Quenching Research Articles

Carbon and Manganese Effects on Quenching and Partitioning Response of CMnSi-Steels

Carbon and Manganese Effects on Quenching and Partitioning Response of CMnSi-Steels

Fluorescence Resonance Energy Transfer Detection of Cobalt Ions by Silver Triangular Nanoplates and Rhodamine 6G

In the present paper, the authors studied fluorescence resonance energy transfer (FRET) phenomenon between silver triangular nanoplates and bovine serum albumin (BSA)/Rhodamine 6G fluorescence complex, and established a fluorescence method for the detection of cobalt ions. We found that when increasing the silver triangular nanoplates added to certain concentrations of fluorescent bovine serum albumin (BSA)/Rhodamine 6G complex, the fluorescence of Rhodamine 6G would be quenched up to 80% due to the FRET between the quencher and donor. However, in the presence of cobalt ions, the disassociation of the fluorescent complex from silver triangular nanoplates occurred and the fluorescence of the Rhodamine 6G recovered. The recovery of fluorescence intensity rate (I/I0) has a good relationship with the cobalt ion concentration (cCO2+) added. Thus, the authors developed a fluorescence method for the detection of cobalt ions based on the FRET of silver triangular nanoplates and Rhodamine 6G.

In Vitro Antioxidant, Antibacterial Activity and Phytochemical Studies of Primula Denticulata An Important Medicinal Plant of Kashmir Himalaya

The present study was designed to evaluate the phytochemical composition, antimicrobial and radical-scavenging activities of ethanolic extract of Primula denticulata- an important medicinal herb of Kashmir Himalaya. Phytochemical study was performed by using various standard phytochemical methods. Free radical scavenging activities of the extract was assessed by employing different in vitro assays such as DPPH free radical scavenging assay, hydrogen peroxide scavenging activity and lipid per oxidation assay. Calf thymus DNA was also monitored by TBARS formation. The results were compared with standard antioxidant (?-tocopherol). Antibacterial activity of the extract was determined by agar well diffusion method. DPPH free radical scavenging assay and hydrogen peroxide scavenging activity revealed plant extract to be an active radical scavenger. P.denticulata extract also dose dependently inhibited the MDA formation or lipid per oxidation and as such might intercept the free radical chain of oxidation. The leaf extract also prevents calf thymus DNA from oxidative damage induced by hydroxyl radical generated by FeSO4 and H2O2 in Fenton reaction. The hydroxyl radical quenching ability of polyphenolic compounds of Primula denticulata could be responsible for the protection against oxidative damage to DNA. The ethanolic extract showed anti-microbial activity which was visible as the zones of inhibition formed in the different cultures of Gram positive and Gram negative bacteria as well as in case of fungal cultures. Among all the maximum activity was seen for Escherichia coli with inhibition zone diameter of 23.53 3.71mm followed by Klebsiella pneumoniae with inhibition zone diameter of 20.74 3.33mm. These findings provide evidence that the considered plant possesses antimicrobial and antioxidant properties and may act as possible antioxidant for biological systems susceptible to free radical-mediated reactions.

A New Hot Stamping Process with Quenching and Partitioning Treatment

A new hot stamping process with quenching and partitioning treatment is proposed in the paper. Compared to direct hot stamping process, the microstructures with some retained austenite not only including martensite are formed according to the constrained carbon equilibrium (CCE) model. During the new hot stamping process, tools with high temperature are used to control the quenching temperature (QT) between Ms and Mf, and the partitioning treatment of the part is also implemented in the tools by prolonging holding times. In this paper, different holding times (partitioning times) controlled by servo press, are used to research the influence of partitioning time on mechanical properties.

