bluuebunny/crossref_metadata_2025_split huggingface dataset:
Superplasticity and high temperature deformation behaviour in nano grain Tungsten compacts
Authors: Ameyama K. , Oda E. , Fujiwara H. 
Published: April 2008

AbstractNano grain tungsten is fabricated by Mechanical Milling (MM) process, and its grain growth behavior and high temperature deformability is investigated. As a result, a nano grain structure, whose grain size is approximately 20 nm or less, is obtained after MM for 360ks. Those nano grains demonstrate an irregular grain boundary structure, i.e., “non‐equilibrium grain boundary”, and they change to a smooth grain boundary structure by annealing at 1023 K for 3.6 ks. Compacts with nano grain structure indicate superior sintering property even at 1273 K (0.35 Tm). Rhenium addition prevents grain growth during sintering and thus the compacts indicate a further improvement in deformability. The compact is composed of equiaxed grain, whose grain size is 420 nm, and has low dislocation density even after the large deformation. The strain rate sensitivity, i.e., m‐value, of 0.41 is obtained in the W‐Re compact at 1473 K. Those results strongly imply that the nano grain W‐Re compacts show superplasticity at less than half of the melting temperature, i.e., 1473 K (0.42 of the solidus temperature).
Magnesium tube hydroforming
Authors: Liewald M. , Pop R. 
Published: April 2008

AbstractMagnesium alloys reveal a good strength‐to‐weight ratio in the family of lightweight metals and gains potential to provide up to 30 % mass savings compared to aluminium and up to 75 % compared to steel. The use of sheet magnesium alloys for auto body applications is however limited due to the relatively low formability at room temperature.Within the scope of this paper, extruded magnesium tubes, which are suitable for hydroforming applications, have been investigated. Results obtained at room temperature using magnesium AZ31 tubes show that circumferential strains are limited to a maximal value of 4 %. In order to examine the influence of the forming temperature on tube formability, investigations have been carried out with a new die set for hot internal high pressure (IHP) forming at temperatures up to 400 °C. Earlier investigations with magnesium AZ31 tubes have shown that fractures occur along the welding line at tubes extruded over a spider die, whereby a non‐uniform expansion at bursting with an elongation value of 24 % can be observed. A maximum circumferential strain of approx. 60 % could be attained when seamless, mechanically pre‐expanded and annealed tubes of the same alloy have been used. The effect of annealing time on materials forming properties shows a fine grained structure for sufficient annealing times as well as deterioration with a large increase at same time. Hence, seamless ZM21 tubes have been used in the current investigations. With these tubes, an increased tensile fracture strain of 116 % at 350 °C is observed as against 19 % at 20 °C, obtained by tensile testing of milled specimens from the extruded tubes. This behaviour is also seen under the condition of tool contact during the IHP forming process. To determine the maximum circumferential strain at different forming temperatures and strain rates, the tubes are initially bulged in a die with square cross‐section under plane stress conditions. Thereafter, the tubes are calibrated by using an optimised pressure‐time curve. The IHP forming process has also been used to demonstrate practicability and feasibility for real parts by manufacturing a technology‐demonstrator part using the magnesium alloy ZM21.
A pilot study of self‐monitoring urine flow in people with long‐term urinary catheters
Authors: Wilde Mary H. , Brasch Judith 
Published: April 2008

AbstractSelf‐monitoring of urine flow may be beneficial in preventing catheter‐related problems. An intervention was pilot tested using a single group design with 11 individuals over 6 months. Feasibility of the intervention, performance of new measures (awareness, self‐monitoring, and self‐ management of urine flow), and health outcomes were assessed. The intervention was well received by participants, none of whom withdrew voluntarily from the study. All data were collected at intake, and bimonthly at 2, 4, and 6 months. Nine of 11 participants reported that the intervention had helped them to pay attention to fluid intake. Episodes of UTI decreased over the course of the intervention, with the greatest drop between 2 and 4 months. © 2008 Wiley Periodicals, Inc. Res Nurs Health 31:490–500, 2008
Microcombustion calorimetry as a tool for screening flame retardancy in epoxy
Authors: Morgan Alexander B. , Galaska Mary 
Published: April 2008

