Fluorescence determination of platinum with dibromohydroxyphenyl-fluorone in microemulsion after separation and enrichment by sulfhydryl dextrose gel

A new fluorescence quenching method has been developed for the determination of platinum in nonionic mieroemulsion medium.This method is based on the fact that platinum can form a stable chelate with dibromohydroxyphenyl-fluorine (DBHPF) when they are in the molar ratio of 12 in the nonionic microemulsion medium.Under optimum conditions,the system,having the maximum excitation and emission wavelengths at 468 nm and 532 nm,respectively,shows constant fluorescence intensity in the pH range of 3.5-4.0 and high selectivity and sensitivity as well as low interference from foreign ions.Furthermore,this fluorescence intensity is a linear function of Pt(Ⅳ) concentration in the range of 0.002-1.00 μg·mL-1 and the limit of detection is 2.90 ng·mL-1.     

Fluorescence determination of europium with pyridine-2,4,6-tricarboxylic acid

Europium can form a stable chelate with pyridine-2,4,6-tricarboxylic acid (PTA) with a ratio of 1:1 in aqueous. The system, having the maximum excitation and emission wavelengths at 311.0 nm and 616.3 nm, separately, shows a constant fluorescence intensity in the pH range of 11.0-12.0. The method has high selectivity and sensitivity as well as low effect from foreign ions. The optimum determinate conditions were obtained. The fluorescence intensity is a linear function of Eu^3 concentration in the range of 0.0029-1.5200 μg.mL^-1 and the limit of detection is 2.90 ng.mL^-1.     

Spectrophotometric determination of platinum after solid-liquid extraction with 1-(2-pyridylazo)-2-naphthol at 90°C

An effective spectrophotometric determination of platinum with 1-(2-pyridylazo)-2-naphthol (PAN) using molten naphthalene as a diluent was studied. A green complex of platinum with PAN is formed at 90℃. In the range of pH 2.5-6.5, the complex is quantitatively extracted into molten naphthalene. The organic phase is anhydrously dissolved in CHCl_3 to be determined spectrophotometrically at 690 nm against the reagent blank. Beer's law is obeyed over the concentration range of 0.5-5.0μtg/mL. The molar absorptivity and Sandell's sensitivity are 1.6×10~5 L·mol~(-1)·cm~(-1) and 0.0048 mg.cm~(-2), respectively. The optimum conditions for determination are obtained, The interferences of various ions are observed in detail. The method has been applied to the determination of platinum in synthetic samples.     

Development and application of titanium alloy casting technology in China

1 Introduction Titanium, which is named as the third metal after iron and aluminum, is an idea structure alloy for aerospace because of its unique properties such as high specific strength and high corrosion resistance [1-4].Using titanium alloy products, the weight of aerocraft can be greatly lightened and the performance of flight can be dramatically improved. In recent years titanium alloys are not only used widely in aerocraft but also in other industries in the world [6-9]. Due to its hig…     

Spectrofluorimetric determination of terbium with terephthalic acid

A spectrofluorimetric method has been developed for the determination of terbium(III) based on the formation ofa complex with terephthalic acid [benzene-1,4-dicarboxylic acid (TPA)] in slighdy acidic aqueous solution in the presenceof gelatin. Terbium ion can form a stable complex with TPA with the stoichiometry of 1:2. The best excitation and maxi-mum emission wavelengths are observed at 260 nm and 545 nm, respectively. The fluorescence intensity of terbium com-plex gets the strongest within 20 min and remains stable up to 10 h, and it is proportional to terbium(III) concentration in therange of 4.0×10-5-1.6×10-7 mol·L-1 under the optimum conditions. The fluorescence system has good selectivity, sensitivityand stability. The relative standard deviation is still within ±4% in the presence of 1200-fold amounts of the other lanthanideions when the concentration of terbium(III) is 1.0×10-6 mol·L-1 and common co-existing ions hardly interfere the determi-nation. It has been applied to the direct fiuori     

High strength bimetallic composite material fabricated by electroslag casting and characteristics of its composite interface

Bimetallic composite material of bainitic steel and PD3 steel was produced with electroslag casting process, and element distribution of its composite interface was investigated by theoretical calculation and energy dispersive spectrometer(EDS). Results show that the tensile strength(1,450 MPa), hardness(HRC 41-47) and impact toughness(94.7J·cm~(-2)) of bainitic steel were comparatively high, while its elongation was slightly low(4.0%). Tensile strength(1,100 MPa), hardness(HRC 31) and elongation(7.72%) of the interface were also relatively high, but its impact toughness was low at 20.4 J·cm~(-2). Results of theoretical calculation of the element distribution in the interface region were basically consistent with that of EDS. Therefore, electroslag casting is a practical process to produce bimetallic composite material of bainitic steel and PD3 steel, and theoretical calculation also is a feasible method to study element distribution of their interface.     

