Hydroxyapatite Nanopowder Synthesis with a Programmed Resorption Rate

A microwave, solvothermal synthesis of hydroxyapatite (HAp) nanopowder with a programmed material resorption rate was developed. The aqueous reaction solution was heated by a microwave radiation field with high energy density. The measurements included powder X-ray diffraction (PXRD) and the density, specific surface area (SSA), and chemical composition as specified by the inductively coupled plasma optical emission spectrometry technique (ICP-OES). The morphology and structure were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A degradation test in accordance with norm ISO 10993-4 was conducted. The developed method enables control of the average grain size and chemical composition of the obtained HAp nanoparticles by regulating the microwave radiation time. As a consequence, it allows programming of the material degradation rate and makes possible an adjustment of the material activity in a human body to meet individual resorption rate needs. The authors synthesized a pure, fully crystalline hexagonal hydroxyapatite nanopowder with a specific surface area from 60 to almost 240 m2/g, a Ca/P molar ratio in the range of 1.57–1.67, and an average grain size from 6 nm to over 30 nm. A 28-day degradation test indicated that the material solubility ranged from 4 to 20 mg/dm3.

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Size-dependent density of zirconia nanoparticles

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.6.4 ◽

2015 ◽

Vol 6 ◽

pp. 27-35 ◽

Cited By ~ 29

Author(s):

Agnieszka Opalinska ◽

Iwona Malka ◽

Wojciech Dzwolak ◽

Tadeusz Chudoba ◽

Adam Presz ◽

...

Keyword(s):

Grain Size ◽

Surface Layer ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Hydrothermal Process ◽

Amorphous Layer ◽

Average Density ◽

Size Dependent ◽

Average Grain Size

The correlation between density and specific surface area of ZrO2 nanoparticles (NPs) was studied. The NPs were produced using a hydrothermal process involving microwave heating. The material was annealed at 1100 °C which resulted in an increase in the average grain size of the ZrO2 NPs from 11 to 78 nm and a decrease in the specific surface area from 97 to 15 m2/g. At the same time, the density increased from 5.22 g/m3 to 5.87 g/m3. This effect was interpreted to be the result of the presence of a hydroxide monolayer on the NP surface. A smaller ZrO2 grain size was correlated with a larger contribution of the low density surface layer to the average density. To prove the existence of such a layer, the material was synthesized using 50% heavy water. Fourier transform infrared spectroscopy (FTIR) permitted the identification of the –OD groups created during synthesis. It was found that the –OD groups persisted on the ZrO2 surface even after annealing at 1100 °C. This hydroxide layer is responsible for the decrease in the average density of the NPs as their size decreases. This study of the correlation between particle size and density may be used to assess the quality of the NPs. In most cases, the technological aim is to avoid an amorphous layer and to obtain fully crystalline nanoparticles with the highest density possible. However, due to the effect of the surface layers, there is a maximum density which can be achieved for a given average NP diameter. The effect of the surface layer on the NP density becomes particularly evident for NPs smaller than 50 nm, and thus, the density of nanoparticles is size dependent.

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Elucidating the Origin of the Toxicity of Nano-CeO2 to Chlorella pyrenoidosa：the Role of Specific Surface Area and Chemical Composition

Environmental Science Nano ◽

10.1039/d0en01177k ◽

2021 ◽

Author(s):

Changjian Xie ◽

Yuhui Ma ◽

Peng Zhang ◽

Junzhe Zhang ◽

Xiaowei Li ◽

...

Keyword(s):

Chemical Composition ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Aquatic Environment ◽

Cerium Dioxide ◽

Environmental Application ◽

Ecotoxicological Effects

With the increasing environmental application and discharge of nano cerium dioxide (nano-CeO2), it is urgent to fully understand its ecotoxicological effects on the aquatic environment. This study for the first...

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Comparative Analysis on Chemical Composition and Charcoal Characterization of Two Miscanthus Species

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.415-417.1265 ◽

2011 ◽

Vol 415-417 ◽

pp. 1265-1272

Author(s):

Wen Biao Zhang ◽

Wen Zhu Li ◽

Bing Song Zheng

Keyword(s):

Chemical Composition ◽

Specific Surface ◽

Water Content ◽

Surface Area ◽

Specific Surface Area ◽

Ph Value ◽

Perennial Grass ◽

Water Extract ◽

Carbonization Temperature ◽

Hot Water

Miscanthus is a highly productive, rhizomatous, C4 perennial grass that should be considered as an excellent active carbon precursor. This paper compares the charcoal characterization and chemical composition between M. sinensis and M. floridulus. Species differed in water content, hot water extract, 1% NaOH extract, organic solvent extract, cellulose, lignin and ash. Carbonization temperatures have effects on charcoal yields of Miscanthus, which ranged from 23.5% to 48.0% for M. sinensis and 11.3% to 37.2% for M. floridulus. Water content, charcoal density, pH value, and specific surface area of charcoal characterization varied between two species of Miscanthus. The specific surface area increased with the increase of carbonization temperature. The highest specific surface area of M. sinensis and M. floridulus was 351.74 m2g−1and 352.74 m2g−1, respectively, when the carbonization temperature was 800°C.

