The combination of powder metallurgy and ball milling method has been widely regarded as the most beneficial route for producing multi-walled carbon nanotubes (MWCNTs)-reinforced aluminum matrix composites. In this study, the effects of different milling times (1, 2, 4, and 8 h) on the structural, morphological, and crystallographic properties of MWCNTs-reinforced Al7075 composite powders were characterized by particle size analyzer, Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). After the morphological and structural characterization of the milled powders, the microstructural and mechanical properties of the hot-pressed composites were evaluated using an optical microscope, SEM, density, and Brinell hardness measurements. Considering milled powder characterization, the MWCNTs were gradually distributed and embedded within the matrix as the milling time increased. Milling for 8 h resulted in a minimum level of particle size (11 µm) with shortened and uniformly dispersed CNTs. Brinell hardness of the composite increased from 91 to 237 HB -a ⁓%160 after 8 h of milling. Such a remarkable increment in hardness could be attributed to several concurrent strengthening effects related to dispersion, solution, grain refinement, and Orowan looping mechanisms. However, relative density results revealed that the composite produced by 2 h milled powders exhibited the highest density (%99.96). The observed differences between hardness and density results were ascribed to powders’ deteriorated packing and sintering behavior due to an increment in the hardness of particles and variation in particle size range and morphology, which resulted from following different milling protocols.

The increasing demand for the development of environmentally friendly alternatives to petroleum-derived materials has increased research efforts on sustainable polymer composites. This study systematically examined the effect of nano-biochar derived from agricultural wastes such as olive pulp on the mechanical and thermal properties of epoxy-resin-based composites. First, the biochar from olive pulp was produced by pyrolysis at 450 °C and turned to nano-biochar using ball milling. Composite samples containing nano-biochar at different rates between 0 and 10% were prepared. The nano-biochar and composite samples were characterized by using different techniques such as SEM-EDS, BET, FTIR, XRD, Raman, TGA, and DMA analyses. Also, the tensile strength, elastic modulus, Shore D hardness, thermal stability, and static toughness of the composite samples were evaluated. The best performance was observed in the sample containing 6% nano-biochar; the ultimate tensile strength increased from 17.37 MPa to 23.46 MPa compared to pure epoxy, and the elastic modulus and hardness increased. However, a decrease in brittleness and toughness was observed at higher additive rates. FTIR and DMA analyses indicated that the nano-biochar interacted strongly with the epoxy matrix and increased its thermal stability. The results showed that the olive-pulp-derived nano-biochar could be used to improve the structural and thermal properties of the epoxy composites as an inexpensive and environmentally friendly filler. As a result, this study contributes to the production of new polymer-based materials that will encourage the production of environmentally friendly composites with nano-scale biochar obtained from olive waste, which is an easily accessible, renewable by-product.

Artan enerji taleplerin karşılanmasında yenilenebilir enerji türleri açısından popüler olan fotovoltaik teknolojiler üzerine verim artırmaya yönelik çalışmalar yapılmaktadır. Boya duyarlı güneş pilleri yüksek altyapı maliyeti gerektirmeyen yapılar olduğundan verim artırmaya yönelik çalışmalar boya duyarlı güneş hücreleri (DSSC) üzerine yoğunlaşmıştır. DSSC’de ışığa duyarlı boya, TiO2 tabakasına tutundurulmaktadır. Kullanım ömrünü tamamlamış NiTi alaşımı endodontik eğeler, farklı asitler üzerinden çözeltiye alınıp metalik değerlerine ayrıştırılmış ve bu metalik değerlerden olan anataz fazında olduğu tespit edilen TiO2 ‘nin boya duyarlı güneş hücrelerinde kullanımına yönelik çalışmalar yapılmıştır. Çalışma kapsamında atık NiTi eğelerden elde edilen kontamine TiO2 ‘nin yapısı karakterize edilmiş ve N719 boya çözeltisinin yüzeye tutundurularak optik özellikleri araştırılmıştır. Boya duyarlı güneş hücrelerinde kullanılan N719 boya çözeltisi uygulanan geri kazanım anataz TiO2 tatbik edilmiş yüzeyle ile görünür bölge spektrumunda belirgin bir etkinlik göstermediği ortaya konulmuştur.

In this study, the structural, thermal, and mechanical properties of nanocomposites obtained by adding zinc oxide (ZnO) nanoparticles (NPs), produced by phyto-mediated synthesis using Dianthus chinensis plant extract, to a PMMA-based photopolymer resin at different ratios (0.05%, 0.10%, 0.15%, 0.20%, and 0.25%, by weight) were evaluated. The prepared composite resins were produced in different test geometries using a DLP (digital light processing)-based 3D printer (Asiga Ultra). Following the structural characterization of ZnO nanoparticles, tensile, compressive, and flexural mechanical tests were performed on the resulting composites, as well as FTIR, TGA, DSC, and DMA analyses. The FTIR results showed that ZnO NPs were physically integrated into the matrix. TGA and DSC analyses revealed that the addition of ZnO NPs, particularly at an addition rate of 0.15%, increased thermal stability. DMA analyses showed an increase in storage modulus and glass transition temperature as the addition rate increased. In mechanical tests, the highest modulus of elasticity and maximum strength values were obtained at additive ratios of 0.10–0.15%. The highest tensile strength (55.31 MPa) and compressive strength (388.53 MPa) were obtained at ZnO contents of 0.10–0.15 wt%, while the maximum flexural strength reached 125.94 MPa at 0.15 wt% ZnO. In addition, the storage modulus increased from 1.469 × 10⁹ Pa for the control resin to 1.872 × 10⁹ Pa for the composite containing 0.15 wt% ZnO, indicating improved stiffness and thermomechanical stability. The stress–strain curves show that improvements in ductility and deformation capacity of the material are achieved at these additive ratios. The findings demonstrate that green-synthesized ZnO nanoparticles are an effective and sustainable additive material for improving the mechanical and thermal performance of DLP-based photopolymer dental resins.

Al 7020 aluminum alloy is mainly preferred in many engineering applications, especially in the aviation and space sectors. Nano graphene (Gr) particles were selected for the study due to their hybrid composite structure, microstructure, mechanical properties, lubrication properties, lightness, and small size compared to the matrix and reinforcement element. For this purpose, SiC and nanographene powder particles were added to the aluminum matrix as reinforcement phases in the study, and composite-hybrid test samples were produced. In the production of Al7020 powder metal matrix SiC/nanographene doped test samples, 10% SiC ceramic phase reinforcement by weight was applied to the matrix material at a fixed rate, and nanographene particle reinforcement was added at the rates of 0.25%, 0.50%, and 1.0%. The prepared matrix powder mixtures were mixed in a high-energy ball mill at 300 RPM and 240 minutes to ensure homogeneous distribution in terms of matrix/reinforcement. After mixing, the powder mixtures were compressed at room temperature using a pressing pressure of 650 MPa. The obtained raw density test samples were sintered at 600°C for 60 minutes under Argon gas flow. Thus, the effect of SiC-nano graphene reinforcement on density, microstructural, hardness, and wear (25N, 900m) results were evaluated. The pore amount increased in the samples containing reinforcement elements. The highest hardness value was 108.476 HBN in the sample containing Al-10%SiC-0.5%Gr.