An electron microscopy and X-ray diffraction study of the microstructures of melt-drawn polyethylene films

Electron microscopy and X-ray diffraction have been used to study microstructures of melt-drawn polyethylene films. During the drawing process, uniplanar structures are formed which consist of crystals with theirb andc axes in the film plane. On annealing the films, the crystal size and orientation increase. Quantitative measures of the crystal thickness, lateral crystallite size and long period were obtained from bright-field and dark-field electron micrographs as well as from wide and small angle X-ray diffraction of stacked layers of the films.     

An X-ray diffraction and electron spectroscopic study of metallic glass In20Te80

Results of X-ray diffraction and X-ray photoelectron spectroscopy investigations on the crystallization behaviour of an amorphous In₂₀Te₈₀ system and the effects of crystallization on the electronic core levels of In and Te atoms are presented. During controlled heat treatments three crystalline phases, Te, -In₂Te₃, and In₂Te₅-I, were observed in this system. In addition, a few splat-cooled samples were found to exhibit a new metastable crystalline phase. Photoelectron measurements revealed that the Te 3d and 4d core levels of amorphous In₂₀Te₈₀ were shifted downwards in energy from their characteristic values of pure Te metal. The In 3d and 4d levels experienced large energy shifts due to alloying, but remained unaffected by heating at temperatures below 520 K.     

The annealing of solution-crystallized polyethylene mats: an X-ray diffraction study

Both low- and wide-angle X-ray diffraction measurements have been made on solution-crystallized mats of high density polyethylene which have been annealed for different periods at 125° C. The low-angle data, in addition to showing the rapid increase in both long period and density defect at each fold surface for the first stages of annealing, also indicate that after annealing for times in excess of 10⁵ sec the density defect is reduced and approaches the value for the unannealed crystal. The wide-angle X-ray studies have centred around the Fourier analysis of the 0 0 2 diffraction peak. The results of this type of measurement on unannealed mats have already been reported [20]. In extending the work to annealed material evidence has been obtained for preferred chain stem lengths which are multiples of the unannealed length. The combination of these observations with the low-angle results has led to the formulation of a model for crystal thickening which invokes the unlooping mechanism proposed by Dreyfuss and Keller [15], but also envisages thickening occurring preferentially from one fold surface to give an asymmetric crystal profile in the [0 0 1] direction.     

An X-ray diffraction study of bismuthate glasses

Now at Government Industrial Research Institute, Osaka, Japan.     

Wide angle X-ray diffraction study of the microstructure of chain-folded polyethylene crystals

The profile of the 002 diffraction peak of polyethylene is related to microstructural parameters for the [001] direction. The parameters considered are the mean crystal thickness, distribution of thicknesses, shape function and the degree of paracrystalline disorder in the lattice.An analytical relation describing the peak profile is derived for trapezium models of the shape function. Calculations are made of peak profiles and their correlation functions for various trapezium models, levels of paracrystalline disorder and Gaussian widths for the distribution of crystal thicknesses. Particular attention is paid to the effect of these parameters on the subsidiary maxima to the 002 peak.The 002 peak of linear polyethylene (RIGIDEX 50) crystallized from solution in xylene at 70°C is analysed in terms of the above parameters. The results are interpreted in terms of the buried fold model and indicate the presence of well defined zones of highly disordered material (probably nematic) within the crystal entities.The frequency of the zones increases as the fold surfaces are approached.     

Internal stresses in cold-drawn and irradiated polyethylene

The influence of high-energy radiation on the internal stress level in cold-drawn, high- and low-density polyethylene, with and without subsequent annealing, has been determined using a stress relaxation method described earlier. The internal stress level (σ _i) is found to increase substantially with the radiation dose for doses below 40 Mrad, while the increase at higher doses is only moderate. It is suggested that the initial increase is due to a preferred cross-linking of the amorphous phase or the fold surface of the lamellae. An exception to this behaviour was observed for cold-drawn low-density polyethylene, where the internal stress decreased as the radiation dose was raised.     

Thermal effects in high density polyethylene and low density polyethylene at high hydrostatic pressures

The temperature changes as a result of rapid hydrostatic pressure applications are reported for high density polyethylene (HDPE) and low density polyethylene (LDPE) in the reference temperature range from 298 to 423 K and in the pressure range from 13.8 to 200 MN m^–2. The adiabatic temperature changes were found to be a function of pressure and temperature. A curve fitting analysis showed that the empirical curve (/P) =ab(P)^b–1 described the experimental thermoelastic coefficients obtained from the experiments. The data were analyzed by determining the predicted thermoelastic coefficients derived from the Thomson equation (/P) = T ₀/C _p. The experimental and predicted Grüneisen parameter _T were also determined.     

冷轧变形纳米晶钴的X射线衍射研究

对冷轧变形前后纳米金属钴的微观应变。晶格常数以及晶粒尺寸的变化进行了研究，对X射线衍射图谱进行了分析计算，结果表明，变形过后晶体内部存有残余内应力并导致了微观应变，应变大小为ε=1．412×10q；对变形前后的晶格常数进行计算，得到变形后的晶格常数为a=0．25241nm；c=0．40782nm；透射电镜的观察和衍射谱线的计算表明变形后纳米金属钴的晶粒大小与形状基本未发生变化，平均晶粒尺寸为18．8nm。有可能是空位的活动降低了变形过程中的晶界迁移几率，使得变形后的晶粒尺寸基本没有发生变化。     

An infra-red spectroscopic study of the setting reactions of a calcium hydroxide dental cement

An infra-red spectroscopic study of a proprietary calcium hydroxide cement based on l-methyl trimethylene disalicylate and calcium hydroxide shows that a chemical reaction occurs, in the cement paste, between the acidic phenol groups and calcium hydroxide. The close proximity of the carbonyl and hydroxyl groups leads to very strong intramolecular hydrogen bonding in the ester and bidentate chelation in the cement. This chemical reaction results in the setting and hardening of the cement.     

