bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships between Impact Sensitivity and Molecular Electronic Structure
Authors: Mullay John
Published: December 2004

A very simple calculational procedure is used to investigate the electronic structure of several classes of organic explosives (polynitroaliphatics with trinitromethyl or fluorodinitromethyl groups, polynitroaromatics, polynitroaliphatic nitramines and aliphatic nitrate esters). The method utilizes a bond electronegativity equalization principle. It is shown that atom charges, bond electronegativities and charge transferred in a bond are all potential indicator quantities for predicting impact sensitivity trends for the various classes. Specifically it is shown that charge transferred to the nitro group through a trigger linkage (CNO2, NNO2, ONO2) can classify and correlate impact sensitivity trends in the compounds studied here. The results also indicate that electronic structure is not sufficient by itself to understand the phenomenon. This work in conjunction with previous work(1) shows that both a global quantity (i.e. related to the whole molecule) and a local quantity (i.e. related to the trigger linkage) are needed to understand impact sensitivity behavior.
Analysis of the Functioning of Bridgewire Igniters based on the fitted wire model
Authors: Prinse W. C. , Leeuw M. W.
Published: December 2004

This paper contains the results of a study concerning the thermoelectrical response of a bridgewire fuze head to a d.c. pulse. The experimental part of the study has been performed using a home‐built, improved version of the Thermal Transient Test. The experimental temperature of the bridgewire fuze head as a function of time and current amplitude is described by means of the “fitted wire model”, an extension of the well‐known Rosenthal model. The experimental results are in excellent agreement with the results obtained with the fitted wire model. On the basis of this fitted wire model and postulating a critical temperature of the bridgewire, induction times and energy and power characteristics can be calculated. Furthermore, the model enables the evaluation of the effects of changes in the model parameters upon the functioning of the bridgewire fuze head.
Ballistic Modification of RDX‐Based CMDB Propellants
Authors: Raman K. V. , Singh H.
Published: December 2004

The effect of lead and copper salts and certain metallic oxides was studied on the burning rates of RDX‐based CMDB propellants in the pressure region 35–105 [kg/cm2]. Lead methylene disalicylate (LMDS), basic copper salicylate (BCS). cobaltic oxide and lead stannate produced higher burning rates by 10%–16%. However, these additives were comparatively more effective with nitramine‐based CMDB propellants than AP‐based CMDB propellants. Fluorides of iron, lead and chromium were ineffective as burning rate catalysts. Inclusion of carbon black along with lead salts or metallic oxide gave only marginally higher burning rates. None of the ballistic modifiers studied produced plateau/mesa effect.
Computations of ESR Coupling Constants in Organic Radicals. II. Nitro derivatives of the phenyl radical
Authors: Hameka H. F. , Seiler F. J.
Published: December 2004

We compute the ESR coupling constants and the geometries of a set of nitro derivatives of the phenyl radical. We consider the three mononitrophenyls, the six dinitrophenyls and 2,4,6‐trinitrophenyl. The computations are based on the use of the Gaussian 82 Program Package with the STO‐3G basis set. There are no experimental data available.
Hazards encountered by firing monergolic liquid gun propellants
Authors: Klingenberg G. , Rockstroh H.
Published: December 2004

The sensitivity and hazard associated with the firing of monergolic liquid gun propellants is described in some detail taking a user oriented point of view. Emphasis is placed on the practical aspects encountered in the ignition and combustion of monopropellants in regenerative gun systems. This analysis is based upon experimental evidence obtained from compression ignition studies, closed bomb work and gun firings.
Dynamic Measurements in Combustible and Detonable Aerosols
Authors: Samirant M. , Smeets G. , Baras Ch. , Royer H. , Oudin L. R.
Published: December 2004

We present all the methods used at the ISL for determining the principal parameters of rapid fuel air aerosol dispersions and of their reactions, i.e. combustion and detonation. In a shock tube or in the free atmosphere. we measure the velocity of the dispersed fuel, the breaking of the droplets, their size distribution and their velocities. The investigation of the thermal variations due to the fuel evaporation allows to obtain the composition of the two‐phase mixture air/combustible gaz – fuel.
A temperature‐profile Study of the Combustion of Black Powder and its constituent binary mixtures
Authors: Brown M. E. , Rugunanan R. A.
Published: December 2004

An earlier thermo‐analytical study of black powder, using small sample masses and slow heating rates, has been extended to an examination of the behaviour of black powder under the less‐controlled conditions of ignition and combustion, by simultaneous measurement of temperature profiles and burning rates.

Burning‐rate against composition curves for various charcoal/KNO3, mixtures (sulphurless black powder) and for charcoal/KNO3, mixtures with various proportions of sulphur, were concave‐down‐type curves. The compositions of mixtures with maximum burning rates did not correspond with the compositions of mixtures with maximum enthalpy‐of‐reaction. Maximum temperatures of ∼1400°C were recorded. Burning rates were found to decrease with increasing particle size of the constituents: with increasing compaction of the mixtures, or when inert diluents or subsidiary fuels were added to the mixtures. Burning rates were also affected by moisture contents above 276, and failure of burning occurred at >15% moisture.
Explosives Research at Cerchar
Authors: Bigourd J. , Michot C.
Published: December 2004

From the very beginning. the Centre d'Etudes et Recherches de Charbonnages dc France (CERCHAR) has devoted part of its activity to explosive products. In the period from 1950 to 1970, this work was concerned only with the use of these products in coal mines, the main purpose being to reduce the risk of firedamp and coal dust ignition. For about the past fifteen years, CERCHAR's activities have also concerned:

the use of explosive products in mines other than coal mines, and in quarries. as regulations have often to bc adapted to new products and new techniques,

the general safety (manufacture, transport, storage and use) of explosive products for civil use, this work being generally directed towards a better appreciation of the risks involved.

