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The energy absorption efficiency of high-intensity (~1016W/cm2) femtosecond laser pulses in a dense jet of large rare-gas clusters has been measured. Experimental results show that the energy absorption efficiency is strongly dependent on the cluster size and can be higher than 90%. The measurement of the ion energy indicates that the average ion energies of argon and xenon can be as high as 90 and 100keV, respectively. The dependence of the average energy of the ions on the cluster size is also measured. At comparatively low gas backing pressure, the average ion energies of argon and xenon increase with increasing gas backing pressure. The average ion energy of argon becomes saturated gradually with further increase of the gas backing pressure. For xenon, the average ion energy drops a little after the gas backing pressure exceeds 9 bar (3.2×105 atoms/cluster). The result showing the existence of a maximum average ion energy has been interpreted within the framework of the microplasma sphere model.

Ionization dynamics of clusters irradiated by chirped femtosecond lasers is investigated by using a linearly chirped pulse spectral interferometry with a time resolution of less than 100 fs. The production of an average charged ~Xe18+ and ~Kr9+ ions indicates a strong energy coupling between laser and cluster. Ultrafast depletion of the probing laser is observed to be strictly coincident with the ionization front as seen in other experiments. Moreover, a two-step ionization process for Xe and Kr clusters irradiated by high-intensity lasers has been observed, which implies the role of resonance enhancement during the cluster explosion.

Very energetic ions, which are detected by time-of-flight spectrometry with maximum energy up to 1.3 MeV and an average energy of 68 keV, are generated in the explosion of large Xe clusters in a dense jet irradiated with a high-intensity (~1016 W/cm2) 50 fs laser pulse from a Ti:sapphire TW laser at 790 nm wavelength. The interaction of intense laser pulses with a jet of argon clusters is also performed and high average ion energies are observed. The dependence of energy of the ions on the gas backing pressure is examined, suggesting that the results are consistent with the absorption efficiency of the laser energy by the cluster plasmas.

Transition metal borides (TMBs) are hard or potential superhard materials due to abrasion resistant, corrosion preventive, oxidation resistance and high hardness. However, few TMBs are superhard materials, so, discussing the strength of TMBs to understand hardness mechanism is necessary. Moreover, there are superconductors, magnetic materials, and catalysts in TMBs. But uncovering more functions in TMBs is important for finding a new kind of functional hard or superhard material. While, high energy is necessary to synthesize TMBs due to strong BB covalent bonds and high melting of transition metal. Thus high temperature or extreme condition is necessary for synthesizing single crystal or bulk sample with high density, which is important for testing physical properties. Various ways of hybridizing boron atoms and high content of valence electron of transition metal are used to induce a large number of structures and potential new properties in TMBs. Boron atoms can form different substructures with different content of boron in TMBs, such as one-dimensional, two-dimensional and three-dimensional (3D) structures. These different boron atom substructures can affect the stability of structure and physical properties, especially hardness, because of the strong covalent bonds between boron atoms. Thus the structure and hardness of TMBs have always received much attention. The multiple electron transfer between transition metal and boron induces diverse chemical bonds in TMBs. All of covalent bonds, ionic bonds, and metal bonds in TMBs determine the mechanic performances, electricitic and magnetic properties, and chemical activity of TMBs. In this work, synthesis method, stability of structure, hardness, and functional properties of TMBs are discussed. The using of high pressure and high temperature is an effective method to prepare TMBs, because under high pressure and high temperature the electrons can transfer between transition-metal atoms and boron atoms in TMBs. There are not only stable TMBs which are even under very high pressure, but also many metastable structures in TMBs. Hardness values of TMBs are discussed by different content of boron, the high boron content or even 3D boron structure is not superhard material. Because insufficient electron transfer can form the distorted BB covalent bond which is weaker than directional covalent bonds like CC in diamond. Thus electron transfer is significant in TMBs for designing hard or even superhard materials. Besides high hardness, there are superconductor, magnetic material, and catalyzers in TMBs, but there are many potential properties of TMBs which are unknown. Further study to uncover the new properties of TMBs is significant for finding a new kind of functional hard material.

