Liquid Nitrogen Temperature Research Articles

Study on the Magnetic Properties of Metal Substrates at Low Temperature by Fabricated Compact SST

In recent years, a development of a high magnetic field magnet using a high temperature superconducting (HTS) wire has been advanced. On the other hand, we are planning to use the HTS wires for superconducting applications cooled by cryocooler. So, it is necessary to measure the temperature dependence of the magnetic properties of the metal substrates (Hastelloy, stainless steel and NiW) for HTS wire under conduction cooling conditions. We have been developing a single sheet tester (SST) that can evaluate the magnetic properties of electromagnetic steel sheets and other materials. However, since the size of an excitation coil in the conventional SST is large, it is difficult to install them in the conduction cooling system. In this study, we fabricated the compact SST and its measurement accuracy was compared with the conventional SST. The magnetic properties of metal substrates were measured at room temperature and liquid nitrogen temperature (77 K). As a result, although the measurement accuracy of the compact SST was slightly reduced by decreasing the coil size, we found that the error of the magnetic field homogeneity of the compact SST was within 2&#x0025; at the center region of the 5 mm length. The magnetic properties of Hastelloy and stainless steel were almost unchanged at both room temperature and liquid nitrogen temperature. However, the magnetic properties of the NiW substrate changed significantly at liquid nitrogen temperature. The <i>B</i>-<i>H</i> characteristics of the NiW substrate in the rolling and transverse directions were clearly different, and the iron loss increased significantly at liquid nitrogen temperature.

Experimental and Theoretical Study on Power Generation Characteristics of 1 kW Class Fully High Temperature Superconducting Induction/Synchronous Generator Using a Stator Winding With a Bending Diameter of 20 mm

We report experimental and theoretical results of power generation characteristics of a 1 kW class fully High Temperature Superconducting Induction/Synchronous Generator (HTS-ISG) that consists of a stator winding using REBCO tape and a rotor winding using BSCCO tape. The bending diameter of REBCO stator winding is 20 mm and its average critical current is 90 A at 77 K. As a result of experiments at liquid nitrogen temperature, we succeeded in a power generation test exceeding 500 W. From this result, we could demonstrate the possibility of a small-sized fully superconducting generator.

HTS Dipole Magnet Model for the Persistent Current Operation

Recent advances in the fabrication of high-temperature superconducting (HTS) coils allow the design of superconducting accelerator magnets that work in a persistent current mode. Many various, rather low-field magnets in particle accelerators operate in the DC current mode. Fermilab designed, fabricated, and tested an HTS dipole magnet model that has 20-mm air gap and a magnetic field up to 0.5 T. The magnet has a primary copper coil that for a short period pumps the energy in the short-circuited secondary HTS coil. The current paper presents the design, fabrication, and testing of this magnet at liquid-nitrogen temperature.

Improving Embryologists’ Sleep Quality: Implementation of a Weight-Based Monitoring System for Gamete and Embryo Cryostorage

Background: Storage of gametes and embryos in our laboratories represents the highest concentration of risk for an ART clinic. A single storage tank may contain material of several hundred patients and vacuum failure is a scenario that haunts embryologists’ nightmares. Temperature sensors are currently the most prevalent mechanism for ‘alarming’ storage tanks, however, such approaches are akin to closing the gate after the horses have bolted. Aim: To assess the implementation of a fully redundant, weight-based monitoring system for ensuring the security of liquid nitrogen storage tanks in a high-capacity ART unit. Method: Forty flat-bed scales were fitted with alarm conversion units allowing a standard ‘open/closed’ alarm output to be relayed in the event a reading fell below the user defined weight limit. Output was routed through a security monitoring system via phone line and mobile-SIM, with no overlap of the existing, internet-based temperature probe system. Relationship between liquid nitrogen level (HC35 vessel), tank weight and temperature reading (probe positioned at top of canister), was established by sequential measurements. Results: Addition of the flat bed scales proved minimally disruptive to the space allocation per tank, requiring no additional ‘width’ but a slight increase in ‘depth’ behind tanks to accommodate the screen support. As expected, a clear, linear relationship was evident between liquid nitrogen level and tank weight, with every 1cm drop in liquid nitrogen equating to approximately 0.5kg weight loss. Concerningly, the temperature probe remained below -190∘ with just 0.5cm of liquid nitrogen remaining, only rising above the alarm trigger threshold once nitrogen had fully evaporated, resulting in a precipitous rise to above devitrification temperature in a matter of hours. Conclusion: Introducing a weight-based tank monitoring system is both feasible and effective. This system provides vastly superior performance in the timely identification of impending tank failure, allowing ample opportunity to ensure safe relocation of material.

