网通传奇私服【经济学人No.29】Industrial


Materials science

材料科学

Industrial plants

工业植物

How to make buildings, cars and aircraft from materials based on natural fibres

如何用基于天然纤维的材料盖房子及造汽车和飞机

USING carrots to create concrete, turning wood into plastic, or even compressing it into a “super wood” that is as light and strong as titanium might sound like a series of almost Frankensteinish experiments. Yet all three are among the latest examples of employing natural fibres from plants as eco-friendly additives or alternatives to man-made materials.

用胡萝卜拌制混凝土;把木头变成塑料;把木头压缩成和钛一样又轻又坚固的“超级木材”。这听起来像是科学怪人鼓捣的一连串疯最新开热血传奇私服狂实验。实际上,这是研究人员尝试把植物中的天然纤维用作环保添加剂或人造材料的替代品的最近三例。

Materials-science researchers are finding that plant fibres can add durability and strength to substances already used in the construction of buildings and in goods that range from toys and furniture to cars and aircraft. A big bonus is that, because plants lock up carbon in their structur海外传奇私服e, using their fibres to make things should mean less carbon dioxide is emitted. The production of concrete alone represents some 5% of man-made global CO2  emissions, and making 1kg of plastic from oil produces 6kg of the greenhouse gas.

材料科学研究人员发现,在建筑材料以及玩具、家具、汽车、飞机等各种商品的原材料中添加植物纤维,能让它们更耐久、更结实。而由于植物可将碳封存在其组织内,使用植物纤维应该还会带来一大好处——减少二氧化碳排放。单是混凝土生产就造成了全球大约5%的人为二氧化碳排放,而用石油生产1公斤塑料会产生6千克温室气体。

Start with the carrots. These are being investigated by Mohamed Saafi at Lancaster University, in England. Dr Saafi and his colleagues do not use whole carrots, but rather what they call “nanoplatelets” that have been extracted from carrots discarded by supermarkets or as waste from food-processing factories. Sugar-beet peelings are also a useful source of nanoplatelets. The researchers are working with CelluComp, a British firm that produces such platelets for industrial applications, including as an additive that helps toughen the surface of paint as it dries.

先来看胡萝卜的妙用。英国兰卡斯特大学的默罕默德·萨菲(Mohamed Saafi)正在探究这种植物的用处。萨菲和同事们用的并不是整根胡萝卜,而是所谓的“纳米薄片”,是从超市丢弃或被食品加工厂当作废料的胡萝卜中提取而来。甜菜皮也是制作纳米薄片的有用材料。研究人员正在和英国公司CelluComp合作。这家公司生产工业用途的纳米薄片,其中有一种可用作添加剂,能让干燥后的油漆表面更牢固。

Each platelet is only a few millionths of a metre across. It consists of a sheet of stiff cellulose fibres. Although the fibres are minute, they are strong. By combining platelets with other materials a powerful composite can be produced. Dr Saafi is mixing the platelets into cement, which is made by burning limestone and clay together at high temperature. (The chemical reaction between them releases carbon dioxide from the limestone.) To turn cement into concrete it is mixed with aggregates such as sand, stones and crushed rocks, which act as reinforcement, and with water, which reacts with the chemicals in the cement to form a substance called calcium silicate hydrate. This starts off as a thick gel, but then hardens into a solid matrix that binds the aggregates together.

每个薄片只有一米的几百万分之一宽,由一层硬的纤维素纤维构成。这种纤维虽然非常细小,却很结实。将薄片与其他材料结合,便能得到强大的复合材料。萨菲正在把薄片与水泥混合。水泥由石灰石与粘土高温烧制而成。(二者发生的化学反应会令石灰石释放二氧化碳。)要将水泥变成混凝土,需要将它与骨料和水混合,骨料包括砂石和碎石,起加固的作用;水会与水泥中的化学物质发生反应,形成一种叫作水化硅酸钙的物质。一开始它是一层厚厚的胶状物,但之后会硬化成一种固体基质,将骨料结合在一起。

Carrot soup

胡萝卜汤

By adding vegetable platelets to the mix, Dr Saafi and his colleagues can make黑龙江网通传奇私服 concrete stronger. This is useful in itself, but it also permits a reduction in the ratio of cement to aggregates that is required to achieve a given level of strength. Reducing the amount of cement in this way consequently reduces CO2 emissions.

萨菲及同事将蔬菜纳米薄片加入混合物,让混凝土变得更坚固。这本身就很有益处,但采用这种手段还可以降低水泥与骨料的比例(这两者需要达到一定比例才能使混凝土达到特定强度)。如此减少水泥的用量,也就可以减少二氧化碳的排放。

The group is still exploring exactly how strong it can make concrete by adding platelets, but initial studies suggest that the impact could be considerable. Just 500 grams of platelets can reduce the amount of cement needed to make a cubic metre of concrete by about 40kg—a saving of 10%. Dr Saafi and his team have now embarked on a two-year study to investigate the process in more detail and to perfect the best mix for use by the construction industry.

