$$\hbox {NO}_{2}^{-}$$ and $$\hbox {SCN}^{-}$$SCN--intercalated layered double hydroxides: structure and orientation of anions in the interlayer gallery

\(\hbox {NO}_{2}^{-}\) and \(\hbox {SCN}^{-}\) are two common small inorganic anions. The former is a common industrial pollutant. The latter is linear and is a good mimic for the toxic \(\hbox {CN}^{-}\) ion. The structures of these two anions are refined within the gallery of the [Zn–Al]-layered double hydroxide (LDH). Both LDHs crystallize as mixed anion phases. The nitrite is found to co-exist with the nitrate ion. The nitrite ion is intercalated with its molecular plane inclined to the metal hydroxide layer. In the case of the \(\hbox {SCN}^{-}\) intercalated LDH, no other anion was detected by ion chromatography, suggesting that the \(\hbox {SCN}^{-}\) deficiency is compensated by intercalated hydroxyl ions. In this case, the \(\hbox {SCN}^{-}\) ion is found to be intercalated with its molecular axis inclined to the metal hydroxide layer.     

Thermo-transport properties of Zn-substituted layered Li-nickel oxide, $$\hbox {LiNiO}_{2}$$

The layered Li-TM-\(\hbox {O}_{2}\) materials have been investigated extensively due to their application as cathodes in Li batteries. The electrical properties of these oxides can be tuned or controlled either by non-stoichiometry or substitution. Hence the thermo-transport properties of Zn-substituted \(\hbox {LiNi}_{1-x}\hbox {Zn}_{x}\hbox {O}_{2}\) for \(0 \le x \le 0.16\) have been investigated in the temperature range of 300–900 K for potential application as a high-temperature thermoelectric material. For \(x < 0.08\), the compounds were of single phase belonging to the space group R-3mH while for \(x > 0.08\) an additional minority phase, ZnO forms together with the main layered phase. All the compounds exhibit a semiconducting behaviour with electrical resistivity, varying in the range of  \(\sim 10^{-4}\) to \(10^{-2}\,\,\Omega \hbox {m}\) between 300 and 900 K. The electrical resistivity is found to increase with increasing Zn-substitution predominantly due to a decrease in the charge carrier hole mobility. The activation energy remains constant, \(\sim \)10  meV, with Zn-substitution. The Seebeck coefficient of the compounds is found to decrease with increasing temperature and increase with increasing Zn-substitution. The Seebeck coefficient decreases from \(\sim \)95 to \(35\ \upmu \hbox {V K}^{-1}\) and the corresponding power factor is \(\sim \)12\(\ \upmu \hbox {W m}^{-1}\ {\hbox {K}}^{-2}\) for the \(x = 0.16\) compound.     

Synthesis and Characterization of Nb Substitution on (Bi-Pb)-2223 Superconductors

In this study, samples of \(\hbox {Bi}_{1.65}\hbox {Pb}_{{ 0.35-x}}\hbox {Nb}_{{ x}}\hbox {Sr}_{2}\hbox {Ca}_{2}\hbox {Cu}_{3}\hbox {O}_{10+\delta }\) were prepared by solid-state reaction method and the effect of Nb substitution for Pb on the structural and superconducting properties of this material was investigated. The room-temperature X-ray diffraction patterns indicated that all the samples have the dominant phase of high-\({T}_{\mathrm{c}}\) (Bi-2223). However, other phases such as Bi-2212 and some impurity phases like \(\hbox {SrCu}_{2}\hbox {O}_{2}\), \(\hbox {CuNb}_{2}\hbox {O}_{6}\), \(\hbox {CaCuO}_{3}\) and CuO were also obtained from XRD patterns. An increasing amount of \(\hbox {Nb}^{+5}\) substitutions for \(\hbox {Pb}^{+2}\) led to a phase transition from Bi-2223 to Bi-2212. Electrical resistivity and magnetic measurements revealed that the critical temperature and the critical current density decreases with increasing Nb content due to the enhancement of Bi-2212 phase and appearance of impurities. SEM images indicated that samples porosity changes due to the disrupted grain growth with the substitution of Pb ions with Nb ions.     

