Influence of heat treatment on the structure and properties of oxide magnets produced by “dry” pressing

Conclusions The preliminary action of a high-gradient electromagnetic field on dry ferrite powder did not change the. optimum sintering temperature of anisotropic magnets and made it possible to significantly reduce the heat treatment time as the result of an increase in heating rate.The resonant texturing method makes it possible to form a fine-grained uniform structure of barium ferrite magnets. Their residual induction increased by 16% and their coercive force by 47% in comparison with specimens produced by wet pressing.Translated from Poroshkovaya Metallurgiya, No. 1(325), pp. 26–29, January, 1990.     

Hydrothermal synthesis, crystal structure and magnetic properties of a Dy~Ⅲ-Fe~Ⅲ heteronuclear complex

A new 3d-4f heteronuclear complex [Fe(phen)3]2[FeDy(H2O)(tiron)3]·6H2O (1,Na2H2tiron=disodium 4,5-dihydro-xybenzene-1,3disulfonate) was synthesized by the hydrothermal reaction. The complex crystallized in the cubic system, space group P213 with the cell parameters:a=2.18786(14)nm, V=10.4727(12)nm3 , Z=4, F(000)=4720, R1=0.0493, wR2 =0.1165, S=1.05. In each [FeDy(H2O)(tiron)3]6-unit, it was revealed that the Fe3+ ion was in a FeO6 distorted trigonal anti-prism coordination polyhedron completed by six phenolate O atoms from three tiron 4- ligands, while Dy3+ in a DyO7 distorted monocapped trigonal anti-prism coordination polyhedron completed by three phenolate μ2-O atoms and three O atoms from sulfonate groups of three ligands and one O atom from water. The magnetic properties of the complex was determined in the range of 2-300K, indicating the antiferromagnetic interaction between the central DyIII-FeIII ions.     

Synthesis,structure and radiative and nonradiative properties of a new Dy3+ complex with sulfonylamidophosphate ligand

In recent years there has been growing interest in lanthanide-based multifunctional materials that exhibit interesting photophysical properties. This work presents spectroscopic and crystallographic characterization of a new dysprosium complex with sulfonylamidophosphate ligand. The crystal structure of [NaDy(SP)₄]₂·i-PrOH was determined and refined. It turns out that the Dy(III) complex is not isostructural with earlier reported compounds and crystallizes in the monoclinic system (space group P2₁). Two crystallographically independent dysprosium atoms are in eight-fold coordination, with a triangular dodecahedron geometry. Absorption, emission (77 and 300 K) and excitation spectra as well as fluorescence decay time measurements allowed optical characterization of obtained complex. Efficient energy transfer from SP^– ligand to Dy³⁺ ion has been demonstrated. The Judd-Ofelt theory was applied to predict fundamental fluorescence properties of Dy³⁺ ion in the title chelate. The Judd-Ofelt intensity parameters were used to determine the emission transition probabilities, fluorescence branching ratios and radiative lifetime of the emitting ⁴F_9/2 level. The obtained results indicate that the investigated chelate can be a potential candidate for OLEDs emitting yellow light.     

Synthesis and structure of a praseodymium (Ⅲ) complex with carboxylate ligand:A thermal and spectroscopic study

One Pr(Ⅲ) lanthanide ion complex was initially synthesized and characterized by TGA-DSC in air atmosphere, as well as characterized by CHN elemental analysis, defining the stoichiometric ratio as Pr(DMBz)_3. The gaseous products evolved during the thermal decomposition were also monitored in N_2 atmosphere employing TGA/FT-IR system. A crystal structure is obtained by state-of-the-art powder X-rays diffraction methods measured in conventional laboratory equipment and refined by the Rietveld method, which defined it as a monoclinic system of the space group P2_1/C with a polymeric crystal structure, [Pr(DMB_Z)_3]_n. FT-IR theoretical spectrum and time-dependent density functional theory(TD-DFT) were calculated from TGA-DSC and crystalline system data. The experimental and theoretical FT-IR spectra present a high correlation degree when the main stretching bands are compared, while the energy transfer(HOMO — LUMO) in their neighborhoods suggests the main contributions of the light-emitting states.     

