Polyimide (PI)/Polyacrylonitrile (PAN) polyblend films were prepared using solution cast technique by spin coating unit. PAN was incorporated within the PI matrix in different concentration i.e. 10 23 , 10 22 , 10 21 , and 1 wt% to prepare polyblend films. The PI polyblend film incorporated with 10 21 wt% PAN and cured at 3308C produces well defined quasi carbon whiskers within the PI matrix. Evidence of the orientation of these carbon whiskers was indicated by optical microscopy and AFM. The improved microhardness, mechanical performance, and hydraulic resistivity of 10 21 wt% PI/PAN polyblend film was observed and attributed to the orientation of these partially carbonized whiskers within PI matrix. The overall property decreases with increasing the concentration of PAN over 10 21 wt%. The incorporation of ultra low concentration of PAN within the PI provides means of achieving excellent combination of microhardness, mechanical, and hydraulic resistance with improved morphology. POLYM. ENG. SCI.,

Molecular dynamics (MD) simulations have been carried out to envisage the sliding friction response of single-wall carbon nanotube (SWCNT) reinforced aluminum (Al) nanocomposites and pure Al. The simulations have been performed with different sliding velocities (0.02-0.11 Å ps −1 ) using the three-layer model. The effect of carbon nanotube (CNT) reinforcement, CNT orientation, and sliding velocities on the coefficient of friction (COF), abrasion rate, and mean square displacement (MSD) have been predicted. The reinforcement of CNT decreased the COF to 0.06 by 45% and the lowest abrasion rate of 0.093%. The reinforcement of CNT in Al parallel to the sliding direction of the Fe rod indenter was found to be more effective for improvement in the tribological properties as compared to perpendicularly reinforced CNT. The increase in sliding velocity of the indenter increased the COF from 0.06 to 0.08 and decreased the abrasion rate from 0.172% to 0.094% for CNT-Al nanocomposites. The ANOVA at the 95% level of confidence revealed that the effect of sliding velocities (0.02-0.11 Å ps −1 ) of indenter was found to be insignificant for the variation in COF and significant for variation of abrasion rate while the type of reinforcement was found to be significant for both COF as well as for the abrasion rate. The MSD revealed the higher migration of Al atoms from the surface of nanocomposites at higher sliding velocity.

A molecular dynamics (MD) simulation method has been used to predict the interfacial behavior of single-wall carbon nanotube (CNT) reinforced aluminum (Al) composites. At the interface of the CNT and the Al, only van der Waals interaction was considered. The effect of CNT volume fraction and chirality on CNT pull-out has been studied for the first time with a proper distinction between them. The length of all the CNTs was kept constant throughout the study. The approach used in this work was validated with an earlier study. The present study revealed that the average pull-out load was found proportional to both the CNT volume fraction as well as the diameter. The smaller diameter CNTs improved the interfacial shear strength (ISS) at lower volume fraction significantly in comparison to that of the larger diameter CNTs. The highest improvement of 38.7% was observed in the ISS during pull-out of (6, 6) CNT at a CNT volume fraction of 3.17%. The average energy increment was found to be increasing with CNT volume fraction and was higher for larger diameter CNTs.

Polyimide (PI) has been extensively investigated as matrix for blends in the search of novel materials for microelectronics and engineering. Tetraethoxysilane (TEOS) is used as precursor for inorganic/organic hybrid material. The processing of PI with TEOS in thin film form offers considerable advantages to the state-of-the art for developing low dielectric constant materials with improved mechanical and hygroscopic properties for microelectronics devices. Taking this into account, the TEOS was incorporated in polyamic acid-a precursor to the PI and a number of properties were evaluated for PI ? TEOS films with different concentrations of TEOS. The films prepared with 10 -3 -10 wt% concentration of TEOS exhibit good overall balance of processing behaviour. The 350°C cured PI ? TEOS films have shown lower dielectric constant with respect to PI. The lower dielectric constant of PI ? TEOS films, as determined by Dielectric Impedance Analyzer was attributed to the in situ generation of air containing silica domains derived from TEOS dispersed within the PI matrix in nano meter regime. FTIR analysis has confirmed the generation of silica while AFM analysis showed the distinct appearance of silica domains dispersed into the PI matrix. The mechanical properties were evaluated by Universal Testing Machine on PI and PI/TEOS films. The films with 10 -3 -1 wt% composition of TEOS showed enhancement in overall mechanical properties while higher concentration i.e. 5 and 10 wt% of TEOS containing PI showed deterioration with respect to pure PI. The water absorption isotherms were measured and their absorption behaviour was correlated with dielectric constant and associated morphology.

No abstract