Preparation of A12O3-ZrO2 Composites by Adjustment of Surface Chemical Behavior

1986 ◽  
Vol 73 ◽  
Author(s):  
S. Baik ◽  
A. Bleier ◽  
P. F. Becher
Keyword(s):  
Particle Size ◽  
Electrolyte Concentration ◽  
Surface Chemical ◽  
Green Density ◽  
Chemical Behavior ◽  
Composite Systems ◽  
Gravitational Forces ◽  
Ph Conditions ◽  
Differential Sedimentation ◽  
Optimum Balance

ABSTRACTAqueous colloidal routes for processing binary suspensions containing Al 2 O 3 and ZrO2 were designed and tested in order to achieve homogeneous microstructures. Effects of particle size and size ratio of each component, pH, and electrolyte concentration of composite suspensions on sedimentation, green density, and ZrO2 distribution in sintered microstructures were examined. The pH conditions for inhibiting differential sedimentation without impairing green density were optimized. Overall suspension and coagulation behavior for these composite systems were explained using the DLVO approach. Optimum balance of colloidal and gravitational forces occurred when the secondary minimum heterocoagulation was maximized.

Chemical Transformation of Fe, Air & Water to Ammonia: Variation of Reaction Rate with Temperature, Pressure, Alkalinity and Iron

2018 ◽  
Author(s):  
Ping Peng ◽  
Fang-Fang Li ◽  
Xinye Liu ◽  
Jiawen Ren ◽  
jessica stuart ◽  
...  
Keyword(s):  
Particle Size ◽  
Reaction Rate ◽  
Electrolyte Concentration ◽  
Iron Concentration ◽  
Reaction Medium ◽  
Iron Particle ◽  
Intermediate Step ◽  
Ammonia Production ◽  
Pure Nitrogen ◽  
Alkaline Reaction

The rate of ammonia production by the <u>chemical </u>oxidation of iron, N<sub>2</sub>(from air or as pure nitrogen) and water is studied as a function of (1) iron particle size, (2) iron concentration, (3) temperature, (4) pressureand (5) concentration of the alkaline reaction medium. The reaction meduium consists of an aqueous solution of equal molal concentrations of NaOH and KOH (Na<sub>0.5</sub>K<sub>0.5</sub>OH). We had previously reported on the <u>chemical </u>reaction of iron and nitrogen in alkaline medium to ammonia as an intermediate step in the <u>electrochemical </u>synthesis of ammonia by a nano-sized iron oxide electrocatlyst. Here, the intermediate <u>chemical </u>reaction step is exclusively explored. The ammonia production rate increases with temperature (from 20 to 250°C), pressure (from 1 atm to 15 atm of air or N<sub>2</sub>), and exhibits a maximum rate at an electrolyte concentration of 8 molal Na<sub>0,5</sub>K<sub>0,5</sub>OH in a sealed N<sub>2</sub>reactor. 1-3 µm particle size Fe drive the highest observed ammonia production reaction rate. The Fe mass normalized rate of ammonia production increases with decreasing added mass of the Fe reactant reaching a maximum observed rate of 2.2x10<sup>-4</sup>mole of NH<sub>3</sub>h<sup>-1</sup>g<sup>-1</sup>for the reaction of 0.1 g of 1-3 µm Fe in 200°C 8 molal Na<sub>0.5</sub>K<sub>0.5</sub>OH at 15 atm. Under these conditions 5.1 wt% of the iron reacts to form NH<sub>3</sub>via the reaction N<sub>2</sub>+ 2Fe + 3H<sub>2</sub>O ®2NH<sub>3</sub>+ Fe<sub>2</sub>O<sub>3</sub>.

