Particulate-Reinforced Precursor-Derived Si–C–N Ceramics: Optimization of Pyrolysis Atmosphere and Schedules

Surface oxidation occurred during pyrolysis of SiC particulate-reinforced composites (PRCs) with a precursor-derived Si–C–N matrix. In contrast, such an oxidation was not observed in pure Si–C–N ceramics. The present investigation discusses the possible reasons for this, and reports on the influence of such an oxidation on the microstructure and the mechanical and thermal properties of PRCs by the precursor-impregnation and pyrolysis method. The high-temperature mass stability of the PRCs in Ar deteriorated owing to the decomposition of SiO₂ formed by oxidation. The effects of the pyrolysis schedule on the processing and mechanical properties of PRCs are also investigated.     

Synthesis of Inorganic Polymeric Materials from Industrial Solid Waste

Silicon - The present paper highlights the high strength of inorganic polymer (geopolymer) prepared from industrial solid waste. Fly ash (industrial solid waste) was used as the starting raw...     

Mullite Coatings on SiC and C/C–Si–SiC Substrates Characterized by Infrared Spectroscopy

Mullite (3Al₂O₃·2SiO₂) coatings on SiC substrates and SiC precoated carbon/carbon composite (C/C-Si-SiC) substrates were produced by pulsed laser deposition (PLD) using pressed mullite powder targets. The layers can be characterized efficiently by IR reflection spectroscopy in the spectral range between 650 and 5000 cm⁻¹. The deposited coatings turn into mullite upon oxidation in air at temperatures between 1400° and 1600°C. Fabry-Perot interferences indicate a high quality and homogeneity of the mullite coating/SiC substrate interface. Amorphous SiO₂ gradually forms during prolonged heating or at higher temperatures.     

陶瓷企业窑炉烟气的余热利用

本文介绍了窑炉烟气余热利用的现状,提出了新型高效的窑炉烟气余热利用方式——余热制冷,并对其进行了可行性分析。     

利用陶瓷废料开发固体混凝土材料的研究

研究了利用陶瓷废料开发的固体混凝土材料,探讨了废粉料和胶粘材料对该固体废弃物混凝土性能的影响,以陶瓷废料为主要原料,辅以水泥和高强粘结剂制备了性能符合标准要求的免烧型广场道路砖。     

A Kinetic Model for Oxidation of Si–Al–O–N Materials

In this paper a new model has been proposed to describe the oxidation of Si–Al–O–N materials in both isothermal and non-isothermal conditions in the form of powders and pellets. All these formulae are analytic with a form of explicit function; therefore, they are not only easy to use but also enable the easy performance of a theoretical analysis. The application of these formulae to practical systems shows that this model is feasible; moreover, these formulae can not only be used to treat the oxidation for Si–Al–O–N materials but also be applied to treat reactions in other fields of materials.     

Formation of Continuous Pore Structures in Si–C–O Fibers by Adjusting the Melt Spinning Condition of a Polycarbosilane–Polysiloxane Polymer Blend

A polymer blend containing polycarbosilane (PCS) and 15 mass% of polyhydromethylsiloxane (H-oil) was prepared and the properties of the polymer melt were investigated in order to clarify the mechanisms of continuous pore formation. Melt viscosity decreased as the H-oil content increased. Moreover, the saturation of the plasticizer effect of H-oil on the viscosity and apparent turbidity of the melting polymer suggested that the compatibility of H-oil to PCS in melting was limited at 15 mass%. Gas chromatography data after heating showed that an amount of evolved hydrogen at 573 K was increased by 15 mass% of H-oil addition. The fibers formed by the melt-spun of the polymer blend at 578 K mainly possessed a single pore at the center of the fibers' cross section. On the other hand, the fibers melt-spun at 543 K usually included multiple pores, and the fibers melt-spun at 538 K included a number of tiny pores. It is proposed that the evolved hydrogen can be dissolved in the polymer melt, and the desaturation process of the dissolved gas during the fiber spinning with a sudden temperature reduction likely determined the size and location of pores in the fibers.     

