Diode laser thermal vaporization inductively coupled plasma mass spectrometry

An approach of sample introduction for inductively coupled mass spectrometry (ICPMS), diode laser thermal vaporization (DLTV) is described. The method allows quantitative determination of metals in submicroliter volumes of liquid samples. Laser power is sufficient to induce pyrolysis of a suitable substrate with the deposited sample leading to aerosol generation. Unlike existing sample introduction systems based on laser ablation, it uses a NIR diode laser rather than an expensive high-energy pulsed laser. For certain elements, this sample introduction technique may serve as an alternative to solution analysis with conventional nebulizers. Using a prearranged calibration set, DLTV ICPMS provides rapid and reproducible sample analysis (RSD ~ 10%). Sample preparation is fast and simple, and the prepared samples can easily be archived and transported. The limits of detection for Co, Ni, Zn, Mo, Cd, Sn, and Pb deposited on the preprinted paper were found to be in the range of 0.4-30 pg. The method was characterized, optimized, and applied to the determination of Co in a drug preparation, Pb in whole blood, and Sn in food samples without any sample pretreatment.     

Investigation of the Equivalence of National Dew-Point Temperature Realizations in the ?50?°C to +?20?°C Range

In the field of humidity quantities, the first CIPM key comparison, CCT-K6 is at its end. The corresponding European regional key comparison, EUROMET.T-K6, was completed in early 2008, about 4?years after the starting initial measurements in the project. In total, 24 NMIs from different countries took part in the comparison. This number includes 22 EURAMET countries, and Russia and South Africa. The comparison covered the dew-point temperature range from ?50?°C to +20?°C. It was carried out in three parallel loops, each with two chilled mirror hygrometers as transfer standards in each loop. The comparison scheme was designed to ensure high quality results with evenly spread workload for the participants. It is shown that the standard uncertainty due to the long-term instability was smaller than 0.008?°C in all loops. The standard uncertainties due to links between the loops were found to be smaller than 0.025?°C at ?50?°C and 0.010?°C elsewhere. Conclusions on the equivalence of the dew-point temperature standards are drawn on the basis of calculated bilateral degrees of equivalence and deviations from the EURAMET comparison reference values (ERV). Taking into account 16 different primary dew-point realizations and 8 secondary realizations, the results demonstrate the equivalence of a large number of laboratories at an uncertainty level that is better than achieved in other multilateral comparisons so far in the humidity field.     

Effects of formulation variables on surface properties of wood plastic composites

Degree of surface quality of wood plastic composites (WPCs) is a function of both raw material characteristics and the manufacturing variables. The WPC panels comprised of different panel densities (800, 950, 1000, and 1080 kg/m³), wood flour contents (50, 60, 70, and 80 wt.%), wood flour sizes (<0.5, ?0.5 to <0.8, 0.8–1, and >1 mm), and hot-pressing temperatures (190 and 210 °C) were manufactured using a dry blend/flat-pressing method under laboratory conditions. The surface smoothness of the WPC panels improved with increasing WPC density, plastic content, and hot-pressing temperature while it deteriorated with increasing wood flour size. The reduction in the particle size of the WF resulted in a more compact structure on the WPC surface. In general, the wettability of the samples increased by increasing surface roughness.     

Influence of process parameters on average particle speeds in a vibratory finisher

Vibratory finishing (VF) employs vibrationally-fluidized granular media to finish the surfaces of workpieces that are entrained in the flowing media. Its application has been based mostly on experience and trial-and-error due to the complexity of the granular material behavior. The present study used discrete element modeling (DEM) to investigate how the movement of a commercial two-dimensional tub finisher influenced the average particle speed of the media in a bed of smooth, steel, spherical particles, and thus the work that would be done on an entrained workpiece. The parameters governing the tub wall motion (frequency, in-plane amplitudes, and phases of vibration) and the coefficient of friction between the media and the wall were systematically varied in 71 three-dimensional DEM simulations. The average particle speed was affected mostly by the vertical amplitude of tub motion rather than by the frequency, and was mostly independent of other parameters of motion and of the wall friction. A strong relationship was found between the average particle speed and the work done by the wall per cycle of vibration. The normal force on the wall was also found to correlate strongly with the normal component of the wall velocity. Together, these relationships offer the potential to enable the analytical prediction of the average particle speed based on the motion parameters of the tub alone. The paper provides a set of practical guidelines for the control of the average particle speed in VF that are explained by the forces between the media and walls of the tub finisher.     

