Liquid Nitrogen Medium Research Articles

EFFICIENCY OF AMIDES AS CRYOPROTECTORS IN THE COMPOSITION OF PROTECTIVE ENVIRONMENTS FOR BULLS SPERM CRYOCONSERVATION

The article highlights the results of research on the effectiveness of the introduction of cryoprotectants of the amide group – dimethylformamide (DMF), dimethylacetamide (DMAC) into the cryoprotective media for bull sperm and to determine their effect on the main physiological characteristics of germ cells. Materials and methods. Immediately after obtaining sperm, it was diluted with medium No. 1 containing 5.6% glycerol and 1.4% DMF (experimental group 1). Experimental group 2 was also diluted and treated with medium No. 1, but with the addition of 5.6% glycerol and 1.4% DMAC. After saturation of the sperm with the protective substances of medium № 1, it was diluted with medium No 2 containing 4% glycerol and 1% DMF (experimental group 1) and 4% glycerol and 1% DMAC (experimental group 2). Control samples were diluted according to a standard two-moment protocol using 7% glycerol in medium No. 1 and 5% glycerol in medium No. 2. Cryopreservation of spermatozoid was carried out by direct immersion of standard flat metal cassettes with coated granules in a liquid nitrogen medium. At the same time, cooling was carried out in the following mode: 4°C to minus 10°C at minus 3°C/min and from minus 10°C to minus 80°C at minus 40°C/min. Deconservation of spermatozoa was carried out at a temperature of 38–39°C. Cows were inseminated by the recto-cervical method. The results. The use of penetrating cryoprotectants from the amide group - dimethylformamide and dimethylacetamide - in media for sperm dilution and cryopreservation ensures a certain increase in the motility of germcells by 5.9% and 9.0%, respectively. The positive effect of the composition of cryoprotectants was also noted regarding the survivat of sperm after deconservation. Thus, the survival rate in the second experimental group was 0.67 hours or 10.3% higher than in the control group. The environments supplemented with cryoprotective substances of the amide group ensured sufficiently high sperm survival at body temperature (38ºС), which significantly exceeded the established minimum physiological norm (5 hours). In percentage terms, this excess was 34.6% and 42.6%. Conclusions. The feasibility of using combinations of endocellular cryoprotectants made from glycerol and dimethylformamide (DMF) or glycerol and dimethylacetamide (DMAC) in cryoprotective media (diluents) for bull sperm has been proven, which increases the quality characteristics of the biomaterial.

Experimental investigations on cryogenic friction-stir welding of similar ZE42 magnesium alloys

In this research, the cryogenic friction stir welding (CFSW) process has been performed using a liquid nitrogen medium to join two similar ZE42 magnesium alloy plates. The new experimental setup has been designed and fabricated to supply low-temperature (−196 °C) liquid nitrogen into the welding zone. The effects of welding parameters (tool pin profile, tool rotational speed, welding speed, and axial load) on the welding characteristics (tensile strength, hardness, and wear rate) have been investigated by the Taguchi technique. The impacts of welding parameters have been analysed to predict the optimum welding characteristics. The predicted best welding settings have been utilized to compare the CFSW and normal friction stir welding (NFSW) performances. The fractography of tensile-tested specimens, hardness distributions, and microstructure of worn-out CFSW welding surfaces have been examined by scanning electron microscopy (SEM) analysis. When compared to the NFSW process, the tensile strength and hardness of CFSW are improved by 41.36 % and 35.13 %, respectively, and the wear rate has decreased by 23.53 %.

