Thermoelectric silicon material reaches recordlow thermal conductivity

first_img The new material, which is a polycrystalline silicon nanowire, breaks two limits: the Casimir limit and the amorphous limit. The Casimir limit is a theory that describes the thermal conductivity of nanostructures, and breaking it means that the thermal conductivity of the new material is lower than the value predicted by Casimir limit theory. The amorphous limit is regarded as the lowest thermal conductivity of a material, since amorphous structures strongly scatter heat carriers. However, due to its unique nanoscale design, the polycrystalline silicon nanowire has a thermal conductivity that is three times lower than that of amorphous silicon materials.The researchers, Yanguang Zhou and Ming Hu at RWTH Aachen University in Germany, have published a paper on the polycrystalline silicon nanowire in a recent issue of Nano Letters.The researchers expect that the new material could be especially useful for thermoelectric applications. By converting heat energy into electricity, thermoelectric materials provide a way to capture some of the waste heat emitted by vehicle tailpipes, power plants, and manufacturing facilities, and then convert the heat into useful energy.In general, good thermoelectric materials are those that simultaneously have high electron conductivity and low thermal conductivity. Together, these two properties lead to a high overall heat-to-electricity conversion efficiency. In the new study, the researchers focused on decreasing the thermal conductivity while maintaining the already high electron conductivity of silicon materials. “In this paper, we report a new structure, polycrystalline nanowire, which can reduce the thermal conductivity to a record low value, only one-third of its amorphous counterpart,” Zhou told Phys.org. “If we keep the electric conductivity and Seebeck coefficient as constants, which can be achieved by doping the material, the efficiency of the polycrystalline nanowire to convert heat to electricity can be enhanced by 277 times with respect to its bulk counterpart.” Engineer creates new technique for testing nanomaterials (Phys.org)—Researchers have theoretically demonstrated the lowest rate of heat transfer, or thermal conductivity, in any silicon-based material developed so far. The key to the new silicon nanowire’s low thermal conductivity is its polycrystalline form, which consists of many crystal structures of varying shapes and sizes in random orientations. Based on the average grain size (about 3 nm) in the polycrystalline silicon nanowires, the Casimir limit predicts that the thermal conductivity cannot be below approximately 3 W/mK. But the researchers’ simulations show that the polycrystalline silicon nanowires have a thermal conductivity of just 0.7 W/mK. For comparison, this value is 269 times lower than that of bulk silicon, 77 times lower than that of pristine silicon nanowires, and three times lower than that of amorphous silicon nanowires.The researchers explain that an important feature of the polycrystalline structure is that the grain boundaries between crystals are discontinuous. As a result, the grain boundaries block and scatter the heat-transporting phonons, so that the phonons cannot move very far (only about 1 nm) through the material compared to how far they can move in other silicon materials (up to 1 µm), in which the grain boundaries form a continuous network. The results here raise the question of what the lowest possible thermal conductivity may be for silicon nanowires of any form. In general, there are two kinds of vibrations that contribute to thermal conductivity: propagons and diffusons. The researchers expect that it should be possible to completely eliminate the contribution of propagons by incorporating disorder in the form of nanotwinned structures into the polycrystalline silicon nanowires to minimize their transport. Diffusons, on the other hand, are caused by the inherent structural disorder of a material, so they cannot be reduced in this way. Nevertheless, by eliminating the contribution of propagons, the researchers expect that the thermal conductivity of the polycrystalline silicon nanowires can be further reduced by 20%. The researchers plan to pursue this goal in future work. © 2016 Phys.org Explore further More information: Yanguang Zhou and Ming Hu. “Record Low Thermal Conductivity of Polycrystalline Si Nanowire: Breaking the Casimir Limit by Severe Suppression of Propagons.” Nano Letters. DOI: 10.1021/acs.nanolett.6b02450 Citation: Thermoelectric silicon material reaches record-low thermal conductivity (2016, October 5) retrieved 18 August 2019 from https://phys.org/news/2016-10-thermoelectric-silicon-material-record-low-thermal.html Journal information: Nano Letters Two types of vibrations, diffusons and propagons, contribute to thermal conductivity in the polycrystalline structures. Credit: Yanguang Zhou and Ming Hu. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Delhiites time to dig in

