•A liquid helium free mechanical property testing system cooled by G-M refrigerators was developed and studied.•The method of decompression cooling is adopted, which helps to decrease the sample temperature.•The sample can be cooled from room temperature to minimum temperature 2.7 K in about 7.5 h.•This system can be installed onto an electronic universal testing machine or a fatigue testing machine to characterize static tension, fracture mechanics or fatigue properties at tunable low temperatures.In the present work, a cryogenic mechanical property testing system conduction-cooled by two G-M cryocoolers was developed. The testing sample can be cooled from room temperature to 2.7 K within 7.5 h. The sample was first cooled down to 11.1 K directly by the two G-M cryocoolers and then cooled down to 2.7 K by decompressing the chamber. Instead of liquid helium, the cooling process is characterized by cooling with recycled helium gas as heat transfer medium. The heat load of the system was analyzed and optimizations were adopted in terms of material selections and design. The static load capacity of the system reaches 200 kN and the fatigue load capacity can reach 50 kN. This system can be installed onto an electronic universal testing machine or a fatigue testing machine to characterize static tension, fracture mechanics or fatigue properties at tunable low temperatures. Tensile properties of 316L austenitic stainless steels at 4.2 K were tested with the system and the results were compared with those obtained by cooled using liquid helium, which demonstrates high reliability.

Cubic NaZn13-type La(Fe1−xCox)11.4Al1.6 compounds were synthesized and extensively explored through crystal structure and magnetization analyses. By optimizing the chemical composition, the isotropic abnormal properties of excellent zero and giant negative thermal expansion in a pure form were both found at different temperature ranges through room temperature. Moreover, the temperature regions with the remarkable abnormal thermal expansion (ATE) properties have been broadened which are controlled by the dM/dT. The present study demonstrates that the ATE behavior mainly depends on special structural and magnetic properties. These diverse properties suggest the high potential of La(Fe1−xCox)11.4Al1.6 for the development of abnormal expansion materials.

•The LaFe10.5Co1.0Si1.5/Cu composite exhibit a tailoring thermal expansion property.•It has high thermal and electrical conductivity properties.•It is stable after several thermal cycles.•Studied the structure of it.•Analyzed the reasons of tailoring stability thermal expansion and conductivity properties.In this work, metal-matrix composites which possess tunable thermal expansion coefficients in combination with high electrical and thermal conductivities were successfully synthesized by a moderate temperature hot-pressing method. The composites are based on incorporating La(Fe, Si, Co)13, a material with a negative coefficient of thermal expansion, within a continuous Cu matrix. The La(Fe, Si, Co)13 enables us to tune the coefficient of thermal expansion in a predictable manner, while the Cu phase is responsible for the electrical and thermal conductivity properties. The resulting materials exhibit coefficients of thermal expansion which can be tuned between the value of pure Cu and La(Fe, Si, Co)13. Thus, by adjusting the relative amount of the two components, the materials can be designed with high electrical and thermal conductivities and tailoring coefficient of thermal expansion properties. This unique combination of electrical and thermal properties enables these Cu-based metal-matrix composites to be applied in the microelectronic, semiconductor and thermoelectric industries.

Lead-free polycrystalline SnSe is a promising thermoelectric compound consisting of earth-abundant elements. However, the poor electrical transport property for low intrinsic defect concentration (3 × 1017 cm−3) limits the usage of the stoichiometric SnSe compound. In this work, Na2Se as an acceptor was doped into SnSe in order to optimize the electrical transport properties, especially to increase the carrier concentration. As a result, the carrier concentrations increased and saturated at about 1.0 × 1019 cm−3 for Na0.01Sn0.99Se at 300 K, and a maximum power factor of 0.48 mW m−1 K−2 was obtained. A maximum zT value of 0.75 was obtained at 823 K for Na0.01Sn0.99Se along the direction perpendicular to the sintering pressure, which is 25% higher than that (0.6) of the undoped SnSe compound.

Solid solution is a potential way to optimize thermoelectric performance for its low thermal conductivity compared to those of the constituent compounds because of the phonon scattering from disordered atoms. Tin(II) sulfide (SnS) shows analogous band structure and electrical properties with tin selenide (SnSe), which was the motivation for investigating the thermoelectric performance of SnS and SnS–SnSe solid solution system. SnS compound and SnS1−xSex (0 < x < 1) solid solution were fabricated using the melting method and they exhibited anisotropic thermoelectric performance along the parallel and perpendicular to the pressing directions. For the SnS compound, the maximum zT∥ value is 0.19 at 823 K along the parallel to pressing direction, which is higher than that along the perpendicular to the pressing direction (zT⊥ = 0.16). The zT values of SnS0.5Se0.5 and SnS0.2Se0.8 were higher than those of the SnS compound and a maximum zT value of 0.82 was obtained for SnS0.2Se0.8 at 823 K, which is more than four times higher than that of SnS.

