Smart materials of material science


  • Non-Newtonian fluid:- A Non-Newtonian fluid is fluid whose flow properties are not described by a single constant value of viscosity. Many polymer solutions and molten polymers are non-newtonian fluids, as are many commonly found substances such as ketchup, starch suspensions, paint, blood and shampoo. In a newtonian fluid, the relation between the shear stress and the strain rate is linear, the constant of proportionality being the coefficient of viscosity. In a non-newtonian fluid, even be time dependent. Therefore a constant coefficient of viscosity cannot be defined. A ratio between shear stress and rate of strain can be defined, this concept being more useful for fluids without time dependent behavior. Although the concept of viscosity is commonly used to characterize a material, it can be in adequate to describe the mechanical behavior of a substance, particularly non-newtonian fluids. They are best studied through several other rheological properties which relate the relations between the stress and strain rate tensors under many different flow conditions, such as oscillatory shear, or extensional flow which are measured using different devices or rheometers. The properties are better studied using tensor valued constitutive equations, which are common in the field of continuum mechanics.

  • Piezoelectricity:- Piezoelectricity is the ability of some materials to generate an electric field or electric potential in response to applied mechanical stress. The effect is closely related to a change of polarization density within the material's volume. If the material is not short  circuited, the applied stress induces a voltage across the material. The piezoelectric effect is reversible in that material exhibiting the direct piezoelectric effect also exhibit the reverse piezoelectric effects.
  • Naturally occurring crystals:-
  • Berlinite
  • Cane sugar
  • Quartz
  • Rochelle salt
  • Topaz
  • Tourmaline group minerals
  • Man made crystal:-
  • Gallium orthophosphate
  • Langasite

  • Temperature responsive polymer:- A temperature responsive polymer is a polymer which undergoes physical change when external thermal stimuli are presented. The ability to undergo such changes under easily controlled conditions makes this class of polymers fall into the category of smart materials. These physical changes can be exploited for many analytical techniques. After numerous investigations of poly (N-isopropylacrylamide) (poly-NIPAAm), there was a sparked interest in the application of this and many other stimuli-responsive polymers. There has been extensive research in the applications of intelligent polymers for use as stationary phases, extraction compounds, surface modifiers, drug delivery, and gene delivery.

  • Ferro fluid:- A ferro fluid, is a liquid which becomes strongly polarized in the presence of a magnetic field. Ferro fluids are colloidal mixtures composed of nanoscale ferromagnetic, or ferrimagnetic, particles suspended in a carrier fluid, usually an organic solvent or water. The ferro magnetic nano particles are coated with a surfactant to prevent their agglomeration. Although the name may suggest otherwise, ferro fluids do not display ferro magnetism, since they do not retain magnetization in the absence of an externally applied field. In fact, ferro fluids display paramagnetism, and are often described as super paramagnetic due to their large magnetic susceptibility. Permanently magnetized fluids are difficult to create at present.
  • Application:-
  • Electronic devices
  • Military
  • Aerospace
  • Medicine

  • Halochromic material:- A halochromic material is a material which changes color when pH change occur. The term chromic is defined as materials that can change colour reversibly with the presence of a factor. In this case, the factor is pH. The pH indicators have this property. Halochromic substances are suited for use in environments where pH changes occur frequently, or places where changes in pH are extreme. Halochromic substances detects alterations in the acidity of substances, like detection of corrosion in metals. Halochromic substances may be used as indicators to determine the pH of solutions of unknown pH. The colour obtained is compared with the colour obtained when the indicator is mixed with with solutions of known pH. The pH of the unknown solution can be estimated obvious disadvantages of this method include its dependency on the colour sensitivity of the human eye, and that unknown solutions that are already coloured cannot be used. 

No comments