4,146 research outputs found
Sol-gel derived hydroxyapatite, fluorhydroxyapatite and fluorapatite coatings for titanium implants
No full textCurrently, most titanium implant coatings are made using hydroxyapatite and a
plasma-spraying technique. There are however limitations associated with the
plasma-spraying process including; poor adherence, high porosity and cost. An
alternative - the sol-gel technique offers many potential advantages but is
currently lacking research data for this application.
Hydroxyapatite (HA), fluorhydroxyapatite (FHA) and fluorapatite (FA) have
been synthesised by a sol-gel method. Calcium nitrate and triethyl phosphite
were used as precursors under an ethanol-water based solution. Different
amounts of ammonium fluoride (NH4F) were incorporated for the preparation of
the FHA and FA sol-gels. Optimisation and characterisation of the sol-gels was
carried out using, X-ray Diffraction (XRD), High Temperature X-Ray Diffraction
(HTXRD), Fourier Transform Infrared Analysis (FTIR) and Differential Thermal
Analysis (DTA).
Rheology and hydrophilicity of the sol-gels showed that increasing fluoride ion
substitution caused an increase in viscosity and contact angle.
The dissolution (Ca2+ and PO4
3-rates) rates of the fluoride-substituted powders
from the sol-gels were considerably lower than that of HA and all rates could be
decreased by increasing the sintering temperature. This suggests the
possibility of tailoring the solubility of any coatings made from the sol-gels
through fluoride ion substitution and increased sintering temperature.
A spin coating protocol has been established for coating the sol-gels onto
titanium. Increasing the coating speed decreased the porosity and thickness of
the coatings. Bond strengths to titanium were investigated. Fluoride substitution
and sintering temperature were shown to be important factors. Cellular proliferation studies revealed that increasing the level of fluoride
substitution in the apatite structure significantly increased the biocompatibility
of the material.
The sol-gel technique may be an alternative to plasma spraying for coating
titanium implants. Furthermore it may also be suitable for producing HA, FHA
and FA as bone grafting materials
Occurrence status of the fall armyworm (Lepidoptera: Noctuidae) in South Korea
No full textSuh, Soo-Jung, Choi, Deuk-Soo, Sol-moon, Na (2021): Occurrence status of the fall armyworm (Lepidoptera: Noctuidae) in South Korea. Insecta Mundi 2021 (850): 1-5, DOI: http://doi.org/10.5281/zenodo.504150
Effect of two-step sol-gel reaction on the mesoporous silica structure
No full textthe present study, we investigated the effects of two-step sol-gel reaction by abrupt pH change on the SBA-15 and mesocellular silica foams (MCF). Mesoporous silica was fabricated by using triblock copolymer templates (poly(ethylene oxide) and poly(propylene oxide)). The prepared silica structure was characterized by X-ray diffraction, transmission electron microscopy, and N-2 sorption experiment. Specifically, we prepared SBA-15 with long-range two-dimensional hexagonal arrangement of 3 to 6-nm feature spacing and MCF with larger pores of a few tens of nanometers. The pore size and ordering were influenced by pH change in a two-step sol-gel reaction and the concentration of organic solvent. Although well-ordered hexagonal arrangement of mesopores was prevalent in acidic conditions, the materials synthesized by a single-step reaction in neutral or basic conditions possessed gel-like structure without mesopores. However, the present two-step reaction (low pH sol-gel reaction followed by high pH reaction) not only produced mesoporous materials but also provided controllability of the pore size. In particular, mesoporous structures with pore sizes as large as those of MCF were successfully fabricated by the two-step reaction without using organic swelling agents. As expected, when xylene was added as a swelling agent, the pore size increased with the xylene/copolymer weight ratio. (C) 2003 Elsevier Science (USA). All rights reserved.This work has been supported partially by grants from
the Brain Korea 21 and IMT-2000 Projects. The authors
thank BASF for their kind donation of the Pluronic P123
block copolymer. The Korea Basic Science Institute is also
acknowledged for allowing us to use TEM (EM912, Carl
Zeiss)
The Development of Nanostructured TiO2 Sol-Gel Derived Coatings – the Influence of Substrate Preparation Method and Post Treatment of Coatings
No full textThe analysis of literature data and experimental results obtained by the Author of the report clearly showed that further researches shall be devoted to the surface preparation method and characterization of the substrate obtained to check the dependency of morphological features whether they are characteristics of sol or substrates
Preparation and characterization of suitable insulating and transparent conducting thin films for thin film electroluminescent devices by sol-gel process
No full textThin film electroluminescent (TFEL) displays are attractive because they are light, have low power consumption, wide viewing angle and long lifetime, are extremely rugged and can be used in hostile environments. Recently, there has been a renewed interest in thin film electroluminescent devices because of their promising application to head mounted displays for use in automobiles, aircraft, microsurgery and virtual reality applications. Both conventional and inverted thin film electroluminescent device structures consist of insulating film, transparent conducting film and luminescent layer. In a thin film electroluminescent device, the luminescent layer is sandwiched between two insulating layers. Electrodes outside both insulating layers are used to apply an electric field, with one electrode being transparent.
