Synthesis and Characterization of Novel Polyurethane Composites Based on Hybrid Inorganic/Organic Phosphazene‐Containing Microspheres

Novel polyurethane (PU) composites were prepared, based on hybrid inorganic/organic phosphazene‐containing microspheres. The FT‐IR spectra have shown that the microspheres have been linked with PU matrix. The microstructure of the composites is investigated by SEM. In comparison with PU, the glass transition temperatures and thermal stability of the composites are increased. The results from tensile testing of the composites have indicated that tensile strength is improved and elongation at break is almost invariable. The investigation on the surface properties of the composites showed that the water contact angles are obviously increased by adding 2 and 4 wt.‐% microspheres to the matrix.

     

耐刮伤有机/无机杂化涂层的制备和性能研究

以甲苯二异氰酸酯与双（三乙氧基硅丙基）胺反应生成的多官能团硅氧烷和正硅酸乙酯为前驱体，采用溶胶-凝胶法以乙醇为溶剂、醋酸为催化剂进行共水解，将得到的溶胶成膜，得到有机／无机杂化涂层。对涂层的一些力学性能（铅笔硬度、耐磨性和附着力等）进行测试，并用红外光谱和热失质量分别对涂层的化学组成及热性能进行了表征。结果表明：当SiO2含量为8．5％时，杂化涂层的力学性能达到一个较停值，其溶胶的离心稳定性和杂化涂层的耐水性及热稳定性优异。     

Effect of Interfacial Adhesion on the Mechanical Properties of Organic/Inorganic Hybrid Nanolaminates

Two different kinds of organic polyelectrolyte (PE)/inorganic silicate nanolaminates carrying dissimilar interfacial adhesion between the organic and the inorganic layers were prepared using the layer-by-layer self-assembly. To investigate the mechanical behavior of the prepared hybrid films, apparent modulus (E'), hardness (H), and crack length were measured by depth-sensing nanoindentation as well as a microVickers experiment. The fracture toughness of the hybrid films was then calculated based on the measured mechanical values. In the case of forming strong interfacial adhesion between the organic and the inorganic layers (A series), the fracture toughness and the crack resistance of hybrid multilayer films were significantly improved as a result of the redistribution of stress concentration and the dissipation of fracture energy by the plasticity of organic PE layers. On the other hand, samples with relatively low interfacial adhesion between the organic and the inorganic layers (T series) had little effect on the improvement of fracture toughness of the hybrid films.     

Effect of Interfacial Adhesion on the Mechanical Properties of Organic/Inorganic Hybrid Nanolaminates

Two different kinds of organic polyelectrolyte (PE)/inorganic silicate nanolaminates carrying dissimilar interfacial adhesion between the organic and the inorganic layers were prepared using the layer-by-layer self-assembly. To investigate the mechanical behavior of the prepared hybrid films, apparent modulus (E′), hardness (H), and crack length were measured by depth-sensing nanoindentation as well as a microVickers experiment. The fracture toughness of the hybrid films was then calculated based on the measured mechanical values. In the case of forming strong interfacial adhesion between the organic and the inorganic layers (A series), the fracture toughness and the crack resistance of hybrid multilayer films were significantly improved as a result of the redistribution of stress concentration and the dissipation of fracture energy by the plasticity of organic PE layers. On the other hand, samples with relatively low interfacial adhesion between the organic and the inorganic layers (T series) had little effect on the improvement of fracture toughness of the hybrid films.     

Mechanical Properties of CoAl Materials with the Combined Additions of ZrO2(3Y) and Al2O3

Intermetallic CoAl powder has been prepared via self-propagating high-temperature synthesis (SHS). Dense CoAl materials (99.6% of theoretical) with the combined additions of ZrO₂(3Y) and Al₂O₃ have been fabricated via spark plasma sintering (SPS) for 10 min at 1300°C and 30 MPa. The microstructures are such that tetragonal ZrO₂ (0.3 μm) and Al₂O₃ (0.5 μm) particles are located at the grain boundaries of the CoAl (8.5 μm) matrix. Improved mechanical properties are obtained; especially the fracture toughness and the bending strength of the materials with ZrO₂(3Y)/Al₂O₃= 16/4 mol% are 3.87 MPa·m^1/2 and 1080 MPa, respectively, and high strength (>600 MPa) can be retained up to 1000°C.     

