<p>    </p> <p>Electrical steels are one type of soft magnetic material. They are based on Fe-Si alloys and are widely used for magnetic cores in transformers and electric motors. It is well known that Fe- 6.5Si wt% is the most efficient composition; however, at such a high silicon concentration (6.5wt.% = 12.1 at.% Si in Fe), the poor workability of the alloy makes it unacceptable for industrial production via conventional sheet steel rolling processes. This problem was approached in two different ways. First, a machining-based approach that suppresses the mechanisms that lead to cracking during conventional rolling was implemented for processing of thin metal strips. Two related machining-based sheet production technologies called free machining (FM), and hybrid cutting extrusion (HCE) were used to produce strips of high resistivity electrical steel. The maximum strip width achieved was 50 mm, and it was produced with a combination of FM and light rolling with a surface roughness comparable to cold-rolled sheet surfaces. Second, a new experimental alloy Fe-4Si-4Cr wt% was developed with improved magnetic properties compared to ~ Fe-3.2Si wt% and outstanding workability. Results report that the new experimental alloy has an electrical resistivity of 85 ± 3 𝜇Ω ∙ 𝑐𝑚 which is higher than Fe-6.5%Si. Also, the results on the Fe-4Si-4Cr workability show that this new alloy can withstand 75% cold-rolled reduction. The magnetic properties characterization was done via standard stacked toroid testing, and results show that Fe-4Si-4Cr experimental alloy exhibits excellent magnetic performance with a reduction in core losses of 33% at 400 Hz compared to commercial alloys with ~ Fe-3.2Si wt%. Recrystallization kinetics and texture evolution in the experimental alloy were evaluated for traditionally rolled and machining-based samples. Results were used to construct annealing maps. These maps represent the stages of the annealing process for a range of temperature versus time conditions, i.e., the annealing maps are a graphical summary showing the different stages of the annealing process for the Fe-4Si-4Cr experimental alloy in the two conditions. Despite the significant differences in the deformation texture of the two conditions, the recrystallization kinetics were similar. Finally, the two conditions retained the as-deformed texture in the intermediate annealing but to a lesser degree after completing a full anneal. In the case of the rolled sample, it is possible to trace the original texture fibers (γ-fiber, the partial α-fiber, and the θ -fiber) in the fully annealed data, but the texture intensity is just 2.5 mrd. On the other hand, the texture of the fully annealed HCE sample changes as compared to the as-deformed condition, located close to (110)[112] with a surprisingly strong peak of ~ 25 mrd. </p>

With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental CO2 . Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2 , CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2 . Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant changes were observed in the binding geometry of the adsorbed complexes on the Al/Fe mineral compared to single phase α-FeOOH, AlOOH, and FeOOH surfaces. ATR-FTIR results combined with vibrational frequency (DFT) calculations suggested the formation of multiple phosphate surface complexes via a variety of configurations such as inner-sphere/outer-sphere bidentate, monodentate depending on the solution pH and the Al mol% substituted into the Fe-oxyhydroxide. Studies investigated the adsorption of CO2 on FerriFh and compared those results to CO2 on ferrihydrite. The CO2 pressures used in these particular studies ranged from 1 to 57.8 bars. It is found that citrate bound species, resulting from the synthesis conditions used to make FerriFh, blocked surface sites for the formation of carbonate and bicarbonate species on the magnetic FerriFh and ferrihydrite oxyhydroxide minerals upon CO2 (gas) exposure. A bicarbonate or bent-CO2 like species (~1220 cm-1) formed at lower CO2 pressures (≤ 3.5 bars) but was absent at the higher pressures. Additional studies investigated the adsorption of various phospholipid molecules on pyrite, and iron sulfide with FeS2 stoichiometry. These studies were focused on suppressing the oxidative decomposition of pyrite to sulfuric acid, the root cause of AMD. Batch and column studies were employed to investigate the ability of phospholipids to reduce AMD over an extended period of time (up to 3 years). In studies that used actual coal mining refuse, which contained significant amount of pyrite, it was shown that the rate of acid production from pyrite decomposition could be reduced by as much as 70% due to the presence of surface bound phospholipid. Assembly of the phospholipid into a bilayer motif on the sulfide surface was hypothesized to form a hydrophobic barrier that kept dissolved O2 and bacteria from facilitating the oxidation of FeS2. Column experiments showed that when water at pH 7 was flowed over the coal mining waste, the effluent had a pH close to 3. In contrast when water at pH 7 was flowed over the pyrite containing waste, which was pretreated with lipid, the effluent had a pH closer to 7, and the total amount of Fe (Fe2+/Fe3+) and SO42- in the effluent waters was also reduced relative to the untreated pyrite containing waste circumstance. These studies showed that the application of phospholipid to pyrite containing coal mining waste could potentially be an environmentally friendly remediation technique. / Chemistry

Ever since the discovery of the giant magnetocaloric effect (GMCE) in the Gd5(Si,Ge)4 phases, magnetic cooling has gained significant interest because of its potential environmental benefits and increased efficiency compared to vapour-based refrigeration. This current work is focused on one of the most promising GMCE systems, the (Mn,Fe)2(Si,P) materials. An alternative synthetic route has been explored for the Mn2-xFexSi0.5P0.5 and MnFeSiyP1-y series which is capable of producing phase-pure samples. The new preparation technique eliminates common impurities that arise from established methods thus providing a more accurate description of the structural and physical properties. The low cost, non-toxicity, abundance of starting materials and easy tuning of the magnetic properties make these materials desirable for potential applications. Phase-pure magnetocaloric Mn2-xFexSi0.5P0.5 materials (x = 0.6, 0.7, 0.8, 0.9) were synthesized through arc-melting followed by high temperature sintering. Structural features of samples with x = 0.6, 0.9 were studied through temperature dependent synchrotron powder x-ray diffraction. Magnetic measurements established the Curie temperature, thermal hysteresis, and magnetic entropy change of this system. According to the diffraction and magnetization data, all of the samples were shown to have a first-order magnetostructural transition which becomes less pronounced for Mn-richer samples. The MnFeSixP1-x phases (x = 0.30, 0.35, 0.40, 0.48, 0.52, 0.54, 0.56) have also been synthesized by the same method. For the first time, single crystals of x = 0.30, 0.40 were successfully grown. Variable temperature x-ray diffraction experiments for x = 0.30 were completed which show the structural changes across the phase transition. This structural data was complemented with magnetization data providing Curie temperatures and thermal hysteresis. / Thesis / Master of Science (MSc)

