Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications Egemen Avcu, Yasemin Yıldıran Avcu, Berzah Yavuzyegit, Mert Guney Coatings, 2025 The two-volume Special Issue “Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications” has brought together a comprehensive collection of 26 peer-reviewed articles, reflecting the rapid scientific progress and sustained global interest in advanced surface modification strategies for biomaterials [...]
Estimating Demolition Waste Recoverable Fractions in Rapidly Transforming Urban Zones Aslan Nauyryzbay, Aiganym Kumisbek, Arna Amangeldiyeva, Jong Ryeol Kim, Mert Guney Sustainability Switzerland, 2025 The construction sector is a major contributor to global solid waste generation, with demolition waste posing substantial environmental and economic challenges. The present study introduces a demolition waste estimation tool and applies it to a rapidly transforming city: Astana, the capital of Kazakhstan. The approach is also readily applicable to cities in transformation with similar characteristics, e.g., those in the Commonwealth of Independent States region and beyond. The key materials of interest were identified as those that can be efficiently extracted from buildings slated for demolition. A comprehensive analysis of current building stocks and demolition plans (2023–2029) was then conducted. Based on the height, purpose, and main material of the building, the main types and subtypes of the building stock in Astana were created. The results for Astana showed that 67.52% or 1736.5 thousand tons of all demolition waste could be recovered. Concrete had the highest recovery potential by mass (162.42 thousand tons annually) and by percent (91%). The economic analysis of construction and demolition waste illustrated a financial potential from construction and demolition waste recovery in Astana at USD 4600 million per year, with concrete having the highest potential among fractions (56% of total).
Towards Sustainable Air Quality in Coal-Heated Cities: A Case Study from Astana, Kazakhstan Akmaral Agibayeva, Aiganym Kumisbek, Aslan Nauyryzbay, Egemen Avcu, Kuanysh Zhalgasbayev, et al. Sustainability Switzerland, 2025 Despite severe particulate matter (PM) pollution in Central Asia, limited air composition and health impact data are hindering sustainable air quality management and resilient urban planning. This study provides the first comprehensive assessment of PM2.5 and PM2.5–10 in the urban environment of Astana, Kazakhstan, a rapidly expanding city with intense winter heating demands. We characterized PM and atmospheric precipitation and assessed health risks using bioaccessible fractions of PM-bound potentially toxic elements (PTEs). Among 388 samples, PM2.5 and PM2.5–10 concentrations peaked at 534 and 1564 μg·m−3, respectively. Scanning electron microscopy (SEM) identified soot and coal fly ash, indicating fossil fuel combustion as a major source. Precipitation characterization also showed elevated SO42− (17.8 μg⋅L−1), V (108 μg⋅L−1), Ni (84.0 μg⋅L−1), and Mn (63.2 μg⋅L−1). Bioaccessibility tests showed high solubility for Fe (16,229 mg·kg−1) followed by V: key indicators of combustion emissions. Non-carcinogenic risk for Ni and V exceeded acceptable limits for adults and children (e.g., HQ: 6.07 for V for adults). Carcinogenic risk exceeded the threshold 10−6 for Cd (adults), Co, Cr, and Ni. These findings may help advance urban air quality management via integrating bioaccessibility-based health risk assessment and source apportionment, supporting evidence-driven policies for environmentally responsible development in rapidly urbanizing cold-climate regions.
Comparative Effects of Fine and Conventional Shot Peening on Surface Morphology, Topography, Wettability, and Antibacterial Activity of Biomedical Ti6Al4V Alloy Egemen Avcu, Mert Guney, Yasemin Yıldıran Avcu, Mine Sulak, Hüseyin Uzuner, et al. Coatings, 2025 Interest in textured surfaces for biomaterials and implants is increasing, with shot peening emerging as a promising method for surface modification. This study investigates the influence of conventional and fine shot peening on the surface morphology, topography, wettability, and antibacterial properties of biomedical-grade Ti6Al4V alloy. Peening was conducted using a custom-built, fully automated system, employing fine (100–200 µm) and coarse (700–1000 µm) shots using well-controlled sets of parameters. Both treatments introduced severe plastic deformation on the surface, resulting in increased roughness. Conventionally shot-peened samples exhibited deeper and wider dimples compared to finely peened ones. Surface wettability shifted from hydrophilic (contact angle: ~4°, untreated) to hydrophobic, reaching contact angles of ~91° and ~100° for fine and conventional shot peening, respectively. Antibacterial assays against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were evaluated by normalizing colony counts to the untreated Ti6Al4V surface. The inherent antibacterial response of Ti6Al4V against E. coli was preserved after both shot peening treatments, showing no notable increase in bacterial proliferation. In contrast, adhesion of S. aureus increased, more notably on fine shot-peened surfaces, indicating a strain-specific response influenced by surface roughness and wettability. In summary, both fine and conventional shot peening altered the surface morphology, topography, and wettability of Ti6Al4V. At the same time, their antibacterial influence was strain-dependent, underscoring the need for careful parameter selection in biomedical applications.
