四级考试长篇阅读模拟题含答案

　　四级考试长篇阅读模拟题(一)

　　B.“Graphene is a wonderful material，”Jeanie Lau，a professor of physics at the University of California at Riverside，told Fortune.“It conducts heat 10 times better than copper and electricity 100 times better than silicon，is transparent like plastic，extremely lightweight,extremely strong,yet flexible and elastic.In the past decade，it has taken the scientific and technology communities by storm，and has become the most promising electronic material to supplement or replace silicon.”

　　C.Graphene has already found its way into a number of compelling applications，Lau said.For instance，“since it is both transparent and electrically conductive—two attributes rarely found in the same material in nature—it has tremendous potential as the transparent electrode in monitors.displays;solar cells，and touch screens，”she explained.“Companies such as Samsung that invest heavily in this area have already secured patents，produced prototypes，and are expected to bring products to market in a few years.”Wearable electronic devices，aviation components，broadband photodetectors(光电检测器)，radiation-resistant coatings，sensors，and energy storage are among numerous other areas of active research.Lau said.

　　D.For many researchers and investors，the ultimate application is graphene-based transistors，the building blocks of modem electronics.But getting there may take some time.

　　A child of graphite

　　E.First produced in a lab back in 2004，graphene is essentially a single layer of pure carbon atoms bonded together in a honeycomb lattice so thin it’s actually considered two-dimensional.“We generally regard anything less than 10 layers of graphene as graphene;otherwise，it’s graphite，”said Aravind Vijayaraghavan，a lecturer in nanomaterials at the University of Manchester.

　　F.Even“graphene”is a bit of an umbrella term.“To oversimplify,there are two major types of graphene，”Michael Patterson，CEO of Graphene Frontiers，said.The first：“Nanoplatelets，”which are powders or flakes made from graphite.These have been around for a while and are“not really super-sexy,”Patterson said.“You mix them into polymers(聚合物)or inks or rubbers to make them conductive.”In flake form，graphene is already on its way to becoming a commodity,Patterson added.The other type—in sheet or film form—is where graphene’s biggest promise lies.Graphene sheets have“incredible potential for electronics，”Patterson said.In the near term，that potential may manifest in situations where the quantity requirements are“not that great”and where quality or conductivity doesn’t have to be as high，such as in basic touch-screen applications，he said.Products that use graphene in this way could arrive to market in the next six to 1 2 months.

　　G.Looking a little further out，graphene can be employed in membranes used for water desalination.Lockheed-Martin already has a patented product known as Perforene.“It’s real and it works，but it won’t be economically viable until the product reaches an industrial scale where the cost is measured in pennies per square inch”rather than dollars or tens of dollars per square inch，Patterson explained.

　　“That’s where we’re working today.”

　　‘It’s expensive and low-capacity’

　　H. But use of graphene in semiconductors—the technology’s Holy Grail—is likely a decade away.“Many of the challenges presented by graphene are common to most new materials，”Paul Smith,a patent associate with the Intellectual Property Law Group at Fenwick & West，told Fortune.“The trick is figuring out how to synthesize graphene in a way that first is manufacturable beyond lab scale;second，preserves the desirable properties of the material;and third，can be integrated into a product or technology.”

　　I.Synthesizing graphene in sheet form is considerably more expensive and time-consuming than producing graphene flakes.Whereas the latter typically involves a“quick and dirty”process by which bulk graphite is disassembled into millions of tiny pieces，Lau explained，large sheets of graphene are carefully“grown”on substrates(基板)such as copper，germanium，or silicon carbide.

　　J. Graphene sheets are also prone to defects and“very difficult to make in good quality,”Ron Mertens，owner and editor of Graphene-Info.tom，said.Production capacity is also very limited.“There are thousands of small companies that can make graphene，but it’s expensive and low-capacity,”Mertens said.alround wafer measuring one inch in diameter,for instance，costs about$1 00，he added.

　　K.An even thornier obstacle on the way to graphene transistors is the fact that the material has no“band gap，”an essential property that allows transistors to be turned on and off without leaking electronic charge in the“off”state，said Elias Towe，a professor of electrical and computer engineering at Carnegie Mellon University.

　　L.“Band-gap engineering has been and remains the biggest challenge in the development of graphene transistors and computer chips.”Lau said.It requires controlling the material almost down at the atomic level，and“that’s really pushing the edges of existing technology,”Patterson said.“In 10 years，we’11 start to see these problems solved.”

