Hydrogen-acceptor interactions in diamond

Hydrogen-acceptor interactions are investigated in boron-doped diamond through deuterium diffusion experiments followed by SIMS measurements and through infrared absorption spectroscopy. From deuterium diffusion, we show that BD interactions can be properly demonstrated in low compensation B-doped homoepitaxial layers. However, the presence of defects in such layers strongly affects this interaction. The degree of passivation of boron acceptors by deuterium depends on the diffusion temperature. At 550°C or below, the B and D concentrations exactly match giving rise to a complete disappearance of the absorption bands related to the electronic transitions of neutral boron acceptors. Under thermal annealing above 500°C, (B,D) pairs dissociate and neutral boron acceptors recover. At deuterium diffusion temperatures of 700°C, the B passivation is absent.     

Capacitance–voltage profiling of deuterium passivation and diffusion in diamond Schottky diodes

Capacitance–voltage measurements have been performed on deuterated boron-doped natural type IIb diamond. They demonstrate the electrical passivation of the boron acceptors, which was manifested by a persistent decrease in capacitance after deuteration. Bias annealing experiments have been carried out to determine the charge state of the diffusing deuterium. The differences between annealing with or without bias lead to the conclusion that boron–deuterium complexes dissociate at about 750 K and that the released deuterium is positively charged.     

Study of the adsorption process of bovine serum albumin on passivated surfaces of CoCrMo biomedical alloy

Adsorption of bovine serum albumin (BSA) on CoCrMo surface was studied by electrochemical techniques in order to determine the mechanism of protein adsorption at different surface conditions (which are reached by considering different passivation times) in phosphate buffered solution (PBS). At open circuit potential (OCP), adsorption kinetic was influenced by surface passivation when passivation time was lower than 1 h, whereas, at higher passivation times, no apparent modification in the kinetic mechanisms of adsorption was observed. On the other hand, at a passive applied potential, the BSA addition decreased the passivation kinetics of the process at all the passivation times.     

Potential dependence of surface crystal structure of iron passive films in borate buffer solution

The effect of passivation potential on surface crystal structure, apparent thickness and passivity of oxide films formed on pure iron prepared by plasma sputter deposition was investigated. The crystallinity was improved with passivation potential and the width of atomically flat terraces was expanded to 6 nm when passivating at 750 mV for 15 min, as observed by ex situ scanning tunneling microscopy (STM) after aging in air (<30% RH). Apparent thickness and passivity are linearly dependent on passivation potential. The former weakly depends on passivation duration, the latter strongly depends on passivation duration. This is well explained by the correlation between crystal structure and passivity.     

Selective iron removal from spent passivation baths by ion exchange

BACKGROUND: Post‐treatment of zinc plated surfaces is required to provide corrosion protection; for this purpose chromium passivation is usually used. In the EU, the older hexavalent chromium passivation baths have been replaced by trivalent chromium conversion coatings. However, the life of Cr(III) passivation baths is reduced due to iron and zinc impurities generated in the process. Thus, the objective of this work was to investigate the regeneration of spent passivation baths from the plating industry by ion exchange using a new chelating resin (Purolite S‐957). RESULTS: Three genuine passivation baths with different iron and zinc concentrations were investigated; the effect of loading flow rate, temperature and resin regeneration conditions on the uptake of iron ions was also studied. The removal performance of iron was increased at higher temperature (55 °C) and lower flow rates. The best regeneration conditions were found to be 6 bed volumes (BV) of 30 wt% HCl. CONCLUSION: This work has shown that iron can be selectively removed from trivalent chromium passivation baths using a new chelating resin (Purolite S‐957) and no addition of chromium (III) is required. Low feed flow rate and high bath temperature (up to 55 °C) are recommended for high iron uptake. Copyright © 2008 Society of Chemical Industry     

Minimizing the surface effect of PDMS–glass microchip on polymerase chain reaction by dynamic polymer passivation