Comparison of Different Alumina Powders for Aqueous Tape Casting Process

2015 ◽  
Vol 820 ◽  
pp. 172-177
Author(s):  
Fernanda P. Santos ◽  
Ediana Gambin ◽  
Cristina Moniz A. Lopes ◽  
Rosa Maria Rocha
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Tape Casting ◽  
Casting Process ◽  
Aqueous System ◽  
Solid Concentration ◽  
Green Density ◽  
Commercial Alumina ◽  
Acrylic Latex ◽  
Final Density

Tape casting process was used to produce Al2O3 substrates in an aqueous system with acrylic latex emulsion as binder. The present work studied the slurry formulations in aqueous medium of Al2O3 powders with different particle size distribution and made correlation to the green and sintered tapes. Two commercial alumina powders, one sub-micrometric and other micrometric were used. Compositions of Al2O3 slurries with 80 and 83 wt% of solids were prepared by dispersing the powders in water with a dispersant with subsequently additions of 7 and 10 wt% of binder. Sub-micrometric Al2O3 resulted in a high densification tapes regardless solid concentration and binder amount in the slurry, though green density was affected. For micrometric alumina, increasing the solid concentration resulted in a little higher final density.

NUMERICAL SOLUTIONS OF SMOLUCHOWSKI'S EQUATIONS FOR THE COAGULATION OF UNCHARGED AEROSOLS

1965 ◽  
Vol 43 (8) ◽  
pp. 2312-2318 ◽  
Author(s):  
J. M. Beeckmans
Keyword(s):  
Particle Size ◽  
Numerical Solutions ◽  
Coagulation Factor ◽  
Dispersion Parameter ◽  
Particle Size Range ◽  
Mean Particle Size ◽  
A Value ◽  
Wide Range ◽  
Differential Sedimentation ◽  
Smoluchowski’S Equation

Smoluchowski's equations for the coagulation of uncharged aerosol particles were programmed for solution by electronic computer. Terms representing differential sedimentation, turbulence, and mean aggregate density in solid aerosols were included. The effect of heterogeneity in the particle-size distribution of the aerosols on their rate of coagulation was illustrated by means of a slip-corrected coagulation factor Fc, which assumes a value of unity in all non-turbulent homogeneous aerosols. Curves of Fc vs. σg, the geometrical standard deviation, were calculated for aerosols of various mean particle-size. The effects due to turbulence, and to differential sedimentation, were illustrated in a similar manner. It was also found that the process of coagulation gives rise to a degree of dispersion which is independent of the original dispersion parameter, and depends only slightly on the mean particle-size of the aerosol over a wide range of particle-sizes. In the particle-size range in which differential sedimentation is inappreciable, the relatively constant value of the dispersion parameter implies that heterogeneous aerosols must obey the simplified integrated form of Smoluchowski's equation, which is applicable to homogeneous aerosols. The coagulation constant exceeds that predicted by the simple theory by about 10% for liquid aerosols of 0.1 μ or less.

MECHANICAL PROPERTIES OF POLYMER COMPOSITES BASED ON BIOPARTICLES (JATROPHA CURCAS L.)

2015 ◽  
Vol 76 (3) ◽  
Author(s):  
Petr VALÁŠEK
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Polymer Composites ◽  
Renewable Resources ◽  
Jatropha Curcas ◽  
Epoxy Resins ◽  
Polymer Materials ◽  
Jatropha Curcas L ◽  
Composite Systems ◽  
Organic Particles

Composites are materials which synergically combine properties of each phase – matrix and filler. Polymer materials can be used as matrix while inorganic and organic particles can be used as fillers. Composite systems based on renewable resources can be designed as an interesting material for engineering. This paper describes on the tribological and other mechanical properties of biocomposites based on polymer resins and microparticles - seed cakes, which were obtained from seeds of the plant Jatropha Curcas L. during pressing. The particle size obtained was 573 µm.The results confirmed that the epoxy and polyurethane resins were capable of forming which corresponds to the interaction with the organic particles prepared from the seeds of Jatropha Curcas L. The presence of particles however, changed the mechanical properties of the resins. In the case of epoxy resins and polyurethane (Sika Force 7723), the hardness according to Shore D identically decreased with a maximum of 1.9. Abrasion resistance decreased due to the presence of particles of 0.0393 cm3 for Glue Epox Rapid, 0.0449 cm3 for Epoxy 1200/324 and 0.0567 cm3 for Sika Force 7723.

