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Bu çalışmada gezegensel tip öğütücüde mekanik alaşımlama yöntemi ile Argon atmosferi altında eş molar nanokristal Fe-Si-Cu (at.%) ve Fe-Si-Nb(at.%) alaşımları sentezlenmiştir. Sentez deneyleri 350 rpm dönme hızı, 10:1 bilye-toz oranında ve 120 saat süre ile gerçekleştirilmiştir. Sentezlenen alaşımların faz yapıları X-Işınları difraktometresi ile, morfoloji ve elementel analizleri SEM-EDS ile, manyetik özellikleri ise oda sıcaklığında titreşimli örnek manyometresi (VSM) tekniği ile araştırılmıştır. XRD incelemelerinden öğütmenin ilk aşamalarından itibaren Fe(SiCu) ve Fe(SiNb) katı çözelti fazlarının oluşmaya başladığı tespit edilmiştir. Fe-Si-Cu alaşımının kristalit boyutu öğütme başlangıcı, 30, 60 ve 120 saat öğütme sonrası sırasıyla 102.3, 22.5, 15.9 ve 8.6 nm, örgü gerinimleri ise % 0.164, % 0.510, %0.672 ve %1.165 olarak bulunurken, Fe-Si-Nb alaşımı için ise kristalit boyutlar 140.8, 42.9, 16.8 ve 7.8 nm, örgü gerinimleri ise % 0.134, % 0.301, % 0.639 ve % 1.271 olarak hesaplanmıştır. SEM-EDS ve elementel haritalama incelemelerinden, öğütme sonucunca her iki alaşımında küresel benzeri yapıda parçacık morfolojisine sahip olduğu ve alaşım elementlerinin homojen dağılım gösterdiği tespit edilmiştir. Manyetizma sonuçlarına göre, Fe-Si-Cu (at.%) alaşımının doyum manyetizasyonu (Ms) 3146 emu/g olarak bulunurken, Fe-Si-Nb (at.%) alaşımının doyum manyetizasyonu 8.91 emu/g olarak bulunmuştur. Fe-Si alaşım sistemine Nb katkısının kuarzivite değerlerinde artışa sebep olduğu belirlenmiştir.

High entropy alloy (HEA) with shape memory effect (SME) has been the subject of great interest for the past few decades. However, with the increased demands for new materials for high thermal applications, the research activities on the multi elemental high entropy shape memory alloys (HESMA) have been increased by many folds recently. The nano crystalline HEA powder with shape memory effect developed in this study, HfZrTiFeMnSi, was produced by mechanical alloying (MA) for the first time. In this method equiatomic ratio of Hf, Zr, Ti, Fe, Mn, and Si were mixed together and milled by MA process for 100 h. The powder formed was of amorphous in nature. Elemental mapping of the powder from SEM-EDS revealed homogeneity of the alloying elements confirming successful fabrication of HfZrTiFeMnSi HEA powder. The DSC studies from ambient to 500 °C of the annealed alloy powders showed reversible austenitic to martensitic (A↔M) transformations. The A↔M transformation hysteresis seemed to vary with the milling time and annealing temperature. The enthalpy values, ΔH, for the transformation were calculated from the DSC plots using tangent method for peak area calculation. Regardless of the annealing temperature, the thermal analysis revealed that the ΔH, equilibrium temperature (T0), and crystallization temperature values decreased with the increasing milling time.

Numerous studies have revealed the properties of composites obtained by adding carbon nanotubes (CNTs) into different polymer matrices. Although CNTs significantly improve the properties of the polymer matrix, problems are experienced in the production of composites due to CNTs. Therefore, only graphene nanoplates (GNPs) at the same rate along with CNTs were added into the polyester matrix which was used as a matrix in this study. In this way, the changes occurring in the properties of polyester were revealed. The mechanical properties of CNTs–GNPs reinforced polyester composite are lower than the composites reinforced only with CNTs. Besides, electrical conductivity of CNTs reinforced polyester composite was lower than CNT + GNP reinforced composite. Mechanical properties and electrical conductivity of both polyester–CNTs composite and polyester–CNT + GNP composite increased with increasing reinforcement ratio. In addition, the thermal properties were examined and glass transition temperature was determined as averagely 79 °C.

