scholarly journals ENTIRELY AQUEOUS SOLUTION-GEL ROUTE FOR THE PREPARATION OF ZIRCONIUM CARBIDE, HAFNIUM CARBIDE AND THEIR TERNARY CARBIDE POWDERS

2016 ◽  
pp. 248-253
Author(s):  
Chunlei Yan
Keyword(s):  
Aqueous Solution ◽  
Zirconium Carbide ◽  
Hafnium Carbide ◽  
Ternary Carbide

Zirconium carbide, hafnium carbide and their ternary carbide nanoparticles by an in situ polymerization route

RSC Advances ◽  
2015 ◽  
Vol 5 (46) ◽  
pp. 36520-36529 ◽  
Author(s):  
Chunlei Yan ◽  
Rongjun Liu ◽  
Changrui Zhang ◽  
Yingbin Cao
Keyword(s):  
In Situ Polymerization ◽  
Zirconium Carbide ◽  
Hafnium Carbide ◽  
Ternary Carbide

An in situ polymerization route for the synthesis of zirconium carbide, hafnium carbide and their ternary carbide nanoparticles.

scholarly journals Synthesis of nanocrystallized zirconium carbide based on an aqueous solution-derived precursor

RSC Advances ◽  
2017 ◽  
Vol 7 (37) ◽  
pp. 22722-22727 ◽  
Author(s):  
Jing-Xiao Wang ◽  
De-Wei Ni ◽  
Shao-Ming Dong ◽  
Guang Yang ◽  
Yan-Feng Gao ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Zirconium Carbide ◽  
Zirconium Acetate

Nanocrystallized zirconium carbide (ZrC) powder was synthesized by an aqueous solution-based process using zirconium acetate and sucrose as starting reagents.

Preparation and Properties of Ultra-High Temperature Ceramics Based on ZrC and HfC

2011 ◽  
Vol 170 ◽  
pp. 37-40 ◽  
Author(s):  
Vlastimil Brozek ◽  
Pavel Ctibor ◽  
Dong Ik Cheong ◽  
Seong Ho Yang ◽  
Libor Mastny ◽  
...  
Keyword(s):  
High Temperature ◽  
Plasma Spraying ◽  
Zirconium Carbide ◽  
Internal Surface ◽  
Chemical Processes ◽  
Hafnium Carbide ◽  
Ultra High Temperature Ceramics ◽  
Water Stabilized Plasma ◽  
Controllable Factors ◽  
Ultra High Temperature

Successful preparation of massive compact bodies from ultra-high temperature ceramics like zirconium carbide, hafnium carbide and their cermets with tungsten matrix with high values of mechanical parameters is difficult. Only limited number of techniques is able to perform it because of their absolutely highest melting points. In our contribution the preparation of these materials by both - hot pressing and plasma spraying techniques is described and chemical processes taking part at the fabrication are studied. Hot-pressed products fabricated at 2000°C and 6 GPa partly react with the internal surface of the BELT-type apparatus. Melting and solidification is taking place at plasma spraying. This process, carried out by water stabilized plasma torch with centerline temperature up to 30 000°C, is joined with undesirable reactions with plasma-forming medium, with oxidation in a turbulent plasma flow and nitridation of free-flight particles. All these chemical processes depend on variety of parameters, such as particle size of the feedstock powders or electric power of the arc. The mentioned parameters are easily controlled. Other, less controllable, factors include trajectory of powder particles in the plasma jet, important for the melting degree as well as for oxidation or nitridation of the powder surface. New knowledge concerning properties of compact ZrC and HfC were obtained.

Synthesis of highly dispersed super-refractory tantalum-zirconium carbide Ta4ZrC5 and tantalum-hafnium carbide Ta4HfC5 via sol-gel technology

2011 ◽  
Vol 56 (11) ◽  
pp. 1681-1687 ◽  
Author(s):  
E. P. Simonenko ◽  
N. A. Ignatov ◽  
N. P. Simonenko ◽  
Yu. S. Ezhov ◽  
V. G. Sevastyanov ◽  
...  
Keyword(s):  
Sol Gel ◽  
Zirconium Carbide ◽  
Hafnium Carbide ◽  
Highly Dispersed

Structures Formed by Cryoprotective Agents Used in Freezc-Etching

1971 ◽  
Vol 29 ◽  
pp. 448-449
Author(s):  
G. G. Cocks ◽  
C. E. Cluthe
Keyword(s):  
Aqueous Solution ◽  
Polyethylene Oxide ◽  
Liquid Nitrogen Temperature ◽  
Ice Crystals ◽  
Etching Technique ◽  
Structural Constituent ◽  
Cryoprotective Agents ◽  
Quick Freezing ◽  
Freeze Etching ◽  
Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

