Fatemeh Mohtaram, Vahid Mottaghitalab, Gholamreza Baghersalimi, Akbar Khodaparast Haghi,
Volume 33, Issue 3 (Journal of Advanced Materials- winter 2015)
Abstract
Today, along with the advances in circuit printing technology it has become possible to fabricate band lines integrated with circuit elements. The band lines are known as microstrip lines and the whole packages are called microstrip antennas. The microstrip antennas have three layers, including conductive patch layer, dielectric sub layer, and ground conductive layer. One of the most important problems of prevalent antennas is their inflexibility, which was addressed in the current paper using textile based structure with proper flexibility and flexural stiffness. This was done using ink jet printing techniques followed by electrolytic plating to provide diverse antenna patterns based on nickel particles. The coated surface was characterized by scanning electron microscope, elemental analysis and optical microscope. Moreover, the washing fastness and the other physical and mechanical specifications were measured using standard techniques. The elemental analysis of metal-coated fabric clearly indicated a high level of nickel. Furthermore, the morphological investigation proved the formation of homogenous nickel nanoparticle in a diameter range of 100-500 nm with an evident boundary and semi-spherical shape. In addition, the cumulative presence of particles in a sequence followed a cabbage-like structure originating from metallic crystals. The washing fastness tests revealed a high stability in electrical resistance after several washing steps. In the meantime, the antenna gain and the corresponding bandwidth were measured using spectrum analyzer. The results indicated a 1 kHz increase in bandwidth and 11 dB decrease in antenna gain for a large size compared to a small one. Meanwhile, the bandwidth of rectangular pattern showed a 0.2 kHz increase and 2.5 kHz decrease compared to spiral pattern. Finally, the four-probe electrical conductivity test demonstrated a high level of conductivity around 2632 S/cm.
F. Haghdoost, V. Mottaghitalab,
Volume 34, Issue 2 (Journal of Advanced Materials- Summer 2015)
Abstract
In the last decade, a significant progress has been made in the wearable medical devices. Scientists are extensively involved in the design of the flexible instruments equipped with garments to fulfill the daily needs and requirements. The fulfillment of this demand particularly needs a conductive fabric substrate with a high level of homogeneity, and the lowest barrier against electrical current. In this study, textile based ECG electrode was prepared by screen printing of activator followed by electroless plating of copper particles. The data acquisition showed the best outcome with pH=8.5 and the plating temperature
of 70 ˚C. The electrical resistance showed a range around 0.08 Ω/sq, which sounds quite proper for ECG signal acquisition since the potential difference according to heart activity on skin surface is in milivolt range. We tested the cardiac signal with a reference electrode of Electroshock monitoring system and the results revealed a very high quality receiving signal. Employing of these types of sensors in textile surface due to their flexibility can bring the users more freedom of action.
M. Mottaghi, M. Ahmadian,
Volume 36, Issue 1 (Journal of Advanced Materials-Spring 2017)
Abstract
In this research, the wear behavior of commercial grades of WC-10wt%Co (H10F), WC-40vol%Co and WC-40vol%FeAl-B composites with different amounts of boron from zero to 1000 ppm has been investigated by the pin on disk test method at high temperature. The wear tests were done under load of 40 N, a distance of 100 m and at ambient temperature, 200 ̊C and 300 ̊C. Wear surfaces were examined by scanning electron microscopy. The results showed that the wear resistance of all composites decreased with increasing temperature. The boron free WC-40vol%FeAl composite showed the lowest wear resistance at all ranges of temperature. In the presence of boron up to 500 ppm in iron-aluminide matrix, the high temperature wear resistance of these composites improves and the wear mechanisms changes from particle pullout into abrasive state. The toughness enhancement of these composites and plasticity enhancement of iron aluminide in the presence of boron, leads to better link of the interface of FeAl matrix and tungsten carbide particles, and thus increases the wear resistance of these composites. WC-40vol% FeAl-500ppmB composite has a higher wear resistance at high temperature than WC-40vol% Co and commercial WC-10wt% Co.