Characterization,crystal structure and luminescence properties of a new europium（Ⅲ） complex with macrocyclic ligand derived from 2,6-diformyl-4-methylphenol and diethylenetriamine

The title compound （13,27-dimethyl-3,6,9,17,20,23-hexaazatricyclo-[23.3.1.1^11,15]-triaconta-1 （29）,2,9,11,13,15（30）, 16,23,25,27- decaene-29,30-diol-N^3, N^6, N^9, O^29, O^30）-bis （nitrato-O,O＇）-europium （Ⅲ） nitrate hydrate （[EuL（NO3）2]（NO3）·H2O, L denotes the macrocyclic ligand） was prepared and characterized by elemental analysis, infrared spectra, and electrospray mass spectra. Its crystal and molecular structure was determined by X-ray diffraction. The crystal crystallized in the monoclinic system, space group C2/c with a=2.3757 （4） nm, b=1.4302（3） nm, c=1.9584（3） nm, β=91.654（5）°, M=818.60, V=6.651（2） nm^3, Z=8, D=1.635 g/cm, F（000）=3312, R=0.0542, wR=0.1045. The central ion Eu^3＋ was nine-coordinated in the coordinaton geometry of a distorted tricapped trigonal prism. The macrocycle was coordinated through two oxygen and three nitrogen atoms. Two nitrate are chelate in the opposite positions of the macrocycle, the third nitrate being ionic. At room temperature, excitation of the title complex gave rise to the characteristic emissions of the Eu^3＋ ion.     

Characterization, crystal structure and luminescence properties of a new europium(Ⅲ) complex with macrocyclic ligand derived from 2,6-diformyl-4-methylphenol and diethylenetriamine

The title compound (13,27-dimethyl-3,6,9,17,20,23-hexaazatricyclo-[23.3.1.111,15]-triaconta-1(29),2,9,11,13,15(30),16,23,25,27-decaene-29,30-diol-N3, N6, N9, O29, O30)-bis (nitrato-O,O')-europium (Ⅲ) nitrate hydrate ([EuL(NO3)2(NO3).H2O, L denotes the macrocyc-lic ligand) was prepared and characterized by elemental analysis, infrared spectra, and electrospray mass spectra. Its crystal and molecular structure was determined by X-ray diffraction. The crystal crystallized in the monoclinic system, space group C2/c with a=2.3757 (4) nm, b=1.4302(3) nm, c=1.9584(3) nm, β=91.654(5)°, M=S18.60, V=6.651(2) nm3, Z=8,D=1.635 g/cm, F(000)=3312, R=0.0542, wR=0.1045. The central ion Eu3+ was nine-coordinated in the coordinaton geometry of a distorted tricapped trigonal prism. The macrocycle was coordi-nated through two oxygen and three nitrogen atoms. Two nitrate are chelate in the opposite positions of the macrocycle, the third nitrate be-ing ionic. At room temperature, excitation of the title complex gave rise to the characteristic emissions of the Eu3+ ion.     

Synthesis, structure and photoluminescent properties of a new Eu(Ⅲ) complex with 5-bromoisophthalic acid

The self-assembly of 5-bromoisophthalic acid (H2BIPA) with Eu(NO3)3·6H2O under the hydrothermal conditions gave a 3D coordination polymer, Eu2(BIPA)3(CH3CH2OH) (1), which was characterized by elemental analysis, IR and single-crystal X-ray diffraction. Complex 1 displayed an unusual three-dimensional network of a rare (4,6)-connected (48.66.8)2(44.62)2(42.84) topology, which was different from Eu2(BDC)3(H2O)2 (BDC=isophthalate), because the -Br substituent of the isophthalate resulted in the different electronic effects and the steric hindrance to change the coordination modes of carboxylate groups in the assembled process. Moreover, the luminescent properties of 1 were also investigated in the solid state.     

Influence of treatment of melts by electromagnetic acoustic fields on the structure and properties of alloys of the Al–Si system

The influence of treating the melts by electromagnetic acoustic fields on the structure and properties of Al–12% Si and Al–20% Si binary alloys is investigated. In the course of experiments, the frequency of the electromagnetic field induced in the loop antenna varies as 500, 1000, and 2000 kHz. The melts are treated after their degassing and refining. It is established that this treatment method of the melts leads to a reduction of the total preparation time of alloy by 12% on average. The short-term treatment of the melts by electromagnetic acoustic fields promotes the refinement of the main phase components of alloys and an increase in their mechanical properties. When treating the Al–12% Si eutectic alloy with a frequency of 500 kHz, α-Al dendrites are refined from 30 to 22 μm and eutectic Si crystals are refined from 13 to 10 μm. When treating the Al–20%Si eutectic alloy with a frequency of 1000 kHz, eutectic Si crystals diminished from 8 to 5 μm and these of primary Si diminished from 90 to 62 μm. The ultimate tensile strength of the Al–12%Si eutectic alloy increases 13% under the mentioned treatment modes, while the relative elongation increases 17%; as for the Al–20% Si eutectic alloy, the same characteristics increases 9 and 65%, respectively. Based on these investigations, it is concluded that the selection of the treatment parameters of the melts of the Al–Si system by electromagnetic acoustic fields should be determined by the silicon content in the alloy. It is necessary to treat the melt by waves with a higher oscillation frequency with an increase in the silicon concentration. This treatment method makes it possible to form the modified fine-crystalline structure of alloy and, consequently, improves their mechanical properties. It can be successfully used when fabricating fine-crystalline foundry alloys and in the production of alloys of the Al–Si system. To determine the optimal treatment parameters depending on the structure of the initial charge and alloy nature, additional investigations are required.     