WAYS OF CHANGING THE STRUCTURAL-MORPHOLOGICAL, PHYSICO-CHEMICAL AND ELECT­RICAL PROPERTIES OF GRAPHENES

A literature analysis of sources on synthesis methods and their influence on the structural-morphological, physico-chemical, and electrochemical properties of graphene and graphene-like structures was carried out. It was established that these properties have a clear dependence on the synthesis method, starting materials, and the composition of the synthesis medium.
 The main ways of changing graphene's structural-morphological, physico-chemical and electrical properties are changes in the synthesis method and conditions that affect the formation of σ-bonds and π-bonds. The presence of these bonds regulates the number of graphene layers and the formation of van der Waals interactions between them, as well as the formation of edge structural defects responsible for electrokinetic and catalytic properties. Changing the gas medium to a liquid one greatly simplifies the synthesis of graphene. Still, in the case of a liquid nitrogen medium, simultaneously with a 2-dimensional structure, it is possible to form 3-dimensional particles up to tens of nanometers in size. Aqueous medium and plasma-arc synthesis methods are the most attractive for obtaining materials with electron-donor conductivity, which have attractive electrochemical and catalytic properties for use in chemical current sources and fuel cells. Using an aqueous environment requires mandatory further heat treatment at temperatures above 250 0C to se­parate chemisorbed water from the structure, which complicates the synthesis procedure. The advantage of the plasma-arc method for the synthesis of graphene and other carbon nanostructures is its ability to shorten the stages of the synthesis of graphene, the possibility of modifying them directly during the synthesis process by changing the environment, easy management, and obtaining a clean final pro­duct. In the modern practice, this method is limited to obtaining coatings on a solid carrier.

An innovative procedure for synthesizing Al70M20(Fe, Co)Cr10 amorphous nanoparticles by arc discharge method and investigation of their magnetic, hardness, and corrosion resistance properties

Al70Fe20Cr10 and Al70Co20Cr10 amorphous nanoparticles were prepared by plasma arc discharge process under arc current of 50 A and 1 atm. pressure in liquid nitrogen medium. XRD patterns of the as-prepared powders exhibit amorphous nature. According to TEM images, the Al70Fe20Cr10 and Al70Co20Cr10 amorphous nanoparticles have a spherical shape with a mean size of 27 and 35 nm, respectively. Static magnetic measurements using a vibrating sample magnetometer (VSM) indicate that the Al70Co20Cr10 amorphous alloy has a higher saturation magnetization of 9.3 emu/g and a lower coercive field of 14 Oe compared with 3.8 emu/g and 45 Oe for the Al70Fe20Cr10 amorphous alloy. In contrast, the Al70Fe20Cr10 amorphous alloy has a higher hardness and shows approximately 20 times more corrosion resistance than the Al70Co20Cr10 amorphous alloy.

CdSO4-CdS COMPOSITE NANOWIRES SYNTHESIZED BY ARC DISCHARGE METHOD

Herein, we successfully carried out the of CdS nanowires doped with CdSO4 nanoparticles by arc discharge method. For this, two cadmium rods with high purity as anode and cathode electrodes were submerged in a liquid nitrogen medium. The cathode electrode was filled with micro-sized sulfur powder to synthesize CdS nanowires. CdS nanowires were obtained by oxidation using low temperature with CdSO4 nanoparticles. After the arc discharge process, the resultant product was characterized to reveal structural and morphological properties. XRD and electron EDX analyses exposed the coexistence of the CdS and CdSO4 phases. Scanning electron microscopy (SEM) investigations revealed that the synthesized nanostructures formed in a 1D wire nanostructure morphology with a diameter of less than 10 nm and several micrometers in length. Besides, the transmission electron microscopy (TEM) analysis was utilized to monitor the CdSO4 nanoparticles located on CdS nanowires surface. It has been found that the absorption band blue-shifted with 0.53 eV. This blue shift originated from the quantum confinement in the nanoparticles.