The elastic-plastic fracture behavior of aluminum alloy Ly12 under mixed I+II mode loading was studied by finite element method and fracture test. A mixed mode elastic-plastic fracture criterion of J-integral was proposed by using the J-resistance curve, and the maximum fracture effective plastic strain ep max of different mixed ratios at crack tip were also calculated. The results show that (1) the initiation J-integral values of different mixed ratios have the equation $$\left\{ \begin{gathered} J_{MC} = J_{Ii} + J_{{\text{II}}i} \hfill \\ J_{{\text{I}}i} /J_{{\text{I}}C} + J_{{\text{II}}i} /j_{{\text{II}}C} = 1, \hfill \\ \end{gathered} \right.$$ where J Ii and J IIi are the mode I and mode II components of the mixed initiation J-integral J MC at a constant ixed ratio, respectively; (2) the relation between the J MC and mixed ratio K I/K II is $$J_{MC} = K_{\text{I}}^{\text{2}} J_{{\text{I}}C} /(K_{\text{I}}^{\text{2}} + \alpha K_{{\text{II}}}^{\text{2}} ) + \alpha K_{{\text{II}}}^{\text{2}} ) + \alpha K_{{\text{II}}}^{\text{2}} J_{{\text{II}}C} /(K_{\text{I}}^{\text{2}} + \alpha K_{{\text{II}}}^{\text{2}} ),$$ α = J IC /J IIC ; (3) J MC increases with an increasing of mode II component, J IIC is twice of J IC for Ly12; and (4) the maximum fracture effective plastic strain ɛ p max and stress triaxiality σ m /σ of different mixed ratios at crack tip satisfy the formula of $$\varepsilon _p {\text{ max exp(3}}\sigma _m {\text{/2}}\sigma {\text{)}} = {\text{constant, }}$$ where the constant is about 9.52 for Ly12. The relation with double parameters, ɛ p max and σm/σ, can be used as the local fracture or damage mechanics parameter under mixed mode I+II loading.

The composition-dependent thermoelectric properties of lead telluride (PbTe) doped with bismuth telluride (Bi2Te3), antimony telluride (Sb2Te3) and (BiSb)2Te3 have been studied at room temperature. All the samples exhibit small thermal conductivity. The figures of merit, 7.63, 1.03 and 8.97×10−4, have been obtained in PbTe with these dopants, respectively. These values are several times higher than those of PbTe containing other dopants with small grain sizes. The high thermoelectric performance is explained by electronic topological transition induced by alloying. The results indicate that these dopants are effective to enhance the thermoelectric performance of PbTe.

There is a widespread interest in lead telluride (PbTe) as a good thermoelectric material. We report the temperature dependence of thermopower S(T) and resistance R(T) for PbTe at the different pressures of from 1.8 GPa to 5 GPa obtained by using the cubic anvil high pressure apparatus. With increasing pressure, R(T) and S(T) decrease. The effect of pressure on R(T) is larger than that on S(T). The power factor that is determined by thermopower and resistivity increases with increasing pressure. This method is an efficient tool for synthesizing good thermoelectric materials at high pressure and high temperature.

Due to unique structure, onion-like carbon has excellent physical and chemical properties that brodens the application in carbon and carbon-based composite materials. The classification and the structure of onion-like carbon were firstly introduced. Its advantages and disadvantages of traditional preparation methods, including arc discharge, plasma, electron-beam radiation, chemical vapor deposition, nanodiamond annealing in vacuum, thermolysis, were summarized. Then, some new synthetic methods developed in recent years were also presented. Subsequently, the application of onion-like carbon on anode materials of lithium ion secondary battery, counter electrode materials of dye-sensitized solar cell, electrodes materials of electrochemical hydrogen storage and super capacitor, friction and wear, and catalyst fields was summarized. Finally, deficiencies of preparation and application on onion-like carbon were pointed out and future research were put forward.

