**2. Advances in ZnO synthesis**

The idea of the interaction of materials with water vapors is a new area of research. Almost all materials have some interaction with moisture that is present in their surroundings. The effects of water can be both harmful and beneficial depending on the material and how it is used. Consequently, the point to determine a correlation between morphological, structural and chemical characterization and the water vapor sorption behavior of the analyzed samples has been emphasized. Consequently, the obtained textiles should find their applicability in textile processing industry subdomains, where a certain level of hydrophilicity/hydrophobicity is mandatory.

fibers as the stabilizer [4]. Pt nanoparticles can catalyze the carbonization of cellulose and mesoporous amorphous carbon is fabricated in high yields. The results are carbon-based functional composites with metal nanoparticles, showing that self-supporting macroporous sponges of silver, gold and copper oxide, as well as composites of silver/copper oxide or silver/ titania can be routinely prepared by heating metal–salt-containing pastes of dextran, chosen as a soft template [5,6]. Polysaccharides could be used as stabilizer to synthesize nanoparticles of metal oxide and sulfides. Zinc oxide nanoparticles can be synthesized using water as a solvent and soluble starch as a stabilizer [7-9] while CdS nanoparticles have been prepared in

In an earlier study, ZnO nanoparticles synthesis can be made with the assistance of MCT-β-CD (monochlorotriazinyl–β -cyclodextrin) by using a sol-gel method [10]. MCT-β-CD, a commercially available β- cyclodextrin with a reactive monochlorotriazinyl group, is used as a stabilizer. The so called anchor group reacting with cellulose hydroxyl radicals and cyclo‐ dextrin molecule is covalently bonded, to the fiber surface. The stable bound of cyclodextrin onto the textile fibers allows its properties to become intrinsic to the modified supports, thus a new generation of *intelligent textiles possessing* enhanced sorption abilities/capacities, as well as possessing active molecules release wasborn. Besides, as polysaccharide, MCT-β-CD shows interesting dynamic supramolecular associations facilitated both by inter- and intra-molecular hydrogen bonding, and polar groups. When a material is exposed to environmental water vapors, the water molecules firstly reacts with surface polar groups, forming a molecular

Zinc oxide (ZnO), an n-type semiconductor, is a very interesting multifunctional material and has promising applications in solar cells, sensors, displays, gas sensors, varistors, piezoelectric devices, electro-acoustic transducers, photodiodes and UV light emitting devices. The adhesion between the ZnO nanoparticles and polymer through simple wet chemical method is rather poor and the nanoparticles may be removed from the host easily. In light of this, it is believed that the hydrothermal method can be a more promising way for fabricating nano‐ materials because it can be used to obtain products with modified morphological and chemical attributes with high purity, as well as stability in terms of water vapour sorption-desorption. Zn2+ ions can penetrate into the interior of linen fibrous support (fabric) easily when soluble salt such as zinc acetate (Zn (OAC)2) is used. Reaction of Zn2+ ions leads to crystallization of ZnO nanoparticles within the linen fabric and to the formation of an encapsulated complex in the hydrothermal environment. The formation procedure can be described through two steps as shown in Fig. 1. Firstly, coordination compounds are formed through chelation between Zn2+ ions and the hydroxyl groups of linen fabric. Secondly, the in-situ crystallization of Zn chelate complex occurs under the hydrothermal treatment and forms a ZnO- coated linen fabric. The ZnO nanoparticles can thus be attached firmly within the linen fiber surface.

The idea of the interaction of materials with water vapors is a new area of research. Almost all materials have some interaction with moisture that is present in their surroundings. The effects

a sago starch matrix.

22 Modern Surface Engineering Treatments

monolayer.

**2. Advances in ZnO synthesis**

The main cause of polymeric materials degradation is the exposure to various factors such as: heat, UV light, irradiation ozone, mechanical stress and microbes. Degradation is promoted by oxygen, humidity and strain, and results in such flaws as brittleness, cracking, and fading [11-13]. There have been research reports targeting nanosized magnetic materials synthesis, having significant potential for many applications.

