Fine Spherical Tungsten Powder Prepared by Precipitation Reaction

2011 ◽  
Vol 117-119 ◽  
pp. 967-970
Author(s):  
Tao Lin ◽  
Yan Jun Li ◽  
Cheng Yi Wu ◽  
Zhi Meng Guo
Keyword(s):  
Particle Size ◽  
Tungsten Powder ◽  
Sodium Dodecyl ◽  
Precipitation Reaction ◽  
Mechanical Agitation ◽  
Ammonium Tungstate ◽  
Fine Tungsten ◽  
Strong Acids ◽  
Addition Amount ◽  
Uniform Particle Size

The spherical tungsten powder was prepared by chemical reaction with ammonium tungstate and strong acids under ultrasonic and mechanical agitation. After precipitation reaction, the precipitate was dried and grinded, and then reduced into tungsten powder with hydrogen. The effects of acid kinds and dispersant on the fine tungsten powder were studied in this paper. The result shows that the acid kinds and its addition amount have great effect on the shape of tungsten particles. The tungsten powder with uniform particle size and spherical could be prepared by adding 17ml sulfric acid into 100ml ammonium tungstate. The tungsten particles can be finer and more dispersive, and have a spherical with addition of dispersant SDS (Sodium dodecyl sulfate). The particle size is about 1.5 micrometer.

Preparation and Characterization of Macromeritic Tungsten Powder Reduced by Ammonium Paratungstate at Medium Temperature

2012 ◽  
Vol 468-471 ◽  
pp. 2584-2587
Author(s):  
Rui Xin Wang ◽  
Zhi Meng Guo ◽  
Jun Jie Hao ◽  
Ji Luo ◽  
Yan Jun Xin
Keyword(s):  
Particle Size ◽  
Hydrogen Reduction ◽  
Tungsten Powder ◽  
Average Particle Size ◽  
Raw Material ◽  
Metal Salts ◽  
Average Particle ◽  
Medium Temperature ◽  
Ammonium Paratungstate ◽  
Ammonium Tungstate

The macromeritic tungsten powder was prepared by wet hydrogen reduction at medium temperature; the coarse powder of Ammonium paratungstate powder (APT) was used as raw material. It is obtained by evaporating and crystallizating adding alkalia metal salts in the solution of ammonium tungstate. The microstructure, phase composition and particle size of the macromeritic tungsten powder were investigated by SEM, XRD and test analysis sieves. The effects of kinds, contents of alkali metal salts and the temperature in the reduction were studied. The results revealed that ideal tungsten powder, with the good fluditity, spherical, integrate and well-distributed, could be obtained. The raw material is the solution of ammonium tungstate adding NaCl, Li2CO3 and KCl , the concentration of them are all 3g/L, and it is under the condition of 1000°C,180min in wet hydrogen atmosphere. The average particle size is 67μm, the maximum is 150μm, the biggest loose density is 13.41g/cm3, and the best powder flowability is 9s/50g.

scholarly journals Microencapsulation of Photochromic Solution with Polyurea by Interfacial Polymerization

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3049
Author(s):  
Yuhua Zhang ◽  
Xi Zhang ◽  
Yurong Yan ◽  
Zhonghua Chen
Keyword(s):  
Particle Size ◽  
Interfacial Polymerization ◽  
Uv Light ◽  
Thermogravimetric Analyzer ◽  
The Core ◽  
Oxygen Ion ◽  
Particle Size Analyzer ◽  
Photochromic Materials ◽  
Addition Amount ◽  
Uniform Particle Size

Photochromic materials are interesting materials because of their color-changing property under UV light and visible light irradiation. However, they are vulnerable to many factors, such as pH oxygen, ion, solvent, etc. because of the unsaturated bonds existing on the photochromic molecular. Microencapsulation of the photochromic materials can separate them from the surroundings. Here, photochromic microcapsules using 3,3-Diphenyl-3H-naphtho[2,1-b] pyran (NP)/solution as core and polyurea as shell via interfacial polymerization were prepared, and bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate (HALS 770) was used as photostabilizer. Fourier transform infrared spectroscopy (FTIR), a laser particle size analyzer, a scanning electron microscope (SEM), a thermogravimetric analyzer and an ultraviolet-visible spectrophotometer were used for characterization. The results showed that the microcapsules had a uniform particle size of about 0.56 μm when the percentage of the oil phase (core) in the emulsion was less than 15%, the addition amount of the emulsifier was 0.4%, and the stirring rate was 1800r/min. The microcapsules showed better performance in thermal stability when the core/shell ratio was 1:1. The photostabilizer had little impact on the color-changing property of the microcapsule, but it could protect the microcapsules from UV light radiation aging.

