Materials Surface Science Research Articles

Local Ionic Displacements and Polarization at the Paraelectric‐Ferroelectric Heterointerface: Effect of Octahedral Distortion

AbstractAt the ferroelectric ABO3 perovskite heterointerface, the broken translational symmetry significantly alters the octahedral network and cation sublattices. Experimentally revealing the interaction between the polarization and atomic structure parameters is beneficial not only for understanding the novel physical phenomena but also for realizing exotic physical functionalities at the materials surface science. Here, it is demonstrated that the induced polarization can be realized by the cooperative interaction between the octahedral distortion and the cation sublattices at the paraelectric‐ferroelectric heterointerface in the (K,Na)NbO3 epitaxial thin film. It is found that the cation–cation displacement scales with the tetragonality of the perovskite unit cell but not with the polarization, which is minimal in the substrate but increases substantially in the thin film. Nevertheless, the oxygen octahedral distortion in the substrate, accompanied by octahedral rotation, is stronger than that in the film, resulting in a translated and stable polarization across the interface. These results demonstrate the octahedral network plays a significant role in the ferroelectric polarization and can also greatly advance the understanding of the heterointerface science for ferroelectrics.

Measurement of isosteric heat of gas adsorption and Brunauer-Emmett-Teller (BET) surface area using a quartz crystal microbalance.

The study of gas adsorption on a solid surface evaluates the affinity between sorbate gas and sorbent substrate and factors that contribute to this. This paper presents a test platform for adsorption experiments of various gases on various solid surfaces. Controlled environmental conditions enable investigations in materials surface science and increase the consistency among adsorption data. The system utilizes a quartz crystal microbalance to perform gravimetric analysis of deposition and adsorption, enabling investigation of the interaction of gaseous molecules with solid surfaces. In this study, a quartz crystal microbalance as gas adsorption detector was integrated with an environmental chamber to create a versatile tool for gas adsorption experiments on thin films. Experimental operation of this apparatus was demonstrated via acquisition of the adsorption isotherms of cyclohexane vapor on a gold surface at 55 and 70 °C. The result indicated International Union of Pure and Applied Chemistry Type II adsorption. Consequentially, application of the Brunauer-Emmett-Teller model to the isotherm data subject to predefined criteria for linear region selection yielded a surface area of the sorbent of 0.53cm2 at 55 °C. From the monolayer region of the isotherms, the isosteric heat of adsorption of the cyclohexane vapor on gold was calculated to be 37 kJ mol-1.

Endothelialization strategy of implant materials surface: The newest research in recent 5 years

In recent years, more and more metal or non-metal materials have been used in the treatment of cardiovascular diseases, but the vascular complications after transplantation are still the main factors restricting the clinical application of most grafts, such as acute thrombosis and graft restenosis. Implant materials have been extensively designed and surface optimized by researchers, but it is still too difficult to avoid complications. Natural vascular endodermis has excellent function, anti-coagulant and anti-intimal hyperplasia, and it is also the key to maintaining the homeostasis of normal vascular microenvironment. Therefore, how to promote the adhesion of endothelial cells (ECs) on the surface of cardiovascular materials to achieve endothelialization of the surface is the key to overcoming the complications after implant materialization. At present, the surface endothelialization design of materials based on materials surface science, bioactive molecules, and biological function intervention and feedback has attracted much attention. In this review, we summarize the related research on the surface modification of materials by endothelialization in recent years, and analyze the advantages and challenges of current endothelialization design ideas, explain the relationship between materials, cells, and vascular remodeling in order to find a more ideal endothelialization surface modification strategy for future researchers to meet the requirements of clinical biocompatibility of cardiovascular materials.

