Thermogravimetric And Differential Thermal Research Articles

Enhancement of optical, electrical, mechanical and thermal properties with Hirshfeld surface analysis of organic piperazine para-nitrophenol crystals: An effective material for NLO device fabrication

Exploring the diversity of materials and improving their usage in real-time applications is very important. Here, the organic piperazine para-nitrophenol (PPNP) single crystals were successfully grown using methanol and mixed solvent (methanol 50%-water 50%) by slow evaporation technique at room temperature. Single and poly-crystal XRD, UV–visible, and FT-IR/Raman studies revealed that the PPNP compound is monoclinic centro-symmetric (CS) with low cutoff wavelength and various functional groups. Fluorescence spectroscopy confirmed that the intense peak was observed in the red region. Hirshfeld surface analysis, fingerprint plot and framework explore the strength of the synthesized compounds' intermolecular interactions. The melting point of grown crystals was about 114 °C by thermo-gravimetric and differential thermal (TG-DTA) analyses. A chemical etching study was carried out on the grown crystal. Nd: YAG laser beam was used to evaluate the laser damage value of the crystal. The dielectric constant (ε՛) and dielectric loss (ε՛՛) of crystals have been studied as a function of frequency and temperatures. The PPNP has a third harmonic generation active crystal structure and exhibits featured absorption and fluorescent properties. A Z-scan technique characterized the improved third-order optical nonlinear properties of the crystal. It is a promising aspirant in optoelectronic devices as it enhancement the linear and nonlinear, encouraging results of organic PPNP.

Reusing Waste Coffee Grounds in the Preparation of Porous Alumina Ceramics

Porous ceramics can be used in various industrial applications, such as thermal insulation, orthopedic implants, high-temperature filtration, lightweight structural components, and catalyst supports, etc., and can be obtained using various methods. In this study, the sacrificial fugitive method was used to prepare a porous alumina ceramic. The appropriate amount of sacrificial fugitive was combined with raw ceramic powder as a pore-forming agent, and was then evaporated or burned out either before or during the sintering process to create the desired pores. Various materials can be used as pore-forming agents; in this work, eco-friendly waste coffee grounds (WCG) were utilized. First, alumina ceramic green bodies were prepared via slip casting of 60 wt. % alumina suspensions with five different amounts of WCG (0 wt. %, 1 wt. %, 5 wt. %, 10 wt. % and 15 wt. %) and the dispersant Dolapix (0.2 wt. %), and using PVA (0.5 wt. %) as a binder for all solutions. The effect of the various amounts of WCG on the alumina ceramic green bodies, and subsequently on the obtained sintered ceramics, was tracked and validated through different analyses. Suspension viscosity was determined through a rotational viscometer. Simultaneous differential thermal and thermogravimetric (DTA/TGA) analyses were used to observe the thermal decomposition of WCG and to determine the sintering regime. After sintering, the density, porosity, and shrinkage of the samples were examined and calculated. In addition, the phase composition and crystallite size of all sintered samples were determined by powder X-ray diffraction (PXRD) analysis, as well as their morphology and composition using Scanning Electron Microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The results show that density decreased from 3.743 to 2.172 g/cm3 and porosity increased from 6.12% to 45.52%, both with the increasing amount of WCG (from 0 wt. % to 15 wt. %).

Influence of RE-Gd3+ ion substitution on structure, morphology, optical, and magnetic analysis of Cu-Cd based nano ferrites synthesized by low-temperature citrate sol–gel auto combustion method

