Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 458
Filter
Add more filters








Publication year range
1.
J Appl Crystallogr ; 57(Pt 5): 1282-1287, 2024 Oct 01.
Article in English | MEDLINE | ID: mdl-39387068

ABSTRACT

The Q resolution in Bonse-Hart double-crystal diffractometers is determined for a given Bragg angle by the value of the crystallographic structure factor. To date, the reflections Si 220 or Si 111 have been used exclusively in neutron scattering, which provide resolutions for triple-bounce crystals of about 2 × 10-5 Å-1 (FWHM). The Darwin width of the GaAs 200 reflection is about a factor of 10 smaller, offering the possibility of a Q resolution of 2 × 10-6 Å-1 provided crystals of sufficient quality are available. This article reports a feasibility study with single-bounce GaAs 200, yielding a Q resolution of 4.6 × 10-6 Å-1, six times superior in comparison with a Si 220 setup.

2.
J Appl Crystallogr ; 57(Pt 5): 1436-1445, 2024 Oct 01.
Article in English | MEDLINE | ID: mdl-39387076

ABSTRACT

High-pressure neutron powder diffraction data from PbNCN were collected on the high-pressure diffraction beamline SNAP located at the Spallation Neutron Source (SNS) of Oak Ridge National Laboratory (Tennessee, USA). The diffraction data were analyzed using the novel method of multidimensional (two dimensions for now, potentially more in the future) Rietveld refinement and, for comparison, employing the conventional Rietveld method. To achieve two-dimensional analysis, a detailed description of the SNAP instrument characteristics was created, serving as an instrument parameter file, and then yielding both cell and spatial parameters as refined under pressure for the first time for solid-state cyanamides/carbodi-imides. The bulk modulus B 0 = 25.1 (15) GPa and its derivative B'0 = 11.1 (8) were extracted for PbNCN following the Vinet equation of state. Surprisingly, an internal transition was observed beyond 2.0 (2) GPa, resulting from switching the bond multiplicities (and bending direction) of the NCN2- complex anion. The results were corroborated using electronic structure calculation from first principles, highlighting both local structural and chemical bonding details.

3.
Molecules ; 29(19)2024 Oct 05.
Article in English | MEDLINE | ID: mdl-39407648

ABSTRACT

Silicate glasses containing silicon, sodium, phosphorous, and calcium have the ability to promote bone regeneration and biodegrade as new tissue is generated. Recently, it has been suggested that adding SrO can benefit tissue growth and silicate glass dissolution. Motivated by these recent developments, the effect of SrO/CaO-CaO/SrO substitution on the local structure and dynamics of Si-Na-P-Ca-O oxide glasses has been studied in this work. Differential thermal analysis has been performed to determine the thermal stability of the glasses after the addition of strontium. The local structure has been studied by neutron diffraction augmented by Reverse Monte Carlo simulation, and the local dynamics by neutron Compton scattering and Raman spectroscopy. Differential thermal analysis has shown that SrO-containing glasses have lower glass transition, melting, and crystallisation temperatures. Moreover, the addition of the Sr2+ ions decreased the thermal stability of the glass structure. The total neutron diffraction augmented by the RMC simulation revealed that Sr played a similar role as Ca in the glass structure when substituted on a molar basis. The bond length and the coordination number distributions of the network modifiers and network formers did not change when SrO (x = 0.125, 0.25) was substituted for CaO (25-x). However, the network connectivity increased in glass with 12.5 mol% CaO due to the increased length of the Si-O-Si interconnected chain. The analysis of Raman spectra revealed that substituting CaO with SrO in the glass structure dramatically enhances the intensity of the high-frequency band of 1110-2000 cm-1. For all glasses under investigation, the changes in the relative intensities of Raman bands and the distributions of the bond lengths and coordination numbers upon the SrO substitution were correlated with the values of the widths of nuclear momentum distributions of Si, Na, P, Ca, O, and Sr. The widths of nuclear momentum distributions were observed to soften compared to the values observed and simulated in their parent metal-oxide crystals. The widths of nuclear momentum distributions, obtained from fitting the experimental data to neutron Compton spectra, were related to the amount of disorder of effective force constants acting on individual atomic species in the glasses.

