In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

Transparent electrodes attract intense attention in many technological fields, including optoelectronic devices, transparent film heaters and electromagnetic applications. New generation transparent electrodes are expected to have three main physical properties: high electrical conductivity, high transparency and mechanical flexibility. The most efficient and widely used transparent conducting material is currently indium tin oxide (ITO). However the scarcity of indium associated with ITO's lack of flexibility and the relatively high manufacturing costs have a prompted search into alternative materials. With their outstanding physical properties, metallic nanowire (MNW)-based percolating networks appear to be one of the most promising alternatives to ITO. They also have several other advantages, such as solution-based processing, and are compatible with large area deposition techniques. Estimations of cost of the technology are lower, in particular thanks to the small quantities of nanomaterials needed to reach industrial performance criteria. The present review investigates recent progress on the main applications reported for MNW networks of any sort (silver, copper, gold, core-shell nanowires) and points out some of the most impressive outcomes. Insights into processing MNW into high-performance transparent conducting thin films are also discussed according to each specific application. Finally, strategies for improving both their stability and integration into real devices are presented.

Metallic Nanowire-Based Transparent Electrodes for Next Generation Flexible Devices: a Review

Smart window refers to the on-demand window that can dynamically modulate light transmittance. It is recognized as a promising technology to economize building energy A smart window that dynamically modulates light transmittance is crucial for building energy efficiently, and promising for on-demand optical devices. The rapid development of technology brings out different categories that have fundamentally different transmittance modulation mechanisms, including the electro-, thermo-, mechano-, and photochromic smart windows. In this review, recent progress in smart windows of each category is overviewed. The strategies for each smart window are outlined with particular focus on functional materials, device design, and performance enhancement. The advantages and disadvantages of each category are summarized, followed by a discussion of emerging technologies such as dual stimuli triggered smart window and integrated devices toward multifunctionality. These multifunctional devices combine smart window technology with, for example, solar cells, triboelectric nanogenerators, actuators, energy storage devices, and electrothermal devices. Lastly, a perspective is provided on the future development of smart windows. Smart Windows

Smart Windows: Electro-, Thermo-, Mechano-, Photochromics, and Beyond

Solar-energy conversion usually takes one of two forms: the 'quantum' approach, which uses the large per-photon energy of solar radiation to excite electrons, as in photovoltaic cells, or the 'thermal' approach, which uses concentrated sunlight as a thermal-energy source to indirectly produce electricity using a heat engine. Here we present a new concept for solar electricity generation, photon-enhanced thermionic emission, which combines quantum and thermal mechanisms into a single physical process. The device is based on thermionic emission of photoexcited electrons from a semiconductor cathode at high temperature. Temperature-dependent photoemission-yield measurements from GaN show strong evidence for photon-enhanced thermionic emission, and calculated efficiencies for idealized devices can exceed the theoretical limits of single-junction photovoltaic cells. The proposed solar converter would operate at temperatures exceeding 200 degrees C, enabling its waste heat to be used to power a secondary thermal engine, boosting theoretical combined conversion efficiencies above 50%.

