Tag Archives: Dry Construction Mix Modification

Activation of Catalysts for Carbon Nanomaterial Production

The most important stage of preparing heterogeneous catalysts for carbon nanomaterial (CNM) is their activation, which is understood as a complex of physical influence on the catalytic material, which allows to significantly increase the efficiency of nanostructure synthesis.

This can be achieved by researching mechanical (dispersion) and physical (electromagnetic and ultrasonic) activation methods.

One of the most important factors defining catalyst efficiency is its granulometric composition. It is known that reduction of the particle size (less than 3 nanometers) causes capsulation inside nanotubes, while increasing it above 25 nanometers leads to uneven size distribution and defects in nanotubes. This is due to the fact the using large catalyst particles (25 to 100 nanometers) prevents carbon scattering from the surfaces where hydrocarbon decay occurs to the surfaces where carbon is deposited; as a consequence, no CNM growth occurs on such particles. Therefore, it is important to define reasonable catalyst particle size, as well as dispersion and classification methods.

Note that dispersion of catalyst microparticles causes both the reduction of size and the changes in the microstructure, e.g. destruction and reduction of pore depth, increasing the boundary of nano-seeds, where graphitized carbon is deposited.

Catalyst was activated in a drum mill and an electromagnetic vortex layer device (AVS). The distinguishing characteristic of the vortex layer in electromagnetic units is the multitude of high frequency and strength shocks, as well as friction, which not only break solid particles, but significantly activate their surfaces due to the deformation of their crystalline lattice. Enormous energy is concentrated in a volume of this process, which direct influence on the material. The influence is so high that it changes the structure as deeply as the atom’s valency shells. The process causes deep changes in the structure of the material.

Mean energy conducted to a volume of the vortex layer reaches 103 kW/m3. This is several orders of magnitude higher than in vibration mills, for instance. Besides, the energy is localized in certain areas, e.g. in the locations where the ferromagnetic particles collide, where mean power reaches even higher.

The electromagnetic vortex layer unit consisted of a process section and a control section, connected by oil tubes and a power cable. The process section consisted of a support, an enclosure, an induction coil for the rotating electromagnetic field, and a detachable operating chamber.

The catalyst activation process was performed with 1…1.5 mm by 10…15 mm PVC encapsulated ferromagnetic particles.

The chamber was loaded with 0.120 kg of the catalyst and 0.060 kg of ferromagnetic particles; retention time varied from 5 to 60 seconds. The granulometric composition of the Ni/MgO catalyst after the dispersion was done by fractionating sieve analysis. The catalyst after activation was separated into fractions and used for CNM synthesis under a unified method of testing various catalyst samples.

The results of the experiment show that the optimal duration time for the finest grinding constitutes 10 seconds, with initial catalyst particle size of 500 micron.

The observed increase of catalyst particle size after 10 or more seconds of dispersion is apparently due to the fact that with time the particles accumulate sufficient energy for spontaneous aggregation.

The analysis of the influence of the catalyst size composition on the mean output of CNM leads to the conclusion: the output increases in inverse proportion to catalyst particle size. This is due to the increased active surface of the catalyst. The experiments demonstrated that the actual method of catalyst dispersion has no significant influence on nanomaterial output.

GlobeCore extends invitation to the International Construction & Utility Equipment Exposition-2019

GlobeCore invites all businesses and parties interested in the implementation of innovative technologies to the International Construction & Utility Equipment Exposition.

This event is biannual, and this year will be hosted by Kentucky Exposition Center, Louisville, Kentucky on 1-3 October. The exhibition focuses, among other things, on electric power transmission and distribution, wastewater treatment, natural gas supply etc.

GlobeCore will be represented in the first two categories by the CMM-G designed to change oil in wind turbine gearboxes and the AVS vortex layer device. You can see these machines and speak with our specialists at booth 2240.

The CMM-G simplifies and accelerates oil change in wind turbines. To protect the new oil from instantly becoming contaminated with impurities left in the gearbox after draining the oil oil, the machine also washes the gearbox with special flushing oil. As for the vortex layer device, it increases the efficiency of the existing wastewater purification systems, reducing process duration and chemical consumption.

Looking forward to meeting you at International Construction & Utility Equipment Exposition-2019!

Methods of Dry Construction Mix Modification

Dry Construction Mix Modification

The high quality of the modern construction mixes is impossible without using special modifying additives. They allow to adjust the properties of the material, making solutions with the required qualities for use in any (even extreme) conditions.

A relatively large amount of such additives is available in the market today. These are mostly surfactants, electrolytes, polymers etc. The history of modifying construction materials begins in the ancient times. Some of the oldest surviving buildings on the planet were built with lime concrete and mortar with vegetable oil, egg whites, dairy, boiled tree bark etc.

Binding materials have replaced the ancient modifiers with time. But, in the beginning of the previous century, modifying additives returned into construction on a new technological level. Many countries have already completely transitioned to modified concrete and mortar (with the market share reaching 90-95%).

The form in which the additives are used depends on the technology of their application. For concrete or otherwise soluble mixes, additives are introduced with water, while in preparation of dry material, they come in the form of powders, which must:

  1. spread evenly through the mix;
  2. have low water absorption ability.

The most widely accepted classification of modifying additives for dry construction mixes is as follows:

  • rheological properties adjustment;
  • structure adjustment;
  • settling and hardening process adjustment;
  • special modifiers;
  • multifunctional modifiers.

The modifiers which change the rheological properties of materials are the most widely used. This is because they can be used for any construction material mix.

Settling and hardening modifying additives are mostly used for modification of dry construction mixes based on gypsum binding, repair mixes, mixes for machine application, flooring materials etc.

Structure regulators are used to improve the qualities of plaster, repair and waterproofing materials.

Special modifiers are required if construction materials are used in special conditions with special requirements.

Each of the additives is supposed to change a certain quality (or several) and must not influence other important properties of construction material mixes and solutions. That is why multifunctional additives were developed: these allow to reduce or completely remove the negative influence of certain components, while retaining their positive effects. Multifunctional additives are used for flooring materials, plasters and special construction material mixes.

Mechanical Activation of Dry Construction Material Mixes Using Magnetic Nano-mills

Research shows that approximately 20% of the cement in concrete does not take part in hydration. These are mostly particles 70 micron and larger.

Magnetic nano-mills facilitate additional pulverization and activation of cement with mean surface area of 4500 – 5000 cm2/g.

The principle of operation of such mill is rather simple. They consist of a hollow cylinder made of non-magnetic material. Inside are ferromagnetic particles in the shape of a needle. Outside of the cylinder is an inducer which generates a rotating magnetic field. When the inducer is powered, the particles move along complex trajectories, forming the so called vortex layer. If large particles of cement are placed inside the cylinder, they will be turned into finely pulverized powder within seconds. Mechanical activation of cement reduces the amount of material used and improves concrete quality.

It should be noted that vortex layer mills can also be used to activate old compacted cement. Construction specialists know that if the сement is not used immediately and stays in storage for a month, activity of the material is reduced by at least 15%. When processed in the vortex layer, the compacted grains are broken and the cement is activated, oxides are removed and the cement is made as good as new.