4.
Chemistry ; : e202403048, 2024 Sep 06.
Article in English | MEDLINE | ID: mdl-39239923

ABSTRACT

Sr4Ba3(BO3)3.83H2.5, as the second compound to combine borate and hydride ions, has been synthesized by a mechanochemical synthesis route. The structure has been elucidated by synchrotron X-ray and neutron diffraction and determined to crystallize in the non-centrosymmetric space group P63mc (186) with the cell parameters a = 10.87762(15) Å and c = 6.98061(11) Å. A detailed investigation of the compound by vibrational spectroscopy in combination with Density Functional Theory calculations reveals the disordered nature of the structure and proves the presence of both borate and hydride ions. Electronic band structure calculations predict a large band gap of 7.1 eV. Hydride states are predicted at the topmost valence band, which agrees well with earlier reported heteroanionic hydrides. We hereby were able to successfully apply previously synthetic and analytical schemes to introduce another member of the rare compounds that contain complex oxoanions simultaneously with hydride ions.

5.
Materials (Basel) ; 17(17)2024 Aug 30.
Article in English | MEDLINE | ID: mdl-39274700

ABSTRACT

As the issue of climate change becomes more prevalent, engineers have focused on developing lightweight Al alloys capable of increasing the power density of powertrains. The characterization of these alloys has been focused on mechanical properties and less on the fundamental response of microstructures to achieve these properties. Therefore, this study assesses the quality of the microstructure of two high-temperature Al alloys (A356 + 3.5RE and Al-8Ce-10Mg), comparing them to T6 A356. These alloys underwent thermal conditioning at 250 and 300 °C for 200 h. Time-of-flight neutron diffraction experiments were performed before and after conditioning. The phase evolution was quantified using Rietveld refinement. It was found that the Si phase grows significantly (13-24%) in T6 A356, A356 + 3.5RE, and T6 A356 + 3.5RE alloys, which is typically correlated with a reduction in mechanical properties. Subjecting the A356 3.5RE alloy to a T6 heat treatment stabilizes the orthorhombic Al4Ce3Si6 and monoclinic ß-Al5FeSi phases, making them resistant to thermal conditioning. These two phases are known for enhancing mechanical properties. Additionally, the T6 treatment reduced the vol.% of the cubic Al20CeTi2 and hexagonal á´¨-Al9FeSi3Mg5 phases by 13% and 23%, respectively. These phases have detrimental mechanical properties. The Al-8Ce-10Mg alloy cubic ß-Al3Mg2 phase showed significant growth (82-101%) in response to conditioning, while the orthorhombic Al11Ce3 phase remained stable. The growth of the beta phase is known to decrease the mechanical properties of this alloy. These efforts give valuable insight into how these alloys will perform and evolve in demanding high-temperature environments.

6.
Materials (Basel) ; 17(17)2024 Sep 07.
Article in English | MEDLINE | ID: mdl-39274807

ABSTRACT

The textures of the ß- and α-phases of the metastable ß-titanium alloy Ti5321 after hot deformation were investigated by neutron diffraction. A hot-rolled bar was solutionized in the ß-phase field and then hot compressed above and below the ß-transus temperature. The initial texture after full recrystallization and grain growth in the ß-phase field exhibits a weak cube component {001}<100> and minor {112}<110> and {111}<110> components. After hot compression, a <100> fiber texture is observed, increasing in intensity with compression temperature. Below the ß-transus temperature, dynamic recrystallization of the ß-phase and dynamic spheroidization of the α-phase interact strongly. The texture of the α-phase is a <11-20> fiber texture, increasing in intensity with decreasing compression temperature. The mechanisms of texture formation during hot compression are discussed.

7.
J Struct Biol ; 216(4): 108126, 2024 Sep 06.
Article in English | MEDLINE | ID: mdl-39244170

ABSTRACT

The global crystallographic texture of calcite and aragonite in the shells of the bivalves Bathymodiolus thermophilus, Mytilus galloprovincialis, M. edulis and M. trossulus was studied by means of neutron diffraction. It was revealed that the general appearance of pole figures isolines of both minerals coincides for the studied species. The crystallographic texture sharpness evaluated by means of pole density on the calcite pole figures ((0006), (101¯4)) and aragonite pole figures ((012)/(121), (040)/(221)) coincides or has close values for deep-sea hydrothermal species B. thermophilus and the studied shallow-water species of the genus Mytilus. The calcite pole figures (0006) and (101¯4) of B. thermophilus show a shift in the position of texture maximum values compared to corresponding pole figures of other mussels. The shell microstructure of all studied mollusks is similar, only the shape of the fibers of B. thermophilus differs. Global crystallographic texture is a stable feature of the family Mytilidae. The extreme habitat conditions of the hydrothermal biotope do not significantly affect the crystallographic texture of B. thermophilus.