Experimental Study on the Accuracy of the Proposed LFAC Method for Measuring the Contact Resistance of NI HTS Coils

No-insulation (NI) winding technique provides high thermal stability, and the turn-to-turn contact resistance is an important factor to characterize the thermal stability and charging delay of NI HTS magnets. Therefore, a method that can accurately measure the contact resistance between turns of NI HTS magnets was required. We have previously proposed a turn-to-turn contact resistance measurement method using a low frequency AC current. The proposed low-frequency-AC-current (LFAC) can accurately evaluate the contact resistance between turns only when the whole AC current flows in the radial direction of the NI HTS pancake coil (there is almost no coil inductance). In addition, the AC current flowing in the radial direction needs to have a uniform current distribution in the plane of winding wire (REBCO wire). Therefore, in this study, an experimental study was conducted to prove the reliability of the proposed LFAC method. In the experiment, three NI test coils with different winding tension (0.5, 1 and 2 kg) were prepared, and four pickup coils were placed under each test coil to evaluate the radial current bypass characteristics. The contact resistance of each test coil was decreased from a few percent to several tens of percent by multiple cooling cycles from room temperature to liquid nitrogen temperature. Although it is a qualitative observation, the validity of the LFAC method was proved by the prepared pickup coils, and it was shown that even a small change of contact resistance in NI coils can be measured.

Electronic band structure in pristine and sulfur-doped Ta2NiSe5

We present an angle-resolved photoemission study of the electronic band structure of the excitonic insulator Ta$_2$NiSe$_5$, as well as its evolution upon Sulfur doping. Our experimental data show that while the excitonic insulating phase is still preserved at a Sulfur-doping level of 25$\%$, such phase is heavily suppressed when there is a substantial amount, $\sim$ 50$\%$, of S-doping at liquid nitrogen temperatures. Moreover, our photon energy-dependent measurements reveal a clear three dimensionality of the electronic structure, both in Ta$_2$NiSe$_5$ and Ta$_2$Ni(Se$_{1-x}$S$_x$)$_5$ ($x=0.25, 0.50$) compounds. This suggests a reduction of electrical and thermal conductivities, which might make these compounds less suitable for electronic transport applications.

Effect of the Testing Temperature on the Impact Property of a Multilayered Soft–Hard Copper–Brass Block

The impact property is one of the most significant mechanical properties for metallic materials. In the current work, a soft–hard copper–brass block with a high yield strength of ~320 MPa and good uniform elongation of ~20% was prepared, and the effect of the testing temperature on its impact property was explored. The results showed that the impact energy was decreased with the increase in testing temperature. The impact energies at liquid nitrogen temperature (LNT), room temperature (RT), and 200 °C were 8.15 J, 7.39 J, and 7.04 J, respectively. The highest impact energy at LNT was attributed to the coordinated plastic deformation effects, which was indicated by the tiny dimples during the process of the delamination of soft–hard copper–brass interfaces. The high temperature of 200 °C can weaken the copper–brass interface and reduce the absorption of deformation energy, result in low impact energy.

Superconductivity above 80 K in polyhydrides of hafnium

Studies on polyhydrides are attracting growing attentions recently due to their potential high temperature superconductivity (SC). We here report the discovery of SC in hafnium polyhydrides at high pressures. The hafnium superhydrides are synthesized at high pressure and high temperature conditions using diamond anvil cell in combination with in-situ high pressure laser heating technique. The SC was investigated by in-situ high pressure resistance measurements in applied magnetic fields. A superconducting transition with onset Tc ∼83 K was observed at 243 GPa. The upper critical field μ0Hc2(0) was estimated to be 24 T by GL theory and the consequent superconducting coherent length ξ to be ∼37 Å. Our results suggest that the superconducting phase is from C2/m-HfH14. This is the first 5d transition metal polyhydride superconductor with Tc above the liquid nitrogen temperature.

