scholarly journals Preparation and Characterization of New Electrically Conductive Composites Based on Expanded Graphite with Potential Use as Remote Environmental Detectors

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1176
Author(s):  
Martin Prostredný ◽  
Igor Krupa ◽  
Zdenko Špitalský
Keyword(s):  
Particle Size ◽  
Film Thickness ◽  
Response Rate ◽  
Filler Particle ◽  
Average Particle Size ◽  
Expanded Graphite ◽  
Detector Response ◽  
Average Particle ◽  
Electrically Conductive ◽  
Conductive Composites

The presented paper is focused on studying electrically conductive composites based on an elastomeric matrix and expanded graphite as the filler. A potential application as an environmental remote detector was studied. The influence of filler particle size, film thickness, detector length, temperature, and the amount of oil on the detector response rate were explored. Peel tests were performed in order to investigate the adhesion of prepared detector films to different materials. Expanded graphite with average particle size 5 µm was chosen for the experiments due to its fastest response. Decreasing the detector film thickness has caused an increase in the response rate but also a decrease in the signal measured. The response rate of the detector system was in a practical range even for lower temperatures. From the obtained data, the proposed detector seems to be suitable for a practical application.

scholarly journals Electrophysical properties of composites based on epoxy resin and carbon fillers

2021 ◽  
Vol 12 (2) ◽  
pp. 104-111
Author(s):  
O. G. Sirenko ◽  
◽  
O. M. Lisova ◽  
S. M. Makhno ◽  
G. M. Gunya ◽  
...  
Keyword(s):  
Particle Size ◽  
Epoxy Resin ◽  
Size Distribution ◽  
Average Particle Size ◽  
Construction Materials ◽  
Expanded Graphite ◽  
Cost Effective ◽  
Average Particle ◽  
Carbon Filler ◽  
Carbon Fillers

Polymeric construction materials based on epoxy resin, carbon fillers, such as graphene nanoplates (GNP), carbon nanotubes (CNT) and fillers of inorganic nature – perlite, vermiculite, sand with improved electrophysical characteristics have been developed. The electrophysical propertieгs of composites obtained in various ways which differ according to the principle of injecting components have been investigated. GNP were obtained in two ways. Size distribution of GNP obtained by electrochemical method is 50 to 150 nm. The average particle size is up to 100 nm. It occurs that these particles tend to aggregate as it is shown by the method of dynamic light scattering. The GNP obtained by dispersing thermally expanded graphite in water in a rotary homogenizer have a particle size distribution of 400 to 800 nm if very small particles and large aggregates are absent. The second method of obtaining GNP is less energy consuming and requires fewer manufacturing cycles, so it is more cost-effective. Obtaining composites using aqueous suspensions of GNP is environmentally friendly. Due to the hydrophobic properties of its surface the electrical conductivity of the system which uses vermiculite is higher than one of that which uses perlite for composites with CNT and GNP. It has been found that the difference of electrophysical characteristics between two systems which contain the same amount of carbon filler is caused by the nature of the surface of dielectric components – sand. By changing the content of dielectric ingredients can expand the functionality of composites if use them for shielding from electromagnetic fields.

scholarly journals Microhardness of сompacted thermally expanded graphite

2019 ◽  
pp. 170-174
Author(s):  
S. L. Revo ◽  
M. M. Melnichenko ◽  
T. G. Avramenko ◽  
K. O. Ivanenko ◽  
V. O. Andruschenko
Keyword(s):  
Particle Size ◽  
Average Particle Size ◽  
Expanded Graphite ◽  
Average Particle ◽  
Middle Region ◽  
Thermally Expanded Graphite ◽  
Cross Sectional ◽  
A Value ◽  
Isotropic Distribution ◽  
Concentric Region

Using the method of continuous microindentation with different loading on the indenter, the microhardness of compacted thermo-expanded graphite (TEG) samples of different dispersion was studied. The analysis of the obtained results showed that, with an increase in the average cross-sectional area of TEG particles from 40 to 120 microns, the microhardness of the samples under investigation also increases. An analysis of the influence of the dispersion and morphology of the TEG particles on the distribution of microhardness on the surface of the compacted samples of TEG was also carried out. The microhardness indicatrix for the samples of the original TEG shows that when the radial displacement from the center of the sample, the microhardness of the material decreases. So in the central part of the discoid sample the values of microhardness lie in the range from 0,04 to 0,025 GPa. In the next concentric region, the microhardness decreases by 30% and gains a value of (0.028 ... 0.014) GPA. When the dispersion of TEG particles changes, the distribution of microhardness also changes. The microhardness indicatrix for a compacted Tg sample with an average particle size of 180 μm shows that the microhardness value at the center of the sample ranges from 0.065 to 0.15 GPa.As you approach the edge of the sample, the microhardness of the material decreases from 0.15 to 0.054 GPa. The study of TEG with an average particle size of 50 μm showed that the indentation in the center and in the middle region of the sample gives an isotropic distribution of microhardness values. The microhardness values coincide in the central and middle regions of the sample and correspond to ≈ 0.1 GPa. The proposed method of research and analysis of microhardness on the surface of compacted specimens of TEG gives an opportunity not only to characterize the micromechanical properties of the investigated material but also to optimize the technological regimes for obtaining samples.