8.
Article in English | MEDLINE | ID: mdl-39320309

ABSTRACT

Magnetic structures of the noncentrosymmetric magnet Sr2MnSi2O7 were examined through neutron diffraction for powder and single-crystalline samples, as well as magnetometry measurements. All allowed magnetic structures for space group P421m with the magnetic wavevector qm = (0, 0, ½) were refined via irreducible representation and magnetic space group analyses. The compound was refined to have in-plane magnetic moments within the magnetic space group Cmc21.1'c (No. 36.177) under zero field, which can be altered to P212121.1'c (No. 19.28) above µ0H = 0.067 (5) T to align induced weak-ferromagnetic components within one layer on the ab plane. All refined parameters are provided following the recent framework based upon the magnetic space group, which better conveys when exchanging crystallographic information for commensurate magnetic structures.

9.
Article in English | MEDLINE | ID: mdl-39320307

ABSTRACT

The magnetic and crystal structures of manganese and nickel monoxides have been studied using high-resolution neutron diffraction. The known 1k-structures based on the single propagation vector [½ ½ ½] for the parent paramagnetic space group Fm3m are forced to have monoclinic magnetic symmetry and are not possible in rhombohedral symmetry. However, the monoclinic distortions from the rhombohedral crystal metric allowed by symmetry are very small, and the explicit monoclinic splittings of the diffraction peaks have not been experimentally observed. We analyse the magnetic crystallographic models metrically compatible with our experimental data in full detail by using isotropy subgroup representation approach, including rhombohedral solutions based on the propagation vector star {[½ ½ ½], [-½ ½ ½], [½-½ ½], [½ ½ -½]}. Although the full star rhombohedral RI3c structure can equally well fit our diffraction data for NiO, we conclude that the best solution for the crystal and magnetic structures for NiO and MnO is the 1k monoclinic model with the magnetic space group Cc2/c (Belov-Neronova-Smirnova No. 15.90, UNI symbol C2/c.1'c[C2/m]).

10.
Molecules ; 29(16)2024 Aug 10.
Article in English | MEDLINE | ID: mdl-39202876

ABSTRACT

Recent research into sodium zirconate as a high-temperature CO2 sorbent has been extensive, but detailed knowledge of the material's crystal structure during synthesis and carbon dioxide uptake remains limited. This study employs neutron diffraction (ND), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) to explore these aspects. An improved synthesis method, involving the pre-drying and ball milling of raw materials, produced pure samples with average crystal sizes of 37-48 nm in the monoclinic phase. However, using a slower heating rate (1 °C/min) decreased the purity. Despite this, the 1 °C/min rate resulted in the highest CO2 uptake capacity (4.32 mmol CO2/g Na2ZrO3) and CO2 sorption rate (0.0017 mmol CO2/g) after 5 min at 700 °C. This was attributed to a larger presence of microstructure defects that facilitate Na diffusion from the core to the shell of the particles. An ND analysis showed that the conversion of Na2ZrO3 was complete under the studied conditions and that CO2 concentration significantly impacts the rate of CO2 absorption. The TGA results indicated that the reaction rate during CO2 sorption remained steady until full conversion due to the absorptive nature of the chemisorption process. During the sorbent reforming step, ND revealed the disappearance of Na2O and ZrO2 as the zirconate phase reformed. However, trace amounts of Na2CO3 and ZrO2 remained after the cycles.

11.
ACS Nano ; 18(35): 24515-24522, 2024 Sep 03.
Article in English | MEDLINE | ID: mdl-39165001

ABSTRACT

Topological spin textures are of great significance in magnetic information storage and spintronics due to their high storage density and low drive current. In this work, the transformation of magnetic configuration from chaotic labyrinth domains to uniform stripe domains was observed in MnFe1-xCoxGe magnets. This change occurs due to the noncollinear magnetic structure switching to a uniaxial ferromagnetic structure with increasing Co content, as identified by neutron diffraction results and Lorentz transmission electron microscopy (L-TEM). Of utmost importance, a hexagonal lattice of high-density robust type-II magnetic bubble lattice was established for x = 0.8 through out-of-plane magnetic field stimulation and field-cooling. The dimensions of the type-II magnetic bubbles were found to be tuned by the sample thickness. Therefore, the stabilization of complex magnetic spin textures, associated with enhanced uniaxial ferromagnetic interaction and magnetic dipole-dipole interaction in MnFe1-xCoxGe through magnetic structure manipulation, as further confirmed by the micromagnetic simulations, will provide a convenient and efficient strategy for designing topological spin textures with potential applications in spintronic devices.

