High-resolution Synchrotron X-ray Diffraction Research Articles

Realizing isotropic negative thermal expansion covering room temperature by breaking the superstructure of ZrV2O7

ZrV2O7 is a well-known isotropic negative thermal expansion (NTE) material. However, the NTE property of ZrV2O7 can only be observed in high temperatures above 375 K. In this paper, we report a facile method to break the superstructure of ZrV2O7 for realizing the NTE property of ZrV2O7 to room temperature by partial substitution of Mo for V atoms. The detailed structure information and the phase transition process are revealed by high-resolution synchrotron x-ray diffraction, neutron powder diffraction, and high pressure Raman spectral analyses. It is found that the incorporation of Mo prompts the V-O2-V/Mo angles to expand from 160° to 180°, which enables the NTE property at room temperature. Different from most open framework structures where NTE is dominated by low energy phonons, here several high energy phonon modes are found to have negative Grüneisen parameters and contribute to the negative thermal expansion.

Leveraging Cu/CuFe2O4-Catalyzed Biomass-Derived Furfural Hydrodeoxygenation: A Nanoscale Metal-Organic-Framework Template Is the Prime Key.

Enormous efforts have been initiated in the production of biobased fuels and value-added chemicals via biorefinery owing to the scarcity of fossil resources and huge environmental synchronization. Herein, non-noble metal-based metal/mixed metal oxide supported on carbon employing a metal-organic framework as a sacrificial template is demonstrated for the first time in the selective hydrodeoxygenation (HDO) of biomass-derived furfural (FFR) to 2-methyl furan (MF). The aforementioned catalyst (referred to as Cu/CuFe2O4@C-A) exhibited extraordinary catalytic proficiency (100% selectivity toward MF) compared with the conventional Cu/CuFe2O4@C-B catalyst which was prepared by the wet impregnation method. High-resolution transmission electron microscopy and synchrotron X-ray diffraction studies evidenced the existence of both metal (Cu) and mixed metal oxide (CuFe2O4) phases, in which the metal could help in hydrogenation to alcohol and metal oxide could assist in the hydroxyl group removal step during HDO reaction. The stabilization of encapsulated metal/metal oxide nanoparticles in the carbon matrix, modulation of the electronic structure, and regulation of geometric effects in the Cu/CuFe2O4@C-A are thought to play an important role in its excellent catalytic performance, confirmed by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy investigations. Furthermore, the structure and activity interconnection was confirmed by in situ attenuated total reflection-IR studies, which manifested the strong interfacial interaction between FFR and the Cu/CuFe2O4@C-A catalyst. This finding was further supported by NH3 temperature-programmed desorption analysis, which suggested that the presence of more Lewis/weak acidic sites in this catalyst was beneficial for the hydrogenolysis step in HDO reaction. Additionally, H2 temperature-programmed reduction studies revealed that the adsorption of H2 was stronger on the Cu/CuFe2O4@C-A than that over the conventional Cu/CuFe2O4@C-B catalyst; thus, the former catalyst promoted activation of H2. A detailed kinetic analysis which demonstrated the lower activation energy barrier along with dual active sites attributed for the activation of the two separate reactions in the HDO process on the Cu/CuFe2O4@C-A catalyst. This work has great implication in developing a highly stable catalyst for the selective upgradation of biomass without deactivation of metal sites in extended catalytic cycles and opens the door of opportunity for developing a sustainably viable catalyst in biomass refinery industries.