Влияние предварительной подготовки картона на определение крахмала ферментативным методом

We determined the amount of starch by the enzymatic method in different samples of corrugated cardboard, including the sample produced of primary semi-finished products and corrugated cardboard made of 100 % waste paper. For starch enzymatic degradation, it is necessary to extract it from the corrugated board structure, since the processes of compression and keratinization of pulp fibers reduce the availability of starch for extraction. Enzymatic treatment requires the use of a complex amylolytic preparation for complete hydrolysis of starch to glucose. We were able to determine, respectively, 70 and 84 % of starch obtained from primary semi-finished products by mechanical methods, such as defibrillation in water and degradation in a liquid nitrogen medium, and added at the production stage of corrugated cardboard. It was shown that extraction with alkaline agents was necessary for more complete extraction of starch from corrugated cardboard. The influence of alkaline treatment on the characteristics of fibers of waste paper fractions obtained at the Sukhonsky Cardboard and Paper Mill has been analyzed. The fibers swell in alkali, resulting in an increase in fiber width and its shortening, as well as a decrease in crystallinity, which can be a positive opportunity for more complete starch extraction. Fiber swelling and crystallinity reduction are more intensive for the short fiber fraction compared to the long fiber fraction. When determining starch in corrugated cardboard using the standard method SCAN-P 91:09 SСAN-W 13:09 it was not possible to detect all the starch added at the production stage of corrugated cardboard from primary semi-finished products. Also the processing conditions of this methodology lead to degradation of the partially hydrolyzed starch. The most complete extraction of starch from corrugated cardboard was achieved by two stages of alkaline extraction under the following conditions: 5 % NaOH, temperature of 20 °C, the duration of each extraction – 2 h. Under these processing conditions it was possible to determine all the starch (22.8 kg/t) in the corrugated cardboard produced of primary semi-finished products with known consumption of starch; the starch content in the corrugated cardboard produced of 100 % waste paper was 48.2 kg/t. For citation: Khadyko I.A., Novozhilov E.V., Chukhchin D.G. Influence of Cardboard Pretreatment on the Determination of Starch Content by the Enzymatic Method. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 150–162. DOI: 10.37482/0536-1036-2021-5-150-162

Testing high-precision electromechanical actuators used for adjustment of deployable antennas of astronomy space missions

Actuators for deployable space antennas operating under temperatures around the liquid helium point (~4.2 K) are in great demand since the number of space missions involving deployable mirrors is growing. We are suggesting a design of actuators to provide adjustment of mirrors with the active surface control system having in view the Millimetron observatory (Spektr-M space mission).Having defined the reference precision, power consumption, and resistance to vacuum and cryogenic temperatures of such actuators, we have analyzed probable solutions, and accordingly created our own cryogenic models based on a well-proven motor previously used for similar but non-cryogenic applications. We are suggesting that these models could be used as the developmental prototypes for batch production thus cutting possible costs.The cryogenic tests of our developmental prototypes have been conducted both in the boiling liquid nitrogen medium and under closest to open space conditions in the cryogenic vacuum chamber with the Cryomech closed-cycle cryorefrigerator PT-407 cooled down to the liquid helium point. The original test setups which were a challenge in itself, test algorithms, and the test results are being presented. The properties and electrical characteristics, and results of the tests of the actuators’ thermal behavior when adjusting a deployable mirror in emulated real-life situations mimicking the conditions of the Millimetron observatory are being discussed.

The Effect of Straining in Liquid Nitrogen Medium on the Kinetics of Water Desorption from Copper and Iron during Heating

The Effect of Straining in Liquid Nitrogen Medium on the Kinetics of Water Desorption from Copper and Iron during Heating

Preparation of Nanocellulose from Nonwood Plant Raw Materials

Abstract—The purpose of this work was to study the possibility of obtaining nanocellulose (NS) by ultrasonic (US) processing of powdered cellulose in a medium of liquid nitrogen (LN). To achieve this goal, it was necessary to determine the effect of the time of ultrasonic treatment in the medium of LN on the dispersed composition, crystallinity index and degree of polymerization (DP) of cellulose samples. Studies were performed using a powder X-ray diffractometer, a laser particle analyzer, and a scanning and transmission electron microscope. The DP of cellulose was determined by the viscosity of its solution in cadoxene by the standard method. It has been found that cryogenic grinding of flax cellulose samples does not lead to significant changes in its structural modification and degree of crystallinity, which indicates the high resistance of this material to such effects. However, ultrasonic exposure in the medium of LN with the subsequent treatment with 25, 45, 65% H2SO4 allows us to obtain cellulose nanospheres with a diameter of 48 to 437 nm and a yield of up to 40%. Unlike other types of nanoparticles (nanofibrillar, nanocrystalline cellulose), cellulose nanospheres have a larger surface area, which opens up the possibility of their effective use for the modification of composite materials.

