The main advantages of this method are the simplicity, the feasibility, and the inexpensiveness with respect to other methods, although it has some drawbacks related to the excessive heating experienced by the matrix when applying the ultrasonic radiation, particularly in the zones closest to the ultrasound probe.
Therefore, the choice of the conditions is very important to obtain viscosity low enough to facilitate the dispersion and the homogenization of the fillers without any re-agglomeration effect. One of the possibilities of overcoming the heating issues is the simultaneous application of high-speed agitation with the ultrasound. This allows one to obtain a more homogeneous dispersion as an effect of the additional agitation together with an improvement of the dissipation of heat generated by the ultrasonic radiation.
Figure 9 a shows a picture of the experimental setup. It is possible to see the ultrasound probe, adapted to the volume and the intensity of the applied radiation, the stripping shovel, whose speed depends on the viscosity of the matrix, and a thermostatic bath to maintain temperature equilibrium. Figure 9 b shows the effect on the temperature of the applied speed for any of the analyzed probes. It is evident that the higher heat dissipation was obtained using the viscojet triple cone at rpm.
The effect of the gear at speeds ranging between 10 and 60 rpm was analyzed. Figure 10 shows the evolution with the time of the size aggregates at the different gear speeds for a two gear head gearbox miller. Unfortunately, with respect to the previous methods, no improvement on the quality of the dispersion was observed. The optical microscopy images in Figure 11 are related to the dispersion obtained using the two gear head a and the three gear head b at 60 rpm. Although the 3 gear head gearbox milling provided the best results this was not good enough to obtain an optimal dispersion.
This mechanical dispersion method used a pressure roller machine. The distance between the rollers, which was of the order of microns, was varied in order to optimize the process of nanofiller dispersion. This method, offering the advantage of constantly driving the nanofilled matrix through the rollers, was highly efficient. Figure 12 shows the evolution with the time of the size aggregates at different distances between the rollers.
Figure 13 shows the optical microscopy of the dispersion obtained with the calendar set with a distance between the rollers of 0. The predominant grey color with few very little white and black spots indicates the good quality of this dispersion method. The parameter to optimize was the distance between rollers, which was studied in a larger range of values. This study highlighted that the optimal distance between the rollers was 0. The mixed-method was a combination of two of the previous methods.
With respect to all the previous methods, this combined method resulted in a nanofilled material with a better dispersion and homogeneity.
This was confirmed by the optical micrograph shown in Figure 14 , which referred to a dispersion obtained in such a condition in which the sample was almost entirely grey. No white spots were evident and only a negligible amount of black spots indicating the presence of nanofillers agglomerate was observable. The laser tests carried out on the examined sample brought about a series of important results regarding the modal-vibrational behavior, with respect to acoustic excitation in the frequency range between 0 and Hz.
In such a way, it was possible to quantify an important acoustic property of the analyzed material: the ability to limit its deformations under the action of a relevant pressure load. Excluding the initial zone with the maximum peaks, several resonances were present in the spectral range between 80 and Hz Figure 15 b. The presence of such maximums allowed us to observe how the most intense modes were recorded for relatively low frequencies, compared to the much higher range of pure acoustic application.
Each natural frequency corresponded to a proper vibrating mode shape: in Figure 16 , six different elastic modes well captured in the interval 80— Hz are represented. Relying upon the transfer function represented above, the damping coefficient for the examined modes was estimated. The results achieved through the previous method were tabulated and diagrammed to make comprehension better Figure The dynamic analysis in the spectral domain highlighted a high dissipating property of the analyzed material mostly in the low-frequency region. The result is encouraging because the highest damping coefficient was found in the correspondence of the "drum" mode 0,1 where the maximum modal participation of the structure was obtained.
Moreover, it also represents a very relevant mode from the vibro—acoustic standpoint, as it is characteristic of an emissive membrane mode. Such a 0,1 planar mode is excited by impacts at any location on the membrane. When vibrating in this mode, the membrane behavior is much like a monopole source, which radiates sound very effectively.