Effect of Processing on Microstructure and J_c of Ag-sheatbed(BiPb)_2Sr_2Ca_2Cu_3O_x Tapes

Ag-sheathed(Bi,Pb)_2Sr_2Ca_2Cu_3O_x tapes were fabricated by a powder-in-tube method.A high criticalcurrent density of 2.8×10~4 A/cm~2 at 77K,0T and 4×10~4 A/cm~2 at 4.2K,5T(H⊥ab),6.3×10~4 A/cm~2 at 4.2K,7T(H∥ab)is obtained.The microstructure of the tapes with high J_c values was in-vestigated by transmission electron microscope(TEM)and X-ray energy dispersive spectrum system(EDS).For comparison,a tape fabricated by a different procedure with a low J_c of about 1×10~4 A/cm~2 at77K,0T was also studied.The relationship between J_c and microstructure of the tapes and the effect of theprocessing on the microstructure and J_c were elucidated.     

Preparation of SO4^2-／TiO2-WO3 solid superacid and its catalytic activity in acetalation and ketalation

SO4^2-/TiO2-WO3 was prepared and its catalytic activity under different synthetic conditions was discussed with estedfication of n-butanoic acid and n-butyl alcohol as probing reaction. The optimum conditions are found that the mass fraction of H2WO4 used in the compound is 12.5%, the calcination temperature is 580℃, the calcination time is 3h, and thesoaked consistency of H2SO4 is 1.0 mol.L^-1. Then SO24-/TiO2-WO3 was applied as the catalyst in the catalytic synthesis of eight similar important ketals and acetals under the optimum conditions and revealed high catalytic activity. On condition that the molar ratio of aldehyde/ketone to glycol is 1:1.5, the mass fraction of the catalyst used in the reactants is 0.5%, and the reaction time is 1.0 h, the yields of ketals and acetals can reach 64.2%-95.1%. Moreover, it can be easily recovered and reused.     

A new method--the inverse strain method(ISM)for preventing welding hot cracking of high strength aluminium alloy LY12CZ

In this paper a new method for preventing welding hot cracking—theinverse strain method(ISM)is developed on the principle of welding mechan-ics.Effectiveness and feasiblity of method in preventing welding hot cracking ofhigh strength aluminum alloy LY12CZ by synchronous rolling during welding(SRDW)along both sides of the weld at a suitable distance behind the weldingarc are examined.Experimental resulte indicate that welding hot cracking ofLY12CY can be effectively prevented and the mechanical properties of weldedjoint can also be improved by the method.It is an important new solution forpreventing hot cracking in welding of sheet metal.     

Determination of Substitutional Carbon in SI-GaAs Thin Wafers by Infrared Microscope

Determination of substitutional carbon in SI-GaAs thin wafers was investigated by FT-IR microscopeat room temperature for the first time.The experimental results showed that the carbon concentration inGaAs thin wafers can be measured directly with simple treatment.The calculation method of carbon concen-tration is in agreement with that for normal IR spectrum with 0.5 cm~(-1)resolution.The resolution of1 cm~(-1)can be taken in order to obtain a high signal-to-noise(S/N)ratio using 2.34×10~(16)cm~(-2)calibration factor for calculating carbon concentration at room temperature.     

Simultaneous Determination of Zirconium and Hafnium by Dual System and Dual Wavelength Spectrophotometry

A dual system and dual wavelength spectrophotometry(DSDWS)used to simultaneously determine Zrand Hf were proposed.《Zr(Hf)-xO-CTMAB》and《Zr(Hf)-CAB-CDMAA-Triton X-100》were chosenas a pair of chromophoric systems.The difference of chromophoric behaviours between Zr and Hf is in-creased by the addition of hydrogen peroxide as masking agent and by adjustment of acidity.The apparentmolar absorptivities of Zr and Hf are 2.0×10~5 and 5.0×10~4 L·mol~(-1)·cm~(-1)respectively.The proce-dure is simple and rapid.     

