Harnessing irreversible thermal strain for shape memory in polymer additive manufacturing

Shape transformation upon annealing of fused filament fabrication additively manufacturing structures is investigated as a one-way shape memory strategy using commodity thermoplastics. Irreversible thermal strain, which is a measurement of shape transformation upon annealing, is shown to depend on both raster angle and layer thickness, both of which are parameters than can be easily adjusted on most FFF printers. We present an algorithm based on our understanding of the underlying micromechanics of the system that allows for input of desired final dimensions and output the necessary print parameters. We also demonstrate that this approach is extensible to other materials and report more complex shape memory geometries. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48239.     

以设计为中心的虚拟制造技术及在化工过程装备中的应用

简述了虚拟制造技术的内涵、关键技术及应用现状。在分析化工过程装备特点基础上 ,对过程装备虚拟制造技术平台的体系结构进行了探讨 ,以典型过程装备螺旋片导流式气液分离器为例 ,对其数字化建模方法、数值仿真技术、虚拟设计和制造环境进行了研究。初步结果表明 :以设计为中心的虚拟制造技术的应用 ,可以有效地减少产品开发的时间和成本 ,提高产品质量     

Material extrusion additive manufacturing of advanced ceramics: Towards the production of large components

Thermoplastic extrusion based additive manufacturing (MEX-AM), is a very interesting fabrication method for the shaping of larger ceramic parts. Commercial filaments are currently available in the market, but due to the lack of information from the suppliers, it is not easy to select the suitable filament material for the 3D printing of individual ceramic objects. In this study, three commercial yttria-stabilized zirconia (YSZ) filaments provided by Fabru GmbH, SiCeram GmbH and PT+A GmbH were investigated. According to our results, it is possible to print YSZ filaments with extremely different flexibility and rheological properties. Compared to the other two filaments, the Fabru filament resulted in significantly higher flexibility, but the extrusion pressure to print it through a 0.25 mm nozzle was significantly higher at 150 °C. Interestingly, in the SiCeram filament, a grain orientation effect could be observed. Based on STA analysis it can be assumed that for the Fabru filament, the polymer which decomposes at a high temperature can already be removed by solvent debinding (SD). Finally, 70 mm tall cup structure including overhang features and different wall thicknesses was used to evaluate the printing and post-processing of YSZ filaments.     

利用Box-Behnken实验设计研究化学外加剂组分对水泥砂浆强度的影响

利用Box-Behnken实验设计(BBD)方法研究三乙醇胺、氯盐、还原糖和二元醇4种化学组分对水泥砂浆各养护龄期抗压强度的影响。通过Box-Behnken设计得出能反映化学组分掺量与水泥砂浆强度关系的二次方程。利用实验设计得到的帕雷托图对各化学组分影响水泥砂浆强度提升的有效性进行排序。结果表明:三乙醇胺在水泥砂浆养护3 d前对强度的贡献强于氯盐,而对于28 d强度贡献低于氯盐。还原糖的作用主要体现在3 d前,二元醇及其与三乙醇胺和氯盐的交互作用能显著提高水泥砂浆的28 d强度。     

Review of additive manufacturing and densification techniques for the net- and near net-shaping of geometrically complex silicon nitride components

Silicon nitride (Si₃N₄) is an advantageous material due its unique combination of mechanical, thermal, chemical, and electrical properties both at ambient and elevated temperatures. Because of these properties there are a wide range of applications for Si₃N₄ components. Applications include heat exchangers, environmental barrier coatings, osteointegration scaffolds, radomes, and integrated circuitry. Such applications often require geometric complexity for efficient and/or effective operation. However, traditional ceramics processing methods such as hot-pressing or die extrusion are typically limited to simple axis-symmetric shapes. With the advent of additive manufacturing, there has been significant advancement into the forming of geometrically complex Si₃N₄ components. This review documents additive manufacturing advancements that have demonstrated, or are capable of, fabricating Si₃N₄ components with complex geometry.     

Hybrid additive manufacturing of the modified electrolyte-electrode surface of planar solid oxide fuel cells

Digital Control of the surface patterning of functional layers of solid oxide fuel cells (SOFCs), via the inkjet printing technique, offers better efficiency in performance. A combination of inkjet printing and tape casting in a single machine system defines as hybrid additive manufacturing, facilitates printing complex structures. Also, implementing this idea removes the blocking of the print head nozzle orifice issue. In this paper, a highly dispersed and long-term stable colloidal zirconia-based suspension, with optimal printability characteristics, is designed to be prepared in approximately three hours to fabricate the macro patterned structure of the SOFC electrolyte. Hybrid Additive Manufacturing is successfully employed to make a symmetric cathode side cell with a modified electrolyte-electrode surface to reduce the electron resistivity.     

