A Compact Device for Colloidal Crystal Studies on Tiangong-1 Target Spacecraft

An experimental device with three crystallization cells, each with two working positions, was designed to study growth kinetics and structural transformation of colloidal crystals under microgravity condition. The device is capable of remote control of experimental procedures. It uses direct-space imaging with white light to monitor morphology of the crystals and reciprocal-space laser diffraction (Kossel lines) to reveal lattice structure. The device, intended for colloidal crystal growth kinetics and structural transformation on Tiangong-1 target spacecraft, had run on-orbit for more than one year till the end of the mission. Hundreds of images and diffraction patterns were collected via the on-ground data receiving station. The data showed that single crystalline samples were successfully grown on the orbit. Structural transformation was carefully studied under electric and thermal field. Using a backup device, control experiments were also performed on the ground under similar conditions except for the microgravity. Preliminary results indicated that the on-orbit crystals were more stable than the on-ground ones.     

Comparative study of nonlinear optical crystals for electro-optic Q-switching of laser resonators

The development of Pockels cells is closely related to the choice of the crystals which are involved in this kind of device. These crystals must satisfy several requirements. In order to clearly establish the crystal ability for the realization of Pockels cells, we define several figures of merit describing its performances for electro-optic Q-Switch and we use these figures of merit to compare the efficiencies of several NLO crystals.     

Measurements of crystal properties for versatile double crystal monochromators in fusion plasma spectroscopy

The spatial dependence of double crystal reflectivities and rocking curve widths is determined for crystals that are suitable for versatile double crystal monochromators to be applied in fusion plasma soft X-ray spectroscopy. Their application is limited by misorientations within large natural crystals or by lattice bending and anisotropies of inadequately surface-treated, commercially available perfect crystals. In the wavelength range from about 0.1 to 2.5 nm there are three groups of crystals that offer high flexibility of the double crystal monochromator device with respect to spectral resolution, photon throughput and mechanical accuracy.     

新型红外探测器材料Hg1-x-y CdxZnyTe研究

采用移动加热器法(THM)进行了新型红外探测器材料 Hg1-x-yCdxZnyTe(MCZT)的晶体生长,获得的MCZT晶片经汞源退火后进行了光学特性、结构特性、电学性能和组分均匀性的检测与分析,并且初步制作成近室温工作的长波光电导器件,对器件性能进行了测试与分析。结果表明用移动加热器法生长Hg1-x-yCdxZnyTe晶体是成功的,获得晶片的材料特性与器件性能初步达到了应用水平。     

Single hot thermocouple technique for the characterization of the crystallization behavior of transparent or translucent liquids

Both time–temperature-transformation (TTT) and continuous-cooling-transformation (CCT) diagrams have been established to characterize the crystallization behavior of slags in a selected temperature range. Therefore, the single hot thermocouple technique based on already existing equipment was constructed showing also some different approaches. Furthermore, the procedure was enhanced using a stretching device enabling the formation of very thin slag layers. This device permits the investigation of not only transparent but also translucent liquids with low amounts of coloring oxides, e.g. Fe₂O₃. For the initiation of this method, a transparent synthetic NCAS-slag showing a high crystallization tendency was used to proper adjust the control parameters. Afterward, two industrial mould slags for the continuous casting of steel were investigated and TTT- as well as CCT-diagrams created. The TTT-diagrams for both mould slags show only one nose but the shapes of crystals formed differ dependent on temperature. This is contributed to the ratio of the growth to nucleation rate which is raised at higher temperatures where dendritic crystals are formed. For the case of continuous-cooling experiments observing only the formation of dendritic crystals precipitating at temperatures close to the liquidus temperatures the same explanation is assumed. Contrary, this ratio is decreased for rather low temperatures where only fine separate crystals precipitate.     