El presente trabajo de investigación analiza la problemática que surge cuando una entidad no cumple con la regularización de una contratación directa por situación de emergencia. Siendo un supuesto excepcional contenido en la normativa de contrataciones del Estado que posibilita a la entidad a requerir a los proveedores de manera inmediata la ejecución de las prestaciones sin sujetarse a los requisitos formales de la norma, con la condición legal que posteriormente se regularice la formalización de la documentación para la aprobación de la contratación directa, ello a fin de obtener en forma oportuna los bienes o servicios necesarios en una situación de emergencia. Sin embargo, si luego de la ejecución de las prestaciones por parte del proveedor, la entidad no realiza la regularización de los documentos para la formalización de la contratación, existen implicancias relacionadas al cumplimiento del pago en favor de los proveedores. Efectuada la argumentación jurídica constitucional y legisprudencial, se determina que si bien no resulta procedente que las entidades realicen un pago bajo el marco de la normativa de contrataciones del Estado, teniendo en cuenta que no se cumple con el requisito legal de la regularización de la formalización de la contratación, entre otros documentos, con la suscripción contractual; por lo cual, no se cuenta con una relación jurídica válida que sustente el referido pago, habiéndose configurado en dichos casos una contratación irregular o al margen de lo establecido en la referida normativa; sin embargo, procede el reconocimiento de las prestaciones ejecutadas teniendo en cuenta la figura jurídica del enriquecimiento sin causa en favor del proveedor que de buena fe realiza la entrega de bienes o ejecuta servicios en favor de la entidad, previa verificación del cumplimiento de requisitos para su configuración. Asimismo, se analizan los riesgos legales respecto a la procedencia de efectuar el reconocimiento económico directo por las prestaciones ejecutadas, evidenciando que resulta una alternativa eficiente y dentro del marco legal a ser aplicada por las entidades, en lugar de esperar que los proveedores acudan a la vía judicial a reclamar el reconocimiento de dicho adeudo por enriquecimiento sin causa. Finalmente, se propone el procedimiento para el referido reconocimiento en forma directa, atendiendo a los criterios establecidos por el OSCE, el cual puede considerarse como una normativa interna por las entidades que optan por esta vía.

El tema de la presente investigación son los ejemplares de Trinidad trifacial producidos en las regiones andinas del virreinato peruano durante los siglos XVII y XVIII, aunque las piezas en cuestión cuentan solo con fechas aproximadas pues han sufrido de una larga disociación de sus contextos originales. Se examinan, en primer lugar, los precedentes de la iconografía en Europa: sus orígenes paganos, su apropiación como motivo decorativo durante la edad media, y su difusión como motivo trinitario durante el renacimiento italiano. Temas tangentes que se tratan en esta fase son también la reiterada asociación errónea de esta iconografía con herejías, presente tanto en fuentes medievales como en autores contemporáneos, y la presencia paralela del motivo trifacial en alegorías y libros de emblemas. Em segundo lugar, con el fin de contextualizar el desarrollo de estas piezas en el nuevo mundo, así como las interpretaciones que de estas se han hecho, se toman en cuenta los siguientes factores: Sus fuentes grabadas, la prohibición de esta iconografía por Roma en el s. XVIII, y la noción de “trinidades precolombinas” en el mundo andino presente en muchas crónicas. Un tema tangente que se enfatiza es la relación frecuente de la Trinidad trifacial con san Agustín, visible en muchos ejemplares. Tras esto, se realiza un acercamiento y análisis puntual de los ejemplares. Estos se incluyen ordenados de acuerdo con sus variantes iconográficas, tanto como a lo que se considera su progresiva transformación en un motivo devocional popular. Se examina el caso del Señor del Gran Poder de La Paz, como una devoción desarrollada alrededor de una Trinidad trifacial en el mundo aymara durante la modernidad, cuyos aspectos distintivos se desarrollan precisamente en función de sus tres rostros. Por último, se hace un breve estudio de la presencia de este motivo en un caso reciente de arte popular, así como en las obras de artistas contemporáneos peruanos y extranjeros, los cuales expresan cómo esta iconografía continúa apelando a la sensibilidad actual bajo nuevas interpretaciones. / Tesis

El presente caso se inicia a raíz de la demanda presentada por la Superintendencia de Bienes Nacionales (SBN) contra todos los titulares registrales del Lote 18-B sito en la Urbanización Los Arces de Monterrico, del distrito de Surco, por la que solicitó se declare la nulidad de los contratos de compraventa del referido predio, por ser su objeto jurídicamente imposible, al ser tal terreno un bien de dominio público. La empresa inmobiliaria, PdT, contestó la demanda indicando que adquirió el bien a título oneroso, por escritura pública, de quien figuraba como su propietario en los Registros Públicos. Tanto en primera como en segunda instancia se declaró la nulidad de los contratos celebrados entre las personas físicas demandadas, por tener un fin ilícito, al ser el objetivo común de los contratantes el introducir en el tráfico mercantil, de forma ilícita (a través de la falsificación de documentos administrativos), un bien de dominio público. En relación a la mercantil, PdT, tanto en primera como en segunda instancia se desestimó la demanda por considerar que no se había desvirtuado su buena fe registral. La Sala Civil Permanente de la Corte Suprema de Justicia de la República revocó dicho fallo y reformandoló declaró fundada la demanda de nulidad de acto jurídico contra PdT, pues consideró que de los documentos archivados en los Registros Públicos, PdT podía saber que el bien objeto de compraventa se trataba de un bien estatal de dominio público que había sido introducido de manera ilícita en el tráfico mercantil; por lo que declaró que su contrato de compraventa era nulo por tener un fin ilícito. / This case begins as a result of the presentation by the Superintendence of National Assets (SBN) of a lawsuit against all the registered owners of Lote 18- B located in District of Surco, for which requested the annulment of the sales contracts for the aforementioned property, because its object was legally impossible, as such land was a public domain asset. The real estate company, PdT, answered the lawsuit indicating that it acquired the property for consideration, by public deed, from the person who appeared as its owner in the Property Registry. Both in the first and second instance, the nullity of the contracts entered into between the natural persons sued is declared for having an illicit purpose, as the common objective of the contracting parties is to enter into commercial traffic in an illicit manner (through the falsification of administrative documents) a public domain asset. In relation to the company, PdT, both in the first and second instance, dismissed the claim on the grounds that its good faith registration had not been distorted. However, the Supreme Court revoked said ruling, considering that from the documents filed in the Public Registries, PdT could know that the property object of sale was a state property in the public domain that had been illegally introduced into traffic. commercial, for which he declared that his purchase and sale contract was void for having an illicit purpose.

