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Investigation of structural and magnetic properties of Fe and Cu doped MoS2 thin films
In this study, structural and magnetic properties of pure and Fe/Cu-doped Fe/Cux:MoS2 (x: 0.50%, 0.75%, and 1.00%) thin film materials were investigated. Crystallizations of films were ensured decomposing of ammonium tetrathiomolybdate (ATTM) precursor at various sintering temperatures under N2 gas flow. Structural and morphological characteristics of all produced samples were investigated by measuring X-Ray Diffraction (XRD), Raman spectroscopy and Scanning Electron Microscope (SEM). It is determined from Raman spectroscopy results that the characteristic vibration modes of 2H-MoS2 formed after performing optimization samples. SEM images of pure sample show that MoS2 crystals formed as back-to-back triangle shape. This shape of crystal was changed to nanorod by doping Fe atoms in to the main structure. Magnetic properties of samples were investigated by using vibration sample magnetometer (VSM). It is observed that magnetic transition temperature of samples decreases when Fe atom is added to the main structure. The magnetization transition temperatures are found as 247.6 and 95.5 K for pure (0.95% wt. ATTM) and 0.75% Fe-doped MoS2. According to the magnetic hysteresis curves measured at 5 K, the magnetic ordering of pure and 0.75% Fe-doped samples are ferro/ferri-magnetic. For Fe-doped samples, all samples, except 0.75% Fe-doped sample, show diamagnetic characteristic at room temperature. In addition, saturation magnetization value increases with introducing of Fe atom into the main structure. For Cu-doped samples, the diamagnetic behavior was observed at room temperature.
Investigation of advanced radar absorber composite materials having high stealth technology to use in various military vehicles
The aim of the stealth technology, which has attracted great attention in the field of defense technologies in recent years, is to reduce the radar cross-sectional area (RCS) of the target object. Reducing the RCS can prevent the potential target object from being seen in enemy radar systems. Radar absorber materials are material groups that actively exhibit the stealth technology by losing the visibility of the target object by reducing and absorbing the energy of electromagnetic waves entering the material with the magnetic and dielectric loss mechanism. In this study, NixCo1-xFe2O4 (0≤x≤1with increments 0.25) and Niy:ZnO (y=0 and 0.1) nanoparticles were synthesized using the sol-gel method. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Distributed X-Ray Spectroscopy (EDS) and Vibrating Sample Magnetometer (VSM) analyzes were performed for determining the crystal structures, particle size and morphology, elemental analysis and magnetic characteristics of the produced nanoparticles, respectively. Various radar absorbing composite structures were obtained by using the epoxy casting method with the addition of the produced nanoparticles into the epoxy resin. Microwave absorption properties of nanoparticle reinforced epoxy matrix composite structures were characterized in the 8-12 GHz (X band) frequency range using a Vector Network Analyzer. In addition to the mechanical properties of composites were evaluated by applying hardness and impact test. It has been observed that the microwave absorption and mechanical properties of the nanoparticle reinforced epoxy matrix composite samples are satisfactory and can be used in potential military land, air and sea applications.
Halloysite nanotubes reinforced polybutylene terephthalate based nanocomposites: mechanical, thermal, structural and morphological characterizations
Polybutylene terephthalate (PBT) nanocomposites were melt-blended with two types of Turkish halloysite nanotubes (HN) using a co-rotating twin-screw extruder. Naturally occurring HN samples were used to produce PBT-based composites at the HN compositions of 1%, 3%, 5%, and 10% by weight. PBT was purchased as bead form under the trade name of Advanite from Sasa polyester A.Ş., Adana, Turkey. Neat and silane-modified grade of HN was supplied by Eczacıbaşı Esan, İstanbul, Turkey with the trade names of ESH HNT and ESH HNT S, respectively. Test samples were prepared by an injection molding process. Mechanical, thermo-mechanical, thermal stability, melt-flow, structural and morphological properties of the produced nanocomposites were reported using tensile, impact and shore hardness tests, dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA), melt flow rate and density measurements and scanning electron microscopy (SEM) methods, respectively. Results of neat and silane coated HN containing composite samples were compared in order to investigate the interfacial adhesion between polymer matrix and reinforcement material.