Since it radiates sound so well when vibrating in this manner, the membrane quickly transfers its vibrational energy into radiated sound energy and the vibration dies away. In addition to the numerous known applications of CNTs in composite materials, in order to improve their mechanical properties, in recent decades research tackled the analysis of the acoustic properties of these carbon structures to exploit their application in many industrial fields, in particular automotive and avionics, with the aim of amplifying the insulating characteristics of various components of aircraft and vehicles.
In view of this function, the study also focused on the assessment of these insulating capacities. In the present analysis, it was interesting to understand how the CNTs panel could reflect and absorb the acoustic power of the sound source, measuring the transmission loss as previously already introduced.
A curve that illustrates the variation of the TL as a function of the frequency associated with the acoustic source was graphically obtained, as in the example in Figure The term in the denominator is the specific impedance characteristic, while the contributions to the numerator depend on the nature of the sample being analyzed, i. The sound insulation performance comparison was performed with respect to other literature data on similar panel configurations, due to the absence of a reference standard formulation.
Koval [ 38 ], performed deep studies in on the transmission of airborne noise into an aircraft cabin: results demonstrated that the noise attenuation provided by a composite shell was not so advantageous as an aluminum wall, mainly due to the increased acoustic radiation efficiency of CFRP. The graph above Figure 20 shows then a good performance of the nanotube based panel exhibiting already a higher STL at low frequencies, in correspondence with the normal mode participation region.
Such behavior can be explained by the modal damping peculiarities of the panel as previously measured. It can be, in fact, assumed that the resonant path for STL is attributed to the coupling of acoustic waves to free bending waves in the panel. It usually dominates the overall response around and above the panel coincidence frequency, where the acoustic wavelength is about the same as the structural wavelength, making the panel radiation more effective. In this frequency range, it is the damping loss factor that primarily controls panel vibration response and consequently the sound transmitted through the panel, so the higher the loss factor, the higher the STL [ 39 , 40 ].
Moreover, an interesting value of the STL increasing up to 30 dB is then measured in the medium frequencies range, next to Hz. This result seems to be of general validity. In fact, the obtained results confirm what has already been published on specimens obtained with the same formulations but using ultrasound as a dispersion method and a modified liquid resin infusion technology for the manufacturing of the panels [ 26 ]. In particular, the authors compared the results obtained for little coupons of CFRP impregnated with filled and unfilled epoxy resin. The obtained results indicated that reinforcing a sample with carbon structured nanofillers positively affect the properties of the sample since they, de facto, contribute to improving the global structural performance and to simultaneously positively enhancing the modal damping determined both in the time and in the spectral domains.
In general, damping in composites is caused by the viscoelastic behavior of the polymer matrix [ 41 ]. Although the load is transferred mainly by fibers, the matrix takes part in its transmission by means of tangential stresses [ 42 , 43 , 44 ]. In [ 26 ] the authors also showed dynamic mechanical characterization DMA of an unreinforced cured coupon made with the same formulation used in this paper and compared the results with those obtained with the same unfilled formulation taken as reference.
Other published works [ 27 , 29 ] demonstrated that in these systems the presence of MWCNT was responsible for a greater mobility of chains belonging to domains finely interpenetrated in the matrix where reversible hydrogen bonds are determined by interaction between epoxy resin and nanocages of POSS compounds. In particular, the two peaks were attributed to the presence of two phases with different cross-linking density and hence with different chain mobility. It was evident that the nanofiller was exerting a strong influence on the structure of the matrix.
The different cross-linking density was ascribed to an interruption of the cross-linking reactions on the part of CNTs during the curing cycle and related to the decrease of curing degree. The result was the formation of a fraction of the resin with a lower Tg characterized by greater mobility. This greater mobility of the chain segments allowed more flexibility of the material and greater damping characteristics.
Moreover, it is well recognized that CNTs improve the dynamic response of carbon fiber reinforced composites according to the concept of the stick—slip mechanism as a consequence of the peculiar strong mechanical characteristics of CNTs [ 45 , 46 , 47 ]. For nanocomposites under applied stress, the load transfer from the polymer to nanotubes causes the deformation of both the matrix and the nanoparticles until a critical shear stress is reached. After this critical shear stress, the nanotube debonds from the polymeric matrix keeping its strain constant while the matrix continues to deform.
