Ultrasonic study of glass prepared using fly ash as glass former Essay

The environmental problem is most concern of in today’s scenario. Use of waste material drawing the attention of scientific community. The waste material like coal fly ash biomass ash and rice husk ash produced abundantly every year. Fly ash, being treated as waste and a source of air and water pollution. This problem growing the interest in recycling of this waste material in some value added product. All type of ash mostly used as raw material in cement industries1. However the use of fly ash in cement is not only the solution as fly ash contain heavy metals which can cause secondary pollution2.The coal fly ash contain near about 60% of silica and can be used as glass former in place of silica3.Since coal ash contain large amount of transition oxide which produced opaque glass having high intensity colour which is not so much useful for practical application4.In Central India large amount of agricultural waste is produced from harvesting, sugar factories and rice mill. This agro waste is like sugarcane Bagasse, rice husk further used as fuel in thermal power plant5.Biomass ash and rice husk ash is natural and immense source of silica and can be used as a raw material for glass formation6.Biomass ash has potential to be used as glass former. Silica contain in both biomass ash, sugarcane bagasse ash and rice husk ash has more than 50% of amorphous silica contain7. Glasses having high transparency, optical property and electrical property attract for more scientific uses. Rowero M.et al8 has tried to crystallize SiO2-Cao-N2O glass from sugarcane Bagasse bottom ash and investigate the feasibility of glass and glass ceramic formation from sugarcane bagasse ash. While Teiveira S. et al9studied glass ceramic material from SiO2-Al-CaO system using sugarcane bagasse ash. Physical and mechanical properties of glass-ceramics fabricated from thermal power plant fly ash were analysed and compared with a temperature-time-mechanical (T-T-M) diagram by Myungkim J et al10 .A.Jabar et al 11prepared the zinc silicate glass from rice husk and studied its properties. Ruangtaweep et.al12prepared rice husk glass doped with other oxides. The result shows that the RHA can be used for glass production with good properties when compared with glass from SiO2. Singh et.al 13explore the fly ash as glass modifier Sristtipokakun et al 14studied the Cuo MnO2 and Fe2O3 doped biomass ash glass. Silvio Rainho Teixeiraw et.al.15 studied the glass and glass ceramic formation of bagasse ash Peng f et.al 16nvestigate the nano composite glass ceramic formed using cole fly ash. With the formation of glass using biomass ash and rice husk ash it also important to study it’s physical and elastic properties of glass. The ultrasonic testing is one of the non-destructive testing used for the structural investigation of glass .The elastic moduli of glasses are influenced by many physical parameters, which may in turn be studied by measuring the ultrasonic velocities17SaddeekY18 study the effect of Cole fly ash on the elastic behaviour of glass. Ultrasonic study of some zinc borate glass were studied by S.Thirumaranand et.al 19. A. Kannappan et al20The evaluated acoustical, elastic, and mechanical properties shows the compactness and rigid network with the doping of ZnO and PbO the structural properties of glass investigated shows the rigidity of glass .P.Vastharani et al21 investigate the ultrasonic and structural studies of lead sodium borate glasses doped with ZnO.The present work aims to measure the elastic properties of glass prepared from biomass ash and rice husk ash as glass former

2: Materials and methods:

