Energetic Materials in Ceramics Synthesis

1992 ◽  
Vol 296 ◽  
Author(s):  
J. J. Kingsley ◽  
L. R. Pederson
Keyword(s):  
Energetic Materials ◽  
Fine Particles ◽  
Impurity Content ◽  
Oxide Ceramic ◽  
Oxide Ceramics ◽  
Ceramic Powders ◽  
Metal Nitrates ◽  
Organic Fuels ◽  
Simultaneous Synthesis ◽  
Fuel Mixtures

AbstractCombustion of a proper combination of an oxidizer and a fuel can produce the exothermicity required for the simultaneous synthesis of oxide ceramic powders. Oxidizers include metal nitrates, ammonium nitrate, and ammonium perchlorate, while urea, carbohydrazide, glycine and others have been used successfully as fuels. Combustion methods are particularly well-suited to producing multicomponent metal oxides, yielding compositionally homogeneous, fine particles with low impurity content. Organic fuels, particularly those containing nitrogen, also serve as a complexant in the precursor, which inhibits inhomogeneous precipitation from occurring prior to combustion. The exothermic redox decomposition of these oxidizer-fuel mixtures is initiated at low temperatures, usually <250°C. Properties of the products are influenced by the nature of the fuel and the oxidizer/fuel ratio. Many technologically important oxide ceramics have been produced by these methods.

Fabrication of Oxide Ceramics Dendrites for Porous Electrodes by Using Stereolithography

2012 ◽  
Vol 2012 (CICMT) ◽  
pp. 000152-000157 ◽  
Author(s):  
Satoko Tasaki ◽  
Naoki Komori ◽  
Soshu Kirihara
Keyword(s):  
Heating Rate ◽  
High Surface ◽  
Ceramic Powder ◽  
Numerical Data ◽  
Porous Electrodes ◽  
Oxide Ceramic ◽  
Layer By Layer ◽  
Oxide Ceramics ◽  
Cross Sectional ◽  
Aspect Ratios

Porous oxide ceramics such as zinc oxide are applied for dye sensitized solar cell. This device requires consideration of high surface area, mechanical strengths and porous networks. Thus, we focused on the dendrite structures constructed from micrometer order rods with coordination numbers of 4, 8, and 12. There perfectly controlled structures were fabricated by stereolithography. Variations of the aspect ratios (lattice length to diameter ratios) were adjusted to control the porosity in the range 50–80 vol. % by using computer graphic software. The dendrite models sliced into a series of cross sectional patterns with uniform thickness by using a stereolithographic file format convertor. These numerical data were transferred into the micro processing equipment. High viscosity slurry material was prepared by mixing oxide ceramic powder and photosensitive acrylic resin. This slurry was spread on a flat stage and smoothed. An ultraviolet laser beam was exposed over the deposited layer to create cross-sectional planes. Through layer-by-layer processes, solid components were fabricated. These precursors were dewaxed at 600°C for 2 h at a heating rate of 1.0°C/min and sintered at 1400°C for 2 h at a heating rate of 5.0°C/min in air. The oxide ceramics microstructure was observed using a scanning electron microscope.

scholarly journals Injection Moulding of Oxide Ceramic Matrix Composites: Comparing Two Feedstocks

2019 ◽  
Vol 809 ◽  
pp. 140-147 ◽  
Author(s):  
Maike Böttcher ◽  
Daisy Nestler ◽  
Jonas Stiller ◽  
Lothar Kroll
Keyword(s):  
High Temperature ◽  
Injection Moulding ◽  
Ceramic Matrix ◽  
Ceramic Composites ◽  
Laboratory Scale ◽  
Oxide Ceramic ◽  
Scale Production ◽  
Oxide Ceramics ◽  
Moulding Process ◽  
Injection Moulding Process

Ceramic materials are suitable for use in the high temperature range. Oxide ceramics, in particular, have a high potential for long-term applications under thermal cycling and oxidising atmosphere. However, monolithic oxide ceramics are unsuitable for use in high-temperature technical applications because of their brittleness. Thin-walled, oxidation resistant, and high-temperature resistant materials can be developed by reinforcing oxide ceramics with ceramic fibres such as alumina fibres. The increase of the mechanical stability of the composites in comparison to the non-fibre reinforced material is of outstanding importance. Possible stresses or cracks can be derived along the fibre under mechanical stress or deformation. Components made of fibre-reinforced ceramic composites with oxide ceramic matrix (OCMC) are currently produced in manual and price-intensive processes for small series. Therefore, the manufacturing should be improved. The ceramic injection moulding (CIM) process is established in the production of monolithic oxide ceramics. This process is characterised by its excellent automation capability. In order to realise large scale production, the CIM-process should be transferred to the production of fibre-reinforced oxide ceramics. The CIM-process enables the production of complicated component shapes and contours without the need for complex mechanical post-treatment. This means that components with complex geometries can be manufactured in large quantities.To investigate the suitability of the injection moulding process for the production of OCMCs, two different feedstocks and alumina fibres (Nextel 610) were compounded in a laboratory-scale compounder. The fibre volume fractions were varied. In a laboratory-scale injection moulding device, microbending specimens were produced from the compounds obtained in this way. To characterise the test specimens, microstructure examinations and mechanical-static tests were done. It is shown that the injection moulding process is suitable for the production of fibre-reinforced oxide ceramics. The investigations show that the feedstocks used have potential for further research work and for future applications as material components for high-temperature applications in oxidising atmospheres.

