Titania and silica powders produced in a counterflow diffusion flame

Earlier publications describe the counterflow diffusion flame burner and its unique capability to produce oxide particles having certain structures, such as spheres of one material coated with another, spheres of one composition with attached bulbs of another composition, and uniform multicomponent mixtures. Here we describe the production and properties of bulk quantities of powders produced using this burner. Measurements were made of specific surface area and, for titania, of phase composition. It was found that the controls over powder characteristics used in other forms of flame-synthesis are equally effective in the counterflow diffusion flame burner. We found that the specific surface area of both silica and titania powders decrease with increasing precursor concentrations. Transmission electron microscopy analysis of the titania powders indicates that the mean size of the particles that comprise these powders increases with increasing concentration. These trends are consistent with the collision-coalescence theory of particle growth. In addition, the crystalline phase of titania can be controlled by selecting the appropriate feed stream. For example, over the ranges TiCl4 precursor concentrations tested, feeding it only into the oxidizer stream yields mainly anatase TiO2 powders, while feeding only into the fuel stream yields mainly rutile TiO2 powders. These trends can be explained by the known atmosphere-dependent anatase-rutile transformation. The present data demonstrate that, in addition to its unique capability to produce certain particle shapes and morphologies, the counterflow diffusion flame burner can be manipulated to produce either of the major commercial titania phases, and also silica, with a wide range of specific surface areas.

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Comparative Assessment of Effectiveness of Calcium Silicate Dispersions Produced Using Sucrose and Lactose as Components of Composite Cement Binder

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1017.11 ◽

2021 ◽

Vol 1017 ◽

pp. 11-20

Author(s):

Evgeny A. Shoshin ◽

Valeria V. Strokova ◽

Zheng Mao Ye

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Calcium Silicate ◽

Setting Time ◽

Inhibitory Effect ◽

Main Element ◽

Residual Content ◽

Nucleation Effect ◽

Wide Range

Silicate micro- and nano-additives are multifunctional in relation to cement systems. Their application can solve a wide range of technological problems while maintaining the economic efficiency of technical solutions. The effect of silicate additives and fillers is determined by their level of dispersion, due to which the technologies for producing nano- and submicro-sized dispersed materials are being developed. The combination of mechanochemical synthesis of modified calcium hydrosilicates with subsequent thermolysis makes it possible to produce calcium silicate dispersions (SCD), which differ in polymodality of the fractional composition including submicro (10–7–10–6 m) and microdimensional (≥10–6 m) modes. The main element of the technology is the use of modifying carbohydrate, which acts as a stabilizer of hydrated phases of silicates. A comparative study of SCD produced using sucrose (sSCD) and lactose (lSCD) revealed the effect of these carbohydrates on the properties of sSCD and lSCD, as well as their effectiveness as a component of cementitious composite binder. It was found that the level of adsorption of modifying carbohydrate determines the physical properties of SCD (granulometry, specific surface area). The relatively high residual content of free sucrose (0.24%) in the composition of sSCD prevents the consolidation of silicates nanoparticles formed during the thermolysis, causes a high content of submicro sized fractions and a high specific surface area with sSCD (26.3 ± 0.7 m2/g). Lactose is absorbed by the silicate phase; the residual content of free lactose does not exceed 0.028% of lSCD. The low content of stabilizing carbohydrate contributes to the development of nanoparticle consolidation, a decrease in the specific surface area of lSCD to 13.0 ± 0.2 m2/g and content of submicrosized fractions. The residual content of free carbohydrates and particle size characteristics of sSCD and lSCD determine the nature of their influence on Cement-SCD-based concrete setting and hardening. The presence of residual sucrose in the composition of sSCD and fine fractions determines the competitive nature of the processes of retardation of hardening and acceleration of hardening of the cement system due to the nucleation effect, as a result of which the curve of the setting time is extreme. In addition, the inhibitory effect of sucrose reduces the strength of concrete on the 7th day. By the 28th day, the inhibitory effect of sucrose has been overcome, and concrete samples demonstrate an 18% increase in compressive strength with a sSCD content of 30%. The low content of residual free lactose in the composition of lSCD causes the nucleation effect. As a result, there is a monotonous reduction in the setting time of concrete mix with an increase in the content of lSCD in the composition of HF, as well as a significant increase in concrete strength (up to 127%) on the 7th day. At the same time, on the 28th day the strength of concrete increases slightly