Properties and Crystallization of Rare-Earth Si–Al–O–N Glasses Containing Mixed Trivalent Modifiers

Thirteen glasses of the general formula (M1, M2)_9.33Si₁₄Al_5.33O_41.5N_5.67 where M1=La or Nd and M2=Y or Er have been prepared with M1/(M1+M2) fractions of 1, 0.75, 0.5, 0.25, and 0. Data for molar volume (MV), glass compactness ( C ), Young's modulus ( E ), microhardness ( H ), glass transition temperatures ( T _g), and dilatometric softening temperatures ( T _d) have been recorded. In addition, temperatures at which crystallization exotherms arise have also been determined as well as crystalline phases present after the glasses had been heat treated to 1300°C in nitrogen. The results clearly demonstrate that glass properties vary linearly with effective cation field strength (CFS) of the combined modifiers (M1, M2), which is calculated from the atomic fractions of M1 and M2 and their associated CFSs. Glass stability in both the La–Y and La–Er systems reaches a maximum at M1 and M2 fractions of 0.5 because of the relative stability of different oxynitride and disilicate phases with changes in ionic radius. Furthermore, La appears to stabilize the α polymorph of yttrium disilicate because of combined La–Y ionic radius effects.     

Synthesis and Characterization of Nano-Composite Alumina–Titania Ceramic Membrane for Gas Separation

A ceramic composite membrane was prepared using a commercial titania ceramic membrane coated by alumina oxide via a sol–gel technique where polyvinyl alcohol (PVA) was used as a binder. The characteristic of the membrane was analyzed in terms of the effect of PVA concentration and sintering temperature on viscosity, pore size, density, porosity and surface area of the membrane. Two vol% of PVA solution containing 4 g of PVA in 100 mL of water was adequate to achieve an appropriate porosity level to avoid cracks on the gel layer. Sol viscosity and pore size of the membrane essentially increased when the PVA concentration was increased. The density of the membrane increased as the sintering temperature increased. The porosity level however, decreased when the temperature was increased. The composite membrane was further characterized in terms of permeability of pure gas at low-temperature region (301 K) where an experimental platform has been developed to perform the permeability studies.     

Effect of Composition on Crystallization of Y/Yb–Si–Al–O–N B-Phase Glasses

The effect of a partial or full replacement of yttrium by ytterbium on the crystallization of an oxynitride B-phase parent glass with composition (e/o) 35Y/Yb:45Si:20Al:83O:17N has been investigated by thermal analysis, X-ray diffractometry and analytical transmission electron microscopy. Single B-phase formation was extended to higher temperatures by low ytterbium:yttrium ratios, while a full replacement resulted in a two-phase B- and J-phase glass–ceramic. The B-phase crystals took up a substantial range of composition that was dependent on the substitution level, and yttrium/ytterbium was always clearly anti-correlated with silicon. Some aluminum was accommodated in the dendritic J-phase crystals, and their yttrium/ytterbium content varied between 64 and 79 cation%.     

陶瓷企业对“三废”和“危废”管理的效果分析

本文根据笔者从事陶瓷企业节能、清洁生产工作的实际经验．针对陶企对于“三废”及“危废”管理上的盲点及漏洞,列举几个有代表性的例子,说明“三废”及“危废”的处理及监测须了解及严格按照相应的法律法规办事。     

陶瓷废料在功能性多孔陶瓷制备中的应用

陶瓷废料日益增多,它不仅对城市环境造成巨大的压力,而且还影响到城市经济的发展及陶瓷工业的可持续发展,所以陶瓷废料的处理与利用就显得非常重要。陶瓷废料的应用领域非常广泛,用途也非常多,本文就此介绍了国内几种利用陶瓷废料来制备功能性多孔陶瓷产品的方法。     

Incorporation of Aluminum into C–S–H Structures: From Synthesis to Nanostructural Characterization

