Piezoelectric Materials

Piezoelectric materials are materials that produce an electric current when they are placed under mechanical stress. The piezoelectric process is also reversible, so if you apply an electric current to these materials, they will actually change shape slightly (a maximum of 4%).

Example: Quartz; Aluminum Nitride; Barium Titanate; Gallium Phosphate; Lead

There are several materials that we have known for some time that posses piezoelectric properties, including bone, proteins, crystals (e.g. quartz) and ceramics (e.g. lead zirconate titanate).

Piezoelectricity is an exciting field of Nanotechnology, and there are already tests being run outside labs to try and harness this form of power. In many places including Japan’s subway, dance floors across the world and football stadiums, engineers have already put in place piezoelectric floors that use the high volume of footfall to decrease their demand for electricity from the grid. With a bit of luck in the years to come, piezoelectricity will become another weapon which we can use to reduce our reliance on fossil fuels and to derive the energy we need.

SHAPE MEMORY ALLOY

A shape-memory alloy is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated. It may also be called memory metal, memory alloy, smart metal, smart alloy, or muscle wire.

The two most prevalent shape-memory alloys are copper-aluminium-nickel and nickel-titanium (NiTi), but SMAs can also be created by alloying zinc, copper, gold and iron. Although iron-based and copper-based SMAs, such as Fe-Mn-Si, Cu-Zn-Al and Cu-Al-Ni, are commercially available and cheaper than NiTi, NiTi-based SMAs are preferable for most applications due to their stability and practicability and superior thermo-mechanic performance. SMAs can exist in two different phases, with three different crystal structures (i.e. twinned martensite, detwinned martensite and austenite) and six possible transformations.

Shape-memory alloys have different shape-memory effects. Two common effects are one-way and two-way shape memory. A schematic of the effects is shown below.

The procedures are very similar: starting from martensite (a), adding a reversible deformation for the one-way effect or severe deformation with an irreversible amount for the two-way (b), heating the sample (c) and cooling it again (d)

One-way memory effect When a shape-memory alloy is in its cold state (below As), the metal can be bent or stretched and will hold those shapes until heated above the transition temperature. Upon heating, the shape changes to its original. When the metal cools again, it will retain the shape, until deformed again.

With the one-way effect, cooling from high temperatures does not cause a macroscopic shape change. A deformation is necessary to create the low-temperature shape. On heating, transformation starts at As and is completed at Af (typically 2 to 20 °C or hotter, depending on the alloy or the loading conditions). As is determined by the alloy type and composition and can vary between −150 °C and 200 °C.

Two-way memory effect The two-way shape-memory effect is the effect that the material remembers two different shapes: one at low temperatures, and one at the high-temperature shape. A material that shows a shape-memory effect during both heating and cooling is said to have two-way shape memory. This can also be obtained without the application of an external force (intrinsic two-way effect). The reason the material behaves so differently in these situations lies in training. Training implies that a shape memory can "learn" to behave in a certain way. Under normal circumstances, a shape-memory alloy "remembers" its low-temperature shape, but upon heating to recover the high-temperature shape, immediately "forgets" the low-temperature shape. However, it can be "trained" to "remember" to leave some reminders of the deformed low-temperature condition in the high-temperature phases. There are several ways of doing this. A shaped, trained object heated beyond a certain point will lose the two-way memory effect.

PROPERTIES

 Sensing materials and devices

 Actuation materials and devices

 Control devices and techniques

 Self-detection, self-diagnostic

 Self-corrective, self-controlled, self-healing

 Shock-absorbers, damage arrest

APPLICATIONS

Smart materials got vast applications in Aerospace, Mass transit, Marine, Automotive, Computers and other electronic devices, Consumer goods applications, Civil engineering, Medical equipment applications, Rotating machinery applications. The health and beauty industry is also taking advantage of these innovations, which range from drug-releasing medical textiles, to fabric with moisturizer, perfume, and anti-aging properties. Many smart clothing, wearable technology, and wearable computing projects involve the use of e-textiles. Intelligent Structures of Architecture and Civil Engineering are been a subject to reveal and unlock the ancient and magnificent architecture by human on the redesigning the earth's geography. The research on archeological technology of Structural engineering, advanced innovations in Civil Engineering, current applied principles of geotechnical, structural, environmental, transportation and construction engineering, sea defense systems against raising sea levels, under water-on water constructions, floating and green cities architecture, case study on Structural & Civil Engineering.

 Archeological technology of structural engineering

 Advanced innovations in civil engineering

 Sea defense systems against raising sea levels

 Under water - on water constructions

 Floating and green cities architecture

 Case study on structural and civil engineering