Particle size and purity control study on ZrW2O8 powders using coprecipitation method

2019 ◽  
Vol 246 ◽  
pp. 27-33 ◽  
Author(s):  
Yan Zhang ◽  
Yingkui Guo ◽  
Lei Chen ◽  
Yujin Wang ◽  
Guangwei Zhang ◽  
...  
Keyword(s):  
Particle Size ◽  
Coprecipitation Method ◽  
Control Study ◽  
Purity Control

scholarly journals Particle size of LDL is affected by the National Cholesterol Education Program (NCEP) step II diet in dyslipidaemic adolescents

2007 ◽  
Vol 98 (1) ◽  
pp. 134-139 ◽  
Author(s):  
Leila Azadbakht ◽  
Parvin Mirmiran ◽  
Mehdi Hedayati ◽  
Ahmad Esmaillzadeh ◽  
Nilufar Shiva ◽  
...  
Keyword(s):  
Particle Size ◽  
Education Program ◽  
National Cholesterol Education Program ◽  
Control Diet ◽  
Saturated Fat ◽  
Outcome Variable ◽  
Favourable Effect ◽  
The Mean ◽  
Total Fat ◽  
Control Study

The objective was to determine the effects of the National Cholesterol Education Program (NCEP) step II diet on LDL and HDL particle size in dyslipidaemic adolescents. Forty-four dyslipidaemic adolescents, aged 10–18 years, participated in this case-control study. The control diet was a diet similar to what most Tehranian adolescents eat. NCEP step II diet was a diet with 30 % of energy as total fat, less than 7 % saturated fat, less than 200 mg cholesterol/d, less than 15 % of energy as MUFA and less than 10 % as PUFA. Lipoprotein particle size was the major outcome variable, which was measured after 3 months of intervention. Comparison was made by the repeated measurement ANOVA. The mean BMI was 26·3 (sd4·2) kg/m2. There were no significant changes in weight or physical activity in the two groups during the study. The NCEP diet resulted in higher reduction in total cholesterol ( − 13 (sd4)v.− 2 (sd0·3) mg/dl,P < 0·001) and LDL ( − 9 (sd2)v.3 (sd0·6) mg/dl,P < 0·01), and higher increase in size of the LDL (1·7 (sd0·4)v.0·1 (sd0·4) nanometer,P < 0·001). HDL particle size did not change significantly. NCEP step II diet had a favourable effect on the LDL particle size. The related mechanism needs to be studied in future experimental designs.

Sintering Kinetics of Hydroxyapatite Prepared by Chemical Coprecipitation Method

2011 ◽  
Vol 233-235 ◽  
pp. 1511-1515 ◽  
Author(s):  
Jian Peng Zou
Keyword(s):  
Particle Size ◽  
Sintering Temperature ◽  
Average Particle Size ◽  
Atomic Emission ◽  
Coprecipitation Method ◽  
Average Particle ◽  
Chemical Coprecipitation ◽  
Particle Size Analyzer ◽  
Controlling Mechanism ◽  
Chemical Coprecipitation Method

With chemical coprecipitation method, high purity hydroxyapatite was successfully prepared in this paper. The microstructure and components of HA were characterized by XRD, SEM, FTIR, atomic emission spectrum and particle size analyzer. The results demonstrate that synthesized HA is very pure and is harmless to human body. Average particle size of HA powder is about 10.4μm. Crystallization degree of hydroxyapatite increases with the increase of sintering temperature and the optimal preparing technique is sintering at 750 for 2h with temperature-rising rate of 5°C·min-1. Grain growing activation energy of HA can be calculated as 24.8 kJ·mol-1 according to the relationship between grain size and sintering temperature. HA’s grain growth mechanism is interfacial diffusion controlling mechanism.

scholarly journals Impact of Health on Particle Size of Exhaled Respiratory Aerosols: Case-control Study

2008 ◽  
Vol 36 (7) ◽  
pp. 572-577 ◽  
Author(s):  
Guillaume Hersen ◽  
Stéphane Moularat ◽  
Enric Robine ◽  
Evelyne Géhin ◽  
Sandrine Corbet ◽  
...  
Keyword(s):  
Particle Size ◽  
Case Control Study ◽  
Case Control ◽  
Control Study

scholarly journals Is the goal of mastication reached in young dentates, aged dentates and aged denture wearers?

