Studying phase formation of 12Х18Н10Т alloy and copper after friction welding

The technology of joining alloy 12X18H10T and copper has been studied. The use of friction welding is proposed. Modern development of technology requires the use of new technologies and materials. Despite the increase in the use of composite materials, and especially on the basis of the polymer matrix, metal alloys remain indispensable. Due to their physical and mechanical properties, metal-based alloys are used in rocket and space technology, mechanical engineering, and other industries. Goal. The aim of this work is the reason for the decrease in the mechanical properties of the connection 12Х18Н10Т – М1, which were obtained under suboptimal conditions. Friction welding was developed in early 1956 in the USSR. Since the 1960s, other countries have also begun to develop friction welding. This tool is a type of pressure welding, during which the metal is heated by friction of one of the parts of the product. At the end of the process, the final connection takes place. This type of welding is used in aircraft construction, rocketry, machine building, etc. In Ukraine, research in this direction is conducted at the Eugene Paton Institute of Electric Welding. The parameters of the friction welding technological process are considered. Results. The samples of welded joints 12Kh18N10T + M1 were studied. The following methods were used: mechanical tests; metallographic and electro-microscopic studies; hardness measurements; micro-X-ray spectral study. Originality. Welding joints with low strength were investigated; they were obtained for the following parameters: relative rotation speed 0.4 m/s, pressure during heating 80 MPa, pressure during forging 80 MPa, upset value 9 * 10-3 m samples with low strength varied in the deformed layer of steel from the joint surface to the base metal from 3240 MPa to 2450 MPa; in a deformed copper layer from 1020 MPa to 690 MPa. On samples that had high strength, the microhardness varied on the steel side from 2260 MPa in the contact surface to 2160 MPa, and in copper from 590 MPa to 460 MPa. Fig. 1 shows the microstructure of the deformed zones of the welded joint 12X18H10T, obtained according to the optimal parameters. Practical value. The reason for the decrease in the mechanical properties of the 12Х18Н10Т – М1 joint was established.

Estimation of the polymorphism of matrix metal proteinase genes in patients with endometrioid ovarian cysts

Aim. To determine the association of the MMP-9 genetic polymorphism with the risk of developing endometrioid ovarian cysts (ECC). Materials and methods. 55 women aged 19 to 47 were examined. 27 women underwent surgery for ECC (group 1). The control (group 2) consisted of 28 patients without endometriosis and operated because of tubal infertility. Single nucleotide polymorphism was investigated. Genotyping was performed by restriction fragment length polymorphism analysis. Results. We did not find statistically significant differences between the group of patients with ECF and the control group in terms of age 29.0 (25.95; 33.1), 34.5 (29.3; 37.0); p0.05, body mass index 21.2 (19.8; 22.6), 21.95 (20.4; 23.9), p0.05, age of menarche onset 13.0 (12.95; 14.0), 13.0 (12.0; 14.0), p0.05, duration of menstrual bleeding 5.0 (5.0; 5.0), 5.0 (5.0; 6.0), p0.05 for the 1st and 2nd groups, respectively, also dysmenorrhea (2 0.019; p=0.8918), the number of births (2 3.441; p=0.3285) and abortions (2 2.822; p=0.0930) in anamnesis. The frequencies of all studied genotypes of metalloproteinase MMP-9 C (1562) T of the MMP9 gene in the group of patients with ECF and the control group are in HardyWeinberg equilibrium (p=0.99, p=0.43 for 1 and 2 group) which excludes differences in the distribution of genotype frequencies of polymorphic loci of MMP9 genes in the group of patients with ECF and the control group. However, the result could be influenced by the severity of the disease and the size of the study groups. Conclusion. Given the undoubted role of matrix metalloproteinases in the pathogenesis of genital endometriosis, further studies with large samples in various populations are needed.

The Influence of Dispersion Time On The Mechanical Properties of Spark Plasma Sintered Carbon Nanotubes Reinforced Nickel-Aluminium Matrix Composites

Nickel (Ni) and aluminium (Al) powders were milled with carbon nanotubes (CNT) by employing the high-speed ball milling approach, and the consolidation was achieved by spark plasma sintering technology (SPS). The microstructural evolution of the milled samples and consolidated samples were examined, and the mechanical properties were investigated. The outcome indicated the agglomeration of CNT within the NiAl matrix, and the CNT dispersions improved with the milling duration. The structural integrity of the CNT was evaluated using the Raman analysis which depicted that the ID/IG ratio decreased from 0.986 to 0.867 as the high-speed ball milling was longer, which also depicts more damage to the CNT. The microhardness of the consolidated composite was enhanced from 287.7 HV-320.4 HV due to better dispersion of CNT within the matrix metal. Furthermore, the predicted tensile strength and yield strength of the composite improved from 4011.9 MPa-4428.8 MPa, and from 5747.9 MPa-6389.3 MPa.

