scholarly journals Sola-gēla pārklājums uz emaljēta leģētā tērauda

2018 ◽  
Vol 35 ◽  
pp. 202-215
Author(s):  
Ilona Pavlovska ◽  
Gundars Mežinskis ◽  
Laimons-Paulis Bīdermanis
Keyword(s):  
Enamel Coating ◽  
Sol Gel ◽  
Thermal Characteristics ◽  
Chemical Properties ◽  
Solar Collectors ◽  
Parabolic Trough ◽  
Solid State Physics ◽  
Steel Pipes ◽  
Long Time ◽  
New Material

Darbā aprakstītas jauna materiāla un tehnoloģijas izstrādes stadijas saules enerģijas kolektoriem. Augstas jaudas saules enerģijas kolektora (AJSEK) cauruļveida materiālam jāspēj ilgstoši izturēt augstas temperatūras, neizmainot savu mikrostruktūru un nezaudējot savus sākotnējos siltumtehniskos raksturlielumus. RTU Silikātu materiālu institūta zinātnieki sadarbībā  ar LU Cietvielu fizikas institūta speciālistu izstrādājuši tehnoloģiju, kas ļauj iegūt AJSEK saules enerģiju uztverošu materiālu un spēj izturēt 600 °C temperatūru vismaz 250 dienas. Šī materiāla pamatā ir nerūsējošā tērauda cauruļveida iz- strādājums, kuram uzklāts stiklkristālisks emaljas pārklājums. Ilgstošu augsttemperatūras izturību nodrošina ne vien emaljas pārklājuma fritei pievienotās specifiskās piedevas, bet arī emaljai uzklātais sola-gēla nanodaļiņu pārklājums.Sol-gel coating on enamelled alloy steelThe stages of development of a new material and a technology for solar  collectors are described. Pipes for parabolic-trough solar collectors (PTSC) must be able to withstand high temperatures for a long time without changing their microstructure and losing their original thermal characteristics. The scientists from the Institute of Silicate Materials (Riga Technical University) together with a specialist from the Institute of Solid State Physics (University of Latvia) have developed a technology that allows the production of PTSC solar-absorbing materials capable of withstanding 600 °C temperatures for at least 250 days. This material is based on glass-crystalline enamel coating on tubular stainless steel pipes. The high-temperature resistance was ensured not only by specific additives added to the frit of enamel coating, but also by a nanosized sol-gel coating over the enamel.Keywords – enamel coatings for steel, sol-gel coatings, thermal properties, chemical properties, microhardness

Solar Energy Absorbing Materials that are Capable of Withstanding Long-Term Exposure at 600 °C: Research Strategy

2018 ◽  
Vol 788 ◽  
pp. 126-134
Author(s):  
Ilona Pavlovska ◽  
Gundars Mežinskis ◽  
Laimons Paulis Bīdermanis
Keyword(s):  
Solar Energy ◽  
Sol Gel ◽  
Research Strategy ◽  
Steel Pipes ◽  
Long Time ◽  
New Material ◽  
Absorbing Material ◽  
Energy Absorbing ◽  
Corrosive Environments

Pipes for parabolic-trough solar energy collectors (PTSC) must be able to operate and withstand high temperatures in corrosive environments for a long time without changing its microstructure and losing its original properties. The stages of development of a new material and technology for solar energy collectors that allows the production of a PTSC solar energy-absorbing material that is capable of withstanding temperatures ≥ 600 °C for at least 250 days are described. This material is a glass-crystalline enamel coating that is adhered to tubular stainless steel pipes. Such enamel coatings have high coefficients of thermal expansion (CTE) that are similar to the metal surface. These matching CTEs allow the enamel coatings to resist flaking during the heating at 900 °C. The high-temperature resistance of the developed coating was ensured not only by specific additives added to the frit of the coating but also by an additional nanosized sol-gel coating over the enamelled metal substrate.

