#nanomaterial

[genesisnanotech]

‘Nano Origami’ - Tiny graphene microchips could make your phones and laptops thousands of times faster, say scientists

‘Nano Origami’ – Tiny graphene microchips could make your phones and laptops thousands of times faster, say scientists

Researchers unlocked the electronic properties of graphene by folding the material like origami paper. Graphene strips folded in similar fashion to origami paper could be used to build microchips that are up to 100 times smaller than conventional chips, found physicists – and packing phones and laptops with those tiny chips could significantly boost the performance of our devices.  New research…

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[crimsonpublishersminingscience]

Effective Purification of Germanium Obtained from Mineral Raw Materials-Crimson Publishers

Effective Purification of Germanium Obtained from Mineral Raw Materials by  Pekar GS in  Aspects in Mining & Mineral Science

 Abstract

By studying the heat treatment of metallic germanium obtained from mineral raw materials, in is experimentally established that germanium heating in a certain narrow temperature range leads to a significant decrease in the concentration of uncontrolled impurities. The use of such a heating as a preliminary germanium purification makes it possible to increase significantly the efficiency of subsequent germanium purification by a zone melting method.

Keywords: Germanium; Purification; Volatile impurities; Zone melting

 Introduction

Single-crystalline and poly-crystalline germanium is one of the main materials of semiconductor technique and is used for fabricating the elements of infrared optics (such as lenses, protective screens, etc.), detectors of ionizing radiation and other devices. Germanium is contained in the earth's crust in the form of a scattered element and may be found in sulfide and iron ores, some coals, almost in all silicates and in a number of minerals (such as argyrodite, confildite, etc.). By means of the use of certain complex and time-consuming operations, germanium may be extracted from the listed materials in the form of oxide GeO2, which may be then chemically reduced with hydrogen at high temperature. Since for most practical applications the high-purity germanium is used as a source material (which subsequently may be doped with certain impurities), processes of metallic germanium purification are very important. Very often the depth of such purification should be very high. For example, to provide germanium transparency in the infrared optical region, i.e. to prepare so-called optical germanium, it should be doped with a certain donor impurity (Sb, Na, etc.) at a concentration from 5∙1013 to 3∙1014cm-3 [1,2]. Therefore, the concentration of uncontrolled impurities in the source germanium before its doping should not exceed at least 1012cm-3. As to detector germanium, it should even be much better refined.

As a main method for germanium purification, zone melting is used. It makes it possible to prepare germanium, which is one of the most chemically pure materials known. However, during zone melting, each germanium ingot must be subjected to repeated purification, i.e. the container with germanium should be many times pulled through a narrow zone of melted germanium. This process is rather long, laborious and energy consuming. Obviously that to increase the efficiency of zone melting, it is desirable to use as much as possible purified source material. In this paper we describe the effect observed by us [3] that makes it easy to lower the content of impurities in the source germanium prior to its purification by zone melting. During a long time we successfully used this effect when preparing the initial material for growing large optical germanium crystals used in modern thermal imaging devices [4].

 Method of Preliminary Purification

Germanium powder obtained by reducing germanium oxide in a hydrogen flow at a temperature about 650-675 °C, weighing approximately 2kg, was placed in a graphite crucible and heated in a closed chamber under a pressure of 10-3 atm with continuous pumping. After the powder was completely melted, the melt was heated to a temperature of 1050-1150 °C. It was found that in this temperature range a quite narrow region existed, up to 20 °C wide, in which a rather unexpected process was observed that looked like boiling of the melt. This process lasted for about 5-10min. Temperature, corresponding to this region, was different depending on the nature of purified germanium. We explained this process by decomposition and evaporation of some chemical compounds whose composition we could not determine. It seems naturally to suggest that such compounds were initially contained in the germanium dioxide, from which the metal germanium was obtained. As a result of the described process, the content of electrically active impurities in the obtained crystalline germanium dropped by about 5-10 times compared with the material in which the heating in the described narrow temperature region was not carried out. Note that the concentration of electrically active impurities in the obtained germanium ingots was evaluated, as is often done, from the measured value of the electrical resistivity.

