Basic study on new cryogenic refrigeration using CO2 solid–gas two phase flow

In this paper, a cryogenic refrigeration method is described, which utilizes CO₂ solid–gas two phase flow and the dry ice. The CO₂ solid–gas two phase flow is achieved by expanding liquid CO₂ and thus refrigeration process less than CO₂ triple point −56.6 °C can be available. The experimental work is divided into two parts and two experimental set-ups were designed, constructed and tested. The interest of the first experiment test is the feasibility of expanding liquid CO₂ into CO₂ solid–gas flow in a horizontal circular tube by expansion valve. The second experiment focuses on the feasibility of the refrigeration of liquid CO₂ expanding into solid–gas two phase flows used in a prototype CO₂ heat pump system. The results show that solid–gas two phase flows can be achieved by expanding liquid CO₂ by expansion valve in a closed CO₂ heat pump system loop and low temperature refrigeration below −56.6 °C is achieved in the experiments, which give greater possibility to create a cryogenic refrigeration process below −56.6 °C for food industries, bio-medical engineering, etc.     

Studies on the formation of Langmuir monolayer and Langmuir–Blodgett films of octadecyl amine-bromocresol purple dye complex

Properties of the monolayer of octadecyl amine (ODA) molecules on aqueous solution of bromocresol purple (Bcp) dye have been studied over a wide range of pH by measuring the surface pressure-area isotherms. A strong interaction of ODA molecule was observed with the dye molecule in the pH range of 4–9. Under the present study, the dye molecules were adsorbed on the ODA monolayer at the water surface and subsequently a Langmuir–Blodgett (LB) film of ODA–dye complex was transferred from the air–water interface onto a solid substrate. Alternatively, dye molecules were incorporated into LB film by immersing the predeposited LB film of pure ODA into the dye solution, i.e. by adsorption of dye molecule at the solid–liquid interface. The adsorption behavior of ODA–Bcp dye complexes obtained through these two different routes was characterised with the help of UV–Visible spectroscopy. The nature of the ODA–dye complex deposited from air–water interface using the LB technique was found to be quite different from that of the complex formed by the adsorption of the dye into the pure ODA LB film. The adsorption spectra of the ODA–dye complex obtained from the air–water interface did not change with pH, while those of the ODA–dye complex formed from the solid–liquid interface showed pH dependence.     

超声强化溶剂提取车前草中总黄酮的研究

采用超声技术对车前草中总黄酮提取进行强化,选择料液比、超声提取时间、提取温度、超声功率四因素进行正交实验,得出影响总黄酮提取率大小的次序先后为：提取温度〉超声功率〉超声提取时间〉料液比。在实验参数的基础上,为了获得较高的提取率和节省溶剂用量,各因素的优化工艺参数为：料液比1：20,超声提取时间30min,超声提取温度为50℃,超声功率为200W,在这个最佳条件下试验,总黄酮的提取率为0．645％。相对常规回流提取法而言,采用超声法提取具有快速、节省溶剂、节省时间、提取的有效成分含量较高等优点。     

Formation of intermetallic compounds in the Cr–Al–Si ternary system

The microstructure and composition of binary and ternary intermetallics have been studied in ternary diffusion couples of Cr and an Al–Si eutectic alloy. The ternary intermetallic always formed in the liquid part of the diffusion couple as a dendritic structure. Two intermetallics compounds, CrSi₂ and Cr₅Si₃, of the Cr–Si binary system have been observed. The CrSi₂ intermetallic has a high solubility of up to 20 at.% Al and forms as faceted plates. A number of intermetallics, namely, CrAl₇, Cr₂Al₁₁, CrAl₄, Cr₄Al₉, Cr₅Al₈ and Cr₂Al, of the Cr–Al system have been observed. The solubility of Si varies from as low as 0.8 at.% in Cr₂Al to as high as 9 at.% in Cr₄Al₉. A schematic of the reaction scheme of the Cr–Al–Si system is presented. This has been based on the observed microstructure and composition of phases.     

