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Aim. The current study aims to evaluate, using scanning electronic microscopy, the sealing ability of two bioceramic endodontic sealers, one consecrated and one experimental. Methods. Twenty monoradicular teeth were included in the study. The teeth were endodontically prepared at the working length. The shaping and cleaning involved the use of chelating gel MM EDTA 19% and continuous irrigation with sodium hypochlorite 2.5%. The radicular filling was performed using gutta-percha in association with a sealer. Ten teeth were filled with consecrated endodontic filling material and the others ten with the experimental bioceramic based sealer Results. The evaluation of the sealers using SEM analysis allowed the identification and the measurement of gaps on the radicular dentin/sealer interface and the degree of apical sealing ability. No significant statistical difference was observed between the gap dimensions in the three areas for the tested bioceramic materials (p

Made available in DSpace on 2022-04-28T19:29:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Objective: To evaluate the surface characteristics of restorations performed after simulated toothbrushing and to compare the results between the composites. Materials and Methods: In total, 80 samples were made (7 mm × 4 mm) from the composites: Bulk Fill One, Bulk Fill Flow, Z350 XT, and Z350 XT flow (3M/ESPE, St. Paul, MN, USA). Half of the specimens was submitted to 60,000 cycles of simulated toothbrushing, while the other half was the control group (n = 10). The surface was evaluated through Scanning electronic microscopy (SEM), surface roughness (Ra), and weight loss, before and after the simulated toothbrushing. To evaluate the statistical analysis, a two-factors variance test and the Tukey's posttest were performed. Results: In the analysis performed by SEM, it was observed the presence of both small and medium protruding particles in all groups after simulated toothbrushing, with the exception of the group which used Z350 flow composite. All materials presented increasing on Ra after simulated toothbrushing. Regarding weight variation, there was not any significant statistical difference in all materials. Conclusions: The abrasive process occasioned by toothbrushing leads to changes on the particles' disposition, which causes changes on the surface and increase on the Ra. On the other hand, there was not any difference regarding to weight variation. Department of Dentistry Federal University of Rio Grande Do Norte Department of Dentistry São Paulo State University Department of Dentistry São Paulo State University

The flow of air and aerosol particles through the filtering half masks material depends on the structure porosity. It is very difficult to determine the behaviour of the filtering material during the process of extraction and retention of aerosols. The samples of five filtering half mask models were used in this investigation. Dynamics of the aerosol filtration through the filtering materials was tested using a method for testing the leakage of aerosol particles through the filtering material and a method for testing the inhalation resistance of filtering material, both specified in the SRPS EN 149:2013. Recording of the structural changes in the samples of the tested materials was carried out by the technique of scanning electron microscopy. The experiments showed a deviation of the results in relation to the theory of filtration the finely dispersed submicron sized particles. It was concluded that the aerosol leakage through the filtering half masks and their resistance to aerosol flow change depend on the aerosol flow rates and the on filtration process duration, as a direct consequence of the newly-made changes in the structure of the filtering material and due to reversibility effect between the filtration process and the changes in the filtering material. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34034 and Grant no. III45019]

Despite cheap and sustainable in nature, the use of natural fiber composites is limited due to their high moisture absorption, poor fiber-matrix interface, and lack of data on evolution of properties when subjected to environmental factor such as temperature and humidity. The aim of this research is to study the interdependence of moisture regain, hydrophobic treatment, and the mechanical properties of jute fiber-reinforced composite materials. Composite samples made from treated and untreated jute fiber-reinforced composites were exposed to humid environment and their moisture regain, mechanical properties and fiber-matrix interface was tested at given time intervals until four weeks. The composites produced with hydrophobic treated reinforcement showed lesser moisture regain and improvement in the tensile and flexural strengths compared to untreated fabric composite. A clear improvement in fiber-resin interface was observed by scanning electronic microscopy. The dynamic mechanical analysis of treated and untreated composites was conducted in a temperature range 20-140 degrees C. An increase in the storage modulus of treated composite materials was noted as compared to untreated ones. Furthermore, it was concluded that developed composite loss their mechanical properties linearly with immersion time. However, this aging was slow in treated fabric composites especially hybrid fluorocarbon and fluorocarbon. Higher Education Commission of Pakistan - NRPU 4239

