Search

Bioactive glasses containing boron oxide have attracted substantial attention owing to their unique attributes and the promising prospects they offer for biomedical uses. The study explores boro calcium fluoro alumino silicate (BCFAS) glass containing boron oxide, highlighting its potential in biomedical applications. The glass was synthesized through melt-water quenching with varying B2O3 ratios, utilizing CaO from clam shell and SiO2 from soda lime silica glass waste. The investigation examined the physical and mechanical properties of the resulting samples. Results showed that increasing B2O3 content caused a reduction in crystallinity, as confirmed by XRD analysis. The incorporation of B2O3 into the glass structure was further supported by the emergence of B‒O‒B and Si‒O‒B bonds observed in FTIR spectroscopy, which may potentially influence the glass's dissolution and degradation characteristics. However, higher B2O3 content also reduced density, impacting the mechanical properties. Vickers microhardness and compressive strength decreased due to the introduction of the BO3 unit, which increased the fragility of the glass. While enhancing glass-like behavior and potentially increasing bioactivity, the addition of B2O3 adversely affected its mechanical attributes. [ABSTRACT FROM AUTHOR]

This research aims to investigate the potential of novel CaF2 − CaO − Na2O − B2O3−SiO2 glass systems and converted to bioactive glass-ceramics. The study involves examining the effects of different heat treatment temperatures and immersion periods, with the goal of exploring these materials as viable alternatives for various biomedical applications. A typical melt-quenching technique was used to synthesize the glass samples, followed by a controlled heat treatment. The main crystalline phases are cuspidine and wollastonite, which have the potential to promote bioactivity, especially in dental and bone-related applications. The sample heat-treated at 700 °C showed an increased microhardness and fracture toughness by more than 116% and 36%, compared to the initial value. Furthermore, the increase in pH and the observed weight loss/gain demonstrated the reactivity of the samples with the phosphate buffer-saline medium, indicating their bioactive properties. Remarkably, the microhardness and fracture toughness exhibited notable improvements after 14 days of immersion, with an enhancement of 4.71% and 4.66%, highlighting their potential durability and longevity in high-strength dental crown applications. Consequently, this research presents a promising method for developing sustainable novel glass and glass-ceramic materials devoid of phosphates. These materials boast enhanced mechanical properties while preserving bioactivity, making them well-suited for dental implants and restorative purposes. [ABSTRACT FROM AUTHOR]

The optimization of glass substrate optical properties for enhanced biosensor sensitivity has recently blossomed into a major research focus, yielding remarkable progress. Nevertheless, attaining precise control over nanoscale morphologies and their light-altering abilities remains a formidable hurdle, necessitating the exploration of diverse strategies to overcome this issue. This study was conducted to investigate how Er2O3 doping affects the physical, optical structural and elastic properties of ZnO-SiO2-B2O3 glasses, which were created using the melt-quenching method. The samples were confirmed to be amorphous and glassy using XRD and FTIR techniques. Many researchers used ultrasonic waves to measure the longitudinal and shear velocities of glasses using the pulse-echo method. The measurements were taken at a temperature within the typical room range and a frequency of 5 MHz. The addition of Er2O3 as a dopant resulted in both decreasing and increasing trends in the longitudinal, Young, shear and bulk moduli. These observations suggest a potential correlation between the increase in acoustic impedance and the presence of bridging oxygen, which leads to stiffer and more compact glass structures. The optical band gap of the material decreased from 3.43 eV to 3.23 eV as the weight percentage of Er2O3 increased from 0.00 to 0.05 wt.%. Surface plasmon resonance was investigated using the Otto configuration. The observed wavelength shift, approximately 6 nm with a gold nanolayer coating in the SPR results, indicated an increase in wavelength with increasing Er2O3 content (0.01-0.05 wt.%). This highlights the potential of this glass substrate for various optical applications, including optical biosensors. [ABSTRACT FROM AUTHOR]

This study focuses on zinc-boro-soda-lime-silica (ZnO − B2O3 − SLS) glasses produced through fast-cooling melt-quenching. The influence of Eu3+ ions on glass properties is explored. As Eu3+ concentration rises, bulk density and molar volume increase from 3.423 to 3.484 g/cm3 and 21.760 to 23.768 cm3/mol, respectively. X-ray diffraction indicates amorphous phase dominance supported by glassy surface morphology. Ultrasonic measurements show the increasing and decreasing trend for ultrasonic velocities and elastic moduli with increasing Eu3+ concentration. Poisson's ratio of the samples signifies their low cross-link density behavior. Moreover, the ZBS-3Eu presents the highest microhardness value of 4.776 GPa. The sample's fractal bond connectivity varies from 1.814 to 2.051, suggesting a 2D structure. Likewise, the ZBS-3Eu glass sample exhibits the most rigidity attributed to its highest fg value of 0.075. These findings suggest that ZBS-3Eu has the potential for applications requiring high-strength glass. [ABSTRACT FROM AUTHOR]

A new formulation of the bismuth-zinc-borate glass system has been fabricated using the conventional melt-quenching method. The amorphous phase of the glass sample has been confirmed by the nonexistent of any crystalline peak presented by X-ray diffraction patterns. The Fourier-transform infrared spectroscopy result displays several bands associated with the Zn–O and B–O–B bonding. The glass samples exhibited a density increase from 3.19 to 4.28 g/cm3 and the molar volume increased from 23.48 to 31.00 cm3/mol. The density of the glasses increases due to the addition of Bi2O3 which has a higher atomic mass compared to the other elements in glass compositions. The addition of Bi2O3 contributes more mass to the glass structure, leading to an increase in overall density. The incorporated Bi2O3 reduced the longitudinal (6134.41–5121.94 ms−1) and shear (3310.50–2848.15 ms−1) velocities. The elastic moduli resulted in a decreasing behavior when Bi2O3 concentration increased, and the values ranged from 120.04 to 112.21 GPa for longitudinal modulus, 34.96–34.69 GPa for shear modulus, 73.43–65.95 GPa for bulk modulus, and 90.52–88.56 GPa for Young's modulus. The Poisson's ratio presents the same trend as the modulus, while the microhardness shows an inversely proportional trend. The BiZnB4 sample demonstrates the lowest Poisson's ratio (0.276) and highest microhardness (5.18 GPa) values. These findings show that the physio-elastic properties are composition-dependent, suggesting potential applications as flexible glass panels for dynamic building glass design. [ABSTRACT FROM AUTHOR]

