All-Carbon Conductors for Electronic and Electrical Wiring Applications

Electrical conductors based on carbons have recently attracted a growing interest due to the prospect of replacing metals. Electrical conductors without metals could represent not only an alternative for traditional wiring, but also a step forward in the progress and advancing of technology. This result can be achieved by combining high electrical conductivity with other properties, that are dexterity, light weight, environmental stability, high strength and flexibility. As the best mechanical properties, high electrical/thermal conductivity of the assembled fibers are all generally associated with low concentration of defects in the fiber backbone and in the individual carbon “building blocks”, a special attention is paid to an empirical relationship between morphology/structure/composition and the electrical properties. In this review, starting from the beginning, from the late 19th century, when the carbon filaments became the lights for urban streets, some of the recent developments in the field of “all-carbon” electrical conductors are discussed. Such conductors can be obtained by assembling nanoscale carbons (i.e., carbon nanotubes, graphene) into macroscopic fibers, yarns and ropes (hereafter fibers). In this perspective, the role played by the chemistry in particular by means of the molecularlevel control and doping, is emphasized. This contribution elucidates most recent results in the field, and envisages new potential applications

Inorganic cesium lead mixed halide based perovskite solar materials modified with functional silver iodide

Inorganic CsPbIBr2 perovskites have recently attracted enormous attention as a viable alternative material for optoelectronic applications due to their higher efficiency, thermal stability, suitable bandgap, and proper optical absorption. However, the CsPbIBr2 perovskite films fabricated using a one-step deposition technique is usually comprised of small grain size with a large number of grain boundaries and compositional defects. In this work, silver iodide (AgI) will be incorporated as an additive into the CsPbIBr2 perovskite precursor solution to prepare the unique perovskite CsI(PbBr2)1-x(AgI)x. The AgI additive in the precursor solution works as a nucleation promoter which will help the perovskite to grow and merge into a continuous film with reduced defects. With detailed characterizations, we found that incorporating AgI additive resulted in a uniform perovskite film with fewer grain boundaries, increased grain size, crystallinity, optical absorption while decreasing carrier recombination and trap density. Using the AgI in an optimum amount, we fabricated CsPbIBr2 perovskite solar cells (PSCs) with a simple structure and achieved a power conversion efficiency (PCE) of 7.2% with a reduced hysteresis index. This work offers an alternative approach towards preparing high-quality CsPbIBr2 perovskite films for solar cells with higher stability and other optoelectronic applications

Synthesis and fabrication of self-sustainable triboelectric energy case for powering smart electronic devices

In recent times, Triboelectric Nanogenerators (TENG) have attained the focus of the scientific community due to its potential as a medium to harvest mechanical energy from the ambient environment. Human motion has been attributed as a source of mechanical energy to drive electronic devices and sensors through TENG. Based on the principles of single electrode TENG, we have developed a Triboelectricity based Stepping and Tapping Energy Case (TESTEC) which magnifies the prospect to power touch electronic devices by utilizing finger tapping and stepping motion. This novel case was constructed with two single electrode TENG operating through the triboelectric mechanism between human skin and Polyethylene terephthalate (PET) film on the front part and Nitrile Butadiene Rubber (NBR) and PET film on the back part. This cost effective device was further tested by attaching with a cell phone at variable load frequency, airgap and finger combinations where the output response increased with the increased frequencies (60–240 BPM) and air gap (1 cm–5 cm). Maximum output voltages of 14.8 V and 50.8 V were obtained for the front and back parts, respectively. Besides, maximum output powers were observed to be 3.78 W/m2 at 0.46 MΩ and 6.21 W/m2 at 1.02 MΩ, respectively. Also, the device was tested by integrating with conventional electronic components including capacitors, bridge rectifiers and 15 LEDs. Based on the results, a electrical circuit has been proposed to power touch cell phones. The device was further modified using Silver (Ag) nanoparticles in the front part. The modified TESTEC provided higher output response compared to the primary TESTEC. The TESTEC can be a self sustainable way to power touch electronic devices which can reudce the necessity to charge electronics devices in the conventional way

A Qualitative Study of Bangladeshi Diaspora in Malaysia: The Role of Social Networking

The theoretical exploration of diaspora entrepreneurship is still in its infancy stage, and hence the underlying mechanisms underpinning strategic behaviours such as resource attrition and networking in this context remain limited. We thus explore the social networking behaviours of diaspora entrepreneurs, and the effect of these networks on entrepreneurial determinants. In doing so, we investigate Bangladeshi diaspora communities and their social interactions and network ecosystem in the Malaysian context. Noting the nuanced and contextual underpinnings of such a study, we examine diaspora entrepreneurship qualitatively, by employing a series of interviews with Bangladeshi diaspora entrepreneurs in Malaysia. Our study demonstrates that the Bangladeshi diaspora entrepreneurs in Malaysia benefit from two types social networking: (i) ethnic-tie, and (ii) non-co-ethnic tie. Our findings additionally establish that these social ties are built on specific network motivators: (i) friendship and personal/familial tie, and (ii) economic interest and mutual benefits. Our study highlights a number of conditions which can help to support entrepreneurship in the diaspora community

