's driving performance was evaluated at both room temperature and cryogenic temperatures. In a 4.5K helium gas ambient, the rotation speed and starting torque were 133rpm and 0.03μNm when the applied voltage was 50Vp–p.

Reduction of particle embedding in solid particle erosion of polymers

Abstract Particle embedding can be an unwanted consequence of abrasive jet micromachining (AJM) of polymeric materials. The embedding of aluminum oxide particles into acrylonitrile butadiene styrene (ABS), polytetrafluoroethylene (PTFE), polydimethylsiloxane (PMDS) and polymethylmethacrylate (PMMA) was studied under cryogenic and room temperature conditions. Scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) showed the fractional area coverage by embedded Al2O3 particles after room temperature AJM to be: 16% (ABS), 19% (PTFE), 25% (PDMS) and 3.2% (PMMA). Under cryogenic conditions, however, the fractional area coverage of embedded Al2O3 was found to be significantly reduced: 10% (ABS), 0.8% (PTFE), and 1.6% (PDMS). For PMMA, it was demonstrated that the surface was shielded by the embedded particles, resulting in an erosion rate that decreased with increasing embedded particle coverage. Several methods for the removal of embedded particles were also studied. A first step of blasting with spherical glass beads dislodged some of the Al2O3 particles embedded during AJM so that the fractional area coverage by embedded Al2O3 particles was reduced to 1.1% from 3.2% for PMMA. After this glass bead blasting, a further reduction in embedded particles could not be achieved by ultrasonic cleaning the PMMA samples with distilled water or with NaOH. However, more embedded particles could be removed using a freezing technique where the samples were first dipped in NaOH mixed with detergent or distilled water and then frozen by immersion in liquid nitrogen for 5 min after which the samples were allowed to warm to room temperature. For samples machined under cryogenic conditions, this freezing technique applied after the preliminary glass bead blast, reduced the area coverage of Al2O3 to 4% for ABS, 0.5% for PDMS and to almost 0% for PTFE. Finally, for PMMA machined at room temperature, using either the freezing method or an adhesive tape to pull out the embedded particles resulted in less than 0.5% embedded Al2O3 coverage. Since it was effective for all the studied polymers, it is recommended that glass bead blasting at 45° followed by the freezing technique be used to substantially reduce particle embedding after AJM.

Cold storage characteristics of mobile HTS magnet

A cold storage system specialized in mobile high-temperature superconducting (HTS) magnets (e.g. for magnetically levitated (maglev) vehicles) has been proposed. In this system, a cooling source is detachable and a HTS coil is capable of maintaining superconducting state with its heat capacity. This system allows a considerably lightweight HTS magnet. An apparatus was constructed to evaluate the possibility of using cold storage systems in maglev vehicles. The thermal characteristic of this apparatus was based on a magnet for previous maglev test vehicles [1]. The operational temperature range of the magnet was assumed from 20 K to 50 K. Some experiments indicated that heat conduction by residual gas was not negligible. Especially over 30 K, gas conduction took a large part of heat input. This phenomenon is attributable to reduction of cryopumping effect. However, activated carbon in the apparatus compensates cryopumping effect. A unique heat capacitor was also used to enhance the cold storage effect. Water ice was chosen as a heat capacitor because water ice has a higher heat capacity than metallic materials at cryogenic temperatures. A small amount of water ice also prolonged cryogenic temperature condition. These results indicate 1 day of cold storage is probable in a magnet for maglev vehicles.

Sb-HEMT: Toward 100-mV Cryogenic Electronics

In this paper, we present a first full set of characteristics (dc, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> , f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> , and noise) of InAs/AlSb high-electron mobility transistors (HEMTs) operating under cryogenic temperature and low-power conditions. Those results are systematically compared and deeply analyzed at room temperature and 77 K. The characteristics improvement achieved at 77 K open up the possibility to develop ultralow-power cryogenic electronics (low-noise amplifier), featuring excellent high-frequency/noise performances below 100-mV dc biasing.

Ion beam degradation analysis of poly(3-hexylthiophene) (P3HT): can cryo-FIB minimize irradiation damage?

In this study, to assess the influence of the temperature on the ion beam degradation, irradiation experiments on organic semiconductor materials were performed for both cryogenic and room temperature conditions. Thin P3HT films on silicon substrates were exposed to increasing ion doses in dual beam FIB. The degradation behaviour by means of a decrease in the C[double bond, length as m-dash]C band which corresponds to a loss of conjugation was investigated by means of Raman spectroscopy. In addition, atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) were used for a characterization of morphology and surface potential which provide information on temperature and ion dose dependent degradation behaviour.

Role of Flexibility and Polarity as Determinants of the Hydration of Internal Cavities and Pockets in Proteins

Molecular dynamics simulations of Staphylococcal nuclease and of 10 variants with internal polar or ionizable groups were performed to investigate systematically the molecular determinants of hydration of internal cavities and pockets in proteins. In contrast to apolar cavities in rigid carbon structures, such as nanotubes or buckeyballs, internal cavities in proteins that are large enough to house a few water molecules will most likely be dehydrated unless they contain a source of polarity. The water content in the protein interior can be modulated by the flexibility of protein elements that interact with water, which can impart positional disorder to water molecules, or bias the pattern of internal hydration that is stabilized. This might explain differences in the patterns of hydration observed in crystal structures obtained at cryogenic and room temperature conditions. The ability of molecular dynamics simulations to determine the most likely sites of water binding in internal pockets and cavities depends on its efficiency in sampling the hydration of internal sites and alternative protein and water conformations. This can be enhanced significantly by performing multiple molecular dynamics simulations as well as simulations started from different initial hydration states.

Basic insulating design of a magnet coil and a bobbin for a conduction cooled HTS SMES system

A conduction cooled high temperature superconducting (HTS) magnetic energy storage (SMES) is operated at a cryogenic temperature and high vacuum condition. Thus, insulation design at this condition is a key and an important element that should be established to accomplish miniaturization that is a big advantage of HTS SMES. However, the properties of insulators for cryogenic conditions in vacuum are virtually unknown. Therefore, we need active research and development of insulation concerning application of the conduction cooled HTS SMES. In this study, we investigated the basic insulation characteristics of some materials such as Kapton films, aluminium nitride (AlN) plates, vacuum and so on. As this result, we possessed basis data for insulation material selection and insulation design for the development of a 600kJ class conduction cooled HTS SMES. Also, the insulating test of the mini-model was performed by the above insulation design.

The Insulation Characteristics of Coil—Cryocooler for Conduction Cooled HTS SMES

The conduction cooled high-temperature superconductor (HTS) SMES (superconducting magnetic energy storage) was operated in cryogenic temperature and high vacuum conditions. Thus, the insulation design at the conditions is an important element that should be established to accomplish compact design is a big advantage of HTS SMES. However, the behaviors of insulators for the conditions are virtually unknown. Therefore, we need to researches and development of insulation concerning application of the conduction cooled HTS SMES. In this study, we experimented on insulation characteristics of SMES system. Also, we investigated about insulation characteristics of suitable materials to insulator for conduction cooled HTS SMES. As these results, we had basic data for insulation materials selection and insulation design of cryocooler-to-magnet coil for the development of 600 kJ class conduction cooled HTS SMES.