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1.
Sensors (Basel) ; 23(13)2023 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-37447700

RESUMO

In this article, we present a novel approach to tool condition monitoring in the chipboard milling process using machine learning algorithms. The presented study aims to address the challenges of detecting tool wear and predicting tool failure in real time, which can significantly improve the efficiency and productivity of the manufacturing process. A combination of feature engineering and machine learning techniques was applied in order to analyze 11 signals generated during the milling process. The presented approach achieved high accuracy in detecting tool wear and predicting tool failure, outperforming traditional methods. The final findings demonstrate the potential of machine learning algorithms in improving tool condition monitoring in the manufacturing industry. This study contributes to the growing body of research on the application of artificial intelligence in industrial processes. In conclusion, the presented research highlights the importance of adopting innovative approaches to address the challenges of tool condition monitoring in the manufacturing industry. The final results provide valuable insights for practitioners and researchers in the field of industrial automation and machine learning.


Assuntos
Algoritmos , Inteligência Artificial , Aprendizado de Máquina , Automação , Comércio
2.
Sensors (Basel) ; 23(3)2023 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-36772151

RESUMO

In this paper, a novel approach to evaluation of feature extraction methodologies is presented. In the case of machine learning algorithms, extracting and using the most efficient features is one of the key problems that can significantly influence overall performance. It is especially the case with parameter-heavy problems, such as tool condition monitoring. In the presented case, images of drilled holes are considered, where state of the edge and the overall size of imperfections have high influence on product quality. Finding and using a set of features that accurately describes the differences between the edge that is acceptable or too damaged is not always straightforward. The presented approach focuses on detailed evaluation of various feature extraction approaches. Each chosen method produced a set of features, which was then used to train a selected set of classifiers. Five initial feature sets were obtained, and additional ones were derived from them. Different voting methods were used for ensemble approaches. In total, 38 versions of the classifiers were created and evaluated. Best accuracy was obtained by the ensemble approach based on Weighted Voting methodology. A significant difference was shown between different feature extraction methods, with a total difference of 11.14% between the worst and best feature set, as well as a further 0.2% improvement achieved by using the best voting approach.

3.
Materials (Basel) ; 15(10)2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35629448

RESUMO

The paper presents the effect of nitrogen ion implantation on the tool life of the tools commonly used in the furniture industry for drilling particleboards. Nitrogen ions with different accelerating voltages of 25, 40, 55, and 70 kV and a fluence of 5 × 1017 cm-2 were implanted into the surface of commercially available high-speed steel (HSS) drills, using the implanters without mass-separated ion beams. The tests were carried out in a computerized numerical control (CNC) machining center used in the furniture industry. Based on the measurements of the direct tool wear indicator (W), the drill wear curves were determined and the relative tool life index, standard deviation, coefficient of variation, and the implantation quality index of tool life were calculated. The studies have shown that the modification of the drill surface layer by the nitrogen ion implantation process increases the tool life. The obtained results allow the research to be the continued in a wider scope.

4.
Sensors (Basel) ; 21(23)2021 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-34884080

RESUMO

The multiclass prediction approach to the problem of recognizing the state of the drill by classifying images of drilled holes into three classes is presented. Expert judgement was made on the basis of the quality of the hole, by dividing the collected photographs into the classes: "very fine," "acceptable," and "unacceptable." The aim of the research was to create a model capable of identifying different levels of quality of the holes, where the reduced quality would serve as a warning that the drill is about to wear down. This could reduce the damage caused by a blunt tool. To perform this task, real-world data were gathered, normalized, and scaled down, and additional instances were created with the use of data-augmentation techniques, a self-developed transformation, and with general adversarial networks. This approach also allowed us to achieve a slight rebalance of the dataset, by creating higher numbers of images belonging to the less-represented classes. The datasets generated were then fed into a series of convolutional neural networks, with different numbers of convolution layers used, modelled to carry out the multiclass prediction. The performance of the so-designed model was compared to predictions generated by Microsoft's Custom Vision service, trained on the same data, which was treated as the benchmark. Several trained models obtained by adjusting the structure and hyperparameters of the model were able to provide better recognition of less-represented classes than the benchmark.