KNN based piezo-triboelectric lead-free hybrid energy films

In recent times, the triboelectric and piezoelectric effects have garnered significant attention towards developing advanced material composites for energy harvesting and sensory applications. In this work, potassium sodium niobate (KNN) based energy films (EF) have been developed to utilize mechanical energy while simultaneously taking advantage of triboelectric and piezoelectric mechanisms. The KNN particles were synthesized using a wet ball milling technique and then incorporated into a polyvinylidene difluoride (PVDF) matrix together with addition of multi wall carbon nanotubes (MWCNT). The film was used to develop a piezoelectric nanogenerator (PENG) fitted with copper electrodes. The piezoelectric output of the film was further tested utilizing copper electrodes, at variable tapping frequency (60 BPM to 240 BPM) and pressure (10–40 psig) were used when activating the pneumatic piston. The open circuit voltage increased with the increase of both tapping frequency and pressure. The maximum piezoelectric output voltage was observed to be 35.3 V while the maximum current was noted as 15.8 µA. The films also showed unique output signals for different types of deformations performed under hand pressure. The film was further utilized to build a piezo-triboelectric hybrid nanogenerator to check its hybrid performance. The maximum output was observed to be 54.1 V and 29.4 µA. This film was integrated with conventional electronic components (bridge rectifiers, resistors, and capacitors) and tested for its ability to harvest energy. The hybrid nanogenerator can charge a 0.1 µF capacitor to 9.4 V in 60 s. The optimum output power for the device was measured to be 0.164 W. The film was further attached with a Kapton film and showed a hybrid output of 113.2 V. This experiment endorsed the potential of the KNN based energy films for multifunctional applications like force, pressure, and motion sensing as well as lead free energy harvesting

On the thermogravimetric analysis of polymers: Polyethylene oxide powder and nanofibers

Thermogravimetric analysis of polyethylene oxide (powder and nanofibers obtained by force spinning water or chloroform solutions of polyethylene oxide) was studied using different theoretical models such as Friedman and Flynn-Wall-Ozawa. A semiempirical approach for estimating the “sigmoid activation energy” from the thermal degradation was suggested and confirmed by the experimental data on PEO powder and nanofibers\u27 mats. The equation allowed for calculating a “sigmoid activation energy” from a single thermogram using a single heating rate without requiring any model for the actual complex set of chemical reactions involved in the thermal degradation process. For PEO (powder and nanofibers obtained from water solutions), the “sigmoid activation energy” increased as the heating rate was increased. The sigmoid activation energy for PEO mats obtained from chloroform solutions exhibited a small decrease as the heating rate was increased. Thermograms\u27 derivatives were fitted to determine the coordinates of the inflection points. The “sigmoid activation energy” was compared to the activation energy determined from the Flynn-Wall-Ozawa model. Similarities between the thermal degradation of polyethylene oxide powder and of the nanofibers obtained from water solutions were discussed. Significant differences between the sigmoid activation energies of the mats obtained from water and chloroform solutions were reported

A CMOS power splitter for 2,45 GHz ISM band RFID reader in 0,18 µm CMOS technology

Identifikacija radio frekvencije (RFID) je jedna od najbrže rastućih tehnologija uporabljiva u gotovo svakom sektoru za pohranu i bežično uzimanje podataka. Trenutni napredak u CMOS tehnologiji pomaže znanstvenicima i tehnolozima smanjiti dimenzije i poboljšati funkcionalnost RFID sklopova. U ovom radu ilustrirana je konstrukcija jednog RF-CMOS razdvajača snage električnog kruga u 0,18 µm Silterra RF-CMOS tehnologiji za 2,45 GHz RFID čitač. Wilkinsonov razdjelnik snage izabran je za predloženi razdvajač snage električnog kruga s induktorima i kondenzatorima na čipu. Predloženi razdvajač snage ostvaruje najveći gubitak zbog umetanja od 10 dB. AWR Microwave Office® koristi se za simulaciju električnog kruga i za određivanje njegovih S-parametara. Za konstruiranje induktora s točnim vrijednostima u 2,45 GHz rabljen je Sonnet® dok je Cadence® rabljen za razmještaj kondenzatora i otpornika.Radio frequency identification (RFID) is one of the most rapidly growing technologies to be utilized in almost every sector for storing and retrieving data wirelessly. Current advancements in CMOS technology help the scientists and technologists to reduce the size and improve the functionalities of the RFID circuits. In this paper, the design of an RF-CMOS power splitter circuit in 0,18 µm Silterra RF-CMOS technology is illustrated for a 2,45 GHz RFID reader. Wilkinson power divider is chosen for the proposed power splitter circuit with on-chip inductors and capacitors. The proposed power splitter achieves a maximum insertion loss of 10 dB. AWR Microwave Office® is used for the simulation of the circuit and for determination of its S-parameters. To design the inductors with accurate values in 2,45 GHz Sonnet® is used whereas Cadence® is used for capacitor and resistor layout