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Two-dimensional (2D) molybdenum diselenide (MoSe2) as one of the ultrathin transition metal dichalcogenides (TMDs) has attracted considerable attention because of its potential applications in thermoelectric and nano-electronic devices. Here, the thermal conductivity of monolayer MoSe2 and its responses to simulated size and defects are studied by nonequilibrium molecular dynamics simulations. With the increase of sample length, the thermal conductivity of monolayer MoSe2 nanoribbons exhibits an enhancement whereas it is insensitive to the width. At room temperature, the thermal conductivities of monolayer MoSe2 along armchair and zigzag directions are 17.758 and 18.932 W (m K)−1, respectively, which are consistent with previous results. The impact of defects on thermal conductivity has also been studied by varying the concentration of the vacancy from 0.1% to 0.5%. The results show that an increase of the defect concentration will greatly suppress the thermal conductivity. The 0.5% defect concentration with a Mo vacancy can result in a thermal conductivity reduction of ∼43%. Such a study would provide a good insight into the tunable thermal transport for potential applications of not only monolayer MoSe2, but also many other TMDs.

In this article, the design, simulation, fabrication and measurement of an ultrathin and wide band radar metamaterial absorber (MMA) are introduced. The unit of the MMA consists of two different si...

In this paper, we reported on the preparation of porous materials via a reaction under Autogenic Pressure at Elevated Temperature (RAPET) at 700°Cusing natural product and alkoxides as precursors. The RAPET is a new simple efficient method to prepare inorganic materials. The porous carbon and its composite materials were prepared via the method of RAPET using natural products such as sweet potato, coriander, the absorbent cotton and viscose fiber doped by tetrabutyl titanate (TBOT) and tetraethoxysilane (TEOS). The reaction temperature of RAPET was 700°C. The carbon and its composites were studied with scanning electron microscopy (SEM), X-ray diffraction (XRD) and nitrogen adsorption-desorption measurements. The BET surface area of the materials are different from 4m2/g to 405m2/g. The XRD investigation indicates that the phases of the TiO2 in the carbon/TiO2 composites are anatase. The materials show a certain charge-discharge performance.

The coral-like Co3O4 nanowires (CNWs) cluster was synthesized by a novel strategy, in which polyurethane (PU) prepolymer was used as soft template during solvothermal process. The diameters of CNWs samples gradually decreased with the increasing of PU prepolymer. Electrochemical measurements showed that the CNWs possessed the largest specific capacitance of 502.6 F g−1, which is 2.2 times higher than that of bulk Co3O4. Moreover, an all-solid-state asymmetric supercapacitor based on CNWs as positive electrode and activated carbon as negative electrode delivered a high energy density of 18.3 Wh kg−1 and good cycling stability.

GTD222 superalloy is a potential candidate for large-scale complex thin-walled castings with high temperature resistance in the next-generation aircraft engines, due to its excellent creep performance, good oxidation resistance and favorable weldability. The precision casting of GTD222 with a complex thin-wall structure was investigated in this work. The good quality of the final cast indicated that the optimized gating system obtained by numerical simulation was satisfying.

A novel method to remove impurity silicon from aluminum melt by the addition of K2TiF6 was studied. The mechanism for silicon removal is the formation and sedimentation of Ti(Al1-x,Six)3 phase and the removal efficiency is mostly decided by the solubility of silicon in TiAl3 phase, which increases with the increasing of the initial silicon concentration in aluminum melt. The effect of holding temperature on the impurity Si purification efficiency was investigated and the result indicated that the effect of holding temperature is very finite.

In this paper, the relationship between the shrinkage of the thin-walled wax part in the investment casting process (ICP) and the process parameters including mold temperature, melt temperature, packing pressure and holding time are investigated through a series of experiments. The relationship is successfully described by a mathematical regression model which is based on the response surface methodology (RSM). The rationality and adequacy of the mathematical model are checked via analysis of variation (ANOVA) and a sensitivity analysis for process parameters on the dimensional shrinkage variation are conducted which shows that the contribution percentages of mold temperature, melt temperature, packing pressure and holding time are 23.77%, 43.67%, 11.85% and 16.99%, respectively. Additionally, the optimal setting of the process parameters is also obtained by calculating the desirability function. The optimal combination of the mold temperature, melt temperature, packing pressure, and holding time is 74°C, 30°C 25bar, and 5 sec, respectively.

