共查询到20条相似文献,搜索用时 93 毫秒
1.
AbstractObjectives were to study mechanical properties of various solid forms of paracetamol and relate to their crystal structures. Paracetamol form I (PRA), its cocrystals with oxalic acid (PRA-OXA) and 4,4-bipyridine (PRA-BPY) and hydrochloride salt (PRA-HCL) were selected. Cocrystals and salt were scaled-up using rational crystallization methods. The resulting materials were subjected to different solid-state characterizations. The powders were sieved and 90–360?µm sieve fraction was considered. These powders were examined by scanning electron microscopy (SEM) and densities were determined. Tablets were made at applied pressures of 35–180?MPa under controlled conditions and the tablet height, diameter and hardness were measured. Tensile strength and porosity of the tablets were estimated using well known models. Crystal structures of these systems were visualized and slip planes were identified. Cocrystal and salt of PRA were physically pure. Sieved powders had comparable morphologies and particle size. The apparent and theoretical densities of powders were similar, but no clear trends were observed. The tensile strengths of these compacts were increased with increasing pressure whereas tabletability decreased in the order oxalic acid?>?PRA-HCL?≈?PRA-OXA?>?BPY?>?PRA-BPY. Tablet tensile strength decreases exponentially with increasing porosity with the exception of PRY-BPY and BPY. Slip plane prediction based on attachment energies may not be independently considered. However, it was possible to explain the improved mechanical properties of powders based on the crystal structure. Cocrystallization and salt formation have introduced structural features that are responsible for improved tableting properties of PRA. 相似文献
2.
对圆柱形金属橡胶结构做静态实验,运用最小二乘法对实验数据进行拟合,得到金属橡胶材料本构方程的各系数,将由实验得到的各系数代入本构方程式中,从而得到理论拟合迟滞回线,将理论拟合迟滞回线与试验迟滞数据进行对比,发现理论拟合迟滞回线与试验迟滞数据吻合较好,同时运用ANSYS有限元软件对金属橡胶结构进行有限元建模、定义边界条件及施加载荷,最后进行应力应变分析,得到应力应变分布图,发现分析结果与实验结果吻合。 相似文献
3.
The friction calibration curves were generalized using ALPID simulations of ring compression tests and were used to establish the friction factor associated in the workpiece-tool interface. ALPID simulations were carried out for different rib-web sections. The metal flow characteristics were closely watched and load requirements for these processes were established. The distribution of effective strain and strain rate and stress were established. 相似文献
4.
通过化学共沉淀-水热合成法制备纳米级羟基磷灰石(HAP),再用自制模具制备出偶联剂改性纳米HAP/高密度聚乙烯(HDPE)挤出复合材料.通过SEM观察以及力学性能测试,研究了偶联剂改性纳米HAP/HDPE复合材料的微观结构和力学性能.结果表明: 添加硅烷偶联剂后,HAP/HDPE复合材料的力学性能获得提高,偶联剂含量为2%(质量分数)时拉伸强度最高.而当HAP含量为20%(质量分数)时,复合材料的拉伸强度和抗弯强度最高.添加了偶联剂,HAP微粒表面与HDPE有较好的亲和性,断裂过程中应力诱发的塑性变形增加,裸露的HAP颗粒明显减少.通过口模挤出可以使得聚乙烯分子链在应力作用下伸直取向,大量平行于长轴且紧密排列的微纤维形成. 相似文献
5.
6.
《Materials Science and Engineering: A》2007,443(1-2):54-59
In this paper a great deal of carbon microspheres with high purity, uniform diameter and good features were synthesized by CVD method, while acetylene and toluene were used as carbon sources. The obtained carbon microspheres were almost amorphous. The products were treated by microwave plasma and temperature vacuum heat treatments respectively, then the samples were analyzed and characterized by FESEM, XRD and HRTEM. The results showed that carbon microspheres were well graphitized while their features were undestroyed. Based on their adsorption isotherms of nitrogen, pore structures of carbon spheres were found to be changed greatly after graphitized treatments. 相似文献
7.
8.
Bogumi? Wronka 《International Journal of Impact Engineering》2011,38(5):309-313
The basic defects occuring in explosive clad plates were properly systemized and the reasons of their formation were explained. Cases of cracks and delaminations in explosive clad plates were examined in this work. Various values of tensile stresses coming from loading and unloading waves were analysed, as they were the main reason of defects. The defects were connected with properties of welded materials in the joint area and beyond it. Some practical aspects of this process were shown as well. 相似文献
9.
Ki D Bae JS Rabbani MM Nam DG Ko CH Yeum JH Oh W 《Journal of nanoscience and nanotechnology》2012,12(7):5870-5874
MWNT-CdSe hybrid nanomaterials were prepared with carboxylic acid-treated CdSe nanoparticles and amino-functionalized MWNTs. The hybridization of MWNT-CdSe nanomaterials was performed by the formation of covalent bond between MWNT and CdSe. Their covalent bond lengths were varied with changing the linking spacers. Amino-functionalized MWNTs were reacted with CdSe nanoparticles which were functionalized with carboxylic acid groups. Their detailed structures were characterized by FT-IR, XPS, and small angle X-ray scattering. Through small angle X-ray scattering experiments, it was found that the structures of CdSe nanoparticles were not regular, and their sizes were broadly distributed in solution. The longer amino-functionalized MWNTs were thermally decomposed at lower temperature. The photoluminescence (PL) of chemically-linked MWNT-CdSe hybrid nanomaterials were weaker than that of CdSe nanoparticles. In addition, their PL intensities more weakened on the MWNT-CdSe with the longer spacers. 相似文献
10.
