2016年12月英语四级阅读长篇阅读练习(五)

　　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.