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As investment castings grow in size and complexity, control of wax pattern dimensions becomes increasingly important and difficult. Conventionally, mold design and dimensions are re-worked by trial-and-error procedures until casting dimensions are produced within acceptable dimensional tolerances, increasing the cost of the castings.Nowadays, numerical simulation is an efficient tool for mold design. However, one of the critical difficulties in using computer models for the simulation of wax injection process is the lack of material properties of the wax. Material property measurements were conducted in this study that can be used as input in Moldflow. Then, 3D numerical simulation could be applied in analysis with mold design of thin-walled wax pattern, with high dependability. Simulation results of filling time and the location of the air traps were analyzed. Consequently, best gate location and reasonable gate system were determined. The paper highlighted the effectiveness of simulation in filling optimization and deformation of wax pattern.

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.

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.