Electrochemical impedance studies of capacity fading of electrodeposited ZnO conversion anodes in Li-ion battery

Electrodeposited ZnO coatings suffer severe capacity fading when used as conversion anodes in sealed Li cells. Capacity fading is attributed to (i) the large charge transfer resistance, \(R_{\mathrm{ct}}\) (300–700 \(\Omega \)) and (ii) the low \(\hbox {Li}^{+}\) ion diffusion coefficient, \(D_{\mathrm{Li}}^{+}\ (10^{-15}\) to \(10^{-13}\hbox { cm}^{2}\hbox { s}^{-1})\). The measured value of \(R_{\mathrm{ct}}\) is nearly 10 times higher and \(D_{\mathrm{Li}}^{+}\) 10–100 times lower than the corresponding values for \(\hbox {Cu}_{2}\hbox {O}\), which delivers a stable reversible capacity.     

Synthesis,structural and dielectric properties of 0.8PMN–0.2PT relaxor ferroelectric ceramic

A 0.8PMN–0.2PT solid-solution ceramic was synthesized by columbite processing technique. The effects of sintering temperature on the density, structure and microstructure and in turn on the dielectric properties were investigated. The ceramics sintered at and above 1050\(^{\circ }\hbox {C}\) resulted in single-phase perovskite formation. However, high density >90% is achieved only after 1170\(^{\circ }\hbox {C}\). Microstructural analysis revealed that grain size increases with increase in sintering temperature. A significant increase in the peak of dielectric permittivity only after 1150\(^{\circ }\hbox {C}\) owing to increase in density is noted in this study. The quadratic law applied to this ceramic demonstrates that the transition is diffused. The broadness in phase transition and lower dielectric relaxation obtained for the composition demonstrate that the ceramic exhibits characteristics of both relaxor and normal ferroelectrics. The ceramic of composition 0.8PMN–0.2PT exhibits excellent dielectric properties \(\varepsilon _{\mathrm{r}\text {-}\mathrm{max}} =\) 20294?27338 at 100 Hz with \(T_{\mathrm{c}} = 100\)–\(96^{\circ }\hbox {C}\) at low sintering temperature 1170–1180\(^{\circ }\hbox {C}\), respectively.     

Canadian Field Soils IV: Modeling Thermal Conductivity at Dryness and Saturation

The thermal conductivity data of 40 Canadian soils at dryness \((\lambda _{\mathrm{dry}})\) and at full saturation \((\lambda _{\mathrm{sat}})\) were used to verify 13 predictive models, i.e., four mechanistic, four semi-empirical and five empirical equations. The performance of each model, for \(\lambda _{\mathrm{dry}}\) and \(\lambda _{\mathrm{sat}}\), was evaluated using a standard deviation (SD) formula. Among the mechanistic models applied to dry soils, the closest \(\lambda _{\mathrm{dry}}\) estimates were obtained by MaxRTCM \((\textit{SD} = \pm ~0.018\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1})\), followed by de Vries and a series-parallel model (\(\hbox {S-}{\vert }{\vert }\)). Among the semi-empirical equations (deVries-ave, Advanced Geometric Mean Model (A-GMM), Chaudhary and Bhandari (C–B) and Chen’s equation), the closest \(\lambda _{\mathrm{dry}}\) estimates were obtained by the C–B model \((\pm ~0.022\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1})\). Among the empirical equations, the top \(\lambda _{\mathrm{dry}}\) estimates were given by CDry-40 \((\pm ~0.021\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1}\) and \(\pm ~0.018\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1}\) for18-coarse and 22-fine soils, respectively). In addition, \(\lambda _{\mathrm{dry}}\) and \(\lambda _{\mathrm{sat}}\) models were applied to the \(\lambda _{\mathrm{sat}}\) database of 21 other soils. From all the models tested, only the maxRTCM and the CDry-40 models provided the closest \(\lambda _{\mathrm{dry}}\) estimates for the 40 Canadian soils as well as the 21 soils. The best \(\lambda _{\mathrm{sat}}\) estimates for the 40-Canadian soils and the 21 soils were given by the A-GMM and the \(\hbox {S-}{\vert }{\vert }\) model.     

