保温时间对低温烧成多孔氧化支撑体性能影响的研究

以Al2O3为骨料,添加一定数量的烧结促进剂,通过挤出成型,在介于1100－1400℃之间的温度下烧成,制备出管式多孔陶瓷支撑体。考察了保温时间对孔支撑体性能的影响。得到具有较高孔隙率、较好渗透性能、较高机械强度以及良好耐腐蚀性能的管式多孔氧化铝支撑体。     

Preparation and visible-light photocatalytic activity of Au-supported porous CeO2 spherical particles using templating

Porous spherical CeO₂ particles were prepared by impregnation of a cerium precursor solution into organic monolith sphere particles, with subsequent firing at 500 °C in air. The single-phase CeO₂ powder had specific surface area of greater than 140 m²/g. Photodeposition with UV illumination loaded Au onto the CeO₂ particle surface, which changed from yellowish to purple because of localized surface plasmon resonance (LSPR). The Au-loading increased photocatalytic decomposition activity of the CeO₂ powder for gaseous 2-propanol (IPA) under visible light. Thermal desorption of IPA, which was adsorbed to all porous spheres, provided flux to the photocatalytic reaction field of the sphere outer surface.     

Viscosity of porous sintered glasses

Following an analogy between flow properties and field or transport properties, an equation which describes the porosity, P, dependence of the viscosity in porous sintered glasses is presented. Not only the pore volume fraction but also pore structure parameters, such as pore shape and orientation, are considered in the calculation and the equation is valid for the whole porosity range. For low porosities (P0.10) the approach coincides with the prediction of Mackenzie for spherical pores with a precision of 1%. The calculated values are in good agreement with experimental data on porous glasses available from the literature, if appropriate pore geometry is assumed at the different porosity levels.     

Coefficients of isothermal mass transfer in a porous body composed of spherical particles

The mass transfer coefficients are calculated for a model porous body composed of identical spherical particles. The results apply to low fluid levels in the threshold space.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 5, pp. 807–813, November, 1972.     

Strength of bond to bone and cytotoxicity of sintered bodies of hydroxyapatite/zirconia composite particles

Regarding sintered bodies of hydroxyapatite (HAP)/zirconia (PSZ) composite particles prepared by covering the surface of HAP particles with PSZ particles, their strength of the bond to bone after implanting them into an organism and their cytotoxicity were evaluated. Cytotoxicity tests were conducted by the colony formation method. Cytotoxicity was not observed in the sintered bodies of HAP/PSZ composite particles, or in sintered monolithic HAP body and sintered monolithic PSZ body. The strength of bond between a sintered body and a bone was evaluated by measuring the shear strength at the interface between them after a fixed period following implantation of a sintered body into a rabbit femur. In all cases of the sintered monolithic HAP body, and the sintered bodies of HAP/PSZ composite particles and monolithic PSZ body, when the implantation period increased, the shear strength of the sintered body/bone interface tended to increase. In particular, this tendency was very high in the case of sintered bodies of HAP/PSZ with weight ratios of 1/1.0 and 1/1.5, the shear strength for each reaching 20 MPa 12 months after implantation.     

Low-temperature sintered pollucite ceramic from geopolymer precursor using synthetic metakaolin

In this article, pollucite ceramic with high relative density and low coefficient of thermal expansion (CTE) was prepared from Cs-based geopolymer using synthetic metakaolin. Crystallization and sintering behavior of the Cs-based geopolymer together with thermal expansion behavior of the resulted pollucite ceramic were investigated. On heating at 1200 °C for 2 h, the amorphous Cs-based geopolymer completely crystallized into pollucite based on crystal nucleation and growth mechanism. Selected area diffraction analysis and XRD results confirmed the resulted pollucite ceramic at room temperature was pseudo-cubic phase with superlattice structure. Compared with Cs-based geopolymer using natural metakaolin, geopolymer using synthetic metakaolin in this article showed a much lower viscous sintering temperature range, which started at 800 °C, reached a maximum value of ?7.47 × 10^?4/°C at 1121.9 °C, and ended at 1200 °C. Cesium volatilization appeared only when temperature was above 1250 °C. Therefore, densified pollucite ceramic can be prepared from Cs-based geopolymer using synthetic metakaolin without cesium volatilization. Abnormal thermal shrinkage of pollucite ceramic was observed at temperature range from 25.3 to 54.6 °C because of pseudo-cubic to cubic phase transition, and its average CTE was 2.8 × 10^?6/°C from 25 to 1200 °C.     

Pressureless sintered ATZ and ZTA ceramic composites

Alumina-20 wt% zirconia (ATZ) and zirconia-20 wt% alumina (ZTA) composites were prepared by conventional sintering of commercial powders, with average particle sizes in the range 0.35–0.70 m. Sintering at 1650 °C for 4 h resulted in final densities up to 96%. Bending strength and hardness increased with the final density. The tetragonal volume fraction was strongly dependent on both the final density and tetragonal grain size. The relatively high fracture toughness of 9 MPa m^1/2 was associated with the highly dense microstructure consisting of tetragonal grains of the critical size.     

