OPPORTUNITIES AND CHALLENGES

There are some outstanding opportunities and challenges that face the nanoscience community. For dispersions and coatings these include four areas:

  1. The foremost area of opportunity is controlling the particle preparation process so that size is reproducible and scaleable. This requires creation of narrow size range particles that can be prepared by processes mentioned in the study such as vapor phase condensation, physical size reduction, or flame and pyrolysis aerosol generators. These same processes must respond to good reproducibility and scaling. In most studies to date, the size of primary particles depends on material properties and the temperature/time history. Two processes, collision and coalescence, occur together, and the processes need to be controlled in order to favorably influence final particle size distribution (Wu et al. 1993).
  2. The second area of opportunity is process control (Henderson 1996). In the concept of a process control methodology, the nature of chemical processes makes it imperative to have means of effectively monitoring and initiating change in the process variables of interest. Accordingly, those involved with production of nanoparticles would monitor outputs, make decisions about how to manipulate outputs in order to obtain desired behaviors, and then implement these decisions on the process. Control system configuration will necessarily have a feeding process from the output such that information can be fed back to the controller. It may also have an opportunity to base controller decision-making on information that is being fed forward; decisions could be made before the process is affected by incoming disturbances. Such would apply to process parameters like temperature, flow rate, and pressure.

    In many chemical setups, product quality variables must be considered, and such measurements often take place in the laboratory.  An objective analysis is needed of any observed deviation of a process variable from its aim, and an objective decision must be made as to what must be done to minimize any deviation.  Here process understanding leads to well behaved reactors in manufacturing that allow for true process verification with data feedback and analysis.  This concept of process control requires the application of statistical methodologies for product and process improvements.  Current interest in statistical process control (SPC) is due to several factors, in particular, interest in realizing consistent high quality so as to sustain the business and obtain greater market share.  Most manufacturing zones are moving toward inline/online sensor technologies coupled with process software and user-friendly computer hardware for factory operators.

    The benefits of process control are many.  They include achieving reduced variability and higher quality, safety enhancement, reduction of process upsets, and in many cases, environmental improvements due to achieving mass balance in processes with material in/product out.  Poor process design can be inherently overcome through SPC.  Reduction in sampling and inspection costs results.

  3. A third area of opportunity is the process/product relationship that leads to continuous uniformity-that is, the specification setting by product users that must be available to relate to process control in manufacturing. Here, nanoparticle formulation and the process used to prepare the particles must be linked and interactive.
  4. A fourth technical opportunity is to develop process models for various dispersions and coatings that lead to shorter cycle time in manufacturing. Table 3.3 shows a comparison of enablers and opportunities in Europe, Japan, and the United States.

These four areas of opportunity, then, represent what lies ahead for advancement in nanotechnology with respect to dispersions and coatings.  Achieving implementation in the industrial market will require close attention to resolving the challenges in the four areas summarized above. In addition, there remains a large gap between the cost of preparing conventional materials and the cost of preparing nanoparticles. This will remain a challenge for the future if nanomaterials are to be competitive.

 

Table 3.3
Dispersions and Coatings-Nanotechnology Comparisons Between the United States, Europe, and Japan

LEVEL

1 (Highest)

2

3

4

Enablers

       

Particle Preparation

U.S./Europe

Japan

   

Stabilization

U.S./Europe

Japan

   

Scaleup

       

Characterization

U.S./Europe

Japan

   

Coating

U.S./Japan/ Europe

     

Opportunities

       

Process Control

   

U.S.

Japan/Europe

Process/Product Co-Design

   

U.S.

 

Modeling

 

U.S./Japan

   


Published: September 1999; WTEC Hyper-Librarian