Nanofilled Composites Research Articles

In Vitro Microleakage Comparison of Flowable Nanocomposites and Conventional Materials Used in Pit and Fissure Sealant Therapy.

Objectives:Pit and fissure sealants are recognized as an effective preventive approach in pediatric dentistry. Composite resin is the most commonly used sealant material. Adding nanoparticles to composite resin could result in production of flowable composite with higher mechanical properties and better flowability than previous sealants. This study aimed to compare the microleakage of a flowable nanocomposite and materials conventionally used as pit and fissure sealants.Materials and Methods:A total of 185 extracted mandibular third molar teeth were selected and randomly divided into 5 groups (n=36): flowable nanocomposite, flowable composite, filled sealants, nano-filled sealants, and unfilled sealants. Five teeth were reserved for examination under a scanning electron microscope (SEM). The samples were thermocycled (5–55°C, 1-minute dwell time) for 1000 cycles and immersed in 0.2% fuchsine solution for 24 hours. Teeth were sectioned buccolingually. Microleakage was assessed qualitatively and quantitatively by means of dye penetration and SEM. Data were analyzed using chi-square, Kruskal-Wallis, and Bonferroni-corrected Mann-Whitney U tests.Results: Qualitative microleakage assessment showed that flowable composite and nanofilled flowable composite had almost no microleakage (P<0.001). Regarding quantitative scores, the nanofilled flowable composite and unfilled fissure sealant showed the lowest and the highest rate of microleakage, respectively. No statistically significant difference was found between the two flowable composites (P=0.317). Filled resin-based sealant had significantly lower microleakage than unfilled resin-based sealant (P<0.001).Conclusion:Use of flowable and nanofilled flowable composites (but not unfilled resin-based fissure sealant) is recommended for sealing of pits and fissures of molars.

Synergistic Improvement in Thermal Conductivity of Polyimide Nanocomposite Films Using Boron Nitride Coated Copper Nanoparticles and Nanowires.

Electronic devices are increasingly dense, underscoring the need for effective thermal management. A polyimide (PI) matrix nanocomposite film combining boron nitride (BN)-coated copper nanoparticles (CuNPs@BN) and nanowires (CuNWs@BN) was fabricated by a flexible and fast technique for enhanced thermal conductivity and the dielectric properties of nanocomposite films. The thermal conductivity of (CuNPs-CuNWs)@BN/PI composite comprising 10 wt % filler loading rose to 4.32 W/mK, indicating a nearly 24.1-fold increase relative to the value obtained for pure PI matrix. The relative permittivity and dielectric loss approximated 4.92 and 0.026 at 1 MHz, respectively. The results indicated that the surface modification of CuNPs and CuNWs by introducing a ceramic insulating layer BN effectively promoted the formation of thermal conductive networks of nanofillers in the PI matrix. This study enabled the identification of appropriate modifier fillers for polymer matrix nanocomposites to improve electronic applications.