Controllable formation of Er–Yb codoped Al2O3 films by the non-aqueous sol–gel method

1 mol%Er³⁺–10 mol%Yb³⁺ codoped Al₂O₃ thin films have been prepared on thermally oxidized SiO₂/Si(110) substrates by a dip-coating process in the non-aqueous sol–gel method from the hydrolysis of aluminum isopropoxide [Al(OC₃H₇)₃] under isopropanol environment. Addition of N,N-dimethylformamide (DMF) as a drying control chemical additive (DCCA) into the sol suppresses formation of the cracks in the Er³⁺–Yb³⁺ codoped Al₂O₃ thin films when the rare-earth ion is doped with a high doping concentration. Homogeneous, smooth and crack-free Er³⁺–Yb³⁺ codoped Al₂O₃ thin films form at the conditions by a molar ratio of 1:1 for DMF:Al(OC₃H₇)₃. A strong photoluminescence spectrum with a broadband extending from 1.400 to 1.700 µm centered at 1.533 µm is obtained for the Er³⁺–Yb³⁺ codoped Al₂O₃ thin films, which is unrelated to the addition of DMF. Controllable formation of the Er³⁺–Yb³⁺ codoped Al₂O₃ thin films may be explained by the fact that the DMF assisted the deprotonation process of Al–OH at the surfaces of gel particles, resulting in enhancement of the degree of polymerization of sols and improvement of the mechanical properties of gel thin films.     

Effects of growth conditions on the domain structure and dielectric properties of (1 − x)Pb(Sc1/2Nb1/2)O3–xPbTiO3 single crystals

The studies of the (1 − x)Pb(Sc_1/2Nb_1/2)O₃–xPbTiO₃ (PSN–PT) single crystals reveal that the chemical and physical properties of the materials are affected by the growth conditions. By the measurements of the dielectric constant as a function of temperature upon cooling, it is found that crystals grown from the same charged stoichiometric composition (x = 0.425), but under different flux environments (i.e. the composition of flux and the flux to PSN–PT ratios are varied), show anomalies (i.e. phase transitions) at different temperatures. This phenomenon is attributed to the complex local chemical structure of the PSN–PT solid solution single crystals with B-site random occupancy of three different cations (Sc³⁺, Nb⁵⁺ and Ti⁴⁺). The dielectric and domain structure of the PSN–PT crystals with composition near the morphotropic phase boundary (MPB) are investigated, showing much more complex situations compared with Pb(Sc_1/2Nb_1/2)O₃.     

Selective extraction of zinc(II) over iron(II) from spent hydrochloric acid pickling effluents by liquid-liquid extraction

The selective removal of zinc(II) over iron(II) by liquid–liquid extraction from spent hydrochloric acid pickling effluents produced by the zinc hot-dip galvanizing industry was studied at room temperature. Two distinct effluents were investigated: effluent 1 containing 70.2 g/L of Zn, 92.2 g/L of Fe and pH 0.6, and effluent 2 containing 33.9 g/L of Zn, 203.9 g/L of Fe and 2 M HCl. The following extractants were compared: TBP (tri-n-butyl phosphate), Cyanex 272 [bis(2,4,4-trimethylpentyl)phosphinic acid], Cyanex 301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid] and Cyanex 302 [bis(2,4,4-trimethylpentyl) monothiophosphinic acid]. The best separation results were obtained for extractants TBP and Cyanex 301. Around 92.5% of zinc and 11.2% of iron were extracted from effluent 1 in one single contact using 100% (v/v) of TBP. With Cyanex 301, around 80–95% of zinc and less than 10% of iron were extracted from effluent 2 at pH 0.3–1.0. For Cyanex 272, the highest extraction yield for zinc (70% of zinc with 20% of iron extraction) was found at pH 2.4. Cyanex 302 presented low metal extraction levels (below 10%) and slow phase disengagement characteristics. Reactions for the extraction of zinc with TBP and Cyanex 301 from hydrochloric acid solution were proposed.     