Small Multiple Fixed-Point Cell as Calibration Reference for a Dry Block Calibrator

A small multiple fixed-point cell (SMFPC) was designed to be used as in situ calibration reference of the internal temperature sensor of a dry block calibrator, which would allow its traceable calibration to the International Temperature Scale of 1990 (ITS-90) in the operating range of the block calibrator from \(70\,^{\circ }\hbox {C}\) to \(430\,^{\circ }\hbox {C}\). The ITS-90 knows in this temperature range, three fixed-point materials (FPM) indium, tin and zinc, with their respective fixed-point temperatures (\(\vartheta _\mathrm {FP}\)), In (\(\vartheta _\mathrm {FP}\,{=}\,156.5985\,^{\circ }\hbox {C}\)), Sn (\(\vartheta _\mathrm {FP}\,{=}\,231.928\,^{\circ }\hbox {C}\)) and Zn (\(\vartheta _\mathrm {FP}\,{=}\,419.527\,^{\circ }\hbox {C}\)). All of these FPM are contained in the SMFPC in a separate chamber, respectively. This paper shows the result of temperature measurements carried out in the cell within a period of 16 months. The test setup used here has thermal properties similar to the dry block calibrator. The aim was to verify the metrological properties and functionality of the SMFPC for the proposed application.     

Preparation,characterization of chitosan/bamboo charcoal/poly(methacrylate) composite beads

Preparation and characterization of a low-cost, novel steam-activated bamboo charcoal (BC) and poly(methacrylate) (PMAA) bound with chitosan (CTS) to form chitosan/bamboo charcoal/poly(methacrylate) (CTS/BC/PMAA) composite beads is reported for the first time in this paper. The characteristics are revealed by techniques such as X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Brunauer Emmett Teller (BET), solution pH and pH at point of zero charge \((\hbox {pH}_{\mathrm {pzc}})\). The composite beads possessed a dominant acidic surface group of 0.663 mmol \(\hbox {g}^{\mathrm {-1}}\), as revealed by Boehm titration method. This acidity was confirmed by its solution pH of 6.46; \(\hbox {pH}_{\mathrm {pzc}}\) of 6.70 and increase in oxygen surface via XPS analysis. \(\hbox {N}_{\mathrm {2}}\) adsorption–desorption isotherms at 77 K of the beads revealed high BET surface area (SA) of 681.15 \(\hbox {m}^{\mathrm {2}}\hbox {g}^{\mathrm {-1}}\). Langmuir model affords a SA of 773.34 \(\hbox {m}^{\mathrm {2}}\hbox {g}^{\mathrm {-1}}\). SEM showed the microporous nature of the composite beads. The properties of CTS/BC/PMAA composite beads were compared to CTS/BC and neat BC. Thermal stability and successful coating of 5.1 wt% of PMAA and 6.8 wt% of CTS to CTS/BC/PMAA beads were shown by DSC and TGA analyses. The composite beads showed low carbon particle released at pH 7.4 and 6.8. Furthermore, dynamic adsorption revealed that CTS/BC/PMAA composite beads can be used to capture a polar substance, such as creatinine.     

Electrical and Thermal Characteristics of the Insulator–Metal Transition in Crystalline $$\hbox {V}_{2}\hbox {O}_{5}$$ Films