Jeopolimerlerin sentezlenmesi ve özellikleri
Continuous cement manufacture has increased the quantity of CO2 released into the atmosphere, increasing the level of global warming, which has a negative impact on the environment. As a result, a more sustainable strategy, as well as a comprehensive review of the existing admixtures used to replace traditional concrete, has become critical. Many studies on geopolymer binders, which has equivalent or higher durability and strength than traditional concrete, have been conducted for this purpose by many researchers. Geopolymer binders offer the advantage of using extra cementitious materials mixed with alkali-activated solutions to replace traditional cement. As a result, this study offers a comprehensive review of geopolymer material, including its ingredients, manufacturing procedures, and curing regimes, as well as a comparison of its physical and mechanical properties to traditional cement structures.
Fabrication and characterization of transition metals (Mn and Co)-doped cds-based photovoltaic cells
In this study, CdS thin films were produced via chemical bath deposition method, individually doped with Mn (0.5%, 1%, 2%) and Co (1%, 3%, 5%, 7%), on indium tin oxide (ITO) coated glass substrates. Additionally, the desired device configuration was achieved by coating N719, P3HT:PCBM, and PEDOT:PSS organic layers, respectively, using spin coating method. Comprehensive XRD, SEM, EDS, transmittance, absorbance, PL analyses were conducted on both Mn and Co-doped CdS thin films and the fabricated solar cells. Furthermore, J-V tests were performed on the fabricated devices. XRD analysis revealed that the produced CdS thin films grew in a cubic structure. Addition of Mn atoms into CdS structure was determined to deteriorate crystal quality based on dislocation density and micro-strain results. Mn doping led to a positive effect on transparency of CdS films, particularly achieving over 90% transmittance in the wavelength range of 500-650 nm for CdS sample with 2% Mn addition. Mn doping was found to increase forbidden energy band gap of CdS, causing a blue-shift in absorption edge. J-V measurements of the fabricated solar cells indicated that Mn doping improved the efficiency of CdS based hybrid solar cells. Highest power conversion efficiency was achieved with a 2% Mn-doped CdS solar cell (0.202%). On the other hand, Co doping led to a change in the unit cell volume and increase in crystalline size of CdS. Additionally, a reduction in grain size of CdS thin films was observed with Co doping. Co doping was found to enhance optical transparency of CdS films and alter the forbidden energy band gap. Photoluminescence results suggested that Co doping caused additional defect states in CdS films. Furthermore, Co doping positively influenced the efficiency of CdS-based hybrid solar cells, with highest efficiency obtained from solar cells with 1% Co doping (0.488%).
Synthesis and characterization of some physical properties of Fe3O4 doped MoS2/PANI hybrid composites
Systems for absorbing electromagnetic waves in materials are essential for stealth applications and vulnerable electronic equipment. However, the ability to absorb EMW over a large bandwidth is still limited by certain limitations in material systems and engineering. Increasing the bandwidth and reducing material system reflections are crucial advancements for the development of future stealth technologies. In this study, hybrid structures were developed using semiconducting MoS2 nanosheets, Fe3O4 magnetic nanoparticles and conductive polyaniline. A systematic approach was employed to examine the structural, magnetic, morphological, thermal, electronic, and electromagnetic properties of these hybrid structures. As a result of the analysis, Fe3O4:MoS2 and PANI@Fe3O4:MoS2 hybrid sturucture, which can effectively absorb electromagnetic waves, were found to have superior EMW absorption properties. In particular, The F10M90 sample achieved a minimum reflection loss of -54.97 dB at a thickness of 3 mm and a frequency of 7.86 GHz, with an effective absorption range of 4.0 GHz. The P50F2.5M47.5 sample achieved a minimum reflection loss of -27.58 dB at a thickness of 2 mm and a frequency of 13.18 GHz, with an effective absorption bandwidth of 8.03 GHz. Based on the experimental findings, it is concluded that hybrid nanocomposites such as PANI@Fe3O4:MoS2, which are characterized by their lightweight structure and high temperature stability, can effectively absorb almost 99% of the EMW in the broadband range.