Cubic La(Fe,Si)13-based compounds have been recently developed as promising negative thermal expansion(NTE) materials, but the narrow NTE operation-temperature window(∼110 K) restricts their actual applications. In this work, we demonstrate that the NTE operation-temperature window of LaFe13–xSix can be significantly broadened by adjusting Fe–Fe magnetic exchange coupling as x ranges from 2.8 to 3.1. In particular, the NTE operation-temperature window of LaFe10.1Si2.9 is extended to 220 K. More attractively, the coefficients of thermal expansion of LaFe10.0Si3.0 and LaFe9.9Si3.1 are homogeneous in the NTE operation-temperature range of about 200 K, which is much valuable for the stability of fabricating devices. The further experimental characterizations combined with first-principles studies reveal that the tetragonal phase is gradually introduced into the cubic phase as the Si content increases, hence modifies the Fe–Fe interatomic distance. The reduction of the overall Fe–Fe magnetic exchange interactions contributes to the broadness of NTE operation-temperature window for LaFe13–xSix.

The cubic NaZn13-type La(Fe,Al)13 compounds were synthesized, and their linear thermal expansion properties were investigated in the temperature range of 4.2–300 K. It was found that these compounds exhibit abnormal thermal expansion behavior, i.e., pronounced negative thermal expansion (NTE) or zero thermal expansion (ZTE) behavior, below the Curie temperature due to the magnetovolume effect (MVE). Moreover, in the La(Fe,Al)13 compounds, the modification of the coefficient of thermal expansion (CTE) as well as the abnormal thermal expansion (ATE) temperature-window is achieved through optimizing the proportion of Fe and Al. Typically, the average CTE of the LaFe13−xAlx compounds with x = 1.8 reaches as large as −10.47 × 10−6 K−1 between 100 and 225 K (ΔT = 125 K). Also, the ZTE temperature-window of the LaFe13−xAlx compounds with x = 2.5 and x = 2.7 could be broadened to 245 K (from 5 to 250 K). Besides, the magnetic properties of these compounds were measured and correlated with the abnormal thermal expansion behavior. The present results highlight the potential application of such La(Fe,Al)13 compounds with abnormal thermal expansion properties in cryogenic engineering.

Recently, La(Fe,Si)13-based compounds have attracted much attention due to their isotropic and tunable abnormal thermal expansion (ATE) properties as well as bright prospects for practical applications. In this research, we have prepared cubic NaZn13-type carbon-doped La(Fe,Si)13 compounds by the arc-melting method, and their ATE and magnetic properties were investigated by means of variable-temperature X-ray diffraction, strain gauge and the physical property measurement system (PPMS). The experimental results indicate that both micro and macro negative thermal expansion (NTE) behaviors gradually weaken with the increase of interstitial carbon atoms. Moreover, the temperature region with the most remarkable NTE properties has been broadened and near zero thermal expansion (NZTE) behavior occurs in the bulk carbon-doped La(Fe,Si)13 compounds.

A zero thermal expansion material in a pure form of NaZn13-type La(Fe,Si)13 was fabricated. Through optimizing the chemical composition, an isotropic zero thermal expansion material is achieved. The obtained materials exhibit a low expansion of |α| < 1.0 × 10−6 K−1 (α is the coefficient of linear thermal expansion) over a broad temperature range (15–150 K). The present study indicates that the thermal expansion behavior of the NaZn13-type La(Fe,Si)13 compounds depends mainly on the content of Si element. This new material is desirable in many fields of industry as a reliable and low-cost zero thermal expansion material.

•The NTE temperature-window could be regulated through optimizing chemical composition.•NTE starting temperatures are lower than that of other La(Fe,Si)13-based compounds.•Coefficient of thermal expansion (CTE) changes slightly with the increase of Mn content.•Such optimization promotes the potential applications in cryogenic engineering.The NaZn13-type La(Fe,Si)13-based compounds with Mn doping were synthesized, and the thermal expansion and magnetic properties were investigated. Results indicate that the negative thermal expansion temperature-window shifts toward lower temperatures, which is due to the decrease of Curie temperature (Tc) by increasing the amount of Mn element, whereas the average CTE around Tc changes slightly with the increase of Mn content in the LaFe11.5−xMnxSi1.5 compounds. Such optimization of Mn element in the La(Fe,Mn,Si)13 compounds with noteworthy negative thermal expansion properties at lower temperatures promotes their potential applications for cryogenic equipment and precise instruments.

