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This article mainly describes the chemical and crystal structure of attapulgite as its unique crystal structure possess special physicochemical properties such as large specific surface area, adsorption performance, and cation exchangeability. By modification of attapulgite, such as purification, high temperature roasting and other physical modification or acid–base salt modification, organic modification, surfactant modification and other chemical modification can further improve its physicochemical properties. In this article, the modification methods of two aspects of physical modification and chemical modification are summarized, at the same time, the research progress and achievements of many scholars in attapulgite modification are reviewed. Through modified attapulgite the number of pores increased, channel become loose, pore diameter increases, pore volume increases, interlayer spacing increases, specific surface area increases, chargeability and adsorption activity change, and the adsorption performance of attapulgite is greatly improved. Many scholars have applied modified attapulgite to the treatment of radionuclides, and achieved remarkable results. It has been found that modified attapulgite has U(VI), Eu(III), Cs(III), Th(IV), both Eu(III) and Sr(II) have good adsorption properties, and the adsorption rate and adsorption capacity are greatly improved compared with the original soil. Based on the Summary of the attapulgite modification method and its application in the treatment of radionuclide, some suggestions on the research and application of attapulgite modification and the possible key research directions in the future are further proposed.

We present a compressed hexagonal photonic crystal fiber (CH-PCF) based on a simple structure with ultra-flattened dispersion, high birefringence and nonlinearity. The propagation characteristics are studied accurately by utilizing full vector finite-element method (FEM). Numerical results indicate that the birefringence of 1.59 × 10−2 was obtained with high nonlinear coefficient of 42.58 W−1 km−1(X) and 52.80 W−1 km−1(Y) at an effective wavelength of 1.55 μm. Furthermore, CH-PCF presents an ultra-flattened dispersion with variation of ± 3.4 ps/nm/km(X) and ± 1.6 ps/nm/km(Y) over 1.3 μm to 1.8 μm (0.5 μm bandwidth), respectively. In addition, this circular-hole structure can be fabricated conveniently at most easy compared with complex designs, which is an advantage for practical applications such as dispersion compensation and nonlinear optics application.

This paper discusses the effects of extended temperature change time of InGaN well growth on the luminescent properties of blue LEDs with sapphire substrate. Extending the temperature change time will increase the area of the In composition gradient in the quantum well, thereby changing the PL luminescence peak shape, which is conducive to increasing the brightness of the LED. The change of EL-luminescent peaks under different current is further studied. In combination with PL, the source of the shoulder peak on the long-wave-side of the main luminescent peak in the blue light InGaN quantum well growing on the sapphire substrate is explored under normal temperature condition. One illumination mechanism related to a main illuminating center provides a research direction for the improvement of the photoelectric performance of the blue-light LED.

An index guiding photonic crystal fiber with a squeezed core is proposed and properties, including birefringence and effective modal area, are numerically analyzed using the multipole method. Numerical results show that high birefringence of 1.544 × 10 −2 and a small modal area of 2.39 μm 2 are achieved at 1.55 μm simultaneously. Moreover, impacts of hole spacing and hole size on birefringence and effective modal area are also investigated in detail.

In this paper, the finite element method and experiment were used to systematically study the influence of different factors on the heat dissipation of high-power ultraviolet light-emitting diode (UV LED) module, including chip spacing and structure, sub-mount, adhesive materials, the packaging area and void ratio of adhesive. The package structure was optimized by introducing Al barrier plate and changing the spacing between adjacent chips. Considering the balance of junction temperature and irradiance, the appropriate chip spacing (∼ 2.5 mm) should be chose. The simulations analysis demonstrated that both sub-mount and adhesive materials play an important role in the thermal performance of the UV LED module. The area ratio (∼0.9) between the adhesive area and the chip area can not only realize the excellent heat dissipation but also minimize the use of adhesive materials. During reflow soldering, the lager coalesced voids should be decreased as soon as possible, which have worse heat dissipation performance than the distributed voids. Furthermore, the reliability and validity of the numerical simulation were verified by the experiment data. The present conclusions provide significant insight on designing and optimizing high-power UV LED devices.

The staggered structure is considered to be one of the key factors for the excellent mechanical properties of bone. In order to solve the problem of non-uniform stress distribution in the hard component of the original biomimetic staggered composites, a novel three-dimensional structure model with pores is proposed in this paper. By generalizing the shear lag theory model of the original staggered structure to the new model, the constitutive relation of the porous structure is established. On this basis, the stress distribution with respect to the aspect ratio of the hard prisms is studied. Finally, the two composite models are simulated by finite element method. The results show that stress in the novel structure tends to be uniformly distributed under external force. So it has higher stiffness and strength to mass ratio, and maintains stronger toughness. It is illustrated that pores in staggered structure can help to fully exploit the mechanical potential of each phase in the composites, providing an explanation for the existing of large number of voids in bone. This study may have an important inspiration for designing lightweight load-bearing composites with high efficiency of vibration isolation and cushioning.

