The study focused on the synthesis of hydrogels using polyvinyl alcohol (PVA) and polyethylene glycol (PEG) as primary components and containing various proportions of carbon nanotubes (CNTs). The findings revealed that the hydrogels containing CNTs exhibited an increase in hydrophobic properties, with the average contact angle increasing from 14.77

Problems such as hydrophilic properties of hydrogels, limited encapsulation of hydrophilic drugs, and unintended release amounts damage normal tissues and lead to overdose or repeated doses. This study investigates the development and characterization of drug carrier hydrogel formulations that can protect normal tissues. In this study, polyvinyl alcohol (PVA) hydrogel was synthesized by adding melamine (M) and tannic acid (TA) at different weight ratios to limit the hydrophilic properties of the hydrogel. In the analysis of the synthesized hydrogel, the efficiency of drug encapsulation increased from 60 to 90

The formability features of 3xxx alloys differ due to mechanical and microstructural alterations. Among these alterations, texture development and intermetallic precipitates are some of the most critical ones which affect formability such as bending behavior of the final product. This paper deals with the effect of microstructural and mechanical changes on the bending of 3xxx alloys. Based on this, 3004 and 3005 alloys were produced by the twin-roll casting method that is an alternative to the traditional casting method. To achieve the required strength along with good bendability, alternative thermo-mechanical processes were carried out on laboratory scale by using a laboratory-type furnace and rolling mill. Tensile tests and bending tests were examined in the perspective of investigate materials' mechanical properties and planar anisotropy values. Microstructural characterizations were accomplished by using optic microscope, stereo microscope and scanning electron microscope in compliance with examining the intermetallic structure, grain distribution and texture development. In addition to this, SEM?EDS&EBSD analyses were carried out to analyze the texture components alteration and intermetallic characterization. It was observed that texture components and intermetallic precipitates have a significant influence on bending. Recrystallization texture components present improved bending behavior and Mg2Si intermetallic precipitates reduce cube texture component ratio.

In this work, we offer an easy approach to develop a novel injectable, pH sensitive and in situ smart drug delivery system for use in cancer treatments. The developed hydrogels containing nitrogen doped carbon quantum dots (NCQD), doxorubicin (Dox) and hydroxyapatite (HA) were obtained by in situ self-crosslinking. Characterization of the synthesized nanomaterials, interactions between NCQD/Dox/HA hydrogel structure were carried out by TEM, FESEM, EDS, FTIR, XPS, XRD, Zeta potential, DLS, UV-Vis, SEM, gelation time, injectability and DIST measurements. In addition, antibacterial evaluation which was performed against Staphylococcus aureus realized that HA compound significantly increased the antibacterial activity of the hybrid hydrogel. The anticancer drug release to the tumor cell microenvironment with a pH of 5.5 was found to be higher compared to the release in the normal physiological range of pH 6.5 and 7.4. MTT and live/dead assays were also performed using L929 fibroblastic cell lines to investigate the cytotoxic behavior of NCQDs, and NCQDs/Dox/HA hydrogels. Furthermore, the NCQDs/Dox/HA hydrogel could transport Dox within a MCF-7 cancerous cell at specifically acidic pH. Additionally, imaging of cell line was observed using NCQDs and their use in imaging applications and multicolor features in the living cell system were evaluated. The overall study showed that in situ formed NCQDs/ Dox/HA hydrogel represented a novel and multifunctional smart injectable controlled-release drug delivery system with great potential, which may be considered as an attractive minimal invasive smart material for future intelligent delivery of chemotherapeutic drug and disease therapy applications.

Nickel-plated ultrahigh molecular weight polyethylene (UHMWPE) samples were prepared by an electroless coating method followed by hot pressing. The concentration of Ni in the composites was varied between 3.98 and 10.88 in volume percentage. XRD results revealed that Ni coating was successfully realized on the surface of UHWMPE particles confirmed by SEM–EDS. Ni thickness on the UHMWPE particles has thickness of 2 μm and there was also self-precipitated Ni plates as well as additive Ni particles according to SEM. Hardness values of Ni-coated UHMWPE–Ni composites increased 30% with increasing Ni content. The EMI-SE of the composite increased from 49 up to 70 dB by increasing Ni content for both X and Ku-band with respect to Ni concentration. Our samples, performed very high shielding within X band and also Ku band compared to most of other reports in the open literature, can be suitable for high-performance requirements especially in aerospace applications.