The BMA and RHA used here was procured from thermal power plant running on biomass fuel, ‘Purti Power and Sugar Limited’, Bela, District Nagpur (MS) India. The ash was subjected to chemical analysis to confirm the presence of silicates form ANACON LAB Nagpur. The percentage of silicates, alumina and other fly ash components is as listed in Table1. The glasses were prepared by using BMA and RHA (Purti thermal power plant)",Zinc oxide and Boric Oxide (AR grade). The molar composition of the glass sample (with increasing percentage of biomass ash and rice husk The powders were weighed on a monopan K Roy balance digital balance having accuracy 0.00001gm.The powder were mixed for 30 minutes thoroughly by repeated grinding in an agate mortar and pestle. Then mixture was transfer in a fire clay crucible in an electrically heated furnace under ordinary atmospheric conditions at a temperature of about 10000C for 3 h to homogenize the melt. The melted mixture was poured on 2×1 cm2 stainless- steel mould to form bulk glass. The glasses were prepared by the melt quench method. The quenching rate is 900C/minute he glasses were immediately transferred to annealing furnace maintained at 3230Cfor 1 hour. The glass sample polished to form parallel faces to study ultrasonic properties. The density of the glass samples were measured using Archimedes’ principle. Ultrasonic longitudinal and shear velocities of the specimen were determined by using Pulse-Echo method by using X-cut and Y-cut quartz transducers having the fundamental frequency of 30MHz was used for the generation and detection of the longitudinal ultrasonic waves. The transducer was coupled to one of the faces of the specimen with a good acoustic couplet (SnotracG-1) to avoid any air gap between the transmitted pulse and the specime.The acoustic couplet provide a better impedance matching between the transducer and specimen as well as reduces the coupling losses. An echo was registered each time, when the transmitted pulse were received by the same transducer after travelling a distance d in the specimen. The amorphous nature of glass sample confirmed by XRD spectra. XRD spectra of glass BZB-1 and BZR-2 given in fig-1.FTIR of glass samples were studied for confirming the presence of silica and alumina in the glasses. FTIR investigation of sampleBZB-1 and BZR-2shown in fig-2and fig-3.TG-DTA analysis of samples were given in fig-4

3. Theoretical calculation:

All the equations to find out the Ultrasonic velocity and elastic constant are given below21

The ultrasonic velocity of glass sample was obtained using

U= ---- (1)

at room temperature using the measured density (ρ), longitudinal velocity (Ul) and shear velocity (US) as given below:

Longitudinal Modulus (L) The ratio between longitudinally applied stress and the longitudinal strain is obtained for longitudinal wave propagation as

L=ρU2l----(2)

Shear Modulus (G) The shear modulus can be found from shear velocity as",

G= ρ Us2 … (3)

Bulk Modulus (K) The ratio between bulk stress and bulk strain is obtained from the ultrasonic velocities as

K= …….4)

Young’s Modulus (E) It is defined as the ratio between unidirectional stress and resultant strain and is given as

E = (1+σ) 2G … (5)

Where σ Poisson’s ratio.

Poisson’s Ratio (σ) it is the ratio between lateral and longitudinal strain produced when tensile force is applied, as given by the relation",

σ= …….. (6)

Acoustic Impedance (Z) The transmission and reflection of sound energy in the glass specimen is determined using the acoustical impedance.

Z =Ulρ… (6)

Micro Hardness (H) it is given by

H= (1-2σ) … (7)

Debye Temperature (θD)

The Debye temperature θD of the sample is calculated from the relation

.θD= … (8)

Where h, K, N and Vm are the Planck’s constant, the Boltzmann’s constant, the Avagadro’s number and the molar volume of the sample, respectively.

The mean sound velocity Um is given by

Um= ------ (9)

Thermal Expansion Coefficient (αP):

Thermal expansion coefficient can be obtained as

αp = 23.2 (Uℓ – 0.57457)------(10)

4 Results and Discussion:

4.1 X-Ray Diffraction Spectra-

The amorphous nature of the glass sample were confirmed using X-Ray diffraction analysis using PW-3050/60XPERT-PRO type-0000000083005381 difractometer and target CuK radiations

4.2 IR-Spectroscopy of glass sample:

The infrared spectra of glass sample BZB-5 and BZR-5 is studied in the wave number range 400-4000cm-1 on Perkin Elmer-467 IR spectrometer .Kbr technique was used .The absorption 20 peaks were obtained in BZB and 12 peaks were obtained in BZR. Details of the appeared peaks are presented in Table 3. The peak assignment is consistent with other published work22-24. Absence of peak around 806 cm–1, which is clear from the inset of Figure 5, indicate that borate network does not contain any boroxol ring25. The peak near 450 cm-1 shows Si-O-Si stretching modes26

4.3 TG-DTA Analysis:

Thermal gravimetric analysis and differential thermal analysis of selected three samples from each series is done. It is used to determine the thermal stability and glass transition temperature (TG) using NETZSCH-Geratebau STA 409C thermal analyser at heating rate of 20C/min and 10ml/min.TG-DTA analysis gives the transition temperature and phase change of the glass. Transition temperature corresponds to the accessibility of new configurational degree of freedom. Glass transition temperature (Tg) for BZB-5 is about 210C and softening temperature (Ts) is 500C and for BZR-5glass transition temperature is 190C and glass softening temperature(Ts) is 510C.