<p>Postojanje ugljeničnih nanocevi (UNC), kao jedne od brojnih alotropskih modifikacija ugljenika, zabeleženo je jo&scaron; pre vi&scaron;e od pola veka. Međutim, do prave eksplozije<br />interesovanja za ovu vrstu nanomaterijala je do&scaron;lo tek 1991. godine kada ih je &quot;ponovo&quot; otkrio japanski naučnik S. Iijima. Od tada, zbog svojih izuzetnih fizičko-hemijskih osobina, UNC počinju da privlače pažnju naučne javnosti i spajaju istraživače iz različitih oblasti sa zajedničkim imeniteljem - nanotehnologija. Otkriće UNC je u znatnoj meri omogućilo razvoj visoke tehnologije u oblastima kao &scaron;to su elektronika, optika, kompozitni materijali, kataliza, za&scaron;tita životne sredine, itd. Danas, primena nanocevi sve vi&scaron;e doprinosi lak&scaron;oj implementaciji principa održivog razvoja u pomenute oblasti. Kataliza je polje od dvostrukog interesa, jer je jedan od načina dobijanja UNC upravo katalitički, a osim toga i same cevi su interesantne kao nosač novog katalizatora.<br />Istraživanje čiji su rezultati prikazani u okviru ove doktorske disertacije je obuhvatilo vi&scaron;e oblasti proučavanja UNC, počev&scaron;i od razvoja metode za njihovu sintezu, preko preči&scaron;ćavanja i funkcionalizacije finalnog proizvoda, pa do primene nanocevi u dva procesa od značaja za oblast za&scaron;tite životne sredine.</p><p>Razvoj katalitičke metode sinteze UNC započet je primenom vertikalnog cevnog kvarcnog reaktora, iz CO i CH4 kao izvora ugljenika, pri čemu su u reakciji testirani<br />monometalni katalizatori na bazi Fe, Co i Ni na Al2O3 kao nosaču (I serija katalizatora). Rezultati ovih preliminarnih eksperimenata su pokazali malu aktivnost I serije monometalnih katalizatora, &scaron;to se može pripisati, kako neadekvatnoj hidrodinamici reaktora i lo&scaron;e odabranim reakcionim parametrima, tako i neodgovarajućoj veličini katalitičkih čestica i načina njihovog pakovanja u vertikalnom<br />reaktoru. Shodno tome, u cilju postizanja boljeg prinosa nanocevi, dalji eksperimenti sinteze izvedeni su u horizontalnom reaktoru u struji C2H4 i u prisustvu II serije<br />monometalnih katalizatora sa Al2O3 i SiO2 kao nosačima, koji se u odnosu na I seriju razlikuju po udelu aktivne faze i veličini čestica katalizatora (pra&scaron;kast oblik). Katalizatori II serije su pokazali zadovoljavajuću aktivnost u reakciji sinteze UNC, a rezultati karakterizacije dobijenih uzoraka nanocevi ukazuju na različit uticaj nosača katalizatora na morfologiju sintetisanih nanocevi. Shodno ostvarenom prinosu ugljenika, a u cilju optimizacije reakcionih parametara, katalizator na bazi Fe sa SiO2 kao nosačem je odabran kao reprezentativan za ispitivanje uticaja vremena trajanja sinteze UNC, kao i zapreminskog udela C2H4 u sme&scaron;i sa azotom, na prinos<br />nanocevi i selektivnost procesa.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Optimizacija reakcionih uslova je u daljoj fazi rada dovela do uvođenja bimetalnih katalizatora sa istim tradicionalnim nosačima &ndash; Al2O3 i SiO2. Najveći prinos ugljenika ostvaren je na katalizatorima sa Fe i Co kao aktivnom fazom, bez obzira na vrstu nosača. UNC sintetisane na pomenutim katalizatorima su karakterisane u cilju<br />ispitivanja uticaja primenjenih nosača na njihove fizičkohemijske osobine, pa je shodno tome i predložen vr&scaron;ni mehanizam njihovog rasta. Rezultati ispitivanja kvaliteta sintetisanih UNC su ukazali da primena SiO2, kao nosača katalizatora, za razliku od Al2O3, favorizuje rast UNC boljeg povr&scaron;inskog i ukupnog kvaliteta. S obzirom na raznolikost mogućnosti primene UNC, istraživanja u tom smeru zahtevaju čiste UNC, pa su shodno tome proizvodi sinteze preči&scaron;ćeni metodom tečne oksidacije. Rezultati fizičko-hemijske karakterizacije preči&scaron;ćenih UNC su ukazali na efikasnost primenjene metode sa aspekta uklanjanja prisutnog katalizatora, ali i na njen različit uticaj na strukturu, odnosno kvalitet preči&scaron;ćenih uzoraka. Kao posledica promena unutar strukture UNC, kao i različitog stepena njihove funkcionalizacije, ukupni kvalitet preči&scaron;ćenih nanocevi je, u zavisnosti od primenjenog nosača katalizatora, promenjen u odnosu na odgovarajuće nepreči&scaron;ćene uzorke.<br />Poslednjih godina se posebna pažnja poklanja nanomaterijalima koji se mogu primeniti za uklanjanje različitih polutanata iz životne sredine, kako u funkciji adsorbenata, tako i u funkciji katalizatora. U okviru ove doktorske disertacije obuhvaćena je primena UNC kao adsorbenta za uklanjanje insekticida tiametoksama iz vode, kao i njihova primena kao nosača katalizatora u reakciji<br />denitracije vode. Rezultati eksperimenata adsorpcije su pokazali da UNC, prethodno tretirane u ccHNO3, predstavljaju dobar adsorbent za uklanjanje insekticida tiametoksama iz vodenog rastvora. Odabir procesnih parametara za proučavanje kinetike adsorpcije, adsorpcione ravnoteže, kao i termodinamike procesa izvr&scaron;en je primenom frakcionog faktorskog dizajna na dva nivoa, 5 1 V 2 , a dobijeni rezultati su ukazali da je pomenuti proces adsorpcije spontan i kontrolisan uglavnom unutra&scaron;njom difuzijom molekula insekticida u mezopore uzorka UNC. Performanse katalizatora sa UNC kao nosačem su testirane u reakciji katalitičke denitracije, pri čemu su dobijeni rezultati pokazali da se novoformirani katalizator karakteri&scaron;e zadovoljavajućom disperzno&scaron;ću sa udelombimetalnih Pd-Cu nanočestica koje omogućavaju 60% konverzije nitratnog jona.