Cleaning of ceramic filter plates

In this thesis, cleaning of ceramic filter plates clogged by iron oxides was studied. Oxalic acid is considered as the most effective cleaning agent for the plates fouled by iron oxides, but when using oxalic acid, sparingly soluble calcium oxalate may be formed and it can blind the filter media. Suitability of another chemical for cleaning the plates clogged by iron oxides was studied in this thesis. The literature part was mostly about the properties of the chemical, about its reactions, industrial uses, safety issues etc. In the experimental part, the efficiency of the chemical for cleaning of the ceramic plates clogged by iron oxides was studied. Two kinds of plates were used in the experiments; the others were clogged by hematite and the others by magnetite. Both soaking and flow-through experiments were done. A suitable concentration, pH and temperature were tried to find in the experiments. Also the effect of ultrasound was studied. The efficiency of the cleaning was examined by measuring the permeability of the plates during the experiments. ICP-OES analysis was performed for determining the amount of dissolved iron in the washing solution. Some experiments were also done with oxalic acid. The results from the oxalic acid experiments were compared to the results from the experiments with the other chemical. In the experiments with the other chemical, the permeability increased more and the amounts of dissolved iron were larger. According to the results from the experiments, the method of application of the washing solutions had an impact on the washing results.

Effect of resin luting film thickness on fracture resistance of a ceramic cemented to dentin

Purpose: The aim of this study was to evaluate the fracture resistance of ceramic plates cemented to dentin as a function of the resin cement film thickness. Materials and Methods: Ceramic plates (1 and 2 mm thicknesses) were cemented to bovine dentin using resin composite cement. The film thicknesses used were approximately 100, 200, and 300 μm. Noncemented ceramic plates were used as control. Fracture loads (N) were obtained by compressing a steel indenter in the center of the ceramic plates. ANOVA and Tukey tests (α = 0.05) were used for each ceramic thickness to compare fracture loads among resin cement films used. Results: Mean fracture load (N) for 1-mm ceramic plates were: control - 26 (7); 100 μm - 743 (150); 200 μm - 865 (105); 300 μm - 982 (226). Test groups were significantly different from the control group; there was a statistical difference in fracture load between groups with 100 and 300 μm film thicknesses (p < 0.01). Mean fracture load for 2-mm ceramic plates were: control - 214 (111); 100 μm - 1096 (341); 200 μm - 1067 (226); 300 μm - 1351 (269). Tested groups were also significantly different from the control group (p < 0.01). No statistical difference was shown among different film thicknesses. Conclusions: Unluted specimens presented significantly lower fracture resistance than luted specimens. Higher cement film thickness resulted in increased fracture resistance for the 1-mm ceramic plates. Film thickness did not influence the fracture resistance of 2-mm porcelain plates. Copyright © 2007 by The American College of Prosthodontists.

Desenvolvimento de microcápsulas ativadas por radiação solar para aplicação em painéis cerâmicos exteriores

Dissertação de mestrado integrado em Engenharia de Materiais

Behaviour of TiO(2)-SiMgO(x) hybrid composites on the solar photocatalytic degradation of polluted air

The photocatalytic performance of TiO(2)-SiMgO(x) ceramic plates for trichloroethylene abatement in gas phase has been evaluated under sun irradiance conditions. A continuous flow Pyrex glass reactor fixed on the focus of a compound parabolic collector has been used. The performance of the hybrid photocatalyst has been evaluated as the variation of TCE conversion and reaction products formation with the solar irradiance at different total gas flow, TCE concentration, and water vapour content. SiMgO(x) not only provides adsorbent properties to the photocatalyst, but it also allows the effective use of the material during low solar irradiance conditions. The adsorption-desorption phenomena play a pivotal role in the behaviour of the system. Thus, TCE conversion curves present two different branches when the sun irradiance increases (sunrise) or decreases (sunset). CO(2), COCl(2) and DCAC were the most relevant products detected. Meanwhile CO(2) concentration was insensitive to the branch analysed, COCl(2) or DCAC were not indicating the ability of these compounds to be adsorbed on the composite. An increase of the UV irradiation at total TCE conversion promotes the CO(2) selectivity. The excess of energy arriving to the reactor favours the direct reaction pathway to produce CO(2). The photonic efficiency, calculated as a function of the rate of CO(2) formation, decreases linearly with the solar irradiance up to around 2 mW cm(-2), where it becomes constant. For decontamination systems high TCE conversion is pursuit and then high solar irradiance values are required, in spite of lower photonic efficiency values. The present photocatalyst configuration, with only 17% of the reactor volume filled with the photoactive material, allows total TCE conversion for 150 ppm and 1 L min(-1) in a wide sun irradiance window from 2 to 4 mW cm(-2). The incorporation of water vapour leads to an increase of the CO(2) selectivity keeping the TCE conversion around 90%, although significant amounts of COCl(2) were observed. (c) 2010 Elsevier B.V. All rights reserved.

