Key Engineering Materials Vol. 814

Abstract: Microcrystalline graphite (MG) was used as raw material and oxidated by Hummers method. And further the graphene oxide (GO) was obtained by ultrasonic stripping. The TP modified graphene (TPG) was prepared by the surface grafting of pure natural green tea extract tea polyphenols (TP) on the surface of GO. Finally, the TPG/epoxy resin composite was prepared by solution blending and heat-curing moulding method.The characterization of structure and properties of TPG was analyzed by X ray diffraction pattern (XRD), infrared spectroscopy (FT-IR), thermo gravimetric analysis (TGA) and X ray photoelectron spectroscopy (XPS). A universal material testing machine was used to test the mechanical properties of epoxy resin composites with different addition of TPG. Field emission scanning electron microscopy (SEM) was used to observe the tensile-sectional morphology of the composites. The thermal stability of the composites was investigated by thermogravimetry and thermal dilatometer. The experimental results showed that the TP molecule was successfully grafted on the oxygen-containing functional groups of the GO surface through the phenolic hydroxyl group.When the addition of TPG was 1.0 wt%, the decomposition temperature of the epoxy resin was increased by 22.2 °C,and the surface resistivity decreased from 1.35×10¹⁴ Ω·m to 1.7×10⁹ Ω·m. When the added amount of TPG was 0.5 wt%, the tensile strength of composites was increased by 13.5% reaching 59.85 MPa.

Abstract: Alumina-Y-TZP composites between 0 to 25 vol% Y-TZP content produced via conventional two-stage sintering with T₁ ranging between 1400°C and 1550°C, heating rate of 20°C/min, followed by T₂ of 1350°C and 12 hours dwelling time. The microstructure, density, Vickers hardness (H_V), Young’s modulus (E) and fracture toughness (K_IC) of the sintered samples were then evaluated. It is observed that all samples up to 10 vol% Y-TZP achieved > 98% T.D. as the T₁ increases. Samples with Y-TZP content above 10 vol% resulted in a significant decrease in density and hardness. Samples with ≤ 10 vol% Y-TZP sintered at T₁ of 1450°C was able to achieve density > 98% T.D., Vickers hardness > 18 GPa and Young’s modulus > 380 GPa and fracture toughness > 6 MPam^1/2 when compared to pure Al₂O₃ ceramics.

Abstract: This article aims to improve the bonding strength between metal and plastic,the metal substrate is subjected to high-energy shot peening to make the surface self-nitrified, and the orthogonal test scheme was designed based on the process parameters of high energy shot peening and spraying. After molding, the bonding strength of the metal matrix composite was tested by the vertical stretching method. We studied the effect of the cast steel shot diameter, the shot peening pressure, the shot peening time and the plasticizing temperature on the bonding strength of the composite. The combination of process parameters was determined when the bonding strength was optimized, then use the numerical fitting method to predict the combination of process parameters when the bonding strength is the highest, the optimization results are verified by experiments. The results show that the diameter of the cast steel shot is 4.96mm-5.04mm, the shot peening pressure is 0.49MPa-0.51MPa, the shot peening time is 10.9min-11.08min, and the plasticizing temperature is 278.2°C-282°C. The bonding strength of the composite is optimal Keywords: Metal matrix composite, High-energy shot peening, Press forming; Bonding strength, Process optimization

Abstract: In this paper, the effect of raw materaisl on the properties of coated Al₂O₃/Al cermet materials were investigated, the raw materials were prepared via different methods, which provide a reference for obtaining higher performance cermet materials. Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn, the density of the composite material increases first and then decreases with the increase of the molding pressure. When the molding pressure is 30 MPa, the density of the composite material reaches the maximum value, that is 93.5%. The greater the applied pressure, the more compact the aluminum powder and alumina powder, and the longer the tissue composition, the more uniform. there is no crack in the c-picture, and there are cracks in the a and b pictures. The microstructure of metal matrix composites prepared at different molding pressures is also different. Sintering of the green body formed at 30 MPa resulted in relatively few cracks and voids in the material. The surface hardness of the composite material increases first and then decreases with the increase of the molding pressure, and the surface hardness of the composite material reaches a maximum value (875 HV) at a molding pressure of 30 MPa.

Abstract: Composite material is considered as a complex system with corresponding system attributes. The systematization of studies on the structure formation of composites is carried out to ensure the fundamentalization of building materials based on the use of analytical methods. The experience of using the linearization of kinetic processes in polydisperse systems is given. The most important cases are considered. Examples of parametric identification of a table-specified and nonlinear kinetic processes are given. The results were used in the development of special purpose composite materials.

Abstract: The structural and phase changes in the carbon nanomaterial of the “Taunit” series were studied depending on the time of mechanochemical treatment (MCT) in a high-speed ball mill. The possibility of the formation of a carbon material with an amorphous and diamond-like component is shown.

Abstract: In this paper, evolution of optical and electrical properties of diamond-like carbon (DLC) films deposited by ECR-CVD system are reported. By varying the deposition different substrates bias (0, -55, -100 V) and volume amount of C₂H₂ from 40 to 55 cc onto substrate Si/TiN and quarts. The structure of the DLC films were analyzed from Raman spectroscopy. DLC films deposited bias at-100 V and C₂H₂ at 40 cc show excellent optical transmittance and high resistivity. As a result, I_D/I_G ratio corresponds to the optical transmittance and resistivity with I_D/I_G ratio decreased making the film like to the diamond. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting substrates bias and volume C₂H₂, is important to many applications, which is improve film properties.

Abstract: We investigate the hybrid structure composed of single-walled carbon nanotubes (SWCNTs) and monolayer graphene to highly increase flow-induced voltage generation by an ionic droplet on these hybrid carbon membranes. These properties were characterized by Raman spectra, a field-emission-scanning probe, and optical microscope. We demonstrated flow-induced voltage generation on the hybrid structure at various ion concentrations of NaCl. The generated voltage for the membrane of SWCNTs/graphene/SWCNTs was 8.636 and 4.92 times larger than for the SWCNTs, and graphene/SWCNTs membranes, respectively, based on the highly increased electron dragging mechanism.

Abstract: Dye-sensitized solar cells have better development prospects than silicon cells, and the main structural components of nanoporous semiconductor films are particularly important. In this experimental study, we used tin dioxide film and investigated the effect of preparing this film on dye-sensitized solar cells under different conditions. Furthermore, SnO₂ powder was prepared through hydrothermal method, and an experiment was conducted through a controlled variable method. The properties of the obtained tin dioxide powder were characterized by SEM, 3D ultradepth microscopy, and XRD. An XRD peak is displayed as tetragonal-phase rutile-type SnO₂, and the SEM indicates that the powder grain size is several nanometers. With the increase in reaction time, the film gradually became flat and uniform from only a small amount of powder coating. At the reaction time of 8 days, the integrity and flatness of the film were optimal, and the pore size was uniform. Moreover, the specific surface area was large. In summary, the reaction time of 8 days is suitable for membrane growth.