12.
Acta Crystallogr A Found Adv ; 80(Pt 5): 379-386, 2024 Sep 01.
Article in English | MEDLINE | ID: mdl-39115463

ABSTRACT

Neutron time-of-flight transmission spectra of mosaic crystals contain Bragg dips, i.e., minima at wavelengths corresponding to diffraction reflections. The positions of the dips are used for investigating crystal lattices. By rotating the sample around a fixed axis and recording a spectrum at each rotation step, the intensity of the transmitted beam is obtained as a function of the rotation angle and wavelength. The questions addressed in this article concern the determination of lattice parameters and orientations of centrosymmetric crystals from such data. It is shown that if the axis of sample rotation is inclined to the beam direction, the reflection positions unambiguously determine reciprocal-lattice vectors, which is not the case when the axis is perpendicular to the beam. Having a set of such vectors, one can compute the crystal orientation or lattice parameters using existing indexing software. The considerations are applicable to arbitrary Laue symmetry. The work contributes to the automation of the analysis of diffraction data obtained in the neutron imaging mode.

13.
Angew Chem Int Ed Engl ; : e202407395, 2024 Aug 13.
Article in English | MEDLINE | ID: mdl-39137132

ABSTRACT

Copper-exchanged zeolite omega (Cu-omega) is a potent material for the selective conversion of methane-to-methanol (MtM) via the oxygen looping approach. However, its performance exhibits substantial variation depending on the operational conditions. Under an isothermal temperature regime, Cu-omega demonstrates subdued activity below 230 °C, but experiences a remarkable increase in activity at 290 °C. Applying a high-temperature activation protocol at 450 °C causes a rapid deactivation of the material. This behavioral divergence is investigated by combining reactivity studies, neutron and in situ high-resolution anomalous X-ray powder diffraction (HR-AXRPD), as well as electron paramagnetic resonance spectroscopy, to reveal that the migration of Cu throughout the framework is the primary cause of these behaviors, which in turn is governed by the degree of hydration of the system. This work suggests that control over the Cu migration throughout the zeolite framework may be harnessed to significantly increase the activity of Cu-omega by generating more active sites for the MtM conversion. These results underscore the power of in situ HR-AXRPD for unraveling the behavior of materials under reaction conditions and suggest that a re-evaluation of Cu-zeolites priorly deemed inactive for the MtM conversion across a broader range of conditions and looping protocols may be warranted.

14.
J Appl Crystallogr ; 57(Pt 4): 1107-1114, 2024 Aug 01.
Article in English | MEDLINE | ID: mdl-39108822

ABSTRACT

Neutron diffraction beamlines have traditionally relied on deploying large detector arrays of 3He tubes or neutron-sensitive scintillators coupled with photomultipliers to efficiently probe crystallographic and microstructure information of a given material. Given the large upfront cost of custom-made data acquisition systems and the recent scarcity of 3He, new diffraction beamlines or upgrades to existing ones demand innovative approaches. This paper introduces a novel Timepix3-based event-mode imaging neutron diffraction detector system as well as first results of a silicon powder diffraction measurement made at the HIPPO neutron powder diffractometer at the Los Alamos Neutron Science Center. Notably, these initial measurements were conducted simultaneously with the 3He array on HIPPO, enabling direct comparison. Data reduction for this type of data was implemented in the MAUD code, enabling Rietveld analysis. Results from the Timepix3-based setup and HIPPO were benchmarked against McStas simulations, showing good agreement for peak resolution. With further development, systems such as the one presented here may substantially reduce the cost of detector systems for new neutron instrumentation as well as for upgrades of existing beamlines.

15.
Adv Sci (Weinh) ; 11(33): e2402048, 2024 Sep.
Article in English | MEDLINE | ID: mdl-38961641

ABSTRACT

Ferro-rotational (FR) materials, renowned for their distinctive material functionalities, present challenges in the growth of homo-FR crystals (i.e., single FR domain). This study explores a cost-effective approach to growing homo-FR helimagnetic RbFe(SO4)2 (RFSO) crystals by lowering the crystal growth temperature below the TFR threshold using the high-pressure hydrothermal method. Through polarized neutron diffraction experiments, it is observed that nearly 86% of RFSO crystals consist of a homo-FR domain. Notably, RFSO displays remarkable stability in the FR phase, with an exceptionally high TFR of ≈573 K. Furthermore, RFSO exhibits a chiral helical magnetic structure with switchable ferroelectric polarization below 4 K. Importantly, external electric fields can induce a single magnetic domain state and manipulate its magnetic chirality. The findings suggest that the search for new FR magnets with outstanding material properties should consider magnetic sulfates as promising candidates.