An octagonal dual core polarization splitter based on highly birefringent photonic crystal fiber (PCF) is proposed and the full vector finite element method (FEM) is employed to analyze the impacts of structural parameters on birefringence and the coupling length, and simulation results show that high birefringence on the order of 10 −3 can be achieved at 1.55 μm, moreover, the hole size and hole pitch both affect birefringence and the coupling length. Based on these results, the PCF's structure is optimized to realize a polarization splitter of 314 μm whose largest extinction ratio is around −50.5 dB at 1.55 μm. Meanwhile, the bandwidth at the extinction ratio of −10 dB is about 170 nm, and around 60 nm at −20 dB.

A soft glass dual core polarization splitter based on highly birefringent photonic crystal fiber (PCF) is proposed and the full vector finite element method (FEM) is employed to analyze the impacts of structural parameters on birefringence and the coupling length, and simulation results show that high birefringence on the order of 10 −2 can be obtained at 1.55 μm, moreover, hole size, hole pitch and elliptic ratio all affect birefringence and the coupling length. Based on these results, the PCF's structure is optimized to realize a polarization splitter of 282 μm whose largest extinction ratio is around −45.42 dB at 1.55 μm. Meanwhile, the bandwidth at the extinction ratio of −10 dB is about 90 nm, and around 32 nm at −20 dB.

The complex resistivity dispersion experiment of the soil with different water content and different chromic salt content is the base of the complex resistivity detection method which will be used for evaluating the field polluted by chromium residue. By the soil complex resistivity dispersion properties experiment in kinds of conditions, we find that complex resistivity amplitude, phase, in-phase resistivity and out-phase resistivity can be influenced by the water content and contamination content; but the complex phase and out-phase resistivity have the obvious dispersion properties. The experiment result shows that the complex resistivity detection technology based on soil dispersion properties can be used to evaluate the field polluted by chromium residue.

The novel high-power vertical-cavity surface-emitting lasers(VCSEL) with radial bridge electrode is fabricated in order to improve the thermal characteristics and increase the out power of high power VCSEL.The analysis on the model of the high-power VCSEL shows the radial bridge electrode can reduce the electric and thermal resistance and the Joule heat of VCSEL.The radial brigde electrode and the conventional electrode high power VCSEL both with 200μm aperture are made and tested comparatively. The testing results show that the differential resistance of the VCSEL is 0.43Ωand the out power is 340 mW,1.7 times higher than the conventional device,which can operate at higher up to 80℃,and its thermal resistance is 0.95℃/mW.The temperature and opto-electric characteristics of radial bridge electrode high power VCSEL are much better than those of the conventional electrode high power VCSEL.