Recovery and regeneration of Al_2O_3 with a high specific surface area from spent hydrodesulfurization catalyst CoMo/Al_2O_3

Aluminum recovery is a key issue for the overall recycling of valuable metals from spent catalysts. This paper focuses on the recovery and regeneration of alumina with high additional value from the spent hydrodesulfurization catalyst CoMo/Al_2O_3. The results indicate that 98.13% alumina is successfully leached from the treated spent catalysts by an alkaline leaching process under the conditions of 5 mol·L~(-1) sodium hydroxide,a liquid/solid ratio of 20 ml·g~(-1),a temperature of 160 0 C and a reaction time of 4 h. In the leaching residue, no difficult leaching compound is found and cobalt and nickel are enriched,both of which are conducive to the subsequent metal recovery step. The reaction order of aluminum leaching is 0.99. This reaction fits well with the interfacial chemical reaction model, and its apparent activation energy is calculated as 45.50 kJ mol~(-1). Subsequently, y-Al_2O_3 with a high specific surface area of 278.3 m~2·g~(-1), a mean size of 2.2 μm and an average pore size of 3.10 nm is then regenerated from the lixivium, indicating its suitability for use as a catalyst carrier. The recovery and regeneration of alumina from spent catalysts can not only significantly contribute to the total recycling of such hazardous spent catalysts but also provide a new approach for the preparation of y-Al_2O_3 with a high specific surface area using spent catalysts as the aluminum sources.     

Spline-based automatic path generation of welding robot

This paper presents a flexible method for the representation of welded seam based on spline interpolation. In this method, the tool path of welding robot can be generated automatically from a 3D CAD model. This technique has been implemented and demonstrated in the FANUC Arc Welding Robot Workstation. According to the method, a software system is developed using VBA of SolidWorks 2006. It offers an interface between SolidWorks and ROBOGUIDE, the off-line programming software of FANUC robot. It combines the strong modeling function of the former and the simulating function of the latter. It also has the capability of with on-line robot. The result data have shown its high accuracy and strong reliability in experiments. This method will improve the intelligence and the flexibility of the welding robot workstation.     

Epoxidation of propylene by molecular oxygen over unsupported AgCu_x bimetallic catalyst

The unsupported Cu and Ag catalysts with different oxidation states were prepared, and their catalytic performances for propylene epoxidation were investigated.The metallic Cu catalyst exhibits much higher catalytic activity and propylene oxide(PO) selectivity than Cu2 O and Cu O catalysts.The Cu0 species are the main active sites for propylene epoxidation, but Cu2 O and Cu O species are in favor of CO2 and acrolein production.The PO selectivity of 54.2 % and propylene conversion of 2.6 % can be achieved over the metallic Cu catalyst at 160 °C in initial stage, but metallic Cu catalyst would be oxidized to Cu2 O during propylene epoxidation, resulting in a sharp decrease in the PO selectivity and propylene conversion.Nanosize Ag Cuxbimetallic catalysts were prepared.It is found that adding Ag to the metallic Cu catalysts can prevent the oxidation of Cu and make Ag Cuxbimetallic catalysts more stable under the condition of propylene epoxidation.The Ag/Cu molar ratio can remarkably affect the catalytic performance of Ag Cuxcatalyst and the selectivity to PO and acrolein.After Ag Cuxwas supported on MOx-modified a-Al2O3, its catalytic performance can be improved and has a close relationship with the acid–base property of support.     

Effect of the Mass Ratio of CaCO3 to CaHPO4·2H2O on in Situ Synthesis of Hydroxyapatite Coating by Laser Cladding

Hydroxyapatite coatings were fabricated on Ti substrates by laser cladding (LC) using mixed powders of CaCO3 and dicalcium phosphate dihydrate (DCPD, CaHPO4·2H2O). The effect of the mass ratio of CaCO3 to DCPD on phase and microstructure formation of the coatings was investigated. The reactions between CaCO3 and DCPD can produce high crystallized hydroxyapatite (HA, Ca5(PO4)3(OH)) in the coatings as well as tetracalcium phosphate (TTCP, Ca4P2O9), α-tricalcium phosphate (α-TCP, α-Ca3(PO4)2), β-tricalcium phosphate (β-TCP, β-Ca3(PO4)2) and Ca2P2O7. The Ca/P molar ratio (CMR) of the mixed powders (CMRP) has a great influence on the contents of the phases in the coating. HA can be produced in the coating only when the CMRP is higher than 1.54, and its content increases slowly as the CMRP increases. The coating contains only about 25wt% HA when CMRP reaches 2.00, and there exists large amount of TTCP in the coating. So a post heat treatment with furnace cooling is recommended to increase the amount of HA in the coating. All the coatings have porous structures because the reactions between the powders produce lots of gases during LC. The pore size in the coating fabricated by the powders with CMR equal to 2.00 is about 100-300 mm. CMRP also has a great influence on the bond strength, porosity and cracks of the coatings. Along with the increase of the CMRP, the bond strength and porosity decrease, whereas the number of cracks increases     

Efects of Washing and Drying on Crystal Structure and Pore Size Distribution（PSD） of Zn4O13C24H12 Framework（IRMOF-1）

