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为何按压晶体也能产生电能? – 译学馆
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为何按压晶体也能产生电能?

How to squeeze electricity out of crystals - Ashwini Bharathula

这是一枚糖晶
This is a crystal of sugar.
它在被按压的时候会产生电流
If you press on it, it will actually generate its own electricity.
为何这样简单的晶体能有像小型能量源一样的作用?
How can this simple crystal act like a tiny power source?
因为糖属于压电晶体
Because sugar is piezoelectric.
压电物质能将机械压力
Piezoelectric materials turn mechanical stress,
如按压
like pressure,
声波
sound waves,
以及其他共振等
and other vibrations
转换为电能 反之亦然
into electricity and vice versa.
这种奇妙的现象首次被发现于1880年
This odd phenomenon was first discovered
发现者是物理学家皮埃尔•居里与其兄雅克•居里
by the physicist Pierre Curie and his brother Jacques in 1880.
他们发现当挤压某种晶片时
They discovered that if they compressed thin slices of certain crystals,
在其相反的两面会产生正负两种电荷
positive and negative charges would appear on opposite faces.
这种电荷的差异 或者说电压的差异
This difference in charge, or voltage,
表明被压缩的晶体可以通过电路产生电流
meant that the compressed crystal could drive current through a circuit,
如同电池一样
like a battery.
反之亦然
And it worked the other way around, too.
这些晶体通电以后会产生形变
Running electricity through these crystals made them change shape.
这两种结论
Both of these results,
即机械能可以转换为电能
turning mechanical energy into electrical,
电能也可以转换为机械能
and electrical energy into mechanical,
实在令人叹为观止
were remarkable.
然而这个发现却沉寂了几十年
But the discovery went uncelebrated for several decades.
直到第一次世界大战才首次被实际应用
The first practical application was in sonar instruments
用于声纳系统以探测德军潜艇
used to detect German submarines during World War I.
位于信号发射器的压电石英晶体
Piezoelectric quartz crystals in the sonar’s transmitter
会在交流电的作用下产生震动
vibrated when they were subjected to alternating voltage.
从而向水中发射超声波
That sent ultrasound waves through the water.
测量超声波反射回的时间
Measuring how long it took these waves to bounce back from an object
即可推测目标物体的远近
revealed how far away it was.
另一方面
For the opposite transformation,
将机械能转换为电能的原理
converting mechanical energy to electrical,
被应用于声控灯
consider the lights that turn on when you clap.
拍手使空气震动
Clapping your hands send sound vibrations through the air
导致压电原件来回弯曲
and causes the piezo element to bend back and forth.
它产生的电能足以为发光二极管供电
This creates a voltage that can drive enough current to light up the LEDs,
然而人们也得不断拍手才能让灯一直亮着
though it’s conventional sources of electricity that keep them on.
那么为何物质会具有这种压电效应呢?
So what makes a material piezoelectric?
答案取决于两种因素
The answer depends on two factors:
物质的原子结构
the materials atomic structure,
及其内部电荷的排布方式
and how electric charge is distributed within it.
许多物质都是透明的
Many materials are crystalline,
说明它们由原子或离子构成
meaning they’re made of atoms or ions
这些粒子排列成规律的三维模式
arranged in an orderly three-dimensional pattern.
构成这种模式的基础材料被称为晶胞
That pattern has a building block called a unit cell
它不断重复
that repeats over and over.
在多数的非压电晶体物质中
In most non-piezoelectric crystalline materials,
原子在晶胞中围绕着对称中心
the atoms in their unit cells are distributed symmetrically
呈对称排布
around a central point.
但一些晶体不具有对称中心
But some crystalline materials don’t possess a center of symmetry
从而使它们具有压电性质
making them candidates for piezoelectricity.
以石英为例
Let’s look at quartz,
这种压电物质由硅元素和氧元素构成
a piezoelectric material made of silicon and oxygen.
氧原子带少量负电荷硅原子带少量正电荷
The oxygens have a slight negative charge and silicons have a slight positive,
造成了电荷分离
creating a separation of charge,
或者说每一个键都带有两极
or a dipole along each bond.
正负两极一般会相互抵消
Normally, these dipoles cancel each other out,
因此晶胞内部不存在电荷分离
so there’s no net separation of charge in the unit cell.
然而一旦朝特定方向挤压石英晶体
But if a quartz crystal is squeezed along a certain direction,
原子将产生位移
the atoms shift.
因为电荷排布的不对称性
Because of the resulting asymmetry in charge distribution,
正负两极不再相互抵消
the dipoles no longer cancel each other out.
延展的晶胞最终将有一侧负电荷
The stretched cell ends up with a net negative charge on one side
另一侧带正电荷
and a net positive on the other.
这种电荷失衡将会在物质内部不断重复
This charge imbalance is repeated all the way through the material,
导致晶体两面会持有相反的两种电荷
and opposite charges collect on opposite faces of the crystal.
它最终形成电压 使电流通过电路
This results in a voltage that can drive electricity through a circuit.
不同的压电晶体有不同的结构
Piezoelectric materials can have different structures.
但他们有一点是一样的即晶胞不呈中心对称结构
But what they all have in common is unit cells which lack a center of symmetry.
而且压电晶体所承受的压力越大
And the stronger the compression on piezoelectric materials,
它所产生的电压也就越大
the larger the voltage generated.
相反地 如果延展晶体 电压就会变化
Stretch the crystal, instead, and the voltage will switch,
使电流流向相反方向
making current flow the other way.
压电物质的数量比你想象中的要多
More materials are piezoelectric than you might think.
DNA
DNA,
骨骼
bone,
以及丝绸
and silk
它们都能将机械能转换为电能
all have this ability to turn mechanical energy into electrical.
科学家们也合成了不少人工压电物质
Scientists have created a variety of synthetic piezoelectric materials
它们被广泛应用于医学造影
and found applications for them in everything from medical imaging
及喷墨打印机等各行各业
to ink jet printers.
石英晶体的谐振现象也归因于压电效应
Piezoelectricity is responsible for the rhythmic oscillations
它使手表时间更精确
of the quartz crystals that keep watches running on time,
使生日贺卡的扬声器能唱出歌来
the speakers of musical birthday cards,
也能在你打开自动打火器时
and the spark that ignites the gas in some barbecue grill lighters
产生电火花点燃瓦斯
when you flick the switch.
鉴于电力需求的加剧 与机械能的过剩
And piezoelectric devices may become even more common
将来压电设备的应用可能会更加广泛
since electricity is in high demand and mechanical energy is abundant.
如今已经有火车站利用乘客的脚步
There are already train stations that use passengers’ footsteps
来控制检票口的开关
to power the ticket gates and displays
舞厅也利用压电效应为灯光供电
and a dance club where piezoelectricity helps power the lights.
篮球运动员可以通过跑步来为计分板供电吗?
Could basketball players running back and forth power the scoreboard?
或者在街上散步就能给电子设备充电?
Or might walking down the street charge your electronic devices?
压电效应未来还有哪些应用?
What’s next for piezoelectricity?

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视频概述

石英是一种特殊的压电晶体,可以将机械能转换为电能,反之亦然。这种压电效应是如何产生的?又如何被广泛应用于各行各业?欢迎来到这种奇妙晶体的世界!

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