Improving the wear and corrosion resistance of nickel aluminium bronze by deep cryogenic treatment

Bearing bushes are plain bearings extensively used in pumps, heavy equipment and marine equipment. These bushes are usually made of Lead Tin Bronzes, Aluminium Bronzes etc. C63200, Nickel Aluminium Bronze is the bearing material employed for flash butt welding machine. As welding operation is performed at extremely high temperature and high pressure, bearing material is subjected to corrosion and wear, which results in significant reduction of durability of the bearing. This paper aims to enhance the mechanical characteristics, wear and corrosion resistance of the bearing material C63200 by performing deep cryogenic treatment at −196 °C in liquid nitrogen medium at different soaking time intervals. The material was tempered at 540 °C for 2 h. Change in microstructure of the specimen; post cryogenic treatment was investigated using SEM. It is observed that there is a notable improvement in mechanical properties and wear resistance of the specimen treated at longer soaking time intervals.

Formation of Coatings under the Action of Laser Radiation in Liquid Media

The influence of the chemical composition of the substrate material on the chemical and phase composition of the formed coating was investigated. A number of experiments aimed at studying the interaction of titanium alloys with ultrashort laser pulses in different reaction media was carried out. A new method for the formation of titanium carbide under the action of ultrashort laser pulses on the surface of a titanium sample in a liquid hydrocarbon and liquid nitrogen medium is described. The description of the experiment is presented. The treated surface was investigated using a scanning electron microscope. Raman spectra from the surface of treated titanium alloys under different exposure conditions are obtained.

Investigating the Effects of Different Liquid Environments on the Characteristics of Multilayer Graphene and Graphene Oxide Nanosheets Synthesized by Green Laser Ablation Method

The present study is dedicated to investigate the effects of ablation environment on the characteristics of carbon nanostructures synthesized by pulsed laser ablation method; particularly for graphene and Graphene Oxide (GO) nanosheets. The beam of a Q-switched Nd:YAG laser of 532 nm wavelength at 7 ns pulse width and 0.5 J/cm2 fluence is employed to irradiate the similar graphite targets as the constant experimental conditions while liquid nitrogen and 0.04 M Cetyltrimethylammonium bromide (CTAB) solution are applied as the variable liquid environments. Also, characteristics of the final ablation products are investigated in detail via UV–Vis-NIR spectroscopy, X-ray diffraction pattern, Raman scattering spectrum, and Transmission electron microscopy (TEM). XRD and UV–Vis-NIR analysis exhibit the oxidation of graphene nanosheets in CTAB solution owing to the presence of oxygen molecules in ablation environment. Raman results indicate that the produced graphene nanosheets in liquid nitrogen medium have represented many layers, low level of defects and large SP2 domains size, while the GO nanosheets which are produced in CTAB solution have represented higher level of defects and smaller SP2 domains size. Furthermore, the characteristic features in Raman spectra also propose that there are two different graphene materials: AB stacked multilayer graphene and disoriented or randomly stacked multilayer GO nanosheets. The experimental results suggest that the characteristics of liquid environment such as nonpolar or cationic properties are the most effective parameters in the mass rate of carbon nanoparticles production. Our results provide useful guidance towards the production of carbon nanostructures with the desired attributes.

