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علم شیمی برای زندگی - جایزه نوبل شیمی ۲۰۱۱ برای کاشف شبه‌بلورها
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دانیل شختمن (Dan Shechtman) برنده جایزه نوبل شیمی 2011 به خاطر کشف شبه‌بلورها(quasicrystals)جایزه نوبل شیمی ۲۰۱۱ به دانیل شختمن (Dan Shechtman) به خاطر کشف شبه‌بلورها(quasicrystals) ، ساختارهای شیمیایی شبه‌موزائیکی که پیش از این پژوهشگران وجود آنها را ناممکن تصور می‌کردند، اهدا شد.

به گزارش آسوشیتدپرس آکادمی سلطنتی علوم سوئد اعلام کرد کشف شختمن در سال ۱۹۸۲ به طور بنیادی نحوه نگرش شیمی‌دانان به مواد جامد تغییر داد. کشف شختمن در ابتدا با مخالفت شدید جامعه علمی روبه‌رو شد، و حتی باعث اخراج او از گروه پژوهشی‌اش در آمریکا شد.

به گفته آکادمی اما از آن هنگام به بعد شبه‌بلورها در آزمایشگاه‌ها تولید شده‌اند و یک شرکت سوئدی آنها در یکی از مقاوم‌ترین انواع فولاد یافت که اکنون در فراورده‌هایی مانند تیغ ریش‌تراشی و سوزن‌های نازک به طور اختصاصی ساخته‌شده برای جراحی چشم، به کار می‌رود.

دانشمندان همچنین در حال آزمایش استفاده از شبه‌بلورها در پوشش‌های ماهی‌تابه‌ها، ایزولاسیون حرارتی موتورها، و دیود‌های گسیل‌کننده نور یا LEDها هستند.

به گفته آکادمی علوم سوئد شبه‌بلورها برای اولین در سال ۲۰۰۹ در روسیه، در طبیعت هم کشف شدند.

شختمن ۷۰ ساله استاد علوم و مهندسی مواد در دانشگاه ایالتی آیووا در شهر ایمس در ایالت آیووای آمریکا در مراسم اهدای جوایز نوبل در ۱۰ دسامبر در استکهلم جایزه ۱۰ میلیون کرونری (۱٫۵ میلیون دلاری) دریافت خواهد کرد.

Daniel Shechtman, winner of Nobel Prize in chemistry, was born in Israel in 1941 and splits his time between Haifa, Israel, and Ames, Iowa. He is a professor of materials science at Technion-Israel Institute of Technology and at Iowa State University in Ames where he is a research scientist at the U.S. Department of Energy’s Ames Laboratory.


Emma Dutton/MEDILL

A hexagon has 6-fold rotational symmetry, with a repeating pattern for each 60 degree rotation. It also has translational symmetry, which means it can be organized in a periodic array without voids or holes. This is the symmetry pattern of atoms in what are considered traditional crystal structures.

Emma Dutton/MEDILL

A pentagon has 5-fold rotational symmetry, with a repeating pattern for each 72 degree rotation. It does not have translational symmetry and cannot be organized in a periodic array without leaving voids or holes. This is a symmetry pattern of atoms in some quasicrystals, which are ordered but do not repeat periodically as traditional crystals do.

Emma Dutton/MEDILL

A square has 4-fold rotational symmetry, with a repeating pattern for each 90 degree rotation. It also has translational symmetry, which means it can be organized in a periodic array without voids or holes. This is the symmetry pattern of atoms in what are considered traditional crystal structures.

 

Israeli scientist Daniel Shechtman won the Nobel Prize in chemistry Wednesday for his 1982 discovery of quasicrystals.

Fighting nearly unaminous rejection of his discovery, the Israeli scientist showed that the assumed natural laws of solid materials were anything but absolute.

Thanks to Shechtman, 70, scientists now study quasicrystals for many applications including highly durable steel, non-stick coatings in frying pans, light-emitting diodes, coatings on turbine blades and thermoelectric materials that convert between heat and electricity.

“He discovered something which could not exist according to laws that we had all believed for over 100 years. It was completely new science, completely out of the box, and probably the biggest shock of the century in materials science,” said Alex King, director of the U.S. Department of Energy’s Ames Laboratory in Ames, Iowa, where Shechtman is a research scientist. “We had to rewrite all of the textbooks on crystallography.”

Crystallography is the study of any object in an ordered array, such as stalks in a cornfield or atoms in crystalline materials. Before Shechtman’s discovery, there were two types of solids: crystalline materials made up of ordered, repeating patterns of atoms, and amorphous materials such as biological tissue or sand. Shechtman’s discovery of quasicrystals didn’t fit in either category.

“This type of crystal had a definite symmetry, but it did not generate a long-range periodicity so it’s kind of like in between. That’s why it’s called quasicrystal,” said Mike Bedzyk, department head of Materials Science and Engineering at Northwestern University. “It took a great deal of courage and perseverance on the part of Professor Shechtman to actually stick to this explanation that there was another phase of solid materials.”

King said his colleague Shechtman is not aggressive or forceful, but that today’s new Noble laureate knew he had proof.

“Danny is the sweetest man you could ever hope to meet. You don’t get the impression of him being a down and dirty fighter, but he knew with absolute certainty that what he had done was right,” King said.

Before his discovery, scientists held that atoms in crystal materials were organized with both translational and rotational symmetry that repeated periodically. Translational symmetry is the ability to step a fixed amount in one direction and find a repeating pattern every time. Rotational symmetry is the ability to rotate a pattern by some fixed amount and again always find the pattern repeated exactly.

In “۲-fold rotation symmetry,” the pattern repeats when it is rotated 180 degrees.

King said that only multiples of 2-fold, 3-fold or 6-fold rotational symmetry existed in the textbooks and the study of crystallography. Shechtman found 5-fold rotational symmetry in a solid material, and he fought convention until the scientific community accepted his results.

With 5-fold rotational symmetry, translational symmetry cannot exist, meaning he had found a crystal with an ordered pattern of atoms that does not repeat over long ranges. Bedzyk explained the quasicrystal structure in a 2-dimensional space but said the general conclusions hold in 3-dimensional space.Using bathroom tiles as an example, a five-sided tile (a pentagon with equal side lengths and angles) cannot fill an entire bathroom floor without voids or holes in the pattern. Squares (with 4-fold symmetry) or hexagons (with 6-fold symmetry), on the other hand, will fill the entire bathroom floor with no voids.The different structure of atoms in quasicrystals results in useful materials properties, including very low friction that King, director of Ames Lab, described as “metallic Teflon.”

“They have thermoelectric properties, which means they can be used to convert between heat and electrical energy, which is a very useful property that is still kind of in the niche phase of being developed,” King said. “There are many potential energy-saving applications.”

Thermoelectric research is looking for ways, for instance, to turn waste heat from cars into electricity.

Following the Nobel announcement, Sven Lidin, member of the Nobel Committee for chemistry, spoke about the future development of quasicrystals in an interview with freelance journalist Joanna Rose, posted on www.NobelPrize.org.

“When quasicrystals came about, we had no idea of how to treat these systems. It turns out that they do have very special properties,” Lidin said. “Embracing this paradigm shift has, I think, made us a little bit more humble about what we know and what we don’t know. There’s a big world out there that we have very little understanding of yet.”





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