Polydimethyl siloxane (PDMS)–glass microchip has a very strong surface effect on polymerase chain reaction (PCR), leading to a very poor PCR yield. In the work reported here, practical dynamic passivation of surfaces of PDMS–glass microchip using polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP) was achieved using a conventional thermocycler. The passivation procedure was cost‐effective and easy to conduct. The effects of polymer molecular weight and polymer concentration on tube PCR efficiency were investigated primarily to prescreen out suitable polymers and polymer concentrations in the PCR mixture. The result from tube PCR indicated that both PEG and PVP could affect the performance of Taq polymerase. A final concentration of 0.025% (w/v) or 0.4% (w/v) polymer in the PCR mixture can enhance the tube PCR, while 1% (w/v) polymer was found to inhibit the reaction. PEG was more effective in tube PCR, although PVP performed better in chip PCR. Instead of employing the polymer directly in the PCR mixture, i.e. the conventional in situ passivation approach, another approach of dynamic passivation by pre‐injecting polymers into the microchip achieved better performance. The efficiency of pre‐passivation was found to follow the order: PVP10000>PVP55000, PEG8000> PEG10000>PEG400. After pre‐passivation with PVP10000, PVP55000 and PEG8000, the PCR efficiency can recover to 93%, 86% and 83%, respectively, of that obtained from tube PCR. Copyright © 2006 Society of Chemical Industry     

热浸镀Zn-Al合金钝化工艺及耐蚀性能研究

在钢板热浸镀Zn-5%Al合金表面制备了钼酸盐钝化膜,探讨了溶液pH、θ及t对钝化膜性能的影响。采用电化学方法对钝化膜耐腐蚀性能进行测试。结果表明,Zn-5%Al合金钝化膜阳极极化曲线呈现钝化特征。用扫描电镜对钝化膜的表面形貌进行观察,发现钝化膜呈片层状结构,用环境扫描电镜配套的能谱仪对钝化膜成分进行分析,结果表明钝化膜由Mo、P、O、Zn和Al等元素组成。     

Effect of alternating voltage passivation on the corrosion resistance of duplex stainless steel

Potentiodynamic polarization and E _corr versus t curves were obtained, together with electrochemical impedance spectroscopy (EIS) measurements, in order to understand the effects of alternating voltage (AV) passivation on the corrosion resistance of duplex stainless steel (DSS). SEM, EDS and XPS were employed to further investigate the influence of AV passivation on the properties of the passive film. The results of the electrochemical measurements showed that AV passivation significantly improved the corrosion resistance of DSS. SEM images indicated that the surface exhibited a unique morphology after AV passivation treatment, and XPS results suggested that AV passivation greatly increased the thickness of the passive film. Furthermore, significant chromium enrichment and a higher ratio of Fe³⁺/Fe²⁺ were observed in the passive film after AV passivation. Mott–Schottky results confirmed that AV passivation had a strong influence on the semiconducting properties of the passive film.     

The p-to-n-type conversion of boron-doped diamond layers by deuteration: New findings

The p-to-n-type conversion of particular B-doped homoepitaxially grown diamond layers upon deuterium plasma treatment was discovered three years ago. However, many questions regarding the reproducibility of the effect for samples of different origins remain unanswered up to now, in particular the role of the electrical contacts and the possibility of a surface inversion layer being responsible for the n-type conductivity, the thermal stability and origin of the donor.Here we address the above questions. We show that the p-to-n conversion is closely related to the presence of defects, which can vary, on a macroscopic scale, in different regions of the same sample. The p-type regions containing a small concentration of defects are found to be converted to n-type upon deuteration. In contrast, the regions counting a high defect density exhibit very low p-type conductivity related to passivation of the boron acceptors by deuterium accompanied by a large uptake of D on defects. We show that the n-type conversion can be equally observed with three different kinds of contacts (silver paint, implanted and evaporated). We prove that the n-type conversion is a bulk effect and not a surface effect. We find that the thermal stability of the n-type complex is limited to temperatures lower than 200 °C. The temperature dependence of the carrier concentration measured by the Hall effect at different stages of the conversion process is fitted following the formalism describing the conduction mechanisms in a partially compensated semiconductor. The fact that the donor concentration in the as-deuterated state is very close to the boron concentration strongly suggests that the new-formed donor complexes contain both D and B.     