STUDY ON FORMATION AND CORROSION RESISTANCE OF AMORPHOUS ALLOY IN U-Co SYSTEM

The formation of amorphous phase has been investigated in U-Co system over a wide range of compositions, namely, UxCo100-x (x=50~87.5) by mean of melt-spinning. Phase identification for the arc-melted ingots and rapidly quenched alloys, and the thermal stability of the amorphous phases thus formed have been examined by XRD and DSC, respectively. The component phases in the ingot alloys were structurally the same as those presented in UCo phase diagram, but were associated with a certain compositional metastability. Rapid quenching experiment revealed that the ease of formation of amorphous phase occurred within the composition range of 58.5≤x≤78, and amorphous phase was most readily formed in the vicinity of U66.7Co33.3 composition. The dynamical crystallization temperatures of the amorphous phases were determined to be 534~550 K at a DSC heating rate of 20 K/min, and the highest reduced crystallization temperature (relative to the liquidus temperature) as *国防基础科研计划项目B1520133007和中国工程物理研究院科技发展基金项目2013A0301015资助 收到初稿日期: 2014-10-27,收到修改稿日期: 2015-02-02 作者简介:黄火根,男, 1980年生,副研究员,博士 DOI: 10.11900/0412.1961.2014.00580 第623-630页 pp.623-630

Interaction of Glycyrrhizin with Human Haemoglobin

This study investigates interaction of glycyrrhizin (an herbal therapeutic agent) with human haemoglobin. The interaction is confirmed by glycyrrhizin-induced quenching of absorbance and fluorescence data. Both hydrophobic and electrostatic interactions appear to be involved in glycyrrhizin-haemoglobin binding. The binding causes no change in the secondary structure of haemoglobin. The interaction decreases H 2 O 2 - induced iron release from haemoglobin and haemoglobin- mediated oxidative reactions. Glycyrrhizin inhibits ferryl-haemoglobin formation, peroxidase and esteraselike activities of the heme protein. Almost no oxygen is released from haemoglobin due to glycyrrhizin binding. The interaction thus reduces haemoglobin-mediated oxidative damage without affecting oxygen-binding capacity of the protein, and may be an advantage in therapeutic application of glycyrrhizin.

2'-羟基-2;4-二溴二苯醚与人血清白蛋白作用机制的光谱研究与计算模拟

The interaction between 2'-hydroxy-2,4-dibromo diphenyl ethers (2'-OH-BDE-7) and human serum albumin (HSA) was investigated with molecular docking, molecular dynamics simulation and spectroscopy techniques. The results of synchronous fluorescence spectroscopy indicated that the conformation of HSA was changed when 2'-OH-BDE-7 binding to HSA, which consistent with the results of molecular dynamics simulations. In addition, the results of fluorescence spectroscopy experiment showed that the intrinsic fluorescence quenching of HSA was reduced by 2'-OOH-BDE-7. Static quenching and non-radiation energy transfer are the two main reasons leading to the fluorescence quenching of HSA by 2'-OH-BDE-7. In the process of binding, the entropy, the enthalpy and the Gibbs free energy were negative, which suggested that the interaction between 2'-OH-BDE-7 and HSA was driven mainly by hydrophobic forces and van de Waals forces. Finally, a similar conclusion was obtained from the competitive experiment and molecular docking, which shown 2'-OH-BDE-7 binded human serum albumin at site I. Excellent agreement was founded between computer simulations results and spectral experiments to provide more information for the mechanism study on the interaction between 2'-OH-BDE-7 and HSA.

Transforming the behavior of conventional chromophores from aggregation-caused quenching to aggregation-induced emission

Conventional chromophores tend to have their fluorescence quenched in aggregate states,which was the notorious aggregation-caused quenching(ACQ)effect.The ACQ effect seriously limited the practical applications of conventional chromophores.In contrast to ACQ,agroup of luminescent materials are weakly emissive or even non-emissive in solutions but highly emissive by aggregate formation.This phenomenon was termed"aggregation-induced emission"(AIE).The swiftly development of AIE materials provided a new strategy,which can elimination the ACQ effect by introducing AIE moieties to the ACQ chromophores.The converted ACQ chromophores may have new properties and can be used in new field.This review was aimed to summarize recent progress on the conversion of ACQ chromophores,such as the conversion of triphenylamine derivatives,fused cyclic compounds and rylene diimides derivatives by introducing siloles,substituted ethenes(including tetraphenylethylene,triphenylethylene and triphe-nylethylene carbazole)or triphenylacrylonitrile moieties to them.In addition,the properties and applications of the new materials are introduced briefly.The development trends of this field are also prospected.