这个团队仍在探究采用添加纳米薄片的方法究竟能让混凝度达到何种强度,但初步研究已仙剑版本传奇私服经显示,其效用可能会相当可观。仅500克纳米薄片就可以使生产一立方米混凝土的水泥用量减少约40公斤,相当于节省10%。萨菲和他的团队如今已开始了一项为期两年的研究,准备更加详尽地探究工艺流程,找出最佳配比,以供在建筑行业应用。

Unlike cement, wood is already a composite material. It is made of cellulose fibres embedded in a matrix of lignin, an organic polymer that serves a number of purposes, including providing woody plants with their rigidity. In May Stora Enso, a Finnish forestry-products company, launched a wood-derived alternative to oil-based plastics. This material, called DuraSense, looks a bit like popcorn. It consists of wood fibres, including lignin, obtained from pulping and other operations. The fibres are mixed with oil-based polymers and other additives, such as colouring agents. The resulting granules can be melted and moulded in the same way as plastic is in factory processes. Ad传奇私服1.85发布网ding wood fibres, the company says, can reduce the amount of plastic needed to make goods with plastic parts by 60%.

和水泥不同,木材已经是一种复合材料了。它是由嵌在木质素基质中的纤维素纤维制成。木质素是一种有多种用途的有机聚合物,其中之一就是赋予木本植物硬度。5月,芬兰林产品公司斯道拉恩索(Stora Enso)发布了一种源自木材的材料,可替代以石油为原料的塑料制品。这种材料名叫DuraSense,看上去有点像爆米花,是由包括木质素在内的木纤维构成,这些纤维是通过制浆等操作方法获取的。该公司将木纤维与基于石油的聚合物以及着色剂等其他添加物混合,所形成的颗粒可以熔化并塑形,就像工厂中为塑料塑形的工艺一样。该公司称,在生产含有塑料配件的商品时如采用这种添加木纤维的做法,可以将塑料的使用量减少60%。

Stora Enso has also found a use for pure lignin, which is often a waste product of papermaking, since most paper is made of pulp with the lignin removed. Stora Enso’s engineers have worked out how to use lignin as a s合击传奇私服网ubstitute for the oil-based resins and adhesives employed in the manufacture of engineered timbers, such as plywoods. Nor are they alone in looking for structural applications for lignin. Along wi1.76金币版传奇私服th others they are seeking ways to use it to replace oil-based materials in carbon-fibre composites, which are used to make lightweight parts for cars and aircraft.

斯道拉恩索还为纯木质素找到了用处。由于大多数纸张都是由去除了木质素的木浆制成,因而这种物质在造纸业中往往是废料。斯道拉恩索的工程师已经研究出方法,既可以将木质素用作石油树脂的替代品,还可以在生产胶合板等工程木料时将它用作黏合剂。为木质素寻找结构性用途的并非只有斯道拉恩索的工程师。其他人也和他们一样,正在探究如何以木质素替代碳纤维复合材料(用来为汽车和飞机制造轻量部件)中的石化材料。

By contrast, Hu Liangbing and Li Teng of the University of Maryland are trying to make a better material by removing, rather than adding, lignin. Their aim is to create a “super wood” that is stronger than most metals. Their approach is to treat blocks of wood with sodium hydroxide and sodium sulphate in a chemical process similar to that used to r合击传奇私服网站emove lignin from papermaking pulp. The difference is that they remove 超级变态传奇私服only enough lignin to make the wooden blocks easier to compress. They do that by squeezing the treated wood at around 100°C, which causes most of the pores and tubelike fibres within the wood to collapse. This increases its density threefold and its strength elevenfold.

马里兰大学的胡良兵和李腾则是尝试通过去除而非添加木质素的方法来制造一种更好的材料。他们的目标是研制出比大多数金属都要坚固的“超级木材”,方法是用氢氧化钠和硫酸钠对木料加以处理,这一化学过程与从造纸用浆中去除木质素类似。只不过,他们仅去除了木料中的部分木质素,使木材恰好达到更易压缩的程度。他们将处理过的木料放到大约100℃的温度下做挤压,木头中的大多数管孔和管状纤维就会被破坏。这会使木料的密度提升至原来的三倍,强度提升11倍。

That puts super wood on a par with some of the lightweight titanium alloys used in high-strength aerospace components. It is also bulletproof. In one test Dr Hu and Dr Li made a laminated sample by placing five sheets of the stuff on top of one another, each sheet having its fibres aligned at right-angles to those of the sheet below. When shot at, this material splintered but was still able to trap a steel projectile that passed effortlessly through a similarly sized sample of natural wood.

这样一来,超级木材就足以和高强度航空航天部件所采用的某些轻量钛合金相媲美了。这种木材还具备防弹功能。在一次测试中,胡良兵和李腾将五层超级木材叠放,制成一个层压板样品,每一层木板中的纤维都与下一层的呈直角。被射击后这种材料发生碎裂,但仍将钢弹卡在了中间。尺寸相近的天然木材样本则被子弹轻松穿透。

The team are now trying to commercialise their process, which Dr Hu thinks will be cheap to scale up. It works on both hardwoods and softwoods, so a range of materials can be created. Dr Hu reckons that, one day, houses, cars, furniture and many other things will be made mainly or partly from densified woo今日新开传奇私服1.85d.

这个团队目前正尝试将这项工艺商业化,胡良兵认为它能以低廉的成本实现规模化。这项工艺在硬木和软木上均适用,因而可以研制出多种材料。胡良兵认为,某一天,房子、汽车、家具以及其他很多东西都会主要或部分由压缩木材制成。

 


Print edition | Science and technology

Jun 14th 2018

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