The xCaF2–45SiO2–25CaO–10B2O3–10Na2O–(10-x)P2O5 based 45S5 bioactive glass, where x = 0, 2, 4, 6, 8 and 10 wt.%. have been fabricated by modified melt-quenching method. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) measurement indicate that the CaF2 addition into the SiO2–CaO–B2O3–Na2O–P2O5 glass increases the stability of the amorphous phase and not lead to the crystallization of the glasses. The field emission scanning electron microscopy (FESEM) micrographs and energy dispersive X-ray (EDX) analysis presented the non-uniform particle distribution and the amorphous glassy structure in all glass samples. The compressive strength (CS) of the glass samples increases with CaF2/P2O5 ratios from 46.80 ± 0.15 MPa to 48.98 ± 0.11 MPa. However, the decrement occurs when further increment in CaF2/P2O5 ratios, which is caused by the excessive CaF2 content in the glass structure. Vickers microhardness (VM) shows a similar trend, increasing from 2.00 ± 0.07 GPa to 3.09 ± 0.07 GPa and suddenly decreasing with the higher addition of CaF2 concentration. Consequently, the BG3F glass sample presents optimum conditions for physical and mechanical performance comparable to the human enamel. [ABSTRACT FROM AUTHOR]

In this study, the impact of thulium oxide on the structural and elastic characteristics of magnesium borotellurite glass systems produced through the melt-quenching technique is examined. The findings reveal a direct relationship between the thulium concentration and several elastic parameters in the glass sample, such as ultrasonic velocity and elastic modulus. The sample's density increased from 4.12 to 4.30 g/cm3, and its molar volume increased from 29.29 to 29.62 cm3/mol as Tm3+ concentration progressed. The XRD study confirmed that the samples were amorphous. The incorporation of Tm2O3 into the glass acts as a network modifier and leads to an increase in NBO content. Moreover, the shear and longitudinal velocities range within the respective ranges of 1966.02 to 2495.90 m/s and 3474.78 m/s to 4085.13 m/s. Young's modulus, bulk, shear, and longitudinal elastic moduli fall between 40.28 and 64.45 GPa, 28.51 and 36.07 GPa, 15.92 and 26.81 GPa, and 49.75 and 71.81 GPa, respectively. Moreover, the sample's Poisson ratio decreases from 0.26 to 0.20 with an increase in Tm3+ concentration. The experimental results are compared to the theoretically calculated results. By comparing to experimental data, the Mackenzie Makishima and Rocherulle models demonstrate a high level of accuracy. [ABSTRACT FROM AUTHOR]

In this work, Eu3+/Sm3+ co-doped zinc borosilicate glass was prepared by modified melt-quenching method. The effect of Eu3+/Sm3+ to the structural and optical properties was investigated. The optical band gaps increased from 5.023 to 5.179 eV, and 3.832 to 3.986 eV for both for direct/indirect transition. Urbach energy decreases from 0.713 to 0.697 eV, while refractive index also decreases from 2.203 to 2.173 with the progress of doping concentration. The photoluminescence measurement reveals the simultaneous amplification of Sm3+ and Eu3+ emission for the co-doping sample, suggesting a synergistic energy transfer between the two ions. The 1EuSmZBS glass samples show the highest emission intensity. The CIE chromaticity coordinates, CCT, and color purity of the glass sample present high intensity of reddish-orange emission color. In conclusion, Eu3+/Sm3+ co-doped zinc borosilicate glass can lead to enhanced and tunable luminescence properties, and potentially use as a glass host phosphor in optoelectronic applications. [ABSTRACT FROM AUTHOR]

The development of high-frequency devices has attracted more research interest in electromagnetic wave–absorbing materials having lightweight, low filler content, thin thickness, minimum reflection loss and broad absorption bandwidth. Nevertheless, none of the materials uses steel waste (mill scale) as a potential low-cost catalyst to synthesize carbon nanotubes (CNT) as an electromagnetic (EM) wave absorber. Hence, multiwalled carbon nanotubes loaded in epoxy resin with an increasing polymer composite thickness of 1 mm, 2 mm, and 3 mm were introduced in this study. With varying milling times of mill scale (4 h, 20 h and 40 h) as catalyst, as-synthesized carbon nanotubes were produced using the chemical vapour deposition (CVD) method. Two main phases (carbon and iron carbide) were obtained from the synthesized carbon nanotubes. The samples' morphology was mostly straight like, spiral, twisted carbon and spring pasta-like structures. The two-dimensional (2D) network structure of as-synthesized CNT loaded into epoxy resin, extends the transmission route of EM wave being absorbed. Moreover, the ratio of ID/IG is consistent at around 1.0 attributed to defective structure or a lower graphitization degree. In addition, higher electrical resistivity in the sample indicates wider separation between CNTs allowing for better EM wave absorption. The as-synthesized carbon nanotubes that are utilized as filler with lightweight properties, improved the reflection loss approach to − 25 dB (10.5 GHz) for growth CNT catalyzed by mill scale milled for 20 h loaded into polymer matrix (GM20h/P) at thickness of 3 mm. As the thickness of the polymer composites increased from 1 to 3 mm, all composite samples reflected a loss peak closer to a lower frequency range. The results demonstrated that the EM wave absorption ability was improved to 99.9% by using nanometer size mill scale waste as a catalyst to grow carbon nanotubes and further used as an EM wave absorber. [ABSTRACT FROM AUTHOR]

