Use of Calixarene Host Molecules to Stabilize Quantum-confined Cadmium Sulfide Formation

1992 ◽  
Vol 272 ◽  
Author(s):  
Robin R. Chandler ◽  
Jeffery L. Coffer ◽  
C. David Gutsche ◽  
Iftikhar Alam ◽  
Hong Yang ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Diameter ◽  
Spectroscopic Studies ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Absorption And Emission ◽  
Zinc Blende ◽  
High Resolution Tem ◽  
Quantum Confined ◽  
Macrocyclic Molecules

ABSTRACTWe describe here the use of calixarenes, methylene (-CH2-) linked phenolic macrocyclic molecules, to stabilize the formation of quantum-confined (Q-) CdS clusters. Specifically, we focus on the use of an amino-derivatized calixarene, para-[(dimethylamino)- methyl]calix[6]arene, to stabilize Q-CdS clusters which have been characterized by High Resolution TEM (HREM), as well as absorption and emission spectroscopies. Under typical preparative conditions, an average particle diameter of 36 Å is obtained. HREM, in combination with Selected Area Diffraction (SAD), confirms the structure of the clusters as zinc blende CdS. Spectroscopic studies using absorption and emission methods indicate that both particle size and cluster photophysics are sensitive to the ratio of CdS to calixarene.

“Colloidal” Zinc Oxide

1937 ◽  
Vol 10 (2) ◽  
pp. 309-311
Author(s):  
H. A. Curran ◽  
T. R. Dawson
Keyword(s):  
Particle Size ◽  
Zinc Oxide ◽  
Manufacturing Industry ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Zinc Oxides ◽  
Two Samples ◽  
Good Grade

Abstract Some ten years ago, when so-called “colloidal” zinc oxides were being introduced to the rubber manufacturing industry, two samples were investigated to determine their behavior in rubber compared with ordinary good quality zinc oxide used in rubber. According to accounts published at the time, “colloidal” zinc oxide possesses an average particle size just within the limit of resolution of high-power microscopes, and an average particle diameter of 0.15 micron. In rubber it has been claimed to impart superior reinforcement, higher tensile strength, greater resistance to abrasion, and enhanced activation of organic accelerators. In the following report, samples A and B represent two samples of the same grade of “colloidal” zinc oxide, and C a good grade of regular zinc oxide.

Preparation of Mesocarbon Microbeads (MCMB) from Suspensions of a Synthetic Naphthalene Isotropic Pitch

2017 ◽  
Vol 753 ◽  
pp. 231-236
Author(s):  
Sheng Juan Ji ◽  
Xiang Lin Cheng ◽  
Jian Hong Zhao ◽  
Qing Ling Bi ◽  
Liu Cheng Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
X Ray ◽  
Mesocarbon Microbeads ◽  
Dispersion Degree ◽  
Isotropic Pitch ◽  
Particle Size Analyzer ◽  
Size Dispersion

A synthetic naphthalene isotropic pitch, which was manufactured with HF/BF3 acting as catalyst, was used as material to prepare mesocarbon microbeads (MCMB) through suspension method. The material pitch was dissolved in tetrahydrofuran (THF) and the pitch-THF solution is dispersed in a 2% polyvinyl alcohol aqueous solution. After THF was volatilized, the solution was cooled and then filtered to attain little pitch sphere. The pitch spheres were oxidized in 65% HNO3 solution, and the oxidized pitch spheres were carbonized up to 1000°C to get MCMB. MCMB was analyzed by scanning electron microscope (SEM), laser particle size analyzer and X ray diffractometer. The result showed that the particle size of MCMB was 2-30 μm and the average particle diameter size of D50 was 15.83 μm. The particle size distribution accords to the normal distribution, and the particle size dispersion degree was 0.7574. The effect of 65% HNO3 oxidation of the pitch sphere showed a satisfactory result. After carbonization at 1000°C, the oxidized pitch sphere exhibited a better orientation arrangement, the distance between the aromatic plane (d002) was decreased, and the thickness of the piled plane is increased.

scholarly journals Synthesis of monodisperse poly(styrene-co-divinyl benzene) microspheres by precipitation polymerization in acetonitrile and n-butanol mixture

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Jiang Hongyan ◽  
Chen Hou ◽  
Liang Ying ◽  
Xuan Yuhong ◽  
Wang Mingliang
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Particle Diameter ◽  
Reaction Medium ◽  
Precipitation Polymerization ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Initiator Concentration ◽  
Reaction Parameters ◽  
Divinyl Benzene

AbstractNarrow disperse poly(styrene-co-divinylbenzene) microspheres were prepared by precipitation polymerization using acetonitrile/n-butanol mixture as the reaction medium and 2,2’-azobis(2-methylpropionitrile) (AIBN) as initiator. The resulting particles have smooth surfaces due to the absence of any additional stabilizer. Effects of the reaction parameters such as n-butanol fraction in the reaction medium, monomer and initiator concentration, and divinylbenzene content were investigated. It was found that the particle size increased with an increasing concentration of monomer and initiator, while the uniformity was kept constant. The number-average particle diameter ranged from 2.36 to 1.63 μm and decreased with an increasing divinylbenzene concentration. In addition, the uniformity was enhanced as the concentration of divinylbenzene increased. On the basis of the DSC and TGA data, the microspheres prepared by the precipitation polymerization possessed a highly crosslinked structure and the thermal stability improved with the DVB concentration.