Single crystals of Dy1-xGdxVO4 for magnetic applications

Single crystals of Dy1-xGdxVO4 with a constant diameter were grown by the Czochralski method. These single crystals are antiferromagnetic in the temperature region below 3 K. The magnetization of the single crystals which have tetragonal symmetry along the a and c axes was measured with a superconducting quantum interference device magnetometer in the paramagnetic temperature region above 3 K. The Jahn–Teller effect for the magnetization on DyVO4 was weakened by the substitution. On the basis of the values of the magnetization, the magnetic entropy change along each crystal axis was estimated for the magnetic refrigeration. Single crystal Dy0.75Gd0.25VO4 is a promising material for the magnetic refrigerants using the Carnot cycle in the temperature range between 4.2 and 20 K. © 1998 Chapman & Hall     

Precise Patterning of Organic Semiconductor Crystals for Integrated Device Applications

Development of high‐performance organic electronic and optoelectronic devices relies on high‐quality semiconducting crystals that have outstanding charge transport properties and long exciton diffusion length and lifetime. To achieve integrated device applications, it is a prerequisite to precisely locate the organic semiconductor crystals (OSCCs) to form a specifically patterned structure. Well‐patterned OSCCs can not only reduce leakage current and cross‐talk between neighboring devices, but also facilely integrate with other device elements and their corresponding interconnects. In this Review, general strategies for the patterning of OSCCs are summarized, and the advantages and limitations of different patterning methods are discussed. Discussion is focused on an advanced strategy for the high‐resolution and wafer‐scale patterning of OSCC by a surface microstructure‐assisted patterning method. Furthermore, the recent progress on OSCC pattern‐based integrated circuities is highlighted. Finally, the research challenges and directions of this young field are also presented.     

A Microchannel-Confined Crystallization Strategy Enables Blade Coating of Perovskite Single Crystal Arrays for Device Integration

Perovskite single crystals (PSCs) possess superior optoelectronic properties compared to their corresponding polycrystalline films, but their applications of PSCs in high-performance, integrated devices are hindered by their heavy thickness and difficulty in scalable deposition. Here, a microchannel-confined crystallization (MCC) strategy to grow uniform and large-area PSC arrays for integrated device applications is reported. Benefiting from the confinement effect of the microchannels, solution flow dynamics is well controlled, and thus uniform deposition of PSC arrays with suitable thickness is achieved, meaning they are applicable for scale-up device applications. The resulting PSCs possess excellent optoelectronic properties in terms of a long carrier lifetime (175 ns) and an ultralow defect density (2 × 10⁹ cm⁻³), which are comparable to the corresponding bulk crystals. The unique embedded structure of PSCs within the microchannels allows the construction of a high-integration image sensor. This work paves the way toward high-throughput growth of PSCs for integrated optoelectronic devices.     

Patterning Techniques for Metal Organic Frameworks

The tuneable pore size and architecture, chemical properties and functionalization make metal organic frameworks (MOFs) attractive versatile stimuli‐responsive materials. In this context, MOFs hold promise for industrial applications and a fervent research field is currently investigating MOF properties for device fabrication. Although the material properties have a crucial role, the ability to precisely locate the functional material is fundamental for device fabrication. In this progress report, advancements in the control of MOF positioning and precise localization of functional materials within MOF crystals are presented. Advantages and limitations of each reviewed technique are critically investigated, and several important gaps in the technological development for device fabrication are highlighted. Finally, promising patterning techniques are presented which are inspired by previous studies in organic and inorganic crystal patterning for the future of MOF lithography.     

A simple mini-furnace for thermo-microscopy and crystal growth experiments

A fairly simple and inexpensive device for the preparation of single crystals (mm dimensions) from a melt is described. This is a minifurnace, permitting atmosphere control as well as continuous visual inspection of the sample through a stereomicroscope. A method to separate the crystals from the melt is also described. The device has been used for the preparation of crystals of several ternary compounds and for phase analysis studies in the $\text{A}$₂O-V₂O₅-V₂O₃ systems ($\text{A}\text{= Rb, Cs}$) in the temperature range 400–800°C and the O₂ pressure range 1–10^?25 atm. The oxygen activity which is crucial for these experiments, was controlled by the use of a ZrO₂(Y₂O₃) solid electrolyte EMF-cell.     

Fabrication of colloidal crystals with hierarchical structure and its water adhesion properties

A facile fabrication method of colloidal crystals with hierarchical structure has been presented. The colloidal crystals were assembled from latex spheres with various uneven surfaces, which were simply synthesized via emulsion polymerization by varying initiator feeding times. The as-prepared colloidal crystals demonstrated the water adhesion properties, which could be modulated by designing the hierarchical structure of latex surface. The result provided a simple fabrication method for colloidal crystals with hierarchical structure and high water adhesion force. This would greatly extend the applications of colloidal crystals to many other important fields, for instance, microfluidic device.     

