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排序方式: 共有564条查询结果,搜索用时 31 毫秒
161.
162.
《Journal of the European Ceramic Society》2023,43(5):2133-2142
Lanthanum oxysulfide (La2O2S) was investigated as infrared transparent ceramic to benefit from stronger chemical bonds and superior mechanical performances to that of non-oxide benchmark infrared materials. La2O2S ceramics were processed by hot-pressing powders prepared by combustion synthesis followed by a sulfurization treatment. Powders and ceramics were characterised through various techniques (XRD, UV-Vis-IR spectroscopy, particle size analysis, SEM, Impulse Excitation Technique, microhardness and fracture toughness tests) to assess their purity, study their microstructure and determine their optical and mechanical properties. The study reports the first IR transmission spectra, Poisson’s ratio, Young’s and shear moduli and fracture toughness values of La2O2S polycrystalline ceramics. The ceramics showed transparency in the 2–11 µm range and their mechanical performances were all superior to that of commercial infrared ceramics. The best transmission (89% of the theoretical transmission) was measured at 7.3 µm for 1 mm-thick ceramics hot-pressed at 1200–1250 °C. 相似文献
163.
《Journal of the European Ceramic Society》2023,43(5):1762-1776
3D printing of technical ceramics using direct ink writing (DIW) of multiphase colloidal inks has the unique ability to create structures with hierarchical features. To facilitate the application of 3D printed hierarchical porous ultra-high temperature ceramics (UHTCs), additional limiting factors such as strength and the effect of 3D printed internal lattice structure need to be better understood. This study reports on the strength dependence of common DIW print parameters including internal lattice structure shape, nozzle diameter and spacings between adjacent filaments. The present study applies Weibull statistics to the experimental array that considers macro features introduced through print parameters as flaw types, which shows strength of 3D printed hierarchical ZrB2 is highly dependent on the introduced 3D printed structure, size and the stressed volume. This work provides essential information that can be used in the initial stages of design when considering implementation of additively manufactured hierarchical porous UHTCs. 相似文献
164.
Ablative property and mechanism of SiC-CuxSiy modified C/C-ZrC composites prepared by a rapid method
《Journal of the European Ceramic Society》2023,43(11):4602-4615
A rapid method was developed to fabricate C/C-ZrC-SiC-CuxSiy composites with low open porosity by precursor infiltration and pyrolysis combining with pressure assisted reactive melt infiltration. Dominant phases of ZrC and SiC with scattered CuxSiy inclusions were present in continuous infiltrated matrix, in which the dimension of submicron ZrC particles displayed gradient change. At ablation test, the heat absorbing effect of CuxSiy-phase and formation of protective ZrO2-SiO2 cover enhanced the ablative property of composites for short-time ablation, causing ablation rates of 30 s ablation reached 1.7 ± 0.1 µm/s and 1.3 ± 0.1 mg/s, respectively. As ablation time extends to 60 s, the massive consumption of Si-phase damaged the integrity of surface oxide cover, but the partial melted ZrO2 improved the viscosity and self-healing ability of ZrO2-SiO2 mixture, protecting substrate from further erosion. Thus, ablation rates were increased and decreased to 3.8 ± 0.2 µm/s and 1.2 ± 0.1 mg/s, respectively. 相似文献
165.
为研究红树莓果渣化学法提取可溶性膳食纤维(Soluble Dietary Fiber,SDF)最佳工艺,本实验分别使用酸法和碱法两种化学方法提取红树莓果渣中的可溶性膳食纤维,研究提取温度、提取时间、提取剂浓度(盐酸或氢氧化钠)和液料比4个影响因素对红树莓果渣SDF得率的影响,分别测定酸法和碱法SDF提取物的纯度,初步判断较优的化学提取方法,进而采用Box-Behnken 4因素3水平响应面组合对其进行优化。结果表明,单因素实验中碱法和酸法工艺条件下的平均得率分别是21.45%±2.3%和3.39%±0.68%,平均纯度分别为73.84%和76.17%,碱法SDF提取效果明显优于酸法;响应面法得到的碱法最佳提取工艺参数为:提取温度40℃,提取时间62 min,氢氧化钠浓度8.13 g/L,液料比25:1(mL/g),在此工艺条件下SDF平均得率高达24.03%±1.01%。因此,酸法和碱法均可用于红树莓果渣SDF的提取,但碱法提取效果明显优于酸法;通过响应面法获得的最佳碱法提取工艺可为红树莓果渣SDF的提取提供理论参考。 相似文献
166.