The power cycling reliability of flexible printed circuit board (PCB) interconnect smaller/thinner (ST) 9.5 mm × 5.5 mm × 0.07 mm and larger/thicker (LT) 13.5 mm × 13.5 mm × 0.5 mm single Si diode samples have been studied. With the assumption of creep strain accumulation-induced fatigue cracking as the failure mechanism of the Sn-3.5Ag solder joints, finite element (FE) simulations predicted a higher power cycling reliability of soldering the flexible PCB on a ST Si diode than on a LT Si diode under similar power cycling conditions. Then the power cycling test results of 10 samples for each type are reported and discussed. The samples were constructed with commercially available ST Si diodes with 3.2/0.5/0.3 μm thick AlSiCu/NiP/Pd topside metallization and LT Si diodes with 5/0.1/1/1 μm thick Al/Ti/Ni/Ag topside metallization. In contradiction with the FE prediction, most ST Si diode samples were less reliable than those LT Si diode samples. This can be attributed to the fact that the failure of the ST diode samples was associated with the weak bonding and hence the shear-induced local delamination of the topside solder joints from the AlSiCu metallization, while the failure of the LT diode samples was mainly caused by the creep strain accumulation-induced fatigue cracking within the solder joints. Such results can be used to not only provide better understanding of the different failure mechanisms, but also demonstrate the importance of employing an appropriate topside metallization on the power devices.

Macroporous polymeric materials were prepared using mixtures of polyphenol:hydrolysable tannins, condensed tannins and lignosulfonate, from pulp industry, as the main raw source. The process used is simple, green and low energy consuming. It consists of a mechanical foaming of aqueous solutions constituted with different proportions of two types of tannins, the lignosulfonate and a hardener in the presence of a surfactant, which maintain the mixture stable before curing.The final formulations, with tannins and lignin were characterized by Scanning Electronic Microscopy, mercury intrusion porosimetry, nitrogen sorption, mechanical and thermal measurements. Then, to determine whether the components react with hexamine but also between them, mixtures were made, first with one polyphenol at a time and then with polyphenols in pairs. Those formulations were characterized through thermal and mechanical properties.Solid, self-standing foams with an average porosity of 89%, an average cell diameter of 105 μm with interconnections of about 7 μm were obtained. The structure of the foams is close to that of phenolic, tannin, lignin and biobased polyurethanes foams already reported in the literature. Concerning mechanical properties, compression modulus between 0.65 MPa and 22.9 MPa were obtained. The thermal conductivity varies between 0035 and 0055 W. m−1.K−1. Keywords: Biobased porous materials, Frothing, Tannins, Lignin