AbstractThrough the use of microcombustion calorimetry several polymer nanocomposite, flame retardant (FR), and polymer nanocomposite + FR systems were screened for flammability performance. The use of this technique allowed for the creation of small batch (less than 50 g) epoxy formulations as compared to 400–500 g needed for cone calorimeter testing of epoxy + fiberglass panels. The results from the microcombustion calorimeter screening suggested that the system with the best flammability performance was a combination of organophosphonate and zinc borate, and not one of the polymer nanocomposite systems. This best candidate was then scaled up and fabricated into a fiberglass‐reinforced composite which was further tested by a cone calorimeter. This paper shows some of the correlations between the microcombustion and cone calorimeter results for this single sample, provides some reasons for why the polymer nanocomposite samples did not provide the best results in flammability reduction, and suggests some caveats when using microcombustion calorimetry as the only screening tool for flammability. Copyright © 2008 John Wiley & Sons, Ltd.
pH sensor based on polyaniline and aniline–anthranilic acid copolymer films using quartz crystal microbalance and electronic absorption spectroscopy
Authors: Ayad M. M. , Salahuddin N. A. , Abou‐Seif A. K. , Alghaysh M. O. 
Published: April 2008

AbstractThe pH sensitivity based on conducting polyaniline (PANI) and copolymer of aniline and o‐anthranilic acid (AA) films were studied using quartz crystal microbalance (QCM) technique and UV–Vis spectroscopy. The sensor was constructed from these polymer films coated on the electrode of the QCM. The resonant frequency changes as a function of pH in the range of 2–12 were measured. These changes are quantitative indication of the degree of dedoping or redoping of the polymer films upon the subsequent exposure of the electrode to 0.25 M sulfuric acid and different pH solutions. There are two linear regressions between the frequency change and pH with two different and opposite slopes in the regions from 2 to 9 and 9 to 12. The pH sensitivity of the copolymer film was found to be less than using the PANI film. Thin films of PANI and copolymer, which were chemically polymerized in a sulfuric acid solution, were deposited onto the inner walls of the quartz cuvettes. The UV–Vis absorption spectra of these films were measured in different pH solutions. Relations between the maximum absorption and its wavelength versus pH were constructed. The copolymer film shows some advantages over the PANI film. The difference between the PANI and copolymer films as pH sensors using the QCM and electronic absorption extends from the determination of pKa for both films. Copyright © 2008 John Wiley & Sons, Ltd.
Monitoring of beet armyworm resistance to spinosad and methoxyfenozide in Mexico
Authors: Osorio Aniceto , Martínez Ana M , Schneider Marcela I , Díaz Ovidio , Corrales José L , Avilés Mayra C , Smagghe Guy , Pineda Samuel 
Published: April 2008

AbstractBACKGROUND: Resistance to spinosad and methoxyfenozide has been studied in several insect pests, but there is a lack of information on Spodoptera exigua (Hübner) in Mexico. Therefore, evidence for the development of resistance in this pest to both compounds was examined. The effects of methoxyfenozide on reproductive parameters of S. exigua adults were also determined.RESULTS: Third instars from a field population were exposed for 24 h to the LC50 of spinosad or methoxyfenozide for over six generations (G2–G7). No significant reduction in susceptibility to either compound was detected for up to five generations. In G7, LC50 values for insects exposed to spinosad and methoxyfenozide were respectively 2.75‐fold and 1.25‐fold greater than for G1 larvae. Oral treatment with methoxyfenozide reduced the fecundity and fertility of G7 adults, confirming sublethal effects on reproduction. Finally, five populations (Se‐La Floriza, Se‐Lazareto, Se‐Bachigualato, Se‐Los Agustinos and Se‐Villa de Arista) of S. exigua were collected from fields in three states of Mexico for resistance monitoring to spinosad and methoxyfenozide. With the exception of Se‐Villa de Arista, the other populations showed significant resistance to spinosad, with resistance ratios between 16‐ and 37‐fold, compared with a susceptible laboratory colony. In contrast, only one population (Se‐Lazareto) showed significant resistance to methoxyfenozide (13‐fold).CONCLUSION: Resistance management programmes should be established, particularly in areas where S. exigua has developed resistance to spinosad. Copyright © 2008 Society of Chemical Industry
Internal quantum efficiency behavior of a‐plane and c‐plane InGaN/GaN multiple quantum well with different indium compositions
Authors: Wang Te‐Chung , Ko Tsung‐Shine , Lu Tien‐Chang , Kuo Hao‐Chung , Gao Run‐Ci , Tsay Jenq‐Dar , Wang Sing‐Chung 
Published: April 2008