Material extrusion-based additive manufacturing of polypropylene: A review on how to improve dimensional inaccuracy and warpage

Material extrusion-based additive manufacturing (ME-AM) is an emerging processing technique that is characterized by the selective deposition of thermoplastic filaments in a layer-by-layer manner based on digital part models. Recently, it has attracted considerable attention, as this technique offers manifold benefits over conventional manufacturing technologies. However, to meet the challenges of complex industrial applications, certain shortcomings of ME-AM still need to be overcome. A case in point is the limited amount of semicrystalline thermoplastics, which are still not established as reliable, commercial filament materials. Particularly, polypropylene (PP) offers attractive properties that are unique among the ME-AM material portfolio. This review describes the current approaches of fabricating PP components by ME-AM. Both commercial and scientific strategies to make PP 3D-printable are elaborated and compared. As dimensional issues are especially problematic for PP, a comprehensive section of this review focuses on the strategies developed for mitigating warpage for PP parts fabricated by ME-AM. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48545.     

基于蜻蜓翅脉结构的连续碳纤维增强树脂基复合材料仿生设计与增材制造

以具有轻质高强优异性能的蜻蜓翅脉结构为设计灵感,在分析翅脉网格结构抗冲击原理的基础上,设计了传统和仿生两类对比结构。采用熔融挤出3D打印机成功制备了具有不同结构的连续碳纤维增强聚乳酸复合材料试样,并对不同结构复合材料试样的拉伸性能和抗冲击性能进行了测试和对比分析。研究分析结果表明：由于拉伸力方向上的连续碳纤维含量相对较少,限制了仿生结构复合材料抗拉强度的提高,但仿生结构的平均抗拉强度为传统结构的1.18倍;当仿生结构复合材料试样受到冲击力时,其内部六边形结构的连接角度会发生变化,从而极大消耗冲击能量,同时具有六边形网格结构的连续碳纤维可以有效阻碍裂纹的扩展,因此仿生结构的平均冲击韧性可以达到传统结构的2.46倍;仿生蜻蜓翅脉结构可以显著提高增材制造复合材料的综合力学性能,且对于抗冲击性能的提高具体突出效果。连续碳纤维增强树脂基复合材料的有效可行的仿生蜻蜓翅脉结构设计和增材制造,可极大扩展其在高冲击载荷领域中的相应应用。     

The conceptual design of a continuous pervaporation membrane reactor for the production of 1,1‐diethoxy butane

Acetals are considered as an important bio‐based diesel additives. Generally, the catalytic production of these compounds from an alcohol and an aldehyde suffers from a low conversion because of thermodynamic limitations. These limitations can be overcome through the in situ removal of the by‐product water using, for example, a water selective membrane. A critical evaluation on the membrane performance, catalyst activity, optimal configuration, and feed composition leads to the conclusion that a combined reaction and separation is unlikely to be advantageous. The water permeance of the selected membrane was assessed to be too low in relation with the catalyst activity. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1862–1868, 2012     

Impact of processing conditions and sizing on the thermomechanical and morphological properties of polypropylene/carbon fiber composites fabricated by material extrusion additive manufacturing

For the 3D printed composites, fiber alignment is affected by the direction of melt-flow during extrusion of filaments and subsequently through the printing nozzle. The resulting fibers orientation and the fiber-matrix compatibility have a direct correlation with mechanical properties. This study investigates the impact of processing conditions on the state of the carbon fiber types and their orientation on the mechanical properties of 3D-printed composites. Short and long carbon fibers were used as starting reinforcing materials, and the state of fibers at the beginning and on the printed parts were evaluated. Strong anisotropy in terms of mechanical properties (flexural and impact properties) was observed for the samples printed with different printing orientations. Interestingly, the number of voids in the printed composites was found to be correlated with the fiber types. The present work provides a step towards the optimization of tailored composite properties by additive manufacturing.     

