PRECIPITATION OF CALCIUM PHOSPHATES FROM A MODEL BLOOD PLASMA SOLUTION ON STEEL GRADE 12X18N10T

В работе представлено исследование процессов осаждения минеральноорганических образований в модельном растворе плазмы крови в присутствии добавок альбумина, глицина, глюкозы, глутаминовой и молочной кислот. Методом рентгенофлуоресцентного анализа изучен фазовый состав образцов. Для измерения площади покрытия образца модифицированным фосфатом кальция были сделаны фотографии. На фотографиях были выделены области покрытия твердой фазой и с помощью программы ToupView произведен расчет степени покрытия образцов стали. Осаждение кристаллической фазы происходит на всех исследуемых образцах. Отличия заключаются в распределении кристаллов по поверхности пластины. Добавка альбумин ингибирует процесс осаждения гидроксилапатита на исследуемых образцах. Показано, что добавки глюкозы, глутаминовой и молочной кислот катализируют процесс осаждения гидроксилапатита на поверхности стального образца. В процентном соотношении, от общей площади фотографии, наибольшее количество осажденного порошка гидроксилапатита наблюдается у образцов с добавлением глюкозы. The paper presents a study of the processes of precipitation of mineral-organic formations in a model solution of blood plasma in the presence of additives of albumin, glycine, glucose, glutamic and lactic acids. The phase composition of the samples was studied by the X-ray diffraction analysis. Photos were taken to measure the surface area of the sample with modified calcium phosphate. The solid phase coating areas were highlighted in the photos and the degree of coating of steel samples was calculated using the ToupView software. The deposition of the crystal phase occurs on all the studied samples. The differences are in the distribution of crystals on the surface of the plate. The additive albumin inhibits the deposition of hydroxyapatite on the studied samples. It is shown, that additions of glucose, glutamic and lactic acids catalyze the process of hydroxylapatite deposition on the surface of a steel sample. As a percentage of the total area of the image, the largest amount of precipitated hydroxylapatite powder is observed in samples with the addition of glucose.

The Corrosion and Wear Behaviors of a Medium-Carbon Bainitic Steel Treated by Boro-Austempering Process

The effects of boro-austempering treatment on growth kinetics of borided layers, microstructure, and properties in a medium-carbon bainitic steel were investigated. The microstructure, distribution in coatings, corrosion, and wear properties of boro-austempered steels were characterized by a microscope, field-emission electron probe micro analyzer, scanning vibrating electrode technique system and wear resistance machine. The results show that the corrosion resistance of steels in different corrosive mediums was significantly enhanced by boro-austempering treatment. In addition, the wear performance of borided layers was improved by more than two times compared to bainitic substrates, proving a better wear property of samples treated through the boro-austempering route. The solubility of carbon and silicon in borides is very little. In addition, the dual-phase coating of FeB and Fe2B was observed, and the internal stress induced during the growth of Fe2B and FeB was almost eliminated. The preferential crystallographic growth directions of Fe2B and FeB are [001] and [010], respectively, which belongs to the (100) plane. Finally, the kinetics equation d2 = 0.125·t of the borided layers at 1223 K was established.

Microstructure Formation and Mechanical Properties of Multi-Phase Coating by Thermos Plasma Nitriding of Gradient Cu-Ti Films on C61900 Cu Alloy

To improve the processing efficiency and the surface properties of C61900 Cu alloy, a gradient Cu-Ti film with a Ti/Cu atom ratio of 7:1, 7:4, and 1:2 was pre-fabricated by the unbalanced magnetron sputtering process and then nitrided by thermos plasma nitriding. The phase structure, elemental composition, and morphology of the modified surface were characterized, and the mechanical properties, including the wear resistance and adhesion properties, were examined. Combining calculation by the first principle method with thermodynamic analysis, the microstructural formation and phase composition of the Cu-Ti-N system were investigated to reveal the mechanism of improved wear resistance, which indicated the possible formation of various Cu-Ti intermetallics and Ti-N compounds. The Al in the C61900 Cu substrate also participated in the generation of the AlCu2Ti compound, which is a ductile phase with good hardness and elastic modulus. Based on the results of a mechanical properties test, it was concluded that an optimized layer structure for the multi-phase coating should include Ti-N compounds as the surface layer and Cu-Ti intermetallics as the intermediate layer.