Effects of temperature and loading direction on deformation mechanism of Ti-10at%Al alloy subjected to rolling and high speed compression

In this paper, Ti-10at%Al alloy samples were subjected to rolling and high speed compression under different temperatures and along different loading directions (the transverse direction (TD) and normal direction (ND) of the pre-rolled samples), to explore the effects of temperature and loading direction on the deformation mechanisms.101̅2 and 112̅1 twins were activated in all these deformed specimens. 112̅1 twins prevailed in both the room temperature rolled and liquid nitrogen rolled specimens but were severely inhibited during hot rolling, while 101̅2 twins did not show obvious change with the temperature. Planar slip of dislocations occurred during room temperature rolling and liquid nitrogen rolling, while cross slip occurred during hot rolling. The change of dislocation behaviors at different temperatures may be caused by the variation in stacking fault energy as an effect of temperature. Moreover, the number of twins in the deformed samples along TD was always higher than that along ND both under rolling and high speed compression. When loaded along TD, most of the grains were with or close to the orientations of<21̅1̅0> and<101̅0> , which were favorable for the activation of 101̅2 and 112̅1 twins. Therefore twinning played a significant role when loaded along TD, while dislocation slip dominated the deformation when loaded along ND. The hardness increased after deformation under different conditions, and the hardness of specimens after rolling or compression along ND was generally higher than that along TD due to the reason that most of the grains were in the hard< 0001 > orientation when loaded along ND, activation of<c+a> dislocations on pyramidal planes with high critical resolved shear stress was required.

CRYOTHERAPY WITH LIQUID NITROGEN FOR ORAL LEUKOPLAKIA TREATMENT: CASE REPORT

Cryotherapy is the use of cryogenic substances aiming for local tissue destruction. Although considered an alternative therapy for oral leukoplakia (OL), postoperative complications may occur, reinforcing the challenge of treat these lesions. A 68-year-old Black female patient was diagnosed with a 5-cm OL with mild epithelial dysplasia in the right gingival mucosa. Cryotherapy with liquid nitrogen at −196°C was proposed. The lesion was mapped for better control of temperature and dispersion of liquid nitrogen occurred every 1.5 cm. Two application cycles were carried out, each with 20 seconds of freezing and 1 minute of thawing. On day 21 of postoperative follow-up (D7-14-21), incomplete re-epithelialization and 4-mm bone exposure were noted. Local cleaning with chlorhexidine digluconate 0.12% for 1 week was performed. Because there was no improvement, necrotic bone was debrided and application on the adjacent areas was interrupted. After 6 months, OL regression was observed in the applied area and intact mucosa.

Half-metallicity in Cu-metalated carbyne predicted by first-principles calculations

Theoretical investigations of the electronic structure of free-standing one-dimensional Cu-metalated carbyne and BN atomic wire are performed using density functional theory. Our calculations demonstrate that the ground state of these two monatomic wires is all half-metallic ferromagnets with 100% spin-polarization. At Fermi level, their density of states is metallic for minority spin channel and shows a semiconductor gap for majority spin channel. Monte Carlo simulation based on Ising mode indicates that the Curie temperature for these two monatomic wires is much higher than the temperature of liquid nitrogen, which promises potential applications in the nanoscale and molecular spintronics in the future.

Cathodoluminescence Response of Barite at Room and Liquid Nitrogen Temperatures

Cathodoluminescence Response of Barite at Room and Liquid Nitrogen Temperatures

Development of a controlled-atmosphere, rapid-cooling cryogenic chamber for tribological and mechanical testing.