CdTe量子点功能化玻片的制备及其对Pb2+浓度的检测

通过羟基化和氨基硅烷化处理,得到表面接枝氨基的玻片载体。水相合成巯基乙酸修饰的CdTe量子点（CdTe-TGA）,采用EDC/NHS活化反应,将量子点偶联到氨基化玻片表面,制备出具有荧光性能的功能化玻片。考察了量子点与EDC的量比、活化时间、偶联温度以及偶联时间对偶联效果的影响。结果表明,在量子点与EDC的量比为1∶30、活化时间1 h、偶联温度30℃、偶联时间4 h条件下获得的功能化玻片具有最佳的荧光性能。将该条件下制备的功能化玻片用于水溶液中Pb2＋的浓度检测,得到玻片相对荧光猝灭强度随Pb^2＋浓度变化的线性曲线,线性范围为1.0×10^-9-4.0×10^-8mol·L^-1,检出限为3.8×10^-9mol·L^-1,且具有良好的选择性。该方法可以灵敏而准确地检测Pb2＋浓度。

高Tb3+离子含量磁光玻璃的Faraday效应及发光性能

采用高温熔融法制备了高Tb3＋离子含量的GeO2-B2O3-SiO2系统磁光玻璃,测试了其Verdet常数和发光性能,探究了玻璃的Faraday效应、发光性能及光学碱度。研究结果表明：Verdet常数和光学碱度均随着Tb2O3含量的增加而线性增大,当Tb2O3摩尔分数为70%时,Verdet常数达到-5 000 min·T^-1·cm^-1（632.8nm）,所有磁光玻璃样品随Tb2O3含量变化均发出明亮的黄绿光。由于浓度猝灭效应,高Tb2O3含量缩短了Tb^3＋离子间距,增强了交叉弛豫效应,降低了发光强度和荧光寿命。

Phase Relations, Precious Elements Distribution, and Activities in the Cu-Fe-Pb-As System Saturated with Carbon at 1473 K (1200 °C)

In order to develop a new pyrometallurgical process for the elimination of detrimental arsenic and the recovery of precious elements, such as, silver, gold, and platinum from arsenic-rich copper-lead scraps, the phase relations in the Cu-Fe-Pb-As system saturated with carbon and the distribution of precious elements between the condensed phases generated during the equilibrium at high temperature were investigated. The investigation was carried out by performing a series of laboratory scale experiments using an electrical furnace at 1473 K (1200 °C), followed by the quenching of molten samples taken on the final stage. The samples obtained from the experiments were analyzed using electron probe X-ray micro analysis, inductively couple plasma, and carbon infrared spectrometry techniques. The results were discussed on the basis of the activity coefficient of arsenic, interaction parameters of minor components, and distribution parameters for precious metals in the three equilibrated alloy phases of lead-rich, copper-rich, and iron-rich that coexists in the corresponding miscibility gap. The present results suggest that the recovery of valuable silver and gold into the copper-rich alloy and lead-rich alloy phases and the elimination of arsenic and iron into the iron-rich alloy phase might be feasible.