Correlating polar distortions and interfacial charge at the polar/non-polar LaCrO3/SrTiO3 (001) interface

The relationship between the sheet carrier concentration, ns, of LaCrO3(LCO)/SrTiO3(STO) heterostructures and their structural properties has been investigated. Under low oxygen partial pressure, the STO substrate is reduced during growth as evidenced by a high ns of 1016 cm−2. By controlling the post-growth annealing conditions, heterostructures with ns of 1013–1016 cm−2 are achieved. The atomic-scale structure of the samples is obtained using high-resolution synchrotron x-ray diffraction measurements. For heterostructures with ns at or below 3 × 1013 cm−2, polar distortions are present within the LCO layers and increase in magnitude with a decrease in sheet carrier concentration. These distortions are absent for samples with ns on the order of 1015–1016 cm−2 where interfacial carriers play a role in alleviating the polar discontinuity at the LCO/STO interface. These results suggest that interfacial charge carriers and polar distortions can act as complementary mechanisms to alleviate the polar discontinuity at polar/non-polar complex oxide interfaces.

Evolution of phases, hardness and magnetic properties of AlCoCrFeNi high entropy alloy processed by mechanical alloying

Abstract AlCoCrFeNi high entropy alloy (HEA) was synthesized by mechanical alloying (MA). Formation of single-phase solid solution of body centered cubic (BCC) structure (a = 2.88 ± 0.01 A) was confirmed from x-ray diffraction (XRD) and high-resolution synchrotron XRD. The nanostructure nature of the milled powder was observed through transmission electron microscopy (TEM). The milled powder was consolidated through conventional sintering at 900 °C (1173 K) for 2 h. The microstructure of the sintered AlCoCrFeNi HEA showed two types of grain distribution. Coarser size of grains varied in the range of ∼18–22 μm and finer grains of ∼ 2–10 μm sizes that are homogeneously distributed in the matrix. Detailed analysis of the x-ray diffraction pattern of sintered HEA showed the phase transition from parent BCC phase to Al–Ni type B2 phase (cP2) (a = 2.91 ± 0.02 A) and Ni3Al type L12 phase (cP4) (a = 3.56 ± 0.01 A) along with Co–Cr type σ phase (tP30) (a = 8.8 A, c = 4.53 A). The sintered samples showed high value of microhardness, i.e. 919 ± 18 HV at 300 g load. Alloy shows fascinating soft magnetic property with saturation magnetization of 70.05 A m2/kg (emu/gm) along with effective Curie temperature (TC) of ∼617 °C (890 K).

Structure and Negative Thermal Expansion in Zr0.3Sc1.7Mo2.7V0.3O12.

A2M3O12-based materials have received considerable attention owing to their wide range of negative thermal expansion (NTE) and chemical flexibility toward novel materials design. However, the structure and NTE mechanism remain challenging. Here, Zr4+ and V5+ are used as a unit to compensatorily replace Sc3+ and Mo6+ in Sc2Mo3O12 to tune its thermal expansion. Its crystal structure, phase transition, NTE property, and corresponding mechanisms are studied by high-resolution synchrotron X-ray diffraction, powder X-ray diffraction, ultralow-frequency Raman spectroscopy, and density functional theory calculations. The results show that Zr0.3Sc1.7Mo2.7V0.3O12 adopts an orthorhombic (Pbcn) structure at room temperature, with V atoms occupying the position of Mo1 atoms and Zr atoms occupying the position of Sc atoms, and transforms to monoclinic (P21/a) structure at ∼133 K (45 K lower than that of Sc2Mo3O12). It exhibits excellent NTE in a broader range. Most of the phonon modes below 350 cm-1 have negative Grüneisen parameters, of which the lowest and next-lowest frequency (38.5 and 45.8 cm-1) optical phonon modes arising from the translational vibrations of the Sc/Zr and Mo/V atoms in the plane of the nonlinear linkage Sc/Zr-O-Mo/V have the largest and next-largest negative Grüneisen parameters and positive total anharmonicity, and contribute most to the NTE.