Influence of the solidification temperature–time parameters on the structure and mechanical properties of nickel aluminide–based alloys

The influence of the technological parameters of directional solidification, namely, the solidification rate and the temperature gradient, on the microstructure, the structure–phase parameters, and the mechanical properties of nickel aluminide–based intermetallic alloys is considered.     

Influence of hot isostatic pressing on the structure and properties of an innovative low-alloy high-strength aluminum cast alloy based on the Al–Zn–Mg–Cu–Ni–Fe system

Hot isostatic pressing (HIP) is applied for treatment of castings of innovative low-ally high-strength aluminum alloy, nikalin ATs6N0.5Zh based on the Al–Zn–Mg–Cu–Ni–Fe system. The influence of HIP on the structure and properties of castings is studied by means of three regimes of barometric treatment with different temperatures of isometric holding: t ₁ = 505 ± 2°C, p ₁ = 100 MPa, τ₁ = 3 h (HIP1); t ₂ = 525 ± 2°C, p ₂ = 100 MPa, τ₂ = 3 h (HIP2); and t ₃ = 545 ± 2°C, p ₃ = 100 MPa, τ₃ = 3 h (HIP3). It is established that high-temperature HIP leads to actually complete elimination of porosity and additional improvement of the morphology of second phases. Improved structure after HIP provides improvement properties, especially of plasticity. In particular, after heat treatment according of regime HIP2 + T4 (T4 is natural aging), the alloy plasticity is improved by about two times in comparison with the initial state (from ~6 to 12%). While applying regime HIP3 + T6 (T6 is artificial aging for reaching the maximum strength), the plasticity has improved by more than three times in comparison with the initial state, as after treatment according to regimes HIP1 + T6 and HIP2 + T6 (from ~1.2 to ~5.0%), which are characterized by a lower HIP temperature.     

Influence of crystallization conditions on the structure and modifying ability of Al–Sc alloys

The influence of the modes of thermal-and-temporal treatment and cooling rate of metallic alloys on crystallization regularities of Al–Sc alloys and their structure, properties, and modifying ability are established. Castings of Al–Sc alloy, which were prepared by the electrolysis of salt melts KF–NaF–AlF₃–Sc₂O₃ at 820–850°C, are used as the initial charge for casting. It is established that, by varying the magnitude of melt overheating and casting temperature, it is possible to vary the crystal shape, amount, and size in wide limits. The modifying action of cast and rapidly quenched master alloys, as well as the master alloy produced by electrolysis, is tested for Al–4.5% Cu alloy. The largest effect of milling the structure of the Al–4.5% Cu–0.4% Sc alloy is attained when using the rapidly quenched master alloy.     

Influence of titanium microalloying on the properties of low-alloy Cr–Mo–V steel

The influence of titanium, which readily forms nitrides, on the structure and the long- and short-term mechanical properties of Cr–Mo–V steel is investigated. Increase in the Ti content to 0.075% increases the thermal stability of the steel. With increase in Ti content to 0.13%, the thermal stability of the steel declines sharply, on account of structural changes.     