Deformation and fracture of sintered iron

Conclusion Metallographic-fractographic evaluation of the distribution of microdeformation processes in the volume of porous iron at the static tensile test demonstrates the influence of porosity on the concentration of deformation flows into the microvolume of connections. The degradation of deformation strengthened active volumes with the subsequent degradation of macrodeformation characteristics can occur in geometrically and structurally slightly developed connections.Published in Fiziko-Khimicheskaya Mekhanika Materialov, No. 3, pp. 50–54, May–June, 1992.     

Preparation of Pt dispersed porous carbon particles from polyimide particles

We investigated the preparation of Pt and Pt/Ru bimetallic fine particles dispersed in polyimide particles by precipitation from various polyamic acid solutions containing Pt and Ru complexes, followed by the carbonization of the resulting polyimide particles. As Pt complexes, platinum(II) acetylacetonate [Pt(acac)₂], trimethylplatinum iodide [PtIMe₃], and (trimethyl) methylcyclopentadienylplatinum [Pt(MeCp)Me₃] were used. As Ru complexes, ruthenium(III) acetylacetonate [Ru(acac)₃], acenaphthylene heptacarbonyl triruthenium [(C₁₂H₈)Ru₃(CO)₇], and tetracarbonylbis(-cyclopentadienyl)diruthenium [Ru₂(CO)₄Cp₂] were used. Bow tie-like polyimide particles containing Pt or Pt/Ru bimetallic particles could be obtained from pyromellitic dianhydride /m-phenylenediamine (PMDA/MPD) polyamic acid containing Pt and Ru complexes. Sheaf-like polyimide particles were obtained by using 4,4-oxydianiline(ODA) as diamine. The morphologies of polyimide particles strongly depend on the kind and the concentration of Pt and Ru complexes. We could obtain Pt or Pt/Ru bimetallic fine particles dispersed in porous carbon particles, which morphologies are the same as the polyimide particles used as carbon precursors, by heat-treatment of the obtained polyimide particles. Pt and Pt/Ru fine particles in the range of 310 nm were contained in bow tie-like or sheaf-like carbon particles. The addition of Ru complexes to polyamic acid solutions decreased the sizes of Pt particles in carbon particles.     

Fabrication of hierarchically porous spherical particles by assembling mesoporous silica nanoparticles via spray drying

A new type of hierarchically porous materials is fabricated by assembling mesoporous nanoparticles via spray drying. Well-dispersed mesostructured silica nanoparticles (MSN), whose particle size distribution was narrow in the range of 20 nm and 50 nm, were prepared by a thermal deposition method. By spray drying a MSN suspension, MSN were assembled into spherical secondary particles. After calcination, the spherical particles have two types of mesopores, mesopores of 3 nm in size inside of calcined MSN and larger inter-nanoparticle mesopores of about 15-20 nm. This hierarchical pore system should provide nanospaces for efficient mass transport of guest species with different sizes.     

Separation of ceramic particles from aluminium metal-ceramic composites

An improved method for separation and quantitative analysis of ceramic particles in aluminiumceramic mixture and cast materials is given. The mixture containing H₂SO₄, HNO₃ and HCI has been found to be most efficient in the separation process. Mixtures containing other acids have been shown to be unsuitable. Optical and scanning electron micrographs of acid-treated aluminium-graphite and talc samples are presented.     

The formation of hollow spherical ceramic oxide particles in a d.c. plasma

Investigations have been carried out to determine the conditions that lead to the production of spherical hollow ceramic oxide particles during melting in a d.c. plasma jet. Reports in the literature indicated that such ceramic particles were formed by plasma spraying spray dried agglomerates, but precise details of the conditions necessary for their formation were not stated. In this study it is shown that for hollow particles to be formed several conditions had to be met. Spherical spray dried agglomerates had to be used as starting materials, the material being sprayed had to melt over a narrow temperature range and the size of the particles had to exceed a certain diameter. Experiments, using yttria, showed that the relative size of the pore was dependent on particle diameter, and it has been proposed that the major controlling factor that influences this dependence is the escape of gas trapped in the spray dried agglomerate during melting rather than surface tension or undercooling which were shown to produce only minor effects. In addition, the results also showed that the nature of porosity within the hollow particles as well as the surface morphology was dependent on the material being sprayed.     