This paper reviews the principal results of this research and outlines the studies now in progress.
A Study of molybdenum/barium chromate/potassium perchlorate delay system(1)
Authors: Rajendran A. G. , Ramachandran C. , Babu V. V.
Published: December 2004

The effect of percentage variation of Mo and KClO4 on Mo‐BaCrO4‐KClO4 delay system has been studied. The reaction sequence has been investigated by means of thermo‐gravimetry (TG): differential thermal analysis (DTA) and X‐ray diffraction studies. KClO4 is found to be essential to start the reaction, but its decomposition is not the rate determining step. Up to 20% of KClO4 leads to enhanced burning rate, while excess had the opposite effect. Mo in excess of stoichiometry increases the reaction rate which seems to depend on thermal conductivity rather than on the heat of reaction. DTA of the tricomponent system shows two exotherms. The first one is due to the reaction between Mo and KClO4 releasing enough heat to start the second reaction between Mo and BaCrO4. Then the products of these reactions viz. BaO and MoO3 combine to give BaMoO4. X‐ray diffraction data confirmed the products as BaMoO4, Cr2O4 and KCl, with excess Mo remaining unreacted.
Relationship between brisance of explosives and their molecular‐atomic structures
Authors: Eremenko L. T. , Nesterenko D. A.
Published: December 2004

The explosives with various molecular‐atomic structures substantially differ by their detonation velocities and brisance but often are similar by the expansion of their detonation products (DP's) which mainly consist of the same molecules. Such explosives referred to as “usual” show the relationship between ϱD and brisance determined by different methods. There are linear correlation relations between the results obtained.

This relationship is not observed with the “unusual” explosives which differ from the “usual” ones by the chemistry of detonation processes. These explosives include liquid explosives, explosive‐oxidants. CNO‐ and HNO‐explosives and also CHNOF‐explosives. Their calculation of thc detonation parameters and brisance from the same criterions which characterize the chemical composition of the explosives and the detonation products, results in some errors.

Taking these differences into account it is possible in some cases markedly to increase the accuracy of the detonation parameters. As an example is the calculation of the detonation pressure to within 3% based on the linear correlation relation between the pressure (PJ) and the relative detonation impulse (Irel) which characterizes the charge ability to do work at the initial stages of thc expansion of the detonation products:

The relative impulse, in its turn, may be calculated both for “usual” and “unusual” explosives from the atomic composition of an explosive, its density and the enthalpy of the formation with the error that does not exceed the experimental (2%).
Thermal Decomposition of Energetic Materials. 42. Fast thermal decomposition of five N‐Methyl substituted ethanediammonium dinitrate salts
Authors: Russell T. P. , Brill T. B.
Published: December 2004

The fast thermolysis of N‐methyl substituted ethanediam‐monium dinitrate salts is described by temperature profiling/FTIR spectroscopy. The salts described are [CH3NH2CH2CH2NH3](NO3)2 (MEDD), [CH3NH2CH2CH2NH2CH3](NO3)2 (SDMEDD), [(CH3)2NHCH2CH2NH3](NO3)2 (UDMEDD), [(CH3)2NHCH2CH2NH2CH3](NO3)2 (TRMEDD) und [(CH3)2NHCH2CH2NH(CH3)2](NO3)2 (TMEDD). MEDD, UDMEDD, SDMEDD and TRMEDD more closely resemble the behavior of alkylammonium mononitrate salts than primary alkanediammonium dinitrates in terms of the temperature at which HNO3 is released. However, TMEDD resembles the dinitrates. Both C‐C and C‐N bond fission occur based on the nature of the alkylamine products that are liberated.
Combustion of Black Powder. Part IV: Effect of carbon and other parameters
Authors: Hussain Ghulam , Rees Gwilym J.
Published: December 2004

Thermo‐analytical techniques such as DSC, TGDTG have been used to study the ternary mixtures of KNO3, S and charcoal/carbon black. S exists in two forms, one is called free sulphur on the surface of grains, while the other is termed adsorbed or trapped S. The first form of S, is removed between 175°C to 300°C while the second form is removed around 375°C. The ratio of two forms is altered by the grain and nature of carbon. Carbon black, as compared to charcoal, produces more energy from the oxidation of carbon. The effect of heating rate and the way the sample is placed, is also observed.
The stability characterization of the pyrotechnic system. The degradation of the nitrate oxidant in the presence of the magnesium under the accelerated aging conditions
Authors: Batinic‐Haberle Ines , Barisin Dubravka , Spasojevic Ivan , Vranic Zoran
Published: December 2004