Effect of Kolavenic Acid on the Structure of Human Serum Albumin

The effect of Kolavenic acid (KA), an active component isolated from the genus Polyalthia, on the structure of human serum albumin (HSA) was investigated by fluorescence polarization, synchronous fluorescence, three-dimensional (3D) fluorescence, and absorption spectroscopy in combination with molecular modeling techniques under physiological conditions. The synchronous and absorption fluorescence spectra confirmed that KA has an effect on the microenvironment around HSA in aqueous solution. The two-dimensional (2D) and 3D fluorescence spectra showed that KA could quench the intrinsic fluorescence of HSA and make its conformation change. Fluorescence polarization measurements provided useful information on the relaxation time and aggregation behavior of the complex formed between HSA and KA, and indicated that the presence of KA caused changes in the fluidity and microviscosity of HSA. The binding constants and thermodynamic parameters for KA-HSA systems were obtained under different temperatures (298, 308, and 318 K). Molecular docking showed that the KA moiety bound to the hydrophobic cavity of HSA, and there were three hydrogen-bonding interactions between KA and the Lys195 and Asp451 residues. Fluorescent displacement measurements confirmed that KA bound to HSA at site II. In addition, the binding mechanism of KA and HSA was revealed by the physicochemical parameters at the molecular level. The results showed that the interaction between KA and HSA was strong, indicating that KA may be stored and transferred by serum albumin.

EFFECT OF MICROSTRUCTURE EVOLUTION ON MECHANICAL PROPERTIES OF ULTRA-HIGH STRENGTH WEAR RESISTANCE STEEL

To well balance the hardness and toughness,existing commercial medium carbon ultra-high strength wear resistance steel plates with hardness above 500 HBW are usually reheated and quenched after hot rolled to production thickness,and then tempered to improve the final mechanical properties of the plates.But the ductility which can be improved by the tempering of martensite is low.Quenching and partitioning(QP) and quenchingpartitioning-tempering(Q-P-T) heat treatment processes were proposed to stabilize the austenite phase via carbon partitioning,and improve the toughness and ductility of martensitic steel by the soft retained austenite.The effects of these heat treatment techniques are much better than conventional quenching and tempering process,but the potential of the procedure before heat treatment during the overall production process is not fully developed.In this work,a medium carbon alloy steel with Nb addition was processed by two-stage control rolling followed by water cooling,low temperature relaxation of supercooled austenite,air cooling(thermo-mechanical rolling process,TMCP).The TMCP state samples were then reheated to 900 ℃ and quenched in water(WQ).After that,the WQ state samples were tempered at 200~400 ℃ for 40 min(QT).On the basis of mechanical properties test,the microstructures of the tested steel at different states were characterized by means of OM,SEM,TEM and XRD,to reveal the effects of microstructure evolution on the mechanical properties.Contributed by the much finer prior austenite grain size,which results in the final microstructure refinement,the TMCP state sample shows better comprehensive mechanical properties than QT state samples.Steel plate with up to 2200 MPa strength,620 HBW hardness and 12% elongation was obtained.The results prove that this designed energy saving TMCP technique without heat treatment also leads to better mechanical properties than conventional quenching and tempering.XRD result shows that the retained austenite volume fraction of the TMCP sample is higher than WQ sample and all the QT samples.During the air cooling process after low temperature relaxation,the slow transformation of the super cooled austenite phase to martensite phase allows the partitioning of carbon from a to g phase,and that will stabilize the retained austenite to room temperature.The retained austenite content decreases with the increase of tempering temperature,and results in the decrease of the toughness and ductility of the quenched and tempered samples.In addition,the observed microstructures of all the experimental samples in this work are consisted of lath martensite and little twinning structure.

Comparison on mechanical properties and microstructure of a C–Mn–Si steel treated by quenching and partitioning (Q&P) and quenching and tempering (Q&T) processes

Abstract A steel containing Fe–0.20C–1.57Mn–1.55Si–0.0029P–0.0018S (wt%) was treated by quenching and partitioning (Q&P) and quenching and tempering (Q&T) process. The resulted mechanical properties indicate that the Q&P process may bring on an excellent combination of strength and elongation for the steel, of which the product was between 14.5 and 20.4 GPa%. The morphological relationship between the retained austenite and martensite was characterized as well. It was found that the TRIP effect of retained austenite plays an important role in enhancing the work hardening rate and instantaneous n -value at high strain level, which further increases the uniform elongation. Fractography of samples treated by Q&P process showed mainly ductile mechanism, while a small percentage of brittle fracture exists in the samples treated by Q&T process. Possible isothermal decomposition of austenite at quenching temperature (QT) and partitioning temperature (PT) and its effect on carbon partitioning was discussed.

