气化灰基腻子粉的制备与性能研究

为实现气化灰综合利用和降低腻子粉制备成本，研究了利用气化灰替代水泥制备腻子粉的技术可行性。以气化灰和 42.5水泥为主要原料，配以少量的羟丙基甲基纤维素和可分散性乳胶粉，制备气化灰基腻子粉，实验考察原料配方变化对腻子粉的性能影响。研究结果表明：利用气化灰替代水泥制品制备腻子粉具有可行性。其中，气化灰替代 50%水泥时，腻子粉的粘结强度为 0.82 Mpa，各项性能均优于建筑外墙用腻子粉标准 JG/T 157—2009要求。在相同条件下，气化灰替代不超过 70%的水泥时，腻子粉的粘结强度及其他指标均满足建筑外墙用腻子粉标准 JG/T 157—2009要求。     

超声波辅助插层-剥离法制备煤系高岭土微粉的研究

我国煤系高岭土储量丰富,为满足造纸、纺织等行业个性化的需求,通常要对其进行深加工。以山西朔州煤系高岭土为原料,分别在恒温磁力搅拌和超声波作用下探究了煤系高岭土/二甲基亚砜(DMSO)插层复合物制备的最佳条件,在插层复合物的基础上对煤系高岭土进行超声辅助剥离,制备得到高岭土微粉,并利用XRD、SEM、BET、TG-DSC等方法分析表征样品。正交实验结果表明在磁力搅拌条件下DMSO用量、插层时间以及插层温度均对插层率具有一定的影响,引入超声波有利于高岭土插层率的提升。插层复合物经超声辅助剥离后晶粒厚度明显减小,高岭土片层状结构大体上呈现碎片化,仅保留少部分大的片状结构,其边缘碎化,整体上也出现碎裂的趋势。剥离样品的比表面积和孔径均大幅度增加,为硬质高岭土的剥离和超微细粉体的制备提供了新的思路。     

Effects of different drying methods on the physicochemical property and edible quality of fermented Pyracantha fortuneana fruit powder

In this study, hot air drying (HAD), hot air-/microwave-assisted vacuum drying (HAMAVD) and hot air-assisted microwave drying (HAAMD) were applied to lactic acid-fermented Pyracantha fortuneana fruit (PFF). Influences of different drying methods on fluidity and dispersion, microstructure, hygroscopicity, rehydration, colour change, sourness and energy consumption were investigated. Results showed that HAAMD had the best overall performance on the quality of the PFF powder. HAAMD PFF powder had higher expansion force (1.65 mL g⁻¹) and water-holding capacity (2.68 g g⁻¹), lower degree of compression (9.09%) and energy consumption, smaller colour change and better taste. Organic acids (mainly malic acids) of all drying powders decreased, but HAAMD and HAMAVD could better improve the acidity characteristics of PFF powders, which may be related to the drying time and the temperature change processes. Consequently, this study can provide references for the utilisation of fresh PFF, the design and commercialisation of PFF-related products.     

Effect of Si/Ti additions on physico-mechanical and chemical properties of FeNiCrCo high entropy alloys manufactured by powder metallurgy technique

FeNiCrCoSi_x and FeNiCrCoTi_x (x=0, 0.3, 0.6, and 0.9 wt.%) high entropy alloys (HEAs) were prepared via the powder metallurgy technique. A homogenous distribution of the elements in all alloys due to the formation of a solid solution phase is observed. The density and hardness of the prepared HEAs are improved by Si and Ti additions, compared to FeNiCrCo HEA. The wear rate of the prepared alloys was studied at different loads and the results indicate that the alloys that contain 0.3 wt.% Si and 0.9 wt.% Ti have the lowest wear rates. X-ray diffraction, SEM, and EDX were used to understand the phases, grain sizes, and microstructures in different investigated HEAs. The effects of Si and Ti content on the corrosion behavior and surface morphologies of sintered FeNiCrCoSi_x and FeNiCrCoTi_x HEAs were studied by immersion in H₂SO₄, HNO₃, and HCl solutions. Uniform corrosion and localized pitting are observed in different sizes in the corrosive media used. Because of the smaller pit size and the reduced pit density, the FeNiCrCoSi_0.3 HEA has an excellent microstructure.     

Effect of Fe doping on structure,magnetic and electrical properties La0.7Ca0.3Mn0.5Fe0.5O3 manganite

The crystal and magnetic structures of La_0.7Ca_0.3Mn_0.5Fe_0.5O₃ compound have been studied by neutron powder diffraction in the temperature range of 10–300 К. The magnetization and electrical resistivity measurements have been also performed in the temperature range of 5–300?K in magnetic fields up to 1?T. These experimental results indicate a formation of a complex magnetic state in which the long-range antiferromagnetic G-type phase coexists with the short-range ferromagnetic clusters. The electrical conductivity of La_0.7Ca_0.3Mn_0.5Fe_0.5O₃ demonstrates an anomalous temperature behavior suggesting a switching between different states. The origin of the unconventional magnetic state, the mechanisms of the electrical conductivity, and correlation between magnetic and transport properties in this manganite have been discussed.     

Synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics

To explore the synergistic effect of glass fibre and Al powder on the mechanical properties of glass-ceramics, blast furnace slag was chosen as the main material, and glass fibre and Al powder as reinforcement materials. The phase compositions, microstructures, compressive properties, and apparent density of the glass-ceramics with varying quantities of glass fibre and Al powder were investigated. The experimental results indicated that Al powder could exist as a simple substance in glass-ceramics and form a dense net coating on the surface of blast furnace slag to improve the plasticity of the glass-ceramic. The glass fibre had better reinforcement effect than Al powder because of its extremely high mechanical strength. The plasticity of glass-ceramics, however, severely decreased; the glass-ceramics exhibited brittle failure during compression. A slight increase in the content of CaSi₂ and SiO₂ in the glass-ceramics was closely related to the addition of glass fibre. Considering safety and economy, glass-ceramics with 6% Al and 14% glass fibre (S4) have the best mechanical properties. The compressive strength, strain at maximum force, and apparent density were 40?MPa, 19% and 1.974?g/cm³, respectively.     

Study on the relationship between the particle size distribution and the effectiveness of the K‐powder fire extinguishing agent

The relationship between the particle size distribution and the extinguishing effectiveness of the new K‐powder fire extinguishing agent has been studied experimentally, to explore the reason of the great extinguishing efficiency exhibited by the new K‐powder fire extinguishing agent on Class B fire (liquid fuel fire). The results of the experiment showed that the extinguishing effectiveness increased along with the decrease of the particle size distribution. In addition, a sharp discontinuity appeared around the limiting size, about 40 μm. The powder with the particle size below 40 μm exhibited highly effective extinguishing with the minimum effective extinguishing concentration C_xr = 23 g·m^?3, while the powder with the particle size above 40 μm exhibited little fire extinguishing efficiency. Compared with other fire extinguishing agents produced by different substances, the new K‐powder fire extinguishing has the bigger limiting size. That means, in the same particle size distribution, the new K‐powder fire extinguishing agent contains more highly effective powder than others contain, and is more effective.     

纳米晶NiCrC涂层长时加热的显微组织和硬度变化

目的 探讨纳米晶NiCrC涂层长时高温条件下的显微组织和硬度演变规律。方法 采用超音速火焰（HVAF）喷涂低温球磨纳米晶合金粉末（液氮介质）制备了纳米晶NiCrC涂层，在650 ℃空气环境中对涂层进行总时长200 h的等温热处理。采用扫描电子显微镜、X射线衍射仪、透射电子显微镜、维氏显微硬度计等方法，对涂层样品的显微组织、物相构成、晶粒尺寸和显微硬度进行了测试分析，同时对原料粉末也进行了相同条件下的对比分析。结果 NiCrC涂层显微组织的主要特征为：纳米晶金属相基体中弥散分布着细小的碳化物颗粒。在保温过程中，纳米晶涂层发生了再结晶和晶粒长大，并伴随有合金基体的脱溶及碳化物的析出、相变和后续生长等现象。该涂层显示出优良的高温热稳定性，在650 ℃保温50 h后，晶粒平均尺寸由初始态的41 nm增长至相对稳定值约100 nm。保温后涂层的硬度总体有所提升，由初始的697HV300（15 s）先升高至最大值801HV300（15 s），而后降至相对稳定值729HV300（15 s）左右。纳米晶粉末的组织和硬度变化特点与涂层相似。结论 在650 ℃保温过程中，纳米晶NiCrC涂层中的合金相脱溶和晶粒长大导致涂层金属相基体的软化，但细小碳化物颗粒的析出强化以及由相变（Cr7C3→Cr23C6）引起的体积分数增加，不但补偿了基体的软化，而且使涂层的整体硬度有所提高。     

原位合成WC-6Co复合粉末制备超细YG6硬质合金

将原位合成WC-6Co复合粉末采用干袋式冷等静压压制成型(压制压力1×10~8 Pa、保压时间15 s),将压制好的坯料采用低压烧结炉烧结(烧结温度1360℃、烧结时间40 min、加压5 MPa、保温保压时间20 min),烧结制备超细YG6硬质合金,对合金的形貌、金相组织及物理力学性能进行分析。结果表明:原位合成WC-6Co复合粉末制备的超细YG6硬质合金,晶粒异常长大,WC平均晶粒尺寸为0.8μm,硬度HV_(30)为(21500±100) MPa,较传统超细YG6X硬度高。再将WC-6Co复合粉末采用滚动湿磨、压力式喷雾干燥、掺成型剂、挤压成型、低压烧结等工序制备超细YG6硬质合金,研究不同晶粒长大抑制剂配比、球磨时间、挤压压力、烧结温度对合金性能的影响。结果表明:添加0.3%VC、0.8%Cr_3C_2(质量分数),湿磨48 h,挤压压力24 MPa,烧结温度1340℃,制备的超细YG6硬质合金WC晶粒均匀,无异常长大的WC晶粒,WC平均晶粒度尺寸0.4μm,呈多边形,外形较圆。强度、硬度最高,抗弯强度TRS为(2250±20) MPa、硬度HV30为(22600±100) MPa。断口形貌为沿晶断裂,沿WC与WC晶界断裂或WC与Co晶界断裂。     

一种电子元器件银浆用玻璃粉的研制

不同基体的银浆需要采用不同成分的玻璃粉才能达到合适的性能。采用Bi2O3-SiO2-B2O3体系，研究了Ag2O对Zn2SiO4介质陶瓷附着力的影响。当Bi2O3含量(质量分数)为65%，SiO2含量为15%，B2O3含量为10%，Ag2O含量为5%，Al2O3含量为5%时，制备的银浆附着力≥20N；所得银浆料的印刷性能、方阻、附着力、与焊料的润湿性及耐焊性等各项指标符合要求。