Smart Materials And Nonequilibrium Thermodynamics

As already mentioned, one of the key features of smart materials is that they frequently have to operate far away from equilibrium. There is considerable freedom in the process of establishing a microscopic model of the smart material and extracting a relevant macroscopic property from it for example, when obtaining the stress from an ensemble of dumbbells via Eq. (12) . This freedom is not complete, however, because any micro- or mesoscopic model that we set up must comply with the rules of...

Piezoelectricity

Relationship Between Crystal Symmetry and Properties All crystals can be classified into 32 point groups according to their crystallographic symmetry. These point groups are divided into two classes one has a center of symmetry, and the other lacks it. There are 21 noncentrosymmetric point groups. Crystals that belong to 20 of these point groups exhibit piezoelectricity. Although cubic class 432 lacks a center of symmetry, it does not permit piezoelectricity. Of these 20 point groups, 10 polar...

O

As barium titanate and PZT) are based on the perovskite structure (Fig. 1). The perovskite structure (ABO3) is the simplest arrangement where the corner-sharing oxygen octahedra are linked together in a regular cubic array smaller cations (Ti, Zr, Sn, Nb, etc.) occupy the central octahedral B site, and larger cations (Pb, Ba, Sr, Ca, Na, etc.) fill the interstices beween octahedra in the larger A site. Compounds such as BaTiO3, PbTiO3, PbZrO3, NaNbO3, and KNbO3 have been studied at length and...

1 1

Overlaid optical fiber evanescent wave spectra obtained duringthe cure ofEpikote 828 and hexanediamine at 40 C (6). Figure 8. Schematic of fluorimetry-based fiber-optic sensor system for monitoring cure. Figure 8. Schematic of fluorimetry-based fiber-optic sensor system for monitoring cure. the spectrum are changed due to changes in the chemical structure of the fluorescent curing agent. The peak shifts of the spectra provide a quantitative measurement ofthe cure state....

Piezoelectric Materials

This section summarizes the current status of piezoelectric materials single-crystal materials, piezoceramics, piezopolymers, piezocomposites, and piezofilms. Table 3 shows the material parameters of some representative piezoelectric materials described here (6,7). Piezoelectric ceramics are widely used at present for a large number of applications. However, single-crystal materials retain their utility they are essential for applications such as frequency stabilized oscillators and surface...

204

Reception, respectively, because each system tries to detect objects at these temperatures. At first glance, the main difference between snake-based and beetle-based infrared detection is the wavelength region of peak intensity (Xmax). Cooler objects, for example, mammals at 37 C, emit maximally in the far-IR, in the 8-12 m atmospheric transmission window. As an object becomes hotter, for example, a forest fire at 750 C, the Xmax shifts to shorter wavelengths that place it in the 3-5 m...

Conclusion

Intrinsically smart structural composites for strain sensing, damage sensing, temperature sensing, thermal control, and vibration reduction are attractive for smart structures. They include cement-matrix and polymermatrix composites, particularly cement-matrix composites that contain short carbon fibers and polymer-matrix composites that contain continuous carbon fibers. The electrical conductivity of the fibers enables the dc electrical resistivity of the composites to change in response to...

Characterization Of Porous Silicon

The body of knowledge about PSi formation has been obtained from current-voltage characteristics, as described earlier (5). Besides electrochemistry, several other methods have been employed to study the morphology of PSi. Among them, transmission electron microscopy (TEM) has contributed a large amount ofinformation about structural details on individual pore propagation and silicon microcrys-tals because it is the only method to visualize microporous silicon directly (4). Scanning electron...

Bibliography

Matthew, Application of chitosan-based polysaccharide biomaterials in cartilage tissue engineering A review. Biomaterials 21 2589-2598 (2000). 2. G.A.F. Robert and K.E. Taylor, The formation of gels by reaction of chitosan with glutaraldehyde. Makromol. Chem. 190, 955-960 (1989). 3. K.D. Yao, T. Peng, M.F.A. Goosen, J.M. Min, and Y.Y. He, pH-sensitivity of hydrogels based on complex forming chitosan-polyether interpenetrating polymer network. J. Appl. Polym. Sci. 48(2),...

Actuators

Generation of electrical stimuli (e.g., a change in potential) as a result of the sensing process can be used to initiate an appropriate response actuation. Consideration of the processes discussed earlier indicates that substantial changes occur when conducting polymers are oxidized reduced. These changes have been studied at the molecular level using a technique known as inverse chro-matography, both in solution (66-68) and in the gas phase (69,70). These studies revealed that at least when...