scholarly journals Investigating the Feasibility of Mefenamic Acid Nanosuspension for Pediatric Delivery: Preparation, Characterization, and Role of Excipients

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 574
Author(s):  
Nikhat Perween ◽  
Sultan Alshehri ◽  
T. S. Easwari ◽  
Vivek Verma ◽  
Md. Faiyazuddin ◽  
...  
Keyword(s):  
Particle Size ◽  
Mefenamic Acid ◽  
Hydroxypropyl Methylcellulose ◽  
Sodium Dodecyl ◽  
Aqueous Solubility ◽  
Oral Route ◽  
Precipitation Method ◽  
Antisolvent Precipitation

Molecules with poor aqueous solubility are difficult to formulate using conventional approaches and are associated with many formulation delivery issues. To overcome these obstacles, nanosuspension technology can be one of the promising approaches. Hence, in this study, the feasibility of mefenamic acid (MA) oral nanosuspension was investigated for pediatric delivery by studying the role of excipients and optimizing the techniques. Nanosuspensions of MA were prepared by adopting an antisolvent precipitation method, followed by ultrasonication with varying concentrations of polymers, surfactants, and microfluidics. The prepared nanosuspensions were evaluated for particle size, morphology, and rheological measures. Hydroxypropyl methylcellulose (HPMC) with varying concentrations and different stabilizers including Tween® 80 and sodium dodecyl sulfate (SLS) were used to restrain the particle size growth of the developed nanosuspension. The optimized nanosuspension formula was stable for more than 3 weeks and showed a reduced particle size of 510 nm with a polydispersity index of 0.329. It was observed that the type and ratio of polymer stabilizers were responsive on the particle contour and dimension and stability. We have developed a biologically compatible oral nanoformulation for a first-in-class drug beautifully designed for pediatric delivery that will be progressed toward further in vivo enabling studies. Finally, the nanosuspension could be considered a promising carrier for pediatric delivery of MA through the oral route with enhanced biological impact.

Electroacoustic Study of n-Hexadecane/Water Emulsions

2001 ◽  
Vol 54 (8) ◽  
pp. 503 ◽  
Author(s):  
Linggen Kong ◽  
James K. Beattie ◽  
Robert J. Hunter
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Volume Fraction ◽  
Sodium Dodecyl ◽  
Surfactant Solution ◽  
Minimum Size ◽  
Water Mixture ◽  
Concentrated Suspensions ◽  
Minimum Concentration ◽  
Median Diameter

n-Hexadecane-in-water emulsions were investigated by electroacoustics using a prototype of an AcoustoSizer-II apparatus. The emulsions were formed by passing the stirred oil/water mixture through a homogenizer in the presence of sodium dodecyl sulfate (SDS) at natural pH (6–7). With increasing oil-volume fraction, the particle size increased linearly after 5 and also after 20 passages through the homogenizer, suggesting that surface energy was determining particle size. For systems in which the surfactant concentration was limited, the particle size after 20 passages approached the value dictated by the SDS concentration. With ample surfactant present, the median diameter was a linear function of the inverse of the total energy input as measured by the number of passes. There was, however, a limit to the amount of size reduction that could be achieved in the homogenizer, and the minimum size was smaller at smaller volume fractions. Dilution of the emulsion with a surfactant solution of the same composition as the water phase had a negligible effect on the particle size and changed the zeta potential only slightly. This confirms results from previous work and validates the equations used to determine the particle size and zeta potential in concentrated suspensions. The minimum concentration of SDS that could prevent the emulsion from coalescing for the system with 6% by volume oil was 3 mM. For this dilute emulsion, the particle size decreased regularly with an increase in SDS concentration, but the magnitude of the zeta potential went through a strong maximum at intermediate surfactant concentrations.

scholarly journals PACKAGING OF HEPATITIS B SURFACE ANTIGEN VACCINE AND MORINGA OLEIFERA EXTRACT INTO CHITOSAN NANOPARTICLES

