What is nanofiltration?

When you think of nanotechnology, you may think of an imperceptible, self-replicating microplague come to wipe out the human race (as in the Michael Crichton novel). Or you may consider the ever-decreasing size of technology. But a form of nanotechnology performs another function: Nanofiltration removes harmful particles from our drinking water every day.

Nanofiltration came to prominence in the 1970s and 1980s as an alternative to reverse osmosis, ultrafiltration, and microfiltration. These forms of water filtration were not totally effective at removing particles of all sizes, however. As filter technology improved, ie, as more technical, advanced membranes were designed, smaller-sized grains were able to be filtered out. By the end of the 1980s, nanofiltration technology had developed such that it filtered out adulterants from water that other filtration technologies could not. This article on nanofiltration says, for instance,

The key difference between nanofiltration and reverse osmosis is that the latter retains monovalent salts (such as sodium chloride), whereas nanofiltration allows them to pass, and then retains divalent salts such as sodium sulphate. Robert Peterson, in his Foreword to Elsevier's Nanofiltration – principles and applications, describes reverse osmosis (especially in the water treatment business) as the main course, the steak perhaps, of a meal, whereas nanofiltration “is like the wine menu … an opportunity for creativity and exploration”.

The key to the development of nanofitraltion technology has been creating better and better filtration technologies. Nanofiltration is a liquid phase membrane separation process; it separates inorganic and organic substances from solution in a liquid. Nanofiltration separates these substances by running them through a membrane under pressure (a smaller amount of pressure than what would normally be used for reverse osmosis, as well). Great advances in nanofiltration generally occurs due to the creation of better membrane technologies. Presently, many nanofiltration systems use an inorganic material; ceramic is an especially popular material.

Ceramics have excellent corrosive-resitance and feature an excellent range of control over their porosity. Ceramic membranes have the advantage of being fully capable of functioning in very high or very low pH environments. Ceramic nanofiltration has industrial applications in the food and dairy sector, chemical processing, pulp and paper industry, and textiles. However, the predominant use of nanofiltration is of course in fresh, process, and waste water filtration.

A growing use of ceramics in nanofiltration is with field of nanofiber media. Nanofibers are made of synthetic materials that are spun into fibers whose diameters range from 10 μm to 100 nm. Advances in spinning techniques have enabled water filtration manufacturers to better utilize ceramic technology. Such ceramic nanofilters feature the high density and durability of ceramics with the capability of removing contaminants to below 0.1 μm. Using ceramics in water filtration technology has increased the robustness and safety of our water supply. And as manufacturers of technical ceramics find ways to decrease cost, we will only see ceramics’ influence in water filtration technology increase.

Mercedes-Benz Stops With Ceramics

Mercedes-Benz has developed new braking technology that utilizes technical, stress-resistant ceramics. Upon request, the automaker will install in a new vehicle an AMG high-performance braking system, which uses composite brake discs.

eMercedesBenz, a Mercedes-Benz blog, describes the AMG high-perfomance braking system as sporting,

ventilated, grooved and perforated brake discs all-round in size 390 x 36 millimetres at the front and 360 x 26 millimetres at the rear ensure excellent deceleration performance. Brake discs in race-tested composite technology are installed at the front axle, with the grey cast iron discs radially and axially floating, and fixed to an aluminium bowl via stainless steel connections. This sophisticated technology ensures highly efficient heat conduction, and therefore outstanding fade-resistance even with a highly dynamic style of driving.

They go on to say that the optional ceramic composite braking system--labeled “AMGCarbon Ceramic” uses discs fashioned from carbon-fiber and reinforced by ceramics in a vacuum at 1700 degrees Celsius. The resulting brake disc is extremely pressure- and stress-resistant, which allows for a markedly decreased braking distance. Not only that, but the composite ceramic disks are 40% lighter than cast iron brake discs and allow for a more direct steering response while driving the car.

This is yet another great use of technical ceramics. It’s almost amazing how designers and engineers are only lately using ceramic materials for such diverse applications calling for extreme heat- and stress-resistance. Historically, the entry cost of working with ceramics has been high, but as manufacturing processes and materials decrease in price, ceramic technologies are being adopted at a high rate, passing on a great value and quality proposition to the consumer.

Georgia Tech Researchers Discovery Mystery Ceramic

Researchers at Georgia Tech have created a new ceramic material that could have revolutionary applications in fuel cell technology. It is still in a nascent, developmental stage, but it could reduce tremendously the cost of creating fuel cells. The high cost of fuel cells has been a barrier to their wider adoption.