It was found that after the subsequent zone melting of the preliminary purified germanium (at 6 passes of the melted zone) the resistivity of almost the entire germanium ingot was approximately 47 Ohm∙cm at room temperature, which corresponded to the intrinsic electrical resistivity of germanium [5] and was indicative of its high purity. At the same time, zone purification of germanium, which was not subjected to the preliminary purification described above, resulted in obtaining ingots with a resistivity about 47 Ohm∙cm only in the front half of each ingot even after 12-fold passage of the melted zone. As for the rest portions of the ingots, their resistivity did not achieve this value even after the multifold zone-melting purification.

 Conclusion

It is shown that heating of the melted metallic germanium obtained from mineral raw materials, carried out in the experimentally determined narrow (approximately 20 °C wide) temperature region, results in a significant decrease of the concentration of contaminants. This results in a significant increase in the efficiency of the subsequent purification of this material by zone melting. The described technique has been successfully used for preparing germanium ingots used as a source material for growing, on an industrial scale, of optical germanium crystals for thermal imaging systems.

 References

Pekar GS, Singaevsky AF (2012) Na-doped optical germanium bulk crystals. Applied Physics A 108(3): 657-664.

Pekar GS, Singaevsky AF (2017) Solubility, diffusion and electrical activity of Na in bulk Ge crystals. Materials Science in Semiconductor Processing 64: 10-15.

Pekar GS, Singaevsky AF, Lokshin MM (2011) Method for obtaining of metal germanium from the germanium dioxide. Patent of Ukraine №

Pekar GS, Singaevsky AF, Lokshin MM, Gordienko VI, Mazurin IV (2018) Large polycrystalline optical germanium Ge: Na plates with improved optical parameters and their application. Semiconductor physics, quantum electronics and optoelectronics 19: 23-27.

Smith RA (1978) Semiconductors. (2nd edn), Cambridge University Press, UK, p. 540.

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[intelligentliving]

Scientists Are Turning Plastic Waste Into Supercapacitors For Energy Storage

Supercapacitors can charge and discharge almost instantly, and they hold great potential for energy storage. Now, scientists at the University of California, Riverside (UCR) have figured out how to make components for advanced energy storage devices from sustainable sources in the form of a nanomaterial made from plastic waste. The...

[sciencenewsforstudents]

Sunflower-like rods could boost efficiency of solar collectors

A new material bends to follow the sun. Rods made from it could soak up far more of the sun’s light than ordinary solar collectors.

This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

The stems of sunflowers move throughout the day so that their flowery heads always squarely face the sun, wherever it is in the sky. This phototropism (Foh-toh-TROAP-ism) helps the plants soak up maximum amounts of sunlight. Scientists had trouble copying this ability with synthetic materials. Until now.

Researchers at the University of California, Los Angeles have just developed a material with the same type of sun-tracking ability. They describe it as the first synthetic phototropic material.

When shaped into rods, their so-called SunBOTs can move and bend like mini sunflower stems. This allows them to capture about 90 percent of the sun’s available light energy. That’s more than triple the energy collection of today’s best solar systems.

People have often been inspired by the world around them. Scientists, too, may look to plants and animals for clues to new discoveries. Ximin He is a materials scientist. She and her team found the idea for their new material in sunflowers.

Other scientists have made substances that can bend toward light. But those materials stop at a random spot. They don’t move into the best position to catch the sun’s rays and then stay there until it’s time to move again. The new SunBOTs do. The whole process happens almost at once.

In tests, the scientists pointed light at the rods from different angles and from a range of directions. They also used different light sources, such as a laser pointer and a machine that simulates sunlight. No matter what they did, the SunBOTs followed the light. They bent toward the light, then stopped when the light stopped moving — all on their own.

On November 4, they described how these SunBOTs work in Nature Nanotechnology.

How SunBOTs are made

SunBOTs are made from two main parts. One is a type of nanomaterial. It’s made from billionth-of-a-meter size pieces of a material that responds to light by heating up. The researchers embedded these nanobits into something known as a polymer. Polymers are materials made from long, bound chains of smaller chemicals. The polymer that He’s team chose shrinks as it heats up. Together, the polymer and nanobits form a rod. You might think of it as being something like a cylinder of solid glitter glue.

When He’s team beamed light on one of these rods, the side facing the light heated and contracted. This bent the rod toward the beam of light. Once the top of the rod pointed directly at the light, its underside cooled and the bending stopped.