first_imgDelhi is one city where you will find cuisines of different regions and even countries. Whether you want French, Thai, Italian, Nepalese or Bihari, Bengali, Marathi, Goan — you can totally satisfy the foodie in you in this city. But while global is good, the Capital also scores high when it comes to its own cuisine. And now, you can sample all of Delhi’s delicacies at the Delhi Tourism organised Delhi Ke Pakwan festiva. The festival brings together the culinary delights from the various lanes of Old Delhi and  other parts of the city as well. Also Read – ‘Playing Jojo was emotionally exhausting’Glorifying the past, and keeping with the present, the food of Delhi is as diverse as the people it consists of. The amalgamation of different recipes from different cultures produced the dishes which are unique and deliciously different. The festival has a collection ranging from Mughlai foods comprising Nihari, kababs, Ulte tawa ki roti, chicken dishes and biryanis. You can also dig into street food like pav bhaaji, pani puri and chaats. Or sample desserts like Also Read – Leslie doing new comedy special with Netflixgulab jamun, moong and gajar ka halwa and kulfis and of course the very Indian refreshner- Banarasi meetha paan. Young and old alike flocked to these stalls and enjoyed the food with obvious relish.The first day also saw a cultural programme consisting of Rajasthan folk dance and songs. Jazzing up the decor are decorated rickshaws and autos for click-happy visitors, a Banyan wishing tree, a handicraft exhibition. A dhaba-like setting with cots scattered around adds a nostalgic touch. There are vendors from Purani Dilli who have set up stalls, the famous chicken dishes from Chandni Chowk are also on sale. The sheer number of visitors who turned up for the opening day of the festival clearly proves that no matter how many Western and modern food outlets have opened in the city, the Capital’s very own cuisine will always remain a hot favourite. Go check it out.last_img read more

Israels Cube Circus to take on Delhi with song and dance routine

first_imgA troupe of performers from Israel, who employ Japanese origami style, are set to display their extravagant puppetry prowess accompanied with a song and dance routine, to entertain Indian audience here.The Train Theatre group from Jerusalem are presenting The Cubes Circus during the ongoing Ishara Puppet Festival, which the troupe is also marking as the 150th show since the inception of its presentation over four years ago.Performers don and use paper folded origami style into cube like structures throughout the puppet show while enacting stories and miming characters, which includes animals, plants and humans. Also Read – ‘Playing Jojo was emotionally exhausting’‘The first scene you see on stage is the cube. The cube becomes all the elements in the entire show. Cube circus is the relation between the very basic form of the three dimensional form getting alive, becoming vivid characters or living characters. In circus there are clowns to perform this, says Dov Meilnik, stage designer and tour manager of the troupe.With no text and no language, the show relies on language of object and body and the relationship between human beings Also Read – Leslie doing new comedy special with Netflix‘The concept of Cube Circus is absolutely Israeli but based on the centuries old origami which originated in Japan,’ says Meilnik.Galia Levy-Grad, the director of the show evolved the concept in Israel four years ago. Incidentally, the first shows of the troupe were performed inside a train wagon.Rerana Loten Ophir and Nir Eliyahu Landa (Sherving) are the performers who manipulations to be staged before audience.‘It’s a total manipulation. The cube is put on stage and opened. It will be one box actually. It can be then changed as a snake and immediately to a horse, a bird and anything else. It is actually like an architectural work in the way of building different elements,’ says Rerana Loten Ophir who equates the show to a circus.‘The form of the play can be related to a circus. it can also be interpreted as drama because we the performers are the clowns of the drama,’ he says. The shows by Train Theatre are not based on any epic or fairy tale, it is open to the interpretation of the audience, especially children.The repertoire has shows scheduled in the India Habitat Centre and in Gurgaon before they head over to Chandigarh.last_img read more

Dhoom 3 highest grossing film in Australia

first_imgAfter collecting Rs 500 crore at the Indian box office, Aamir Khan-starrer Dhoom 3 has now become the highest grossing foreign film of 2013 in Australia and emerged as the first Bollywood film to win the award.The award was recently received by the film distributing Company Mind Blowing Films at the 69th Australian International Movie Convention which hosted the annual Box Office Achievement Awards in Queensland.The title was accepted by Mind Blowing Films director Mitu Bhowmick Lange and her partner John Molloy. Lange said that film was the biggest release of an Indian movie which had opened in over 30 screens across the country and ran for more than a month.last_img