These thin films are found to be sensitive to preparation conditions and can be prepared by a variety of methods, such as, magnetron sputtering, chemical vapour deposition, reactive electron beam evaporation, reactive thermal deposition, spray pyrolysis, laser ablation and more recently by sol-gel process. Nowadays, the sol-gel process is a wellaccepted technology for the preparation of thin films, monoliths, fibers and monosized powders. Compared to conventional thin film forming processes such as CVD, evaporation or sputtering, sol-gel film formation requires considerably less equipment and is potentially less expensive; however the most important advantage of sol-gel processing over conventional coating methods is the ability to control precisely the microstructure of the deposited film, i.e., the pore volume, pore size and surface area.
The sol-gel process is a method where the substrate to be coated is dipped into a liquid solution containing the active material. When the substrate is removed from the solution a thin layer remains. On exposure to the atmosphere a hydrolysis reaction takes place which solidifies the liquid film.
In this work, all the thin films have been prepared by using sol-gel process. Insulating films of titanium dioxide and tantalum oxide were prepared from titanium and tantalum alkoxides respectively and their characteristics have been investigated. The most important requirements for the insulating layers are high dielectric constant and high electric field strength. The dielectric constants of the films were calculated from the maximum capacitance of the Al/film/Si structure. The maximum dielectric constants for Ti02 and Ta20 5 films were approximately 50 and 82 respectively annealed at 700°C in oxygen. These results suggest that the Ti02 and Ta2Os thin film can be used as a high dielectric constant insulating layer in thin film electroluminescent devices.
Highly conductive and transparent aluminum-doped zinc oxide thin films have been prepared from the solution of zinc acetate and aluminum nitrate in ethanol by the sol-gel process. The effect of changing the aluminum-to-zinc ratio from 0 to 5 at. % and annealing temperature from 0 to 700°C in air, oxygen and nitrogen has been investigated. The resistivities of thin films were measured as a function of annealing temperature and also as a function of aluminum dopant concentration in the solution. As-deposited films have high resistivity and high optical transmission. Annealing of the as-deposited films in atmosphere leads to a substantial reduction in resistivity. The films have a minimum value of resistivity of 1.3xl0'4 Q-cm for 0.8 at. % aluminum-doped zinc oxide annealed at 500°C in nitrogen and a maximum transmission of about 88% when deposited on glass substrates. X-ray diffraction measurements employing CuKa radiation were performed to determine the crystallinity of the ZnO:Al films which showed that the films were polycrystalline with a hexagonal structure when annealed at higher temperatures in air, oxygen and nitrogen.
Transparent conductive indium tin oxide (ITO) thin films have been prepared by a solgel
process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0-20 % by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400°C. The electrical, optical and structural properties of ITO thin films were investigated. The electrical resistivity was measured by using four-point probe method. The ITO thin films containing 10 wt.% Sn showed the minimum resistivity of p = 8.0xl0'4 Q-cm annealed at 500°C in nitrogen. The films have an optical transparency up to 89% at 900 nm. X-ray diffraction measurements employing CuKa radiation were performed to determine the crystallinity of the ITO films which showed that the ITO films were polycrystalline with a cubic bixbyite structure annealed in air, oxygen and nitrogen.