16.
Angew Chem Int Ed Engl ; 63(42): e202410326, 2024 Oct 14.
Article in English | MEDLINE | ID: mdl-39054680

ABSTRACT

High-voltage ultrahigh-Ni cathodes (LiNixCoyMn1-x-yO2, x≥0.9) can significantly enhance the energy density and cost-effectiveness of Li-ion batteries beyond current levels. However, severe Li-Ni antisite defects and their undetermined dynamic evolutions during high-voltage cycling limit the further development of these ultrahigh-Ni cathodes. In this study, we quantify the dynamic evolutions of the Li-Ni antisite defect using operando neutron diffraction and reveal its coupling relationship with anionic redox, another critical challenge restricting ultrahigh-Ni cathodes. We detect a clear Ni migration coupled with an unstable oxygen lattice, which accompanies the oxidation of oxygen anions at high voltages. Based on these findings, we propose that minimized Li-Ni antisite defects and controlled Ni migrations are essential for achieving stable high-voltage cycling structures in ultrahigh-Ni cathodes. This is further demonstrated by the optimized ultrahigh-Ni cathode, where reduced dynamic evolutions of the Li-Ni antisite defect effectively inhibit the anionic redox, enhancing the 4.5 V cycling stability.

17.
Acta Crystallogr B Struct Sci Cryst Eng Mater ; 80(Pt 4): 281-293, 2024 Aug 01.
Article in English | MEDLINE | ID: mdl-38940679

ABSTRACT

Results of the neutron powder diffraction measurements carried out for R5Pt2In4 (R = Tb-Tm) are reported. The compounds crystallize in an orthorhombic crystal structure of the Lu5Ni2In4-type with the rare earth atoms occupying three different sublattices. Neutron diffraction data reveal that at low temperatures the rare earth magnetic moments order below the critical temperature equal to 105, 93, 28, 12 and 3.8 K for R = Tb, Dy, Ho, Er and Tm, respectively. With decreasing temperature the rare earth magnetic moments at the 2a and 4g2 sites order first, while the moments at the 4g1 site order at lower temperatures. Ferrimagnetic order along the c axis, described by the propagation vector k1 = [0, 0, 0], develops in Tb5Pt2In4 below the Curie temperature (TC = 105 K). At lower temperatures, an antiferromagnetic component in the ab plane appears. The component is incommensurate with the crystal structure (k2 = [0, 0.66, ½]), but it turns into a commensurate one (k3 = [0, 0, ½]) with decreasing temperature. Antiferromagnetic order along the c axis, described by k4 = [½, 0, 0], is found in Dy5Pt2In4 below the Néel temperature (TN = 93 K). The k4-related component disappears below 80 K and the magnetic structure transforms into a ferro/ferrimagnetic one described by k1 = [0, 0, 0]. Further decrease in temperature leads to the appearance of an incommensurate antiferromagnetic component within the ab plane below 10 K (k2 = [0, 0.45, ½]), which finally turns into a commensurate one (k5 = [0, ½, ½]). In Ho5Pt2In4, a sine-modulated magnetic structure with moments parallel to the c axis (k6 = [⅓,0,0]) is observed below 28 K. With a decrease in temperature, new components, related to k1 = [0, 0, 0] (bc plane) and k4 = [½, 0, 0] (c axis), appear. The coexistence of two orderings - in the ab plane (k1 = [0, 0, 0]) and a modulated one with moments along the b axis (k7 = [kx, 0, 0]) - is found in Er5Pt2In4 below 12 K. Decreasing temperature leads to the order-order transformation of the k1-related component to another one with magnetic moments still constrained to the ab plane and preserved value of the propagation vector (i.e. k1 = [0, 0, 0]). Tm5Pt2In4 orders antiferromagnetically below TN = 3.8 K. Thulium magnetic moments lie in the ab plane, while the magnetic structure is described by k5 = [0, ½ , ½]. The direction of magnetic moments depends on the rare earth element involved and indicates an influence of single ion anisotropy resulting from interaction with the crystalline electric field.