Iako termalno indukovane transformacije mrežnih alumosilikata daju jedinstven metod za formiranje novih faza sa poboljšanim osobinama, zbog kompleksnosti samog procesa, mehanizam konverzije još uvek nije u potpunosti razjašnjen. Usled male jedinične ćelije (Na12Si12Al12O4827H2O) i dobro proučene mrežne strukture i raspodele van-mrežnih katjona, zeolit Na-LTA predstavlja model supstancu za ispitivanje promena u uređenju na kratkom, srednjem i dugom dometu u procesu termalnih transformacija zeolita u popunjene derivate SiO2 polimorfa. Iako su još prva istraživanja pokazala da svaki sintetisan Na-LTA zeolit nije čist u kristalografskom smislu i u zavisnosti od uslova sinteze sadrži različite količine Na, Al i Si inkluzija unutar  i  kaveza, u literaturi ne postoje podaci o katalitičkom uticaju ovih vrsta na mehanizam termalne konverzije Na-LTA zeolita. Prezentovana teza sumira rezultate istraživanja uticaja Na, Al i Si inkluzija na mehanizam termalno indukovanih transformacija Na-LTA zeolita u karnegitske i nefelinske polimorfe. U prvom delu teze opisan je potupak sinteze Na-LTA zeolita sa različitim sadržajem Na, Al i Si inkluzija. Ispitan je uticaj variranja Na2O : Al2O3 : SiO2 odnosa u polaznoj reakcionoj smeši na stehiometriju sintetisanih Na-LTA zeolita i morfologiju kristalnih zrna. Kao postupak uklanjanja inkluzija zaostalih u Na-LTA zeolitima nakon sinteze, predložen je tretman refluksovanja Na-LTA zeolita na 100 ºC, koji ne izaziva amorfizaciju i dodatne strukturne promene u Na-LTA zeolitima. Drugi deo teze fokusiran je na ispitivanje uticaja Na, Al i Si inkluzija na termalnu stabilnost Na-LTA zeolita i njegovu konverziju u karnegitske i nefelinske polimorfe. Posebna pažnja je posvećena ispitivanju mehanizma fazne transformacije Na-LTA zeolita u nisko-temperaturni karnegit koji je u literaturi prezentovan dvema različitim šemama: kao direktna topotaktička transformacija Na-LTA → nisko-temperaturni karnegit i kao dvostepeni mehanizam Na-LTA → Amorfna faza → nisko-temperaturni karnegit. Metodama XRPD, DTA i IR spektroskopije je utvrđeno da Na i Al inkluzije podstiču fazni prelaz Na-LTA zeolita u nisko-temperaturni karnegit uz nemogućnost detekcije kolapsa LTA mreže u amorfnu strukturu, izazivajući brzo raskidanje i formiranje novih veza, pri čemu brzina termalne transformacije raste sa povećanjem sadržaja Al. Sa druge strane, u slučaju faznog prelaza refluksom tretiranih Na-LTA zeolita idealne stehiometrije u niskotemperaturni karnegit, utvrđen je kolaps LTA mreže u stabilnu amorfnu strukturu iz koje je zatim kristalisala faza nisko-temperaturnog karnegita. Karakterizacijom amorfne NaAlSiO4 faze infracrvenom i ramanskom spektroskopijom, utvrđeno je prisustvo četvoročlanih i šestočlanih tetraedarskih prstenova čime je zaključeno da su kolapsom zeolita u amorfnu fazu zadržani fragmenti LTA mreže, što može biti polazna osnova u sintezi „perfektnih“ stakala. Na višim temperaturama, ispitani su uslovi formiranja nefelinskih struktura, rekonstruktivnom faznom transformacijom nisko-temperaturnog karnegita, što je usled velikog broja nefelinskih polimorfa različite simetrije, veoma aktuelna problematika. Rezultati ispitivanja su pokazali da Na, Al i Si inkluzije u Na-LTA zeolitu uslovljavaju transformaciju nisko-temperaturnog karnegita u smešu monokliničnog trinefelina i osnovnog heksagonalnog nefelina, dok se u procesu termalno indukovanih transformacija refluksom tretiranih zeolita idealne LTA stehiometrije, formira faza čistog osnovnog heksagonalnog nefelina. Takođe, ispitani su uslovi termalne konverzije monokliničnog trinefelina u osnovni heksagonalni nefelin. U prisustvu Na i Si inkluzija sintetisana je intermedijerna faza nefelinskog („ABABAB...“) strukturnog tipa koja nije mogla biti identifikovana na osnovu poznatih nefelinskih struktura. Razlike u uređenju na kratkom i srednjem dometu visokotemperaturnih NaAlSiO4 polimorfa dobijenih termalnom konverzijom Na-LTA zeolita različite stehiometrije, pripisane su uticaju Na, Al i Si inkluzija u kavezima zeolita. Ovim istraživanjem predloženo je da Na-LTA zeolit predstavlja primer mnogo šireg problema uticaja nestehiometrije na tok i mehanizam termalno indukovanih transformacija zeolita, kao i da se isti zaključci mogu primeniti i na druge tipove zeolita koji sadrže različite van-mrežne katjone. Although thermally induced transformations of framework aluminosilicates provide unique method for synthesis of materials with advanced properties, conversion