The degradation of the nitrate oxidant was followed in the course of the aging process of tracer pyrotechnic mix containing 22.0 % Mg, 46.0 % Sr(NO3)2, 22.0 % KCIO4, 9.0 % Al‐Mg alloy and 4.0 % organic binder. The accelerated aging was conducted under the conditions of the increased humidity (98.5 %, 85.0 %, 78.5 %) at the increased temperature (75 °C). Nitrate content as a function of aging time was calculated by substracting nitrite nitrogen from total nitrogen content determined by Devarda's alloy reduction method. The degradation products of the nitrate (nitrite and carbonate) were determined by UV/VlS (Griess reaction) and IR spectroscopy, respectively. Nitrate proved to have a great instability in the presence of the metal, the extent of its conversion to nitrite and carbonate being rather great in comparision to the previously studied alkali metal nitrates in the presence of Mg as well. The loss of the nitrate and the formation of the nitrite and carbonate are governed by the same kinetic laws as fuel degradation to the hydroxide. The rate of the metal oxidation to the hydroxide was faster than the rate of the nitrate degradation process. The failure of the mix is connected to the rather small content of the nitrite (0.4 %) while the texture was significantly destroyed.
Combustion of Boron‐Based Slurries in a Ramburner
Authors: Liehmann W.
Published: December 2004

In a combustion chamber equipped with windows, boron and boron alloy slurries were burnt. The fraction of the solids in these mixtures was 25%. For the quantitive analysis of the reaction products, three spectrometer systems were used: an optical multichannel analyzer for the range 0.2 μm to 0.9 μm, an acusto‐optical tunable IR‐filter for the range 1.2 μm ‐ 2.4 μm, and rotating IR‐filters covering the range from 2.5 μm to 14.5 μm. The determination of the gas‐phase temperature of the exhaust plume was obtained by evaluation of the OH rotation bands. The particle temperature was measured with a fast two‐color pyrometer. During the burning process of boron with an average particle size of 2 μm, only a weak background radiation was detected. Mg and AlB2, produced a greater amount of particles in the exhaust due to their particle size of about 50 μm.

The spectra of the exhaust plume show typical bands for the particular metals and the combustion products of the JET Al fuel. Particle size distribution, surface characteristics, and temperature are important parameters for the ignition and combustion of solids. Also, the flow field inside the combustion chamber influences the burning behaviour of the solid particles. Therefore the slurries were injected against the main flow direction to produce high turbulence.
Developement of neutral polymeric bonding agents for propellants with polar composites filled with organic nitramine crystals
Authors: Kim C. Sue , Youn H. , Noble Paul N. , Gao Andrew
Published: December 2004

Versatile neutral polymeric bonding agents (NBPA's) have been developed for energetic propellants in which polar HMX particles are dispersed in a polar binder matrix containing highly polar plasticizers (TMETN, NG, etc.). Using a semi‐empirical approach through adjustment of solubility parameters and molecular weight, neutral acrylonitrile interpolymers were synthesized which mix uniformly with the submix and still have a high affinity for the HMX particles when they are added. Addition of about 0.2 % w/w of NPBA to HMX‐filled PEG binders increases the strength by a factor of as high as five compared to samples with no NPBA, and also eliminates the sudden decrease in modulus (knee) which occurs at relatively low elongation. The degree of filler reinforcement achieved by our NPBA's in energetic propellants is far superior to that achieved by adding nitrocellulose or any other previously proposed bonding agents, and similar to the effect of precoating the HMX particles with polyurea shells.
The importance of jet tip velocity for the performance of shaped charges against explosive reactive armor
Authors: Held Manfred , Schwartz Wolfgang
Published: December 2004

It is shown, that the portion of a shaped charge jet that emerges from explosive reactive armor is longer or at least less disturbed if the jet tip velocity can be raised. Generally, the residual jet length largely depends on the ratio of the reaction time of the armor and the standoff of the shaped charge from the armor.
Kinetic Deuterium Isotope Effects in the combustion of formulated nitramine propellants
Authors: Trulove Paul C. , Chapman Robert D. , Shackelford Scott A.
Published: December 2004

The kinetic deuterium isotope effect was used to investigate the rate‐limiting process in the combustion of formulated nitramine propellants. Model propellant formulations containing either octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), or their deuteriated analogues were pressed into pellets and burned under nitrogen pressure in a window bomb. The magnitudes of the observed deuterium isotope effects indicate that the HMX and RDX exert significant control over the combustion phenomenon of the propellants studied. Furthermore, assuming a consistent mechanism between decomposition and combustion, the observed isotope effects suggest that a carbon‐hydrogen bond rupture in HMX or RDX is the rate‐controlling step in the combustion of the model nitramine propellants. Observed isotope effect values for HMX‐CW5 and RDX‐CW5 formulated propellants at 1000 psig (6.99 MPa) pressure were 1.29 ± 0.09 and 1.24 ± 0.07, respectively, compared to a theoretical estimate of 1.29 for a primary effect due to CH bond rupture at 673 K.
Stabilizer reactions in cast double base rocket propellants. Part V: Prediction of propellant safe life
Authors: Sammour M. H.
Published: December 2004

Propellant deterioration can be kinetically analysed by both Berthelot's law and Arrhenius' law. Kinetic analysis of the mixed stabilizer para‐nitro‐N‐Methylaniline(pNMA)/2‐nitrodiphenylamine (2NDPA) based propellant deterioration at different temperatures, during the time necessary for the complete consumption of the more reactive stabilizer pNMA, which can be taken as a measure of the safe life of these propellant compositions, gave results for both Berthelot's law and the Arrhenius' law which are satisfactory. However, it was found that the predicted safe life for the propellant compositions according to the Arrhenius law was much longer than that obtained from Berthelot's law. Therefore, from the safety point of view, it is preferable to use Berthelot's law analysis to assess the safe life of double base propellant compositions.
Analysis of Strains, Strain Rates and Temperatures during the early stages of shaped charge liner collapse
Authors: Zernow Louis , Chapyak Edward J.
Published: December 2004

In trying to understand the extraordinarily high dynamic ductility of a copper shaped charge jet, prior work by the authors has utilized the Eulerian MESA 2D code with a novel form of the LaGrangean tracer particle technique as well as the experimental “soft recovery” and metallurgical examination of partially collapsed copper liners.

