75 resultados para 1200°C
Resumo:
The EU intends to increase the fraction of fuels from biogenic energy sources from 2% in 2005 to 8% in 2020. This means a minimum of 30 million TOE/a of fuels from biomass. This makes technical-scale generation of syngas from high-grade biomass, e.g. straw, hay, bark, or paper/cardboard waste, and the production of synthetic fuels by Fischer-Tropsch (FT) synthesis highly attractive. The BTL concept (Biomass to Liquids) of the Karlsruhe Research Center, labeled bioliq, focuses on this challenge by locally concentrating the biomass energy content by fast pyrolysis in a coke/oil slurry followed by slurry conversion to syngas in a central entrained flow gasifier at 1200C and pressures above 4MPa. FT synthesis generates intermediate products for synthetic fuels. To prevent the sensitive catalysts from being poisoned the syngas must be free of tar and particulates. Trace concentrations of H2S, COS, CS2, HCl, NH3, and HCN must be on the order of a few ppb. Moreover, maximum conversion efficiency will be achieved by cleaning the gas above the synthesis conditions. (T>350C, P>4MPa). The concept of an innovative dry HTHP syngas cleaning process is presented. Based on HT particle filtration and suitable sorption and catalysis processes for the relevant contaminants, an overall concept will be derived, which leads to a syngas quality required for FT synthesis in only two combined stages. Results of filtration experiments on a pilot scale are presented. The influence of temperature on the separation and conversion, respectively, of particulates and gaseous contaminants is discussed on the basis of experimental results obtained on a laboratory and pilot scale. Extensive studies of this concept are performed in a scientific network comprising the Karlsruhe Research Center and five universities; funding is provided by the Helmholtz Association of National Research Centers in Germany.
Resumo:
The diatomite is a natural material that has numerous applications due to changes in their physical and chemical properties after processing. It is currently used in the industry as a sound insulator , filter aid and industrial load . The filter material shall be inert chemical composition , which will diatomite confers a high commercial value and performance not found in other particulate materials , for this application. The diatomite surface undergoes changes after thermal treatment at high temperatures , from 800ºC , with properties that enable its application in the food , beverage , pharmaceutical , cosmetic and textiles . In this work , we developed a study on thermal treatment on natural diatomite to adapt their properties to the application as a filter aid . The heat treatments were performed in an open oven at temperatures of 800ºC , 1000ºC and 1200ºC for a time of 24 hours. Reagents were added in the constitution of the samples analyzed. The reagents used were sodium carbonate (Na2CO3 ) and sodium chloride (NaCl) . The samples were characterized by x - ray diffraction , x -ray fluorescence , scanning electron microscopy , analysis and particle size distribution , specific surface area by the BET method , and pore volume by BJH method. The results showed a reduction in porosity of the material as well as a significant increase in specific surface area after heat treatment and the reactants in the ratio of 3 wt%. The diatomaceous earth , after heat treatment , undergone changes in its coloration , varying in white, cream and beige , which directly interferes with the speed of filtration materials process. All results obtained before and after heat treatment of the material with the values obtained for samples already used industrially , Brazilian and American industry , which were characterized using the same test methods performed with the samples in the study were compared and showed promising efficiency when material studied in the region of Punaú - RN , after processing , reagent addition and heat treatment, as an element in the composition of filter .