The applications of ZnO particles are numerous: varistors and other functional devices, reinforcement phase, wear resistant and anti-sliding phase in composites due to their high elastic modulus and strength. Otherwise, ZnO particles exist in anti-electrostatic or conductive phase due to their current characteristics. Few studies have been concerned with the applica‐ tion of ZnO nanoparticles in coatings system with multi-properties. The nano-coatings can be obtained by the traditional coatings technology, i.e., by filling with nanometer-scale materi‐ alsBy filling with nano-materials, both structure and functional properties of coatings can be modified. Super-hardness, wear resistant, heat resistance, corrosion resistance, and about function, anti-electrostatic, antibacterial, anti-UV and infrared radiation all or several of them can be realized.

Another idea this paper review was centered to was to study the thermal degradation behavior of some textile nanocomposites made of nano/micron particle grade zinc oxide and linen fibrous supports, and to discuss the thermal degradation mechanism of the above mentioned structures. There is also potential to highlight the effect of the functionalization agent - MCTβ-CD (monochlorotriazinyl–β–cyclodextrin) on the thermal stability and degradation mecha‐ nism of ZnO nanocoated linen fibrous samples.

In order to characterize the surface morphology and chemical composition of the treated supports, instrumental methods were conducted to measure the particle sizes of the reduced zinc oxide particles. The understanding of the thermal behavior of these fibers is very impor‐ tant since in general several conventional techniques used in textile processing industry, are conducted at high temperature.

The MCT-β-CD (monochlorotriazinyl–βeta-cyclodextrin) under the trade name CAVATEX or CAVASOL® W7 MCT (CAVATEX) from Wacker Chemie AG, Zn(OAc)2, with an assay of 97%, urea and acetic acid (assay 99%) from CHIMOPAR, cetyltrimethylammonium bromide (CTAB) from Merck Company, with an assay of 97% were utilized

Two 100 % twill linen desized, scoured and bleached supports, each of size 3 cm × 3 cm were used as fibrous support. One of the supports has been coated with a certain concentration of MCT-β-CD (monochlorotriazinyl– β -cyclodextrin) [14-17].


**Table 1.** Synthesis conditions for each of the sample

#### **2.1. Fundamental technique for synthesizing and characterizing nano-ZnO particles**

The review was focused onto the fibrous supports (yarns) previously grafted/functionalized with MCT-β-CD. The grafting process of the textile fabric was performed following two other processes: the exhaustion and squeezing treatment and the heat treatment at 160°C. The purpose of these two treatments was the grafting the linen [18-20].

**Figure 1.** Flow chart for the preparation of nanoparticle coated linen support [10]

up to 350°, 450° respectively.

recorded at 2θ angles between 20 <sup>o</sup>

**2.2. Evaluation of crystallinity**

with a proportional detector [21-25].

Thermal treatment relied into two main stages, into the calcination oven. Firstly, the samples were subjected to an increasing of temperature up to 150°C; secondly the probes were heated

Zinc Oxide — Linen Fibrous Composites: Morphological, Structural, Chemical, Humidity Adsorptive and Thermal

Scanning Electron Microscope (SEM) images were acquired with a Quanta 200 3D Dual Beam type microscope, from FEI Holland, coupled with an EDS analysis system manufactured by EDAX - AMETEK Holland equipped with a SDD type detector (silicon drift detector). Taking into account the sample type, the analyses have been performed, using Low Vacuum working mode, (as in High Vacuum working type). Both for the acquisition of secondary electrons images (SE – secondary electrons) and EDS type elemental chemical analyses, LFD (Large Field Detector) type detector was used, running at a pressure of 60 Pa, and a voltage of 30 kV.

The ZnO–MCT-β-CD treated fabrics were tightly packed into the sample holder. X-ray Diffraction (XRD) data for structural characterization of the various prepared samples of ZnO were collected on an X-ray diffractometer (PW1710) using Cu-Kα radiation (k = 1.54 Å) source (applied voltage 40 kV, current 40 mA). About 0.5 g of the dried particles were deposited as a randomly oriented powder onto a Plexiglass sample container, and the XRD patterns were

and 80◦, with a scan rate of 1.5<sup>o</sup>

The extent of crystallinity (*I*c) was estimated by means of Eq. (1), where I020 is the intensity of the 020 diffraction peak at 2θ angle close to 22.6°, representing the crystalline region of the material, and Iam is the minimum between 200 and 110 peaks at 2θ angle close to 18º, repre‐

