Preparation of sintered foam glass with high fly ash content

Foam glasses with 50 wt.%, 60 wt.% and 70 wt.% fly ash are prepared using fly ash and flux agent sodium borate with sodium silicate as foaming agent at the temperature of 800 °C. Heat treatment at 800 °C for 1 h of pellets having different fly ash mass percentages results in well-sintered bodies of dark gray color featuring a vitreous aspect with smooth surface. The effect of amount of fly ash on the density, porosity, mechanical strength and microstructure is evaluated. The experimental results show that the foam glass with 70 wt.% fly ash exhibits the excellent comprehensive properties and the suitable sintered temperature is 800 °C.     

Radiation shielding of concretes containing different aggregates

The shielding of γ-rays by concrete has been investigated for concretes containing different amounts of barite and normal weight aggregates. The linear attenuation coefficients (μ, cm⁻¹) have been calculated at photon energies of 1 keV to 100 GeV using XCOM and the obtained results compared with the measurements at the photon energies of 0.66 MeV and 1.33 MeV. It is shown that the type of the aggregate is more important than the amount of aggregate used in concrete for γ-ray shielding.     

Low temperature phase barium borate: A new optical limiter in continuous wave and nano pulsed regime

Low temperature phase barium borate was synthesized by hydrothermal method. XRD analysis confirms the formation of γ-BBO or hydrated barium polyborate (Ba₃B₆O₉(OH)₆) which crystallizes in monoclinic system in the P2/c space group. The molecular structure analysis shows the presence of dominant BO₄ unit and the hydrated nature of material. γ-BBO exhibits sharp absorption edge at 202 nm and highly transparency in the UV–Visible–NIR region. The peak at 347 nm in the emission spectrum is due to the presence of self-trapped exciton. The third order nonlinear optical properties and limiting behavior of low temperature barium borate in both pulsed and continuous wave regime were studied. The effective 2PA absorption coefficient of γ-BBO under ns pulse excitation is estimated to be 0.38 × 10⁻¹⁰ m/W. The nonlinear absorption coefficient, refractive index and optical susceptibility of the material in cw regime were found to be in the order of 10⁻⁵ m W⁻¹, 10⁻¹² m² W⁻¹, 10⁻⁶ esu respectively. In both regimes, low temperature phase barium borate exhibits better optical limiting properties than high temperature phase β-BBO.     

Ultrasonic investigation of the relaxor behaviour of ferroelectric ceramics (Pb1−xCax)TiO3 for x = 0.475, 0.50 and 0.55

Three samples of calcium modified lead titanate (Pb_1?xCa_x)TiO₃ with x = 0.475, 0.50 and 0.55 were studied in terms of their ultrasonic properties. The samples were prepared using the solid state reaction technique. Ultrasonic attenuation and velocity were measured as a function of the temperature at 5 MHz and 10 MHz with X-cut quartz transducers, using the ultrasonic pulse-echo technique and Papadakis method for accuracy determination of the transit time of ultrasonic RF pulses. An equation regarding elastic–electric coupling between strain and spontaneous polarization was used in order to fit the elastic modulus. The nature of the phase transition was characterized through the diffusivity exponent obtained from this fit. Our results show that, as calcium concentration increases from 0.475 to 0.55, the behaviour of ferroelectric phase transition changes from normal to relaxor. This process is accompanied by a systematic decrease of the critical temperature.     

Structure investigation of TeO2–BaO glass employing ultrasonic study

Tellurite glasses of the system (100 − x)TeO₂–xBaO for different compositions of BaO (x = 9, 12, 15, 18, 20 and 22 wt.%) have been prepared by rapid quenching method. A decrease in ultrasonic velocities and density, which is followed by an increase in attenuation with a progressive increase in BaO content has been observed at room temperature and also over a wide range of temperatures. The above results reveal the softening of the glass network due to the progressive transformation of the rigid framework characteristics of TeO₂ resulting in the formation of distorted TeO_3 + 1 units followed by the creation of regular TeO₂ (4 → 3 + 1 → 3) sites and the formation of ionic character bond (NBO).     