•The LaFe10.5Co1.0Si1.5/Cu exhibits near zero thermal expansion around RT.•It has high thermal and electrical conductivity properties.•It is stable after several thermal cycles.•Studied the structure of it.•Analyzed the reasons of near zero thermal expansion property and stability.In this work, a new kind of La(Fe, Si, Co)13/Cu composite with near zero thermal expansion property was successfully synthesized. The composite shows almost zero thermal expansion with a coefficient of thermal expansion of 0.8 × 10−6 K−1 in the temperature range of 301–325 K. In addition, the thermal conductivity and electrical resistivity were investigated. Compared with pure La(Fe, Si, Co)13 materials, the La(Fe, Si, Co)13/Cu composite shows significant improvement in both thermal and electrical conductivities. The thermal conductivity of the LaFe10.5Co1.0Si1.5/Cu composite is 25.1 W m−1 K−1, which is about five times than that of the pure LaFe10.5Co1.0Si1.5. The electrical resistivity reaches 0.16 × 10−6 Ω m. This offers a new kind of metal matrix composites with low/near zero thermal expansion, high thermal and electrical conductivity properties.

•Negative thermal expansion of LaFe11.2Al1.8−xSix was improved by introducing Si.•The structure of LaFe11.2Al1.8−xSix was studied by X-ray diffraction measurement.•We analyze the mechanism of NTE in LaFe11.2Al1.8−xSix by magnetic measurement.The cubic NaZn13-type LaFe11.2Al1.8−xSix(x = 0.2, 0.3, 0.4 and 0.5) compounds with different Si content were fabricated by conventional arc-melting method, the structures of which were confirmed by powder X-ray diffraction (XRD) measurement at ambient temperature. Besides, the thermal expansion and magnetic properties of these samples were also researched by means of a strain gage and a physical property measurement system (PPMS). Significantly, it was found that the negative thermal expansion (NTE) behavior have been remarkably enhanced with substituting Al with Si atoms. Furthermore, the NTE operation-temperature window concurrently shifts toward a higher temperature region. The variable temperature XRD results indicate that LaFe11.2Al1.8−xSix retain cubic NaZn13-type structure when temperature varies from 20 K to 270 K, including the temperature region where NTE occurs. The further theoretical analysis combined with magnetic characterization reveal that the improvement of NTE behavior is attributed to the enhancement of Fe–Fe magnetic exchange interactions with doping Si atoms. It is noteworthy that this study displays a new pathway to improve the NTE property of La(Fe,Al)13-based compounds at low temperature region, which highlights the potential applications of NTE materials in cryogenic engineering.

Using spark plasma sintering (SPS), Mn3Cu0.6Ge0.4N crystallites have been fabricated with different crystallite sizes, and their magnetic properties and thermal behaviors were systemically investigated. With decreasing crystallite size, the magnetic transition becomes increasingly slow, accompanied by broadening of the negative thermal expansion (NTE) operation-temperature window. The NTE operation-temperature window for the 12-nm crystallite sample reaches at 140 K, which is about 75% larger than that of the 74-nm crystallite sample. The magnetic properties and NTE operation-temperature window can be tuned by varying the crystallite size. This discovery will promote an even wider range of practical applications in precision devices.

Experiments have been performed to enhance negative thermal expansion (NTE) in the La(Fe,Co,Si)13-based compounds by optimizing the chemical composition, i.e., proper substitution of La by magnetic element Pr. It is found that increasing the absolute value of the average coefficient of thermal expansion (CTE) in the NTE temperature region (200–300 K) attributes to enhancement of the spontaneous magnetization and its growth rate with increasing Pr content. Typically, the average CTE of La1–xPrxFe10.7Co0.8Si1.5 with x = 0.5 reaches as large as −38.5 × 10–6 K–1 between 200 and 300 K (ΔT = 100 K), which is 18.5% larger than that of x = 0. The present results highlight the potential applications of La(Fe,Co,Si)13-based compounds with a larger NTE coefficient.

•Fe3O4@Hydroxyapatite magnetic spheres with tunable shell thickness were prepared.•Their interactions with Pb(II), Y(III), Eu(II) and Sb(III) toxic metals were studied.•Rare-earth metals were inserted via ion-exchange in the hydroxyapatite structure.•Pb and Sb led to the precipitation of hydroxypyromorphite and senarmontite.•Fe3O4@Hydroxyapatite nanocomposites are promising sorbents for water remediation.HypothesisHydroxyapatite and magnetite are two environmentally-friendly mineral phases that have fruitful properties for remediation process. The formation of magnetic core@sorbent shell nanostructures should provide efficient materials for toxic metal removal from aqueous media. However the nanoscale confinement of hydroxyapatite may influence its reactivity.ExperimentsFe3O4@Hydroxyapatite nanocomposites were prepared by surface-controlled precipitation of hydroxyapatite layers from 10 nm to 150 nm in thickness on iron oxide spheres. The surface reactivity of the core–shell particles toward selected inorganic ions of environmental relevance (Pb(II), Y(III), Eu(III), Sb(III)) was studied by batch sorption experiments, X-ray diffraction and electron microscopy.FindingsThe reactivity of the hydroxyapatite coating varied from partial cation exchange to dissolution/transformation of the shell. The nature and extent of the reactions depended significantly on the hydroxyapatite layer structure but was not significantly influenced by the magnetic core. These novel nanocomposites should be useful for environmental applications.Graphical abstract