An assessment of bioplastic applications in agriculture within a sustainable framework
The Earth's surface temperature has been exceeding normal levels since the 1950s. Global warming poses threats to human and living health. Various solutions are being explored to protect water resources. Another challenge facing humanity is the increasing demand for food due to population growth. Enhancing agricultural productivity is necessary to meet this demand. The effective use of plastic mulches in agriculture, as evidenced by numerous studies, positively impacts water efficiency, productivity, and quality. However, petroleum-based plastics contribute to global warming by increasing carbon emissions and can persist in the environment for years, even when they begin to degrade, breaking down into small particles that mix into soil, water, and food, posing risks to human, animal, and environmental health. The use of biodegradable bioplastic mulch materials, which naturally decompose without polluting soil and the environment, has become essential in agriculture. To replace petroleum-based mulches with biodegradable and eco-friendly bioplastic alternatives, it is imperative to achieve significant product quality, including water vapor permeability and mechanical properties, to meet the economic expectations of supply and demand. This study demonstrates the strong relationship between sustainability and the agricultural sector, examines research related to bioplastic mulch materials, evaluates the current state of products in the market, compares their characteristics, and also assesses research conducted to the perspectives of production, application, and characterization.
Production of multifunctional nanoparticle-reinforced polymer composite surfaces by photopolymerization method and investigation of performance characteristics
In the recent years, Stereolithography (SLA) type three-dimensional (3D) printers have gained increasing importance in the production of composite materials due to their high precision, low surface roughness, and minimal material waste. Also known as additive manufacturing (AM), 3D printing enables the fabrication of complex geometries that are difficult or impossible to achieve with conventional manufacturing techniques. This technology offers design flexibility and production efficiency, making it widely used in biomedical, automotive, aerospace, and defense sectors [1,2]. SLA technology, first introduced in the 1980s using UV lasers, is based on the principle of layer-by-layer polymerization of liquid photopolymer resins via computer-controlled ultraviolet light. During the process, semi-liquid raw materials are solidified into high-resolution and dimensionally accurate geometries. The mechanical, thermal, and electrical properties of parts produced using SLA can be precisely optimized compared to conventional production methods. With recent technological advancements, research on the fabrication of nanocomposite materials via SLA has significantly increased. The design freedom, cost-effectiveness, and production speed offered by SLA technology have accelerated investigations in this field. In this thesis, nanocomposite surfaces were fabricated by incorporating nanoparticles into a photopolymer resin with concentrations of 1%, 3%, and 5%. The specimens were produced layer-by-layer using an Anycubic SLA printer with a layer thickness of 50 microns. Surface resistivity measurements were performed in accordance with the TS EN 1149-1:2006 using an ELME Multimeg device under controlled conditions of 25°C and 50% relative humidity. The results indicated that all samples exhibited surface resistivity values exceeding 1012 ohms, confirming their high electrical insulation performance. Additionally, antibacterial activity tests, conducted in accordance with TS ISO 22196, revealed that all formulations exhibited more than 99% effectiveness against S. aureus and E. coli. Electromagnetic shielding effectiveness (EMSE) was evaluated based on scattering parameters, and the materials demonstrated a shielding effectiveness of less than 5 dB in the 8–12 GHz frequency range. Consequently, the developed nanocomposites show potential for use in applications requiring electrical insulation, antimicrobial surfaces, and partial permeability to electromagnetic waves. Keywords : SLA resin, 3D printer, photopolymer, additive manufacturing, composite materials
Titanyum diborürün bağlayıcı alaşım ile basınçsız sinterlenmesi ve karakterizasyonu
Bu çalışmada TiB2 takviyeli Ni ve Fe alaşım matrisli kompozitler nispeten düşük sıcaklıkta basınçsız sinterleme ile üretilmiştir. TiB2 yüksek sertlik ve korozyon direncine sahip olan bir yüksek sıcaklık seramiğidir. Bağ yapısı ve düşük difüzyon katsayısı nedeniyle TiB2'yi saf halde sinterlemek güçtür. Bu nedenle sinterlenmesi için 1800 oC ve üzerinde sıcaklıklar gerekmektedir. Sinteleme sıcaklığı, metal bağlayıcı eklenerek düşürülebilmektedir. Ni, Fe ve alaşımları TiB2'nin sıvı faz sinterlenmesi için faydalı katkılar olarak bilinmektedir. Bu çalışmada ağırlıkça % 10, 17,5 ve 25 oranlarında TiB2 içeren Ni, Fe ve alaşımı matrisli kompozitler argon atmosferinde basınçsız sinterleme ile 1375 oC'de üretilmiştir. %10 Ni matrisin, bu sıcaklıkta sürekli bir matris oluşturmak için yeterli olmadığı bulunmuştur. Üretilen kompozitlerde ham bağıl yoğunluklar yaklaşık %65-70 ve sinterlenmiş bağıl yoğunluklar % 88-90 olmuştur. En yüksek sertlik ve eğme dayanımı değerleri, %25 Ni matrisli kompozitte sırasıyla 1556±115 HV0.2 ve 279 MPa değerleri ile elde edilmiştir. PEG kullanımı veya ılık sıkıştırma uygulaması yoğunluğu veya mikrosertliği arttırmada etkili bulunmamıştır. TiB2 parçacıklarının 6-10 mikrometre aralığında olduğu görülmüştür. Bazı deneylerde başlangıç tozlarına WC-Co ortamında bilyeli öğütme uygulanmıştır. Öğütülmüş tozlardan üretilmiş olan kompozitlerin mekanik özellikleri diğerleri ile benzer olmuştur fakat TiB2 parçacıkları 2-4 mikrometre aralığında olarak daha küçüktür. Kompozitlerin öğütme ortamından kaynaklanan WC parçacıklarını içerdiği SEM ve EDS analizleri ile belirlenmiştir. Fe, Fe+Ni ve Fe+Ni+Co matrisli kompozitlerin özellikleri, Ni matrisli kompozitlerden daha düşük olmuştur.