Determination of grinding parameters of fenugreek seed

1970 ◽  
Vol 26 (1) ◽  
pp. 16 ◽  
Author(s):  
S Balasubramanian ◽  
Rajkumar Rajkumar ◽  
K K Singh
Keyword(s):  
Particle Size ◽  
Energy Consumption ◽  
Moisture Content ◽  
Specific Energy ◽  
Feed Rate ◽  
Average Particle Size ◽  
Specific Energy Consumption ◽  
Average Particle ◽  
Fenugreek Seeds ◽  
Fenugreek Seed

Experiment to identify ambient grinding conditions and energy consumed was conducted for fenugreek. Fenugreek seeds at three moisture content (5.1%, 11.5% and 17.3%, d.b.) were ground using a micro pulverizer hammer mill with different grinding screen openings (0.5, 1.0 and 1.5 mm) and feed rate (8, 16 and 24 kg h-1) at 3000 rpm. Physical properties of fenugreek seeds were also determined. Specific energy consumptions were found to decrease from 204.67 to 23.09 kJ kg-1 for increasing levels of feed rate and grinder screen openings. On the other hand specific energy consumption increased with increasing moisture content. The highest specific energy consumption was recorded for 17.3% moisture content and 8 kg h-1 feed rate with 0.5 mm screen opening. Average particle size decreased from 1.06 to 0.39 mm with increase of moisture content and grinder screen opening. It has been observed that the average particle size was minimum at 0.5 mm screen opening and 8 kg h-1 feed rate at lower moisture content. Bond’s work index and Kick’s constant were found to increase from 8.97 to 950.92 kWh kg-1 and 0.932 to 78.851 kWh kg-1 with the increase of moisture content, feed rate and grinder screen opening, respectively. Size reduction ratio and grinding effectiveness of fenugreek seed were found to decrease from 4.11 to 1.61 and 0.0118 to 0.0018 with the increase of moisture content, feed rate and grinder screen opening, respectively. The loose and compact bulk densities varied from 219.2 to 719.4 kg m-3 and 137.3 to 736.2 kg m-3, respectively.  

Formulating SLN and NLC as Innovative Drug Delivery Systems for Non-Invasive Routes of Drug Administration

2020 ◽  
Vol 27 (22) ◽  
pp. 3623-3656 ◽  
Author(s):  
Bruno Fonseca-Santos ◽  
Patrícia Bento Silva ◽  
Roberta Balansin Rigon ◽  
Mariana Rillo Sato ◽  
Marlus Chorilli
Keyword(s):  
Drug Delivery ◽  
Particle Size ◽  
Drug Release ◽  
Drug Loading ◽  
Average Particle Size ◽  
Delivery Systems ◽  
Average Particle ◽  
Minor Importance ◽  
Routes Of Administration ◽  
Non Invasive

Colloidal carriers diverge depending on their composition, ability to incorporate drugs and applicability, but the common feature is the small average particle size. Among the carriers with the potential nanostructured drug delivery application there are SLN and NLC. These nanostructured systems consist of complex lipids and highly purified mixtures of glycerides having varying particle size. Also, these systems have shown physical stability, protection capacity of unstable drugs, release control ability, excellent tolerability, possibility of vectorization, and no reported production problems related to large-scale. Several production procedures can be applied to achieve high association efficiency between the bioactive and the carrier, depending on the physicochemical properties of both, as well as on the production procedure applied. The whole set of unique advantages such as enhanced drug loading capacity, prevention of drug expulsion, leads to more flexibility for modulation of drug release and makes Lipid-based nanocarriers (LNCs) versatile delivery system for various routes of administration. The route of administration has a significant impact on the therapeutic outcome of a drug. Thus, the non-invasive routes, which were of minor importance as parts of drug delivery in the past, have assumed added importance drugs, proteins, peptides and biopharmaceuticals drug delivery and these include nasal, buccal, vaginal and transdermal routes. The objective of this paper is to present the state of the art concerning the application of the lipid nanocarriers designated for non-invasive routes of administration. In this manner, this review presents an innovative technological platform to develop nanostructured delivery systems with great versatility of application in non-invasive routes of administration and targeting drug release.