The kesterite compound Cu2ZnSnS4(CZTS) is one of the most interesting materials for absorber layers of thin-film solar cells,not only because it is composed of earth abundant and non-toxic elements,but also owing to the fact that its absorption coefficient is high (on the order of 104 cm-1) and its optimal band gap is 1.5 eV for single-junction solar cells. Plenty of methods are used to deposit the CZTS layer,such as evaporation,sputtering,spray-pyrolysis,sol-gel, pulsed laser deposition and electro-chemical deposition.Among these methods,sputtering is considered as one of the most viable deposition techniques for producing a large-scale panel of thin film solar cells with demonstrable productivity and easy adjustment.In this paper,Cu2ZnSnS4 thin films are prepared by in-situ annealing after being sputtered with a quaternary compound target.This technology can reduce the extrinsic defects in the thin film.It is desirable to control the growth of grain boundary,increase grain size and make the thin film more compact and smooth. The in-situ annealing is a method which can heat a work piece fast to a certain temperature and maintain the temperature for some time after sputtering.As is well known,one of the major reasons for affecting CZTS device performance is the low open circuit voltage (Voc),and it is also a challenge to obtain a high value because there are a lot of defect states at the grain boundaries.The experiment shows that using the method of in-situ annealing after sputtering can obtain large size grains and smooth and compact surface.The obtained thin films are Cu-poor,Zn-rich and Sn-poor,which can restrain the Cu vacancies (VCu) and anti-site defects (CuZn,SnZn,and SnCu).The free carrier concentration (NA) increases with the increase of Zn content,while the open circuit voltage of CZTS solar cells increases with the increase of NA. In order to develop CZTS solar cells based on the thin films,the n-type CdS buffer layer (70 nm) is grown using chemical bath deposition,and intrinsic ZnO (70 nm) and ZnO:Al (250 nm) films are deposited by RF-magnetron sputtering.In the end,Ni-Al metal grids as the top electrode are prepared by thermal evaporation.The final solar cells with an active area of 0.25 cm2 are determined by mechanical scribing.The solar cell based the CZTS film with in-situ annealing has better-performance parameters,its open circuit voltage and short-circuit current density are 575 mV and 8.32 mA/cm2,respectively.The photoelectric conversion efficiency of 1.82% is achieved.In order to enhance the efficiency of device,it is important to minimize Cu/Zn disorder in CZTS film and control the element composition by optimizing high-temperature crystallization process.The relevant research work on reducing defects in the films,increasing the carrier collection and enhancing the Jsc is under way. This method not only avoids the contamination caused by the external annealing but also simplifies the preparation process of the thin film,which greatly saves the preparation time of the solar cell and is beneficial to industrial production.annealing is a method which can heat a work piece fast to a certain temperature and maintain the temperature for some time after sputtering.As is well known,one of the major reasons for affecting CZTS device performance is the low open circuit voltage (Voc),and it is also a challenge to obtain a high value because there are a lot of defect states at the grain boundaries.The experiment shows that using the method of in-situ annealing after sputtering can obtain large size grains and smooth and compact surface.The obtained thin films are Cu-poor,Zn-rich and Sn-poor,which can restrain the Cu vacancies (VCu) and anti-site defects (CuZn,SnZn,and SnCu).The free carrier concentration (NA) increases with the increase of Zn content,while the open circuit voltage of CZTS solar cells increases with the increase of NA. In order to develop CZTS solar cells based on the thin films,the n-type CdS buffer layer (70 nm) is grown using chemical bath deposition,and intrinsic ZnO (70 nm) and ZnO:Al (250 nm) films are deposited by RF-magnetron sputtering.In the end,Ni-Al metal grids as the top electrode are prepared by thermal evaporation.The final solar cells with an active area of 0.25 cm2 are determined by mechanical scribing.The solar cell based the CZTS film with in-situ annealing has better-performance parameters,its open circuit voltage and short-circuit current density are 575 mV and 8.32 mA/cm2,respectively.The photoelectric conversion efficiency of 1.82% is achieved.In order to enhance the efficiency of device,it is important to minimize Cu/Zn disorder in CZTS film and control the element composition by optimizing high-temperature crystallization process.The relevant research work on reducing defects in the films,increasing the carrier collection and enhancing the Jsc is under way. This method not only avoids the contamination caused by the external annealing but also simplifies the preparation process of the thin film,which greatly saves the preparation time of the solar cell and is beneficial to industrial production.

In this paper, an a-Si/Ge thin film with a buried layer of Ge and an a-Si thin film are prepared on Si substrates at a temperature of 500 ℃ by magnetron sputtering. The prepared films are annealed for 5h at different temperatures in vacuum. The annealed films are characterized by Raman scattering, X-ray diffraction, atomic force microscope and field emission scanning electron microscope. The results reveal that Ge can induce amorphous Si (a-Si) growing at a temperature of 500 ℃ by magnetron sputtering crystallize after annealing at a temperature of 600 ℃ for 5h. And in the a-Si/Ge thin film the degrees of crystallization of a-Si are 44% and 54% at the annealing temperatures of 600 ℃ and 700 ℃, respectively. By comparison, a-Si thin film without Ge is crystallized at an annealing temperature of 800 ℃ for 5h and the degree of crystallization is 46%. The crystallization temperature of a-Si/Ge is reduced by 200 ℃ compared with that of a-Si film without buried Ge layer in the film. The prepared poly-Si thin film possesses high Si(200) orientation with a grain size of 76 nm. The preparation of poly-Si film by Ge-induced crystallization might be a useful technology for developing high-quality poly-Si film.

InAs/GaSb superlattice (SL) short wavelength infrared photoconduction detectors are grown by molecular beam epitaxy on GaAs(001) semi-insulating substrates. An interfacial misfit mode AlSb quantum dot layer and a thick GaSb layer are grown as buffer layers. The detectors containing a 200-period 2ML/8ML InAs/GaSb SL active layer are fabricated with a pixel area of 800 x 800 mu m(2) without using passivation or antireflection coatings. Corresponding to the 50% cutoff wavelengths of 2.05 mu m at 77K and 2.25 mu m at 300 K, the peak detectivities of the detectors are 4 x 10(9) cm.Hz(1/2)/W at 77K and 2 x 10(8) cm.Hz(1/2)/W at 300 K, respectively.

We investigate the molecular beam epitaxy growth of GaSb films on GaAs substrates using AlSb buffer layers. Optimization of AlSb growth parameter is aimed at obtaining high GaSb crystal quality and smooth GaSb surface. The optimized growth temperature and thickness of AlSb layers are found to be 450 degrees C and 2.1 nm, respectively. A rms surface roughness of 0.67 nm over 10 x 10 mu m(2) is achieved as a 0.5 mu m GaSb film is grown under optimized conditions.