Single crystals of RAlO3 (R: Dy, Ho and Er) for use in magnetic refrigeration between 4.2 and 20 K

Single crystals of RAlO3 (R: Dy, Ho and Er) were grown using the Czochralski technique. The magnetization of the single crystals along the a-, b- and c-axes was measured in the paramagnetic region using a superconducting quantum interference device (SQUID) magnetometer. Using these values of the magnetization, the magnetic entropy change, which depends on the crystal axis direction, was calculated. Single crystals of DyAlO3 oriented along the b-axis and c-axis oriented ErAlO3 single crystals are promising materials for use in magnetic refrigeration systems using the Carnot cycle in the temperature range between 4.2 and 20 K. This revised version was published online in November 2006 with corrections to the Cover Date.     

Device for the reversed-phase separation and on-target deposition of peptides incorporating a hydrophobic sample barrier for matrix-assisted laser desorption/ionization mass spectrometry

The separation of peptide mixtures from proteolytic cleavage is often necessary prior to mass spectrometry (MS) to enhance sensitivity and peptide mapping coverage. When buffers, salts, and other higher abundance peptides/contaminants are present, competition for charge during the electrospray ionization and matrix-assisted laser desorption/ionization (MALDI) processes can lead to ion suppression for the targeted analyte(s). In this note, a simple reversed-phase microcolumn sample separation and deposition device (Sep-Dep) is described. The use of this device improves or renders possible the analysis of complex or contaminated peptide mixtures by MALDI-MS. The method is simple and inexpensive and utilizes single-use low-cost Geloader-type columns packed with reversed-phase material. The device described utilizes an open column, allowing for a gradient or narrow-step gradient to be applied by any solvent delivery system or manually with a pipet. A key feature of the device is a deposition chamber that can be custom-built to hold any MALDI target. The Sep-Dep device is attached directly to an in-house vacuum line and draws solvent from the open-ended LC column. The elution of separated peptides is performed directly onto a target that has been treated with a hydrophobic barrier. This barrier effectively isolates fractions and improves the quality and morphology of the matrix crystals. The method produces efficient separations of proteolytic peptides, significantly reducing signal suppression effects in MALDI.     

Study of shear-induced interfacial crystallization in polymer-based composite through in situ monitoring interfacial shear stress

In order to further investigate shear-induced interfacial crystallization of polymer-based composites, an improved fiber-pulling device was designed and built. Its peculiar characteristic is that a force transducer is assembled to in situ monitor the variation of interfacial shear stress between the polymer matrix and pulling fiber. Thus, the relationship between interfacial shear stress and the subsequent crystalline morphology can be quantitatively established. In the preliminary study via this device, isotactic polypropylene (iPP)/glass fiber composite was adopted as a model system. The results indicate that interfacial crystallization kinetics is promoted by the presence of interfacial shear stress. Furthermore, there are two thresholds of interfacial shear stress for interfacial crystalline morphology. To be specific, one (0.017 MPa) is for the induction of iPP nucleation, above which α-form iPP crystals are obviously encouraged during the subsequent isothermal crystallization; the other is for the generation of β-form iPP crystals (0.042 MPa), above which β-form crystals are favored to be triggered in the transcrystalline region.     

Controllable Growth of High-Quality Inorganic Perovskite Microplate Arrays for Functional Optoelectronics

Inorganic perovskite single crystals have emerged as promising vapor-phase processable structures for optoelectronic devices. However, because of material lattice mismatch and uncontrolled nucleation, vapor-phase methods have been restricted to random distribution of single crystals that are difficult to perform for integrated device arrays. Herein, an effective strategy to control the vapor-phase growth of high-quality cesium lead bromide perovskite (CsPbBr₃) microplate arrays with uniform morphology as well as controlled location and size is reported. By introducing perovskite seeds on substrates, intractable lattice mismatches and random nucleation barriers are surpassed, and the epitaxial growth of perovskite crystals is accurately controlled. It is further demonstrated that CsPbBr₃ microplate arrays can be monolithically integrated on substrates for the fabrication of high-performance lasers and photodetectors. This strategy provides a facile approach to fabricate high-quality CsPbBr₃ microplates with controllable size and location, which offers new opportunities for the scalable production of integrated optoelectronic devices.     