The Effect of Nanometer Polysilicon Material on Properties of Wax-Diesel Oil Systems

2013 ◽  
Vol 774-776 ◽  
pp. 1237-1241
Author(s):  
Ren Yuan Sun ◽  
Kun Kun Fan ◽  
Lei Wang ◽  
Xiao Meng Huang ◽  
Chao Sun
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Dispersion Model ◽  
Particle Diameter ◽  
Diesel Oil ◽  
Average Particle ◽  
Scattering Method ◽  
Average Particle Diameter ◽  
Laser Scattering

The effect of nanometer polysilicon material (NMPM) on properties of wax-diesel oil systems was experimentally studied. The particle size distribution of NMPM-diesel oil, wax-diesel oil system and wax-NMPM-diesel oil system were measured by laser scattering method. The viscosity of wax-diesel oil system was compared with that of systems with NMPM addition. A new wax growth and dispersion model was built up to analyze the mechanism for wax solubility increasing and size changing. Experiments show that the solubility of wax increases with the increase of temperature and the NMPM concentration in the wax-diesel oil system. The average particle diameter of NMPM-wax-diesel oil system is larger than that of wax-diesel oil system. The viscosity of wax-diesel oil system decreases with the NMPM addition.

A Critical Evaluation of the Reduced-Iron Method for Reduction of Nitrates

1963 ◽  
Vol 46 (4) ◽  
pp. 599-603
Author(s):  
J A Brabson ◽  
W G Burch ◽  
T C Woodis
Keyword(s):  
Particle Size ◽  
Reaction Time ◽  
Critical Evaluation ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Electrolytic Iron ◽  
Large Excess

Abstract The first action reduced iron method for nitrogen in fertilizers specifies the use of electrolytic iron and indicates that a large excess of iron is required for the reduction of nitrates. Iron reduced by hydrogen, however, is a more efficient reductant than electrolytic iron, but it requires a longer reaction time. The specified amount of iron is excessive. The particle size of the iron is important, and 250-mesh is the largest particle size that should be used; specification of the average particle diameter in microns is recommended. The reduced iron method is, at best, a cumbersome procedure, and other, more efficient, reductants for nitrate should be sought.

scholarly journals Effect of Particle Size Distributions on Minimum Fluidization Velocity with Varying Gas Temperature

2020 ◽  
Vol 11 (11) ◽  
pp. 524-529
Author(s):  
Krittin Korkerd ◽  
◽  
Chaiwat Soanuch ◽  
Pornpote Piumsomboon ◽  
Benjapon Chalermsinsuwan
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Particle Diameter ◽  
Skewed Distribution ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Gas Temperature ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization

The particle size distribution (PSD) is an important property that can influence the hydrodynamics and chemical conversion in fluidized bed system. The objective of this study is to investigate the effect of PSDs of particle and gas temperature on minimum fluidization velocity (Umf). Here, the silica sand with three average diameters and five PSDs including narrow cut, Gaussian, Gaussian with high standard deviation, negative skewed distribution and positive skewed distribution were used. The considered gas temperature ranged from 30 to 120 °C. The results showed that the Umf values with wide PSDs were lower than the Umf values for narrow cut particle with the same average diameter. The reason can be explained by the addition of smaller particle will improve the fluidization characteristics. The standard deviation and skewness of PSD also influenced on the Umf. The Umf was observed to decrease with increasing gas temperature. In addition, the effect of average particle diameter could also be seen. The Umf increased with the increasing of average particle diameter.

scholarly journals Preparation of Polyetherimide Nanoparticles by a Droplet Evaporation-Assisted Thermally Induced Phase-Separation Method

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1548
Author(s):  
Peng Zhu ◽  
Huapeng Zhang ◽  
Hongwei Lu
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Phase Separation ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Droplet Evaporation ◽  
Average Particle ◽  
Thermally Induced Phase Separation ◽  
Thermally Induced ◽  
Pei Nanoparticles

The droplet evaporation effect on the preparation of polyetherimide (PEI) nanoparticles by thermally induced phase separation (TIPS) was studied. PEI nanoparticles were prepared in two routes. In route I, the droplet evaporation process was carried out after TIPS. In route II, the droplet evaporation and TIPS processes were carried out simultaneously. The surface tension and shape parameters of samples were measured via a drop shape analyzer. The Z-average particle diameter of PEI nanoparticles in the PEI/dimethyl sulfoxide solution (DMSO) suspension at different time points was tested by dynamic light scattering, the data from which was used to determine the TIPS time of the PEI/DMSO solution. The natural properties of the products from both routes were studied by optical microscope, scanning electron microscope and transmission electron microscope. The results show that PEI nanoparticles prepared from route II are much smaller and more uniform than that prepared from route I. Circulation flows in the droplet evaporation were indirectly proved to suppress the growth of particles. At 30 °C, PEI solid nanoparticles with 193 nm average particle size, good uniformity, good separation and good roundness were obtained. Route I is less sensitive to temperature than route II. Samples in route I were still the accumulations of micro and nanoparticles until 40 °C instead of 30 °C in route II, although the particle size distribution was not uniform. In addition, a film structure would appear instead of particles when the evaporation temperature exceeds a certain value in both routes. This work will contribute to the preparation of polymer nanoparticles with small and uniform particle size by TIPS process from preformed polymers.