THE EVALUATION OF CONVENTIONAL AND DIGITAL RADIOGRAPH FOR RADIOPACITY ASSESSMENT OF RESTORATIVE MATERIALS

Radiopacity is an important characteristic for restorative materials as dentists have got different abilities in interpreting a lesion or caries in a radiograph. The enforcement of secondary caries diagnosis is a challenge for dentists because they often mistake the diagnosis for restorative materials with low radiopacity. This study aims to determine the differences in the average radiopacity values of certain restorative materials by using conventional and digital radiographs. Moreover, to know the right types of radiographs in distinguishing between radiopacity of certain restorative materials and radiodensity of secondary caries. This is an analytical descriptive study with cross sectional design. The sample was divided into 10 groups of 6, which is dental radiograph filled with glass ionomer cement, resin modified glass ionomer cement, nanofiller and micro hybrid composites as well as teeth with secondary caries which were obtained from conventional and digital radiographs. Next, conventional and digital radiographs were interpreted by observations of 5 dental specialists in which measurement was done by using Image J software to get the average radiopacity values of secondary caries and each restorative material. The results showed that the average radiopacity values for glass ionomer cement are 177.633 ± 6.465 and 187.879 ± 9.305, resin modified glass ionomer cement are179.498 ± 5.597 and 192.078 ± 11.006, composite nanofillers are 194.847 ± 4.952 and 184.401 ± 9.170, microhybridcomposites are 189.109 ± 4.251 and 179.585 ± 6.809, finally secondary caries are 161.772 ± 9.256 and 109.988 ± 7.684 for conventional and digital radiographs respectively. Then the data was analyzed by using T test with significance value of p &lt;0.05. As a conclusion, this study shows no significant difference in the radiopacity of four restorative materials if compared between conventional and digital radiographs while digital radiograph shows significant difference between radiopacity values of restorative materials and secondary caries. Whereas, conventional radiograph does not show significant difference between restorative materials and secondary caries.&#x0D; Radiopacity is an important characteristic for restorative materials as dentists have got different abilities in interpreting a lesion or caries in a radiograph. The enforcement of secondary caries diagnosis is a challenge for dentists because they often mistake the diagnosis for restorative materials with low radiopacity. This study aims to determine the differences in the average radiopacity values of certain restorative materials by using conventional and digital radiographs. Moreover, to know the right types of radiographs in distinguishing between radiopacity of certain restorative materials and radiodensity of secondary caries. This is an analytical descriptive study with cross sectional design. The sample was divided into 10 groups of 6, which is dental radiograph filled with glass ionomer cement, resin modified glass ionomer cement, nanofiller and micro hybrid composites as well as teeth with secondary caries which were obtained from conventional and digital radiographs. Next, conventional and digital radiographs were interpreted by observations of 5 dental specialists in which measurement was done by using Image J software to get the average radiopacity values of secondary caries and each restorative material. The results showed that the average radiopacity values for glass ionomer cement are 177.633 ± 6.465 and 187.879 ± 9.305, resin modified glass ionomer cement are179.498 ± 5.597 and 192.078 ± 11.006, composite nanofillers are 194.847 ± 4.952 and 184.401 ± 9.170, microhybridcomposites are 189.109 ± 4.251 and 179.585 ± 6.809, finally secondary caries are 161.772 ± 9.256 and 109.988 ± 7.684 for conventional and digital radiographs respectively. Then the data was analyzed by using T test with significance value of p &lt;0.05. As a conclusion, this study shows no significant difference in the radiopacity of four restorative materials if compared between conventional and digital radiographs while digital radiograph shows significant difference between radiopacity values of restorative materials and secondary caries. Whereas, conventional radiograph does not show significant difference between restorative materials and secondary caries.

Microwave Absorption Properties of Polyaniline/Titanium Dioxide (PAni/TiO2) Doped with Different Types of Fullerenes

In this work, Polyaniline/titanium dioxide (PAni/TiO2) nanocomposites without and with addition of fullerene such as pristine fullerene (C60) and small gap fullerene (S.G.F) were prepared through template‐free method by using hexanoic acid (HA) as a dopant. FTIR and UV‐Vis spectra confirmed the chemical structure of conjugated PAni and indicated that the resulted PAni is in conducting state. The existence of fillers in PAni nanocomposites were confirmed by the characteristic peaks of TiO2 and fullerene in XRD pattern. Based on FESEM images obtained, nanocomposites formulated with C60 (PAni/HA/TiO2/C60) formed the nanorods/nanotubes and microrods/microtubes with the biggest diameter (240 nm), followed by PAni with S.G.F (PAni/HA/TiO2/S.G.F) and PAni without the addition of fullerene (PAni/HA/TiO2) with diameter of 180 nm and 160 nm, respectively. Besides, PAni/HA/TiO2/C60 also possessed the highest electrical conductivity of 1.708 × 10−1 S/cm as compared to PAni/HA/TiO2/S.G.F and PAni/HA/TiO2 (4.531 × 10−3 S/cm to 1.439 × 10−2 S/cm). Microwave absorption studies of PAni nanocomposites were carried out by using Microwave Vector Network Analyzer (MVNA) in the frequency range of 0.5–18.0 GHz. Among all nanocomposites, PAni/HA/TiO2/C60 exhibited a narrow and the highest reflection loss (RL) peak of −61.3 dB at 9 GHz due to the highest conductivity (1.708 × 10−1 S/cm), dielectric permittivity (0.46) and heterogeneity of PAni (larger amount of nanorods/nanotubes and microrods/microtubes) that have induced more disordered motion of charge carrier along the backbone of PAni. Thus, it eventually enhanced the molecular polarization such as greater space charge relaxation and hopping of confined charges.