Eu3+-doped Zn2SiO4/ZnO phosphor-based composites were prepared using a simple thermal treatment method. The effect of Eu3+ content on the morphological and photoluminescence performance was examined using XRD, FTIR, FESEM, UV–Vis, and PL measurement. The existence of two crystal phases by the XRD measurement confirmed the development of zincite (ZnO) and zinc silicate (Zn2SiO4) crystal phases. Besides, the FTIR spectra and FESEM micrograph support the XRD result by verifying ZnO and Zn2SiO4 phase formation through the existence of their characteristic Zn–O–Si and Zn–O vibration modes with the decrement of SiO4 broad absorption band as the Eu3+ concentration increased. Also, UV–Vis absorption spectra presented by the composite samples displayed a broad absorbance that confirmed the addition of Eu3+ ions in the ZnO/Zn2SiO4 has caused the absorption edge of the curve having red shift. The photoluminescence spectrum showed red shift light emissions at 485 and 615 nm, associating with the Zn2SiO4 crystal phase, in addition to the ZnO crystal phase. From the interesting results achieved, this ZnO/Zn2SiO4 phosphor-based composite material can be a potent candidate in optoelectronic applications. [ABSTRACT FROM AUTHOR]

Four series of CaO-ZnO-B2O3-SLS (CZBS) glasses have been synthesized by using waste materials which are eggshell (EG) and soda lime silica (SLS) glass. We utilized eggshells to source calcium oxide (CaO) in this work, whereas we utilized SLS glass to substitute silica. CZBS1, CZBS2, CZBS3 and CZBS4 are the glass series containing weight percentages of CaO (15%, 20%, 25% and 30%) and SLS (70%, 65%, 60% and 55%), respectively, with the addition of 10% of B2O3 and 5% of ZnO in each sample. A conventional melt and quenching method was applied in this work to fabricate the CaO-ZnO-B2O3-SLS glass system. The glass transition temperature (Tg) was determined using differential scanning calorimetry (DSC), which revealed that the Tg increased from 714 to 735 °C, as the CaO content increased. Meanwhile, the glass structural properties were investigated, revealing an amorphous nature with no sharp peak. The experimental elastic moduli obtained by acquiring ultrasonic speeds using the ultrasonic pulse-echo method were compared to the hypothetical elastic moduli obtained by direct estimation of the hypothetical model. [ABSTRACT FROM AUTHOR]

The effects of the addition of carbon nanotubes (CNTs) on the morphology and microstructure of Al-Al2O3 nanocomposites and the subsequent effects on their densification and mechanical behavior are studied. From the morphologic study, ball milling was found to be more intensified in the presence of 2 wt.% of CNTs wherein steady state was reached after 5 h of milling. The addition of CNTs as a mixing agent facilitates dispersion of Al2O3 nanoparticles and exerts extensive grain refinement. Compressibility and sinterability were found to be positively correlated with the milling time. Compressibility and sinterability were improved by increasing milling time owing to severe particle size reduction and minimizing the agglomeration of reinforcement particles. The micro-hardness (HV), nano-hardness (HN) and Young's modulus (E) values of Al-2CNT-10Al2O3 nanocomposites increased by ~ 19%, 26% and 34%, respectively, as the milling time proceeds. At each milling time, Al-2CNT-10Al2O3 nanocomposites possess superior mechanical properties compared with Al-10Al2O3 nanocomposites owing to the morphologic and microstructural variations caused in the presence of CNTs. [ABSTRACT FROM AUTHOR]

Microwave absorption properties were systematically studied for double-layer carbon black/epoxy resin (CB) and Ni0.6Zn0.4Fe2O4/epoxy resin (F) nanocomposites in the frequency range of 8 to 18 GHz. The Ni0.6Zn0.4Fe2O4 nanoparticles were synthesized via high energy ball milling with subsequent sintering while carbon black was commercially purchased. The materials were later incorporated into epoxy resin to fabricate double-layer composite structures with total thicknesses of 2 and 3 mm. The CB1/F1, in which carbon black as matching and ferrite as absorbing layer with each thickness of 1 mm, showed the highest microwave absorption of more than 99.9%, with minimum reflection loss of −33.8 dB but with an absorption bandwidth of only 2.7 GHz. Double layer absorbers with F1/CB1(ferrite as matching and carbon black as absorbing layer with each thickness of 1 mm) structure showed the best microwave absorption performance in which more than 99% microwave energy were absorbed, with promising minimum reflection loss of −24.0 dB, along with a wider bandwidth of 4.8 GHz and yet with a reduced thickness of only 2 mm. [ABSTRACT FROM AUTHOR]

Strontium titanate is a promising candidate for applications in thermoelectric, thermal management applications, and modern electronic devices because of its desirable thermal stability, chemical stability, and semiconducting behaviour. However, the absence of its important systematic development, having grain size from several nanometric up to micronic size with evolving thermal diffusivity behaviour, triggers the need for filling up the vacuum. Two different heat treatments have been carried out onto the samples which were with presintering and without presintering. Nanometer-sized compacted powder samples were sintered from 500 to 1400 °C using 100 °C increments. The parallel characterizations of structural, microstructural and thermal diffusivity properties were systematically carried out. Interestingly, three significant value-differentiated groups: weak, moderate, and strong thermal diffusivity were observed, resulting from the influence of different phonon-scattering mechanisms through a systematic development of microstructural properties for both heat treatments. [ABSTRACT FROM AUTHOR]