Preparation and pharmacokinetics of cefquinome sulfate liposomes in goats

2018 ◽  
Author(s):  
Haigang Wu ◽  
Jinni Liu ◽  
Gugangke Xu ◽  
Zhaowei Ye ◽  
Jicheng Liu and Benchi Yi
Keyword(s):  
Plasma Concentration ◽  
Particle Diameter ◽  
Entrapment Efficiency ◽  
Maximum Plasma Concentration ◽  
Maximum Plasma ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Ethanol Injection ◽  
Elimination Half ◽  
Time Point

We evaluated the pharmacokinetics of cefquinome sulfate (CEF) liposomes in eight healthy goats following intramuscular administration at 4 mg/kg. The average particle diameter of CEF liposomes prepared by the ethanol injection method was 335nm with a CEF entrapment efficiency of 69.56%. The elimination half-life (t1/2b) of CEF liposomes was 33.04h compared with 16.21 h for CEF injected without carrier (p less than 0.05). The area under the concentration curve (AUC) for CEF liposomes was approximately three-times greater than for CEF alone (P less than 0.05). The time-point of maximum plasma concentration of the drug (Tp) and the maximum plasma concentration (Cmax) were 4.38 h and 1.99 ìg/mL for CEF liposomes, compared with 1.86 h and 3.55 ìg/mL for CEF without carrier, respectively. 

scholarly journals Morphology and Degradation of Multicompartment Microparticles Based on Semi-Crystalline Polystyrene-block-Polybutadiene-block-Poly(L-lactide) Triblock Terpolymers

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4358
Author(s):  
Nicole Janoszka ◽  
Suna Azhdari ◽  
Christian Hils ◽  
Deniz Coban ◽  
Holger Schmalz ◽  
...  
Keyword(s):  
Cross Sections ◽  
Ring Opening ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Selective Degradation ◽  
The Core ◽  
Transmission Electron ◽  
And Control ◽  
Triblock Terpolymers

The confinement assembly of block copolymers shows great potential regarding the formation of functional microparticles with compartmentalized structure. Although a large variety of block chemistries have already been used, less is known about microdomain degradation, which could lead to mesoporous microparticles with particularly complex morphologies for ABC triblock terpolymers. Here, we report on the formation of triblock terpolymer-based, multicompartment microparticles (MMs) and the selective degradation of domains into mesoporous microparticles. A series of polystyrene-block-polybutadiene-block-poly(L-lactide) (PS-b-PB-b-PLLA, SBL) triblock terpolymers was synthesized by a combination of anionic vinyl and ring-opening polymerization, which were transformed into microparticles through evaporation-induced confinement assembly. Despite different block compositions and the presence of a crystallizable PLLA block, we mainly identified hexagonally packed cylinders with a PLLA core and PB shell embedded in a PS matrix. Emulsions were prepared with Shirasu Porous Glass (SPG) membranes leading to a narrow size distribution of the microparticles and control of the average particle diameter, d ≈ 0.4 µm–1.8 µm. The core–shell cylinders lie parallel to the surface for particle diameters d < 0.5 µm and progressively more perpendicular for larger particles d > 0.8 µm as verified with scanning and transmission electron microscopy and particle cross-sections. Finally, the selective degradation of the PLLA cylinders under basic conditions resulted in mesoporous microparticles with a pronounced surface roughness.

Research on the Efficient Application of Silica Fume in High-Tech Cement-Based Materials

2011 ◽  
Vol 374-377 ◽  
pp. 1537-1540
Author(s):  
Dong Lin ◽  
Zi Yun Wen
Keyword(s):  
Compressive Strength ◽  
Silica Fume ◽  
Packing Density ◽  
Particle Diameter ◽  
High Tech ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Cement Based Materials ◽  
Pre Treatment

The comparison experiments are carried out at different silica fume dosage between the silica fume with pre-treatment and the silica fume without pre-treatment. The results show that the pre-treatment of silica fume improved the strength greatly and the silica fume dosage corresponding to the strength peak somewhat moved forward from 0.20 for the cement-based materials with pre-treatment of silica fume to 0.21 for the cement-based materials without pre-treatment of silica fume. The particles distribution experiment results indicate that after the pre-treatment of silica fume, the average particle diameter of silica fume reduced from 2.865μｍto 0.151μｍ. Based on Aim-Goff model, it is concluded that the increase in the compressive strength and flextural strength of cement-based materials with pre-treatment of silica fume, are attributed to the dispersion of silica fume agglomeration and the increase in the packing density of the cement-based materials.

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