p-Type PbTe is an outstanding high temperature thermoelectric material with zT of 2 at high temperatures due to its complex band structure which leads to high valley degeneracy. Lead-free SnTe has a similar electronic band structure, which suggests that it may also be a good thermoelectric material. However, stoichiometric SnTe is a strongly p-type semiconductor with a carrier concentration of about 1 × 1020 cm−3, which corresponds to a minimum Seebeck coefficient and zT. While in the case of p-PbTe (and n-type La3Te4) one would normally achieve higher zT by using high carrier density in order to populate the secondary band with higher valley degeneracy, SnTe behaves differently. It has a very light, upper valence band which is shown in this work to provide higher zT than doping towards the heavier second band. Therefore, decreasing the hole concentration to maximize the performance of the light band results in higher zT than doping into the high degeneracy heavy band. Here we tune the electrical transport properties of SnTe by decreasing the carrier concentration with iodine doping, and increasing the carrier concentration with Gd doping or by making the samples Te deficient. A peak zT value of 0.6 at 700 K was obtained for SnTe0.985I0.015 which optimizes the light, upper valence band, which is about 50% higher than the other peak zT value of 0.4 for GdzSn1−zTe and SnTe1+y which utilize the high valley degeneracy secondary valence band.

Electrophoretic deposition (EPD) was employed as a method to deposite amine – functionalized multiwall carbon nanotubes (A-MWCNTs) onto insulating woven glass fiber and A-MWCNT-glass fiber layers were prepared. Then multiscale A-MWCNTs-woven glass fibers reinforced cyanate ester/epoxy (GFRP) composites were manufactured using the A-MWCNT-glass fiber layers. Mechanical and thermal properties of the A-MWCNTs reinforced GFRP composites were characterized at different temperatures. Results show that interlaminar shear strength and thermal conductivity of A-MWCNTs composites are significantly improved compared with those of pure GFRP composites. Meanwhile, the reinforcing mechanism was investigated and enhanced interfacial bonding between A-MWCNT, matrix and glass fibers were demonstrated.

•Bi85Sb15−xGex alloys were synthesised by a relatively easy powder-based process.•Increasing Ge doping changes the magnitude or sign of the Seebeck coefficient.•A maximum ZT value of 0.07 was obtained at 140 K.Bulk polycrystalline Bi85Sb15−xGex (x=0, 0.5, 1, 1.5, 2) composites were prepared by mechanical alloying followed by pressureless sintering. The thermoelectric properties were studied in the temperature range of 77–300 K. The results indicate that increasing the Ge concentration causes the Seebeck coefficient to change sign from negative to positive. Moreover, it is found that the maximum value of the Seebeck coefficient can be precisely controlled with the Ge concentration. The maximum dimensionless figure of merit reaches 0.07 at 140 K. These results suggest that the preparation of p-type Bi–Sb alloys is possible by using the Ge-doping approach.

Generating electric energy from mechanical vibration using a piezoelectric circular membrane array is presented in this paper. The electrical characteristics of the functional array consisted of three plates with varies tip masses are examined under dynamic conditions. With an optimal load resistor of 11 kΩ, an output power of 21.4 mW was generated from the array in parallel connection at 150 Hz under a pre-stress of 0.8 N and a vibration acceleration of 9.8 m/s2. Moreover, the broadband energy harvesting using this array still can be realized with different tip masses. Three obvious output power peaks can be obtained in a frequency spectra of 110 Hz to 260 Hz. The results show that using a piezoelectric circular diaphragm array can increase significantly the output of energy compared with the use of a single plate. And by optimizing combination of tip masses with piezoelectric elements in array, the frequency range can be tuned to meet the broadband vibration. This array may possibly be exploited to design the energy harvesting for practical applications such as future high speed rail.

La(Fe, Si)13-based compounds are well-known magnetocaloric materials, which show a pronounced negative thermal expansion (NTE) around the Curie temperature but have not been considered as NTE materials for industrial applications. The NaZn13-type LaFe13–xSix and LaFe11.5–xCoxSi1.5 compounds were synthesized, and their linear NTE properties were investigated. By optimizing the chemical composition, the sharp volume change in La(Fe, Si)13-based compounds was successfully modified into continuous expansion. By increasing the amount of Co dopant in LaFe11.5–xCoxSi1.5, the NTE shifts toward a higher temperature region, and also the NTE operation-temperature window becomes broader. Typically, the linear NTE coefficient identified in the LaFe10.5Co1.0Si1.5 compound reaches as much as −26.1 × 10–6 K–1, with an operation-temperature window of 110 K from 240 to 350 K, which includes room temperature. Such control of the specific composition and the NTE properties of La(Fe, Si)13-based compounds suggests their potential application as NTE materials.