Fluorescence enhancement of Tb（Ⅲ） complex with a new β-diketone ligand by 1,10-phenanthroline

A novel β-diketone, 1-(3,4,5-trisbenzyloxy)benzoyl-5-benzoyl acetylacetone (TBAA), and its corresponding binary Tb(III) complex Tb(TBAA)₃·2H₂O and ternary complex Tb(TBAA)₃Phen with 1,10-phenanthroline (Phen) were prepared. The ligand was characterized based on elemental analysis, FT-IR, and ¹H NMR. The complexes were characterized with elemental analysis, FT-IR and thermogravimetry and derivative thermogravimetry (TG-DTG). Photoluminescence measurements indicated that the energy absorbed by the organic ligand was efficiently transferred to the central Tb³⁺ ions, and the complex showed intense and characteristic emissions due to the ⁵D₄→ ⁷F_J transitions of the central Tb³⁺ ions. Both complexes showed longer fluorescence lifetimes. After the introduction of the second ligand Phen group, the relative emission intensities and fluorescence lifetimes of the ternary complex Tb(TBAA)₃Phen enhanced more obviously than that of the binary complex Tb(TBAA)₃·2H₂O. This indicated that the presence of the ligand TBAA and the second ligand Phen could sensitize fluorescence intensities of Tb(III) ions, and the introduction of Phen group resulted in the enhancement of the fluorescence properties of the Tb(III) ternary rare earth complex.     

Fluorescence enhancement of Tb(Ⅲ) complex with a new β-diketone ligand by 1,10-phenanthroline

A novel β-diketone, 1-(3,4,5-trisbenzyloxy)benzoyl-5-benzoyl acetylacetone (TBAA), and its corresponding binary Tb(Ⅲ) complex Tb(TBAA)3·2H2O and ternary complex Tb(TBAA)3Phen with 1,10-phenanthroline (Phen) were prepared. The ligand was characterized based on elemental analysis, FT-IR, and 1H NMR. The complexes were characterized with elemental analysis, FT-IR and thermogravimetry and derivative thermogravimetry (TG-DTG). Photoluminescence measurements indicated that the energy absorbed by the organic ligan...     

Study of K~+ doping on structure and properties of γ-Ce_2S_3

In this study,K~+-doped γ-Ce_2 S_3 was successfully prepared via a gas-solid reaction method using CeO_2,K_2 CO_3,and CS_2 as raw materials.The effects of the suitable sulfide system and different molar ratios of K to Ce(n_(K/Ce)=0-0.30) on the phase composition,crystal structure,chromaticity and thermal stability ofγ-Ce_2 S_3 were systematically investigated.Pure γ-Ce_2 S_3 was obtained by calcining the doped samples at840℃ for 150 min.After calcination at the same temperature the undoped K+samples exhibit a pure α-phase.Samples with a K/Ce molar ratio(n_(K/Ce)) of 0.10-0.25 comprise only the γ-phase;and when n_(K/Ce) exceeds 0.25,a new heterogeneous phase,KCeS_2,emerges.For values of n_(K/Ce) in the range of0-0.25,the γ-Ce_2 S_3 lattice parameters gradually increases with increasing K~+ content.When n_(K/Ce)exceedes 0.25,the lattice parameters remains unchanged.As n_(K/Ce) increased,the synthesized color gradually changes from red to orange—red and finally,to yellow.The redness value a~* reaches the maximum(L~*=33.86,a~*=36.68,b~*=38.15) when n_(K/Ce)=0.10,The n_(K/Ce)=0.10 composition continues to exhibit the y-phase after heat treatment at 420℃ for 10 min in air.The K+doping fills the internal vacancies of γ-Ce_2 S_3 and formed a solid solution,which is beneficial for the stability of its lattice,thus improving the thermal stability of γ-Ce_2 S_3(from 350 to 420℃).     

Influence of thermal storage on microstructure and properties of Sn–9Zn–xIn alloys

Abstract

This study investigated the solidification behaviour and microstructural properties of Sn–9Zn–xIn alloys cooled under various crucible environments (i.e. gypsum or graphite moulds). Sn–9Zn–xIn solder specimens were prepared with the addition of In ranging from 0 to 0·5 wt-%. The specimens were melted at 200°C, poured into gypsum or graphite moulds and then allowed to cool in air. The microstructure, chemical composition and hardness properties of various specimens were then systematically examined. It was found that the microstructure (and hence the mechanical properties) of the solder samples can be controlled by manipulating the variables of the solidification process, such as cooling rate, element diffusion rate, solubility among elements and the crucible environment.

Cette étude a examiné le comportement de solidification et les propriétés de la microstructure des alliages Sn–9Zn–xIn refroidis dans divers creusets (c’est-à-dire des moules en plâtre ou en graphite). On a préparé des spécimens de soudure de Sn–9Zn–xIn avec des additions d’In variant de 0 à 0·5% en poids. Les spécimens étaient fondus à 200°C, coulés dans des moules en plâtre ou en graphite, et ensuite refroidis à l’air. Ensuite, on a systématiquement examiné la microstructure, la composition chimique et la dureté des divers spécimens. On a trouvé que l’on pouvait contrôler la microstructure (et ainsi les propriétés mécaniques) des échantillons de soudure en manipulant les variables du procédé de solidification, comme la vitesse de refroidissement, la vitesse de diffusion de l’élément et la solubilité entre les éléments ainsi que la nature du creuset.     