镀锌层三价铬黑色钝化工艺与性能研究

采用正交试验法对镀锌层三价铬黑色钝化工艺组分进行优化,研究了工艺参数对钝化膜外观和耐蚀性的影响。根据实验结果优选出镀锌层三价铬黑色钝化工艺,该工艺含有三价铬盐、硝酸盐、钴镍盐和磷酸根,采用有机羧酸作配位剂。此工艺能够获得外观均匀黑亮、附着力良好的膜层,中性盐雾试验出白锈时间大于120h。     

Recoveries of deuterium from the separation of water–isotope mixture in batch-type thermal diffusion columns under unsteady-state operation

Heavy water (D₂O) is the most feasible moderator and coolant in nuclear-fission reactors while deuterium (D) will be the nuclear fuel for thermonuclear fusion in the distant future. The recoveries of deuterium in D₂O and HDO from the separation of water–isotope mixture (H₂O–HDO–D₂O) by thermal diffusion has been estimated. First, the degrees of separation for each component of water–isotope mixture in thermal diffusion columns were predicted, then the recoveries of deuterium in each component were estimated from the molecule weights. It was found that the maximum recovery of deuterium might be obtained when the feed concentration of D₂O is 0.22 mass fraction.     

预硫化加氢催化剂膨胀床钝化工艺研究

研究了预硫化催化剂膨胀床钝化工艺条件对催化剂加氢（HYD）活性和硫化度的影响。对钝化后的催化剂进行了ONU自热测试和XRD、DTA、BET等表征。结果表明,预硫化后催化剂需要经过钝化处理;反应温度、O₂浓度、反应时间及膨胀率是影响钝化效果的主要因素。     

Effect of some aromatic nitro compounds on the passivation of copper anodes during electrorefining

The effect of some aromatic nitro compounds on the passivation of copper anodes during electrorefining was investigated by galvanostatic methods and by scanning electron microscopy. The results showed that the passivation delay efficiency of the tested aromatic nitro compounds depended strongly on their molecular structure: 3,5-dinitrosalicylic acid (DNSA), which is not only an oxidizing agent but also a chelating agent, inhibited the passivation of copper anodes significantly, particularly that of the pure copper anode; 3,5-dinitrobenzoic acid was also a good inhibitor of passivation of copper anodes; mononitrocompounds were ineffective and the di- or trinitrocompounds, which do not contain carboxyl groups in the molecule, did not significantly influence the passivation. The mechanism of the passivation of the copper anode and the delay mechanism of DNSA are discussed.     

Corrosion monitoring of type 304L stainless steel in nuclear near-high level waste by electrochemical noise

Electrochemical noise (EN) monitoring of 304L stainless steel (SS) and sensitized 304 SS in 3 N nitric acid and nuclear near-high level waste (HLW) solution was carried out using a three nominally identical electrode configuration under open circuit conditions. EN signals characteristics of passivation process was obtained for 304L SS in 3 N nitric acid throughout the measurement period, while in near-HLW solution, features of passivation and depassivation were observed. Potentiodynamic polarization of 304L SS in 3 N nitric acid and near-HLW showed spontaneous passivation. Noise resistance was evaluated from EN time record and this parameter was used in the present investigation to qualitatively assess the corrosion behavior during the immersion period. The average noise resistance was found to be lower in near-HLW solution when compared to 3 N nitric acid. The results of the investigation are presented in this article.     

An effective oxidation approach for luminescence enhancement in CdS quantum dots by H2O2

The effects of surface passivation on the photoluminescence (PL) properties of CdS nanoparticles oxidized by straightforward H₂O₂ injection were examined. Compared to pristine cadmium sulfide nanocrystals (quantum efficiency ≅ 0.1%), the surface-passivated CdS nanoparticles showed significantly enhanced luminescence properties (quantum efficiency ≅ 20%). The surface passivation by H₂O₂ injection was characterized using X-ray photoelectron spectroscopy, X-ray diffraction, and time-resolved PL. The photoluminescence enhancement is due to the two-order increase in the radiative recombination rate by the sulfate passivation layer.     

Deuterium as a tracer in coal liquefaction Part 2. Non-catalytic studies

A bituminous Australian coal (Liddell) was liquefied in the absence of catalyst using tetralin as vehicle, and molecular deuterium and hydrogen—deuterium gas mixtures. The structures of the liquid and gaseous products were investigated by mass spectroscopy, ¹H-and ²H-NMR spectroscopy and gel permeation chromatography (GPC). The proportion of ²H to ¹H in the liquid products was found to be higher at 425°C than at 400°C because deuterium preferentially enters more aromatic rings at the higher temperature.The distributions of deuterium in the deuteromethanes formed during liquefaction show that deuterium randomly enters the structural groups in the coal which produce methane before the methane is released to the gas phase. This illustrates the extreme mobility of hydrogen, including the hydrogen that originates from the coal. As a consequence, it is proposed that hydrogen released as methane arises from a pool in which memory of the original bonding is lost.     