This work had indicated that localized material processing occurs during the earliest stages of liner collapse and causes dramatic visible grain size refinement, evident in the photomicrographs. Further computational analysis shows that the localized plastic flow is accompanied by very high localized engineering strains (>200), extremely high (>4 × 107 s−1) localized strain rates, as well as elevated temperatures, all of which favor a dynamic recrystallization process.

In this paper, the focus is on a detailed quantitative analysis of strain, strain rate and temperature distribution history within the collapsing liner, in the region of the inner liner apex and the early location of the moving collision zone, where the early material conditioning first occurs. Correlations are sought between the computed, time‐dependent values of these three paremeters and the microstructures observed in the interiors of the partially collapsed liners, in those regions where the grain size changes are observed. This data may ultimately permit quantitative comparisons with the predictions of dynamic recrystallization models.
Determination of the Thermal Diffusivity of a Zr/PbCrO4 Pyrotechnical Mixture and of the arrhenius parameters of the ignition reaction in presence of an oxidizing atmosphere
Authors: Marlin F. , Roux M. , Brassy C. , Espagnacq A.
Published: December 2004

An experimental device with main features closely related to those of Cook‐Off type(1) devices has been developed to attain the specific study requirements. The tested product is a pyrotechnical compound containing zirconium and lead chromate in the proportion of 60% Zr and 40% PbCrO4.

An iterative calculation method has been developed to determine thermal diffusivity without any reaction and to evaluate the Arrhenius kinetic parameters of the product ignition reaction.

The Zr/PbCrO4 compounds appear as cylindrical tablets dia. 14 mm and 11.7 mm high. From room temperature to about 100°C, thermal diffusivity ranges between 3.2 and 3.9. 107 m2/s. The ignition reaction kinetic parameters in an oxidizing atmosphere are as follows: Ea = 47 kJ/mol and Z = 10 · s−1. With the results from thermal analysis, we demonstrate that initiation can be attributed to the oxygen contained in air, which diffuses into the product porosities. Lead chromate behaves as an inert substance throughout the ignition phase.
Application of Crystal Lattice Disintegration Criteria to Compute Minimum Shock induced reactive conditions in solid explosives and inert materials
Authors: Billingsley James P. , Adams Carl L.
Published: December 2004

A threshold particle velocity criteria derived by E.R. Fitzgerald for the beginning of crystal lattice breakup and disintegration has been applied to shocked explosives and an inert material. In shocked explosives, reactions leading to detonation occur above a certain “threshold” magnitude. The computed crystal lattice breakup shock pressures compare rather well with observed experimental “threshold” shock pressures for six high explosives. The six explosives are: Comp‐B3, Comp‐B, TNT, PBX‐9404, Tetryl, and H‐6.

In addition, the crystal lattice breakup criteria provides an explanation for the observed lowering of the detonation “threshold” shock pressure as the explosives are made more porous or less dense.

Finally, the shock pressures, at which output from thermocouples embedded in shocked materials (PBX‐9404 and Plexiglass) increases dramatically, compare favorably with predictions based on crystal lattice disintegration criteria.

Consequently, it is tentatively concluded that crystal lattice breakup, or self‐sustained phonon fission as Fitzgerald calls it, is responsible for the initiation of detonation in shocked explosives and enhanced thermocouple output in shocked materials. It is also postulated that the lattice breakup phenomena is also responsible for phase changes, increased chemical reactivity, and anomalous electrical activity which are observed in certain inert materials under relatively low level shock loading.
Ignition mechanism of the Zr/PbCrO4 pyrotechnic mixture in presence of an oxidizing atmosphere
Authors: Brassy C. , Marlin F. , Roux M.
Published: December 2004

In presence of oxygen, the Zr/PbCrO4 (60%/40%) solid mixture exhibits a high amplitude exothermal reaction at low temperature (before reaching the oxidant decomposition temperature). We assume that the reaction is entertained by the air oxygen which continuously diffuses into the mixture pores.