Willemite is an inorganic semiconductor material used for optoelectronic applications. The present study purposes a new polymer thermal treatment method involving calcination temperature to fabricate the willemite nanoparticles. The effects of polyvinylpyrrolidone (PVP) on the structural and optical properties of the material were thoroughly investigated. Thermogravimetric and its derivative confirmed the decomposition behavior of PVP. The minimum calcination temperature to decompose PVP was appraised at 740 °C. The FTIR and the Raman analyses confirmed the presence of organic source before the calcination process and the formation of the crystalline structure of the willemite nanoparticles after the heat treatment. The optimum PVP concentration in this study based on the FTIR results was found to be 40 g L−1. This is the minimum concentration at which the willemite nanoparticles remained pure with homogenous distribution. X-ray diffraction analysis of the PVP samples before calcination was confirmed to be amorphous, and upon calcination between 800 and 1000 °C, an α-willemite phase was obtained. The morphology and the average particle size were determined with FESEM and HR-TEM analysis. The average particle size is between 23.8 and 36.7 nm. The optical energy band was found to be increasing from 5.24 to 5.32 eV with the corresponding increase in PVP concentration from 20 to 50 g L−1. The findings in this study provides a new pathway to understand the effects of PVP concentrations on the structural and optical properties of willemite semiconductor nanoparticles as it may have key potential applications for future optoelectronic devices. The primary task of polyvinylpyrrolidone (PVP) is to serve as a capping agent and to stabilize the metallic salts. The interaction between the PVP and the metallic salts (zinc acetate dihydrate and silicon tetraacetate) is through the strong ionic bonds between the metallic ions and the amide group via oxygen in the PVP chain. The PVP stabilizes the dissolved metallic precursor by amide group steric and electrostatic stabilization. In the drying process at the temperature about 80 °C, the PVP decompose to the shorter polymer chains which they cap the metallic ions. In the step of calcination at the range of 900 °C for 1–4 h, the polymer content and unwanted anions are entirely removed and the nucleation of willemite nanoparticles achieved. [ABSTRACT FROM AUTHOR]

In this research indentation instrument testing is used as a new method for local characterization to study different zones of friction stir welded AA6061 alloy. For this purpose nanoindentation and microhardness are applied for samples in as-weld and post weld heat treatment conditions. Nugget zone, thermomechanically affected zone, and heat affected zone are examined by using nanoindentor in both conditions. The observations say that an estimation of the truncated indenter tip defect is necessary because of pile-up. Whereas post weld heat treatment (PWHT) can recover elastic modulus and nanohardness as well as hardness in AA6061 weldment. [ABSTRACT FROM AUTHOR]

Microwave absorbers of cobalt ferrite and graphite composite have been fabricated to investigate the broadening of absorption frequency by mixing small and large particles and comparing single- and double-layer composites in order to broaden the absorption frequency and to enhance multireflection and scattering of electromagnetic wave. CoO and Fe2O3 precursors were mechanically alloyed and sintered at 800, 900, 1000 and 1100 ∘C in order to synthesise various particle sizes and shapes. A mixed sample of powders sintered at the above mentioned temperatures was also formed. The morphological, phase, and magnetic properties of these samples were studied. Two series of samples have been synthesised which were single- and double-layer composites. Single-layer composite consisted of mixed particles, and their thickness parameters were varied. Double-layer composite was also prepared with various particle sizes of CoFe2O4 as a layer and graphene as another layer. The effect of these layers as matching and absorbing layer was studied. The degree of crystallinity of CoFe2O4 was increased with increase of sintering temperature. Microstructural study showed the evolution of particle size and shape subjected to sintering temperature. Arrhenius plot showed two stages of growth process with activation energy calculated at 26.85 and 83.091 kJ/mol. The critical size of single domain of this sample plotted from the coercivity against particle size was 63.44 nm. Single-layer composite with mixed particle size was not able to show good electromagnetic (EM)-wave absorption; however double-layer composite showed good return loss. The mechanism of the EM-wave absorption of double-layer composite was discussed in this paper. [ABSTRACT FROM AUTHOR]

The effect of different sintering temperatures on structural and optical properties of ZnO-Zn2SiO4 composite was investigated. In this study, a ZnO-Zn2SiO4 composite was prepared by encapsulated zinc nitrate hexahydrate with amorphous silica nanoparticles in deionized water. The amorphous silica nanoparticles were prepared by reacting sodium silicate with ethanol. Zinc nitrate was mixed with the obtained amorphous silica nanoparticles with the ratio of 2:1 and 1.25:1 for Zn:Si and subjected to the different sintering temperatures from 600 to 1000 °C. Field emission scanning electron microscope (FESEM) microstructure showed that samples exhibit spherical morphology up to 700 °C and dumbbell morphology above 800 °C sintering temperature. The formation of Zn2SiO4 crystal phase appears from 700 °C and onwards together with ZnO crystal phase. The gaining of sintering temperature has also raised the amount of Zn2SiO4 phase and band gap values of the ZnO-Zn2SiO4 composite. [ABSTRACT FROM AUTHOR]

In this research, Tm2O3 doped zinc silicate based glass-ceramics were prepared by using conventional melt-quenching method and has been successfully derived from ZnO-WRHA glasses with control heat treatment process. The formation of zinc silicate phase affected by heat treatment process was investigated using X-ray diffraction. Fourier transform infrared reflection spectroscopy (FTIR) analysis was used to determine the crystallization of Zn2SiO4 in the glass matrix. FTIR analysis showed the appearance of Zn2SiO4 and SiO2 bands that supported the formation of Zn2SiO4 crystal phase in the glass matrix. The optical absorption and energy band gap of the glass and glass-ceramics was investigated using UV-Vis spectroscopy. The absorption edge shows the movement towards longer wavelength with increasing heat treatment temperature. Besides, the energy band gap decreased with the progression of heat treatment. This ability to enhance optical properties in glass-ceramics was expected to have bright future in the opto-electronics devices. [ABSTRACT FROM AUTHOR]

The microwave absorption properties of single- and double-layer doped strontium hexaferrite (SrCoZnFe16O27) and graphite nanocomposite were investigated. W-type SrCoZnFe16O27 nanoparticles was prepared via solid state reaction using high energy ball milling and sintered at different sintering temperatures. Microwave absorption properties of single- and double-layer structures of different thicknesses were investigated in the frequency range of 8-18 GHz using a network analyzer, and their behavior analyzed based on electromagnetic transmission line theory. The results show that double-layer absorbing material showed better microwave absorption properties than single-layer. Double-layer absorbing material which consisted of graphite as the matching layer and SrCoZnFe16O27 as the absorbing layer demonstrated higher reflection loss values of − 19.5 dB when both layers were 1 mm thick. The bandwidth corresponding to the reflection loss below − 10 dB (i.e. 90% absorption) was 3.8 GHz (11.0-14.8 GHz). The excellent microwave absorption properties of double-layer structures were influenced by good impedance match, multiple internal reflections and coupling interactions between the matching and absorbing layers. [ABSTRACT FROM AUTHOR]