Microscopic observation of cold-deformed Al–4Cu–Mg alloy samples after semi-solid heat treatments

Wrought aluminum alloys can be effectively fabricated by a strain-induced, melt-activated (SIMA) process. The SIMA method involves plastic deformation of an alloy to some critical reduction point and a semi-solid heat treatment in the solid–liquid temperature range. The semi-solid heat treatment is a key process to control the semisolid microstructures. In this paper, the microscopic morphology of a cold-deformed SIMA treated Al–4Cu–Mg alloy has been investigated, and the effects of microstructural evolution, precipitation behavior and dislocation morphology on the mechanical properties are discussed. The experimental results show that the number of CuAl₂ (θ phase) precipitates and the dislocation density of Al–4Cu–Mg alloy decreased gradually by the semi-solid heat treatment. Moreover, unique dislocation morphologies including helical dislocations and dislocation loops appeared and evolved to reduce the stored energy. With an increase of the holding time in the semi-solid heat treatment, the ultimate strength and yield strength decreased. The reduction of these mechanical properties of the SIMA treated Al–4Cu–Mg alloy is mainly due to the decrease of refinement strengthening, solution strengthening, and dislocation strengthening in the semi-solid heat treatment.     

Growth of Fe3O4 whiskers from solid solution nanoparticles of Fe–Cu and Fe–Ag systems produced by DC plasma jet method

Fe–Cu and Fe–Ag binary systems are virtually immiscible for a whole range of composition in equilibrium. In the present study, the nanoparticles of Fe–Cu and Fe–Ag systems were produced by direct current plasma jet method. These produced nanoparticles had mean particle sizes of about 70 nm, and were a mixture of bcc and fcc phases. It was revealed by analytical high-resolution TEM observations that the nanoparticles of Fe–Cu and Fe–Ag systems were supersaturated solid solution. It has been found that numerous whiskers with a particle on their tip grow from these nanoparticles by heating above the temperature of 860 K under an Ar–O₂ atmosphere. The whiskers grow as the result of the phase separation in these solid solutions. The whiskers are composed of a Fe₃O₄ rod and a Cu₂O particle on the tip.     

VUV spectroscopy of a new fluoride system NaF–(Er, Y)F3

Emission and excitation spectra as well as luminescence decay kinetics of a new complex fluoride system Na_0.4(Y_1−xEr_x)_0.6F_2.2 (x=0.01, 0.1, 1) have been studied in the vacuum ultraviolet (VUV) spectral range. It has been shown that these crystals have intense VUV luminescence due to the interconfiguration 5d–4f transitions in Er³⁺ ion. The spin-allowed 5d–4f luminescence of Er³⁺ in this system is very weak, i.e., in these crystals there exists an efficient non-radiative relaxation from higher-lying 5d states of Er³⁺ to the lowest 5d level responsible for spin-forbidden luminescence. This makes the studied new fluoride system a promising active medium for the production of VUV solid state laser with optical pumping. Due to rather large bandwidth of Er³⁺ 5d–4f luminescence in this system there is a possibility for the construction of tuneable VUV laser.     

The investigations of adsorption layers on material surfaces by means of the thermogravimetry technique

A simple method has been adopted to obtain information about properties of the adsorbed liquid films, adsorbate–adsorbent interactions and the heterogeneity surfaces of the materials studied. The method utilizes Q-TG mass loss and the first derivative Q-DTG mass loss curves with respect to temperature and time obtained during programmed liquid thermodesorption in quasi-isothermal conditions. The obtained Q-TG and Q-DTG mass loss curves consist of steps and inflections which are associated with the properties of adsorbed liquid films and mechanism of the solid surfaces wetting process. Moreover, the Q-DTG curves reflect the energetical and geometrical heterogeneity of the solid surfaces. The heights of these steps and inflections depend on the adsorption capacity, desorption energy, the nature and number of the active centers of the samples studied. The values of the total porosity and the adsorption capacity obtained by this method are in good agreement with those estimated on the basis of independent methods. The experimental results provided novel data on the properties of liquid adsorbed films, heterogeneous properties of solid surfaces and thermal stability of the liquid/solid interface.     

