Fabrication of barium titanate ceramics via digital light processing 3D printing by using high refractive index monomer

A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices.     

3D-printing of polymer‐derived SiCN ceramic matrix composites by digital light processing

In this study, we present a DLP 3D-printing strategy for the fabrication of SiCN ceramic matrix composites (CMCs). The polysilazane-based preceramic polymer containing inert fillers was UV-cured into a green body and then converted to SiCN CMCs after pyrolysis. The introduced fillers (Si₃N₄ particles and Si₃N₄ whiskers) as reinforcements are well dispersed in the matrix, which can not only effectively reduce the linear shrinkage and weight loss, but also greatly improve the mechanical properties of the SiCN CMCs. The bending strength of the SiCN CMCs reinforced with 10 wt% Si₃N₄ whiskers (without surface polished) reached 180.7 ± 15.6 MPa. Furthermore, the effect of fillers content on microstructure and porosity of the SiCN CMCs are discussed, and it was found that the excessive fillers led to increased pore defects and decreased continuity of the matrix, thereby reducing the mechanical properties of the SiCN CMCs. This strategy provides a promising ceramic manufacturing technique to fabricate polymer‐derived CMCs with complex-shaped and high-performance for potential demanding applications.     

一种大型球铁飞轮冒口工艺改进

铸造车间生产的N330飞轮在加工Ф1025处M20螺栓孔时会出现一处或多处缩松缺陷,造成了该品种废品率的增加,为解决此缩松问题对飞轮进行了跟踪研究,分析并改进了飞轮的造型、冒口补缩和浇注工艺,通过试制验证了工艺改进的合理性。     

Synergistic effect of binary fluoride sintering additives on the properties of silicon nitride ceramics

A variety of combinations of YF₃ and MgF₂ were used as sintering aids in the fabrication of Si₃N₄ ceramics via gas pressure sintering (GPS). The synergistic effects of YF₃ and MgF₂ on the liquid viscosity, mechanical properties, thermal conductivities, and grain growth kinetics of the Si₃N₄ ceramics were investigated. The results showed that appropriately adjusting the YF₃/MgF₂ ratio could decrease liquid viscosity, reducing the diffusion energy barrier of the solute atom and promoting mass transfer. Meanwhile, the chemical bonding strength in the grain boundary complexions formed by the metal cations also influenced grain boundary migration. Samples doped with 4 mol% YF₃ and 2 mol% MgF₂ achieved the lowest grain growth exponent (n = 2.9) and growth activation energy (Q = 616.7 ± 16.5 kJ mol^?1) as well as the highest thermal conductivity (83 W m^?1 K^?1) and fracture toughness (8.82 ± 0.13 MPa m^1/2).     

采用八叉树和OSG分页结点的海量点云三维可视化

针对现有海量点云可视化方法存在索引构建时间长、内存占用大等问题，研究一种八叉树索引结合OSG分页结点的快速可视化方法，可在占用较小内存的基础上快速建立点云索引并实时调度。采用八叉树索引结构对海量点云进行数据组织，建立各层级的八叉树结点并以文件映射的方式分块保存，对结点文件重组织转换为支持OSG渲染引擎的多分辨率点云数据。采用基于OSG分页结点的实时调度技术，对海量点云进行高质量可视化。与目前两款主流的点云数据处理商业软件进行实验对比分析，结果表明所提方法具有索引建立速度快、内存占用小等优点，同时可视化交互更加流畅，适用于各种配置计算机下海量点云数据的调度管理与实时可视化。     

Flame Front Deformation Instabilities of Filtration Combustion for Initial Thermal Perturbation

The flame front deformation instability of low-velocity filtration combustion within an inert packed bed is studied based on the initial preheating non-uniformity. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed so as to predict the deformation behaviors of the flame front instabilities. The numerical prediction indicates that the assumption of an initial thermal perturbation is a feasible explanation as the cause of the flame front inclination instability. As the initial thermal perturbation increases, the phenomena of the flame front break and shrinking instabilities could easily occur at high filtration velocity or low equivalence ratio. Moreover, the evolutions of the flame front break rate and the shrinking rate are quantitatively analyzed.     

