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Researchers from the Institute of low temperature and structure research in Wroclaw, Poland, developed a new efficient white light source that uses graphene foam excitated by a continuous-wave laser. The laser opens up a bandgap in graphene which results in light emission that ranges from 360nm (UV) or 405nm (visible) to 980nm-1064nm (near-infrared).
The researchers say that the light spectrum of this device is similar to the spectrum of the sun which is better than current light sources such as LEDs that offer light spectrum with strong peaks (the main problem is the strong blue light emission in LED lighting). This design can achieve a high efficiency (over 200 lm/W), high color rendering index (CRI > 99) and a broadband warm white color. The lifetime depends on the laser, which can be over 10,000 hours.
Graphene-nanotube hybrid boosts lithium metal batteriesMay 18, 2017
Lithium metal coats the hybrid graphene and carbon nanotube anode in a battery created at Rice University. The lithium metal coats the three-dimensional structure of the anode and avoids forming dendrites. Credit: Tour Group/Rice UniversityRice University scientists have created a rechargeable lithium metal battery with three times the capacity of commercial lithium-ion batteries by resolving something that has long stumped researchers: the dendrite problem.
Graphene aerogel converts sunlight into heat to produce water vapour at room temperature
A sunlight-harvesting graphene film can produce steam without boiling the water. The material, which has been made by Chinese scientists, could convert sea or wastewater into drinking water in places where fuel or access to electricity is limited.
Desalinating seawater to make drinking water usually means boiling it, and then collecting and condensing the steam. Heating water to its boiling point, however, requires a great deal of energy either in the form of fuel or electricity. There are solar stills that desalinate water using only sunlight, but they’re slow and not always efficient enough to provide sufficient drinking water for a person’s daily needs.
Xianbao Wang and colleagues from Hubei University have now made a graphene aerogel film capable of producing water vapour at room temperature using only sunlight. The aerogel floats on the surface, where it heats up only a small section of the water column, ‘while the temperature of the bulk water is far below the boiling point’, as Wang explains.
Source: American Chemical Society
The researchers tested how the addition of different materials affected the heating of water in simulated sunlight, including reduced graphene oxide (rGO), graphene oxide (GO), graphene oxide aerogel membrane (GOAM) and the graphene aerogel (GA) that performed best of all
Under simulated sunlight, the aerogel could heat up 100ml of water to 45°C – 13°C higher than water without the aerogel. The material’s porous structure pumps the generated steam away from the surface, allowing water to evaporate 13 times faster than it would without the aerogel.
While other steam-generating materials are based on expensive raw materials such as gold, the basis for Wang’s aerogel is powdered graphite – a cheap and widely available resource. ‘In the context of solar steam generation, the current work has a major contribution in fabricating an efficient sunlight absorber in a simple method, which is scalable,’ comments Satoshi Ishii, a photonics nanoengineering researcher at the National Institute for Materials Science in Japan.
Generating solar steam with the graphene aerogel could be more efficient than using electricity from a photovoltaic cell. ‘The efficiencies of commercial photovoltaic cells are 10–20%, such that the efficiencies of generating steam using photovoltaic cells cannot exceed 20%,’ explains Ishii. Wang’s floating graphene has an efficiency of 54%, reaching up to 83% under focused sunlight.
However, if the material is to be used in a desalination device, Wang’s team will need to improve the material’s toughness – it is easily broken when picked up. ‘I do not see fundamental difficulties in bringing the current technology into real-life applications, although much more feasibility studies should be done,’ adds Ishii.
Talga reports impressive concrete strength test results using its graphene
May 21, 2017
Australia-based technology minerals company, Talga Resources, recently announced impressive initial concrete prototype strength results from trials undertaken at the commercial concrete/cement laboratory of Betotech Baustofflabor in Germany.