Use of steel slag and recycled concrete in GeoBarrier system for slope stabilization Rezat Abishev, Alfrendo Satyanaga, Mert Guney, Aswin Lim, Jong Kim Frontiers in Built Environment, 2025 Improving slope stability against rainfall-induced slope collapses is a current area of study interest in geotechnical structure design for climate change mitigation. The GeoBarrier system (GBS) concept used recycled concrete and steel slag to avoid these kinds of failures. The present study investigated the practicability of incorporating recycled concrete and steel slag, two types of recycled materials, into the GBS design. Extensive experimental investigations were conducted to determine the index properties and hydraulic characteristics, including permeability functions, soil-water characteristic curves (SWCCs), and unsaturated shear strength parameters of steel slag and recycled concrete. A finite element transient seepage analysis and limit equilibrium slope stability study were conducted to evaluate the impact of precipitation on the pore water pressure profile of the slope and its stability under rainfall circumstances, respectively. According to the findings, no breakthrough into the steel slag, a coarse-grained layer within the GBS, was observed. Based on the pore-water pressure profiles and the variation in the factor of safety (FOS) over time, steel slag and recycled concrete were found to be applicable for use as coarse- and fine-grained layers in the GBS, respectively. The incorporation of these waste materials facilitated the slope protection against infiltrated rainwater into the slope and increased the FOS for a slope with a height of 10 m and a slope angle of 70°.
Modification of surface and subsurface properties of cold-rolled Ti6Al4V sheets through water jet shot peening Egemen Avcu, Mustafa Armağan, Yasemin Yıldıran Avcu, Eray Abakay, Emirhan Çalım, et al. Materials Research Express, 2025 Titanium alloys possess remarkable properties, such as high strength, biocompatibility, and resistance to corrosion. Nonetheless, both their surface and subsurface properties require improvements, particularly for applications where surface contact is unavoidable. The present study utilises an emerging mechanical surface treatment technique (water jet shot peening) for modifying the surface and subsurface characteristics of cold-rolled Ti6Al4V sheets. Water jet shot peening was applied on Ti6Al4V samples following an L18 full factorial experimental design, focusing on the variable parameters of process time, standoff distance, and shot mass flow rate. ANOVA indicated that the shot mass flow rate had the greatest impact on the roughness parameters (p < 0.0001). The roughness values of Ra, Rp, and Rv decreased as the shot’s mass flow rate increased, and this decrease was more pronounced as the standoff distance diminished. The surface morphologies of the samples were notably modified by plastic deformation resulting from the repeated impact of shots. The water jet shot peening method modified the grains within the microstructure near the surface region. The grains in the microstructure were oriented perpendicularly to the peening direction to a depth of 5.36 μm beneath the surface, even at minimal peening levels. The surface hardness increased by approximately 64% relative to the hardness of untreated Ti6Al4V alloy (512.43 Hv versus 311.52 Hv), attributed to significant plastic deformation and strain hardening induced by the high kinetic energy of the impacting shots during water jet peening.
Cavitation erosion behaviour of MAB-CU4 alloy: influences of cavitation number, attack angle, time, and stand-off distance Sedat Can Tini, Adalet Zeren, Yasemin Yıldıran Avcu, Eray Abakay, Mert Guney, et al. Materials Research Express, 2024 The present study comprehensively examines the cavitation erosion behaviour of a manganese aluminium bronze alloy (MAB-CU4 alloy) as a function of several parameters (i.e., cavitation angle, cavitation number, time, and stand-off distance), particularly focusing on the influences of cavitation angle on the surface morphology and topography of the alloy. According to the design of experiment (Taguchi experimental design) analysis, mass loss increased with cavitation number and attack angle, while increasing the stand-off distance resulted in a decrease in mass loss and an increase in the surface area affected by cavitation erosion. Cavitation erosion behaviour was most affected by the cavitation attack angle, with the cavitation attack angle contributing 69.1% to total erosion, according to variance analysis. At 90° cavitation attack angle, MAB-CU4’s erosion rate was 64% greater than that at 30°. Scanning electron microscopy and optical profilometry revealed that cavitation erosion damage at 90° occurred mostly in the grain interiors as cavitation pits due to severe plastic deformation and surface corrosion, whereas pit formation was restricted around the hard secondary phases at the grain boundaries. At 30°, deep cavitation pits were limited, the erosion crater expanded, and the number of pits was reduced. Overall, finer microstructures with more grain boundaries and secondary phases may improve cavitation erosion resistance at 90°. The present study is the first to comprehensively capture erosion damage at the microstructural scale and analyse the impact of microstructural features on the erosion damage during the cavitation erosion of MAB-CU4 alloy.
In-situ soil carbon dioxide flux measurement from forest floor in Karasu Forests in Western Black Sea Region of Turkey 12th International Conference on Computer Methods and Advances in Geomechanics 2008, 2008