In this study, nanocomposites ZnO-doped graphene+boron nitride nanosheets (BNNS) were produced, and their electrical and optical properties were investigated. The graphene+BN nano-hybrid layer used as a reinforcement element was synthesized using a liquid-phase exfoliation method. TEM images support the nanosheet’s structure of the graphene and boron nitride. ZnO produced by sol-gel showed nanoscale spherical particles, while the commercial ZnO showed the micrometer scale with rod-like and hexagonal shapes. Composite materials were provided by reinforcing this reinforcement element into ZnO matrices, which were commercially available and were produced using the sol-gel procedure at different ratios. To compare the results, the BN nanosheets were synthesized using liquid-phase exfoliation. Using the same method, samples for comparison were produced by reinforcing these nano-hybrid sheets into the commercially available ZnO matrix and the sol-gel synthesized ZnO matrix. A limited increase was shown for the 0.1 wt% and 0.5 wt% in the nanocomposites’ electrical conductivity ratios, along with the rise of the graphene + BN nano-hybrid sheet. The Eg values of the as-produced nanocomposites first decreased and then increased as the reinforcement ratio increased. The bandgap changing for all reinforcing types exhibits similar characters. The studied materials can be used in wide-scale electronic and optoelectronic devices, environmental, biomedical, and catalytic/photocatalytic activities.

There are many production methods for graphene production. One of the most successful production methods in terms of scale-up is liquid phase exfoliation (LPE) method. In this study, after optimizing the sonication time and sonication power that are effective in the production to increase the efficiency of the LPE method, the experiments were continued at moderate sonication powers and the effect of liquid media, another important parameter, was examined. In this study, hexagonal graphite powders were subjected to direct liquid phase exfoliation process by using different liquid media (N-Methyl-2-Pyrrolidone (NMP), N,N-Dimethylformamide (DMF), ethanol, 2-propanol, acetone, methanesulfonic acid, ethanol + Sodium dodecyl sulphate (SDS), 2-propanol + SDS) and the obtained samples were characterized. As a result of the characterization, the liquid media with the highest efficiency was determined to be NMP. Besides, it was observed that a new hybrid solvent obtained by adding a surfactant such as SDS into low-cost and environmentally friendly liquid media such as ethanol and 2-propanol showed a higher efficiency than NMP. It was observed that 3–5 layer graphene ranged between 15 and 19 wt% in either graphene produced by using hybrid solvents containing NMP or SDS. The amount of double or single-layer graphene was negligibly small. The production with the lowest efficiency was observed in the use of acetone. The produced graphenes were dispersed in the liquid and their sedimentation time was observed. The sedimentation time of graphenes, produced using NMP and SDS-doped hybrid solvents, in liquid was more than 120 days. The sedimentation time of graphene produced using acetone was less than 20 days. In the use of graphene as a reinforcing material or adsorbent, large amounts of graphene are needed. In such applications, mass production of graphene is important rather than the number or quality of sheets of graphene. Therefore, optimization of production parameters of LPE method, which is suitable for mass production, is significance.

In the present study, graphene nanosheets were synthesised by liquid phase exfoliation process, and the obtained graphene was reinforced in the rates of 0.1, 0.2, 0.3 and 0.6 wt.%. After the composites were characterised, they were exposed to Equal Channel Angular Pressing (ECAP) process. While 0.1 wt.% and 0.2 wt.% graphene reinforced composite samples successfully completed the ECAP process, 0.1 wt.% and 0.2 wt.% graphene reinforced composite samples were broken during the ECAP process. Electrical, thermal, and mechanical properties of the composite increased with the increased amount of graphene. The mechanical properties of ECAP-processed samples showed significant increases compared to non-ECAP processed samples. To figure out the effect of the ECAP process, moulds with different channel angles were used, the ECAP temperature was changed, and different passes were performed and the angles of 120° and 90° were used. ECAP-processed samples in both mould angles showed similar mechanical properties. With the increasing ECAP temperature, the mechanical properties of the sample decreased, but its electrical conductivity increased. As the number of passes increased, mechanical properties increased and crack formation in material increased. In addition, it was not possible to successfully remove the matrix composites containing more than 0.3 wt.% graphene from the ECAP process. Especially in the sample containing 0.6 wt.% graphene, brittle fractures were seen during the ECAP process and the sample was divided into many parts. The results showed that the composite responded better to the ECAP process when low amounts of graphene were reinforced in the al matrix. Significant improvements were observed in the properties of these composites after the ECAP process. In this study, the properties of composites with and without ECAP process were extensively investigated. The results were compared in detail with the previous studies. The graphene was produced using a simple method and it was reinforced with the Al matrix with the easiest possible method.