This paper reports a study of the microwave absorption properties of multiferroic BiFeO3 (BFO) epoxy resin composites. The effects of various sintering temperatures on the crystalline phase of BFO and its microwave absorption characteristics were critically analyzed. BFO nanoparticles were synthesized by mechanical activation high energy ball milling (HEBM) with post heat treatment over various temperatures ranging from 700 to 800 °C. The XRD results showed by using the HEBM method, BFO phase is formed at a lower sintering temperature of 700 °C compared to conventional solid state reaction due to the enhanced diffusion rates. The phase composition and the grain sizes had significant influence on the permeability, permittivity and reflection loss values of BFO composites measured by a network analyzer in the frequency range from 8 to 18 GHz. It was observed that the purity fraction of BFO phase and the grain sizes increased with the sintering temperature. By increasing the sintering temperature up to 775 °C, the microwave absorption properties were enhanced over a broad working frequency range corresponding to the reflection loss below − 10 dB (i.e. 90% absorption) due to crystalline phase changes. BFO samples sintered at 775 °C demonstrated higher absorption ability with RLmin − 40.5 dB over a 1.31 GHz bandwidth, showing that BiFeO3 has great potential as a microwave absorbing material. [ABSTRACT FROM AUTHOR]

Microwave-absorptive polymer composite materials provide protection against interference to communication systems caused by microwave-inducing devices. Microwave-absorptive polymer composites were prepared from polylactic acid (PLA) biocomposite blended with oil palm empty fruit bunch (OPEFB) fiber and commercial Iron oxide (Fe2O3) as filler using the melt-blending method. The composites characterization was carried out using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The coefficient of reflection S11 and coefficient of transmission S21 of the composites for various Fe2O3 filler percentages were determined using a rectangular waveguide in connection with microwave vector network analyser (HP/Agilent model PNA N5227). These coefficients were then used to calculate microwave-absorption properties (in decibels). XRD analysis showed that increasing amounts of reinforced material (Fe2O3) reduces the crystallinity of the composites. SEM data indicated that Fe2O3 filler ratio increased in the composites, and adhesion to the cellulose fiber grew gradually until the highest percentage of filler was added. The complex relative permittivity and relative permeability were obtained within the broad frequency range of 8-12 GHz at room temperature for various percentages of filler and were measured by the transmission/reflection method using a vector network analyser. Fe2O3 embedment in OPEFB/PLA was observed to have resulted in enhancing the dielectric and magnetic properties. The values of permittivity and permeability increased with increasing Fe2O3 filler content. Theoretical simulation studied the relation between ε′ and ε″ of the relative complex permittivity in terms of Cole-Cole dispersion law. The result indicated that the processes of Debye relaxation in Fe2O3/OPEFB/PLA, the unique dielectric characteristics of Fe2O3 cannot be accounted for by both the Debye dipolar relaxation and natural resonance. Results further showed that the material transmission, reflection, and absorption properties could be controlled by changing the percentage of Fe2O3 filler in the composites. [ABSTRACT FROM AUTHOR]

Lithium hafnium phosphate LiHf2(PO4)3 (LHP) was synthesized via solid-state synthesis technique. The sintering behavior, structure, and phase composition of the as-prepared sample was analyzed using X-ray diffraction (XRD) characterization technique. The XRD-Rietveld refinement analysis showed that after sintering at low temperatures 500 to 1000 °C, it exhibited various secondary phases. However, a single phase was observed as the sintering temperature increases from 1100 to 1200 °C. LHP sintered at 1100 °C produced real features of sodium superionic conductor type (NASICON-type) with hexagonal crystal axis indicating R-3c space group. The electrical properties were studied using impedance spectroscopy technique. Frequency and temperature dependence behavior of conductivity (ac and dc) and dielectric permittivity were studied. The results obtained describes the conduction mechanism in the system. Electric modulus formalism was performed to investigate the relaxation behavior which showed that as measuring temperature increases, the relaxation frequency increases whereas relaxation time decreases. This behavior explains the hopping mechanism of the charge carriers in the system. Likewise, the correlated barrier hopping model elucidates the dominant hopping mechanism. [ABSTRACT FROM AUTHOR]

In this paper, using heat treatment approach has achieved a successful synthesis of copper oxide (CuO) nanoparticles with monoclinic structure. Thus, copper(II) nitrate trihydrate has been employed as a metal precursor, polyvinylpyrrolidone as a capping agent, while the solvent was deionized water by altering the calcining temperatures from 500 to 800 °C. The XRD patterns, EDX and FTIR spectra have proved that the CuO nanoparticles obtained have a high level of purity, crystallinity and nano-size. The FESEM images showed that nanoparticles are spherical with a tendency of agglomeration while calcining temperature being increased. Additionally, it has been noted that as the calcining temperature rose, the average particles sizes increased as demonstrated by TEM images. The optical properties have been demonstrated by using the UV visible spectrophotometer; the obtained results have revealed that the energy band gab decreases in relation with the calcination temperature increment. Further results have shown that the photoluminescent intensity has been increased with the calcination temperature increment as demonstrated by photoluminescence. [ABSTRACT FROM AUTHOR]