AbstractWe had investigated the potential of non‐polar a‐plane InGaN/GaN multiple quantum well (MQW) for high indium content blue/green emission. By comparisons of a‐plane and c‐plane MQW with different indium compositions, we concluded that without piezoelectric field, high indium content non‐polar a‐plane InGaN/GaN MQW is suitable for green light emitting diode (LED). Furthermore, similar to c‐plane GaN InGaN/GaN MQW, the localized state might enhance the performance of a‐plane MQW while the indium composition about 24% although the threading dislocation density (TDD) is quite high. On the other hand, the indium phase separation might also occur on a ‐plane InGaN/GaN MQW while the indium composition about 30% so that the photoluminescence intensity of the sample 810 °C low down and spectrum bandwidth broaden. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron stabilized ferromagnetism in GaGdN
Authors: Roever M. , Mai D.‐D. , Bedoya‐Pinto A. , Malindretos J. , Rizzi A. 
Published: April 2008

AbstractWith the aim of understanding the observed roomtemperature giant magnetic moment of highly diluted GaGdN reported in literature GaGdN, GaGdN:Si and GaGdN:H have been grown by molecular beam epitaxy (MBE) and the Gd concentration is between 1016 and 1021 cm3. All samples are ferromagnetic at 300 K as measured by SQUID and the very high saturation magnetic moment in this type of samples is confirmed by our experiments.With co‐doping of hydrogen or silicon we were able to decrease or increase the strength of the magnetic moments in the layers, respectively. All our findings indicate that ferromagnetism is stabilized by electrons. Electrical measurements on GaGdN layers grown on highly resistive 6H‐SiC (0001) show a typical temperature dependence of hopping conductivity. The resistivity of the material is 0,1 to 13 kΩ cm in the temperature range from 60 to 10 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of high quality InN on production style PA‐MBE system
Authors: Gherasoiu I. , O'Steen M. , Bird T. , Gotthold D. , Chandolu A. , Song D. Y. , Xu S. X. , Holtz M. , Nikishin S. A. , Schaff W. J. 
Published: April 2008

AbstractWe have demonstrated step‐flow growth mode of InN, with monolayer height terrace steps (0.281 nm), using a production‐style PA‐MBE system, GEN200®. The surface morphology exhibits the step‐flow features on relatively large areas and the RMS roughness over an area of 5 × 5 μm2 is 1.4 nm. We also investigated the consequences of In droplets formation during the growth and we have found that the vapor‐liquid‐solid growth mechanism generates defective layer areas underneath droplets that have been formed early in the growth process. The Hall mobility of 1µm thick InN layers, grown in such step‐flow mode is slightly higher than 1400 cm2/Vs while for other growth conditions we have obtained mobility as high as 1904 cm2/Vs at room temperature. The samples exhibit high intensity photoluminescence spectra with a band edge that shifts with free‐carrier concentration. For the lowest carrier concentration of 5.6 × 1017 cm‐3 we observe PL emission at ∼0.64 eV. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved performance of GaInN based deep green light emitting diodes through V‐defect reduction
Authors: Detchprohm T. , Zhu M. , Xia Y. , Li Y. , Zhao W. , Senawiratne J. , Wetzel C. 
Published: April 2008

AbstractThe strong correlation between V‐defect density in the active region and light output power of GaInN based green and deep green light emitting diodes (LEDs) has been evaluated. The formation of such defects is confirmed as the major cause for rough growth morphology, drift of well and barrier widths, emission linewidth broadening, large color shift with current density, and thus poor light emission performance. We have optimized the epitaxial processes for the active region and successfully eliminated such defects from the entire device structure. The electroluminescence intensities from these V‐defect‐free devices with dominant wavelengths ranging from 520 to 570 nm, improve by a factor of two under high injection current density up to 100 A/cm2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessment of scanning spreading resistance microscopy for application to n‐type GaN
Authors: Sumner J. , Oliver R. A. , Kappers M. J. , Humphreys C. J. 
Published: April 2008

