Analysis of the sintering process of 316l – Hydroxyapatite composite biomaterials

The 316L-hydroxyapatite biocomposites were produced by the powder metallurgy technology. The properties and microstructure of these materials are affected by the chemical composition of the powders mixture and the sintering temperature. The sintering temperature of 1240°C and hydroxyapatite addition in an amount of 3% of mass obtained the highest density and hardness and smaller open and closed porosity. Hydroxyapatite addition to austenitic stainless steel modified sintering behaviour. During heating the thermal decomposition of hydroxyapatite took place, which led to the formation of a CaO phase. However, phosphorus diffused into the austenitic matrix and was involved in the eutectic transformation

Microstructure and properties of sintered 410L steel with copper addition

In the present study copper modificated 410L stainless steel was investigated. This steel was fabricated based on powders, by the pressing and sintering. By varying amount of copper and sintering temperature the properties of the 410L stainless steel can be improved. At sintering temperature of 1240°C and at high copper levels the microstructure of steel is predominately martensitic. The sintered density of steel increases as the copper level increases, with a drop-off in density at 4 w/o Cu. It has been shown that stainless steels with higher copper levels have higher hardness and better density in comparison to steels sintered in 1260°C. In general, higher sintering temperature and low copper levels favor the formation of ferrite. An examination of the microstructures of these steels reveals that they are a mixture of ferrite and martensite

AISI 316L-hydroxyapatite sintered composite biomaterials

The combinations of good biocompatibility of hydroxyapatite and good mechanical properties of 316L steel should lead to obtain better biomaterial. 316L-hydroxyapatite composites were produced by the PM technology. Microstructure and properties of these materials were affected by chemical composition of powders mixture and sintering temperature. Sintering temperature of 1240°C and hydroxyapatite addition of 3 wt. % provide to obtain the best density and hardness sintered 316L-hydroxyapatite compositions

The Effect of BN or SiC Addition on PEO Properties of Coatings Formed on AZ91 Magnesium Alloy

Currently, due to the economic and ecological aspects, light alloys are increasingly important construction material, in particular in the transport industry. One of the popular foundry magnesium alloys is the alloy AZ91, which among others due to mechanical properties and technological features, is used, for example, for light structural parts. The paper presents the results of research on modification of the AZ91 alloy surface layer in the plasma electrolytic oxidation process. The change of usable properties of the produced coatings was obtained by introducing additions of silicon carbide or boron nitride. The thickness and hardness of the protective layers produced, resistance to scratches and corrosion resistance were determined. Moreover, the friction coefficient of the coating-steel pair was investigated. The quality of the connections made between the coating and the substrate, i.e. the magnesium alloy, was also evaluated. The results obtained for coatings with silicon carbide or boron nitride additives were always compared to the results obtained for unmodified samples. On the basis of the obtained results, it was shown that the introduction of boron nitride additive to the AZ91 alloy coating produced in the plasma electrolytic oxidation process significantly improves the resistance to: (i) corrosion and (ii) abrasive wear of the coating

Influence of Alkaline Earth Metals on Structure Formation and Magnesium Alloy Properties

The main aim of this work is to improve the structure and properties of the magnesium alloy ML5 by modifying it with alkaline earth metals (ALM). The separate and joint influence of calcium and barium on the macrostructure and microstructure of the alloy of Mg-Al-Zn system was investigated. The qualitative and quantitative estimation of the structural components was carried out. Alkali earth metals were included in complex intermetallic phases and serve as additional crystallization centers. Modification of magnesium alloys with alkaline earth metals is established in an amount of 0.05 to 0.1 wt. % increased the bulk percentage of intermetallic phases by ~1.5 times, shifting them towards smaller size groups while simultaneously forming spherical intermetallic phases located in the grain centre and serving as additional crystallization centers. In this case, grain size reduction and significant refinement of the alloy structural components were provided. The dependency of the separate and joint influence of alkali earth metals on the castings complex of properties of the magnesium alloy has been established. Thus, a separate modification of the ML5 alloy provided the maximum level of its strength and ductility with the addition of 0.1% Ca or Ba. The modification of the complex (0.1% Ca + 0.1% Ba) of the magnesium alloy decreased the dimensions of its structural components 1.5 times and increased the strength of the alloy by 20%, the ductility by 2 times and the long-term heat resistance 1.5 times due to the formation of the intermetallic phases of the complex composition. Linear dependences were obtained that describe the influence of the characteristics of the structural components of the modified magnesium alloy on its mechanical properties. The developed technology for modifying cast magnesium alloys with alkaline earth elements provides an improvement in casting quality and allows the reliability and durability of responsible casting operation