The electrical and thermal properties with respect to the crystallization in \(\hbox {V}_{2}\hbox {O}_{5}\) thin films were investigated by measuring the resistance at different temperatures and applied voltages. The changes in the crystal structure of the films at different temperatures were also explored using Raman measurements. The thermal diffusivity of the crystalline \(\hbox {V}_{2}\hbox {O}_{5}\) film was measured by the nanosecond thermoreflectance method. The microstructures of amorphous and crystalline \(\hbox {V}_{2}\hbox {O}_{5}\) were observed by SEM and XRD measurements. The temperature-dependent Raman spectra revealed that a structural phase transition does not occur in the crystalline film. The resistance measurements of an amorphous film indicated semiconducting behavior, whereas the resistance of the crystalline film revealed a substantial change near \(250\,{^{\circ }}\hbox {C}\), and Ohmic behavior was observed above \(380\,{^{\circ }}\hbox {C}\). This result was due to the metal–insulator transition induced by lattice distortion in the crystalline film, for which \(T_{\mathrm{c}}\) was \(260\,{^{\circ }}\hbox {C}\). \(T_{\mathrm{c}}\) of the film decreased from 260 \({^{\circ }}\hbox {C}\) to \(230\,{^{\circ }}\hbox {C}\) with increasing applied voltage from 0 V to 10 V. Furthermore, the thermal diffusivity of the crystalline film was \(1.67\times 10^{-7}\,\hbox {m}^{2}\cdot \hbox {s}^{-1}\) according to the nanosecond thermoreflectance measurements.     

Effect of CTAB coating on structural,magnetic and peroxidase mimic activity of ferric oxide nanoparticles

In the present work, pristine and cetyl trimethyl ammonium bromide (CTAB)-coated ferric oxide nanoparticles \((\hbox {CTAB@Fe}_{2}\hbox {O}_{3} \hbox { NPs})\) were synthesized and studied as enzyme mimics. The w/w ratio of \(\hbox {Fe}_{2}\hbox {O}_{3}\) to CTAB was varied as 1:1 and 1:2. Transmission electron microscopic analysis revealed that pristine NPs had an average size of 50 nm, whereas the presence of CTAB resulted in the formation of nanorods with length of 130 nm. BET studies confirmed enhancement of surface area on CTAB coating, which was maximum for w/w ratio 1:1. The synthesized pristine NPs and CTAB-coated NPs were evaluated for their peroxidase mimic activity using o-dianisidine dihydrochloride as substrate. Optimum pH, temperature, substrate and NPs concentration for the reaction were 1, \(25^{\circ }{\mathrm{C}}\), \(0.16~\hbox {mg}~\hbox {ml}^{-1}\) and \(1~\hbox {mg}~\hbox {ml}^{-1}\), respectively. Peroxidase mimic activity of \(\hbox {CTAB@Fe}_{2}\hbox {O}_{3}\hbox { NPs}\) (w/w 1:1) was higher than that of pristine NPs. However, further increase in CTAB coating (w/w 1:2) resulted in lowering of peroxidase mimic activity. Kinetic analysis was carried out at optimized conditions; maximum velocity (\(V_{\mathrm{max}})\) and Michaelis constant (\(K_{\mathrm{m}})\) value of \(\hbox {CTAB@Fe}_{2}\hbox {O}_{3}\hbox { NPs}\) at 1:1 w/w ratio were 7.69 mM and \(1.12~\upmu \hbox {mol}~\hbox {s}^{-1}\), respectively.     

Effects of electrolyte concentration and current density on the properties of electro-deposited NiFeW alloy coatings