Enhanced infrared transmission characteristics of microwave-sintered $$\hbox {Y}_{2}\hbox {O}_{3}$$–$$\hbox {MgO}$$MgO nanocomposite

Infrared (IR) transparent ceramics are found to have applications in demanding defence and space missions. In this work, \(\hbox {Y}_{2}\hbox {O}_{3}\)–\(\hbox {MgO}\) nanocomposites were synthesised by a modified single-step combustion technique. The characterisation of the as-prepared powder by X-ray diffraction and transmission electron microscopy revealed the presence of cubic phases of ultra-fine nanostructured \(\hbox {Y}_{2}\hbox {O}_{3 }\) and MgO, with an average crystallite size of \({\sim }19 \hbox { nm}\). For the first time the resistive and microwave heatings were effectively coupled for sintering the sample, and it was found that the sintering temperature and soaking time were reduced considerably. The pellets were sintered to 99.2% of the theoretical density at \(1430{^{\circ }}\hbox {C}\) for a soaking duration of 20 min. The well-sintered pellets with an average grain size of \({\sim }200 \hbox { nm}\) showed better transmittance properties relative to pure yttria. The promising percentage transmission of 80% in the UV–visible region and 82% in the mid-IR region shown by \(\hbox {Y}_{2}\hbox {O}_{3}\)–\(\hbox {MgO}\) nanocomposites can be tailored and made cost-effective to fabricate high-quality IR windows for strategic defence and space missions.     

A comparative study on dielectric behaviours of Au/(Zn-doped PVA)/<Emphasis Type="Italic">n</Emphasis>-4H-SiC (MPS) structures with different interlayer thicknesses using impedance spectroscopy methods

Three different thicknesses (50, 150 and 500 nm) Zn-doped polyvinyl alcohol (PVA) was deposited on n-4H-SiC wafer as interlayer by electrospinning method and so, Au/(Zn-doped PVA)/n-4H-SiC metal–polymer–semiconductor structures were fabricated. The thickness effect of Zn-doped PVA on the dielectric constant (\(\varepsilon ^{\prime }\)), dielectric loss (\(\varepsilon ^{{\prime }{\prime }}\)), loss-tangent (tan \(\delta \)), real and imaginary parts of electric modulus (\(M^{\prime }\) and \(M^{{\prime }{\prime }})\) and ac electrical conductivity \((\sigma _{\mathrm{ac}})\) of them were analysed and compared using experimental capacitance (C) and conductance (\(G/\omega \)) data in the frequency range of 1–500 kHz at room temperature. According to these results, the values of \(\varepsilon ^{\prime }\) and \(\varepsilon ^{{\prime }{\prime }}\) decrease with increasing frequency almost exponentially, \(\sigma _{\mathrm{ac}}\) increases especially, at high frequencies. The \(M^{\prime }\) and \(M^{{\prime }{\prime }}\) values were obtained from the \(\varepsilon ^{\prime }\) and \(\varepsilon ^{{\prime }{\prime }}\) data and the \(M^{\prime }\) and \(M^{{\prime }{\prime }}\) vs. f plots were drawn for these structures. While the values of \(\varepsilon ^{\prime }\), \(\varepsilon ^{{\prime }{\prime }}\) and tan \(\delta \) increase with increasing interlayer thickness, the values of \(M^{\prime }\) and \(M^{{\prime }{\prime }}\) decrease with increasing interlayer thickness. The double logarithmic \(\sigma _{\mathrm{ac}}\) vs. f plots for each structure have two distinct linear regimes with different slopes, which correspond to low and high frequencies, respectively, and it is prominent that there exist two different conduction mechanisms. Obtained results were found as a strong function of frequency and interlayer thickness.     

Exfoliated $$\hbox {WS}_{2}$$ nanosheets: optical,photocatalytic and nitrogen-adsorption/desorption characteristics

In this work, we report on structural, optical, photocatalytic and nitrogen adsorption–desorption characteristics of \(\hbox {WS}_{2 }\) nanosheets developed via a hydrothermal route. X-ray diffraction (XRD) studies have revealed a hexagonal crystal structure, whereas nanodimensional sheets are apparently observed in scanning and transmission electron microscopy (SEM and TEM) micrographs. As compared to the bulk counterpart, the \(\hbox {WS}_{2}\) nanosheets exhibited a clear blue shift. Through Brunauer–Emmett–Teller (BET) surface area analysis, average surface area, pore volume and pore size of the NSs were calculated as 211.5 \(\hbox {m}^{2}~\hbox {g}^{-1}\), 0.433 cc \(\hbox {g}^{-1}\) and 3.8 nm, respectively. The photocatalytic activity of the \(\hbox {WS}_{2}\) nanosheets was also examined with malachite green (MG) as the target dye under both UV and day light (visible) illumination conditions. Accordingly, a degradation efficiency as high as 67.4 and 86.6% were witnessed for an irradiation time duration of 60 min. The nano-\(\hbox {WS}_{2}\) systems have immense potential in optoelectronics, solid-lubrication and other next generation elements.     