The solid‐phase diffusion of oxygen through a zircon layer seems to constitute the limiting step of the reaction. To verify this assumption, a model allowing for diffusion in a protective oxide is developed. The results obtained with this model correspond to the tests for an apparent energy diffusion value varying between 130 kJ/mol and 170 kJ/mol. A value of 130 kJ/mol corresponds to the migration energy of the anionic gaps in a porous zircon layer. The evolution of the apparent diffusion energy can be attributed to the formation energy of crystalline defects (in particular anionic gaps).
Flame Atomic Absorption Spectrometric Determination of lead and titanium in samples of double‐base propellants
Authors: Baqir Sadiq J. , Jasim Fadhil
Published: December 2004

This research demonstrates how additives such as Pb(II) and Ti(IV) in powders of double‐base propellants (D‐BP) could be analysed by flame atomic absorption spectrometry (F‐AAS). No separation or preconcentration is needed. Both direct and spiked techniques have been applied successfully. The use of synthetic (simulated) D‐BP calibration standards is advocated for the analysis of real (D‐BP) samples. The effects of diverse ions and matrix modifiers are investigated. Sensitivity, detection limit, linearity, RSD% and recovery percent are calculated. It is foreseen that this analysis is suited to further application in other additives (usually present in D‐BP) e.g., nickel, cobalt, zinc, manganese, calcium and iron.
The Solubility of ϵ‐CL‐20 in Selected Materials
Authors: von Holtz Erica , Ornellas Donald , Foltz M. Frances , Clarkson Jack E.
Published: December 2004

The solubility of the epsilon polymorph of CL‐20 was determined in thirteen liquids over the temperature range of ambient to 74°C using high performance liquid chromatography. The experiments included ϵ‐CL‐20 produced by two different synthesis routes; one lot contained a higher level of polymorphic impurity, the other lot contained a higher level of non‐CL‐20 impurity.In general, the ϵ‐CL‐20 was found to be highly soluble in the solvents with carbonyl groups, and relatively insoluble in hydrocarbons and materials containing ether linkages. The amount of phase conversion to γ‐CL‐20 which occured during the solubility testing was measured using FTIR, and ranged from essentially zero to ∼ 10% conversion. It appears that the presence of β‐CL‐20 in the virgin ϵ‐CL‐20 lots will affect the amount of gamma‐phase present in the final residue.
Influence of Longitudinal Gaps on the Detonation Front
Authors: Held Manfred
Published: December 2004

Precursor air shocks with velocities that are 50 % higher than the velocity of detonation occur not only in cylindrical holes, but also in flat slits. By attaching to the test charge a sufficiently long plexiglass body with the same hole or slit profiles it is possible to observe the end face of the test charge and, thus, to record the changes in the detonation profile caused by slits, in particular by such that are oblique to the direction of detonation. One result is, that there is no through‐detonation across thin slits that are at a flat angle to the detonation wave.
Insights into OLED functioning through coordinated experimental measurements and numerical model simulations
Authors: Berner D. , Houili H. , Leo W. , Zuppiroli L.
Published: December 2004

Applying this method to the standard OLED device structure that has received broad attention in the literature, we have found a number of surprising results. From our experiments, we have demonstrated that the average electric field inside the hole transport layer is larger than or equal to the average field in the emission layer over the entire current range. The device simulations fully clarify the situation, giving insight into the space charge effects as well as the hole and the electron current distributions in the device. In particular, we found that there is a leakage of unrecombined holes towards the cathode at low voltages. We also found a strong variation of the electric field in the Alq3 layer due to space charge effects. By using the laser dye derivatives DCM‐TPA with electron trapping capabilities and DCM‐II with both electron and hole trapping capabilities as dopants in a standard OLED architecture, we could study the effect on transport and emission characteristics. In the case of the exclusively electron trapping dopant, a blue‐shift of the emission color with increasing bias is observed which we find is due to a splitting of the recombination zone.

Applying this method to the standard OLED device structure that has received broad attention in the literature, we have found a number of surprising results. From our experiments, we have demonstrated that the average electric field inside the hole transport layer is larger than or equal to the average field in the emission layer over the entire current range. The device simulations fully clarify the situation, giving insight into the space charge effects as well as the hole and the electron current distributions in the device. In particular, we found that there is a leakage of unrecombined holes towards the cathode at low voltages. We also found a strong variation of the electric field in the Alq3 layer due to space charge effects. By using the laser dye derivatives DCM‐TPA with electron trapping capabilities and DCM‐II with both electron and hole trapping capabilities as dopants in a standard OLED architecture, we could study the effect on transport and emission characteristics. In the case of the exclusively electron trapping dopant, a blue‐shift of the emission color with increasing bias is observed which we find is due to a splitting of the recombination zone.
A review of electron–phonon coupling seen in the high‐Tc superconductors by angle‐resolved photoemission studies (ARPES)
Authors: Cuk T. , Lu D. H. , Zhou X. J. , Shen Z.‐X. , Devereaux T. P. , Nagaosa N.
Published: December 2004

This issue of pss (b) – basic solid state physics contains a collection of Review Articles on the rather controversially discussed topic of Electron–Phonon Interaction in High‐Temperature Superconductors, guest‐edited by Miodrag Kulić, Johann Wolfgang Goethe‐Universität Frankfurt/Main, Germany, with a Preface written by V. L. Ginzburg and E. G. Maksimov [1].

The cover picture, taken from the review [2] by T. Cuk et al., shows plots of the electron–phonon coupling vertex, g2(k, k′), where k, k′ are the initial and final electron momentum for electrons scattered by the bond‐buckling phonon B1g (the out‐of‐phase vibration of the in‐plane oxygen) in a tight‐binding model of the copper–oxygen plane. The momentum dependence of this vertex, along with the d‐wave superconducting gap and the van Hove singularity at the anti‐node, accounts for the momentum dependence of the collective mode coupling seen in angle‐resolved photoemission data on Bi2212.