Influence of In3＋ ions concentration on spectroscopic properties of Ho：LiNbO3 crystals

In:Ho:LiNbO3 crystals doped with various concentrations of In3+(0, 1 mol.%, 3 mol.%, 5 mol.%), fixed concentrations of Ho3+ (1 mol.%) were grown by Czochralski method. The X-ray powder diffraction, infrared and UV-visible absorption spectra were measured and modified. Judd-Ofelt approach was employed to study the effect of In doping on spectroscopic properties of Ho:LiNbO3 crystals. In concentrations in crystals were analyzed by an inductively coupled plasma optical emission spectrometry (ICP-OE/MS). For In (3 mol.%):Ho (1 mol.%):LiNbO3 crystal, the obtained intensity parameters were: Ω2=9.6563, Ω4=4.2195, Ω6=14.1526. The results showed that the Ω2 and Ω6 parameters increased with the increase of In3+ concentration. When the In doping concentration was up to 5 mol.%, Ω2 and Ω6 suddenly decreased. In2O3 incorporation had a strong effect on the radiative lifetime, but had less influence on fluorescence branching ratios. The effective distribution coefficient of In3+ in In:Ho:LiNbO3 crystals was less than 1 and increased with increasing concentration of In3+ in the melt.     

Influence of urea on microstructure and optical properties of YPO4：Eu^3＋ phosphors

YPO4:Eu 3+ phosphors were synthesized by solution coprecipitation method assisted by urea in the precursor reaction solution. X-ray diffraction spectral analysis showed that the samples synthesized with urea had smaller particle size and lower crystallinity than those samples synthesized without urea.Moreover,the calculated strain result indicated that the Eu 3+ site in the former exhibited a lower crystal field symmetry than that in the latter.Hence,the influence of crystal field symmetry dominated luminescence efficiency rather than crystallinity because the luminescence intensity observed in Eu0.05Y0.95PO4 synthesized with 1.0 g urea was six-fold higher than that of the as-synthesized sample.With increased concentration of Eu 3+ ion,the luminescence intensity initially increased,and then subsequently decreased as the concentration of Eu 3+ ion exceeded 12 mol.%due to concentration quenching.The optimal condition for YPO4:Eu 3+ phosphor was Eu0.12Y0.88PO4 with 1.0 g urea added in the precursor.The luminescence intensity of the optimal condition was again enhanced 1.6-fold relative to that of Eu0.05Y0.95PO4 synthesized with 1.0 g-urea.     

Influence of concentration and sintering temperature on luminescence properties of Eu^3＋：SnO2 nanocrystallites

The nanopowders of SnO2 doped with different Eu3+ concentrations were synthesized using the modified Pechini method. The Eu3+ concentrations were high above solubility limit. The average size of crystallites was controlled by the sintering temperatures. The structure and the morphology of obtained powders were examined using the XRD (X-ray diffraction) and TEM (transmission electron microscopy) analyses. The Eu2Sn2O7 phase separation was observed at relatively high concentration of Eu3+ ions. The ZnS:Ag micropowders were mixed with the Eu3+:SnO2 powders and their normalized emission was used to measure a relative efficiency of Eu3+:SnO2. The photoluminescence spectra of mixed powders were measured in function of Eu3+ concentration and average size of nanocrystallites. The reference peak method was used for comparison of intensities of the samples and selection of optimal one. The influence of the average grain size and Eu3+ concen-tration on the phosphor’s efficiency was discussed. The presented results confirmed the rightness of synthesis of the Eu3+:SnO2 in form of nanocrystalites with relatively high Eu3+ concentration.     

Influence of ingot homogenization on the impact properties of 4X5MΦC steel strip

The homogenization of 4X5MΦC (1.2343/H11) steel ingots and cooling of the rolled bar are corrected so as to obtain a transverse work of impact of ?200 J in the vacuum-treated product with constant forging. Longer holding in homogenization reduces the liquation in the metal, while intermediate air cooling of the metal prior to slow pit cooling prevents the formation of a carbide network in the microstructure. Over the whole cross section of the final metal bar (diameter 165–190 mm), the work of impact meets Bohler specifications and exceeds 200 J.