Mechanical testing of seals, bearing materials, and mechanisms in cryogenic environments is a rapidly growing field of research, as it promises improvements in equipment performance and reliability for applications such as space exploration, liquid hydrocarbon storage, and superconducting devices. Cooling of test equipment is usually performed within a well-insulated test chamber, via direct or indirect evaporation of liquid cryogen. State-of-the-art equipment is frequently insufficient for rigorous testing, being expensive and cumbersome, cooling slowly, struggling to replicate relevant environmental conditions, and/or failing to reach the temperature of the cryogen. Herein, we employ a rapid prototyping approach using polymer 3D printing to iteratively refine cryogen-based cooling of a tribometer. The final design greatly exceeds the minimum temperature of state-of-the-art equipment, cooling a chamber to liquid nitrogen temperatures (-196 °C) while maintaining dry test conditions. When modified for use on a cryogenic tensile tester, the design cools to -150 °C in 149s, significantly improving upon state-of-the-art performance. By utilizing this 3D-printed equipment, we find that components produced via Fused Deposition Modeling with unmodified, commodity polylactic acid have favorable mechanical properties in a cryogenic environment: tensile strength of 110 MPa, elongation at break of 10%, and specific wear of 5.6 × 10-5mm3/Nm against stainless steel. By leveraging 3D printing for rapid manufacture of production-quality parts, highly refined cooling chamber designs have been experimentally developed for both a tribometer and a load frame in rapid succession, enabling significant improvements in cryogenic test capabilities.

Mid-Infrared Laser Generation of Zn1-xMnxSe and Zn1-xMgxSe (x ≈ 0.3) Single Crystals Co-Doped by Cr2+ and Fe2+ Ions-Comparison of Different Excitation Wavelengths.

Two different mid-infrared (mid-IR) solid-state crystalline laser active media of Cr, Fe:ZnMnSe and Cr, Fe:ZnMgSe with similar amounts of manganese or magnesium ions of x ≈ 0.3 were investigated at cryogenic temperatures for three different excitation wavelengths: Q-switched Er:YLF laser at the wavelength of 1.73 m, Q-switched Er:YAG laser at 2.94 m, and the gain-switched Fe:ZnSe laser operated at a liquid nitrogen temperature of 78 K at ∼4.05 m. The temperature dependence of spectral and laser characteristics was measured. Depending on the excitation wavelength and the selected output coupler, both laser systems were able to generate radiation by Cr or by Fe ions under direct excitation or indirectly by the Cr→ Fe energy transfer mechanism. Laser generation of Fe ions in Cr, Fe:ZnMnSe and Cr, Fe:ZnMgSe (x ≈ 0.3) crystals at the wavelengths of ∼4.4 and ∼4.8 m at a temperature of 78 K was achieved, respectively. The excitation of Fe ions in both samples by direct 2.94 m as well as ∼4.05 m radiation or indirectly via the Cr→ Fe ions’ energy transfer-based mechanism by 1.73 m radiation was demonstrated. Based on the obtained results, the possibility of developing novel coherent laser systems in mid-IR regions (∼2.3–2.5 and ∼4.4–4.9 m) based on AB matrices was presented.

Structural and magnetoelastic properties of non-stoichiometric TbFe2Mnx Laves phase

In this paper, we studied TbFe2Mnx alloys using x-ray powder diffraction, x-ray fluorescent analysis, differential scanning calorimetry, scanning electron microscopy, and magnetostriction measurements. It was established that single phase non-stoichiometric TbFe2Mnx compounds are formed up to Mn concentration x = 0.25. The non-stoichiometric TbFe2Mnx compounds possess huge spontaneous magnetostriction in [111] direction (up to 2550 ppm) which result to distortion cubic MgCu2-type structure to rhombohedral (R3¯m) at room temperature. The formation of non-stoichiometric TbFe2Mnx compounds results from partial substitution of Tb by Mn in (6c) positions. It was found a characteristic value for the cubic MgCu2-type lattice parameter ac ≈ 7.2 Å. If binary RT2 (R is a rare-earth metal, T – 3d transitional metal) compounds have lattice parameter smaller than 7.2 Å, we can expect large values of Mn concentration (x > 0.4) in non-stoichiometric RT2Mnx compounds. The Mn doping in TbFe2Mn0.25 compound led to significant increase of magnetostriction at liquid nitrogen temperature (λ|| ≈ 2400 ppm in magnetic field 18 kOe) which is 25 % larger than that of initial TbFe2. It also preserve large magnetostriction at room temperature (λ|| ≈ 1530 ppm in magnetic field 18 kOe). This make non-stoichiometric TbFe2Mn0.25 compound promising material for various magnetostrictive applications in wide temperature range.