Ion transport dynamics in ionic liquid incorporated CuBTC–metal-organic framework based composite polymer electrolyte

Cu based metal-organic framework (MOF), copper 1,3,5-benzenetricarboxylate (CuBTC) has been incorporated with ionic liquid (IL) 1-butyl-3 methylimidazolium bromide at different wt% to be used as composite nanofiller in poly (ethylene oxide) polymer electrolyte system. Shifting of carboxylate vibrational modes is observed from FTIR and significant changes of binding energies of Cu spin–orbit peaks are obtained from XPS spectra suggesting strong interaction between Cu metal cluster of MOF and Br− anions of the IL. Oscillation periodicity and local coordination structure of Cu K-edge are investigated in k-space and R-space from the scanning XANES and EXAFS spectra. Dielectric modulus spectra show non-Debye relaxation dynamics and optimum ionic conductivity of 5 × 10−3 S cm−1 is obtained for the nanocomposite containing 50 wt% IL at 380 K. The frequency dependent AC conductivity curves depict ion concentration and temperature independent scaling behavior by collapsing to a single curve. The electrochemical stability and cycling performance increases with increasing IL concentration and attains electrochemical stability of 6.1 V with discharge capacity of 152.5 mAh/g after 500 cycles at 50 wt% of IL.

Impact of Silanization on the Structure, Dispersion Properties, and Biodegradability of Nanocellulose as a Nanocomposite Filler

For nanocellulose to function effectively as a nanofiller in polymers, its interfacial properties are often modified to enhance the dispersion of nanocellulose in the polymer matrix. However, the e...

Effectiveness of Two Type Coupling Agent of Dental Composite Nanofiller Prototype with Addition of Acetone in Preparation

Nano size of ceramic filler (nanofiller) are tend to possess difficulties to be covered by resin matrix due to large surface area to volume ratio. Addition of aceton known as the diluent agent by introducing more content of filler as well as helping distribution of the filler in the resin matrix in application of dental composite restoration. In this study, a total 24 specimens of dental composite prototype; nanofiller-TMPS and nanofiller-MPTS were prepared using a customized acrylic mold and they were divided into two groups based on filler/resin ratio (n=6 each group). In the process of dental composite making, acetone were added into resin; 1 ml (filler/resin, 50/50) and 5 ml (filler/resin, 80/20) untill specific consistency obtained. The specimens were stored in distilled water for 24 hours at 37°C then subjected to hardness test using Vickers hardness tester machine, LECO – Japan M– 400–H1 with the load of 200 grams for 15 seconds (ADA Specification No. 27). Data were statistically analyzed using t independent test (α=0.05). The result revealed that dental composite prototype contain nanofiller-MPTS with filler/resin rasio (50/50) were statistically significant higher than dental composite prototype contain nanofiller-TMPS with same ratio (p&lt;0.05). Otherwise, dental composite prototype with filler/resin ratio (80/20) were no observed statistically significant differences for both nanofiller-TMPS and nanofiller-MPTS (p&gt;0.05). As conclusion, nanofiller modified MPTS are more effective to elevate surface hardness of dental composite prototype than nanofiller-TMPS for 50/50 filler/resin ratio

Effect of Carbon Nanotube Aspect Ratio on the Thermal and Electrical Properties of Epoxy Nanocomposites

The novel properties of carbon nanotubes have generated much interest in polymer nanocomposites. The thermal and electrical properties of multi-walled carbon nanotube-epoxy composites were investigated both experimentally and theoretically. Experiments were performed to evaluate the effect of the aspect ratio of carbon nanotubes. Comparisons were made between the results obtained for the nanocomposite materials containing carbon nanotubes with a high (800) and a low (80) aspect ratios. Design recommendations were made, and potential applications were also discussed. It was shown that the aspect ratio plays an important in determining the physical properties of the epoxy nanocomposite. The electrical conductivity of the nanocomposite is highly dependent on the aspect ratio of carbon nanotubes. In contrast, the aspect ratio plays a considerable role in the thermal conductivity of the nanocomposite. Carbon nanotubes have clearly demonstrated their capability as thermally and electrically conductive fillers in epoxy nanocomposites. In contrast to the orders of magnitude enhancement in electrical conductivity with a very low loading of carbon nanotubes, the thermal conductivity of the nanocomposite has shown only moderate improvement. The improvement in physical properties of the nanocomposite can be interpreted in terms of carbon nanotube networks.

