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Recently multielements solid solution has shown significant improvement to the mechanical properties of parent MAX phases. Therefore, in this work, five elements with different radii were incorporated to check the effect on properties of MAX phases. (Nb0.8Ti0.05Zr0.05Mo0.05Hf0.05)4AlC3 (MAXHf) and (Nb0.8Ti0.05Zr0.05Mo0.05Ta0.05)4AlC3 (MAXTa) ceramics were successfully synthesized using the spark plasma sintering technique. The microstructure and elemental map analysis results further confirmed that the five transition metals were successfully solid soluted at the M‐sites of the hexagonal M4AlC3 unit cell. The mean elemental compositions for M‐site elements were achieved as Nb0.85Ti0.052Zr0.035Mo0.027Hf0.036 and Nb0.847Ti0.051Zr0.043Mo0.025Ta0.033 for MAXHf and MAXTa ceramics, respectively. The electrical and thermal conductivities of multielement solid solution MAX phases were decreased compared to pure Nb4AlC3. However, Mechanical properties were significantly increased with the solid solution of five transition metals. The fracture toughness, flexural strength, compressive strength and Vickers hardness (10 N) of MAXHf and MAXTa ceramics were achieved as 8.87 MPa m1/2, 448 MPa, 867 MPa, 6.5 GPa and 10.36 MPa m1/2, 557 MPa, 1039 MPa, 8.2 GPa, respectively. The enhanced mechanical properties suggest the effectiveness of the solid solution strengthening effect and provide new opportunities to further tailor the mechanical properties of the MAX phase ceramics. [ABSTRACT FROM AUTHOR]

In this paper, the results of our research were presented into the sliding wear behaviors of reinforced epoxy composites made with 3D networked carbon fibers ornamented with nanowires of cobalt oxides (NWRs@CFs). Composites are made using the cast-in-place method. Under different normal loads and sliding velocities, these composites' wear and friction coefficient performances are assessed. Tests were performed at 400 rpm spindle speed, 10, 20, and 30 N normal load, and a duration of 300 seconds. Pure epoxy exhibits wear rates of 0.449, 0.481, and 0.501 * 10-5 mm³/Nm at 10, 20, and 30N. Conversely, 3D CFs/epoxy composites exhibit lower wear rates (0.334, 0.360, and 0.390 * 10-5 mm³/Nm) at the same pressure. The epoxy composites of NWRs@CFs wear less, measuring 2.1, 3.5, and 0.4 * 10-5 mm³/Nm under applied loads. The effects of speed on the tribological characteristics were also studied, the friction coefficients for 400, 800, and 600 rpm at 10 N. Pure Epoxy has fraction coefficients of 0.449, 0.494, and 0.552µ at 400, 800, and 600 rpm. In comparison, three-dimensional carbon fibers and epoxy composites show reduced wear rates (0.334, 0.376, and 0.304 µ) under identical loads. Epoxy composites of NWRs@CFs have friction coefficients of 0.261, 0.304, and 0.332µ. Pure epoxy has high wear, indicating less friction resistance. [ABSTRACT FROM AUTHOR]

Applications of carbon fiber reinforced epoxy-based composites have been highly restricted due to their high cost in the manufacturing process. Cellulose, a cheap and abundant material from nature, shows excellent mechanical property and structural stability. It shows huge potentials in substituting carbon fiber/epoxy with cellulose/epoxy composites to fulfill the great demands for composites with good performance and a reasonable price. This paper first reviews works about the preparation and regulation of cellulose materials based on the very basic concepts of top-down and bottom-up. Then research about the interfacial regulation between cellulose and epoxy has been discussed in two broad classes of covalent and non-covalent modification. Finally, the enhancement effect of cellulose reinforcement has been discussed in two broad classes of dispersive reinforcement and continuous phase reinforcement. The latter can be further divided into three classes according to the dimension feature (1D, 2D, and 3D). The results show that the nanolization of cellulose is necessary for guaranteeing the strength of composites, while the formation of macroscopic and continuous structures can ensure Young’s modulus of composites.

