Advanced ceramic materials offer significant thermodynamic efficiency advantages over metals and alloys because of their higher use temperatures. Using ceramic components results in higher temperature industrial processes which convert fuels to energy more efficiently, reducing environmental emissions. Ceramics have always offered high temperature strength and superior corrosion and erosion resistance. However, brittleness, poor thermal shock resistance and catastrophic failure have slowed industrial adoptions of ceramics in environmental applications.

This paper will focus on environmental applications of three new advanced ceramic materials that are overcoming these barriers to industrial utilization through improved toughness, reliability, and thermal shock performance. PRD-66, a layered oxide ceramic with outstanding thermal shock resistance and high use temperature with utility in catalyst support, insulation, and hot gas filtration applications, is discussed. Tough silicon carbide fiber reinforced silicon carbide (SiC/SiC) and carbon fiber reinforced silicon carbide (C/SiC) ceramic composites made by chemical vapor infiltration, and silicon carbide particulate reinforced alumina (SiCp/A12O3) composites made through Lanxide Corporation's DIMOX™ directed metal oxidation process are described. Applications of these materials to pollution reduction and energy efficiency in medical and municipal waste incineration, heat management, aluminum remelting, pyrolysis, coal combustion and gasification, catalytic pollution control, and hot gas filtration, will be discussed.

An important cause of deactivation of alumina supported transition metal (oxide) catalysts is a solid state reaction between the active component and the support. We therefore studied the hightemperature behavior of Me layers (Me = Co, Ni, Cu and Fe) on polycrystalline α-A12O3 and γ- Al2O3 substrates. The samples were first oxidized at moderate temperatures and then annealed at high temperatures (up to 1000 °C) in O2, N2, or N2/O2 mixtures. The interfacial reaction to MeA12O4 was assessed using Rutherford Backscattering Spectrometry and X-ray diffraction. The reaction rate strongly depends on the transition metal element Me: Fe < Ni < Co < Cu. Low oxygen pressures favour spinel formation. γ-A12O3 shows a much higher reactivity towards the MeOx overlayers than α-Al2O3.

Monoclinic ZrO2 and its supported catalysts Co/Ni/ZrO2 for catalytic decomposition of N2O have been studied with FTIR, EDAX, XPS, and the evaluation of activity of the catalysts. It is found that monoclinic ZrO2 alone has the catalytic effect for N2O decomposition although the gas decomposes on Co/Ni/ZrO2 more efficiently. The XPS study shows that only Co exists in the surface region of ZrO2. In evaluation experiments, it is found that when Co/Ni exceeds a threshold concentration, the conversion of N2O is no longer accelerated with the increase of Co/Ni content. The gas decomposition on Co/Ni/ZrO2 can be described as first order with respect to partial pressure of N2O. No nitrogen N(ls) photoelectrons were detected for the catalysts after N2O decomposition. Surface reactions on ZrO2 and Co/Ni/ZrO2, including the behaviour of retained carbon (Cls) and N2O decomposition mechanism, will also be addressed.

Ultrafine silica fibers were coated with nanosized particles by an aerosol process. The fibers were introduced in a diffusion flame reactor where silica particle formation took place by oxidation of SiCl4. Coagulation of particles with fibers resulted in fractal-like structures on the latter, enhancing the specific surface area of the product fibers. Ferrocene used as an additive at a mole fraction of 6.6 × 10−5 in the flame promoted the surface area enhancement. A sol-gel coating technique was also used to produce particle coated fibers.

We have characterised the WO3T'iO2 (anatase) catalyst system using High Resolution Electron Microscopy. We will show that the overlayer preserves the surface roughness of titania and consists of 2D-hexagonal clusters that have a definite orientation relationship with the support. The contrast observed from these clusters is discussed in terms of existing structural models. A comparison between traditional chemical methods of preparation and simple mechanical mixing is made to assess the effectiveness of the latter to disperse WO3.