We report the synergistic effects of boron nitride and graphene nanosheets on physical, structural, and nuclear radiation attenuation properties of polyester matrix-incorporated nanocomposites. Some critical material properties are thoroughly evaluated for several types of synthesized samples. Polyester is employed to strengthen graphene and boron nitride nanolayers, and their characteristics are investigated in detail. Additionally, we report the gamma-ray and fast neutron attenuation characteristics of synthesized nanocomposites to get a better understanding of the reinforcing effect as a function of material type and weight percentage. Thermal analysis findings indicate that adding graphene lowers the decomposition temperature but co-adding graphene and BNNS enhances thermal decomposition in comparison to graphene itself. Tensile tests showed that the inclusion of both GRP and GRP/BNNS strengthens the material. Among the polyester composite samples analyzed, the G3 sample with the most GNP reinforcement had the lowest HVL values throughout the broadest range of energy levels investigated. The recent findings may be beneficial to the scientific community in terms of incorporating these reinforcing types and ratios into polyester materials for a variety of applications, including industrial and research purposes. © 2022 2-s2.0-85130401014

This study was performed to investigate the effects of nanoporous hematite (Fe2O3) the electrical and optical properties on zinc oxide. Zinc oxide powder was commercially obtained. The nanoporous hematite with iron core was prepared using a specific method including ball milling and annealing processes. The particle size of the nanoporous hematite was determined to be 40–50 nm using an electron microscope. The electrical conductivity values of pure ZnO and the composites with 1% Fe2O3, 3% Fe2O3, and 5% Fe2O3 were obtained to be 6.55 × 10−5, 5.35 × 10−4, 3.79 × 10−4 and 1.29 × 10−4 S/cm, respectively. The nanoporous Fe2O3 with iron core increases the electrical conductivity of the ZnO-nanoporous:Fe2O3 composites. The optical band gap (Eg) values of the composites were determined by the Kubelka-Munk theory based on the diffused reflectance. As the nanoporous Fe2O3 content is increased, the Eg values of the composites are decreased. The obtained results indicate that the electrical and optical properties of the ZnO semiconductor is improved with the nanoporous Fe2O3.

The soft ferromagnetic materials are of great industrial importance for their applications in magnetic cores for transformers, electric motors, inductors, and generators. In recent years, the trend has been to use magnetic high entropy alloys (HEAs) owing to their superior magnetic properties compared to the conventional magnetic materials. In this study, the traditional magnetic materials, (NiFeCo)95Mo5 and (NiFeCo)90Mo10 produced by conventional mechanical alloying method, were compared with the NiFeCoMo high entropy alloy produced by the sequential mechanical alloying method. Unlike conventional mechanical alloying, NiFeCoMo HEA was produced by mechanical alloying using sequential additions of Co and Mo to the preformed Fe-Ni alloy. Besides its magnetic properties, the effect of Co and Mo on the overall characteristics of the alloy was also investigated. In 60 h milled samples of the (NiFeCo)95Mo5 and (NiFeCo)90Mo10 alloys, the crystallite sizes were estimated as 10.5 and 10.8 nm respectively, whereas the crystallite size for the NiFeCoMo HEA was 15 nm. The presence of Mo in the alloy induced the formation of lamellar or layered structures of the particles. During the sequential milling to form NiFeCoMo HEA, it was noticed that the addition of Co into the preformed Fe-Ni alloy increased the magnetic saturation value due to the formation of FeCoNi alloy phase. However, further addition of Mo into the FeCoNi alloy phase reduced the magnetic saturation value of NiFeCoMo alloy significantly. After 60 h of milling the magnetic saturation value was dropped from 102.48 emu/g for the NiFeCo alloy to 60.52 emu/g for the NiFeCoMo alloy.