Predicting $$\hbox {CO}_{2}$$ Solubility in Imidazole Ionic Liquids for Use in Absorption Refrigeration Systems by Using the Group Contribution Equation of State Method

Traditional absorption refrigeration such as \(\hbox {H}_{2}\hbox {O}\)–LiBr- and \(\hbox {NH}_{3}\)–\(\hbox {H}_{2}\hbox {O}\)-based refrigeration has limited applications because of several issues, including crystallization, corrosion, and large volume. \(\hbox {CO}_{2}\)–ionic liquids (ILs) as new absorption working pairs were investigated in this study. The objective was to use the group contribution equation of state (GC-EOS) method to predict the solubilities of binary systems containing high-pressure \(\hbox {CO}_{2}\)–imidazole bis(trifluoromethanesulfonimide) ILs and to investigate the applicability and accuracy of the GC-EOS model. The results showed that at pressures up to 11.0 MPa and temperatures of 273 K to 400 K, the \(\hbox {CO}_{2}\) solubility in the ILs increased with increasing system pressure but decreased with increasing temperature, and its variation rate was lower at higher pressures or temperatures. Also, \(\hbox {CO}_{2}\) solubility increased in the order of [emim][\(\hbox {Tf}_{2}\hbox {N}\)] < [bmim][\(\hbox {Tf}_{2}\hbox {N}\)] < [hmim][\(\hbox {Tf}_{2}\hbox {N}\)] < [omim][\(\hbox {Tf}_{2}\hbox {N}\)], indicating that longer alkyl chains of identical IL families resulted in higher \(\hbox {CO}_{2 }\) solubility. The model prediction of \(\hbox {CO}_{2}\) solubility in the four different ILs showed reasonable consistency with the corresponding experimental results from the literature; the largest deviation was 5.7 % for \(\hbox {CO}_{2}\)-[emim][\(\hbox {Tf}_{2}\hbox {N}\)]. Therefore, it can be concluded that the GC-EOS model is a promising theoretical solution that can be used to search for suitable \(\hbox {CO}_{2}\)–IL working pairs for absorption refrigeration systems.     

The Influence of Impurities on the Zinc Fixed Point

Impurities are considered to be the most significant source of uncertainty for the realization of the International Temperature Scale of 1990 by means of metal fixed points. The determination and further reduction in this uncertainty require a traceable chemical analysis of dissolved impurities in the fixed-point metal and accurate knowledge of the specific temperature change caused by impurities (slope of the liquidus line). We determined the slope of the liquidus line for three binary systems and present results and conclusions from the chemical analysis of zinc with a nominal purity of 7N. For the Fe–Zn system, we determined a liquidus slope of (\(-0.91\pm 0.14\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) from the evaluation of freezing plateaus and (\(-0.76~\pm 0.20\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) from the evaluation of melting plateaus; for the Pb–Zn system, the corresponding results are (\(-0.27~\pm 0.05\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) and (\(-0.26~\pm 0.05\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)). Although for the Sb–Zn system, we determined a liquidus slope of about \(-0.8\) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)), our investigations showed that a correction of the influence of antimony is highly questionable because antimony can be found in zinc in a fully dissolved state or precipitated as an insoluble compound. Iron is the only impurity where a correction of the fixed-point temperature was possible. For the realization of the zinc fixed point at PTB, this correction is between 2 \(\upmu \)K and 16 \(\upmu \)K depending on the batch of zinc used. The influence of the sum of all impurities was estimated by means of the OME method. The resulting uncertainty contribution is between 12 \({\upmu }\hbox {K}\) and 48 \({\upmu }\hbox {K}\).     