Structure and Mechanical Properties of Polyurethane/Silica Hybrid Coatings

Summary: Polyurethane/silica hybrid coatings were prepared via in situ (IS) or blending (BL) method using different acidic silica sols. The effects of preparation methods, silica types, and content on the structure and mechanical properties of the hybrid coatings were investigated. It was found that there existed two types of silica phases in the hybrid coatings: silica‐rich agglomerate and primary silica‐rich phase, whose size and compactness depended upon the silica types and the preparation methods. Introducing silica could result in obvious changes in surface free energy, atomic composition, and mechanical properties of the hybrid coatings.

Typical SEM image of the fractured surface of hybrids obtained by the in situ method.     

Effect of Nb2O5/ZnO Addition on Microwave Properties of (Zr0.8Sn0.2)TiO4 Ceramics

The effects of Nb₂O₅ and ZnO addition on the dielectric properties, especially the quality factor, of (Zr_0.8Sn_0.2)TiO₄ (ZST) ceramics were investigated in terms of the sintered density acquired by the zinc. For ZST ceramics with 2 mol% added ZnO, the relative density of the samples decreased with >0.5 mol% addition of Nb₂O₅. On the other hand, for samples with 6 mol% added ZnO, the relative density remained >97%, even when the amount of Nb₂O₅ was increased to 2.0 mol%. When >0.5 mol% Nb₂O₅ was added, both the quality factor and the dielectric constant exhibited similar trends with sintered density. The ZST ceramics with 6 mol% added ZnO, especially, still manifested a quality factor >40 000 and a dielectric constant of 37, even when the amount of Nb₂O₅ was increased, values that are not explainable by the previously suggested electronic defect model.     

SBA-15／PMMA杂化材料力学性能及热性能研究

采用溶胶一凝胶法制备了二维六方介孔结构的SBA-15,利用原位分散聚合法制备（SBA-15／0wt％DBP／PMMA,SBA-15／15wt％DBP／PMMA和SBA—15,25wt％DBP／PMMA）三种三维纳米网络结构的杂化材料。通过FT—IR、XRD、TEM、DSC和SEM等方法对SBA-15／DBP／PMMA杂化材料进行了表征。结果表明：DBP和SBA-15的加入对PMMA分子链的化学结构未造成任何影响,且SBA-15在PMMA基体中仍能保持介观有序结构;SBA-15对脆性PMMA具有较好的增强增刚作用,且DBP的含量越高,杂化材料拉伸强度和模量提高程度相对减小;三种杂化材料的rrg均随SBA-15含量的增加而提高,且DBP的含量越高,杂化材料的Tg提高幅度越小。     

Effect of nonstoichiometry on mechanical properties of reactive hot‐pressed monolithic ZrCx Ceramic

The reactive hot pressing (RHP) of Zr:C powder mixture at various molar ratios (1:0.5, 1:0.6, and 1:0.67) at applied pressures of 4‐7 MPa and 1200°C resulted in dense ZrC_x ceramics. Nano‐hardness values of ZrC_x are reported to be 21‐31 GPa as “x” was varied from 0.5 to 1.0. However, indentation modulus for all ZrC_x compositions remained at ~350 GPa. Microhardness of the ZrC_x increased from 13 to 15 GPa as the stoichiometry was increased from 0.5 to 1.0. The indentation fracture toughness for ZrC_0.5 was 4 MPa m^1/2, and for ZrC_0.67 it was reduced to 3.6 MPa m^1/2. The 3‐point flexural strength for ZrC_0.5 was determined to be 386 ± 26 MPa, which decreased to 316 ± 20 MPa as the carbon content (ZrC_0.67) was increased. The dry sliding wear of ZrC_0.5 to ZrC_0.6 indicated that the coefficient of friction was increased from 0.73 to 0.86 at 5 N load and 500 m sliding distance. Further, ZrC_0.67 showed a reduction in friction coefficient of 0.81, and this was due to the increase of strong Zr–C covalent bond and unreacted graphite.     