C–A–S–H (C=CaO, A=Al₂O₃, S=SiO₂, H=H₂O in cement nomenclature) phases have been synthesized from CaO, SiO₂, and AlNaO₂. The initial CaO/SiO₂ (C/S_initial) ratios varied from 0.8 to 1.5 and the initial Al₂O₃/SiO₂ (A/S_initial) ratio was set to 0.1. Samples were characterized by X-ray diffraction and chemical analyses of their equilibrium solutions. This paper describes experiments using a low-voltage scanning transmission electron microscopy (STEM-in-SEM) imaging system that allows transmission observations in an environmental scanning electron microscope. Observations of the nanostructure were also performed by transmission electron microscopy (TEM). Two types of morphologies were clearly observed: fine fibrillar aggregates and small plates, the latter being particularly sensitive to beam damage. Despite their different appearance, both of these phases were amorphous, and the small plates were richer in aluminum. The fraction of the small plate phase increased with the C/S_initial ratio. TEM interpretations showed that C–A–S–H phases were not stable under the electron beam and high-magnification observations could significantly modify their structure. Images and chemical analyses acquired with STEM-in-SEM appeared as valuable sources of information because they offered a large observation field comparable to a transmission electron microscope and better magnification resolution than a classical scanning electron microscope.     

Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure

Oxidized amorphous Si₃N₄ and SiO₂ powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si₂ON₂) was observed from amorphous silicon nitride (Si₃N₄) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si₂ON₂ coexisted with β-Si₃N₄ with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si₂ON₂. Pressing a mixture of amorphous Si₃N₄ of lower oxygen (1.5 wt%) and SiO₂ under 1.0–5.0 GPa between 1000° and 1350°C did not give Si₂ON₂ phase, but yielded a mixture of α,β-Si₃N₄, quartz, and coesite (a high-pressure form of SiO₂). The formation of Si₂ON₂ from oxidized amorphous Si₃N₄ seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure.     

Polymeric g-C3N4 Derived from the Mixture of Dicyandiamide and Mushroom Waste for Photocatalytic Degradation of Methyl Blue

Topics in Catalysis - Metal-free, visible light-responsive, carbon-based graphitic carbon nitride (g-C3N4) is a well-known photocatalyst. It is necessary to develop a g-C3N4 for use as a...     

焦炉气制甲醇装置中汽提塔废水热量回收

介绍转化和精馏废水经汽提塔回收气体,避免外排污染环境,并通过内部多级换热,回收汽提塔废水的热量,再将汽提塔废水送脱盐水站作为原水循环使用,达到节能降耗的目的.     

Steady-State Creep Behavior of Si–SiC C-Rings

Because of the ease of experimental setup as well as economics in sample preparation, C-ring specimens are sometimes chosen for the evaluation of mechanical behavior. In this paper, the long-term creep of siliconized silicon carbide (Si–SiC) C-rings is investigated. Creep tests on a number of Si–SiC C-rings were carried out under constant compressive loads at 1300°C in air. Load-point displacements were continually monitored as a function of time, thereby establishing the steady-state regime as a function of load and ring geometry. Optical micrography on the postcrept specimens was performed to obtain damage zone sizes. A simple curved beam theory was employed to analyze the stress state developed throughout the body during steady-state creep. Loadpoint displacement rates were numerically calculated using both geometric and energy methods. Observed damage zone sizes and shapes within the specimen agreed with those predicted theoretically. Results obtained on the stress solutions are useful as local loading parameters in the study of high-temperture fracture behavior of a cracked C-ring.     

Synthesis of Spinel-Based Ceramic Pigments from Hydroxycarbonates

A technology for the production of pigment based on spinel Co_1–x Mg_xAl₂O₄ is developed, where 0.67 ≤ x ≤ 0.80. The pigment has a bright blue color and is identical to the reference standard, although its cobalt content is 2 – 3 times lower.     

Gas Processing Waste: Promising Raw Material for Designing the Composition of Ceramic Grinding Bodies

Glass and Ceramics - The chemical and mineralogical characteristics of alumina-containing wastes—catalysts used in the gas processing industry — and the possibility of using them in the...