The Georgia Tech researchers were supported by the U.S. Department of Energy’s Basic Energy Science Catalysis Science Program. Using the government money, they developed a new material for use in solid oxide fuel cells (SOFC). A SOFC generally uses a ceramic electrolyte, which in this case is a yttria-stabilized zirconia (YSZ) ceramic. Traditionally, YSZ operates poorly in an SOFC because it is inefficient, clogs easily, and must operate at a high temperature due to its poor conductivity at low temperatures. The new ceramic material, though, gets around all these drawbacks.

The material is a Barium-Zirconium-Cerium-Yttrium-Ytterbium Oxide (BZCYYb), which can be used as a coating on a traditional anode or a replacement for YSZ altogether. It has been lab-proven for performance up to 1,000 hours of continuous use, but it requires more testing to determine its stability and lifespan.

Researcher Meilin Liu says,

“Solid oxide fuel cells offer high energy efficiency, the potential for direct utilization of all types of fuels including renewable biofuels, and the possibility of lower costs since they do not use any precious metals... We are working to reduce the cost of solid oxide fuel cells to make them viable in many new applications, and this new material brings us much closer to doing that.”

Ceramic Semi-Conductors?

Dr. Jagdish Narayan, a researcher at North Carolina State University, has developed a new ceramic material that has exciting applications in semi-conductor technology. By adding some strategically selected impurities to their ceramics research, they have created a chip that can hold one bit of data in a space that is 90% smaller than existing technologies. Narayan says,

"Instead of making a chip that stores 20 gigabytes, you have one that can handle one terabyte, or 50 times more data."

This development is extremely exciting. If the research turns out to be scalable and mass-producible, then it could lead to the spread technical ceramics applications outside of areas like ceramic wear components and such.

Surfer Dude Saves Indonesian Town

Here’s a great story that involves surfers, earthquakes, and ceramic water filters. Jon Rose, a Long Beach, CA resident whose father, Jack Rose, has a non-profit called Rain Catcher. The non-profit helps to educate villagers in Africa about rainwater collection and filtration. The son had just launched Waves for Water, which follows a similar idea and applies it to popular surf regions.

Jon Rose had been surfing in Indonesia when a massive 7.6-on-the-Richter Scale earthquake struck on 30 September. Luckily, the surfer had stowed some ceramic clay water filters in his surf bag. Through immediate, attentive effort, Mr. Rose was able to provide filtration for the region, which has a population of over 750,000 residents. The earthquake had wiped out their previous water supply.

Maybe we should change the filter more frequently?

At our company, we drink tap water. Besides saving money, drinking tap money has been shown time and again to be as clean--if not cleaner--than bottled water. However, we noticed that our water was starting to taste a little bit off, so we examined the water filter. A ha! Take a look at this.
That cylinder on the top is the one that's been in (over)use, the one on the bottom is the replacement filter. The filters are made of ceramic. Ceramic makes an excellent water filter due to its density and porosity, both of which can be easily controlled. This particular filter features Sterasyl ceramic, which has a highly consistent and controlled pore structure, which can remove a wide range of water borne contaminants. They don’t restrict the flow of the water, and they make the water taste great, which means like nothing at all!

A New Report on the Market Outlook for Silicon Carbide

Silicon carbide (SiC), which is also known as carborundum, is a compound of silicon and carbon. It occurs in nature as the extremely rare mineral moissanite. It’s been used as an abrasive since 1893, and nowadays it is used in applications as various as car brakes and ceramic bulletproof vests to light-emitting diodes and radio detectors. SiC is also widely used in high-temperature semiconductor electronics, due to its amazing temperature-resistant properties.

There was a recent report from tech consultant Yole Développement outlining a curious absence of silicon carbide-based transistors, which was reporter in Semiconductor International. According to the report, the total market for SiC devices is $2.6 billion, more than 20% of the entire silicon-based power business in 2008. However, this share is expected to grow as various factors constraining SiC’s market penetration are overcome.

One factor slowing down SiC market penetration is its high cost. Low-voltage applications comprise the vast majority of SiC-based devices, which tend to have low margins. Medium-voltage (1.2 to 1.7 kV) applications are expected to increase over the next two to three years. High-voltage applications are expected to appear slowly beginning in 2013 or 2014 as technological improvements and cost reductions make SiC applications viable.

Total SiC substrate merchant market reached approximately $48 million in 2008, and it is expected to exceed $300 million during the decade. However, its relative share is looking like it will decrease. Currently, Chinese production companies are driving growth in the SiC transistor market. On the high end of projections, a yearly $800 million market can be expected for the SiC substrate transistor sector.