Development and application of six-channel fiber optic sensing drug dissolution monitor

The drug dissolution test is an important examination of drug testing, which plays a very important role in the drug quality assessment. Automation and proceduring monitoring of drug dissolution can be implemented by the optical fiber sensing technology. Two modes of detection of UV-Vis absorption and fluorescence quenching were established by software implementation, with xenon lamp, deuterium lamp or halogen tungsten lamp as fluorescence, UV and visible light source, branch Y type optical fiber as light path transmission medium, UV-Vis probe and fluorescence molecular probe as light response devices, and CCD as detector. Optical fiber sensing drug dissolution monitor not only solves the current problems of time-consuming, and sampling of off-line analysis, but also provides real-time information of drug dissolution process. Thus, our study may provide a better evaluation method for the drug quality control.

Electrochemical Behavior of Carbon and Thermo-Treated Steel Rebars Embedded in Concrete Exposed to Chlorides

One of the most used materials to reinforce concrete structures is the carbon steel rebar, however raw materials to produce carbon steel according to ASTM-A-615 standards are have become more expensive, so most of the production of this type of steel reinforcement is made from ferrous metal waste material; but, their physical and mechanical properties are barely sufficient for the requirements that the applications demand and the fact of using raw materials of a known stoichiometric composition to improve them can result in an increase of the cost production, so the implementation of heat treatment has been the most feasible alternative to achieve the required quality checks at reasonable prices. There is a great quantity of electrochemical data related to the mild steel rod, but the heat treatment produces a martensite outer layer, which may cause electrochemical differences. For this reason the main objective of this work was compare the electrochemical behavior between two different types of reinforcement, such as carbon steel and thermo-treated steel by QTB (Quenching Temperature Bar) process. The research was conducted in an accelerated exposure environment through immersion-drying cycles, using reinforced concrete specimens fabricated with water/cement ratios of 0.45 and 0.65.These specimens were monitored through electrochemical tests, such as the half-cell potential (HCP) and the linear polarization resistance (LPR). Finally the determination of the critical chloride concentration was performed with a potentiometric titration. A critical chloride concentration of 0.45% and 0.73% for total chlorides by weight of cement were obtained for thermo-treated steel and carbon steel, respectively; where the critical chloride concentration is parameter which defines the activation for a reinforced concrete structure. In this case the activation time was different, but the electrochemical results obtained in all the exposure period for both of the two reinforcing steels were similar. The results were used for develop two explications about of the activation time differences between the two reinforcing bars.

EFFECT OF ALUMINUM ON THE SOLIDIFICATION MICROSTRUCTURE OF M2 HIGH SPEED STEEL

The effect of aluminum on the solidification microstructure of M2 high speed steel, particularly the morphology and microstructure of eutectic carbides, has been investigated by OM, TEM, SEM, EBSD and XRD. The results show that the as-cast microstructure consists of dislocation martensite and M2C eutectic ledeburite. Excessive amount of aluminum, 1.2%, favors the formation of ferrite and needle-like carbides. After the addition of aluminum, eutectic carbides are distributed more homogeneously. Additionally, the morphology of M2C eutectic carbides transforms from the fibrous to the plate-like, and their microstructure also changes significantly.The plate-like M2C has crystal defects, such as micro-twins and stacking faults, and different growing orientation between adjacent plates whereas the fibrous carbides have few defects and single crystal orientation. Compared to fibrous carbides, the plate-like carbides are much difficult to get spheroidized at high temperature, which is unfavorable for carbide refinement. The ferrite, formed by adding excessive amount of aluminum, cannot be eliminated by ordinary heat treatments, decreasing remarkably the hardness of high speed steel after quenching.