Assuntos
Benchmarking , Redes Neurais de Computação
5.
ACS Nano ; 15(1): 1016-1029, 2021 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-33400494

RESUMO

Micelles of Pluronic F108 (EO132PO50EO132)/P104 (EO27PO61EO27) surfactant mixtures swollen with toluene were found to template silica nanotubes that formed double-helical structures under appropriately selected aqueous acidic solution conditions. In particular, the double-helical nanotube structure (DHNTS) formed as a main product at 15 °C for 30-37.5 wt % of Pluronic P104 in a surfactant mixture, with 35 wt % being particularly suitable. The formation of DHNTSs appears to involve a spontaneous wrapping of micelle-templated nanotubes around one another, while a similar structure was known to form only under confinement of anodic alumina pores of appropriate diameter. In addition to DHNTSs, other helical or circular structures, such as a helical nanotube tightly wrapped around a straight nanotube, or nanotube(s) wrapped around a sphere, were observed in many cases as minor components. DHNTSs formed as a major component at a well-defined proportion of silica precursor to surfactant at 15 °C, while the relative amount of the swelling agent and the hydrochloric acid concentration could be varied considerably. The hydrothermal treatment temperature was used to adjust the pore diameter of the DHNTS. However, structures formed without the hydrothermal treatment or with the treatment at a moderate temperature appeared very soft, while the treatment at excessively high temperature resulted in a development of significant gaps in the nanotube walls. Our results establish DHNTS as a well-defined ordered mesoporous silica with ultralarge (∼35 nm) helical mesopores of some degree of diameter adjustability, accessible under aqueous conditions using common nonionic surfactants as templating agents.

6.
J Colloid Interface Sci ; 544: 312-320, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30861436

RESUMO

Subambient temperatures are employed in Pluronic-block-copolymer-templated syntheses of many large-pore silicas: SBA-15 (2-D hexagonal with cylindrical mesopores), FDU-12 (face-centered cubic with spherical mesopores), nanotubes and hollow nanospheres. Herein, the origin of a significant temperature dependence of the unit-cell parameter and pore diameter of silicas templated by swollen micelles of Pluronics under subambient conditions was elucidated. The temperature dependence of size of swollen spherical micelles of Pluronic F127 (EO106PO70EO106) in 2 M HCl solution was studied in 12-25 °C range using dynamic light scattering and was correlated with structure types, unit-cell sizes and pore sizes of silicas synthesized at four silica-precursor/Pluronic ratios with a swelling agent (toluene, ethylbenzene). The increase in size of swollen micelles with temperature decrease was paralleled by the increase in the unit-cell size and pore diameter, even if the micelle shape changed in the process of formation of the micelle-templated silica. The decrease in the silica-precursor/Pluronic F127 ratio at constant temperature triggered a succession of phases, including SBA-15 - nanotube sequence that may involve an intermediate nanotube bundle structure, which is uncommon and potentially useful. The temperature decrease also led to a succession of phases, including FDU-12 - SBA-15, hollow nanospheres - nanotube bundles, and nanotubes - SBA-15 sequences.