Mechanochemically Carboxylated Multilayer Graphene for Carbon/ABS Composites with Improved Thermal Conductivity.

Dry ball milling of graphite under carbon dioxide pressure affords multilayer-functionalized graphene (MFG) with carboxylic groups as nanofiller for composites of carbon and acrylonitrile–butadiene–styrene copolymers (ABSs). Produced in a single-step process without requiring purification, MFG nanoplatelets are uniformly dispersed in ABS even in the absence of compatibilizers. As compared to few-layer graphene oxide, much larger amounts of MFG are tolerated in ABS melt processing. Unparalleled by other carbon nanofillers and non-functionalized micronized graphite, the addition of 15 wt % MFG simultaneously results in a Young’s modulus of 2550 MPa (+68%), a thermal conductivity of 0.321 W∙m−1∙K−1 (+200%), and a heat distortion temperature of 99 °C (+9%) with respect to neat ABS, without encountering massive embrittlement and melt-viscosity build-up typical of few-layer graphene oxide. With carbon filler at 5 wt %, the Young’s modulus increases with increasing aspect ratio of the carbon filler and is superior to spherical hydroxyl-functionalized MFG, which forms large agglomerates. Both MFG and micronized graphite hold promise for designing carbon/ABS compounds with improved thermal management in lightweight engineering applications.

Influence of adhesive-composite application modalities on their bonding to tooth structure and resistance of the performed restorations to failure

Background/purposeThe longevity of bonded composite restorations could be affected by the utilized adhesive-composite application techniques. This in vitro study aimed to evaluate the influence of adhesive-composite application modalities on their bonding values to tooth structure and on the failure resistance of the performed restorations on loading. Materials and methodsResin composite studs, 2 mm in diameter and 4 mm high, were bonded in 2 groups to flattened enamel and dentin surfaces of 80 extracted premolars using pre-cured (PC) and co-cured (CC) self-etch resin adhesive. Studs in each group were built-up in 4 subgroups using either multiple increments of nano-filled composite (IF, control) or single increment of preheated nano-filled (PH), bulk-fill (BF) and sonic-activated bulk-fill composites (SF). Another 80 premolars with standard class II cavities were also restored using the same adhesive-composite application modalities. All specimens were then stressed on a universal testing machine to assess the composite-tooth shear bond strength and the resistance of the performed restorations to failure. The modes of specimens’ failure were also assessed following each test. ResultsThe PC adhesive provided higher bond strength to dentin (p < 0.05) and comparable bond strength to enamel in comparison to the CC one (p>0.05%). Both PH and BF composites showed lower bond strength to dentin in presence of PC adhesive (p < 0.05). Comparable bond strengths were noticed for PH, BF and SF composites to dentin in presence of CC adhesive (p > 0.05). PH and SF restorations presented the highest resistance to failure (p < 0.05). ConclusionBoth incrementally and bulky-inserted composites offer clinically acceptable bond strength in presence of pre-cured resin adhesive. Both Preheated and sonic-activated composite restorations offer the highest resistance to failure on loading. The preheating procedure renders regular composite material suitable for bulk-fill applications.

Studies on the mechanical properties of carbon black-halloysite nanotube hybrid fillers in nitrile PVC nanocomposites for oil seal applications

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Influence of Shrinkage and Viscosity of Flowable Composite Liners on Cervical Microleakage of Class II Restorations: A Micro-CT Analysis.

