In the present study, the effect of varying titanium dioxide (TiO2) nanoparticles on the dielectric, thermal, and corrosion characteristics of PI-based composites prepared by spark plasma sintering was investigated. The results obtained revealed that the TiO2 nanoparticles were uniformly dispersed within the PI matrix. Addition of TiO2 into the neat PI markedly reduced its dielectric constant and electrical conductivity by 72.7% and 82.3%, respectively, as well as enhancing its breakdown strength by 16.7% at 8 wt% TiO2 loading. The nanocomposites depict better thermal stability and heat-resistance index characteristics when compared to the PI. Additionally, the produced nanocomposites exhibit improved corrosion resistance than that of the neat PI. The remarkable improvement in the dielectric, thermal stability, and corrosion resistance of the nanocomposites is achieved by better dispersion of the TiO2 particles in the polymer matrix. The enhancement in properties suggests TiO2/PI-based nanocomposites potential for a variety of applications in electrical insulation, thermal management, and harsh environment.
Interest has grown in recent time on the development of three-component polymer nanocomposite with enhanced properties. However, the study focuses on the effect of TiO 2 nanofiller on the mechanical, tribological, dielectric, and corrosion resistance properties of boron-free glass fiber (BGF) reinforced polyimide (PI) composite produced with spark plasma sintering route. Microstructure of the samples was examined using scanning electron microscopy. Mechanical, tribological, dielectric, thermal, and corrosion behaviour of the samples were characterized by nanoindenter, ball-on-disc, LCR meter, TGA, and potentiodynamic polarization test, respectively. The SEM results show that the introduction of the nanoparticles into the BGF/PI composite aids in more uniform distribution of the BGF particles within the PI matrix, and thus good interfacial interaction of the glass fiber and the PI matrix structure. Comparing the BGF/PI composite sample with BGF/TiO 2 /PI nanocomposite, it was observed that the nanocomposite depicted better hardness, elastic modulus, low friction coefficient and wear rate, dielectric, and enhanced corrosion properties. With TiO 2 additions, hardness and modulus of the PI composite was improved by 56.6% and 10.1%, respectively. In addition, PI composites filled with TiO 2 depicted a 0.07 coefficient of friction and wear rate of about 67.7% in reduction than that of neat PI and 9.0% in reduction than that of the pristine BGF/PI composites. Improved interactions between the reinforcements and the host matrix are suggested as the possible mechanism resulting to the desirable properties of the three-component PI nanocomposite recorded. Finally, the developed nanocomposite is suggested to be favourable for automobile, aerospace, and microelectronic device applications.
ABSTRACTPolyimide is one of the most high-performance and effective engineering polymers with excellent mechanical, thermal, dielectric, and chemical stability characteristics. However, its further improvement with nanofiller incorporation is of great importance in broadening its candidature for engineering applications. Thus, the review focused on the role of TiO2 nanoparticles on the mechanical, tribological, thermal, permeability, and dielectric performance of polyimide-based nanocomposites. Herein, it is worth knowing that TiO2 is a promising reinforcement material for improving polyimide nanocomposites for advanced engineering applications. Additionally, the authors concluded the study with challenges and recommendations for further improvement of TiO2/polyimide-based nanocomposite characteristics for high-tech fields.KEYWORDS: DielectricmechanicalnanocompositesPolyimidethermal stabilityTiO2 nanoparticlestribology AcknowledgmentsThe authors wish to thank the Centre for Energy and Electric Power (CEEP), Ezebuike Aluminium Company Limited (EACL), and Tshwane University of Technology (TUT) South Africa for their financial support in the course of this work.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationNotes on contributorsVictor E. OgbonnaVictor E. Ogbonna received his BEng and MSc degree in Metallurgical and Materials Engineering from Federal University of Technology, Owerri, Nigeria, in 2012, and University of Lagos, Nigeria, in 2017, respectively. From 2017 to 2019, he was a corrosion control supervisor at the Eclat Oil and Gas, Nigeria. He is currently a Doctoral student and works as a Research Assistant at the Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, South Africa under the mentorship of Professor Popoola. He is an author & co-author of numerous review articles and research articles in high-impact Journals and Conference Proceedings, as well as a reviewer for different Journals. Ogbonna major research interest is on corrosion control engineering, polymer engineering, and advanced materials development/characterization for engineering applications.Patricia I. PopoolaProf Patricia Popoola is a Full Professor at the Department of Chemical, Metallurgical and Materials Engineering, at the Tshwane University of Technology, Pretoria, South Africa. Prof Patricia Popoola obtained her BSc (Honours) degree in Metallurgical and Materials Engineering from Obafemi Awolowo University, Ile- Ife, Nigeria; Master’s and