Hybrid 3D bioprinting of functionalized structures for tissue engineering
Tissue engineering is an interdisciplinary field of research aiming at developing methods and technologies for regenerating damaged tissues. It relies on a combinatory platform of biomaterials with cells and bioactive molecules to resemble the human microenvironment to stimulate tissue constructs. Hence, numerous factors, including biochemical, biophysical, and mechanical aspects of the host tissue, have to be taken into account for developing a successful tissue replacement. Skin replacements caused by traumas, injuries, and burns are a burden to the healthcare system globally. The human body cannot fully regenerate the tissue with all the functionalities and features in severe wounds or skin loss. Poor mechanical properties, scarring, delayed cell and biomolecules infiltration, and non/poor vascularization are the main challenges yet to be addressed. Three-dimensional (3D) bioprinting, also known as additive manufacturing (AM), a layer-by-layer fabrication method, is regarded as a gold standard technique with the ability of controlled deposition of biomaterials in the desired geometry by using computer-aided design (CAD) models. Together with the development of biomaterials and architecture design, 3D bioprinting could ease the long and complicated journey towards functional tissue regeneration. In this context, the fabrication of small fibers mimicking natural extracellular matrix (ECM), selection of functional material with good mechanical and biochemical properties, the inclusion of bioactive molecules to enhance functionality, and printability are prerequisite factors of successful scaffold fabrication. In this work, novel hybrid 3D bioprinting approaches have been developed for functionalized structures, mainly for skin tissue engineering. Within this framework, we first optimized the effect of printing parameters on fiber diameter for Melt Electrospinning Writing (MEW), a special 3D printing process, using response surface methodology (RSM) as a predictive tool. Then we copolymerized polycaprolactone (PCL) with polypropylene succinate to improve its degradation rate and hydrophilicity and functionalized it with silver nitrate to induce antibacterial properties, and finally, it was 3Dprinted using an extrusion-based printer. For preparing hybrid 3D bioprinting, we used a composite support-bath system based on Pluronic PF127 was formulated with the inclusion of Laponite RDS and calcium chloride as rheological modifier and stabilizer, respectively. The rheological characterization of support-bath showed thixotropic behavior with a high degree of recoverability which facilitated bioprinting of complex hydrogel structures within the support-bath through an extrusion system. Then, we fabricated a polymer-hydrogel construction using MEW-casting for skin tissue substitute. In this context, we first investigated the geometrical effect of melt electrowritten scaffolds on cord-like structure formation for pre-vascularization. Mesh scaffolds with 0-90and 60-120 degree orientations and honeycomb shape were explored and cell-laden gelatin hydrogels were infiltrated inside those PCL scaffolds, and the results suggested the potential of honeycomb structure for better mechanical and invitro properties. In the final stage, a functionalized hybrid MEW-hydrogel scaffold for wound healing was fabricated. A functionalized mesh structure of PCL-bioactive glass was created via MEW, and a gelatin hydrogel comprising basic fibroblast and vascular endothelial growth factors was cast within the mesh scaffold. In vivo implantation of hybrid scaffolds showed promising results for accelerating and functionality of the healed parts according to wound closure and histological evaluation.