应用在食品行业中的冷封胶薄膜 总被引:5,自引:1,他引:5
概述了冷封胶薄膜的结构种类、制备工艺以及优点,接着陈述了冷封薄膜在软包装中的应用以及局限性,指出了实际生产中遇到的问题并对问题进行分析,提出改进方法.最后探讨了冷封薄膜未来的发展方向. 相似文献
11.
用双辊快淬工艺制备了纳米晶AB5型富镧稀土贮氢合金。对热处理后的合金进行X射线衍射和扫描电镜SEM分析,并测试合金的吸放氢等温平衡曲线PCT。结果表明,处理的合金晶粒尺寸〈50nm,该合金具有良好的吸放氢动力学性能。 相似文献
12.
在制取力学性能试样的机械加工中常发现试样有不同程度的弯曲与扭转变形,严重影响试样加工精度和力学性能测试的准确性。对宽带试样变形的产生原因及其对试样机械加工质量的影响进行了分析,并提出了相应措施,取得了较好的效果,保证了加工质量,提高了加工速度。 相似文献
13.
Single crystals of calcium iodate and barium iodate were grown by simple gel technique by single diffusion method. The optimum
conditions were established by varying various parameters such as pH of gel solution, gel concentration, gel setting time,
concentration of the reactants etc. Crystals having different morphologies and habits were obtained. Prismatic, dendritic
crystals of barium iodate and prismatic, needle shaped, hopper crystals of calcium iodate were obtained. Some of them were
transparent, some transluscent, and few others were opaque. Both the crystals were studied using XRD, FT-IR, and thermal analysis.
The crystals were doped by iron impurity. The effect of doping was studied using IR spectroscopy and thermal analysis. 相似文献
14.
Carbon tissues prepared using types of gelatin differing in raw material and process were sensitized by dichromate and their photographic characteristics were investigated. Sensitivity and gamma were dominantly determined by the higher molecular weight components of the gelatin, sharpness and resolving power were dominantly determined by viscosity; these properties were little affected by its origin. 相似文献
15.
应用浸浴法研究多壁碳纳米管(MWCNTs)对鲤鱼(cyprinl Jscarpioio)腮、肝、肾和脑中超氧化物歧化酶(SOD)的影响,结果显示:低浓度(0.1,lmg·L^-1)处理组暴露后3d,腮和肝中的SOD活性显著高于对照组(p〈0.01),肾和脑中SOD活性与对照组无显著差异(p〉0.05)。随着暴露时间延长,各组活性降低,至9d,肝和肾中SOD活性显著低于对照组(p〈0.05),腮和脑中SOD活性与对照组无显著差异(p〉0.05)。高浓度(10mg·L^-1)处理组,整个暴露期间,肝中SOD的活性显著低于对照组(p〈0.01),脑中SOD的活性与对照组无显著差异(p〉0.05),腮和肾中SOD活性在暴露后3d,与对照组无显著差异(p〉0.05),暴露后6d、9d,活性显著低于对照组(p〈0.05)。提示:MWCNTs对鲤鱼各组织中SOD酶活性的影响有时间和浓度依赖性。 相似文献
16.
航空产品包装运输设计的研究 总被引:1,自引:1,他引:0
详细介绍了在民用航空领域飞机产品运输时的方式、包装设计种类以及它们各自的优缺点,对飞机产品在包装设计过程中应注意的方面进行了详细而深入的研究,阐述了产品包装逐步向环保、节能方向发展的设计过程,尤其介绍了目前采用的高强度新型环保包装箱的设计思路和应用前景,从成本和实用性等方面做了详细的阐述,在民用航空运输领域有较大的实用参考价值。 相似文献
17.
18.
19.
Porous anodic films formed on aluminum in a phosphoric acid electrolyte were used to develop selective solar coatings by double precipitation of cobalt acetate and ammonium sulfide indide the pores. The black coatings containing cobalt sulfide were then sealed in hot water and their optical, mechanical and thermal degradation properties were tested. Multiple linear regression routines were used to optimize the absorptance and emittance values and the coating formation conditions were accordingly adjusted. After optimization, the coatings were characterized by scanning and transmission electron microscopy, and thermal stability tests were performed to determine the long-term quality of the coatings. The coatings were found to have good thermal stability up to 150°C and high adhesion strength as well as absorptances of up to 0.965 at emittances ranging from 0.15 to 0.25. 相似文献
20.
Blood samples from 2,500 injured drivers were analysed for alcohol, cannabinnoids, benzodiazepines and stimulants. Overall, three-quarters of drivers tested negative for drugs. Alcohol was the most frequently detected drug. Cannabinoids were also detected at high rates, but the majority of drivers tested positive for THC-acid, the inactive metabolite of THC. Benzodiazepines and stimulants were detected at low rates, and detection rates for combinations of drugs were also low. Males were more likely to test positive for drugs, especially alcohol and THC, whereas females were more likely to test positive for benzodiazepines. A similar proportion of car drivers and motorcycle riders tested positive for drugs, although riders were more likely to test positive for THC. Single-vehicle crashes were particularly associated with alcohol for both car driver and riders, and for riders, multiple-vehicle crashes were particularly associated with THC. 相似文献