Synthesis,characterization and catalytic application of Ni catalysts supported on alumina–zirconia mixed oxides

Alumina and alumina–zirconia mixed oxides were compared as supports to prepare nickel catalysts. The oxides were prepared by the sol–gel method using aluminum tri-sec-butoxide and zirconium (IV) propoxide as precursors, and its physicochemical properties were determined by BET, TGA, DTA, XRD, SEM and TEM. The catalysts of nickel were obtained by the impregnation of the supports with nickel nitrate (10 wt%) and were heat-treated at \(700{^{\circ }}\hbox {C}\). The specific area of the supports and catalysts decreased with the increase in the zirconia content in agreement with the crystalline phase formed. TEM micrographs of nickel catalysts revealed particles in the size range of 10–30 nm. The \(\hbox {Ni/Al}_{2}\hbox {O}_{3}\)–\(\hbox {ZrO}_{2}\) catalysts were tested in the steam reforming reaction of ethanol (SRE) at \(500{^{\circ }}\hbox {C}\), and the obtained results suggest that the differences in catalytic activities depended on the content of \(\hbox {ZrO}_{2}\). The selectivity towards \(\hbox {H}_{2}\) was \({\sim }56\%\) for the named catalyst Ni–Al–0.25Zr.     

Synthesis,characterization and electrochemical performance of $$\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}$$ cathode materials for lithium ion batteries

\(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) (\(x = 0\), 0.2, 0.4, 0.6, 0.8 and 1) samples were prepared by a sol–gel process. The crystal structure of prepared samples of \(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) was characterized using an X-ray diffractometer. Different crystallographic parameters such as crystallite size and lattice cell parameters have been calculated. Scanning electron microscopy and Fourier transform infrared spectroscopy investigations were carried out, which reveal the morphology and function groups of the synthesized samples. Furthermore, electrochemical impedance spectra measurements are performed. The obtained results indicated that the highest conductivity is achieved for the \(\hbox {Li}_{2}\hbox {Ni}_{0.4}\hbox {Fe}_{0.6}\hbox {SiO}_{4}\) electrode compound. It was observed that Li–\(\hbox {Li}_{2}\hbox {Ni}_{0.4}\hbox {Fe}_{0.6}\hbox {SiO}_{4}\) battery has initial discharge capacity of 164 mAh \(\hbox {g}^{-1}\) at 0.1C rate. The cycle life performance of all \(\hbox {Li}_{2}\hbox {Ni}_{x}\hbox {Fe}_{1-x}\hbox {SiO}_{4}\) batteries ranged between 100 and 156 mAh \(\hbox {g}^{-1}\) with coulombic efficiency range between 70.9 and 93.9%.     

Chemical synthesis and characterization of nano-sized rare-earth ruthenium pyrochlore compounds $$\hbox {Ln}_{2}\hbox {Ru}_{2}\hbox {O}_{7}$$ (Ln = rare earth)

The rare-earth ruthenium pyrochlores \(\hbox {Ln}_{2}\hbox {Ru}_{2}\hbox {O}_{7}\) (\(\hbox {Ln} = \hbox {La}^{3+}\), \(\hbox {Pr}^{3+}\), \(\hbox {Nd}^{3+}\), \(\hbox {Sm}^{3+}\) and \(\hbox {Gd}^{3+}\)) have been synthesized by the tartrate co-precipitation method, which allowed control of their composition and morphology. The preparation processes were monitored by thermal studies (TG-DTA). The obtained ruthenates were characterized by X-ray diffraction (XRD), TEM, d.c. electrical conductivity, thermoelectric power and dielectric constant measurements. X-ray diffraction patterns for all pyrochlore samples indicate a single-phase crystalline material with a cubic structure except for \(\hbox {LaRuO}_{3}\), which shows perovskite orthorhombic structure. The structural parameter for the solid obtained was successfully determined by Rietveld refinement based on the analysis of powder XRD pattern. The TEM photographs of these compounds exhibited the average particle size in the range of 36.4–73.8 nm. The data on the temperature variation of d.c. electrical conductivity showed that all rare-earth ruthanates are semiconductors and major carriers are electrons. The conduction mechanism of these compounds seems to be oxygen non-stoichiometry. The variation of dielectric constant at various frequencies showed initially interfacial polarization up to 275 kHz and beyond, which shows domain wall motion.     