/min. Radiation was detected

Barrier Attributes

25

http://dx.doi.org/10.5772/55705

ZnO nanoparticles were synthesized *in-situ* on linen fibrous supports (yarns) having a certain concentration of MCT-β-CD by using the hydrothermal method. The linen samples with sizes of 30 x30 cm2 were immersed in the solution prepared as follows: zinc acetate Zn(CH3COO)2. 2H2O, purity – 99%) (0,005 mol/1000mL) as precursor was solved in de-ionized water to form a uniform solution by stirring and then 0,1 mol of urea solution was added drop-wise with constant stirring. Second, the pH value of the mixed solution was adjusted to 5 by adding acetic acid drop wise. The final reaction mixture was then vigorously stirred for two hours at room temperature and poured into 100 mL stainless-steel autoclaves made of Teflon (poly[tetra‐ fluoroethylene), followed by immersion of the fibrous supports (yarns). Then the autoclaves were placed in the oven for the hydrothermal treatment at 90*°C* overnight. The autoclaves were then cooled down to room temperature. The treated fabrics were then removed from the autoclaves. The treated fabrics were washed several times with distilled water. After complete washing the composites were dried at 60◦C overnight for complete conversion of the remain‐ ing zinc hydroxide to zinc oxide

Zinc Oxide — Linen Fibrous Composites: Morphological, Structural, Chemical, Humidity Adsorptive and Thermal Barrier Attributes http://dx.doi.org/10.5772/55705 25

**Figure 1.** Flow chart for the preparation of nanoparticle coated linen support [10]

Thermal treatment relied into two main stages, into the calcination oven. Firstly, the samples were subjected to an increasing of temperature up to 150°C; secondly the probes were heated up to 350°, 450° respectively.

Scanning Electron Microscope (SEM) images were acquired with a Quanta 200 3D Dual Beam type microscope, from FEI Holland, coupled with an EDS analysis system manufactured by EDAX - AMETEK Holland equipped with a SDD type detector (silicon drift detector). Taking into account the sample type, the analyses have been performed, using Low Vacuum working mode, (as in High Vacuum working type). Both for the acquisition of secondary electrons images (SE – secondary electrons) and EDS type elemental chemical analyses, LFD (Large Field Detector) type detector was used, running at a pressure of 60 Pa, and a voltage of 30 kV.

The ZnO–MCT-β-CD treated fabrics were tightly packed into the sample holder. X-ray Diffraction (XRD) data for structural characterization of the various prepared samples of ZnO were collected on an X-ray diffractometer (PW1710) using Cu-Kα radiation (k = 1.54 Å) source (applied voltage 40 kV, current 40 mA). About 0.5 g of the dried particles were deposited as a randomly oriented powder onto a Plexiglass sample container, and the XRD patterns were recorded at 2θ angles between 20 <sup>o</sup> and 80◦, with a scan rate of 1.5<sup>o</sup> /min. Radiation was detected with a proportional detector [21-25].

#### **2.2. Evaluation of crystallinity**

**Sample Specifications**

24 Modern Surface Engineering Treatments

**Table 1.** Synthesis conditions for each of the sample

of 30 x30 cm2

ing zinc hydroxide to zinc oxide

Reference 1 linen fibrous support

Reference 2 ZnO powder hydrothermally synthesized, non-calcinated

the assistance of P123

Sample 7 MCT- β –CD (**M**ono**C**hloro**T**riazinyl–**β** -**C**yclo**D**extrin)

purpose of these two treatments was the grafting the linen [18-20].

support

Sample 1 Functionalization of linen support with MCT- β –CD (**M**ono**C**hloro**T**riazinyl–**β** - **C**yclo**D**extrin) by exhaustion and thermal treatment

Sample 3 ZnO powder hydrothermally synthesized onto linen fibrous support

Sample 4 ZnO powder hydrothermally synthesized onto functionalized linen fibrous

Sample 5 ZnO powder hydrothermally synthesized onto functionalized linen fibrous with

Sample 6 ZnO powder hydrothermally synthesized onto functionalized linen fibrous with

(**M**ono**C**hloro**T**riazinyl-β – **C**yclo**D**extrin)

**2.1. Fundamental technique for synthesizing and characterizing nano-ZnO particles**

The review was focused onto the fibrous supports (yarns) previously grafted/functionalized with MCT-β-CD. The grafting process of the textile fabric was performed following two other processes: the exhaustion and squeezing treatment and the heat treatment at 160°C. The