The current study focused on the influence on physical, thermal, spectral, optical, and magnetic properties with the replacement of Fe3+ ions by large ionic radii rare-earth Gd3+ ions in CuCdFe2O4 nano-ferrites. The Gd3+ doped CuCdFe2O4 ferrite samples with chemical composition Cu0.8Cd0.2GdxFe2-xO4 (x = 0, 0.025, 0.05, 0.075 and 0.1) were produced by citrate sol–gel auto combustion route from the metal nitrates of the corresponding compounds. With the help of Thermo-gravimetric and differential thermal (TG-DTA) analysis, the temperature-dependent spinel phase formation and weight loss percentages were examined. The results of Powder X-ray diffraction patterns and FTIR spectra revealed the development of a cubic single-phase structure with α-Fe2O3 secondary phase, and stretching of metal ion bonds with the addition of Gd3+ ion in CuCdFe2O4 ferrites. From XRD data the observed lattice parameter was in the range of 8.323–8.469 Å and the average crystalline size was increased from 13 to 18 nm. “Field emission scanning electron microscopy” (FE-SEM) and “high-resolution transmission electron microscopy” (HR-TEM) analysis was used to give the particle size, shape, clear agglomeration, and dense structure of Gd3+ doped Cu-Cd nanoparticle. The semiconducting nature of the fabricated samples were confirmed from the characteristic UV–Vis spectra and the respective optical band gap values (1.70–1.74 eV). Electron spin resonance spectroscopy (ESR) analysis was provided the information about the various factors including g-value, peak to peak line width (ΔHPP), resonance field (Hr), and time relaxation (T2). The magnetic characteristic hysteresis loops of synthesised samples at 300 K and 15 K temperatures were obtained by VSM. The results showed that all Gd3+ doped samples exhibited a ferromagnetic nature at 300 K and enhanced hard magnetic nature at 15 K. The maximum saturation magnetisation (MS) was observed for x = 0.025 at both the temperatures (31.66 emu/g at 300 K and 39.65 emu/g at 15 K). The HC values were found in the range of 169.23–557.29 Oe at 300 K and 374.69–749.85 Oe at 15 K. The observed SQR (Mr/Ms) values revealed the single domain structure of prepared samples.

Effects of production conditions on the properties of limestone briquettes aimed for acid soil liming

This paper presents the results of experiments performed to determine how the quantity of the binder (bentonite) and the parameters of the laboratory roll press affect the quality of the briquettes obtained from limestone powder. These experiments aim to examine the conditions in which limestone briquettes are formed and to determine their use for agricultural purposes. During the experiments various mass fractions of bentonite was added to limestone (from 1 to 10 %), while the force of roll press drums ranged from 2 to 25 kN. The briquettes have been tested by applying scanning electron microscopy (SEM), differential thermal and thermo-gravimetric (DTA/TG) analyses, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Bentonite distribution was found to be uniform within the compact briquette structure. Formation of new compounds was not evidenced. The experiments also demonstrated that during briquetting, limestone properties remain unchanged, the changes are only physical, water solubility is not reduced, mechanical properties (impact resistance, compressive strength and abrasion resistance) are satisfactory by the transport and storage terms if the binder mass fraction is over 5% and the briquetting force exceeds 10kN and finally there is no loss due to wind dispersal during application. The only downside of the ?green? briquettes obtained is the time required for their complete disintegration if totally immersed in water.

Mixture of Graphene Oxide/Phosphoric Acid/Melamine as Coating for Improved Fire Protective Performance and Enhancement of Surface Electrical Properties on Wood Chipboard.

Looking for multifunctional materials, an assessment of the performances both as fire retardant and generator of electrically conductive surfaces for a three component mixture of graphene oxide, phosphoric acid and melamine applied on wood chipboard was performed. A simple approach was used to investigate the intumescent char formation and quantify the loss mass during vertical burning tests, in which the prepared samples were exposed for a certain time interval to a flame generated by an ethanol lamp in ambient conditions. Moreover, mass loss evolution and structural changes that occur during the burning process were more comprehensive investigated by differential thermal and thermogravimetric (DTA/TGA) techniques. By comparing the performances between the wood chipboard samples without any coverage and those covered with one or multiple component mixture, an increase of protection against the fire action was noticed when the three component mixture was used. Also, an improvement of the electrical properties was observed, after flame exposure of the samples covered with multiple layers (i.e., two and three), when the three component mixture was used. Morphological and structural investigations by microscopy (optical and electronic-SEMEDX), X-ray diffraction (XRD) and spectral (Raman, FTIR) methods are described. An assessment of market potential is also discussed.

Experimental investigation of the ultrasonic wave effects on the viscosity and thermal behaviour of an asphaltenic crude oil

In this study, the influence of ultrasonic waves on the viscosity and thermal behaviour of a crude oil with high asphaltene content at different irradiation times and powers/frequencies was investigated. It was found that the ultrasonic radiation significantly reduced the oil viscosity before the oil cooled down. The viscosity was then remeasured after the irradiated oil cooled down to the ambient temperature to evaluate the reversibility in viscosity at various time intervals. For each ultrasonic frequency, an optimum irradiation time was found at which the cooled-down irradiated oil reached a minimum viscosity. For the ultrasonic radiation with a frequency of 46 kHz and an output power of 50 W, it was found that the permanent viscosity loss of the cooled-down oil irradiated for an optimum time of 8 min was 10 %. The effects of ultrasonic irradiation on thermal behaviour of the oil were analysed using thermogravimetric and differential thermal (TGA/DTA) methods to evaluate the relation between changes in viscosity and thermal properties of the oil. It was found that the weight loss of the irradiated-oil was more than that of the non-irradiated oil at the end of both the pyrolysis and oxidation stages.