Pellicular particles with spherical carbon cores and porous nanodiamond/polymer shells for reversed-phase HPLC

A new stationary phase for reversed-phase high performance liquid chromatography (RP HPLC) was created by coating spherical 3 μm carbon core particles in a layer-by-layer (LbL) fashion with poly(allylamine) (PAAm) and nanodiamond. Unfunctionalized core carbon particles were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and Raman spectroscopy. After LbL of PAAm and nanodiamond, which yields ca. 4 μm core-shell particles, the particles were simultaneously functionalized and cross-linked using a mixture of 1,2-epoxyoctadecane and 1,2,7,8-diepoxyoctane to obtain a mechanically stable C(18)/C(8) bonded outer layer. Core-shell particles were characterized by SEM, and their surface area, pore diameter, and volume were determined using the Brunauer-Emmett-Teller (BET) method. Short stainless steel columns (30 × 4.6 mm i.d.) were packed and the corresponding van Deemter plots obtained. The Supporting Information contains a MATLAB program used to fit the van Deemter data. The retentions of a suite of analytes were investigated on a conventional HPLC at various organic solvent compositions, pH values of mobile phases, including extreme pH values, and column temperatures. At 60 °C, a chromatogram of 2,6-diisopropylphenol showed 71,500 plates/m (N/m). Chromatograms obtained under acidic conditions (pH 2.7) of a mixture of acetaminophen, diazepam, and 2,6-diisopropylphenol and a mixture of phenol, 4-methylphenol, 2-chlorophenol, 4-chlorophenol, 4-bromophenol, and 1-tert-butyl-4-methylphenol are presented. Retention of amitriptyline, cholesterol, and diazinon at temperatures ranging from 35 to 80 °C and at pH 11.3 is reported. A series of five basic drugs was also separated at this pH. The stationary phase exhibits considerable hydrolytic stability at high pH (11.3) and even pH 13 over extended periods of time. An analysis run on a UHPLC with a "sandwich" injection appeared to reduce extra column band broadening and gave best efficiencies of 110,000-120,000 N/m.     

天然沸石陶瓷分离膜的制备与表征

以天然沸石为原料,采用挤压成型的方法,制备出多孔陶瓷分离膜管.探讨并研究了沸石的反应烧结过程,以及烧成温度、保温时间对多孔陶瓷膜管微观结构的影响,测试了不同温度烧成样品的氮气通量、水通量和弯曲强度,讨论了抗热震性和骤冷温差之间的关系,并尝试对材料的上述性能进行了解释.     

Microstructure and properties of Ni-Zn ferrites sintered from slipcast colloidally precipitated particles

The microstructural dependence of magnetic permeability and magnetic loss of Ni-Zn ferrites sintered from split-cast colloidally precipitated ultrafine particles was investigated. A low-loss Ni-Zn ferrite (tan δ/μ₀=4.92×10^-5 at 1 MHz) having nearly maximum attainable density, fairly uniform and small grain size, and no significant zinc loss was prepared by sintering at 1100°C. There was considerable discrepancy in the permeability-grain size relationship between ferrites sintered at ⩽1100°C and at >1100°C. The zinc loss and intragranular pores in 1100°C sintered ferrites may explain this discrepancy     

Synthesis of anion exchange adsorbent particles by surface functionalization of polystyrene-divinylbenzene based spherical porous matrices

The replacement of Br⁻ by trimethylamine for the synthesis of anion exchange adsorbent particles by surface functionalization of polystyrene-divinylbenzene based spherical porous particles was studied experimentally and theoretically. The calculated values of the kinetic parameters indicate that the net rate of the replacement of Br⁻ by trimethylamine is dominated by the kinetic mechanism involving the formation and opening of an epoxide,

where P represents the polymeric backbone. The theoretical results obtained from the solution of the equations of the mathematical model that describes the dynamic behavior of the kinetic mechanisms, clearly indicate that the highest concentration of the desired product,

on the surface of the pores of the particles, is obtained when the initial concentration of trimethylamine is highest. The equilibrium adsorption of bovine serum albumin (BSA) into the anion exchange adsorbent particles produced in this work was also studied, and the results indicate that the maximum value of the concentration of BSA in the adsorbed phase is a weak function of the concentration of the desired product,

, on the surface of the pores of the particles.     

Microstructure and mechanical behavior of porous sintered steels

The microstructure and mechanical properties of sintered Fe–0.85Mo–Ni steels were investigated as a function of sintered density. A quantitative analysis of microstructure was correlated with tensile and fatigue behavior to understand the influence of pore size, shape, and distribution on mechanical behavior. Tensile strength, Young's modulus, strain-to-failure, and fatigue strength all increased with a decrease in porosity. The decrease in Young's modulus with increasing porosity was predicted by analytical modeling. Two-dimensional microstructure-based finite element modeling showed that the enhanced tensile and fatigue behavior of the denser steels could be attributed to smaller, more homogeneous, and more spherical porosity which resulted in more homogeneous deformation and decreased strain localization in the material. The implications of pore size, morphology, and distribution on the mechanical behavior and fracture of P/M steels are discussed.