Resumo:
Porous structures are being widely investigated for use in biomedical implants, aiming to mechanically integrate and functionally the implant inside the bone tissue. Moreover, this structure is also important for drugs that can be stored and can induce and accelerate the process of osseointegration. With the purpose to investigate this effect, Ti, Nb and Sn metal powders, were sintered by plasma using a hollow cathode discharge. Sintering was performed in argon plasma set at 4 mbar pressure and temperatures of 500 ° C, 600 ° C and 700 ° C. Samples were also sintered in the electrical resistance furnace at 1200 ° C in order to compare plasma sintering with the conventional method. It was observed that plasma samples sintered with the hollow cathode configuration showed a gradient in porosity, while the samples sintered in the resistive furnace did not. Furthermore, differences in the microstructure of the samples were found, were a surface with higher porosity and ales porous core were obtained at different temperatures. The percolation profile of distilled water and the chemical compositions of the porous layers of the plasma treated samples were the main results obtained. Based on these results, we can conclude that this structure is particularly important for application in the biomedical field such as scaffolds for drug delivery and implants
Resumo:
There is great difficulty in forming a composite refractory metal niobium with copper. This is due to the fact that Nb-Cu system is almost mutually immiscible and may be neglected solubility between them. These properties hinder or prevent obtaining homogeneous and high-density structures, conventionally prepared. This study aims to analyze the use of high-energy milling process (MAE) to implement these natural difficulties, with regard to the densification of the sintered bodies. The MAE and the press were used in the preparation of powders, to obtain a fine and homogeneous distribution of the grain size. Four loads Nb and Cu powders containing 15% by weight of Cu were then milled for MAE in a planetary type ball mill under various milling times and speeds. The results obtained by MAE were analyzed by scanning electron microscopy (SEM), according to the parameters of time and grinding speed. The samples were compacted under pressure of 200 MPa, were then sintered in liquid phase in a vacuum furnace at temperatures of 1100 ° C / 60 min and 1200 ° C / 60 min. Then it was used to characterize diffraction of X-rays to identify the phases. The microstructures of the sintered samples were observed and evaluated using scanning electron microscopy (SEM). Vickers Microhardness tests were performed, obtaining higher values for the sintered bodies in the largest of the post milling times and the larger grinding speeds. It was found that the liquid phase sintering of the samples that were processed by MAE produced at the end of a homogeneous and densified structure in 77,4% relative to the value of the theoretical density of the composite
Resumo:
From an economic standpoint, the powder metallurgy (P/M) is a technique widely used for the production of small parts. It is possible, through the P/M and prior comminution of solid waste such as ferrous chips, produce highly dense sintered parts and of interest to the automotive, electronics and aerospace industries. However, without prior comminution the chip, the production of bodies with a density equal to theoretical density by conventional sintering techniques require the use of additives or significantly higher temperatures than 1250ºC. An alternative route to the production of sintered bodies with high density compaction from ferrous chips (≤ 850 microns) and solid phase sintering is a compression technique under high pressure (HP). In this work, different compaction pressures to produce a sintered chip of SAE 1050 carbon steel were used. Specifically, the objective was to investigate them, the effect of high pressure compression in the behavior of densification of the sintered samples. Therefore, samples of the chips from the SAE 1050 carbon steel were uniaxially cold compacted at 500 and 2000 MPa, respectively. The green compacts obtained were sintered under carbon atmosphere at 1100 and 1200°C for 90 minutes. The heating rate used was 20°C/min. The starting materials and the sintered bodies were characterized by optical microscopy, SEM, XRD, density measurements (geometric: mass/volume, and pycnometry) and microhardness measurements Vickers and Rockwell hardness. The results showed that the compact produced under 2000 MPa presented relative density values between 93% and 100% of theoretical density and microhardness between 150 HV and 180 HV, respectively. In contrast, compressed under 500 MPa showed a very heterogeneous microstructure, density value below 80% of theoretical density and structural conditions of inadequate specimens for carrying out the hardness and microhardness measurements. The results indicate that use of the high pressure of ferrous chips compression is a promising route to improve the sinterability conditions of this type of material, because in addition to promoting greater compression of the starting material, the external tension acts together with surface tension, functioning as the motive power for sintering process. Additionally, extremely high pressures allow plastic deformation of the material, providing an intimate and extended contact of the particles and eliminating cracks and pores. This tends to reduce the time and / or temperature required for good sintering, avoiding excessive grain growth without the use of additives. Moreover, higher pressures lead to fracture the grains in fragile or ductile materials highly hardened, which provides a starting powder for sintering, thinner, without the risk of contamination present when previous methods are used comminution of the powder.
