Multi-material stereolithography

A multi-material stereolithography (MMSL) machine was developed by retrofitting components from a commercial 3D Systems 250/50 stereolithography (SL) machine on a separate stand-alone system and adapting the components to function with additional components required for MMSL operation. The MMSL machine required construction of a new frame and the development of a new rotating vat carousel system, platform assembly, and automatic leveling system. The overall operation of the MMSL system was managed using a custom LabVIEW^® program, which included controlling a new vat leveling system and new linear and rotational stages, while the commercial SL control software (3D Systems Buildstation 4.0) was retained for controlling the laser scanning process. During MMSL construction, the sweeping process can be inhibited by previously cured layers, and thus, a deep-dip coating process without sweeping was used with low viscosity resins. Low viscosity resins were created by diluting commercial resins, including DSM Somos^® WaterShed™ 11120, ProtoTherm™ 12120, and 14120 White, with propoxylated (2) neopentyl glycol diacrylate (PNGD). Several multi-material complex parts were produced providing compelling evidence that MMSL can produce unique parts that are functional, visually illustrative, and constructed with multi-materials.     

基于低共熔溶剂稀土金属钇、钐、铽的电沉积研究

低共熔溶剂是一种新型离子液体类似物,具有宽的电化学窗口和独特的物理化学性质,在电沉积领域有着潜在的应用前景。本研究提出以氯化胆碱-尿素基低共熔溶剂为介质,系统研究3种稀土金属(钇、钐、铽)在该介质中的电沉积行为,并采用循环伏安法和恒电位法成功实现了稀土金属(钇、钐、铽)的电沉积。研究结果表明,60℃时,在该低共熔溶剂中钇、钐、铽的电沉积过程为扩散控制过程,扩散系数分别为7.3744×10^-13、1.1032×10^-12和9.2936×10^-13 cm²·s^-1,沉积获得的稀土金属钇、钐、铽具有二维纳米网络结构。本研究为稀土金属的电沉积及提炼提供新的策略。     

Frequency response studies for the plasma electrolytic oxidation process

This paper introduces a methodology for obtaining a fundamental characteristic of the plasma electrolytic process — that is the frequency response (magnitude and phase angle). A methodology is developed for plasma electrolytic oxidation (PEO) of aluminium; however, it can be applied to any plasma electrolytic process. For PEO the frequency response was evaluated as a complex impedance of the electrolyser. It was found that the impedance magnitude decreases with frequency growth from 10³-10⁴ to 10-10² Ω and the phase angle decreases from 0 to − 70 − 80°. This fact appears to be consistent with a hypothesis of active-capacitive load behaviour for the PEO process. Evolution of the frequency response during PEO is consistent with that of the surface state; therefore, it can be used for process diagnostics and control. Frequency response adds a new dimension to the investigation of plasma assisted electrochemical processes. Major benefits of this approach are expected in the field of the process automation and the development of new pulsed plasma electrolytic technologies.     

Stress corrosion cracking of B13, a new high strength aluminium lithium alloy

The present paper focuses on the study of SCC behaviour of a new Al–Cu–Li alloy. For this purpose, two conventional media – NaCl and NaCl + H₂O₂ – were used for comparison with commercial alloys 7075 and 8090. This new alloy shows lower susceptibility to SCC than conventional alloys as it does not undergo environmentally-induced embrittlement in NaCl solutions and in 1 M NaCl + 0.3% H₂O₂ in which the 7075 and 8090 alloys, respectively, undergo environmentally-induced fracture.Solution composition was modified in order to determine the environmental conditions and strain rates under which this new alloy will crack due to a stress corrosion cracking phenomenon. The addition of 0.6 M sulphates to 1 M NaCl + 0.3% H₂O₂ solution allows the definition of a range of strain rate (between 10⁻⁷ and 10⁻⁶ s⁻¹) in which this new alloy undergoes stress corrosion cracking.     