An advanced fabrication route for alkali silicate glass by non-firing process

An amorphous silica powder surface was treated separately and combining mechanical and chemical treatment processes. The raw silica powder was mechanically modified using a planetary type mill at a rotation speed of 200 rpm for 15 min using a 5 mm size ball. The raw and the mechanically modified silica powders were hydrothermally treated for 5, 15 and 24 h lengths of time. Silanol surface groups successfully produced by the treatments were measured by diffuse reflectance infrared fourier transform (DRIFT) spectroscopy. The results show that the combination of mechanical and chemical, so call mechanochemical treatment, is the most efficient in enhancing the quantity of surface silanol groups. The mechanochemically treated powder was used for the fabrication of glass. Silica glasses were successfully fabricated without firing by mixing the treated powders with KOH 5 M solutions. Morphology and transparency of the obtained glasses were analyzed using SEM and UV–VIS–NIR techniques. Possible mechanism reactions of powder surface activation occurring during the mechanochemical and condensation processes are also discussed.     

Porous β-NaCaPO4 containing borate glass-ceramic scaffolds

A novel β-NaCaPO₄ containing borate glass-ceramic is prepared. Two porous glass-ceramic scaffolds are prepared by binding particles with the size of 200–300 μm by 5 wt.% sodium silicate solution and 2 wt.% chitosan solutions, respectively. The reaction of the scaffolds in the SBF solution is characterized by weight loss analysis, XRD, FTIR, and SEM. The same is done to the 45S5 glass scaffolds as comparison. XRD and FTIR indicate that the carbonate hydroxyapatite has formed more rapidly on the borate glass-ceramic scaffolds. The carbonated hydroxyapatite depositing on chitosan binding scaffolds has lower crystallization degree than that on sodium silicate binding scaffolds and is similar to that of the human bone, which makes the chitosan binding scaffolds a good potential prospect in the field of tissue engineering.     

Effect of cooling rate on the morphology of γ′ precipitates in a nickel-base superalloy under directional solidification

The morphological evolution of γ′ precipitates in a nickel-based superalloy K5 was studied by zone melting directional solidification under vacuum conditions. The results show that at the lower cooling rate of 12.42 K s⁻¹, γ′ precipitates remand big cuboids. γ′ particles become smaller at the cooling rate ranges from 12.42 to 38.80 K s⁻¹. For a rather fast cooling rate of 50.16 K s⁻¹, γ′ particles retain a spherical shape. The experiments show that big cuboids will become unstable and split into several small ones at the lower cooling rate of 1.1 K s⁻¹. The mechanism of the evolution of the γ′ morphologies is also analyzed by introducing a new parameter-shape factor which classifies the total energy into several energy levels. Based on this, the effect of the cooling rate on the γ′ morphology is discussed.     

Gamma irradiation aging of NBR/CSM rubber nanocomposites

The effect of gamma-irradiation on the acrylonitrile butadiene/chlorosulphonated polyethylene rubber blends (NBR/CSM) based nanocomposites containing carbon black (CB) and silica filler (Si) were investigated by TG-DTG and ATR-FTIR techniques. The silica (with primary particle size of 22 nm) was added in content of 0, 10, 20 and 30 phr and carbon black (with primary particle size 40–48 nm) was added in content of 30 phr and rubber blend compounds were prepared. The obtained elastomeric materials were aging to different γ-irradiation doses (100, 200 and 400 kGy). The cure and mechanical properties of obtained nanocomposites were determined. Incorporating 20 phr of silica to the control NBR/CSM rubber blends containing 30 phr CB resulted 152% increase in tensile strength, 116%, in elongation at break and 142% modulus at 100% elongation, according to synergistic effect between the fillers. FTIR measurements of aged samples estimated the formation of alcohols, ethers and small amounts of lactones, anhydrides, esters and carboxylic acids after exposure to lower doses of γ-radiation (100 kGy). On the basis of the obtained spectra the formation of shorter polyene sequences and aromatic rings in aged elastomeric samples are assumed. The results show that 30 phr of carbon black (CB) and 20 phr of silica are needed for the best gamma aging resistance of NBR/CSM rubber nanocomposites. The result of radiation exposure is decrease in mechanical properties. The dose at which ultimate mechanical properties decreased was at 200 kGy. TG-DTG measurements estimated decrease in thermal stability of gamma-irradiated NBR/CSM rubber blend based nanocomposites. Silica reinforced NBR/CSM rubber blend had better radiation resistant than carbon black. Rough and heterogeneity of fracture surfaces has been observed for NBR/CSM rubber blends filled with silica. More uniform morphology of fracture surfaces according to high polymer–filler interaction and low filler–filler interaction has been observed for CB/Si filled NBR/CSM rubber blend.     

