功能材料5：Ch4 能源材料简介2013.ppt

Can Your Smartphone See Through Walls? The chips generate and radiate high-frequency electromagnetic waves, called terahertz (THz) waves, that fall into a largely untapped region of the electromagnetic spectrum -- between microwaves and far-infrared radiation -- and that can penetrate a host of materials without the ionizing damage of X-rays. When incorporated into handheld devices, the new microchips could enable a broad range of applications in fields ranging from homeland security to wireless communications to health care, and even touchless gaming. In the future, the technology may lead to noninvasive cancer diagnosis, among other applications. Researchers have long touted the potential of the terahertz frequency range, from 0.3 to 3 THz, for scanning and imaging. Such electromagnetic waves can easily penetrate packaging materials and render image details in high resolution, and can also detect the chemical fingerprints of pharmaceutical drugs, biological weapons, or illegal drugs or explosives. However, most existing terahertz systems involve bulky and expensive laser setups that sometimes require exceptionally low temperatures. The potential of terahertz imaging and scanning has gone untapped because of the lack of compact, low-cost technology that can operate in the frequency range. Terahertz (THz) waves Non-Destructive Testing3D THz Imaging of IC Package Terahertz Image of Shoe with Hidden Ceramic Knife Plastic Explosive Pyroelectricity （热释电） Pyroelectricity is the ability of certain materials to generate a temporary voltage when they are heated or cooled. The change in temperature modifies the positions of the atoms slightly within the crystal structure, such that the polarization of the material changes. This polarization change gives rise to a voltage across the crystal. If the temperature stays constant at its new value, the pyroelectric voltage gradually disappears due to leakage current . Pyroelectricity should not be confused with thermoelectricit