The dependence of aluminum lattice orientation on semiconductor lattice parameter in planar InAs/Al hybrid heterostructures

Abstract We present a detailed study of 7-nm thick Al layers epitaxially grown on InxAl1−xAs or Al1−xGaxSbyAs1−y (0 0 1) semiconductors using high-resolution transmission electron microscopy (HRTEM) and synchrotron X-ray diffraction (XRD). These techniques provide high spatial and high reciprocal space resolution information about Al lattice orientations and interfacial structure, highlighting the existence of a strong correlation between the surface lattice parameter of the semiconductor and the normal orientation of the aluminum film. The normal orientation of Al layers is found to be [1 1 1] when the in-plane semiconductor surface lattice parameter, aS, is smaller than 5.98 A, and is [1 1 0] when aS is larger than this value. In the transition between these lattice parameters where one orientation is preferred, both orientations may be observed. Concomitant with the change in normal orientation is an inversion in the strain state of the aluminum film. When the normal orientation is [1 1 1], the Al film is compressively strained; while for [1 1 0] normal orientations, the Al in-plane strain is tensile. An energy balance model, accounting for surface, interfacial, side-face, and strain energy, and the registry of ( 1 1 1 ¯ ) lattice planes across the semiconductor/aluminum interface provide explanations for the observed normal orientation and strain inversion.

Strong Negative Thermal Expansion in a Low-Cost and Facile Oxide of Cu2P2O7.

Negative thermal expansion (NTE) behaviors have been observed in various types of compounds. The achievement in the merits of promising low-cost and facile NTE oxides remains challenging. In the present work, a simple and low-cost Cu2P2O7 has been found to exhibit the strongest NTE among the oxides (αV ∼ -27.69 × 10-6 K-1, 5-375 K). The complex NTE mechanism has been investigated by the combined methods of high-resolution synchrotron X-ray diffraction, neutron powder diffraction, X-ray pair distribution function, extended X-ray absorption fine structure spectroscopy, and density functional theory calculations. Interesting, the direct experimental evidence reveals that the coupling twist and rotation of PO4 and CuO5 polyhedra are the inherent factors for the NTE nature of Cu2P2O7, which is triggered by the transverse vibrations of oxygen atoms. The present new NTE material of Cu2P2O7 also has been verified for the practical application.

Anomalous thermal expansion in ErFe11.4Nb0.6

The thermal expansion properties of the rare earth transition metal compound ErFe11.4Nb0.6 (Curie temperature Tc = 520(10) K) have been investigated in detail by variable temperature high resolution synchrotron x-ray diffraction measurements over the temperature range 300 K–640 K. The findings from the Rietveld analyses reveal significant anomalies in the thermal expansion of ErFe11.4Nb0.6 below the Curie temperature with negative thermal expansion also evident around Tc = 520(10) K. The structural changes that occur around the Curie temperature lead to a spontaneous volume magnetostriction of ∼6.3 × 10−3 at 300 K. The minimum values of the linear thermal expansion coefficients αa and αc for ErFe11.4Nb0.6 around TC are determined to be −3.56 × 10−6 K−1 and -1.30 × 10−6 K−1 respectively. Details of the structural features of ErFe11.4Nb0.6 (including Wigner-Seitz cell volumes and average bond lengths for Er atoms (2a site) and Fe atoms (8i, 8j, 8f sites) to neighbouring Fe atoms) that contribute to the thermal expansion behaviour have been investigated in detail. The persistence of finite magnetostriction values λa and λc (along the a-axis and the c-axis respectively) and volume magnetostriction ωs, above the magnetic transition temperature, indicates the likely occurrence of short-range magnetic correlations in this region.

Observation of the asphericity of 4f-electron density and its relation to the magnetic anisotropy axis in single-molecule magnets.

The distribution of electrons in the 4f orbitals of lanthanide ions is often assigned a crucial role in the design of single-molecule magnets, which maintain magnetization in zero external field. Optimal spatial complementarity between the 4f-electron density and the ligand field is key to maximizing magnetic anisotropy, which is an important factor in the ability of lanthanide complexes to display single-molecule magnet behaviour. Here we have experimentally determined the electron density distribution in two dysprosium molecular complexes by interpreting high-resolution synchrotron X-ray diffraction with a multipole model. The ground-state 4f-electron density is found to be an oblate ellipsoid, as is often deduced from a simplified Sievers model that assumes a pure |±15/2> ground-state doublet for the lanthanide ion. The large equatorial asymmetry-determined by a model wavefunction-was found to contain considerable MJ mixing of |±11/2> and only 81% of |±15/2>. The experimental molecular magnetic easy axes were recovered, and found to deviate by 13.1° and 8.7° from those obtained by ab initio calculations.