The present issue also sees the start of our rapid research letters, the fastest peer‐reviewed publication medium in solid state physics. For more information see www.pss‐rapid.com and the Editorial by the Editor‐in‐Chief Martin Stutzmann on page 7 [3].
Microwave‐Assisted Synthesis of Pyrimidine Libraries
Authors: Bagley Mark C. , Hughes David D. , Lubinu M. Caterina , Merritt Eleanor A. , Taylor Paul H. , Tomkinson Nicholas C. O.
Published: December 2004

Di‐ or trisubstituted pyrimidine libraries are prepared in good yield by the microwave irradiation of an alkynone and either an amidine or guanidine at 120–150 °C in acetonitrile in the presence of sodium carbonate or at 100 °C after treatment with methanolic sodium methoxide in a sealed tube using a monomodal microwave synthesiser. These rapid and efficient methods often require no chromatographic purification and so are appropriate for automated combinatorial methodology and have been applied in the synthesis of a small library of potentially useful novel ligands for the estrogen receptor based on the pyrimidine template.
Solid Phase Synthesis of 2‐substituted Melatonin Derivatives via Palladium‐mediated Coupling Reactions using Microwave Irradiation
Authors: Berthault Aurélie , Berteina‐Raboin Sabine , Finaru Adriana , Guillaumet Gérald
Published: December 2004

A comparative study between conventional thermal and microwave assisted procedures on solid support to generate pharmacomodulated melatonin analogues using Stille, Sonogashira, Heck and Suzuki palladium mediated reaction.
Rapid Access to a Pentacyclic Library Core Structure: A Microwave Assisted Approach
Authors: Patterson Stephen , Lorenz Christiane , Slawin Alexandra M. Z. , Westwood Nicholas J.
Published: December 2004

High throughput synthetic chemistry continues to develop in response to the challenges set by the genome projects. The ability to prepare large numbers of potentially bioactive compounds requires both technology and robust chemistry. Synthetic approaches that combine the use of microwave irradiation with facile isolation of products are therefore of importance. Here we describe a flexible approach to highly functionalised pentacyclic structures using microwave techniques. A range of pentacycles differing both in substituent patterns and ring size are prepared to exemplify the approach. Rapid access to these structures paves the way for the synthesis of libraries based on these cores.
Microwave Assisted Domino Knoevenagel Condensation/6π‐electron Electrocyclization Reactions for the Rapid and Efficient Synthesis of Substituted 2H,5H‐pyrano[4,3‐b]pyran‐5‐ones and Related Heterocycles
Authors: Leutbecher Heiko , Conrad Jürgen , Klaiber Iris , Beifuss Uwe
Published: December 2004

Both natural and unnatural compounds with a 2H,5H‐pyrano[4,3‐b]pyran‐5‐one skeleton are of interest to medicinal chemistry as they exhibit several different biological activities. This heterocyclic ring systems is accessible by a Domino Knoevenagel condensation/6π‐electron electrocyclization. A simple and rapid microwave assisted protocol of this Domino process has been developed for the preparation of libraries of substituted 2H,5H‐pyrano[4,3‐b]pyran‐5‐ones and related heterocyclic systems in a single preparative step by reaction of an α,β‐unsaturated aldehyde with a 6‐substituted 4‐hydroxy‐2H‐pyran‐2‐one.
Indirect Coupling of the 2(1H)‐pyrazinone Scaffold with Various (oligo)‐saccharides via “click chemistry”: en route towards Glycopeptidomimetics
Authors: Ermolat'ev Denis , Dehaen Wim , Van der Eycken Erik
Published: December 2004

The indirect coupling via a 1,2,3‐triazole ring system, of the 2(1H)‐pyrazinone scaffold with various saccharides is described. A microwave‐enhanced Cu(I)‐catalyzed Huisgen [2+3] dipolar cycloaddition reaction is applied. This opens the way for the generation of an interesting new class of glycopeptidomimetics.
XPS and Auger LMM analysis of ZnO/Si and ZnO/SiO2 interfaces
Authors: Raven M. S.
Published: December 2004

The interface between ZnO/Si and ZnO/SiO2 was studied by etching through the junction region and analyzing XPS and Auger LMM spectra. By comparing XPS shifts and peak splitting in the Si2p spectra, chemical complexes of the form Si—Ox—Zn (x≃1) were identified at the ZnO/Si interface. The transition from ZnO/SiO2 was characterized by intensity variations in the O1s spectra. Relative to metallic zinc the Auger LMM shifts were −4 eV for ZnO on Si and −3 eV for ZnO on SiO2. Such shifts were attributed mainly to extra‐atomic relaxation. Correspondence of levels (zero Auger shifts) was observed in the spectra from the two interface regions suggesting that zinc extra‐atomic relaxation was constant throughout a region of varying chemical composition.
Surface analysis of aromatic polyimide films using ESCA
Authors: Leary H. J. , Campbell D. S.
Published: December 2004

