Mercury intrusion porosimetry showed interagglomerate and intraagglomerate pores in the case of spray-dried powder compacts. The precursor gels of HfC and HfB 2 were also used to dip coat SiC fibre bundles, on heat treatment, a continuous coating of HfC and HfB 2 was obtained. The effects of calcination dwell time and Hf:C and Hf:B molar ratio on the purity and morphology of the final powder have been studied and the mechanism of anisotropic growth of HfB2 has been investigated. In the present research, gel-cast Al2O3 foams with open porosity in the form of spherical cells connected by circular windows were pressurelessly infiltrated using an Al-8 wt% Mg alloy. Cr3+ fluorescence and Raman spectroscopy were applied to the indent centre and around the indentation in order to investigate the origin of the signal, the effect of indentation loads and zirconia phase transformation on the residual stress and plastic deformation in the plastic zone. This resulted in the foams having a very open and interconnected structure that could be easily infiltrated by the molten metals.
This limits the high-temperature range of SiC-bearing ceramics for ultra-high temperature applications. Little variation in ionic conductivity was noted over the range of grain sizes examined; rather the yttria content had the largest effect. Jon has published about 220 research papers, as well as editing or contributing to 19 books, given around 60 keynote, plenary and invited talks at international conferences and holds 7 patents. The approach has been used on a number of different ceramics with a range of characteristics, yielding comparative information on the microstructural and mechanical characteristics of ceramics deemed successful in terms of ballistic performance. The paper discusses the mechanics and performance of a new, non-thermal pulsed discharge cleaning method based primarily on experimental investigations and evaluates its potential impact on fuel consumption, system complexity and engine operation A novel method for the removal of soot from a diesel particulate filter using pulsed electric discharges is presented. Major focuses for his recent work include ultra-high temperature ceramic composites for which he has recently held a ¡ê4.
The wear mechanism was investigated and the effects of the foam density and cell size on the wear properties were determined. The color scale corresponds to the partial fractions of each respective cation. The samples were oxidized between 2100 and 2300 °C. The brittle nature of ceramics can limit their ability to resist multiple ballistic impacts. Jones and Nazanin Bassiri-Gharb, Effect of microstructure on irradiated ferroelectric thin films , Journal of Applied Physics , 10. Advanced Processing Concepts for Increased Ceramic Reliability Processing of Silicon Nitride Powders Wet Forming Processes as a Potential Solution to Agglomeration Problems Processing of Electronic Ceramics Processing of Ceramic Composites Injection Moulding of Fine Ceramics Electrophoretic Deposition as a Processing Route for Ceramics Microwave Processing of Ceramics Thin Film Deposition Processes for Electronic and Structural Ceramics References Index.
Abstract Polycrystalline beta-alumina ceramics containing yttria-doped zirconia particles have be. Zirconium diboride ceramics containing 10vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB2. The rapidity and less demanding processing conditions associated with the microwave assisted method augers well for the general applicability of the technique for the production of nanocrystalline powders. The flowability and fill density of the granules increased with an increase in the solid content of the starting suspension, whilst the crushability decreased. He was Director for the Center for Dielectric Studies 1997 ~ 2013, and Co-Director of the Center for Dielectrics and Piezoelectrics 2013-2015, still serving as Technical Advisor.
Granulation of nanostructured 3 mol% yttria stabilised zirconia using spray freeze drying was investigated to achieve flowable and crushable granules for subsequent die pressing. The results obtained showed that, compared with pure conventional heating, the presence of the microwave field led to higher sintered densities and crystallinity in the samples, indicating that the microwave field enhanced the sintering of the sol-gel alumina films and supporting the existence of the microwave effect. Hence the present work has focused on investigating the potential for using gravity-fed infiltration. The influence of laser energy input during processing was associated with the evolution of component porosity, measured via optical and scanning electron microscopy in combination with gas expansion pycnometry. Within the field of ceramic processing, his work has mainly focused on colloidal processing, where the aim is to understand and hence control the rheology of ceramic suspensions, and microwave processing, where the aim is to generate a detailed understanding of the interaction between microwaves and advanced non-metallic materials and then to use this to develop improved process routes. With an optimum solid content, it is possible to have a granulated nanopowder with reasonable flowability and compactability resulting in homogeneous green bodies with ~54 % of theoretical density.