Prediction of Abrasive Waterjet Machining Parameters of Military-Grade Armor Steel by Semi-Empirical and Regression Models

Rolled homogeneous armor steel (RHA) with a high tensile strength, toughness, and hardness is often used in military combat vehicles. RHA is a high-strength low alloy steel suitable for all battlefield usage in military vehicles. The present work examines the prediction output responses in the material removal rate (MRR), surface roughness (Ra), and kerf angle (Ka) for the AWJM of armor steel using regression and semi-empirical models. The AWJM trials were performed using an L27 factorial design with each process variable set to three levels, namely, the standoff distance (SOD), jet traversing speed (JT), and jet water pressure (P). A regression model was constructed using the response surface method (RSM) and data from the trials. Through dimensional analysis and with Buckingham’s π-theorem, a semi-empirical model was built using both the experimental data and material property data. Predictions made by the models were proportionate with the results of the experiments under the same conditions. Microscopic investigations on MRR and Ra were performed using a scanning electron microscope (SEM). The optimal values of the output responses of the machined armor steel plate were obtained with higher MRR = 298.92 mm3/min, lower Ka = 0.651°, and lower Ra = 2.23 µm. The present work established that semi-empirical models accurately predict the output responses in the AWJM of armor steel

Development of Geopolymers Based on Fly Ashes from Different Combustion Processes

The main aim of this research is to assess different fly ashes as raw materials for the manufacturing of geopolymers. Three different fly ashes have been investigated. First, a conventional fly ash from the Skawina coal power plant (Poland), obtained at a temperature of 900–1100 °C. Second, ultra-fine fly ash from a power plant in China; the side product received at 1300 °C. The third fly ash was waste was obtained after combustion in incineration plants. To predict the properties and suitability of materials in the geopolymerization process, methods based on X-ray analysis were used. The applied precursors were tested for elemental and chemical compounds. The investigations of geopolymer materials based on these three fly ashes are also presented. The materials produced on the basis of applied precursors were subjected to strength evaluation. The following research methods were applied for this study: density, X-ray fluorescence (XRF), X-ray diffraction analysis (XRD), Scanning Electron Microscopy (SEM), flexural and compressive strength. The obtained results show that materials based on fly ashes had a similar compressive strength (about 60 MPa), while significant differences were observed during the bending test from 0.1 to 5.3 MPa. Ultra-fine fly ash had a lower flexural strength compared to conventional fly ash. This study revealed the need for process optimization for materials based on a precursor from a waste incineration plant

A Review of Synthesis and Applications of Al₂O₃ for Organic Dye Degradation/Adsorption

This comprehensive review investigates the potential of aluminum oxide (Al2O3) as a highly effective adsorbent for organic dye degradation. Al2O3 emerges as a promising solution to address environmental challenges associated with dye discharge due to its solid ceramic composition, robust mechanical properties, expansive surface area, and exceptional resistance to environmental degradation. The paper meticulously examines recent advancements in Al2O3-based materials, emphasizing their efficacy in both organic dye degradation and adsorption. Offering a nuanced understanding of Al2O3’s pivotal role in environmental remediation, this review provides a valuable synthesis of the latest research developments in the field of dye degradation. It serves as an insightful resource, emphasizing the significant potential of aluminum oxide in mitigating the pressing environmental concerns linked to organic dye discharge. The application of Al2O3-based catalysts in the photocatalytic treatment of multi-component organic dyes necessitates further exploration, particularly in addressing real-world wastewater complexities

Silver Nanoparticles for Waste Water Management

Rapidly increasing industrialisation has human needs, but the consequences have added to the environmental harm. The pollution caused by several industries, including the dye industries, generates a large volume of wastewater containing dyes and hazardous chemicals that drains industrial effluents. The growing demand for readily available water, as well as the problem of polluted organic waste in reservoirs and streams, is a critical challenge for proper and sustainable development. Remediation has resulted in the need for an appropriate alternative to clear up the implications. Nanotechnology is an efficient and effective path to improve wastewater treatment/remediation. The effective surface properties and chemical activity of nanoparticles give them a better chance to remove or degrade the dye material from wastewater treatment. AgNPs (silver nanoparticles) are an efficient nanoparticle for the treatment of dye effluent that have been explored in many studies. The antimicrobial activity of AgNPs against several pathogens is well-recognised in the health and agriculture sectors. This review article summarises the applications of nanosilver-based particles in the dye removal/degradation process, effective water management strategies, and the field of agriculture