7.
Comput Methods Programs Biomed ; 160: 75-83, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29728249

RESUMO

BACKGROUND AND OBJECTIVE: The aim of computer-aided-detection (CAD) systems for mammograms is to assist radiologists by marking region of interest (ROIs) depicting abnormalities. However, the confusing appearance of some normal tissues that visually look like masses results in a large proportion of marked ROIs with normal tissues. This paper copes with this problem and proposes a framework to reduce false positive masses detected by CAD. METHODS: To avoid the error induced by the segmentation step, we proposed a segmentation-free framework with particular attention to improve feature extraction and classification steps. We investigated for the first time in mammogram analysis, Hilbert's image representation, Kolmogorov-Smirnov distance and maximum subregion descriptors. Then, a feature selection step is performed to select the most discriminative features. Moreover, we considered several classifiers such as Random Forest, Support Vector Machine and Decision Tree to distinguish between normal tissues and masses. Our experiments were carried out on a large dataset of 10168 ROIs (8254 normal tissues and 1914 masses) constructed from the Digital Database for Screening Mammography (DDSM). To simulate practical scenario, our normal regions are false positives asserted by a CAD system from healthy cases. RESULTS: The combination of all the descriptors yields better results than each feature set used alone, and the difference is statistically significant. Besides, the feature selection steps yields a statistically significant increase in the accuracy values for the three classifiers. Finally, the random forest achieves the highest accuracy (81.09%), outperforming the SVM classifier (80.01%)) and decision tree (79.12%), but the difference is not statistically significant. CONCLUSIONS: The accuracy of discrimination between normal and abnormal ROIs in mammograms obtained with the proposed gray level texture features sets are encouraging and comparable to these obtained with multiresolution features. Combination of several features as well as feature selection steps improve the results. To improve false positives reduction in CAD systems for breast cancer diagnosis, these features could be combined with multiresolution features.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Mamografia/estatística & dados numéricos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Bases de Dados Factuais/estatística & dados numéricos , Árvores de Decisões , Reações Falso-Positivas , Feminino , Humanos , Design de Software , Máquina de Vetores de Suporte
8.
J Colloid Interface Sci ; 524: 445-455, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-29677613

RESUMO

Bridged-organosilica nanotubes with a variety of bridging groups (methylene, ethylene, ethenylene, phenylene and p-xylylene) were synthesized using swollen mixtures of Pluronic triblock copolymer surfactants as micellar templates. The mixtures consisted of Pluronic F127 surfactant (EO106PO70EO106) with long poly(ethylene oxide), PEO, blocks, which help prevent the formation of consolidated structures, and another Pluronic with shorter PEO blocks and higher poly(propylene oxide) content, which promote swelling and the cylindrical micelle morphology. In the presence of toluene as a swelling agent, the use of Pluronic P123 (EO20PO70EO20) in the mixture allowed us to readily generate organosilica nanotubes, but the products were often contaminated, sometimes substantially, with large nanospheres and other impurities. On the other hand, the use of Pluronic P104 (EO27PO61EO27) instead of Pluronic P123 typically afforded nanotube products of significant purity. The nanotube morphology was well preserved upon the surfactant removal via extraction or calcination, even though the resulting nanotubes were often more clustered. The nanotubes exhibited high surface areas and uniform inner diameters in the range from ∼12 to 21 nm, depending on the composition and synthesis conditions. Our results indicate that the swollen mixed Pluronic surfactant templates provide an unprecedented access to mesoporous bridged-organosilica nanotubes.

9.
Langmuir ; 32(3): 900-8, 2016 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-26714054

RESUMO

A variety of organosilicas with p-xylylene bridging groups in the framework were synthesized using Pluronic F127 triblock copolymer as a micellar template under moderately acidic conditions in the presence of xylene as a micelle swelling agent. The resulting materials were characterized by using nitrogen adsorption, small-angle X-ray scattering, transmission electron microscopy, and (29)Si and (13)C cross-polarization magic angle spinning NMR. As the ratio of the organosilica precursor to Pluronic F127 was decreased, the structure evolved from highly ordered periodic mesoporous organosilica (PMO) to weakly ordered PMO, loosely aggregated hollow organosilica nanospheres, and finally to a significantly aggregated disordered structure. The highly ordered PMO with primarily face-centered cubic structure was effectively a closed-pore material. However, the weakly ordered variant exhibited large-diameter (∼15 nm) spherical mesopores, which were accessible after calcination under appropriate conditions or after extraction. The hollow nanospheres had readily accessible, uniform inner cavities whose size was readily tunable by adjusting the amount of the swelling agent used. It was also possible to convert the organosilica nanospheres into hollow silica nanospheres with inaccessible (closed) mesopores. The formation of distinct well-defined morphologies with spherical mesopores for an organosilica with large bridging groups in the framework shows that block-copolymer-surfactant templating is a powerful and versatile method for controlling the nanoscale structures of these remarkable materials.

