A 1/17th water physical model of a 200-ton steel ladle furnace with a single gas injection was used to simulate bath heating using a single burner to mimic the heat flux due to electric arcs in the ...industrial steel ladle. Two phases were considered, using water to simulate the molten steel and air to simulate the argon injection at a flow rate of 1.54 NL min
−1
. The planar Laser-Induced Fluorescence (PLIF) technique was for the first time experimentally implemented to measure temperature fields in a longitudinal plane of the gas-stirred ladle model. PLIF employs a laser source of 532-nm wavelength to light water seeded with rhodamine B, which emits fluorescence depending on its temperature, after a complex calibration is made. Next, the fluorescence is captured by a camera with a 550-nm wavelength filter. The PLIF measurements were validated by local thermocouple measurements at five different locations in the measurement plane. Temperature fields measured by PLIF are in good agreement with those obtained locally by thermocouples, so the PLIF technique can be used to measure temperature fields with the advantage of getting a complete temperature contour field, in contrast to point values of temperatures with thermocouples. Experiments were carried out to study the thermal mixing for two common tuyere positions,
i.e.,
axisymmetric and eccentric (mid-radius) positions. Results on the injection mode show that axisymmetric gas injection is a more efficient heat transfer configuration between the burner and the liquid phase than is the symmetric injection mode for the particular heating configuration studied in this work.
The effect of isothermal pre-oxidation treatments on the β-(Ni,Pt)Al + IDZ + René N5 system degradation is reported here. The pre-oxidation treatments were carried out from 900 °C (mostly θ-Al2O3 ...growing conditions) to 1200 °C (mainly α-Al2O3 growing conditions) for 5 h, under an Ar-stream with pO2 = 1 × 10−5 atm. The correlation between the structural, microstructural, and chemical properties of the β-(Ni,Pt)Al BC show that pre-oxidation parameters have an important effect on the multi-elemental counter diffusion phenomena along the BC. Heat treatments performed above 1100 °C resulted in loss of stability of the BC, partially disordering of the β phase promoting the β → β + L10 and β → β + L12 transformations. A significant BC + IDZ thickness increase of 55% at 1200 °C was observed with respect to the as-received specimen resulting in a severe BC degradation. Multi-elemental inward diffusion is the main mechanism responsible for BC degradation at high temperatures.
•BC microstructural degradation is highly dependent on the pre-oxidation temperature.•An unbalanced diffusivity due to TGO formation promotes an excessively TGO/BC-interfacial voids and a BC Pt-enrichment.•The two-sublattice model adequately describes the elemental distribution within the β phase.•A partially disordering and phase transformations β → β + L10 and β → β + L12 take place for pre-oxidation above 1100 °C.
This work presents silicon-substituted hydroxyapatite preparation through planetary ball milling using biogenic hydroxyapatite and different wt% of S53P4 bioactive glass (5, 10, 15, and 20 wt%) ...sources for the first time. The prepared mixtures showed a BHAp lattice contraction with SiO44− incorporation; rich- and poor-Si phases were subsequently identified. Furthermore, two types of interaction among the functional groups in the S53P4 and BHAp mixtures are proposed. First, the 95-5 (wt.%) sample displayed a BHAp lattice with SiO44−, CO32−, and OH− ions substitution. In samples with S53P4 BG content higher than 95-5, the lattice substitution was related to SiO44−, PO43−, and CO32− ions, and a dehydroxylation process occurred in the BHAp. Finally, the bioactive behavior of the samples was studied by immersion in Hank's solution for 7, 14, and 28 days. The results showed that the mixtures formed a bone-like apatite layer with a dune-like morphology that increased in size and quantity with increasing S53P4 content in the mixtures.
Display omitted
•S53P4/BHAp mixtures preparation through high energy milling.•Si-substituted HAp preparation through a mechanical process.•SiO44− occupying PO43− and CO32− sites within the BHAp lattice by milling process.•Substitution of SiO44− for PO43− and CO32− in the BHAp lattice by mechanical energy.•Enhanced bioactive behavior with increasing S53P4 content in BHAp/BG mixtures.
Structural evolution during the synthesis of B2–NiAl intermetallic compound by mechanical alloying of equiatomic elemental mixtures was studied by Rietveld analysis, DSC and HTXRD. The lattice ...parameter, crystallite size, microstrain, amount of phase and ordering of the B2 phase were monitored as a function of milling time. Formation of the B2–NiAl phase shows a sigmoidal behavior, which suggests that Johnson–Mehl–Avrami nucleation and interface-controlled growth are the responsible mechanisms in the transformation. Almost complete transformation (~ 97 mol%) was obtained after 25 h of milling. A specific phase transformation sequence during milling was not absolutely determined, however, the sequence Ni + Al → NiAl
3
→ Ni
2
Al
3
→ B2–NiAl was identified by HTXRD. This sequence was confirmed by DSC. The transformation temperature of the B2–NiAl phase and the presence of additional intermetallic compounds show a direct dependence on the Ni–Al layer spacing. Using a production-scale Simoloyer horizontal Attritor Mill, the presence of Ni
2
Al
3
phase was observed prior to the full synthesis of B2-NiAl.