Antiferroelectric antiferromagnetic type-I multiferroic Cu9O2(SeO3)4Cl6

We report that $\mathrm{C}{\mathrm{u}}_{9}{\mathrm{O}}_{2}{(\mathrm{Se}{\mathrm{O}}_{3})}_{4}\mathrm{C}{\mathrm{l}}_{6}$ is a new multiferroic compound. Comprehensive studies of this compound have been carried out on single crystals as well as polycrystalline samples. Magnetic susceptibility $\ensuremath{\chi}$ and specific heat $C$ with $H\ensuremath{\parallel}c$ axis both reveal an anomaly at ${T}_{N}=37\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ associated with the long-range antiferromagnetic order. However, no signature of this phase transition is seen with the $H\ensuremath{\parallel}b$ axis, providing evidence of the anisotropic nature of its magnetic properties. The results of $\ensuremath{\chi}$ measurements are consistent with the temperature evolution of the intensity of magnetic reflections from the neutron diffraction experiments. The magnetic structure derived from neutron scattering measurements shows that half of the Cu(5) ions carry no moments. Furthermore, an anomaly in the dielectric constant near ${T}_{N}$ and observable magnetoelectric coupling below ${T}_{N}$ are found. At high temperatures, a dielectric peak at ${T}_{E}=267\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ is identified with no measurable spontaneous polarization below ${T}_{E}$, thereby suggesting an antiferroelectric order. A steplike anomaly seen in $\ensuremath{\chi}(T)$ at ${T}_{E}$ hints the weak spin-lattice coupling. Concomitantly, high-resolution temperature-dependent synchrotron x-ray diffraction experiments elucidate a local structural distortion at ${T}_{E}$.

Structural, electronic, magnetic, and transport properties of the equiatomic Ni-based quaternary Heusler alloys

This work reports on three quaternary Heusler alloys NiCuFeGa, NiCuMnGa, and NiFeMnGa. We have investigated the phase stabilities and ordering tendencies in these compositions through, first principle calculations followed by the study of structural, electronic, magnetic, and transport properties through experimental techniques. The crystal structure of all three compositions is characterized using high–resolution synchrotron X-ray diffraction (XRD). NiCuMnGa adopts a cubic LiPdMgSn–type crystal structure, while NiFeMnGa and NiCuFeGa form a mixed phase of tetragonal and cubic symmetry. Transport and magnetic properties have been measured as a function of temperature and magnetic field. The saturation magnetization at 5 K is 4.06 μB/f.u., 3.30 μB/f.u., and 2.42 μB/f.u. for NiCuMnGa, NiFeMnGa, and NiCuFeGa, respectively. All the compositions show typical metallic resistivity with a residual resistivity ratio of 1.32, 2.33, 3.99 for NiCuFeGa, NiCuMnGa, and NiFeMnGa, respectively. First-principles calculations suggest high degree of spin polarization in NiFeMnGa, which is reflected through the power law fittings carried out for its resistivity data. Also, the transition metals present strong ferromagnetic correlations between them, resulting in the Curie temperatures (TC) lying above room temperature in all three compositions.