10.
Chemistry ; 21(36): 12747-54, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26178137

RESUMO

The unit-cell size and pore diameter as functions of temperature are investigated in the syntheses of FDU-12 silicas with face-centered cubic structure templated by Pluronic (PEO-PPO-PEO) block copolymer micelles swollen by toluene. The temperature range in which the unit-cell size and pore size strongly increase as temperature decreases is correlated with the critical micelle temperature (CMT) of the surfactant. While Pluronic F127 affords a wide range of unit-cell parameters (28-51 nm) and pore diameters (16-32 nm), it renders moderately enlarged pore sizes at 25 °C. The use of Pluronic F108 with higher CMT affords FDU-12 with very large unit-cell size (∼49 nm) and large pore diameter (27 nm) at 23 °C. Large unit-cell size (40-41 nm) and pore size (22 nm) were obtained even at 25 °C. The application of Pluronics F87 and F88 with much smaller molecular weights and higher CMTs also allows one to synthesize FDU-12 with quite large unit-cell parameters and pore sizes at room temperature. The present work demonstrates that one can judiciously select Pluronic surfactants with appropriate CMT to shift the temperature range in which the pore diameter is readily tunable.

11.
Langmuir ; 31(27): 7623-32, 2015 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-26090923

RESUMO

The syntheses of silicas with highly ordered cubic Ia3d structure templated by Pluronic P123 (EO20PO70EO20) block copolymer surfactant and sodium dodecyl sulfate (SDS) additive in the presence of swelling agents are demonstrated. It was found that the cubic Ia3d silica forms at 25 °C when a moderate amount of a swelling agent, such as 1,3,5-triisopropylbenzene (TIPB), 1,4-diisopropylbenzene (DIPB), or 1,3,5-triethylbenzene (TEB), is added. However, 1,3,5-trimethylbenzene was not found suitable, suggesting that the success of the synthesis requires a careful selection of a swelling agent. An increase in the relative amount of the swelling agent in a limited range tends to cause an increase in the unit-cell size, while a further unit cell parameter increase can be accomplished with TIPB through a concomitant decrease in the synthesis temperature and increase in the relative amount of the swelling agent. Many of the cubic Ia3d products, including those with the largest attained unit-cell sizes, were highly ordered. When TIPB was used as a swelling agent, the products typically had unusually high mesopore volumes. The latter was largely independent of the ratio of the silica precursor to the Pluronic P123 surfactant for high quality products obtained under particular conditions, which suggests that the cubic Ia3d structure forms at a nearly constant silica-to-surfactant ratio.

12.
Anal Quant Cytopathol Histpathol ; 36(3): 147-60, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25141491

RESUMO

OBJECTIVE: To present a computerized system for recognition of Fuhrman grade of cells in clear-cell renal cell carcinoma on the basis of microscopic images of the neoplasm cells in application of hematoxylin and eosin staining. STUDY DESIGN: The applied methods use combined gradient and mathematical morphology to obtain nuclei and classifiers in the form of support vector machine to estimate their Fuhrman grade. The starting point is a microscopic kidney image, which is subject to the advanced methods of preprocessing, leading finally to estimation of Fuhrman grade of cells and the whole analyzed image. RESULTS: The results of the numerical experiments have shown that the proposed nuclei descriptors based on different principles of generation are well connected with the Fuhrman grade. These descriptors have been used as the diagnostic features forming the inputs to the classifier, which performs the final recognition of the cells. The average discrepancy rate between the score of our system and the human expert results, estimated on the basis of over 3,000 nuclei, is below 10%. CONCLUSION: The obtained results have shown that the system is able to recognize 4 Fuhrman grades of the cells with high statistical accuracy and agreement with different expert scores. This result gives a good perspective to apply the system for supporting and accelerating the research of kidney cancer.