The accuracy of the wax patterns used in the investment casting process has a direct bearing on the accuracy of the final cast part. Wax injection process plays a key role in production of nearly net shape wax pattern. Dimension shrinkage is one of the most significant problems of a wax pattern in terms of dimensional stability in the wax injection molding. This study aimed to determine the effects of injection parameters on the dimensional accuracy of the wax patterns. Linear contractions normal to flow direction and weight of wax patterns were measured and dimensional variations were evaluated. The results highlight it is important that when dealing with thick gates, short packing time appears to be the best way to avoid gate area over packing and dimensional variations, high packing pressure appears to increase expansion and dimensional variation of wax pattern.

Conducting polyaniline (PANI) nanofibers were synthesized by interfacial polymerization with ethanol/water, n-butyl alcohol/water and n-hexyl alcohol/water as reaction media, respectively. It was characterized by four-probe method, FTIR, UV-Vis, XRD, SEM techniques etc. The results showed that the n-butyl alcohol/water system provided a better reaction environment for the preparation of PANI nanofibers. The optimal conductivity value of PANI nanofibers was 3.55 S/cm; the diameter was between 60 and 100nm and the length was from 600nm to several microns. The electromagnetic shielding effectiveness of the PANI nanofibers was from 38dB to 79dB, which was measured by coaxial method from 10KHz to 4GHz. According to the results, the PANI nanofibers could be used as electromagnetic shielding materials.

A kind of radar absorber is designed and produced based on circular microstructure, which is composed of a circular microstructure, carbonyl iron rubber radar absorbing patch and metal backboard composition. Numerical simulation of effect of the circular microstructure on absorbing properties of carbonyl iron rubber radar absorbing patch is performed by means of the time domain finite integral method. Simulated results indicate that by using the holding absorber with the unchanged thickness of 2.5 mm, when the absorber unit size was P = 30 mm and the circular radius was R = 5 mm, the value of the minimum absorption peak can reach −43 dB, −10 dB absorption band shifted from 5.8–9.3 to 4.6–8.2 GHz, changing the parameters of circular microstructure greatly, expanding the absorbing bandwidth of microwave absorbing patch, reducing the reflectivity of resonance frequency. According to the simulation results, the samples are prepared and tested. The test results are in agreement with the simulation results.

In this paper Polyglycol (PG) was used as ‘soft’ template to induce the polymerization of aniline in aqueous ethanol and hence control both the nucleation and growth of polyaniline (PANI) nanofibers. The products were characterized by Transmission electro microscope (TEM) and X-ray diffraction (XRD) techniques. TEM photos showed that the diameter of PANI nanofibers synthesized in pure water is 100nm while that of PANI nanofibers synthesized in aqueous ethanol is 50nm. It revealed that the volume fraction of ethanol showed really important effect on the morphological parameters of the PANI nanofibers. The X-ray diffraction patterns of the PANI nanofibers showed high crystallinity. Moreover, the resulting PANI nanofibers exhibited an unusual electromagnetic loss at the microwave frequency (f = 8.2~12.4 GHz) . Compared with 1.79, the highest electrical loss, tanδe, of the microparticles PANI at 8.47 GHz and 0.72, the highest magnetic loss, tanδm at 10.93 GHz, it was noted that the highest electrical loss, tanδe, of PANI nanofibers reached 3.26 at 10.4 GHz, and the highest magnetic loss, tanδm, was 2.85 at 9.35 GHz. It might arise from order arrangement of polaron as charge carrier caused by nanofibers morphology and can be used for the potential application as microwave absorbing materials.