Exotic magnetic behaviour and evidence of cluster glass and Griffiths like phase in Heusler alloys Fe2-xMnxCrAl (0\u2009\u2264\u2009x\u2009\u2264\u20091)

We present a detailed study of structural, magnetic and thermodynamic properties of a series of Heusler alloys Fe2-xMnxCrAl (x = 0, 0.25, 0.5, 0.75 and 1). Structural investigation of this series is carried out using high resolution synchrotron X-ray diffraction. Results suggest that with increasing Mn concentration, the L21 structure of Fe2CrAl is destabilized. The DC magnetization results show a decrement in paramagnetic (PM) to ferromagnetic (FM) phase transition temperature (TC) with increasing Mn concentration. From the systematic analysis of magnetic memory effect, heat capacity, time dependent magnetization, and DC field dependent AC susceptibility studies it is observed that, Fe2CrAl exhibits cluster glass(CG)-like transition approximately at 3.9 K (Tf2). The alloys, Fe1.75Mn0.25CrAl and Fe1.5Mn0.5CrAl exhibit double CG-like transitions near Tf1 ~ 22 K, Tf2 ~ 4.2 K and Tf1 ~ 30.4 K, Tf2 ~ 9.5 K respectively, however, in Fe1.25Mn0.75CrAl, a single CG-like transition is noted at Tf2 ~ 11.5 K below TC. Interestingly, FeMnCrAl shows the absence of long ranged magnetic ordering and this alloy undergoes three CG-like transitions at ~22 K (Tf*), 16.6 K (Tf1) and 11 K (Tf2). At high temperatures, a detailed analysis of temperature response of inverse DC susceptibility clearly reveals the observation of Griffiths phase (GP) above 300 K (T*) in Fe2CrAl and this phase persists with Mn concentration with a decrement in T*.

Influence of Tb on easy magnetization direction and magnetostriction of PrFe1.9 alloy**Project supported by the National Natural Science Foundation of China (Grant No. 51901052) and the Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2018GXNSFAA281294).

The crystal structures, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase Pr1 − xTbxFe1.9 compounds are investigated in a temperature range between 5 K and 300 K. High resolution synchrotron x-ray diffraction (XRD) analysis shows that different proportions of Tb in Pr1 − xTbxFe1.9 alloys can result in different easy magnetization directions (EMD) below 70 K, i.e., [100] with x = 0.0, and [111] with x ≥ 0.1. This indicates Tb substitution can lead the EMD to change from [100] to [111] with x rising from 0.0 up to 0.1. The Tb substitution for Pr reduces the saturation magnetization Ms and the magnetostriction to their minimum value when x = 0.6, but it can increase low-field (0 ≤ H ≤ 9 kOe, the unit 1 Oe = 79.5775 A · m−1) magnetostriction when x = 0.8 and 1.0 at 5 K. This can be attributed to the larger magnetostriction of PrFe1.9 than that of TbFe1.9, as well as the decrease of the resulting anisotropy due to Tb substitution at low temperatures.

Zn-Al LDH growth on AA2024 and zinc and their intercalation with chloride: Comparison of crystal structure and kinetics

The dissimilarities and features of the crystal structure of ZnAl LDH-NO3 conversion layers grown directly on pure zinc and aluminum alloy 2024 were investigated in the present paper. Although the nature of the cations in the double hydroxides are the same in both cases (Al3+ and Zn2+), their sources differ according to the substrate. This leads to a difference in the cationic layers and interlayer structure, which consequently influences the anionic exchange reaction. In the frame of this work, the kinetics of the anion-exchange of nitrate by chloride was investigated as well as the crystal structure of the resulting ZnAl LDH-Cl on both substrates. Synchrotron high-resolution X-ray diffraction was the main method to obtain structural information and was supported by additional calculations and scanning electron microscopy.The current study revealed noticeable changes on the positioning of the interlayer atoms for the ZnAl-LDH-Cl on zinc in comparison with the ones on AA2024 substrate.

Iodine Adsorption in a Redox-Active Metal-Organic Framework: Electrical Conductivity Induced by Host-Guest Charge-Transfer.