The cold-drawing of high density polyethylene

The cold-drawing of high density polyethylene has been studied over a wide range of temperatures and strain rates for a series of samples of very different molecular weight distribution. A natural draw-ratio was observed which was almost independent of temperature and strain rate, but was sensitive to the weight average molecular weight. A good correlation was observed between the Young's modulus of the drawn mono-filaments and the natural draw-ratio, and it is proposed that the Young's modulus is primarily related to molecular orientation rather than to interlamellar ties.     

Compatibility study of high density polyethylene with bioethanol–gasoline blends

In order to evaluate the compatibility of high density polyethylene (HDPE) in E5 (5% v/v bioethanol, 95% v/v gasoline) and E10 (10% v/v bioethanol, 90% v/v gasoline), immersion tests have been performed in fuel blends at 45 °C during 2000 h. Different mechanical and physical–chemical properties of HDPE have been assessed before and after the execution of these tests.     

An investigation of the microstructure and mechanical properties of high density polyethylene spherulites

Scanning transmission electron microscopy and related techniques have been used to characterize the micromorphologies of high-density polyethylene spherulites produced under different crystallization conditions. The experimental techniques used in the investigation are summarized, as are some relationhips between spherulite morphology, crystallization conditions and mechanical properties. A preliminary model for the micromorphology of banded polyethylene spherulites is proposed.     

An X-ray study of splat-quenched Sn-Bi and Cu-Sb alloys by energy-dispersive diffraction

A metastable shift of the solubility limit was produced by splat-quenching in Sn-Bi alloys containing 15, 20 and 25 at. % bismuth. Decomposition of the supersaturated a phase was investigated in the temperature range –40 to O° C. An activation energy of 39.8±3.0 kJ mol^–1 was obtained for the decomposition of Sn-25 at. % Bi. Splat-quenched Cu-Sb alloys with different compositions were also studied. The decomposition of the retained high-temperature phase was followed at 200 and 330° C. Neither an increase of solubility of copper into antimony nor new phases at the eutectic composition were observed in quenched foils.     

In-situ high temperature X-ray diffraction study of Co/SiC interface reactions

In situ experiments on the Co/SiC interface reaction were carried out with a high temperature X-ray diffractometer capable of measuring the X-ray diffraction pattern in 1–4s using an imaging plate. The kinetic formation processes of the interface reaction layer were measured in short-period exposure experiments with the apparatus. The time-temperature phase diagram of Co/SiC in N₂was determined. Co₂Si and CoSi were formed at the Co/SiC interface between 921 and 1573 K in N₂. The formation of CoSi obeyed the parabolic rate law. The value of the activation energy was 95 kJ/mol. The results of thermal expansion coefficient measurements suggest that when a sample is cooled to room temperature, compressive strain caused by CoSi occurs on SiC.     

In-situ high temperature X-ray diffraction study of Ni/SiC interface reactions

In-situ experiments on the Ni/SiC interface reaction were carried out with a high temperature X-ray diffractometer capable of measuring the X-ray diffraction pattern in 1–2 s using an imaging plate. The kinetic formation processes of the interface reaction layer were measured in short-period exposure experiments with the apparatus. The time-temperature phase diagram of Ni/SiC in N2 was determined. -Ni2Si and -Ni2Si (high temperature phase of -Ni2Si) were formed at the Ni/SiC interface between 1072 K and 1418 K in N2. The formation of -Ni2Si obeyed the parabolic rate law. The value of the activation energy suggests that the diffusion of Ni through -Ni2Si controls the rate of formation. The results of thermal expansion coefficient measurements suggest that when a sample is cooled to room temperature, compression caused by -Ni2Si occurs on SiC.     

稻壳/高密度聚乙烯复合材料与稻壳炭/高密度聚乙烯复合材料性能对比

采用挤出法制备稻壳/高密度聚乙烯（HDPE）和稻壳炭/HDPE复合材料。利用SEM、XRD对稻壳/HDPE和稻壳炭/HDPE复合材料进行表征,并对其力学性能和抗蠕变性能进行测试对比。结果表明,稻壳和HDPE之间的结合方式与稻壳炭和HDPE之间的结合方式存在根本性的差异,稻壳/HDPE复合材料表现为稻壳被HDPE所包裹,稻壳炭/HDPE复合材料表现为HDPE嵌入稻壳炭的孔隙中;稻壳和稻壳炭的加入都会影响HDPE基复合材料的结晶峰强度,但不会对其微晶结构产生影响;无论是抗弯强度、拉伸强度还是抗蠕变强度,稻壳炭/HDPE复合材料都远远强于稻壳/HDPE复合材料。     

Chemical vapour deposition of silicon carbide: An X-ray diffraction study

Low-pressure chemical vapour deposition of siliconcarbide from tetramethyl silane pyrolysis was studied by X-ray diffractometry.In situ measurements at high temperature gave kinetic information. The crystallization state, grain size, microstrains and residual macrostresses were measured at room temperature.