Synthesis and Characterization of a Dual-Cation Organomontmorillonite Nanocomposite.

In this study, a novel dual-cation organomontmorillonites (OMt) nanocomposite was synthesized by two kinds of modifiers cetyltrimethylammonium chloride and cysteamine hydrochloride, and the adsorption behavior of modifiers into montmorillonite (Mt) has been investigated. The OMt were characterized by techniques, such as X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and thermogravimetric and differential thermal (TG-DTA) analyses. The effects of temperature, contact time, the order of addition and the concentration of organic modifiers on the amounts of organics adsorbed were investigated. The adsorption amount of cetyltrimethylammonium chloride (CTAC) and cysteamine hydrochloride (CSH) increased with the increase of the added CTAC amount and contact time, while the addition order of modifiers and modification temperature had no significant effect on the actual adsorption amount of CTAC and CSH on Mt, as confirmed by the XRD patterns. The experimentally determined isotherms showed a good fit with the Langmuir adsorption models. The adsorption kinetics demonstrated that the adsorption of CTAC and CSH by Mt followed the pseudo-second-order model, and CTAC adsorption rate on Mt was faster than that of CSH. FTIR spectrum clearly revealed the incorporation of surfactant ions into the interlayer region. The TG-DTA analyses showed that the total mass losses of OMt strongly depended on the molecular volume of modifiers.

Bio-synthesis of Barleria gibsoni leaf extract mediated zinc oxide nanoparticles and their formulation gel for wound therapy in nursing care of infants and children

Bio-synthesis of nano-metal oxide particles is gaining lot of significance and recommended as promising substitute not only physical methods but also chemical methods. Here in, we demonstrate the nano-zinc oxide (nano-ZnO) particles were successfully prepared by an eco-friendly process using plant Barleria gibsoni (B. gibsoni) aqueous leaf extract. The water leaf extract of B. gibsoni responsible for not only reducing source but also protective agent. The prepared nano-ZnO particles were studied by UV–Vis diffuse reflectance (UV-DRS), Photoluminescence (PL), Fourier transform (FT-IR) infrared spectroscopy, X-ray diffraction spectroscopy (X-RD), transmission electron microscopy (TEM), thermal stability was studied by thermogravimetric and differential thermal (TG-DTA) analysis and particle size by zeta sizer, dynamic light scattering (DLS). UV-DRS spectrum of nano-ZnO particles showed below at wave length 400 nm. FT-IR spectra showed that plant metabolites like polyphenols, flavonoids and amino acids etc., are act as reducing and protective agent. X-RD studies revealed the formed nano-ZnO particles have hexagonal (wurtzite) structure. TEM analysis confirmed the range of nanoparticles between 30 and 80 nm, which is supported by DLS analysis. The antibacterial property of synthesized nano-ZnO particles was tested with bacterial pathogens showed good results. The developed nano-ZnO gel act as an efficient and superior another tropical antimicrobial formulations for healing of burn infections. Moreover, the formulated nano-ZnO gel exhibited a remarkable wound healing potential in rats.

Sol-gel synthesis of Mn1.5Co1.5O4 spinel nano powders for coating applications

Mn1.5Co1.5O4 oxide spinels are widely used as protective coatings for stainless steel interconnects within planar solid oxide fuel cell stacks. Containing both cubic and tetragonal crystalline phases, these Mn/Co oxide spinels exhibit favorable thermal stability and electronic conductivity for the SOFC interconnect application. Slurry-based coating applications of Mn/Co oxides require precursor powders, which can benefit from being nano-structured. In this study, the sol-gel synthesis of nanocrystalline Mn1.5Co1.5O4 spinel is investigated. The decomposition of sol-gel precursors, as well as the crystalline phase structures and microstructures of the product Mn1.5Co1.5O4 are characterized by differential thermal and thermogravimetric (DTA/TG) analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The effects of various sol-gel annealing temperatures (T), treatment times (t), and citrate-to-metal ratios (Rc) are evaluated. Results suggest that nanocrystalline Mn1.5Co1.5O4 spinel can be synthesized around 1050 °C, and that T = 1050 °C, t = 6 h and Rc = 2 are optimum conditions for producing the smallest grain size. Image analysis of TEM results shows that the size of Mn1.5Co1.5O4 crystallites increases with increasing temperature, with average particle sizes ranging from ∼70 nm to ∼1 μm. Selected area diffraction pattern (SADP) of Mn1.5Co1.5O4 spinel synthesized at 800 °C confirms the dual (cubic/tetragonal) structure of Mn1.5Co1.5O4.