•We studied the radiation resistance of the glass fiber reinforced epoxy composite.•The ILSS at 77 K was not affected up to 5 MGy but decreased significantly at 10 MGy.•The Tg of the resin decreased slightly with the increase of irradiation dose.•The composite appears to be resistant to a dose of 5.0 MGy.Effect of gamma irradiation on the mechanical, thermal properties and structure of glass fiber reinforced epoxy composites was investigated. The interlaminar shear strength (ILSS) at 77 K and the fracture morphology of the composites were evaluated as a function of radiation dose. In addition, the molecular structure and the thermal stability of epoxy matrix were investigated by means of UV–Vis spectra, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). It is found that the ILSS at 77 K was affected scarcely up to 5 MGy but decreased significantly after 10 MGy irradiation. The thermal properties of the resin decreased with the increasing irradiation dose. These results can be interpreted by the crosslinking and degradation of the epoxy matrix. The composite appears to be resistant to a dose of 5.0 MGy.

In this study we have investigated the effect of the Pb on the thermoelectric propertied of Bi–Sb alloy with different Pb-content. The Pb-doped Bi85Sb15−xPbx (x = 0, 0.5, 1, 2, 3) alloys were synthesized by mechanical alloying followed by pressureless sintering. The crystal structure was characterized by X-ray diffraction. The Seebeck coefficients, electrical conductivities, and thermal conductivities were measured in the temperature range of 77–300 K. The results show that all the Pb-doped alloys are p-type thermoelectric materials in the whole measurement temperature range. A minimum thermal conductivity of 1.7 W/mK was obtained for Bi85Sb12Pb3 sample at 150 K. A maximum ZT value of 0.11, which is higher than those previous reported, was obtained for Bi85Sb14Pb1 at 210 K.Highlights► A series of Bi85Sb15−xPbx alloys were synthesized by a relatively easy powder-based process. ► The measurement of the Seebeck coefficients showed that all the doped alloys are p-type. ► The lattice thermal conductivities were reduced by doping the element of Pb. ► A maximum ZT value of 0.11 has been obtained, which is higher than previous report.

Boron-free glass fiber reinforced isopropylidenebisphenol bis[(2-glycidyloxy-3-n-butoxy)-1-propylether]/triglycidyl-p-aminophenol (IPBE/TGPAP) epoxy matrix composite cured by diethyl toluene diamine (DETD) was prepared by vacuum press impregnation (VPI). The thermal behaviors of the composite, such as thermal expansion coefficient and thermal conductivity, between room temperature (RT) and liquid nitrogen temperature (77 K) were investigated before and after 1 MGy of 60Co γ-ray radiation. In addition, thermogravimetric analysis and Fourier transform infra-red spectroscopy were used to evaluate thermal stability and chemical structural changes of epoxy matrix. Results revealed that the thermal properties of the composites and the chemical structure of epoxy resin matrix was not affected by the γ-ray radiation with a dose of 1MGy.Highlights► Boron-free glass fiber reinforced composite was prepared by VPI process. ► The thermal expansion coefficient of the composite was investigated. ► The thermal conductivity of the composite was investigated.

Epoxy resin insulating materials used in superconducting feeder system of fusion device are required to be low thermal expansion coefficient (TEC). In this paper, negative thermal expansion (NTE) material ZrW2O8 filled epoxy resins were fabricated. To improve the dispersion of fillers in epoxy matrix, plasma polymerization was performed on the surface of ZrW2O8 powders. Transmission electron microscope (TEM) and surface wettability analysis were performed before and after the surface modification of ZrW2O8 powders. The TEC of ZrW2O8/epoxy composites were measured from 77 K to room temperature. The results show the doping of ZrW2O8 can significantly reduce the TEC of epoxy resins. The sedimentation rate of ZrW2O8 before and after modified in epoxy was compared by density measurement. It can be seen that the ZrW2O8 surface modified by plasma polymerization can enhance its dispersion properties in epoxy matrix.Highlights► Tailored thermal expansion epoxy composites were fabricated by filling ZrW2O8. ► Plasma assisted surface modification of ZrW2O8 particles were performed. ► Low temperature thermal expansion coefficients of composites were investigated. ► We find dispersion of ZrW2O8 in epoxy was enhanced after plasma coated. ► Thermal expansion coefficients of composites were decreased.

In the present work, oil-field wastewater purification through superconducting magnetic separation technique using a novel magnetic nanoparticle was investigated. The magnetic nanoparticle, which has a multi-shell structure with ferroferric oxide as core, dense nonporous silica as inter layer and mesoporous silica as outer layer, was synthesized by co-precipitation method. To functionalize the magnetic nanoparticle, plasma polymerization technique was adopted and poly methyl acrylate (PMA) was formed on the surface of the nanoparticle. The multi-shell structure of the nanoparticle was confirmed by transmission electron microscope (TEM) and the characteristic is measurable by FTIR. It is found that most of the pollutants (85% by turbidity or 84% by COD value) in the oil-field wastewater are removed through the superconducting magnetic separation technique using this novel magnetic nanoparticle.Highlights► Novel magnetic seeds are applied in superconducting magnetic separation system. ► These magnetic seeds consist of magnetic core, dense and mesoporous silica layer. ► The plasma coating technique aids functionalizing the magnetic seeds with polymers. ► These magnetic seeds have appropriate magnetic and adsorptional properties. ► Experiments of purification of oil field wastewater show positive results.