2007 ◽  
Vol 99 (1) ◽  
pp. 121-128 ◽  
Author(s):  
Anne Mishellany-Dutour ◽  
Johanne Renaud ◽  
Marie-Agnès Peyron ◽  
Frank Rimek ◽  
Alain Woda
Keyword(s):  
Particle Size ◽  
Size Reduction ◽  
Emg Activity ◽  
Particle Size Reduction ◽  
Masticatory Function ◽  
Whole Saliva ◽  
Group 3 ◽  
Group 2 ◽  
The Impact ◽  
Control Study

The objective of the present study was to assess the impact of age and dentition status on masticatory function. A three-arm case–control study was performed. Group 1 (n 14) was composed of young fully dentate subjects (age 35·6 ± 10·6 years), group 2 (n 14) of aged fully dentate subjects (age 68·8 ± 7·0 years) and group 3 (n 14) of aged full denture wearers (age 68·1 ± 7·2 years). Mastication adaptation was assessed in the course of chewing groundnuts and carrots to swallowing threshold. Particle size distribution of the chewed food, electromyographic (EMG) activity of the masseter and temporalis muscles during chewing, and resting and stimulated whole saliva rates were measured. Aged dentate subjects used significantly more chewing strokes to reach swallowing threshold than younger dentate subjects (P < 0·05), with increased particle size reduction, longer chewing sequence duration (P < 0·05) and greater total EMG activity (P < 0·05) for both groundnuts and carrots. In addition, aged denture wearers made significantly more chewing strokes than aged dentate subjects (P < 0·001) to reach swallowing threshold for groundnuts. Particle size reduction at time of swallowing was significantly poorer for denture wearers than for their aged dentate counterparts, despite an increase in chewing strokes, sequence duration and EMG activity per sequence. Masticatory function was thus adapted to ageing, but was impaired in denture wearers, who failed to adapt fully to their deficient masticatory apparatus.

Synthesis of Cubic and Rhombohedral Phased Nanocrystalline SnO2 Doped In2O3 [ITO] Powders with Coprecipitation Method

1999 ◽  
Vol 581 ◽  
Author(s):  
Bong-Chull Kim ◽  
Jeong-Joo Kim ◽  
Se-Hong Chang
Keyword(s):  
Particle Size ◽  
Aging Time ◽  
Spherical Shape ◽  
The State ◽  
Coprecipitation Method ◽  
Hydroxide Coprecipitation

ABSTRACTNanocrystalline ITO powders have been prepared by a hydroxide coprecipitation method. Through the variation of aging time after precipitation, we have characterized the size, morphology and the structure of the precipitates. It was found that the precipitates are in the state of InOOH at first. Further aging up to 48 h changed it to In(OH)3 structure. After calcinations of the precipitates, rhombohedral nanocrystalline ITO powder with spherical shape was produced from InOOH structured precipitates, while cubic nanocrystalline ITO powder was produced from In(OH)3. Fraction of the rhombohedral ITO powder decreased as the aging time increased. The particle size of the cubic ITO increased with aging time but that of rhombohedral ITO (∼15 nm) was almost invariant.