A device for the light polarization selection

The properties of defect modes in chiral photonic crystals with anisotropic defects are considered, and changes in these properties caused by variations of the position of a defect layer in the system are analyzed. It is shown that, for certain thicknesses of a defect layer, a change in its position leads to a change in the ellipticity of the transmitted (reflected) light. This phenomenon can be used to create a device capable of selecting the polarization of light by changing the position of a defect layer. Such a device can also operate as a light modulator, a purely optical diode, or a bidirectional asymmetric switch. In a certain wavelength range, this light polarization selector can produce controlled rotation of the polarization plane.     

Growth and electrical characterization of the lead magnesium niobate-lead titanate (PMN-PT) single crystals for piezoelectric devices

The lead magnesium niobate-lead titanate is one of the new generations of piezoelectric materials with outstanding properties. Single crystals of 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-PT) show superior properties as compared to piezoelectric ceramics and piezoelectric films in device applications. Large size crystals are required for specific applications. Previously, transparent and high quality PMN-PT single crystals have been grown in our laboratory using the high temperature flux method. The size of the obtained crystals was small and varied from 2 to 8 mm³, mostly showing regular prismatic shape. In present attempt, PMN-PT crystals are grown from the vertical gradient freeze method with no flux using congruent melt. Processing conditions and growth parameters have been optimized to increase the size and yield of the perovskite crystals including cooling rate, soak time and soak temperature. The size of the grown crystals obtained by this method is very large relatively and varied from 5 to 30 mm³. The microstructure of the as grown single crystals is investigated by scanning electron microscopy. Piezoelectric properties of the grown crystals are also investigated. PMN-PT plates show excellent piezoelectric properties. Samples were poled under an applied electric field of 5 kV/cm. Dielectric properties at a frequency of 1 kHz are examined. Finally, the variation of pyroelectric coefficient with temperature is studied. The grown PMN-PT crystals show typical relaxor dielectric properties.     

A hybrid multiplexer/de-multiplexer for wavelength-mode-division based on photonic crystals

A hybrid multiplexer/de-multiplexer (HMUX/HDeMUX) for wavelength-mode-division based on photonic crystals (PCs) is presented. The proposed device consists of a point-defect cavity, a wavelength-selective cavity and asymmetrical parallel waveguides. Coupled-mode theory (CMT) is applied to the analysis, and the finite-difference time-domain (FDTD) method is used for the simulations. The simulation results show that the device can multiplex the fundamental and first-order modes of 1550 and 1310 nm. It exhibits not only a low insertion loss (<0.37 dB) but also low mode crosstalk (相似文献   

超声场中声压与空化对冰晶分裂的影响

为了探讨超声波强化冰晶二次成核的机理,利用自行研制的超声波冷却实验台,研究了超声波对未脱气蔗糖稀溶液和脱气蔗糖稀溶液中树枝状冰晶体的影响.实验结果表明:未脱气蔗糖稀溶液中的树枝状冰晶体受超声波辐射2s后已发生分裂,而脱气溶液中的树枝状冰晶体受功率相同的超声波辐射6s后却仍未分裂.说明超声场中冰晶发生分裂的主要原因是空化效应,而不是超声波在溶液中传播所引起的声压.     

Creation of line defects in holographic photonic crystals by a double-exposure thresholding method

Recording of periodic variations of amplitude and phase by the interference of coherent laser beams in a hologram offers a natural means for creating one-, two-, and three-dimensional photonic crystals. For device applications such as waveguides in optical communications, one usually needs to create defects in photonic crystals. We present an analysis and an experimental demonstration of a double-exposure method for creating photonic crystals with line defects. The idea is based on the principle of superposition of holographic grating patterns of different spatial periods while the recording medium is held stationary and on the application of a threshold to the recording medium. We use the same symmetrical optical architecture to achieve nondefective and defective holographic photonic crystals. The technique may be extended to the creation of defects based on functional synthesis by means of Fourier series, by use of light sources of other wavelengths with an appropriate high-contrast recording material.