Ultradispersed Powders Research Articles

Study of circular slip of superdispersed powder materials in continuous formation processes

The article presents the main results of an experimental study of the circular slipping of ultradispersed composite powder materials. The method is used in an experimental study of the coefficient of the circular slip of powder materials with respect to machining tools during the continuous working of volumetric nanostructural articles made from metal powders.

Study of the structure and mechanical properties of nano- and ultradispersed mechanically activated heavy tungsten alloys

Mechanisms of sintering and the structure and mechanical properties of nano- and ultradispersed W-Ni-Fe (WNF) and W-Ni-Fe-Co (WNFC) heavy tungsten alloys are investigated. The effect of tungsten particle sizes on the optimal sintering temperature is studied. The size of particles has been changed by the mechanical activation (MA) of the source W-Ni-Fe coarse-grained (CG) charge and by adding ultradispersed particles obtained using plasmochemical synthesis. Nanodispersed powders and ultradispersed powders (UDPs) have been sintered using the techniques of free sintering and pulse plasma sintering (PPS). It has been revealed that the dependence of the alloy density on heating temperature is nonmonotonic, with the maximum corresponding to the optimum sintering temperature. It has been shown that an increase in the time of MA and acceleration of grinding bodies in the process of MA accompanied by a decrease in the size of alloy particles and formation of nonequilibrium solid solutions lead to a reduction in the optimal sintering temperature. It has been shown that, using planetary high-energy milling methods and high-rate spark plasma sintering, it is possible to obtain ultrastrong tungsten alloys whose mechanical properties (macroelasticity stress and yield stress) substantially exceed analogous properties of commercial alloys.

Investigating the surface of particles of ultradispersed copper powders obtained by gas-phase condensation

Ultradispersed powders of metal copper obtained by evaporation-condensation technology are investigated. It is shown that, depending on the evaporation rate, various dispersities and degrees of agglomeration of copper powders are attained with the conservation of the weight fraction of copper in them no lower than 99.0%. It is established using the XPES method that a 5- to 6-nm-thick CuO layer (on the surface of which there is a Cu2O layer up to 1 nm thick) is always present on the surface of Cu particles of all powders under consideration. It is assumed that, because of a low residual air pressure in industrial installations, the surface layer of copper oxidizes to the lower oxide Cu2O during the evaporation of metal, while oxide CuO is formed as a result of the decomposition of Cu2O during the condensation of copper particles. The smaller the particle size of the powder is, the higher the content of oxides is.

Structure of ultradispersed powders obtained by thermal decomposition of ftoroplast-4 in presence of ammonium hydrogen difluoride

Study of the structure of ultradispersed powders of polytetrafluoroethylene (PTFE) obtained by thermal decomposition of ftoroplast-4 in the presence of ammonium hydrogen difluoride is performed. Using methods of electron microscopy, IR and NMR spectroscopy, TGA and DSC, and others, the peculiarities of the molecular and morphological structure of the powders and their thermal properties are established, and a comparison with the structure of other ultradispersed PTFE powders is performed.

Surface characteristics of polypropylene fibrous materials modified with ultradisperse polytetrafluoroethylene

This paper is devoted to analysis of the surface properties of polypropylene fibrous materials modified during molding via introduction of polytetrafluoroethylene ultradisperse powder into polypropylene melt. It is shown that the modification changes not only the bulk, but also surface, characteristics of the fibrous material. Evidence is provided of the presence of polytetrafluoroethylene particles on the fiber surface, and its content is determined. The effect of fiber modification on its tangential resistance coefficient and its amenability to processing is considered. The effect of ultradisperse polytetrafluoroethylene introduced into polypropylene melt on the hydrophobicity of the modified fibrous material is analyzed in detail.

Physicomechanical properties of a composite material based on ultrahigh-molecular-weight polyethylene filled with ceramic particles

The effect of the shape of filler particles on the mechanical properties of a composite material based on ultrahigh-molecular-weight polyethylene produced by thermal compacting after preliminary mechanical activation of the initial materials is studied. As a filler, Al2O3 in the form of an ultradispersed powder with a particle size of 200 nm or as 1-μm microspheres is used. The effects of the fillers of both types on the mechanical properties of the composite material is found to be positive and comparable in the concentration range under study (1–10 wt %). The degree of matrix hardening depends on the shape of filler particles.

Nanoscale ceria for new functional materials

Ultra dispersed ceria powders with crystallite size from 10 to 20 nm were synthesized by modified sol-gel and hydrothermal methods using cerium (III) nitrate as source of metal. N,N-dimethyloctylamine, monoethanolamine or tetraethylammonium hydroxide were used as a surfactant in syntheses. It was shown that increase of surfactant/Ce molar ratio value resulted in decreasing dispersion of obtained cerium oxides. It was shown that surfactant nature in the hydrothermal method had no significant effect on the dispersion of ceria obtained. Ceria had mesoporous structure with pore size less than 15 nm.

Special and New Monolithics

The paper shows the constituents and technical properties of low calcium aluminates cement concretes with ultra dispersed mineral powders and admixtures.

BULK NANOSTRUCTURED MATERIALS OBTAINED BY SHOCK WAVES COMPACTION OF ULTRAFINE TITANIUM AND ALUMINUM

Theoretical and experimental Investigations of shock wave consolidation processes of Ti - Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatic of Ti and Al . The normal and tangential stresses in the cylindrical steel tube (containers of Ti - Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (≤ 50nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallics with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al . Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20) GPa. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallics phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.

