Influence Of Residual Impurities Research Articles

Influence of residual impurities on ring‐opening metathesis polymerization after copper(I)‐catalyzed alkyne‐azide cycloaddition click reaction

ABSTRACTBottlebrush polymers (BBPs) are three‐dimensional polymers with great academic and industrial potential owing to their highly tunable and intricate architecture. The most popular method to synthesize BBPs is ring‐opening metathesis polymerization (ROMP) with Grubbs' catalyst, allowing living grafting‐through polymerization of macromonomers of up to ultrahigh molecular weights with narrow molecular weight distribution. In this case, it has been well recognized that the purity of macromonomers (MMs) is critical for a successful ROMP reaction. For MMs synthesized from reversible‐deactivation radical polymerization, Grubbs and Xia demonstrated that the better control of ROMP reaction can be achieved when they are prepared via “growth‐then‐coupling” method that is coupling a norbornenyl group to end‐functionalized prepolymers. However, these MMs can also contain various residual impurities from previous synthetic steps, which can potentially poison the catalyst and hamper the ROMP reaction. Herein, we intentionally doped possible impurities into purified MMs to identify the most poisoning species. As a result, it was found that alkyne‐functionalized norbornene most significantly retarded the ROMP reaction due to a formation of Ru‐vinyl‐carbene intermediates having low catalytic reactivity, whereas the other reagents such as solvent, Cu‐catalyst, ligands, and azido‐terminated prepolymers were relatively inert. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 726–737

Влияние неконтролируемых примесей на спектр поглощения лазерного кристалла NaGd(WO-=SUB=-4-=/SUB=-)-=SUB=-2-=/SUB=-

Three NaGd(WO4)2 single crystals have been grown by Czochralski technique using the initial chemicals with different purity. Impurity concentrations were determined by the inductively coupled plasma mass-spectrometry. The optical absorption spectra of the crystals were measured and the influence of residual impurities' contents on optical properties and coloration of the crystals was determined. It was demonstrated that the green coloration which is sometimes observed for NaGd(WO4)2 crystals results from the presence of residual impurities of d-elements, for which the cromium impurity is the most important

Luminescence Characteristics of N-Polar GaN and InGaN Films Grown by Metal Organic Chemical Vapor Deposition

Nitrogen- and Ga-polar GaN and InGaN/GaN multiple quantum-well (MQW) films were prepared via metal organic chemical vapor deposition and evaluated via photoluminescence at reduced temperatures in order to compare their optical characteristics. While N- and Ga-polar GaN films grown at standard high temperatures were comparable in terms of photoluminescence at tested temperatures, the N-polar InGaN MQW quality was inferior to their Ga-polar counterparts, confirmed with greater enhancement in luminescence intensity from 300 to 10 K and unobservable phonon replicas at 10 K for the N-polar InGaN MQW due to the broad emission peak. Additionally performed electroluminescence studies on N-polar light-emitting diode samples indicated that the poor luminescence of the N-polar samples was not related to electric field effects. Influence of residual impurities (C and O) was strongly suggested via secondary ion mass spectroscopy, leading us to conclude that the poor luminescence properties of the N-polar InGaN MQWs were predominantly caused by the elevated residual impurity concentrations in the N-polar (In,Ga)N layers grown at low temperatures.

Influence of residual oxygen impurity in quaternary InAlGaN multiple-quantum-well active layers on emission efficiency of ultraviolet light-emitting diodes on GaN substrates

The influence of residual impurities in quaternary InAlGaN active layers on the emission efficiency of 350nm band ultraviolet light-emitting diodes on GaN substrates has been investigated. Secondary ion mass spectrometry and capacitance-voltage measurements have revealed that a large amount of oxygen is incorporated into the InAlGaN active layers owing to relatively low growth temperatures for Al-content epitaxial films. The increase of the InAlGaN growth temperature from 780to830°C results in both the residual oxygen level decrease from 1×1018to4×1017cm−3 and the output power improvement from 0.6to2.6mW at 100mA. It is also found that devices containing lower oxygen concentration in the InAlGaN active layers demonstrate a higher electroluminescence intensity ratio of the band-edge emission from the well layers to the donor-acceptor-pair emission from the p-type layers at low temperatures. These experimental results, in conjunction with numerical calculations, suggest that the reduction in the oxygen impurity level in the InAlGaN active layers has an effect on suppressing the electron leakage current into the p-type layers, and thus improving the internal quantum efficiency of InAlGaN-based ultraviolet light-emitting diodes.