Estudo de formulação de massa para aplicação em placas cerâmicas

The sector of civil construction is strongly related to the red ceramic industry. This sector uses clay as raw material for manufacturing of various products such as ceramic plates. In this study, two types of clay called clay 1 and clay 2 were collected on deposit in Ielmo Marinho city (RN) and then characterized by thermogravimetric analysis (TG/DTG), differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), rational analysis and particle size distribution and dilatometric analyses. Ceramic plates were manufactured by uniaxial pressing and by extrusion. The plates obtained by pressing were produced from the four formulations called 1, 2, 3 and 4, which presented, respectively, the following proportions by mass: 66.5% clay 1 and 33.5% clay 2, 50% clay 1 and 50% clay 2, 33.5% clay 1 and 66.5% clay 2, 25% clay 1 and 75% clay 2. After firing at 850, 950 and 1050 °C with heating rate of 10 °C/min and soaking time of 30 minutes, the following technological properties were determined: linear firing shrinkage, water absorption, apparent porosity, apparent specific mass and tensile strength (3 points). The formulation containing 25% clay 1 produced plates with most satisfactory results of water absorption and mechanical resistance, because of that it was chosen for manufacturing plates by extrusion. A single firing cycle was established for these plates, which took place as follow: heating rate of 2 °C/min up to 600 ºC with soaking time of 60 minutes, followed by heating using the same rate up to 1050 ºC with soaking time of 30 minutes. After this cycle, the same technological properties investigated in the plates obtained by pressing were determined. The results indicate (according to NRB 13818/1997) that the plates obtained by pressing from the mixture containing 25 wt% clay 1, after firing at 1050 °C, reach the specifications for semi-porous coating (BIIb). On the other hand, the plates obtained by extrusion were classified as semi-stoneware (group AIIa)

Propriedades físico-químicas de vidrados cerâmicos preparados com rejeitos galvânicos atuando como corantes

Pós-graduação em Física - IGCE

Avaliação do desempenho de argamassas à base de cimento Portland para rejuntamento de placas cerâmicas tipo II com adição de pó de borracha de pneus

In this work it is assessed the performance of Portland cement-based mortar to the grouting of type II ceramic plates with the addition of unusable tire rubber powder. It is presented a bibliographical review about the subject in which is done the theoretical and methodological foundation of the whole investigative process. The analyzed universe comprises a sample of mortar to the grouting of conventional ceramic plates type II (reference sample) and five more samples to the grouting of ceramic plates type II, which were made up of the addition of unusable tire rubber powder in the respective proportion (in mass) of 4%, 8%, 12%, 16% and 20%. These mortar samples were subject to the trials of determination of the consistency index (Brazilian Standard NBR 13276:2005), water retention ( Brazilian Standard NBR 14992 Attachment B:2003), permeability in 240 minutes (Brazilian Standard NBR 14992 Attachment G:2003), absorption of water by immersion (Brazilian Standard NBR 9781:2013), resistance to compression (Brazilian Standard NBR14992 Attachment D: 2003), resistance to traction in the flexion (Brazilian Standard NBR 13279:2005), resistance of traction adherence (Brazilian Standard NBR 14081 part 4:2012) and hardened mass density (Brazilian Standard NBR 13280: 2005). It has been found out from the analyzes of the results in the trial the following situation: the reference mortar used met the established requirements in the norms of specifications corresponding to only six from the eight parameters assessed in the research; the mortar with addition of 4,0% of tire rubber powder met the established requirements corresponding to only the resistance to compression and the resistance of adherence to traction. Thus, the other kinds of mortar with addition of 8,0 %, 12,0 %, 16,0 % and 20,0 % of tire rubber powder met the requirements of specifications corresponding to only the resistance to compression and the resistance of adherence to traction. This result concludes that the adding of tire rubber powder does not grant improvement to the mortar of type II grouting to the laying of ceramic plates.

