Diffuse Cluster Superparamagnetism in Inconel X750

Four different mixtures such as complex mixture A, [Co(H2O)4(HPO4)](C3H4N2)(H2O)2 ∙ 0.2 (C3H4N2), complex mixture B, [Co(H2O)6](H2PO4)(OH)(H2O) ∙(C3H4N2)2, mixture C, 0.34 Co(PO3)2∙0.15(C3H3N2Na), and complex mixture D, 0.03Co(PO3)2∙0.25(C3H3N2Na) ∙0.1 [Co(H2O)6]SO4.H2O∙0.6(C3H4N2), were synthesized using ortho-phosphoric acid and meta-phosphoric acid with cobalt sulfate heptahydrate and imidazole in ambient conditions. These mixtures have been well characterized by different thermo-analytical techniques. Differential Scanning Calorimetry (DSC) has been carried out at different heating rates such as 5, 10, 20, and 30 K min−1 at atmospheric conditions. The specific heat capacity was measured at low temperatures up to 173 K for mixture C at a rate of 10 K min−1. From the thermal analysis, it can be observed that the complex mixtures A and B prepared using phosphoric acid and mixture C prepared using meta-phosphoric acid behave as heat repellent material owing to their exothermic behavior at high temperature. The anomalous negative specific heat capacity exhibited by the mixtures is explained using partial molar quantities. Among all the four complex mixtures, the complex mixture A has been found to be the best heat repellent material. The complex mixture B can be used as heat storage material up to temperature ~550 K due to its endothermic behavior. These phosphate materials can be used for longer period of time due to their stability and insolubility in aqueous media. The heat can be extracted from any system that is coated with these phosphate mixtures using high conductivity copper rod.

We report magnetic susceptibility (chi) and heat capacity Cp measurements along with ab-initio electronic structure calculations on PbCuTe2O6, a compound made up of a three dimensional 3D network of corner-shared triangular units. The presence of antiferromagnetic interactions is inferred from a Curie-Weiss temperature (theta_CW) of about -22 K from the chi(T) data. The magnetic heat capacity (Cm) data show a broad maximum at T^max ~ 1.15 K (i.e. T^max/theta_CW ~ 0.05), which is analogous to the the observed broad maximum in the Cm/T data of a hyper-Kagome system, Na4Ir3O8. In addition, Cm data exhibit a weak kink at T^* ~ 0.87 K. While the T^max is nearly unchanged, the T^* is systematically suppressed in an increasing magnetic field (H) up to 80 kOe. For H > 80 kOe, the Cm data at low temperatures exhibit a characteristic power-law (T^{\alpha}) behavior with an exponent {\alpha} slightly less than 2. Hopping integrals obtained from the electronic structure calculations show the presence of strongly frustrated 3D spin interactions along with non-negligible unfrustrated couplings. Our results suggest that PbCuTe2O6 is a candidate material for realizing a 3D quantum spin liquid state at high magnetic fields.

The metallic compound EuCo2P2 with the body-centered tetragonal ThCr2Si2 structure containing Eu spins 7/2 was previously shown from single-crystal neutron diffraction measurements to exhibit a helical antiferromagnetic (AFM) structure below TN = 66.5 K with the helix axis along the c axis and with the ordered moments aligned within the ab-plane. Here we report crystallography, electrical resistivity, heat capacity, magnetization and magnetic susceptibility measurements on single crystals of this compound. We demonstrate that EuCo2P2 is a model molecular-field helical Heisenberg antiferromagnet from comparisons of the anisotropic magnetic susceptibility chi, high-field magnetization and magnetic heat capacity of EuCo2P2 single crystals at temperature T < TN with the predictions of our recent formulation of molecular field theory. Values of the Heisenberg exchange interactions between the Eu spins are derived from the data. The low-T magnetic heat capacity ~ T^3 arising from spin-wave excitations with no anisotropy gap is calculated and found to be comparable to the lattice heat capacity. The density of states at the Fermi energy of EuCo2P2 and the related compound BaCo2P2 are found from the heat capacity data to be large, 10 and 16 states/eV per formula unit for EuCo2P2 and BaCo2P2, respectively. These values are enhanced by a factor of ~2.5 above those found from DFT electronic structure calculations for the two compounds. The calculations also find ferromagnetic Eu-Eu exchange interactions within the ab-plane and AFM interactions between nearest- and next-nearest planes, in agreement with the MFT analysis of chi{ab}(T < TN).

Magnetic properties and magnetocaloric effect of a metallic triangular lattice antiferromagnetic DyAl2Ge2 single crystal

Microstructure and transformation of Al-containing nanostructured 316L stainless steel coatings processed using spark plasma sintering

The superhydrophobic surface was prepared by nanosecond laser on 304 stainless steel in this paper. After laser and low temperature heat treatment, the surface of stainless steel is transformed from hydrophilic to hydrophobic. The use of lauric acid in the heating process makes the surface of 304 stainless steel become superhydrophobic and self-cleaning, and the contact angle reaches upto 159.36°. The low temperature heat treatment accelerates the wettability transition process, and the use of organic matter significantly improves the hydrophobic performance. Self-cleaning stainless steel plate surface can be widely used in a variety of food machinery, convenient cleaning.