He’s team made their first version of the SunBOT using tiny pieces of gold and a hydrogel — a gel that likes water. But they found that they also could make SunBOTs from many other things. For instance, they substituted tiny pieces of a black material for the gold. And instead of the gel, they used one type of plastic that melts when it gets hot.

This means scientists can now mix and match the two main parts, depending on what they want to use them for. For example, ones made with a hydrogel might work in water. SunBOTs made with the black nanomaterial are less costly than ones made with gold.

This suggests that “scientists can use [SunBOTs] in different environments for different applications,” says Seung-Wuk Lee. He’s a bioengineer at the University of California, Berkeley, who did not work on the SunBOTs.

Little SunBOTs for a sunnier future

UCLA’s He envisions that SunBOTs could be lined up in rows to cover an entire surface, such as a solar panel or window. Such a furry coating would be “like a mini sunflower forest,” she says.

Indeed, coating surfaces with SunBOTs might solve one of the biggest problems in solar energy. While the sun moves across the sky, stationary things — such as a wall or rooftop — don’t. That’s why even today’s best solar panels capture only about 24 percent of the sun’s light. Some solar panels could be pivoted by day to follow the sun. But moving them requires a lot of energy. SunBOTs, in contrast, can move to face the light all on their own — and they don’t need added energy to do it.

By tracking the sun, SunBOTs are able to absorb almost all of the sun’s available light, says Lee, at Berkeley. “That is a major thing that they achieved.”

Ximin He thinks that unmoving solar panels might one day be upgraded by coating their surfaces with a SunBOT forest. By putting the little hairs on top of the panels, “We don’t have to move the solar panel,” she says. “These little hairs will do that job.”

[becoming-one-with-the-bomb]

[crimsonpublishersminingscience]

Design and Construction of Rock Crushing Machine from Locally Sourced Materials for Indigenous Use-Crimson Publishers

Design and Construction of Rock Crushing Machine from Locally Sourced Materials for Indigenous Use by  Ocheri C in  Aspects in Mining & Mineral Science

The design and construction of a prototype rock crushing machine was performed this is with a view to ensuring that the designed crusher is capable of crushing rocks, lime stone and solid minerals for indigenous use. The research work was tailored mainly on the design and production of locally fabricated rock crushing machine for indigenous use. To accomplish the entire work within the scope of time therefore necessary parameters were considered, the following activities were also performed according to the procedures discussed in the research work. Available crushing machines in mines were studied to ascertain their associated prospects, challenges and problems. Extensive research was carried out using existing data and information-based literature survey that was used. Detailed design analysis was performed with a view to catering for all the identified challenges. A prototype was constructed to evaluate the design analysis carried out. Rock crushing machines are highly essential in the mineral processing and extractives industries. The few machines in use today in most industries are imported, thus raising the cost of production and depleting foreign exchange earnings. Locally designed rock crushing machines have lot of benefits which translate to job creation, revenue generation and wealth creation. This provides amble opportunities for Government, stakeholders, corporate bodies and individual alike to own such machine since they are affordable since they are manufactured locally which signifies that such machines could be attended to easily by the manufacturer in case of any failure or malfunctioning. It reduces importation, thus fighting the depleting foreign exchange earnings.

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[dr-afsaeed]

Groundbreaking 2D Nanomaterial Rolls Into a New Dimension - Science News

MXene nanoscrolls transform flat 2D materials into conductive 1D structures, unlocking advances in energy storage, sensing, wearables, and superconductivity. Nearly 15 years after identifying a versatile two-dimensional conductive nanomaterial known as MXene, researchers at Drexel University have unveiled a method to create its one-dimensional counterpart, called the MXene nanoscroll. These newly…

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[newstodays1]

Nanotechnology and Supercomputing: A Synergy for the Future

Introduction The intersection of nanotechnology and supercomputing is driving unprecedented advancements in computational power, energy efficiency, and miniaturization. As traditional silicon-based computing approaches its physical limits, nanomaterials and quantum-scale innovations are paving the way for next-generation supercomputers capable of solving complex global challenges. This blog…

Nanotechnology and Supercomputing: A Synergy for the Future