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3-D image-based numerical computations of snow permeability: links to specific surface area, density, and microstructural anisotropy

The Cryosphere ◽

10.5194/tc-6-939-2012 ◽

2012 ◽

Vol 6 (5) ◽

pp. 939-951 ◽

Cited By ~ 74

Author(s):

N. Calonne ◽

C. Geindreau ◽

F. Flin ◽

S. Morin ◽

B. Lesaffre ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Three Dimensional ◽

Analytical Models ◽

Simple Relationship ◽

Snow Density ◽

Average Value ◽

Wide Range ◽

Snow Samples

Abstract. We used three-dimensional (3-D) images of snow microstructure to carry out numerical estimations of the full tensor of the intrinsic permeability of snow (K). This study was performed on 35 snow samples, spanning a wide range of seasonal snow types. For several snow samples, a significant anisotropy of permeability was detected and is consistent with that observed for the effective thermal conductivity obtained from the same samples. The anisotropy coefficient, defined as the ratio of the vertical over the horizontal components of K, ranges from 0.74 for a sample of decomposing precipitation particles collected in the field to 1.66 for a depth hoar specimen. Because the permeability is related to a characteristic length, we introduced a dimensionless tensor K*=K/res2, where the equivalent sphere radius of ice grains (res) is computed from the specific surface area of snow (SSA) and the ice density (ρi) as follows: res=3/(SSA×ρi. We define K and K* as the average of the diagonal components of K and K*, respectively. The 35 values of K* were fitted to snow density (ρs) and provide the following regression: K = (3.0 &pm; 0.3) res2 exp((−0.0130 &pm; 0.0003)ρs). We noted that the anisotropy of permeability does not affect significantly the proposed equation. This regression curve was applied to several independent datasets from the literature and compared to other existing regression curves or analytical models. The results show that it is probably the best currently available simple relationship linking the average value of permeability, K, to snow density and specific surface area.

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Manufacture of Fine-Pored Ceramics by the Gelcasting Method

Advances in Materials Science and Engineering ◽

10.1155/2017/5923976 ◽

2017 ◽

Vol 2017 ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Bronisław Psiuk ◽

Anna Gerle ◽

Małgorzata Osadnik ◽

Andrzej Śliwa

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Design Theory ◽

Nanoporous Materials ◽

Silica Sol ◽

High Porosity ◽

Simple Method ◽

Fine Grained ◽

Wide Range

The fine-pored materials represent a wide range of applications and searches are being continued to develop methods of their manufacturing. In the article, based on measurements on fine-grained powders of Al2O3, TiO2, and SiO2, it has been demonstrated that gelcasting can be relatively simple method of obtaining of nanoporous materials with high values of both specific surface area and open porosity. The powders were dispersed in silica sol, and the gelling initiator was NH4Cl. The usefulness of experiment design theory for developing of fine-pored materials with high porosity and specific surface area was also shown.

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A Case Study of Waste Scrap Tyre-Derived Carbon Black Tested for Nitrogen, Carbon Dioxide, and Cyclohexane Adsorption

Molecules ◽

10.3390/molecules25194445 ◽

2020 ◽

Vol 25 (19) ◽

pp. 4445 ◽

Cited By ~ 1

Author(s):

Zuzana Jankovská ◽

Marek Večeř ◽

Ivan Koutník ◽

Lenka Matějová

Keyword(s):