针对海参内脏多肽气味特殊、口感苦麻刺激,难以加工利用的现状,本文探讨了脂肪酶对海参内脏多肽制品的气味与口感可接受性优化作用。本文将蛋白酶与脂肪酶复合作用制备海参内脏多肽制品,以感官评价分数为指标考察其优化程度。单因素实验结果表明,脂肪酶对海参内脏多肽具有显著的风味矫正作用,可有效脱除其刺激性气味与苦涩麻辣口感。在单因素实验基础上采用Box-Behnken设计对加工条件进行优化,结果表明,对海参内脏多肽感官评价分数影响的大小依次为第二次酶解温度 > 第二次酶解时间 > 脂肪酶用量;在第二次酶解温度42 ℃,第二次酶解时间2.2 h,脂肪酶用量为质量分数0.09%时,得到最高感官评价分数9.6分,加工工艺条件最优。将响应面法获得的最优条件下的制备的产品与漂洗法获得的产品对比,脂肪酶法的感官得分与色泽指标显著优于后者;脂肪酶法产率为8.15%,远高于同等条件下漂洗法的产率4.43%。 相似文献
167.
为研究羊栖菜褐藻糖胶的结构及其抗氧化活性,以羊栖菜为原料,经CaCl2溶液提取、DEAE-Sepharose fast flow分离纯化得到褐藻糖胶组分SFP-2。采用高效凝胶渗透色谱法(HPGPC)、化学法、高效液相法(HPLC)以及傅里叶变换红外光谱法(IR)对多糖的纯度、分子量、理化性质、单糖组成以及官能团进行测定,并通过测定DPPH自由基清除活性、超氧阴离子清除活性、ABTS+自由基清除活性、亚硝酸盐清除活性和还原力,对多糖的体外抗氧化活性进行了评价。结果表明,SFP-2分子量均一,为707.0 kDa;总糖含量为66.9%,蛋白含量为3.1%,硫酸基含量为21.2%,不含糖醛酸;SFP-2主要由岩藻糖和半乳糖构成,还含有少量的甘露糖和氨基葡萄糖;红外光谱显示,SFP-2具有硫酸化多糖常见官能团的特征吸收峰;上述结果表明SFP-2是一种不含糖醛酸的硫酸化岩藻聚糖。SFP-2具有良好的清除DPPH自由基、超氧阴离子、ABTS+自由基、亚硝酸盐活性,其EC50分别为8.94、8.30、16.04、9.87 mg/mL,且具有一定的还原能力。因此,SFP-2是一种不含糖醛酸的,抗氧化活性良好的羊栖菜褐藻糖胶。 相似文献
168.
《Nuclear Instruments and Methods in Physics Research》1981,185(1-3):7-11
A novel method for isotope separation is presented. In the proposed system, the ions are generated by a pulsed ion source having large angular and energy spread, then move through a field-free region to an electrodynamic reflecting filter, where the ions are separated according to their charge-to-mass (q/m) ratio. The collection angle is nearly 4π sr. A numerical example for separating hydrogen isotopes is presented. 相似文献
169.
170.
介绍了μC/FS嵌入式文件系统的主要功能,着重说明了μC/FS的移植步骤,实现了μC/FS在SD上的移植。测试结果表明,基于SD卡的μC/FS文件系统移植在采集系统中的应用满足了设计要求,并具有良好的性能。 相似文献