The flammability of the manufactured panels was analyzed with the cone calorimeter and the results were compared to those obtained on panels made in the same conditions but using a commercially available epoxy resin. The heat release rate for both composites made with the RTM6 and nanofilled resins is shown in Figure Compared to the traditional RTM6 resin, the panel with the epoxy nanofilled resin exhibited a significant improvement in fire resistance properties. These data highlight that the flammability of the panel with the nanocomposite formulation is strongly reduced. Figure 22 shows a picture of the sample after the cone calorimeter test.
The non negligible presence of unburned resin is evident. The sample was almost self-extinguishing. This behavior may be due to the formation of non-intumescent char. In their paper, the authors analyzed the results of the cone calorimeter test and made some consideration of the pictures of the residues after the test. An improvement of the fire performance was observed when any kind of POSS compound was included in the composite.
The inhibition of the intumescent effect was attributed, in that paper, to the increase in thermal conductivity all over the sample but it may be also due to the increase of the viscosity due to the presence of CNT as highlighted in [ 33 ]. This increase in the viscosity could be also responsible for the increase in the time of ignition, as an increase of the viscosity inhibits the kinetics of the degradative phenomena and hence the velocity of the fuel formation in the gas phase. The char formation promoted by CNT is also well observable in Figure 22 , for the carbon fiber panel manufactured in this work.
Different dispersion methods suitable for the incorporation of carbon nanotubes in an epoxy formulation containing solubilized GPOSS nanocages were investigated. Listen to America. From Our Partners. You Are One Step Closer… To being empowered and on a positive pathway to achieving success in your next real estate transaction.
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Above all, I am impressed on Guiseppe's generousity. Because when my buddy left me alone, he accomodated me without asking any money and helped me to reorganize the last 2 days of my holiday I'll never forget his support.. Each room at this bed and breakfast is air conditioned and is equipped with a flat-screen TV.
The unit is air conditioned and has a TV. I was staying in this apartment 5 nights everything was great!! The apartment looks the same as in roses, clean, spacious, with a huge balcony with splendid sea and mountain views. Very nice owners. It was a wonderful accommodation. Congratulations and thanks for everything.
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I recommend this apartment for 10! Kindly Catalina Popovici. A terrace or balcony are featured in certain rooms. It features free Wi-Fi throughout. Quiet room, in spite of central location. Featuring free WiFi throughout the property, Numero Uno offers pet-friendly accommodation centrally located in Salerno, 1. The rooms have a flat-screen TV. You will find a coffee machine in the room.
Salerno city centre is 3 km from the property. People who need it quite should go for the room "China". Watch out for the great fotos all taken by the host. Wi-Fi is free in public areas. L'Infinito is set in a 19th-century building in the centre of Salerno, and offers air-conditioned rooms with a private bathroom. Free WiFi throughout and a shared kitchen are provided. Room was big, light , clean and nice. I had everything I need. Ketty was very nice and did everything so that quests enjoyed their stay.
Thank you. Next time I defenetly stay there again. Situated in Salerno, 3. Each room has a flat-screen TV with cable channels. He came to pick us up in town when we got lost, then gave us his own parking space so that the car would be safe, helped us carrying the bags and very friendly. The room was beautiful, everything was great.
Every room has a flat-screen TV. Some rooms include views of the garden or city. A 5-minute walk from Salerno promenade and metres from the city Cathedral, Ospiti in Centro offers air-conditioned modern apartments. The property is 1 km from Salerno Train Station. The flat is freshly decorated and has everything you would need for self-catering. Also, there is a reasonably sized supermarket next door to the property. Although quiet, the flat is very well located for other shops and restaurants as well as local places of historical interest eg the duomo.
Residenza Eleonora is located in Salerno, 2. A flat-screen TV is provided. The holiday home is equipped with air conditioning and free WiFi. The apartment is located perfectly and well equipped. Everything is in perfect condition and shows lovely details. Monica and Vito are really great and friendly hosts, very welcoming and generous, also providing us good advices for dinner or undertakings.