Activated Carbon ◽

Carbon Black ◽

Specific Surface ◽

Surface Area ◽

Sorption Capacity ◽

Specific Surface Area ◽

Textural Properties ◽

Pyrolytic Carbon ◽

Surface Areas ◽

Wide Range

Waste scrap tyres were thermally decomposed at the temperature of 600 °C and heating rate of 10 °C·min−1. Decomposition was followed by the TG analysis. The resulting pyrolytic carbon black was chemically activated by a KOH solution at 800 °C. Activated and non-activated carbon black were investigated using high pressure thermogravimetry, where adsorption isotherms of N2, CO2, and cyclohexane were determined. Isotherms were determined over a wide range of pressure, 0.03–4.5 MPa for N2 and 0.03–2 MPa for CO2. In non-activated carbon black, for the same pressure and temperature, a five times greater gas uptake of CO2 than N2 was determined. Contrary to non-activated carbon black, activated carbon black showed improved textural properties with a well-developed irregular mesoporous-macroporous structure with a significant amount of micropores. The sorption capacity of pyrolytic carbon black was also increased by activation. The uptake of CO2 was three times and for cyclohexane ten times higher in activated carbon black than in the non-activated one. Specific surface areas evaluated from linearized forms of Langmuir isotherm and the BET isotherm revealed that for both methods, the values are comparable for non-activated carbon black measured by CO2 and for activated carbon black measured by cyclohexane. It was found out that the N2 sorption capacity of carbon black depends only on its specific surface area size, contrary to CO2 sorption capacity, which is affected by both the size of specific surface area and the nature of carbon black.

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Gold Cementation by Dendritic Zinc Powders in Percolation Mode

Materials Science Forum ◽

10.4028/www.scientific.net/msf.989.543 ◽

2020 ◽

Vol 989 ◽

pp. 543-547

Author(s):

K.D. Naumov ◽

Vladimir G. Lobanov

Keyword(s):

Particle Size ◽

Physical Properties ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

High Specific Surface Area ◽

Alkaline Solutions ◽

Wide Range ◽

Zinc Powders ◽

Cyanide Solutions

In present article gold cementation features from cyanide solutions using dendritic zinc powders are studied. The powders were obtained by electroextraction from alkaline solutions. Powders with different physical properties were obtained by means of change in current density (from 0.5 to 2 A/m2) and NaOH concentration in solution (from 100 to 400 g/dm3) at the constant zinc concentration (10 g/dm3). The physical properties of mentioned powders were studied using SEM (Jeol JSM-6390LA), BET (Gemini VII 2390) and laser diffraction (Sympatec HELOS & RODOS). It is shown that electrolytic powders have high specific surface area, which is 1.8–2.6 times larger than the surface area of the zinc powder currently used for cementation. At that electrolytic powders particle size is 8-22 times larger than the particle size of powder currently used for cementation. The reason of high specific surface area is the electrolytic zinc powders dendritic structure. It was found that the obtained powders precipitate gold from cyanide solutions with a greater efficiency in a wide range of productivity. Laboratory unit simulating Merrill-Crow technology was used for cementation. Immediately ahead conducting the experiments, Na2SO3 was added to the solution in excess to remove dissolved oxygen. Zinc powders were plated by dendritic lead before loading into the laboratory setup by cementation. Lead was added as acetate (Pb (CH3COO)2). The consumption of lead acetate was 10% by weight of zinc. Correlation between the powders physical properties and the gold extraction is shown.

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The Influence of Biogenic and Synthetic Starting Materials on the Properties of Porous Hydroxyapatite Bioceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.614.11 ◽

2014 ◽

Vol 614 ◽

pp. 11-16 ◽

Cited By ~ 2

Author(s):

Kristine Salma-Ancane ◽

Liga Stipniece ◽

Janis Locs ◽

Vitalijs Lakevičs ◽

Zilgma Irbe ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Precipitation Method ◽

Porous Hydroxyapatite ◽

Calcium Carbonates ◽

Porous Bodies ◽

Wide Range ◽

Egg Shells ◽

Viscous Mass

The aim of this study was to investigate the influence of biogenic and synthetic starting materials on properties of porous hydroxyapatite (HAp) bioceramics. HAp powders were synthesized by modified precipitation method using biogenic calcium carbonates (ostrich (Struthio camelus) egg shells, hen (Gallus gallus domesticus) egg shells, snail (Viviparus contectus) shells) and synthetic calcium oxides (Sigma-Aldrich and Fluka). Specific surface area, molecular structure and morphology of obtained powders were determined. As-synthesized HAp powders had a varied specific surface area with a wide range from 83 to 150 m2g-1 depending on CaO source. Porous bodies of HAp were prepared by in situ viscous mass foaming with NH4HCO3 as pore forming agent. Foamed and dried green bodies were sintered at 1100 °C. The obtained bioceramics were investigated using Archimedes method, field emission scanning electron microscopy and Brunauer-Emmett-Teller method. There are considerable differences between porous HAp bioceramics structures prepared from different sources of CaO. The choice of starting material substantially affects the macro-and microstructure of prepared porous bioceramics.