Azithromycin nanosuspension preparation using evaporative precipitation into aqueous solution (EPAS) method and its comparative dissolution study

2020 ◽  
Vol 17 ◽  
Author(s):  
Mohammad Hossain Shariare ◽  
Tonmoy Kumar Mondal ◽  
Hani Alothaid ◽  
Md. Didaruzzaman Sohel ◽  
MD Wadud ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Dissolution Rate ◽  
Average Particle Size ◽  
Scale Up ◽  
Average Particle ◽  
Total Drug ◽  
Residual Solvent ◽  
Dissolution Study ◽  
Drug Content

Aim: EPAS (evaporative precipitation into aqueous solution) was used in the current studies to prepare azithromycin nanosuspensions and investigate the physicochemical characteristics for the nanosuspension batches with the aim of enhancing the dissolution rate of the nanopreparation to improve bioavailability. Methods: EPAS method used in this study for preparing azithromycin nanosuspension was achieved through developing an in-house instrumentation method. Particle size distribution was measured using Zetasizer Nano S without sample dilution. Dissolved azithromycin nanosuspensions were also compared with raw azithromycin powder and commercially available products. Total drug content of nanosuspension batches were measured using an Ultra-Performance Liquid Chromatography (UPLC) system with Photodiode Array (PDA) detector while residual solvent was measured using gas chromatography (GC). Results: The average particle size of azithromycin nanosuspension was 447.2 nm and total drug content was measured to be 97.81% upon recovery. Dissolution study data showed significant increase in dissolution rate for nanosuspension batch when compared to raw azithromycin and commercial version (microsuspension). The residual solvent found for azithromycin nanosuspension is 0.000098023 mg/ mL or 98.023 ppb. Conclusion: EPAS was successfully used to prepare azithromycin nanoparticles that exhibited significantly enhanced dissolution rate. Further studies are required to scale up the process and determine long term stability of the nanoparticles.

scholarly journals Evaluation of the Effects of Filler Fineness on the Properties of an Epoxy Asphalt Mixture

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2003
Author(s):  
Wei Xu ◽  
Jintao Wei ◽  
Zhengxiong Chen ◽  
Feng Wang ◽  
Jian Zhao
Keyword(s):  
Particle Size ◽  
Average Particle Size ◽  
Asphalt Mixture ◽  
Average Particle ◽  
Fine Dust ◽  
Bonding Structure ◽  
Epoxy Asphalt ◽  
Mineral Powder ◽  
Marshall Stability ◽  
Mixture Sample

The type and fineness of a filler significantly affect the performance of an asphalt mixture. There is a lack of specific research on the effects of filler fineness and dust from aggregates on the properties of epoxy asphalt (EA) mixtures. The effects of aggregate dust and mineral powder on the properties of an EA mixture were evaluated. These filler were tested to determine their fineness, specific surface area and mineral composition. The effects of these fillers on the EA mastic sample and mixture were evaluated. The morphology of the EA mastic samples was analyzed using scanning electron microscopy (SEM). The effects of the fillers on the Marshall stability, tensile strength and fatigue performance of the EA mixture were evaluated. The dust from the aggregates exhibited an even particle size distribution, and its average particle size was approximately 20% of that of the mineral powder. The SEM microanalysis showed that the EA mastic sample containing relatively fine dust formed a tight and dense interfacial bonding structure with the aggregate. The EA mixture sample containing filler composed of dust from aggregate had a significantly higher strength and longer fatigue life than that of the EA sample containing filler composed of mineral powder.

scholarly journals Surface Activity of Humic Acid and Its Sub-Fractions from Forest Soil

2021 ◽  
Vol 13 (15) ◽  
pp. 8122
Author(s):  
Shijie Tian ◽  
Weiqiang Tan ◽  
Xinyuan Wang ◽  
Tingting Li ◽  
Fanhao Song ◽  
...  
Keyword(s):  
Surface Tension ◽  
Particle Size ◽  
Humic Acid ◽  
Forest Soil ◽  
Surface Activity ◽  
Self Assembly ◽  
Average Particle Size ◽  
Gaussian Model ◽  
Exponential Model ◽  
Average Particle

Surface activity of humic acid (HA) and its six sub-fractions isolated from forest soil were characterized by surface tension measurements, dynamic light scattering, and laser doppler electrophoresis. The surface tension of HA and its sub-fractions reduced from 72.4 mN·m−1 to 36.8 mN·m−1 in exponential model with the increasing concentration from 0 to 2000 mg·L−1. The critical micelle concentration (CMC) and Z-average particle size ranged from 216–1024 mg·L−1 and 108.2–186.9 nm for HA and its sub-fractions, respectively. The CMC have related with alkyl C, O-alkyl C, aromatic C, and carbonyl C (p < 0.05), respectively, and could be predicted with the multiple linear regression equation of CMC, CMC = 18896 − 6.9 × C-296 × alkyl C-331 × aromatic C-17019 × H/C + 4054 × HB/HI (p < 0.05). The maximum particle size was 5000 nm after filtered by a membrane with pore size of 450 nm, indicating HA and its sub-fractions could progressed self-assembly at pH 6.86. The aggregate sizes of number-base particle size distributions were mainly in six clusters including 2 ± 1 nm, 5 ± 2 nm, 10 ± 3 nm, 21 ± 8 nm, 40 ± 10 nm, and >50 nm analyzed by Gaussian model that maybe due to the inconsistency of the components and structures of the HA sub-fractions, requiring further study. It is significance to explore the surface activity of HA and its sub-fractions, which is helpful to clarify the environmental behavior of HA.