Surface Chemical Behavior of Uranium Metal in Hydrogen Atmosphere Studied by XPS

2003 ◽  
Vol 10 (02n03) ◽  
pp. 325-330 ◽  
Author(s):  
Xiaolin Wang ◽  
Xiaoguo Fu ◽  
Zhengping Zhao
Keyword(s):  
Chemical Structure ◽  
Uranium Oxide ◽  
Main Product ◽  
Profile Analysis ◽  
Hydrogen Atmosphere ◽  
Pure Hydrogen ◽  
Surface Chemical ◽  
Chemical Behavior ◽  
Uranium Metal ◽  
Good Agreement

The surface chemical behavior of clean uranium metal in a hydrogen atmosphere at 80°C and 120°C has been studied using XPS and thermodynamic calculation. The main product is uranium oxide rather than hydride uranium on the uranium surface after the exposure of uranium to extremely pure hydrogen, and the U4f7/2 binding energy of UH3 has been found to be 378.6 ± 0.1 eV. An elevated temperature (120°C) is beneficial to the formation of UH3 species at the same hydrogen exposures. The depth profile analysis of XPS indicates that the chemical structure of the surface layer was UO2/UH3/U after the exposure of hydrogen reached 1.31 × 10-6 L (1 L = 10-6 Torr·s). Results of thermodynamic calculations are in good agreement with the above conclusions.

ELECTROPHORESIS OF RESIN EMULSIONS: I. THE EFFECT OF EMULSIFYING AGENTS

1953 ◽  
Vol 31 (3) ◽  
pp. 287-296 ◽  
Author(s):  
L. A. Munro ◽  
F. H. Sexsmith
Keyword(s):  
Particle Size ◽  
Hydrogen Bonding ◽  
Vinyl Acetate ◽  
Electrolyte Concentration ◽  
Chemical Change ◽  
Charged Particles ◽  
Emulsifying Agent ◽  
Glass Cell ◽  
Partial Chemical

A modified Briggs electrophoretic glass cell was used to measure the mobility of over 2500 particles of vinyl acetate latices prepared with different emulsifying agents. Although anionic and cationic agents conferred negative and positive mobilities respectively, nonionic agents invariably resulted in negatively charged particles. This is attributed to partial chemical change to anionic materials or to hydrogen bonding and polarization processes. The nature of the emulsifying agent and electrolyte concentration rather than concentrations of the latex or particle size were the most significant variables affecting the mobility of any latex.

scholarly journals The Optimum Dispersion of Carbon Nanotubes for Epoxy Nanocomposites: Evolution of the Particle Size Distribution by Ultrasonic Treatment

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Tomas Roll Frømyr ◽  
Finn Knut Hansen ◽  
Torbjørn Olsen
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Power Level ◽  
Curing Agent ◽  
Ultrasonic Dispersion ◽  
Multiwalled Carbon ◽  
Freely Suspended ◽  
Differential Sedimentation ◽  
Energy Dissipated

The ultrasonic dispersion of multiwalled carbon nanotube (MWCNT) suspensions was assessed by studying the differential sedimentation of the particles in an acid anhydride often employed as a curing agent for epoxy resins. The particle size distributions were characterized by the means of a disc centrifuge, and the effect of dispersion time, power density, and total energy input, for both bath and circulation probe ultrasonic dispersing equipment was investigated. The mass of freely suspended MWCNTs relative to agglomerated MWCNTs was estimated as a measure of the quality of the dispersions, and the results showed that this ratio followed a power law scaling with the energy dissipated in the sonication treatment. If the sonication power level was too high, sonochemical degradation of the curing agent could occur. The mean agglomerate MWCNT size distribution was estimated, and the fragmentation of the agglomerates was modeled by means of fragmentation theory. Indications of both rupture and erosion fragmentation processes for the MWCNT agglomerates were observed.

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