The effect of Co substitutions for Ni on microstructure, mechanical properties and corrosion resistance of Fe50Mn25Cr15Ni10 medium-entropy alloy

The microstructure, mechanical properties, and corrosion resistance of Fe50Mn25Cr15Ni10-xCox medium-entropy alloys (MEAs) with varying Co and Ni contents were investigated in this study. With increasing Co concentration, the microstructure of the MEAs changes from FCC single phase to FCC + HCP dual-phase. At room temperature, a rise in Co concentration increases the strength and ductility of the MEAs, while at liquid nitrogen temperature, the ductility, and the product of tensile strength and ductility of the MEAs decrease significantly. Furthermore, the corrosion resistance of the MEAs decreases significantly with increasing Co content. This work provides a research object for the further development of low-cost MEAs with excellent mechanical properties and corrosion resistance.

Improving Bi-2212 multi-filament wire quality and superconductivity by cryogenic drawing

Bi2Sr2CaCu2O8+δ (Bi-2212)/Ag round wires were fabricated by cryogenic drawing under liquid nitrogen temperature (77 K). The influences of cryogenic drawing on the metallic sheath mechanical properties, filament densification, filament size uniformity, and superconducting properties have been systematically studied. Significant improvement of both strength and plasticity of Ag sheath was achieved under low temperature. Higher wire uniformity and densification state have been obtained by applying cryogenic drawing under 77 K, leading to the critical current density promotion by nearly 40 %. It is believed that cryogenic drawing of Bi-2212 wire is a feasible and effective way to improve the wire quality due to the mechanical reinforcement of metal sheath.

Enhanced thermal stability of nanocrystalline Cu-Al alloy by nanotwin and nanoprecipitate

The structural stability of nano-grained Cu-Al alloy synthesized by ball milling under liquid nitrogen temperature was analyzed. The hardness of the alloy drops only 6 % after annealing at 1173 K for 30 min, in comparison to the as-milled condition. X-ray diffraction (XRD), transmission electron microscopy (TEM), and Molecular dynamics (MD) simulation was incorporated to get an insight into the enhanced thermal stabilization of the alloy. Cryogenic ball milling introduces extensive deformation twins in the microstructure and a significant amount of twins are present after annealing. The retained nanoscale twins along with the annealing induced Al2Cu nano-precipitate synergistically contribute toward the structural stability of the alloy.

Transformation from a high-temperature superconductor yttrium-barium-copper oxide to a photocatalytic material yttrium-barium oxide, a DFT-based investigation

Novel semiconductor photocatalysts are currently a hot research topic. We are inspired by the phenomenon that high-temperature superconductors can achieve superconductivity only under certain conditions (e.g., liquid nitrogen temperature). Here, based on the analysis of the energy band structure of the high-temperature superconductor YBCO (YBa2Cu3O7-x, YBCO), two new yttrium barium oxide (YBO) semiconductor materials, Y2Ba3O6 (YB3O) and Y2Ba4O7 (YB4O), are reported in this study. According to first-principles calculations, we find that YB4O and YB3O have stable formation energies, as well as forbidden band gaps, which are suitable for the visible light response. In addition, YB4O possesses a larger effective mass difference of carrier and stronger electron delocalization in various directions than that of YB3O, while YB3O possesses a larger light absorption threshold than that of YB4O. These two innovative yttrium-barium oxide materials show strong semiconducting properties and have great potential as photocatalysts.

Hydrogen Isotope Separation Using a Metal–Organic Cage Built from Macrocycles

AbstractPorous materials that contain ultrafine pore apertures can separate hydrogen isotopes via kinetic quantum sieving (KQS). However, it is challenging to design materials with suitably narrow pores for KQS that also show good adsorption capacities and operate at practical temperatures. Here, we investigate a metal–organic cage (MOC) assembled from organic macrocycles and ZnII ions that exhibits narrow windows (&lt;3.0 Å). Two polymorphs, referred to as 2α and 2β, were observed. Both polymorphs exhibit D2/H2 selectivity in the temperature range 30–100 K. At higher temperature (77 K), the D2 adsorption capacity of 2β increases to about 2.7 times that of 2α, along with a reasonable D2/H2 selectivity. Gas sorption analysis and thermal desorption spectroscopy suggest a gate‐opening effect of the MOCs pore aperture. This promotes KQS at temperatures above liquid nitrogen temperature, indicating that MOCs hold promise for hydrogen isotope separation in real industrial environments.