Catalytic activity of electrodeposited copper-containing compounds in conversion of carbon monoxide by steam

Possibility of using an ultradisperse copper-containing powder produced by the electrolytic method as an efficient catalyst for conversion of carbon monoxide by steam was studied.

Potassium polytitanates intercalated with nickel ions and their thermal transformations

The intercalation of nickel ions into the layered structure of ultradispersed amorphous potassium polytitanate powder on treatment with an aqueous solution of nickel sulfate was studied. The limiting nickel content that can be attained by intercalation is 12.8 wt %. The nickel ion intercalation results in a decrease in the average particle size of potassium polytitanate and in the structural ordering. Heat treatment of the resulting intercalate promotes the formation of a nanocomposite consisting of the solid solution K1.35(NixTi8 − x)O16 with the hollandite structure, Ti2O3, and, depending on the treatment schedule, either NiO nanocrystals or Ni metal.

Formation of nanostructured particles of cerium-activated yttrium aluminum garnet by the combustion method

The synthesis of ultradispersed powders of the yttrium aluminum garnet (activated by ions of cerium, lithium, silicon, and manganese) by the combustion method in the presence of hexamethylenetetramine has been optimized. The structural, physicochemical, and spectral-luminescence properties of synthesized finely dispersed samples have been studied. It has been found that exclusively the phase of garnet Y3Al5O12 of the cubic modification is identified in the products of the synthesis performed under optimum condition.

Transformation-strengthened ZrO2-CeO2 ceramic on the basis of powders synthesized using the ultrasonic spray pyrolysis method

The possibility of obtaining submicron ceramic powders with a composition of ZrO2 + 12 mol % CeO2 using the ultrasonic spray pyrolysis method is examined. The effects of the technological parameters of the process on the characteristics of powder particles and their sintering abilities are investigated. The structure and mechanical characteristics of polycrystalline ceramics from aerosol powders indicate sufficiently high properties of this material comparable to similar parameters of ceramics from standard ultradispersed powders. However, to obtain this novel type of ceramic, one does not require pretreatment of the initial powder or use of special expensive methods of powder compaction.

Nanostructure of the products of the thermal treatment of ultradisperse molybdenum powder

Nanomaterials obtained by treatment of ultradisperse molybdenum powder in air at 25–650°C were studied by X-ray diffractometry. Changes in the phase composition, mean size of crystallites, microdistortions (microstresses), crystal lattices of crystallites, and texture were investigated.

Study of the triboengineering characteristics of ultradispersed composite powder materials

The main results from experimental research on the triboengineering characteristics of ultradispersed composite powder materials are discussed. An experimental procedure for studying the triboengineering characteristics and yield stress of powder materials is elaborated as applied to the processes of continuous forming of nanostructural solid items from metallic powders.

X-ray photoelectron spectroscopy of ultradispersed copper alloy powder surface after processing by fluorinated polyethers

Ultradispersed powders of Cu-Sn alloy were processed by fluorinated polyethers of different compositions. X-ray photoelectron spectroscopy was used to show that a polymeric film no thicker than 2 nm was formed on the surface of particles as a result of processing. The film formed by fluorinated polyethers with a molecular mass of 3000 prevents the interaction of metal particles of Cu-Sn alloy with atmospheric oxygen and provides dielectric properties of the surface.

Tribological behavior of piston alloy reinforced by micro- and ultradispersed ceramic particles

The paper deals with the structure, phase and elementary compositions, and tribological behavior of eutectic silumin AK12M2MgN modified by micro- and ultradispersed refractory powder fillers BNAl and SiO2(B,Ti) that are alloyed with elements reactive to aluminum. It is shown that the reinforcement of silumin is accompanied by the formation of nanosized ceramic inclusions AlN, AlB2, TiB2, and α-Al2O3 due to in situ reactions which operate during the production of the modifiers and composites. They have a great modifying impact on the structure of the original alloy. In addition, the presence of these compounds boosts the wear resistance of silumin 1.7–2.9 times; its carrying capacity increases and its friction coefficient decreases by 1.5–4.0 times.

Formation of a uniform charge composed of highly dispersed and ultradispersed powders

In modern powder metallurgy, powders that are in a highly dispersed state are being used more and more to create new materials composed of powders which are dissimilar from one another. This trend has engendered a need to mix charges that are made up of powders which differ in their physico-mechanical properties. The mixing operation must be highly productive while also ensuring the disintegration of conglomerates in the charge. This article describes a method and equipment that solve these problems by subjecting the powder charge to vibro-aereational mixing.

СИНТЕЗ И БАКТЕРИЦИДНЫЕ СВОЙСТВА УЛЬТРАДИСПЕРСНОГО ПОРОШКА МЕДИ

Possibility of application of an ultradisperse powder of the copper received by temperature destruction of copper oxalate, as a biocidal additive is shown. Antibacterial activity copper at concentration above 1 mkg/ml is established concerning clinical Staphylococcus aureus № 92

Mechanochemical synthesis of ultradispersed powders of manganese and zinc oxides

Synthesis by a method of mechanochemistry of nanopowders of manganese and zinc oxides intended for use as modifying agents to polymers was investigated. The obtained oxides were investigated by X-ray analysis, scanning electron microscopy, measurements of specific surface by BET, and a laser analyzer of the sizes of particles. It was established that the proposed technique allows oxide particles with the average size of 60–140 nm to be obtained.