We report a comparative study of the binding of I2 (iodine) in a pair of redox-active metal–organic framework (MOF) materials, MFM-300(VIII) and its oxidized, deprotonated analogue, MFM-300(VIV). Adsorption of I2 in MFM-300(VIII) triggers a host-to-guest charge-transfer, accompanied by a partial (∼30%) oxidation of the VIII centers in the host framework and formation of I3– species residing in the MOF channels. Importantly, this charge-transfer induces a significant enhancement in the electrical conductivity (Δσ = 700000) of I2@MFM-300(VIII/IV) in comparison to MFM-300(VIII). In contrast, no host–guest charge-transfer or apparent change in the conductivity was observed upon adsorption of I2 in MFM-300(VIV). High-resolution synchrotron X-ray diffraction of I2@MFM-300(VIII/IV) confirms the first example of self-aggregation of adsorbed iodine species (I2 and I3–) into infinite helical chains within a MOF.

Tunnel structure of tetragonal tungsten bronzes BaTa2O6, Ba0.8Ta2O5.8, and Ba0.5Ta2O5.5 studied using synchrotron X-ray and neutron diffraction

The complex oxide system of Ba-Ta-O presents interesting cases of tetragonal tungsten bronze (TTB) phases being formed over a wide compositional range of Ba1−xTa2O6−x, 0 ≤ x ≤ 0.65 [X. Kuang et al., Inorg. Chem., 2013, 52, 13244−13252]. Compared to the common formalism of the TTB phase AB2O6, Ba1−xTa2O6−x is highly off stoichiometric and is presumed to involve substantial structural modifications. In this study, Ba1−xTa2O6−x samples were prepared with the chemical compositions of BaTa2O6 (x = 0), Ba0.8Ta2O5.8 (x = 0.2), and Ba0.5Ta2O5.5 (x = 0.5). Rietveld refinement and Fourier electron density calculation, using high-resolution synchrotron X-ray diffraction data, revealed that the above three compositions have distinct local structural features, and the irregularity escalates with the increase of x. In all the three compositions, the Ba position inside the pentagonal tunnel (A2 site) was lightly split, reflecting the oversize polyhedral cavity. Additionally, Ba0.8Ta2O5.8 and Ba0.5Ta2O5.5 contained segments of (TaO)3+ chains in the pentagonal tunnel and Ta5+ in the triangular tunnel (A3 site). Hence, the unit cell structure of BaTa2O6, Ba0.8Ta2O5.8, and Ba0.5Ta2O5.5 can be represented as Ba5[Ta10O30], Ba4.26(TaO)0.04Ta0.22[Ta10O30], and Ba2.84(TaO)1.19Ta0.18[Ta10O30], respectively. Dielectric constants (κ) of Ba1−xTa2O6−x were measured in the temperature range of 30–450 K and at frequencies of 100 kHz−1 MHz. Compared to BaTa2O6, which displayed high κ (≈100 at 300 K) and broad relaxation peaks below 50 K, Ba0.8Ta2O5.8 and Ba0.5Ta2O5.5 exhibited markedly reduced lattice polarizations.

Evidence for pressure-induced polarization rotation, octahedral tilting, and reentrant ferroelectric phase in tetragonal (Pb0.5Bi0.5)(Ti0.5Fe0.5)O3