This study determined the influence of shrinkage and viscosity of flowable composite liners on the cervical microleakage of Class II restorations using micro-CT. Seven composites of varying viscosities were selected and included five giomers (Shofu Beautifil II [BF], Flow Plus F00 and F03 [F00 and F03], Flow F02 and F10 [F02 and F10]) and 2 nano-filled composites (3M-ESPE Filtek Z350 [Z350] and Filtek Z350 Flowable [Z350F]). Polymerization shrinkage (n=7) was assessed with the Acuvol volumetric shrinkage analyzer while complex viscosity was determined with the advanced rheometric expansion system at 25°C. Standardized Class II restorations incorporating 1-mm horizontal layers of different flowable liners and 3-mm oblique layers of BF or Z350 were subjected to a silver nitrate test for 24 hours and examined using micro-CT. Microleakage was determined at 0.1-mm intervals from the buccal to lingual surfaces providing 30 sites per specimen and scored accordingly. Statistical analysis was performed with the one-way ANOVA, Kruskal-Wallis test, and Spearman's rho correlation at a significance level of p<0.05. Mean volumetric shrinkage ranged from 5.33±0.17% to 2.35±0.02% for F02 to Z350, respectively. The flowable materials had significantly higher shrinkage than did their sculptable counterparts (BF and Z350). Complex viscosities ranged from 9.65 to 4.20 (Z350 and F10, respectively) at a frequency of 10 rad/s and from 8.16 to 3.28 (Z350 and F03, respectively) for 100 rad/s. Giomer restorations had significantly less leakage than did those restored with nano-filled composites. No microleakage was observed with restorations lined with F02 or F10. The use of flowable liners reduced cervical microleakage of Class II restorations. Interfacial integrity of Class II restorations was significantly correlated with liner viscosity, filler volume, and shrinkage.

Tensile, thermal, and antibacterial characterization of composites of cellulose/modified Pennisetum purpureum natural fibers with in situ generated copper nanoparticles

Eco-friendly all cellulose composites were developed using cellulose as matrix and nanocomposite (in situ generated copper nanoparticles modified Napier Grass Fibers (NGFs)) as fillers for the antibacterial applications. The content of the nanocomposite filler was increased from 1 wt.% to 5 wt.% in the cellulose matrix. All these composites were characterized by Scanning Electron Microscopy (SEM), Tensile, Thermo Gravimetric Analysis (TGA), and antibacterial tests. SEM-EDX analysis revealed the in situ generation of copper nanoparticles on the surface of the films. Further, all cellulose composites showed good thermal stability. A minimum of 30% increase in char residue was observed in all cellulose nanocomposites compared to matrix. Antibacterial analysis indicated an excellent clear zone formation against both Gram Negative (Escherichia coli) and Gram Positive (Staphylococcus) bacteria. Hence, all these cellulose nanocomposite films can be considered as antibacterial packaging and dressing materials in medical field.

Techno-Economic Assessment, Scalability, and Applications of Aerosol Lignin Micro- and Nanoparticles.

Lignin micro- and nanoparticles (LMNPs) synthesized from side-streams of pulp and paper and biorefinery operations have been proposed for the generation of new, high-value materials. As sustainable alternatives to particles of synthetic or mineral origins, LMNPs viability depends on scale-up, manufacturing cost, and applications. By using experimental data as primary source of information, along with industrial know-how, we analyze dry and spherical LMNPs obtained by our recently reported aerosol/atomization method. First, a preliminary evaluation toward the commercial production of LMNPs from industrial lignin precursors is presented. Following, we introduce potential LMNPs applications from a financial perspective. Mass and energy balances, operating costs, and capital investment are estimated and discussed in view of LMNPs scalability prospects. The main potential market segments identified (from a financial perspective) include composite nanofillers, solid foams, emulsion stabilizers, chelating agents, and UV protection. Our technical, financial, and market assessment represent the basis for R&D planning and efforts to lower the risk related to expected industrialization efforts. Manufacturing costs were estimated between 870 and 1170 USD/t; also, minimum selling prices varied from 1240 and 1560 USD/t, depending on raw materials used. Sensitivity analysis indicated that manufacturing cost can be as low as 600 USD/t, depending on the process conditions considered. Finally, based on the financial assessment, potential applications were identified.