Cu Doped TiO2: Visible Light Assisted Photocatalytic Antimicrobial Activity and High Temperature Anatase Stability

2018 ◽  
Author(s):  
Snehamol Mathew ◽  
Priyanka Ganguly ◽  
Stephen Rhatigan ◽  
Vignesh Kumaravel ◽  
Ciara Byrne ◽  
...  
Keyword(s):  
Visible Light ◽  
Visible Light Irradiation ◽  
Density Functional ◽  
Anatase Phase ◽  
Sol Gel ◽  
Chemical Properties ◽  
Light Irradiation ◽  
Health Concern ◽  
Bacterial Inactivation ◽  
X Ray

Indoor surface contamination by microbes is a major public health concern. A damp environment is one potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using semiconductors like titania (TiO<sub>2</sub>) can effectively curb this growing threat.<b> </b>Metal-doped titania in anatase phase has been proved as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu) doped TiO<sub>2 </sub>(Cu-TiO<sub>2</sub>) was evaluated against <i>Escherichia coli</i> (Gram-negative) and <i>Staphylococcus aureus</i> (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO<sub>2 </sub>was carried out <i>via</i> sol-gel technique. Cu-TiO<sub>2</sub> further calcined at various temperatures (in the range of 500 °C – 700 °C) to evaluate the thermal stability of TiO<sub>2</sub> anatase phase. The physico-chemical properties of the samples were characterised through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV-visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO<sub>2</sub> was maintained well, up to 650 °C, by the Cu dopant. UV-DRS results suggested that the visible light absorption property of Cu-TiO<sub>2 </sub>was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasises the introduction of Cu<sup>+</sup> and Cu<sup>2+</sup> ions by replacing Ti<sup>4+</sup> ions in the TiO<sub>2</sub> lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9%) was attained in 30 mins of visible light irradiation by Cu-TiO<sub>2</sub>.

Preparation and properties of a long time durable superhydrophilic titanium dioxide film obtained by a sol-gel process

2017 ◽  
Vol 59 (1) ◽  
pp. 81-85
Author(s):  
Jianjun Zhang ◽  
Hao Zeng ◽  
Chun Liu ◽  
Chao Li ◽  
Sude Ma ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Sol Gel ◽  
Titanium Dioxide Film ◽  
Sol Gel Process ◽  
Long Time ◽  
Dioxide Film

A comprehensive review of parabolic trough solar collectors equipped with turbulators and numerical evaluation of hydrothermal performance of a novel model

2021 ◽  
Vol 45 ◽  
pp. 101103 ◽  
Author(s):  
Muhammad Shahzad Nazir ◽  
Amin Shahsavar ◽  
Masoud Afrand ◽  
Müslüm Arıcı ◽  
Sandro Nižetić ◽  
...  
Keyword(s):  
Numerical Evaluation ◽  
Solar Collectors ◽  
Parabolic Trough ◽  
Comprehensive Review ◽  
Novel Model

scholarly journals Kittel’s Brief Comments Endorsing an Alternative View on Barium Titanate

2021 ◽  
Vol 6 (1) ◽  
pp. 10
Author(s):  
Akira Kojima
Keyword(s):  
State Physics ◽  
Barium Titanate ◽  
Cell Structure ◽  
Experimental Studies ◽  
Alternative View ◽  
Solid State Physics ◽  
Text Book ◽  
Long Time ◽  
Unit Cell Structure ◽  
Displacive Type

Charles Kittel has written a masterpiece book, “Introduction to Solid State Physics” (ISSP). He mentions in the chapter on ferroelectrics in detail that barium titanate is the typical displacive-type ferroelectric compound where the Ti4+ displacement develops a dipole moment, which has made a deep impression in our mind. The author’s group, however, has arrived at an alternative viewpoint on the unit cell structure of barium titanate based on their exhaustive experimental studies. Accordingly, the author sent his relevant papers in 2006 and 2007 to Kittel. He endorsed the results frankly with reminiscence. He mentioned revising the ferroelectric chapter of ISSP according the author’s suggestions. It appears to be admissible to publish details now after Kittel has passed away. A long time misunderstanding of the phase transition in barium titanate is due to the text book knowledge of ISSP.

scholarly journals Development of Novel Oral Formulations of Disulfide Antioxidants Based on Porous Silica for Controlled Release of the Drugs