Resumo:
The present study aims to evaluate the potential use of bagasse ash from sugar cane (CBC) as a flux, replacing phyllite and/or feldspar in standard industrial mass production of enameled porcelain, verifying the possibility of the CBC contribute to the overall reduction of the coefficient of thermal expansion of the ceramic mass. To this end, as a result of the research, we characterized the raw material components of the standard mass (clay, phyllite, kaolin, feldspar, quartz and talc) and the residue of BCC, by testing by XRF, XRD, AG, DTA and ATG. Specimens (CDP) were manufactured in the dimensions of 100 mm x 50 mm x 8 mm in uniaxial matrix under compaction pressure of 33 MPa, assembled in batches of 3 units subsequently sintered at temperatures of 1150°C to 1210°C by varying the Rating Scale at 10°C, heating and cooling ramp of 50°C/min and 25°C/min, with levels of 1 min, 3 min, 5 min, 8 min, 10 min, 15 min, 30 min and 60 min. analyzing the results of the physical properties of water absorption (WA), linear firing shrinkage (LFS), dilatometric analysis (DTA), flexural strain (SFT) and SEM of the sintered bodies in order to verify the adequacy of CDP to ISO 13006, ISO 10545, NBR 13816 standards; NBR 13817 and NBR 13818. The study showed that the formulations that best suit the requirements of the standards are:. G4 - which was applied in 10% of replacing the CBC phyllite, sintering temperature 1210 ° C for 10 min and porch, and F3 - with application of 7.5% of CBC to replace the feldspar in the sintering temperatures of 1190°C, 1200°C and 1210°C for 10 min and porch. These formulations showed better performance regarding the formation of primary and secondary mullite, with considerable reduction of cracks and pores, meeting the prerequisites of standards for glazed porcelain. The results shows that the use of the CBC as a flux in the preparation of porcelain mass meets standard parameters for the manufacture of the product, and thereby can reduce environmental impact and the cost of production. Therefore, it is recommended to use this residue in the ceramics industry, due to its industrial, commercial and collaborative viability for sustainability.
Resumo:
In States of Paraíba (PB) and Rio Grande do Norte (RN), northeast of Brazil, the most significant deposits of non-metallic industrial minerals are pegmatites, quartzites and granites, which are located in Seridó region. Extraction of clay, quartz, micas and feldspars occurs mainly in the cities of Várzea (PB), OuroBranco (RN) and Parelhas (RN). Mining companies working in the extraction and processing of quartzite generate large volumes of waste containing about 90% SiO2 in their chemical composition coming from quartz that is one of the basic constituents of ceramic mass for the production of ceramic coating. Therefore, this work evaluates the utilization of these wastes on fabrication of high-quality ceramic products, such as porcelain stoneware, in industrial scale. Characterization of raw materials was based on XRF, XRD, GA, TGA and DSC analysis, on samples composed by 57% of feldspar, 37% of argil and 6% of quartzite residues, with 5 different colors (white, gold, pink, green and black). Samples were synthesized in three temperatures, 1150°C, 1200°C and 1250°C, with one hour isotherm and warming-up tax of 10°C/min. After synthesizing, the specimens were submit to physical characterization tests of water absorption, linear shrinkage, apparently porosity, density, flexural strain at three points. The addition of 6% of quartzite residue to ceramic mass provided a final product with technological properties attending technical norms for the production of porcelain stoneware; best results were observed at a temperature of 1200°C. According to the results there was a high iron oxide on black quartzite, being their use in porcelain stoneware discarded by ethic and structural question, because the material fused at 1250°C. All quartzite formulations had low water absorption when synthesized at 1200°C, getting 0.1% to 0.36% without having gone through the atomization process. Besides, flexural strain tests overcame 27 MPa reaching the acceptance limits of the European Directive EN 100, at 1200°C synthesizing. Thus, the use of quartzite residues in ceramic masses poses as great potential for the production of porcelain stoneware.
