钽低温离子渗氮工艺参数对渗氮层物相的影响

利用组合的二次回归正交实验设计方案 ,对钽低温离子渗氮条件下 ,表面物相及固溶体中氮的含量随渗氮温度、气氛总压力和氢氮摩尔比的变化进行了系统研究。发现表面渗氮层由化合物Ta6N2 .57、超晶格TaN0 .1和固溶体相组成。氮在钽中的固溶度随气压、温度和氢摩尔分数的增加而增加 ,化合物和超晶格相含量随温度增加而增加 ,同时化合物相随氢摩尔分数增加有一个极大值 ,该极大值随温度增加而下降。     

固体透氧膜法制备金属Ta

利用固体透氧膜（SOM）法进行了从Ta2O5中提取金属Ta的实验．在1150℃，外加直流电解电压3．2V下，以55．5％MgF2-44．5％CaF2的熔盐体系为介质，阴极为经过预烧成型的Ta2O5，阳极为氧化锆管内的碳饱和铜液．测试结果显示：Ta2O5阴极中氧含量大大降低甚至消失，Ta2O5还原为金属Ta．     

水洗钽粉中氮的测定

针对水洗钽粉中杂质元素的干扰,采用EMGA-620W氧氮分析仪,测定了水洗钽粉中的氮,并与脉冲气相色谱法测氧氮(联测)进行了比较,认为该法快速、准确、可靠。     

Morphological and electrochemical investigation of RuO<Subscript>2</Subscript>–Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> oxide films prepared by the Pechini–Adams method

Preparation methods can profoundly affect the structural and electrochemical properties of electrocatalytic coatings. In this investigation, RuO₂–Ta₂O₅ thin films containing between 10 and 90 at.% Ru were prepared by the Pechini–Adams method. These coatings were electrochemically and physically characterized by cyclic voltammetry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The composition and morphology of the oxide were investigated before and after accelerated life tests (ALT) by EDX and SEM. SEM results indicate typical mud-flat-cracking morphology for the majority of the films. High resolution SEMs reveal that pure oxide phases exhibit nanoporosity while binary compositions display a very compact structure. EDX analyses reveal considerable amounts of Ru in the coating even after total deactivation. XRD indicated a rutile-type structure for RuO₂ and orthorhombic structure for Ta₂O₅. XPS data demonstrate that the binding energy of Ta is affected by Ru addition in the thin films, but the binding energy of Ru is not likewise influenced by Ta. The stability of the electrodes was evaluated by ALT performed at 750 mA cm⁻² in 80 °C 0.5 mol dm⁻³ H₂SO₄. The performance of electrodes prepared by the Pechini–Adams method is 100% better than that of electrodes prepared by standard thermal decomposition.     

Nonaqueous sol‐gel synthesis of InTaO4 nanoparticles and their assembly into macroscopic aerogels

Due to their band gap energy, metal tantalates absorb both ultraviolet and visible parts of the solar spectrum, which is beneficial to applications in photocatalysis. However, tantalates are very challenging to synthesize. In comparison to traditional solid‐state reactions, which often lead to impurities, wet‐chemical approaches starting from molecular precursors offer better homogeneity. In this study, amorphous InTaO₄ nanoparticles were synthesised in a nonaqueous sol‐gel method. Subsequent annealing at 800°C yielded crystalline and phase‐pure nanoparticles. In addition, the amorphous nanoparticles could be used as building blocks for the assembly into macroscopic gels by careful centrifugation. After supercritical drying, the three‐dimensionally interconnected microstructure was preserved, resulting in highly porous aerogel monoliths with a large surface area of 357 m² g^?1. Upon calcination, crystallization and 46% shrinkage of the aerogel occurred and a decrease in surface area to 49 m² g^?1 was observed. Uniaxial compression tests revealed the mechanical stability of these nanoparticle‐based aerogels. Although the large surface area and the ability to absorb visible light, combined with the unique mechanical properties, are ideal prerequisites to make these aerogels promising for photocatalytic reactions, the degradation of methylene blue only showed limited success.     

Adsorptive removal of refractory sulfur compounds by tantalum oxide modified activated carbons

Adsorptive desulfurization of a model diesel fuel consisting of dibenzothiophene (DBT) or 4,6‐dimethyldibenzothiophene(4,6‐DMDBT) in hexadecane was performed over activated carbons and tantalum oxide modified (Ta‐x/ACC, x= 2, 5 or 10 wt % Ta, Activated Carbon Centaur) activated carbons at 50°C. The adsorption isotherm for ACC followed the Langmuir model while the adsorption on Ta‐5/ACC fitted the Sips equation indicating more than one type of adsorption sites. Characterization studies indicated new types of adsorption site resulting from the incorporation of Ta oxide into the porous structure of the ACC. XPS data suggested interaction of Ta with the S atom in DBT. The heats of adsorption in the liquid phase determined from micro flow calorimetry for DBT in C16 confirmed the interaction of Ta with DBT. Ta‐5/ACC exhibited the highest adsorption capacity for 4,6‐DMDBT compared to literature reports. Competitive adsorption experiments showed the adsorption capacity as follows: quinoline> DBT? naphthalene. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Controlling phase separation of TaxHf1−xC solid solution nanopowders during carbothermal reduction synthesis