Solid-State Preparation of BaTiO3-Based Dielectrics, Using Ultrafine Raw Materials

BaTiO₃ and Ba(Ti,Zr)O₃ dielectric powders have been prepared from submicrometer BaCO₃, TiO₂, and ZrO₂. By use of submicrometer BaCO₃ the intermediate formation of Ba₂TiO₄ second phase can be widely suppressed. Monophase perovskites of BaTiO₃ were already formed at 900°C and Ba(Ti,Zr)O₃ at 1050°C. Aggregates of very small subgrains could be easily disintegrated to particle sizes <0.5 μm.     

Phytic Acid-Iron/Laponite Coatings for Enhanced Flame Retardancy,Antidripping and Mechanical Properties of Flexible Polyurethane Foam

The use of flexible polyurethane foam (FPUF) is severely limited due to its flammability and dripping, which can easily cause major fire hazards. Therefore, choosing an appropriate flame retardant to solve this problem is an urgent need. A coating was prepared on the FPUF surface by dipping with phytic acid (PA), Fe₂(SO₄)₃·xH₂O, and laponite (LAP). The influence of PA-Fe/LAP coating on FPUF flame-retardant performance was explored by thermal stability, flame retardancy, combustion behavior, and smoke density analysis. FPUF/PA-Fe/LAP has a good performance in the small fire test, which can pass the UL-94 V-0 rating and the limiting oxygen index reaches 24.5%. Meanwhile, the peak heat release rate values and maximum smoke density of FPUF/PA-Fe/LAP are reduced by 38.7% and 38.5% compared with those of neat FPUF. After applying PA-Fe/LAP coating, the value of fire growth rate index decreases from 10.5 kW/(m²·s) to 5.1 kW/(m²·s), dramatically reducing the fire risk. Encouragingly, the effect of PA-Fe/LAP coating on cyclic compression and permanent deformation is small, which is close to that of neat FPUF. This work provides an effective strategy for making a flame-retardant FPUF with antidripping and keeping mechanical properties.     

Microstructure and Mechanical Properties of Three-Dimensional Textile Hi-Nicalon SiC/SiC Composites by Chemical Vapor Infiltration

Three-dimensional textile Hi-Nicalon SiC-fiber-reinforced SiC composites were fabricated using chemical vapor infiltration. The microstructure and mechanical properties of the composite materials were investigated under bending, shear, and impact loading. The density of the composites was 2.5 g·cm⁻³ after the three-dimensional SiC perform was infiltrated for 30 h. The values of flexural strength were 860 MPa at room temperature and 1010 MPa at 1300°C under vacuum. Above the infiltration temperature, the failure behavior of the composites became brittle because of the strong interfacial bonding and the mismatch of thermal expansion coefficients between fiber and matrix. The fracture toughness was 30.2 MPa·m^1/2. The obtained value of shear strength was 67.5 MPa. The composites exhibited excellent impact resistance, and the dynamic fracture toughness of 36.0 kJ·m⁻² was measured using Charpy impact tests.     

Hybrid Organic/Inorganic UV‐Cured Acrylic Films with Hydrophobic Surface Properties

Hybrid organic/inorganic acrylic nanostructured films were prepared by a UV/thermal dual‐curing process. The role of a fluorinated hydroxyl acrylate monomer (AF) as coupling agent was investigated. Increased T_g values and modulus of the dual‐cured films were achieved by increasing the TEOS inorganic precursor. The coupling agent deeply modified the surface properties of the cured films: the formation of hybrid films characterized by high hydrophobicity together with an increase on surface hardness was achieved. TEM analysis clearly evidenced the reducing of the nanosize dimensions of the inorganic silica domains by increasing the coupling agent content in the photocurable formulation.