Zinc silicate (ZnO-SiO) glass system were fabricated using melt-quench method with zinc oxide (ZnO) and white rice husk ash (WRHA) with compositions of (ZnO)(WRHA) where (x = 0.55, 0.60, 0.65 and 0.70 wt%). Energy Dispersive X-ray Fluorescence (EDXRF), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy and UV-Visible (UV-Vis) absorption spectroscopy were used to investigate the structural and optical properties of the samples. From XRD measurement, only one sample is glass and others were in crystalline form as WRHA is used to replace silica (SiO). This is because WRHA possess nucleating agents in its composition and this causes the samples to be highly crystalline. ZnO in the other hand is a highly crystalline material and encourages the formation of crystalline phase in the samples. FTIR analysis shows that the non-bridging oxygen's (NBO's) are formed as the amount of ZnO in the samples increases. The optical band gap shows that the optical band gap rises due to direct forbidden transition. ZnO-SiO glass system has variety of applicable characteristic because it possesses high level of chemical inertness for variety of chemical applications and it also gives various color emission which can be used in the plasma display panels (PDPs) and cathode-ray phosphor. [ABSTRACT FROM AUTHOR]

Low-cost Mn-doped willemite (α-ZnSiO:Mn) based glass-ceramics were synthesized by conventional melt-quenching technique using waste soda lime silica (SLS) glasses, zinc oxide (ZnO) and Manganese oxide (MnO) as precursors. The effect of different MnO percentage doping on physical, structural, optical and luminescent performance α-ZnSiO:Mn based glass-ceramics were comprehensively studies in this work. The presence of α-ZnSiO:Mn crystal phase and microstructure was confirmed by X-ray diffraction and field emission scanning electron microscopy spectroscopy. From the Scherrer's formula, α-ZnSiO:Mn have an average crystallite size of 30-40 nm, respectively. Fourier transform infrared reflection spectroscopy displays the structural growth of α-ZnSiO:Mn crystal. The green emission centered at about 527 nm from the α-ZnSiO:Mn crystal exhibit a resulted from T-A energy transition of Mn ions. Intense emissions of Mn ions at 260 nm excitation were occurs may be caused by the increase of Mn ions into α-ZnSiO crystal structure with lower phonon. Based on the results achieved, this low-cost α-ZnSiO:Mn based glass-ceramic exhibit a huge potential to act as a green phosphor in opto-electronic devices. [ABSTRACT FROM AUTHOR]

The aim of the present research is to examine the effect of Cu metal addition in nano-scale particle size on the mechanical properties and porosity of porous alumina ceramics using commercial rice husk ash as pore forming agent and silica (SiO2) source. Porous alumina ceramics reinforced were prepared using nano-scale Cu metal particles as their strengthening phase. Solid-state and sacrificial techniques were used to prepare the porous alumina reinforced ceramics. A field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and transmission and electron microscope (TEM) were used to analyze the microstructure and ceramic phases. Different ratios of Cu metal were added (3, 6, 9, and 12 wt%) at different ratios of commercial rice husk ash. The results of this investigation show that with increasing ratios of Cu metal, the porosity decreased and the mechanical properties increased. The increase in the mechanical properties could be attributed to the decrease in the porosity, the toughening mechanism, increase density of porous alumina ceramics, and formation of the tenorite (CuO) phase due to sintering at high temperature (1600 °C). Some potential applications include purging of gas filtration and thermal insulation. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the microstructure, hardness and density of sintered (1129°C, 45 min) specimens of iron-base powder alloys containing 0.8 - 2.5% C, 2% Cu and additives of chromium- and molybdenum-alloyed Astaloy E iron powder is studied. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on thermal, structural and optical properties of novel willemite glass-ceramics. The precursor glass in the ZnO-SLS glass system was successfully prepared using conventional melt-quenching technique and willemite (ZnSiO) glass-ceramics were derived from this precursor glass by a control crystallization process. The effect of heat-treatment temperature on the phase transformation, morphology and size of ZnSiO crystal phase was examined using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) techniques. Furthermore, fourier transform infrared reflection (FTIR) spectroscopy was used to evaluate the ZnSiO crystal structural evolution. The average size of ZnSiO crystallite obtained from calculation of XRD is found to be in the range 30-60 nm, whereas the grain size observed in FESEM is in range of 200-400 nm. The appearance of SiO, ZnO and Zn-O-Si bands detected from FTIR indicate the formation of ZnSiO crystal phase. Besides, the study of the optical band gap has found that optical band gap of the glass-ceramics decreased as the heat treatment temperature increased. The photoluminescence spectra of willemite glass-ceramics exhibit two different emissions around 525 nm (green) and 585 nm (yellow); exhibit a characteristic of broad absorption band around 260 nm. These two different spectra reveal that the luminescence performance of the willemite glass-ceramics was enhanced with the progression of heat treatment temperature due to different located energy levels of the β-ZnSiO and α-ZnSiO crystalline phase. Such luminescent glass-ceramics was expected to find potential applications in phosphors and opto-electronic devices. [ABSTRACT FROM AUTHOR]

The properties of aluminum alloy AA6061-T6 after aging at 220°C for 0.5 - 8 h are studied by the methods of light and scanning electron microscopy and fractography. The mechanical characteristics of the alloy are determined by tensile tests. [ABSTRACT FROM AUTHOR]

This paper reported the uses of ark clam shell calcium precursor in order to form hydroxyapatite (HA) via the wet chemical precipitation method. The main objective of this research is to acquire better understanding regarding the effect of sintering temperature in the fabrication of HA. Throughout experiment, the ratio of Ca:P were constantly controlled, between 1.67 and 2.00. The formation of HA at these ratio was confirmed by means of energy-dispersive X-ray spectroscopy analysis. In addition, the effect of sintering temperature on the formation of HA was observed using X-ray diffraction analysis, while the structural and morphology was determined by means of field emission scanning electron microscopy. The formation of HA nanoparticle was recorded (~35-69 nm) in the form of as-synthesize HA powder. The bonding compound appeared in the formation of HA was carried out using Fourier transform infrared spectroscopy such as biomaterials that are expected to find potential applications in orthopedic and biomedical industries . [ABSTRACT FROM AUTHOR]