Threshold Fluence Measurement for Laser Liftoff of InP Thin Films by Selective Absorption

We explore conditions for achieving laser liftoff in epitaxially grown heterojunctions, in which single crystal thin films can be separated from their growth substrates using a selectively absorbing buried intermediate layer. Because this highly non‐linear process is subject to a variety of process instabilities, it is essential to accurately characterize the parameters resulting in liftoff. Here, we present an InP/InGaAs/InP heterojunction as a model system for such characterization. We show separation of InP thin films from single crystal InP growth substrates, wherein a ≈10 ns, Nd:YAG laser pulse selectively heats a coherently strained, buried InGaAs layer. We develop a technique to measure liftoff threshold fluences within an inhomogeneous laser spatial profile, and apply this technique to determine threshold fluences of the order 0.5 J cm^?2 for our specimens. We find that the fluence at the InGaAs layer is limited by non‐linear absorption and InP surface damage at high powers, and measure the energy transmission in an InP substrate from 0 to 8 J cm^?2. Characterization of the ejected thin films shows crack‐free, single crystal InP. Finally, we present evidence that the hot InGaAs initiates a liquid phase front that travels into the InP substrate during liftoff.

     

Directed Nanoscale Self‐Assembly of Low Molecular Weight Hydrogelators Using Catalytic Nanoparticles

The work presented here shows that the growth of supramolecular hydrogel fibers can be spatially directed at the nanoscale by catalytic negatively charged nanoparticles (NCNPs). The NCNPs with surfaces grafted with negatively charged polymer chains create a local proton gradient that facilitates an acid‐catalyzed formation of hydrogelators in the vicinity of NCNPs, ultimately leading to the selective formation of gel fibers around NCNPs. The presence of NCNPs has a dominant effect on the properties of the resulting gels, including gelation time, mechanical properties, and network morphology. Interestingly, local fiber formation can selectively entrap and precipitate out NCNPs from a mixture of different nanoparticles. These findings show a new possibility to use directed molecular self‐assembly to selectively trap target nano‐objects, which may find applications in therapy, such as virus infection prevention, or engineering applications, like water treatment and nanoparticle separation.     

Focussed Ion Beam

Focussed Ion Beam -“Cutting Edge” Technology of Material Analysis With the focussed ion beam technique it is possible to sputter almost any material with nanometer scale accuracy and directly image or chemically analyze structures below the surface. The major advantage towards conventional cross-section polishing is the high precision which allows to investigate even the smallest local defects. Applications of the focused ion beam even extend to the generation of complex nano structures. This article describes the operational modes, limits and constraints of the method and gives application examples from the field of material analytics.     

A model for warehouse layout

This paper describes an approach to determine a layout for the order picking area in warehouses, so that the average travel distance for the order pickers is minimized. We give analytical formulas that can be used to calculate the average length of an order picking route under two different routing policies. The optimal layout can be determined by using these formulas as the objective function in a nonlinear programming model. The optimal number of aisles in an order picking area appears to depend strongly on the required storage space and the pick list size.     

The development of an audit technique to assess the quality of safety barrier management

This paper describes the development of a management model to control barriers devised to prevent major hazard scenarios. Additionally, an audit technique is explained that assesses the quality of such a management system. The final purpose of the audit technique is to quantify those aspects of the management system that have a direct impact on the reliability and effectiveness of the barriers and, hence, the probability of the scenarios involved.

First, an outline of the management model is given and its elements are explained. Then, the development of the audit technique is described. Because the audit technique uses actual major hazard scenarios and barriers within these as its focus, the technique achieves a concreteness and clarity that many other techniques often lack. However, this strength is also its limitation, since the full safety management system is not covered with the technique. Finally, some preliminary experiences obtained from several test sites are compiled and discussed.     

Quantitative description of the microstructure–porosity of sialons and iron silicide inclusions

Sialon ceramics are a modern type of engineering ceramics with excellent mechanical, thermal and corrosion resistant properties. This paper describes the structure characterisation of porous sialon ceramics. It is possible to significantly improve the strength and crack resistance of sialon ceramics as a result of a reduction of the volume fraction of porosity.