Synthesis of single‐phase tantalum hafnium carbide (Ta_xHf_1?xC, 0<x<1) solid solution nanopowders via carbothermal reduction (CTR) reaction is complicated due to the difference in reactivity of parent oxides with carbon and presence of a miscibility gap in TaC‐HfC phase diagram below ~887°C. These can lead to phase separation, ie, formation of two distinct carbides instead of a single‐phase solid solution. In this study, nanocrystalline Ta_xHf_1?xC powders were synthesized via CTR of finely mixed amorphous tantalum‐hafnium oxide(s) and carbon obtained from a low‐cost aqueous solution processing of tantalum pentachloride, hafnium tetrachloride, and sucrose. Particular emphasis was given to investigate the influences of starting compositions and processing conditions on phase separation during the formation of carbide phase(s). It was found that due to the immiscibility of Ta‐Hf oxides and relatively fast CTR reaction, individual nano‐HfC and TaC phases form quickly (within minutes at 1600°C), then go through interdiffusion forming carbide solid solution phase. Moreover, the presence of excess carbon in the CTR product slows down the interdiffusion of Ta and Hf dramatically and delays the solid solution formation, whereas DC electrical field (applied through the use of a spark plasma sintering system) accelerates interdiffusion significantly but leads to more grain growth.     

Photoluminescence characterization and heat treatment effect on luminescence behavior of BaTa2O6:Dy3+ phosphor

Undoped and Dy³⁺‐doped barium tantalate phosphors were synthesized by the solid‐state reaction method at 1425°C. Also, 10 mol% Dy³⁺‐doped BaTa₂O₆ was sintered between 1150 and 1425°C in order to determine temperature effect on structural and luminescence properties. Afterwards, they were characterized by XRD, SEM‐EDS and photoluminescence (PL) analyses. PL spectra exhibited the excitation peaks between 300 and 440 nm. Two typical emissions were observed at 486.2 nm (blue) and 577.7 nm (yellow) due to the ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions, respectively. Emission intensities increased with increasing doping concentration of Dy³⁺ up to 10 mol% and then decreased due to the concentration quenching effect. Moreover, depending on the increase in heat treatment temperature, the intensity of emission reached maximum at 1425°C. The calculated CIE chromaticity coordinates of phosphors located in the white light region.     

All‐in‐One Theranostic Nanoplatform Based on Hollow TaOx for Chelator‐Free Labeling Imaging,Drug Delivery,and Synergistically Enhanced Radiotherapy

Despite extensive use of radiotherapy in cancer treatment, there has been huge demand to improve its efficacy and accuracy in tumor destruction. To this end, nanoparticle‐based radiosensitizers, particularly those with high‐Z elements, have been explored to enhance radiotherapy. Meanwhile, imaging is an essential tool prior to the individual planning of precise radiotherapy. Here, hollow tantalum oxide (H‐TaOx) nanoshells are prepared using a one‐pot template‐free method and then modified with polyethylene glycol (PEG), yielding H‐TaOx‐PEG nanoshells for imaging‐guided synergistically enhanced radiotherapy. H‐TaOx‐PEG nanoshells show strong intrinsic binding with metal ions such as Fe³⁺ and ^99mTc⁴⁺ upon simple mixing, enabling magnetic resonance imaging and single photon emission computed tomography imaging, respectively, which are able to track in vivo distribution of those nanoshells and locate the tumor. With mesoporous shells and large cavities, those H‐TaOx‐PEG nanoshells show efficient loading of 7‐ethyl‐10‐hydroxycamptothecin (SN‐38), a hydrophobic chemotherapeutic drug. By means of the radiosensitization effect of Ta to deposit X‐ray energy inside tumors, as well as SN‐38‐induced cell cycle arrest into radiation‐sensitive phases, H‐TaOx‐PEG@SN‐38 can offer remarkable synergistic therapeutic outcome in the combined chemoradiotherapy. Without appreciable systemic toxicity, such hollow‐TaOx nanostructure may therefore find promising applications in multimodal imaging and enhanced cancer radiotherapy.     

Density Measurement of Liquid Ni-Ta Alloys by a Modified Sessile Drop Method

The density of liquid Ni- Ta alloys was measured by using a modified sessile drop method. It is found that the density of the liquid Ni- Ta alloys decreases with the increasing temperature, but increases with the increase of tantalum concentration in the alloys. The molar volume of liquid Ni- Ta binary alloys increases with the increase of temperature ancl tantalum concentration.