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Streszczenie:
Abstract
In the present study, ab initio-based density functional theory (DFT) calculations were used to determine the effects of certain phenomena that can occur in the synthesis of Beryllium-Oxide (BeO) few-layer sheets, such as various types of defects, attaching nanocages onto the surface of graphene and attaching layers to each side of it on the mechanical and electronic properties of BeO graphene sheets. We also used the density of states (DOS) calculations to obtain a better understanding of the electronic properties of the studied nanostructures. In the first step, we calculated Young’s modulus for the pristine BeO graphene sheet that was found to be equal to 1.110 TPa. Next, the effect of small and large defects on the mechanical properties of the BeO graphene-like structure was examined, and we found that extracting one Be atom resulted in a lower Young’s modulus compared to that obtained after extracting one oxygen atom (1.087 TPa versus 1.104 TPa), demonstrating that Be had a greater effect on the stability and mechanical strength of BeO graphene than did oxygen. The same trend was found when comparing three atom vacancies with two missing Be atoms to those with two missing oxygen atoms. Furthermore, the effect of circular and rectangular shape defects was investigated, and the obtained results demonstrated that the increase in the diameter of defects with both shapes significantly decreased Young’s modulus and band gap energy values. Additionally, due to the number of detached atoms in shape defects which are more than those of small defects, this type of defect had a more destructive effect on the structure’s stability so that it decreased the Young’s modulus more than small defects. Moreover, the mechanical properties of the BeO graphene nanobud structure were determined in terms of placing different numbers of Be12O12 nanocages onto the graphene surface, and a similar decreasing trend was observed for Young’s modulus. Finally, we considered the mechanical properties of the bi- and three-layer BeO graphene-like structures and found that increasing the number of layers reduced Young’s modulus slightly. For both of the latter phenomena of attaching nanocages and layers, the band gap energy decreased.

Słowa kluczowe:
Young’s modulus

Streszczenie:
An investigation of nanosilica (SiO2), influencing the mechanical and thermal attributes of carbon fiber (CF)/polycarbonate (PC) laminates, is described in this study. Polycarbonates with four different weight percentages of SiO2 (PC-SiO2, 0.1, 0.3, 0.6 and 1.0 wt%) were prepared using a melt-blending technique. The PC-SiO2 nanocomposites were then used to fabricate planar CF/PC laminates through a hot hydraulic press machine. The prepared laminates were characterized by a number of different techniques; namely, tensile tests, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The tensile test findings revealed that when 0.6 wt% of SiO2 was added to the laminate layers, the maximum tensile modulus and yield stress were achieved. The mechanical properties obtained by DMTA supported the tensile test results. It should be noted that the 0.6 wt% of SiO2 had the highest mechanical properties. The DMTA and DSC analyses were used to measure the glass transition temperatures (Tg) of laminates. We found that with the addition 0.6 wt% of SiO2 the Tg increased to approximately 1°C compared to 0 °C for the neat CF/PC laminate, meaning that by adding up 0.1 to 0.6 nanosilica to the polymer, the value Tg first increased and then decreased. To characterize the mass loss, the thermal degradation of polycarbonate influenced by nitrogen was investigated through TGA. According to our TGA results, the highest thermal stability was achieved by adding 0.6 wt% of SiO2 to the PC.

Słowa kluczowe:
Polycarbonate,Fiber Carbon,SiO2

Streszczenie:
Abstract
In the current study, we Investigated the adsorption properties of zinc (Zn) and lead (Pb) atoms on the surface of carbonic and non-carbonic graphene using Density functional theory calculations. The procedure for this research can be divided into two sections. First, we calculated the adsorption value of single zinc and lead atoms with such non-carbonic graphene-like structures as Boron-Nitride (BN), Aluminum-Nitride (AlN), Gallium-Nitride (GaN), Silicon-Carbide (SiC), and Silicene. We found that the silicene was more powerful to detect the stated heavy metal atoms compared with others. The calculated adsorption values between the single zinc and lead atoms with silicene monolayer sheet were equal to −0.90 eV and −3.80 eV, respectively. We also used electron transfer calculations after adsorbing the stated heavy metal atoms and found that the calculated charge transfer was equal to 0.42 and 0.12 electrons for Silicene/Pb and Silicene/Zn complex, respectively. The density of states (DOS) results demonstrated that a strong hybridization could occur between the Pb atom and the silicene graphene. Then, we performed DFT calculations to determine the interaction energy between the mentioned metal atoms with pristine carbonic graphene. We found that the interaction in graphene/Zn (−0.09 eV) and graphene/Pb (−0.45 eV) was so weak, especially for graphene and zinc. To overcome this issue, we first activated the surface of graphene by carboxyl and hydroxide group. The interaction energy values between the zinc and lead atoms with graphene-COOH were approximately −0.18 eV and −1.01 eV, respectively, which showed improvements in the adsorption energy. Then, we approached the mentioned metal atoms on the surface of single bondOH-decorated graphene and demonstrated that the interaction energy between the single zinc and lead atoms with graphene-OH were about −0.78 eV and −3.33 eV. In other words, it improved by 755% and 623% compared with graphene/Zn and graphene/Pb, respectively. The strong adsorption between the hydroxyl group and the stated metals atom caused the OH group to be isolated from the graphene surface and become an individual molecule.

Słowa kluczowe:
DFT ,Adsorption