Using High Resolution Electron Microscopy, we have investigated the structure/function relationships of the Nd2O3/MgO and MgO/Nd2O3 catalyst systems which are active in the oxidative coupling of methane. In both cases catalytic performance was found to depend critically on the morphology of Nd2O3. We demonstrate that high selectivities are associated with a thin disordered film of neodymia on the MgO surface for the Nd2O3/MgO system whilst for the reverse catalyst, the dominant morphology is a highly disordered cubic form of Nd2O3.

An oxygen-deficient magnetite (Fe3O4–8) has been found to form by passing H2 gas through magnetite powder at 300°C with its spinel structure retained. The oxygen-deficient magnetite is a metastable phase in the transformation of magnetite into α-Fe. The lattice constant of the oxygen-deficient magnetite enlarged to 0.8407nm in the maximum value which is substantially larger than that of the stoichiometric magnetite (a0=0.8396nm). The formation mechanism of the oxygen-deficient magnetite was studied at 300°C using two specimens of magnetite powders with developed orientations on the (111) and (100) planes. These are referred to as (111)- and (100)-magnetite, respectively. The formation of α-Fe was suppressed over the crystal of (111)-magnetite, where wUstite and oxygen-deficient magnetite were formed while keeping the f.c.c. arrangement of the oxygen ions in the solid. On the other hand, over the (100)-magnetite, the formation of a-Fe was enhanced. It is considered that, on the (111)- magnetite, the Fe2+ ion formed by H2-reduction on the surface can move into interstices of the f.c.c. lattice of bulk to form the oxygen deficient state. This will come from the fact that the Fe2+ ion on the surface is so strongly supported with three Fe-O bondings that the Fe2+ ions cannot readily diffuse on the surface when the surface oxygen ions are removed on the (111)- magnetite.

An oxygendeficient magnetite (Fe3O4–8) has been found to exist in the range of (0<Δ<0.12) in the course of H2-reduction of magnetite to αFe at 300°C. The formation of the oxygendeficient magnetite was studied kinetically. In the temperature range of 250 350°C, the rate constants, k1, and k2, were determined for the forward and reverse reactions, respectively. The rate of formation of the oxygendeficient magnetite depended on the partial pressure of H2 gas. The rate constant, k1, was 109.58 at 300°C and the reaction order was 1.11 with respect to the partial pressure of H2 gas. The rate of reverse reaction depended on the partial pressure H2O gas and the oxygen deficiency of magnetite, Δ. The rate constant of the reverse reaction, k2, was 10−2.54 at 300°C, and the reaction orders were 0.45 and 0.99 with respect to the partial pressure of H2O gas and the Δ value respectively. The activation energies for the forward and reverse reactions were determined to be 63.8 kJ.mol−1 and 25.5 kJ.mol−1 from the Arrhenius' equation.

The carbon-bearing magnetite (CBM) was prepared by the carbon-deposition on the H2- treated magnetite with CO2 at 300 °C. The CBM reacted with H2O and evolved H2 gas at 300- 350 °C. The surface of the CBM was composed of a new iron(II)oxide / carbon layer (CIOlayer). X-ray diffractometry and chemical analysis showed that the CIOlayer was transformed to an amorphous carbide phase by allowing to stand in Ar stream at 300 °C, which is so reactive as to decompose H2O into H2. The mole ratio of the evolved H2 gas to the evolved CO2 was nearly equal to that in the carbide (Fe3C) decomposition reaction with H2O. During the H2O decomposition, oxygen ions are transferred to the surface layer forming iron oxide. When the carbon-bearing Ni(II)-ferrite (CBNF) was used as the solid phase, the hydrogen evolution reaction takes place without decreasing in the carbon content in the CBNF, and the evolved H2 volume was approximately 8 times higher than that evaluated from the oxidized amount of the iron ions in the CBNF. This result suggests that some amount of oxygen in the CBNF is released while allowing to stand the sample in Ar stream at 300 °C. These H2 evolution reactions can proceed at low temperature of around 300 °C. This will provide us the way to establish a unique chemical heat pump system, where the waste heat around 300 °C be transferred to chemical energy of H2. The surface layer composed of iron(II) oxide/carbon is the key compound for this reaction.

