**2. Conservation of the recovered marine shipwrecks**

lignin (hydrophobic heteropolymer). The delignification will weaken the water resistance capacity of wood. By heating, the hygroscopicity, moisture uptake rate, and sorption hys-

Also, wood is an environmentally friendly material, a structural organic tissue, which consists of cellulose fibers embedded in a lignin matrix together with some minor components: terpe-

Wood is hydrophilic; the physico-mechanical properties decrease with increasing the relative humidity below the saturation point, and the surface degradation is accelerated in weathering conditions. Wood quality is mainly influenced by the following external factors: high humidity and oxygen presence, (micro)biological organisms such as fungi, molds, insects, temperature, and electromagnetic radiation (UV, IR, high-energy β or γ,

Taking into account these principles, the traditional conservation-restoration methods that in some cases can produce irreversible effects on wooden objects over time have been replaced with modern procedures due to the intensive development of nanotechnologies [6]. The wood protection with micro- and nanopolymeric systems exceeds the disadvantage of multilayer coatings that could affect the optical properties and the surface quality and also reduce the

The degradation induced by UV light represents the main drawback and induces the organic compound decomposition due to the increase in photon's energy that breaks the chemical bonds. An inefficient polymer coating can lead to loss in mechanical properties and integrity of the matrix and wood discoloration due to lignin degradation. New composite materials were developed, as aromatic impregnating agents (insecticides or fungicides) such as creosote, halogenated carbamates, benzothiazoles, pentachlorophenol, (alkyl) imidazoles, bis (tributyltin) oxide, or salt-based impregnates such as borates, quinolinolates, naphthenates of copper, zinc or chromated copper arsenate-based preservatives (CCA) in several commercial variants and so forth [8–10], fluoroalkyl functional oligomeric silane system [11], short-chain amino silicones [12], alkoxysilanes with different organic groups [R'Si(OR″)] [13], zinc oxide (ZnO) nanoparticles dispersed in maleic anhydride-modified polypropylene (MAPP) [14],

During the last decades, an intensification of historical wood artifacts preservation researches has intensified, and the new materials should present reversibility, must be compatible with all the materials encapsulated by the object, must not leech from wood, must be ecologic and biodegradable, and the "artistic" materials are to be treated as a whole [20]. Nanotechnology may provide interesting alternatives to develop new and efficient wood treatments to overcome technologies less feasibly used in the past decades to improve wood properties like heat treatment, chemical modification and impregnation, methods that can expand the dimensional stability, and resistance against microorganism [16]. Due to their very small dimensions (less than 100 nm), the nanomaterials have new properties, especially improved chemical reactivity and high mechanical properties. The nanostructures confer hardness and high wear resistance to the protected wood artifacts in some measure due to the increased

) nanoparticles [15–19].

teresis will be reduced, due to hemicellulose degradation [3].

noids, resin and fatty acids, pectin, proteins, and inorganics [4].

and so forth) [5].

74 New Uses of Micro and Nanomaterials

water vapor transmission rate (WVTR) [7].

and titanium dioxide (TiO2

density of the material [21, 22].

The unanimously used method of conserving the marine shipwrecks consisted of water replacing from the wooden material with polyethylene glycol (PEG), obviating the uncontrolled dehydration that would cause drastic damage of artifacts by fracturing the fragile wood cells [21, 23–25]. In such preserved shipwrecks, an accumulation of sulfur and iron compounds was observed, leading to the acidity increase which facilitates the cellulose depolymerization by the destruction of cellular wood walls and residual lignin degradation [23, 26, 27]. The increase of the system acidity can also produce PEG degradation into acidic byproducts that can act as ionic transporters [28–30]. For the preservation of these shipwrecks, the wood deacidification by using neutralizing alkaline compounds was required. The studies established that the maximal effect of acidity neutralization of archeological wood is achieved with nanodispersed alkaline hydroxides (20–150 nm) in alcoholic or PEG solutions, the most used being Na and Mg hydroxide. The alkaline nanoparticles dispersed into the polymer solution (low-molecular weight PEG: 200–2000 g/mol) deeply penetrate the degraded cellulosic cells, completely neutralizing the acids resulted from the wood degradation and further inhibiting the cellulose hydrolysis [21, 31, 32]. The deposition of calcium and magnesium hydroxide nanoparticles in the wood wall cells inhibits the oxidation of wood, thus increasing the conservation degree of the shipwrecks [22].
