Currently, the fossil fuel sources are the major contributors to the world's energy mix. However, these conventional energy sources are depleting very fast due to their finite nature and extensive uses. An addition to their finite nature, environmental problems related to their uses are getting progressively worse and worse, initiating challenging debates for scientific communities. Biodiesel, a renewable fuel, has shown promising prospects due to its strong socioeconomic benefits and motivations in most of the countries of the world. Bifunctional heterogeneous catalysts are strongly recommended for biodiesel production from different feedstocks to simplify the process. This review highlights the challenges and opportunities associated with the heterogeneous catalysts and some recommendations to design an efficient bifunctional heterogeneous catalyst for economical biodiesel production from waste cooking oil.
Part of the book: Frontiers in Bioenergy and Biofuels
Fabrication of electronic devices on different flexible substrates is an area of significant interest due to low cost, ease of fabrication, and manufacturing at ambient conditions over large areas. Over the time, a number of printing technologies have been developed to fabricate a wide range of electronic devices on nonconventional substrates according to the targeted applications. As an increasing interest of electronic industry in printed electronics, further expansion of printed technologies is expected in near future to meet the challenges of the field in terms of scalability, yield, and diversity and biocompatibility. This chapter presents a comprehensive review of various printing electronic technologies commonly used in the fabrication of electronic devices, circuits, and systems. The different printing techniques based on contact/noncontact approach of the printing tools with the target substrates have been explored. These techniques are assessed on the basis of ease of operation, printing resolutions, processability of materials, and ease of optimization of printed structures. The various technical challenges in printing techniques, their solutions with possible alternatives, and the potential research directions are highlighted. The latest developments in assembling various printing tools for enabling high speed and batch manufacturing through roll-to-roll systems are also explored.
Part of the book: Hybrid Nanomaterials
Optoelectronic devices are advancing from existing rigid configurations to deformable configurations. These developing devices need transparent electrodes (TEs) having high mechanical deformability while preserving the high electrical conductivity and optical transparency. In agreement with these requirements, vacuum-fabricated conventional TEs based on transparent conducting oxides (TCOs) are receiving difficulties due to its low abundance, film brittleness, and low optical transmittance. Novel solution-processed TE materials including regular metal meshes, metal nanowire (NW) grids, carbon materials, and conducting polymers have been studied and confirmed their capabilities to address the limitations of the TCO-based TEs. This chapter presents a comprehensive review of the latest advances of these vacuum-free TEs, comprising the electrode material classes, the optical, electrical, mechanical and surface feature properties of the soft TEs, and the vacuum-free practices for their fabrication.
Part of the book: Nanofibers