</p> / <p style="text-align: justify;">The existance of carbon nanotubes (CNTs), as one of the carbon allotropes, was noted over half century ago. However, the true interest for these nanomaterials appeared at 1991, when they were &quot;redescovered&quot; by Japanese scientist S. Iijima. Since then, due to their unique physico-chemical properties, CNTs begin to attract attention of the scientific community and to gather researchers from different areas within the common field of interest &ndash; nanotechnology. The CNTs discovery substantially enabled the high technology development in the fields such as electronics, optics, composite materials, catalysis, environmental protection, etc. Nowdays, the application of nanotubes is increasingly contributing to easier implementation of sustainable development principles in the above mentioned areas. Catalysis is the field of double interest &ndash; one of the CNTs synthesis method is catalytical, and the nanotubes can also be used as the support of the new catalyst.<br />The research, which results are shown within this PhD Thesis, includes few different CNTs research fields, starting from the synthesis method development, over the purification and functionalization of the final product, to the application of<br />nanotubes in two processes of significance for the field of environmental protection.<br />The development of the CNTs catalytic synthesis method was started by the use of vertical quartz tube reactor, in the flow of CO and CH4 as the carbon source, and in the presence of monometallic catalysts based on Fe, Co and Ni at Al2O3 as the support (the first series of catalysts). The results of these preliminary experiments have shown the low activity of these monometallic catalysts, which can be attributed to the inadequate reactor hydrodynamics and selected reaction parameters, as well as the inadequate size of the catalytic particles and the type of their packing in the vertical reactor. Consequently, in order to achieve the higher nanotubes yield, further synthesis experiments were carried out in a horizontal reactor in the flow of C2H4 as the carbon source, and in the presence of the second series of monometallic catalysts with Al2O3 and SiO2 as the supports. The catalysts of the second series have shown satisfactory activity in the CNTs synthesis reaction, and the results of the obtained samples characterization idicate a different influence of the catalyst support on the synthesized CNTs morphology. In order to optimize the reaction parameters, Fe/SiO2 catalyst was chosen as a representative to examine the effect of the CNTs synthesis duration, as well as the volume percentage of C2H4 in the mixture with nitrogen to the CNTs yield and process selectivity. In a further phase of work, the optimization of thereaction parameters led to the introduction of the bimetallic catalysts with the same traditional supports, Al2O3 and SiO2. The highest carbon yield was achieved over Fe, Co based catalysts, regardless of the type of the catalyst support. CNTs synthesized over the above mentioned catalysts were characterized in order to study the effect of the used supports on their physico-chemical properties, and consequently the CNTs tip growth mechanism was proposed. The results of quality examination of the synthesized CNTs showed that the use of SiO2, as a catalyst support, unlike Al2O3, favors the growth of nanotubes of better surface and overall crystalline quality. In view of the diversity of possible CNTs applications, investigation in that direction requires purified CNTs and accordingly the final CNTs products were purified by liquid oxidation method. The results of physico-chemical characterization of the purified CNTs showed that the applied purification method was effective in terms of removing the present catalyst, but on the other hand it had different influence on the structure and quality of the purified samples. As a consequence of CNTs structural changes, as well as their different degree of functionalization, the overall crystalline quality of the purified nanotubes, originating from different catalyst supports, was changed in comparison to the corresponding unpurified samples. Over the past few years, special attention was focused on<br />nanomaterials that can be applied as adsorbents or catalysts for the removal of various pollutants from the environment. This PhD Thesis considers the use of CNTs, as adsorbent, for the removal of insecticide thiamethoxam from water, as well as their use as catalyst support for water denitration reaction. The results of adsorption experiments have shown that the CNTs, pretreated in ccHNO3, represent a good adsorbent for the removal of thiamethoxam from the aqueous solutions. The<br />selection of the process parameters in order to study the adsorption kinetics and equilibrium, as well as the thermodynamics of the process, was conducted using the<br />fractional factorial design at two levels, 5 1 V 2 . The obtained results showed that the adsorption process is spontaneous and controlled mainly by an internal diffusion of molecules of insecticide in the mesopores of CNTs. The performance of the catalyst with the CNTs as the support were tested in catalytic water denitration reaction, whereby the results showed that the newly formed catalyst is characterized by satisfactory dispersion of Pd-Cu bimetallic nanoparticles which enable the 60% conversion of nitrate ions.</p>