Assuntos
Carcinoma de Células Renais/patologia , Processamento de Imagem Assistida por Computador , Neoplasias Renais/patologia , Máquina de Vetores de Suporte , Carcinoma de Células Renais/diagnóstico , Citodiagnóstico , Humanos , Neoplasias Renais/diagnóstico , Gradação de Tumores , Prognóstico
13.
Biomed Tech (Berl) ; 59(1): 79-86, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23945111

RESUMO

The paper presents a method for nucleolus detection in images of nuclei in clear-cell renal carcinoma (CCRC). The method is based on the similarity of the nuclei image and the two-dimensional paraboloidal window function. The results of numerical experiments performed on almost 2600 images of CCRC nuclei have confirmed the good accuracy of the method. The developed algorithm will be used to accelerate further research in computer-assisted diagnosis of CCRC.


Assuntos
Carcinoma de Células Renais/patologia , Nucléolo Celular/patologia , Interpretação de Imagem Assistida por Computador/métodos , Neoplasias Renais/patologia , Microscopia/métodos , Reconhecimento Automatizado de Padrão/métodos , Algoritmos , Humanos , Aumento da Imagem/métodos , Gradação de Tumores , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
14.
Acc Chem Res ; 45(10): 1678-87, 2012 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-22931347

RESUMO

The surfactant-micelle-templating method has revolutionized the synthesis of high-surface-area materials with mesopores (diameter 2-50 nm) that have well-defined shapes and sizes. One of the major benefits of this method is the ability to tailor the pore size by manipulating the size of the templating micelles. The uniform pores typically form ordered arrays. Although the choice of surfactant can tune the size of the micelles, it is more convenient to use a single surfactant and tailor the micelle size by adding a swelling agent. Unfortunately, the swelling agent tends to induce disorder or heterogeneity in the resulting structures, which can make this approach difficult to implement. We hypothesized that the swelling agents that are moderately solubilized within the micelles of a particular surfactant could generate well-defined micelle-templated structures with significantly enlarged pores. Using this idea, we could judiciously select candidate swelling agents from families of compounds whose extent of solubilization in the surfactant micelles systematically changes with variations in the compound structure. Alkyl-substituted benzenes proved very useful as swelling agents, because their extent of solubilization in micelles of common Pluronic surfactants (EO(m)PO(n)EO(m); EO = ethylene oxide, PO = propylene oxide) significantly increases as the number or size of alkyl substituents decreases. On the basis of these principles, we identified 1,3,5-triisopropylbenzene and cyclohexane as swelling agents for the synthesis of ultralarge-pore SBA-15 silica (pore diameter up to 26 nm) and organosilicas with 2-D hexagonal structures of cylindrical mesopores. Moreover, we used xylene, ethylbenzene, and toluene as swelling agents for the synthesis of large-pore (pore diameter up to 37 nm) face-centered cubic silicas and organosilicas with spherical mesopores. During the early stages of the synthesis, the entrances to large cylindrical and spherical mesopores of these materials were much smaller than the inner pore diameter. Therefore we can often use calcination at sufficiently high temperatures (400-950 °C) to produce closed-pore silicas. Using hydrothermal treatments, we can obtain materials with large pore entrance sizes. In Pluronic-templated synthesis, we observed the propensity for formation of single-micelle-templated nanoparticles as the ratio of the framework precursor to surfactant decreased, and this process afforded organosilica nanotubes and uniform hollow spheres with inner diameters up to ∼21 nm. Consequently, the adjustment of variables in the micelle-templated synthesis allows researchers to tailor the pore size and connectivity and to form either periodic pore arrays or individual nanoparticles.