Doctoral degrees in Metallurgical Engineering at the Tshwane University of Technology. Prof Patricia Popoola is an NRF rated researcher (C3-category) with research focus in Advanced Engineering Materials. She is an author/co-author of more than 400 Journal articles (in high-impact Journals and Conference Proceedings) and more than 30 book chapters. As a researcher, her publications have shown dedication to research and development in the engineering field, which is an indication of her ability to work independently. To date, Prof Patricia Popoola has made a lot of impact with her publications, which have been acknowledged both locally and internationally. Google Scholar Citation - (h-index 32, i10-index 183, citations 6097). Currently, she has produced thirty Masters’ and fifteen Doctoral degree graduates. Prof Popoola and her students are recipients of numerous academic excellence awards. Prof Patricia Popoola continues to network with numerous national and international scientists. Mentorship of students remains her prime objective.Olawale M. PopoolaProf Olawale Popoola is an Engineer/technologist/lecturer/author with diverse experience in the Electrical and Power Industry, Oil and Gas Sector, Shipping Building Industry, Education and Quality Management field. A Certified Measurement and Verification Professional (CMVP) with a proven record and extensive knowledge of the energy industry. An author & co-author of numerous scientific publications, as well as a reviewer for different journals. His research interest includes Energy Management, Energy and Behaviour, Renewable and Sustainable Energy, Quality Management, Power electronics application in Power Systems, New Materials as well as Laser Applications. He has made several presentations both locally and internationally. Prof Popoola has received awards, support funding and accolades for his knack and drives for research interest that contributes to sustainable energy/society, especially with a multidisciplinary approach. Furthermore, innovative product development in new materials and load management with emphasis on proficient operation/utilization, effective management, affordability, cost savings, etc. are some high points in his career.Samson O. AdeosunSamson Oluropo Adeosun is a full Professor in the Department of Metallurgical and Materials Engineering, The University of Lagos, Nigeria. His works are in the area of materials development, processing and characterisation. He currently works on biodegradable polymer composites for orthopaedic applications and ferrous/non-ferrous alloy and its composites for high temperature and wears applications. Professor Adeosun is a Registered Engineer with the Council for the Regulation of Engineering in Nigeria (COREN).
This paper presents the mechanical behaviour of novel class composites consisting of ECR-glass type reinforced polyimide (PI) composite loaded with TiO 2 nanoparticles. ECR glass reinforced PI composites were fabricated by adding TiO 2 particles at three different concentrations namely; 2, 4, and 6 wt% using 3D-Turbula dispersion and Spark Plasma Sintering (SPS) method. The morphologies, crystallinity, mechanical, and electrical properties of the produced composites were evaluated using scanning electron microscope (SEM), X-ray diffractometer, nanoindentation test, and LCR meter device. The SEM results revealed that the TiO 2 nanoparticles were homogenously dispersed into the PI composites. The mechanical properties, such as hardness, stiffness, and elastic modulus of the pure PI and ECR glass reinforced PI composite was improved by the incorporation of TiO 2 nanoparticles. Maximum hardness and elastic modulus values of 2.19 GPa and 13.99 GP, respectively, was observed in ECR reinforced PI composited loaded with 6 wt% TiO 2 nanoparticles. In addition, ECR glass reinforced PI composites with 6 wt% TiO 2 nanoparticles depicted the lowest dielectric constant (1.18), dielectric loss (1.14) and electrical conductivity (3.16 × 10 −6 S/cm). Finally, the findings suggest the easy processability of PI nanocomposites and their potential for mechanical and electrical insulation applications.
This research evaluates the influence of process parameters of the spark plasma sintering (SPS) technique on the densification and hardness properties of ECR/TiO2/PI nanocomposite. Taguchi's design of experiment was employed for designing the sintering process, while analysis of variance (ANOVA) was adopted to evaluate the contribution of the factor variables to the response variable of hardness and density. 10 wt% ECR-glass and 4 wt% TiO2 were used as reinforcements in the polyimide matrix at varying pressure and temperature for the physical experiment. The sintered samples were examined using a scanning electron microscope, nanoindentation tests, and an Archimedes-based density tester. The optimization was performed on total 9 numbers of runs of experiments. The most desirable SPS processing parameters were recorded at 320 °C and a pressure of 30 MPa. Under this processing condition, a density of 1.49 g/cm3 (relative density of 98.7%), Vickers hardness, and nanoindentation hardness value of 33.46 HV and 361.30 MPa, respectively, were obtained. This research work suggests a facile way to produce high-performance PI nanocomposite for various engineering applications, such as mechanical load-bearing and insulation applications.