Surface nanotextures on aluminium

Chemical polishing and electropolishing of aluminium result in fine cellular textures of nanometre dimensions, which play a role in the electrochemical behaviour of aluminium and its response to further treatment processes such as conversion coating and anodizing. Concerning the latter, the surface texture is highlighted by porous anodic film growth for protection of the substrate. The influence of residual impurities and low additions of alloying elements on the development of the textures is investigated here for superpure aluminium (99.99%) and an Al–0.4wt.%Mn alloy, respectively. Complementary analytical approaches, including atomic force microscopy and transmission electron microscopy, disclose scalloped cellular textures comprising adjacent peaks and troughs, with a dependence on the grain orientation of the aluminium substrate. In addition to texture development, enrichment of copper impurity in the alloy occurs adjacent to the alloy/oxide film interface, as revealed by in-depth elemental profiles generated by r.f. glow discharge optical emission spectroscopy. The absence of similar enrichments of iron and silicon in the alloy suggests that these elements are distributed mainly as fine segregates in the aluminium, unlike copper, which is in solid solution. At low alloying levels, manganese reveals limited enrichment and is also probably present mainly as segregates. The origin of the textures and their dependence on grain orientation are thus considered to be related to the presence and location of relatively high-melting-point elemental impurities in the alloy and their local electrochemical responses relative to the adjacent alloy surface. Copyright © 2002 John Wiley & Sons, Ltd.

Impurities and defects in multicrystalline silicon for solar cells: low-temperature photoluminescence investigations

The low-temperature photoluminescence (PL) measurements (down to 4.2 K) were employed for the investigations of the defects and impurities in multicrystalline silicon (mc-Si) samples grown by block-casting method. The optical properties of as-grown, irradiated by gamma-rays, heat and hydrogen plasma treated samples were studied. It was found that carbon and oxygen as the residual impurity atoms are responsible for the formation of the zero-phonon PL lines with 0.9355 eV (T line) and 0.9652 eV (I line) after heat treatments at about 350–550°C. The appearance of PL lines with the energies of 0.9697 eV (A line) and 0.7894 eV (C line) after a gamma-rays irradiation can be attributed to the formation of carbon- and oxygen-related centers, respectively. The comparison of the PL properties of the mc-Si samples with the mono-crystalline one is performed. It is shown that the main peculiarities of the low-temperature PL spectra of mc-Si can be explained both by the influence of residual impurities and the residual strains in this material.

Mechanism of the drop in the dependence of yield stress on neutron irradiation dose for low-alloy steel

In the present work, influence of irradiation on tensile and impact properties of Cr-Ni-Mo steel using for WWER-1000 type reactor pressure vessel (RPV) manufacturing was studied. An abnormal behavior of tensile properties of the investigated materials under irradiation was observed. Decrease in yield stress and ultimate tensile stress at the first stage of irradiation was revealed while ductile-to-brittle transition temperature (DBTT) was continuously increasing with damage dose. A model of the phenomenon considering influence of residual impurities and alloying elements on α-Fe lattice tetragonality under irradiation was proposed. Some experimental evidences of the model were found. Nickel was supposed to govern the radiation sensitivity of WWER-1000 type steel.