MfMm 1 MfMm

In which M is the elastic modulus of interest, E22, G12, or V23 Mf the constituent reinforcing fiber modulus Ef, Gf, vf and Mm the constituent matrix modulus Em, Gm, vm. The reinforcement factor is determined empirically by curve-fitting the experimental results. When < x), the Halpin-Tsai formulas lead to the classical rule-of-mixtures relation, and when 0, the Halpin-Tsai formulas lead to the inverse form of the rule-of-mixtures For reinforcing fibers such as carbon or Kevlar, which exhibit...

Ef1 Vf EmVf

Composite lamina elastic properties derived on the basis of the isostress loading condition provide only marginal agreement with actual results. The isostress derivation does not take into account the effects of the Poisson contraction. Therefore other mesomechanics approaches are necessary for evaluating lamina elastic constants from constituent materials that exhibit highly anisotropic elastic behavior. According to more realistic assumptions that account for the Poisson contraction and...

S i [P fdf S J2 S i3

Where P( f) is the power spectrum density, S is the total power distributed across the frequency range considered, and (S )i is the power at frequency level i. Here, the level i( 1-4) stands for the range of frequencies given in Table 2. Discrimination of Skin that has Atopic Dermatitis. The neural network was trained to recognize atopic and normal healthy skins. The neural network employed was a hierarchical network the training method used was instructor-assisted training, in which the...

80

Schema of animal experiment. Figure 19. Opening closing functions of valve driven by transcu-taneous energy transformer system. Figure 20. Schematic of the artificial sphincter using SMA. Figure 20. Schematic of the artificial sphincter using SMA. transformer system. The distance between the primary and secondary coils was 3-4 mm, and the induced current to the heating wire was 7.6 V in the peak-to-peak amplitude. The figure shows that the valve started to open and released the...

10

11.4(4 x 10 ) 12.4(8 x 10 ) 11.3(3 x 10-2) 1.02(3 x 10-3) 0.82(4 x 10-3) 0.78(2 x 10-3) two laminae to press onto one another and hence contact tightly. In the unidirectional sample, the fibers of one of the laminae just sank into the other lamina at the junction, so pressure helped relatively little in the contact between fibers of adjacent laminae. Moreover, in the crossply, every fiber at the lamina-lamina interface contacts many fibers of the other lamina, whereas, in the unidirectional...

Conclusions

The discovery of inherently conducting polymers just over 20 years ago provided materials that could be utilized as an organic alternative in areas previously limited to the use of inorganic materials. The use of inherently conducting polymers in areas such as sensors, electrochemical actuators, photovoltaic materials, electronic components, and light-emitting coatings has subsequently been pursued. In many instances, the polymers were coupled with the new processing and fabrication approaches...

392

Excitatory spectra of DGEBA-DDS epoxy obtained in situ at 180 C as a function of cure time (spectra plotted without regard to intensity) (8). fiber core by reflecting at the boundary between the fiber core and the resin in the stripped region. The reflection-type sensor uses Fresnel reflection at the cut end of the fiber, which contacts the polymer (5,12,13). The changes in the intensity of light result from changes in the reflection rate at the boundary between the fiber core and the...

Optical Properties Of Porous Silicon

The demand for visible light-emitting devices made entirely from silicon is enormous because silicon is the dominant material for electronic and optical devices such as waveguides, detectors, and modulators. However, silicon is an indirect semiconductor, and thus light emission is inefficient. A direct photon transition at the energy of the minimum band gap does not meet the requirement of conservation of momentum in silicon. Therefore, electrons at the minimum ofthe conduction band need a...

85

Structures of ceramic actuators. Figure 13. Structures of ceramic actuators. Figure 14. Two types of piezoelectric bimorphs (a) antiparallel polarization type and (b) parallel polarization type. as shown in Fig. 14. Two poled piezoelectric plates t 2 thick and L long are bonded so that their polarization directions are opposite or parallel to each other. In the cantilever bi-morph configuration where one end is clamped, the tip displacement < 5z under an applied voltage V is < 5z...

Introduction

Many materials emit light during the application of a mechanical energy. This phenomenon is usually referred to as mechanoluminescence (ML) or triboluminescence (1). The more historical term is triboluminescence. It stands for tribo-induced luminescence, and this was the term used for more than a century to refer to light emission induced by any type of mechanical energy (2). The term mechano-luminescence was not proposed until 1978 (3). The prefix mechano is correlated to the general...

008 007 006 005 004 003 002 001

Relation between delamination extent and electric resistance of CFRP laminate. Numbers in the figures indicate the positions of delamination (95). I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 0.2 0.4 0.6 Delamination size a L 02 904 02 s Figure 37. Relation between delamination extent and electric resistance of CFRP laminate. Numbers in the figures indicate the positions of delamination (95). C C composites are used for aerospace structures that operate at high temperature due to the...