Microstructure Characterization of Ag Nanoparticles Prepared by Hydrothermal Method

2012 ◽  
Vol 476-478 ◽  
pp. 1138-1141
Author(s):  
Zhi Qiang Wei ◽  
Qiang Wei ◽  
Li Gang Liu ◽  
Hua Yang ◽  
Xiao Juan Wu
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
Hydrothermal Method ◽  
Ag Nanoparticles ◽  
Average Particle Size ◽  
Average Particle ◽  
Face Centered Cubic ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Face Centered

Ag nanoparticles were successfully synthesized by hydrothermal method under the polyol system combined with traces of sodium chloride, Silver nitrate(AgNO3) and polyvinylpyrrolidone (PVP) acted as the silver source and dispersant respectively. The samples by this process were characterized via X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET) adsorption equation, transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED) to determine the chemical composition, particle size, crystal structure and morphology. The experiment results indicate that the crystal structure of the samples is face centered cubic (FCC) structure as same as the bulk materials, The specific surface area is 24 m2/g, the particle size distribution ranging from10 to 50 nm, with an average particle size about 26 nm obtained by TEM and confirmed by XRD and BET results.

scholarly journals Wheat Grinding Process with Low Moisture Content: A New Approach for Wholemeal Flour Production

Processes ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 32
Author(s):  
Waleed H. Hassoon ◽  
Dariusz Dziki ◽  
Antoni Miś ◽  
Beata Biernacka
Keyword(s):  
Particle Size ◽  
Moisture Content ◽  
Average Particle Size ◽  
Average Particle ◽  
Grinding Process ◽  
Mixing Properties ◽  
New Approach ◽  
Grain Moisture ◽  
Flour Production ◽  
And Storage

The objective of this study was to determine the grinding characteristics of wheat with a low moisture content. Two kinds of wheat—soft spelt wheat and hard Khorasan wheat—were dried at 45 °C to reduce the moisture content from 12% to 5% (wet basis). Air drying at 45 °C and storage in a climatic chamber (45 °C, 10% relative humidity) were the methods used for grain dehydration. The grinding process was carried out using a knife mill. After grinding, the particle size distribution, average particle size and grinding energy indices were determined. In addition, the dough mixing properties of wholemeal flour dough were studied using a farinograph. It was observed that decreasing the moisture content in wheat grains from 12% to 5% made the grinding process more effective. As a result, the average particle size of the ground material was decreased. This effect was found in both soft and hard wheat. Importantly, lowering the grain moisture led to about a twofold decrease in the required grinding energy. Moreover, the flour obtained from the dried grains showed higher water absorption and higher dough stability during mixing. However, the method of grain dehydration had little or no effect on the results of the grinding process or dough properties.

COMPARATIVE STUDY OF DIELECTRIC BEHAVIOR OF Mn0.4Zn0.6Fe2O4 NANOFERRITE BY CITRATE PRECURSOR METHOD

2008 ◽  
Vol 22 (16) ◽  
pp. 2537-2544 ◽  
Author(s):  
PREETI MATHUR ◽  
ATUL THAKUR ◽  
M. SINGH
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Comparative Study ◽  
Average Particle Size ◽  
Dielectric Behavior ◽  
Average Particle ◽  
Oxidizing Agent ◽  
Precursor Method ◽  
Citrate Precursor ◽  
Citrate Precursor Method

In the present work, comparative study of the dielectric behavior of Mn 0.4 Zn 0.6 Fe 2 O 4 ferrite synthesized with and without H 2 O 2 (hydrogen peroxide) has been presented. The dc resistivity has been improved by the citrate precursor method as compared to the ceramic method, and it is further improved by the addition of H 2 O 2, which acts as a strong oxidizing agent. We have shown by means of X-ray diffraction that the resulting ferrite is made up of nanocrystallites and the average size of these nanocrystallites–calculated by Scherrer's formula–depends on the polarizer. The average particle size was found to be ~70 nm with H 2 O 2 and ~88 nm without H 2 O 2. The particle size is further confirmed by scanning electron microscopy. Both the results are found to be in good agreement. The decrease in dielectric constant and dielectric loss factor by addition of oxidizing agent is justified by inverse proportionality between the resistivity and dielectric constant. Possible mechanisms contributing to these processes have been discussed.

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