Concentration quenching,surface and spectral analyses of SrF2:Pr3+ prepared by different synthesis techniques

Pr³⁺ doped strontium fluoride (SrF₂) was prepared by hydrothermal and combustion methods. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Photoluminescence (PL) spectroscopy. XRD patterns indicated that the samples were completely crystallized with a pure face-centred cubic (space group: Fm3m) structure. SEM images showed different morphologies which is an indication that the morphology of the SrF₂:Pr³⁺ phosphor strongly depends on the synthesis procedure. Both the SrF₂:Pr³⁺ samples exhibit blue–red emission centred at 488 nm under a 439 nm excitation wavelength (λ_exc) at room temperature. The emission intensity of Pr³⁺ was also found to be dependent on the synthesis procedure. The blue–red emission has decreased with an increase in the Pr³⁺ concentration. The optimum Pr³⁺ doping level for maximum emission intensity was 0.4 and 0.2 mol% for the hydrothermal and combustion samples, respectively. The reduction in the intensity for higher concentrations was found to be due to dipole–dipole interaction induced concentration quenching effects.     

硬质合金焊接刀具刀体材料及淬火工艺

硬质合金焊接刀具刀体在钎焊过程中被正火和回火,引起刀体硬度和强度下降,导致刀具性能不稳定,刀具容易出现折断损坏或扭曲变形。虽然采用9Si Cr可以缓解刀体硬度和强度的下降,但制造成本较高。试验表明,只要将淬火温度控制在900℃以下,采用油淬火冷却剂和焊接刀片刀体一体淬火的新工艺可以保证40Cr刀体的淬火硬度达到40HRC以上,完全能够满足使用性能要求,降低原材料成本。     

Water–air online quenching process of 3Cr2Mo steel based on numerical simulation

A three-dimensional finite element model was established to investigate the water–air online quenching process of 3Cr2Mo steel with 130-mm thickness. The temperature, metallographic structure and stress–strain fields of the steel were calculated under single-pass continuous quenching, multi-pass continuous quenching and multi-pass interrupted quenching (MPIQ) processes. The results show that the three quenching processes can avoid the pearlite appearance, and MPIQ process could be more effective to decrease the brittleness of steel. Besides, MPIQ process is able to reduce stress–strain, minimise deformation and avoid cracking problem. The hardness and the metallographic structure were tested after MPIQ process and tempering. After tempering, the metallographic structures were all tempered sorbite, and the hardness difference of the whole steel was less than 3HRC with no cracks. It can draw the conclusion that the MPIQ process is a suitable quenching process for 3Cr2Mo steel.     

焦化厂干熄焦提升机控制系统

结合莱钢焦化厂4#干熄焦的现场实际，介绍了4#干熄焦提升机控制系统的构成、主要功能、提升和走行速度曲线，重点对提升机控制系统的PLC构成和控制做了介绍，整套系统自动化程度高，控制稳定、可靠。从目前的生产情况看，4#干熄焦提升机控制系统的设计完全满足干熄焦系统工艺安全、自动、高效的设计要求。     

一种快速冷却超高温流体方法的数值模拟

在许多强吸热化学反应的化工过程中，常常需要对反应流体流出反应器时进行快速急冷来避免副反应或逆反应发生，以期最终获得可观的目标产物。在本实验室前期开展的热等离子体裂解二氧化碳实验研究中，采取在高温反应器出口加装收缩喷管将裂解气高速导入夹套水冷管的方法，实现了对高温裂解气的快速急冷，显著地避免了裂解气中CO与O的逆反应，获得了意想不到的CO₂高转化率。本文利用计算流体力学软件模拟这一过程，以期揭示这种新的冷却方法导致极快速冷却的机制。模拟结果表明，加装收缩喷嘴确实可以期待对高温射流产生10⁷ K·s^-1量级的温降速率。深入分析表明，仅仅靠气体动力学效应不能完全解释如此快速的冷却速率。从喷管高速喷出的黏性流体在夹套水冷管内形成高速涡流，这种涡流一方面增强了主流体对周围气体的卷吸，另一方面加强了被卷吸流体在被卷入之前与夹套水冷管壁面的强制换热过程，是导致快速急冷的主要机制。     

Element segregation behavior of aluminum-copper alloy ZL205A

In aluminum-copper alloy, the segregation has a severe bad effect on the alloying degree, strength and corrosion resistance. A deeper understanding of element segregation behavior will have a great significance on the prevention of segregation. In the study, the element segregation behavior of ZL205A aluminum-copper alloy was investigated by examining isothermally solidified samples using scanning electron microscopy and energy dispersive spectroscopy. The calculated results of segregation coefficients show that Cu and Mn are negative segregation elements; while Ti, V and Zr are positive segregation elements. The sequence of element segregation degree from the greatest to the least in ZL205A alloy is Cu, Mn, V, Ti, Zr and Al. The density of residual liquid is expected to increase with a decrease in the quenching temperature ranging from 630℃ to 550 ℃. The calculated results confirm that the quenching temperature has an insignificant effect on the liquid density; and the variation of density is mainly due to element segregation. Consequently, segregations of Al, Cu and Mn lead to an increase in density, but Ti, V and Zr present the opposite effect. The contribution of each element to the variation of the liquid density was analyzed. The sequence of contributions of alloying elements to the variation of total liquid density is Cu〉Al〉Mn〉V〉Ti〉Zr.     

FTIR在淬火油检测中的应用

FTIR是从傅立叶级数转换而来的红外定性和定量分析法的缩写,能有效监测淬火油在使用过程中的老化过程和监控基础油的质量,对于稳定淬火剂质量和监测淬火剂在使用过程的变化具有重要作用。     

Photo- and electroluminescence of ambipolar,high-mobility,donor-acceptor polymers

Donor-acceptor polymers with narrow bandgaps are promising materials for bulk heterojunction solar cells and high-mobility field-effect transistors. They also emit light in the near-infrared. Here we investigate and compare the photoluminescence and electroluminescence properties of different narrow bandgap (<1.5 eV) donor-acceptor polymers with diketopyrrolopyrrole (DPP), isoindigo (IGT) and benzodipyrrolidone (BPT) cores, respectively. All of them show near-infrared photoluminescence quantum yields of 0.03–0.09% that decrease with decreasing bandgap. Bottom-contact/top-gate field-effect transistors show ambipolar charge transport with hole and electron mobilities between 0.02 and 0.7 cm² V⁻¹ s⁻¹ and near-infrared electroluminescence. Their external quantum efficiencies reach up to 0.001%. The effect of polaron quenching and other reasons for the low electroluminescence efficiency of these high mobility polymers are investigated.