NiWP alloy coatings were prepared by electrodeposition, and the effects of ferrous chloride (\(\hbox {FeCl}_{2})\), sodium tungstate (\(\hbox {Na}_{2}\hbox {WO}_{4})\) and current density (\(D_{\mathrm{K}}\)) on the properties of the coatings were studied. The results show that upon increasing the concentration of \(\hbox {FeCl}_{2}\), initially the Fe content of the coating increased and then tended to be stable; the deposition rate and microhardness of coating decreased when the cathodic current efficiency (\(\eta \)) initially increased and then decreased; and for a \(\hbox {FeCl}_{2}\) concentration of \(3.6\, \hbox {g\,l}^{-1}\), the cathodic current efficiency reached its maximum of 74.23%. Upon increasing the concentration of \(\hbox {Na}_{2}\hbox {WO}_{4}\), the W content and microhardness of the coatings increased; the deposition rate and the cathode current efficiency initially increased and then decreased. The cathodic current efficiency reached the maximum value of 70.33% with a \(\hbox {Na}_{2}\hbox {WO}_{4}\) concentration of 50 g \(\hbox {l}^{-1}\), whereas the deposition rate is maximum at 8.67 \(\upmu \hbox {m}\,\hbox {h}^{-1}\) with a \(\hbox {Na}_{2}\hbox {WO}_{4}\) concentration of \(40\, \hbox {g\,l}^{-1}\). Upon increasing the \(D_{\mathrm{K}}\), the deposition rate, microhardness, Fe and W content of the coatings increased, the cathodic current efficiency increases first increased and then decreased. When \(D_{\mathrm{K}}\) was 4 A dm\(^{-2}\), the current efficiency reached the maximum of 73.64%.     

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.     

Thermodynamic Properties at Saturation Derived from Experimental Two-Phase Isochoric Heat Capacity of 1-Hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide

New measurements are reported for the isochoric heat capacity of the ionic liquid substance 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C6mim][NTf2]). These measurements extend the ranges of our earlier study (Polikhronidi et al. in Phys Chem Liq 52:657, 2014) by 5 % of the compressed liquid density and by 75 K. An adiabatic calorimeter was used to measure one-phase \((C_{\mathrm{V1}})\) liquid and two-phase \((C_{\mathrm{V2}})\) liquid + vapor isochoric heat capacities, densities \((\rho _s)\), and phase-transition temperatures \((T_s)\) of the ionic liquid (IL) substance. The combined expanded uncertainty of the density \(\rho \) and isochoric heat capacity \(C_\mathrm{V}\) measurements at the 95 % confidence level with a coverage factor of \(k = 2\) is estimated to be 0.15 % and 3 %, respectively. Measurements are concentrated in the immediate vicinity of the liquid + vapor phase-transition curve, in order to closely observe phase transitions. The present measurements and those of our earlier study are analyzed together and are presented in terms of thermodynamic properties \((T_s\), \(\rho _s\), \(C_{\mathrm{V1}}\) and \(C_{\mathrm{V2}})\) evaluated at saturation and in terms of key-derived thermodynamic properties \(C_\mathrm{P}\), \(C_\mathrm{S}\), \(W_\mathrm{S}^{{\prime }}\), \(K_{\mathrm{TS}}^{{\prime }}\), \(\left( {\partial P/\partial T} \right) _{\mathrm{V}}^{\prime }\), and \(\left( {\partial V/\partial T} \right) _\mathbf{P}^{\prime })\) on the liquid + vapor phase-transition curve. A thermodynamic relation by Yang and Yang is used to confirm the internal consistency of measured two-phase heat capacities \(C_{\mathrm{V2}} \), which are observed to fall perfectly on a line as a function of specific volume at a constant temperature. The observed linear behavior is exploited to evaluate contributions to the quantity \(C_{\mathrm{V2}} = f(V, T)\) from chemical potential \(C_{{\mathrm{V}\upmu }} =-T\frac{\mathrm{d}^{{2}}\mu }{\mathrm{d}T^{2}}\) and from vapor pressure \(C_{\mathrm{VP}} =VT\frac{\mathrm{d}^{2}P_{\mathrm{S}} }{\mathrm{d}T^{2}}\). The physical nature and specific details of the temperature and specific volume dependence of the two-phase isochoric heat capacity and some features of the other derived thermodynamic properties of IL at liquid saturation curve are considered in detail.     