2

Cylindrical gyroscope commercialized by Tokin (Japan). Figure 8. Cylindrical gyroscope commercialized by Tokin (Japan). signals through the piezoelectric effect. Examples of these applications are given in the following sections. Pressure Sensor Accelerometer Gyroscope The gas igniter is one of the basic applications of piezoelectric ceramics. Very high voltage generated in a piezoelectric ceramic under applied mechanical stress can cause sparking and ignite a gas. Piezoelectric...

Pzt

The highest bandwidth of the microactuators and has among the highest displacements. Electrostrictive PMN possesses the lowest hysteresis of any of the actuator materials. However, the temperature operating limits for PMN would require special insulation. Although PZT is preferred for most applications, future commercial applications may favor direct replacement of PZT with PMN because of its superior hysteresis efficiency. The shape memory material, Nitinol, produces the greatest displacements...

Anticounterfeiting And Tamper Indicator Devices

Counterfeiting, forgery, tampering, and piracy of valuable documents and products has existed from time immemorial. Counterfeiting has become a multibillion dollar business that is prospering more than many of the victim companies. This highly organized trade results in lost revenue to both companies and governments, as well as loss jobs in private and public sectors. The motivation for professional counterfeiters is the ease of making huge profits and the risk of being caught and penalized is...

Porous Silicon Chemosensors

Most chemical sensors based on PSi use the material's unique property to emit light efficiently at room temperature. Reversible reduction of photoluminescence due to the specific or nonspecific adsorption of analytes from vapor to the porous matrix renders PSi a fast responding sensor for many vapors and, if suitably functionalized, for adsorbents in liquids. A typical photoluminescent spectrum of PSi usually has a bandwidth of 200 nm and the wavelength of maximum emission varies from 500-900...

Info

Sources Data after Flinn and Trojan, (4, pp. 560-573) Hull (5, pp. 29-33) NASA LeRC DuPont AMS. Sources Data after Flinn and Trojan, (4, pp. 560-573) Hull (5, pp. 29-33) NASA LeRC DuPont AMS. candidate PMCs with much higher upper service temperature capabilities. PMCs consolidated with thermosetting polyimides such as PMR (polymerization of monomer reactants), Avimid-R, AMB-21 and VCAP-75 are replacing epoxies for elevated temperature applications. PMR (e.g., PMR-15, PMR-II-50) and the other...

Ii

Idealized structure of a Ln1-xAxMnO3 distorted perovskite. Figure 4. Idealized structure of a Ln1-xAxMnO3 distorted perovskite. Figure 6. Double-exchange mechanism according to Zener. Figure 6. Double-exchange mechanism according to Zener. which gives rise to the tilting of the MnO6 octahedra. This distortion is quantified by the Goldsmith tolerance factor t dA-O V2(dMn-O) , where dA-O and dMn-O are the A cation-oxygen and Mn-oxygen bond lengths, respectively. Usually, for manganites...

E

Effective strain range eeff(TN) of Ti-Ni that corresponds to an optimal force zone is much larger than the eef(SS) of stainless steel. Hence, a superelastic device can provide constant pressure even if the pressed part recedes by a limited amount during the installed period. On the other hand, the pressure exerted by an appliance made from stainless steel will drop drastically if the pressed part deforms, so that performance deteriorates. The orthodontic arch wire that is presented as an...

Charge Ordering In Perovskite Manganites

Charge carriers doped into antiferromagnetic insulators as in La2NiO4 and La2CuO4 tend to be arranged in stripes for favorable doping levels. An electronic phase separation is created by stripes of holes interspaced by anti-ferromagnetic electron-rich regions (40). A different kind of electronic phase separation also occurs in half-doped Ln0.5AE0.5MnO3 manganites, where the eg carriers eg0 eg1 are delocalized in the paramagnetic state but localized in alternating Mn4+ and Mn3+ planes below the...

Fiber Optics Bragg Grating Sensors

Fiber Bragg Grating Sensor Demodulation 408 Fiber Bragg Grating Sensor Applications 412 Fiber Optics, Theory and Applications 415 Fiber Optic Sensors for Smart Structures 415 Fiber Optic Smart Structure Applications 419 Applications of Smart Materials and Smart Structures in Fish Aquatic Studies 424 Flip-Chip Applications, Underfill Materials 438 Development of No-Flow Flip-Chip Underfills 441 Development of Novel Reworkable Underfills 444 Development of Molded (Tablet) Flip-Chip Underfills 446...

Piezoelectric Magnetohetrological Application In Civil Engineering

The Encyclopedia of Smart Materials (ESM) contains the writings, thoughts, and work of many of the world's foremost people (scientists, educators, chemists, engineers, laboratory and innovative practitioners) who work in the field of smart materials. The authors discuss theory, fundamentals, fabrication, processing, application, applications and uses of these very special, and in some instances rare, materials. The term smart structure and smart materials are much used and abused. Consideration...