The mechanism of industrial wastewater treatment using superconducting magnetic separation is investigated. Fe3O4 nanoparticles were prepared by liquid precipitation and characterized by X-ray diffraction (XRD). Polyacrylic acid (PAA) film was coated on the magnetic particles using plasma coating technique. Transmission electron microscope (TEM) observation and infrared spectrum measurement indicate that the particle surface is well coated with PAA, and the film thickness is around 1 nm. Practical paper factory wastewater treatment using the modified magnetic seeds in a superconducting magnet (SCM) was carried out. The results show that the maximum removal rate of chemical oxygen demand (COD) by SCM method can reach 76%.

A self-circulation helium liquefaction system (SCHLS) with five 4 K G-M cryocoolers is developed to supply liquid helium (LHe) for SECRAL (a superconducting ECR ion source used in Lanzhou city, China). LHe is vaporized in SECRAL and warmed up to room temperature. SCHLS will re-liquefy the helium gas at a rate of 83.2 L/day under normal atmosphere pressure. With SCHLS, SECRAL system can run online without any interruption of refilling LHe.Research highlights► A self-circulation helium liquefaction system (SCHLS) with five 4 K G-M cryocoolers is developed. ► Helium gas is re-liquefy at a rate of 83.2 L/day under normal atmosphere pressure. ► With SCHLS, SECRAL system can run online without any interruption of refilling LHe. ► SCHLS is suitable for a lot of the devices whose consumption of LHe is lower than 80 L/day.

The nanocrystalline materials with the general formula Bi85Sb15−xNbx (x=0, 0.5, 1, 2, 3) were prepared by mechanical alloying and subsequent high-pressure sintering. Their transport properties involving electrical conductivity, Seebeck coefficient and thermal conductivity have been investigated in the temperature range of 80–300 K. The absolute value of Seebeck coefficient of Bi85Sb13Nb2 reaches a maximum of 161 μV/K at 105 K, which is 69% larger than that of Bi85Sb15 at the same temperature. The power factor and figure-of-merit are 4.45×10−3 WK−2m−1 at 220 K and 1.79×10−3 K−1 at 196 K, respectively. These results suggest that thermoelectric properties of Bi85Sb15 based material can be improved by Nb doping.

Anti-perovskite manganese nitrides with the general formula Mn3(Cu0.5SixGe0.5−x)N (x = 0.05, 0.1, 0.15, 0.2) were fabricated by mechanical ball milling followed by solid state sintering. The temperature dependence of thermal expansions, magnetic properties and electrical conductivities were investigated in the temperature range of 77–300 K. The results show that the operation-temperature window of negative thermal expansion (NTE) shifts to lower temperature and the magnitude of NTE becomes smaller with increasing Si content. Very low average coefficients of thermal expansion of 1.3 × 10−6 K−1 and 1.65 × 10−6 K−1 were observed in Mn3(Cu0.5Si0.1Ge0.4)N and Mn3(Cu0.5Si0.15Ge0.35)N within the temperature range of 77–300 K, respectively. In addition, the electrical conductivities of all the samples are in the range of 2.5–3.5 × 105 (ohm m)−1.

Antiperovskite manganese nitrides Mn3(Cu0.6SixGe0.4−x)N (x=0.05x=0.05, 0.1, 0.15) were prepared and their negative thermal expansion, magnetic and specific heat properties were investigated. A frozen state with a freezing temperature was found at ∼207 K in Mn3(Cu0.6Si0.15Ge0.25)N. This indicates that Mn3(Cu0.6Si0.15Ge0.25)N exhibits a spin glass state at low temperatures. We discussed the cause of spin glass behavior and correlated this spin glass behavior with broadening of the negative thermal expansion operation-temperature window of the manganese nitrides Mn3(Cu0.6Si0.15Ge0.25)N.

Polyetheretherketone (PEEK) has been widely used as matrix material for high performance composites. In this work, 30% chopped glass fibers reinforced PEEK composites were prepared by injection molding, and then the tensile, flexural and impact properties were tested at different temperatures. The modulus, strength and specific elongation of glass fibers reinforced PEEK at room temperature, 77 K and 20 K have been compared. And the fracture morphologies of different samples were investigated by scanning electron microscopy (SEM). The results showed a dependence of mechanical properties of glass fibers reinforced PEEK composites on temperature. The coefficient of thermal expansion of unfilled PEEK and glass fibers reinforced PEEK were also investigated from 77 K to room temperature. The results indicated that the thermal expansion coefficient (CTE) of PEEK matrix was nearly a constant in this temperature region, and it can be significantly decreased by adding glass fibers.