Stability and instability in isothermal CFSTRs with complex chemistry: Some recent results

Although the classical 1955 paper by Bilous and Amundson was largely devoted to the study of nonisothermal systems, they also found it worthwhile to establish the stable behavior of a model isothermal multireaction continuous flow stirred tank reactor for all values of residence time, rate constants, and feed concentrations. Over a half century later, there remains a predisposition to the idea that isothermal reactors are prone to dull, stable behavior even when the underlying chemistry is complex. That idea is revisited in light of some recent findings in chemical reaction network theory. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3403–3411, 2013     

Integrating process and power grid models for optimal design and demand response operation of giga-scale green hydrogen

Electrolysis-based hydrogen production can play a significant role in industrial decarbonization, and its economic competitiveness can be promoted by designing demand response operating schemes. Nevertheless, the scale of industrial supply plants may be significantly large (on the order of gigawatts), meaning that electricity prices cannot be treated as an input for scheduling problems, that is, the “price taker” approach. This article presents a framework for the optimization of a large-scale, electricity-powered hydrogen production facility considering its integration with the power grid. Using a computational case study, we present an iterative scheme for integrating the process model with a model for power grid optimization and capacity expansion, taking the popular GenX model as an example.     

Wet‐spinning of biomedical polymers: from single‐fibre production to additive manufacturing of three‐dimensional scaffolds

Wet‐spinning of polymeric materials has been widely investigated for various biomedical applications, such as extracorporeal blood treatment, controlled drug release and tissue engineering. This review is aimed at summarizing and assessing current advances in wet‐spinning of biomedical polymers to manufacture single fibres and three‐dimensional scaffolds, as well as their functionalization through loading with bioactive agents. The theoretical principles and the main technological aspects of fibre production by wet‐spinning on either a laboratory or an industrial scale are outlined. The non‐solvent‐induced phase inversion determining polymer coagulation during the wet‐spinning process is discussed by highlighting its influence on the resulting fibre morphology and how it can be exploited to induce a nano/microporosity in the solidified polymeric matrix. The versatility of wet‐spinning in material selection, bioactive agent loading and fibre morphology tuning is underlined through an overview of significant literature reporting on the processing of various naturally derived and synthetic polymers. A special focus is given to cutting‐edge advancements in the application of additive manufacturing principles to wet‐spinning for enhanced control and reproducibility of three‐dimensional polymeric scaffold morphology at different scale levels (i.e. macrostructural to micro/nanostructural features). © 2017 Society of Chemical Industry     

Probabilistic reactor design in the framework of elementary process functions

Computational process models in combination with innovative design methodologies provide a powerful reactor design platform. Yet, model-based design is mostly done in a pure deterministic way. Possible uncertainties of the underlying model parameters, prediction errors due to simplifying assumptions regarding the reactor behavior and suboptimal realizations of the design along the reaction coordinate are in general not considered. Here we propose a systematic design approach to directly account for the impact of such variabilities during the design procedure. The three level design approach of Peschel et al. (2010) based on the concept of elementary process functions (EPF) serves as basis. The dynamic optimizations on each level are extended within a probabilistic framework to account for different sources of randomness. The impact of these sources on the performance prediction of a design is quantified and used to robustify the reactor design aiming at a more reliable performance and thus design prediction. The uncertainties of model parameters, non-idealities of the reactor behavior and inaccuracies in the design are included via statistical moments. By means of the sigma point method (Julier and Uhlmann, 1996) random variables are mapped to the design objective space via the nonlinear process model. Importantly, this work introduces a full probabilistic orthogonal collocation approach, i.e. random and stochastic variables can be described. Whereas the former one relates to randomness independent on the reaction time (e.g. kinetic model parameters or initial conditions), the latter one describes stochasticity along the reaction time (e.g. fluctuating pressure or temperature control). As an example process the hydroformylation of 1-dodecene in a thermomorphic solvent system consisting of n-decane and N,N-dimethylformamide is considered.Our probabilistic EPF approach allows designing robust optimal reactors, which operate within an estimated confidence at their expected optimum considering almost any kind of randomness arising in the design procedure. An additional value is that with increased predictive power of the reactor performance its embedding in an overall process is strongly simplified.     