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The referential grain size and effective porosity in the Kozeny–Carman model

10.5194/hess-2015-524 ◽

2016 ◽

Author(s):

K. Urumović ◽

K. Urumović Sr.

Keyword(s):

Grain Size ◽

Hydraulic Conductivity ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Effective Porosity ◽

Critical Conditions ◽

Saturated Porous Media ◽

New Developments ◽

Mean Grain Size

Abstract. In this paper, the results of permeability and specific surface area analyses as functions of granulometric composition of various sediments (from silty clays to very well-graded gravels) are presented. The effective porosity and the referential grain size are presented as fundamental granulometric parameters expressing an effect of the forces operating on fluid movement through the saturated porous media. This paper suggests procedures for calculating referential grain size and determining effective (flow) porosity, which result in parameters that reliably determine the specific surface area and permeability. These procedures ensure the successful application of the Kozeny–Carman model up to the limits of validity of Darcy’s law. The value of effective porosity in the referential mean grain size function was calibrated within the range of 1.5 μm to 6.0 mm. The reliability of the parameters applied in the KC model was confirmed by a very high correlation between the predicted and tested hydraulic conductivity values (R2=0.99 for sandy and gravelly materials; R2=0.70 for clayey-silty materials). The group representation of hydraulic conductivity (ranging from 10–12 m/s up to 10–2 m/s) presents a coefficient of correlation of R2=0.97 for a total of 175 samples of various deposits. These results present new developments in the research of the effective porosity, the permeability and the specific surface area distributions of porous materials. This is important because these three parameters are critical conditions for successful groundwater flow modeling and contaminant transport. Additionally, from a practical viewpoint, it is very important to identify these parameters swiftly and very accurately.

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Preparation of Nanosize Anatase TiO2 Powders by Hydrothermal Synthesis

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.2017 ◽

2007 ◽

Vol 336-338 ◽

pp. 2017-2020 ◽

Cited By ~ 2

Author(s):

Fan Yong Ran ◽

Wen Bin Cao ◽

Yan Hong Li ◽

Xiao Ning Zhang

Keyword(s):

Grain Size ◽

Hydrothermal Synthesis ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Reaction Temperature ◽

Reaction System ◽

Anatase Tio2 ◽

Holding Time ◽

Precursor Concentration

Nanosize anatase TiO2 powders have been synthesized by hydrothermal synthesis by using technical grade TiOSO4 as precursor and urea as precipitating agent. The initial pressure of the reaction system was set at 6 MPa. Stirring speed was fixed at 300r/min. The reaction system reacted at the temperature ranged from 110 to 150°C for holding 2hrs to 8hrs and the concentration of the precursor was ranged from 0.25M to1.5M. XRD patterns show that the synthesized powders are in the form of anatase phase. Calculated grain size is ranged from 6.7 to 8.9nm by Scherrer method from the line broadening of the (101) diffraction peak of anatase. The specific surface area of the powders synthesized under different conditions is ranged from 124 to 240m2/g. The grain size of the powders increases with the increase of the reaction temperature, holding time and precursor concentration, respectively. The specific surface area decreases with the increase of reaction temperature and holding time, and does not obviously change with the change of precursor concentration when the concentration of the precursor is less than 1M. However, when the concentration is higher than 1M, the specific surface area will decrease quickly with the increase of the precursor concentration. XRD and DSC-TG analysis shows that the synthesized anatase TiO2 will begin to transform to rutile TiO2 at about 840°C. When heated to 1000°C for holding 1h, the anatase powders will transform to rutile completely.

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Retrieval of Snow Properties from the Sentinel-3 Ocean and Land Colour Instrument

Remote Sensing ◽

10.3390/rs11192280 ◽

2019 ◽

Vol 11 (19) ◽

pp. 2280 ◽

Cited By ~ 14

Author(s):

Alexander Kokhanovsky ◽

Maxim Lamare ◽

Olaf Danne ◽

Carsten Brockmann ◽

Marie Dumont ◽

...

