The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Elements Of X Ray Diffraction

The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.

Advanced Thermoelectric Design: From Materials and Structures to Devices

Encountering development: the making and unmaking of the Third World

Leu-M

Heterolayered Composite of Carbon Nanofibers Sandwiched between Poly(ethylene terephthalate) and Polyurethane for Flexible Electromagnetic Shielding Application

Highly flexible, bendable, stretchable, and ultralightweight microwave absorbers (MA) that can handle harsh environments are essential for conformal surface coating in aerospace and defence industries. Hence, crystalline carbon nanotubes (CNTs) are grown on carbon fibers (CFs) using the chemical vapour deposition technique (CVD) and embedded in polyurethane (PU) to obtain MA. The fabricated MA is flexible, highly stretchable (>400%), has a low percolation threshold (0.1 wt %), ultralightweight (0.35 wt %), and thin nanocomposite for enhanced microwave absorber performance. The thickness of MA is optimized to achieve the impedance matching condition by utilizing the CST microwave studio simulation and verified experimentally. The minimum reflection loss (RL) of −52.53 dB with effective absorber bandwidth (EAB) covering the complete X band at a 2.4 mm thickness is obtained for just 0.35 wt % CFCNT. The negligible change in RL and EAB after 1000 bending cycles and 2 h of water-bath sonication confirms the operating efficiency of MA in harsh environmental conditions. The mechanism of microwave absorption in the case of CF and CFCNT-based MA is elucidated concerning microwave properties, electrical conductivity, and morphology. The CST microwave studio simulation is also extended from the X band to the Ku band (12.4–18 GHz) for broadband microwave absorber application. 

Flexible, Stretchable, and Lightweight Hierarchical Carbon-Nanotube-Decorated Carbon Fiber Structures for Microwave Absorption

The cost-efficient fabrication of cathode catalyst layers with low Pt-loadings and high oxygen reduction reaction (ORR) performances is of prime importance towards the commercialization of low temperature fuel cells. Here, an attempt has been made to fabricate a hierarchically structured cathode catalyst layer consisting of Pt-nanoparticle clusters supported on defective carbon nanotube (CNT) coated carbon fiber (CNTCF). CNTs were grown on carbon fiber (CF) using chemical vapor deposition (CVD), while electrodeposition was employed to deposit Pt-nanoparticle clusters onto the CNTCF. The effect of Pt-loading on the oxygen reduction reaction (ORR) performance of the Pt-coated CNTCF (Pt-CNTCF) electrocatalysts was studied by varying the electrodeposition time (ted) between 5 and 30 min, which resulted in a variation of the Pt weight fraction in Pt-CNTCF from almost zero to ∼0.3. Linear sweep voltammetry using a Pt-CNTCF modified glassy carbon (GC) rotating disc electrode (RDE) was employed to study the ORR performance of the samples. The CNTCF support, due to the defective structure of the CNTs, itself exhibits significant ORR activity with an electron transfer number (n) of ∼2.6, which leads to a synergistic enhancement of the overall electrocatalytic performance of Pt-CNTCF. For low Pt-loading on the GC (∼5 μg cm−2), the contribution of the CNTCF support dominated, while the Pt-nanoclusters governed the ORR performance at higher Pt-loading (>10 μg cm−2), with n > 3.5. Hence, a very low Pt-loading (∼5 μg cm−2) may not be suitable for polymer electrolyte membrane fuel cells as the production of substantial amounts of H2O2 on the catalyst supports may accelerate membrane degradation.

Hierarchically structured catalyst layer for the oxygen reduction reaction fabricated by electrodeposition of platinum on carbon nanotube coated carbon fiber

The ‘Some for All’ dictum may work well for the water sector but is not appropriate and workable for the sanitation sector. We live in a paradox of concern for water quality for drinking, while displaying less concern about the haphazard and uncontrolled contamination of the sources of natural water. By contrast, the principle of ‘at least something for all/why not basics for all?’ on which Community‐led Total Sanitation (CLTS) is based, leads to collective behaviour change on a grand scale and empowers communities to completely eliminate open defecation and thus protect water bodies as well as improve health and livelihoods outcomes. This is achieved through a process of collective local action with no upfront individual hardware subsidy and no prescribed models. With some 50 countries in Asia, Africa and Latin America now adopting the approach, future challenges include sustainability, scaling‐up with quality, gaining political buy in and addressing issues concerning environmental health and waste disposal.

/pdf/why-not-basics-for-all-scopes-and-challenges-of-community-x4jce7w31a.pdf

Why not Basics for All? Scopes and Challenges of Community‐led Total Sanitation

In this research work, Carbon-carbon composites (CCCs) were fabricated via carbonization of carbon nanotubes (CNTs)-coated carbon textile (CNT-CF) reinforced polymer matrix composites (PMCs) prefor...

Enhanced electrical, mechanical, and viscoelastic properties of carbon-carbon composites using carbon nanotubes coated carbon textile as reinforcement:

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