C 1s, N 1s and O 1s core spectra were measured for well‐cured polyimide films of poly(N,N′‐(p,p′‐oxydiphenylene)promellitimide), and of poly(p,p′‐oxybis(phenylene)‐3,3′,4,4′‐benzophenonetetracarboxylimide). Resolvable were: multiple C 1s, two N 1s and two O 1s components. A carbonyl deficiency not due to X‐ray‐induced decarboxylation was detected. Approximately 45% of the surface carbon matrix was found to be comprised of partially oxidized, non‐carbonyl‐containing moieties of unknown origin. C 1s chemical shift behavior showed that imide bond formation does occur on curing; the imidization reaction in the surface region is incomplete (or altered) based on the changes in the O 1s and N 1s data with increasing temperature of curing. A surface chemical structure inconsistent with the bulk structural formula is observed.
Electron beam effects in Auger electron spectroscopy and scanning electron microscopy
Authors: Fontaine J. M. , Duraud J. P. , Le Gressus C.
Published: December 2004

Electron beam effects on Si(100) and 5% Fe/Cr alloy samples have been studied by measurements of the secondary electron yield δ, determination of the surface composition by Auger electron spectroscopy and imaging with scanning electron microscopy. Variations of δ as a function of the accelerating voltage Ep (0.5<Ep<5 ke V), of the spot diameter ϕ (1 μm<ϕ<200 μm) and of the electron bombardment time t can be represented by simple expressions. The variations mainly affect the very low energy range of the n(E) distribution and correspond to volume phenomenon and surface effect. Impurities diffusing into or out of the irradiated regions cause changes in the contrast of scanning electron microscopy images at low bombardment levels. In contrast, the Auger electron spectroscopy peaks are modified only at high damage levels. The residual vacuum lower than 10 −9 Torr has no effect on technological samples covered with their reaction layers; the sensitivities to the beam depend rather on the earlier mechanical, thermal and chemical treatment of the surfaces.
The use of a new inelastic electron tunnelling spectrometer in the study of isomers of benzenedicarboxylic acid
Authors: Oxley D. P. , Bowles A. J. , Horley C. C. , Langley A. J. , Pritchard R. G. , Tunnicliffe D. L.
Published: December 2004

A spectrometer is described with particular reference to its resolution and to a novel quick change specimen holder. For the benefit of new workers in the field, the need for four‐point probe measurements is reiterated, together with the importance of suitable cleaning procedures during sample preparation and rigorous electrical screening of the spectrometer. A high resolution spectrum of benzoic acid is presented together with spectra of 1,2‐, 1,3‐ and 1,4‐benzenedicarboxylic acids. Brief mention is made of the use of a computer data acquisition system with the latter, full details being described elsewhere.
The dependence on the angle of incidence of the steady state sputter yield of silicon bombarded by oxygen ions
Authors: Warmoltz N. , Werner H. W. , Morgan A. E.
Published: December 2004

The increased dependence of the sputter yield of silicon on the angle of incidence under oxygen ion bombardment, as compared to argon ion bombardment, observed during a SIMS analysis is discussed. Taking into account that the sputter yield depends on the implanted oxygen concentration, a relation is derived between the steady state sputter yield and the implanted oxygen surface concentration for different angles of incidence. Since this relation is in itself insufficient to determine the steady state values of the sputter yield and the surface concentration actually obtained, a graphical method is used to combine it with a second one, viz. the dependence of the momentary sputter yield on the momentary surface concentration. Measurements of the steady state sputter yield of silicon, bombarded by oxygen ions in the lower keV range at different angles of incidence, agree with the predicted values.
Quantitative depth profiling in surface analysis: A review
Authors: Hofmann S.
Published: December 2004

After a brief survey of the various non‐destructive and destructive methods used for obtaining in‐depth composition profiles, the generally applicable method of ion sputtering in combination with a surface analysis technique is discussed in more detail. The quantitative evaluation of sputtering profiles requires the conversion of a measured signal intensity versus sputtering time into a true concentration versus distance from the original surface. Basically, this procedure comprises the quantification of the surface analysis method applied and the sputtering rate, both being dependent on sample composition. Furthermore, various phenomena limit the quantitative evaluation of depth profiles; the most important of which are ion and/or electron beam induced changes of surface composition and surface microtopography. Different factors such as information depth, ion beam inhomogeneity, original and beam induced roughness, knock‐on and atomic mixing effects, preferential sputtering, enhanced atomic migration etc. are discussed with respect to their influence on depth resolution and its dependence on sputter depth. Model calculations and their comparison with experimental data reveal the influence of these factors. In conclusion, the basic requirements for the optimization of sputter profiling are stated.
XPS and AES study of antimony oxides
Authors: Garbassi F.
Published: December 2004

XPS and AES have been applied to the surface analysis of antimony oxides, Sb2O3, Sb2O4 and Sb2O5. By means of the computer‐operated separation of oxygen and antimony contribution, the oxygen to metal atomic ratios calculated from XPS data were found to be close to the expected values. An antimony powder sample was found to be covered by a surface layer of Sb2O4 and the variations in shape of Auger MNN peaks of Sb during depth profiling are shown and discussed.
Results of a Ta2O5 sputter yield round robin
Authors: Bevolo A. J.
Published: December 2004

The ASTM E42.08 subcommittee on ion beam sputtering has sponsored a round robin to measure the sputter yield of anodic Ta2O5 films grown on tantalum. The purpose of this study was to compare the results from different laboratories and to test the suitability of this material as a standard for sputter yield measurements. Six different laboratories made 42 separate measurements of the sputter yield of Ta2O5 by determining the time to the Ta2O5/Ta interface during Auger depth profiles using 2 ke V Ar+ ions. The scatter of an individual set of measurements varied from 3 to 6% (except for one laboratory) while the means of the individual set of measurements varied about 10% from the average of all of the measurements. This result indicated the presence of systematic errors among the various laboratories. The possible sources of these errors are discussed.
Ion scattering spectrometry: A versatile technique for a variety of materials
Authors: Baun W. L.
Published: December 2004