Structural and physical properties of $$\hbox {Sm}^{3+}$$ doped magnesium zinc sulfophosphate glass

Samarium (\(\hbox {Sm}^{3+})\) doped magnesium zinc sulfophosphate glass system of composition (60–\(x)\hbox {P}_{2}\hbox {O}_{5}\)–20MgO–20ZnSO\(_{4}\)–\(x\hbox {Sm}_{2}\hbox {O}_{3}\) (\(x =\) 0.0, 0.5, 1.0, 1.5 and 2.0 mol%) were synthesized using melt-quenching technique. The structure and physical properties of prepared glass samples were characterized. The X-ray diffraction pattern verified their amorphous nature. The physical properties such as density, refractive index, molar volume, rare earth ion concentration, etc. were calculated. The decrease in the optical bandgap energy with increasing \(\hbox {Sm}_{2}\hbox {O}_{3}\) contents was attributed to the alteration in the glass network structures. Fourier transformed infrared spectra and Raman analyses manifested the depolymerization of \(\hbox {ZnSO}_{4}\) in the phosphate host matrix. The present findings may be beneficial for the advancement of functional glasses.     

Thermal Conductivity of Pyroclastic Soil (<Emphasis Type="BoldItalic">Pozzolana</Emphasis>) from the Environs of Rome

The paper reveals the experimental procedure and thermo-physical characteristics of a coarse pyroclastic soil (Pozzolana), from the neighborhoods of Rome, Italy. The tested samples are comprised of 70.7 % sand, 25.9 % silt, and 3.4 % clay. Their mineral composition contained 38 % pyroxene, 33 % analcime, 20 % leucite, 6 % illite/muscovite, 3 % magnetite, and no quartz content was noted. The effective thermal conductivity of minerals was assessed to be about \(2.14\,\hbox {W}{\cdot } \hbox {m}^{-1}{\cdot } \hbox {K}^{-1}\). A transient thermal probe method was applied to measure the thermal conductivity (\(\lambda \)) over a full range of the degree of saturation \((S_{\mathrm{r}})\), at two porosities (n) of 0.44 and 0.50, and at room temperature of about \(25\,^{\circ }\hbox {C}\). The \(\lambda \) data obtained were consistent between tests and showed an increasing trend with increasing \(S_{\mathrm{r}}\) and decreasing n. At full saturation (\(S_{\mathrm{r}}=1\)), a nearly quintuple \(\lambda \) increase was observed with respect to full dryness (\(S_{\mathrm{r}}=0\)). In general, the measured data closely followed the natural trend of \(\lambda \) versus \(S_{\mathrm{r}}\) exhibited by published data at room temperature for other unsaturated soils and sands. The measured \(\lambda \) data had an average root-mean-squared error (RMSE) of \(0.007\,\hbox {W}{\cdot } \hbox {m}^{-1}{\cdot } \hbox {K}^{-1}\) and \(0.008\,\hbox {W}{\cdot } \hbox {m}^{-1}{\cdot } \hbox {K}^{-1}\) for n of 0.50 and 0.44, respectively, as well as an average relative standard deviation of the mean at the 95 % confidence level \((\hbox {RSDM}_{0.95})\) of 2.21 % and 2.72  % for n of 0.50 and 0.44, respectively.     

Structural,dielectric and piezoelectric study of Ca-, Zr-modified $$\hbox {BaTiO}_{3}$$ lead-free ceramics

We prepared a lead-free ceramic (\(\hbox {Ba}_{0.85}\hbox {Ca}_{0.15})(\hbox {Ti}_{1-x}\hbox {Zr}_{x})\hbox {O}_{3}\) (BCTZ) using the conventional mixed oxide technique. The samples were prepared by an ordinary mixing and sintering technique. In this study we investigated how small amounts of \(\hbox {Zr}^{4+}\) can affect the crystal structure and microstructure as well as dielectric and piezoelectric properties of \(\hbox {BaTiO}_{3}\). X-ray diffraction analysis results indicate that no secondary phase is formed in any of the BCTZ powders for \(0 \le x \le 0.1\), suggesting that \(\hbox {Zr}^{4+}\) diffuses into \(\hbox {BaTiO}_{3}\) lattices to form a solid solution. Scanning electron microscopy micrographs revealed that the average grain size gradually increased with \(\hbox {Zr}^{4+}\) content from 9.5 \(\upmu \!\hbox {m}\) for \(x = 0.02\) to 13.5 \(\upmu \!\hbox {m}\) for \(x = 0.1\); Curie temperature decreased due to the small tetragonality caused by \(\hbox {Zr}^{4+}\) addition. Owing to the polymorphic phase transition from orthorhombic to tetragonal phase around room temperature, it was found that the composition \(x = 0.09\) showed improved electrical properties and reached preferred values of \(d_{33} = 148\) pC \(\hbox {N}^{-1}\) and \(K_{\mathrm{p}} = 27\%\).     