Effect of diamantane on the thermal stability of cryomilled aluminum alloy

The thermal stability behavior of Al-5083 cryomilled nanocrystalline powders stabilized by diamantane nanoparticles was studied in comparison with the alloy without diamantane. Nanocrystalline Al 5083 powders were produced by mechanical milling in a liquid nitrogen medium. The results revealed that Al 5083 with diamantane showed higher thermal stability than the cryomilled alloy without diamantane in the temperature limit from 473 °K to 773 °K (0.56 to 0.91Tm) for various annealing times from 0.5 h to 48 h. In this regard, calculations showed that while the grain size was still in the nano scale in the presence of diamantane, it was in the ultrafine range (> 150 nm) in the absence of diamantane. The above finding was qualitatively explained in terms of Zener’s concept.

PREPARATION OF NANOCELLULOSE FROM NON-WOOD PLANT RAW MATERIALS

The purpose of this work was to study the possibility of obtaining nanocellulose (NC) by ultrasonic (US) processing in the medium of liquid nitrogen (LN) powdered cellulose. To achieve this goal, it was necessary to determine the effect of the time of ultrasonic treatment in the medium of LN on the dispersed composition, crystallinity index and degree of polymerization (DP) of cellulose samples. Studies were performed using a powder X-ray diffractometer, a laser particle analyzer, and a scanning and transmission electron microscope. DP of cellulose was determined by the viscosity of its solution in cadoxene by the standard method. It has been found that cryogenic grinding of flax cellulose samples does not lead to significant changes in its structural modification and degree of crystallinity, which indicates the high resistance of this material to such effects. However, ultrasonic exposure in the medium of LN with the subsequent treatment with 25%, 45%, 65% H2SO4 allows to obtain cellulose nanospheres with a diameter of 48 to 437 nm and a yield of up to 40%. Unlike other types of nanoparticles (nanofibrillary, nanocrystalline cellulose), cellulose nanospheres have a larger surface area, which opens up the possibility of their effective use for the modification of composite materials.

Grain size stability in a cryomilled nanocrystalline Al alloy powders containing diamantane nanoparticles

The thermal stability of nanocrystalline Al-5083 alloy powders stabilized by diamantane molecular diamonds was compared with that of the nanocrystalline Al-5083 alloy powders with no diamantane. Both materials were produced by mechanical milling in a liquid nitrogen medium. The results revealed that Al-5083 with diamantane exhibited greater thermal stability than the alloy without diamantane in the temperature range of 473 °K to 773 °K (0.56 to 0.91Tm) for various annealing times from 0.5 h to 48 h. In this regard, calculations showed that while the grain size was still in the nanoscale range (< 100 nm) in the presence of diamantane, it was in the ultrafine range (> 150 nm) in the absence of diamantane. The above finding can be qualitatively explained in terms of Zener's particle pinning concept. The stability of nanocrystalline Al-5083 powder by adding diamantane is discussed in terms of retaining the nanostructure and maintaining hardness and strength over long periods of time when the powder is used in surface coating via cold spray

Effects of green laser fluence on the characteristics of graphene nanosheets synthesized by laser ablation method in liquid nitrogen medium

We have studied the effects of laser fluence on the characteristics of graphene nanosheets produced by pulsed laser ablation technique. In this work, The second harmonic of a Q-switched Nd:YAG laser at 532 nm wavelength and 5 Hz repetition rate with different laser fluences in the range of 0.5–1.8 J/cm2 was used to irradiate the graphite target in liquid nitrogen medium. The products of ablation were characterized using Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction pattern, UV–Vis absorption spectroscopy, Raman spectrum and transmission electron microscopy. The Raman spectroscopy indicates that the quality of the graphene nanosheets was decreased while their structure defects were increased as the laser fluence was increased from 0.5 to 1.4 J/cm2. Our results suggest that the amount of defects and the number of layers in graphene nanosheets can be changed by adjusting the laser fluence. This study could be a useful guidance for producing of high quality of graphene nanosheets by laser ablation method.