Optimization of Laser Processing Parameters and Their Effect on Penetration Depth and Surface Roughness of Biomimetic Units on the Surface of 3Cr2W8V Steel

Biomimetic coupling surface is a recent development in surface science of materials. One of the important methods to achieve this surface is to manufacture large numbers of structural units by certain techniques, arranging them regularly on the surface layer of materials to form the biomimetic structure. The penetration depth and the surface roughness of units are two crucial factors that affect strongly the properties of materials. In this paper, a YAG pulsed laser with varied parameters (electrical current 200 A to 300 A, pulse duration 5 ms to 15 ms, frequency 4 Hz to 10 Hz and scanning speed 0.24 mm·s −1 to 0.72 mm·s −1) was used to fabricate these units on the surface of 3Cr2W8V die steel. The penetration depth and surface roughness of the units were investigated based on orthogonal experimental design. To maximize the penetration depth and minimize the surface roughness, the range analysis and subsequently overall balance method were adopted to identify the most significant factor and level. Meanwhile the most preferable combination of the laser processing parameters was selected. The effect of laser processing parameters on the penetration depth and surface morphology of units was analyzed. The interrelationship among the processing parameters, the penetration depth and the surface roughness was discussed.

Book Review of Introduction to Materials Chemistry

Allcock says the text focuses on a large spectrum of topics rather than in-depth coverage of a few topics, and on chemical concepts rather than equations. This approach makes the text a flexible book because students do not necessarily need to have two-three years of chemistry to take a course that uses it. Parts of the applications chapters as well as the descriptions of polymers, ceramics, and glasses could be brought into general chemistry courses. The text has a broader appeal than just to chemistry students. Any student with a year of introductory chemistry or physics who wishes to learn about materials science could learn something from a course in which Introduction to Materials Chemistry was used. My own experience with materials science has involved mainly structure and bonding, physical properties, and spectroscopy. For me, sample preparation involved picking up the telephone to order whatever adsorbates or substrates I needed, so most of Chapter 2, Basic Synthesis and Reaction Chemistry, was new. This chapter in particular has added an additional dimension to the way I think about teaching materials science, and it has given me some new ideas to bring in to my general chemistry classes (for example, Figure 3.4, which shows how oil leads to polymers). Each chapter ends with approximately a dozen study questions. Rather than the typical problems one might find in a chemistry text, these are conceptual questions. Some questions probe key vocabulary words: for example, Chapter 3 has questions that ask students to define “magic angle spinning”, “elastic modulus”, and “compliance”. Other questions are more open ended and may require some additional research. These study questions would all be great for starting classroom discussions. Starting with Chapter 6, Polymers, each chapter has a section called Future Challenges In... or Unsolved Problems In.... These are the most interesting sections to read because they are quick snapshots of current research trends in each area. Incorporating sections like these in textbooks seems to be a new trend (if one can say a sample size of two constitutes a trend), but I like it. I think this is a great way to start exposing undergraduate students who may have to do a senior thesis project to research. I enjoyed the last three chapters the most (Surface Science of Materials; Biomedical Materials; andMaterials in Nanoscience and Technology) because they were the most readable. The author's broad brushstroke approach at the expense of depth makes the first 14 chapters a rather dry read. The early chapters are more encyclopedia-like. For example, Chapter 6, Section F is eight pages long; in these eight pages, key features and properties of approximately 24 polymers are described. These eight pages were very informative, but they did not capture my interest in the way the last three chapters or the sections on future challenges did. I think Introduction to Materials Chemistry is a great text for looking up a specific topic and getting a quick snapshot of that topic. Its encyclopedic style reminds me of Herzberg's three volumes on molecular spectroscopy (1). In graduate school, I read all three volumes because they were on the reading list for a class. My professor told me no one ever reads Herzberg; they use it as a reference book. While I understood far more of Introduction to Materials Chemistry than I did when I read Herzberg for the first time, it was not an engaging read. For example, I would not recommend this text for a conventional course in which students are expected to read Chapter 1 and come to class prepared to discuss it. However, I think this book would work well in the hands of an instructor who could bring it to life by picking out some of the endof- chapter questions and asking students to come to class prepared to discuss them. I also think it would be interesting to base a course only on Part III: Materials in Advanced Technology and discuss these chapters in some depth while using the first two parts as the reference or background material. This is a book I would be happy to have on my bookshelf. I would use it for supplemental material or place it on reserve for students. I am not certain that I would adopt it as a stand-alone text for a course in materials chemistry. I am reasonably confident that I will not pack this book to take with me on vacation, but as with Herzberg's text, I am glad I read Allcock's Introduction to Materials Chemistry once, and I know where to find it when I need it.