L’industrie automobile cherche constamment à augmenter la part des pièces fabriquées à partir de tôles minces en aciers plus résistants et à plus bas coût. Le parallèle entre les diagrammes de phases Fe-N et Fe-C montre qu’il est possible de développer des aciers similaires dans le système Fe-N. Les objectifs de cette étude étaient l’élaboration des aciers binaires Fe-N et le développement des structures équivalentes à celles dans les aciers au carbone. Les approches envisagées s’articulent autour de : Elaboration : la nitruration gazeuse en phase austénitique suivie de traitements d’homogénéisation ont permis de charger des tôles minces de fer pur en concentrations importantes d’azote. Une simulation de la diffusion de l’azote a été proposée. Genèse des microstructures : Le refroidissement lent de l’austénite Fe-N conduit à des structures perlitiques lamellaires et globulaires, constituées de ferrite et du nitrure non-stoechiométrique Fe4N. Une structure aciculaire particulière a été identifiée. Il s’agit de la ferrite se développant dans le nitrure Fe4N. Le refroidissement lent de la ferrite Fe-N sursaturée conduit à la précipitation des nitrures stables Fe4N et métastable Fe16N2. Des microstructures multiphasées [alpha+alpha'+gamma] ont été obtenues par des maintiens dans le domaine intercritique suivis de trempe. Le domaine intercritique a été réexaminé en utilisant le modèle des sous-réseaux. Des essais in-situ en MET ont relevé l’évolution des précipités de Fe16N2 dans la ferrite au cours du vieillissement à 85 °C. Des proportions importantes de l’austénite résiduelle ont été relevées, ce qui serait à la base du développement des aciers TRIP à l’azote / Car designers are seeking ways to increase the proportion of parts made of sheet steels of higher strength and lower cost. The parallel between the Fe-N and Fe-C phase diagrams shows that it is possible to develop similar steels in the Fe-N system. The objective of this study was to prepare binary Fe-N steels and to develop structures equivalent to those in carbon steels. Approaches to meet the objectives are considered: Preparations of Fe-N steels: gas nitriding in austenite domain followed by homogenization treatments allowed to introduce high amount of nitrogen in pure iron sheet. A simulation of the nitrogen diffusion was proposed to describe the weight increase during nitriding. Genesis of microstructures: The slow cooling of the Fe-N austenite led to lamellar and globular pearlitic structures composed of ferrite and nitrideFe4N. An acicular microstructure, which is the consequence of the precipitation of the ferrite in the nitride Fe4N, was also identified. The slow cooling of the supersaturated Fe-N ferrite led to the precipitation of the stable nitride Fe4N and the metastable nitride Fe16N2, which witnessed a rapid diffusion of nitrogen in ferrite at low temperature, comparable to that of carbon. The multiphase microstructures [alpha+alpha'+gamma] were obtained by intercritical treatments followed by quenching. The intercritical domain was reviewed using the sub-lattice model. In-situ TEM investigations have identified the precipitation of Fe16N2 nitride in the ferrite during the aging at 85 °C. High amount of the residual austenite have been identified, which would be the basis for development of TRIP nitrogen steels

In der vorliegenden Habilitationsarbeit wurden technisch-konstruktive Lösungsansätze basierend auf einem entwickelten strömungs-thermomechanischen/magneto-hydro-dynamischen Simulationsmodell zur Entwicklung/Charakterisierung eines physikalischen Prozesswirkprinzips des betrachteten Mikro- und Hochleistungs- sowie Orbital-Plasma-Schweißprozesses und dessen physikalischer Effekte entwickelt. Dabei wurden die differenten Einflussgrößen beim Plasmaschweißprozess erfasst, analysiert und ihre Wirkung auf Schweißprozessverhalten und Brennerkonstruktion charakterisiert. Die damit gewonnenen Ergebnisse wurden zur werkstofflichen, technisch-konstruktiven Entwicklung der Brennerkopfmodelle hinsichtlich der Ausführungsgeometrien des Prozessgaszuführungs- und Brennerkühlsystems genutzt. Im Rahmen des erarbeiteten thermomechanischen Simulationsmodells wurden die beim Plasma-Auftragschweißen von Verbundbauteilen auftretenden Temperaturfelder, Verformungen und Eigenspannungen vorausbestimmt, untersucht und analysiert. Mittels des erarbeiteten Simulationsmodells wurden werkstoffliche, konstruktive und fertigungstechnische Maßnahmen zur Minimierung/Beeinflussung schweißbedingter Verformungen und Eigenspannungen simulativ untersucht und bewertet. / In this work, technical and constructive solutions were developed based on simulation models (process and structural) for fluid mechanical, thermomechanical and magneto-hydrodynamic effects. The simulation process included improving and characterising the physical operating principles for micro plasma welding, high performance plasma welding and orbital plasma welding. Also, the physical effects for the above plasma welding processes were studied and analysed. From these different physical properties of the parameters for the plasma welding processes, and their effects on plasma welding process behaviour and torch design were analysed and characterised. The results were used for the development and construction of plasma welding torch models, which included material selection and geometrical design such as, process gas supply design, torch cooling system design, and other related torch designs. By developing the thermomechanical simulation model, deformations and residual stresses that were generated by heating during the plasma welding process were investigated and analysed. The developed thermomechanical model included material, structural and welding specifications such as buffering and preheating. Simulations utilizing this model were used in order to reduce the residual stresses and deformations of the welded components.