Resumo:
The present study aims the characterization of thermally affected carbonate rocks from Jandaíra Formation in contact with Paleogene and Neogene basic intrusions in the region of the Pedro Avelino and Jandaíra municipalities (RN), northeastern Brazil. For this study, field, petrographic, x-ray diffraction, electron microprobe, and whole rock litogeochemistry data of carbonates were undertaken. The thermally unaffected limestones are classified like wackstones, grainstones and packstones. They may constitute carbonates grains of benthic foraminifera, echinoderm spines, ostracods, algae, corals, bivalves, gastropods, peloids and intraclasts. The porosities are classified like vug, intraparticle, interparticle, intercrystal and moldic types. The major minerals are calcite, ankerite and dolomite; the detrital are montmorillonite, pyrite, limonite, quartz and microcline. The thermally affected limestones are very coarse to very fine-grained and light to dark gray color. The fossiliferous components totally disappear, and the porosity tends to disappear. With the data obtained, it can be inferred that the carbonate protoliths would be calciferous to dolomitic limestones, both with small amount of clay minerals. Crystalline carbonates from dolomitic protolith have rhombohedral calcite and iron oxides / hydroxides, making the rocks much darker. The carbonates from calciferous protolith have a wide variation of grain size according to the recrystallization degree, increasing toward contact with the basic bodies. In this group, it was identified the minerals lizardite and spinel in weakly to moderately affected samples, and spinel and spurrite in strongly affected rocks, as well as calcite, that occur everywhere. The geological context (shallow level diabase intrusions), the crystallization of the pyrometamorphic minerals spurrite and olivine, and comparison with diagrams from the literature allow estimating temperatures and pressures around 1050-1200 °C and 0.5-1.0 kbar, respectively, for PTOTAL=PCO2. The post-intrusion cooling would have afforded the releasing of metasomatic / hydrothermal fluids, allowing the opening of the metamorphic system, with possible contribution of chemical elements from host units (sandstones, shales) and from basic intrusions. This would induce hydration of previous phases, allowing the formation of serpentine, chlorite and brucite. The results discussed here reveal the strong influence of the heat from basic intrusions within the sedimentary pile. Whereas in the offshore portion of the basin occur sills with up to 1000 m thickness, the understanding of pyrometamorphism might be useful for understanding and measuring the thermally affected rocks.
Resumo:
The present study aims the characterization of thermally affected carbonate rocks from Jandaíra Formation in contact with Paleogene and Neogene basic intrusions in the region of the Pedro Avelino and Jandaíra municipalities (RN), northeastern Brazil. For this study, field, petrographic, x-ray diffraction, electron microprobe, and whole rock litogeochemistry data of carbonates were undertaken. The thermally unaffected limestones are classified like wackstones, grainstones and packstones. They may constitute carbonates grains of benthic foraminifera, echinoderm spines, ostracods, algae, corals, bivalves, gastropods, peloids and intraclasts. The porosities are classified like vug, intraparticle, interparticle, intercrystal and moldic types. The major minerals are calcite, ankerite and dolomite; the detrital are montmorillonite, pyrite, limonite, quartz and microcline. The thermally affected limestones are very coarse to very fine-grained and light to dark gray color. The fossiliferous components totally disappear, and the porosity tends to disappear. With the data obtained, it can be inferred that the carbonate protoliths would be calciferous to dolomitic limestones, both with small amount of clay minerals. Crystalline carbonates from dolomitic protolith have rhombohedral calcite and iron oxides / hydroxides, making the rocks much darker. The carbonates from calciferous protolith have a wide variation of grain size according to the recrystallization degree, increasing toward contact with the basic bodies. In this group, it was identified the minerals lizardite and spinel in weakly to moderately affected samples, and spinel and spurrite in strongly affected rocks, as well as calcite, that occur everywhere. The geological context (shallow level diabase intrusions), the crystallization of the pyrometamorphic minerals spurrite and olivine, and comparison with diagrams from the literature allow estimating temperatures and pressures around 1050-1200 °C and 0.5-1.0 kbar, respectively, for PTOTAL=PCO2. The post-intrusion cooling would have afforded the releasing of metasomatic / hydrothermal fluids, allowing the opening of the metamorphic system, with possible contribution of chemical elements from host units (sandstones, shales) and from basic intrusions. This would induce hydration of previous phases, allowing the formation of serpentine, chlorite and brucite. The results discussed here reveal the strong influence of the heat from basic intrusions within the sedimentary pile. Whereas in the offshore portion of the basin occur sills with up to 1000 m thickness, the understanding of pyrometamorphism might be useful for understanding and measuring the thermally affected rocks.
Resumo:
The reuse of industrial by-products is important for members of numerous industrial sectors. However, though the benefits of reuse are evident from an economical point of view, some compounds in these materials can have a negative effect on users' health.In this study, the radon emanation and exhalation features of red mud were surveyed using heat-treatment (100-1200 °C). As a result of the 1200°C-treated samples, massic radon exhalation capacity reduced from 75 ± 10 mBq kg-1 h-1 to 7 ± 4 mBq kg-1 h-1, approximately 10% of the initial exhalation rate.To find an explanation for internal structural changes, the porosity features of the heat-treated samples were also investigated. It was found that the cumulative pore volume reduced significantly in less than 100 nm, which can explain the reduced massic exhalation capacity in the high temperature treated range mentioned above.SEM snapshots were taken of the surfaces of the samples as visual evidence for superficial morphological changes. It was found that the surface of the high temperature treated samples had changed, proving the decrement of open pores on the surface.