Despite the technological significance of the tetragonal PbTiO3 for the piezoelectric transducer industry, its high pressure behaviour is quite controversial as two entirely different scenarios, involving pressure induced (1) morphotropic phase boundary (MPB) like structural transition with concomitant rotation of the ferroelectric polarization vector and (2) antiferrodistortive (AFD) phase transition followed by emergence of a reentrant ferroelectric phase, have been proposed in recent theoretical and experimental studies. We have attempted to address these controversies through a high resolution synchrotron x-ray diffraction study of pressure induced phase transitions in the tetragonal phase of a modified PbTiO3 composition containing 50% BiFeO3, where BiFeO3 was added to enhance the AFD instability of PbTiO3. We present here the first experimental evidence for the presence of the characteristic superlattice reflections due to an AFD transition at a moderate pressure pc1 ~2.15 GPa in broad agreement with scenario (2), but the high pressure ferroelectric phase belongs to the monoclinic space group Cc, and not the tetragonal space group I4cm predicted under scenario (2), which permits the rotation of the ferroelectric polarization vector as per scenario (1). We show that the monoclinic distortion angle and ferroelectric polarization of the Cc phase initially decrease with increasing pressure for p < 7 GPa, but start increasing above pc2 ~ 7 GPa due to an isostructural Cc-I to Cc-II transition reminiscent of MA(apc > bpc ~ cpc) to MB(apc< bpc ~ cpc) transition predicted for MPB systems. We also show that octahedral tilting provides an efficient mechanism for accommodating pressure induced volume reduction for the stabilisation of the reentrant ferroelectric phase Cc-II.

Stabilization of the pyrochlore phase of Mn2Sb2O7 by double substitution

Polycrystalline samples of (Ce4+Mn2+3)(Ga3+Sb5+3)O14 were synthesized by a high-temperature solid-state reaction. In contrast with the parent Mn2Sb2O7 compound that adopts a rhombohedral or monoclinic structure at T > 600 °C, the pyrochlore structure of CeMn3GaSb3O14 is retained up to at least T = 1070°C. High-resolution synchrotron x-ray diffraction measurements show no sign of a superstructure or distortion from cubic symmetry in the substituted compound. The stabilization of the pyrochlore structure can be attributed to the effect of configurational disorder due to partial substitution of A and B site. Magnetization and heat capacity data suggest a spin-glass transition below T ≈ 2 K. Our results extends the range of available pyrochlore oxides, and demonstrate that entropic stabilization is a viable route to stabilize novel materials with complex structure types.

Protein/Ice Interaction: High-Resolution Synchrotron X-ray Diffraction Differentiates Pharmaceutical Proteins from Lysozyme.

Protein/ice interactions are investigated by a novel method based on measuring the characteristic features of X-ray diffraction (XRD) patterns of hexagonal ice (Ih). Aqueous solutions of four proteins and other solutes are studied using high-resolution synchrotron XRD. Two pharmaceutical proteins, recombinant human albumin and monoclonal antibody (both at 100 mg/mL), have a pronounced effect on the properties of ice crystals, reducing the size of the Ih crystalline domains and increasing the microstrain. Lysozyme (100 mg/mL) and an antifreeze protein (1 mg/mL) have much weaker impact on Ih. Neither of the proteins studied exhibit preferred interactions with specific crystalline faces of Ih. It is proposed that the pharmaceutical proteins interact with ice crystals indirectly by accumulating in the quasi-liquid layer next to ice crystallization front, rather than directly, via a sorption on ice crystals. This is the first report, to the best of our knowledge, of major difference in the protein/ice interaction between non-antifreeze proteins. Another important finding is a detection of a second (minor) population of ice crystals, which is tentatively identified as a high-pressure form of ice, possibly IceIII or IceIX. This finding highlights a potential role of mechanical stresses in freeze-induced destabilization of proteins.

Variation of elastic mechanical properties with texture, porosity, and defect characteristics in laser powder bed fusion 316L stainless steel

Elastic mechanical properties of 316 L stainless steel samples fabricated using laser powder bed fusion were studied non-destructively through resonant ultrasound spectroscopy. Samples in five different conditions were obtained by varying the laser power from 103 W (the highest density condition) to 68 W (the lowest density condition) at constant laser speed, producing samples with a volume energy density in the 24.5–16.5 J/mm3 range and volumetric porosity in the 0.1–10% range. The observed elastic mechanical properties are discussed taking into consideration the bulk texture developed and quantitative pore characteristics studied using high-energy high-resolution synchrotron X-ray diffraction and X-ray computed micro-tomography, respectively. Furthermore, empirical exponential relationships are provided to express the functional dependence of Young's and shear moduli with porosity.