4.4 Ultrasonic velocity and elastic constant:

The experimental values of density (ρ), longitudinal ultrasonic velocity (Ul) and shear ultrasonic velocity (US) of the different glass specimen with respect to the change in the mol% of BMAand RHA are listed in Table-3. The calculated longitudinal modulus (L), shear modulus (G), bulk modulus (K) and Young’s modulus (E) are also reported in Table-4. The Poisson’s ratio (σ), acoustic impedance (Z) and micro hardness (H) Debye temperature (θD) and thermal expansion coefficient (αP).which are reported in Table-5

Density of (ρ) of sample increases and molar volume decreases with increasing percentage of BMA and RHA due to structural changes in glass network .The structure of glass depends on the nature of ions entering in the network and hence the density27-28. For BZB and BZR glasses, B2O3 is a well-known network glass former, the network of pure B2O3 glass consists of three coordinated trigonal (B3) boron atoms. In addition to B2O3, SiO2 in the form of BMA and RHA also act as a glass former and all the four oxygen in SiO4 tetrahedral are randomly connected to one, two, three or four, depending upon the other oxides present in the glass network29-30.The vitreous B2O3 consist planar [BO3/2] units. The addition of BMA and RHA as silica source to B2O3 network creates [BO4/2] units. This leads to increase in the network dimensionality and connectivity of silver borate glass structure. Hence both ultrasonic moduli increases with the increase in BMA and RHA concentration.31It is seen from the Table 3 that both longitudinal velocity (Ul) and shear velocity (US) decrease almost linearly with the concentration of BMA and RHA. The increase in velocity is caused by the increase in the packing density32.Increase in packing density responsible for the increase in ultrasonic velocity and elastic modules. .Elastic constants and thermal expansion coefficient, micro hardness have increasing trend with the increasing mole percentage of BMA in BZB sample and RHA in BZR sample series. Thus rigidity of sample increases. The variation of Poisson’s ratio with mole percent of BMA and RHA is shown in Table-4. Poisson’s ratio (σ) shows increasing trend with increasing concentration of ash. Generally, as the glass structure weakens, the value of poison’s ratio (σ) increases. This glass system shows the same nature33-34The increase in Poisson’s ratio shows that the atoms experience higher transverse contraction strain action on them and hence become more tightly packed35 .The continuous increase in Poisson’s ratio and micro hardness revels that the addition of BMA and RHA as glass former does not form non-bridging oxygen and giving rise to formation of Glass network. The observed results are further confirmed by considering another parameter, Debye temperature, obtained directly from the measured velocity. The Debye temperature (θD ) plays an important role in solid materials in the determination of elastic constant and atomic vibrations. θD represents temperature at which all modes of vibrations in a solid are excited and its increase implies an increase in rigidity of glass. The increase the Debye temperature is possibly due to the charged centre coming closer than the distance required statistically achieving a more effective Colombian interaction. Such interaction can give rise to high energy vibrational modes, thereby increasing the Debye temperature36.This increase in Debye temperature with the addition of BMA and RHA shows the glass structure strengthen. The thermal expansion coefficient increases with increase in mol% BMA and RHA and hence the rigidity of the structure of the glass.

5 Conclusion:

It is concluded that the evaluated acoustical elastic and mechanical parameters of the glass specimen (BZB, BZR) throw light on the rigidity and compactness in structural network. The BZB and BZR glass possess higher rigidity, strength and compactness in structural network with the addition of biomass ash and rice husk as silica source for glass former.

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