In this study,the efects of various methods of washing and drying of MOF-5 nanocrystals on structure formation were investigated.Eight samples of MOF-5 were synthesized under diferent conditions.TGA,XRD and PSD analysis were applied to characterize of the samples.The methods of washing and drying were found to be important in determining the final structure of MOF-5s.MOF-5 with high BET surface area can be obtained by choosing a suitable method of washing and drying.According to the results obtained in this work,it was found that vacuum drying at 425℃ is sufcient to dissolve the MOF-5-DMF.Similar results were obtained by washing method(with℃H2Cl2and℃HCl3),when compared with vacuum drying at 425℃ according to XRD test.The pore size distribution of samples 1-5 and 8 were calculated by SHN1 method and results showed that the samples in which solvent vacuum was DMF,have lower pore volume,uniform pore size distribution and the pore size are smaller than samples 3,4 and 8.It was also found that activated MOF-5can be converted to its deactivated form prior to drying of the samples.     

Micellar sensitized catalytic kinetic spectrophotometry for highly accurate and reproducible determination of Ⅴ(Ⅳ) and Ⅴ(Ⅴ)

A highly accurate and reproducible micellar sensitized kinetic method was proposed for determination of V(VI). The method is based on its catalytic effect on the oxidation of Coomassie brilliant blue R 250(CBB?) by bromate at pH 2.0. The reaction was monitored spectrophotometrically by measuring absorbance change with a fixed-time method of 5 min at 594 and 552 nm with and without surfactant. The variables influencing the calibration sensitivity were extensively investigated, and the optimal conditions were established. The linear calibration range was 10–1,600 lg L-1with a relative SD ranging from 0.35 % to 3.35 %(for five replicate measurements of75, 500, 1,000, and 1,500 lg L-1) and a detection limit of3.8 lg L-1. The selectivity was also investigated, and greatly enhanced by suitable masking agents. The method was successfully applied to the analysis of V(IV) in presence of excess V(V) up to 25 fold in environmental waters with the recoveries of 100.0 %–102.8 % for V(IV) and95.7 %–99.7 % for total V. Its accuracy was validated by analysis of certified reference material via the present kinetic method and standard flame atomic absorption spectrometric method after extractive preconcentration with good agreement between certified and found values.     

Microstructure and properties of TP2 copper tube with La microalloying by horizontal continuous casting

The TP2 copper tube was prepared with La microalloying by horizontal continuous casting(HCC). The absorptivity of La and its effects on microstructure, tensile and corrosion properties of HCC TP2 copper tube were studied by means of the inductively coupled plasma optical emission spectrometer(ICP-OES), optical microscope(OM), scanning electron microscope(SEM) and potentiodynamic polarization measurements. The results show that the absorptivity of La in the HCC TP2 copper tube is about 15% under antivacuum conditions due to the good chemical activities of La. The impurity elements in copper tube such as O, S, Pb and Si can be significantly reduced, and the average columnar dendrite spacing of the copper tube can also be reduced from 2.21 mm to 0.93 mm by adding La. The ultimate tensile strength and the elongation with and without La addition are almost unchanged. However, the annual corrosion rate of the HCC TP2 copper tube is reduced from 10.18 mm·a~(-1) to 9.37 mm·a~(-1) by the purification effect of trace La.     

Solubility of ammonium paratungstate in the system NH_3·H_2O·H_2O

The equilibrium solubilities of 5(NH4)O·12WO3·5H2O (APT·5H2O) were determined at the terminal ammonia concentration of 2 mol/L at 87-95℃. Experimental data were regressed. The linear functional relation between the solubility of APT- 5H2O and the temperature (t /℃) is given as y = - 588.08 + 7.28t. The solubility of the species as a function of the terminal ammonia concentration (x / mol · L-1) is also achieved: y = 36.76 + 18.86x. The solubility of APT · 5H2O produced by ion-exchange method in China is much lower, which is due to much lower silica, much higher NH4Cl, and a small amount of APT · 7H2O with low solubility in the APT crystals. APT · 7H2O forms because of a large amount of NH4Cl and the low activity of water in the crystallization.     

Precision control of inverter welding power sources by using T-S fuzzy systems

The functional relationship of approximation accuracy and number of fuzzy sets is used to find the rational balance point between the control accuracy and the control cost of fuzzy systems. This approach efficiently eliminates the drawback of rapid control cost increase caused by blind increase of fuzzy set number in practical engineering. The sufficient conditions for TS fuzzy systems as universal approximators are derived. A special T-S fuzzy system that satisfied these conditions is analyzed, and the simulation results show that when the number of fuzzy sets is increased moderately, the model parameters＇ training epochs can be effectually decreased while the model accuracy improved significantly. A practical welding power source controlled by a T-S fuzzy system is developed with satisfactory experimental results.