Preparation and characterisation of vanadium pentoxide supported rhodium catalyst

1988 ◽  
Vol 46 ◽  
pp. 946-947
Author(s):  
A. Legrouri
Keyword(s):  
Aqueous Solution ◽  
Thermal Decomposition ◽  
Physicochemical Properties ◽  
Surface Area ◽  
Vanadium Pentoxide ◽  
High Purity ◽  
Gas Adsorption ◽  
Rhodium Catalyst ◽  
Optical Methods ◽  
Reducible Oxides

The industrial importance of metal catalysts supported on reducible oxides has stimulated considerable interest during the last few years. This presentation reports on the study of the physicochemical properties of metallic rhodium supported on vanadium pentoxide (Rh/V2O5). Electron optical methods, in conjunction with other techniques, were used to characterise the catalyst before its use in the hydrogenolysis of butane; a reaction for which Rh metal is known to be among the most active catalysts.V2O5 powder was prepared by thermal decomposition of high purity ammonium metavanadate in air at 400 °C for 2 hours. Previous studies of the microstructure of this compound, by HREM, SEM and gas adsorption, showed it to be non— porous with a very low surface area of 6m2/g3. The metal loading of the catalyst used was lwt%Rh on V2Q5. It was prepared by wet impregnating the support with an aqueous solution of RhCI3.3H2O.

TEM observation of iron oxide pillars in montmorillonite

1990 ◽  
Vol 48 (4) ◽  
pp. 882-883
Author(s):  
H. Mori ◽  
Y. Murata ◽  
H. Yoneyama ◽  
H. Fujita
Keyword(s):  
Aqueous Solution ◽  
Iron Oxide ◽  
Fine Particles ◽  
Aqueous Suspension ◽  
Volume Ratio ◽  
Exchange Capacity ◽  
Nano Composites ◽  
Pillared Montmorillonite ◽  
Topographic Features ◽  
Transmission Electron

Recently, a new sort of nano-composites has been prepared by incorporating such fine particles as metal oxide microcrystallites and organic polymers into the interlayer space of montmorillonite. Owing to their extremely large specific surface area, the nano-composites are finding wide application[1∼3]. However, the topographic features of the microstructures have not been elucidated as yet In the present work, the microstructures of iron oxide-pillared montmorillonite have been investigated by high-resolution transmission electron microscopy.Iron oxide-pillared montmorillonite was prepared through the procedure essentially the same as that reported by Yamanaka et al. Firstly, 0.125 M aqueous solution of trinuclear acetato-hydroxo iron(III) nitrate, [Fe3(OCOCH3)7 OH.2H2O]NO3, was prepared and then the solution was mixed with an aqueous suspension of 1 wt% clay by continuously stirring at 308 K. The final volume ratio of the latter aqueous solution to the former was 0.4. The clay used was sodium montmorillonite (Kunimine Industrial Co.), having a cation exchange capacity of 100 mequiv/100g. The montmorillonite in the mixed suspension was then centrifuged, followed by washing with deionized water. The washed samples were spread on glass plates, air dried, and then annealed at 673 K for 72 ks in air. The resultant film products were approximately 20 μm in thickness and brown in color.

The microstructure of functionalized poLyacrylonitrile beads for bioseparations

1990 ◽  
Vol 48 (4) ◽  
pp. 1094-1095
Author(s):  
Eduardo A. Kamenetzky ◽  
David A. Ley
Keyword(s):  
Aqueous Solution ◽  
Affinity Chromatography ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Surface Coverage ◽  
Vacuum Impregnation ◽  
Thin Sections ◽  
Selective Staining ◽  
Low Viscosity ◽  
Diamond Knife

The microstructure of polyacrylonitrile (PAN) beads for affinity chromatography bioseparations was studied by TEM of stained ultramicrotomed thin-sections. Microstructural aspects such as overall pore size distribution, the distribution of pores within the beads, and surface coverage of functionalized beads affect performance properties. Stereological methods are used to quantify the internal structure of these chromatographic supports. Details of the process for making the PAN beads are given elsewhere. TEM specimens were obtained by vacuum impregnation with a low-viscosity epoxy and sectioning with a diamond knife. The beads can be observed unstained. However, different surface functionalities can be made evident by selective staining. Amide surface coverage was studied by staining in vapor of a 0.5.% RuO4 aqueous solution for 1 h. RuO4 does not stain PAN but stains, amongst many others, polymers containing an amide moiety.

Sign in / Sign up

Export Citation Format

Share Document