Striking a spiritual chord

first_imgAfter three days of devotional music and expressions of selfless bhakti, curtains came down at the Bhakti Sangeet Festival, with Kabir bhajans and other strains of spiritual music echoing through the air.Kabir Café, a music band that draws inspiration from a deep understanding of Saint Kabir’s beautiful verses, performed on the last day, with its ‘Kabir bhajans’ vowing one and all. Others who performed on the last day were Arshad Ali Khan who sang Krishna bhakti poetry, Sumitra Guha whose performance was dedicated to Ram Bhakti, and Master Saleem who rendered the mellifluous Punjabi Sufiana Kalaam. Also Read – ‘Playing Jojo was emotionally exhausting’Delhi’s much-loved annual Bhakti Sangeet festival was presented by Sahitya Kala Parishad and Department of Art, Culture & Languages, Govt of Delhi. This year it had nine individual and group performances of Bhakti and Sufiana renditions over three days at Nehru Park, Chanakyapuri.No matter what language we speak or which culture we adhere to, there are certain elements of human consciousness that transcend all tangible differences. Devotion to the Ultimate Being is one of those universal sentiments that find expressions in multiple forms. Be it in the form of bhajans or qawwalis or Gospel music, devotional music is one form of expression that does not fail to strike the chords of believers. Also Read – Leslie doing new comedy special with NetflixOver three days popular singers such as Anup Jalota and Shubha Mudgal performed different devotional strains of music.“Every individual soul finds its own way to connect with the eternal reality. Some perceive the Creator as a formless transcendent reality; others conceptualise Him in a human form. In different cultures and languages, people develop and nurture their own devotional traditions. Each region borrows from the saints that roamed in their lands. Music is a form that resonates with people across the world by aligning the mystic frequencies of a mind to verbal expression of love,” says Shubha Mudgal. From devotional traditions of South India to Meera bhajans, to ‘Nirgun’ bhakti and kalams of Bulleshah, the three-day festival showcased the variety of devotional music of India.Other singers who performed at the festival were Meeta Pandit who introduced the Delhi audience to the beautiful devotional traditions of South India; Iqbal Ahmad Khan who sang Meera bhajans; the adorable Nooran sisters who rendered the kalams of Bulleshah, and Dhruv Sangari who also performed Sufiana kalams. The annual Bhakti Sangeet Festival serves the purpose of unifying and bringing together the multiple traditions of Indian devotional music at one stage.last_img read more

State to go for massive Bixa plantation extract food manufacturing dye from

first_imgKolkata: The use of artificial colour in food products is soon coming to an end as the state Agriculture department has taken steps to ensure massive plantation of Bixa trees in the state for its seeds.Yellow-orange dye extracted from its seed is a safe colouring agent for food. The state Agriculture department would also discuss the issue with the state Science and Technology department for using updated technology to process the seeds and extract natural dye from it. Also Read – Rain batters Kolkata, cripples normal lifeTaking the unique move, the state Agriculture department would initially go for plantation of the same in all the farms and help increase the yield of Bixa seeds.During a recent visit to Fulia Agriculture Training Centre in Nadia, the state Agriculture minister Asish Banerjee noticed two Bixa trees, which is commonly known as lipstick tree. After getting to knowing the usefulness of the seeds, the minister gave direction to take necessary steps to increase the yield of the same. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedBanerjee said: “Direction has been given to increase plantation of Lipstick Trees. At the same time, there will be discussions with the state Science and Technology department in connection with the updated process of extraction of colour from its seeds.”Following the direction of the state Agriculture minister, senior scientists at Fulia Agriculture Training Centre initiated their work to increase its production.With the immense success of the scientists, around 2 kg of seeds have been kept ready and using the same, lipstick cultivation is possible on a plot 70-bigha. Initially, the state Agriculture department will carry out cultivation of Lipstick trees in all its farms across different parts of the state. The state Agriculture department has also taken steps so that no place in farms is left vacant. Once the yield of lipstick seeds goes up, the natural yellow-orange Bixa dye would become easily available in the state.With proper promotion of the Bixa seed dye, it will become popular among food product manufacturers and the tendency of using artificial colour will go down.Often the use of artificial colour in food products turns out to be an issue in certain parts of the state. Steps need to be taken to check such practice. But with this move, there would be a permanent solution to the menace.It may be mentioned that Bixa tree has become commonly known as the Lipstick tree as its seeds were used to make lipstick and body paint in certain parts of America.last_img read more