Electric energy production with photovoltaic (PV)/thermal solar hybrid systems can be enhanced with the employment of a bifacial PV module. Experimental model of a PV/thermal hybrid system with such ...a module was constructed and studied. To make use of both active surfaces of the bifacial PV module, we designed and made an original water-heating planar collector and a set of reflecting planes. The heat collector was transparent in the visible and near-infrared spectral regions, which makes it compatible with the PV module made of crystalline Si. The estimated overall solar energy utilization efficiency for the system related to the direct radiation flux is of the order of 60%, with an electric efficiency of 16.4%.
We present a detailed theoretical study of the role of long-range dipole-dipole interactions on the angular dependence of ferromagnetic resonance spectra in a two-dimensional array of nanocubes. ...Variations of polar (
φ
) and azimuthal (
θ
) angles are studied numerically and analytically to illustrate the effect of the magnetocrystalline properties and the dipole-dipole interactions, forming complex resonance bands. In addition, we show that when the static magnetic field lies in the arrays’ plane under the angle of 129° with the edge of the array or when its tilted around 15° to the plane’s normal, the spectra of absorption transform into a plateau spanning from 0.1 T to 0.4 T, which is prominent enough for experimental observation.
The present contribution aimed at exploring the HVOF deposition process of bioactive multilayered HAp/titania composite coatings on Ti-6Al-4V substrates. These coatings can be regarded as ...functionally graded as the weight fraction of the constituent phases gradually changes layer by layer, from pure titania at the substrate–coating interface to pure HAp at the outer surface of the coating. Microstructural investigations were carried out on the graded coatings using scanning electron microscopy coupled with EDS microanalysis to confirm that the compositional gradient met the initial specifications. On the other hand, the in vitro properties of the coatings were studied in simulated body fluid (SBF) for periods ranging from 1 to 14 days. Moreover, mechanical characterization of both as-sprayed and soaked coatings in SBF was carried out by performing Vickers microhardness measurements through their cross section. The apparent interfacial toughness (
K
Ca
) of HAp/titania coatings, which is representative of their interfacial crack initiation resistance, was determined by performing indentation tests at the coating–substrate interface. Fracture toughness of both pure hydroxyapatite and functionally graded coatings was also calculated. The results revealed that the graded coatings produced in this work exhibited good reactivity and mechanical stability after being immersed in SBF indicating their potential for biomedical applications.
The θ-Al
2
O
3
→ α-Al
2
O
3
phase transformation was investigated in thermally grown oxide formed on β-(Ni,Pt)Al bond coats during isothermal exposures at 900–1,200 °C in an argon atmosphere stream ...with the O
2
partial pressure of 1 × 10
−5
atm. Local curve fitting was used to evaluate the evolution of the parabolic rate constant,
k
p
, using a general kinetic model (
t
=
A
+
B
Δ
m
+
C
Δ
m
2
), during the first 5 h of oxidation. All net mass–gain curves exhibited deviations from the classic parabolic model, Δ
m
=
k
p
t
½
; a steady state regime was established only after 4 h of exposures, except for the sample oxidized at 1,100 °C.
The effect of pre-oxidation treatment and surface preparation of optimized NiCoCrAlY coatings deposited by high-velocity oxygen fuel (HVOF) spraying and exposed to a low-temperature corrosive ...environment is reported herein. Coatings with two surface finish conditions (as-sprayed and ground) were heat treated under two different oxygen partial pressures (air and argon). The electrochemical corrosion behavior was evaluated in CO
2
-saturated brine via potentiodynamic polarization, polarization resistance, and electrochemical impedance measurements. The results show that the grinding process and pre-oxidation treatment in argon enhanced growth and formation of α-Al
2
O
3
scale. The potentiodynamic polarization results show that both pre-oxidation and surface treatment had a positive influence on the corrosion resistance of the coating. The reduction of the porosity and the formation of a dense, uniform, and adherent oxide scale through pre-oxidation treatment led to an increase of the corrosion resistance due to a decrease in active sites and blocking of diffusion of reactive species into the coating. However, according to the results, complete transformation from metastable alumina phases to α-Al
2
O
3
in addition to formation and growth of dense α-Al
2
O
3
is required to ensure full protection of the coating and base material over long periods.
This paper deals with the deposition of La
2
Zr
2
O
7
(LZO) and LaAlO
3
(LAO) mixtures by air plasma spray (APS). The raw material for thermal spray, single phase LZO and LAO in a 70:30 mol.% ratio ...mixture was prepared from commercial metallic oxides by high-energy ball milling (HEBM) and high-temperature solid-state reaction. The HEBM synthesis route, followed by a spray-drying process, successfully produced spherical agglomerates with adequate size distribution and powder-flow properties for feeding an APS system. The as-sprayed coating consisted mainly of a crystalline LZO matrix and partially crystalline LAO, which resulted from the high cooling rate experienced by the molten particles as they impact the substrate. The coatings were annealed at 1100 °C to promote recrystallization of the LAO phase. The reduced elastic modulus and hardness, measured by nanoindentation, increased from 124.1 to 174.7 GPa and from 11.3 to 14.4 GPa, respectively, after the annealing treatment. These values are higher than those reported for YSZ coatings; however, the fracture toughness (
K
IC
) of the annealed coating was only 1.04 MPa m
0.5
.