The extraordinary surface sensitivity of low energy ion scattering spectrometry may be applied to the characterization of a wide variety of materials. On the one hand, the surface chemistry may be determined, using ion scattering spectrometry for engineering materials used in diverse technologies such as lubrication and adhesive bonding; such surface chemistry, perhaps involving only a few monolayers, may govern the success or failure of a process. On the other hand, ion scattering spectrometry is also useful in investigating the chemistry and physical and electronic structure of single crystals. The presence of fine features in the spectra enable shadowing and selective neutralization effects to be observed. Striking spectral features are seen in III–V, II–VI, and I–VII compounds. Scattered ion yield curves show a potential for the use of ion scattering spectrometry to determine bonding and electronic structure in some elements. In addition, conventional scattering experiments may be used to determine subtle elemental changes on crystal faces having different orientations. Adsorption‐desorption characteristics of different orientations may also be studied in conjunction with the complementary secondary ion mass spectrometry technique.
The depth dependence of the depth resolution in sputter profiling
Authors: Werner H. W.
Published: December 2004

It is shown that data from different authors on the depth dependence of the depth resolution can be compared only when both the instrumental parameter (β) and the intrinsic parameter (α) are taken into account. These two essential parameters are shown to be unique for every given ‘set of instrument and sample’. A linear z‐dependence was derived in a first approximation from experimental data. In this case it is shown that a power approximation in a (log (Δz/z)vs log z) plot, can have any value for the exponent between −1 and 0, dependent on the z‐interval considered. The z‐interval for which a given value of the exponent is obtained, in turn depends on α and β. The influence of the acceptance area and the primary ion energy on the intrinsic parameter α and the influence of the beam inhomogeneity on the parameter β are discussed. The implications of a non‐linear z‐dependence on the interpretation of experimental data are considered.
Electron inelastic mean free paths in several solids for 200 eV ⩽ E ⩽ 10 keV
Authors: Ashley J. C. , Tung C. J.
Published: December 2004

Values of k and p are given for predicting inelastic mean free paths for electrons with energies from 200 eV to 10 keV from the simple formula λ = kEp, based on theoretical calculations for ten elemental and compound solids. These results indicate that in the energy range 400 eV ⩽ E ⩽ 2000 eV, the value of p lies in the range 0.65–0.80. For Si and SiO2, presentation of the available experimental data and theoretical results illustrate the differences which exist in the values of electron mean free paths.
X‐ray photoelectron spectra of the U 4f levels in UF4, UF5 and UF6
Authors: Trowbridge L. D. , Richards H. L.
Published: December 2004

UF6, UF5 and UF4 have been studied by X‐ray photoelectron spectroscopy. U 4f7/2 binding energies for these compounds were observed to be 384.9, 383.4 and 382.3 eV, respectively. The corresponding U 4f5/2 energies were 395.7, 394.2 and 393.2 eV. Solid UF6 was formed by condensation of a molecular beam onto Ni and Cu substrates at −80° C. UF4 was produced by reaction of the UF6 beam at higher substrate temperatures (−30° C and 25 °C). UF5 was produced at higher temperature and pressure by reaction of Cu and UF6. In the X‐ray photoelectron spectroscopy vacuum chamber, the UF5 converted slowly to UF4, probably by disproportionation and loss of UF6.
Multilayer analysis of ion implanted GaAs using spectroscopic ellipsometry
Authors: Erman M. , Theeten J. B.
Published: December 2004

The large number of independent data measured by spectroscopic ellipsometry as well as the marked optical contrast between the amorphous and crystalline state of GaAs are the basic reasons for the feasability of a multilayer analysis from the ellipsometric data taken on an ion implanted GaAs sample. The mathematical method and its limitations (convergence, influence of noise and systematic errors) are discussed. It is illustrated with the case of 10 ke V B+ ions implanted in GaAs (100) at room temperature at a dose of 1014 ions cm−2. The depth profile of lattice damage is obtained and discussed. The effect of thermal annealing up to 400° C is also examined.
Topographic images of supported catalysts
Authors: Gómez A. , Hernández P. , José‐Yacamán M.
Published: December 2004

The topographic mode of imaging has been used to study the systems Pd on graphite, Pt on graphite and Pt on alumina. It is shown that this method can provide information on the shape of the particles, on the morphology of the substrates (including steps on their surfaces) and on the distribution of the particles with respect to substrate features. It is also shown that with this method particles can be detected which, due to their smallness and to the presence of substrate noise, are otherwise invisible.
Fast atom bombardment mass spectrometry for applied surface analysis
Authors: Surman D. J. , van den Berg J. A. , Vickerman J. C.
Published: December 2004

Fast atom bombardment mass spectrometry permits the detection of secondary ions from surfaces of insulator materials without the necessity for charge neutralization of the surface by electron bombardment. It thus opens the possibility of routine mass spectral analysis of surfaces yielding data concerning not only their elemental composition but also their chemical structure. The possibilities are illustrated from examples of the analysis of glass and catalyst surfaces.