In this paper, the literature will be reviewed, and various research works conducted to improve the thermal performance of flat panel solar collectors will be summarized. It will be summarized in more than one way. Firstly, by design using different methodologies and methods to improve the efficiency and the thermal performance of the solar collector by introducing twisted strips that cause increased mixing. Fluids and Friction for FPSCs. To increase heat transfer as well as use porous materials to enhance heat and improve the effectiveness of absorption panels to absorb as much solar radiation as possible as well as thermal insulation methods to reduce losses to surrounding areas. And improve the permeability of the glass cover. Secondly, the use of nanofluids enhances the performance of flat solar collectors instead of the core fluid, and its effect is to improve the thermophysical properties such as thermal conductivity by summarizing previous research using mono nanofluids and hybrid nanofluids. Through studies and research related to the use of mono nanofluids, it was noted that the best nanofluids are those that use CuO and Al2O3 particles due to their ease of availability and high thermal conductivity. As for hybrid nanofluids, the best fluids are (CuO + Al2O3/water) for the same reason above. As a result of design improvements and the use of nanofluids, temperatures up to (75C°) were obtained. [ABSTRACT FROM AUTHOR]

The use of wickless heat pipe heat exchangers has been improving a wide range of thermal applications such as solar water heaters. Therefore, more scientific research needs to be conducted to improve its performance. In the present study, a wickless heat pipe heat exchanger test rig has been designed and fabricated to investigate the effect of different parameters on its performance. Two different heat pipe working fluids have been used namely pure water and water with nanoparticles (Al2O3) using different fluid volume ratios (20%,40%,60%,80%, and 100%). The concentrations of the nanoparticles in water range between 1.3 and 7 % wt. For the heat exchanger, various inlet hot air temperatures (50, 55, and 60 ℃) have been tested at the hot side (heat pipe evaporator) whereas the inlet temperature of the cold side (heat pipe condenser) has been maintained at 20 ℃. The effect of airflow Reynolds number has also been examined with a range of 2583-20664. Results showed that the best heat exchanger effectiveness is achieved at a Reynolds number of 10332 and nanoparticles concentration of 7% wt. Also, the use of nanoparticles reduced the thermal resistance in the heat pipe due to the significant reduction in its surface temperature compared to that of pure water. [ABSTRACT FROM AUTHOR]

A one-step thermo-chemical approach was employed to synthesize ZnFe2O4/rGO nanohybrids with increasing GO concentrations (0, 10, 20, and 30 wt. %). This approach was used to reduce GO while simultaneously synthesizing ZnFe2O4 nanoparticles and adhering them to rGO sheets. The nanohybrids were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and impedance analyzer. The XRD patterns confirmed the formation of a face-centered cubic single phase of ZnFe2O4/rGO nanohybrid and SEM images revealed the decoration of ZnFe2O4/rGO nanoparticles on rGO sheets. The dielectric properties improved as GO loadings increased. At 100 Hz, the dielectric constant and dielectric loss increased to 2.04 × 104 and 1.20 × 105 for ZnFe2O4/rGO nanohybrid with 30 wt. % of GO when compared to pure ZnFe2O4 of 4.23 × 102 and 1.92 × 103, respectively. The feasibility of this method implies that this nanohybrid can be used for charge storage devices. [ABSTRACT FROM AUTHOR]

NiFe 2 O 4 /MWCNTs nanohybrids were synthesized via novel one step ultrasonication assisted method using ortho-xylene as a dispersive medium with varying MWCNTs concentration (0.0%, 1.0%, 1.5%, 2.0% and 2.5%). The nanohybrids were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Impedance Analyzer techniques. XRD indexed patterns confirmed the formation of NiFe 2 O 4 /MWCNTs nanohybrid. The SEM images showed the decoration of nickel ferrite nanoparticles on MWCNTs. The FTIR results show two absorption bands. The Cole-Cole plots of impedance show the resistance was only due to the grain boundary contribution. The dielectric properties were found to be increasing with increasing MWCNTs concentration. For 2.5% MWCNTs concentration, dielectric constant and loss 1.06×10 5 , 1.99×10 6 were achieved as compared to pure nickel ferrite 6.17×10 3 , 3.87×10 4 , respectively. Such increase in the dielectric properties renders its application at high frequency [ABSTRACT FROM AUTHOR]