Physical and optical properties of Co2+, Ni2+ doped 20ZnO + xLi2O + (30 − x)K2O + 50B2O3 (5 ≤ x ≤ 25) glasses: Observation of mixed alkali effect

Co²⁺ and Ni²⁺ ions doped 20ZnO + xLi₂O + (30 ? x) K₂O + 50B₂O₃ (5 ≤ x ≤ 25) mol% glasses are prepared using melt quenching technique. Structural changes of the prepared glasses by addition of transition metal oxides, CoO and NiO are investigated by UV–vis–NIR, FT-IR spectroscopy and XRD. The XRD pattern indicates the amorphous nature of prepared glasses. FT-IR measurements of the all glasses revealed that the network structure of the glasses are mainly based on BO₃ and BO₄ units placed in different structural groups in which the BO₃ units being dominant. The optical absorption spectra suggest the site symmetry of Co²⁺ and Ni²⁺ ions in the glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. The optical band gap and Urbach energies exhibited the mixed alkali effect. Various physical parameters such as density, refractive index, optical dielectric constant, polaron radius, electronic polarizability and inter-ionic distance are also determined.     

Biological performance of zinc borate-incorporated particleboard: Effects of leaching on efficacy

The decay and termite resistance and effects of a robust leaching process on the efficacy of zinc borate-incorporated particleboard were examined. Particleboards (300 × 300 × 15 mm) prepared from particles of mixed wood species generated from demolished construction materials were incorporated with zinc borate at target retentions of 0%, 1%, 1.5% and 2% of the particle weight. An in-line treatment method was utilized to introduce the powdered chemical during the blending stage. ICP analysis indicated that the amount of zinc borate was not lost during manufacturing. Standard static bending tests demonstrated that there was no significant loss in mechanical properties. The decay and termite tests indicated that the efficacy of zinc borate at a higher retention was enough to suppress the biological activity, even after application of a robust leaching process.     

Effects of heat treatments on the microstructure and mechanical properties of Rene 80

Effects of heat treatments on room temperature mechanical properties and stress-rupture properties of Rene 80 have been investigated. The microstructures were analyzed by optical microscope and scanning electron microscope after each step of heat treatments. With the decrease of aging temperature, the average size of γ′ phase decreases, but the volume fraction of γ′ phase increases. The lower aging temperature suppresses the growing of the coarse γ′ particles, but facilitates the growth of the fine γ′ particles. After the optimum heat treatment, the ultimate tensile strength and yield strength are respectively higher than 1040 MPa and 950 MPa, the stress-rupture life at 871 °C/310 MPa is higher than 170 h with excellent ductility. The improved tensile strength and stress-rupture life are primarily due to the increased volume fraction of γ′ phase. The borides precipitate at grain boundaries at about 913 °C. The primary MC is found to decompose into M₆C at about 873 °C and M₂₃C₆ at 840–873 °C at grain boundaries. The precipitate of the carbides may partly contribute to the improved mechanical properties.     