<p>Kao &scaron;to je poznato, RS-2-(4-hlor-o-toliloksi)propionska kiselina (MCPP),&nbsp;(4-hlor-2-metilfenoksi)sirćetna kiselina (MCPA) i 3,6-dihlorpiridin-2-karboksilna kiselina &nbsp;(klopiralid) su herbicidi sa veoma &scaron;irokim spektrom dejstva, a pored toga su rastvorljivi u&nbsp;vodi, te&scaron;ko biorazgradljivi i prema literaturnim podacima su, nažalost, veoma često prisutni&nbsp;herbicidi u pijaćoj vodi. Proces heterogene fotokatalize uz primenu TiO₂i UV zračenja se&nbsp;pokazao kao veoma pogodan način za njihovo uklanjanje iz vode. Međutim, zbog velikog&nbsp;energetskog procepa od 3,2 eV (anataze-oblik), odnosno, 3,0 eV (rutil-oblik), veoma mali&nbsp;udeo bliskih UV zraka iz sunčeve svetlosti (oko 3&minus;4%) biva iskori&scaron;ćen u toku&nbsp;fotokatalitičkog procesa, &scaron;to ukazuje na to da je TiO_2&nbsp;praktično neaktivan u prisustvu&nbsp;sunčeve svetlosti. Na osnovu literaturnih podataka je zapaženo da postoji mogućnost&nbsp;fotorazgradnje pojedinih supstrata u prisustvu TiO_2&nbsp;primenom vidljive svetlosti. Na&nbsp;primeru MCPP je ispitana aktivnost TiO_2&nbsp;Degussa P25 kao fotokatalizatora u prisustvu&nbsp;vidljive svetlosti. Na osnovu refleksionih spektara je utvrđeno da MCPP adsorbovan na&nbsp;TiO_2&nbsp;Degussa P25 apsorbuje vidljivi deo spektra (&lambda; &ge;400 nm). Nastali prelazni kompleks&nbsp;je potvrđen FTIR merenjima. Efikasnost TiO2Degussa P25 primenom vidljive svetlosti je&nbsp;upoređena sa sunčevim i UV zračenjem, kao i direktnom fotolizom u prisustvu pomenutih&nbsp;izvora zračenja. Brzina fotokatalitičke razgradnje MCPP primenom vidljive svetlosti iznosi&nbsp;0,86 &mu;mol dm^&minus;3min^&minus;1, &scaron;to je oko 4 puta brže u poređenju sa direktnom fotolizom. Nadalje&nbsp;je ustanovljena optimalna masena koncentracija katalizatora od oko 8 mg cm^&minus;3, koja je&nbsp;znatno vi&scaron;a u poređenju sa primenom UV zračenja. Razlog je najverovatnije različit&nbsp;mehanizam fotorazgradnje koji se odvija primenom vidljivog i UV zračenja. Naime,&nbsp;prisustvo 2-metil-2-propanola (poznatog hvatača&nbsp;^&bull;OH-radikala) praktično ne utiče na&nbsp;brzinu fotokatalitičke razgradnje MCPP p rimenom vidljive svetlosti, &scaron;to ukazuje da se&nbsp;mehanizam razgradnje MCPP primenom &nbsp;vidljive svetlosti ne odvija posredstvom&nbsp;^&bull;OH-radikala, za razliku od onog uz primenu UV zračenja.</p><p>S obzirom da se katalizator TiO_2&nbsp;Degussa P25 uz primenu vidljive svetlosti nije&nbsp;<br />pokazao kao naročito efikasan kada je u pitanju razgradnja sva tri herbicida i imajući u&nbsp;vidu da se u poslednje vreme iz razloga praktične primene sve vi&scaron;e pribegava procesu dopovanja TiO_2&nbsp;različitim tipovima metala (alkalnih, zemnoalkalnih, prelaznih i dr.) i nemetala (halogenida, halkogenida i dr.), u okviru ove doktorske disertacije je ispitana aktivnost N-TiO₂(sintetisanih mokrim i suvim putem) i TiO_2&nbsp;(rutil) dopovanog sa različitim količinama Fe³⁺-jona (0,13&minus;1,48 at.%) pri razgradnji herbicida MCPP i MCPA primenom vidljive svetlosti. Pored toga je ispitana efikasnost TiO_2&nbsp;(anataze) takođe dopovanog sa različitim količinama Fe³⁺-jona (0,71&minus;1,80 at.%) na primeru MCPP.&nbsp;</p><p>Poredeći N-TiO_2&nbsp;(sintetisan mokrim putem) i N-TiO_2&nbsp;(sintetisani suvim putem), primećeno&nbsp;je da je u drugom slučaju efikasnost katalizatora veća oko 2 puta. Isto tako je zapažena u&nbsp;slučaju MCPP ne&scaron;to veća fotokatalitička aktivnost N-TiO_2&nbsp;(sintetisani suvim putem) u&nbsp;poređenju sa TiO_2&nbsp;(anataze). Kada je u pitanju MCPA aktivnost sva tri katalizatora je&nbsp;veoma slična. Pored toga je zapažena veća efikasnost N-TiO_2&nbsp;(sintetisan mokrim putem) u&nbsp;poređenju sa TiO_2&nbsp;Degussa P25 (oko 1,5 puta) i oko 5 puta u odnosu na direktnu fotolizu,&nbsp;dok su N-TiO_2&nbsp;(sintetisani suvim putem) oko 3 puta efikasniji u poređenju sa TiO_2&nbsp;Degussa P25 i oko 10 puta u &nbsp;poređenju sa direktnom fotolizom. Brzina solarne razgradnje&nbsp;je preko 100 puta manja nego primenom vidljivog i UV zračenja, &scaron;to je posledica različitih&nbsp;intenziteta pomenutih izvora ozračivanja i različitih uslova pri kojima je vr&scaron;ena razgradnja. &nbsp;Ustanovljena je optimalna masena koncentracija N-TiO_2&nbsp;(sintetisan mokrim putem) od&nbsp;4 mg cm^&minus;3.</p><p>Prilikom razgradnje MCPP i MCPA je nađeno da je brzina veća kada se kao&nbsp;katalizator &nbsp;koristi TiO_2&nbsp;(rutil) u poređenju sa Fe-TiO_2&nbsp;i da sa povećanjem količine Fe³⁺-jona fotokatalitička aktivnost uglavnom opada. Kada je kao fotokatalizator kori&scaron;ćen TiO_{2 &nbsp;}<br />(anataze) dopovan različitim količinama Fe³⁺-jona (od 0,71 do 1,80 at.%), razgradnja&nbsp;<br />MCPP je u svim slučajevima znatno sporija u odnosu na TiO_2&nbsp;(anataze).