Key Engineering Materials Vol. 861

Abstract: In recently year, the plastic product is almost made by injection molding method. In this paper, a hot gas was used for mold heating with the gas temperature varied from 200°C to 400°C. The results showed that with three types of gas temperature, the heating rate is high in the first 20 s and the highest heating speed of 8.25°C/s could be achieved with 400°C gas. In all cases, the mold temperature has a limitation after 30 s of heating. In our experiment, the limitation of cavity temperature is 172.2°C. This cavity temperature is almost good for the melt flow in to the cavity, especially with the thin wall molding cases.

Abstract: It is important to improve dynamic performance of rotating machinery by reducing the mass of shaft and increasing the natural frequency. Many studies have focused on dynamic characteristics of shaft in rotating machinery with the utilization of composite material. This paper mainly investigates the structural design and dynamic analysis of a CFRP/Metal hybrid shaft. The finite element method (FEM) has been used to determine the selection of design variables include fiber orientation angle, layers stacking sequence and layers thickness. Also, experimental test was carried out using a FFT analyzer with impact hammers. The differences between the FEM analysis result and the experiment test result were respectively less than 4.5% and 6.3% for the first two natural frequencies; therefore, the results of FEM analysis are acceptable. The results reveal that the fiber orientation angle is the most significant factor affecting the dynamic characteristics of CFRP/Metal hybrid shaft. In addition, there have some effect of the layer stacking sequence on natural frequency.

Abstract: The property of superabsorbent polymer (SAP) was investigated as component of composite material for corrosion control application. The composite material is a multilayer coating consisting of SAP particles, epoxy and hardener. The absorption property of SAP at different concentrations of sodium chloride was measured. It included 3% NaCl concentration, which represent the concentration of salt in sea water, an environment which is corrosive to carbon steel. Results showed decreasing absorbency of SAP at increasing concentration of sodium chloride. Predetermined amount of SAP and epoxy were mixed to obtain a homogenous mixture after which the hardener was added and mixed homogenously to form the composite material’s main component. The composite material was studied for absorption properties in an HDPLE substrate and then later applied onto a carbon steel specimen of size 40 mm x 100 cm and thickness of 0.70 mm using paint brush forming a film on the carbon steel surface. After curing, the film was scratched with a definite length using a sharp knife. Immediately, the samples were exposed to cyclic immersion in 3% sodium chloride solution and subsequent drying to run the corrosion test. Results showed that the composite material was able to control corrosion on the surface of the carbon steel which could be attributed to its self-healing property.

Abstract: This study was aimed to develop conductive packaging for ohmic heating. Polypropylene (PP) was mixed with conductive material (CM) in the ratios of 70:30 (CM30), 75:25 (CM25), and 80:20 (CM20) (w/w), then the conductive bottles were developed using extrusion blow molding process. The bottles were suspended in different sodium sulfate (Na₂SO₄) solutions (0.2, 0.3, and 0.5% w/w) as a transmitting current medium for ohmic heating and heated for 8 min. The CM30 and CM 25 had the highest electrical conductivity compared to the CM20, however the CM20 exhibited best processability, hence it was selected to be used for ohmic heating of orange juice. Different concentrations of Na₂SO₄ solutions had the effects on ohmic heating. The CM20 bottle suspended in 0.2% Na₂SO₄ solution resulted in the most uniform heating and suitable for ohmic processing of orange juice. The new conductive bottles developed could potentially be used for beverage processing by ohmic heating.

Abstract: Sodium niobate catalysts with different morphologies of nanowires and microcubes have been prepared by hydrothermal method. The photocatalytic performance of NaNbO₃ nanowires and microcubes was evaluated by degradation of rhodamine B (RhB) and cationic red X-GRL (CRX). The photodegradation reaction of organic dyes is shown to be kinetically first-order. The as-prepared NaNbO₃ nanowires exhibit higher photo-catalytic activity for organic dyes degradation than NaNbO₃ microcubes, which is attributed to the larger specific surface area and ferroelectric phase structure.