耐火物中の不純物の高温蒸発がジルコニア焼結体表面の着色に及ぼす影響

Coloration is an important effect in zirconia ceramics. We have observed a phenomena of coloration on the surface of 3mo1%Y2O3-doped zirconia in sintered processing used some of new refractory. XPS, TG and IR analyses have proved that the problem is caused by the influence of residual impurities in the refractory.The authors however have found a interested results that the phenomena was improved by reheating the refractory in the high temperature for several times before using, and the doping of Y203 or A1203 content into ZrO2 ceramics(PSZ) has improved the coloration.

Secondary poly(propylene) from used accumulators reused as raw material

A reuse process, as raw material, of secondary poly(propylene) from used accumulators, is presented. The importance of solving the scientific aspects, concerning the influence of residual impurities and those resulted from ageing, on properties of regenerated polymers, in certifying the reliability of reusing the secondary polymers as a raw material, is underlined.

Influence of Residual Impurities on Phase Partitiioning and Grain Growth Processes of Y‐TZP Materials

Microstructural evolution at 1450°C of two 3 mol% Y2O3─ZrO2 tetragonal polycrystals (Y‐TZP) containing different residual impurity amounts has been investigated by analytical and scanning electron microscopy in order to clarify the role of the amorphous intergranular phases. Phase partitioning is interpreted as a process based on dissolution/reprecipitation reactions involving mass transport via the liquid impurity phase. Grain growth is inhibited by yttria migration before the phase equilibrium is reached, then increases drastically.

The Properties of Undoped InP and GaP Bulk Crystals Prepared by Floating Zone Melting

AbstractUndoped GaP and InP crystals which are produced by floating zone melting without a crucible were investigated. The background concentration was 1015cm−3 after several passages of the molten zone. The fundamental residual impurities are carbon and silicon penetrating into the crystals during the crystallization process. After purification, the electron mobility of GaP was 200 cm2/V. s, and for InP – 4000 cm2/Vs. The compensation decreased to 20%. A very effective purification was observed with respect to the carbon atoms, but for silicon this result is observed only after several passages of the molten zone.GaP and InP are basic materials for optoelectronic devices and it is important to investigate the possibility for production of pure bulk crystals. A proper method for this aim is the floating zone melting, where the crucible effect is removed and the influence of residual impurities is observed. In this work the influence of the number of floating zone passages on the electrical and luminescence properties of InP and GAP bulk crystals has been investigated.

Preparation and Properties of InGaAsP p-n Junction for Fabrication of Photodetectors in Optical Communication Systems

The opto-electronic properties of diffused InGaAsP p-n junction diodes have been investigated for the fabrication of well-controlled photovoltaic detector in the near-infrared spectral region. These diodes have been fabricated by Zn or Cd diffusion into n-type undoped InGaAsP LPE layers, and it has been found that Cd diffusion into InGaAsP is easier to control than Zn diffusion. The influence of residual impurities or vacancies in InGaAsP LPE layers can be seen in the current-voltage characteristics of the diffused p-n junction in both the current directions. Photoresponse of Cd-diffused diodes shows larger signals than Zn-diffused diodes in the higher energy side of the bandgap. The acceptor levels have been also measured by photoluminescence.

Rekristallisationsverhalten von zonengeschmolzenem nickel

The process of primary recrystallization and the subsequent grain growth were investigated in high purity zone melted nickel after 60 and 80% cold work.The formation of nuclei occurred predominantly at original grain boundaries by growth of subgrains which had already been formed during the deformation process.The rate of grain growth during and after primary recrystallization was determined by observing the time dependence of the largest and of the average grain diameters. The results may be interpreted in terms of the concept that the elementary process of grain boundary motion consists of a diffusion of single atoms across the grain boundary. Then the rate determining process is the grain boundary diffusion. The activation energy of grain growth was about 28–30 kcal/Mol and was equal to the activation energy of nuclei formation for large degrees of deformation.During the primary recrystallization the time dependence of the isothermally recrystallized fraction XR of the matrix may be described by the equation xr = 1 − exp(−Btκ). The K-value of 1.38 suggests a predominantly one-dimensional grain growth.The experimental data for the rate of grain growth after primary recrystallization indicate an influence of residual impurities still present in the crystal.