We have synthesized single crystals of Na$_3$Co$_2$SbO$_6$ and characterized the structure and magnetic order by measuring anisotropic magnetic properties, heat capacity, x-ray and neutron single crystal diffraction. Magnetic properties and specific heat of polycrystalline Na$_3$Co$_2$SbO$_6$ were also measured for comparison. Na$_3$Co$_2$SbO$_6$ crystallizes in a monoclinic structure (space group $C2/m$) with [Co$_2$SbO$_6$]$^{3-}$ layers separated by Na$^+$ ions. The temperature dependence of magnetic susceptibility shows significant anisotropic behavior in the whole temperature range 2\,K-350\,K investigated in this work. An effective moment of about 5.5\,$\mu_B$/Co$^{2+}$ from a Curie-Weiss fitting of the magnetic susceptibility is larger than the spin only value and signals significant orbital contribution. Na$_3$Co$_2$SbO$_6$ single crystal undergoes a transition into a long-range antiferromagnetically ordered state below $T_N$=5\,K. Neutron single crystal diffraction confirmed the zigzag magnetic structure with a propagation vector k\,=\,(0.5, 0.5, 0). The ordered moment is found to be 0.9\,$\mu_B$ at 4\,K and align along the crystallographic \textit{b}-axis. Density functional theory calculations suggest that the experimentally observed zigzag order is energetically competing with the Neel order. It is also found that the covalency between Co $d$ and O $p$ is quite strong and competes with the local spin-orbit coupling, suggesting a $J_{eff}$=1/2 ground state may not be realized in this compound.

The specific heat of Mn3−xFexSi was measured over a wide temperature range. Aside from the lattice and electronic specific heat components, another component had a significant contribution to the specific heat at low temperatures in the case of x = 0.2; however, its contribution decreased when x = 1.0. It is observed that the net component was retained at temperatures significantly higher than TN for both x. The XAFS spectra of the Mn K-edge for x = 0 not only indicated a smooth structure near the edge, but also an unusually small amplitude in the extended high energy region; however, these features disappeared with Fe doping. The specific heat and XAFS data were discussed in terms of the charge degree of freedom or electronic inhomogeneity.

A boltzon (low density) gas at reduced temperature must ultimately be described by quantum mechanics. The statistical mechanical treatment of such ensembles requires retention of summation forms to admit noncontinuum behavior. Anomalous specific heat is demonstrated with the prospect of multiple peaks for anisotropic energy surfaces. Moreover, a new equation of state arises which reflects the presence of a zero-point translational energy, requiring departure from the ideal gas law asT→0. It is also shown that passage from wave mechanical to kinetic theory of gases follows both simply and naturally via de Broglie’s relation.

Chapter 18 - Superconductivity

Drawability of stainless steel sheets

Comparative life cycle cost assessment of (lean) duplex stainless steel in wastewater treatment environments

The tetragonal Mo5PB2 compound was recently reported to show superconductivity with a critical temperature up to 9.2 K. In search of evidence for multiple superconducting gaps in Mo5PB2, comprehensive measurements, including magnetic susceptibility, electrical resistivity, heat capacity, and muon-spin rotation and relaxation measurements were carried out. Data from both low-temperature superfluid density and electronic specific heat suggest a nodeless superconducting ground state in Mo5PB2. Two superconducting energy gaps Δ0 = 1.02 meV (25%) and 1.49 meV (75%) are required to describe the low-T electronic specific-heat data. The multigap features are clearly evidenced by the field dependence of the electronic specific-heat coefficient and the Gaussian relaxation rate in the superconducting state (i.e., superfluid density), as well as by the temperature dependence of the upper critical field. By combining our extensive experimental results with numerical band-structure calculations, we provide compelling evidence of multigap superconductivity in Mo5PB2.

Magnetic properties of CoCl 2-intercalated graphite

An experimental program was conducted to determine the feasibility of reducing the chromium content in the widely used commercial Type 304 stainless steel and still maintain comparable corrosion resistance. Potentiodynamic anodic polarization characteristics in 1N H2SO4 and NaCl solutions were selected as the prime criteria to predict the corrosion resistance of the experimental alloys. Results showed that passivation deteriorated markedly upon removal of chromium from Type 304 stainless steel. Alloy substitutes of Mo and Si were effective in improving the passivation behavior of a stainless steel alloy with 12% Cr. Although Al led to further deterioration of corrosion properties when added to the 12% Cr alloy, an improvement in anodic polarization characteristics was noted when Al was combined with Mo. An optimized composition, austenitic alloy exhibited anodic polarization corrosion properties comparable to those of a commercial Type 304 stainless steel alloy. The optimized composition was 12Cr-10Ni-1.5Si-1 Al-2Mo (in Wt%), plus Mn and C at their normal levels. The experimental alloy provides the potential of conserving one-third the chromium used to produce Type 304 stainless steel and still maintains comparable anodic polarization characteristics.