Resumo:
The synthesis and optimization of two Li-ion solid electrolytes were studied in this work. Different combinations of precursors were used to prepare La0.5Li0.5TiO3 via mechanosynthesis. Despite the ability to form a perovskite phase by the mechanochemical reaction it was not possible to obtain a pure La0.5Li0.5TiO3 phase by this process. Of all the seven combinations of precursors and conditions tested, the one where La2O3, Li2CO3 and TiO2 were milled for 480min (LaOLiCO-480) showed the best results, with trace impurity phases still being observed. The main impurity phase was that of La2O3 after mechanosynthesis (22.84%) and Li2TiO3 after calcination (4.20%). Two different sol-gel methods were used to substitute boron on the Zr-site of Li1+xZr2-xBx(PO4)3 or the P-site of Li1+6xZr2(P1-xBxO4)3, with the doping being achieved on the Zr-site using a method adapted from Alamo et al (1989). The results show that the Zr-site is the preferential mechanism for B doping of LiZr2(PO4)3 and not the P-site. Rietveld refinement of the unit-cell parameters was performed and it was verified by consideration of Vegard’s law that it is possible to obtain phase purity up to x = 0.05. This corresponds with the phases present in the XRD data, that showed the additional presence of the low temperature (monoclinic) phase for the powder sintered at 1200ºC for 12h of compositions with x ≥ 0.075. The compositions inside the solid solution undergo the phase transition from triclinic (PDF#01-074-2562) to rhombohedral (PDF#01-070-6734) when heating from 25 to 100ºC, as reported in the literature for the base composition. Despite several efforts, it was not possible to obtain dense pellets and with physical integrity after sintering, requiring further work in order to obtain dense pellets for the electrochemical characterisation of Li Zr2(PO4)3 and Li1.05Zr1.95B0.05(PO4)3.
Resumo:
The WTP produce many kinds of residue on your treatment stages, but the sludge is the more problematic from the final disposition point view. The actual rate of residue production deriving from technological evolution and the crescent population needs prevents the subtle equilibrium generation between consumption and recycling/reuse, creating problems of pollution resulting from inappropriate management of residues. Thus, is necessary achieve a new equilibrium between the grow from raw materials and energy and the residue generation. This equilibrium should be achieved by technical and economic feasibility of environmental supported models through recycling and reuse. The red ceramic industry stand out in residue absorption question as raw material due their clay mass heterogeneity, constituted by clay minerals and non-clay minerals with wide mineralogical variation, allowing residue inclusion which act like plastic or non-plastic materials, contributing to retain heavy metals contained in residues in the vitreous mass formed during the burning of the ceramic bodies. This work propose the study of the influence of incorporation of 25 wt.% sludge from wastewater treatment plant, according preliminary results, in the mass to produce ceramic bodies. The raw materials was characterized through chemical composition analyses by XRF, mineralogical analyses by XRD, thermal analyses by TG and DTA, Atterberg limits and thermodilatometry. Subsequently was composed the mass with 75 wt.% of clay and 25 wt.% of dried wastewater sludge from UFRN WWTP. Samples with 6,0 x 2,0 x 0,5 cm was produced with unidirectional compacting under pressure of 20MPa and burned in temperatures between 950 and 1,200ºC. After fired, the ceramic bodies have been submitted to physical and mechanical analyses through the measure of firing shrinkage, water absorption, density, apparent porosity and flexural strength; crystallographic analyses through XRD and microstructure analyses by SEM. The technological properties obtained was satisfactory to production of roof tiles with 25 wt.% at 1,200 ºC, but the production of others products at lower temperatures was not feasible
Resumo:
The continuous advances in ceramic systems for crowns and bridges infrastructure getting researchers and manufacturers looking for a material that has good mechanical properties and aesthetic. The purpose of this study was to verify in which composition and sintering temperature the ceramic system for infrastructure composed of alumina and zirconia would have the best mechanical properties. With this objective we made in UFRN laboratories 45 test bodies in the form of rectangular bars with the following dimensions: 30mm x 8mm x 3mm, where we separated by the sintering temperature: 1200°C, 1300ºC and 1400ºC, and by comp osition: 33% Zirconia + 67% Alumina; 50% Zirconia + 50% Alumina and 25% Zirconia + 75% Alumina, these test bodies were not infiltrated with glass. Also, were made nine test bodies by a technical from a