Desorption and ionization mechanisms in desorption atmospheric pressure photoionization

The factors influencing desorption and ionization in newly developed desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS) were studied. Redirecting the DAPPI spray was observed to further improve the versatility of the technique: for dilute samples, parallel spray with increased analyte signal was found to be the best suited, while for more concentrated samples, the orthogonal spray with less risk for contamination is recommended. The suitability of various spray solvents and sampling surface materials was tested for a variety of analytes with different polarities and molecular weights. As in atmospheric pressure photoionization, the analytes formed [M + H](+), [M - H](-), M(+*), M(-*), [M - H + O](-), or [M - 2H + 2O](-) ions depending on the analyte, spray solvent, and ionization mode. In positive ion mode, anisole and toluene as spray solvents promoted the formation of M(+*) ions and were therefore best suited for the analysis of nonpolar compounds (anthracene, benzo[a]pyrene, and tetracyclone). Acetone and hexane were optimal spray solvents for polar compounds (MDMA, testosterone, and verapamil) since they produced intensive [M + H](+) ion peaks of the analytes. In negative ion mode, the type of spray solvent affected the signal intensity, but not the ion composition. M(-*) ions were formed from 1,4-dinitrobenzene, and [M - H + O](-) and [M - 2H + 2O](-) ions from 1,4-naphthoquinone, whereas acidic compounds (naphthoic acid and paracetamol) formed [M - H](-) ions. The tested sampling surfaces included various materials with different thermal conductivities. The materials with low thermal conductivity, i.e., polymers like poly(methyl methacrylate) and poly(tetrafluoroethylene) (Teflon) were found to be the best, since they enable localized heating of the sampling surface, which was found to be essential for efficient analyte desorption. Nevertheless, the sampling surface material did not affect the ionization mechanisms.     

Adhesion of extrusion‐coated polymer sealing layers to a fiber‐based packaging material with an atomic layer deposited aluminum oxide surface coating

Adhesion of extrusion‐coated polymer sealing layers on an atomic layer deposited (ALD) aluminum oxide (Al₂O₃) surface coating was investigated with a view to gain information on the applicability of ALD deposited barrier layers in fiber‐based packaging materials. The polymers used for the sealing layer were low density polyethylene (LDPE), polyethylene terephthalate (PET), and polylactide (PLA). They were extrusion‐coated onto the ceramic side of paper/PET/Al₂O₃ substrates, where the Al₂O₃ layer was a few tens of nanometers thick. According to the results, good adhesion was obtained for LDPE coating, whereas the other coatings showed a considerable lack of adhesion. Presumably, the oxidation faced by LDPE in the air gap of the extrusion‐coating process was able to create an extensive number of reactive sites that strongly bonded with the hydroxyl groups on the oxide surface of the substrate. With the PET and PLA coatings, such oxidation did not occur and the adhesion obtained remained at a relatively poor level. With all of the coatings, the adhesion levels were improved using corona discharge equipment as a pretreatment prior to the extrusion‐coating process. POLYM. ENG. SCI., 52:1985–1990, 2012. © 2012 Society of Plastics Engineers     

Utilisation of continuous atomic layer deposition process for barrier enhancement of extrusion-coated paper

The feasibility of a novel continuous atomic layer deposition process in improving the barrier properties of extrusion-coated papers was investigated. The polymer coatings on paper were low-density polyethylene, polypropylene, polyethylene terephtalate and polylactide. The new method was tested by depositing 100 nm aluminium oxide layers on the polymer side of the structures. According to test results, the aluminium oxide layer produced significant barrier improvements. The water vapour and oxygen transmission rates measured were approximately 3-5 times lower than those of the untreated samples. Even better improvements were found for the water vapour transmission rates of polyethylene terephtalate and polylactide coated papers being over 10 times lower than for the untreated structures. It is proposed that the better water vapour barrier improvements were found because of these polymers' disposition to water sorption in the non-processed samples. The continuous atomic layer deposition process caused also considerable changes in the topography and morphology of some polymers, which reduced the barrier properties and applicability of the structures. Further research is needed to enable the use of lower process temperatures in the continuous atomic layer deposition process, which would improve the feasibility of the new method.     

A Test of Two Methods for Waste Rock Drainage Quality Prediction: Aqua Regia Extraction and Single-addition Net-acid Generation Test Leachate Analysis

Mine Water and the Environment - The mobility of contaminants from mine waste can be assessed using different extraction methods. Aqua regia (AR) extraction is the most commonly used method in...     

A Novel Porous Tube Reactor for Nanoparticle Synthesis with Simultaneous Gas-Phase Reaction and Dilution

A novel porous tube reactor that combines simultaneous reactions and continuous dilution in a single-stage gas-phase process was designed for nanoparticle synthesis. The design is based on the atmospheric pressure chemical vapor synthesis (APCVS) method. In comparison to the conventional hot wall chemical vapor synthesis reactor, the APCVS method offers an effective process for the synthesis of ultrafine metal particles with controlled oxidation. In this study, magnetic iron and maghemite were synthesized using iron pentacarbonyl as a precursor. Morphology, size, and magnetic properties of the synthesized nanoparticles were determined. The X-ray diffraction results show that the porous tube reactor produced nearly pure iron or maghemite nanoparticles with crystallite sizes of 24 and 29 nm, respectively. According to the scanning mobility particle sizer data, the geometric number mean diameter was 110 nm for iron and 150 nm for the maghemite agglomerates. The saturation magnetization value of iron was 150 emu/g and that of maghemite was 12 emu/g, measured with superconducting quantum interference device (SQUID) magnetometry. A computational fluid dynamics (CFD) simulation was used to model the temperature and flow fields and the decomposition of the precursor as well as the mixing of the precursor vapor and the reaction gas in the reactor. An in-house CFD model was used to predict the extent of nucleation, coagulation, sintering, and agglomeration of the iron nanoparticles. CFD simulations predicted a primary particle size of 36 nm and an agglomerate size of 134 nm for the iron nanoparticles, which agreed well with the experimental data.