scholarly journals Transformation of oxide ceramic textiles from insulation to conduction at room temperature

2020 ◽  
Vol 6 (6) ◽  
pp. eaay8538 ◽  
Author(s):  
Jianhua Yan ◽  
Yuanyuan Zhang ◽  
Yun Zhao ◽  
Jun Song ◽  
Shuhui Xia ◽  
...  
Keyword(s):  
Phase Transition ◽  
Lithium Batteries ◽  
Room Temperature ◽  
Reduction Method ◽  
The Self ◽  
Oxide Ceramic ◽  
Oxide Ceramics ◽  
Current Collectors ◽  
Enhanced Electrochemical Performance ◽  
Rapid Transformation

Oxide ceramics are considered to be nonconductive brittle materials, which limits their applications in emerging fields such as conductive textiles. Here, we show a facile domino-cascade reduction method that enables rapid transformation of ceramic nanofiber textiles from insulation to conduction at room temperature. After putting dimethylacetamide-wetted textiles, including TiO2, SnO2, BaTiO3, and Li0.33La0.56TiO3, on lithium plates, the self-driven chemical reactions induce defects in oxides. These defects initiate an interfacial insulation-to-conductive phase transition, which triggers the domino-cascade reduction from the interface to the whole textile. Correspondingly, the conductivity of the textile sharply increased from 0 to 40 S/m over a period of 1 min. The modified oxide textiles exhibit enhanced electrochemical performance when substituting the metallic current collectors of lithium batteries. This room temperature reduction method can protect the nanostructures while inducing defects in oxide ceramic textiles, appealing for numerous applications.

Polymer-Coated Ultra-Fine Particles

2005 ◽  
Vol 896 ◽  
Author(s):  
Patrick Brousseau ◽  
Charles Dubois
Keyword(s):  
Energetic Materials ◽  
Fine Particles ◽  
Energetic Material ◽  
Relative Viscosity ◽  
Accelerated Ageing ◽  
Coated Particles ◽  
Metallic Particles ◽  
Positive Effects ◽  
Coating Methods ◽  
Ultra Fine Particles

AbstractUltra-fine metallic particles have demonstrated recently their potential in tailoring the performance of energetic materials. DRDC Valcartier has explored methods to create controllable nanometric coatings on metallic particles and has opted to use polymers to treat the particles. Those coatings can have multiple positive effects. For example, in the case of aluminium, small particles are very reactive and tend to cause interations with the surrounding media. One example is the ageing of aluminium nanoparticles in the presence of air and humidity. Ultra-fine particles age much faster than micron-size particles. The long-term stability of energetic material mixes containing ultra-fine particles will be affected by this reactivity, and coatings would help to solve this problem. Another example is the interaction of aluminium nanoparticles with nitramines that causes gassing. Three coating methods will be presented: by thermoplastics using a Ziegler-Natta reaction, by thermosets through a polycondensation reaction initiated at the surface of the particles, and in-situ coating of particles by on-line polymerization during the plasma production of powders. The results of coating experiments using those methods will be presented. It will be shown that, for aluminium particles, adequate dispersion is a challenge and affects the results of the coating experiments. To assess the performance of the coating methods, ageing tests were carried out on coated and uncoated nanoparticles. The results of ageing tests with those methods will be presented and compared. It will be shown that the polymer coatings reduce significantly the loss of active metal content during accelerated ageing tests. Since the purpose of the powders is to be used in energetic materials, a study on the rheological effects of the coated particles in polymeric solutions will be presented as well. Coated particles increase the relative viscosity of HTPB-Al solutions by a factor of 100 at low shear rates, but much less with PPG.

Spray-Dried YSZ Ceramic Powders: Influence of Slurry Stability on Physical Characteristics of Agglomerates

2008 ◽  
Vol 591-593 ◽  
pp. 465-470 ◽  
Author(s):  
L.P. Santana ◽  
Dolores Ribeiro Ricci Lazar ◽  
Walter Kenji Yoshito ◽  
Valter Ussui ◽  
José Octavio Armani Paschoal
Keyword(s):  
Surface Area ◽  
Fine Particles ◽  
Suspension Stability ◽  
Ceramic Powders ◽  
Compaction Process ◽  
Electrophoretic Mobilities ◽  
Coprecipitation Route ◽  
The Stability ◽  
Slurry Stability ◽  
Spray Dried

Zirconia stabilized with 8 mol% yttria (YSZ) is the most effective material for use as electrolytes in solid oxide fuel cell. Ceramic powders of YSZ were synthesized in IPEN by coprecipitation route and are composed by fine particles (less than 01μm) with large surface area (~60m2.g-1). These powders have a strong tendency to agglomerate. and it make difficult the compaction process and to achieve a good density. To exert control over the compaction process. the powders were spray dried to obtain spherical granules. Thus the stability of slurries of these powders was studied by adding ammonium polyacrylate (Duramax D3005) as dispersant and the suspension stability was measured by electrophoretic mobilities. Slurries prepared with the better conditions were dried in a laboratory scale spray dryer. The prepared granules were characterized by morphology observation (SEM). surface area (BET). Vickers hardness and sintered ceramics bodies density were measured.

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