15.
ACS Nano ; 6(7): 6208-14, 2012 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-22721578

RESUMO

The design and control of polymeric nanoscale network structures at the molecular level remains a challenging issue. Here we construct a novel type of polymeric nanoscale networks with a unique microporous nanofiber unit employing the intra/interbrush carbonyl cross-linking of polystyrene side chains for well-defined cylindrical polystyrene molecular bottlebrushes. The size of the side chains plays a vital role in the tuning of nanostructure of networks at the molecular level. We also show that the as-prepared polymeric nanoscale networks exhibit high specific adsorption capacity per unit surface area because of the synergistic effect of their unique hierarchical porous structures. Our strategy represents a new avenue for the network unit topology and provides a new application for molecular bottlebrushes in nanotechnology.

16.
Langmuir ; 28(23): 8737-45, 2012 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-22607203

RESUMO

Large-pore ethenylene-bridged (-CH═CH-) and phenylene-bridged (-C(6)H(4)-) periodic mesoporous organosilicas (PMOs) with face-centered-cubic structure (Fm3m symmetry) of spherical mesopores were synthesized at 7 °C at low acid concentration (0.1 M HCl) using Pluronic F127 triblock copolymer surfactant in the presence of aromatic swelling agents (1,3,5-trimethylbenzene, xylenes-isomer mixture, and toluene). In particular, this work reports an unprecedented block-copolymer-templated well-ordered ethenylene-bridged PMO with cubic structure of spherical mesopores and an unprecedented block-copolymer-templated face-centered cubic phenylene-bridged PMO, which also has an exceptionally large unit-cell size and pore diameter. The unit-cell parameters of 30 and 25 nm and the mesopore diameters of 14 and 11 nm (nominal BJH-KJS pore diameters of 12-13 and 9 nm) were obtained for ethenylene-bridged and phenylene-bridged PMOs, respectively. Under the considered reaction conditions, the unit-cell parameters and pore diameters were found to be similar when the three different methyl-substituted benzene swelling agents were employed, although the degree of structural ordering appeared to improve for phenylene-bridged PMOs in the sequence of decreased number of methyl groups on the benzene ring.

17.
J Colloid Interface Sci ; 365(1): 137-42, 2012 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-21996009

RESUMO

Ultra-large-pore FDU-12 (ULP-FDU-12) silica with face-centered cubic structure (Fm3m type) of spherical mesopores was synthesized using Pluronic F127 triblock copolymer (EO(106)PO(70)EO(106)) and ethylbenzene as a new micelle expander at initial temperature of 14 °C. Ethylbenzene was identified on the basis of its reported extent of solubilization in poly(ethylene oxide)-poly(propylene oxide)-type surfactant micelles, which was similar to that of xylene, the latter having been shown earlier to afford ULP-FDU-12. The unit-cell parameter of as-synthesized ULP-FDU-12 was 55 nm, which is similar to the highest value reported when xylenes (mixture of isomers) were used and larger than that achieved with trimethylbenzene. The unit-cell parameter of calcined ULP-FDU-12 reached 52 nm. For the obtained materials, the nominal pore cage diameter calculated from nitrogen adsorption reached 32 nm, whereas the actual pore cage diameter calculated using the geometrical relation was 36 nm. The pore entrance size was below 5 nm before the acid treatment, but was greatly enlarged as a result of the treatment. The sample prepared without hydrothermal treatment was converted to ordered closed-pore silica at as low as 400-450 °C. Our study confirms the ability to select micelle expanders on the basis of data on solubilization of compounds in micelle solutions.