The rational design of small molecules that target specific DNA sequences is a promising strategy to modulate gene expression. This report focuses on a diamidinobenzimidazole compound, whose selective binding to the minor groove of AT DNA sequences holds broad significance in the molecular recognition of AT-rich human promoter sequences. The objective of this study is to provide a more detailed and systematized understanding, at an atomic level, of the molecular recognition mechanism of different AT-specific sequences by a rationally designed minor groove binder. The specialized method of X-ray crystallography was utilized to investigate how the sequence-dependent recognition properties in general, A-tract, and alternating AT sequences affect the binding of diamidinobenzimidazole in the DNA minor groove. While general and A-tract AT sequences give a narrower minor groove, the alternating AT sequences intrinsically have a wider minor groove which typically constricts upon binding. A strong and direct hydrogen bond between the N-H of the benzimidazole and an H-bond acceptor atom in the minor groove is essential for DNA recognition in all sequences described. In addition, the diamidine compound specifically utilizes an interfacial water molecule for its DNA binding. DNA complexes of AATT and AAAAAA recognition sites show that the diamidine compound can bind in two possible orientations with a preference for water-assisted hydrogen bonding at either cationic end. The complex structures of AAATTT, ATAT, ATATAT, and AAAA are bound in a singular orientation. Analysis of the helical parameters shows a minor groove expansion of about 1 Å across all the nonalternating DNA complexes. The results from this systematic approach will convey a greater understanding of the specific recognition of a diverse array of AT-rich sequences by small molecules and more insight into the design of small molecules with enhanced specificity to AT and mixed DNA sequences.
High entropy alloy developed with spark plasma sintering was modelled with COMSOL Multiphysics. This focus at examining the effect of spark plasma sintering fabrication parameters on thermal and mechanical stress distribution in the sintered Al 20 Cr 20 Fe 25 Ni 25 Mn 10 high entropy alloy (HEA). And to achieve this, a fully thermal-electrical-mechanical integrated and dynamic finite element model (FEM) was adopted. The simulation utilised the optimal parameters employed in the laboratory to produce the samples. The geometry for the modelling was 2D axisymmetric as the parameters were based on temperature-dependent characteristics noting that only the sintered sample was modelled and simulated in order not to simplify the modelling. The FEM maintained constant sintering temperature, pressure, and heating rate but concentrated on the impact of residence durations. To verify the simulation results, morphological alterations and densification validation tests were conducted. The microstructural characterization of the sintered sample demonstrated the relationship between the stress distribution and computational temperature found in the current FEM. Noting good particle-to-particle necking. From the model, results showed that the sintered sample at different points depicted a yield stress far greater than the von Mises stress with least thermal stress at 30 MPa. This validate that the developed sample is mechanically stable based on the factor of safety failure criterion and design. However, the study recommend that further work should be conducted considering different sintering pressure of variation 10 to 30 MPa.
In the current study, the enhancement of the mechanical and tribological behavior of polyimide (PI) composites with varying TiO2 nanoparticles fabricated with spark plasma sintering (SPS) technique was examined. The morphology, mechanical, and tribology of the produced nanocomposites were characterized using scanning electron microscope (SEM), nanoindenter, and tribometer analyzer. The SEM result shows that the TiO2 were diffused uniformly in the polymer matrix. The hardness and modulus of the PI increased with the incorporation of the TiO2 nanoparticles by 314.1% and 76.4%, respectively. Furthermore, the friction coefficient and wear resistance of the nanocomposites was remarkably improved with the TiO2 incorporation.
'%3e%3cpath fill='%23001489' d='M0 0v6h9V0z'/%3e%3cpath fill='%23e03c31' d='M0 0v3h9V0z'/%3e%3cg stroke='%23fff' stroke-width='2'%3e%3cpath id='d' d='m0 0 4.5 3L0 6m4.5-3H9'/%3e%3cuse xlink:href='%23b' stroke='%23ffb81c' clip-path='url(%23c)'/%3e%3c/g%3e%3cuse xlink:href='%23d' fill='none' stroke='%23007749' stroke-width='1.2'/%3e%3c/g%3e%3c/svg%3e)