Avaliação do desempenho de argamassas à base de cimento Portland para rejuntamento de placas cerâmicas tipo II com adição de pó de borracha de pneus

In this work it is assessed the performance of Portland cement-based mortar to the grouting of type II ceramic plates with the addition of unusable tire rubber powder. It is presented a bibliographical review about the subject in which is done the theoretical and methodological foundation of the whole investigative process. The analyzed universe comprises a sample of mortar to the grouting of conventional ceramic plates type II (reference sample) and five more samples to the grouting of ceramic plates type II, which were made up of the addition of unusable tire rubber powder in the respective proportion (in mass) of 4%, 8%, 12%, 16% and 20%. These mortar samples were subject to the trials of determination of the consistency index (Brazilian Standard NBR 13276:2005), water retention ( Brazilian Standard NBR 14992 Attachment B:2003), permeability in 240 minutes (Brazilian Standard NBR 14992 Attachment G:2003), absorption of water by immersion (Brazilian Standard NBR 9781:2013), resistance to compression (Brazilian Standard NBR14992 Attachment D: 2003), resistance to traction in the flexion (Brazilian Standard NBR 13279:2005), resistance of traction adherence (Brazilian Standard NBR 14081 part 4:2012) and hardened mass density (Brazilian Standard NBR 13280: 2005). It has been found out from the analyzes of the results in the trial the following situation: the reference mortar used met the established requirements in the norms of specifications corresponding to only six from the eight parameters assessed in the research; the mortar with addition of 4,0% of tire rubber powder met the established requirements corresponding to only the resistance to compression and the resistance of adherence to traction. Thus, the other kinds of mortar with addition of 8,0 %, 12,0 %, 16,0 % and 20,0 % of tire rubber powder met the requirements of specifications corresponding to only the resistance to compression and the resistance of adherence to traction. This result concludes that the adding of tire rubber powder does not grant improvement to the mortar of type II grouting to the laying of ceramic plates.

Ceramic foam plates: a new tool for processing fresh radical prostatectomy specimens

Procurement of fresh tissue of prostate cancer is critical for biobanking and generation of xenograft models as an important preclinical step towards new therapeutic strategies in advanced prostate cancer. However, handling of fresh radical prostatectomy specimens has been notoriously challenging given the distinctive physical properties of prostate tissue and the difficulty to identify cancer foci on gross examination. Here, we have developed a novel approach using ceramic foam plates for processing freshly cut whole mount sections from radical prostatectomy specimens without compromising further diagnostic assessment. Forty-nine radical prostatectomy specimens were processed and sectioned from the apex to the base in whole mount slices. Putative carcinoma foci were morphologically verified by frozen section analysis. The fresh whole mount slices were then laid between two ceramic foam plates and fixed overnight. To test tissue preservation after this procedure, formalin-fixed and paraffin-embedded whole mount sections were stained with hematoxylin and eosin (H&E) and analyzed by immunohistochemistry, fluorescence, and silver in situ hybridization (FISH and SISH, respectively). There were no morphological artifacts on H&E stained whole mount sections from slices that had been fixed between two plates of ceramic foam, and the histological architecture was fully retained. The quality of immunohistochemistry, FISH, and SISH was excellent. Fixing whole mount tissue slices between ceramic foam plates after frozen section examination is an excellent method for processing fresh radical prostatectomy specimens, allowing for a precise identification and collection of fresh tumor tissue without compromising further diagnostic analysis.

DEVELOPMENT OF A MICRO-HEAT EXCHANGER WITH STACKED PLATES USING LTCC TECHNOLOGY

A green ceramic tape micro-heat exchanger was developed using Low Temperature Co-fired Ceramics technology (LTCC). The device was designed by using Computational Aided Design software and simulations were made using a Computational Fluid Dynamics package (COMSOL Multiphysics) to evaluate the homogeneity of fluid distribution in the microchannels. Four geometries were proposed and simulated in two and three dimensions to show that geometric details directly affect the distribution of velocity in the micro-heat exchanger channels. The simulation results were quite useful for the design of the microfluidic device. The micro-heat exchanger was then constructed using the LTCC technology and is composed of five thermal exchange plates in cross-flow arrangement and two connecting plates, with all plates stacked to form a device with external dimensions of 26 x 26 x 6 mm(3).

Development of a micro-heat exchanger with stacked plates using LTCC technology

A green ceramic tape micro-heat exchanger was developed using Low Temperature Co-fired Ceramics technology (LTCC). The device was designed by using Computational Aided Design software and simulations were made using a Computational Fluid Dynamics package (COMSOL Multiphysics) to evaluate the homogeneity of fluid distribution in the microchannels. Four geometries were proposed and simulated in two and three dimensions to show that geometric details directly affect the distribution of velocity in the micro-heat exchanger channels. The simulation results were quite useful for the design of the microfluidic device. The micro-heat exchanger was then constructed using the LTCC technology and is composed of five thermal exchange plates in cross-flow arrangement and two connecting plates, with all plates stacked to form a device with external dimensions of 26 x 26 x 6 mm(3).