Development of the Z Specimen for Tensile-Tensile, Tensile-Compression, Compression-Compression Wire Testing

A new wire test specimen was developed as part of the Safe Technology consortium project to produce a nitinol algorithm for the fe-safe^? fatigue postprocessor. The requirements for the design were permit tensile and compressive loading, accommodate data collection of strains from ±0.1 to 6% at high-frequency cycling. The requirements for the wire were inexpensive, stable, consistent, and commercially available. The requirements for the processing were incorporate deformation and multiple anneal cycles to simulate manufacturing methods associated with vascular stent production. The final design was 0.508 mm (0.020 in.) diameter wire formed in a two-stage process to produce a Z-shaped specimen. The final part met all requirements for testing. Subsequently, a second specimen, Z3, and a straight wire specimen were produced to supply additional data to the consortium.     

Dynamic recrystallization mechanisms operating in a Ni–20%Cr alloy under hot-to-warm working

The structural mechanisms responsible for the development of new grains in a Ni–20%Cr alloy during hot-to-warm working were studied in compression at temperatures of 500–950 °C. A bilinear relationship between the flow stresses and the dynamic grain sizes was obtained with an inflection point at 7 × 10^?3 G. The dynamic grain size can be related to the flow stress through power-law functions with grain size exponents of ?0.7 and ?0.25 for low and high flow stresses, respectively. The variation of the stress versus grain size dependence is attributed to the change in mechanisms of new grain development from discontinuous to continuous reactions with increasing flow stress. The former is associated with the grain boundary bulging and the latter is related to a strain-induced phenomenon involving the development of large angular misorientations between deformation subgrains after large strains.     

Electrochemical behaviour of chromium-implanted magnesium in hydroxide, chloride and sulphate solutions

Despite the development and subsequent improvement of new Mg-based alloys, their vulnerability to oxidation and corrosion continues to pose a major obstacle to their more generalized use. The possibility of blocking high diffusivity paths, such as grain boundaries, by ion implantation may help to improve their oxidation and corrosion resistance, because mass transport through these short circuiting paths is reduced.Electrochemical techniques were used to investigate the effect of Cr ion implantation in the electrochemical behaviour of Mg in aqueous solutions. In particular ion implanted fluences of 5 × 10¹⁶ and 5 × 10¹⁷ at./cm² have been evaluated in solutions of NaCl, NaOH and Na₂SO₄.The corroded surfaces and products were analysed by ion beam analysis, scanning electron microscopy and X-ray diffraction. A model of the corrosion mechanism is proposed to explain the obtained results.     

Vacuum Analysis of Metals for Oxygen,Nitrogen, and Hydrogen

A brief review of recent papers on the analysis of oxygen, nitrogen, and hydrogen in metals by vacuum methods has been made. Further experience with vacuum fusion apparatus designed and described earlier by one of the authors is reported.¹ A new set of Bureau of Standards steel samples have been analyzed and the acceptable values for oxygen and nitrogen, predicted earlier, have been confirmed. ¹Critical comments on the limitations of methods and suggestions for improvements are presented.     

Photoluminescence properties and energy-transfer of thermal-stable Ce, Mn-codoped barium strontium lithium silicate red phosphors

A series of thermal-stable Ce³⁺, Mn²⁺-codoped barium strontium lithium silicate (BSLS) phosphors was synthesized by a high-temperature solid-state reaction. The XRD patterns of this phosphor seem to be a new phase that has not been reported before. BSLS:Ce³⁺, Mn²⁺ showed two emission bands under 365 nm excitation: one observed at 421 nm was attributed to Ce³⁺ emission, and the other found in red region was assigned to Mn²⁺ emission through Ce³⁺-Mn²⁺ efficient energy transfer. The Mn²⁺ emission shifted red along with the replacement of barium by strontium, which was due to the change of crystal field. A composition-optimized phosphor, BSLS:0.10Ce³⁺, 0.05Mn²⁺ (Ba = 65), exhibited strong and broad red-emitting and supreme thermal stability. The results suggest that this phosphor is suitable as a red component for NUV LED or high pressure Hg vapor (HPMV) lamp.     