V

Where Sc and Tc are the generalized electric strain and stress vectors. The work done by the electrical forces can be written as where Se is a vector of electrical field (potential length), Te is a vector of electrical displacement (charge area), and Vp is the volume pertaining to the piezoelectric material. To apply piezoelectric materials in adaptive composite systems, the properties are defined relative to the poling direction through the thickness, and the material is approximately...

T

Application of a TTI as a food quality monitor (19). the wick from the reservoir pad (paper pad), and adhesives. The response temperature is usually the melting point of the specialty chemical. The prepared TTI tag remains inactive until it is activated. The indicator is activated when a polyester pull-strip is removed and allows contact between the porous paper and the reservoir. When exposed to temperatures higher than the threshold temperature, the chemical in the reservoir melts...

Electromagnetic Applications Of Biomimetic Research

When examining the landscape of biomimetics, the application is obvious in many areas, and many of these applications are defense-related. The study of fish swimming has obvious tie-ins to underwater locomotion and naval interests (36). Much of the work in structural biomimet-ics has Army interest due to the potential of producing next-generation, lightweight armor based on naturally occurring, biological composites (37,38). From a commercial standpoint, few biomimetic results have been as...

1

As a result, in n-type silicon, an excess of positive charges in the semiconductor renders the silicon surface susceptible to nucleophilic attack. Nucleophiles such as H2O and CH3OH react with this surface of reverse-biased PSi (20). Less active nucleophiles such as trifluo-roacetic, acetic, and formic acids, however, react only with the silicon surface and produce a silyl-ester-modified surface upon irradiation (20-22). Because this kind of reaction takes place only under...

6

Illustration of the Jahn-Teller distortion in manganese oxides (a) Mn4+ 3d3 that has cubic symmetry (no JahnTeller distortion) and (b) Mn3+ 3d4 that has tetragonal symmetry (Jahn-Teller distortion). to the Jahn-Teller distortion of the single electron in the eg orbitals of a high spin Mn3+ 3d4 ion (Fig. 17). A cooperative distortion of the MnO6 octahedra that have long Mn-O bonds along the c axis and short Mn-O bonds along the a and b axes results in macroscopic tetragonal symmetry...

E11 E Ef Vf EmVm or 1 Vf

Loads applied to the composite lamina that are perpendicular or transverse to the fiber direction follow a similar derivation, but the loading is referred to as an isostress condition (see Fig. 9 for isostrain vs. isostress). Under the isostress assumption, the stresses are assumed to be the same in the lamina, fibers, and matrix. However the strains become a function of the area fractions of fibers and matrix to that of the total composite. It follows that the isostress condition can be...

Glucose Sensors

Much of the recent literature on biomedical sensing has focused on methodologies for detecting glucose levels in diabetic patients to sense the need for insulin release without requiring self-diagnosis through needle sticks. Diabetes is a highly prevalent disease in the United States, and many researchers have been searching for methods of mimicking a naturally functioning pancreas through tissue engineering, encapsulating pancreatic islets of Langerhans cells, creating insulin pumps that use...

Alferd Hans Rzeppa Full History

Vitsab was formerlly known as I-Point. Vitsab was formerlly known as I-Point. Wells and Singh investigated the use of these indicators as a quality change monitor for perishable and semiper-ishable products such as tomatos, lettuce, canned fruitcake, and UHT sterilized milk (22). It was shown that the response kinetics of these indicators correlates with quality loss in the products studied. The indicators studied have activation energies of 84 to 105 kJ mol (20 to 25 kcal mol). Major...

220 0705 035 054

Sand is a much more common component in concrete than silica fume. It differs from silica fume in its relatively large particle size and negligible reactivity with cement. Sand gives effects that are opposite from those of silica fume sand addition decreases the specific heat and increases the thermal conductivity 99 . Table 7 99 shows the thermal behavior of cement pastes and mortars. Comparison of the results on cement paste without silica fume and those on mortar without silica fume shows...

Contributors

Michelle Addington, Harvard, University, Cambridge, MA, Architecture Yasuyuki Agari, Osaka Municipal Technical Research Institute, Joto- ku, Osaka, Japan, Polymer Blends, Functionally Graded U.O. Akpan, Martec Limited, Halifax, NS, Canada,Vibration Control in Ship Structures Samuel M. Allen, Massachusetts Institute of Technology, Cambridge, MA, Shape-Memory Alloys, Magnetically Activated Ferromagnetic Shape-Memory Materials J.M. Bell, Queensland University of Technology, Brisbane Qld,...