高效液相色谱法测定卫生用纺织品中5种荧光增白剂的研究

本文主要通过研究色谱条件,萃取条件,方法的检测低限、回收率、重复性等内容,确定了利用高效液相色谱-二极管阵列检测器法测定纺织品中5种荧光增白剂(C.I.351,C.I.71,C.I.85,C.I.199:1,C.I.393)含量的最佳测试方法,即:检测波长为360nm,由乙腈和乙酸铵溶液为流动相梯度洗脱,萃取溶剂为水+N,N-二甲基甲酰胺(DMF)(40+60),萃取溶剂体积为25 m L,超声萃取时间为30min,萃取温度为60℃,5种荧光增白剂在0.1~50 mg/L浓度范围内的线性相关系数r为0.9993~0.9999,检测低限为0.5~2.5 mg/kg,不同添加水平时,回收率为83.5%~102.8%,相对标准偏差为2.1%~5.4%。该方法具有简便、快速、准确的优点,适用于纺织品中荧光增白剂的检测。     

Effects of peptizing conditions on nanometer properties and photocatalytic activity of TiO2 hydrosols prepared by H2TiO3

TiO₂ hydrosols were prepared from metatitanic acid (H₂TiO₃) by chemical precipitation–peptization method under various peptizing conditions. The effects of peptizing conditions on nanosized properties and photocatalytic activity of TiO₂ hydrosols were investigated. The crystal structure, crystallinity, particle size distribution, and transparency (T%) of as-obtained hydrosols were characterized by means of X-ray diffraction, transmission electron microscopy, light-scattering size analyzer, and UV–vis transmittance spectra. The results showed that the properties of hydrosols depended on peptizing conditions including a molar ratio of H⁺/Ti, temperature, and solid content. The photoactivity of TiO₂ hydrosols was evaluated in terms of the degradation of rhodamine B (RhB) in aqueous solution, and formaldehyde (HCHO) and methyl mercaptan (CH₃SH) in gaseous phase. The results showed that increase in H⁺/Ti ranging 0.19–0.75 led to the decrease in particle size and the increase in transparency. With increasing of temperature, particle sizes increased while the transparency and photoactivity decreased steadily when the temperature was higher than 65 °C. The particle size, transparency and photoactivity of the hydrosols hardly depended on solid content when it was not less than 2%. It should be confirmed that the hydrosols with higher crystallinity, smaller particle size and higher transparency could have the higher photoactivity for the degradation of RhB, CH₃SH, and HCHO. In this study, the optimal peptizing conditions were determined to be H⁺/Ti = 0.75, temperature = 65 °C and solid content = 2–6%.     

Microstructure and mechanical properties of two-phase Cr–Cr2Nb, Cr–Cr2Zr and Cr–Cr2(Nb,Zr) alloys

The microstructures and mechanical properties of binary and ternary Cr-based alloys containing Nb, Zr, or both Nb and Zr, have been studied in both the as-cast and annealed conditions. The level of alloying in each instance was targeted to lie below, or approximately at, the maximum solubility in chromium. The as-cast microstructures of these alloys consisted of Cr-rich solid solution surrounded by small amounts of interdendritic Cr–Cr₂X eutectic structure. Annealing at 1473 K resulted in solid-state precipitation of the Cr₂X Laves phase in the Cr–Nb and Cr–Nb–Zr alloys, but not in the Cr–Zr alloys. The binary Cr₂Nb phase consisted of an extensively twinned ({111}<112> twins) C15 structure whereas the presence of Zr modifies its appearance substantially; the twinned C15 structure persists. Oxides were occasionally present and their compositions were qualitatively determined. Vickers hardness primarily depended upon the volume fraction of the Cr₂X Laves phase present. Age hardening due to solid-state precipitation of Cr₂X Laves phase within the Cr-rich matrix was observed in the Nb-containing alloys. The room temperature bend strength of the alloys was strongly affected by the presence of grain-boundary Cr₂X phase. It is considered that porosity as well as oxides in the alloys also lowers their bend strength.     