Influence of Synthesis Temperature on the ZnNb2O6 Powders Prepared via Co-Precipitation Method

2014 ◽  
Vol 1033-1034 ◽  
pp. 1044-1047
Author(s):  
Yong Du ◽  
Jin Liang Huang ◽  
Yong Jun Gu
Keyword(s):  
Particle Size ◽  
Phase Composition ◽  
Chemical Composition ◽  
High Purity ◽  
Raw Materials ◽  
Particle Morphology ◽  
Synthesis Temperature ◽  
Coprecipitation Method ◽  
Precipitation Method ◽  
Co Precipitation

ZnNb2O6powder was successfully synthesized via coprecipitation method with Nb2O5、Zn(NO3)2·6H2O as raw materials and ammonia as precipitant agent. This precursor on heating at750°C, produced ZN powders. Phase composition, morphology and chemical composition were studied via a combination of XRD, TEM and EDS technique. The effects of synthesis temperature on phase composition and particle morphology were investigated in this paper. The results showed that with the increase of the synthesis temperature, the particle size decreases. We could get the ZnNb2O6powder with high purity, fine crystalline when the synthesis temperature is at 50°C.

Microstructural characterization of laser-melted/roller-quenched dicalcium silicate

1988 ◽  
Vol 46 ◽  
pp. 582-583
Author(s):  
C. J. Chan ◽  
K. R. Venkatachari ◽  
W. M. Kriven ◽  
J. F. Young
Keyword(s):  
Particle Size ◽  
Raw Materials ◽  
Shape Change ◽  
Microstructural Characterization ◽  
Particle Size Effect ◽  
Dicalcium Silicate ◽  
Laser Melting ◽  
Uniform Size ◽  
Cell Shape Change ◽  
Wide Range

Dicalcium silicate (Ca2SiO4) is a major component of Portland cement. It has also been investigated as a potential transformation toughener alternative to zirconia. It has five polymorphs: α, α'H, α'L, β and γ. Of interest is the β-to-γ transformation on cooling at about 490°C. This transformation, accompanied by a 12% volume increase and a 4.6° unit cell shape change, is analogous to the tetragonal-to-monoclinic transformation in zirconia. Due to the processing methods used, previous studies into the particle size effect were limited by a wide range of particle size distribution. In an attempt to obtain a more uniform size, a fast quench rate involving a laser-melting/roller-quenching technique was investigated.The laser-melting/roller-quenching experiment used precompacted bars of stoichiometric γ-Ca2SiO4 powder, which were synthesized from AR grade CaCO3 and SiO2xH2O. The raw materials were mixed by conventional ceramic processing techniques, and sintered at 1450°C. The dusted γ-Ca2SiO4 powder was uniaxially pressed into 0.4 cm x 0.4 cm x 4 cm bars under 34 MPa and cold isostatically pressed under 172 MPa. The γ-Ca2SiO4 bars were melted by a 10 KW-CO2 laser.

Analytical Electron Microscopy study of two vehicle-aged automotive exhaust catalysts having dissimilar activities

1989 ◽  
Vol 47 ◽  
pp. 272-273
Author(s):  
Sooho Kim ◽  
M. J. D’Aniello
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Noble Metal ◽  
Catalyst Deactivation ◽  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Metal Particles ◽  
Automotive Exhaust ◽  
Exhaust Catalysts ◽  
Analytical Electron

Automotive catalysts generally lose-agtivity during vehicle operation due to several well-known deactivation mechanisms. To gain a more fundamental understanding of catalyst deactivation, the microscopic details of fresh and vehicle-aged commercial pelleted automotive exhaust catalysts containing Pt, Pd and Rh were studied by employing Analytical Electron Microscopy (AEM). Two different vehicle-aged samples containing similar poison levels but having different catalytic activities (denoted better and poorer) were selected for this study.The general microstructure of the supports and the noble metal particles of the two catalysts looks similar; the noble metal particles were generally found to be spherical and often faceted. However, the average noble metal particle size on the poorer catalyst (21 nm) was larger than that on the better catalyst (16 nm). These sizes represent a significant increase over that found on the fresh catalyst (8 nm). The activity of these catalysts decreases as the observed particle size increases.

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