　　‘It is largely a matter of time’

　　M.If graphene is to succeed as a replacement for silicon，every unit of cost and performance will make a difference，Towe said.

　　N.“Silicon is hard to displace，with all the billions dollars of investments made in manufacturing infrastructure，”he said.“A replacement for silicon has to offer extraordinary performance at extremely rock-bottom cost to compel industry to change its way.”

　　O.Though graphene is just 10 years old—in contrast,use of silicon in transistors dates to the early 1950s—considerable progress has already been made.For example，the largest graphene sheet was produced by hand in a laboratory eight years ago;its width was less than that of a human hair.“Nowadays，roll-to-roll printing of graphene sheets up to 1 00 meters long has been achieved，”Lau said.“With the increasing interest，investment，and research in graphene-based technology,I think it is largely a matter of time before the economy of scale kicks in and truly low-cost，large-scale production ofhigh-quality graphene is accomplished，”she added.

　　46.Nanoplatelet is the powder-or flake-type of graphene that has been used for some time to make conductors and that is being launched on the market.

　　47.To encourage industry to replace silicon with graphene，it is necessary for graphene to provide high property at an extremely low expense.

　　48.While graphene flakes are roughly processed with bulk graphite，graphene sheets are carefully made on substrates like copper，germanium，or silicon carbide.

　　49.In the past ten years.graphene has become a hot topic among the scientific and technology groups.

　　50.Perforene won’t come into the market before it can be manufactured at a very low cost.

　　51.Despite of a much younger age than silicon，great progress has been made in graphene;and with ever increasing interest，investment and research in graphene technology,it’s probable to manufacture cost- effective graphene of high quality.

　　52.Graphene has been attempted to be used for plenty of noticeable applications.

　　53.Yet it still needs to take ten years for graphene to be used in semiconductors，which lies at the heart of the technology.

　　54.With today’s technology,it is still impossible to control material down at the atomic level.

　　55.Elias Towe pointed out that having no“band gap”，the dispensable feature of transistors，makes it more difficult to produce graphene transistors.

　　四级考试长篇阅读模拟题答案

　　46.Nanoplatelet is the powder-or flake-type of graphene that has been used for some time to make conductors and that is being launched on the market.纳米片是粉末状或者薄片状的石墨烯，被用于制作导体已经有一段时间了，而且开始被推向市场。

　　47.To encourage industry to replace silicon with graphene.it is necessary for graphene to provide high property at an extremely low expense.为了让业界用石墨烯代替硅，就必须让石墨烯在造价极低的同时保持高性能。

　　48.While graphene flakes are roughly processed with bulk graphite，graphene sheets are carefully made on substrates like copper,germanium，or silicon carbide.石墨烯薄片是由块状石墨粗略加工而成的，而石墨烯薄膜则是在铜，锗或者碳化硅等基板上仔细加工而成的。

　　49.In the past ten years，graphene has become a hot topic among the scientific and technology groups.在过去的十年间，石墨烯已经成了科学技术界的热点话题。

　　50.Perforene won’t come into the market before it Can be manufactured at a very low cost.Perforene在能够以低成本大量生产之前是不会上市的。

　　51.Despite of a much younger age than silicon，great progress has been made in graphene;and with ever increasing interest，investment and research in graphene technology,it’s probable to manufacture cost-effective graphene ofhigh quA.ity.虽然出现得比硅要晚很多年，石墨烯仍取得了很大进展;而且随着石墨烯技术利益，投资及研究的日益增加，很有可能以低成本生产大量高质量的石墨烯。

　　52.Graphene has been attempted to be used for plenty of noticeable applications.石墨烯已经被尝试着用于许多引人注意的应用程序。

　　53.Yet it still needs to take ten years for graphene to be used in semiconductors，which lies at the heart of the technology.但是，将石墨烯用于半导体制造(技术的核心)仍需要十年的时间。

　　54.With today’s technology,it is still impossible to control material down at the atomic level.以今天的技术还无法将材料控制在原子层面。

　　55.Elias Towe pointed out that having no“band gap”，the dispensable feature of transistors，makes it more difficult to produce graphene transistors.艾利亚斯•陶威指出，由于缺少晶体管必备的“带隙”，使得制造石墨烯晶体管更加困难。