As having one of the major economies and rising population, Turkey's energy demand is increasing substantially. The main objective of this research was to apply ridge regression to estimate Turkey's primary energy consumption. Gross domestic product, population, automobile ownership, export and import rates, manufacturing and electricity consumption values of the country were involved in the forecasting model as independent variables. Although regression models end up closer estimates to the real values, having multi-collinearity between variables makes those models unreliable. Therefore, other techniques such as time series, artificial neural networks and genetic algorithms have been tried and performed better than regression models. Ridge regression, a rarely applied and underappreciated model in the literature, is used to overcome the multi-collinearity problem which means high correlation among independent variables. In this study, the ridge regression technique was compared with time series methods and artificial neural networks. The principal results showed that ridge regression is better to estimate energy demand and gave lower mean squared error than other techniques (16.51 for ridge regression followed by 19.00 for neural network). Moreover, estimated values were also found closer to the real energy demand than official projections of the Ministry (only 5% deviation with the proposed model, while official projections occurred by 20% error). Since the accurate forecasting of energy demand is significant for the proper policy design, the best methodology should be opted for and ridge regression seems one of those alternative techniques. In addition, the easiness of the ridge regression makes it applicable to several forecasting methods.

The present study reports on iron (Fe) silicides produced on 31CrMoV9 steel by using the pack-cementation method. Pack siliconizing was carried out using metallic silicon (Si), ammonium chloride (NH4Cl) and alumina (Al2O3) at 1000–1100–1200°C and with varying deposition times of 3–5–7 h in an open atmospheric furnace. The morphology and structure of silicide layers were analyzed by optical microscopy and scanning electron microscopy–energy-dispersive X-ray spectroscopy. It was observed that there was good bonding between the matrix and silicide layers, which were smooth, homogenous and dense and had no remarkable porosity. Dominant phases of Fe3Si, as well as some FeSi, were detected by X-ray diffraction analysis. The layer thickness was measured from the surface to the matrix and changed from 40 to 800 μm, which increased with increasing process time and temperature. The observed silicide layer growth obtained at 1200°C was much higher than those at 1000 and 1100°C. The hardness profile showed that there was no diffusion zone. The matrix hardness is 225 HVN, while the hardness of the coating layer rose to 1021 HVN with the process time and temperature. The activation energy for the growth of the siliconizing layer was determined as 292 (kJ/mol)/K according to the kinetic study. It can be claimed that the optimum siliconizing layer was obtained up to 1100°C for 5 h due to the formation of a layer with smoother morphology, less porosities and oxygen impurities and adequate thickness.

In this study, it was aimed to investigate the effect of subzero heat treatment duration as well as tempering on some microstructural and mechanical properties of commercial Calmax cold work tool steels. Firstly, five steel samples were austenitized at 960C following by quenching at 170°C and one of them was remained as just quenched for reference. After quenching, one of other four samples was tempered at 525°C for 30 min, while two of four samples were exposed to subzero heat treatment in liquid nitrogen medium having -197°C for 15 and 60 min, respectively and last sample was subjected to subzero heat treatment for 60 min. and then tempered at 525°C for 30 min. The hardness of quenched, quenched and tempered, quenched and subzero heat treated and quenched, subzero heat treated and tempered test materials were determined as 755, 527, 807, 829, 616 HV(0.1), respectively. The microstructure of test samples investigated by Scanning electron microscopy was mainly consisting of martensite and small amount of alloy carbides after heat treatments. On the other hand, martensitic zones in the microstructure increased by increasing deep cryogenic (sub-zero) duration and seconder alloy carbides became more visible by applying of tempering. XRD analysis revealed that remained austenite was considerably eliminated by only sub-zero heat treatment, but effectiveness of the process increased with additive tempering by observing of the ferritic and austenitic peaks. The presence of carbides (Cr23C6, Cr7C3) was also verified by XRD and SEM-dot EDS analysis. The retained amount of austenite in the microstructures of samples determined by quantitative analysis of austenitic and ferritic iron peaks was calculated as 9.8% for quenced sample, 2.5 % for quenced and tempered, 1.9% for only sub-zero heat treated for 15 min., 1.4% for only sub-zero heat treated for 60 min. and 0.6% for quenced and sub-zero heat treated for 60 min. following by tempering at 525 °C, in volume, respectively. The results of the study indicated that both sub-zero heat treatment and tempering decreases the amount of retained austenite. Sub-zero heat treatment increases the hardness of test materials, while tempering decreases the hardness of samples. Additionaly, it was found that applying of subzero heat treatment for only 15 min. is enough for eliminating the amount of remained austenite to desirable level.

