Selim Erturk - Academia.edu (original) (raw)

Papers by Selim Erturk

In this study, effect of mechanical activation in planetary ball mill and disc mill, on carbother... more In this study, effect of mechanical activation in planetary ball mill and disc mill, on carbothermic reduction of celestite ore with coke was investigated. Celestite ore (96% SrSO4) from Sivas district was blended with excess metallurgical coke and mechanically activated for 1, 5, 15 and 45 min. Mechanically activated blends were analyzed by Particle Size Analyzer, Thermal Gravimetric Analyzer (TGA), Differential Scanning Calorimetric Analyzer (DSC), and X-Ray Diffractometer (XRD). The finest particles were obtained at 45 min disc milling, of which d50 was 1.30 µm. TGA and DSC analyses showed that the reaction temperature was decreasing from 973°C to 892°C, by 1 min disc milling and 45 min planetary ball milling, respectively. XRD peaks broadened and peak intensities decreased by extending the mechanical activation time in both type of milling processes. All of the mechanically activated powders were roasted at 900, 1000, and 1100°C. According to XRD analyses; it is possible to see ...

Metallography, Microstructure, and Analysis, 2020

Strontium master alloy is widely used in today’s aluminum foundries for modification of Al–Si all... more Strontium master alloy is widely used in today’s aluminum foundries for modification of Al–Si alloys. In this study, Al–Sr master alloy was produced in molten Al alloy directly from strontium carbonate instead of using the pure strontium metal which is difficult to store in the air due to its high oxygen affinity. In a laboratory-scale induction furnace, SrCO3 and SrO powders were injected into the liquid metal via argon flow and subjected to reduction reaction. The oxygen-free medium required for the reduction was provided by the gas purged on both the surface and the inside of the liquid metal. Hence, the master alloy was produced directly by an economical process. Moreover, the addition of Mg to the reducing melt decreased the surface tension of the liquid aluminum; as a result, the reduction efficiency was increased. At the best of the results, the master alloy containing 5.15% Sr was obtained by reducing approximately half of the fed SrO by Al6Mg. This master alloy was used to modify A360 alloy, and the same modification effect as the commercial Al5Sr master alloy was observed.

Gazi Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi, 2018

Investigation of leaching characteristics of celestite concentrate in acidic media and SrCO 3 pro... more Investigation of leaching characteristics of celestite concentrate in acidic media and SrCO 3 production via precipitation,

Mining, Metallurgy & Exploration, 2005

In this study, the effects of stirring speed (80, 180,400 and 600 rad/min) , propeller type (two-... more In this study, the effects of stirring speed (80, 180,400 and 600 rad/min) , propeller type (two-,four-and six-h/aded I, soluiion temperature (25° and 60°C) and initial silver eoncentration (lOand 40 g/L) on the recovery o(li/verfi'o/ll.\'ill'l'r nitrate solutions by copper were investigated. A cementation system withforced convectiol1 was del'eloped to (}\'erCO/lll' the problems observed in teehnological applications where copper particles adhere t01!,ether and CClllent sill'er eneapsulates copper. The effeets of various conditions of the fore'ed convection system on ce/llellt si/I'er II/orph%gr, product quality and cementation effieiency were examined. Experimental results show that more than 9Wk cellll'lIfl1tion efficiency ean be reaehed within two hours by applying effective stirrin1!, (> 400 rad/min). Silver ion COI/celltration deereases as the stirring speed increases (4,312 ppm at 80 rad/min compared to 1.85 ppm at 600 rad/II/il/ a/ier 4 IIr. \). The cementation rate was determined by the grain size and adhesion strength ofthefirst and secrJ/ld larers of'the ('('li/eilt silver. It was ascertained that the eementation proeess could be aeeeierated hy creating a mechanical effeet so that fhe cement layer atop copper could break. Thus, in a system of foreed convection, the cementation rate hecOI11 l'.1 independent of the initial coneentration and inereases with inereasing temperature .

Journal of bone and joint infection, 2018

Bone and soft tissue infections are among the least desired complications after orthopaedic surge... more Bone and soft tissue infections are among the least desired complications after orthopaedic surgery. This study analysed the in vivo effects of the local application of nano-silver particles (AgNPs) [1nm = 1 billionth of a meter] in soft tissue infections. Materials-Method: An experimental osteomyelitis model was formed by inoculating both tibias of 24 rats with methicillin-resistant Staphylococcus aureus. The rats were followed without treatment for 21 days. Blood samples and tibial x-rays at day 21 confirmed the development of infection. Then, the rats were divided randomly into two groups. One group (12 rats) underwent surgical debridement and received 21 days of teicoplanin therapy. The second group had the same treatment, with the addition of local nano-silver. All of the rats were sacrificed at day 42. Blood and wound swab samples were taken and the culture results were analysed. Results: No differences were observed between the groups in healing values at pathological examination, or in changes in the number of colonies at days 21 and 42. No differences in white blood cell count (WBC) were observed between the groups before and after the treatment. Conclusion: Although in vitro studies suggest the effectiveness of AgNPs on pathogens, we found that the application of nano-silver did not make any difference when used in addition to the classical osteomyelitis treatment with antibiotics and local surgical debridement. We believe that additional in vivo studies using repeated nano-silver application could be beneficial.