Graphene and graphite enhanced cement and concrete are key priority product targets for Talga. Concrete test prototypes were formulated with Talga graphene and graphite additives combined with a European industry cement and aggregate mixture. Results from the trial showed significant increases, about 26% in flexural strength and 14% in compressive strength, using Talga materials over reference concrete at 28 days cure time.
Further optimization of the formulation is planned along with a larger range of performance tests including abrasion, shrinkage and permeability, among other tests. Electrical conductivity tests are also underway. Talga will continue to progress its product and commercialization strategy in the construction sector using these prototype test results as the catalyst to initiate joint development programs with global suppliers.
Over the past 4 years we’ve dedicated 27 articles to educating investors about “the graphene industry” and so far, we have to say it’s been a bigger disappointment than carbon nanotubes, which were also expected to change the world. Graphene stocks just haven’t performed leaving us wondering if graphene will ever live up to its expectations.
From Mason Graphite most recent financials: On October 28, 2016, Group NanoXplore Inc. completed a non-brokered private placement of 125,068 Class A common shares for gross proceeds of $2,255,000 of which Mason Graphite purchased 55,463 Class A common shares for gross proceeds of $1,000,000. After giving effect to the financing, Mason Graphite holds a 32% interest (31% prior) in NanoXplore.
Researchers at the Harbin Institute of Technology and Ministry of Education in China have released a paper demonstrating the use of graphene oxide in a 3D printable ink.
The material developed by the team in China exhibits a tensile strength putting it in the same performance range as high-strength concrete, and a level of electrical conductivity among the highest conductive ceramic nanocomposites.
3D printed test structures made from graphene oxide/geopolymer ink. Image via Zhong, Zhou, He, Yang and Jia.
Finding the flow
At its base, the 3D printable ink in this study is a geopolymer – a material first defined in the 1950s with heat resistant and insulating properties, and an ability to encapsulate waste material in its structure. Examples of geopolymers include high temperature ceramics, and concrete made from recycled materials, such as the géobéton created by Russian construction company Renca.
As a raw material, the geopolymer alone does not have the rheological properties to flow through a nozzle for 3D printing. And so, in order to change its rheology (flowability), researchers investigate the use of graphene oxide as an additive.
Materials in the mix
The base geopolymer is made from a mixture of alkaline-source particles, found in soil or clay, and aluminosilicates particles, which is a mineral consisting of aluminium, silicon, and oxygen. During stirring, graphene oxide (GO) particles are injected into the mixture to create four samples of the material with different GO to geopolymer ratios.
Molecular structure of the ink to be extruded. Image via Zhong, Zhou, He, Yang and Jia.
What happens in the molecular structure of the geopolymer is that the GO particles act as a kind of lubricant in between the alkaline-source particles and aluminosilicates. The study assumes that interaction between the particles creates a thick layer of water film between them and, as such, GO/Geopolymer inks with higher GO concentration are more fluid than the others.
Printing the un-printable
3D printing this ink is performed using a modified commercially available UP Plus2 3D printer. After direct writing the ink into a design, the structures are cured in a controlled chamber for 5 days. They are then sintered at 1000? to turn the graphene oxide particles of the mixture into graphene, giving extra strength and conductive properties.
3D printing of the GO/Geopolymer ink. Image via Zhong, Zhou, He, Yang and Jia.
As a conclusion, authors state that
The unique properties of GO as we show in this study will further expand the range of applications where GO can be used. In particular, our strategy makes it possible to explore the employment of GO as rheology property modifier by encapsulation, and enable 3D printing materials that was un-printable previously, and thus offer opportunity to create new 3D printing materials
In the form of carbon nanotubes, graphene is gaining widespread popularity in the 3D printing industry. Award winning 3D printer company Markforged is a leader in the field of carbon fiber 3D printers, and fiber-reinforced materials have become a hot topic for applications in automotive and aerospace components.
Featured image: Molecular structure of 3D printable graphene oxide/geopolymer ink, developed by Harbin Institute of Technology and the Chinese Ministry of Education. Image via Zhong, Zhou, He, Yang and Jia.