基于平面复合降阻材料的杆塔基础接地降阻研究

杆塔基础自然接地作为输电线路重要的接地装置,能减少外延接地及降阻施工成本。针对特高压输电线路杆塔基础接地提出基于平面复合降阻材料的塔基外敷接地降阻策略,首先,采用CDEGS仿真计算软件建立特高压杆塔单根浇注桩接地计算模型,分析均匀土壤、多层土壤、混合土壤三种条件下的外敷接地降阻效果;然后,通过单个塔基外敷计算模型分析外敷材料不同敷设方式的降阻效率;最后,计算完整杆塔基础外敷接地降阻效率和散流分布特征,并与水平人工外延接地降阻方式进行对比。结果表明,外敷接地降阻效率与土壤条件、敷设位置等因素有关,在高土壤电阻率条件下,塔基外敷接地降阻效率超过22%,与水平人工外延接地相比,塔基外敷接地降阻的散流比超过96%,接地材料利用率高,可减少征地和二次接地施工成本。     

Rapid polymerization synthesizing high-crystalline g-C3N4 towards boosting solar photocatalytic H2 generation

Graphitic carbon nitride (g-C₃N₄) is a promising metal-free photocatalyst for solar photocatalytic hydrogen gas (H₂) generation from water. In particularly, high-crystalline g-C₃N₄ (GCN-HC) material with fewer structural defects possesses the fast photoexcited electron-hole pair's separation efficiency as comparison with bulk g-C₃N₄ (GCN-B) powders, leading to the drastic improvement of photocatalytic activity. However, the fabrication of such GCN-HC photocatalyst by a simple and economical synthesis approach still remains a challenge. Herein, we firstly develop a one-step rapid polymerization strategy for synthesizing the GCN-HC, that is direct calcination of melamine at 550 °C not only without the early heating process, but also without the assistance of any additive or salt intercalation. As a result, the GCN-HC exhibits an obviously boosting visible-light-induced photocatalytic H₂-generation performance, which is over 2.06-folds much greater than that of GCN-B. Our work provides an available one-step synthetic strategy for the large-scale preparation of high performance GCN-HC towards sustainable solar-to-chemical energy conversion.     

赤泥对玉米秸秆催化热解生物油的影响规律研究

将经过不同温度煅烧的赤泥与玉米秸秆按照一定质量比混合，在500℃下进行催化热解实验，研究赤泥对玉米秸秆生物油组成的影响规律。经TG-DTG和XRD分析发现：600℃煅烧后赤泥（RM600）中含水矿物失水，1 000℃煅烧后赤泥（RM1000）中碳酸盐类化合物分解完全，并且发生了烧结反应。对生物油进行GC/MS分析发现：经过干燥的赤泥（RM）和600℃煅烧的赤泥对羧酸酮基化反应具有明显促进作用，酸类的量降低，酮类的量相应增加，同时对呋喃类的生成也有促进作用。其中，干燥赤泥降酸作用更明显，玉米秸秆与赤泥质量比1：5时，生物油中酸类的量由未添加赤泥时的23.85%降至0.90%。此外，2种赤泥对糖类和醛类都有抑制作用，而1 000℃煅烧的赤泥发生烧结反应，催化作用大幅降低，对生物油组分影响较小。     

Microencapsulation of camellia oil to maintain thermal and oxidative stability with focus on protective mechanism

Camellia oil (CO) microcapsules were developed using chitosan–soybean protein isolate (CS-SPI) complexes as wall materials and transglutaminase (TGase) as the cross-linking agent. Results indicated that CO/SPI under the ratio of 1:2 exhibited the highest microencapsulation efficiency and yield, possessing the best encapsulation effect. Morphology observation showed that CO microcapsules were intact, compact and nearly spherical. The microencapsulated CO exhibited the improved thermal resistance and significantly lower peroxide values after 3 days storage, demonstrating that the produced microcapsule was a promising way to maintain the thermal and oxidative stability of camellia oil. It could be found evidence from FTIR, which indicated that covalent cross-linking and hydrogen bonding might be involved among wall materials, and physical interactions between the core and wall materials. Therefore, the produced CO microcapsules could be an effective way to protect camellia oil, which was helpful for improving the processing and storage qualities of camellia oil.