Generation In MgO Research Articles

Eco-friendly lactose/tannin-based binder in MgO–C refractories produced from MgO–C recyclate

This study deals with the design and development of a new generation of MgO–C refractory material implementing spent MgO–C recyclate as a partial replacement of fresh raw materials, and a non-hazardous environment-friendly lactose- and tannin-based binder system. Throughout the experimental campaign the used MgO–C recyclate, which was received in three size fractions, was analysed, and building on the obtained results, multiple batches of various compositions of next-generation MgO–C bulks were prepared. These bulks varied in the ratio between the individual size fractions of the MgO–C recyclate, the ratio between the individual binder components and the amount of water used during the preparation of the raw material batches. The bulk samples were prepared in the form of cylinders through uniaxial pressing, cured and coked, and studied in terms of their cold crushing strength, microstructural parameters, thermal behaviour, residual carbon content, and microstructure. The proposed next generation of MgO–C composites represents a potential eco-friendly alternative to MgO–C refractories prepared from traditional raw materials while utilizing waste material which would otherwise end up landfilled.

Demonstration of nonperturbative and perturbative third-harmonic generation in MgO by altering the electronic structure

The surge of interest in nonperturbative high-harmonic generation in solids has been driven by the appeal of compact solid-state extreme ultraviolet sources and the prospect of untangling the material properties through high-harmonic generation response to strong fields. The traditional assumption is that the brighter, lower-order harmonics are purely perturbative in nature. However, the border between the perturbative and nonperturbative regimes often remains unclear. Here, we show that third-harmonic generation (THG) using 800-nm, 40-fs pulses displays a nonperturbative response in a wide-band-gap insulator MgO. Furthermore, we show that with the introduction of dopants, the nonperturbative THG reverts to the perturbative behavior. We attribute this to the blocking of intraband oscillations and the increased linear absorption pathways introduced by the dopant energy levels.

Optimal generation of delay-controlled few-cycle pulses for high harmonic generation in solids

Delay-controlled two-color, few-cycle pulses are powerful tools for ultrafast nonlinear optics. In this Letter, 35-fs, 800 nm pulses were injected into a noble-gas-filled hollow-core fiber to obtain over-octave spectra (450–1000 nm) and were divided into two parts for dispersion management by a Mach–Zehnder–type interferometer. Two few-cycle pulses with pulse widths of 9.3 and 4.5 fs were generated in the long-wavelength side and the short-wavelength side, respectively. The temporal profiles were measured as the function of the different delay between the two pulses. The shortest 3.6 fs, 0.75 mJ near-single-cycle pulses were synthesized at an optimal delay. The delay-controlled high-harmonic generation in MgO was experimentally demonstrated leading to twofold enhancement of high-order harmonic (HH) yields at 10.3 eV and the extension of HH frequency under time-delay modulation. This method provides an extensive way for manipulating delay-controlled multi-color pulses, which can be used for controlling ionization dynamics in extreme nonlinear optics. We believe that it will be a powerful tool for ultrafast science.

Corrosion Mechanism of MgO–CMA–C Ladle Brick with High Service Life

Carbon‐bonded magnesia and magnesia alumina carbon (MAC) bricks have been used in the sidewalls and bottom of steel ladles for over 20 years. Due to the increasing ratio of scrap to steel, higher working temperature, and prolonged refining time, steel producers seek refractories with enhanced service lifetime. Therefore, a new generation of MgO–C bricks with addition of calcium magnesium aluminate (CMA) aggregates is tested in a ladle lining of an integrated steel shop for 138 cycles. The corrosion mechanisms are evaluated by digital light microscopy and with scanning electron microscopy (SEM) equipped with energy‐dispersive X‐ray spectroscopy (EDS). The industrial trial tests reveal the formation of a slag coating at the hot face, leading to a much slower corrosion rate compared with a common MgO–C lining. The dissolution of the CMA aggregates and MgO grains results in a significant change of the slag chemistry and viscosity causing a reduced infiltration and corrosion behavior of the ladle slag. Also, the ability of bonding iron plays a major role, leading to the formation of brownmillerite phase in the protective slag coating on top of the bricks.

Effect of interactions between Fe–Al alloy and MgO-based refractory on the generation of MgO·Al2O3 spinel

ABSTRACTIn the present study, interactions between Fe-2.1 wt-%Al and Fe-5.1 wt-%Al alloys and different tundish refractories, and a spinel generation in the Fe–Al alloys were investigated in laboratory experiments at 1550°C in an alumina crucible using a high-frequency induction furnace. The results indicated that the formation of a spinel layer at the interface was owing to both the oxidation–reduction reactions and the phase transformation at the interface according to initial phases in refractories. The thickness of the interface layer increased with increasing the content of the [Al] in Fe–Al alloys, the SiO2 content in the refractory and the immersion time, however, the [Al] content was a dominant factor. Both experimental results and thermodynamic calculations concluded that MgO·Al2O3 spinel inclusions along with a small amount of CaO–MgO–Al2O3 were the main inclusions in Fe–Al alloys. MgO·Al2O3 inclusions were mainly formed at the interface by alloy/refractory interactions and then mechanically transferred into molten alloys.

Acoustically tunable photonic band gap generation in MgO doped Lithium Niobate micro-dimension plate

Refractive index contrast generation in MgO doped LiNbO3 plate via Lamb wave perturbation for induction of acoustically tunable photonic band gap is theoretically studied. Fundamental symmetric Lamb mode is excited in micro dimension thin plate structure to produce symmetric disturbance for periodic contraction and rarefaction along the length of plate. Effect of contraction and rarefaction on production of refractive index contrast is studied using photo–elastic effect. The generated quasi static low–high optical index region in plate modifies electromagnetic wave propagation and provides photonic band gaps, which are investigated using Bloch's theorem and transfer matrix method. The induced photonic band gap shows great dependency on optical contrast and unit cell dimension created by acoustic frequencies. These acoustically tunable photonic band gaps have rewarding applications in acousto optical devices, laser and sophisticated sensing.

