دانلود رایگان مقاله سه فاز- فوم سخت شده و تقویت شده

abstract

Currently and in the past several lightweight materials were evolved focusing on different applications. Many developments are based on biomimetic approaches to reach material and cost savings with a simultaneous combination of thermal insulation and sustainability, for example. The desire of needed high porosity and lower density lead to less strength of the materials. Thus, applications are limited. One way to solve this problem is the creation of foams based on three phases. A new approach is the implementation of nanotubes and further chemical treatment of the inorganic foams to avoid further energy consuming thermal treatment for strengthening. Three-phase-foams consist of pozzolanic active nanomaterials as a third phase, which can be varied and surface treated. The resulting materials can be combined with other binders to further improve their properties or used as self-contained materials. Aided by chemical treatment a hardening of the foams has been achieved. Implementation of prefabricated and synthesized nanotubes as a nanoreinforcement were successfully done and properties of the foams investigated. Results based on studies of the microstructure and phase formation will be illustrated and discussed.

4. Conclusions

Finally, different properties of three-phase-foams were figured out by using several types of nanotubes. After drying, the foams show no more destabilizing influences. The most stable wet threephase-foams were prepared without nanotubes and with coatCNTs. All in all, stability of the resulting foams is also related to betaine adjustment which has to be done in further investigations. The pore size distribution was shifted to smaller pore sizes compared to previous investigation due to improved foaming conditions. Due to hardening process porosity in the foam structures was reduced, lamellae/border widths increased and strengthening reaction products like C-S-H-phases or Cc were built, respectively. Investigating influences of used additives on pozzolanic reactivity lead to the conclusion that C-S-H-phases were formed in almost every sample but are strongly influenced by the surfactant betaine. The latter also results in the formation of hydrotalcite-like structures in calcium hydroxide solution. Also, betaine has a big influence on the crystallinity and particle sizes of both calcium hydroxide and carbonate. In addition, it was shown that TiNTs have a high calcium affinity but oxCNTs tend to adsorb preferred betaine molecules. Thus, the formation of reaction products and foam stability is mainly referred to the used surfactant which provides a high sorption ability. In sum, a waiver of thermal treatment or additional binders should be possible as well as produce future lightweight materials with densities of less than 100 kg/m3 and based on long-chain environmentally friendly surfactant. These advantages lead to energy and cost savings in the production of raw materials. Moreover, well-dispersed nanotubes in three-phase-foams could further integrate in other binding materials to adapt certain properties of those and also provide strengthening reaction products by seeding effect or pozzolanic reaction, respectively.