Ion source improvements at the Jena C-AMS facility

We report on an ongoing program of improvements of the Jena AMS system. The present contribution focuses on the improvement of the High Voltage Engineering Europe (HVEE) ion source 846. Furthermore it is described how the usable current range is determined at the Jena lab.     

Simulation of electrically tunable semiconductor nanopores for ion current/single bio-molecule manipulation

We show that a semiconductor membrane made of two thin layers of opposite (n- and p-) doping can perform electrically tunable ion current rectification and filtering in a nanopore. Our model is based on the solution of the 3D Poisson equation for the electrostatic potential in a double-cone nanopore, combined with a transport model. It predicts that for appropriate biasing of the membrane-electrolyte system, transitions from ohmic behavior to sharp rectification with vanishing leakage current are achievable. Further more, ion current rectifying and filtering regimes of the nanopore correspond to different charge states in the p–n membrane which can be tuned with appropriate biasing of the n- and p-layers.     

Dynamic neural network modeling for hydrochloric acid recovery process

This paper describes neural network models for the prediction of the concentration profile of a hydrochloric acid recovery process consisting of double fixed-bed ion exchange columns. The process is used to remove the Fe²⁺ and Fe³⁺ ion from the pickling liquor, resulting in increasing the acid concentration for reusing in the pickling process. Due to the complexity and highly nonlinearity of the process, the modeling of the process based on the first principle is difficult and involve too many unknown parameters. Therefore, an attractive alternative technique, neural network modeling, has been applied to model this system because of its ability to model a complex nonlinear process, even when process understanding is limited. The process data sets are gathered from a real hydrochloric acid recovery pilot plant and used for neural network training and validation. Backpropagation and Lenvenberg-Marquardt techniques are used to train various neural network architectures, and the accuracy of the obtained models have been examined by using test data set. The optimal neural network architectures of this process can be determined by MSE minimization technique. The simulation results have shown that multilayer feedforward neural network models with two hidden layers provide sufficiently accurate prediction of the concentration profile of the process.     

低压锅炉给水硬度分析检测方法综述

综述为保证低压锅炉给水总硬度不超过0．03mmol/L，根据不同情况采用相应的分析检测方法，控制离子交换器的运行终点。大部分方法经过宣传或培养操作人员后，已得到广泛地使用，并取得了良好的社会效果。     

Mechanical response of nitrogen ion implanted NiTi shape memory alloy

In the paper a change of material (mechanical) parameters of NiTi shape memory alloy subjected to ion implantation treatment is investigated. The spherical indentation tests in micro- and nano-scale and tension test have been performed to study an evolution of local superelastic effect in different volumes of nonimplanted and nitrogen ion implanted NiTi alloy. The differential scanning calorimetry has been applied to measure the change of characteristic temperatures due to ion implantation treatment. The structure of implanted material has been investigated using electron microscopy technique. It has been found that the ion implantation process changes the properties not only in a thin surface layer but also in bulk material. In the layer the pseudoelastic effect is destroyed, and in the substrate is preserved, however its parameters are changed. The characteristic phase transformation temperatures in substrate are also modified.     

Reducibility of Ce1−xGdxO2−δ in prospective working conditions

Nanocrystalline powders of CGO materials with different contents of Gd were prepared by a freeze-drying method and used to prepare dense ceramic samples. This method allowed one to obtain good quality samples to re-examine the reducibility of CGO materials. These materials were characterized by a combination of coulometric titration, impedance spectroscopy and ion blocking measurements to evaluate changes in point defect chemistry and mixed conducting properties. We have examined the onset of n-type conductivity as a function of temperature and oxygen partial pressure, and this information was used to re-examine the mixed transport properties in reducing conditions imposed by fuels, and also the OCV obtained with CGO solid electrolyte cells under air/CGO/fuel gradients. The polaron mobility was also evaluated and was found to depend slightly on temperature and to decrease with increasing oxygen deficiency. This confirmed that the electronic conductivity is mainly dependent on reducibility.     

A simple synthesis of magnetically modified zeolite

A composite of zeolite with magnetite was prepared by urethane coating. Formation of magnetic modified zeolite (MMZ) was confirmed by magnetization measurements and X-ray diffraction (XRD) pattern analysis. Also, scanning electron microscopic (SEM) analysis reveals the presence of zeolite and magnetite particles. It is thought that approximately 16% urethane polymer is retained in composite particle as a result of thermogravimetric analysis (TGA).     

Determination of biogenic amines in fresh and processed meat by ion chromatography and integrated pulsed amperometric detection on Au electrode

A selective cation exchange chromatographic method, coupled to integrated pulsed amperometric detection, has been developed to quantify biogenic amines in fresh and processed meat. The method is based on gradient elution of aqueous methanesulfonic acid with post column addition of a strong base to obtain suitable conditions for amperometric detection. A potential wave-form able to keep long time performance of the Au electrode was set up. The analysis time is about 68 min. Amounts of tyramine, putrescine, cadaverine, histamine, agmatine, spermidine and spermine were measured, after extraction with perchloric acid. The method was used to determine analytes in fresh and processed meat. Analyte quantification was made with external calibration method after demonstration that matrix effects were not present. All analytes were identified in real samples except phenethylamine which is eluted in a zone of the chromatogram rich of interfering peaks. Repeatabilities, computed on their amounts in real samples, were better than 9% for all of them. Detection limits were computed according to the Hubaux–Vos method. The obtained values ranged between 0.70 and 2.12 mg/l corresponding to 7–21 mg/kg, low enough to determine all analytes in real matrices.     

Electrostatic probe measurement in an industrial furnace for high-temperature air conditions

Electrostatic probe measurements are reported that identify flame location, displacement speeds of reaction region, and other flame properties within an industrial furnace that is operated with high-temperature preheated air. The electrostatic probe has advantages over other methods when a furnace is operated with high-temperature air. The probe consisted of a fine detection wire and a supporting tube that played a role of the reference electrode. The reaction regions were found to be widely dispersed and weakened as they moved downstream. However, the ion-current signals still included many sharp peaks, perhaps associated with the thin reaction thickness, contrary to the flame structure expected from the high-temperature air combustion. It was also possible to estimate the displacement speeds of reaction region by using the cross-correlation method between two ion current records detected by parallel detection components. The results demonstrate that the electrostatic probe is useful to detect the structure and state of the reaction mode in industrial furnaces even in the presence of high-temperature air combustion.     

Mass transfer of metal ion implantation into metal targets at elevated temperatures

A mass transfer model for metal ion implantation into a metal target at elevated temperatures has been built up based on transport of ions in matter and radiation enhanced diffusion. It is used to calculate concentration-depth profiles and compositional changes of the implanted species. The ion implantation at elevated temperatures was simulated by a dynamic Monte Carlo (MC) method, which takes into account a local saturation in the crystalline target by using a maximum atomic fraction allowed in the matrix. For the diffusion process, the transport of the implanted species was obtained from the diffusion equations for the implanted species and nonequilibrium vacancies. The radiation enhanced diffusion coefficient was obtained by taking into account linear annealing of the defects. A nonequilibrium vacancy source function and surface sputtering were introduced into the diffusion equations. Concentration-depth profiles of Cr, Fe and Ni ions implanted into Al at a temperature range from 200 to 510 °C were calculated. The calculated results principally were consistent with measured concentration-depth profiles obtained by Rutherford backscattering spectroscopy (RBS). In some cases deviations occur, which are discussed.