By characterizing and then modifying molecular structures chemical engineers are able to:
- Enhance desirable physical properties and performance attributes, and
- Suppress unwanted ones.
With each new development a greater understanding of the complex relationships between specific modifications and the changes they bring about is achieved. While enormous advances have been made in recent years, there are still many challenges remaining.
Chemical engineers are developing advanced materials with superior properties that allow for successful performance under increasingly punishing operating conditions. Initially created to respond to the challenges of space travel, many impressive advances have been made using materials from each of the major material classes—plastics, ceramics, and metals.
Advances that are out of this world
Following the launch of the Space Age in the late 1950s, chemical engineers played an important role in making safe, successful space exploration a reality.
To withstand the rigors of space travel, highly specialized, high-performance materials had to be developed. Demanding conditions in extreme environments necessitated the use of ever-more-advanced materials. New ways of manipulating chemistry and internal structures had to be devised in order to create materials able to survive in:
- Extremely hot or cold temperatures,
- Severely corrosive environments, and
- Highly erosive and high-friction conditions.
These materials also had to be able to withstand enormous loads without bending or deforming. Ultralight weight had to be combined with such superior mechanical properties as strength and fatigue and fracture resistance.
Chemical engineers have strived to reach these goals, and their efforts have resulted in the ongoing realization of numerous high-performance plastics, ceramics, and metals. Many of the imaginative materials originally developed for space programs have now found their way into industrial and consumer applications where high performance is in demand.
High-performance plastics are replacing more traditional materials for use in hostile environments. These advanced plastics possess such characteristics as exceptional strength, light weight, temperature resistance (in excess of 160oC), chemical resistance, and dimensional stability. They are also relatively easy to process, can be colored or transparent, and can be molded to create desirable structures.
Today high-performance ceramics are found in industrial equipment where they are likely to encounter extreme temperatures, harsh operating conditions, and excessive abrasion. This equipment includes pump components, cutting tools and extrusion dies, bearings and seals, high-temperature filters and membranes, as well as sensors, electronic components, and automotive engine parts. Advanced ceramics exhibit improved mechanical strength and greater resistance to fracture and chipping and in some cases can be fired at considerably lower temperatures, which provides cost savings.
Advanced metal alloys based on aluminum, magnesium, and titanium, which provide greater structural strength at reduced weight, are used for aircraft and spacecraft applications as well as prosthetics and artificial joints. Stainless steel is found in industrial processing equipment and surgical instruments that must resist corrosion under harsh operating conditions.
Chemical engineers are also pioneering significant advances in metal matrix composites, which are combinations of one or more nonferrous metals with carbon particles or ceramics dispersed throughout the metal matrix. These new materials exhibit improved structural strength, wear resistance, and thermal conductivity.
Incredibly small, nanoscaled materials are produced with particle sizes measured in terms of nanometers. A nanometer is equal to one billionth of a meter. In recent years chemical engineers have been responsible for engineering systems able to produce and use ultra-small particles in a growing number of applications, from sunscreen to biomonitoring sensors that can explore inside a cell.
How small can you go?
Chemical engineers design experiments involving nanotubes in order to improve the materials used in space-system architectures and thus help advance our exploration of outer space and other applications. Photo courtesy Aerospace Corporation.
The field of nanotechnology - one of the newer areas of materials science—makes use of the functional advantages that many materials demonstrate when they are produced in extremely small particle sizes. The prefix nano itself refers to a billionth (10-9), and in nanotechnology the basic unit of measurement is a nanometer, which is one-billionth of one meter.
A growing number of nanoscale materials and nanotechnology-related manufacturing techniques are already being used to:
- Produce advanced composite materials that have such improved properties as electroconductivity, catalytic activity, hardness, scratch resistance, and self-cleaning capabilities;
- Produce consumer products, such as cosmetics and sunscreens, that have improved aesthetic appeal and effectiveness;
- Improve the performance of compact, ultra-sensitive sensors and other analytical devices used for detecting disease, monitoring food quality, and assessing environmental, radiological, biological, and nuclear hazards; and
- Enable such medical advances as nanoscale drug-delivery particles that allow for the earlier diagnosis and improved treatment of cancer and other diseases.
Today specialized techniques developed by chemical engineers enable many common materials to be produced with individual particle dimensions measured in nanometers. Nanometer-sized particles demonstrate a broad range of more favorable physical properties compared with larger-sized particles. These properties include:
- Improved chemical resistance,
- Improved hardness and abrasion resistance,
- Increased tensile strength and flexibility,
- Favorable melting points,
- Favorable magnetic properties,
- Increased thermal and electrical conductivity, and
- Favorable surface-chemistry effects that improve the ability of a powder to be dispersed in a liquid.
Out of the lab into our lives
Chemical engineers are heavily involved in the ongoing discovery of nanoscaled materials that demonstrate desired properties. They are also instrumental in the development of the complex engineered systems required to produce these materials in commercial-scale quantities for use in real-world applications.