High Quality on a Nanoscale

Highly accurate instrumentation is leading to an increasing use of nanoscale powders to create value-added ceramic products.

What do you do when your product becomes a commodity? How do you stay in the market while differentiating your product line from that offered by the (often much lower-priced) competition? And how can you effectively add value to your products without spending a fortune in material and R&D costs?

For an increasing number of ceramic manufacturers, the answer is nanomaterials. These ultrafine particles (typically less than 100 nanometers in size) can be engineered at the atomic, molecular or macromolecular level to provide novel properties and functions that cannot be achieved through any other means. By using nanomaterials, companies can develop products with enhanced electrical conductivity, magnetic properties, transparency, ultraviolet protection, thermal properties, optical properties, and even hardness and other structural properties. Additionally, since nanomaterials tend to sinter much faster and at much lower temperatures than conventional materials, companies can save energy and improve production efficiency. In some cases, the lower sintering temperatures required by nanoscale powders can reduce the need for more expensive materials, such as palladium, platinum, silver or other conducting materials, enabling manufacturers to save even more money.

However, just using small powders is not enough. According to Tapesh Yadev, chairman and chief executive officer of NanoProducts Corp., Longmont, Colo., the quality of the nanomaterials used is a key factor in achieving success.

"Nanotechnology is about precision at the nanometer scale-high performance and reliability are paramount," says Yadev. "For us to be able to provide the industry with high-quality nanomaterials, we have to rely on advanced instruments that provide us with reliability and precise information that we can trust."

NanoProducts Corp. uses the NOVA 3000, supplied by Quantachrome Instruments, to develop nanoscale materials with surface area characteristics that are precisely engineered to meet specific application requirements.

The Importance of Surface Area

The reason that nanomaterials are different from larger-sized particles of the same material is that all properties of a material change as the particle size approaches molecular dimensions. Many of these changes take place in the specific surface area (surface area per unit volume) of the particles. For instance, the extremely large surface area of nanocrystalline yttrium-samarium-cobalt grains can yield magnets with very unusual magnetic properties. Typical applications for these high-power rare-earth magnets include quieter submarines, automobile alternators, land-based power generators, motors for ships, ultra-sensitive analytical instruments and magnetic resonance imaging (MRI) in medical diagnostics.1 With other materials, a change in surface area can provide enhanced optical properties or electrical conductivity, leading to broader applications in the electronic or automotive fields. For this reason, the ability to precisely measure and analyze surface area is key to manipulating a nanomaterial to achieve the desired properties.

At NanoProducts Corp., instruments such as the NOVA® 3000, supplied by Quantachrome Instruments, Boynton Beach, Fla., are helping the company develop and deliver nanoscale materials with surface area characteristics that are precisely engineered to meet specific application requirements.

"We put all of our instruments through a very rigorous evaluation, and the NOVA 3000 was no exception," says Yadev. "The instrument has excellent gage R&R*-by far the best in its class. It meets the exacting standards we place on ourselves, as well as the standards our customers demand and rely on."

*Gage R&R, which stands for gage repeatability and reproducibility, is a statistical tool that measures the amount of variation in the measurement system arising from the measurement device and the people taking the measurement.

Accurate Surface Area Analysis

The NOVA instrument-which stands for NO Void AnalysisTM-operates on the principle of gas sorption, which takes advantage of the tendency of all solid surfaces to attract surrounding gas molecules. Unlike other surface area instruments, which typically use helium to measure void (free space) volumes, the patented NOVA technique is based on a separate calibration of sample cells prior to analysis. Sample cell calibrations are simply one-time blank analyses of empty sample cells performed under the same experimental conditions (temperature and relative pressure range) as the sorption measurements. The influence of thermal gradients on the effective sample cell volume can be reduced to a negligible fraction (less than 0.1%) of the overall system volume by applying a software-based mathematical procedure (TempCompTM). This patented feature allows the instrument to correct for temperature changes along the length of the cell stem due to the evaporation of liquid nitrogen.

Any cell can be calibrated using a suitable adsorptive at any desired temperature. NOVA cell calibrations (blank runs) are fast and only need to be performed once for a given type of sample cell. Thereafter, the calibration is stored in permanent memory, eliminating the need to calibrate new cells. Sample cells "calibrated" in such a way can be used in any of the (up to four) sample ports on a NOVA sorption analyzer. The calibration/blank curve for each cell type is stored in the memory of the automated instrument and is recalled every time such a cell is used for an analysis with the NOVA apparatus. This calibration/blank curve is then automatically subtracted from the sample analysis curve, and accurate adsorption/desorption data are obtained after minor corrections are made to account for both the relatively small sample volume and its gas non-ideality contribution to the empty cell profile. The sample volume is obtained by automated pycnometric measurement with nitrogen at room temperature at the start of the analysis (or, for additional time savings, by the operator entering a known sample density).

In addition to these advantages, the principle of separating the void volume determination from the adsorption experiment (and consequently the elimination of the use of helium) allows the instrument to significantly shorten the analysis time (in particular, in case of simple BET surface area analysis). This is because, unlike conventional volumetric static methods, the NOVA principle performs the sorption experiment without simultaneous void volume measurements. In addition, uncertainties related to gas non-ideality corrections are virtually eliminated because their influence is restricted to the small volume occupied by the sample. Because cell calibration and sample analysis are performed with the same gas, any contribution by adsorption on the sample cell walls is also subtracted automatically when generating isotherm data, further ensuring the instrument's accuracy.2

NanoProducts Corp. is continuously adding capacity and refining its ability to make high-precision nanomaterials in commercial quantities.

Expanding Nanomaterial Applications

The last several years have seen expanded applications for nanomaterials, particularly in the ceramic industry. "Electronic ceramics and ceramic additives and coatings are the areas in which we're seeing the largest use of nanomaterials today," Yadev says. "Growth in these areas over the last two years has been particularly sharp-we have seen increases of about 200% in this time period, and we anticipate continued annual growth rates of 100% or more for the years to come."

Yadev notes that nanotechnology is still in its infancy, so this growth is occurring from a relatively low base. However, several important factors are laying the groundwork for future success in this field. One such factor is the demand for more value-added products, as manufacturers increasingly search for ways to distinguish their products from their competitors. Another factor is that nanomaterials research has been under way in a number of companies over the last several years. With each new success, companies have become increasingly comfortable taking on advanced projects.

But perhaps most important are the advances being made by nanomaterial suppliers such as NanoProducts Corp., along with improvements in instrumentation. "As demand for our products increases, we are adding capacity and refining our processing methods so that we can now make high-precision nanomaterials in commercial quantities," says Yadev. "Highly accurate instruments such as the NOVA 3000 provide us with the reliability and surface area data we need, at a speed and cost that enables us to serve the demanding requirements of the ceramic and other industries."

For more information about nanomaterials, contact NanoProducts Corp. at 14330 Longs Peak Court, Longmont, CO 80504; (970) 535-0629, ext. 240; fax (970) 535-9309; e-mail sales@nanoproducts.com ; or visit http://www.nanoproducts.com .

For more information about surface area analysis, contact Quantachrome Instruments, 1900 Corporate Dr., Boynton Beach, FL 33426; 800-989-2476 or 561-731-4999; fax 561-732-9888; e-mail qc.sales@quantachrome.com ; or visit http://www.quantachrome.com .

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