AbstractThis paper investigates the behaviour of scanning spreading resistance microscopy (SSRM) when applied to GaN. To this end, appropriate Si‐doped multilayers were grown to test SSRM's carrier concentration sensitivity and it was found that, for samples with no undoped regions, layers with dopant concentrations ranging from 1×1019 cm–3 to 2.5×1018 cm–3 could be distinguished. However we have noted that the relationship between SSRM signal, applied bias and dopant level is complex and that further work is needed before quantification of unknown samples can be attempted. Furthermore, in samples with undoped layers, it is very difficult to obtain any SSRM signal. In terms of recommended operating parameters, it was found that SSRM only usefully distinguished between dopant layers for applied DC biases in the range of ∼2 ‐ 7 V. Above this voltage damage to the sample occurs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemical lift‐off of GaN epitaxial films grown on c‐sapphire substrates with CrN buffer layers
Authors: Goto H. , Lee S. W. , Lee H. J. , Lee Hyo‐Jong , Ha J. S. , Cho M. W. , Yao T. 
Published: April 2008

AbstractGaN epitaxial films are grown on c‐plane sapphire substrates with CrN buffer. The GaN layers show high crystalline quality and smooth surface morphology without being cracked. Selective etching of CrN buffer is performed by wet etching using conventional Cr metal etchant, which results in success ful lift‐off of GaN thick layers. We confirm that the crystalline quality of GaN does not change through the etching process. These results indicate that the chemical lift‐off process using CrN buffer is promising for production of both freestanding GaN substrates and vertical‐structure devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Palladium‐based on‐wafer electroluminescence studies of GaN‐based LED structures
Authors: Salcianu C. O. , Thrush E. J. , Plumb R. G. , Boyd A. R. , Rockenfeller O. , Schmitz D. , Heuken M. , Humphreys C. J. 
Published: April 2008

AbstractElectroluminescence (EL) testing of Light Emitting Diode (LED) structures is usually done at the chip level. Assessing the optical and electrical properties of LED structures at the wafer scale prior to their processing would improve the cost effectiveness of producing LED‐lamps. A non‐destructive method for studying the luminescence properties of the structure at the wafer‐scale is photoluminescence (PL). However, the relationship between the on‐wafer PL data and the final device EL can be less than straightforward (Y. H Aliyu et al., Meas. Sci. Technol. 8, 437 (1997) [1]) as the two techniques employ different carrier injection mechanisms. This paper provides an overview of some different techniques in which palladium is used as a contact in order to obtain on‐wafer electroluminescence information which could be used to screen wafers prior to processing into final devices. Quick mapping of the electrical and optical characteristics was performed using either palladium needle electrodes directly, or using the latter in conjunction with evaporated palladium contacts to inject both electrons and holes into the active region via the p‐type capping layer of the structure. For comparison, indium was also used to make contact to the n‐layer so that electrons could be directly injected into that layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
EpiEL provides advanced optical characterization for nitride LED epi‐wafers
Authors: Ma Max Xianyun , Jia Helen Jinghong 
Published: April 2008

AbstractA virtual LED device fabrication and characterization technology, called EpiEL, has been developed to non‐destructively measure LED device parameters directly on LED epiwafers. As through a finished device, the system reveals not only the electro‐luminescence (EL) but also the electrical properties of the material. The developed EpiEL mapping system can rapidly obtain EL spectrum, LIV, output characteristics, wavelength & FWHM shift curves, as well as wafer‐level uniformity about slope quantum efficiency, emission intensity, peak/dominant wavelength, FWHM, driving voltage/current, etc.. EL measurement is usually performed on finished device (such as LED) since it needs a device structure to inject current. EpiEL mapping system overcomes this limitation by instantly forming a well‐defined LED device inside the material. With such capability, EpiEL technology provides a unique electroluminescence solution for optoelectronic (especially emerging solid‐state lighting) industry which brings better capability and efficiencies: instant feedback for material development and device‐level quality control right after material growth. Recent investigation indicated that most of current nitride‐based LED epiwafers have a non‐uniform material structure which leads to different optical observations at epitaxial and substrate sides. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence properties of GaPN layer grown by OMVPE
Authors: Hatakenaka S. , Wakahara A. , Nakanishi Y. , Furukawa Y. , Okada H. , Yonezu H. 
Published: April 2008