•We conduct the tensile test of the full-size TF conductor jacket at 4.2 K.•The fracture of the jacket at 4.2 K is a combination of ductile and brittle.•The TF conductor jacket satisfied the ITER requirements of the mechanical properties.•The result of full-size tube at 4.2 K is more representative and important.316LN stainless steel is selected as a material for toroidal-field (TF) conductor jacket of International Thermonuclear Experimental Reactor (ITER). In order to evaluate the true mechanical performance of the jacket material at 4.2 K and its suitability as the ITER TF conductor jacket, the mechanical properties of the full-size TF conductor jacket tube and sub-size specimens at 4.2 K and 300 K were investigated according to ASTM standards. The measured yield strength and elongation at 4.2 K for sub-size specimens and full-size tubes are more than 950 MPa and 20%, respectively. In addition, the fractographies of all fractured specimens were observed using scanning electron microscope (SEM). These results suggest that the TF conductor jacket can satisfy ITER requirements and the result of the full-size tube at 4.2 K is more representative and important for practical applications.

•We studied the processing properties of various epoxy matrices.•We studied the radiation resistance of TGPAP-based and DGEBF-based composites.•TGPAP-based systems are more suitable for VPI process than DGEBF-based systems.•TGPAP systems present more radiation resistant than DGEBF systems.Glass fiber reinforced epoxy-based composites were developed as insulating materials for fusion superconducting magnets. The processing properties of various epoxy matrices were investigated in terms of the isothermal viscosity at 45 °C. The interlaminar shear strength (ILSS) at 77 K and the thermal expansion coefficient (CTE) of the composites were assessed before and after gamma irradiation at ambient temperature up to 10 MGy. It is found that the TGPAP-based systems showed lower initial viscosities, longer working life and higher radiation resistance compared to the DGEBF-based systems with the same modifier. Furthermore, there was no significant effect of the irradiation dose on the CTE of the composites.

•Irradiation resistance of glass fiber reinforced cyanate ester/epoxy composite was investigated.•The cyanate ester/epoxy resin system has a low viscosity and long pot life.•The Tg of the matrix resin decreased slightly with the increase of irradiation dose.•The ILSS of GFRP composite increased slightly when exposed to 10 MGy of gamma irradiation.Cyanate ester/epoxy resin was used as a cryogenic-grade polymer matrix and glass fiber reinforced polymer (GFRP) composite was manufactured. The processing properties of matrix resin in terms of the isothermal viscosity at 45 °C were investigated. The specimens were exposed with gamma irradiation of 1 MGy, 5 MGy and 10 MGy, respectively. The effect of gamma irradiation on thermal properties and structure of cyanate ester/epoxy matrix was investigated. The interlaminar shear strength (ILSS) of the composites before and after irradiation were investigated at room temperature, 77 K and 4.2 K. Results showed that cyanate ester/epoxy system had a low viscosity and a long pot life at 45 °C. The glass transition temperature of the matrix resin decreased with the increasing irradiation dose. Moreover, the ILSS of GFRP composite slightly increases after irradiation and toughening mechanism was also discussed.

BiSb/nano-SiC composites were fabricated by ball milling and spark plasma sintering. The figure of merit (ZT) was calculated with the electrical conductivity, the Seebeck coefficient and the thermal conductivity. The thermal conductivity decreased, the electrical conductivity and the Seebeck coefficient decreased a little by adding nano-SiC into Bi-Sb thermoelectric materials. As a result, the thermoelectric properties increased. The maximum ZT value at room temperature is 0.53, which was increased 13% than that of the Bi-Sb matrix.

In the present study, the Bi85Sb15-xSnx (x=0, 1, 2, 3) thermoelectric materials have been fabricated through mechanical alloying followed by pressureless sintering. The phase composition and the microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Electrical conductivity, Seebeck coefficient and thermal conductivity were measured in the temperature range of 77∼300 K. The electrical conductivity was characterized by using four-probe method. The Seebeck coefficient was determined from measured temperature and electric potential difference between the two ends of the bar-shape specimen. The thermal conductivity was measured by means of a heat and sink steady state method. Then the power factor and ZT were calculated according to the measurement values. The results showed that the Sn-doped samples changed from n-type to p-type at low temperature. A maximum power factor of 1.67 ×10-3W/mK2 and a minimum thermal conductivity of 1.8 W/mK were obtained. The optimum ZT value of 0.15 was obtained at 300 K.