Hexagonal graphite (HG) and hexagonal boron nitride (h-BN) show various characteristics that are different from each other in addition to their similar features. It is thought that hybrid nanosheets which are formed of nano-layered graphene and nano-layered boron nitride (BNNS) will show very extraordinary characteristics. In this study, the production of a new Hybrid structure containing graphene and BN nanosheet structures was performed by using the liquid-phase exfoliation method. For this purpose, as the starting material, HG and h-BN were mixed at the same ratio and added into an acid mixture and thus an intermediate structure called as Hybrid intercalated compound (HIC) was obtained. Then, the HIC structure obtained was subject to a thermal treatment and a structure called as expanded hybrid structure (EHS) was obtained. In order to produce a Hybrid nanosheet, the EHS structure was sonicated in dimethylformamide (DMF), which was used as a solvent. At the end of the treatment, the material floating in the solvent was filtered. The samples were subject to transmission electron microscope (TEM), scanning electron microscopy (SEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy, and UV–vis spectroscopy examinations. As a result of the analyses, it was determined that the hybrid nanosheets containing graphene and BN nanosheets were successfully produced.

In this study, ZnO–Fe 2 O 3 nanocomposites were synthesized by powder metallurgy route and characterized through X-ray diffraction, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy, electrical conductivity measurement device. The amount of Fe 2 O 3 in the ZnO and milling time were varied in order to investigate their influence on the electrical and optical properties of the samples. Powder mixture containing milled and unmilled Fe 2 O 3 at the rates of the 1, 3 and 5 wt% was sintered in vacuum environment. Results show that the conductivities of ZnO–Fe 2 O 3 nanocomposites slightly increased by increasing the Fe 2 O 3 content and these composites have potential materials for photocatalysis. Besides, electrical and optical properties of ZnO–Fe 2 O 3 nanocomposites varied according to status of unmilled Fe 2 O 3 and milled Fe 2 O 3 .

Graphene–boron nitride (BN) nanosheet heterostructures have become one of the highly interesting matters in recent times owing to their advantages. In this study, the liquid phase exfoliation method was preferred for production of graphene–BN nanosheet heterostructures. However, a pre-milling process was applied to starting materials, instead of the classical liquid phase exfoliation method previously used in the literature. Hexagonal graphite (h-G) and h-BN mixtures were milled for 50 h and the milled powders were subjected to the liquid phase exfoliation process. As a result of the examinations, it was observed that graphene–BN nanosheet heterostructures were successfully synthesized. The widths of the synthesized nanosheets were 300–500 nm and nanosheets were multi-layers. It was seen that a large part of the powder mixture were occurred at high amorphization during the ball milling process. According to X-ray diffraction (XRD) peaks, the amorphization ratio was almost 90%. But, almost all of amorphous structures were removed during acid mixing and the thermal process. But, amorphous structures still existed in samples. In addition, the ball milling process damaged the sheets and defects formed. Despite all these disadvantages, the milling process carried out in this study provided formation of thinner and larger sheets compared with previous similar studies.

Mechano-thermal method was used for synthesizing the carbon nanotubes (CNTs) in this study. In this method, graphite powders in the elemental form were firstly exposed to milling process in high-energy ball milling and then the milled powders were annealed at high temperatures. As a result of milling of the graphite, ultra-active disordered carbon structures were obtained. This structure serves as a carbon source for the formation of nanotubes during the annealing process. This study investigated the effect of the milling process. For this purpose, graphite powders were milled at different periods such as 5 and 150 h and then annealed at 1600 °C. The transmission electron microscopy and scanning electron microscopy examinations demonstrated that CNTs formed in samples milled both for 5 and 150 h. However, the difference in the milling time influenced the amount of CNTs, their size and the formation of other structures except from nanotubes.

