INFLUENCE OF DOUBLE SOLUTION TREATMENT ON HARDNESS IN 17-4 PH STEEL

The investigated material is a corrosion-resistant, Cu precipitation hardened steel 17-4PH, which undergoes a macroscopic contraction, as a result of applying the following heat treatment: double solution treatment at 1028°C for 1 h (condition A), ageing at 540°C for 4 h (condition H1025). The second solution treatment at 1028°C was found to eliminate the retained austenite, being the evidence of a completely finished martensitic transformation.Indeed, the only phase identified in all samples was fcc lath martensite exhibiting a parallel striped structure. Unfortunately, this additional heat-treatment operation leads likewise to significant and irregular grain growth, which consequently causes a drop in material hardness. Moreover, the second solution annealing, caused a shift in the XRD peaks to higher 2θ angles, resulting from a lattice parameter decrease by0,25%. The two subsequent heat-treatment procedures bring the lattice parameter back to its initial value. This seemingly reversible process of decrease and increase of the lattice parameter was observed for samples subjected to all the heat treatment operations, strongly suggesting the existence of a relation between the microstructural changes and the macroscopic contraction of the steel material. In addition to the martensitic phase, in the unaged samples, a δ- ferrite phase could be identified by TEM and electron diffraction, which is favorable for ductility and toughness of the material. In all samples, non-coherent fcc-NbC precipitates identified by electron diffraction and EDX mapping having sizes up to 70 nm were found

INFLUENCE OF DOUBLE SOLUTION TREATMENT ON HARDNESS IN 17-4 PH STEEL

The investigated material is a corrosion-resistant, Cu precipitation hardened steel 17-4PH, which undergoes a macroscopic contraction, as a result of applying the following heat treatment: double solution treatment at 1028°C for 1 h (condition A), ageing at 540°C for 4 h (condition H1025). The second solution treatment at 1028°C was found to eliminate the retained austenite, being the evidence of a completely finished martensitic transformation.Indeed, the only phase identified in all samples was fcc lath martensite exhibiting a parallel striped structure. Unfortunately, this additional heat-treatment operation leads likewise to significant and irregular grain growth, which consequently causes a drop in material hardness. Moreover, the second solution annealing, caused a shift in the XRD peaks to higher 2θ angles, resulting from a lattice parameter decrease by0,25%. The two subsequent heat-treatment procedures bring the lattice parameter back to its initial value. This seemingly reversible process of decrease and increase of the lattice parameter was observed for samples subjected to all the heat treatment operations, strongly suggesting the existence of a relation between the microstructural changes and the macroscopic contraction of the steel material. In addition to the martensitic phase, in the unaged samples, a δ- ferrite phase could be identified by TEM and electron diffraction, which is favorable for ductility and toughness of the material. In all samples, non-coherent fcc-NbC precipitates identified by electron diffraction and EDX mapping having sizes up to 70 nm were found

Nitridation of InP(1 0 0) surface studied by synchrotron radiation

The nitridation of InP(1 0 0) surfaces has been studied using synchrotron radiation photoemission. The samples were chemically cleaned and then ion bombarded, which cleaned the surface and also induced the formation of metallic indium droplets. The nitridation with a Glow Discharge Cell (GDS) produced indium nitride by reaction with these indium clusters. We used the In 4d and P 2p core levels to monitor the chemical state of the surface and the coverage of the species present. We observed the creation of In-N and P-N bonds while the In-In metallic bonds decrease which confirm the reaction between indium clusters and nitrogen species. A theoretical model based on stacked layers allows us to assert that almost two monolayers of indium nitride are produced. The effect of annealing on the nitridated layers at 450 $^\circ$C has also been analysed. It appears that this system is stable up to this temperature, well above the congruent evaporation temperature (370 $^\circ$C) of clean InP(1 0 0): no increase of metallic indium bonds due to decomposition of the substrate is detected as shown in previous works [L. Bideux, Y. Ould-Metidji, B. Gruzza, V. Matolin, Surf. Interface Anal. 34 (2002) 712] studying the InP(1 0 0) surfaces

Exhumation of the central Wasatch Mountains, Utah: 2. Thermokinematic model of exhumation, erosion, and thermochronometer interpretation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95279/1/jgrb13381.pd

Heterogeneously Nd³⁺ doped single nanoparticles for NIR-induced heat conversion, luminescence, and thermometry