18.
J Colloid Interface Sci ; 361(2): 472-6, 2011 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-21703633

RESUMO

Highly ordered mesoporous SBA-15 silica with large pore diameter of 18 nm (nominal BJH pore diameter ~22 nm) and short pore length (~500 nm) was synthesized using a micelle expander 1,3,5-triisopropylbenzene in the absence of ammonium fluoride by employing short initial stirring time at 17 °C followed by static aging at low temperature. Scanning and transmission electron microscopies revealed that the material comprised of platelet particles in which large mesopores were nearly flawlessly arranged within uniform domains up to 3 µm in size. The platelet SBA-15 had the (100) interplanar spacing of 17 nm, high surface area (~470 m(2) g(-1)) and large pore volume (~1.6 cm(3) g(-1)). The hydrothermal treatment at 130 °C for 2 days was employed to eliminate constrictions from the pore channels. The control experiment showed that a sample prepared with prolonged stirring had very similar mesoporous properties, but the particle size was smaller and the domains were irregular, proving that the static conditions facilitate the formation of SBA-15 with platelet particle morphology. The absence of ammonium fluoride was also critical in attaining the platelet particle shape.

19.
Langmuir ; 26(18): 14871-8, 2010 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-20726611

RESUMO

Ultralarge-pore FDU-12 (ULP-FDU-12) silicas with face-centered cubic structures (Fm3m symmetry) of spherical mesopores were synthesized at low initial temperature (∼14 °C) using commercially available PEO-PPO-PEO triblock copolymer Pluronic F127 as a micellar template and xylene as a micelle expander. Xylene was selected on the basis of its predicted higher swelling ability for the Pluronic surfactant micelles in comparison to 1,3,5-trimethylbenzene that was used previously to obtain large-pore FDU-12. The optimization of the synthesis conditions afforded as-synthesized ULP-FDU-12 materials with unit-cell parameters up to 56 nm, which is comparable to the highest reported values for Fm3m structures templated by custom-made surfactants. Calcined silicas were obtained with unit-cell parameters up to 53 nm and pore diameters up to ∼36 nm (for N(2) adsorption at 77 K, the capillary condensation relative pressure was up to 0.938). The preferred silica source was tetraethylorthosilicate, but tetramethylorthosilicate was also found suitable. The pore diameter was dependent on the unit-cell size of the as-synthesized material, but was further tuned by adjusting the time and temperature of the treatment in the HCl solution. If the synthesis was performed at low temperature only, highly ordered closed-pore silicas were obtained at calcination temperatures as low as 450 °C. On the other hand, the hydrothermal treatments, including the acid treatment at 130 °C, afforded silicas with large pore entrance sizes. The present synthesis constitutes a major advancement in the synthesis of ordered silicas with very large open and closed spherical mesopores.

20.
Langmuir ; 26(4): 2688-93, 2010 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-20141209

RESUMO

The azide-alkyne cycloaddition "click" reaction was used to covalently bond high loadings of polymers and monosaccharides to the surface of an ordered mesoporous silica. The functionalization process was followed using thermogravimetry, gas adsorption, small-angle X-ray scattering, and infrared spectroscopy. Large-pore SBA-15 silica with cylindrical mesopores of diameter approximately 15 nm was synthesized using triisopropylbenzene as a micelle expander. The surface of the silica was modified with aminopropyl groups that were converted to propargyl-bearing groups through a reaction with 4-pentynoyl chloride. Thus prepared "clickable" pores were reacted with azide-functionalized poly(methyl methacrylate) (PMMA) and oligo(ethylene glycol) as well as protected and deprotected D-galactose. The new "grafting to" procedure allowed us to introduce uniform polymer films of thickness up to about 2 nm without any appreciable pore blocking, even for the polymer loading as high as 25 wt %. Uniform layers of monosaccharides with loadings up to 20 wt % were also obtained with remarkable grafting efficiency. No change in the periodic structure of the silica support was observed throughout the grafting process. These results demonstrate that the "click" reaction is a powerful approach to ordered mesoporous silicas with accessible pores functionalized with high loadings of various macromolecules and biomolecules.


Assuntos
Etilenoglicol/química , Monossacarídeos/química , Polimetil Metacrilato/química , Dióxido de Silício/química , Membranas Artificiais , Porosidade , Propriedades de Superfície
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