THE TEXTURE EVOLUTION AT THE CENTER OF PEARLITIC STEEL WIRE DURING DRAWING AND ITS INFLUENCE ON THE MECHANICAL PROPERTIES

The cold drawing pearlitic steel wires are widely used in industry such as the automobile tire and ropes. And it possesses an ultra high strength, almost the highest in all the steel products. So many investigations are focused on the hardening mechanisms of pearlitic steel wire during cold drawing, including the microstructure fining, texture evolution and cementite dissolution. In this study, the electron backscatter diffraction (EBSD) and the visco-plastic selfconsistent (VPSC) model are used to investigate the texture evolution law at the center of wire during the drawing, as well as its influences on the mechanical behaviors. The EBSD results show that the asreceived wires after dry drawing and quenching have a little fiber texture along the drawing direction. And with wet drawing strain increasing, the intense of fiber texture increases apparently. The calculations using *贝卡尔特(亚洲)研发中心合作项目,国家自然科学基金项目51034009和广东省中国科学院全面战略合作项目2012B091100251资助 收到初稿日期: 2013-12-09,收到修改稿日期: 2014-02-27 作者简介:赵天章,男, 1987年生,博士生 DOI: 10.3724/SP.J.1037.2013.00799 第667-673页 pp.667-673

Vibrational and rotational excitation of CO2 in the collisional quenching of H2(v = 1)

Energy transfer in H2 (1,1) +CO2 collisions was investigated using high resolution transient laser spectroscopy. Rotational state selective excitation of v = 1 for rotational level J = 1 was achieved by stimulated Raman pumping. Energy gain into CO2 resulting from collisions with H2 (1,1) was probed using transient absorption techniques, Distributions of nascent CO2 rotational populations in both the ground (00 degrees 0) state and the vibrationally excited (00 degrees 1) state were determined from overtone absorption measurements. Translational energy distributions of the recoiling CO2 in individual rovibrational states were determined through measurement of Doppler-broadened transient line shapes. A kinetic model was developed to describe rates for appearance of CO2 states resulting from collisions with H2(1,1). From scanned CARS (coherent anti-stokes Raman scattering) the spectral peaks population ratio n0/n1 was obtained, where n0 and n1 represent the number densities of H2 at the levels (0,1) and (1,1), respectively. Using rotational Boltzmann distribution of H2 (v = 0) at 300 K, n1 was yielded. Values for rate coefficients were obtained using data for CO2 (00 degrees 0) J = 48 to 76 and CO2 (00 degrees 1) J = 5 to 33. The rate coefficients derived from appearance of the (00 degrees 0) state have values of K(tr) = (3.9 ± 0.8) x 10(-11) cm3 x molecule(-1) x s(-1) for J = 48 and k(tr) = (1.4 ± 0.3) x 10(-10) cm3 x molecule(-1) x s(-1) for J = 76, with a monotonic increase for the higher J states. For the (00 degrees 1) state, values of k(tr) remain fairly constant at k(tr) = (4.3 ± 0.9) x 10(-12) cm3 x molecule(-1) x s(-1). Rotational populations for the nascent CO2 states were measured at 0. 5 μs following excitation of H2. The transient population for each state was fit using a Boltzmann rotational distribution. The CO2 (00 degrees 0) J = 48-76 rotational states were populated substantially relative to the initial 300 K CO2 distributions, and the distribution is described by Trot. The excited (00 degrees 1) state has T(rot), 310 K. The center-of-mass translational temperatures for the (00 degrees 0) state are all much greater than 300 K, with T(rel) = 1 532 K for J = 76. In contrast, transient line profiles for the J = 5 - 33 levels of excited (00 degrees 1) state do not show any broadening above the initial 300 K distributions, indicating that excitation to the (00 degrees 1) state is not accompanied by translational energy change.

Ultra high strength in steel.

Very high strength levels in steel, not obtained by conventional methods of hardening by quenching and low temperature tempering, are obtained by mew hardening techniques involving the thermal-mechanical treatment of metastable austenite.The earlier attempts on such hardening techniques and the development of new processes such as 'Ausforming' investigated in the Ford Motor Company Research Laboratories and ''Maraging'' developed and patented by the International Nickel Company (Mond)Limited, are briefly reviewed here.