Designing superhard,self-toughening CrAlN coatings through grain boundary engineering

One of the toughest challenges that hinders the application of ceramic coatings is their poor damage tolerance. Addressing this problem requires the development of novel micro- or nanostructures that would impart to these coatings both high hardness and high toughness. In this paper, CrAlN coatings, with varying Al contents up to 30 at.%, were engineered onto steel substrates using the magnetron sputtering technique. Whilst the addition of Al does not significantly alter the columnar microstructure, it does change the preferred grain orientation and increase the compressive residual stress. Moreover, the hardness, elastic strain to failure (H/E) and plastic deformation resistance (H³/E²) of the resultant CrAlN coating with the highest Al content were found to increase ～47, ～29 and ～140%, respectively, as compared to CrN. Evidence collected from transmission electron microscopy and X-ray photoelectron spectroscopy experiments shows that AlN, existing in an amorphous state at the columnar CrN grain boundaries, has a crucial role in providing the unusual combination of high hardness and exceptional damage resistance. The results provide a new pathway to developing durable ceramic coatings suitable for applications involving severe loading conditions.     

High Strength,Weldable Precipitation Aged Steels

The family of plate steels represented by ASTM Specification A710¹ is finding increasing applications. These low carbon, Cu-Ni-Cr-Mo-Cb, copper precipitation hardened steels have been identified by a number of designations over the years. During early development in the late 1960’s and first commercial production in 1970, the steels were known as IN-787 (trademark of International Nickel Company).² ASTM specifications were subsequently developed for structural (A710) and pressure vessel (A736) applications over ten years ago. More recent interest and application of this family of steels by the U.S. Navy has lead to development of a military specification MIL-S-24645 (SH),³ also initially known as “HSLA-80.” Significant tonnage is being produced for the U.S. Navy as a replacement for HY80 (MIL-S-16216) in cruiser deck, bulkhead and hull applications.⁴ In these applications, the enhanced weldability and requirement of no preheat at this high strength and toughness level has been the main motivation for its use. Over the past 15 years, A710 type steels have also been used in a variety of applications, including off-shore platforms, pressure vessels, arctic linepipe valves and off-highway mining truck frames.     

A bridge from monotectic alloys to liquid-phase-separated bulk metallic glasses: Design,microstructure and phase evolution

The Zr–Ce–La system is characterized by a miscibility gap and a monotectic reaction. It separates into Zr-rich and CeLa-rich liquids upon cooling through the gap. Based on this system, a new Zr–Ce–La–Al–Co monotectic system was created to synthesize liquid-phase-separated bulk metallic glasses (LPS-BMGs) by copper mold casting. A systematical investigation was performed for the effects of the relative atomic ratios of Zr:CeLa, Co:Al and Ce:La on the microstructure features and chemical compositions of the two coexistent phases. Dual atom pairs with positive heat of mixing (Zr–Ce: +12 kJ mol^?1 and Zr–La: +13 kJ mol^?1) are originally adopted to develop such LPS-BMGs. A series of in situ formed LPS-BMGs with a critical thickness of 2.5 mm has been successfully synthesized. By combining the kinetics of liquid–liquid phase separation with the formation of metallic glasses, the mechanisms of phase formation and the microstructure evolution in the rapidly cooled alloys are discussed in detail. Furthermore, a thermodynamic model is proposed for LPS-BMG design, attempting to build a bridge from monotectic/immiscible (M/I) alloys to LPS-BMGs. This work not only provides opportunities for new insights into the synthesis of LPS-BMGs and their properties but also opens new perspectives for processing and research of M/I alloys.     