Scheduling-informed optimal design of systems with time-varying operation: A wind-powered ammonia case study

The time-varying operation of chemical plants offers economic advantages, particularly in the presence of time-sensitive electricity markets and renewable energy generation. However, the uncertainty and short-timescale variability associated with renewable energy production, as well as the nonconvex process and cost models typically associated with chemical processes, make finding the optimal design of such systems challenging. In this work, a new approach is presented to finding the optimal design of systems with time-varying operation, called scheduling-informed design, whereby the optimal operation of many designs is determined and the resulting cost correlations into the optimal design problem are embedded. This method is applied to a case study of wind-powered ammonia generation and showed that it greatly improves the computational tractability of the optimal design problem and predicts with greater accuracy operating costs realized because of uncertainty in forecasting. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16434 2019     

Optimal design of large‐scale chemical processes under uncertainty: A ranking‐based approach

An approach for the optimal design of chemical processes in the presence of uncertainty was presented. The key idea in this work is to approximate the process constraint functions and model outputs using Power Series Expansions (PSE)‐based functions. The PSE functions are used to efficiently identify the variability in the process constraint functions and model outputs due to multiple realizations in the uncertain parameters using Monte Carlo (MC) sampling methods. A ranking‐based approach is adopted here where the user can assign priorities or probabilities of satisfaction for the different process constraints and model outputs considered in the analysis. The methodology was tested on a reactor–heat exchanger system and the Tennessee Eastman process. The results show that the present method is computationally attractive since the optimal process design is accomplished in shorter computational times when compared to the use of the MC method applied to the full plant model. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3243–3257, 2014     

Quality control in the polypropylene manufacturing process: An efficient,data‐driven approach

In the propylene polymerization process, the melt index (MI), as a critical quality variable in determining the product specification, cannot be measured in real time. What we already know is that MI is influenced by a large number of process variables, such as the process temperature, pressure, and level of liquid, and a large amount of their data are routinely recorded by the distributed control system. An alternative data‐driven model was explored to online predict the MI, where the least squares support vector machine was responsible for establishing the complicated nonlinear relationship between the difficult‐to‐measure quality variable MI and those easy‐to‐measure process variables, whereas the independent component analysis and particle swarm optimization technique were structurally integrated into the model to tune the best values of the model parameters. Furthermore, an online correction strategy was specially devised to update the modeling data and adjust the model configuration parameters via adaptive behavior. The effectiveness of the designed data‐driven approach was illustrated by the inference of the MI in a real polypropylene manufacturing plant, and we achieved a root mean square error of 0.0320 and a standard deviation of 0.0288 on the testing dataset. This proved the good prediction accuracy and validity of the proposed data‐driven approach. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41312.     

化工设备设计中焊后热处理的分析

热处理能够很好地完善金属本身的材质,延长金属设备使用的时间。但是,热处理还有很多薄弱的环节。在化工设备设计中,热处理的方式主要有以消除应力为主要目的的焊后热处理、降低材料中氢含量的焊后消氢处理以及提升材料性能的恢复材料性能热处理。阐述焊后热处理的定义及目的,并对化工设备设计中焊后热处理提出可行方案。     

The role of plasticizer in optimizing the rheological behavior of ceramic pastes intended for stereolithography-based additive manufacturing

Adding plasticizer is an efficient way to regulate the rheological behavior of ceramic paste and quality of green body in stereolithography-based additive manufacturing. The type and content of plasticizers (polyethylene glycol (PEG) and dibutyl phthalate (DBP)) had substantial effects on the rheological behavior and solid loading of ceramic paste, leading to varied macro / micro structure and strength of the green and sintered parts. DBP significantly reduced the viscosity and increased solid loading, and could adjust the flexibility of the green body by reducing the crosslinking density of UV curing system. PEG could inhibit crack initiation to some extent, but it was less effective for preventing cracking than DBP on ceramic parts with large-sized cross sections. It was concluded that DBP was more suitable as a plasticizer in alumina paste for SL additive manufacturing to form dense parts without defects.     

Conceptual design of ammonia‐based energy storage system: System design and time‐invariant performance

Chemicals‐based energy storage is promising for integrating intermittent renewables on the utility scale. High round‐trip efficiency, low cost, and considerable flexibility are desirable. To this end, an ammonia‐based energy storage system is proposed. It utilizes a pressurized reversible solid‐oxide fuel cell for power conversion, coupled with external ammonia synthesis and decomposition processes and a steam power cycle. A coupled refrigeration cycle is utilized to recycle nitrogen completely. Pure oxygen, produced as a side‐product in electrochemical water splitting, is used to drive the fuel cell. A first‐principle process model extended by detailed cost calculation is used for process optimization. In this work, the performance of a 100 MW system under time‐invariant operation is studied. The system can achieve a round‐trip efficiency as high as 72%. The lowest levelized cost of delivered energy is obtained at 0.24 $/kWh, which is comparable to that of pumped hydro and compressed air energy storage systems. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1620–1637, 2017