© 2017 The Royal Society of Chemistry. The current frontier in nanomaterials engineering is to intentionally design and fabricate heterogeneous nanoparticles with desirable morphology and composition, and to integrate multiple functionalities through highly controlled epitaxial growth. Here we show that heterogeneous doping of Nd3+ ions following a core-shell design already allows three optical functions, namely efficient (η > 72%) light-to-heat conversion, bright NIR emission, and sensitive (SR > 0.1% K-1) localized temperature quantification, to be built within a single ca. 25 nm nanoparticle. Importantly, all these optical functions operate within the transparent biological window of the NIR spectral region (λexc ∼ 800 nm, λemi ∼ 860 nm), in which light scattering and absorption by tissues and water are minimal. We find NaNdF4 as a core is efficient in absorbing and converting 808 nm light to heat, while NaYF4:1%Nd3+ as a shell is a temperature sensor based on the ratio-metric luminescence reading but an intermediate inert spacer shell, e.g. NaYF4, is necessary to insulate the heat convertor and thermometer by preventing the possible Nd-Nd energy relaxation. Moreover, we notice that while temperature sensitivity and luminescence intensity are optically stable, increased excitation intensity to generate heat above room temperature may saturate the sensing capacity of temperature feedback. We therefore propose a dual beam photoexcitation scheme as a solution for possible light-induced hyperthermia treatment

INFLUENCE OF DOUBLE SOLUTION TREATMENT ON HARDNESS IN 17-4 PH STEEL

The investigated material is a corrosion-resistant, Cu precipitation hardened steel 17-4PH,which undergoes a macroscopic contraction, as a result of applying the following heat treatment:double solution treatment at 1028°C for 1 h (condition A), ageing at 540°C for 4 h (conditionH1025). The second solution treatment at 1028°C was found to eliminate the retained austenite,being the evidence of a completely finished martensitic transformation.Indeed, the only phaseidentified in all samples was fcc lath martensite exhibiting a parallel striped structure.Unfortunately, this additional heat-treatment operation leads likewise to significant and irregulargrain growth, which consequently causes a drop in material hardness. Moreover, the secondsolution annealing, caused a shift in the XRD peaks to higher 2θ angles, resulting from a latticeparameter decrease by0,25%. The two subsequent heat-treatment procedures bring the latticeparameter back to its initial value. This seemingly reversible process of decrease and increase of thelattice parameter was observed for samples subjected to all the heat treatment operations, stronglysuggesting the existence of a relation between the microstructural changes and the macroscopiccontraction of the steel material. In addition to the martensitic phase, in the unaged samples, a δ-ferrite phase could be identified by TEM and electron diffraction, which is favorable for ductilityand toughness of the material. In all samples, non-coherent fcc-NbC precipitates identified byelectron diffraction and EDX mapping having sizes up to 70 nm were found

Passivation of InP(100) substrates: first stages of nitridation by thin InN surface overlayers studied by electron spectroscopies

International audienceThis article investigates the nitridation effect of InP(100) semiconductor surfaces performed by a glow discharge cell (GDS). Electron spectroscopies (AES, ESCA) were used to understand the different steps of this process. An important point is the initial quantity of metallic indium on the InP(100) surfaces. Indeed the indium droplets, created in well known quantity, play the role of precursor. At a relatively low temperature T = 523 K, the system undergoes surface restructuration which includes removal of the In droplets and the elaboration of two InN monolayers. P-N bonds and InN bonds have been detected by the analysis of PLMM and InMNN Auger peaks and In4d ESCA peak. However, the presence or not of metallic indium inside this InN overlayer is crucial for the passivation of the substrate. Ex-situ photoluminescence measurements correlated to the electron spectroscopies results have put i

Room temperature photoluminescence studies of nitrided InP(100)

The evolution of thin InN overlayer grown on InP(100) substrate versus the duration of nitridation process, performed by means of glow discharge source (GDS), and the angle of reactive nitrogen flux was investigated. The correlations between the electronic properties, gathered from photoluminescence (PL) measurements, and the chemical composition of InN-InP interfaces, derived from Auger electron spectroscopy (AES) were found. AES revealed that the nitridation process proceeds quickly in time showing self-limiting behavior. It is more effective for grazing nitrogen flux. The interface state density distributions, NSS(E), were determined via advanced computer-aided analysis of dependencies of band edge PL efficiency, YPL, versus excitation light intensity, & The analysis showed that the substrates were well passivated with NSS(E) minima on the order of 5∙1011 cm-2eV-1. The nitrogen flux angle during the nitridation was found to have an influence on YPL(&¬) spectra. In all analyzed cases the grazing nitrogen flux generated the interface with slightly improved NSS(E) distribution. Finally, the behavior of YPL versus & and NSS(E) was precisely examined