One-year clinical evaluation of bulk-fill flowable vs. regular nanofilled composite in non-carious cervical lesions

The aim of this double-blind, randomized trial was to evaluate the 1-year clinical performance of a bulk-fill flowable and a regular nanofilled composite in non-carious cervical lesions (NCCLs). Twenty-two subjects with at least two NCCLs were enrolled in the study. A total of 89 restorations were performed by a single operator using Filtek Supreme (FS) Ultra Universal or Filtek Bulk (FB) Fill Flowable. A universal adhesive (Scotchbond™ Universal Adhesive) was used with a self-etching approach in dentin. The restorations were evaluated by two independent and previously calibrated examiners at baseline (7days), 6months and 1year, according to the USPHS modified criteria. Mann-Whitney U test was used to analyze the differences between composites and Wilcoxon signed rank test for comparisons between the baseline and follow-ups (α = 5%). One restoration was considered clinically unacceptable due to loss of retention after 6months in the FS group. FS presented statistically high scores for surface roughness when compared to FB after 1year (p < 0.05), but both were considered clinically acceptable. After 1year, the frequency of clinically unacceptable rates was 3.3% for anatomical form in the FB group, 1.1% for retention in the FS group, and 2.2% for marginal adaptation in both groups. All restorations, in both groups, presented score 0 over the 1-year period for marginal staining, postoperative sensitivity, and secondary caries. Both composite resins showed acceptable clinical performances for the restoration of NCCLs after 1year. Both bulk-fill flowable and regular nanofilled composites showed good clinical performances for the restoration of NCCLs after 1year.

Effect of functional groups on the agglomeration of graphene in nanocomposites

A base wash procedure was used to partially remove the oxygen functional groups from the graphene oxide (GO) flakes to prepare the base-washed GO (BwGO). It is found that the base wash treatment does not alter the physical properties (size, thickness etc.) of the GO significantly but the chemical composition is changed. Nanocomposites were prepared by incorporating the BwGO flakes obtained in a poly(vinyl alcohol) (PVA) matrix. It was found the storage modulus of the nanocomposites is enhanced from 4.4 GPa to 6.5 GPa with 5 wt% of BwGO. This is in agreement with the micromechanical estimation obtained by using Raman spectroscopy that follows the interfacial stress transfer from the matrix to the BwGO fillers. The lower effective modulus of BwGO than GO as calculated using the classical ‘rule of mixtures’ is due to the loss of functional groups on GO that serve as a surfactant to prevent the flakes from re-agglomerating. An agglomeration factor ηa is therefore proposed and a concept of ‘effective volume fraction’ is introduced to quantify and evaluate the level of agglomeration of fillers in nanocomposites, which can be otherwise difficult to visualize optically. It is found that the removal of the functional groups causes the flakes to re-agglomerate, and reduces the ‘effective volume fraction’ by about 10–20%.

Comparison of light propagation in dental tissues and nano-filled resin-based composite

This study used three LASERs (red, green, and blue) with a spectrophotometer to compare the light propagation for the following: absorption (A), transmittance (T), attenuation (K), and scattering anisotropy coefficient (g) in dental tissues and nano-filled resin-based composites. This study used three distinct incremental build-up techniques, which included one shade (body), two shades (enamel and dentin), and three shades (enamel, transparent, and dentin). Twenty human, un-erupted, recently extracted third molars (shade B1) were used to obtain 40 tooth slabs. The samples were randomized and equally distributed into four experimental groups. The Positive Control Group included dental tissues with enamel, dento-enamel junction DEJ, and dentin; the Technique 1 group (T1) included one shade tissues, B1B; the Technique 2 group (T2) included two-shades tissues, A2Dentin and B1Enamel; and the Technique 3 group (T3) included three shade tissues, A2Dentin, Transparent, and B1Enamel. Cavity preparation was standardized, and, using the spectrophotometer, each specimen was irradiated by three LASERs. A voltmeter recorded the light-output signal, and from this raw data, the following optical constants (A, T, K, g) were calculated. ANOVA, followed by a post hoc Tukey's test (p < 0.05), revealed that absorption and transmittance in dental tissues were significantly different when comparing the three build-up technique groups. However, when examining attenuation coefficient, there was no significant difference in dental tissues for T2 and T3 as analyzed by blue and red lasers. There was also no significant difference among the three lasers for T2 and T3. There was also no significant effect of the types of experiments on the value of scattering anisotropy factor g for blue laser among the four experimental groups. Within the limitations of this study, none of the build-up techniques were able to reproduce the dental tissues optical properties, and T2 and T3 resulted in a similar pattern of light propagation. The clinical success of restorative procedures depends on selecting materials and techniques that emulate the natural tooth and provide long-term stability in color and optical properties.