mechanism is not explained yet because of the complexity of the process. Because of the small unit cell (Na12Si12Al12O4827H2O) and well known framework structure and extra-framework cation distribution, zeolite Na-LTA represents ideal model for investigation of changes in the short, middle and long range order, in the processes of zeolite thermal transformation into stuffed derivatives of SiO2 polymorphs. Even though investigations showed that Na-LTA zeolite is not pure from crystallographic point of view and, depending on synthesis procedure, contains different amounts of Na, Al and Si inclusions inside α and β cages, there are no data regarding catalytic influence of these species on the mechanism of thermal conversions. Presented thesis surmises results of investigations of the influence of Na, Al and Si inclusion species on the mechanism of Na-LTA thermally induced transformations into carnegieite and nepheline polymorphs. The first chapter of thesis deals with Na-LTA synthesis procedure with different amounts of Na, Al and Si inclusions. The influence of small variations of Na2O:Al2O3:SiO2 ratio in initial reaction mixture on stoichiometry of synthesized Na-LTA zeolites and crystal grain morphology is described. Refluxing treatment at 100 ºC is suggested as method for removing extra-framework species remained after synthesis process, which does not induce amorphization or other structural changes of zeolite. The second chapter of the thesis is focused on the investigation of the influence of Na, Al and Si inclusions on zeolite Na-LTA thermal stability and conversion into carnegieite and nepheline polymorphs. Special attention is dedicated to the investigation of the mechanism of zeolite Na-LTA transformation into low-temperature carnegieite, which is presented with different conversion routes in the literature. In one aspect Na-LTA zeolite transforms directly into low-temperature carnegieite: Na-LTA → low-temperature carnegieite, while in the other, unfolds through amorphous phase: Na- LTA →Amorphous phase → low-temperature carnegieite. XRPD, DTA and IR investigations showed that Na, Al and Si inclusions catalyze zeolite Na-LTA transformation into low-temperature carnegieite, without the possibility of detection of amorphous phase, inducing rapid breaking and formations of bonds, whereby the rate of transformation increases with increasing Al content. On the other hand, in the case of reflux treated Na-LTA zeolite with ideal stoichiometry, thermal transformation into low-temperature carnegieite is preceded by collapse of LTA framework and formation of stable amorphous phase, which subsequently crystallized into low-temperature carnegieite. Characterization of amorphous NaAlSiO4 phase by IR and Raman spectroscopy showed the presence of four- and six-membered tetrahedral rings, which lead to conclusion that by the collapse of zeolite into amorphous phase, relicts of LTA frameworka are retained. This can can be used as a starting point in synthesis of perfect glasses. On higher temperatures, formation conditions of nepheline structures by reconstructive phase transformations of low-temperature carnegieite were investigated. Because of the various nepheline polymorphs with diverse symmetry, formation conditions of different nepheline structures are current problem in mineralogy. Investigation showed that Na, Al and Si inclusion species in Na-LTA zeolite, induce transformation of low-temperature carnegieite into mixture of monoclinic trinepheline and basic hexagonal nepheline, while in the process of thermally induced transformation of reflux treated samples with ideal stoichiometry, pure basic hexagonal nepheline was formed. Also, conditions of thermal conversion of monoclinic trinepheline into basic hexagonal nepheline were investigated. Intermediate phase of nepheline (“ABABAB…”) structure type, which could not be identified according to known nepheline phases, was synthesized in the presence of Na and Si inclusion species. Differences in the short and middle range order between hightemperature NaAlSiO4 polymorphs, formed by thermal conversion of Na-LTA with different stoichiometry, were ascribed to the influence of Na, Al and Si inclusions in zeolite cages.By this investigation we propose that Na-LTA is the example of much wider problem of non-stoichiometry influencing the course of zeolite thermal transformation route and can be extended to other zeolite types containing various extra-framework cations.