Active control in flexible plates with piezoelectric actuators using linear matrix inequalities

The study of algorithms for active vibrations control in flexible structures became an area of enormous interest, mainly due to the countless demands of an optimal performance of mechanical systems as aircraft, aerospace and automotive structures. Smart structures, formed by a structure base, coupled with piezoelectric actuators and sensor are capable to guarantee the conditions demanded through the application of several types of controllers. The actuator/sensor materials are composed by piezoelectric ceramic (PZT - Lead Zirconate Titanate), commonly used as distributed actuators, and piezoelectric plastic films (PVDF-PolyVinyliDeno Floride), highly indicated for distributed sensors. The design process of such system encompasses three main phases: structural design; optimal placement of sensor/actuator (PVDF and PZT); and controller design. Consequently, for optimal design purposes, the structure, the sensor/actuator placement and the controller have to be considered simultaneously. This article addresses the optimal placement of actuators and sensors for design of controller for vibration attenuation in a flexible plate. Techniques involving linear matrix inequalities (LMI) to solve the Riccati's equation are used. The controller's gain is calculated using the linear quadratic regulator (LQR). The major advantage of LMI design is to enable specifications such as stability degree requirements, decay rate, input force limitation in the actuators and output peak bounder. It is also possible to assume that the model parameters involve uncertainties. LMI is a very useful tool for problems with constraints, where the parameters vary in a range of values. Once formulated in terms of LMI a problem can be solved efficiently by convex optimization algorithms.

Development of a micro heat exchanger made with ceramic multi-layers (LTCC) and its setup to gas flow measurements

A green ceramic tape micro heat exchanger was developed using LTCC technology. The device was designed by using a CAD software and 2D and 3D simulations using a CFD package (COMSOL Multiphysics) to evaluate the fluid behavior in the microchannels. The micro heat exchanger is composed of five thermal exchange plates in cross flow arrangement and two connecting plates; heat exchanger dimensions are 26 × 26 × 6 mm3. Preliminary tests were carried out to characterize the device both in atmospheric pressure and in vacuum. The same techniques used in vacuum technology were applied to check the rotameters and to prevent device leakages. Thermal performance of the micro heat exchanger was experimentally tested. © 2009 Elsevier B.V. All rights reserved.

A comparison of the film thickness of two adhesive luting agents and the effect of thermocycling on their microTBs to feldspathic ceramic.

The aim of the present study was to evaluate the effect of thermocycling (TC) on the microtensile bond strength (microTBS) of two luting agents to feldspathic ceramic and to measure their film thickness (FT). For the microTBS test, sixteen blocks (6.4 x 6.4 x 4.8 mm) were fabricated using a feldspathic ceramic, etched with 10% hydrofluoric acid, rinsed and treated with the silane agent. The ceramic blocks were divided into two groups (n= 8): Gr1: dual-cured resin cement and Gr2: flowable resin. The luting agents were applied on the treated surfaces. Microsticks (1 +/-0. 1mm2) were prepared and stored under two conditions: dry, specimens immediately submitted to the microTBS test, and TC (6,000 cycles; 5 degrees C-55 degrees C). The microTBS was evaluated using a universal testing machine (1 mm/min). The microTBS data (MPa) were submitted to two-way ANOVA and Tukey' test (5%). For the FT test (ISO 4049), 0.05 ml of each luting agent (n=8) was pressed between two Mylar-covered glass plates (150 N) for 180 seconds and light polymerized. FT was measured using a digital paquimeter (Model 727-2001). The data (mm) were submitted to one-way ANOVA. The luting cement did not influence the microTBS results (p= 0.4467). Higher microtensile bond values were found after TC (20.5 +/- 8.6 MPa) compared to the dry condition (13.9 +/- 4. 7MPa), for both luting agents. The luting agents presented similar film thicknesses: Gr1- 0.052 +/- 0.016 mm; Gr2-0.041 +/- 0.003 mm. The luting agents presented similar film thickness and microTBS values, in dry and TC conditions and TC increased the bond strength regardless of the luting agent.

Paired Evaluation Of Calvarial Reconstruction With Prototyped Titanium Implants With And Without Ceramic Coating.

To investigate the osseointegration properties of prototyped implants with tridimensionally interconnected pores made of the Ti6Al4V alloy and the influence of a thin calcium phosphate coating. Bilateral critical size calvarial defects were created in thirty Wistar rats and filled with coated and uncoated implants in a randomized fashion. The animals were kept for 15, 45 and 90 days. Implant mechanical integration was evaluated with a push-out test. Bone-implant interface was analyzed using scanning electron microscopy. The maximum force to produce initial displacement of the implants increased during the study period, reaching values around 100N for both types of implants. Intimate contact between bone and implant was present, with progressive bone growth into the pores. No significant differences were seen between coated and uncoated implants. Adequate osseointegration can be achieved in calvarial reconstructions using prototyped Ti6Al4V Implants with the described characteristics of surface and porosity.