Investigations on microstructure and mechanical properties of TiO2 Nanoparticles addition in Al 3003 alloy joints by gas tungsten arc welding

Al 3003 alloy is well known for its industrial use as heat exchangers, radiators, oil tanks and household utensils. In case of heat exchangers, fabrication becomes mandatory by a welding process which is carried out by gas tungsten arc welding (GTAW). It is preferred due to its advantages of superior mechanical properties. Thus by involving GTAW process and reinforcing with suitable nanoparticles, the strength of Al 3003 alloy can be improved at the joints. Hence this technical paper deals with the fabrication of Al100–x – x wt% TiO2 (x = 0, 0.75, 1.5, 2.25 and 3) nanocomposite filler metal through accumulative roll bonding (ARB) technique to weld Al 3003 alloy through GTAW. Further characterization studies have been made through various electron microscopic techniques besides X‐ray diffraction analysis (XRD), vicker's microhardness and tensile testing. It was observed that the incorporation of TiO2 nanoparticles reduced the grain size much due to the formation of more nucleation sites and deceleration growth. XRD results revealed the presence of TiO2 peaks in the composite. FESEM confirmed the distribution of second phase nanoparticles regularly in the Al matrix. TEM analysis showed that the nanoscale TiO2 distribution and strain fields due to thermal mismatch between matrix and reinforcement. The improvement in mechanical properties was owing to good interfacial bonding between the Al matrix and ceramic nanoparticles.

Surface roughness of nanofilled and nanohybrid composite resins exposed to kretek cigarette smoke

Background: Cigarette smoking is a public health issue that may influence the physical properties of dental composites. Surface roughness is one of the physical properties of restorative materials potentially influencing their success. The use of nanofilled and nanohybrid composites in dentistry has increased substantially over the past few years. Purpose: The purpose of this study was to evaluate the surface roughness of nanofilled and nanohybrid composite resins exposed to kretek cigarette smoke. Methods: Twelve cylindrical specimens of each material were prepared and divided into two groups (n=6). In the control groups, the specimens were immersed in distilled water for 24 hours at 37°C, with the water being renewed daily. For the experimental groups, the specimens were exposed to kretek cigarette smoke on a daily basis, then washed and soaked in distilled water at 37°C. After 21 days, the specimens were measured using a Surface Roughness Tester and the data was then statistically analyzed. Results: An Independent-T Test revealed that there were statistically significant differences in the surface roughness between the control and experimental groups of both nanofilled and nanohybrid composites, as well as between the nanofilled experimental group and the nanohybrid experimental group. Conclusion: Exposure to kretek cigarette smoke can increase the surface roughness of nanohybrid composites to a significantly greater extent than nanofilled composites.

Synthetic talc as a new platform for producing fluorescent clay polyurethane nanocomposites

As a non-swelling clay, talc generally interacts very weakly with organic molecules. However, two new nanometric synthetic talcs that incorporate berberine chloride were successfully used as fluorescent fillers in clay polyurethane nanocomposites obtained by the blending method. A micrometric natural talc filler was also used for comparison. The clay polymer nanocomposites (CPN) were characterized by FTIR, molar mass analysis and XRD. All talc fillers were well dispersed into the polyurethane matrix even at high filler content of 5 wt%, as supported by TEM and SEM analyses. Morphological changes were confirmed by AFM. The optical properties of the fluorescent talcs, dye-doped polymer and CPN were compared. While the dye-doped polymer suffered from conventional fluorescence quenching due to dye aggregation, the emission quantum yield of the CPN was increased with increasing the filler content. The best emission efficiency was observed for the CPN that contains the smallest talc-berberine hybrid particles. The use of fluorescent synthetic talc resulted in materials with good thermal and mechanical properties, and can be considered as a new method to produce fluorescent CPN in view of multiple applications.