The reactivity of the H2-activated Ni(II)- and Co(II)-bearing ferrites with different levels of metal substitution have been studied for CO2 → C decomposition in comparison with that of the H2-activated magnetite. Ni 2+ and Co2+ have been substituted for Fe2+ or Fe3+ in magnetite with the spinel-type structure up to 14 % and 26 % of the mole ratio of Ni2+ and Co2 + to the total Fe content respectively. The reactivity of the Ni(II)- and Co(II)-bearing ferrite increased with the level of metal substitution. Especially, the Ni(II) substitution significantly facilitated the CO2 → C decomposition in a batch system. The rates of H2-activation (reduction) and CO2-decomposition (oxidation) for N(II)-bearing ferrite were studied by a thermogravimeteric analysis. The rates of both H2-activation and CO2-decomposition were much improved in the Ni(II)-bearing ferrite with the Ni(II)/Fetoul mole ratio of 14%. It is considered that the reduced Ni(II) ions which were formed on the surface of the ferrite is very active to facilitate both dissociation reactions of 1) H2 → 2 Hads and 2) CO2→ Cads + 2Oads,. From the change in the lattice constant of the Ni(II)-bearing ferrite during the H2-activation and CO2-decomposition, the oxygens in CO2 were considered to be incorporated into the oxygen deficient spinel lattice of the oxygen deficient Ni(II)-bearing ferrite which had been formed by the H2-activation.

The reaction of CC12F2 (CFC 12) has been studied on a γ- A12O3 catalyst with and,withoutH2 and with H2 on a Pt/γ-A12O3 catalyst containing 0.5, 2 and 5 wt % of Pt at a temperature of 300°C. The extent of conversion, was shown to be highly dependent both on the metal coverage; and on the temperature.

Carbon fibers are produced commercially from rayon, phenolics, polyacrylonitrile (PAN), or pitch. The last are further divided into fibers produced from isotropic pitch precursors, and those derived from pitch that has been pretreated to introduce a high concentration of carbonaceous mesophase. Over the past few decades, interest in research and manufacturing carbon fibers has overwhelmingly centered on producing fibers with high tensile strength and high modulus for lightweight, high performance composites, where polymers, metals, and carbon can form the continuous matrix. The fibers most commonly used in advanced materials are produced from PAN or mesophase pitch. Graphitized mesophase pitch fibers tend to have higher modulus and lower tensile strength than the PAN-based equivalents. They have advantages in applications requiring high stiffness, high electrical and thermal conductivity, low thermal expansion, and high temperature oxidation resistance, while PAN fibers are employed where high strength is required.

In this paper, the characteristic of a new preparation technique of activated carbon fiber (ACF) was discussed. The structures and properties of the ACF produced were investigated simultaneously. The experimental results indicated that this new technique is a high efficient method for the preparation of ACF. It needs simple facilities and is easy to be operated. The products obtained possess high specific surface area and adsorption capacity.

In order to improve the reduction ability and capacity of ACF, some metal-containing ACF (Me-ACF) were prepared. Their structures and reduction properties were investigated at the same time. On the basis of experimental results, a redox mechanism was proposed.

Copper-series, nickel-series, and copper-cobalt composite-series catalysts supported on activated carbon fiber were prepared in this paper. Their structures and catalytic activities for the reduction of nitric oxide with ammonia were investigated simultaneously.

Catalytic combustion is an emerging technology in which fuels can be combusted homogeneously supported by a catalyst. The catalyst allows non-flammable mixtures of fuel and air to be oxidized with the resulting heat generated used to initiate thermal or homogeneous combustion. With the proper catalysts the fuel can be combusted with efficiencies so high that unburned CO or HC emissions are less than 10 ppm. Furthermore, because the fuel-air mixtures are relatively lean compared to conventional processes the adiabatic temperatures are below that required for the formation of NOx i.e. > 1500°C. The success of this technology would eliminate the need for expensive after-treatment of emissions from gas fired power plants and boilers.