Rectifying resistance-switching behaviour of Ag/SBTO/STMO/$$\hbox {p}^{+}$$-Si heterostructure films

The \(\hbox {Sr}_{0.88}\hbox {Bi}_{0.12}\hbox {TiO}_{3}/\hbox {SrTi}_{0.92}\hbox {Mg}_{0.08}\hbox {O}_{3}\) (SBTO/STMO) heterostructure films were prepared on \(\hbox {p}^{+}\hbox {-Si}\) substrates by sol–gel spin-coating technique, and the films had good crystallinity and uniform grain distribution. The heterostructure films with a structure of Ag/SBTO/STMO/\(\hbox {p}^{+}\hbox {-Si}\) exhibited a bipolar, remarkable resistance-switching characteristic, and \(R_{\mathrm{HRS}}/R_{\mathrm{LRS}}\,\,{\sim }10^{4}\). More importantly, the heterostructure films showed rectifying characteristic in the low resistance state (LRS), and the rectification ratio can reach \(10^{2 }\) at \(\pm 1\hbox { V}\). The dominant resistive-switching conduction mechanism of high resistance state (HRS) was Ohmic behaviour, and the LRS changed to space charge-limited current (SCLC).     

Solid-State Thermal Reaction of a Molecular Material and Solventless Synthesis of Iron Oxide

Solid-state thermal decomposition reaction of a molecular material \(\{\hbox {As}(\hbox {C}_{6}\hbox {H}_{5})_{4}[\hbox {Fe}^{\mathrm{II}}\hbox {Fe}^{\mathrm{III}} (\hbox {C}_{2}\hbox {O}_{4})_{3}]\}_{\mathrm{n}}\) has been studied using non-isothermal thermogravimetry (TG) in an inert atmosphere. By analyzing the TG data collected at multiple heating rates in 300 K–1300 K range, the kinetic parameters (activation energy, most probable reaction mechanism function and frequency factor) are determined using different multi-heating rate analysis programs. Activation energy and the frequency factor are found to be strongly dependent on the extent of decomposition. The decomposed material has been characterized to be hematite using physical techniques (FT-IR and powder XRD). Particle morphology has been checked by TEM. A solid-state reaction pathway leading the molecular precursor to hematite has been proposed illustrating an example of solventless synthesis of iron oxides utilizing thermal decomposition as a technique using innocuous materials.     

Temperature and Heat Flow Rate Calibration of a Calvet Calorimeter from $$0\,{^{\circ }}\hbox {C}$$ to $$190 \,{^{\circ }}\hbox {C}$$19

This study describes the temperature and heat flow rate calibrations of a Calvet calorimeter (SETARAM, BT2.15) in the temperature range of 0–190 \({^{\circ }}\hbox {C}\). Temperature calibration is carried out using three reference materials, namely water, gallium, and indium, as specified in the International Temperature Scale of 1990 (ITS-90). The sample temperature of the Calvet calorimeter is corrected by the obtained mean value, \(-0.489 \,{^{\circ }}\hbox {C}\), of the measured extrapolated peak onset temperature (\(T_{e})\) when the heating rate (\(\upbeta )\) is zero (\(\Delta T_\mathrm{corr }(\upbeta ~=~0\))). The heat flow rate is calibrated using a reference material with a known heat capacity, namely SRM 720 \(\alpha \)-\(\hbox {Al}_{2}\hbox {O}_{3}\) (synthetic sapphire), which is traceable to the National Institute of Standards and Technology. From the heat flow rate measurements of the blank baseline and SRM 720, the proportional calibration factor, \(\hbox {K}_{\Phi }\), in the 0–190\( \,{^{\circ }}\hbox {C}\) temperature range was determined. The specific heat capacity of copper was measured with the obtained calibration values, and the measured data show consistency with the reference value.     

