World's most heat resistant material found

December 25, 2016

London, Dec 25: Scientists have identified materials that can withstand temperatures of nearly 4,000 degrees Celsius, an advance that may pave the way for improved heat resistant shielding for the faster-than-ever hypersonic space vehicles.heat

Researchers from Imperial College London in the UK discovered that the melting point of hafnium carbide is the highest ever recorded for a material.

Tantalum carbide (TaC) and hafnium carbide (HfC) are refractory ceramics, meaning they are extraordinarily resistant to heat. Their ability to withstand extremely harsh environments means that refractory ceramics could be used in thermal protection systems on high-speed vehicles and as fuel cladding in the super-heated environments of nuclear reactors.

However, there has not been the technology available to test the melting point of TaC and HfC in the lab to determine how truly extreme an environment they could function in. The researchers developed a new extreme heating technique using lasers to test the heat tolerance of TaC and HfC.

They used the laser-heating techniques to find the point at which TaC and HfC melted, both separately and as mixed compositions of both.

They found that the mixed compound (Ta0.8Hf0.20C) was consistent with previous research, melting at 3,905 degrees Celsius, but the two compounds on their own exceeded previous recorded melting points. The compound TaC melted at 3,768 degrees Celsius, and HfC melted at 3,958 degrees Celsius.

The findings may pave the way for the next generation of hypersonic vehicles, meaning spacecraft could become faster than ever.

"The friction involved when travelling above Mach 5 -hypersonic speeds - creates very high temperatures," said Omar Cedillos-Barraza, currently an Associate Professor at the University of Texas.

"So far, TaC and HfC have not been potential candidates for hypersonic aircraft, but our new findings show that they can withstand even more heat than we previously thought - more than any other compound known to man," said Cedillos-Barraza, who carried out the research as a PhD student at Imperial College London

"This means that they could be useful materials for new types of spacecraft that can fly through the atmosphere like a plane, before reaching hypersonic speeds to shoot out into space," he said.

"These materials may enable spacecraft to withstand the extreme heat generated from leaving and re-entering the atmosphere," he added.

Examples of potential uses for TaC and HfC could be in nose caps for spacecraft, and as the edges of external instruments that have to withstand the most friction during flight.

Currently, vehicles going over Mach 5 speeds do not carry people, but Cedillos-Barraza suggests it may be possible in
the future.

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Agencies
July 2,2020

Leiden, Jul 2: Astronomers have discovered a luminous galaxy caught in the act of reionizing its surrounding gas only 800 million years after the Big Bang.

The research, led by Romain Meyer, PhD student at UCL in London, UK, has been presented at the virtual annual meeting of the European Astronomical Society (EAS).

Studying the first galaxies that formed 13 billion years ago is essential to understanding our cosmic origins. One of the current hot topics in extragalactic astronomy is 'cosmic reionization,' the process in which the intergalactic gas was ionized (atoms stripped of their electrons).

Cosmic reionization is similar to an unsolved murder: We have clear evidence for it, but who did it, how and when? We now have strong evidence that hydrogen reionization was completed about 13 billion years ago, in the first billion years of the universe, with bubbles of ionized gas slowly growing and overlapping.

The objects capable of creating such ionized hydrogen bubbles have however remained mysterious until now: the discovery of a luminous galaxy in which 60-100 percent of ionizing photons escape, is likely responsible for ionizing its local bubble. This suggests the case is closer to being solved.

The two main suspects for cosmic reionization are usually 1) a population of numerous faint galaxies leaking ~10 percent of their energetic photons, and 2) an 'oligarchy' of luminous galaxies with a much larger percentage (>50 percent) of photons escaping each galaxy.

In either case, these first galaxies were very different from those today: galaxies in the local universe are very inefficient leakers, with only <2-3 percent of ionizing photons escaping their host. To understand which galaxies governed cosmic reionization, astronomers must measure the so-called escape fractions of galaxies in the reionization era.

The detection of light from excited hydrogen atoms (the so-called Lyman-alpha line) can be used to infer the fraction of escaping photons. On the one hand, such detections are rare because reionization-era galaxies are surrounded by neutral gas which absorbs that signature hydrogen emission.

On the other hand, if this hydrogen signal is detected it represents a 'smoking gun' for a large ionized bubble, meaning we have caught a galaxy reionizing its surroundings. The size of the bubble and the galaxy's luminosity determines whether it is solely responsible for creating this ionized bubble or if unseen accomplices are necessary.