抗肿瘤新药甲啶铂的合成工艺研究

为合成抗肿瘤药物甲啶铂，采用醋酸铵与K2PtCl4反应生成K[Pt(NH3)Cl3]，再先后与碘化钾、2-甲基吡啶、硝酸银、氯化钾反应生成甲啶铂。采用元素分析、质谱、核磁共振氢谱和红外光谱对其结构进行了表征。结果显示合成的化合物与理论一致，产率约为40%，可为甲啶铂的合成提供一条新的工艺路线。     

蓝光材料FIrpic的合成、结构表征及光物理性能测试

以水合三氯化铱和 dfppy 为原料,在乙二醇单乙醚溶剂中反应得氯桥二聚体(dfppy)2Ir(μ-Cl2)Ir(dfppy)2,然后在碱性条件下与2-吡啶甲酸反应合成出 FIrpic。通过核磁共振谱(1HNMR、13CNMR)、质谱、红外光谱和单晶X射线衍射等确定了分子结构,高效液相色谱法(HPLC)测试了纯度,利用紫外-可见吸收光谱和光致发光光谱对其光物理性能进行了测试。结果表明：FIrpic为电中性八面体配合物,在476 nm处出现了较强的蓝光发射,其合成产率大于90%,纯度为99.22%,该方法适于FIrpic的批量制备。     

O,O'-二(2-苯乙基)二硫代磷酸二乙铵在HCl溶液中对Q235钢的缓蚀性研究

合成了一种新型缓蚀剂O,O'-二(2-苯乙基)二硫代磷酸二乙铵(EPP),并用元素分析和红外光谱对其进行了表征。采用静态失重法、极化曲线法和电化学阻抗法研究了EPP在HCl溶液中对Q235钢的缓蚀性能,探讨了其在Q235钢表面的吸附行为,考察了HCl浓度、腐蚀体系温度等因素对其缓蚀率的影响。结果表明:EPP是一种高效的混合型缓蚀剂,其缓蚀率随缓蚀剂浓度增加而增大,随腐蚀系统温度升高而缓慢减小。在30℃,1.0 mol·L-1的HCl溶液中,EPP浓度为60 mg·L-1时,其缓蚀率高达98.48%。EPP在Q235钢表面的吸附符合Langmuir吸附等温式,属于自发进行的化学吸附。量子化学计算结果表明,EPP通过配位键和反馈键与金属Fe形成了多中心、稳定的化学吸附。     

Molecule- and polymer-based magnets,a new frontier

Molecule- and polymer-based magnets prepared by relatively low temperature organic synthetic methodologies are of increasing interest in materials research. The three distinct models enabling the design of new molecule- and polymer-based magnetic materials are given. Bulk ferromagnetic behavior with hysteresis was first observed below the critical (Curie) temperature, T_c, of 4.8 K for [Fe^III(C₅Me₅)₂]⁺ [TCNE] ⁻ (Me = methyl; TCNE = tetracyanoethylene). Since then, many new classes of molecule- and polymer-based magnets have been discovered, including those with T_c above room temperature, such as V(TCNE)_x· y(CH₂Cl₂). The important roles of spin and spatial anisotropy and also disorder are illustrated. The, anticipated properties of such molecule- and polymer-based magnetic materials may enable their use in future generations of electronic, magnetic and/or photonic/photronic devices ranging from information storage and magnetic imaging to static and low frequency magnetic shielding and magnetic induction.     

Combustion synthesis of long-persistent luminescent MAl2O4: Eu2+, R3+ (M = Sr,Ba, Ca,R = Dy,Nd and La) nanoparticles and luminescence mechanism research

Eu²⁺, R³⁺ co-doped alkaline earth aluminates MAl₂O₄: Eu²⁺, R³⁺ (M = Sr, Ba and Ca; R = Dy, Nd and La) nanoparticles with high brightness and long afterglow have been prepared by solution-combustion synthesis at 600 °C without a post-annealing process for the first time. The morphologies and the phase structures of the products have been characterized by transmission electron microscopy and X-ray diffraction. The excitation and emission spectra of the products have been measured by an Edinburgh FLS920 spectrometer at room temperature. The characteristic luminescence of the as-prepared sample has been evaluated, and the reason why the wavelength changed from yellow-green to blue-green and then to blue-purple in visible range when the composition changed from SrAl₂O₄: Eu²⁺, Dy³⁺ to BaAl₂O₄: Eu²⁺, Nd³⁺ and then to CaAl₂O₄: Eu²⁺, La³⁺ has been explained. Furthermore, a new persistent luminescence mechanism was proposed in this article.     