Abstract: In this paper, the effect on the properties of alumina/aluminum cermet by changing the sintering temperature, and comparing the advantages and disadvantages of different characterization methods and their application range, it provides a reference for selecting the characterization technology suitable for alumina/aluminum composites.Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn: the higher the vacuum sintering temperature, the more aluminum material is melted out of the body to form aluminum balls on the surface, and the green body The more severe the cracking. When the sample is sintered at a temperature of 600 °C, the density is the highest and the appearance is the best. When the molding pressure is 40 MPa and the sintering temperature is 700 °C, the microstructure of the sintered alumina/aluminum cermet is better. It can be seen from SEM and EDS analysis that the particles are continuously distributed and the larger one is metal Al, and the particles are discontinuously distributed and finer is Al₂O₃.

Abstract: In this paper, the effect of sintering temperature on the interfacial structure of the composite was investigated and three different formulation groups were used to compare the respective properties. To obtain a composite material with excellent interface, the law between reference number and performance is obtained. Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn: As the temperature increases, the density and hardness increase. The sample melts at 1500 °C, and there is no specific data. When the temperature reaches 1450 °C, the density and hardness reach the highest. When the formulation is Fe:Al₂O₃:SiO₂=18:1:1 and the temperature reaches 1450 °C, the properties of the sample materials are optimized. The density is as high as 95% and the hardness reaches 42.9HBW.

Abstract: Yttrium aluminum garnet is abbreviated as YAG, which has many excellent high temperature characteristics. YAG structural materials and functional materials are promising candidates. In this paper, YAG porous ceramic materials with different mechanical properties are prepared by adjusting the parameters of the sintering process to provide reference for the preparation of high-performance porous ceramics. From the experimental results, the following conclusions can be drawn: when the sintering temperature is 1450°C and the holding time is 2h, the YAG gradient porous ceramics have no deformation and shrinkage, have a regular good shape, and have good strength after sintering. The sintering rate was 8 °C/min and carbon emission temperature is 800°C, the structure of the YAG gradient porous material is good, the pores are uniform, and the strength of the sintered sample is high, The porosity is 25.7%, the compressive strength is 8.12MPa.

Abstract: The effect of forming technology on the properties of quartz sand porous materials were researched with the low grade quartz sand along the Yangtze River via the pressureless sintering method in this paper, which lay technology foundation for researching new heat insulating materials. The wear of ball milling media is investigated through adjusting the ball milling parameter via the weigh methods. The results are shown that the porosity of quartz sand porous materials are decreased with increasing a forming pressure. The porosities of Φ30 and Φ50 materials are decreased with increasing a holding pressure time, however, the porosity decreasing rate of Φ30 is slower than that of Φ50. The porosity of Φ50 is higher than that of Φ30 under same forming conditions. Through optimized the forming conditions, the porosity of sintered Φ50 quartz matrix porous materials reaches 54.52% under the forming pressure for 5MPa and the holding pressure time for 5min.

Abstract: Cermet is an important new engineering material that not only maintains the excellent properties of ceramic materials, but also has the advantages of metal materials. In this paper, the encapsulated alumina-aluminum composite powder was prepared by ball milling and characterized, which laid a foundation for the development of high properties cermet materials. Through the analysis of experimental results, the conclusions are shown when the ball milling time is greater than 3 h, the alumina particles are more evenly distributed around the aluminum powder. the ball milling for 6 h may have reached a limit of the mixing uniformity of the two powder, so the ball milling is determined 6 h as the better ball milling time. Under the ball milling condition of 50 r/min, the distribution of alumina particles around the aluminum powder is more uniform around the aluminum powder than the ball mill under 75 r/min, the ball milling speed is preferably 50 r/min. As the content of aluminum powder increases, the distribution of alumina in aluminum powder is large and uniform, and there is a small amount of pinning. It provides a package-like composite for the preparation of cermet with a wrapped structure and the thermal conduction mechanism of the controlled cermet.