laboratory with a commercial ceramic system: in the Ceram Zircônia (Vita - Zahnfabrik) with the following dimensions: 20mm x 10mm x 0.5mm, these test bodies following all recommendations of the manufacturer and were infiltrated with glass. Were realized optical and electronic microscopy analyses, hardness testing, resistance to bending in three points, porosity and bulk density. After analysis of the results we verified that with the increasing of sintering temperature, increased the value of resistance to bending, but with the same temperature there was no significant difference between the different compositions, samples made with the commercial ceramic that were infiltrated, presented a resistance to bending six times greater than the samples sintered to 1400°C and which have not been infiltra ted. There was no significant difference between the values of apparent porosity for the samples made in UFRN laboratories, but the samples of commercial ceramic obtained 0% in porosity apparent value. In tests of Rockwell Hardness there is an increase in the value of Hardness, with the increase of sintering temperature for the samples not infiltrated. Samples infiltrated showed similar values as the samples sintered in 1400°C. There was no significant difference between the values of apparent density among samples manufactured in UFRN laboratories and samples made with a commercial ceramic
Resumo:
The power industry generates as waste ceramic bodies of electrical fuses that are discarded after use. The formulation of ceramic bodies for porcelain electrical insulators using waste from the bodies fuse allocation promotes environmentally appropriate, through the reuse of the material. This work evaluated the technical feasibility of using waste for use in electrical porcelains with formulations containing the residue, feldspar and kaolinite. The raw materials were processed through grinding and sieving to 200 mesh. The ceramic material obtained from the proposed formulations with 25%, 30%, 34% and 40% of the residue went through a vibratory mill for grinding and homogenization, and then were sieved at 325 mesh. The samples were shaped in a uniaxial press, with the application of 25 MPa and sintered at 1100° C, 1150°C, 1200°C, 1225°C and 1250°C, at levels of 20 and 45 minutes. Were also developed bodies of evidence with reference formulations obtained without residue, to establish a comparison on physical, mechanical and electrical. The tests were conducted and technology: linear shrinkage, porosity, water absorption, resistance to bending to three points, measuring insulation resistance electrical resistivity of the material, X-ray diffraction and X-ray fluorescence Waste characterizations pointed to the existence of two phases: mullite and quartz phases are of great importance in the microstructure of the ceramic and this fact reveals a possibility for reuse in electrical porcelains. The mullite is an important constituent because it is a phase that makes it possible to increase the mechanical strength in addition to the body allows the use at high temperatures. The use of ceramic bodies residue fuses, proved feasible for application in electrical porcelain and the most significant results were obtained by the formulations with 25% waste and sintering at 1200°C
Resumo:
Ceramic composites produced with polymerics precursors have been studied for many years, due to the facility of obtaining a complex shape, at low temperature and reduces cost. The main objective of this work is to study the process of sintering of composites of ceramic base consisting of Al2O3 and silicates, reinforced for NbC, through the technique of processing AFCOP, as well as the influence of the addition of LZSA, ICZ and Al as materials infiltration in the physical and mechanical properties of the ceramic composite. Were produced ceramic matrix composites based SiCxOy e Al2O3 reinforced with NbC, by hidrosilylation reaction between D4Vi and D1107 mixtured with Al2O3 as inert filler, Nb and Al as reactive filler. The specimens produced were pyrolised at 1200, 1250 and 1400°C and infiltred with Al, ICZ and LZSA, respectively. Density, porosity, flexural mechanical strength and fracture surface by scanning electron microscopy were evaluated. The microstructure of the composites was investigated by X-ray diffraction to identify the presence of crystalline phases. The composites presented apparent porosity varying of 31 up to 49% and mechanical flexural strength of 14 up to 34 MPa. The infiltration process improviment of the densification and reduction of the porosity, as well as increased the values of mechanical flexural strength. The obtained phases had been identified as being Al3Nb, NbSi2, Nb5S3, Nb3Si and NbC. The samples that were submitted the infiltration process presented a layer next surface with reduced pores number in relation to the total volume