Double perovskite oxide Sr2CoFeO6 (SCFO) has been obtained using a high-pressure and high-temperature (HPHT) synthesis method. Valence states of Fe and Co and their distributions in SCFO were examined with X-ray photoelectron spectroscopy. The electric transport behavior of SCFO showed a semiconductor behavior that can be well described by Mott?s law for variable-range hopping conduction. The structural stability of SCFO was investigated at pressures up to 31 GPa with no pressure-induced phase transition found. Bulk modulus B0 was determined to be 163(2) GPa by fitting the pressure?volume data to the Birch?Murnaghan equation of state.

Structural and spectroscopic properties of Sr2ZnTeO6 (SZTO) were investigated by angle-dispersive synchrotron X-ray powder diffraction and Raman spectroscopy in a diamond anvil cell up to 31 GPa at room temperature. Although SZTO remained stable up to the highest pressure, the different pressure coefficients of the normalized axial compressibility were obtained as βab = 8.16 × 10−3 GPa−1 and βc = 7.61 × 10−3 GPa−1. The bulk modulus B0 was determined to be 190(1) GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. All the observed Raman modes exhibited a broadening effect under high pressure. The vibrational band v1 around 765 cm−1, which is associated with the Te—O stretching mode in the basal plane of the TeO6 octahedron had the largest pressure coefficient, and the Gruneisen parameters for all the observed phonon modes were also calculated and presented. These parameters could be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for monitoring the magnitude of the shift of phonon frequencies with strains.

One-step synthesis of a carbon nano sheets-carbon nanotubes composite by plasma enhanced chemical vapor deposition and its field emission properties are investigated. We obtain the carbon nano sheets-carbon nanotube composite on the Co thin film with 20 nm Ti interlayer. We gain carbon nano sheets only on the Co thin films without Ti interlayer in the same growth conditions. The carbon nano sheets are distributed on the side wall and the top of carbon nanotubes. The Ti interlayer hinders the diffusion of Co into the silicon substrate and improves the catalytic capability of Co, thus it will help the growth of carbon nanotubes. When the thickness of Co film is 11 nm, the carbon nanotubes are vertically aligned on the flat Co film surface. Most of the carbon nano sheets are distributed on the top of the carbon nanotubes under this condition, which increases the number of emitters and enhances the field emission properties of the composites.

Bulk titanium borides (TiB2) have been successfully synthesized from the stoichiometric boron and titanium powders at high pressure and high temperature (HPHT). The density of TiB2 is higher than 99%. The Vicker's hardness of TiB2 as synthesized is 39.6 GPa which is near to result of the supehard materials. While TiB2 show good metallic characters with the resistivity, 10-8 Ωm, which is near to the value of the single crystal of TiB2. The enhanced properties of TiB2 as synthesized may be attributed to the higher density and uniform crystal size.

Using the density-functional theory, the structural stability and the effect of in-plane electric field on the electronic structure of zigzag graphene nanoribbin (OH-ZGNR), which is terminated by hydroxyl, are explored. It is found that hydroxyl bonding on the ZGNR edge is much more stable than H-terminated ZGNR(H-ZGNRs). The ground state of the ZGNR is spin-polarized with a narrow energy gap. Furthermore, transition from semiconducting to metallic phase in ZGNR can be achieved if a proper in-plane electric field is applied across the edges OH-ZGNR.

Functional gradient materials (FGMs) in thermoelectric materials can raise the maximal power output of the thermoelectric generator (TEG). We report an FGM of n-PbTe with continuous carrier concentration successfully prepared by a unidirectional solidification method. The continuous carrier concentration for n-PbTe was optimized by different dopants of PbI2, Al and Zr and solidifying temperature. The effective maximum outputting power for continuous FGM PbTe is about 30% larger than that for jointed FGM PbTe.