The discovery of a luminous galaxy 800 million years after the Big Bang supports the scenario where an 'oligarchy' of bright leakers emits most of the ionizing photons.

"It is the first time we can point to an object responsible for creating an ionized bubble, without the need for a contribution from unseen galaxies.

Additional observations with the upcoming James Webb Space Telescope will enable us to study further what is likely one of the best suspects for the unsolved case of cosmic reionization," said Meyer.

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Agencies
May 30,2020

The GST Council is unlikely to make major changes in the indirect tax structure at its next meeting slated mid June.

A top government source said that the Centre is not in favour of increasing tax rates on any goods or service as it could further impact consumption and demand that is already suppressed due the COVID-19 pandemic and lockdown.

It was widely expected that the GST Council could consider raising tax rates and cess on certain non-essential items to boost revenue for states and the Centre. Several states have reportedly taken an over 80-90 per cent hit in GST collections in April, the official data for which has not yet been released by the Centre.

"The need of the hour is to boost consumption and improve demand. By categorising items into essential and non-essential and then raising taxes on non-essential is not what Centre favours. But, the issue on rates and relief will be decided by the GST Council that is meeting next month," the finance ministry official source quoted above said.

The GST Council is chaired by the Union finance minister and thus the views of the Centre play out strongly in the council meetings.

However, the Council will also have to balance the expectations of the states whose revenues have nosedived after the coronavirus outbreak and wide scale disruption to businesses while they have still not been paid GST compensation since the December-January period.

To the question of wider scale job losses in the period of lockdown as businesses get widely impacted, the official said that the Finance Ministry has asked the labour ministry to collect data on job losses during Covid-19 and is constantly engaging with the ministry to oversee job losses and salary cuts.

On restrictions put on Chinese investment in India, the official clarified that no decision had yet been taken to restrict China through the Foreign Portfolio Investment (FPI) route.

Asked about monetising government debt, the official said that the issue would be looked at when we reach a stage. It has not come to that stage yet.

In the government's over Rs 20 lakh crore economic package, the official defended its structure while suggesting that comparisons with the economic packages of other countries should not be drawn as India's needs were different from others.

"We have gone in more reforms that is needed to give strength to the economy. This is required more in our country," the official source said.

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Agencies
February 26,2020

New Delhi, Feb 26: With the government pushing for the disinvestment of Air India, industrial conglomerate Adani Group may emerge as one of the bidders for the debt-laden national carrier, sources said.

According to highly placed sources, the Group has held internal rounds of deliberations on whether or not to submit an Expression of Interest (EoI) and the discussions are still in the preliminary stage.

If the company actually submits an EoI, it would be a major move towards further diversification of the company which has business interests across sectors right from edible oil, food to mining and minerals. 

It also entered into airport operations and maintenance business and won bids for privatisation of six airports, Ahmedabad, Lucknow, Jaipur, Guwahati, Thiruvananthapuram and Mangaluru in 2019. 

On being contacted by IANS, the company did not comment on the matter.

Air India is one of the most important divestment proposals for the current fiscal to reach the huge Rs 2.1 lakh crore target.

The government in January restarted the divestment process of the airline and invited bids for selling 100 per cent of its equity in the state-owned airline, including Air India's 100 per cent shareholding in AI Express Ltd. and 50 per cent in Air India SATS Airport Services Private Ltd.

After its unsuccessful bid to sell Air India in 2018, the government this time has decided to offload its entire stake. In 2018, it had offered to sell its 76 per cent stake in the airline.

Of the total debt of Rs 60,074 crore as of March 31, 2019, the buyer would be required to absorb Rs 23,286 crore.

Air India, along with its subsidiary Air India Express, has a total operational fleet of 146 aeroplanes.

Further, the disinvestment department has extended the last date for submission of written queries on the Performance Information Memorandum and Share Purchase Agreement to March 6.

The last date for submission of written queries on PIM and SPA was originally set for February 11, following which the Department of Investment and Public Asset Management (DIPAM) on February 21 issued 20 clarifications on the queries raised and expected.

Any delay in the tentatively rolled out timeline would also delay DIPAM's plan to identify the pre-qualified bidders by March 31 and the financial bids invitation as well. It is expected to take more than two months after the selection of the pre-qualified bidders to complete Air India's sale.

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