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 963
Author(s):  
Ekaterina S. Dolinina ◽  
Elena V. Parfenyuk
Keyword(s):  
Antioxidant Activity ◽  
Surface Chemistry ◽  
Sol Gel ◽  
Porous Silica ◽  
The Body ◽  
Oral Drug ◽  
Therapeutic Concentration ◽  
Release Process ◽  
Zero Order Kinetics ◽  
Long Time

Powerful antioxidant α-lipoic acid (LA) exhibits limited therapeutic efficiency due to its pharmacokinetic properties. Therefore, the purpose of this work was to evaluate the ability of silica-based composites of LA as well as its amide (lipoamide, LM), as new oral drug formulations, to control their release and maintain their therapeutic concentration and antioxidant activity in the body over a long time. The composites synthesized at different sol–gel synthesis pH and based on silica matrixes with various surface chemistry were investigated. The release behavior of the composites in media mimicking pH of digestive fluids (pH 1.6, 6.8, and 7.4) was revealed. The effects of chemical structure of the antioxidants, synthesis pH, surface chemistry of the silica matrixes in the composites as well as the pH of release medium on kinetic parameters of the drug release and mechanisms of the process were discussed. The comparative analysis of the obtained data allowed the determination of the most promising composites. Using these composites, modeling of the release process of the antioxidants in accordance with transit conditions of the drugs in stomach, proximal, and distal parts of small intestine and colon was carried out. The composites exhibited the release close to the zero order kinetics and maintained the therapeutic concentration of the drugs and antioxidant effect in all parts of the intestine for up to 24 h. The obtained results showed that encapsulation of LA and LM in the silica matrixes is a promising way to improve their bioavailability and antioxidant activity.

An Optical Scanner for Testing Parabolic Trough Solar Collectors

1982 ◽  
Vol 11 (1) ◽  
pp. 18-22
Author(s):  
B. K. Roy ◽  
P. N. Puntambekar ◽  
D. Sen
Keyword(s):  
Solar Collectors ◽  
Parabolic Trough ◽  
Optical Scanner

scholarly journals Green Synthesis of N/Zr Co-Doped TiO2 for Photocatalytic Degradation of p-Nitrophenol in Wastewater

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 235
Author(s):  
Hayette Benkhennouche-Bouchene ◽  
Julien G. Mahy ◽  
Cédric Wolfs ◽  
Bénédicte Vertruyen ◽  
Dirk Poelman ◽  
...  
Keyword(s):  
Visible Light ◽  
Tio2 Nanoparticles ◽  
Sol Gel ◽  
Visible Region ◽  
Chemical Properties ◽  
Pure Tio2 ◽  
Molar Ratio ◽  
Xps Spectra ◽  
Doped Tio2 ◽  
Co Doped

TiO2 prepared by a green aqueous sol–gel peptization process is co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. Two nitrogen precursors are used: urea and triethylamine; zirconium (IV) tert-butoxide is added as a source of zirconia. The N/Ti molar ratio is fixed regardless of the chosen nitrogen precursor while the quantity of zirconia is set to 0.7, 1.4, 2, or 2.8 mol%. The performance and physico-chemical properties of these materials are compared with the commercial Evonik P25 photocatalyst. For all doped and co-doped samples, TiO2 nanoparticles of 4 to 8 nm of size are formed of anatase-brookite phases, with a specific surface area between 125 and 280 m2 g−1 vs. 50 m2 g−1 for the commercial P25 photocatalyst. X-ray photoelectron (XPS) measurements show that nitrogen is incorporated into the TiO2 materials through Ti-O-N bonds allowing light absorption in the visible region. The XPS spectra of the Zr-(co)doped powders show the presence of TiO2-ZrO2 mixed oxide materials. Under visible light, the best co-doped sample gives a degradation of p-nitrophenol (PNP) equal to 70% instead of 25% with pure TiO2 and 10% with P25 under the same conditions. Similarly, the photocatalytic activity improved under UV/visible reaching 95% with the best sample compared to 50% with pure TiO2. This study suggests that N/Zr co-doped TiO2 nanoparticles can be produced in a safe and energy-efficient way while being markedly more active than state-of-the-art photocatalytic materials under visible light.

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