Effect of annealing temperature and $$\hbox {CdCl}_{2}$$ treatment on the photo-conversion efficiency of $$\hbox {CdTe/Zn}_{0.1}$$CdTe/Zn0.1$$\hbox {Cd}_{0.9}$$Cd0.9S thin film solar cells

We report the effects of annealing in conjunction with \(\hbox {CdCl}_{2}\) treatment on the photovoltaic properties of \(\hbox {CdTe/Zn}_{0.1}\hbox {Cd}_{0.9}\)S thin film solar cells. CdTe layer is subjected to dry \(\hbox {CdCl}_{2}\) treatment by thermal evaporation method and subsequently, heat treated in air using a tube furnace from 400 to \(500{^{\circ }}\hbox {C}\). AFM and XRD results show improved grain size and crystallographic properties of the CdTe film with dry \(\hbox {CdCl}_{2}\) treatment. This recrystallization and grain growth of the CdTe layer upon \(\hbox {CdCl}_{2}\) treatment translates into improved photo-conversion efficiencies of \(\hbox {CdTe/Zn}_{0.1}\hbox {Cd}_{0.9}\)S cell. The results of dry \(\hbox {CdCl}_{2}\) treatment were compared with conventional wet \(\hbox {CdCl}_{2}\) treatment. Photo-conversion efficiency of 5.2% is achieved for dry \(\hbox {CdCl}_{2}\)-treated cells in comparison with 2.4% of wet-treated cell at heat treatment temperature of \(425{^{\circ }}\hbox {C}\).     

Constitutive modeling of polycarbonate over a wide range of strain rates and temperatures

The mechanical behavior of polycarbonate was experimentally investigated over a wide range of strain rates (\(10^{-4}\mbox{ to }5\times 10^{3}~\mbox{s}^{-1}\)) and temperatures (293 to 353 K). Compression tests under these conditions were performed using a SHIMADZU universal testing machine and a split Hopkinson pressure bar. Falling weight impact testing was carried out on an Instron Dynatup 9200 drop tower system. The rate- and temperature-dependent deformation behavior of polycarbonate was discussed in detail. Dynamic mechanical analysis (DMA) tests were utilized to observe the glass (\(\alpha \)) transition and the secondary (\(\beta \)) transition of polycarbonate. The DMA results indicate that the \(\alpha \) and \(\beta \) transitions have a dramatic influence on the mechanical behavior of polycarbonate. The decompose/shift/reconstruct (DSR) method was utilized to decompose the storage modulus into the \(\alpha \) and \(\beta \) components and extrapolate the entire modulus, the \(\alpha\)-component modulus and the \(\beta\)-component modulus. Based on three previous models, namely, Mulliken–Boyce, G’Sell–Jonas and DSGZ, an adiabatic model is proposed to predict the mechanical behavior of polycarbonate. The model considers the contributions of both the \(\alpha \) and \(\beta \) transitions to the mechanical behavior, and it has been implemented in ABAQUS/Explicit through a user material subroutine VUMAT. The model predictions are proven to essentially coincide with the experimental results during compression testing and falling weight impact testing.     

Photoacoustic Study on the Structural Variation of Titania Nanomaterials Using the Pr (III) Ion as a Spectral Probe

In this work, \(\hbox {Pr}^{3+}\)-doped titania nanomaterials were prepared by a sol–gel method. The structural variations of the samples during the phase transitions were studied by using the \(\hbox {Pr}^{3+}\) ion as a photoacoustic spectral probe. The result shows that for the gel sample heated at \(80\,^{\circ }\hbox {C}\), the coordination environment of \(\hbox {Pr}^{3+}\) is similar to that of its aqueous ion. The f–f transitions of \(\hbox {Pr}^{3+}\) exhibit a continuous red shift along with the gel-to-anatase transition, indicating an increase of the ‘degree of covalency’ for the \(\hbox {Pr}^{3+}\) bonding. For the sample calcined at \(1100\,^{\circ }\hbox {C}\), however, the f–f transitions of \(\hbox {Pr}^{3+}\) show obvious blue shift. This can be attributed to the segregation of \(\hbox {Pr}^{3+}\) ions to the external surface during the anatase-to-rutile transition, forming \(\hbox {Pr}_{4}\hbox {Ti}_{9}\hbox {O}_{24}\). The stabilization effect of the doped \(\hbox {Pr}^{3+ }\)ions on the anatase phase of the samples is also discussed.     