Copyright 2015 American Association for Aerosol Research     

Preparation of Mono‐, Di‐ and Hemicalcium Ferrite Phases via Melt for Reduction Kinetics Investigations

Iron ore concentrates that are used in the iron production are usually agglomerated into sinter or pellets in order to improve their properties in the blast furnace. The main minerals in the magnetite base sinters are hematite, magnetite and Si and Al containing calcium ferrites of which the latter can exist as either monocalcium ferrite, dicalcium ferrite or hemicalcium ferrite depending on the conditions and on the material's iron/calcium‐ratio. In order to study the reduction behaviour of the sinter in the iron production, samples of monocalcium ferrite, dicalcium ferrite and hemicalcium ferrite were prepared by melting different proportions of pure calcium and iron oxides. After melting the samples were cast and cooled. Samples of hemicalcium ferrite were also heated at a certain temperature before the actual reduction experiments in order to ensure the wanted phase composition of the samples. The mineral compositions of the samples were verified using scanning electron microscopy (SEM‐EDS) as well as X‐ray diffraction (XRD). The verification showed that it was possible to produce the samples of calcium ferrites via melting. The conditions needed to reduce the calcium ferrites were estimated with thermodynamic calculations.     

Screw optimization of a co-rotating twin-screw extruder for a binary immiscible blend

The effect of the screw configuration of a closely intermeshing co-rotating twin-screw extruder on residence time and mixing efficiency was studied for an uncompatibilized immiscible PA6/PP (80:20) bend. Alternative screw configurations were investigated systematically. The residence time distribution (RTD) was found to be a poor indicator of the total mixing efficiency, whereas the mixing intensity function yielded considerably better information. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good dispersion of the minor phase. The evolution of morphology along the screw axis depended strongly on the screw configuration. The downstream flow characteristics after the screw end determined the final morphology of the blend.     

Trends of phosphorus,nitrogen and chlorophyll a concentrations in Finnish rivers and lakes in 1975-2000

During recent decades the amounts of nutrients discharged to Finnish surface waters have markedly decreased. This has been achieved by considerable investments in water protection, which were made mainly to improve municipal and industrial wastewater purification. We investigated whether these water protection measures have decreased phosphorus and nitrogen concentrations in Finnish rivers and lakes. In addition, possible trends in chlorophyll a concentrations in lakes were studied. The data consisted of a total of over 68000 monitoring results of 22 rivers and 173 lakes (or sub-basins of lakes) with different types of catchment areas. The study period covered the years 1975-2000 and the non-parametric Kendall Tau b and Seasonal Kendall tests were applied for detecting trends. Decreasing nutrient concentration trends were typical in many lakes and rivers earlier polluted by municipal and industrial wastewaters. Increasing nutrient concentration trends were common in smaller rivers and lakes receiving diffuse loading from agriculture. The results show that the investments directed towards wastewater purification have effectively improved the quality of Finnish inland waters. However, no clear effects of decreasing non-point loading were found. Thus, more effective measures should be directed towards decreasing non-point source loading.     

Textural changes in metallurgical coke prepared with polyethylene

The effect of high-density polyethylene （HDPE） on the textural features of experimental coke was investigated using polar- ized-light optical microscopy and wavelet-based image analysis. Metallurgical coke samples were prepared in a laboratory-scale furnace with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% HDPE by mass, and one sample was prepared by 100% coal. The amounts and distribution of textures （isotropic, mosaic and banded） and por~s were obtained. The calculations reveal that the addition of HDPE results in a decrease of mosaic texture and an increase of isotropic texture. Ethylene formed from the decomposition of HDPE is considered as a probable reason for the texture modifications. The approach used in this study can be applied to indirect evaluation for the reactivity and strength of coke.     

Comparative experimental study of sand and binder for flowability and casting mold quality

A good sand mold is an indispensable prerequisite to obtaining a good metal casting. Although sand casting is one of the oldest metal forming technique known to humans, it still has a lot to discover. In a bid to meet the ever-growing demand for quality, economics and increasing environmental restrictions, research is still ongoing to optimize for example the process of making the sand mold. This paper presents a comparative study of six different foundry sands for flowability using simple inexpensive apparatus and some quality parameters achieved by these sands when used with three different types of binder, two organic and one inorganic. The study aims to facilitate the choice of mold materials with a more extensive outlook into their characteristics through a serious of sand and mold tests. A good comparison of already existing materials provides a good reference point when novel materials are investigated. All the sands exhibited ‘good’ flow property according to the simple flowability tests done. However, not the same consensus for flowability rank is reached by all the flow tests. The mold quality tests reveal the strength, loss on ignition and permeability values achieved with each of the binder and sand combination which can also be used in mold material selection.