Mineralogy and crystallographic properties of Heu-type zeolitic tuff from the Novakovic deposit, Bosnia and Herzegovina

This paper presents mineralogical and crystallographic characterization of the zeolitic tuff from the Novakovic deposit, Republic of Bosnia and Herzegovina. The zeolitic tuff is of a whitish color composed of Ca-clinoptilolite and an amorphous phase (volcanic glass and amorphous SiO2). The zeolitic tuff was analyzed by X-ray diffraction of the polycrystalline sample (XRPD), scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), and differential thermal and thermo- gravimetric (DTA/DTG) methods. According to the results obtained, it can be concluded that the studied zeolitic tuff is composed of Heu-type minerals. Based on the chemical analysis, thermal treatment and XRPD analysis it was determined that this is a mineral Ca-clinoptilolite. Thermal analysis in the temperature range from 300 up to 700?C showed that the examined zeolite minerals from the Novakovic deposit are stable up to the temperature of 600?C. The crystal structure of Ca-clinoptilolite has been refined in the centrosymmetric space group C2/m (S.G. 12) with disordered distribution of Al and Si in the tetrahedral framework. The unit-cell parameters are as follows: a = 17.662 ?, b = 17.874 ?, c = 7.402 ?, ? = 116.32? and V = 2122.73 ?3. The basic structural motif is represented by four channels. Three channels are composed of eight-membered rings, and one of ten-membered rings. The ten-membered (channel A) and one eight-membered channel (B) are parallel to the crystallographic axis c, and the other eight-membered channel is parallel to the a-axis. Ca-clinoptilolite comprises approximately 90 % of the studied zeolite tuff while the rest 10 % is the amorphous phase. The overall cation exchange capacity (CEC) amounts to 187 mmolM+/100g, and calcium represents the most abundant cation in the studied sample. The atomic ratios of Si/Al, Na+/(Na++K+), and Ca2+/(Ca2++Mg2+) are as follows: 4.36, 0.14, and 0.55, respectively. The zeolite tuff is both thermally and structurally stable and has applications in various areas of industry and agriculture.

Bio-derived MgO nanopowders for BOD and COD reduction from tannery wastewater

MgO nanopowders were synthesised via a simple and “greener” route using Carica papaya leaf extract at 500°C. The bio-derived MgO nanopowders (MgONPs) were characterised by Brunauer–Emmett–Teller (BET), differential thermal and thermogravimetric (DTA-TGA) analysis, powder X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS). The COD and BOD reduction efficiency of the MgO—NPs was evaluated in the presence of raw and simulated tannery wastewater. Under optimum conditions, the COD of raw tannery wastewater reduced from 2725.9mg/L to 126.5mg/L and BOD from 1899.5mg/L to 104.5mg/L in a batch system. Also, the turbidity was reduced from the initial concentration of 588 NTU to a level of 98 NTU within 120min. Impressively, 93.5% COD reduction and 96.9% BOD reduction were obtained by the fixed-bed system. The spent MgO was regenerated and reused several times without significant loss of capacity. Hence, the bio-derived MgO nanopowders offered potential benefits for BOD and COD removal from tannery wastewater.

Synthesis, structural, optical and thermal studies on 3, 5-diethyl-2, 6-di (4-fluorophenyl)-4-oxopiperidinium chloride

A new organic compound 3, 5-diethyl-2, 6-di (4-fluorophenyl)-4-oxopiperidinium chloride (DFOC) was synthesized and its crystal was grown from ethanolic solution adopting the slow evaporation solution growth technique. The structure of the grown crystal was analyzed by single crystal X-ray diffraction study. The compound crystallizes in the orthorhombic system with space group Pnma. 1H and 13C Fourier transform nuclear magnetic resonance spectra of DFOC were recorded to elucidate its molecular structure. UV–vis–NIR spectral study showed that the grown crystal is transparent in the entire visible region with the lower cut-off wavelength of 269 nm. The thermal stability of DFOC was studied by thermogravimetric and differential thermal (TG-DTA) analyses.