This is a very demanding application, especially for natural gas fueled combustors, since the catalyst will have to initiate reaction between 400 and 500°C, at linear velocities exceeding 50 ft/sec, and retain its activity after experiencing temperatures up to 1400°C. Furthermore, the monolithic ceramic or metallic support upon which the catalyst is deposited must also retain structural integrity after experiencing high temperatures and severe thermal shock.

This paper will describe the fundamental concepts of this new technology, the major technical problems being addressed and the progress being made.

We have performed ab initio studies to understand the electronic and geometric aspects of the Pd-CO bond in small carbonyl clusters and the CO covered (2 × 1)p2mg superstructure of the Pd(110) surface. We have used the standard quantum chemistry package Gaussian to study the former system and an LDA formalism using ab initio pseudopotentials and a plane wave basis to study the latter. The latter results are preliminary; we intend to study thicker slabs in the future.

Transition metal sulphides (TMS) have the ability to catalyze the hydrodesulphurization (IDS) of thiophenes occurring in oil. The catalytic activity varies strongly across the TM series, and can in some cases be significantly enhanced by the addition of promotor elements (e.g. Co/Ni in MoS2).

From a series of density functional (DF) scattered-wave electronic structure calculations on first, second and third row TMS, electronic parameters related to the catalytic activity have been identified. The occupation and topology of metal-sulphur antibonding orbitals near the Fermi level are particularly important. An activity parameter, I, which is a measure of the strength of the interaction between metal d and sulphur 3p electrons, correlates well with the experimental HDS activities.

Nanocrystalline processing by inert gas condensation has the inherent advantages of generating: (1) high surface area nanoclusters, (2) non-stoichiometric oxides, and (3) high dispersions of dopants. This approach is exploited in the synthesis of fluorite-structured catalysts for SO2 reduction by CO. Nanocrystalline CeO2-x, La-doped CeO2-x, and Cu-doped CeO2-x were produced by magnetron sputtering from a pure or mixed metal target, followed by controlled oxidation of the metallic clusters. The as-prepared doped and undoped nanocrystalline CeO2-x materials were found to be excellent catalysts for complete SO2 conversion to elemental sulfur. Undoped nanocrystalline CeO2-x enabled light-off at 460 °C, a temperature ∼120 °C lower than that over polycrystalline CeO2, which is a novel effective catalyst itself. The high catalytic activity of the nanocrystals was associated with their high concentration of oxygen vacancies. Excellent poisoning resistance was also exhibited by the nanocrystalline CeO2-x samples. These materials have stable activity in the presence of excess CO2.

Three preparation methods of ZSM-5 supported copper were studied. The first sample is the mechanical mixture of CuCl2·2H2O with NaZSM-5 (Cu+ZSM-5), the second sample is the mechanical mixture of CuCl2·2H2O with NaZSM-5 followed by microwave treatment (Cu/ZSM-5), and the third sample is copper ion exchanged with NaZSM-5 (CuZSM-5). All the samples were characterized by XRD, DTA, and n-hexane adsorption. Cu+ZSM-5 samples showed characteristic XRD peaks of both NaZSM-5 and CuCl2·2H2O and Cu/ZSM-5 samples showed only NaZSM-5 XRD peaks; these results suggest that CuCl2·2H2O no longer exists in the crystalline state in Cu/ZSM-5 samples, possibly in a highly dispersed state. DTA experiments showed that Cu+ZSM-5 samples did exhibit the melting point of CuCl2 and Cu/ZSM-5 did not. Furthermore, as compared with Cu+ZSM-5 and CuZSM-5, the n-hexane adsorption on Cu/ZSM-5 samples require higher n-hexane pressure to reach the saturated adsorption; these results suggest that the copper salt has entered the zeolite channels during microwave treatment, resulting in the change of channel circumstance for ZSM-5 zeolite. All these results suggest that microwave technique is a potential method for preparing highly dispersed metal salts in the channels or cages of zeolites.