Nanocomposite Coatings in Corrosion Protection Applications: An Overview

Corrosion is one of the biggest problems which affects the economy of the country, which occurs as a result of the interaction of the metal with its surroundings. One of the easiest ways to prevent corrosion is coatings of the metals with paint, plastic or wood. Several types of coatings have been adopted by corrosion scientists in the prevention of corrosion that are mainly based on electrochemical principles. Fortunately, based on cost and effectiveness, four types of coatings are variably employed by the metal and metallurgy industries. One among the cheapest and effective way to prevent corrosion is to use barrier coatings like plastic, powder and paint. Hence, nanocomposite coatings by electrochemical deposition offers an excellent, scratch and corrosion resistance on the metal surface. These coatings may be used to restoration of the components instead of interchanging them, resulting in reduced maintenance costs and disturbance. Significant improvements in the corrosion protection of steel have been reported by using metal-metal matrix, metal-metal oxide matrix, metal-polymer matrix, and ceramic-metal matrix nanocomposite. This review presents an overview of works related to nanocomposite coatings and to re-evaluate the literature for the future research in the field that still lacks validation.

Synthesizing Aluminum Matrix Composites by Combining a Powder Metallurgical Technique and an In Situ Method

A method of synthesizing dispersion-strengthened aluminum matrix composites using a powder metallurgical technique and an in situ method was considered. Methods combination was aimed at ensuring energy efficiency, avoiding vacuum treatment of the reaction medium, and using inert gasses to protect from oxidation. Reinforcement phase precursors are capable of ensuring good wettability of dispersed particles by the molten matrix metal. The options of the methods’ practical implementation are presented by the example of producing aluminum matrix composites filled with various functional particles.

Wear Characteristics of Al7075/Al2O3/SiC Hybrid Metal Matrix Nano Composites

In the present investigation Aluminum matrix composites (AMMCs), Al7075 Alloy as matrix metal and Al2O3/SiC particles (2-8%) with an average particulate size of 20, 50 nm as strengthened material have been processed by the stir casting method. For the counter surface wear testing, a computerized pin on a wear tester was used as EN31 (58-60 HRC) steel disc and composite pin. The wear rate for the matrix metal and composites in terms of weight loss per unit sliding distance, friction coefficient, and volume loss were achieved. The composite results show better resistance to wear than matrix metal. SEM was used to investigate the microstructural characterization of worn surfaces. Sample weight loss was calculated and the change in cumulative wear loss at a sliding distance was uniform both for metal matrix as well as for composites. The wear speed for composites was also noted to be small compared to the metal matrix. In addition, experiments have shown that, with the increasing weight fraction of Al2O3/SiC and the coefficient of friction increases with increasing sliding velocity and weight fraction of Al2O3/SiC, the wear rate reduces. The wear characteristics (wear rate, coefficient of friction and wear loss) were better than those of other composites and the matrix metal with 6wt% Al2O3/SiC composites.

Study of wetting and impregnation kinetics of oxide fibers with lead melts and its alloys

The effect of metal coverings on wetting of oxide fibers by lead, bismuth, tin-lead-bismuth-cadmium alloy in vacuum 2·10-3 Pa in the temperature range 400–600 oC was studied by the sessile drop method using the capillary purification method of melt. Oxide fibers plaits that have been placed on a silicon oxide substrate as wetting substrates used. Titanium and nickel powders were used as metal coatings. There is no wetting. The contact angles are close to or greater than 90 degrees and only in the case of the lead-titanium melt system at 600 oC the value of the angle is 15, respectively. The use of a dropper allows separate heating of the melt and the substrate, capillary and thermo vacuum cleaning of the melt, as well as thermo vacuum cleaning of the coatings surface. This is a model scheme of the impregnation process of non-metallic frames with matrix melts in the manufacture of composite materials by spontaneous free impregnation. The metal titanium, nickel powder coatings for the method of spon¬taneous free impregnation was used. The study of the kinetics of impregnation of plaits of oxide fibers with melts of lead and tin-lead-bismuth-cadmium alloy was performed at 600–700 oC. The metal melt impregnates metal powders well. The rate of impregnation is quite high 1,1–1,8 mm/s. The obtained results allow the use of titanium pastes for the manufacture of composites from oxide materials with lead matrices. Composites were made. Oxide fiberglass made of CRT waste was selected as the reinforcing material. Lead was chosen as the matrix metal. Despite the fact that lead is a harmful material, but its use as a matrix phase for composites from the action of ionizing radiation is indispensable. Keywords: spontaneous free impregnation, composites, lead melts, oxide fibers, wetting, metal coverings.