</p><p>S obzirom da su prema literaturnim podacima kinetika i mehanizam fotokatalitičke&nbsp;<br />razgradnje klopiralida nepoznati, ispitana je njegova stabilnost pri različitim&nbsp;eksperimentalnim uslovima. Tokom ispitivanja uticaja pH kako u prisustvu, tako i u&nbsp;odsustvu dnevne svetlosti u intervalu pH od 1,0&minus;9,0, nađeno je da ni u jednom slučaju ne&nbsp;dolazi do razgradnje supstrata u periodu od sedam meseci koliko je proces praćen. Takođe&nbsp;je ispitana kinetika fotokatalitičke razgradnje klopiralida primenom UV i vidljivog&nbsp;zračenja u prisustvu TiO_2&nbsp;Degussa P25, kao i direktna fotoliza primenom oba izvora&nbsp;zračenja. Nađeno je da je brzina fotokatalitičke razgradnje primenom UV zračenja veća&nbsp;oko 5 puta u odnosu na direktnu fotolizu. Za praćenje toka fotokatalitičke razgradnje&nbsp;klopiralida je izabrana pH-vrednost od 3,2. Nadalje je zapaženo da se u ispitivanom opsegu početnih koncentracija supstrata (0,5&ndash;3,0 mmol dm^&minus;3) kinetika fotokatalitičke razgradnje klopiralida može opisati pseudo-prvim redom. Pri ispitivanju uticaja masene koncentracije katalizatora (0,5&ndash;8 mg cm^&minus;3) na brzinu razgradnje klopiralida, ustanovljena je optimalna masena koncentracija primenjenog fotokatalizatora od oko 4 mg cm^&minus;3. Izračunata ukupna &nbsp;prividna energija aktivacije iznosi 7,74 kJ mol^&minus;1. Pored toga, prisustvo kiseonika ubrzava reakciju 2 puta, dok dodatak elektron-akceptora kao &scaron;to su (NH₄)₂S₂O₈, H₂O_2&nbsp;i KBrO_3&nbsp;pokazuje značajan i različit efekat na kinetiku fotokatalitičke razgradnje klopiralida. Pri ispitivanju uticaja etanola, kao hvatača slobodnih radikala, nađeno je da se heterogena fotokataliza odvija uglavnom preko ^&bull;OH-radikala.</p><p>Na osnovu LC&ndash;MS/MS (ESI+) merenja ustanovljeno je prisustvo nekoliko&nbsp;intermedijera: 3,6-dihlor-piridin-2-ol, 3,6-dihlor hidroksipiridin-2-karboksilna kiselina i&nbsp;3,3&#39;,6,6&#39;-tetrahlor-2,4&#39;-bipiridin-2&#39;-karboksilna kiselina. Na osnovu identifikovanih&nbsp;intermedijera, kao i kinetičkih rezultata, predložen je mogućput mehanizma fotokatalitičke&nbsp;razgradnje klopiralida.</p><p>Prilikom ispitivanja uticaja strukture molekula na brzinu razgradnje, konstatovano&nbsp;<br />je da u slučaju klopiralida praktično ne dolazi do fotokatalitičke razgradnje u prisustvu&nbsp;TiO_2&nbsp;(anataze) i N-TiO_2&nbsp;(sintetisani suvim putem) uz primenu vidljive svetlosti, kao i u&nbsp;slučaju TiO_2&nbsp;Degussa P25. Pored toga, primenom TiO_2&nbsp;(rutil) i Fe-TiO_2&nbsp;kao&nbsp;fotokatalizatora, sa povećanjem količine Fe³⁺-jona od 0,13 do 1,27 at.% raste brzina&nbsp;razgradnje klopiralida, ukazujući da strukturne osobine supstrata utiču na brzinu njihove&nbsp;razgradnje.</p> / <p>It is well known that RS-2-(4-chloro-o-tolyloxy)propionic acid (MCPP), (4-chloro-2- methyl-phenoxy)acetic acid (MCPA) and 3,6-dichloropyridine-2-carboxylic &nbsp;acid&nbsp;(clopyralid) are herbicides of wide activity spectrum. They are soluble in water, hardly&nbsp;biodegradable and, unfortunately, often present in drinking water.</p><p>Heterogeneous photocatalysis by application of TiO_2&nbsp;and UV radiation proved to&nbsp;be very suitable for their removal from water. However, due toits large energy gap, i.e.&nbsp;3.2 &nbsp;eV (anatase-form) and 3.0 eV (rutile-form), a very small fraction of sunlight in the near&nbsp;UV range (about 3&ndash;4%) is used during photocatalytic process, which is an indication of&nbsp;TiO_2&nbsp;inactivity in the presence of this light source. Some literature data report on the&nbsp;possibility of photodegradation of certain substrates by visible light in the presence of&nbsp;TiO₂. MCPP served as substrate for testing TiO_2&nbsp;Degussa P25 &nbsp;photocatalytic activity in the&nbsp;presence of visible light. On the basis of reflection spectra it was established that MCPP&nbsp;adsorbed on TiO_2&nbsp;Degussa P25 was absorbing visible spectrum radiation (&lambda; &ge;400 nm).&nbsp;The existence of thus formed &nbsp;charge-transfer complex was confirmed with FTIR analysis.&nbsp;The efficiency of &nbsp;TiO_2&nbsp;Degussa P25 with application of visible light was compared to&nbsp;sunlight and UV radiation, as well to directphotolysis in the presence of these light&nbsp;sources. The rate of MCPP photocatalytic degradation by means of visible light is&nbsp;0.86 &mu;mol dm^{&minus;3&nbsp;}min^&minus;1, which is about 4 times faster than direct photolysis. In addition, the&nbsp;optimal &nbsp;catalyst concentration of about 8 mg cm^&minus;3, much higher than using UV radiation,&nbsp;<br />was established. The reason is, probably, a different mechanism of &nbsp;hotodegradation &nbsp;in the&nbsp;presence of visible and UV irradiation. Namely, the presence of 2-methyl-2-propanol&nbsp;(well-known&nbsp;^&bull;OH radical scavenger) has practicallyno effect on the rate of &nbsp;MCPP&nbsp;photocatalytic degradation using visible light, which points that this degradation&nbsp;mechanism does not involve&nbsp;^&bull;OH radicals, in contrast to that established &nbsp;for UV radiation.</p><p>Since the catalyst TiO_2&nbsp;Degussa P25 with application of visible light was not very&nbsp;<br />efficient in degradation of all three herbicidesand in view that nowadays is very &nbsp;popular&nbsp;doping process of TiO₂ with different types of metals (alkali, alkaline-earth, transition, etc.)