Synthesis, structural, optical and thermal studies on 3,5-diethyl-2, 6-di (4-methoxyphenyl)-4-oxopiperidinium chloride

A new organic compound 3, 5-diethyl-2, 6-di(4-methoxyphenyl)-4-oxopiperidinium chloride (DMOC) was synthesized and its crystals were grown from an ethanolic solution adopting slow evaporation solution growth technique. The structure of the grown crystal was analyzed by single crystal X-ray diffraction study. The compound crystallizes in the orthorhombic system with space group Pnma. 1H and 13C Fourier transform nuclear magnetic resonance spectra of DMOC were recorded to elucidate its molecular structure. UV-vis-NIR spectral study showed that the grown crystal is transparent in the entire visible region. The thermal stability of DMOC was studied by thermogravimetric and differential thermal (TG-DTA) analyses.

Waste chicken eggshell as a natural valuable resource and environmentally benign support for biosynthesis of catalytically active Cu/eggshell, Fe3O4/eggshell and Cu/Fe3O4/eggshell nanocomposites

This paper is reported on the green synthesis of Cu/eggshell, Fe3O4/eggshell and Cu/Fe3O4/eggshell nanocomposites through an environmental and economical method using aqueous extract of the leaves of Orchis mascula L. without any stabilizer or surfactant. The nanocomposites showed high catalytic activity in the reduction of a variety of dyes and characterized by Fourier transform infrared spectroscopy (FT-IR), differential thermal and thermogravimetric (DTA-TGA) analysis, field emission scanning electron microscopy (FESEM) equipped with an energy dispersive spectroscopy (EDS), elemental mapping, X-ray diffraction analysis (XRD), Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM) and UV–vis spectroscopy. The possible mechanism leading to the formation of copper nanoparticles (NPs) is also suggested. The facile and clean synthesis, simple preparation procedure, excellent properties, alterable supports and low cost allow these catalysts to be used in reduction of 4-nitrophenol (4-NP), Methyl orange (MO), Congo red (CR), Methylene blue (MB) and Rhodamine B (RhB) in water at room temperature. The progress of the reaction was monitored using UV–vis spectroscopy. The catalysts could be easily removed from the reaction media by mild centrifugation or an external magnet and reused several times without any negative effect on the initial results.

Characterization and microstructure observation of sintered red mud–fly ash mixtures at various elevated temperature

This study investigated the characterization and microstructure observation of sintered red mud–fly ash mixtures at various elevated temperature. The detailed analysis of the phase evolution during sintering process of red mud and fly ash as the function of sintering temperature were explored. Phase evolution and microstructure observation were carried out by X-ray diffraction method (XRD) and scanning electron microscope (SEM) method. Thermal analysis was carried out by thermogravimetric and differential thermal (TG-DTA) analysis. The mineralogical evolution revealed that quartz and goethite originates from the parent composition of red mud and fly ash. Microstructure observation revealed the transformation of globular grains towards elongated grains during the sintering process. Mass loss around 11% is observed in the thermal analysis patterns due to the dehydration, hydroxide-oxide phase transitions from iron (primary phase) and aluminum (secondary phase). The phase transition, evolution and dissolution as the function of sintering temperature were correlated as the function of temperature and the amount of fly ash content. The disappearance and appearance of the different phases confirms the decomposition and formation reaction suggested by thermal analysis.

Third order nonlinear optical properties of potassium dichromate single crystals by Z-scan technique

Single crystal of potassium dichromate (KDC) has been grown from aqueous solution by slow evaporation technique. The lattice parameters of the grown crystal were determined by X-ray diffraction analysis. The optical absorption studies reveal that the crystal has UV cut-off wavelength around 240nm. Thermo gravimetric and differential thermal (TGA/DTA) studies revealed that the crystal thermally stable up to 397.1°C. The mechanical strength of the grown crystal was carried out by Vickers micro hardness test. The crystal perfection was confirmed by etching studies. Third order nonlinear optical studies was performed using by single beam Z-scan technique using continuous Nd:YAG laser. Closed aperture Z-scan studies reveal the negative nonlinearity in the crystals and open aperture Z-scan reveals the saturation absorption. Also various parameters such as nonlinear refractive index n2, absorption co-efficient β and nonlinear optical susceptibility χ(3) were calculated for the grown crystal.