Six ways to protect your babys skin this winter

first_imgWinter is here, which means your baby needs extra care and attention. Baby skin requires a lot more nourishment during winter, as the temperature drop tends to make the skin dry. Winter also brings with it various skin problems for babies, as their skin is more delicate when compared to adults. Experts shares a few tips to nourish your baby’s skin: Oil massages: Nourishing the skin with regular oil massages before bath significantly reduces skin dryness and improve skin softness. Choose an oil infused with olive and winter cherry (Ashvagandha); this helps improve the skin tone and soothes the baby’s skin. Also Read – Add new books to your shelfBaby bath: It is advisable to bathe the baby once in two days with lukewarm water. If the water is too hot, it can hurt the top, protective layer of the skin. Bathing a baby for long can also strip the moisture off the skin. Hence, reducing bath time during winters is recommended. Using cleansers: Using a gentle cleanser infused with the goodness of aloe vera, almond oil and milk, can help prevent post-bath dryness in the baby’s skin and soothe excessively dry skin. Also Read – Over 2 hours screen time daily will make your kids impulsiveMoisturising: Using these post-bath enhances the skin’s wellness by locking in the moisture, which keeps the skin hydrated. Opt for a baby lotion enriched with natural oils and licorice (Yashtimadhu) to keep the skin supple and nourished. Creams: Using a baby cream with the goodness of country mallow (Bala) and licorice (Yashtimadhu) will condition and protect your baby’s skin, especially chapped cheeks, “crawler’s knee”, tender nose, and rubbed elbows. Wrapping the baby: Avoid wrapping your baby in a woollen sweater or blanket directly, as the rough fibre will scratch baby’s sensitive skin, leading to a rash. It’s best to use breathable winter clothing to keep the baby warm. Almond and olive oils, aloe vera, winter cherry, licorice, honey, and milk are a few handy herbs/ingredients which are known to lock in moisture and will help provide the best skin care for your baby during winters.last_img read more

Lakhs join Martyrs Day event but no mess traffic congestion

first_imgKolkata: The Kolkata Municipal Corporation and Kolkata Police did a commendable job on Sunday by cleaning the heart of the city and managing of lakhs of Trinamool Congress supporters who came from various parts of the state to take part in Martyr’s Day (Sahid Divas) programme at Esplanade.The elaborate arrangements by the civic body’s Solid Waste Management (SWM) department ensured that the road was restored to its normal state in terms of cleanliness in less than an hour after the programme concluded. Also Read – Rs 13,000 crore investment to provide 2 lakh jobs: Mamata”We had deployed four mechanical sweepers and 10 mobile compactor machines. The usual garbage carrying hand carts and some battery-operated cleaning vehicles were also pressed into service for cleaning operation. There was 200 employees involved by our department for cleaning,” Debabrata Majumder, Member Mayor in Council (SWM) said. Pieces of paper, food packets, tea cups and various waste products were found strewn in the Esplanade area as people in large number from various parts of the state had gathered here during the programme. Also Read – Lightning kills 8, injures 16 in stateElaborate advance planning made by the civic body ensured prompt cleaning of waste products. Kolkata Police was successful in keeping the roads free from congestion throughout the day with an elaborate advanced traffic plan and crowd management. “It is a team effort. Everything was well-planned and our officials followed the instructions. The day was Sunday so vehicular movement in the city was not as much as it is witnessed on a regular day. There were hardly any problems. Citizens reached their destinations without any hassle,” deputy commissioner of Traffic Pandey Santosh. The police had planned to allow vehicles coming from districts to enter city from three areas. A specific route was earmarked for vehicles converging at the meeting venue. This was to ensure that the other roads did not get clogged by any means. Vehicles followed the earmarked route and traffic movement was absolutely normal. The entire area in and around the meeting venue was under the coverage of surveillance cameras ensuring that there were no untoward incidents. The police had also taken precautionary steps to check spreading of rumours as lakhs of people had gathered in Esplanade and adjacent areas. Cops provided necessary guidance to people so that they could return home without facing any trouble.last_img read more