The electrical and optical properties of carbon nanotubes hybrid zinc oxide (ZnO-CNTs) nanocomposites synthesized by ball mill technique have been investigated. The nanocomposites were prepared using zinc oxide (ZnO) powder and carbon nanotube (CNT) synthesized by catalytic thermal chemical vapor deposition (CVD). The diameters and lengths of the CNTs were respectively determined to be 20–30 nm and about 3–5 µm. DC conductivity measurements reveal that the nanocomposites are good conductive material. The room temperature DC electrical conductivity σdc of the un-doped ZnO and ZnO-CNT nanocomposites with 0.1% CNT, 0.5% CNT, and 1% CNT were found to be 6.55 × 10−5, 5.46 × 10−4, 1.49 × 10−3, and 4.01 × 10−3 S/cm, respectively. This indicates that there is a remarkable improvement of the electrical conductivity as the CNTs' content increases. The optical band gaps of the composites were determined by Kubelka-Munk theory based on the analysis of diffuse reflectance. The band gap (Eg) values of the composites de...

In this study, composite materials reinforced with carbon nanotubes (CNT) containing cadmium oxide were produced and investigated optical and electrical properties of them. Carbon nanotubes which used support materials were synthesized by chemical vapor deposition. After then, they were reinforced in to the cadmium oxides which were sold by commercial. As another group, cadmium oxides were synthesized by sol-gel method and reinforced carbon nanotubes with different rate. Synthesized CNT’s were subjected to TEM investigation. Obtained CNT’s were also subjected to SEM as structural. After those, gained composite samples were investigated for both electrical conductivity, changing temperatures and optical properties by UV-vis spectrometers. It was clear, as a result that electrical conductivity was increased by raising CNT rates for both groups. Beside composites containing CdO, synthesized by sol-gel method have higher conductivity than composites containing CdO bought by commercial have. To sum up, CdO composites synthesized by sol-gel have both higher conductivity and optical properties comparing with commercials have.

Buçalışmada, kimyasal buhar çöktürme metodu (CVD) ile sentezlenen karbonnanotüpler (KNT) titanyum dioksit (TiO2) matrisi içerisine ağırlıkça%0.1, 0.2, 1 ve 2 oranlarında takviye edilmişlerdir. Elde edilen numunelerinyapısal karakterizasyonu Taramalı elektron mikroskobu (SEM) kullanılarakyapılmıştır. Numunelerin sıcaklığa bağlı elektriksel iletkenlikleriölçülmüştür. UV-VIS spektrometresi kullanılarak optik özellikleri tespitedilmiştir. Kompozitteki karbon nanotüp miktarının artışı gerek odasıcaklığında gerekse artan sıcaklıklarda elektriksel iletkenliğin artmasınaneden olmuştur. Ayrıca, KNT’ler TiO2’in UV ışınlarını absorbe etmeözelliğini arttırmış, yasak enerji aralığının (Eg) azalmasına sebep olmuştur., Inthis study, Carbon Nanotubes (CNT) synthesized with Chemical Vapour Deposition(CVD) were reinforced with 0.1, 0.2, 1 and 2% weight in Titanium dioxide (TiO2).Structural characterization of samples was analyzed by Scanning ElectronMicroscope (SEM). Electrical conductivities of samples, based on temperature,were surveyed. Optical properties were determined using UV-VIS spectrometer.Increase in CNT rate in composites caused electrical conductivity both room andrising temperature. Furthermore, CNT caused the increases in ability of TiO2'sto absorb UV beam, and the reduces on forbidden energy gap (Eg).

In this study, low carbon steel specimens with surface alloyed composites were produced by means of powder metallurgy. Vanadium carbide, graphite (1·2 wt-%) and Fe were used for the surface alloyed composite, while Fe and graphite (0·2 wt-%) were used for the low carbon steel side. The powder mixtures were compacted together in the same mould. On the surface alloyed side the vanadium carbide content was changed from 5 to 25 wt-%. Microstructural investigations including EDX and X-ray, hardness measurement and abrasive wear tests were performed. The results showed that V8C7 formed in the alloyed surface and carbon diffusion from the alloyed surface to the parent metal created a functionally graded material. The hardness values decreased towards the parent metal. Wear resistance increased as the vanadium carbide increased in the surface alloyed composite. Thus, a functionally graded steel having a surface composite that is resistant to abrasive wear can be obtained via the powder metallurgy route.