Modification of UHMWPE by ion,electron and γ-ray irradiation

Due to good wear resistance Ultrahigh Molecular Weight Polyethylene (UHMWPE) is the material of choice for the load bearing surfaces of total joint implants. In order to improve its performance polymer parts are often modified by the use of ionizing radiation. Here we report on the use of electron and ion beams and γ-rays for the purpose. UHMWPE samples were irradiated with 600 keV and 1.5 MeV electron beam with doses ranging from 50 to 500 kGy and bombarded with 1–10 MeV He- and 9 MeV Cl-ions to fluences ranging from 10¹² to 5 × 10¹⁶ ions/cm². Co-bomb was used for γ-ray irradiation. Polymer radiolysis due to the irradiations was studied by means of nuclear reaction analysis (NRA) using the ¹H(¹⁵N, αγ)¹²C reaction. Hydrogen release increases with the applied dose and was correlated to the linear energy transfer (LET). Irradiated polymers oxidize rapidly when exposed to the air. Oxygen uptake profiles were determined using RBS. Correlation between radiolysis and oxidation has been revealed. Enriched in oxygen region extends to the depth at which radiation induced hydrogen release took place. Once started oxidation proceeds until the saturation concentration of about 10 at.% was attained.     

Phase transitions of bulk and nanocrystalline La1−xSrxMnO3 (x = 0.35 and 0.37) perovskite manganite materials using in situ ultrasonic studies

La_1−xSr_xMnO₃ perovskite manganite materials with two compositions, namely x = 0.35 and 0.37, both at bulk and nanoscale, were prepared by solid-state reaction and sonochemical reactor methods, respectively. The magnetic phase transition temperature of the prepared bulk and nanosamples was evaluated by in situ ultrasonic velocity and attenuation measurements. A home-made experimental setup was used for in situ measurement of ultrasonic velocities and attenuation over a wide range of temperatures (from 300 to 400 K). The observed anomalous lattice-softening behavior in the ultrasonic parameters was used to study the phase transition temperature (Curie temperature, T_C), i.e., from paramagnetic to ferromagnetic phase, both in bulk and nanostructured perovskite samples. Further, the ultrasonic measurements confirmed that sharp and broad transitions occur in bulk and nanostructured perovskite manganite materials, respectively. The Curie temperature for nanostructured perovskite samples was lower than that for the corresponding bulk perovskite sample, which was clearly identified by ultrasonic measurements.     

Influence of temperature, [Ca2+], Ca/P ratio and ultrasonic power on the crystallinity and morphology of hydroxyapatite nanoparticles prepared with a novel ultrasonic precipitation method

Nanocrystalline hydroxyapatite was prepared by a precipitation method with the aid of ultrasonic irradiation using Ca(NO₃)₂ and NH₄H₂PO₄ as source material and carbamide (NH₂CONH₂) as precipitator. The influence of Ca/P molar ratio, precipitation temperature, concentration of Ca²⁺ ([Ca²⁺]) and ultrasonic power on the crystallinity of the nanopowder were systematically investigated by XRD analysis. The size of the as-prepared particles was analyzed using TEM and XRD methods. The results revealed that the monophase hydroxyapatite could be obtained at the following technological conditions: [Ca²⁺] = 0.01–0.1 mol/L, ultrasonic power = 300 W, Ca/P (mol) = 1.2–2.5 and T = 313–353 K. In addition, the acicular and spherical particles could be prepared at different ultrasonic powers of 300 and 200 W, respectively.     

Preparation,characterization and microwave absorption properties of barium-ferrite-coated fly-ash cenospheres

Magnetic composites of barium ferrite coated on fly-ash cenospheres (BFACs) were prepared by sol–gel auto-combustion method. To promote surface activity, we modified fly-ash cenospheres (FACs) surfaces using γ-aminopropyltriethoxysilane (APS) as coupling agent and silver nitrate as activating agent before coating barium ferrite films on FACs. The morphology, composition, crystal structure, magnetic and microwave absorption properties of these composite powders were characterized by scanning electron microscope, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, and vector network analyzer. Continuous and uniform coatings of barium ferrite were found on the surfaces of the FACs. The BFACs powders-epoxy composite possesses excellent microwave absorption properties in the 2–18 GHz frequency range. The maximum microwave reflection loss reaches ?15.4 dB at 8.4 GHz with a thickness of 3.0 mm, and the widest bandwidth less than ?12 dB is 6.2 GHz with a sample thickness of 2.0 mm. The intrinsic reasons for microwave absorption were also investigated. Applications of this composite material in magnetic recording, electromagnetic wave shielding, and lightweight microwave-absorbing fields are promising.     