$Research paper thumbnail of A biomechanical comparison of two cephalomedullary nails; one using a single lag screw with antirotator blade and a nail using two lag screws for unstable intertrochanteric fractures$

International Journal of Research in Orthopaedics, 2016

Implant choice for fixation of intertrochanteric fractures remains controversial despite being on... more Implant choice for fixation of intertrochanteric fractures remains controversial despite being one of the most commonly performed operations. Although use of sliding hip screws (SHSs) is still considered a gold standard in treatment of these fractures, there is a wide tendency in using cephalomedullary nails because of their ABSTRACT Background: Implant choice for fixation of intertrochanteric fractures remains controversial despite being one of the most commonly performed operations. Although use of sliding hip screws is still considered a gold standard in treatment of these fractures, there is a wide tendency in using cephalomedullary nails because of their biomechanical superiority over sliding hip screws. This trial was initiated in order to compare the biomechanical properties of two different cephalomedullary nails, aPFN and the PROFIN under axial loading, based on the questions that can a single lag screw with an antirotator blade render better rotational stability? Is there a difference between one lag screw or two lag screws with respect to superior migration or cutout of the screws? And do different nail designs cause different types of failure and what are the pros and cons of classical and new designs from the view point of biomechanical aspects? Methods: Ten pairs of third generation synthetic bone models simulating unstable intertrochanteric fracture were used for biomechanical testing. Results: No posterior displacement of screws was recorded in both groups suggesting rotational unstability. There was not a significant difference between forces values loaded at the time of failure. Conclusions: Although there was no statistically significant difference between compressive strengths at the time of failure, aPFN may provide equal rigid fixation with less possible cutout which may have an important consequences in real clinical applications.

This experimental study deals with recovering the metal contents of dental amalgam wastes by phys... more This experimental study deals with recovering the metal contents of dental amalgam wastes by physical and chemical separation techniques. Within the framework of this study, distilled dental amalgam wastes were subjected to size reduction and leached with hot concentrated nitric acid. Leach liquor was filtered and both solution and leach residue were characterized. Results have shown that, leaching efficiency was above 99.8% and leach solution contained 16,000 mg/L Ag+, and 8,500 mg/L Cu2+ ions. Later, silver was recovered from solution by cementation with copper. The basic parameters in the cementation experiments, such as cementator quantity, stirring rate, and pH were examined. Cementation efficiency reached above 99.9% and chemical analysis has shown that silver concentration of solution decreased from 16,000 mg/L to 10 mg/L.

$Research paper thumbnail of A biomechanical comparison of proximal femoral nails and locking proximal anatomic femoral plates in femoral fracture fixation$

Indian Journal of Orthopaedics, 2015

Background: The incidence of fractures in the trochanteric area has risen with the increasing num... more Background: The incidence of fractures in the trochanteric area has risen with the increasing numbers of elderly people with osteoporosis. Although dynamic hip screw fixation is the gold standard for the treatment of stable intertrochanteric femur fractures, treatment of unstable intertrochanteric femur fractures still remains controversial. Intramedullary devices such as Gamma nail or proximal femoral nail and proximal anatomic femur plates are in use for the treatment of intertrochanteric femur fractures. There are still many investigations to find the optimal implant to treat these fractures with minimum complications. For this reason, we aimed to perform a biomechanical comparison of the proximal femoral nail and the locking proximal anatomic femoral plate in the treatment of unstable intertrochanteric fractures. Materials and Methods: Twenty synthetic, third generation human femur models, obtained for this purpose, were divided into two groups of 10 bones each. Femurs were provided as a standard representation of AO/Orthopedic Trauma Associationtype 31-A2 unstable fractures. Two types of implantations were inserted: the proximal femoral intramedullary nail in the first group and the locking anatomic femoral plate in the second group. Axial load was applied to the fracture models through the femoral head using a material testing machine, and the biomechanical properties of the implant types were compared. Result: Nail and plate models were locked distally at the same level. Axial steady load with a 5 mm/m velocity was applied through the mechanical axis of femur bone models. Axial loading in the proximal femoral intramedullary nail group was 1.78-fold greater compared to the plate group. All bones that had the plate applied were fractured in the portion containing the distal locking screw. Conclusion: The proximal femoral intramedullary nail provides more stability and allows for earlier weight bearing than the locking plate when used for the treatment of unstable intertrochanteric fractures of the femur. Clinicians should be cautious for early weight bearing with locking plate for unstable intertrochanteric femur fractures.

Material Science & Engineering International Journal, 2019

Alloys produced with mercury and other metals are called amalgam. Dental amalgams are important a... more Alloys produced with mercury and other metals are called amalgam. Dental amalgams are important alloys and contain 40-50% mercury with the addition of silver (22-39%), tin (12-18%) and copper (2-18%). Therefore, these amalgams have high economic value and need to be evaluated. This experimental study deals with recovering their metal contents by physical and chemical separation techniques. Within the framework of this study, distilled non-contact dental amalgam wastes were subjected to size reduction, leaching with nitric acid and cementation with copper. Leach liquor was filtered and both solution and leach residue were characterized. Results have shown that, leaching efficiency was above 99.8% and leach solution contained 16 g/L Ag + , and 8.5 g/L Cu 2+ ions. Later, silver was recovered from solution by cementation with copper. The basic parameters in the cementation experiments, such as cementator quantity, stirring speed, pH, and temperature were examined. Cementation efficiency reached above 99.9% and chemical analysis has shown that silver concentration of solution decreased from 16g/L to 1.7 mg/L.