Highly recommended. The room was sunny and cosy, and the view was fantastic! Noise from the port never bothered us. Also the old beautiful building, where the hotel is situated, was real pleasure to live in. Centrally located, Salernoprestige is just a 5-minute walk from Salerno Train Station, bus station and ferry harbour. It offers free Wi-Fi and modern rooms with air conditioning and a balcony.
MOB DON ‘TONY DUCKS’ DIES IN PRISON AT 88
Very comfortable and quiet. The room was spacious and nicely decorated. Thank you Mimma! Set on a hill, with panoramic views over the Salerno Port, Villa Sorriso is a minute drive from the sandy beach of Torrione. Some units have views of the sea or city. All rooms include a private bathroom Thank you Mario and Donato!! Each room at this bed and breakfast is air conditioned and is fitted with a flat-screen TV with cable channels Free Wi-Fi access is available in all areas.
I needed to have a different room the host could not have been nicer in spite of having extra work. Set 3. There is a fully equipped kitchen and a flat-screen TV is provided. The owners are very kind and helpfull. They suggested us a very good restaurant. It takes half an our to get to Pompeia or the north part of the Malfitan Coast. The terrace has no views but it's a good place to relax. This bed and breakfast has a shared lounge with a TV and rooms with a work desk. Located in Salerno, the property is metres from Salerno Station.
Free WiFi is available. Really central, only some Minutes to walk to Old Town and the Sea. Tutto Bene! Petros Apartments offers pet-friendly accommodation in Salerno. Some units include a seating area to relax in after a busy day. Casa Castagna is a adorable accomondation. The hosts are very helpful, kind and great baker. The breakfast was versatile and the room was spacious and clean.
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Thank you for everything. WiFi is free. Every room at this bed and breakfast is air conditioned and has a flat-screen TV. With a terrace offering panoramic city views, La Rosa dei Venti is centrally located in Salerno, metres from the sea promenade.
Located in Salerno, 2. Room was very big, new furniture and fully equipped. The best thing was the homemade lemon pie. Everything was perfect! All rooms come with a flat-screen TV. Dimora Tafuri is located in Salerno, 3. Certain rooms have a private bathroom with a spa bath, while others have free toiletries and a hairdryer. Staff is extremely friendly and make a great effort to make your stay enjoyable, for example by preparing a nice breakfast table at the desired time every morning.
Bathroom etc are brand-new and very clean. Benvenuti in Centro offers pet-friendly accommodation in Salerno. Each room at this bed and breakfast is air conditioned and is equipped with a TV. Situated in central Salerno, Dimora Salernum is a minute walk from the ferry harbour. This property offers free Wi-Fi and a furnished garden, where guests can enjoy a sweet and savoury breakfast. Believe every review about them They could not have been more helpful.
Located in Salerno, Il Reticolo is metres from the seafront. It offers air-conditioned rooms featuring free WiFi.
MOB DON ‘TONY DUCKS’ DIES IN PRISON AT 88
Lovely breakfast and great location. Each room at this bed and breakfast is air conditioned and comes with a flat-screen TV. It was a very good experience. Set in Salerno, 2. Rooms have a flat-screen TV. The bed was great, the bathroom and shower were huge, the view from the balcony was delightful, the room itself was beautiful, and the breakfast was exactly what we asked for.
He was also available for hire for us as a driver into the mountain towns and the Amalfi coast for a very good price. The building is safe, the location is perfect, and he made excellent recommendations for dinner. Thank you Marco! Set in Salerno, 1. Rooms have period furnishings and a flat-screen TV. Rooms all come with a flat-screen TV, air conditioning and a kettle. Rooms are fitted with a flat-screen TV. Panoramic Rooms is set in Salerno, 3.
Rooms are fitted with a flat-screen TV with satellite channels. It features free WiFi throughout, free private parking, and a shared terrace. Lovely big spotlessly clean room and en-suite. Very nice terrace to eat or enjoy a glass of wine on. It's run by the host Pasquale, who absolutely could not have done any more for me, he is a complete gentleman and excellent host. We spend a realy Nice holydays! Offering a terrace and views of the sea, Divina Salerno is situated in Salerno.