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3-D image-based numerical computations of snow permeability: links to specific surface area, density, and microstructural anisotropy

The Cryosphere Discussions ◽

10.5194/tcd-6-1157-2012 ◽

2012 ◽

Vol 6 (2) ◽

pp. 1157-1180 ◽

Cited By ~ 1

Author(s):

N. Calonne ◽

C. Geindreau ◽

F. Flin ◽

S. Morin ◽

B. Lesaffre ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Three Dimensional ◽

Analytical Models ◽

Wide Range ◽

Sphere Radius ◽

Snow Microstructure ◽

Microstructural Anisotropy ◽

Good Agreement

Abstract. We used three-dimensional (3-D) images of snow microstructure to carry out numerical estimations of the full tensor of the intrinsic permeability of snow (K). This study was performed on 35 snow samples, spanning a wide range of seasonal snow types. Because the permeability is related to a characteristic length, we introduced a dimensionless tensor K*=K/ res2, where the equivalent sphere radius of ice grains (res) is computed from the specific surface area of snow (SSA) and the ice density (ρi) as follows: res=3/(SSA x ρi). Values of K*, the average of vertical and horizontal components of K*, were plotted vs. snow density (ρs) and compared to analytical models and data from the literature, showing generally a good agreement. The 35 values of K* were fitted to ρs and provide the following regression: K*=2.94 x exp(–0.013 ρs), with a correlation coefficient of 0.985. This indicates that permeability, if assumed isotropic, can be reasonably determined from SSA and ρs, which are both easily measurable in the field. However, the anisotropy coefficient of K, induced by the snow microstructure, ranges from 0.74 to 1.66 for the samples considered. This behavior is consistent with that of the effective thermal conductivity obtained in a previous work.

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Intercomparison of retrieval algorithms for the specific surface area of snow from near-infrared satellite data in mountainous terrain, and comparison with the output of a semi-distributed snowpack model

The Cryosphere ◽

10.5194/tc-7-741-2013 ◽

2013 ◽

Vol 7 (2) ◽

pp. 741-761 ◽

Cited By ~ 23

Author(s):

A. Mary ◽

M. Dumont ◽

J.-P. Dedieu ◽

Y. Durand ◽

P. Sirguey ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Near Infrared ◽

Winter Season ◽

Added Value ◽

Mountainous Terrain ◽

Multiple Reflections ◽

Topographic Correction ◽

Wide Range

Abstract. This study compares different methods to retrieve the specific surface area (SSA) of snow from satellite radiance measurements in mountainous terrain. It aims at addressing the effect on the retrieval of topographic corrections of reflectance, namely slope and aspect of terrain, multiple reflections on neighbouring slopes and accounting (or not) for the anisotropy of snow reflectance. Using MODerate resolution Imaging Spectrometer (MODIS) data for six different clear sky scenes spanning a wide range of snow conditions during the winter season 2008–2009 over a domain of 46 × 50 km in the French Alps, we compared SSA retrievals with and without topographic correction, with a spherical or non-spherical snow reflectance model and, in spherical case, with or without anisotropy corrections. The retrieved SSA values were compared to field measurements and to the results of the detailed snowpack model Crocus, fed by driving data from the SAFRAN meteorological analysis. It was found that the difference in terms of surface SSA between retrieved values and SAFRAN-Crocus output was minimal when the topographic correction was taken into account, when using a retrieval method assuming disconnected spherical snow grains. In this case, the root mean square deviation was 9.4 m2 kg−1 and the mean difference was 0.1 m2 kg−1, based on 3170 pairs of observation and simulated values. The added-value of the anisotropy correction was not significant in our case, which may be explained by the presence of mixed pixels and surface roughness. MODIS retrieved data show SSA variations with elevation and aspect which are physically consistent and in good agreement with SAFRAN-Crocus outputs. The variability of the MODIS retrieved SSA within the topographic classes of the model was found to be relatively small (3.9 m2 kg−1). This indicates that semi-distributed snowpack simulations in mountainous terrain with a sufficiently large number of classes provides a representation of the snowpack variability consistent with the scale of MODIS 500 m pixels.