This paper presents a study on synthesis and optical properties of ZnSiO:1 wt% Eu at different heat treatments. The objective of the research is to synthesize ZnSiO:1 wt% Eu phosphor by using low cost solid state reaction method with recycled waste bottle glasses as the silicate source. The X-ray diffraction results showed that the prepared ZnSiO:1 wt% Eu phosphors have a sharp diffraction peak as the heat treatment temperatures were increased from 600 to 1000 °C. Furthermore, the morphology from the Field emission scanning electron microscope analysis were shown the formation of well crystalline samples with dense packed grains due to the increment of heat treatment temperatures. Fourier transform infrared spectra has confirmed the present elements in ZnSiO:1 wt% Eu phosphors while the narrow width of Raman line spectra were observed at temperatures ranging from 700 to 1000 °C indicates good homogeneity and crystallinity of synthesized powders. In addition, the energy band gap of europium doped zinc silicate increased dramatically up to 3.62 eV at temperature of 1000 °C. Photoluminescence measurements has also exhibited the red emission corresponding to the D → F (600 nm) when viewed under blue excitation. [ABSTRACT FROM AUTHOR]

The electrical properties of a ceramic obtained from white rice husk ash (WRHA) was reported in this study for electronic applications. Some material's characteristics were evaluated for better understanding. The ceramic was prepared using die-pressing technique and bulk density was determined using Archimedes' method. The residual pore contents of the sample were investigated using SEM micrographs. XRD and XRF analysis were done to investigate the molecular structure and chemical composition of the ceramic. Dielectric characteristics of the specimen were measured using LCR meter. Sawyer-Tower circuit was the method to measure polarization-electric field (P-E) hysteresis loop. The WRHA ceramic has low dielectric constant of 16.4 and dielectric loss tangent of 0.36 at 100 kHz. The highest dielectric constant (65.2) of the specimen possessed by sintering temperature of 900 °C and frequency of 1 kHz. P-E loop measurement indicates that the WRHA ceramic is 'capacitor-like', when sintered at 900 and 1200 °C. The best temperature for sintering the sample was evaluated 1200 °C, to be a good dielectric material. [ABSTRACT FROM AUTHOR]

An experiment was conducted to characterize microstructural and mechanical behavior of AA6061 alloy during an artificial aging treatment through destructive and ultrasonic nondestructive techniques. Identical aluminum plates of AA6061-T6 aluminum alloy were solutionized at ≈800 K, followed by quenching and artificial aging at 493 K up to 8 h. The microstructural evolution was analyzed using scanning electron microscopy. The variations in hardness, yield stress, and ultimate tensile strength with respect to aging time were discussed. Besides, ultrasonic parameters velocity and attenuation were measured and correlated with the microstructural evolution as well as certain mechanical properties. The ultrasonic measurements showed a good correlation with the microstructural features and mechanical properties of the alloy during aging, whereby an excellent correlation was found between the longitudinal wave velocity and strength properties of the aged specimens. The longitudinal wave velocity was found to be directly related to the hardness with a correlation coefficient of 0.99. [ABSTRACT FROM AUTHOR]

The characterization and optimization of the microstructures of materials pertaining to material properties is a primitive necessity to ensure the performance and service life of the materials and components. In the demand of new characterization and evaluation techniques, nondestructive ultrasonic techniques have shown a good potential to characterize the microstructures and mechanical properties of a wide variety of materials. Measurements of ultrasonic parameters such as velocity and attenuation can provide information on the structural and microstructural variations of those materials that have undergone the heat-treatment procedure. In the current review, the correlation of ultrasonic parameters with microstructural features of ferrous and nonferrous metals such as steels, aluminum, and superalloys is investigated. It is proven that ultrasonic parameters are closely correlated to the microstructural evolutions which frequently occur during the heat-treatment procedures in practical situations. To conclude, the ultrasonic measurements contribute to a feasible and accurate characterization of the materials and evaluation of their microstructures and mechanical properties in a straightforward, reliable, and fast, nondestructive manner for practical applications. [ABSTRACT FROM AUTHOR]

In this work, Polarization-Electric field (P-E) hysteresis loop was evaluated and dielectric studies of the ceramic obtained from white rice husk ash (WRHA) and soda lime silica (SLS) glass was reported for electronic applications. Dielectric properties and hysteresis loop of the specimens were measured using a LCR meter and Sawyer-Tower circuit, respectively. The dielectric analysis clearly shows that the different amount of SLS glass content gives the different value of dielectric constant and loss to the ceramic. Sample with 2.5 wt% SLS glass content includes the lowest dielectric constant (11.13) among others, at 100 kHz, when sintered at 1,200 °C. The results show dielectric constant and loss of the specimens decrease with increasing applied frequency. P-E loop measurement indicates that the WRHA ceramic, generally, had capacitor capability and became more 'resistor-like' than 'capacitor-like', with addition of SLS glass content. [ABSTRACT FROM AUTHOR]

The occurrence of pattern formation within physical dimension and mechanical property changes was systematically investigated based on the addition of various amounts of pre-alloyed Astaloy E and carbon to iron powder. Powder samples were prepared in a similar manner by mixing in a Y-type mixer, compacting in a floating die under constant pressure and sintering in a hydrogen atmosphere tunnel furnace at 1,120 °C for 45 min. An optical microscope equipped with image analysis was employed to study the microstructure. Physical properties, such as the green density, sintered density and dimensional changes, as well as the hardness were measured. The results indicate that the addition of Astaloy E and carbon results in increased green density, sintered density and hardness. An increase in the carbon content resulted in physical dimension growth of the parts. [ABSTRACT FROM AUTHOR]