Aluminum doped zinc oxide thin films have been deposited on titanium dioxide and
tantalum oxide films on glass by sol-gel process. The resistivity of ZnO:Al thin films
deposited on titanium dioxide and tantalum oxide films on glass have a minimum value
of 2.5xl0'3 Q-cm and 9.6xl0'4 Q-cm respectively annealed at 500°C in nitrogen. ZnO:Al
thin films deposited on titanium dioxide film on glass have a higher resistivity than that
deposited on glass. This increase in resistivity on titanium dioxide film is due to the
diffusion of titanium into the zinc oxide layer.
Indium tin oxide thin films have been deposited on titanium dioxide and tantalum oxide
films on glass for thin film electroluminescent devices. The resistivity of ITO films
deposited on titanium dioxide and tantalum oxide films has a minimum value of 9.5x1 O'4
Q-cm and 9.0x10'4 Q-cm respectively annealed at 500°C in nitrogen which are as low as
the resistivity of ITO films deposited on glass. This combination of transparent conductive ITO thin films and titanium dioxide or tantalum oxide insulating layer can be
used for thin film electroluminescent devices
Unsupervised classification of iron ores based on elemental and isotopic signatures from atomic and molecular emissions of laser-induced plasma
No full textBackground: Iron ore classification by grade and origin is critical for quality assurance in steel manufacturing. However, traditional analytical methods can be time-consuming and may not provide comprehensive information for accurate classification. Results: The present study introduces a novel classification approach utilizing laser-induced breakdown spectroscopy (LIBS) to simultaneously discriminate iron ore grades (fine, lump, and concentrate) and origins (Australia, Brazil, and South Africa), without necessitating prior knowledge of the samples. A key aspect of this approach is to leverage multiple spectral features from laser-induced plasma: (i) atomic lines representing elemental composition, and (ii) molecular bands reflecting isotopic signatures. Based on this comprehensive spectral data, principal component analysis (PCA) was employed to visualize the correlations among the datasets, thereby illustrating how elemental composition and isotopic abundance correlate with grades and origins. Subsequently, the k-means clustering algorithm was utilized as an unsupervised classifier, eliminating the need for previously labeled training data. Consequently, the present approach could achieve an accuracy exceeding 94 % in determining the grade and origin of ores. Significance: This study successfully established the rapid and versatile classification method for unknown iron ores, offering significant benefits for various industrial applications.
Deep Reinforcement Learning in Continuous Action Spaces: a Case Study in the Game of Simulated Curling
No full textMany real-world applications of reinforcement learning require an agent to select optimal actions from continuous spaces. Recently, deep neural networks have successfully been applied to games with discrete actions spaces. However, deep neural networks for discrete actions are not suitable for devising strategies for games where a very small change in an action can dramatically affect the outcome. In this paper, we present a new selfplay reinforcement learning framework which equips a continuous search algorithm which enables to search in continuous action spaces with a kernel regression method. Without any handcrafted features, our network is trained by supervised learning followed by self-play reinforcement learning with a high-fidelity simulator for the Olympic sport of curling. The program trained under our framework outperforms existing programs equipped with several hand-crafted features and won an international digital curling competition
NOVEL MUTANT MICROORGANISM FOR PRODUCING SUCCINIC ACID AND METHOD FOR PREPARING SUCCINIC ACID USING SAME
No full textFigures 1–6 in Occurrence status of the fall armyworm (Lepidoptera: Noctuidae) in South Korea
No full textFigures 1–6. Three species of Spodoptera moths. 1) Funnel trap baited with pheromone for fall armyworm. 2–3) Spodoptera frugiperda (J.E. Smith) male captured in surveillance traps and genitalia. 4) Spodoptera frugiperda (J.E. Smith), male. 5) Spodoptera exigua (Hübner), male. 6) Spodoptera litura (Fabricius), male.Published as part of Suh, Soo-Jung, Choi, Deuk-Soo, Sol-moon & Na, 2021, Occurrence status of the fall armyworm (Lepidoptera: Noctuidae) in South Korea, pp. 1-5 in Insecta Mundi 2021 (850) on page 3, DOI: 10.5281/zenodo.504150
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