BIMETAL/CARBON NANOCOMPOSITES CuCo@C BASED ON SYNTHETIC HUMIC ACIDS

The new original method for the synthesis of bimetal-carbon nanocomposites of copper and cobalt (CuCo@C) of various compositions using synthetic humic acid as a carbon source has been developed. The technique includes the synthesis of humates of copper and cobalt, preparation of their mixture and its pyrolysis in a hydrogen atmosphere. For characterize the final product, the methods of diffraction, cyclic voltammetry, and scanning electron microscopy were used. Comparison of diffractograms of bimetal nanocomposites shown two systems of reflexes from fcc structures, which correspond to metallic copper and cobalt. Diffractometric measurements also indicate the amorphous nature of the carbon matrix. Carrying out the pyrolysis of the metal humates in the reducing atmosphere afford remove almost completely the contained oxygen from the final product, partly in the form of CO2, partly in the form of water. Ions of the transition metal in these conditions are reduced to the metal atoms, forming nanoparticles surrounded by carbon. The formation of a carbon matrix metal around nanoparticles, on the one hand, can ensure their high thermal stability, and on the other hand, contributes to the stabilization of metal nanoparticles and prevents their aggregation. The size of cobalt nanoparticles in nanocomposites varies from 35 to 54 nm, and copper nanoparticles - from 56 to 88 nm, depending on the ratio used in the synthesis of metal humates. It was found that nanoparticles of an alloy of these metals (alpha-cobalt phase) are formed in nanocomposites containing 20% ​​copper and 80% cobalt. Cyclic voltammogrames of bimetallic nanocomposites indicate the presence of dead pores in their composition. It has been established by scanning electron microscopy that in the case of an excess amount of copper in the nanocomposites, spherical formations about 1000 nm in size with faceting signs are formed. As part of the «bottom up» concept proposed a three-stage model of formation.

Polyphenols as Potential Therapeutics for Pain and Inflammation in Spinal Cord Injury

: Spinal cord injury (SCI) and associated pain and inflammation caused by the trauma or infection is one of the serious health care issues world-wide. The various inflammatory, redox-sensitive and apoptotic events are contributing factor but altered neuronal function, axonal degeneration, activated microglia, endothelial cells, astrocytes, fibroblasts,pericytes, Schwann cells, meningeal cells are the major player in its pathogenesis. Further, monocytes and neutrophil infiltration get recruited and facilitate the release of chemokines, cytokines, and other mediators of inflammation. This event leads to the production of different amino acids, neuropeptides kinin, prostaglandins, prostacyclin, thromboxane, leukotrienes, bradykinin, histamine, matrix metal proteinases and serotonin that stimulate nerve endings and manifests the inflammation and pain processes, etc. Arachidonic acid (AA), NF-kB, NLRP3 inflammasome, and nitric oxide pathways along with P2X7 receptor and ion channel transient receptor potential (TRP) vanilloid are some of the recently explored targets for modulation of pain and inflammation in SCI. Till now, NSAIDs, opioids, antidepressants, anticonvulsants, NMDA antagonists, α2-adrenergic agonists, and GABA-receptor agonists are used for the management of these pathological conditions. However, these drugs are associated with various side effects. Additionally, the number of available animal models for SCI has enhanced the understanding of the complex pathological mechanisms involved in the generation of chronic inflammatory pain in SCI. These findings enable us to identify and validate several potent natural analgesic-anti-inflammatory drug candidates with minimal side effects. However, until now, these compounds have been studied in preclinical models and shown promising results but no clinical studies have been performed. Therefore, a detailed exploration of these natural compounds is important for bringing them from bench to bedside.