新型金属蜂窝板燃烧器的高效燃烧现象分析

新型金属蜂窝板燃烧器是通过采用双层或多层金属薄片制成,能有效地解决普通燃气灶具燃烧器存在的不足,使产品结构更加合理完善,性能更加稳定可靠,能效更加优越。本文以红外燃气灶具的核心部件—新型金属蜂窝板燃烧器为研究对象,利用红外摄像仪对红外燃气灶具和普通燃气灶具进行了对比研究。结果表明,红外燃气灶的火焰集中,温度分布均匀,燃烧效率比普通燃气灶高12.7%。     

A New Capillary Electrophoresis Apparatus with Piezoelectric Ceramics High Voltage Source and Amperometric Detector

IntroductionHighperformancecapiliar}'electrophoresis(HPCE)isanewanalyticaltechnology'rapidly'developedinrecentyears.Withtheadvantagesofsmallsample.highsensitivity,highresolution.rapidanalysisandverycheaprunning,ithasbeenappliedinchemistry'.lifescienc...     

Electric field assisted annealing effects on microstructure and ionic conductivity in ceria/YSZ oxide heterostructures

The effect of electric field assisted annealing on the microstructure, composition and ionic conductivity properties in CeO₂/YSZ oxide heterostructures have been investigated using molecular dynamics simulations. Amorphization–recrystallization steps were performed with and without external electric field of strength 10?MV/cm along three different orientations: in-plane (YZ), normal (X) and 45° resultant (XY) with respect to the oxide heterointerfaces. The microstructural and compositional differences at the interfaces and in the interior of the oxide heterolayers were evaluated and were found to show a clear correlation with the orientations of the applied field. In particular, the XY configuration displayed a compressive lattice strain of ～9% along with a reduced oxygen vacancy concentration when compared to the others. Ionic density profiles suggest pronounced segregation (～60% higher compared to the average value in the interior) of yttrium ions closer to the YSZ/CeO₂ interface for the XY configuration. Other configurations exhibit minimal to no such variations. These microstructural differences are found to affect the number of mobile charge carriers and the activation barriers associated with ionic migration through the oxide lattice and consequently, influence the ionic conductivity.     

Carbon dioxide reforming of methane on monolithic Ni/Al2O3-based catalysts

Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.     

Hyperbranched polymers as scaffolds for multifunctional reversible addition–fragmentation chain‐transfer agents: A route to polystyrene‐core‐polyesters and polystyrene‐block‐poly(butyl acrylate)‐core‐polyesters

Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition–fragmentation chain‐transfer (RAFT) agents. The polyester‐core‐based RAFT agents were subsequently employed to synthesize star polymers of n‐butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free‐radical process. Although the polyester‐core‐based RAFT agent mediated polymerization of n‐butyl acrylate displayed a linear evolution of the number‐average molecular weight (M_n) up to high monomer conversions (>70%) and molecular weights [M_n > 140,000 g mol^?1, linear poly(methyl methacrylate) equivalents)], the corresponding styrene‐based system reached a maximum molecular weight at low conversions (≈30%, M_n = 45,500 g mol^?1, linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n‐butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene‐based star polymers were successfully cast into highly regular honeycomb‐structured microarrays. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3847–3861, 2003     

Characterization of lead and lead leaching properties of lead glazed ceramics from the Solis Valley, Mexico, using inductively coupled plasma-mass spectrometry (ICP-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT)

Ingestion of relatively small amounts of lead is now recognized to cause significant neurological and cognitive effects in humans. Large quantities may be fatal, yet lead poisoning, especially of children, is still a major public health concern in many parts of the world. In rural Mexican communities lead oxide (PbO) is added to ceramic glaze as a fluxing agent, lowering starting firing temperatures to 500 °C. The purpose of this study is to characterize the lead chemical forms in ceramic glazes from the Solis Valley, Mexico, to investigate lead leaching properties of these ceramics, and to demonstrate the applicability of lead isotope signatures as a means of tracing lead source origins. Ceramics were collected from the rural village of Santa Maria de Canchesda, State of Mexico, Mexico. Dried liquid glazes, post-fired glaze material, and pure PbO were analyzed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). Results from DRIFT analysis indicate that PbO (1429 cm⁻¹ band) is the active form of lead found in liquid glazes and ceramics. Some shifting of 1429 cm⁻¹ PbO peak to lower wavenumbers occurs in post-fired ceramics, and this may be due to the formation of lead bisilicate during firing. Ceramics samples were leached in 0.02 M citric acid solution for 1 min, and leached lead concentrations were measured using inductively coupled plasma-mass spectrometry (ICP-MS). Lead concentrations in these leachates varied from 0.4-80.4 μg ml⁻¹, while the control pottery from the US leached only 0.1 μg ml⁻¹ lead. Elemental distributions on glaze surfaces were identified by laser ablation (LA)-ICP-MS. Nitric acid extracts of soils, teeth, and ceramic glazes were analyzed for lead isotope ratios (²⁰⁷Pb/²⁰⁶Pb vs. ²⁰⁸Pb/²⁰⁶Pb) using ICP-MS. Similarities of tooth and ceramic lead isotope ratios indicate that ceramics may be a substantial source of body lead burden in the Solis Valley. This study demonstrates the applicability of lead isotope ratios for lead source identification, and it identifies potential health risks from ceramic use induced lead toxicity within the Solis Valley.     

Influence of the Grain Boundaries on the Heat Transfer in Laser Ceramics

Grain boundaries play a key role in determining several key properties of polycrystalline laser ceramics. Heat transfer measurements at low temperature constitute a good tool to probe grain boundaries. We review the results of heat transfer measurements in polycrystalline Y₃Al₅O₁₂ garnets as well as Y₂O₃ and Lu₂O₃ sesquioxide materials obtained by self-energy-driven sintering of nano-particles. The average phonon mean free path in Y₃Al₅O₁₂ was found to be significantly larger than the average grain size and to scale with temperature as T ⁻² at low temperature. Existing models describing the interaction between phonons and grain boundaries are reviewed. Correct temperature dependence of the mean free path and order of magnitude of scattering rates were found by assuming the existence of a grain boundary layer having acoustic properties different from those of the bulk. A different temperature dependence of phonon mean free path was found for the sesquioxides and was ascribed to the stronger elastic anisotropy of these materials. The thermal resistance associated to the grain boundaries of laser ceramics was found to be lower than in other dense polycrystalline ceramic materials reported in the literature.     

Mass spectrometric analysis of ceramics after decomposition with elemental fluorine

The features of a combustion with elementary fluorine for the case of compact SiC ceramics and model substances for boron containing ceramics (H₃BO₃ and Na₂B₄O₇) were investigated with the aim of their decomposition and analysis. On-line detection of the gaseous decomposition products by quadrupole mass spectrometry using electron impact ionisation was studied. Limitations by blanks and transport interferences were investigated. Standard addition as well as the isotope dilution technique were used for calibration in the case of B, C and W at the trace and major component level.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthdayDeceased May 1995.     

氧化锆陶瓷的摩擦磨损行为与机理

氧化锆陶瓷的工程应用前景广阔，在许多场合都必须与水或水溶液接触，但有关这种陶恣在水中的摩擦磨损行为和机理的研究报道不多见，而且已有的工作也不够深入。因此，对氧化锆陶瓷分别在水润滑和干摩擦下的摩擦学特性及其磨损机理进行了考察。