Cement formation by microbial poly(γ-glutamic acid) and fluoroalumino-silicate glass

The feasibility of using microbial poly(γ-glutamic acid) (γ-PGA) in cement formation was analyzed. FT–IR and elemental analyses by energy-dispersive spectroscopy (EDS), indicate that calcium and aluminum carboxylates are formed after the reaction of γ-PGA with fluoroalumino-silicate glass powder. The effect of the formulation variables, i.e., (polymer + glass) / liquid ratio (P / L), glass / polymer ratio (G / P), the average glass particle size and the molecular mass of γ-PGA, on the compressive strength is discussed. A maximum compressive strength value of 130 MPa was obtained when cement samples were aged for 7 days. The compressive strength was achieved with a P / L ratio of 2.5 g/ml, a G / P ratio of 2.5 : 1, an average glass particle size of 1 μm and a γ-PGA molecular mass (M ¯w) of 115 000.     

Texture and magnetic properties of electrodeposited FePd films

FePd films were deposited on brass substrates through electrodeposition using an alkaline electrolyte, which were annealed at 500, 600, and 700 °C for 1 h to form the ordered γ₁-FePd fct phase. After annealing, the γ₁-FePd fct phase is observed at 500, 600 and 700 °C. FePd films show the normal direction close to <101>, <111> and <421> directions after annealing 500, 600 and 700 °C, respectively. After annealing 500, 600 and 700 °C the average area grain size is 0.28 μm, 0.37 μm and 1.22 μm, respectively. The maximum coercivity H_c of 309 Oe observed at 500 °C can be explained with both effects of the <001> easy axis and the small grain size.     

Development of biomimetic coatings on Sm oxide doped ELB (Eu–Li–borate) glasses

The in-vitro biomineralization of Eu/Li–borate glasses containing Sm₂O₃ was investigated by immersion in simulated body fluid (SBF) up to 72 h. Back scattering scanning electron microscope supplemented with EDX was used to follow the development of the phosphatic layer post 72 h SBF immersion. Biochemical analyses of calcium and inorganic phosphorus (Ca²⁺ and iP) ions were conducted using relevant biochemical kits and spectrophotometer. Spectra of TF-X-ray analyses and Fourier transform infrared were obtained for the samples post 72 h immersion and compared to the host one.The role of Sm₂O₃ in the biomineralization and crystallinity of the (ELB) borate glasses is proved by the developed rounded nano particles and the presence of elemental Eu and Sm in the formed layer beside Ca and P as presented by EDX. The continuous reduced values of ionic iP accompanying the adsorption and release of Ca ions in SBF with time assured the biolayer formation. The formed phosphatic layer presented shifted XRD peaks due to ionic incorporations especially of Sm³⁺. FT-IR proved the selectivity of BO₃ group for phosphatic deposition. Deconvolution of ν₄ and ν₃ regions, for carbonates and phosphates, respectively, proved the enhanced peak areas with increased Sm³⁺ content.     

129I targets for studies of nuclear waste transmutation

Nuclear incineration of long-lived fission products and minor actinides is being investigated as an alternative means of reactor waste disposal. ¹²⁹I is of particular interest because of its long half-life and high mobility in the environment. Lead iodide targets of ¹²⁹I for neutron capture cross-section measurements were prepared from 210 l fuel reprocessing waste solution containing 1.3 g l⁻¹ iodine and other fission products. The iodine was separated by oxidation to I₂ and extraction into chloroform, reduction to iodide by sodium sulphite and re-extraction into an aqueous phase. Iodide was precipitated using lead nitrate and dried. The chemistry was carried out batch-wise using 400 ml starting solution each time and recycling the chloroform. An extraction efficiency of about 90%, determined by γ-ray spectrometry, was achieved.