&nbsp;and non-metals (halogen, chalcogen, etc.), in the scope of this Ph.D. &nbsp;thesis activities of N-TiO_2&nbsp;(synthesized by wet and dry procedure) and TiO_2&nbsp;(rutile) doped with various amounts&nbsp;of Fe^3+&nbsp;(0.13&ndash;1.48 at.%) in degradation processes of &nbsp;herbicides MCPP and MCPA using&nbsp;visible light were studied. In addition, the efficiency of TiO_2&nbsp;(anatase) doped with various&nbsp;amounts of Fe^3+&nbsp;(0.71&ndash;1.80 at.%) was also tested for MCPP degradation. When comparing&nbsp;N-TiO_2&nbsp;(synthesized by wet procedure) and N-TiO₂ (dry procedure), it was observed that&nbsp;in the latter case the catalyst efficiency was about two times higher. In this case for MCPP&nbsp;was also observed somewhat higher photocatalytic activity of N-TiO₂ (synthesized by dry&nbsp;procedure) in comparison with TiO₂. When activities of all three catalysts towards MCPA&nbsp;are compared, the results are very alike. In addition, higher efficiency of N-TiO_{2 &nbsp;}(wet&nbsp;procedure) comparing to TiO_2&nbsp;Degussa P25 (about 1.5 times) and about 5 times in&nbsp;comparison to direct photolysis were recorded, while N-TiO₂ (dry procedure) was about 3&nbsp;times more efficient than TiO_2&nbsp;Degussa P25 and about 10 times in comparison with direct&nbsp;photolysis. The rate of solar degradation is about 100 times lower than by application of&nbsp;UV and visible radiation, as a consequence of various intensities of the mentioned light&nbsp;sources and different conditions of photodegradation. An optimal concentration of N-TiO₂&nbsp;(wet procedure) of 4 mg cm^&minus;3<br />&nbsp;was established.</p><p>During degradation of MCPP and MCPA it was observed that the rate is higher if&nbsp;TiO₂(rutile) was applied comparing to Fe-TiO_2&nbsp;and with increasing amount of Fe^3+&nbsp;photocatalytic activity mostly decreases. When TiO₂ (anatase) doped with various amounts&nbsp;of Fe^3+&nbsp;(0.71 to 1.80 at.%) was applied for MCPP degradation, the process was much&nbsp;slower than with undoped catalyst.</p><p>Since we have not found relevant literature data on kinetics and mechanism of&nbsp;photocatalytic degradation of clopyralid, its stability in different experimental conditions&nbsp;was tested. In investigating of influences of pH (1.0&ndash;9.0) both in presence and in absence&nbsp;of daylight, in no cases decomposition was observed during seven months experiments.&nbsp;Also, the kinetics of photocatalytic degradation of clopyralid using UV and visible&nbsp;irradiation in the presence of TiO_2&nbsp;Degussa P25 and in direct photolysis by application of&nbsp;both irradiation sources was studied. It was found that the &nbsp;rate of photocatalytic&nbsp;decomposition using UV radiation was 5 times higher comparing to direct photolysis. For&nbsp;clopyralid photocatalytic monitoring a pH value of &nbsp;3.2 was chosen. In addition, in the investigated concentration range (0.5&ndash;3.0 mmol &nbsp;dm^&minus;3) the photocatalytic degradation kinetics of clopyralid in the first stage of the reaction follows approximately a pseudo-first kinetic order. In investigation of influence of catalyst concentration (0.5&ndash;8 mg cm^&minus;3) on the rate of clopyralid degradation the highest reaction rate was observed at 4 mg cm^{&minus;3&nbsp;}of catalyst concentration The apparent activation energy of the reaction being 7.74 kJ mol^&minus;1. The absence of molecular oxygen resulted in a significant decrease (about 2 times) in the rate of clopyralid photodegradation. The effect of the presence of (NH₄)₂S₂O₈, H₂O_2&nbsp;and KBrO₃, acting as electron acceptors along with molecular oxygen affects clopyralid photocatalytic degradation considerably and indifferent ways. By studying the effect of ethanol as a hydroxyl radical scavenger it was shown that the heterogeneous catalysis takes place mainly via ^&bull;OH radicals.</p><p>LC&minus;MS/MS (ESI+) monitoring of the process showed that several pyridine-containing intermediates are formed: 3,6-dichloropyridin-2-ol, 3,6-dichloro&nbsp;hydroxypyridine-2-carboxylic acid and 3,3&#39;,6,6&#39;-tetrachloro-2,4&#39;-bipyridine-2-carboxylic&nbsp;acid. Based on the identified intermediates and overall kinetic results, a probable&nbsp;photocatalytic degradation mechanism was proposed.&nbsp;</p><p>Finally, in the case of clopyralid it was established that practically no degradation&nbsp;<br />occurs in the presence of TiO_2&nbsp;(anatase) and N-TiO₂ (dry procedure) with visible light &nbsp;and&nbsp;also with TiO_2&nbsp;Degussa P25. Besides of that, by using TiO_2&nbsp;(rutile) and Fe-TiO_2&nbsp;as&nbsp;photocatalysts it was noted that increasing the concentration of Fe^3+&nbsp;from 0.13 to 1.27 at.%&nbsp;comes to increasing photodegradation rate of clopyralid. Results indicate that differences&nbsp;in molecular structure of chosen compound, influence obtained photocatalytic activity to a&nbsp;great extent.</p>