Keyword(s):

Grain Size ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Environmental Changes ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

The Arctic ◽

Observation Data ◽

Snow Properties

The Sentinel Application Platform (SNAP) architecture facilitates Earth Observation data processing. In this work, we present results from a new Snow Processor for SNAP. We also describe physical principles behind the developed snow property retrieval technique based on the analysis of Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A/B measurements over clean and polluted snow fields. Using OLCI spectral reflectance measurements in the range 400–1020 nm, we derived important snow properties such as spectral and broadband albedo, snow specific surface area, snow extent and grain size on a spatial grid of 300 m. The algorithm also incorporated cloud screening and atmospheric correction procedures over snow surfaces. We present validation results using ground measurements from Antarctica, the Greenland ice sheet and the French Alps. We find the spectral albedo retrieved with accuracy of better than 3% on average, making our retrievals sufficient for a variety of applications. Broadband albedo is retrieved with the average accuracy of about 5% over snow. Therefore, the uncertainties of satellite retrievals are close to experimental errors of ground measurements. The retrieved surface grain size shows good agreement with ground observations. Snow specific surface area observations are also consistent with our OLCI retrievals. We present snow albedo and grain size mapping over the inland ice sheet of Greenland for areas including dry snow, melted/melting snow and impurity rich bare ice. The algorithm can be applied to OLCI Sentinel-3 measurements providing an opportunity for creation of long-term snow property records essential for climate monitoring and data assimilation studies—especially in the Arctic region, where we face rapid environmental changes including reduction of snow/ice extent and, therefore, planetary albedo.

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Study on Comparison among Papermaking Powder Properties

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.512-515.2434 ◽

2012 ◽

Vol 512-515 ◽

pp. 2434-2438

Author(s):

Quan Xiao Liu ◽

Wen Cai Xu

Keyword(s):

Particle Size ◽

Chemical Composition ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Preparation Method ◽

Powder Properties

In this paper the comparison among some papermaking powder properties are studied. It shows that the properties of different powders are different because of different chemical composition and different preparation method and their particle size is different for different purpose such as filler and pigment. The particle size of powder for pigment powder is smaller than that for filler. The specific surface area of papermaking filler is lower than 20m2/g, the absorption value of DBP is about 45cm3/100g, the whiteness is up to 90%, and the particle size is about 3µm. The specific surface area of papermaking pigment is lower than 25m2/g, the absorption value of DBP is from 40 cm3/100g to100cm3/100g, the whiteness of clay is up to 50%, the whiteness of GCC and PCC is up to 90%, and the particle size is lower than 2µm. The specific surface area of silica is up to 100m2/g, the absorption value of DBP is up to 100cm3/100g, the whiteness is up to 97%, and the particle size is around 5µm.

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Study on Nano-Hydroxyapatite Assisted Preparing by Ionic Liquids

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1015.501 ◽

2014 ◽

Vol 1015 ◽

pp. 501-504 ◽

Cited By ~ 1

Author(s):

Yong Guang Bi ◽

Xu Si Xu

Keyword(s):

Grain Size ◽

Ionic Liquids ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Large Scale ◽

Preparation Method ◽

Raw Material ◽

Large Scale Preparation ◽

Scale Preparation

Papers with Ca (NO3)2• 4H2O and (NH4)2HPO4as raw material, prepared by ionic liquids assisted nanoHAP, resulting hexagonal nanoHAP are crystal grain size are 10-20nm level, are smaller nanometer range ; specific surface area, the findings show that ionic liquids have the technology to promote the significance of the preparation method can provide a reference for large-scale preparation of biomedical nanomaterials.

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Synthesis and Characterization of Porous Mo-W Oxide Nanostructures

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2008.18404 ◽

2008 ◽

Vol 8 (12) ◽

pp. 6445-6450

Author(s):

F. Paraguay-Delgado ◽

Y. Verde ◽

E. Cizniega ◽

J. A. Lumbreras ◽

G. Alonso-Nuñez

Keyword(s):

Electron Microscopy ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Synthesis Method ◽

Atomic Ratio ◽

High Specific Surface Area ◽

X Ray Diffraction ◽

Transmission Electron ◽

Before And After

The present study reports the synthesis method, microstructure characterization, and thermal stability of nanostructured porous mixed oxide (MoO3-WO3) at 550 and 900 °C of annealing. The material was synthesized using a hydrothermal method. The precursor was prepared by aqueous solution using ammonium heptamolibdate and ammonium metatungstate, with an atomic ratio of Mo/W = 1. The pH was adjusted to 5, and then the solution was transferred to a teflon-lined stainless steel autoclave and heated at 200 °C for 48 h. The resultant material was washed using deionized water. The specific surface area, morphology, composition, and microstructure before and after annealing were studied by N2 physisorption, scanning electron microscopy (SEM), analytical transmission electron microscopy (TEM), and X-Ray diffraction (XRD). The initial synthesized materials showed low crystallinity and high specific surface area around (141 m2/g). After thermal annealing the material showed higher crystallinity and diminished its specific surface area drastically.

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