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Chemical Aspects of Rubber Reinforcement by Fillers

Rubber Chemistry and Technology ◽

10.5254/1.3538376 ◽

1996 ◽

Vol 69 (3) ◽

pp. 325-346 ◽

Cited By ~ 237

Author(s):

Siegfried Wolff

Keyword(s):

Research And Development ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Rolling Resistance ◽

Nineteen Seventies ◽

Rubber Industry ◽

Tire Industry ◽

Carbon Blacks ◽

Wide Range

Abstract For decades, the rubber industry, and the tire industry in particular, have been using mainly carbon blacks as reinforcing fillers. Since their structure and specific surface area can be varied over a wide range, carbon blacks are capable of meeting a wide range of different requirements. Even today, we are unable to exert a specific influence on the third component of reinforcement, the “surface activity” (surface energy) of carbon blacks. This problem and new, more stringent tire performance requirements lend new significance to the need for further carbon black research and development. Silicas, which were developed during the nineteen forties and fifties, were mainly used in shoe soling materials. Specific surface area and structure of the silicas were constantly adjusted to meet new requirements in this area. As our knowledge of the reinforcing mechanism of silicas in rubber increased, the benefits and drawbacks of silicas in rubber, in comparison to carbon blacks, became more and more apparent. The challenge to improve their reinforcing effect was then taken up. Since the beginning of the nineteen seventies, the chemical industry has concentrated on developing silanes for the rubber industry. The significance of the formation of covalent rubber-to-filler bonds for rubber reinforcement was recognized, and ways and means for the optimum and most efficient use of silicas and silanes were found, in a long and difficult process. During the past ten years, research and development efforts were dominated by the demand for increasing abrasion resistance, improving wet traction, and achieving the lowest possible rolling resistance. The combined use of silicas and silanes opened up new possibilities for meeting the requirements of the tire industry. After first adapting silanes to the silicas available, research and development efforts have recently been focused on adjusting the silicas to the silanes in order to achieve optimum effectiveness of this reinforcing system. All in all, a process seems to have been initiated in the tire industry which aims at using the silica/organosilane system to much greater advantage.

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Restricted Dynamics in Polymer-Filler Systems

MRS Proceedings ◽

10.1557/proc-661-kk4.4 ◽

2000 ◽

Vol 661 ◽

Author(s):

V. Arrighi ◽

S. Gagliardi ◽

Julia S. Higgins

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Dynamic Properties ◽

Polymeric Materials ◽

Weight Fraction ◽

Average Diameter ◽

Hydrogen Atoms ◽

Polymer Filler ◽

Wide Range

ABSTRACTComposites in which fibres or fillers are incorporated into a polymeric component exhibit improved mechanical strength compared to the polymer matrix. This reinforcement effect strongly depends on the properties of the interphase and the specific interactions between the polymer and the reinforcing additive.A wide range of experimental methods have been used to assess the effect of active fillers on the mobility of the polymer chains. The experimental results from NMR, dielectric spectroscopy and dynamical thermal analysis reveal that the mobility of chain units adjacent to the adsorbed surface differs considerably from the bulk.We have used quasielastic neutron scattering to investigate the dynamic properties of poly(dimethyl siloxane) (PDMS) filled with silica particles. This technique which probes the motion of the hydrogen atoms has been extensively used to study the local dynamics of polymeric materials. In this paper we show that QENS provides detailed information on the reduced mobility of chain segments in polymer-filler systems.QENS measurements were carried out on PDMS filled with hydrophilic Aerosil with different specific surface area (average diameter 7 and 20 nm). Detailed data analysis indicates that the QENS spectra of the polymer-filler composites can be described by the sum of two contributions: (a) a quasielastic component due to chains not affected by the presence of the fillers and (b) an elastic term from those chain segments strongly affected by the presence of fillers. The latter depends on the specific surface area of the particles and their weight fraction in the composite.

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