Effect of calcium phosphate coating on polyamide substrate for biomaterial applications

A new type of material from polyamide coated with calcium phosphate was developed aiming to have potential application as biomaterial. Coating was obtained by the sol-gel method and calcium phosphate was obtained after contact with body fluid solution. The coated polyamide (before and after contact with body fluid solution) was characterized by thermogravimetric and differential thermal (TGA/DTA) analyses, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). These characterizations revealed that the calcium phosphate coating has a thickness of less than 3 µm, which resulted in an increase in the melting point and improved the thermal stability of polyamide. After contact with body fluid, the interactions between the coating and the substrate remained, and there was formation of crystalline and amorphous phosphates on polyamide surface.

Intercalation and electrical behavior of Ta xMo1-xS2 (x > 0.5) layered mixed disulfides

This work reports a systematic study of the structural and electrical behavior of three ternary phases of the TaxMo1-xS2 system (x = 0.55, 0.75 and 0.90) and their intercalation compounds resulting from both chemical and electrochemical lithium insertions, as well as from pyridine and poly(ethylene oxide) intercalations. The three ternary phases were prepared by direct reaction of their constituting elements, without any other additive, at 900 oC in inert atmosphere. The resulting compounds were characterized by means of X-ray powder diffractometry (XRD), thermogravimetric and differential thermal (TGA/DTA) analyses, energy dispersive X-ray fluorescence (EDX) and field emission-scanning electron microscopy (FE-SEM). The electrical conductivity of the different products was measured in the 1.5-300 K temperature range using the conventional four probe van der Pauw method in the presence of a 9 T magnetic field in order to verify the occurrence of magnetoresistivity phenomena.

Crystallization and magnetic behavior of nanosized nickel ferrite prepared by citrate precursor method

NiFe 2O 4 nanoparticles have been synthesized by citrate precursor gel formation with subsequent heat treatment. Differential thermal and thermogravimetric (DTA/TG) analyses show that the metal citrates decomposed around 230 °C followed by crystallization of the ferrite. X-ray diffraction (XRD) patterns reveal the formation of the cubic spinel phase in the samples after sintering the gel at 350 °C, 500 °C and 700 °C. For the samples annealed at 350 °C and 500 °C a small amount of α-Fe 2O 3 was detected whereas single phase was obtained for the sample annealed at 700 °C. The lattice constant a for all the samples is comparable to the value of the bulk material. The mean crystallite size D XRD of the samples determined from XRD line broadening is 26.2–28.5 nm. Transmission electron microscope (TEM) analysis shows that the single-phase particles form clusters with the particle size in the range of 21–82.5 nm and the most probable value D TEM of 55.4 nm. Magnetic measurements show that its Curie temperature T C is close to the bulk value while the spontaneous magnetization M s at 5 K is lower than that of the bulk. The thermal variation of M s in the temperature range from 5 to 300 K can be best fitted to a modified Bloch T α law with the exponent value α ≈ 2. The magnetization data are explained with reference to the disordered surface spins and the finite size effects. In this investigated temperature range, the coercive force H c decreases linearly with increasing temperature. The coercivity mechanism in the nanoparticle sample with broad particle size distribution is expected to be complex and different factors which affect the H c value were proposed.

Synthesis and characterization ofKTiOPO4 nanocrystals and their PMMA nanocomposites

KTiOPO4 (KTP) nanocrystals have been synthesized by the modified Pechini method usingethylenediaminetetraacetic acid (EDTA) and ethylene glycol (EG) as chelating andsterification agents, respectively. Orthorhombic KTP has been obtained by calcination at1073 K for several hours. Differential thermal and thermogravimetric (DTA-TG) analyseshave been used to study the optimized heat treatment used on the precursor powder toobtain KTP nanocrystals. X-ray powder diffraction (XRD) studies on the thermallytreated precursor powders indicated that nanocrystals began to crystallize at 923 K.Nanocrystals with a size dispersion distribution that fit to a lognormal functioncentered at 25 nm were observed by electronic microscopy. KTP nanocomposites wereprepared by embedding nanocrystals in poly(methyl methacrylate) (PMMA).The photoinduced second-order susceptibility parameter and the piezo-opticalcoefficient were measured for the KTP nanocomposites. The optimal conditionsfor the generation of the frequency-doubled second harmonic generation wererecorded at 391 K, and at a fundamental laser wavelength of 1064 nm and underadditional treatment by polarized UV light, provided the maximum value obtained of3.23 pm V−1. The piezo-optical coefficients were recorded at room temperature underphotoinduced treatment by a UV laser beam; the maximum value achieved was0.673 × 10−14 m2 N−1 at a pump–probe delaying time of 160 s.