The Dual Character of MAX Phase Nano-Layered Structure Highlighted by Supersonic Particles Deposition

MAX phase compounds offer an attractive mixture of ceramic–metallic properties due to their covalent ionic–metallic nature. Since their discovery, a great interest was attributed to their synthesis and potential applications, but the processing of pure compounds as coatings for industrial large-scale application is still considered a challenge. To date, a limited number of papers have evaluated the build-up of MAX phase coating by cold spray (CS), a novel cost-effective and productive spray technology used in both areas of research and industry. Employing CS, the hot gas-propelled material particles have ballistic impingement on a substrate where they undergo plastic deformation. Because of the brittleness, internal delamination, and limited deformability, the deposition of the pure MAX phase is rather challenging. This paper presents the building-up ability of dense MAX-phase coatings by CS with retained structures and compositions, in close relation with the substrate characteristics and phase composition that influences the dual character ceramic–metallic behaviour. Besides recent literature, the originality of this research consists of pioneering deposition of Ti3AlC2 that emphasizes the ceramic–metallic character influenced by the particle speed and the mechanical properties of both substrate and compound.

Toprak İşleme Makinalarının Aktif Elemanlarında Yüzey Kaplama Uygulamaları

Tillage machines such as plow, cultivator, rotavator, and rototiller are widely used for this purpose. However, one of the major problems in working with tillage machines is the wear of active parts over time. Abrasion occurs differently in active parts of tillage machines and can cause the machines used to lose the functionality expected of them. It is preferred to cover the active parts with wear-resistant coating materials to reduce the level of wear to meet both agro technical demands and high tillage efficiency. The way of wear the active parts of the machines; it is abrasive wear caused by friction against solid materials in the soil (clods, stones, harder materials, etc.) and/or adhesive wear caused by soil moisture. Reducing the wear on the active parts with the coating process to be made will both prevent material loss caused by abrasion in the active part and increase the efficiency/effectiveness of the machine. Because of the limited number of studies on this subject in the agricultural sector shows that the subject is open to improvement. In this study, the use of new coating methods used in other production sectors (especially in mold manufacturing) for the last decade in coating the active parts of soil tillage machines and their effects on product performance and life by increasing wear resistance are compiled. Coating methods that can be adapted to the agricultural sector can be listed as; Gas Phase, Liquid Phase and Melted/Semi-Melted Phase. Among these, studies on Plasma Thermal Spraying (Molten / Semi-Molten Phase Coating Methods) and thin film coating (Vapor Phase Coating Methods) are prominent. On the other hand, it is predicted that the desired wear resistance can be further improved by applying different coating methods and combinations.

Biomimetic vs. Direct Approach to Deposit Hydroxyapatite on the Surface of Low Melting Point Polymers for Tissue Engineering

Polymers are widely used in many applications in the field of biomedical engineering. Among eclectic selections of polymers, those with low melting temperature (Tm < 200 °C), such as poly(methyl methacrylate), poly(lactic-co-glycolic acid), or polyethylene, are often used in bone, dental, maxillofacial, and corneal tissue engineering as substrates or scaffolds. These polymers, however, are bioinert, have a lack of reactive surface functional groups, and have poor wettability, affecting their ability to promote cellular functions and biointegration with the surrounding tissue. Improving the biointegration can be achieved by depositing hydroxyapatite (HAp) on the polymeric substrates. Conventional thermal spray and vapor phase coating, including the Food and Drug Administration (FDA)-approved plasma spray technique, is not suitable for application on the low Tm polymers due to the high processing temperature, reaching more than 1000 °C. Two non-thermal HAp coating approaches have been described in the literature, namely, the biomimetic deposition and direct nanoparticle immobilization techniques. In the current review, we elaborate on the unique features of each technique, followed by discussing the advantages and disadvantages of each technique to help readers decide on which method is more suitable for their intended applications. Finally, the future perspectives of the non-thermal HAp coating are given in the conclusion.