INFLUENCE OF RELAXATION PROCESSES ON MECHANICAL STRESS SHIFTS IN AMORPHOUS AND NANOCRYSTALLINE RIBBON ALLOYS AT ELECTROPULSE EXPOSURE

Relaxation processes in amorphous and nanocrystalline alloys in temperature range of –196 ÷ 80 °C have been studied. It was established that in amorphous alloy stress relaxation occurs in two stages. At the same time, decrease in initial mechanical stress in the sample by 5 % only occurs during the holding time of at least 1 hour. An increase in temperature of the sample leads to more intensive relaxation, which is manifested in an increase in rate of mechanical stress decrease. At the temperature of liquid nitrogen, stress relaxation is not observed. It has been established that in nanocrystalline alloy relaxation processes proceed in a similar manner, but relaxation rate is much lower. Dependences of residual mechanical stress on temperature and holding time were studied. It was found that in amorphous and nanocrystalline alloys, areas of stabilization of residual mechanical stresses are observed at small holding time (less than 5 min) in temperature ranges of 50 – 60 and 40 – 50 °C. Increase in holding time leadsto monotonousfall in residual mechanical stresses. Heating up to 40 °C results in complete relaxation of mechanical stresses in the sample 15 minutes after the start of the testing. It is shown that preliminary relaxation of stresses in amorphous alloy leads to decrease in value of mechanical stress relieving during electropulse ipmact in samples subjected to stretching. In nanocrystalline alloy, value of relieving remains practically unchanged under the indicated impact. It is also shown that the observed effect occurs due not only to thermal expansion, but also to change in the value of reversible component of directed structural relaxation. In the course of work it was established that value of mechanical stress relieving in amorphous alloy depends on medium in which electric current impulse is supplied. In particular, in liquid nitrogen medium, decrease in value of relieving is observed. Such a decrease is not observed in nanocrystalline alloy.

Nanostructured tungsten through cryogenic attrition

Nanostructured pure tungsten (W) powders have been fabricated through cryogenic attrition (i.e., cryomilling) in a liquid nitrogen medium for the first time. The microstructure and chemistry of W powders before and after 4 and 12h of cryomilling were thoroughly examined by gas fusion chemical analysis, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy (TEM). Cryomilling in liquid nitrogen protected the tungsten from oxygen and hydrogen contamination while introducing nitrogen. Results showed that the W grain size decreased with cryomilling time, and reached approximately 5nm after 12h of cryomilling. High resolution TEM suggested that nitrogen reacted with W to form tungsten nitride (WN). Additionally, amorphous W was identified in the 12h cryomilled W powder. Tungsten carbide (WC) contamination from the milling media and minor Fe–Cr–Ni-containing impurities from the stainless steel vessel were also documented. The WC had grain size ranging from 20nm to 150nm, and was homogeneously dispersed in W matrix.

Research on preparation of poly(1, 4-phenylene-terephthalamide) with in-situ phase transition aided heat transfer and its engineering scale study

Thermal management of the polymerization reaction process is one of key factors influencing polymer quality and success in engineering scale-up. Liquid nitrogen is introduced in PPTA polymerization process in the paper, so as to investigate influence on PPTA polymerization process and polymer performance when the inertia heat transfer medium of liquid nitrogen is adopted as the auxiliary heat transfer medium during polycondensation of traditional cryogenic fluid. It is indicated from results that addition of proper amount of liquid nitrogen during PPTA polymerization process can improve logarithmic viscosity and thermal stability, and improve the surface wettability of PPTA. It will not cause obvious influence on the chemical structure, aggregation structure and liquid crystal pattern of PPTA. The logarithmic viscosities of polymer obtained from the polymerization scale-up experiment of 140, 300 and 1000 L reaction vessels are above 6 dL/g.

Gold nanoparticle production by laser ablation in liquid nitrogen medium followed by cryogenic medium substitution with ethanol

The use of liquid nitrogen as a medium for laser ablation made it possible to obtain Au particles shaped as cores, cores/hollow shells, and hollow shells by radiation of a picosecond Nd:YAG laser. In this case, the substitution of the cryogenic liquid medium of the colloid by evaporating on the surface of a room-temperature liquid causes the shift and broadening of the plasmon resonance peak of Au nanoparticles, which results from the formation of fractal nanoparticle aggregates.