A Surface‐Functionalized Ionovoltaic Device for Probing Ion‐Specific Adsorption at the Solid–Liquid Interface

Aqueous ion–solid interfacial interactions at an electric double layer (EDL) are studied in various research fields. However, details of the interactions at the EDL are still not fully understood due to complexity induced from the specific conditions of the solid and liquid parts. Several technical tools for ion–solid interfacial probing are experimentally and practically proposed, but they still show limitations in applicability due to the complicated measurements. Recently, an energy conversion device based on ion dynamics (called ionovoltaic device) was also introduced as another monitoring tool for the EDL, showing applicability as a novel probing method for interfacial interactions. Herein, a monitoring technique for specific ion adsorption (Cu²⁺ and Pb²⁺ in the range of 5 × 10^?6–1000 × 10^?6m ) in the solid–liquid interface based on the ionovoltaic device is newly demonstrated. The specific ion adsorption and the corresponding interfacial potentials profiles are also investigated to elucidate a working mechanism of the device. The results give the insight of molecular‐level ion adsorption through macroscopic water‐motion‐induced electricity generation. The simple and cost‐effective detection of the device provides an innovative route for monitoring specific adsorption and expandability as a monitoring tool for various solid–liquid interfacial phenomena that are unrevealed.     

Sol–gel deposition and characterization of Mn-doped silicate phosphor films

Mn²⁺-doped Zn₂SiO₄ and Mg₂Gd₈(SiO₄)₆O₂ phosphor films were deposited on silicon and quartz glass substrates by sol–gel process (dip-coating). The variations of sol viscosity with time and film thickness with the number of layers were investigated in Zn₂SiO₄: Mn system. The results of XRD and IR showed that the Zn₂SiO₄: Mn films remained amorphous below 700°C and crystallized completely around 1000°C. From AFM studies, it was observed that the grains with 0.5–0.8 μm size packed closely in Zn₂SiO₄: Mn films, which were uniform and crack free. The luminescence properties of Zn₂SiO₄: Mn films were characterized by absorption, excitation and emission spectra as well as luminescence decay. These properties were discussed in detail by a comparison with those of Mn²⁺ (and Pb²⁺)-doped Mg₂Gd₈(SiO₄)₆O₂ phosphor films.     

Influence of processing conditions on the luminescence of YVO4:Eu nanoparticles

Single-phase YVO₄:Eu³⁺ nanopowders were synthesized by sol–gel combustion method using citric acid as a chelating agent and reducer. The microstructures and photoluminescence (PL) properties of the as-prepared YVO₄:Eu³⁺ nanopowders were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and PL spectroscopy. The luminescence intensities of the YVO₄ nanoparticles doped with 5 mol% Eu³⁺ ions strongly depended on the calcination temperature, the molar ratio of citric acid to nitrates and the amounts of the Li⁺ additive.     

Glass formation and conductivity in the Pb2P2O7–Ag4P2O7–AgI system

A large glass-forming domain has been identified in the Pb₂P₂O₇–Ag₄P₂O₇–AgI system. The physical properties have been determined as a function of AgI content. The ionic conductivity has been studied as a function of the Ag⁺ ion total concentration and the Ag⁺ ion concentration issued from the AgI component. The structure and electrical properties of obtained glasses are compared with those of ionic glasses of the Ag₄P₂O₇–AgI system.     

Atomistic study of structural correlations at a liquid–solid interface

Structural correlations at a liquid–solid interface were explored with molecular dynamics simulations of a model aluminium system using the Ercolessi–Adams potential and up to 4320 atoms. Substrate atoms were pinned to their equilibrium crystalline positions while liquid atoms were free to move. The density profile at the interface was investigated for different substrate crystallographic orientations and temperatures. An exponential decay of the density profile was observed, ρ(z)e^−κz, leading to the definition of κ as a quantitative measure of the ordering at the liquid solid interface. A direct correlation between the amount of ordering in the liquid phase and the underlying substrate orientation was found.     

Rate dependence of hysteresis in one-dimensional phase transitions

Two models for solid–solid phase transitions in one-dimension are examined. Thermal dissipation and a rate-type viscosity are added to a stress with strain gradient. Numerical examination of both models reveal similar results, in particular, stress–strain hysteresis, which is a commonly observed phenomena, and stability of single-phase boundary solutions.