A zero thermal expansion material in a pure form of NaZn13-type La(Fe,Si)13 was fabricated. Through optimizing the chemical composition, an isotropic zero thermal expansion material is achieved. The obtained materials exhibit a low expansion of |α| < 1.0 × 10−6 K−1 (α is the coefficient of linear thermal expansion) over a broad temperature range (15–150 K). The present study indicates that the thermal expansion behavior of the NaZn13-type La(Fe,Si)13 compounds depends mainly on the content of Si element. This new material is desirable in many fields of industry as a reliable and low-cost zero thermal expansion material.

p-Type PbTe is an outstanding high temperature thermoelectric material with zT of 2 at high temperatures due to its complex band structure which leads to high valley degeneracy. Lead-free SnTe has a similar electronic band structure, which suggests that it may also be a good thermoelectric material. However, stoichiometric SnTe is a strongly p-type semiconductor with a carrier concentration of about 1 × 1020 cm−3, which corresponds to a minimum Seebeck coefficient and zT. While in the case of p-PbTe (and n-type La3Te4) one would normally achieve higher zT by using high carrier density in order to populate the secondary band with higher valley degeneracy, SnTe behaves differently. It has a very light, upper valence band which is shown in this work to provide higher zT than doping towards the heavier second band. Therefore, decreasing the hole concentration to maximize the performance of the light band results in higher zT than doping into the high degeneracy heavy band. Here we tune the electrical transport properties of SnTe by decreasing the carrier concentration with iodine doping, and increasing the carrier concentration with Gd doping or by making the samples Te deficient. A peak zT value of 0.6 at 700 K was obtained for SnTe0.985I0.015 which optimizes the light, upper valence band, which is about 50% higher than the other peak zT value of 0.4 for GdzSn1−zTe and SnTe1+y which utilize the high valley degeneracy secondary valence band.

Solid solution is a potential way to optimize thermoelectric performance for its low thermal conductivity compared to those of the constituent compounds because of the phonon scattering from disordered atoms. Tin(II) sulfide (SnS) shows analogous band structure and electrical properties with tin selenide (SnSe), which was the motivation for investigating the thermoelectric performance of SnS and SnS–SnSe solid solution system. SnS compound and SnS1−xSex (0 < x < 1) solid solution were fabricated using the melting method and they exhibited anisotropic thermoelectric performance along the parallel and perpendicular to the pressing directions. For the SnS compound, the maximum zT∥ value is 0.19 at 823 K along the parallel to pressing direction, which is higher than that along the perpendicular to the pressing direction (zT⊥ = 0.16). The zT values of SnS0.5Se0.5 and SnS0.2Se0.8 were higher than those of the SnS compound and a maximum zT value of 0.82 was obtained for SnS0.2Se0.8 at 823 K, which is more than four times higher than that of SnS.

The cubic NaZn13-type La(Fe,Al)13 compounds were synthesized, and their linear thermal expansion properties were investigated in the temperature range of 4.2–300 K. It was found that these compounds exhibit abnormal thermal expansion behavior, i.e., pronounced negative thermal expansion (NTE) or zero thermal expansion (ZTE) behavior, below the Curie temperature due to the magnetovolume effect (MVE). Moreover, in the La(Fe,Al)13 compounds, the modification of the coefficient of thermal expansion (CTE) as well as the abnormal thermal expansion (ATE) temperature-window is achieved through optimizing the proportion of Fe and Al. Typically, the average CTE of the LaFe13−xAlx compounds with x = 1.8 reaches as large as −10.47 × 10−6 K−1 between 100 and 225 K (ΔT = 125 K). Also, the ZTE temperature-window of the LaFe13−xAlx compounds with x = 2.5 and x = 2.7 could be broadened to 245 K (from 5 to 250 K). Besides, the magnetic properties of these compounds were measured and correlated with the abnormal thermal expansion behavior. The present results highlight the potential application of such La(Fe,Al)13 compounds with abnormal thermal expansion properties in cryogenic engineering.

Recently, La(Fe,Si)13-based compounds have attracted much attention due to their isotropic and tunable abnormal thermal expansion (ATE) properties as well as bright prospects for practical applications. In this research, we have prepared cubic NaZn13-type carbon-doped La(Fe,Si)13 compounds by the arc-melting method, and their ATE and magnetic properties were investigated by means of variable-temperature X-ray diffraction, strain gauge and the physical property measurement system (PPMS). The experimental results indicate that both micro and macro negative thermal expansion (NTE) behaviors gradually weaken with the increase of interstitial carbon atoms. Moreover, the temperature region with the most remarkable NTE properties has been broadened and near zero thermal expansion (NZTE) behavior occurs in the bulk carbon-doped La(Fe,Si)13 compounds.

Cubic NaZn13-type La(Fe1−xCox)11.4Al1.6 compounds were synthesized and extensively explored through crystal structure and magnetization analyses. By optimizing the chemical composition, the isotropic abnormal properties of excellent zero and giant negative thermal expansion in a pure form were both found at different temperature ranges through room temperature. Moreover, the temperature regions with the remarkable abnormal thermal expansion (ATE) properties have been broadened which are controlled by the dM/dT. The present study demonstrates that the ATE behavior mainly depends on special structural and magnetic properties. These diverse properties suggest the high potential of La(Fe1−xCox)11.4Al1.6 for the development of abnormal expansion materials.