In the casting of liquid metal, the feeding stops when the mushy zone is clogged and does not allow the transfer of feeding liquid. The growing resistance of the solid dendrites against the fluidity of the feeding liquid is defined as the critical fraction of solid (CFS). CFS value varies depending on many factors such as alloy solidification range, initial mold temperature, and the grain size. Therefore, in many casting simulation applications, it is quite common to get inconsistent results due to insufficient information about the CFS. In this study, a fuzzy expert system (FES) model has been developed in order to determine the value of the CFS in the die casting process, based on the parameters of the alloy type, the initial mold temperature, Al5Ti1B addition and Al10Sr addition. In order to create the rule base for the FES model, 54 die casting experiments have been carried out. The CFS values obtained using the FES model has revealed that the developed model of the FES predicts the CFS value in a high performance.

In this study a novel composite containing fMWCNT and Ag, Zn or Co doped hydroxyapatite (HA) and undoped HA successfully synthesized using biomimetic process and coated on the chemically silane functionalized Ti via facile surface functionalization and deposition approach through the covalent immobilization. In this approach, the properties of Ti pretreated with NaOH and APTES were examined before the composite coating. Functional groups with oxygen were created on the MWCNT surface by acidic treatment. The synthesized powders were characterized using SEM, XRD, EDS, TGA, FTIR, Raman. Surface energies were decreased from 46.03 mN/m (Ti) to 43,79 mN/m (Ti-/fMWCNT/Ag, Zn or Co doped HA). The contact angles of APTES, fMWCNT and undoped or doped HA containing Ti surfaces increased from 40.03 ± 1.2 to 49.05 ± 1.6°. The bond strengths between the coatings and Ti substrates were measured using an adhesive strength test which indicates that the crosslinking process increased the adhesion strength (from 14.6 ± 0.9 to 19.8 ± 1.2 MPa). The results indicated that the Ag+, Zn2+ or Co2+ added in prepared SBF medium have been located in the HA lattice structure at rate of 1.06, 1.86 and 1.78 at.%, respectively. The biocompatibility of the synthesized composites was evaluated using MTT assays in vitro and no negative effect was observed on cell viability. This work shows that the fMWCNT/Ag, Zn or Co doped HA coating promise for the potential implementation in biomaterial coating fields.

Nano-sized hydroxyapatite (HA) particles were synthesized by sol-gel through water and ethanol based mediums of phosphoric acid (H 3 PO 4 ) and calcium hydroxide (Ca(OH) 2 ) at pH = 11 for different calcination time (1 h, 2 h, 4 h). The effects of calcination time and solution on the crystallinity, morphology and impurity phases of the HA nanoparticles were examined via Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). It was found that crystallite size and the fraction crystallinity of the synthesized samples increased with calcination time. According to solution medium, only CaO as impurity was appeared in the water-based solvent, CaO and Ca(OH) 2 impurities were appeared in the ethanol-based solvent. The lowest crystallinity was 0.92 and the highest crystallinity was 1.73 respectively, depending on the process parameters. The Ca/P atomic ratio closest to the bone was found as 1.5178. As a result, the employed water-based sol-gel processes for 1 h calcination time was determined as the optimum for the formation of nano-sized HA powders using calcium hydroxide and phosphoric acid.

A novel pack-aluminizing diffusion coating has been conducted on -Inconel 718 alloy at 600 and 650 degrees C for 2 and 4 h. The aluminising powder packs have been prepared using Al powder as a source for depositing aluminium, Al2O3 powder as an inert filler and ammonium chloride NH4Cl as an activator. The microstructures of the coatings formed on the alloy surface are characterized by means of SEM/EDS and XRD analysis. Optical microscope and SEM analysis reveal that coating layers are homogenous, compact and nonporous and there is a good bonding at the interface of the coating and matrix. Layer thickness variation is measured from the surface to the matrix and changed from 10 to 40 mu m which is increased with increasing process time and temperature. The hardness of the coating layer increased to 1174 HVN with the increasing process time and the temperature while the hardness of the matrix is 300 HVN.

Casting simulation programs are the computer programs that digitally model the casting of an alloy in the sand, shell or permanent mold and then the cooling and solidification processes. However, obtaining consistent results from the casting modeling depends on providing many parameters and boundary conditions accurately. Critical fraction of solid (CFS), which is one of the most important of these parameters, is defined as the point where the solid dendrites do not allow any flow of the liquid metal in the mushy zone. Since the CFS value varies depending on many factors, inconsistent results can be experienced in the modeling applications. In this study, the CFS value obtained during the solidification of various commercial aluminum alloys' casting process carried out using low pressure die casting method, is predicted by using artificial neural network (ANN) method based on alloy type, grain refiner and modifier additions, initial mold temperature, pressure level parameters. In the scope of the study, 162 experiments are conducted. The results obtained from the low pressure die casting experiments using a special model designed for the study are validated by using SOLIDCast casting simulation. The CFS values obtained from this validation range from 33% to 61%.