2019 ◽  
Vol 12 (1) ◽  
pp. 346
Author(s):  
Diky Mudhakir ◽  
Adik Ahmadi ◽  
Muhamad Insanu ◽  
Neny Nuraini
Keyword(s):  
Immune Response ◽  
Particle Size ◽  
Hepatitis B ◽  
Surface Antigen ◽  
Moringa Oleifera ◽  
Hepatitis B Surface Antigen ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Chitosan Nanoparticles ◽  
Entrapment Efficiency

Objective: Oftentimes, the recombinant antigen for the use of vaccines is less immunogenic than live attenuated or inactive vaccines. Hence, a potent adjuvant is needed to enhance the immune response. Moreover, the role of vector design is also important to facilitate the improvement of the immune response. The aim of this research was to develop hepatitis B surface antigen (HBsAg)-loaded nanoparticles and Moringa oleifera aqueous leaf extracts as an adjuvant using chitosan polymer. Methods: Chitosan nanoparticles were prepared by the ionic gelation method using sodium tripolyphosphate as the cross-linking agent. A system was composed of chitosan core in which HBsAg and M. oleifera extracts were incorporated. The concentration of HBsAg used in this combination was 10 μg/ml, and the concentrations of extracts were 10, 50, and 100 μg/ml, respectively. In this study, three types of nanoparticles were produced: HBsAg-loaded nanoparticles, M. oleifera-loaded nanoparticles, and combination of HBsAg–M. oleifera-loaded nanoparticles. The nanoparticles formed were characterized by the particle size, HBsAg entrapment efficiency using sodium dodecyl sulfate polyacrylamide gel electrophoresis, and the entrapment efficiency of extracts using the total flavonoid method. Results: The results showed that the particle size was between 111 and 245 nm. The entrapment efficiency of HBsAg in the separate formula was 79%, while that in the combined formula was approximately 96–98%. Furthermore, the entrapment efficiency of the extracts in the separate formula was around 64–91%, while that in the combined formula was 55–82.5%. Particularly, HBsAg–M. oleifera-loaded chitosan nanoparticles with the extract concentrations of 50 μg/ml showed the highest entrapment efficiencies of HBsAg and M. oleifera extracts of approximately 98 and 82.5%, respectively. Conclusion: Collectively, the system has been successfully developed, so it is then plausible to determine the function of the devices to enhance the immune response in the future.

Particle Size Distribution of ZrO2:Pr3+ – Influences of pH, High Power Ultrasound, Surfactant and Dopant Quantity

2007 ◽  
Vol 128 ◽  
pp. 97-100 ◽  
Author(s):  
Stephanie Möller ◽  
Janusz D. Fidelus ◽  
Witold Łojkowski
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
High Power ◽  
Average Particle Size ◽  
Sodium Dodecyl ◽  
Average Particle ◽  
Power Ultrasound ◽  
High Power Ultrasound ◽  
Influence Of Ph

The aim of the work was to examine the influence of pH, high power ultrasound, surfactant and dopant quantity on the particle size distribution of ZrO2:Pr3+, with praseodymium content varying between 0.05 and 10 %. The nanopowders were obtained via a hydrothermal microwave driven process. To establish if the dopant was located on the surface of the zirconia nanoparticles, the particle size distribution, as a function of pH, was measured to obtain an estimate of the isoelectric point of the samples. All results indicated that the dopant was concentrated on the surface: the measurements of the particle size distribution show that the pH corresponding to maximum average particle size changes towards higher values when the Pr content increases. Measurements of the particle size distribution dependency on the application of high power ultrasound and the addition of the sodium dodecyl sulphate surfactant show that, under certain conditions, there is a better stabilisation of the nanopowders in a dispersion and undesirable agglomeration is hindered.

Effect of Tungsten Powder Particle Size and Shape on Consolidation and Microstructure of W-xCu Composites by Selective Laser Melting

2016 ◽  
Vol 43 (2) ◽  
pp. 0203007
Author(s):  
闫岸如 Yan Anru ◽  
杨恬恬 Yang Tiantian ◽  
王燕灵 Wang Yanling ◽  
马志红 Ma Zhihong ◽  
杜云 Du Yun ◽  
...  
Keyword(s):  
Particle Size ◽  
Selective Laser Melting ◽  
Powder Particle ◽  
Tungsten Powder ◽  
Powder Particle Size ◽  
Laser Melting ◽  
Size And Shape ◽  
Particle Size And Shape
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