Thermo-mechanical fatigue (TMF) tests and strain to crack (SC) tests at elevated temperature are important aspects to the total fatigue life for many engineering applications. During a TMF test, crack inspections are commonly done in a disruptive manner using an acetate replication method; and post-test crack evaluations are done using both optical and scanning electronic microscopy methods. Similarly, inspections during a typical SC test are also performed in a disruptive manner. This paper demonstrates that infrared imaging can be used as an in-situ inspection approach to detect crack during TMF and SC tests at high temperature. It is also demonstrated that this technique allows for the reduction or elimination of the need for downtime that is typically required for disruptive inspection. The results obtained by induction thermography are compared to those obtained via traditional methods and post-test evaluation. The induction thermography inspections were carried out at several temperatures and showed that the temperature used during the test does not influence the crack detection capability. It is demonstrated that induction thermography can detect cracks smaller than 500 μm and has potential for monitoring and generating a crack growth curve. © 2013 SPIE., Thermosense: Thermal Infrared Applications XXXV, April 30 - May 1, 2013, Baltimore, MD, USA, Series: Proceedings of SPIE; no. 8705

International audience; The roughness of etched SiC surfaces must be minimized to obtain surfaces with a smooth aspect, avoiding micromasking artifacts originating from re-deposited particles during the etching process. Four varieties of masks, Al, Ni, Si and C, were deposited on the SiC surface by photolithographic process. The C structures were formed by annealing conversion of patterned thick photoresist. On these surfaces, dry etching was performed with an SF6/O2 plasma produced in a Reactive-Ion-Etching (RIE) reactor. Although a better aspect of the surface is obtained with Ni in comparison with Al mask, micromasking could also occur even with Ni if the mask design was not enough spaced out. With C and Si masks, which produce fluorides species with negative boiling temperature, smooth etched surface was obtained without micromasking, even for tight masks covering up to 90% of the SiC surface.

The objective of this study was to evaluate the push-out bond strength of fiberglass resin reinforced bonded with five ionomer cements. Also, the interface between cement and dentin was inspected by means of SEM. Fifty human canines were chose after rigorous scrutiny process, endodontically treated and divided randomly into five groups (n = 3) according to cement tested: Group I – Ionoseal (VOCO), Group II – Fugi I (GC), Group III – Fugi II Improved (GC), Group IV – Rely X Luting 2 (3M ESPE), Group V – Ketac Cem (3M ESPE). The post-space was prepared to receive a fiberglass post, which was tried before cementation process. No dentin or post surface pretreatment was carried out. After post bonding, all roots were cross-sectioned to acquire 3 thin-slices (1 mm) from three specific regions of tooth (cervical, medium and apical). A Universal test machine was used to carry out the push-out test with cross-head speed set to 0.5mm/mim. All failed specimens were observed under optical microscope to identify the failure mode. Representative specimens from each group was inspected under SEM. The data were analyzed by Kolmogorov-Smirnov and Levene’s tests and by two-way ANOVA, and Tukey’s port hoc test at a significance level of 5%. It was compared the images obtained for determination of types of failures more occurred in different levels. SEM inspection displayed that all cements filled the space between post and dentin, however, some imperfections such bubles and voids were noticed in all groups in some degree of extension. The push-out bond strength showed that cement Ketac Cem presented significant higher results when compared to the Ionoseal (P = 0.02). There were no statistical significant differences among other cements.