Blue and Orange Two-Color CW Laser Based on Single-Pass Second-Harmonic and Sum-Frequency Generation in MgO:PPLN

We demonstrate a compact blue and orange-two color continuous wave laser source emitting at 487 nm and from 597.4 to 600.3 nm, respectively. The temperature tunable coherent orange radiation is achieved by frequency mixing 974 nm laser diode (LD) and a C-band amplified spontaneous emission laser source while the temperature insensitive blue radiation is generated by second-order quasi-phase-matching frequency doubling of 974 nm LD. We implement the simultaneous nonlinear processes in a single magnesium oxide doped periodically poled lithium niobate bulk crystal without the need of an aperiodic design.

High power continuous wave second harmonic generation in a phase matching insensitive MgO doped LiNbO_3 waveguide

This paper reports an efficient method of using a chirped grating to reduce the phase-matching sensitivity and increase the output power of continuous wave second harmonic generation in a MgO doped LiNbO3 waveguide. It was found that using a chirped grating with decreasing periods from 6.96 μm to 6.95 μm significantly improved the phase mismatch tolerance and increased the second harmonic generation output power from 0.64 W (using uniform grating) to 1.13 W. This design was shown to lead to a phase matching insensitive waveguide. This indicates that there is a possibility of obtaining higher output power with the MgO doped LiNbO3 waveguide.

Robust and broadband frequency conversion in composite crystals with tailored segment widths and χ(2) nonlinearities of alternating signs.

We propose an efficient, robust, and broadband nonlinear optical frequency conversion technique, which uses segmented crystals constructed in analogy with the composite pulses in nuclear magnetic resonance and quantum optics. The composite crystals are made of several macroscopic segments of nonlinear susceptibilities of opposite signs and specific thicknesses, which are determined from the condition to maximize the conversion efficiency with respect to variations in the experimental parameters. These crystals deliver broadband operation for significantly lower pump intensities than single bulk crystals. We demonstrate this technique by numerical simulation of sum-frequency generation in MgO:LiNbO3 crystal.

Multiple-wavelength quasi-phase-matching for efficient idler generation in MgO:LiNbO3 based nanosecond optical parametric oscillator

We present numerical results for optimization of the overall idler conversion efficiency of a nanosecond optical parametric oscillator (OPO), wherein the signal generated in the OPO process is also used as the pump for a difference frequency generation (DFG) process in a quasi-periodic MgO:LiNbO(3) crystal. The phase-matching conditions are considered such that the generated idler frequencies in both the processes (i.e., OPO and DFG) coincide. Optimization for the idler generation has been performed with respect to the different parameters, such as input pump power, pump pulse duration, and the output coupler reflectivity, for quasi-phase-matched interaction in MgO:LiNbO(3). Wavelength of the pump, signal, and idler waves considered in the optimization are 1.064 μm, 1.456 μm, and 3.95 μm, respectively. A maximum overall idler generation efficiency of ≈33% could be obtained in the simultaneous OPO+DFG process for a pump pulse duration of 72 ns and output coupler reflectivity (R(s)) of 90%, whereas for the stand-alone OPO process, the maximum idler generation efficiency was found to be ≈15%. The optimization has been illustrated for an average pump power of 8 W at a pulse repetition frequency (PRF) of 10 kHz. This approach of simultaneous OPO+DFG process can be employed to significantly enhance the idler generation efficiency of nanosecond OPOs.

Broadband quasi-phase-matched second-harmonic generation in MgO:LiNbO3 waveguide

The quasi-phase-matched (QPM) condition of broadband second harmonic generation (SHG) in Ti-diffused MgO:LiNbO3 waveguide is theoretically simulated. The results show that the center wavelength of broadband SHG dependent on the waveguide width is around 1550 nm and the bandwidth is 50 nm.

Thermally induced dephasing of high power second harmonic generation in MgO:LiNbO3 waveguides

High power second harmonic generation (SHG) in MgO-doped LiNbO3 waveguides is investigated using a three-dimensional (3D) coupled thermo-optical model. Simulations performed for a 1 111.6-nm fundamental laser show the influence of the absorptions and the thermally induced dephasing on the conversion efficiencies of the different waveguides. The onset of the thermally induced dephasing effect for each waveguide is also indicated. As a result of high light intensity in the waveguide, nonlinear absorptions are identified as the possible main factors in efficiency losses in specific cases.

Effect of Ambient Atmosphere on Defect Generation in MgO during Mechanical Activation

AbstractAs previous studies have shown (Spitsyn et al.; Henderson, Wertz; Steinike et al. 1981, 1984; Hennig et al.), mechanical activation of MgO in air results in the generation of anion and cation vacancies in the lattice, thus causing heterogeneous lattice distortions. These anion and cation vacancies are identified as F+‐ and V−‐centres, respectively, by EPR spectroscopy. F+‐centres are anion vacancies filled with electrons, V−‐centres are cation vacancies filled with holes. The electrons and defect electrons filling the vacancies are generated essentially during γ‐irradiation. Since the effect of the ambient atmosphere on the generation of electronic and structural defects upon mechanical activation is known (Bystrikov et al.), the studies of mechanical MgO activation in air were extended to the generation of above defects in an argon atmosphere. The results are compared with those obtained in air.