Microwave dielectrics: solid solution,ordering and microwave dielectric properties of $$(1{-}x)\hbox {Ba}(\hbox {Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}{-}x\hbox {Ba(Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}$$ ceramics

The effect of Ba(\(\hbox {Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}\) phase on structure and dielectric properties of \(\hbox {Ba(Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}\) was studied by synthesizing \((1{-}x)\hbox {Ba(Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}{-}x\hbox {Ba}(\hbox {Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}\) (\(x = 0\), 0.005, 0.01 and 0.02) ceramics. Superlattice reflections due to 1:2 ordering appear as low as \(1000^{\circ }\hbox {C}\). \(\hbox {Ba}(\hbox {Mg}_{1/3}\hbox {Nb}_{2/3})\hbox {O}_{3}\) forms solid solution with \(\hbox {Ba}(\hbox {Mg}_{1/8}\hbox {Nb}_{3/4})\hbox {O}_{3}\) for all ‘x’ values studied until \(1350^{\circ }\hbox {C}\). Ordering was confirmed by powder X-ray diffraction pattern, Raman study and HRTEM. Ceramic pucks can be sintered to density \({>}92\%\) of theoretical density. Temperature and frequency-stable dielectric constant and nearly zero dielectric loss (tan \(\delta \)) were observed at low frequencies (20 MHz). The sintered samples exhibit dielectric constant (\(\varepsilon _{\mathrm{r}})\) between 30 and 32, high quality factor between 37000 and 74000 GHz and temperature coefficient of resonant frequency (\(\tau _{\mathrm{f}})\) between 21 and \(24\hbox { ppm }^{\circ }\hbox {C}^{-1}\).     

Characterization and optical properties of $$\hbox {Pr}_{2}\hbox {O}_{3}$$-doped molybdenum lead-borate glasses

\(\hbox {Pr}^{3+}\) doped molybdenum lead-borate glasses with the chemical composition 75PbO?[25–(x \(+\) y)\(\hbox {B}_{2}\hbox {O}_{3}]\)–\(y\hbox {MoO}_{3}\)–\(x\hbox {Pr}_{2}\hbox {O}_{3}\) (where \(x = 0.5\) and 1.0 mol% and \(y = 0\) and 5 mol%) were prepared by conventional melt-quenching technique. Thermal, optical and structural analyses are carried out using DSC, UV and FTIR spectra. The physical parameters, like glass transition \((T_{\mathrm{g}})\), stability factor \((\Delta T)\), optical energy band gap \((E_{\mathrm{gopt}})\), of these glasses have been determined as a function of dopant concentration. The \({T}_{\mathrm{g}}\) and optical energy gaps of these glasses were found to be in the range of 290–350\({^{\circ }}\hbox {C}\) and 2.45–2.7 eV, respectively. Stability of the glass doped with \(\hbox {Pr}^{3+}\) is found to be moderate (\(\sim \)40). The results are discussed using the structural model of Mo–lead-borate glass.     

Onsite Calibration of a Precision IPRT Based on Gallium and Gallium-Based Small-Size Eutectic Points

Onsite thermometer calibration with temperature scale transfer technology based on fixed points can effectively improve the level of industrial temperature measurement and calibration. The present work performs an onsite calibration of a precision industrial platinum resistance thermometer near room temperature. The calibration is based on a series of small-size eutectic points, including Ga–In (\(15.7 \,{^{\circ }}\hbox {C}\)), Ga–Sn (\(20.5 \,{^{\circ }} \hbox {C}\)), Ga–Zn (\(25.2 \,{^{\circ }} \hbox {C}\)), and a Ga fixed point (\(29.7 \,{^{\circ }} \hbox {C}\)), developed in a portable multi-point automatic realization apparatus. The temperature plateaus of the Ga–In, Ga–Sn, and Ga–Zn eutectic points and the Ga fixed point last for longer than 2 h, and their reproducibility was better than 5 mK. The device is suitable for calibrating non-detachable temperature sensors in advanced environmental laboratories and industrial fields.     