http://absimage.aps.org/image/MAR10/MWS_MAR10-2009-006451.pdf

Photon Enhanced Thermionic Emission for Solar Concentrator Systems

DOI: 10.1002/admt.201800546 manufacturing processes and relatively high production cost.[12,13] PE has been explored for the manufacturing of flexible and stretchable electronic devices by printing functional inks containing soluble or dispersed materials,[14–16] which has enabled a wide variety of applications, such as transparent conductive films (TCFs), flexible energy harvesting and storage, thin film transistors (TFTs), electroluminescent devices, and wearable sensors.[17–24] The global PE market should reach $26.6 billion by 2022 from $14.0 billion in 2017 at a compound annual growth rate of 13.6%.[25] PE devices are manufactured by a variety of printing technologies. Typical printing technologies can be divided into two broad categories: noncontact patterning (or nozzle-based patterning) and contact-based patterning. The noncontact techniques include inkjet printing, electrohydrodynamic (EHD) printing, aerosol jet printing, and slot die coating, while screen printing, gravure printing, and flexographic printing are examples of the contact techniques. Each of these techniques has its own advantages and disadvantages, but they all rely on the principle of transferring inks to a substrate. Understanding the characteristics and recent advances of each printing technique is important to further the progress in PE. Moreover, to promote the lab-scale printing technologies to large-scale production process, roll-toroll (R2R) printing, which is one of the manufacturing methods to obtain large-area films with low cost and excellent durability, has drawn much attention from both industry and the research community. Nearly all of devices based on PE require conductive structures, interconnects, and contacts; therefore, highly conductive patterns, usually with high transparency and/or high resolution, fabricated by means of printing conductive materials are one of the most critical components in PE devices. Various printable conductive nanomaterials, such as metal nanomaterials (e.g., metal nanoparticles and metal nanowires) and carbon nanomaterials (e.g., graphene and carbon nanotubes (CNTs)), have been explored and used as major materials for PE. Applying printing technology to deposition of the conductive nanomaterials requires formulation of suitable inks. After depositing inks on different substrates, post-printing treatment, Printed electronics is attracting a great deal of attention in both research and commercialization as it enables fabrication of large-scale, low-cost electronic devices on a variety of substrates. Printed electronics plays a critical role in facilitating widespread flexible electronics and more recently stretchable electronics. Conductive nanomaterials, such as metal nanoparticles and nanowires, carbon nanotubes, and graphene, are promising building blocks for printed electronics. Nanomaterial-based printing technologies, formulation of printable inks, post-printing treatment, and integration of functional devices have progressed substantially in the recent years. This review summarizes basic principles and recent development of common printing technologies, formulations of printable inks based on conductive nanomaterials, deposition of conductive inks via different printing techniques, and performance enhancement by using various sintering methods. While this review places emphasis on conductive nanomaterials, the printing techniques and ink formulations can be applied to other materials such as semiconducting and insulating nanomaterials. Moreover, some applications of printed flexible and stretchable electronic devices are reviewed to illustrate their potential. Finally, the future challenges and prospects for printing conductive nanomaterials are discussed.

Printing Conductive Nanomaterials for Flexible and Stretchable Electronics: A Review of Materials, Processes, and Applications

Micro tunnel boring machines (MTBM) are the smaller size of tunnel boring machines for installing pipelines beneath the earth’s surface with minimum disturbance to the regular life of the community above the tunneling location. The micro tunneling process is a remotely controlled continuous process to insert the pipes under the ground with the different types of soil and rock conditions using the hydraulic pipe jacking technique. MTMB consists of several components such as cutting shield, shield skin, shaft, bearing, motor, thrust cylinders, slurry pipes, etc., The cutting shield is driven by the shaft that experiences the loads transferred from Earth pressure, water pressure, building loads over the tunneling locations and seismic loads. Also, the shaft may experience sudden jerks during the restarting of the evacuation process. There are many possibilities in failures of cutting blades, shaft, and bearings during the excavation process. The accessibility and repair of failures in micro tunneling are challenging because of the smaller diameter of pipes. Therefore, the shaft is the major driving system that needs to be designed to withstand all the operating loads. In this paper, the major loads acting on the MTBM machine and the loads that transfer to the MTBM shaft are carried out and the shaft design is verified for its safety by Finite Element Analysis. 

Load study and analysis of shaft of micro tunnel boring machine

Methods for the treatment of wastewater from centralized and decentralized plants were evaluated using membrane technology based on empirical findings from the experimental analysis. The comparison enables small industries to choose either a centralized treatment or a decentralized treatment plant approach to effectively treat wastewater. The experimental treatment of the centralized wastewater treatment plant (CETP) concerned the direct passage of the entire feed through a depth filter, followed by adsorption and ultrafiltration. Decentralized approach involves reclaiming water at most stages of textile processing and reusing it before rejecting and dyeing wastewater at each stage through the same process as CETP wastewater. A powder activated carbon (PAC) / ultrafiltration (UF) hybrid system was used for the experimental analysis. PAC of 1.5 g per 800 ml of waste water was mixed before being allowed to settle for 1 hour. Filtration of the settled mixture through a cloth filter followed before being passed into a UF unit with a molecular separation point of 100 kDa. The same UF unit was used to recover water from wastewater in different phases of the textile process and to assess reusability. In the CETP sample, the colour removal was 97.15%, the chemical oxygen demand (COD) 92.86 and the TDS 98.11%. The color removal from the decentralized sample was 97.8%, the COD around 98%. Model equations for the recovery of water with UF in different stages were created from experimental data. The recovery from decentralized approaches has been better than excessive from CETP approaches. In addition to a decentralized approach with a potential of up to 45% water savings, the recovered water would be of better quality by processing less effluent. 

S. Kiruthika

Papers

Load study and analysis of shaft of micro tunnel boring machine

Comparative assessment of managing dye effluents through centralized and decentralized plant