His current one — a major international research programme for which he has won £4. He obtained his Bachelors and PhD from the Ceramics Department at Leeds University and has since worked as an academic at the Universities of California at Los Angeles, Leeds, Nottingham and Brunel; he was also Head of Department at both Brunel and Loughborough. He was also Head of Department at the latter. Only the cationic dispersants were effective for the as-received SiC, with polyethyleneimine being superior to Hyamine 2389 probably as a result of a greater electrosteric interaction. Results are for crystallized films that were pyrolyzed at 300°C left column , 350°C middle column , and 400°C right column. The mechanism of anisotropic growth of HfB2 rods has been discussed in this study.
It was also found that zirconia phase transformation reduced the compressive residual stress in the alumina matrix within the plastic zone, except at the indentation centre, due to the tensile residual microstress generated by the zirconia phase transformation. The phenomena governing the plasma electrical energy deposition in honeycomb structures are of particular interest as the creation of a uniform, stable and effective plasma in the narrow channels of the honeycomb presents a considerable challenge. It is the behaviour of the latter that is crucial, so that interactions between different materials, the joining processes, the behaviour of the different parts under extreme conditions and how they can be made to work together, must be understood. There is a considerable current interest in learning how to process genuinely nanostructured ceramics as they offer the potential for significantly enhanced properties; however, it is often difficult to make large enough components to allow more than the most basic of property measurements. He holds six patents with two more in the pipeline. The oxidation products formed were characterized and found to comprise different phases of Ta2 O5.
Sintering was carried out using three different heating approaches: pure conventional heating and hybrid heating with 600 W and 1000 W of microwave radiation, respectively. He is a Visiting Professor at both Beijing University of Chemical Technology and Kunming University in China. A micro-Raman study on the post-tested samples suggested that the transformation toughening absorbed the energy from the impact and protected the samples from breaking. Even though reaction-based processes and chemical synthesis methods are mainly used for research studies, they are powerful tools for producing diborides because they provide the ability to tailor purity and particle size. This article is protected by copyright. Hafnium diboride HfB2 powder has been synthesized via a sol—gel-based route using phenolic resin, hafnium chloride, and boric acid as the source of carbon, hafnium, and boron, respectively, though a small number of comparative experiments involved amorphous boron as boron source.
This was found to depend on the method of manufacture of the different commercial nanopowders investigated. The approach is also helping the research team to pinpoint the precise failure mechanisms and material properties that are directly relevant to the development of a verifiable, multi-scale ceramic material model. The decrease in the wear rate in the second stage in the latter is attributed to an Al2O3 network protruding out of the worn surface, which protects the direct wear of the Al Mg alloy by the counter ball. The composites were produced at atmospheric pressure by infiltrating 2—10 wt. To obtain some answers to this enigma and determine when microwaves should be used to process technical ceramics, three case studies are explored.
Whilst this was much slower, often taking several minutes, when optimised it is believed it will offer the potential for the production of large and complex-shaped pieces. This project investigated their cutting resistance with a view to understanding the underpinning mechanisms. The color scale on the right corresponds to the partial fractions of each respective cation. The combination of properties make these materials potential candidates for a variety of high-temperature structural applications, including engines, high-speed vehicles, plasma arc electrodes, advanced nuclear fuels, fusion first walls and divertors, cutting tools, furnace elements and high temperature shielding. After calcination, a good dispersion was achieved for suspensions with up to 80 wt% solids using a polyacrylic-based dispersant combined with tetramethylammonium hydroxide and 10 min of ultrasound. Some of his research is associated with the defence industry and ranges from developing superior armour materials through to ceramic composites that can withstand temperatures up to nearly 3000oC for the leading edges and other components on vehicles for hypervelocity flight. These properties were achieved using processing times approximately one sixth of those required conventionally.