     

PO／PS合金的相态结构与力学性能

以氢化ＳＢＳ（ＳＥＢＳ）为增容剂的聚烯烃／聚苯乙烯（ＰＯ／ＰＳ）合金，与聚烯烃相比具有更好的力学性能，尤其是抗冲击强度随机容剂的增加而大幅度提高，应用ＴＥＭ，ＳＥＭ、ＤＳＣ、偏光显微技术对一系列合金相形态，相容程度及分散相颗粒尺的考察研究发现，合金中分散相多数呈卵石状，随ＳＥＢＳ含量增加，分散相粒径显著变小，而合金抗冲击强度增大，分散相形态结构。颗粒尺寸与材料力学性能密切相联。     

Mechanical Properties of Monoclinic Zirconia

Fracture toughness and fracture strength data are presented for the first time for monoclinic zirconia. An undoped nanocrystalline zirconia powder was sintered at 1100°C and yielded a theoretical density of more than 90% with a grain size of about 150 nm. The surface crack in flexure (SCF) technique was deemed most suitable for nanocrystalline materials. Measurements of Young's modulus and the determination of the fracture origin are also provided.     

有机/无机填料混杂增强木塑复合材料制备与性能

针对木塑复合材料力学性能较低和湿热环境下易变形的不足,研究了矿物填料和木粉混杂增强高密度聚乙烯(HDPE)木塑复合材料的力学性能和湿热特性,初步分析了矿物填料微观结构和增强作用的关联关系。结果表明,添加矿物填料对木塑复合材料的弯曲、拉伸和冲击性能有不同程度的改善作用,对模量的提高尤为明显。具有丝束或丝絮状纤维结构的海泡石、硅铝酸纤维和硅灰石对木塑复合材料的增强作用要低于具有长条状纤维结构的水镁石纤维,纤维缠结导致的分散困难可能是其增强作用差的主要原因。海泡石对耐热温度和洛氏硬度的提高作用要优于其它矿物填料,添加了25份海泡石纤维的木塑复合材料的硬度和耐热温度分别提高57. 7%和26%。     

有机无机杂化丙烯酸乳液的制备及涂膜性质研究

为了制备一种疏水抗覆冰涂料,采用种子半连续乳液聚合法,通过添加乙烯基三乙氧基硅烷(A-151)和纳米二氧化硅粉末,分别合成了纯丙乳液、硅丙乳液和纳米二氧化硅/硅丙复合乳液,并将乳液涂覆在铝片表面,室温干燥成膜.利用红外光谱、粒度分析、扫描电镜等测试手段对3种乳液及其涂膜性能进行表征.结果表明:添加A-151可以使涂膜交联度提高到95%,吸水率降低到5%;添加纳米二氧化硅,可提高乳液涂膜的热分解温度,使乳液粒径大小分布均匀.此方法中,A-151和纳米二氧化硅改性的乳液涂膜疏水作用有限,仅使接触角增加到约30°.     

纤维类型对C/SiC复合材料性能的影响

利用化学气相浸渗法制备了Cf-C/SiC复合材料,借助SEM、TEM等研究了纤维类型对Cf-C/SiC复合材料力学性能的影响.实验证明T300碳纤维增韧补强效果优于M40碳纤维,利用T300碳纤维制备出弯曲强度为459M,断裂韧性为20.0MPa*m1/2,断裂功为25170J/m2的Cf-C/SiC复合材料.2种碳纤维增韧效果的差异是由纤维的原始强度、热膨胀系数和弹性常数的不同决定的.     

PP/PB共混材料的力学及流变性能研究

采用哈克双螺杆挤出机制备了聚丙烯/聚丁烯-1(PP/PB)共混材料,考察了PB的熔体流动速率(MFR)和用量对PP流变性能和力学性能的影响。结果表明:PP与PB二者相容性良好,当PB质量分数为30%时,PP/PB200(MFR为200 g/10 min)共混材料的MFR最大为37.90 g/10 min,约是纯PP的4.15倍,PP/PB0.5(MFR为0.5 g/10 min)共混材料的MFR最小为7.59 g/10 min,与纯PB相比降低了16.87%;随着PB MFR的增加,PP/PB共混材料的熔体强度降低;当PB MFR为0.5 g/10 min时,对PP有明显的增强和增韧效果,PP/PB共混材料的拉伸强度为31.11 MPa,冲击强度为48.52 kJ/m²,与纯PP相比分别提高了28.82%和185.24%。