In this study, we describe new collagen/functionalized multiwalled carbon nanotube/chitosan/hydroxyapatite (Col/f-MWCNT/CS/HA) composite scaffolds which were fabricated by freezing (-40 °C at 0.9 °C/min) and lyophilization (48 h, 0 °C and 200 mtorr). The compressive stresses (from 523 to 1112 kPa), swelling (from 513.9 ± 27 to 481.05 ± 25%), porosity (from 98 ± 0.15 to 95.7 ± 0.1%), contact angle (from 87.8 to 76.7°) properties examined before and after biomineralization for comparison 3D porous Col, CS, Col/f-MWCNT and Col/f-MWCNT/CS scaffolds. Biomineralization was performed by biomimetic method in concentrated SBF (10 × SBF, at 37 °C and 6.5 pH). XRD, SEM, EDS, FTIR, TGA, Optical microscopy and BET results showed that compared to Col, CS and Col/f-MWCNT scaffolds, Col/f-MWCNT/CS scaffolds had higher in vitro bioactivity, large surface area (11.746 m2/g) and a good pore volume (0.026 cc/g), interconnected porous microstructure (with 20-350 μm pore size) and incorporates the advantageous properties of both Col, f-MWCNT, CS and HA. Finally, the methyl thiazolyl tetrazolium (MTT) assay was performed to evaluate scaffolds cytotoxicity which showed that Col/f-MWCNT/CS scaffolds have the best biocompatibility.

This study compared the flexural performance of hybrid beams produced by using concrete in glass fiber reinforced plastic box profiles with concrete beams of the same dimension and concrete properties. Hybrid beams were evaluated in two groups, including standard beams and hybrid beams whose certain properties are improved. Five samples were collected from each test group. Flexure tests were performed on 1500 × 100×100 mm hybrid, improved hybrid and reinforced concrete beams, and flexural strength and fracture toughness values were compared. The flexural behavior of hybrid materials, which provide a higher performance increase due to their components than concrete beams, was analyzed. Analyses showed that hybrid materials provided the users with various advantages due to their components; the improved hybrid design had high flexural strength and fracture toughness, while reinforced concrete beams had a higher rigidity than hybrid beams.

Ti6Al4V plates were exposed to soaking alkali treatment resulted in Na0.23TiO2 phase on the surface before realizing biomimetic Calcium-Phosphate (CaP) coating in prepared m-5xSBF and 5xSBF solutions at 37 degrees C and pH 6. The aim of the present study was to examine CaP nucleation on the Ti6Al4V substrate in the new biomimetic medium, which allows the precipitation of uniform and monophasic CaPs coating within 2 days. Characterizations of coated surfaces were performed by SEM and EDX, FESEM, FTIR, Raman and contact angle measurements. Phase formation (Na0.23TiO2, 22-1404; TiO2, 21-1276; CaHPO4(H2O)(2), 72-0713 and Ca-5(PO4)(3)OH, 09-0432), average particle size distribution (0.1 - 1.8 mu m for HA, 0.5 - 4.7 mu m and 10.7 - 239.4 mu m for width and length of Brushite), the specific surface area (85,623 and 1,169,412 m(2) g(-1) for Brushite and HA, respectively) and phase transformations (from brushite to calcium pyrophosphate) of the coated CaP powders on the surface were also examined by XRD, DLS technique, BET, and TGA, respectively. As a result, it has been possible to obtain for the first time monophasic brushite phase coated on Ti6Al4V in m-5xSBF biomimetic medium and monophasic brushite coated surface characterization was compared with hydroxyapatite coated surface obtained in 5xSBF.