Background: In fabrication of ZnO-based low voltage varistor, Bi2O3 and TiO2 have been used as former and grain growth enhancer factors respectively. Therefore, the molar ratio of the factors is quit important in the fabrication. In this paper, modeling and optimization of Bi2O3 and TiO2 was carried out by response surface methodology to achieve maximized electrical properties. The fabrication was planned by central composite design using two variables and one response. To obtain actual responses, the design was performed in laboratory by the conventional methods of ceramics fabrication. The actual responses were fitted into a valid second order algebraic polynomial equation. Then the quadratic model was suggested by response surface methodology. The model was validated by analysis of variance which provided several evidences such as high F-value (153.6), very low P-value (<0.0001), adjusted R-squared (0.985) and predicted R-squared (0.947). Moreover, the lack of fit was not significant which means the model was significant. Results: The model tracked the optimum of the additives in the design by using three dimension surface plots. In the optimum condition, the molars ratio of Bi2O3 and TiO2 were obtained in a surface area around 1.25 point that maximized the nonlinear coefficient around 20 point. Moreover, the model predicted the optimum amount of the additives in desirable condition. In this case, the condition included minimum standard error (0.35) and maximum nonlinearity (20.03), while molar ratio of Bi2O3 (1.24 mol%) and TiO2 (1.27 mol%) was in range. The condition as a solution was tested by further experiments for confirmation. As the experimental results showed, the obtained value of the non-linearity, 21.6, was quite close to the predicted model. Conclusion: Response surface methodology has been successful for modeling and optimizing the additives such as Bi2O3 and TiO2 of ZnO-based low voltage varistor to achieve maximized non-linearity properties. [ABSTRACT FROM AUTHOR]

Background: The complexity of reactions and kinetic is the current problem of photodegradation processes. Recently, artificial neural networks have been widely used to solve the problems because of their reliable, robust, and salient characteristics in capturing the non-linear relationships between variables in complex systems. In this study, an artificial neural network was applied for modeling p-cresol photodegradation. To optimize the network, the independent variables including irradiation time, pH, photocatalyst amount and concentration of p-cresol were used as the input parameters, while the photodegradation% was selected as output. The photodegradation% was obtained from the performance of the experimental design of the variables under UV irradiation. The network was trained by Quick propagation (QP) and the other three algorithms as a model. To determine the number of hidden layer nodes in the model, the root mean squared error of testing set was minimized. After minimizing the error, the topologies of the algorithms were compared by coefficient of determination and absolute average deviation. Results: The comparison indicated that the Quick propagation algorithm had minimum root mean squared error, 1.3995, absolute average deviation, 3.0478, and maximum coefficient of determination, 0.9752, for the testing data set. The validation test results of the artificial neural network based on QP indicated that the root mean squared error was 4.11, absolute average deviation was 8.071 and the maximum coefficient of determination was 0.97. Conclusion: Artificial neural network based on Quick propagation algorithm with topology 4-10-1 gave the best performance in this study. [ABSTRACT FROM AUTHOR]

In this paper the effect of sintering temperature on NiZnFeO is examined closely. The evolution of toward magnetically ordered materials was to be tracked with the parallel evolving microstructure subjected to sintering temperatures in an ascending order. The starting powder of NiZnFeO was prepared via mechanical alloying and later molded into toroidal samples. After each sintering, we observed the resulting changes in the materials. The XRD data showed a single phase being formed as early as 600 °C and the peak intensity was increasing with the sintering temperature indicating an increase in the degree of crystallinity. The BH hysteresis loops showed the evolution from paramagnetism to moderate ferromagnetism to strong ferromagnetism with microstructural changes. For lower sintering temperatures, the samples showed paramagnetic behavior dominating the samples. As sintering temperature increased, paramagnetic states decreased and, at 900 °C, a moderately ferromagnetic state appeared. Sintering at 1000 °C produced a strongly ferromagnetic state giving a well-formed sigmoid-shape hysteresis loop. [ABSTRACT FROM AUTHOR]

Background: The interactions of p-cresol photocatalytic degradation components were studied by response surface methodology. The study was designed by central composite design using the irradiation time, pH, the amount of photocatalyst and the p-cresol concentration as variables. The design was performed to obtain photodegradation % as actual responses. The actual responses were fitted with linear, two factor interactions, cubic and quadratic model to select an appropriate model. The selected model was validated by analysis of variance which provided evidences such as high F-value (845.09), very low P-value (<.0.0001), non-significant lack of fit, the coefficient of R-squared (R2 = 0.999), adjusted R-squared (R2adj = 0.998), predicted R-squared (R2pred = 0.994) and the adequate precision (95.94). Results: From the validated model demonstrated that the component had interaction with irradiation time under 180 min of the time while the interaction with pH was above pH 9. Moreover, photocatalyst and p-cresol had interaction at minimal amount of photocatalyst (< 0.8 g/L) and 100 mg/L p-cresol. Conclusion: These variables are interdependent and should be simultaneously considered during the photodegradation process, which is one of the advantages of the response surface methodology over the traditional laboratory method. [ABSTRACT FROM AUTHOR]

Synthesis of nanocrystalline strontium ferrite (SrFe12O19) via sol-gel is sensitive to its modification parameters. Therefore, in this study, an attempt of regulating the pH as a sol-gel modification parameter during preparation of SrFe12O19 nanoparticles sintered at a low sintering temperature of 900 °C has been presented. The relationship of varying pH (pH 0 to 8) on structural, microstructures, and magnetic behaviors of SrFe12O19 nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning microscope (FESEM), and vibrating sample magnetometer (VSM). Varying the pH of precursor exhibited a strong effect on the sintered density, crystal structure and magnetic properties of the SrFe12O19 nanoparticles. As the pH is 0, the SrFe12O19 produced relatively largest density, saturation magnetization, Ms, and coercivity, Hc, at a low sintering temperature of 900 °C. The grain size of SrFe12O19 is obtained in the range of 73.6 to 133.3 nm. The porosity of the sample affected the density and the magnetic properties of the SrFe12O19 ferrite. It is suggested that the low-temperature sintered SrFe12O19 at pH 0 displayed Ms of 44.19 emu/g and Hc of 6403.6 Oe, possessing a significant potential for applying in low-temperature co-fired ceramic permanent magnet. [ABSTRACT FROM AUTHOR]