Synthesis and up-conversion emissions of $$\hbox {Yb}^{3+}{/}\hbox {Er}^{3+}$$, $$\hbox {Yb}^{3+}{/}\hbox {Tm}^{3+}$$Yb3+/Tm3+ and $$\hbox {Yb}^{3+}{/}\hbox {Tm}^{3+}{/}\hbox {Gd}^{3+}$$Yb3+/Tm3+/Gd3+ co-doped $$\hbox {KLu}_{2}\hbox {F}_{7}$$KLu2F7

\(\hbox {Yb}^{3+}/\hbox {Er}^{3+}\), \(\hbox {Yb}^{3+}/\hbox {Tm}^{3+}\), or \(\hbox {Yb}^{3+}/\hbox {Tm}^{3+}/\hbox {Gd}^{3+}\) co-doped \(\hbox {KLu}_{2}\hbox {F}_{7}\) up-conversion (UC) materials were synthesized through a hydrothermal method or an additive-assisted hydrothermal method. The X-ray diffraction (XRD) results suggested that the materials crystallized in orthorhombic phase, yet, the potassium citrate (CitK) introduction affected immensely the crystalline purity of final material. The field emission scanning electron microscopy (FE-SEM) results suggested that the additive adding had effects on size and morphology of the material, which affected the UC emissions further. Green/red UC emissions of \(\hbox {Er}^{3+}\), UV/blue/IR UC emissions of \(\hbox {Tm}^{3+}\), and UV UC emissions of \(\hbox {Gd}^{3+}\) were observed in the orthorhombic phase of \(\hbox {KLu}_{2}\hbox {F}_{7}\) materials. The excitation power-dependent UC emissions illustrated that the UC emission intensity initially increased, then decreased with the increase in excitation power. At the same time, the variation rates of different transitions in \(\hbox {Er}^{3+}\) or \(\hbox {Tm}^{3+}\) are also different. In addition, the \(\hbox {Er}^{3+}\) or \(\hbox {Tm}^{3+}\) concentration-dependent UC emission results suggested that the optimal doping concentration of \(\hbox {Er}^{3+}\) is 2 mol% and \(\hbox {Tm}^{3+}\) is 0.5 mol% with the \(\hbox {Yb}^{3+}\) concentration fixed as 20 mol%. The experimental results suggest that the orthorhombic phase of \(\hbox {KLu}_{2}\hbox {F}_{7}\) should be a good host lattice for UC emitters.     

Effect of Pressure on Deep-Ocean Thermometers

A laboratory experiment was devised and performed to investigate the pressure dependence of Sea-Bird Electronics SBE35 and SBE3 deep-ocean thermometers. The thermometers were mounted in a massive brass comparator together with a calibrated standard platinum resistance thermometer. The measurements were performed in a pressure chamber in the pressure range 0.1 MPa to 60 MPa. The results showed that both the investigated SBE35 and SBE3 thermometers are pressure dependent, with a pressure sensitivity of +41 \(\upmu \)K\(\cdot \)MPa\(^{-1}\) and \(-77\) \(\upmu \)K\(\cdot \)MPa\(^{-1}\), respectively. Nevertheless, the results obtained in only one individual device per model (one SBE35 and one SBE3) cannot be generalized and further investigations of a larger number of devices per model are needed.     

A facile approach for the synthesis of porous $$\hbox {KTiNbO}_{5}$$ catalyst with good activity for hydrogenation of p-nitrophenol

Through simple ions exchange and hydrothermal reaction, the porous structure of \(\hbox {MnO}_{2}\)-pillared \(\hbox {KTiNbO}_{5}\) composites were synthesized. The fabricated porous structure makes \(\hbox {KTiNbO}_{5}\) as good absorbance property for methylthionine chloride (MB). Furthermore, the as-synthesized porous \(\hbox {KTiNbO}_{5}\) can perform photocatalytic degradation of MB with good effectivity. What’s more, after loading Au nanoparticles into it, a novel catalyst for catalytic hydrogenation of p-nitrophenol was obtained. The possible ‘layer-by-layer quilt expose’ mode of \(\hbox {Au-MnO}_{2}\hbox {-KTiNbO}_{5}\) composites for catalytic hydrogenation of p-nitrophenol was proposed.