In this study, we describe new collagen/functionalized multiwalled carbon nanotube/chitosan/hydroxyapatite (Col/f-MWCNT/CS/HA) composite scaffolds which were fabricated by freezing ( - 40 degrees C at 0.9 degrees C/min) and lyophilization (48 h, 0 degrees C and 200 mtorr). The compressive stresses (from 523 to 1112 kPa), swelling (from 513.9 +/- 27 to 481.05 +/- 25%), porosity (from 98 +/- 0.15 to 95.7 +/- 0.1%), contact angle (from 87.8 to 76.7 degrees) properties examined before and after biomineralization for comparison 3D porous Col, CS, Col/f-MWCNT and Col/f-MWCNT/CS scaffolds. Biomineralization was performed by biomimetic method in concentrated SBF (10 x SBF, at 37 degrees C and 6.5 pH). XRD, SEM, EDS, FTIR, TGA, Optical microscopy and BET results showed that compared to Col, CS and Col/f-MWCNT scaffolds, Col/f-MWCNT/CS scaffolds had higher in vitro bioactivity, large surface area (11.746 m(2)/g) and a good pore volume (0.026 cc/g), interconnected porous microstructure (with 20-350 mu m pore size) and incorporates the advantageous properties of both Col, f-MWCNT, CS and HA. Finally, the methyl thiazolyl tetrazolium (MTT) assay was performed to evaluate scaffolds cytotoxicity which showed that Col/f-MWCNT/CS scaffolds have the best biocompatibility.

Intermetallics are known as a group of materials that draws attention with their features such as ordered structure, high temperature resistance, high hardness and low density. In this paper, it is aimed to obtain intermetallic matrix composites and also to maintain some ductile Nb and Ti metallic phase by using 99.5% purity, 35-44 μm particle size titanium, niobium and aluminium powders in one step via recently developed powder metallurgy processing technique - Electric current activated/assisted sintering system (ECAS). In this way, metallic reinforced intermetallic matrix composites were produced. Dominant phases of TiAl3 and NbAl3 which were the first compounds formed between peritectic reaction of solid titanium, niobium and molten aluminum in Ti-Al-Nb system during 10, 30 and 90 s for 2000 A current and 1.5-2.0 voltage were detected by XRD and SEM-EDS analysis. Hardness values of the test samples were measured by Vickers indentation technique and it was detected that the hardnesses of intermetallic phases as 411 HVN whereas ductile metallic phase as 120 HVN.

In this study, hydroxyapatite coating on titanium material substrate was successfully performed by using biomimetic method. Titanium plates immersed in 1.5 SBF at pH 7.4 and 37 °C were analyzed at the end of the first, second, and fourth weeks. At the end of the first week, the immersion process was continued with the sample exposed to the optimum selected surface pretreatment. Three different treatments have been applied to determine the optimum surface treatment: each substrate immersed into NaOH, HCl, and NaOH + HCl solutions before heat treatment at 600 °C for 1 h and immersed in NaOH solution was selected the optimum surface treatment. The presence of biphasic hydroxyapatite (HA, Ca5(PO4)3(OH)) and tricalcium phosphate (TCP, Ca3(PO4)2) on Ti surfaces were confirmed by XRD. SEM studies showed that denser HA coating which have nano-sphere-like morphology formed on Ti pretreated with NaOH solution at the end of first week than other hydroxyapatite (HA)-coated Ti pretreated with NaCl and NaOH + NaCl solutions and coating thickness increased by increasing immersion time. The HA coating thickness of the samples immersed in optimum pretreatment solution was found as 178 and 340 μm for at the end of second and fourth weeks, respectively. The particle size analysis of the biphasic HA powders scraped from the coating layer on the substrate before and after sintering was carried out by Zetasizer and it showed that HA powders have 0.58 μm average particle size and their particle size distribution has less dimensional dispersion after sintering. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed that the Ca/P ratio in HA powders was near to 1.5. Raman and Fourier transform-infrared spectroscopy (FTIR) results combined with the X-ray diffraction (XRD) indicated the presence of biphasic hydroxyapatite after biomimetic coating process and increment in crystallinity of the powders after sintering. It was found that HA nucleation on Ti pretreated with NaOH solution was higher than Ti pretreated with other solutions which is confirmed by electrochemical impedance spectroscopy (EIS).

A recently developed powder metallurgy processing technique - Electric Current Activated (Assisted) Sintering (ECAS) was employed to produce intermetallic Nb-NbAl3 composites. In this study, to produce Nb-NbAl3 in-situ intermetallic composites, Nb (99.8 % purity, less than 44 mu m) and Al (99.5 % purity, less than 44 mu m) elemental powders were mixed in the stoichiometric ratio corresponding to the Nb-Al phase diagram. The effect of different processing times, for (10, 30, 60) s, under maximum of 2000 A and 1.5-2.0 V, was investigated. Scanning electron microscopy and X-ray diffraction analysis were used to characterize the produced samples. X-ray diffraction studies revealed that the dominant phases are NbAl3 and Nb. Scanning electron microscopy examinations showed a dense microstructure with a very low amount of porosity and also a trace amount of residual aluminium. The microhardness of the test materials sintered for 60 s via electric-current-activated sintering was about 405 HV +/- 46 HV0,05.