18.
J Appl Crystallogr ; 57(Pt 3): 690-699, 2024 Jun 01.
Article in English | MEDLINE | ID: mdl-38846768

ABSTRACT

Scintillator-based ZnS:Ag/6LiF neutron detectors have been under development at ISIS for more than three decades. Continuous research and development aim to improve detector capabilities, achieve better performance and meet the increasingly demanding requirements set by neutron instruments. As part of this program, a high-efficiency 2D position-sensitive scintillator detector with wavelength-shifting fibres has been developed for neutron-diffraction applications. The detector consists of a double scintillator-fibre layer to improve detection efficiency. Each layer is made up of two orthogonal fibre planes placed between two ZnS:Ag/6LiF scintillator screens. Thin reflective foils are attached to the front and back scintillators of each layer to minimize light cross-talk between layers. The detector has an active area of 192 × 192 mm with a square pixel size of 3 × 3 mm. As part of the development process of the double-layer detector, a single-layer detector was built, together with a prototype detector in which the two layers of the detector could be read out separately. Efficiency calculations and measurements of all three detectors are discussed. The novel double-layer detector has been installed and tested on the SXD diffractometer at ISIS. The detector performance is compared with the current scintillator detectors employed on SXD by studying reference crystal samples. More than a factor of 3 improvement in efficiency is achieved with the double-layer wavelength-shifting-fibre detector. Software routines for further optimizations in spatial resolution and uniformity of response have been implemented and tested for 2D detectors. The methods and results are discussed in this manuscript.

19.
J Phys Condens Matter ; 36(35)2024 May 31.
Article in English | MEDLINE | ID: mdl-38740073

ABSTRACT

Local magnetostructural changes and dynamical spin fluctuations in doubly diluted spinel TixMn1‒x(FeyCo1‒y)2O4has been reported by means of neutron diffraction and magnetization studies. Two distinct sets of compositions (i)x(Ti) = 0.20 andy(Fe) = 0.18; (ii)x(Ti) = 0.40 andy(Fe) = 0.435 have been considered for this study. The first compound of equivalent stoichiometry Ti0.20Mn0.80Fe0.36Co1.64O4exhibits enhanced tetragonal distortion across the ferrimagnetic transition temperatureTC= 258 K in comparison to the end compound MnCo2O4(TC∼ 180 K) with a characteristic ratioct/√2atof 0.99795(8) demonstrating robust lattice-spin-orbital coupling. However, in the second case Ti0.40Mn0.60Fe0.87Co1.13O4with higherB-site compositions, the presence of Jahn-Teller ions with distinct behavior appears to counterbalance the strong tetragonal distortion thereby ceasing the lattice-spin-orbital coupling. Both the investigated systems show the coexistence of noncollinear antiferromagnetic and ferrimagnetic components in cubic and tetragonal settings. On the other hand, the dynamical ac-susceptibility,χac(T) reveals a cluster spin-glass state with Gabay-Toulouse (GT) like mixed phases behaviour belowTC. Such dispersive behaviour appears to be sensitive to the level of octahedral substitution. Further, the field dependence ofχac(T) follows the weak anisotropic GT-line behaviour with crossover exponent Φ lies in the range 1.38-1.52 on theH-Tplane which is in contrast to theB-site Ti substituted MnCo2O4spinel that appears to follow irreversible non-mean-field AT-line behaviour (Φ âˆ¼ 3 +δ). Finally, the Arrott plots analysis indicates the presence of a pseudo first-order like transition (T< 20 K) which is in consonance with and zero crossover of the magnetic entropy change within the frozen spin-glass regime.

20.
Sensors (Basel) ; 24(9)2024 Apr 24.
Article in English | MEDLINE | ID: mdl-38732810

ABSTRACT

With neutron diffraction, the local stress and texture of metallic components can be analyzed non-destructively. For both, highly accurate positioning of the sample is essential, requiring the measurement at the same sample location from different directions. Current sample-positioning systems in neutron diffraction instruments combine XYZ tables and Eulerian cradles to enable the accurate six-degree-of-freedom (6DoF) handling of samples. However, these systems are not flexible enough. The choice of the rotation center and their range of motion are limited. Industrial six-axis robots have the necessary flexibility, but they lack the required absolute accuracy. This paper proposes a visual servoing system consisting of an industrial six-axis robot enhanced with a high-precision multi-camera tracking system. Its goal is to achieve an absolute positioning accuracy of better than 50µm. A digital twin integrates various data sources from the instrument and the sample in order to enable a fully automatic measurement procedure. This system is also highly relevant for other kinds of processes that require the accurate and flexible handling of objects and tools, e.g., robotic surgery or industrial printing on 3D surfaces.

SELECTION OF CITATIONS
SEARCH DETAIL