AbstractThe effect of carbon incorporation on luminescence properties of GaPN grown by organometallic vapor phase epitaxy (OMVPE) has been investigated. Trimethylgallium (TMGa) and trimethylgallium (TEGa) were used as Ga precursors. The carbon concentration of 1.1×1017cm–3 was obtained by using TEGa, whereas that of GaPN grown using TMGa was 4.0×1017cm–3. Non‐radiative recombination rate was also reduced to about 1/100 by using TEGa. Moreover, the spatial fluctuation of N content and Non‐radiative rate was reduced with increasing substrate temperature. Therefore, luminescence properties of GaPN could be improved by using TEGa at high substrate temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanisms of AlInN growth by MOVPE: modeling and experimental study
Authors: Yakovlev E. V. , Lobanova A. V. , Talalaev R. A. , Watson I. M. , Lorenz K. , Alves E. 
Published: April 2008

AbstractFactors affecting the AlInN layer composition have been studied, using both modelling and experimental approaches. The experiments have been performed in a single‐wafer Aixtron AIX 200/4 RF‐S reactor at setpoint temperatures ranging from 760 to 840 °C, which corresponds to the InN content variation in a wide interval from 13 to about 24%, if other process parameters remain unchanged. The computations fit well the compositional experimental data, and can be used to identify the mechanisms governing the incorporation of the indium atoms into MOVPE grown AlInN layers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ measurement of the strain relaxation of GaN nanograins during X‐ray irradiation
Authors: Choe Hyeokmin , Lee Sanghwa , Sohn Yuri , Kim Chinkyo 
Published: April 2008

AbstractGaN nanograins were grown on a c‐plane sapphire substrate and their strain relaxation due to x‐ray irradiation was investigated in‐situ by utilizing synchrotron xray scattering. The GaN nanograins were constantly exposed to the synchrotron X‐ray and θ ‐2θ scans through the (002) Bragg peak of GaN were repeatedly carried out during the irradiation.The Bragg peak of the compressively strained GaN nanograins gradually shifted toward higher angle, which implies that the GaN nanograins in compressive strain experienced strain relaxation during x‐ray irradiation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
RF‐MBE growth of cubic InN films on YSZ(001) vicinal substrates
Authors: Nakamura T. , Kataoka T. , Katayama R. , Yamamoto T. , Onabe K. 
Published: April 2008

AbstractCubic InN (zincblende structure) films have been directly grown on yttria‐stabilized zirconia (YSZ) (001)‐oriented and vicinal substrates by rf‐plasma‐assisted molecular beam epitaxy (RF‐MBE) (The vicinal substrates are misoriented by 1° toward 〈110〉.), and structurally characterized by X‐ray diffraction and atomic force microscopy. Compared with the growth on the (001)‐oriented substrate, the surface grain size of the cubic InN film is remarkably large for the growth on the vicinal substrates. From the 2θ/ω and ω X‐ray reciprocal space mapping measurements, hexagonal InN is found to be preferentially generated on the c‐InN{111} facets. By using the YSZ(001) vicinal substrate, the hexagonal phase incorporation ratio decreased from 16.3% on the (001)‐oriented substrate to 11.7% with the same growth condition. And on the vicinal substrate, hexagonal InN is generated predominantly from the c‐InN(111) facets which are inclined to the upward direction of the atomic steps. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN compositional patterning by ultraviolet photoexcitation during NH3‐based MOMBE – A pathway to 3D epitaxy
Authors: Pritchett D. , Henderson W. , Billingsley D. , Doolittle W. A. 
Published: April 2008

AbstractLateral compositional patterning of InGaN during NH3‐based MOMBE by digital micromirror patterning of UV photoexcitation is demonstrated. Preferential desorption of In/In‐methyl species during InGaN surface exposure to an elliptically focused 5 kW Hg‐Xe arc lamp (λ = 365 nm) limits the incorporation of indium during growth. Localized photoexcitation results in the preferential In/In‐methyl desorption, resulting in indium mole fractions of 0.10 in unexposed regions to as low as 0 in fully exposed regions. The technique demonstrates promise for integration of micromirrors for dynamic and maskless selective epitaxy towards the realization of complex, 3D device structures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)