ZnO nanoparticles were synthesized *in-situ* on linen fibrous supports (yarns) having a certain concentration of MCT-β-CD by using the hydrothermal method. The linen samples with sizes

2H2O, purity – 99%) (0,005 mol/1000mL) as precursor was solved in de-ionized water to form a uniform solution by stirring and then 0,1 mol of urea solution was added drop-wise with constant stirring. Second, the pH value of the mixed solution was adjusted to 5 by adding acetic acid drop wise. The final reaction mixture was then vigorously stirred for two hours at room temperature and poured into 100 mL stainless-steel autoclaves made of Teflon (poly[tetra‐ fluoroethylene), followed by immersion of the fibrous supports (yarns). Then the autoclaves were placed in the oven for the hydrothermal treatment at 90*°C* overnight. The autoclaves were then cooled down to room temperature. The treated fabrics were then removed from the autoclaves. The treated fabrics were washed several times with distilled water. After complete washing the composites were dried at 60◦C overnight for complete conversion of the remain‐

were immersed in the solution prepared as follows: zinc acetate Zn(CH3COO)2.

the assistance of CTAB (Cetyl TrimethylAmmonium Bromide)

The extent of crystallinity (*I*c) was estimated by means of Eq. (1), where I020 is the intensity of the 020 diffraction peak at 2θ angle close to 22.6°, representing the crystalline region of the material, and Iam is the minimum between 200 and 110 peaks at 2θ angle close to 18º, repre‐ senting the amorphous region of the material in cellulose fibres [26-28]. *I020* represents both crystalline and amorphous materials while *Iam* represents the amorphous material.

$$I\_C = \frac{I\_{020} - I\_{am}}{I\_{020}} \propto 100 \text{(\%)}\tag{1}$$

**a) reference 1x1200 b) Reference 2x10000** 

Zinc Oxide — Linen Fibrous Composites: Morphological, Structural, Chemical, Humidity Adsorptive and Thermal

Barrier Attributes

27

http://dx.doi.org/10.5772/55705

**c)Sample 1x1200** 

**Figure 2.** SEM images of: reference samples and of the functionalized linen support with MCT- β –CD sample [10]

**x1270 x5000** 

**a. Sample 6** 

**x 5000 x 5000 b. Sample 4 b. Sample 5** 

**Figure 3.** images of some textile composites [10]

A *shape factor* is used in x-ray diffraction to correlate the size of sub-micrometre particles, or crystallites, in a solid to the broadening of a peak in a diffraction pattern. In the Scherrer equation,

$$\tau = \frac{K \bullet \lambda}{\beta \cos \theta}$$

where *K* is the shape factor, λ is the x-ray wavelength, β is the line broadening at half the maximum intensity (FWHM) in radians, and θ is the Bragg angle [29]. τ is the mean size of the ordered (crystalline) domains, which may be smaller or equal to the grain size. The dimen‐ sionless shape factor has a typical value of about 0.9, but varies with the actual shape of the crystallite.

FTIR was used to examine changes in the molecular structures of the samples. Analysis has been recorded on a FTIR JASCO 660+ spectrometer. The analysis of studied samples was performed at 2 cm-1 resolution in transmission mode. Typically, 64 scans were signal averaged to reduce spectral noise.

For the studied samples dynamic vapours sorption (DVS) capacity, at 25o C averaging in the domain of relative humidity (RH) 0-90% has been investigated by using an IGAsorp apparatus, a fully automated gravimetric analyzer, supplied by Hiden Analytical, Warrington - UK). It is a standard sorption equipment, which has a sensitive microbalance (resolution 1μg and capacity 200 mg), which continuously registers the weight of the sample in terms of relative humidity change, at a temperature kept constant by means of a thermostatically controlled water bath. The measuring system is controlled by appropriate software.

To study water sorption at atmospheric pressure, a humidified stream of gas is passed over the sample.

The differential scanning calorimetry analysis (DSC) of fibrous supports - ZnO composites were carried out using a NETZSCH DSC 200 F3 MAIA instrument under nitrogen. Initial sample weight was set as 30-50 mg for each operation. The specimen was heated from room temperature to 350°C at a heating rate of 10°C/min.