The combination effects of trivalent gold ions and gold nanoparticles with different antibiotics against resistant Pseudomonas aeruginosa

Despite much success in drug design and development, Pseudomonas aeruginosa is still considered as one of the most problematic bacteria due to its ability to develop mutational resistance against a variety of antibiotics. In search for new strategies to enhance antibacterial activity of antibiotics, in this work, the combination effect of gold materials including trivalent gold ions (Au³⁺) and gold nanoparticles (Au NPs) with 14 different antibiotics was investigated against the clinical isolates of P. aeruginosa, Staphylococcus aureus and Escherichia coli. Disk diffusion assay was carried out, and test strains were treated with the sub-inhibitory contents of gold nanomaterial. Results showed that Au NPs did not increase the antibacterial effect of antibiotics at tested concentration (40 μg/disc). However, the susceptibility of resistant P. aeruginosa increased in the presence of Au³⁺ and methicillin, erythromycin, vancomycin, penicillin G, clindamycin and nalidixic acid, up to 147 %. As an individual experiment, the same group of antibiotics was tested for their activity against clinical isolates of S. aureus, E. coli and a different resistant strain of P. aeruginosa in the presence of sub-inhibitory contents of Au³⁺, where Au³⁺ increased the susceptibility of test strains to methicillin, erythromycin, vancomycin, penicillin G, clindamycin and nalidixic acid. Our finding suggested that using the combination of sub-inhibitory concentrations of Au³⁺ and methicillin, erythromycin, nalidixic acid or vancomycin may be a promising new strategy for the treatment of highly resistant P. aeruginosa infections.     

茜素红-S螯合形成树脂吸附测定地质样品的金、铂和钯

以茜素红-S(1,2-二羟基蒽醌-3-磺酸钠)为螯合剂,与大孔强碱性阴离子树脂D296-R合成茜素红-S螯合形成树脂,能够在酸性介质中使螯合形成树脂中的-OH离解出H⁺,变成-O-,与大体积的贵金属碘络阴离子[MeI4]^2-相遇形成稳定的螯合物。在较宽的酸度范围内使Au、Pt、Pd与贱金属有效分离,并抑制NO3^-对贵金属吸附的影响。与高压密闭溶矿方式相结合,Au、Pt、Pd的回收率均大于92%,检出限:Au 0.047 ng/g、Pt 0.082 ng/g、Pd 0.051 ng/g。应用于铂族元素地球化学成分分析一级标准物质中Au、Pt、Pd的测定,结果与认定值的相对误差(RE)为-7.58% ~10.9%,相对标准偏差(RSD)均小于9.86%。     

Designing molecular protection: new paradigm for developing corrosion resistant materials uniting high throughput studies,multiscale modelling and self-repair

Abstract

Over the past decade, three technologies, high throughput studies, multiscale modelling (MSM) and self-repair, have entered the field of corrosion science. MSM links processes from 10⁶ to 10^?7 m and allows an understanding of how metal protection systems interact with the environment and with surface electrochemical processes. Potentially MSM has the ability to accurately predict component life and so permit virtual design. In virtual design, a huge range of possible design (including molecular designs) can be assessed on a PC before selecting the best performing inhibitor for a specific application. High throughput experimentation permits many tests to be undertaken at one time. As well as allowing a huge range of inhibitors to be tested under a variety of conditions, it allows the inhibitors of the one family with subtly different molecular configurations to be tested. Self-repair is based on the principle that no matter how well we design and construct a material, it will always develop defects and thus the safest way to design is to build in agents that can cause the material to repair itself. These materials by themselves can hasten our material development and provide more reliable materials; however, if combined synergistically, they will permit radically new materials with tailored functionalities to be developed.