Resistance-switching properties of Bi-doped $$\hbox {SrTiO}_{3}$$ films for non-volatile memory applications with different device structures

\(\hbox {SrTiO}_{3}\) and Bi-doped \(\hbox {SrTiO}_{3}\) films were fabricated with different device structures using the sol–gel method for non-volatile memory applications, and their resistance-switching behaviour, endurance and retention characteristics were investigated. \(\hbox {SrTiO}_{3}\) and \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si or Pt have the same phase structure, morphologies and grain size; however, the grain size of the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si is slightly larger than those of the \(\hbox {SrTiO}_{3}\) films grown on Si and the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Pt. The \(\hbox {SrTiO}_{3}\) or \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films grown on Si or Pt all exhibit bipolar resistive-switching behaviour and follow the same conductive mechanism; however, the \(\hbox {Ag}/\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}/\hbox {Si}\) device possesses the highest \(R_{\mathrm{HRS}}{/}R_{\mathrm{LRS}}\) of \(10^{5}\) and the best endurance and retention characteristics. The doping of Bi is conducive to enhance the \(R_{\mathrm{HRS}}{/}R_{\mathrm{LRS}}\) of the \(\hbox {SrTiO}_{3}\) films; meanwhile, the Si substrates help improve the endurance and retention characteristics of the \(\hbox {Sr}_{0.92}\hbox {Bi}_{0.08}\hbox {TiO}_{3}\) films.     

Production Procedure and Characterization of Zn-Doped Y-123 Superconducting Samples Prepared by Sol-Gel Method

The superconducting YBa₂Cu_3?xZn_xO₇ (Y-123) bulk materials have been synthesized by using the sol-gel method. Samples are produced as undoped Y-123 and transition metal (Zn)-doped Y-123. Before the final heat treatment, the samples are calcined at 850 °C for 24 h. This process is repeated three times. Then, samples are sintered at 950 °C for 24 h in an air environment and at 500 °C for 5 h in an oxygen atmosphere. The synthesized products are characterized by XRD, R-T, and Vickers microhardness tester. The XRD investigation revealed that the prepared sample has an orthorhombic structure. According to XRD measurements, an orthorhombic structure has not changed with Zn doping. It was observed that undoped and Zn-doped samples have superconductivity properties by electrical measurements. \(T_{\mathrm {c}}^{\text {onset}}\) is 89 K for undoped Y-123 sample, and the \(T_{\mathrm {c}}^{\text {onset}}\) value decreases monotically with Zn addition. All samples show metallic behavior above \(T_{\mathrm {c}}^{\text {onset}}\) temperature. As a result of Vickers microhardness measurements, it is observed that all samples have reverse indentation size effect (RISE) behavior.     

Mesoscale evolution of non-graphitizing pyrolytic carbon in aligned carbon nanotube carbon matrix nanocomposites

Polymer-derived pyrolytic carbons (PyCs) are highly desirable building blocks for high-strength low-density ceramic meta-materials, and reinforcement with nanofibers is of interest to address brittleness and tailor multi-functional properties. The properties of carbon nanotubes (CNTs) make them leading candidates for nanocomposite reinforcement, but how CNT confinement influences the structural evolution of the PyC matrix is unknown. Here, the influence of aligned CNT proximity interactions on nano- and mesoscale structural evolution of phenol-formaldehyde-derived PyCs is established as a function of pyrolysis temperature (\(T_{\mathrm {p}}\)) using X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. Aligned CNT PyC matrix nanocomposites are found to evolve faster at the mesoscale by plateauing in crystallite size at \(T_{\mathrm {p}}\) \(\sim\)800 \(^{\circ }\hbox {C}\), which is more than \(200\,\,^{\circ }\hbox {C}\) below that of unconfined PyCs. Since the aligned CNTs used here exhibit \(\sim\)80 nm average separations and \(\sim\)8 nm diameters, confinement effects are surprisingly not found to influence PyC structure on the atomic-scale at \(T_{\mathrm {p}}\) \(\le \)1400 \(^{\circ }\hbox {C}\). Since CNT confinement could lead to anisotropic crystallite growth in PyCs synthesized below \(\sim\)1000 \(^{\circ }\hbox {C}\), and recent modeling indicates that more slender crystallites increase PyC hardness, these results inform fabrication of PyC-based meta-materials with unrivaled specific mechanical properties.     

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 \(K_{\mathrm{p}} = 27\%\).