复合型高分子自限温发热材料及元器件在汽车冷启动方面的应用

采用HDPE／CB复合型高分子自限温发热材料制备了适于在汽车上使用的自限温加热带、发热管及相应的加热器，通过实验室模拟试验，研究了加热器的电热特性。在冬季的柴油车冷启动试验表明，组合加热装置对柴油车的冷启动及正常运行非常奏效，所研制的复合型高分子自限温发热材料及元器件用于汽车领域是可行的。     

Applications of atomic layer chemical vapor deposition for the processing of nanolaminate structures

Atomic layer chemical vapor deposition (ALCVD) is a variant of a CVD process that involves surface deposition for the controlled growth of nano-thickness films. ALCVD is based on the self-limiting surface reaction with less than a monolayer chemisorption of chemical precursors. Advantages of the ALCVD process are uniform film growth on large area substrate, easy control of composition in atomic level, low growth temperature, multi-layer thin film growth with various composition, and wide process window. Since initially developed by Suntola in 1977, ALCVD has been used for the growth of various materials, including oxides, nitrides, metals, elements, and compound semiconductors. This article reviews the basic principle, mechanism, characteristics, and applications of ALCVD.     

炭黑填充聚合物基PTC导电复合材料及制品的研究进展

介绍了PTC效应的几种主要机理,讨论了不同基体、填充物和加工工艺对此类复合材料PTC效应的影响,NTC效应产生的主要原因以及减缓或推迟NTC效应的方法,并对其商业推广应用进行了较为深入的探讨.     

UV-enhanced atomic layer deposition of ZrO2 thin films at room temperature

A UV-enhanced atomic layer deposition (UV-ALD) process was developed to deposit ZrO₂ thin films on poly(ethylene terephthalate) (PET) polymer substrates using zirconium tetra-tert-butoxide (ZTB) and H₂O as precursors with UV light. In the UV-ALD process, the surface reactions were found to be self-limiting and complementary enough to yield uniform, conformal, and pure ZrO₂ thin films on polymer substrates at room temperature. The UV light was very effective to obtain the high-quality ZrO₂ thin films with good adhesive strength on polymer substrates. The ZrO₂ thin films exhibit large-scale uniformity, sharp interfaces, and unique electrical properties.     

Self-limiting low-temperature growth of crystalline AlN thin films by plasma-enhanced atomic layer deposition

We report on the self-limiting growth and characterization of aluminum nitride (AlN) thin films. AlN films were deposited by plasma-enhanced atomic layer deposition on various substrates using trimethylaluminum (TMA) and ammonia (NH₃). At 185 °C, deposition rate saturated for TMA and NH₃ doses starting from 0.05 and 40 s, respectively. Saturative surface reactions between TMA and NH₃ resulted in a constant growth rate of ~ 0.86 Å/cycle from 100 to 200 °C. Within this temperature range, film thickness increased linearly with the number of deposition cycles. At higher temperatures (≥ 225 °C) deposition rate increased with temperature. Chemical composition and bonding states of the films deposited at 185 °C were investigated by X-ray photoelectron spectroscopy. High resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 73.02 and 396.07 eV, respectively. Films deposited at 185 °C were polycrystalline with a hexagonal wurtzite structure regardless of the substrate selection as determined by grazing incidence X-ray diffraction. High-resolution transmission electron microscopy images of the AlN thin films deposited on Si (100) and glass substrates revealed a microstructure consisting of nanometer sized crystallites. Films exhibited an optical band edge at ~ 5.8 eV and an optical transmittance of > 95% in the visible region of the spectrum.     

Fabrication of Coaxial Si<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Heterostructure Nanowires by O<Subscript>2</Subscript> Flow-Induced Bifurcate Reactions

We report on bifurcate reactions on the surface of well-aligned Si_1−x Ge _x nanowires that enable fabrication of two different coaxial heterostructure nanowires. The Si_1−x Ge _x nanowires were grown in a chemical vapor transport process using SiCl₄ gas and Ge powder as a source. After the growth of nanowires, SiCl₄ flow was terminated while O₂ gas flow was introduced under vacuum. On the surface of nanowires was deposited Ge by the vapor from the Ge powder or oxidized into SiO₂ by the O₂ gas. The transition from deposition to oxidation occurred abruptly at 2 torr of O₂ pressure without any intermediate region and enables selectively fabricated Ge/Si_1−x Ge _x or SiO₂/Si_1−x Ge _x coaxial heterostructure nanowires. The rate of deposition and oxidation was dominated by interfacial reaction and diffusion of oxygen through the oxide layer, respectively.     

Characterization of ultrathin electroactive films synthesized via the self-limiting electropolymerization of o-methoxyaniline

The electropolymerization of o-methoxyaniline under self-limiting deposition conditions yields ultrathin (<20 nm) coatings of an insoluble, low-molecular-weight polymer on planar indium-tin-oxide electrode substrates. The self-limiting nature of the electropolymerization is achieved by using citrate-buffered aqueous electrolytes (pH 4.7) in which the developing polymer that deposits at the electrified interface is neither conductive nor permeable to monomer. Although non-conductive as electrodeposited, the resulting poly(o-methoxyaniline) coating becomes electroactive when transferred to acidic aqueous electrolytes. The morphology and chemical structure of the poly(o-methoxyaniline) coatings are characterized by surface-sensitive methods including atomic force microscopy, specular-reflectance infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemistry. Fundamental understanding of the structure/property relationships derived from these investigations on planar substrates will ultimately be applied to three-dimensional electrode nanoarchitectures that incorporate such electroactive coatings for enhanced charge-storage functionality.     

Self-limiting growth of anatase TiO2: A comparison of two deposition techniques

Self-limiting deposition of titanium dioxide thin films was accomplished using pulsed plasma-enhanced chemical vapor deposition (PECVD) and plasma-enhanced atomic layer deposition (PEALD) at low temperatures (T < 200 °C) using TiCl₄ and O₂. TiCl₄ is shown to be inert with molecular oxygen at process conditions, making it a suitable precursor for these processes. The deposition kinetics were examined as a function of TiCl₄ exposure and substrate temperature. The quality of the anatase films produced by the two techniques was nominally identical. The key distinctions are found in precursor utilization and conformality. Pulsed PECVD requires 20 times less TiCl₄, while PEALD must be used to uniformly coat complex topographies.     

The fabrication of large-scale sub-10-nm core-shell silicon nanowire arrays

A combination of template-assisted metal catalytic etching and self-limiting oxidation has been successfully implemented to yield core-shell silicon nanowire arrays with inner diameter down to sub-10 nm. The diameter of the polystyrene spheres after reactive ion etching and the thickness of the deposited Ag film are both crucial for the removal of the polystyrene spheres. The mean diameter of the reactive ion-etched spheres, the holes on the Ag film, and the nanowires after metal catalytic etching exhibit an increasing trend during the synthesis process. Two-step dry oxidation and post-chemical etching were employed to reduce the diameter of the silicon nanowires to approximately 50 nm. A self-limiting effect was induced by further oxidation at lower temperatures (750°C ~ 850°C), and core-shell silicon nanowire arrays with controllable diameter were obtained.