Corrosion behaviour of brazing material AA4343

This paper is part of a work devoted to corrosion of brazed AA4343/AA3003/AA4343 materials on water side of automotive heater cores. The microstructure of the superficial resolidified AA4343 brazing material has been previously characterised [1] and [2]. It is composed of large (Al) grains separated by valleys containing multiphase deposits of (Al), Si and α-Al(Mn,Fe)Si. The present study focuses on its electrochemical behaviours in neutral water-ethylene glycol mixtures at different temperatures with and without chloride ions. Three types of behaviour are revealed: (i) passivation, (ii) defective passivation and (iii) pitting corrosion at the corrosion potential. The defective passivation is investigated in greater depth. The results show that Si needles do not participate in the corrosion progress whereas the α-Al(Mn,Fe)Si particles are preferential sites for corrosion attacks. α-Al(Mn,Fe)Si particle/matrix interactions are responsible of the defective passivation at valleys level where the α-Al(Mn,Fe)Si phase particles are mainly concentrated. Increasing the temperature enhances this reactivity whereas addition of ethylene glycol decreases it and favours a transition from defective passivation to passivation for ethylene glycol content higher than 55%.     

无钴硫酸体系三价铬黑色钝化工艺

以过渡金属硫化物M替代钴(镍)盐作发黑剂,在镀锌层表面得到黑色钝化膜。钝化液的配方与工艺为:Cr2(SO4)335g/L,有机羧酸X6g/L,柠檬酸32g/L,过渡金属硫化物M2g/L,FeSO410g/L,NaNO37g/L,NaH2PO415g/L,pH=2.0,室温,时间30s。钝化膜层乌黑均匀、附着力合格;经封闭后的三价铬黑色钝化膜,其耐蚀性等级高于市售含钴盐发黑剂的三价铬黑色钝化膜,且达到六价铬钝化的耐蚀等级;钝化膜中不含六价铬;钝化液性能稳定。     

Electrochemical Behavior of TiCN–Ni-Based Cermets

The electrochemical behavior of TiCN–20 wt% Ni cermets containing different secondary carbides (10 wt% WC, NbC, TaC, and HfC) was investigated in freely aerated 0.2 mol/L sulfuric acid. A comparison has also been made with polarization behavior of pure Ni. All the materials (except HfC-containing cermet) exhibited active–passive polarization behavior, characterized by two passive regions. The first passive region, obtained on polarizing past the zero current potential, was attributed to passive film formation due to TiCN, while the second passive film is presumably due to the presence of a Ni binder phase. The passivation behavior in the case of cermets containing various secondary carbides (WC, TaC, and NbC) was similar to baseline TiCN–20Ni cermets, while poor passivation behavior was observed in the case of TiCN–20Ni–10HfC. Efforts have been made to correlate the passivation behavior with the microstructural characteristics of sintered cermets.     

Platinum on Carbon‐Catalyzed H–D Exchange Reaction of Aromatic Nuclei due to Isopropyl Alcohol‐Mediated Self‐ Activation of Platinum Metal in Deuterium Oxide

An efficient and simple deuteration method of arenes using the platinum on carbon‐isopropyl alcohol‐cyclohexane‐deuterium oxide combination under hydrogen gas‐free conditions was accomplished. Since the hydrogen–deuterium exchange reaction cannot be promoted without isopropyl alcohol, zerovalent platinum metal (on carbon) is self‐activated by the in situ‐generated very low amount of hydrogen or hydrogen–deuterium gas derived from isopropyl alcohol or isopropyl alcohol‐d₁. Deuterium‐labeled compounds with high deuterium contents can be easily isolated by the filtration of platinum on carbon and simple extraction. The present hydrogen gas‐free method is safe from the viewpoint of process chemistry and various arenes possessing a variety of reducible functionalities within the molecule could be effectively and directly deuterium‐labeled without undesired reduction.